THE DIMENSIONAL RELATIONSHIPS BETWEERI THE CRANIAL BASE, BODY HEIGHT, AND THE FACIAL COMPLEX.

A thesis submitted in conformity with the requirements for the degree of Master of Science

Faculty of Dentistry Discipline of Orthodontics

University of Toronto

Wopyright by Rana Targownik, 2001

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The Dimcnsional Rettionships Between t h -1 Base, Body Height, and the Facial Cornplex. R Taxgowdc, B Tompson, RB ROSS, DG Woodside. Master of Science (2001), Discipline of Ortbodontics, University of Toronto

ABSTRACX

The a- of this snidy were to investigate the dimensional rektionships between the

cranial base, body heght, and the facial complex and to establish a method of size

adjusting hear masuremenu d e n cornpuhg groups with overall size differences. Data

were obtained from lateral cephalomeuic radiographs, uacings, and history profiles of 117

onhodonticdy unneated males (ages 12 and 18 +) from the University of Toronto's

Burlington G m d Srudy.

'Zhe total cania base length (either NBa or {S-N + S-Ba)) and body height dispiayed

the snongest cornlaions to the linear facial dimensions. At age 12, smng comlations

(rs.4) existed between {S-N + S-Ba} and m&bular length, upper face height, and body

height N B a smngiy correlated to niaiollary iengrh At age 18+, the comlations to

mandibular length and upper face height weakened. Body height comlated suongly to

rnandi'bular length and upper face height at both ages.

Independent t-tests demonsmted that children who were short, or who had small total

c d base lengths exhibited smaller linear facial dimensions than children who were d e r

or had longer total cranial base lengthr; t h e ~ b ~ validating the need for linear size adjusùng

among diveae populations. Equations were generated that p~dic ted the adjusted hear

facial dimensions based on known total c d base length and body height.

The evidence suggested that size adjusting was statistically valid when studying

populations that differed in overall body, cranial base, and face size, where cornparisons

of absolute measurements would otherwise be invalid. This is especially important when

comparing groups with craniofacial anomalies.

ACKNOWLEDGEMENTS

I wodd like to thank the following people for their invahiable assistance with this ~ s e a r c h

endeavor:

Dr. Bruce Ross for the direction to begin this thesis and for his ongoing fascination wirh

the c d base

Dr. Bi)an Tompson and Dr. Don Woodside for their suggestions and supervision as

rnembea of my cornmittee

Dr. Hexenia Lawrence who provided me with inc~dibly helpfd statistical guidance

Joanne Hoffmekter and Gemude Jorgensen d o assisted with organUation of the

dographic records

My parents for instilling in me a smng wotk ethic and the confidence to

realue my dreams.

My brother and sister for king unique individuals d o taught and challenged me with

their differiences.

And to Morris: my fiancé, my best friend and my one mie love, 1 thank p u for the

unwavering support.

TABLE OF GONTENTS . .

ABSTRACT' ................................................................................................ u . . . ACKNOWLEDGEMENCLS .................................................................... UI

TABLE OF CONTENT5 ....................................................................... iv . . LIST OF TABLES .................................................................................... vii

LIST OF FIGURES .................................................................................. k

1 STATEMENT OF THE PROBLEM ...................................................... 1

II SIGNIFICANCE OF ï H E PROBLEM ................................................ 3

CHAPTER 2

GENETiC AND ENVIRONMENTAL CDNTRIBUI'iON!5 TO DEVELOPMENT OF THE CRANIAL BASE ............................................................................. 4

EMBRYOLOGICAL ORIGIN OF THE CRANIAL BASE AND FACIAL STRlKfIZlRES ................................................... 6 A TheGandBase ................................................................................. 6 B . CianialBase Anghion .................................................................... 9

................................................................................. C Facial Svuctu~es 9

POST-NATAL GROWTH AND DEVELOPMENT OF THE CRANIAL BASE ................................................................... 10

................................................................... A D e f i i the G a n d Base 11 i) Anterior Ganial Base ............................................................. 12 ii) Posterior Cranial Base .......................................................... 13

................................................................. h) Total Ganial Base 14 B . Gmwth Pattern of the Gania Base .................................................. 14 C Cessation of Growth of the Gand Base .......................................... 16

i) Anteior C d Base .............................................................. 16 ............................................................ ii) Posterior Ganial Base 18

hi Total Ganiai Base .................................................................. 20

VARIATIONS OF CRANIAL BASE REFERENCE LINES ............................................ FOR SUPERIMPOSITION PURPOSES 20

.......................................................................... A Antenor Cranial Base 20 . . . .......................................................................... 3 Reprodwbhty 20 . ......................................................................... B Posterior G d a l Base 22

............................................................................... C Total Ganial Base 22

V RELATiONSHIPS BETWEEN THE . BASE AND FAClAL AND SKELETAL DEVELOPMENT ..................... 23 A The Relationship of Cranial Base Length to l h x i h y

and Mandibuiar Lengths ............................................................. 26 B . The Reiarionship of Ganial Base Length to Body Hkight ........... 28 C The Reiarionship of ....... Base Length to G a d

Base F k m ....................................................... 28 D . The Relationship of Ganial Base Length to N a d Length .......... 30 E . ï h e Relationship of G.anial Base Le& to Face He&ts .......... 30 F . Defects involving the Gand Base and the Influence on

Facial Development ............................................... 31

VI CRANIAL BASE LENGTH IN ADULTS WITH VARIOUS MORMONAL DISORDERS ................................................ 32 A Childmn wah and Ylperthyroidisrn ............................ 33

.......... . B Children with Defiient and Excessive Gmwth Hormone 33 .............................. C Qddren Born S d for Gestational Age 34

. ............................................. D Boys with Delayed Puberty 35 E . Ad& with Achondroplasia ............................................ 35

METkiODS AND MATE RIALS ............................................... 37

II SAMPLE ............................................................................... 37 A Chamteristics of the Popuiation Selected from the

................................................... Burikgton Study 37 B . Ages of the Sample Pupularion ........................................... 38

III ANALYSIS OF THE RECORDS ...................................... 38 A Tmcing the Records ..................................................... 38

................................................. . B Cephalomeuic A n a i ~ i s 39 C Statisticai Methodology .................................................. 41

........................................................................... RESULTS 43

1 DESCRIPTIVE ANALYSES ............................................. 43 II CORRELATIONS BETWEEN THE CRANIAL BASE.

BODY HEIGHT. AM> THE FACIAL CDMPLEX ................. 45

III BIVARIATE ANALYSES ................................................ 49

......................................... IV ANALBIS OF COVARIANCE 52

V WNE AR REGRESSION .................................................. 57

DISCUSSION ....................................................................................... 58

..................................................................................... II CORRELAnONS 58 ............................................................................ A. Anterior G a n d Base 58

. ........................................................................ B Postenor Ganial Base 60 .................................................................................. C T o d Cianial Base 61

........................................................................................... D . Body Wight 62

III BIVARIATE ANALYSES ..................................................................... 64

V LINEAR REGRESSION ........................................................................ 68

CONCLUSIONS ................................................................................... 70

...................... ...... SUGGE STIONS FOR FUTURE RE SE ARCH ... 72

REFERENCES .................................................................................................. 73

APPENDIX A: Definitions of Gdofacial L a n u .................................................................. 81

APPENDIX B: ........................................... The Cianial Base in Relation to the Facd Cornplex 82

APPENDIX C; Examples of Comlationr B m e n the Ganial Base and the Facial Dimensions ................................................................................................... 83

APPENDIX D: Exampies of Differing Definitions of the Ganial Base ...................................... 84

APPENDXX E: List of Abbreviations ................................................................................................. 85

LI= OF TABLES

TABLE 2.1

TABLE 3.1

TABLE 32

TABLE 4.1

TABLE 4 2

TABLE 4.3

TABLE 4.4

TABLE 4.5

TABLE 4.6

TABLE 4.7

TABLE 4.8

TABLE 4.9

TABLE 4.1 1

Primordial cardages and their derivatives ................................................ 7

Body height categorized as short or ta11 at age 12 and 18+ .............................................................................................. 41 TCB length categorized as small or l q e

.......................................................................................... at age 12 and 18+ 41

Tabie of means, q e s , and standard devkions of the facd and c r d dimensions and

.................................................................... body height at age 12 (n4 17) 43

Table of means, ranges, and standard deviations of the facial and c d dimensions and

................................................................. body height a age 18 + (n -1 17) 44

Cornlarion coefficients and P values k e n the size of the segments of the c d base, the faciai

...................................... dimensions and body heght at age 12. (n- 1 17) 45

Comiation coefficients and P values between the size of the segments of the c r d base, the facial

................................... dLnensions and body height at age 18 +. (n-117) 46

Correlation coefficients and P values k e n body height and the facial dimensions ar age 12. (no1 il) ..................... 47 Comlation coefficients and P values b n body height and the facial dimmiom at age 18 +. (n -1 17) .................. 47 Correlations (r2.4) benmen the facial compLx and the

...................... c d base and the associated 95% confidence intervals 48

Correlations (-4) betwieen height and the c d base ............................ and face and the associated 950h confidence intervaL 48

T-tests of unadjusted values to compare faciai k n s i o m -en short and taIl groups at

............................................................................................. age 12. (n1117) 49

T-tests of unadjusted values to cornparie facial dimensions benmen short and call groups at age 18+. (n=117) ........................................................................................ 49

T-tests of unadjusted values to compare facial dimensions benmen gmup with krge and s m a l l

........................................... total craniai base length 1 at age 12. (n-117) 50

vii

TABLE 4.12

TABLE 4.13

TABLE 4.14

TABZ 4.15

TABLE 4.16

TABLE 4.17

TABLE 4.18

TABLE 4.19

TABLE 4.20

TABLE 421

TABLE 4.22

TABLE 423

TABLE 424

T-tests of d j u s t e d vaiues to compare fariai dimnsions becween groups with iarge and small

.......................................... t o d c d base kngth 2 ar age 12. (n=-117) 50

T-tem of unadjusted vaiues to compare faciai dimensions h n groups with iarge and small

........................................ totai c d base length 1 at age 18 +. (n- 1 17) 5 1

T-tem of unadjusted vaiues to compare facial dimensions bemmn groups wirh iarge and s d

........................................ total c d base length 2 at age 18 +. (n-117) 51

Adjusted R squared and sigdicance of the effects of body height and TCB on the facial dunensions at age 12 from ANOOVA &is. (n=117) ................................................. 52

Adjusted R squared and sigdicance of the effects of body height and TCB on the facial dimensions at age 18+ from ANOOVA modek. (n-117) .............................................. 53

Adjusted means and 95% confidence intervais of the facial dimensions for short and taIl groups conuollmg

................................................. for the covanate T a at age 12. (n- 1 17) 54

Adjusted means and 95% confidence internais of the facial dùnensions for short and tail groups conu~lluig for the c o v k e Ta3 at age 18 +. (n-117) ........................................ 54

Gmparison of adjurted and d j u s t e d means of facial dimensions ar age 12 where TCi3 is adjusted

....................................................................... to the gnnd mean. (N=li7) 55

Cornparison of adjusted and unadjusted mans of facial dimensions at age 18 + w h e ~ TCB is adjusted

..................................................... to the grand mean. (N-117). (n-117) 55

hkgmmde of difference in rneam k e n short and taii groups before and after adjusting for the c o v h e TCB at age 12. (n-117) ............................................................. 56

Magnitude of difference in maris b n short and t d groups befom and after adjusting for the

........................................................... covariate TCB at age 18 +. (n = 1 17) 56

Fomuiae for predrung means of the facial dimensions ushg height and mean total

....................................................... c r d base length ar age 12. (n-117) 57

Fonnulae for predming means of the facial dimensions using height and rnean total

.................................................... c d base length at age 18+. (n-117) 57

LIST OF FIGURES

FIGURE 2.1 Primordial Carulages of the Skuii Bare and their De rivarives ............... 7 FIGURE 2 2 Mi& Ganial Base .................................................................................. 14

FIGURE 2.3 Length of the Intemai ACB ........................................................................ 17 FIGURE2.4 N-SLength ................................................................................................... 17

FIGURE 2.5 Thickness of the Frontal Bone ................................................................... 18

FIGURE 2.6 S-Ba Length ............................................................................................. 19

INTRODUCTION

I STATEMENT OF THE PROBLEM

Cephalorneuic studies on facial growth or morphology employ linear, &, and

proportional measurements to compare groups of people. In doing so, many assume rhat the

groups are identical in terms of body size. Any significant differences in h e a r dimensions

are considered to be secondary to treatment or some other extianeous variable, but this is

not always the case. Overail size differences becween groups can arise a number of ways.

Diffemnces in age, gender or ethnic background can cause large variations in the size of the

body and craniofaciai suuctures arnong groups. A b n o d u e s in homonal, nutritional or

developmental statu may create a gene&d increase or decrease in o v e d size. If the

sample was randomly chosen, it may be that the individuais in one group are on avenge

smaller than the individuah in the other p w l y by chance. Radiographie technique is yet

another possible explanation for size differences. If f i were not taken in a standardized

rnanner, they can not be accurately compared.

The problems associated with linear measurements m u t be overcome. One way is to

develop a mechanisrn which would recognize the size differences berween diveise groups

and adjust the linear measurements to facilitate more accurate comparisons.

The major problem with rnany orthodontie studies is that the groups compared are

not simiiar in generai size and the differences in the absolute linear measurements are

misinterpreted In these cases, researchen and readen may faîsely conclude that differences

in a study were due to treatment insread of ~ a i u n g that the differences were due to inherent

problems of an unmatched sample. A method of size adjusting linear measurements would

addRss the problemr associated with faulty sample design.

The cranial base is the complex of bones that form the flwr of the canial cavity and

the roof of the face. Because of this location, gmwth of the c d base is often linked to

p w t h of the facial complex and it is genedy agreed that the c d base has considerable

influence on the developing facial morphology. In fact, the c d base may be the h e a r

s m i c n u e that serves as the foundation for size adjusting. Manystudies have related cranial

base form and flewre to degree of prognathism of the jaw bases. Hcwever, there is very

linle in the liteature mlatiug the size of the c d base to the absolute size of other facial

stmctwes and to the size of the body as a whole. If the cranial base size is strongly linked to

the facial skeleton and body height then it could feasibly serve as the basis for size adjusting

linear rneasurements.

SiLe adjusting all the facial dimensions would not be valid in cases where a

disturbance affecting the skeled suucnires is localized n i e presence of pathology,

ueatxnent, suigery or environmentai factors rnay affect some craniofacial suucnires and not

othen. In these instances, the c r d base may not be affected d e some of the iinear facd

svucnues are affeaed. For these cases, the influence of the disturbance should be

recognized locally and size adjusting performed only on the unaffected structures.

SIGNIFICANCE OF THE PROBLEM

It would be useful to demonstrate whether the size of the c r a d base is a direct

comlate to the size of other facial suurrures and to the o v e d body size of the population

as well. If this were proven to be true, then a group of chiidten srnall in stature and cranial

base wuld possess lesser facial dimensions than a group of larger children. This discovery

wouid highlght the need for "rnatched" samples in human research efforts. Body height and

o v e d size would become important parameten in study design. In cases where the study

had pcmrly matched samples, this mseamh is significant as it would yield a mechanism to size

adjust the groups and allow for more accuate evaluation of the findqs.

Of special interest are children with developrnental anomalies. These children tend

to be srnaller than the noms for their age. Often, when they are compared to their "nomial"

peers in snidies on facial morphology, the basic suucniral diffemnces between these IWO

groups are not considered and any absolute h e u resulu leave a fahe impression. For more

accuate and valid fidings, size adjusting is necessq to precisely relate the cranial base size

to body height and to the absolute sùe of suucnires in the facd cornplex.

Knodedge of these relationships would serve as an indispensable ~ference for

future scientific studies inves tigating c raniof a c d p w t h and morphology in dissimilar

populations.

LITERATURE REVIE W

1 GENETIC AND ENWRONMENTAL CONTRIBUTIONS TO DEVELOPMENT OF THE CRANIAL BASE

The field of orthdontics has k e n concemed with identifymg the relative contributions

of genetic and environmentai faon to craniofacial growth. Most of the hteratwr on

cranfofacial growth has focused on bonychanges. At first, it was thought thar bones were

geneticaily progammed to grow and were not influenced by outside factors. %=ver, over

time, the role of environmental factors was given credence and is now recognizd as a

crucial part of morphogenesis.

