INVITED ARTICLE

J. K. Stanley, MCh Orth, FRCS, FRCS Ed, Consultant in Hand and UpperLimb SurgeryI. A. Trail, MD, FRCS, Consultant in Hand and Upper Limb SurgeryCentre for Hand and Upper Limb Surgery, Wrightington Hospital for JointDisease, Hall Lane, Appley Bridge, Wigan, Lancashire WN6 9EP, UK.

Correspondence should be sent to Mr J. K. Stanley.

©1994 British Editorial Society of Bone and Joint Surgery0301-620X/94/5844 $2.00J Bone Joint Surg [Br] 1994; 76-B:691-700.

VOL. 76-B, No. 5, SEPTEMBER 1994 691

CARPAL INSTABILITY

J. K. STANLEY, I. A. TRAIL

From Wrightington HospitalNHS Trust, Wigan, England

Carpal instability is the term used for a group of conditions

which results from injuries to the carpus, ranging from a

simple sprain to a major fracture-dislocation. In the

English literature Gilford, Bolton and Lambrinudi (1943)were the firstto note the potential for instability, describingthe wrist as a link joint which was stable under tension

because of the position and size of the scaphoid bone, andin 1970 Fisk described carpal instability from nonunion

of a scaphoid fracture as a zig-zag or concertina deformity.

Linscheid et al (1972) proposed a classification and

offered the definition “carpal injury in which a loss ofnormal alignment of the carpal bones develops early or

late”.

INCIDENCE

In 1975 Dobyns et al reviewed their own experience and

that of the B#{246}hlerClinic and reported that 10% of all

carpal injuries resulted in instability. Jones (1988) studied

a consecutive series of 100 wrist injuries with no

radiological evidence of fracture; he took special radio-

graphs of the wrist including a clenched-fist view. In 19

patients there was an increase in the scaphoid-lunate gap

and five of these had scaphoid-lunate instability. Kellyand Stanley (1990) reviewed 98 consecutive wristarthroscopies and identified many ligamentous injuries,

findings that were confirmed by Sennwald, Fischer andJacob (1993) who carried out arthroscopy on 41 injured

wrists and found at least one ligamentous lesion in 25%

and two or more distinct lesions in 75%.

The incidence of carpal instability in association

with other injuries is unclear. In a large series of fractures

of the distal radius, Tang (1992) found radiological

evidence of carpal instability in 30.6%. Nakamura et al( 1991), however, performed arthroscopy on the wrists of

a group of patients with ununited scaphoid fractures and

found that most did not have serious ligamentous injuries.

PATHOMECHANICS

Understanding carpal instability requires a thorough

knowledge of the anatomy and mechanics of the carpus.

The distal row of bones, the trapezium, trapezoid, capitate

and hamate, forms a stable platform upon which the

metacarpals ride and there is very little motion between

these bones. Similarly, the distal radius and ulna, althoughthey move in pronation and supination, are essentially

stable. The proximal row of the carpus, however, is an

intercalated segment with no muscle insertions; its

stability depends entirely on the capsular and interosseous

ligaments between the scaphoid, lunate and triquetrum

(Fig. 1). Flexion and extension of the wrist result from

movements between the radius and the lunate, between

the lunate and the capitate in the centre of the wrist,

between the trapezium, trapezoid and scaphoid on the

lateral side, and between the triquetrum and the hamate

on the medial side (Fig. 2). There is no differential motion

between the medial and lateral sides of the wrist andapproximately half the range of flexion/extension occurs

at the radiocarpaljoint and half at the midcarpal joint.

In radialdeviation the distance between the trapezium

and the radial styloid shortens and in ulnar deviation it

lengthens (Fig. 3). Two principal movements allow this

to occur. First, there is sliding of the scaphoid into the

lunate fossa during radial deviation and sliding of the

lunate into the scaphoid fossa during ulnar deviation.