Sicher (1944) felt that growth of the bones was inherent and that the sutures acted as

growth centers to primarily direct growth. Gnveaely, othen believed that the function of

tissues and spaces determined the arnount and direction of growth. This concept was

induced by Van der Klaaw (1946) and emphasizeci later by Moss (1960). Thus, in their

opinions, the growing brain provided the impetus for growth of the cranium Bjork (1955)

suggested that antenor crand base (ACB) incmased in length because of s d gmwth but

that it did so to keep in step with the growing brain. He feh that posterior c r d base ( P a )

increased in length d y because of growth at the spheno-occipital synchondrosis.

Therefore, Bjork recognized both geneuc and environmental influences.

To discover the effect of heredity on the facial s keleton, Lundsmm (1954) snuied

fatemal and identicai twLis while Kraus (1959) lwked at fraternal and identical triplets.

Lundsmm found the genetic factors to be more significant than the non-genetic facto=

with respect to the dissimil~ties between fratemai twins. Regardmg identical rwins,

cephdornetric andysis revealed differences in facial suucnue. The non-genetic factors

responsible are probably the intemai environmenta facton that are active mainly early in

embryonic life. One example is that the genes thernselves rnay not express themselves

precisely, leading to stnrcwal alteratiom. Lundsnom quotes Dahlberg (1948) who said rhat

"giwn the ermernely complicated developrnent of the body one can hardly expect that, even

if we codd give two geneticaily identicd individuals the same extemal environments, they

would develop edyal ike". Kraus divided the head Mo tum parts, the facial complex and

the cranial complex, and uied to determine the influence of genetic and environmentai

factors. When the individuai parts of the calvarial bones and the c r a d base were ex;unined

it was impossible to discriminate between predominance of heredity or environment.

SLnilarly in the facial complex, Kraus recognized that aah so many complex interactions

o c c e simuitaneously the specific role of heredity (or environment) was difficult to

discem. K m then snidied bones in temis of their "profile linesn as seen in a cephalometxic

radograph. Me found that the profides superirnposed almost perfectly in identicd tiplets,

and very poorly in fiatemal triplets. Hk felt that this demonstrated that the morphologie

configuration of the skeietal units of the craniofacial complex were subject predominantly to

the influence of heredity. n i e strong presence that environmentai factors have is apparent in

the differiog soft tissue profides. Kaus felt that the bones have a multitude of inter- and

intra-relationships (non-genetically conuoled) f i c h combine to foxm the face and head

Enlow (1962) felt growth was a highly controiled process, modulated by remodehg

which conUnuously maintains the shape, proportions, and relationships of the various

~ g i o n s of bone. Van Limborgh (1983) thought gmwth of the c d base was largely due to

inuinsic factors that were genetic and inheritabie. In his view, environmental facton played

only a minor d e .

The philosophy to which most subscribe is that the facial bones aie geneticdy

prognmmed to grow in size, but through function are innuenced in form and

interrelationship, and then furrher modified by many external factors dong the way. As

Baume said, "Dunng the time of gmwth, heredity and function overlap in their rash as bone

pducing and bone forming elernents" (WatNk, 1972).

s-ry..

No definitive conclusions have been ~ a c h e d as to which factors predominate in

detennining the size and shape of the cranial base. An investigation into the p w t h

processes of the parts of cranial base gives some insight into the morphogenetic

pathways involved.

II EMBRYOLOGICAL ORIGIN OF THE CRANIAL BASE AND FACIAL STRUCI'URES

A. The Ganial Base:

Pre-natally, the entire cranial skeleton is a comective tissue framewok The eariiest

evidence of s M formation is in the fourth week intmuterine (Lu.). This is compaatively

iate considering that the brain, c d nerves, eps, and blooci vessels have akady begun

their development. In the late somite period, the occipital sclerotomai mesenchyme

concentrares arowid the notochord underiying the developing hindbrain. From this region,

the mesenchymal concentmion extends cephaiically and forms the floor of the brain

Conversion of the c d base mesenchyme into carulage starts at day 40 i.u.

Around the 8& week i.u., bone starrs CO form in the cantkge of the cranial base via

endochoncirai ossification. The formation of carulage is Liitially dependent on the pmsence

of the growing brain, and it requires an epithelial-mesenchyme interaction to have d e n

place.

The midline c d base develops from piimordial cardages of the

chondrocranium. Their derivatives are listed:

F i g u ~ 2.1 Primordial cartilages of the s k d base and their deiivatives

Table 2.1 PNnordial cartilages and their deht ives S p e k r (1989)

The chondrocranium is important as a shared junction between the nemranial and

Cimkge Type Parachorda

Occipital Sclemtomes Postsphenoid Pres phenoid

Orbitosphenoid Alisphenoid Mesethmoici

faciai s keletons. The rnidline chonchranial base in a newborn skull is s d e r than the

Denvative Basioccipid region

Boundary of foramen magnum SeUa m i c a and posterior part of the body of the sphenoid

Anterior part of the sphenoid bone Lesser wing of sphenoid Greater wing of sphenoid

Perpendicular phte of ethmoid and crisu galli

desmocranial part which extends l a tedy and posteriorly. Derivatives of the desmocranium

include the occipital and temporal bones including the region where the mandible articulates

with the cranial base.

The developing brain lies in a shallow p v e f o m d by the chondrocmniwn. The

deep hypophyseal fossa is bounded antenody by the presphenoid cardage of tubu~icuiwn

seiiae and posteriorly by the postsphenoid canilage of the donurn seiiae. These canilages

foxm the seiia nircica and anterior and posterior parts of the sphenoid bone.

Some camlagiaous mmnants peaist between adjacent bones in the c d base.

These mas are known as synchondroses and are the areas where gmwth occurs. As with

most gmwth centers, a synchondrosis is believed to represent a pressure adapted mechanism

that allows for the lengthening of bone in a field of direct compression (Enlow, 1976).

Intra-uterine growth of the cranial base is highly uneven. It develops an irregular

shape to accommodate the undulating surface of the growing brain. The antexior and

postenor parts of the midline cranial base, divided at seiia m i c a , are known to grow at

different rates. Between the IO" to 40" weeks i.u, the A(B increases in length and width

sevenfold while the PCB increases only fivefold (Sperber, 1989). Pre-nady, the spheno-

occipital synchondrosis (SOS) does not conuibute to growth as much as it does post-nataliy.

Growth of the c d base initiallytakes place as a result of p w t h at the synchondroses,

and expansive forces originating from the p w i n g brain that displace the bones at the su-

lines. Specificaiiy, the sutures involved in antenor- postenor growth of the ACB are the

sphenefrontal, fmntczethmoida, and the spheno-ethmoidai. Many sutures fuse at the &ne

of birth or slightly thereafter, but the latter two continue to grow dter birth. Although the

s pheneethmoidal su- is known to persist und adolescence, desmolytic degene ration of

the cardage produces a suture that is of rninMal significance in postnatal growth (Sperber,

1989).

B. Crrnial Base Anguiatiorx

The c e n d region of the cranial base is composed of prpchordal and chordal pans

*ch meet at an angle at the sella m ica . In the sagittai plane, these pans form an angle

which is often ~ f e n e d to as the ''canial base angle" or NS-Ba In the 4 week old ernbqm,

this angle is initially obtuse (150 degrees). The angle flexes to about 130 degrees in the 7-8

week old embryo, and becomes even more acute at 10 weeks (120 degrees). As the head

staxts to raise, and the c d base begins to ossdjr, there is sLght opening of the angle back

up to 130 degrees. Thk angle is fairlystable pst-natdy. Flattening of the c r a d base angle

is thought to be caused by rapid brain p w t h in the fetai p e n d as the chondrocanium

mains its onginal obtuse angle in cases of anencephaiy (Sperber, 1989).

Facial S t n t c t u ~ ~ ~ :

The facial prirnordia begin to appear early in the 4& week, as pmminences around the

iarge stomodeum, or primitive mouth. nie facial pmminences are the single rnedian

fmntonasai prominence, and the paired d a r y and mandibular prominences. The p a k d

mandibular prominences are derived from the fkt branchial arch. niey jre produced as

neural crest cells migrate into the arches and proliferate. These cells are a major source of

connective Ussue components including cartilage, bone, and iigaments from the orefacial

regions (Sperber, 1989). Development of the face occurs prirndy between the 4& and 8&

weeks. Facial development occun slowly and ES& from changes in the proportions and

positions of the facd components (Moore, 1993).

1) Mandible:

The mandible is the first pair of the face to form. It results from merging of the media

ends of the rwo mandibular prominences in the median plane in the 4" week

2) Nose and nasal cavities:

Bythe end of the 4 week, thiclcenings of the surface ectoderm have developed

Mesenchyme proMerates in these thickenings and forms honeshoe shaped elevations

known as the medial and lateal nasal prominences. The centea, or "pitsn of these

elevations are the prirnordia of the nosuils and nasa cavities.

3) Maxilh

The maidkiy prominences pmliferate and grow medidy towards each other and the

nasal prominences. Bythe end of the 6& week, each maiallary prominence has begun to

merge with the lateral nasal prominence. Between the 7'' and 1 0 ~ weeks, the media1 nasal

prominences merge with each other and the maxhîy and laterai nasai prominences,

resulting in continuity of the upper jaw and lip.

III POST-NATAL GROWH AND DEVELOPMENT OF THE CRANIAL BASE

The bones of the c d base are LiiUallyformed in cardage and are uansfomied

into bone through the process of endochondral ossification. In terms of p s t -nad pwth ,

the most important synchondroses to persist are the sphen*ethmoidal sync hondrosis (SES)

and the spheneoccipital synchondrosis (SOS). Growth at the SES is said to be responsible

for ACB growth. IniUally, the SES gmwth ~roceeds at a faster rate than the SOS, but there is

negligible activiqr afier age seven. The SOS however, does not fuse und adolescence and is

the main contributor to PCB g m d . This prolonged gmwth provides space for the growing

nasopharynx and for continued rnaiallary lengthening to d o w for the molan to empt

(Sperber, 1989). Gben (1998) holds the opinion that the SOS is the "missing link" in

caniofacial growth. He maintains that gmwth at the SOS translates the ACB and its

attached upper face u p d and fornards, away from the foramen rmgnum and the

vertebral column. In adàition to proliferative synchondmsal gmwth, the c d base

undergoes selective remodehg by resorption and deposition. By this merhod, growth

continues even after the synchondroses fuse.

The lateml c r d base increases in size by suturai gmwth which translates the

temporal bone, and hence the glenoid fossa, in a down and back direction. n i e lateral c d

base is active even in cases of achondroplasia where the SOS does not conuibute to p w t h .

This iliustrates the concept of differend development arnong the parts of the c d base

(Bjork, 1955).

Summary:

The cmnial base demonstntes an extremely complicated and higldy controveaial

pattern of p w t b Many mechanisms are involved including deposition and

resorption, displacement, flexing, and inteatitial gmwth at the synchondroses.

A Defining the Cranial Base

Different authoa have wide and v+g opinions on what the exact landmarks are

which define the c r a d base and its constituent parts. Anatomicdy, the cranial base is the

stnicture that serves as the floor of the brain and the roof of the face. Because of this

location, facial and neural landmarks are often included as points in the cranial base. Sorne

authors even differenüate bemen the "extemaln c d base &ch ends on the facial point

nasion, and the "intemal" cranial base &ch ends neurally, before the frontal sinus

(Stmmrud 1959). The rnidline c d base includes the basioccipital, the body of the

sphenoid, and the mesethmoid bones. If taken ro extend ro nasion, it will also include pan of

the f m n d bone. The following is an effort to accumulare and present the many definitions

of c d base.

Anterior Ganial Base:

The most cornmon way of i d e n h the ACB is by the line seila-nasion (S-N).

However, nasion is not technicaiiy part of the cranial base. This notation most likely came

about due to the relative ease of locajwig points N and S on a lateral cephalognm Other

extemai points such as glabella have &O been chosen as the anterior limit of the A(31

(woowaia, 1998). Noreworthy is the fact that if glabella is chosen as the antenor limR in a

growth study, then the influence of the frontal bone a d sinus are excessive. On the basis of

pure logic, choosing internai points to defie ACB should yield more accuncy as the effects

of facd stnicnues wdi be eliminated. Unfortunately, the reality is that Liternal structues are

often more difficult to locate on a radiograph.

DeCoster (1951) used foramen cecum as the antenor limit of ACEL Bjork chose

ethmoidak, the lowest median point of the contour of the anterior c d fossa,

correspondhg to the cnbifoxm plate of the ethmoid bone. Stramrud (1959) defied the

length of ACi3 as the N S distance minus the thickness of the frontal bone, thereby staying

"intemal". The inner surface of the frontal sinus is probably easier than foramen cecum to

locate radographically. In this investigation, another internal point was used and named

"Intersection point", or "1" point. This is the point d e r e the roof of the orbit (bûected)

interseas with the midplaned surface of the internal contour of the frontal bone. This point

proved to be easy to find and reproducible. Sirianni (1979) chose a similar point in a study

on nonhuman primates but he used the innexmost wall of frontal bone and not the

rnidpianed surface.

Nasion is located on an anatomic edge and the~fore easy to identify. Baumrind and

Fmtz (1971) found that estimates of this point were quite good, but that the presence of

outliea p d u c e d an unexpectedy large standard deviation. Because these outlien wen so

inaccu~clte, they were assumed to be the result of idenufications of entirely different

anatomic suuctures. Nasion stands as the most diable and repmducible point to define

ACB.

The postenor limit of the ACB is most commonly designated by sella, the midpoint

of the pituitary fossa However, Ford (1958) preferred the pituitary point, which is the

rnidline point on the anterior rnargin of the pituitary fossa In other analyses, the posterior

miq in of the piniiraiy fossa is used. The antenor waU is thought to be stable after age six,

but the postenor wail is known to resorb und age 16- 17 (Sperber, 1989). BaumMd and

Frantz (1971) found that midpoint seila was easily reproducible, and quite accurate, since it

involves visual estimation of the center of a suucwe. This type of mental averaging system

is known to yield low dispersion. In spite of some people's preference for the pituitary point,

or matguial landma& s e h has proven to be a popular and biologically valid ieference point

(woowah, 1998).

ii) Postenor Canial Base

Most authon defiie the PCB as sella-basion (S-Ba). G e n e d y s e h is agreed on as

the origin of P a , but there is controvenyover the terminus. In the early days of

cephalomeuy, the large metallic ear rods used to orient the patient often obscured basion, so

using this point was questionable. Bolton (Bo) point has &O been considered, but is usudy

negated due to the difficulty in reproducing it on a d i o p p h . For these reasons, Bjork

(1947) i n d u c e d articulare (Ar) as a fundamental reference point clauiiuig that it 'always

shows up clearlf . Interesringly, articulare is an d ic ia l ly consuucted point formed by the

intenecring shadows of the occipital bone and the mandible. As f i technique improved,

the ability to locate basion &O impmved and its ppulanty soared (Seward, 198 1).

iii) Total Cranial Base

The most cornmon terminai points of AQ3 and PCB are N and Ba respectively.

These points ate logicaliy used to amive at the prevaiiing definition for total cranial base

va). Those authors thar consider the terminal points of PCg to be Bo (Anderson, 1983)

or Ar (B jork, 1955) define TCE3 as N B o and N- Ar. Other authors consider TCi3 to be the

sum of its collective pans: S-N + S-Ba

Figure 2.2: Midline cranial base

B. GrPwth Patterns of the &nial Base

The cranial base is a panicddy interesting complex as it is closely related to both c d

and facial structuxzs. Many studies have examlied the growth patterns of the cranial base in

attempts to identify whether its gmwth is more closely associated with the b& or the face.

Ganial growth largely depends on growth of the brain and therefore follows the neural

pattern of growth in the fit two to three years, fallmg off rapidiy and completed by age

seven or eight. Facial gmwth is independent of brain gmwth and fo11ows the general skektal

pattem of most bones and muscles. This pattern is fairlyeven from birth to adulthood with

characteristic spurts at and around pubeq. A knowiedge of which pattern the c d base

foiiows gives insight inro its c h ~ e r i s ü c behavior.