Secondly, there is a movement which can be described as

simple flexing of the scaphoid under the compression of

the trapezium during radial deviation, and passiveextension during ulnar deviation. The triquetrum passively

follows the other two bones of the proximal row. Mostwrists show both types of motion, but in varying

proportions. Wrists which mainly slide are called ‘row’

types and those in which flexion predominates are called

‘column’ types. The triquetrum articulates with the hamate

at a helicaljoint which allows sliding and flexing to occur.

Flexion of the scaphoid, however, is greater than that of

the triquetrum and the lunate becomes therefore anintercalated torque converter between scaphoid and

triquetrum during radial and ulnar deviation. The lunate

is also an intercalated segment between the radius and the

capitate.

Taleisnik’s (1985) modification ofNavarro’s concept

of longitudinal columns (Fig. 4) has made the collapse

deformities of the wrist much easier to understand. When

the ligamentous supports of the scaphoid are ruptured,

.,1�:i:w? �.

The extrinsic ligaments of the carpus (a) palmar (b) dorsal. 1) radioscaphocapitate ligament, 2) radiolunateligament, 3) ulnar triquetrocapitate ligament, 4) space of Poirier, 5) radiotriquetral ligament, 6) scaphotriquetralligament.

Fig. 2

The normal wrist in flexion and extension.

The normal wrist in radial and ulnar deviation.

692 J. K. STANLEY, I. A. TRAIL

THE JOURNAL OF BONE AND JOINT SURGERY

Fig. 4

The carpal bones shown as (a) three columns: scaphoid; lunate, capitate,hamate, trapezoid and trapezium; triquetrum and as (b) two rows: scaphoid,

lunate and triquetrum; hamate, capitate, trapezoid and trapezium.

Fig. 5

CARPAL INSTABILITY 693

VOL. 76-B, No. 5, SEPTEMBER 1994

compensates by flexing (Fig. 6). Subluxation of the

midcarpal joint is seen at rest on lateral radiographs and

this pattern is termed volar intercalated segment instability

(VlSI).

The normal kinematics of radial/ulnar deviation and

flexion/extension were investigated in detail by Youm et

al (1978). They found that rotation occurred around a

fixed axis in the middle of the head of the capitate and

that this was independent of the position of the hand. The

distance from the base of the third metacarpal to the distal

articular surface ofthe radius (the carpal height), measured

along the axis of the third metacarpal, was constant

throughout radial and ulnar deviation; the perpendicular

distance of the fixed axis of rotation from the distally

projected longitudinal axis of the ulna was also constant.

�

�

� .‘:�� �. �

Anteroposterior and lateral radiographs of a wrist with dorsal intercalated segment instability (DISI). The linesrepresent the long axes of the lunate and the scaphoid.

longitudinal compression forces the scaphoid into a flexed

position. The lunate, being narrower anteriorly than

dorsally, tends to extend under compression. Coincident

extension of the lunate with flexion of the scaphoid can

occur only if the ligamentous connections between themare damaged. Both bones collapse into their ‘default’

positions only when there is severe ligament injury on theradial side of the carpus and this pattern is termed dorsalintercalated segment instability (DISI) (Fig. 5). The

classical mechanism of this injury is a fall on the

outstretched, extended wrist. If the thenar eminencestrikes the ground first, there is an additional supination

element to the extension and compression forces.

If the hypothenar eminence strikes the ground first

the resulting pronation disrupts the dorsal ulnar-triquetral

ligament complex, the triquetrolunate interosseous liga-

ment and the anterior midcarpal capsule. This allows the

capitate to hyperextend in relation to the lunate, which

These measures can be used to quantify respectively

carpal collapse and carpal translocation. Ruby et al (1988)

used a similar but more sophisticated technique to showthat the wrist functions as two carpal rows, the proximal

row acting as an intercalated segment of variable geometry

which was confirmed by Sennwald Ct al(1993). Movement

of the intercarpaljoints in the proximal row accounted for

40% of flexion, 33% of extension and 10% of ulnar

deviation (Seradge et al 1990).

The intercarpal ligaments have been studied by

several authors. The scapholunate ligament was first

investigated by Logan et al (1986) who described its

dorsal and volar components. Hixson and Stewart (1990)

examined the radioscapholunate ligament and found that

it had an abundant blood supply. Berger, Kauer and

Landsmeer (1991) thought that the structure should notbe considered a ligament, but this was disputed by

Taleisnik (1985). The dorsal capsular ligaments were

Fig. 6

694 J. K. STANLEY, I. A. TRAIL

ThE JOURNAL OF BONE AND JOINT SURGERY

Anteroposterior and lateral radiographs of a wrist with volar intercalated segment instability (VlSI).

studied by Mizuseki and Ikuta (1989) who found that

neither the dorsal radioulnar ligament nor the ulnar

collateral ligament could be isolated as discrete conden-

sations.

Viegas et al (1989) considered how loads were

transmitted across the wrist. They found that the scaphoid

fossa constituted 60% of the total contact area and the

lunate fossa 40%. At the midcarpal joint load was

distributed as follows: 23% at the scaphotrapeziotrapezoid

joint, 28% at the scaphocapitate joint, 29% at the

lunocapitate joint and 20% at the triquetrohamate joint

(Viegas et al 1993).

Although the injury which causes carpal instability

is almost always hyperextension, the precise patho-

mechanics are little understood. A study of cadaver wrists

by Mayfield (1984) identified four stages of lunate

instability:

1) Instability limited to the scapholunate joint.

2) Added instability of the capitolunate joint.

3) Added damage to the triquetrolunate joint.

4) Dorsal disruption of the radiocarpal ligament leaving

the lunate totally unstable.

The displacements required to produce this type of

injury were extension, ulnar deviation and intercarpal

Supination.

Other research on specific instabilities has sought to

identify those structures which need to be damaged to

produce the observed radiological appearances. Trumble

et al (1990) found that the pattern of VlSI required rupture

of the triquetrohamate and triquetrolunate ligaments. Hon

et al (1991) concluded that the essential lesion to produce

such an instability pattern was rupture of the dorsalradiotniquetral and dorsal scaphotniquetral ligaments plus

damage to the lunotniquetral ligament and intenosseous

membranes.

The long-term effects of instability on the wrist were

evaluated by Blevens et al (1989) who used pressure-sensitive film to record changes in the radioscaphoid and

radiolunate contact areas after sequential ligament section.

They found that the scapholunate interosseous ligamentwas essential for preventing scapholunate diastasis and

that the change in contact area after its division would

explain the later development of degenerative arthritis.

Benninghaus, Koob and Steffens (1992) showed that

carpal instability does indeed lead to degenerative arthritis.

CLASSIFICATIONS

The International Wrist Investigators Workshop Nomen-

clature Committee was set up to define the terms used to

describe carpal instability but as yet no one system has

been agreed on. The most frequently used terms are those

introduced by Linscheid et al (1972) and Dobyns et al

(1975) who identified four groups of carpal instability:dorsal flexion instability (DISI); volar flexion instability(VlSI); ulnar translocation; and dorsal subluxation.

The radiological appearances of the dorsal flexion

and volar flexion instability patterns have already been

discussed. Ulnar translocation describes ulnar shift of thecarpus on the radius and is commonly seen in patientswith rheumatoid arthritis. Dorsal subluxation describes

dorsal shift of the carpus, often seen after malunion of

distal radial fractures (Dias and McMohan 1988).

Taleisnik (1985) introduced the concepts of static

and dynamic instability. Static instability is an end state,

with marked scapholunate dissociation, fixed flexion of

the scaphoid and fixed extension of the lunate. Dynamic

instability exists when partial ligament injuries cause pain

but with minimal or even no changes on the staticradiograph, the diagnosis being made by dynamic

Fig. 7

Pseudostability test for carpal instability undertaken with the examiner holding the carpus firmly with one hand

and the distal forearm with the other and performing anteroposterior translation. Often in carpal instability this

translation is reduced.