Bjork (1955) feit that the cranial base followed both the facial and the neural p w t h

partem. De Coster (1951) referred to the ACB as the "Radiographic Basai Line". This

consvucted line extended from the anterior lip of seUa across the sphenoidai sinus to

foramen cecum and then up verticaliy behind crista fmntalis. Hé found that this line was

stable after age seven and therefo~ must foilow a neural pattern of growth and be under

"ahost purely hereditary control". Nanda (1955) agreed rhat the curve of ACB (S-N) had

steady growth und around age six and therefom folowed neural growth. However, he also

noted a srnall circurnpubertal spuir which suggested a component of skeletal growth (most

likely due to nasion). Therefore, Nanda concluded that the ACB foliowed both the ne&

and the skeletaî gmwth cuves. Ford (1958) showed that rwo paru of the cranid base had

n e d growth rates, and two other parts followed the skeletal curve. H e was convinced that

the pans must grow in one pattem or the other and not by an intermediate pathway From

nasion to foamen cecum, and from pituitary point to basion, the c r d base folowed a

skeletai growth rate. A neural growth pattern was seen fmm foramen cecum to the pituitary

point, and from basion to opisthion. Ford wamed that when several of the c d base p m

are involved in one measurement, it gives the emneous impression of an average growth

pathway when redy the paths are separate and distinct. Barnbha (1961) disagreed, and

showed that the growth of S-N was a composite of skeletai and n e 4 growth, and followed

an intexmediate path. Mitani's studies (1973) found that the growth rate of c d base

seerned to Vary with the neural growth cuve early in life, and the general skeletal gmwth

cuwe at pubelty.

Lewis and Roche (1972,1974) discovered that sorne c d base lengths (SN, Ba-N) of

girls and boys were about 9597% of their adult size at the mean age d e n peak height

velocity is reached Pubertal spuns can not occur in bones that reach adult size

before puberty begins. Therefore, only very small p u b e d spuns are possible in c d base

le@ d e s s they occur befom peak height velociry. AccorduigIy, they found only small

increments in le& of S-Ba after PHV. ï h i s data questions whether the developing c d

base can foilow a facial curve of growth. Later, Hiiioowaia (1998) ais0 found that the gmwth

of the P a is complete before puberty. Since the growth spun of mandibular length and

height is after puberty, facial growth cannot be responsible for development of cranial base.

Perhaps it is the contrary, and the facial complex follom the growth pattern of the cranial

base instead!

Sunirnary:

The general consensus is that the constituent parts of the cranial base foliow

either a neural or a skeletal pathway. The total pattern of cnniofacial matuxity

oscilktes between these two patterns.

C Cessation of Gn,wth of the Ctanial Base

Thele are different opinions as to &en the cranial base stops growing.

i) Anterior Cranial Base:

De Coster (1% 1) defined the anterior limit of the ACB as the h e r contour of the

frontal bone. H e felt that afrer age 7 there is no more gr& of the AQ3 because the brain

has ceased to grow. Scott (1958) and Ford (1958) agme with this age and state that change in

the cnbiform plate is imrnutable after eruption of the first permanent molars. Growth at the

spheneethmoidal and fmnteethmoidal s u m were found to be complete at age seven,

thereby ending active growth of the "intemal" antenor cranial base.

F i g w 2.3: Length of the intemal ACB (sella to the b e r contour of frontal bone) (Sudmnid, 1959)

However, most of the tirne, the anterior limit of the cranial base is designated by

nasion. Facial growth, anterior to foramen cecum, occun by a different method: remodehg

of the frontal and ethmoid bones. What results is an increase in the frontal sinus and the

development of glabelia. Melsen (1974) confimed that the funher inc~ase in bone thickness

was due to ectocanial surface remodeling. Behrents (1985) showed that the length S N

continued to remode1 weli beyond the age of 25. Bondevik (1995) aiso found a significant

increase in length of the ACB (SN) in a f e d e population aged 22-33. SLnilariy, Bishara

(1994) reported that the cranial base length increased in fernales and males from age 25-45.

F i g u ~ 2.4: N-S length (Stramrud,l959)

Bjork (1955) recognized that at glabella, growth of the frontal bone continues

beyond puberty. Some authon like Isael(1973) and W o o d (1998) chose to define die

antenor lirnit of c d base to be glabeiia instead of nasion. Using this landmark, the length

of ACE3 would continue to remodel, and reach a maximum at mund thirtyfive pars of age

(Israel1973; Behrents, 1985).

Figure 2.5: Thickness of the frontal bone (S- 1959)

Because the distance from S to foramen cecum changes littie after 7 pan, it is clear

that the posterior movement of S due to resorption on the postenor wall of the pituitary

fossa contributes o d y very slightly to the elongation of S-N. Although posterior p location is

agreed upon @tham, 1972; Melsen, 1974), the exact amount has not been detennined

accuately. a b e n (196 1) indicated that the movement would be less than 0.5 mm from ages

8- 16. Therefore, there is no doubt that the major increase in S-N after age 7 is due to

apposition at nasion (Roche and Lewis, 1976).

ii) Posterior Canial Base:

The posterior movement of S just considered would tend to slightly shorten the

distance S-Ba Elongation occurs two possible ways.

1) The svhenwxci~ital sychondmsis:

Larham (1972) iliusuated that in pximates the distance berween sella and the SOS did not

increase much after six month of age. niese msults wexr similar to human findmgs. His

theory was that the gmwth of the Pcl) is secondary to gmwth of the SOS and is esponsible

for the lengthening of the clivus. The age d e n the PCB ceases to gmw varies dependmg on

the different thoughts on when the SOS closes. Sicher (1944) felt that the SOS penists und

skteen to twenty pars 016 d e Powel and Brodie (1963) suggested that closure was as

early as pubenai onset (eleven to fourteen for girls, and thineen to sixteen for boys).

Generally it is agreed that the SOS is invariably closed by age twenty.

2) Basion:

Snidies show increases in S-Ba after fusion of the SOS. Any further gmwth in length

of PCB is pmbably due to shght postenor migation of the foramen magnum (Enlow, 1968).

Ueisen proposed that resorption in this area is not completed before age nineteen in males

and seventeen in femaies. Meken (1974) ais0 showed that apposition occurs at B a This

conttadicts the weii documented findmgs thar Ba is stable and that ail MB elongation is

secondasyto growth at the SOS (Roche and Lewis, 1976). Interestingly, Behrents (1991)

documented that S-Ba continues to remodel after 25 pars of age.

Figure 2.6: SBa length (Suamruci, 1959)

iii) Total Crrnial Base:

Essentialiy, elongation depends on the curnuiative changes that occur at N, the SES,

SOS, and Ba In addition, remodeling cm result in a repositionuig of N d o r Ba (Meken,

1974).

N VARIATIONS OF CRANIAL BASE REFERENCE LINES FOR SUPERIMPOSITION PURPOSES

Artificial constructs like reference planes are necessary to ~ f o m facial

morphology imo numericd measurements that can be easily interpreted Refe~nce planes

must be clearly defined and stan-d, accwately and consistently located, valid, and

stable (Ghafari, 1987). For purposes of evaluating facial changes from p w t h , the most

fundamental requkrnent is stability of the reference points and chosen superimposition

plane. Such a plane is usually consvucted in the ACB area as it is considerrd constant by the

end of the f i t decade (Ross, 1959). Hbwever, just as there exist different points d e f i i

constituent parts of the c d base, so are there different planes of fere en ce. Som authon

advocate using reference planes in the PCB (Gben, 1986), and some recornmend using the

total length of the c d base. (Broadbent, 1937 and Seward, 198 1).

A. Anterior Crânial Base:

DeCoster proposed using a h e that started at the anterior lip of sella mica ,

conrinued over the sphenoidal sinuses to foramen cecum, and then ran vertically on the

inner contour of frontal bone. He felt that this iine was almost purely hereditary and

undisturbed by facial p w t h or mechanical influences (unlike nasion). This line proved to be

constant after age seven. Melsen (1974) agreed that rhe interna1 surface of the frontai bone

and ctibiform plate were stable by about age seven in both the sagittal and vertical planes.

The sella-nasion line, pioneered by Brodie (1941), is used frequently as a reference

for superimposition. Both S and N are easily identified points and the superimpositions

p d u c e consistent and diable patterns. Bjork (1955) initially advocated the use of S-N

because of the high me of constancy berween S, N and the deepest median contour of the

anterior craniai fossa Later however, Bjork (1960) questioned whether S N was as stable as

he had once thought. He and Scott (1958) both stated that an upward or d o w n d

displacement of nasion rnay occur with growth at the fronto-nasal suture. Likewise, a

posterior displacement of seUa rnay be induced by the remodeiing of donum s e k

conneaed with growth of the pituitaxy gland Ford (1958) &O pointed out that these two

points (S and N) are hown to a a independently. As sella moves upward, nasion moves

forward and upward, malong their relations hip somewhat unstable. nirs new position of

nasion places it above the cnbiform plate and therefore above the face as a whole during

growth. Bjork ultknately chose ethmoidaie as a point and formed the re fe~nce line ESL

(edunoidale-sella iine). As opposed to abandoning S-N, othen argue that the amount of

upward movement is e q d for both seiia and nasion and therefore a satisfactory result can

s d be obtained d e n using this line, parriciilarlywhen the observation time is short.

Seward (1981) proposed that if the saddle angle (Ba-SN) changes then superimposition on

S-N plane can produce an apparent progressive provusion of the lower face that is not

observed clinicdy.

Studies have compared the S-N plane to DeGsrer's ''Basai Linen. BaumrLid et al.

(1976) concluded that in De Coster's methoci, registdon errors weR unexpectedly s d e r

than those for S-N and that emrs of interpretation of ma* or mandibular lan-

were remarkably simiiar. Panchen and W e n (1984) found the opposite to be tnae: that

~gistmion ermr was kss using S-N.

S d (1959) c o m p a ~ d SN plane with Bjork's ESL and found ESL to be

prefemd in studies that cornlate the c d base to the rotation of the facial skeleton.

i) Repducibility

Mitgard et al. (1974) stated that some cephalometic landmarks are located on the

outlines of the canium and are compa~~~tively easy to idenufy due to the sharpness in

convasf on the radiograph. For this reason, S-N is the preferred plane. The stnrtures on the

inner ctanium are often indistinct because of superimposition of other anatomic suuctures.

This is substantiated by Richardson (1966) d o said that De Gster's cribiform plane was

only moderately successfd as far as reproducibility was concemed.

B. Posterior Ganial Base:

Coben (1986) described basion-articulare (Ba-Ar) as his ideai reference line to

evaiuate growch, and found it to be ''essentidif stable pst-natally over tirne. He found the

mandibular to menton distance to exhibit a constant s a g d spatial relationship to foramen

magnum as the mandible uaveled down and f o d away from the ci.anial base. It could be

argued that basion-articulaxr is not at all stable, and not well accepted by orthodontie peen.

Basion is difficult to locate, and the small distance berween Ba and Ar make t h region

susceptible to e m n of orientation ( B u s c h , 1998).

Another plane cornes from Baer and Nanda (1976) who recomrnend superimposing

on the doaum of the cliws, re@tered on basion, in situations where the c d base is

affected bytrauma or a congenital defect.

C Total Cranial Base:

There are many advocates of using the TCB for superimposition. While mort agree

that nasion is the anterior terminus, difierences arise over the posterior tenninus of this

mference plane. Seward (1981) used Ar posteriorly due to its relative ease of location

compared to basion. However, most authors freely use Ba without hesitation.

A study by Ghafaxi et al. (1987) compared four planes of c d supeximpositions

and found that there was no preference arnong the methods. What is important to recognize

is that no one supelimposition plane can be used to perfe~tl~depict growth patterns. Moyrn

and B o o k i n (1979) iament the inappropriateness of conventional cephaiomeuic

l a n a . They propose highly technicd methods involving the-dimensional cornputer

geometry to overcome the current limitations of cephaiomeuics.

Summary:

Because of their supposed stability, many diffe~nt clanial base reference

planes have been used for the piupose of superimposition. Howewr, none of the

cnnial structures will be perfecdy constant in times whem growth is active. The S N

line is the most popuhr refe~nce plane for supetimposition and has ~rnained in

favor for so long because of its dative stability, practicality, and ease of location of

its anatomic points.

V RELATIONSHIPS BETWEEN THE CRANIAL BASE AND FACIAL AND SKELETAL DEVELOPMENT

The si=, shape and position of the individual cranial parts are inter-related in varying

degrees. These relationships are determined by cenain geneal p ~ c i p l e s conditioned by

growth rate and proportion, and by the compensatory and adapUve mechanisms within the

SU (Smahel, 1988). The f i t anthropological comktion study between the lengths and

widths of slaiUs of varied xacial backgrounds was first published by Pearson in 1896, and a

number of sLniLr s d e s have followed suit. Broadbent (1% 1) had influence on these

studies as he inuoduced the x-ny cephalomeuic technique. Because of this, detailed

longitudina data on facd development could be coliected and interpmted. Over the yem,

Solow (1966) and othen have cautioned against over-interpreting the correlations between

various cephalometxic variables. When rwo lines share a common reference point, these two

lines will show more comlation than two other Lines wirh no cornmon point, and this must

be rernembered d e n reviewing the literature.

While the importance of c r d base morphology as a contributory factor to o v e d

facial pattern has been svessed by Bjork (1955), &ben (1955), and Hopkin (1958), other

researchen (Stevens and Freer, 1979) have demonstrated the unpredictability and variability

of this contribution. Hopkin believed that the cranial base area has considerable influence on

both facial prognathism and in establishq the antenor-posterior ielationship of upper jaw

to lower jaw. Bjork (1955) and Coben (1955) felt that in developrnent, a dec~ase in c d

base angle would dis place the glenoid fossa f o d relative to ACB and there by contribute

to rnandibular pmtrusion, whde an increased angle would lead to mandibular retrusion.

Stevens and Freer thought that any generalizations in associating a given c d base angle

with a p k c u k r skeletal or dental pattern is unreasonable considering that there are so rnany

other factors that corne imo play. Nanda (1955) found genedythat in development, the

subjects he studied retained their relative positions in all rneasurements. That is, a boy who

matuns early with respect to sella-nasion was probably early for all other masures as well. If

he was small faced to begbi with, then he would still be s d faced at the end of

development.

Most of the previously mentioned s d e s focus on cranid base angulation and its

influence on the relative position of facial components. However, not much literam is

available on how the length of the cx-aniai base influences the absolute size of other facial

dimensions. In one such study, Smahel and Shadova (1988) report that the characteristics

of shape and position of individuai smrnues were more closely related than the

characteristics of size. The Burkngton cephalometric analysis (Popovich, 1977) considers the

length of the ACa (SN) in relation to the lengths of facial measurernents. This analysis was

cteated to evaiuate the face in duee planes of space (anteroposterior, width, and height) plus

age to better analyre cases and anticipate their changes. Tempiates were developed to

gxaphically illusuate facial growth and its variation arnong children. The lateral projection

template is oriented on the S-N plane and registered on the center of seiia. AU other facial

landmarks are plotted and compaied relative to the patient's measure of SN. This method

dows for evaluation of a penon's degree of ske1eta.I baiance or imbalance. For example, if

N, ANS, A point, B point, and menton were ali close ro the 12 yvar old standard, it would be

an average size face. But, if the same dimensions were all larger, the face would be

considered iarger than average.

Ross (1959) svongly felt that linear rneasurements were more vaiuable in assessing

actual growth and development than angular analyses, as the angukr snidies could only

concentrate on changes in proportions. Linear measuements though, were more awkward 4

to use. Populations of different sizes or ages can not be compared directly unless the linear

dimensions were reduced to a proportion, or unless the vaiues were adjwted to correct for

the overall s k differences. In Ross's 1987 study, he introduced the notion of size adjusting

linear measurements to s t m e cephalomeuic records that came from many different

centers. He proposed that the hea r values had to be adjusted to an internai standard such as

the c d base. Furchermore, size adjuthg these dimensions would ovenrorne any

morphological differences caused by variation in age. Ross arbRrariy set the totai cranid

base line N B a at 1 10 mm for al plots and superimposed them to evaluate the profiles. He

discovered that manipulation of the plots provided a clearer presentation of the facial

reiatioaships than would show if the TCB lengths were unequal.