CARPAL INSTABILITY 695

VOL. 76-B, No. 5, SEPTEMBER 1994

radiology or arthroscopy. The terms carpal instabilitydissociative (CID), carpal instability non-dissociative

(CIND) and carpal instability complex (CIC) were

introduced by Dobyns in 1990. CID describes instability

due to loss of linkage between the individual bones of

either row; CIND means that there is no dissociation

between individual carpal bones but instability at theradiocarpal or midcarpal joints; and CIC includes insta-

bilities which were not otherwise classifiable.

DIAGNOSIS

Clinical tests. Of paramount importance in the diagnosis

of carpal instability are a careful history and physical

examination. Attention must be paid to the position of the

wrist at the time of injury and the location of pain.

Swelling and local tenderness are noted and the ranges of

motion and grip strengths of the injured and uninjured

sides are measured. The most important differential

diagnosis for pain on the radial side of the wrist is a

fracture of the scaphoid. The problems of early diagnosis

of this injury are well known, but after two to three weeks

the standard tests for carpal instability can be performed.The pseudoinstability test, described by Kelly and Stanley

in 1990, in which there is loss of the normal forward glide

of the carpus (Fig. 7) is useful. Lack of this motion due to

protective spasm is akin to the positive apprehension sign

of shoulder instability. Other tests include that of Watson,

Ryu and Akelman (1986) which stresses the scapholunate

interosseous ligament (Fig. 8). Scapholunate or lunotn-

quetral ballotment may reveal specific joint instability

and Lichtman et al (1981) described a pivot shift test for

midcarpal instability. All of these are specific for a

particular ligamentous lesion but overlap is not uncommon

and perhaps the most specific and reliable test is point

tenderness over the affected ligament.Imaging. The work of Schernberg (1990) on the

radiological examination of the normal wrist has shown

the importance of the quality and reproducibility of the

films. On the posterior/anterior view, the width of the

scapholunate gap should be no greater than that of the

triquetrolunate gap, and Gilula and Weeks (1978) found

that a scapholunate angle greater than 80#{176}was indicative

of DISI. Schernberg (1990) found that stress views were

needed to diagnose 18 out of 27 cases of wrist injury.

Degreif et al (1990) advocated comparison of both wrists

because of the considerable variations in normal anatomy.

Larsen et al (1991) reported great interobserver variation

in radiographic measurements and recommended the use

of well-defined axes. Other authors (Lichtman et a! 1981;

Stanley 1993) have found that examinations under an

image intensifier are useful for dynamic instabilities.

Special investigations including narrow-bore colli-

mator scintigraphy, ultrasound, MRI and CT may be

useful and three-phase arthrograms and three-dimensional

reconstruction of CTR arthrography can be used to

Fig. 9

696 J. K. STANLEY, I. A. TRAIL

THE JOURNAL OF BONE AND JOINT SURGERY

demonstrate leakage of contrast between the various

intercarpal joints. Herbert et al (1990) showed, however,

that an arthrogram is of little diagnostic value unless it

can be compared with that of the opposite undamaged

wrist.

Fig. 8

In Watson’s test for scapholunate disruption the examinerpresses firmly with his thumb on the anterior aspect ofthe distal tubercle of the scaphoid with the wrist in ulnardeviation. The carpus is then rotated radially in anattempt to flex the scaphoid against resistance. Inscapholunate dissociation, the scaphoid will subluxdorsally resulting in a painful ‘clunk’.