Ross also developed proportions bywhich to compare the measurements in his sdy.

The raw linear measurements were adjusted b y dividtng by the actual TCB length and

multiplying by IOO. For example, if the mean maodbular length was 128 mm and the mean

N B a length was 116 mm, the adjusted mandibular length would be {(128/116) x 100) or

110% of the total cranial base. Ross strongly believed that adjusment of ail the linear

dimensions into proportions of TCB was mquired for comparisons. No other attempts at

size adjusting have been reported It would be highly beneficial to criticdy review the

lirerantre on how the absolute size of the c d base segments correlate to facial and

skeletai development. This would enable us to identify the significant associations t h exist,

examine how they idluence morphogenesis, and investigate the concept of size adjusting.

k The Relationship of Ganial Base Length to Maxiliay and Mandibular Lengths

The d and mandible each attach to a different part of the cranial base. Therefore,

it would seem logical that the le& of the cranial base would have an influence on jaw

~lationships. It would also be presumed that the maxilla wodd be more closely related to

the antenor c d base, and the mandible would be more closely associated with the

rniddle, lateral and postenor regions.

Enlow (1976) believed that the dimensions and orientation of the nasomaiollary complex

relate directly to the corresponding site uid alignment of certain parts of the c d base.

The midface s pecifically relates to the flmr of the antenor cranial fossa d e the posterior

border of the antenor c d fossa corresponds to the postenor margin of the maxdhy

tubemsity. Enlow felt that there is less communality arnong the gr& fields of the

mandible and the c d base. Therefore, more variation exists in mandibular dimensions

and placement ~lat ive to the c d floor rhan nasomamlky dimensions and positions.

&ben (1998) conuadicts this logicd principle. Hi cl& that the P a , via the SOS, is

intimately related to the upper face and maxdh In growth, the SOS vanslates the ACB and

its attached mamUa forward up and away from the foramen magnum. At the same tirne, the

mandible moves down and f o d away from the cranial base. Bemen these two general

vectoa, space is created for vertical Qvelopment of the face and the eruption of the

dentition.

Scott (1953) felt that gruwth of the cranid base is important in fornrard growth of the

face. Fmm a sample of "remarkable unifo~mitf' , he found that a reduction in TCa length

(NBa) is associated with a reduction in the size of the face and its projection forward fmm

the vertebral column. Hopkin et al. (1968) conducted an age rnatched s d y and reponed

that the c d base has an important role in determining antenor- postenor jaw relationships

and occlusion of the teeth. This is based on their findings that the mean linear dimensions of

the c r d base (SN, S-Ar, NAr))y as weli as the c d base angle, are ali smaiiest in the

a s III groups and largest in the Class II groups. Unfonunately, in this studythe jaws were

not looked at in ternis of absolute size. More recently, Kerr and Adams (1988) made an

effort to establish the relationslip between c d base size and shape, and jaw patterns.

Their sample was matched accordmg ro age and incûor relationship. Like Hopkin, they

found that c d base length (SN, SBa, N-Ba) increased as the jaws became more (lass II.

Regardmg absolute size of the TC23 @Ba), Kerr and Adams dkcovered a suong comlation

with maxdhy length, and a weak comktion with mandibular length (Co-Gn). Inte~stingiy,

even wnh this stmng correlation to the maxilla, they did not find a significantly prouusive

maxiüa in malocclusions 4th longer craniai bases. This suggests that some form of

compensation k at work In a study by Kasaï (l995), cranial base length WBa) was more

highly comlated to the mandible than the maxih The dircrepancy between this finding and

that by Ken and AdaM (1988) is likely due to the differences in their respective

populations. The latter sample consisted of 10 year old Scottish boys and Kasaï's was

Japanese males ages 16-60. Anterior and posterior c d base lengths, as well as total c r d

base length all showed positive correlations 4th mandibular length, mandibukr body length,

and symphysis height in Kasai's study. The result of their principai component analysis

provided good evidence that the antenor and posterior cranial base were associated in

different ways with different aspects of facial morphology. This has been substantiated by

the different p w t h patterns and anatomic relationships between the structm~s. Their study

was not age matched, but was tested for the effect of age. They found that there were no

"important biological relationships berween age and the variables considered" . In 1998,

Woowala et al. looked at the intemlationships of brain, c d base and mandible in a

sample with si& occlusion and developmental state. They chose glabella instead of nasion

to delineate the most anterior point of cranial base, and they split the antenor cranial base

into two parts: sella-foramen cecum (S-Fc) and foramen cecum-glabelia (Fc-Go. They found

a higher correlation factor d e n mandibuiar height and length were related to Fc-Gl as

opposed to Fc-Nasion. Lkly, this is due to fan that frontal bone growth is increased at

glabeUa and therefore more s& to the type of growth that the mandible displays.

B. The Rehtionship of Cranial Base Length to Body Height

B u s h (1949) conducted a comparative analysis on breadth, length, and height of the

cranium in relation to stature and uwik length. nie large group represented a wide cross-

sehon of ages and racial backgrounds. I-k found that the highest conelations wem to vunk

length. Thus, it appears that the increase in size of the cmnium tends to keep pace in a

verricd direction with body height. Barnbha (196 1) &O found a correlation berween cranial

measurements and body stature in hir age/sex rnatched sample. In addition, he noticed that

faciai and craniai measurements in individuah who were relatively late maturing in body

height tended to show similar delayed maturation in the face and cranium, wtllle early

developen tenàed to manire early in facial and c d measures and in body height too.

This suppom the theory that the cranid base does to some extent foliow a skeletai pattern

of growth. Solow (1966) showed that the= exists a general association between the s k of

the head and that of the body in young male ad&. This was ~presented by a set of low

positive associations b e ~ e n most of the body measurements, including height, and most of

the lïnear cepMometric measurements.

C The Relations hip of Cranial Base Length to Cranial Base Flexm:

Manysnidies report correlations between canial base length and flexure. Anderson and

Popovich (1983) used the Burluigron study to look at the cranial base segments individually

as well as the TC33 length. They found that PCB (S-Bo) was larger in boys with the smallest

c d base angle at ages rwelve and skeen. Smahei and Skvariiova (1988) also found that

PCB increased in length as cranial base angle decreased Conversely, Bjork (1955) using S

Ba, found that PCB was longest where the flexure was greatest in tweive year old boys.

Andenon and Popovich found that TCB @Bo) was smaliest in girls who had the

smallest cranial base angle. B jork agreed with these fiiduigs, using the lïne N- B a Weidenrich

(1941) &O agreed that closure of the c d base shonened the NBa line.

Andenon and Popovich found that ACES lengrh (NS) did not &fer significdy

benmen groups of children who had large flexures and those who had small flexures.

Srnahe1 and Skvarilova &O discovered that AC6 could not be correlated to f l e m . in fact,

in their sndy on Gech males, A m showed no correlations to m y of the Livestigated faciai

c haracteristics . D. The Relationship of Canial Base Length to Head Length

Ross (1961) studied the c d base in cleft and non-cleft populations. He found tbat the

cranial base was smaller in size in the cleft gmup compared to the conuol group. Hk

posntlated that the observed difference in cranial base size wu merely a reflection of a

generalized difference in body SM, as cleft chiidren are genedy smaller rhan unaffected

children. To prove this theory, Ross measured TCB length as a proportion of greatest head

length. Ganial base length was de f i id as ACE5 (NS) plus PCB (S-Ba). E dixovexed that

the c d base length was equally proportioned ro the cIanium length in both groups.

Overail, no significant differences were found.

E. The ReLtionship of Ganial Base Length to Face Heights

In 1953, Scott wrote that it was difficult to find associations in the craniofacial skeleton

because of the wide variation of the paru. In his investigations, he found no comlations

between c r d base le& (N-Ba) and face height. Smahel and Skvaxilova (1988) looked at

multiple comlations in the facial complex and found an association between PCE3 length (S-

Ba) and posterior upper face height (PM- S-N he) . ï h e other important parameten

contributing ro the postenor upper face height CUFI-q included craniai base angle and

mandibular dimensions. Kasai (1995) showed th the le+ of ACB, PCE3 and TCB ali

were sigruficantly correlated to UFH, while only ACB and TC33 (but not PCB) were

comlated to lower face height 0. Koski (1960) stated that the growth of the upper face

and the clivus seem to be of equal magnitude in the vertical direction. The significaace of

this fin& was in showing how SOS gmwth rnay be adaptive, secondary to enlargement of

the brain.

In Smahel and Skvarilova's 1988 multiple correlation study, they attempted to use

correlations as a method of predicting development of the craniofacial region. They

discovered that it was not possible to disclose any combinations of parameters adequate for

the estimation of the lengths of the pans of the c d base. In their opinion, cranial base

lengrhs, especially Am, had very low comlation coeffecients, &ch showed the marked

degree of developmend independence of the c d base. However, other studies have

displayed moderate to high cornlarions between length of the c d base and facial

dtnensions. For this reason, the canial base length should be considered in the diagnostic

assessment of the craniofacial complex and general characteristics of the individual.

F. Defects invohing the Ganial Base and the Influence on Facial Dewloprnent

In a case study by Evans and Christiansen (1979), the role of the c d base in facial

development was illuminated as a result of a PCB defect. A geomeuic model of a n o d

SU was constructed and the identicai defect was re-created within the skull. This alteration

caused the face to rotate cIockwise in the model. In the uue s h i l however, this did not

occur, and the anterior suuctures maintained neariy nomial anterqmsterior directionai

gmwth. This proves that some compensation system exists to prevent the undeslable

cloc kwise rotation of facial components.

Studies on syndromes kivolving craniosynostosis reponed a marked effect on the

cranial base (Moss 1959, Kreiborg and Bjork 1982). Moss even suggested that the

derangements in size and s hape of the c h o n d r o c ~ u m were not necessarily secondary to

the premanue ossification of the cdvark sums . Stewait et d. (1977) presented a case

report on a stiilbom fetus that had all the chaacreristic features of Apen's syndrome.

However, they found no evidence of premature fusion in any sunires or synchondroses. 'This

led them to believe that Apen's syndrome was pnmarilycaused by a malformation of the

skull base, with the secondary effect of premature craniosynostosis. 'Ibis philosophy is not

genedy accepted Public opinion is that the primary event is the fusion &ch in tum leads

to the c d base a b n o d t y . Regarding c d base, Bachmaytr (1985) stated that most

studies found anterior and posterior c d base lengths to be shoner in Apen's patients

compared to n o d . The maicillae were hypoplastic and the mandibles normal, thereby

creating the false illusion of mandibular pmgnathism. In Fedun's 1971 thesis on the

craniofacial characteristics of Crouron and Apen's syndromes, he confinned these findmgs

and even suggested that the rnandible was short. Fedun stated that aithough no

measmrnents were d e n for height and size in the sample, Crouzon and Apert's subjects

appeared to have normal development in stature. Kreiborg (198 1) conducted a cluiicai and

radiographc study on 61 patients with Gowon's syndrome. L k Fedun, he also found the

mandible to be d e c ~ a s e d in length and ramal height. However, contraryto Fedm,

Kmiborg's evaluation of somatic measurements discovered that body height and d u s

length were significandy shoner in the Crouzon sample compared to conmis. Srnalier than

average rnan l l a ry l ee and face heghts dong with the previous fmduigs suggest that

Gouzon chilhn am generally smaller in ali aspects of craniofacial and sornatic

development .

VI CRANIAL BASE LENGTH IN CHILDREN AND ADULTS WITH VARIOUS HORMONAL DISORDERS

An investigation into these conditions gives insight into gmwth patterns and correlations

in the craniofacial cornplex. They can be viewed as experimental models for studying the

effecu of abnormal development on the SM and its vaxious pans.

A Children with Hypo- and Hyperthpidism

Spiegel et al. (1971) researched a sxnall sample of patients with various

endocrinopathies . Those patients with hypothyroidism dis played letardation of vertical facial

gmwth and PU3 kngth (S-Ba). Gntraryto what would be expected, the ACB was advanced

in the rnajority of patients. niis can be explained by the fact that hypothyroidism has a late

onset and therefore the ACB development would have h a d y been complete and ntn&red

unaffected by the disease. Patients with hyperthyroidism exhibited advanced growth in al

dimensions. Antenor and postenor c d base were both advanced, more due to PCB and

the longer period of endochondral gmwth. Intetestingly, TCB length (NBa) was not

increased as it was compensated for by increased flexure of the c d base angle.

B. Chiidren with Deficient and Excessive h w t h Hotmone

childhood growth is mainly regulated by the secretion of growth hormone, provided

that the nutritional s t a t u and other homeostatic maintenance factors are normal. Piinen et

al. (1994) looked at patients with either deficient or excessive growth hormone (GH) to

elucidate the role of GH in craniofacial growch. Two control groups were used: one matched

for age and sex, and another matched for height and weight. In a previous study by Poole

(1982), comaion for skeletal age helped to eliminate a lot of craniofacial differences.

Qiildren deficient in growth hormone had linear c d base dimensions s d e r

than those of the age/sex matched and ais0 than those of the heighdweight matched

conuols. This suggests that GH deficiency ovemdes the known correlations between body

height and c d dimensions. The main caniofacial feanues of deficient GH were short

PCB, s d maxilia and mandible, and a short face. The sigdicant variables in patients with

excessive GH were increased P a length and increased mandibular gmwth. GH has

profound effects on cadage gmwth. Therefore, cranioffacial changes with deficient or

excessive GH w e ~ most conspicuous in the clivus and the mandible, the c a d a p o u s SOS,

and the condylar carulage. These results are in line with those of Spiegel et al. (1971) d o

found that patients with pituitary insufficiency s howed severe gm& retardation in hear

facial measurements, particuiariy with small antenor and posterior cranial base lengths, and

small mandibular sizes.

Jensen et ai. (1997) conducted a study on cmniofacial development after surgical

resection of craniopharytigioma. These tumors are the most cornmon supraîellar neoplasms

in children, and they arise from embpnic squamous ce1 rests in Rathke's pouch. After they

are removed, the patients experience endocrinologie deficiencies including reduced GH. Like

previous shidies, these subjects showed smaller d b l e s and a shorter PCB (S-Ba). ACB

(NS) showed normal dimensions as these patients probably had a more n o d production

of GH in eariy childhood d e the A(33 was formhg. The authoa point out that the role of

ugeneral growth potenthln may be important in these patients, where nearly ail caniofacial

measurernenu were sigruficantiylarger in the tallest patients than in the srnallest. This

illustrates the strong relationship between stature and craniofacial measures.

C Chüdren Born Srnaii for Gestational Age

Van Erum and CO-worken (1997,1998) published studies on children bom small for

gestational age (SGA). In many of these children, no underiying cause is ever found. These

children d s howed an o v e d delay of craniofacial growth, es pecialiy in the rnandible and

cranial base. Angular facial proportions were not affected, but the linear dimensions weR

much smaller compared to age matched conmls. In fact, aii the linear craniofacial sizes in

the entire group were extremely short relative to their Bolton standards. These SGA children

s howed a marked similarity to children with piniitary deficienc y even though the y themselves

w e ~ not GH deficient. The latgest difference between these two groups was that the SGA

children had small mknllas and the GH deficient children exhibited nonnal mamllaty

le+. Treatrnent in some cases involved adminicvation of G H Here, the success

depended on the age treaunent was starteci, with the earliest adminisuaùon being most

swcessful. n i e Van Enun study (1997) showed that even with treatrnent, some children

failed to have catch-up growrh. In these children, not onlywas their stature retardecl, but

their cnniofacial development as weU This clearly strengthens the cornlarion berween

somatic and caniofacial development.

D. Boys with Delayed Puberty

Delayed puberty is a variant of n o d development. These boys have a srnail stature

for their chr~nolo~ical age, but are u s d y appropriate for their skeletd age. Verdonck et aL

(1999) studied these teenaged males and found that in addition to the srnall stature, the

mandibular rarnus length, and T a length @Ba) were significantly shoner than in the

conuols. Verdonck explained this by conelating stature to nmus and T a lengths. He felt

that there is a generalized Qlay of these parameten because the pubertal gmwth spurt is

delayvd. No signtficant differences were found in total mandibular length, ACE! le& or

PU3 length. This studyagain shom the reiationship between somatic g r o d patterns and

the craniofacial cornplex.

E . Adults with Ac hondmplas ia

Achondruplasia is the most coxnmon foxm of short limbed d d i m This disorder

can be used to studythe effects of a b n o d endochondral bone formation on the

development of the skidi. Cohen et al. (1985) conducted a morphometric d y s i s of the

craniofacial c o n f i i t i o n in achondroplasia. They believed that if one part of the s k d was

affected adversely, inevitably other pans would suffer. Their investigation reveaied srnlang

ciifferences between achondroplastic and normal subjects. The achondroplastic subjects had

eniarged caivaria, shortened PCB, short UFH, shon maallary length, and short nasai bones.

These findings were consistent with those of Mitchell (1966). The mandible was of normal

size but of variable position. The most Lueresting discovery was that the ACI3 was found to

be normal. This was surprising as c d base is preformed in cartilage and endochondd

bone foxmation is known to be affected by achondroplasia. Therefore, one would expect to

find rnarked ~duction in ACi3 length. Cohen et al. explain rhis fmduig by referring to Moss's

Functiod Maviv Hypothesis. They state that since the brain is enlarging, the ACB is able to

respond to this increase in size and foliow the neural pattern of gmwth wirhout its

endochondml bone being affected Fuxthermore, they hypothesizd that since ACB contains

frontai bone, and frontal bone grows by membranous rather than endochondral gmwth, it

should not be affected by a pathologie endochondal process. The reduction in length of the

PCB is easier to understand as most of the deficiency is due to lack of gmwth at the SOS.

Smdies of achondroplastic children show that closure of the SOS happens fairiy eariy

pmbably pnor to age eight or nine. This serves to illustrate the concepts of diffemnd

developrnent of the various p m of the c d base. N o d growth and development of

SOS is essend for harmonious development of the c d base (Bjork, 1955). Short

mkuillary length and UFH are probably related to the hypoplastic gmwth of the nasal

capsule. This follows Scott's ideas that nasa cardage is integral to the development of the

face. The fact that mandibular size was not affected also &s sense as rnost of the

mandible &velops from membanous bone and therefore d d not be affected (Cohen et

al., 1985). Furthemore, the condylar cardage of the mandible is said to develop with a

different histology and biochemical composition than growth type carùlage, rendering no

effect from the achondroplasia gene (Weinmann and Sicher, 1955).

(3IAPTER3:

METHODS AND lMATERlALS

1 INTRODUCTION

It was the intention of this study to demonstrate the need for size adjusunent of

linear measurements in populations of diverse backgrounds and to develop a size adjusting

mechanism based on the c d base le&. A gmup of "ncrmal" children were used to

illustrate this principle. Groups of children such as those in the Buriington Gmwth Study

(BGS) show nomial disuibutions and variance for craniofaciai chammeristics and are useful

for study of craniofacd growth and developrnent. Tnditional cephalometric analyses were

performed on the radiogmphic records from the BGS, and the dimensions pertinent to this

study were recoded from cephalometric uacings. Heights were recorded from the patient

history profiles. The data were then analpd to idenufy comlations between the canial

base, body height and the dimensions of the face. A prediction mode1 for size adjusting the

iinear facial measurements based on the cranial base length was then attempted

II SAMPLE

A. Characteristics of the Population Selected from the Butlington Study

The Burimgton Growth Studysample was established in 1952 to evaluate the efficacy

and cost effectiveness of interceptive and preventive orthdontic marnent. Growth data

consisting of physical anthropomeuic measurernents and dentofacial recorb x r e

accumulated and used as a control sample for research purposes. The predominant racial

group compRsing the BurLngton population in the 1950's was Caucasian and mostly Anglo-

Saxon. 'Ihrough chance, no other ethnic populations were represented, yielduig a

homogeneous sampk. The local population in Burimgton at this time was of siightly higher

income rhan the national average. The birth yem of the sample used in this study ranged

from 1942 to 1952. The BurLngton sample is ideal to use in this project as the records were

d e n with a standardized technique. The magdication factor for the Burlington

cephdorneuic radiographs has been calculated as 9.84%

B. Ages of the Sample Populations

Lateral cephdograms and tmcings of the same onhodonticaUy untreated male individuah

(11-117) were snidied at two chronological ages: 12 and 18 +. At age 18, future growth of the

c d base and facial stnrctures is considered to be minimal and could therefore serve as a

reference that is relativeiy free of confounding variables.

It is useful to evaluate the need for size adjusting at age 12 as this is the age when most

orrhodontists will be taking iateral cephalogra~ for treatrnent pliammg puiposes.

Therefore, this is ais0 the age &ch serves as a &tabase for many research endeavors that

muid potentialy benefit from size adjusting. Confounduig variables at this age include

variation in the onset of puberty and the fact that growth is hghly inconsistent; either ahead

o r behind average values. 'Ihis serves to make cornparisons more difficult.

III ANALYSIS OF THE RECORDS

Hkights of the 117 individuals were obtained from the history profiles in the BGS.

Cephalometric data was obtained from iadiographs of the Burluigron sample.

k Tiacing of the radiographs

The cephalograms utilized in th& study have ali been traced by a skilled technician

(G.J.). Most of the luidmarks pertinent to thk investigation were plotted directlyoff the

uacings except for a few landmarks 0: intexsection point, ANS': antenor nasal spine', Gl:

glabelia) &ch had to be uaced from the original cephalogran See Appendix B page 82 for

an illustration of the kndrnarkr of the c r d base and facial complex.

Each of the r adopphs was secured to a light box in a darkened room and the

acetate m i n g was overiaid ont0 the cephalogram. A second piece of acetate was secured on

top and conventionai cephaiomeaic svucnues and points were ploned ont0 this sheet.

Important landmarks represented on the uacings were copied ont0 the second acetate, and

those that were not on the vacing n m ploned directly from the cephalomevic dog raph .

B. Cephalometric analysis

Once ploned on a traflsparency, the t h e e n landmarks were digitized u s h g the Dente

Facial Planner (Waker, 1995) and a custom made cephalometric analysis. ?bis custom

analysis consisted of seventeen measurernents from the c d base and the face. As noted,

the litemture reveded seved ways of defining the anterior and posterior iimits of each

parameter. niis study included a few different defiinitions of antenor and totai cranial base as

weJl as a few definitions for mandibular and nmdaty length and upper and lower face

height. Several definitions were used for each pamneter with the goal of idenufyuig those

craniai and facial segments that yield the most significant correlations. Onlythose paameteis

with the htghest level of correlations were carried further with statistical analyses. See

Appendix A (pg. 81) for definitions of the craniofacial landmarks in this study.

The cranial base measurements were as follows:

Antenor Ganial Base- 1 (S-N) mm Antenor G a n d Base-2 (S-1 point) mm Anterior G a n d Base-3 (S-Gr) mm Posterior Base (S-Ba) mm Total Oanial Base-1 WBa) mm Total Cranial Base-2 (SON + SBa) mm Total Ganiai Base-3 (I point-Ba) mm Ganial Base FIewre (N-SBa) degrees

The facial measurements were as foliows:

Mandibular Length- 1 (Con- Gn) mm Mandibular Length-2 (Ar-Gn) mm ltlhdhy Iangth-1 (Pm-ANS) mm Mamllary Length-2 (PNSSn) mm Ma2ahykngth-3 -ANS? mm Upper Face Ekight- 1 (N-ANS) mm Upper Face Fkight-2 (NAN!S? mm Lower Face IlkJeight- 1 (ANS-&) mm Lower Face Height-2 (ANS9-Me) nun

The sornatic dimension studied w:

Statclre (inches)

C Statistical mediodology

Descriptive statistics (means, ranges, standard deviations) of ali parameten were

calculated for the sample of 117 males at both age groups. No data were missing.

AU cranial base parameten for each iadividual were related to all facial, somatic, and

angular parameters by means of Peatsons correlation coefficients. Comlations were also

calculated berween body height and both the craniai and facial dimensions. The statistics

program MINITEMP was used to calculate these data. Based on an interpretation of Kappa

statistic, an r factor e q d to or above 0.4 was recognized as a good correlation. For each part

of the face and the cranial base, odythe segments with the smngest correlation coefficients

were carried further with statisrical analyses.

The worlaag hypothesis was that a group of children srnall in stature and cranial base

length should possess facial dimensions that are significantly less then those of a group of

larger children. To test rhis hypothesis, two different sets of t-tests were perfotmed using

SPSS. The nuii hypothesis assumed no differences in the linear facial dimensions.

Fint, the sample was divided into rwo groups bared on height (shodtall). The shon

group (O) consisted of the shortest individuai up to and including the mean height. The tall

group (1) was comprised of those individuals with heiphts above the mean. Ihe rnean was

chosen as a cutoff point as the sample displwd normal disnibution for height.

Table 3.1: Body height categotized as short or taii at age U and 18+

Ar both ages all 117 records were accounted for. The standard emr was reponed

A S Short (O)

instead of the standard deviation because the sizes of the groups were slightly different.

The second set of t-tests was camied out dividuig the sample into two groups based

on the length of the TCB to see if clifferences in facial dimensions existed berween those

n at 18+ 62

l2 54.0 - 59.1 1 inches

with srnail and large TCB lengths. The small group (O) consisted of the individual with the

n a t u 1 18 + 60 1 64.3 - 69.73 inches

shortest TCB length to the mean length. The mean was chosen as the cutoff point since the

disuibutions for T a were n o d n i e large group was coded as (1) and was comprised of

ail individuals above the mean.

Table 3.2: TCB length categotized as smaii or large at age 12 and 18+

n at 18+ 60

Age Srnail N-Ba (O) Large N B a (î) Mean TU3 1

12 97.7 - 108.82 mm 108.83 - 118.7 mm

108.82 mm

n at U 61 56

18 + 105.1 - 117.17 mm

1

117.18 - 127.2 mm 117.17 mm

57

From the correlation studies, both TCBl and T a 2 were found to have svong

relationships to the facd cornplex, and both wem used in funher analyses. At both ages all

117 record were accounted for. The t-tests were pexfonned pauing that paiticu1a.r TCE5

length and facial dimension diar had the strongest correlation. Because of the inequaiity in

sample six, standard erron were again dispiayzd instead of standard deviations. Note that

d mesuremenu were in rnillimetea except for the cranial base angle, which was in degrtes

and the height , wtiich aas in inches.

A N a V A (analysis of covariance) models were run to establish the iektionships

between body height and the facial dimensions while adjusting for TQ3 as a covariate. AU

adjustrnents were perfomd to the grand mean of the covariate TCB. ANCOVA modek

assumed the existence of a paralle1 rehtionship berween the short and tall groups. Height

was coded as (0) for short and (1) for tail, and the covariate TCü war continuous. The

significance of each of these factors and their contxibution to the variance of the facial

parametea were tabulated.

ANGOVA models were &O used to predict, within a 95% confidence interval, the

adjusted means of the facial dimensions for shon and tail groups while c o n m h g for the

covariate TCB. Adjusted means were compared to the unadjusted means to evaluate the

clinicai significance of t h pmess.

Lastly, a linear regression mode1 was developed. The anempt was to develop

fomulae rhat could be used to p~dict the adjusted means of the hear facial dimensions in

groups of people of hown height (short or di) using the mean TC8 base length as a guide.

ANGOVA models used for t h purpose would have yielded the same resulu.

Ail anaiyses were carried out at age 12 and again at age 18 +. AU tests were m t a i l e d

with the significance set at p < .OS.

DESCRIPTIVE ANALYSES

Linear measuremenrs were recorded for the facial and cruiial paameten from the

cephaiomeuic radiographs and for the heights of the individuah. No data sets were missuig

and d tables are based on a sample size of 117. nie means, anges, and standard deviations

were tabuiated for each parameter at age 12 and also ar age 18 and over.

Table 4.1: Table of means, ranges and standard deviations of the facial and cnnial dimensions and body height at age îî. (n=lll)

Dimension

Height ACB1

KEY: &ight Aa3I A m 2 AC83 PCB T C 8 1 TC82 TC83 MdLl

Range Mean

4

I MdLl I 1 14.05 1 104.9-123.0 [ 3.9 I

Standard Deviation

PCB 46.37 39.9 - 52.6

- Body height (iches) - Anterior cranial base 1, S-N (mm) - Antenor cranial base 2, S-1 point (mm) - Anterior cranial base 3, S-Gl (mm) - Posterior c d base, S-Ba (mm) - Total craniai base 1, N Ba (mm) - Total cranial base 2, S-N + S-Ba (mm) - Total c d base 3,1 point-Ba (mm) - Mandibuiar length 1, Con-Gn (mm)

2.6 3 .O

59.1 1 72.52

2.9

= Mandibubr kngth 2, Ar-Gn (mm) - Maxihy iength 1, PNS-ANS (mm) - Maxillary length 2, PNS-Sn (mm) - Maralkry length 3, PNS-ANS' (mm) - Upper face height 1, NAM (mm) - Upper face height 2, N'-ANS' (mm) - Lowier face he&t 1, ANS-Me (mm) - Lowr face height 2, ANS'-= (mm) - Ganial base flexure, NS-Ba ( Q g ~ s )

3.5

54.0-64.5 66.9 - 81.0 58.4 - 73.9 AU32

TCBl 108.82 a

65.36

TCB2 TCB3

118.9 105.42

110.5 - 128.5 1 4.3 94.9-115.6 1 4.1

Table 4.2: Table of rneans, ranges and standard deviations of the facial

KEY: He1ght ACB1 AC82 A m 3 PCB Ta31 Ta2 TC83 ml

and canial d 0 i n s & s and body height at age 18+. (n=117)

- Body height (inches) - Anterior cranial base 1, SN (mm) - Antenor c d base 2, S-1 point (mm) - Anterior c d base 3, SGl (mm) - Posterior cranial base, S-Ba (mm) - Total crand base 1, N-Ba (mm) - Tata c d base 2, SN + S-Ba (mm) - T d c d base 3,1 point-Ba (mm) - Mandibular length 1, Con-Gn (mm)

- Mandibuiar length 2, Ar-Gn (mm) - M;urillary iength 1, PNS-ANS (mm) - Maxilliuy iength 2, PNS-Sn (mm) - MaxiUary kngth 3, PNS- ANS' (mm) - Upper face height 1, IV-ANS (mm) - Upper face height 2, NAM' (mm) - Lower face height 1, ANS-Me (mm) = Lower face height 2, ANS-Me (mm) - Ganiai base flexure, NS-Ba (degrees)

Standard Deviation

2.6 3 -4 3.7

Dimension

Height ACB1 A-2

Mean

69.73 77.8 1 65.90

Range

64.3 - 76.4 69.9 - 87.2 58.4 - 74.1

II CORRELATIONS BETW'EEN THE CRANIAL BASE. BODY HEIGHT. AND THE FACIAL COMPLEX

Correlation coefficients and P values were tabulated to identdy the degree of

inter-~lationships berween the cranial base, body height, and the facial complex at age 12

and again at 18 +.