As mentioned above, scintigraphy has been used to

diagnose Preiser’s disease, Kienbock’s disease and avas-

cular necrosis of the capitate but bone scans are not useful

in the diagnosis of carpal instability. CT has now replaced

other forms of tomography in the assessment of complex

injuries of the carpus (Stewart and Gilula 1992).MRI appears to have the greatest potential (Zlatkin

and Greenan 1992) but, like CT, it gives only static

images. Even the use of surface coils, improved software

and the addition of gadolinium contrast have failed to

improve its diagnostic accuracy and the method often

fails to reveal minor tears of the triquetrolunate interos-

seous ligament (Munk et al 1992).

Arthroscopy. Arthroscopy ofthe radiocarpal and midcar-

pal joints is the best method for the diagnosis of carpal

instability. Roth and Haddad (1986), Kelly and Stanley

(1990) and Cooney (1993) have all advocated its use and

there is no doubt that it can provide much informationabout the altered mechanics and pathology of the wrist at

all levels. Kelly and Stanley (1990) and Dautel, Goudot

and Merle (1993) examined groups of patients with

symptoms suggestive of scapholunate interosseous liga-

ment tear but with normal radiographs and established the

diagnosis by dynamic manoeuvres undertaken during

radiocarpal and midcarpal arthroscopy (Fig. 9). Fischer

and Sennwald (1993) detected ligament tears by arthro-

scopy in every wrist in 20 cases of carpal instability.

TREATMENT

Scapholunate dissociation. When this condition is

diagnosed early and treatment is indicated, an attempt

should be made to bring about healing of the torn

interosseous ligament. Palmer, Dobyns and Linscheid(1978) reported good results from immobilisation for

eight weeks in plaster if treatment started within four

weeks of injury and if an anatomical reduction was

Arthroscopic views of scapholunate dissociation from the radiocarpaljoint (a) showing the gap or fissure betweenthe scaphoid and lunate. The view from the midcarpal joint (b) shows an obvious widening between the twobones.

CARPAL INSTABILITY 697

VOL. 76-B. No. 5, SEPTEMBER 1994

maintained. This often required the use of closed pinningwith a Kirschner wire under radiographic control. Cases

that cannot be reduced and held by this technique, and

those diagnosed later, do poorly with immobilisation, and

often require surgery. Ligament reconstruction, whether

undertaken through a volar or a dorsal approach (Taleisnik

1985), often needs supplementary Kirschner-wire fixation

and the results range from good to fair depending on the

quality of the tissue available for repair.If the diagnosis is delayed for three months or more

it becomes even more difficult to repair what is left of the

interosseous ligament. If the disability is minor, with

more than 80% of the range of motion and grip strength

retained, no treatment is required (Dobyns et al 1975),

but if there is a significant disability, a number of surgicalprocedures are available. Dobyns et al (1975) advocated

splitting one of the radial wrist extensor tendons and

passing half of it as a loop through the scaphoid and

lunate; Taleisnik (1985) advocated the use ofa free tendongraft in the same way. Glickel and Millender (1984)reviewed 21 cases so treated and found that range of

motion and grip strength had improved slightly but that

the radiographs showed loss of much of the early

correction. Almquist et al (1991) used a four-bone-

ligament reconstruction and also reported clinical im-provement and radiological recurrence of the deformity;most of the patients returned to their preinjury activities

including heavy labour. Conyers (1990), who performed

imbrication of the palmar ligaments and chondrodesis

between the scaphoid and lunate, reported improvementof the pinch and grip strengths and the range of motion.

Lavernia, Cohen and Taleisnik (1992) advocated direct

scapholunate ligament repair and dorsal radioscaphoid

capsulodesis for most scapholunate dissociations in which

there was no osteoarthritis present, regardless of the time

lapse since injury. Blatt and Nathan (1992) described

dorsal capsulodesis for rotatory subluxation of the

scaphoid. In this procedure palmar flexion ofthe scaphoidis prevented by a dorsal capsular check-rein; a long-term

review of 30 patients showed satisfactory clinical results

and MRI suggested physiological hypertrophy of the

transferred tissue.

The indifferent results of ligament reconstruction

have persuaded many surgeons to perform an intercarpalarthrodesis, the most logical of which is scapholunate

arthrodesis. Hom and Ruby (1991) reported, however,

that of seven patients only one showed radiographic

fusion and three still had significant symptoms; Alnot, De

Cheveigne and Bleton (1992) had similar problems. Inview of these difficulties, attention turned to the scaphoid-

trapezoid-trapezium (SiT) joint. Watson and Hempton(1980) found that 511.’ fusion was readily obtained andwas successful in rotatory subluxation of the scaphoid,

preserving 80% ofthe range of flexion/extension and 66%

of the range of radial and ulnar deviation. These findings

were supported by Kleinman, Steichen and Strickland(1982), nine of their 12 patients returning to preinjury

activities without wrist pain and with 80% of the

preoperative range of motion. More recently, however,

Eckenrode, Louis and Greene (1986) reported less good

results. Voche et al (1991) found that patients maintained

60% of their preoperative range of motion but that the

radiographs revealed styloid impingement in 34% of

cases. Fortin and Louis (1993) showed that 8 out of 14

patients had significant residual symptoms and 1 1 had

complications including radiocarpal and trapeziometacar-

pal arthritis and nonunion.

Scaphocapitate arthrodesis is easier to undertake.

Pisano et al (1991) found that although it reduced wrist

movement, particularly radial deviation, grip strength was

good and only two patients out of 17 required reoperation

for nonunion. Our own experience, and that of Kleinman

(1990) of this procedure, is that a few patients develop

osteoarthritis due to the excessive force between the

scaphoid and the dorsal half of the scaphoid fossa.

Lunotriquetral dissociation. This is a less common

problem than scapholunate dissociation but it occasionally

requires surgical treatment. Reagan, Linscheid and

Dobyns (1984) found that simple immobilisation was

useful only for acute injuries; capsulodesis, tenodesis and

arthrodesis have been used for chronic cases. Pin et al

(1989) had no failure of fusion in 1 1 cases, but three

patients had persistent pain. Most of the range of motion

was preserved but only 59% of grip strength. Kirschen-

baum, Coyle and Leddy (1993) also advocated fusion but

Nelson et al (1992) reported problems of nonunion andrecommended using a Herbert screw as well as a Kirschner

wire for fixation, plus a cast for at least eight weeks.

We recommend triquetrohamate fusion as being

easier to achieve. If, however, on arthroscopy a posterior

triangular fibrocartilaginous complex tear is found but no

midcarpal instability, then a reconstruction of the ulnar

dorsal capsule using half the tendon of extensor carpi

ulnaris is preferred. For combined midcarpal and trique-

trohamate instability the so-called ‘four-corner’ or luno-

triquetrocapitohamate fusion is indicated.

Midcarpal instability. Lichtman et al (1981) described

this instability and investigated its pathomechanics. They

also described a diagnostic test, which causes a painful

click on ulnar deviation, compression and pronation of

the wrist. The radiographs are usually normal but

cin#{233}fluoroscopy can show dissociation between the

proximal and distal carpal rows with volar collapse

deformity. Laboratory studies have shown volar subluxa-

tion of the capitate and hamate on the lunate and

triquetrum. Johnson and Carrera (1986) identified attenu-

ation of the radiocapitate ligament as the cause of this

condition and advocated tightening the ligament to

obliterate the space of Poirier, but soft-tissue reconstruc-

tions have usually failed and midcarpal arthrodesis is

preferred (Lichtman et al 1993).

Carpal instability resulting from malunion of a

fracture of the distal radius in dorsal angulation can be

effectively treated by distal radial osteotomy (Sennwald,

Fig. 10

698 J. K. STANLEY, I. A. TRAIL

THE JOURNAL OF BONE AND JOINT SURGERY

Scapholunate advanced collapse (SLAC), pattern of arthritis.