Table 4.k Cordation coefficients and P values between the size of the segments of the cnnial base, the facial dimensions and body height at age U. (n =IV)

KEY: Hr AU31 A m 2 A m 3 P m Tm1 TU32 TC83 MdLl

M d 3 .385 .123 .362 .187 .459* .394 .315 P= .O0 .185 .O0 .O43 .O0 .O0 .O0 1

- Body height (iches) - Antenor c d base 1, SN (mm) - Anterior c d base 2, S I point (mm) - Antenor cranid base 3, S-Gl (mm) - Posterior cranial base, S-Ba (mm) - Total c r a d base 1, N B a (mm) - Totai c d base 2, S N + SBa (mm) - Totai c d base 3,1 point-Ba (mm) - Mandibubr kngth 1, Con-Gn (mm)

,

MdL2 ml MxL2 MYCL3 UFHl W H 2 LFHl LFH2 CB<

- Mandibular length 2, Ar-Gn (mm) - M d l a r y Iength 1, PNS-ANS (mm) - M;uàllary hngth 2, PNS-Sn (mm) - Maxillary kngth 3, PNS- ANS' (mm) - Upper face height 1, NANS (mm) - Upper face height 2, N-ANS' (mm) = Lower face height 1, ANS-Me (mm) = Lower face height 2, ANS'-Me (mm) - Cranial base flexure, N S B a (degrees)

UFHI P=

UFHZ P=

LFHf ,

.182 -05

-200 .O3 .168 ,

-.O55 .558 -.O04 .965 .O69 ,

.191

.O39

.180

.O53

.140 ,

.416* .O0

.403* .O0 .158 ,

,386 .O0

,399 .O0

.272 ,

.406* .O0

.410* .O0

.225 ,

.266

.O04 (

.299

.O0 1

.206 ,

Table 4.4: Comiation coefficients and P values between the size of the segments of the cranial base, the facial dimensions and body height at age la+. (n=117)

KEY: Kr A m 1 Am2 AC83 P m Ta31 T a 2 TC83 MdLl

- Body height (inches) = Antenor c d base 1, S N (mm) - Anterior cranial base 2, S-1 point (mm) - Antenor cxaniai base 3, SGI (mm) - Posterior cranial base, S B a (mm) - Tod c d base 1, N-Ba (mm) - Total c d base 2, S-N + S-Ba (mm) = Total c d base 3,1 point-Ba (mm) - Mandibular length 1, Con-Gn (mm)

- Mandibular length 2, Ar-Gn (mm) - Maxhyiength 1, PNS-ANS (mm) - Maxdhy iength 2, PNS-Sn (mm) - Maxdary kngth 3, PNS- ANS' (mm) - Upper face height 1, N ANS (mm) = Upper face height 2, N-ANS' (mm) - Lower face height 1, ANS-Me (mm) - Lower face height 2, ANS'-Me (mm) - Ganial base fiexure, NS-Ba (âegnxs)

Conelation coefficients and P values were also tabulated to identify the relationships

berween body height and the facial parameten.

Table 4.5 Comelation coefficients and P values between body height and the facial dimensions at age 12. (n=ll7)

= good conelation exists (r24)

Table 4.6: Conelation coefficients and P values between body height and the facial dimensions at age 18+. (n=117)

CB< - .121 .194

L F M 258 .O05

* = good correlation exists (ra4)

LFHl 243 .O08

KEY: Ht Ta31 TC82 TG33 MdLl MdL2 MxL1 MxL2 MxL3 UFHl uFH2 LFHl LFH2 CB<

- CB < -.192 ,038

- Body height (iiches) - Total cranial base 1, N-Ba (mm) - T o d c r a d base 2, S-N + S- Ba (mm) - Tod c r a d base 3,1 point-Ba (mm) - Mandibular length 1, Con-Gn (mm) - Mandibular length 2, Ar-Gn (mm) - Mwlkry length 1, PNSANS (mm) - Mvallary length 2, PNSSn (mm) -; MaiciUary hngth 3, PNS ANS' (mm) - Upper face height 1, N-ANS (Mn) = Upper face height 2, N-ANS' (mm) = Lower face height 1, ANS-Me (mm) - Lower face height 2, ANSs-Me (mm) - Cranial base flexure, NS-Ba (degrees)

UFHl .506 * .O00

Ht UFHZ ,481 * .OW

, MxL2 234

LFH1 .160 .O85

MxU .259

MdLl -583 *

LFH2 .183 .O49

MxL3 .O73 .435

MxL2 .O78 .401

.O05 P

MxL1 .O28 .767

MdL2 -582 *

UFHl .398 .O00

MdL2 ,414 * .O00

Ht P

.O00

, MxLl .304

UFH2 .380 .O00

MdLl .470 " .O00

,000 .O01 1 .O1 1

The svongest comlatiom between al1 segments of the c d base, body height and facial

complex were as follows at age 12 and 18 +:

Table 4.7: Comelations ( r 2.4) between the facial complex and the c ranial base and the associated 95% confidence interrals.

Table 4.8: Coneiations (r 2.4) between height and the cranial base and face and the

Facial Parameter

associated 95% confidence inte&&.

Cranial Parameter

r at age 12 L

.303 -.592

.303 -.592

.250 -.552

.236 -.542

Con-Gn PM-ANS' N- ANS' CB angle

CI

Height

At both ages, body height dispiayed the strongest conelations to rnandibular length, upper face

height and totai c d base length. The weakest comlation was to m+ length.

Of all aspects of the c d base, total craniai base length pmved to be the smngest correlate

to the face and body height.

For both age groups, total cranial base length (N-Ba) correlated the smngest with maxillary

length and c d base angle. N-Ba to lowr face height was weakly correlated.

At age 12, total c r d base length (SN + S-Ba) displayed the smngest comlations to

rnandibular length and upper face heght. At age 18 + the relationships weakened

Al1 further statistical analyses were perfomed using only the panmeters in the tables

above whic h demonstrated the stmngest conelations. Furdier discussion includes

only those conelations stmnger than r 20.4

-37 .48 .23 .39

S-N +S-Ba N-Ba

S-N + S-Ba N-Ba

r at age 18 +

.201 -.SI7

.327 -.609

.O50 - 395

.225 -.534

.46

.46

.4 1

.40

GaniaVFacial Panameter

L

95% U

Fkight Height Ekkht

r at age 12

S-N 4-Ba Con- Gn NANS'

.5 1

.58

.5 1

.362 - .633

.445 - .689 ,362 -.633

.39 -47 .39

9S0h Ci ' r at age 18 +

.225 - .534

.315 - .6W 225 - .534

9S0/0 CI

III BIVARIATE ANALYSES

T-tests perfoxmed with the sample categorizd by height found significant

differences between the short and d groups for aU linear dimensions at age 12 and ail but

maxdhylength at age 18+.

Table 4.9: T-tests of unadjusted values to cornpart facial dimensions between short and ta1 groups at age 12. (n =IV)

P value (2 taiied) .O00 *

Facial dimension Mandibular length

Con-Gn Maxillary length

PNS-ANS' Upper face height

N-ANS' Lower face height

ANS'-Me

: P value under .OS; t-test for 2 independent samples

Short TaIl Short

Cranial base angle

Table 4.10: T-tests of unadjusted values to compare facial dimensions between short and tall gmups at age 18 +. (n =IV)

Stanlrd emr -4 t -43

Height' Short Ta11

Short Ta11

Mean 11 1.9 1 16.3

Tail 55.8 -3 5

50.4 51.6 53.5

1: Short - 54.0 - 59.1 1" with a mean of 57.1n, TaU = 59.12 - 64.5" with a mean of 61.3"

Short Ta11

1: Short - 64.3 - 69.75" with a rnean of 67.7", Tall = 69.76 - 76.4" with a mean of 72.0"

62.9 65.1

Facial dimension Mandibular length

Con-Gn Maxillary length

PNS-ANS' Upper face height

N-ANS' Lower face height

*: P value under .OS; t-test for 2 independent s-amples

.3 1

.43 -36

L - -

132.0 130.9

.O29 *

.O00 *

.5 1 -63

ANS'-Me 'I

Ta11 74.2 .64 Cranial base angle Short 132.2 .57 .O73

I Ta11 130.4 .80

Heightl Short Ta11

.O07 * I

-59 .74

Mean 129.0 133.2

.257

Standard e m r .54 .59

Short Ta11 Short Ta11 Short

P value (2 taiied) .O00 *

.35 -46 .37 .46 .72

55.9 56.5 58.6 60.7 7 1.7

.3 16

.O00 *

.O12 *

T-tests performed with the sample categorized by T a length found signifiant

clifferences berween the small and large TCB groups for al1 linear dimensions at age 12 and

al but LFW at age 18+.

Table 4.11: T-tests of wiadjusted values to compare facial dimensions between p u p s with large and small total cranial base length 1 at age 12. (n=117)

1: N-Ba length is defined as Sm&= 97.7 - 108.82 mm with a mean of 105.5 mm, Large - 108.83 - 118.7 mmwith a mean of 112.5 mm

*: P value under .OS; t-test for 2 independent samples

P value (2 taiied) .OOO *

.O25 * Q

M ' - M e Ganiai base angle

Table 4.12. T-tests of unadjusted values to compare facial dimensions between p u p s with large and small total cnnial base length 2 at age 12. (n=117)

Facial dimension Maiullary lengrh

PNS-ANS' Lower face heieht

Facial dimension 1 S N + SBa 1 Mean 1 Standard error 1 P value (2 taiied)

Mean 49.7 52.3 63.1

N-Ba le@ 1

SmaU Laqe Srnall

e Smali Large

Standad e m r .3 1 .38 .54

1: SN + S B a le& is defined as Small - 110.5 - 118.9 mm with a mean of 115.4 mm, Large = 118.91 - 128.5 rnmwith a mean of 122.6 mm

*: P value under .05; t-test for 2 independent samples

Mandibuiar length Con-Gn

Upper face height N- ANS'

.O00 * 65.0 129.8 133.3

-62 .62 -64

le* 1

Srnall Large Srnall

e

112.7 115.4 53.7 55.6

-49 -46 .40 .34

.O00 *

.O01 *

Table 4.13: T-tests of uiiadjusted values to compare facial dimensions between p u p s with large and srnall total cnnial base length 1 at age 18 +. (n =IV)

1: N-Ba length t defined as Srnail - 105.1 - 117.17 mm with a mean of 113.5 mm, Large - 117.18 - 127.2 mm with a mean of 121.1 mm.

: P value under .05; t-test for 2 independent samples

P value (2 taiied) .O00 *

.945

Facial dimension m

PNS-ANS' Lower face height

M ' - M e Gluiia base -le

Table 4.14: T-tests of unadjus ted values to compare facial dimensions between gmups with large and small total cnnial base length 2 at age 18 +. (n =IV)

[ Facial dimension 1 S N + SBa 1 Mean 1 Standard e m r 1 P value (2 tded)

N-Ba le*' S d Large Srnall L q e S mal1

Mean 55.0 57.5 72.9 72.9 129.5

length t Mandibuk le& 1 Small

1: S-N + S-Ba length is defined as Small = 116.9 - 128.08 mm with a mean of 124.6 mm, Large = 128.09 - 138.1 mmwith a rnean of 132.4 mm

*: P value under .05; t-test for 2 inde pendent samples

Standard e m r .36 .37 .74

V

Con-Gn Upper face height

N- ANS'

KEY: TCB 1 - Total cranial base 1, N- Ba (mm) TCB2 - Total c m d base 2, S-N + S-Ba (mm) MdLl - Mandibular length 1, Con-Gn (mm) MxW - Maxiliary length 3, PNS- ANS' (mm) UFHZ - Upper face height 2, N-ANS' (mm) L.FHî -Lowerface height2,ANS'-Me (mm) CB < - Ganial base flexure, N-S-Ba (degrees)

-67 .6 1

130.0

.O00 *

.56

.O03 * Large Small Lame

.O12 * 132.2 58.8 60.6

$67 -40 .44

ANALYS1 S OF COVARIANCE

ANCDVA (analysis of covariance) models wete canïed out to mesure one or more

concomitant variables in addition to the dependent variable. In this study, the farial

parameter (ie: xnandibular length) war the outcome variable and the effects of body height

and T a length were both considered as factors in the analysis. The folowing tables

illusvate the variance in the facial parameten explained by these rwo variables (Ta and

height), and their signrficance. Genedy, both body height and TCB length were found to

be important factors in explainhg the facial dimensions with a few exceptions. Ar age 12,

body height did not contribute significandy to maiollary length and LFTL At age 18 +, body

height did not contribute significantiyto m;uallary length and TCB length did not contribute

sisnificantly to upper or lower face height. In ternis of the variance, the adjusted R s q m d

value is reponed in the tables as the mode1 accounts for two variables instead of just one.

Table 4.15: Adjusted R s q u a ~ d and significance of the effects of body height and TCB on the facial dimensions at age It h m ANGOVA models. (n=117)

- -

Code (O) = Short (54.0 - 59.1 1 inches), Code (1) = Ta11 (59.12 - 64.5 inches)

Adjusted R squared .365

.198

.202

.O85

.223

P value .O00

Facial dimension Mandibular length

Variables Cat. Height (0,1)

Con-Gn Maxillary length

PNS-ANS' Upper face height

N-ANS' Lower face height

ANS7-Me Cranial base angle

S-N + S-Ba Cat. Height (O, 1)

N-Ba

.O00

.693

.O00 Cat. Height (O, 1) 1 .O10

S-N + S-Ba 1 .O02 Cat. Height (O, 1) ] .O78

N-Ba Cat. Height (O, 1)

S-N + S-Ba

.O29

.O01

.O00

Table 4.16: Adjusted R s q u a ~ d and significance of the effects of body height and TU3 on the facial dimens ions at age II) + h m ANGOVA rnodels. (n =IV)

Code (O) - Short (64.3 - 69.75 inches), G x i e (1) = TaU (69.76 - 76.4 inches)

Adjusted R s q u a ~ d .22S

.213

Fac h l dimension Mandibular length

Con-Gn Maxillary length

PNS-ANS'

Cranial base angle

KEY: Height - Body height (inches) Ta1 = Total c r d base 1, N-Ba (mm) TCB2 - Total cranial base 2, S-N + S-Ba (mm) MdL 1 - Mandibular length 1, Con- Gn (mm) MxL3 - Maxillary length 3, PNS ANS' (mm) U F W = Upper face height 2, N- A N S (mm) W H 2 = Lower face height 2, ANS'-Me (mm) CB < - Ganial base flexure, N-S-Ba (degrees)

Upper face height N-ANS'

Lower face height ANS'-Me

Variables Cat. Height (0,l)

S-N + S-Ba Cat. Height (0,l)

N-Ba

Cat. Height (O, 1) S-N + S-Ba

P value ,, .O00

.O09 ,726 .O00

Cat. Height (O, 1) S-N + S-Ba

Cat. Height (O, 1) N-Ba

.O0 1

.O00 .2 14

.O05 -102

.204

.O25

.4 12 .O43

ANOOVA was also used to p d c t , with a 95% confidence intend, the adjusted

means of the facial dimensions in shorc and ta11 groups while convoiling for the covariate

Table 4.17: Adjusted means and 95% confidence intenals of the facial dimensions for shori and taii gmups conttouing for the covanate T a at age 12. (n=ll7)

Facial dimension

Mandibular length Con-Gn

Maxillary length PNS-ANS'

Upper face height N-ANS'

Lower face height ANS'-Me

Table 4.18: Adjusted means and 95% confidence intemis of the facial dimensions for shoir and tau gmups conttolüng for the covanate TCB at age 18 +. (n=117)

Cranial base angle

Height

Short Tall

Short Ta11

Short Ta11 Short Ta11 Short 132.9 131.7 1 134.1 1

Adjusted means 1 12.3 1 15.9 50.9 51.0 53.9 55.4 63.3 64.8

Facial dimens ion

Mandibular length Con-Gn

Maxillary length PNS-ANS' ( Upper face height

N-ANS'

95% Confidence interval

KEY: Height -Bodyheight (inches) MxW - Maxilky length 3, PNS-ANS' (mm) Ta1 - Total c r d base 1, N B a (mm) UFH2 - Upper face height 2, NANS' (mm) TC82 - Total cranial base 2, S-N + S-Ba (mm) LFH2 - Lowier face height 2, m ' - M e (mm) MdLl - Mandibubr length 1, Con-Gn (mm) Cl3 < - G.anial base flemire, N S B a (degrees)

95% Confidence intewal .

Height

Short Tall

Short Ta11

Lower bound 128.3 131.5 55.6 55.3

Short Ta11 1 Lower face height

ANS'-Me Cranial base angle

Lower bound 11 1.5 115.0 50.2 50.4 53.2 54.6 62.1 63.6

Adj us te d means 129.4 132.7 56.3 56.1

Upper bound 130.5 133.9 56.9 56.8

71.8 74.1

- --

short Tall

Upper bound 113.2 1 16.8 5 1.6 5 1.8 54.6 56.1 64.4 65.9

58.8 60.6

- ----

Short Ta11

70.5 72.7

57.9 59.7

73.2 75.5

1

59.6 61.5

134.0 131.0

132.8 129.8

13 1.6 128.5

Table 4.19: Cornpanson of adjusted and unadjusted rneans of facial dimensions at age 12 where TCB is adjusted to the grrnd mean (n=117)

Table 4.20: Cornpanson of adjusted and unadjusted means of facial dimensions at age 18+ when: TCB is adjusted to the gnnd mean. (n=117)

Facial dimens ion Height Unadjusted 1 Adjusted 1 Diffe R nce 1

Diffe~ience

0.4 -0.4 0.5 -0.5 0.4 -0.4 0.4 -0.3 0.9 -1.0

Facial dimension -

Mandibular length Con-Gn

Maxillary length PNS-ANS'

Upper face height N-ANS '

Lower face height ANS7-Me

Cranial base angle

Height

Short Ta11

Short Ta1 1

Short Ta1 1

Short Ta11

Short Ta11

~andibul&-lëngth Con-Gn

Maxillary length 1 PNS-ANS'

Unadjusted means 11 1.9 1 16.3 50.4 51.6 53.5 55.8 62.9 65.1 132.0 130.9

Short Tai1

1 upp& face height N-ANS'

Adjus ted means 1 12.3 1 15.9 50.9 51.1 53.9 55.4 63.3 64.8 132.9 129.9

Short Ta11

Lower face height ANS'-Me

KEY: Height - Body height (inches) MdLl - Man&& length 1, Con-Gn (mm) M x U =1VLiOllYylen&3,PNS-ANS(mm) UFHZ = Upperface height 2,N-AP'Pi'(mm) LFW2 - Lowr face height 2, ANS'-Me (mm) CB < = G.anial base flexure, N-SBa (degrees)

129.0 133.2

Short Ta11

Cranial base angle

55.9 56.5

Short Ta11

129.4 132.7

58.6 60.7

Short Ta11

O .4 -0.5

56.3 56.1

71.7 74.2

0.4 -0.4

58.8 60.6

132.2 130.4

0.2 -0.1

1

7 1.8 74.1 132.8

O. 1 -0.1 0.6

129.8 -0.6 .

Also important is the magnitude of difference in the means of the facial panmeten

between short and ta11 groups before and after adjus* for the covariate TC8 lengrh. As the

short and d groups genedy exhibit a p d e l relationship, this difference would be

constant regardfess of whar vaiue the covariate TCB was adjusted to. 'Ihis is crue except for

the dimension of UFH at age 18 +.

Table 4.21: Magnitude of difierence in meam between short and taIl gmups befoa-e and a k r adjusting for the covnriate TCB at age 12. (n=117)

Con-Gn

Facial dimens ion

Maxillary length PNS-ANS'

Upper face height N-ANS'

1 Lower face heirrht 1 Unad

1 Cranial base angle K

Absolute difference

Short

sted 1 1 12.3 1 1 15.9 1 3.6

TaU

iusted 50.4 51.6 1.2 sted 50.9 5 1 . 1 0.2 mted 53.5 55.8 2.3 sted 53.9 55.4 1.5 usted 62.9 65.1 2.2 sted 63.3 64.8 1.5 usted 132.0 130.9 1 . 1 sted 132.9 129.9 3 .O

Table 4.22: Magnitude of difference in means between short and tau gmups b e f o ~ and a k r adjus ting for the covanate TCB at age 18 +. (n =IV)

Facial dimension

Mandibular length Con-Gn

Maxillary length PNS-ANS'

Absolute difference

Short

U n a d j ~ e d Adiusted

Upper face height N-ANS'

KEY. Helght - Body height (iches) MdL1 - Mandibuiar length 1, Con-Gn (mm) M d 3 - Miucillary kngth 3, PNSANS' (mm)

Tau

~nadjusted Adiu~ted

Lower face height ANS '-Me

Cranial base angle

UFH2 - Upper face height 2, N-ANS' (mm) LFI-I2 - Lower face height 2, ANS'-Me (mm) Ci3 < - Ganiai base flexure, NS-Ba (degrees)

129.0 129.4 55.9 56.3

~nadjmted ' 58.6

133.2 132.7

60.7 60.6 Adius ted

2.5 2.3 1.8 3 .O

~mdjusted i 7 1.7 74.2

4.2 3.3 -

56.5 56.1

2.1 1.8 58.8

0.6 0.2

74.1 130.4 129.8

Ahjus ted Unrdjued

Adjusted

7 1.8 132.2 132.8

Formulae were developed to predict the mean lengths of the facial parameters

considering the height of the group (shon versus tall) and the mean length of the

continuous variable TCB.

Table 4.23 Formulae for predicting means of the facial dimensions using height and mean total cnnial base length at age U. (n=117)

Code (O) = Short (54.0 - 59.1 1 inches), Code (1) = Tall(59.12 - 64.5 inches)

Facial dimens ion MdL: Con-Gn MxL: PNS-ANS' UFH: N-ANS' LFH: ANS'-Me Cranial base angle

Table 4.24: F o d a e for p~dicting means of the facial dimensions using height and mean total cranial base length at age 18 +. (n=117)

Linear mgmssion prediction fornida MdL = 86.35 + 3.57 (0) or (1) +.22 (TCB2) MxL = 17.95 + .205 (0) or (1) + .30 (TCBI) WH = 30.20 + 1.46 (0) or (1) + .20 (TCBS) LFH = 39.1 1 + 1.52 (0) or (1) + .22 (TCBI)

CB< = 66.55 + (-3.01) (0) or (1) + .61 (TCE31)

Code (O) = Short (64.3 - 69.75 inches), Code (1) = Ta11 (69.76 - 76.4 inches)

Facial dirnens ion MdL: Con-Gn MxL: PNS-ANS' W H : N-ANS' LFH: ANS'-Me Cranial base angle

MASTER KEY for ali tables in Chapter four:

Linear rrgmssion p~diction formula MdL = 98.85 + 3.3 l(0) or (1) + .24 (TCB2)

MxL = 18.40+ (-. 184)(0) or (1) + .32 (TCB1) UFH = 47.760 + 1.82 (0) or (1) + 8.6 (TCB2) LFH=61.17+2.29(0)or( l )+9.1 (TCBl)

CB< = 70.57 + (-2.99) (0) or (1) + .53 (TCBI)

Height ACB1 AC82 AC33 Pa3 TC81 TC82 TC83 ml

- Body height (inches) - Anterior c d base 1, S N (mm) - Antenor craniai base 2, S-I point (mm) = Anterior c d base 3, SGl (mm) - Posterior cranial base, SBa (mm) - Total c d base 1, N B a (mm) - Total c d base 2, S-N -t S-Ba (mm) - Total cranial base 3,1 point-Ba (mm) - Mandibuiar kngth 1, Con-Gn (mm)

- MandibuLu lengrh 2, Ar-Gn (mm) - Maxillary length 1, P I S ANS (mm) - Maxdhy le& 2, PNS-Sn (mm) = M;uallary length 3, PNS-ANS' (mm) - Upper face heght 1, N ANS (mm) - Upper face herght 2, N-ANS' (mm) - Lower face height 1, M M e (mm) - Lower face height 2, ANS-Me (mm) - Ganial base flexure, NS-Ba (depes)

DISCUSSION DESCRIPTIVES

Descriptive statistics of ail panmeters were cakulated. The data appeared to foilow

normal patterns and disuibutions for the age groups stuclied and h o s i s was not significant.

The means and ranges were used in the statisticai anaiyses to recode the data In this study,

body height was often used as a categoncal variable, and renarned "Caregoricd Wight" with

the value (0) for short, and (1) for tall. For exarnple, at age 12, the range in height was from

54.0 - 64.5 inches and the mean was 59.1 1 inches. The disuibution of height was n o d

and the mean was chosen as the cutoff points in categorization. The group was then recoded

into a short group (O) spanning 54 to 59.1 1 inches and a td gmup (1) from 59.12 to 64.5

inches.

II CORRE LATIONS

Based on an interpretation of Landis and Koch's (1977) Kappa classifications, an r of

O - 39 was a margmal comlation, good correlations were considemd 1) - .75, and above .75

was excellent.

A. Antenor Cxanial Base

The ma& attaches to the midline ACB and the ~iatldible attaches to the laterai

aspect of the posterior c d base. Therefore, the m d a was assurned to have stronger

conektions than the mandible to the Am. In this study, rhat premise was supported with

srronger comlations found between ACB and m;uollary length than ACB and mandibular

length at age 12 and also at age 18 +. The strongest correlations involving ACB at both ages

were between S-N and mkuillary le@ PNSANS' (.39 at 12, .45 at 18 +). This is interesring,

as it confirms the popular use of S N to define the AC6 and also suggests that maxdhy

length may best be defined as PNSANS' instead of the typicd PNSANS. The point ANS is

often obscured in radiographs, o r is a cWenge to identify. ANS' is the rnidpoint b e m e n Sn

and Sn', which mark the most inferior and superior points on the anterior concavity of the

m;utill? with a vertical distance of 3mm between them. This poim c m readdy be found even

when ANS is impossible to visualize. In light of this, perhaps ANS' should be recognized as

a better anterior limit of the d in cephalornetnc studies.

At age 12 and 18+, as expected, marginal comktions were found between ACB and

rnandibular length. The strongest of these comktions (35 at 12, .3 1 at 18 +) was berween S

N and mandibular length Gn-Gn.

Kasai (1995) found sigruficant comlations between ACB and UFH as weli as ACf3

and LFtt In this study, only vely weak correlations were discovered for these parameters.

Marginal comlations were also found for ACE3 and cranial base flexure as well as ACB and

body height.

For ail correlations tabulared, S-1 point had much lower r-values than the other

definitions of A a . 1-point was the "intersectionn point developed in this study where the

midplaned roof of the orbit inteaected the inner contour of the frontal bone. This point

kept this segment of ACE3 purely intemal, free of any influence of the frontal bone.

had its tennllia point at nasion and AU33 ended at glabella, therefore both were affected by

growth of the face and frontal bone. One can assume these "extemal" c d base segments

displayed higher comlations to the facial parameten, as both were affected by the skeletal

pattern of growth.

Poste nor Cranial Base

Posterior c d base conelated weakiy to both the maxïlla and the mandible,

although the comlation was srronger to the mandible. Ar age 12, the correlation between

PCE3 and rnandibular length Con-Gn was fair with a r-value of .32, but it decreased ro 22 at

age 18 +. Noteworthy is that at both ages, the comlation was much svonger to Con-Gn

than Ar-Gn. This suppom using the dimension Con-Gn to define the length of the

ma~ldible.

The suongest correlation factor involving PCB was to body height. This factor was

good (.43) at age 12 but m a r g d (.34) at age 18 +. The svength of this correlation is likely

due to the fact that SOS growth rates into puberty are similar to growth rates for stanire.

Smahel and S M o v a (1988) reported correlations between P a and postenor upper

face height (PNS to the SN he). Kasai (1995) aiso found sigruficant conelations between

PCB and UFH (NANS). In this study, good comlations wex discovered benveen PCB and

UFH at age 12, but they decreased into only fair conelations at age 18 +. Very weak

comlations were reported for PCE3 and LFH at both ages. Conelations were similar whether

ANS or ANS' was used Therefore ANS does not seem to provide as much challenge or

ermr d e n used for masuremenu involving vertical heights as it does d e n used as a

terminal point for horizontal lengths such as maxdhy lengdi.

At both age 12 and 18+ PCB displayed an inveae ~lationship to c r d base

flexure. Our data is in agreement with previous work done by Andenon and PopovKh

(1983) who also used the BuXiington Growth Study and found the same inveae relationship

between PCB (S-Bo) and c d base flexure in children aged 12 and 16.

C Total &niai Base

The totai c d base was defined three different ways in this study. 1-point to Ba

displayed no smng correlations to any of the facial panmeten and could therefore be

eliminated from the discussion. Again, the reason is because when 1 point is use& the

mesure is suictly "intemal" and therefoie does not comiate as wel to linear facial

dimensions which axt affected bythe "extemai" or skeletai pattern of gmwth.

The svongest comlations involving mandibular length Con-Gn were when TCB

was defined as S N + S-Ba 'Ibis comlation factor was good (.46) at age 12 but m;uguial

(.37) at age 18 +. Regarding mknllary length, the smngest comlations were found between

N B a and PNSANS'. At both ages the correlations were good (A6 at 12, .48 at 18+). Kasai

(1995) reported fin* in 10 p r old boys d e n : N B a had a smng correlation to

rnaxillary length but a weak comiation to mandibular le&. 'Ihis was &O found in this

study where N B a showed consistently stronger correlations to the length of the maxiila.

Convashg opinions exist on whether TCl3 correlates to facial height. Scon (1953)

~ p o r t e d that N B a did not correlate to the face height d e Smahel and Skadova (1988)

showed that N B a was conelated to both upper and lower face heights. In this study at age

12, a good correlation (-41) was found between S-N + S-Ba and UFH. The conehtion was

aimost identical d e t h e r ANS or ANS' was used At age 18+, ail comlations between UFH

and T(B were insignificant. For both ages, correlations between LFH and TC6 weie also

veiy weak and will be excluded fmm the discussion.

Body height and S-N + S-Ba were ml1 comlated at both ages (.5 1 at 12, -39 at 18).

G a n d base flexuce exhibited a good comiation to N B a (.40 at 12, .39 at 18+). This

pattern supports p~v ious studies b y Andenon and Popovich (1983), and Bjork (1955) who

demonsvated that where the T a length is small the CB angle is accordingly small.

D. Body Height

Bahmba (1961) reported correlations between c d measurements and body

facial and c d dimensions. Solow (1966) &O found that a gened association existed

between cranial measu~s and the size of the body in young male ad&. Hk rereporred on a

set of low positive correlations becween height and rnost of the linear cephalomeuic

measuriements.

In this study, the correktions were also positive at both ages except for the

interaction of height and c d base angle, *ch displayed an inverse relauonship. Ar age

12, the facial and c d comlations to stature were good for mandibular length (.58),

upper face height (.SI), and total c r d base length (SI). At age 18 +, the correlation to

mandibukr length was still smng (.41), but the comlations to upper face height and T a

decreased (.39). Gnelations to lower face height and maxhtylength were marginal at 12

and 18+.

One can specuiate that body height, length of the mandible, UFH, and T a ail

follow the sarne gened skeletal pattern of growth. Body height is known to be genetically

determineci, as is the length of the mandible. The position of the mandible may be

influenced by environmental factors that cause rotation, but the absolute lengrh rernains

unchanged Upper face height could also foilow a genetically detennined path which is

closely related to growth of the cïvus. Furthemore, ANS is more likelyto be affected

horizontally byenvironmental factors than in a vertical direction. This means any

environmental influences would not sigdicantly affect the measurement of UEFL The

midline c d base is known to foilow n e 4 growth c w e s in some amas and skeletal

g m d c w e s in others (Ford 1958). In this study, TC!3 (SN + S-Ba) appears to foilow the

skeled pattern of growth more closely than the neural pattern based on its correlations to

mandibular length and body heïght.

Interestingly, maxihy length and LFH were poorly correlated to body height. 'Iliis

suggests that they folow different counes of growth or are largely affected by enWonmental

factors. An example of the duence of environmentai facton on the length of the manlla is

reported by Linder- Aronson (1970). His s d y compared children d o underwent

adenoidectomy for obsuucted nose brearhing to a conuol group of children with no

adenoids. Those cM&n with large adenoids tended to be mouth breathers and continually

held their mouths in an open position. The open mouth p o s ~ brought about supra-

eruption of the postenor dentition &ch war associated with a down and backwards

rotation of the mandible causing an increase in LFH The hyperactive lip muscles then

created a svain on the maxdhy bones that caused remodeling of the mavilla anterioriy.

SUMhrlARY

Existing correlations between the cranial base, height, and the facial complex were

identif ied Furthe r statistical analyses involved only those parameten with the svonges t

interactions as they offered the most meanuigful results. The definitions of these parameters

should be used in future studies involving craniofacial growth and development.