Fischer and Stahelin 1992) but if the carpal ligamentshave been damaged it is rarely successful.

Post-traumatic ulnar translation of the carpus has not

been successfully treated by soft-tissue repair (Chamay,

Della Santa and Vilaseca 1983; Rayhack et al 1987) and

most authors now advocate radiolunate fusion for thisproblem.

Secondary osteoarthritis. The loss of motion and altered

biomechanics which result from intercarpal arthrodesis

may give rise to osteoarthritis in the long term. The

particular contribution of each intercarpal joint to totalwrist motion was measured by Gellman et al (1988).Palmer et al (1985) measuredJlmctional wrist motion and

found that the normal range was 5#{176}of flexion, 30#{176}of

extension, 10#{176}of radial deviation and 15#{176}of ulnardeviation, values which lie well within the range of mostwrists after intercarpal arthrodesis. Scaphotrapeziotrape-zoidal fusion and scaphocapitate fusion have been found

to produce a similar reduction in range of motion. Both

procedures increased the sliding motion of the lunate on

the radius (Garcia-Elias et al 1989) and Viegas et al

(1990) found that afterwards virtually all the load was

transmitted to the scaphoid fossa. Other fusions, scapho-lunate, scapholunocapitate and capitolunate, all distrib-

uted the load more equally through both the scaphoid and

lunate fossae. The position of the scaphoid in scaphotra-

peziotrapezoid fusions is important; if it is vertical there

is a greater loss of flexion and ulnar deviation; if it is

horizontal, extension and radial deviation are lost. If the

scaphoid is in anatomical alignment scaphotrapeziotra-

pezoid and scaphocapitate fusion result in similar patterns

of motion (Ambrose et al 1992).

The treatment of carpal instability when there are

already arthritic changes in the wrist was described by

Watson and Ballet (1984). They defined scapholunate

advanced collapse (SLAC), a sequential pattern of arthritisaffecting first the radial fossa and then the capitolunate

joint but sparing the radiolunate joint (Fig. 10). They

recommend reduction of the so-called DISI, excision of

the scaphoid and fusion of the capitate, hamate, lunate

and triquetrum. Of the 19 patients treated, 18 had some

pain reliefwhile maintaining an adequate range of motion.

Krakauer, Bishop and Cooney (1992) operated on 55

patients with SLAC and obtained the best results with

scaphoid excision and a ‘four-corner fusion’. Saffar and

Fakhoury (1992) compared proximal row carpectomy

with partial wrist arthrodesis and found that the latter

gave better results.

Conclusions. Carpal instability may result from a varietyof wrist injuries and is important in the differential

diagnosis of chronic wrist pain. Over the last decade,

much has been added to our knowledge about these

injuries but more remains to be understood. Diagnosis

and treatment are often difficult and require special skills.

At this time the authors’ preferred method of investigation

includes a thorough clinical and radiological examination

including stress views. Most patients then undergo

arthroscopy to confirm the provisional diagnosis and toexclude other pathology. Treatment depends on the

patients’ symptoms. For those with little disability andmore than 80% of the range of motion and grip strength,

surgical treatment is not indicated.

For those with more serious problems from acute

scapholunate dissociation (within six weeks of injury),

direct repair and dorsal capsulodesis are recommended;

for cases seen later a full Blatt dorsal capsulodesis is

required. If, however, reduction of the dorsal intercalated

segment cannot be maintained, scaphocapitate fusion ispreferred. For an isolated lunotriquetral disorder arthro-

desis of this joint only is performed; for midcarpalinstability a triquetrohamate arthrodesis is preferred.

Finally, for patients with secondary arthritis either a ‘four-

corner fusion’ with scaphoid excision or a total wrist

arthrodesis is advised depending upon the extent of thearthritis and the patients’ individual requirements.

No benefits in any form have been received or will be received from acommercial party related directly or indirectly to the subject of this article.

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