Correlations were generally smnger at age 12 compared to 18 +. This is likely due to

the similanty in facial and c d growth patterns and mes while the chiid is entering

pubeny. The correlations weaken at age 18 as the growth rates diversify. The TCB length

demonsvated the highest correlations to body height and the facial complex. At both ages,

N B a was found to have good comlaüons to maxd.hy length and cranial base flexure but

weak correlations to lower face height. At age 12, N-S + S-Ba had good comlaüons to

mandibukr length, upper face height, and body height bm these relationships were weaker at

age 18 +. Body height was also well correlated to rnandibular length and upper face height.

III BIVARIATE ANALYSES

Body height and the length of the TCa were both identified as parameters that were

comlated to the linear dimensions of the facial complex. Therefore, one can make the

assumption that groups who ue short, or who possess srnail mean TC5 lengths d ais0 be

small in linear dimensions of the facial complex. The converse should also be valid for dl

groups with large mean TCB length. T-tests were perfonned to test this hypothesis. The t-

test for two independent samples iiiustrated whether differences existed for the unadjusted

linear facial measurements between short and r d groups, and between groups with s m d

and large TC5 lengths.

The f i t set of t-tests was done with the sample divided by height into t w ~ groups:

short (0) and ta11 (1) as descnbed on page 41. The n d hypothesis was that the= were no

differences in linear dimensions of the face between groups who were short and tall. The

folowing facial parameten were investigated: mandibular length Con-Gn, mk.ollary length

PNS-Alr3S9, upper face height N-ANS', lower face height ANS9-Me, and c r a d base angle

NS-Ba At age 12, based on the Fvaiues, the nul hypothesis was rejected for ail parameters

except c d base angle. Therefore, differences did exist in linear facial dimensions between

short and tall groups of people. At age 18 +, the n d hypothesis was re jected for all

parameters except cranial base angle, and maxillary length.

For those parameters where significant differences exkted, the premise of s k

adjuthg is valid. Size adjusting for body height would mean that if the heights of the groups

were conuolled, the facial measurements would becorne more sirnilar and the groups could

be compared with more accuacy.

The second set of t-tests was performed to idenufy if there were differences in the

facial parameten of groups d o had small (O) and large (1) TCB lengths. The ndi hypothesis

assumed that there were no differences. 'Ihe TCa Lngth used depended on the faciai

dimensions to which it besr comlated NBa was used with m a x d h y length PNS-ANS',

lower face height M ' - M e , and c d base angle. S N + SBa was used with mandibuiar

length Con-Gn, and upper face height NAM'. Ar age 12, the n d hypothesis was rejected

for every parameter, thereby showing that groups with large TCB lengrhs have facial

measurements that are significantly diffemnt from groups with srnall TCB. At age 18 +, the

null hypothesis was rejected in ali parameten except for LFHi

Again, these fiidings pmvide support to the notion of size adjusting and specificdy

to ushg the TCa as the foundation of the adjusunenu. If the 12 par old population was

adjusted so that all TCB lengths were controiied for, the differences in linear facial

measurements would reduce.

N ANCOVA

ANGOVA was used to study the effea of height on the facial parameters aher

adjusting for TCa length. TCB length was adjusted to its grand mean at 12 and at 18 +.

ANGOVA models ais0 established whether TCa and height, (separately and combined)

contributed sigrilficantly to the faciai dimensions. The mode1 provided an adjusted R

squaried, wtiich is the proportion of variance that can be explained by the variables body

height and T a . The R squared was adjusted as two variables were accounted for instead of

just one.

At age 12, both height and S N + SBa conuibuted sipficantiy to mandibular

length and together accoumed for 37% of its variance. N B a sxgnificantly conuibuted to

r m x i h y length, but height did not. These factors together accounted for 20°/0 of iu

variance. Both he&t and S N + SBa conuibuted sgnt.ficantiy to UFH, accounting for 20%

of its variance. N B a contributed significanrly to LFH but height did not, together

accounting for ody9% of the variance. Hiight and TCB both significantiy conuibuted to

the c d base angle, accounring for 22% of its variance.

At age 18+, both height and S-N + %Ba influenced mandibular length and

c d base angle significantly and conuibuted to 23940 and 219/0 of the variance respectively.

N B a significantiy contributed to m+ length but height did not, accounting for 2 1% of

its variance. For UFH, body height had a significant influence, but TCB did not, accounting

for 10Y0 of the variance. Similady, NBa Bad not contribute significantly to LFH but body

height did, accounting for only 49/0 of the variance.

At both ages, the variance was moderate at best, suggested that other variables exkt

which conuibute to the lengrh of the faciai dimensions. Bone thichess, specificdy of the

radius, and head size may be other mas of the body that would likely be linked to

craniofacial linear measurements.

ANGOVA was ais0 used to predict the facial dimensions based on body height

(short and taU) and adjusting for the covariate TCB. Hkight was recoded into (O) for short

and (1) for talL The ANCOVA equation was as folIoas:

y = a, +b, +x, ,or

Adjusted facd dimension - intercept + difference in height (O) or (1) + coefficient (Ta)

Cornparisons of the adjusted and d j u s t e d means m found in tables 4.19 and

4.20. Because the adjusted means axe predictions, it is impossible to nui t-tests to detemine

if s~gNficant differences sd rernain between the groups. However, by analyzing the data it is

evident that adjusting for the mean TCB d e considering the influence of height brings the

values closer together and facilitates compakons. This method of size adjusting is a

statistically valid p ~ c i p l e where the 95% confidence intervals do not overlap (mandibular

length, upper face height, c d base angle).

Clinicaily however, the significance is questionable as at most an adjustrnent of 1 mm

occuned. Ar age 12, the adjutment ranged from -1.0 mm to 0.9 mm and at age 18+, the

adjustment ranged from -0.6 mm to 0.6 mm

It is &O important to examine the difference in means between the short and d

groups before and after adjuting for the covariate T a . ANGOVA models assume

parallelism bemen the short and ta11 groups with respect to the faciai parametea.

Therefore, this difference is constant for any value TCB is adjusted to and not just the mean.

This type of cornparison c o d i that adjustments bring the linear measurements of the taIl

and short groups closer together.

Ross (1987) had the %ht idea d e n he inmduced the principle of size adjusting

based on his clùiicai observations and impressions. This reseamh aimed to support Ross's

theory with statistically significant data. However, even after much research the idea may

remain hypothetical because clinicaily such a sxnall adjustment may not be relevant.

Adjustments may have been larger if the groups were comprised of individuals at the

extremes of the normal frequency distribution. For example, if the taIl and short samples

were selected from outside +/- 1 standard deviations from the mean, the amount of

adjustment may have been both clinically and statistically significant. Size adjusting would

also be more clinically relevant where a group 4th a craniofacial abnormality is compared to

V LINEAR REGRESSION

FormuIae were developed using linear regression to predict the mean lengths of the

facial parameten based on known mean TCa and whether the groups would be considered

short o r taiI.

As an example, at age 18 + mean muidibular length can be predicted as foilows:

Mean Con-Gn - 98.85 + 3.3 1 (0) or (1) + 24('T'CB2)

Code (O) in this case was under 69.75 inches and (1) was over 69.75 inches. Therefore,

different formulas existed dependmg on the rnean height of the group. If the group was

below 69.75 inches then the formula was:

Mean Con-Gn ~98.85 + 3.31(0) +.24(128.08) = 129.6 mm

The confidence interval was 128.3 to 130.5 mm

If the group was above 69.75 inches the fornula was:

Mean Con-Gn =98.85 + 3.31(1) + .24(128.08) = 132.9 mm

The confidence interval was 13 1.5 to 133.9 mm

In this case the confidence intervals don't overiap, thereby demonsmting the sigrilficance

for size adjusting for the outcome of mean mandibular length.

A god in this research endeavor nas to develop formulae that could be applied to

any study that may potentially benef it from size adjusting iinear measures. Unfortunately this

goal proved to be unattainable as the formulae were study specific. The confidence intervais

of the predicted outcornes were too large to predict faciai rneasurements of other srudies

with any accuracy. However, these fomulae have some use as refelences in snidies with

similar sample size and standard deviatiom. Future studies may take note of how this

formula cm be achieved and use that information to denve their own study-specific

foxmulae or they rnay choose to utilize the fomulae presented as rough guidelines.

One important consideration is that body height was parc of the equation. Most

studies do not include height as part of the data reported. This study demonsmted that

hetght was a statistically signif icant factor in size adjusring linear measurernents and s hould

be included in future growth and development snidies. Studies should be designed so that

samples are rnatched for overall body size, (face size, head size, and body height) , and not

just for age. Again, this may not be essentia for studies involving nomial populatioons but

certainly would be relevant when studying groups with craniofacial anomalies.

CONuUsIONS

A study was conducted on the dimensional relationships between the cranial base,

the facial complex, and body height. The longitudinal data from 117 onhodontically

untreated males from the BurLngton Growth Study yielded the following conclusions:

Of al1 the c d base components, the total cranial base (TC6) length disphyed the highest comlations to the linear parameten of the facial cornplex. Good correlations were found to rnandibular length, mamllary length, and upper face height. Therefore, TCi3 length is a svong correlate to the face and can be used in a model to size adjust linear facial dimensions. Correlations were good at age 12 and slightly weaker at age 18 +.

At age 12, body height displayed smng correlations to mandibular kngth, upper face height and TC6 length. niese comlations were slightly weaker at age 18 +. Stmng correlations between facial parameten and body heighr suggest that future cephalometric stdies shouid record stature, and that body height can also be used in a model to size adjust linear facial dimensions.

The following landmarks should be used to defiie facial and cranial parameten in funire cephalometric snidies:

Anterior Chniid Base = S-N Postenor G a n d Base = S-Ba T o t a l G d B a s e = either N B a or { S-N + S-Ba) Mandibular Length = Con-Gn -LeWh = PM-ANS' Upper Face Height = either N-ANS or N-ANS'

0 Lower Face I-kight = either ANS-Me or ANS'-Me

T-Tests indicated that there w e ~ significant differences in the size of the iinear facial dimensions b e m e n groups d o were shon and groups d o were d. At age 12, significant differences were seen for upper and lower face height, mandibular length and maxilhy length. Ar age 18 + significant differences were seen for upper and lower face height and mandibular le&. Therefore, shon children generaliy have s d e r facial dimensions then taIl children.

T-tesu indicated that there weR significant differences in the size of the linear facial dimensions benveen groups who had small TCü lengths and groups Who had large TCB lengths. Ali the facd parameters examined displayed significant differences at age 12 and aii bia lower face height were significantly different between groups at 1 8 +. Therefore, children with s m d l TCB lengths genedy have smaller facial dimensions then children with large T(-B le&.

6. Size adjusting is a statistically valid principle and can be canied out to overcome o v e d size differences between diverse gmups. Clinicd significance of size adjusting was questionabk in this population of normal childnm.

7. Priediction models to adjust the linear facial &mensions should be based on the known values for mean TCB length and body height. These formulae are smdy specific and can ody be used as rough guidelines for other studies.

'Iheoreticaiiy, it is valid to make size adjustments between groups to account for the

general size differences in unmatched populations and facilitate more accurate comparisons.

Totd c d base length and body height are two important variables which should be used

in developing a mode1 for size adjusting.

CHAPTER 7:

SUGGESTIONS FOR FUTURE RESEARCH

This study demonsmed that size adjustïng was not a clinicaüy vahd concept for nomial

populations. It would be worthwhile to repeat this study using two sampks: one group of

nomial children and one group of children with a marked developmentai anomaly. In this

extirme case, the effects of size adjusUng would be more pronounced It is most likelythat

the results would yield both statistical and clinical significance.

Aiso, to examine the effeca of size adjusring berween the sexes, thir study could be

repeated using a female population.

The conclusions of this study highlight the importance of ensuring that samples are

matched for overall body size. In future studies, researrhen s hodd keep in mind the

fundamental principles of sample selection and study design.

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APPENDIX A=

DEFINITIONS OF CRANIQFAQAL LANDMARKS

Seh (S): Nasion (N):

Inteaection point (1) :

Ghbeila (a): Basion (Ba):

Gmdylion (Con): Gnathion (Gn) :

Artic u l a ~ (Ar):

Posterior Nasal Spine (PNS): Antenor Nasal Spine (ANS):

Subnasale (Sn):

Antenor Nasal Spine' (ANS'):

Menton (Me):

The midpoint of sella m i c a detennifled by inspection. The most antenor part of the nasefrontal suture. The consuucted point where the rnidpianed roof of the orbit interseas the inner contour of the frontai bone. The most anterior point on frontal bone. The median point of the anterior nq$n of foramen magnum. The most superior & postenor point on the head of the condyle. The point on the lower border of the mandible where the anterior c w a m becornes confluent with the base. The constructed point where the donal edge of the mandibular ramus intenects the basioccipital bone. The most posterior point on palatal plane. The most antenor point on nasal spine. The deepest point on the concavity of the anterior surface of the maxiila in the midline withui 3 mm of the floor of the nose. The midpoint berween Sn and Sn'. ( Sn': the most srqiaa point of the concavity of the anterior surface of the mamlla which is separated from Sn by 3 mm vekcally) The most inferior point on the midsagittal plane of the symphysis of the mandible

APPENDIX B:

THE CRANIAL BASE I N RELATION TO THE FAUAL COMPLEX

F oramen Caecum

M A X ILLA

APPENDIX C.

EXAMPLES OF CORRELATIONS BETWEEN THE CRANIAL BASE AND THE FACIAL DIMENSIONS

ACB + PCB

-Maxiua FH = Face Wight

Tumor surgery 7 Gmwth Hormone 7 Gmwth Honnone 7

LFH = Lower ~ a c e Height UFH =UpperFaceHkight

APPENDIX D:

EXAMPLES OF DEFINITIONS FOR PARTS OF THE CRGNIAL BASE

TCB N B a

- ACi3+PCB

N B a N - B d N A r

- - -

N- Ar

PU3 S-Ba

- S-Ba

- S-Ba& Ar

PP-Ba -

S-Bo S- Ar

P ~ c i p l e Author B d e (41)

DeCoster (5 1) Ross (51) Scott (53) Bjork (55) Ford (58)

SUWIXU~ (59) Bhamba (61) Hopkin (68)

ACB SN S-Fc S- N

- S-N

PP-N N S minus frontal bone

S- N S- N

Spiegel(71) SOr-S S-Ba SOr- Ba Seward (8 1)

Anderson (83) Ghen (85) Smahel(88)

Kerr (88) Pirinen (94) Kasai (95)

Jensen (97) Van Erum (97) ~ 0 0 ~ (98) Verdonck (99) N a Nasion S - Sella Ba = Basion B o =Bolton Ar = Articulare S O r = Supra-orbitale PP - Pituitary point Fc - F o m n cecum Gl ==Glabeiia

S-N S-N S-N S-N S- N S N S - N S- N S-N S- GI S-N

S- Ar S-Bo S-Ba S-Ba S-Ba S-Ba S-Ba S-Ba S-Ba S-Ba S-Ba

N A r - N B o N B a

- N B a N-Ba N-Ba

- N B a

- N-Ba

Aa3 Pa3 i.u SOS SES S-N N S S-Ba Ba Bo Ar Ta3 PHV ESL Ba- Ar S-FC Fc-GL S-Bo UFH LFH G H SGA BGS 1 ANS' G1 Con Gn Pl% ANS Sn Me MdL MXL a<

LIST OF ABBREVIATIONS (in onier of appearance)

= Antenor Gzuiia Base = Posterior G a r d Base - in=-uterine - Spheno-occipital Synchondrosis -; Spheneethrnoidal Synchondrosis = Sella-Nasion line = Nasion - Seiia - Sella-Basion line - Basion - Bolton = Articulare - Total Gand Base = Peak Height Velocity = Ethmoidale-Sella Line = Basion- Articulare line = Sella-Foramen cecum line = Forarnen cecum-Ghbeh line = Sella-Bolton line = Upper Face Height - b w e r Face Hkight - Growth Hormone - Small for Gestational Age - Burlington Gmwth Study - Intersection Point = Anterior Nasal Spine - GlabeUa = Condyiion - ~nath;on = Postenor Nasal Spine = Antenor Nasal spine - Subnasale - Menton - Mandibuiar Length - Ma>ollary I-ength - Oanial Base Angle