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In vitro study on biomechanical characteristics of tendons of limbs of the buffalo*

S.C.dubal, 1 K.N.Vyas 2 and Y.L.Vyas 3

Department of Anatomy

College of Veterinary Sc. & A.H., Gujarat Agricultural University,

Anand 388 001 (Guj) India

Key words: Biomechanical characteristics, tendons, limbs, buffalo.

ABSTRACT

The biomechanical characteristics of tendons of distal part of the fore and hind

limbs of six young (6 to 10 months old) and adult (5 to 10 years old) male Surti buffaloes

were utilized to understand quantitatively the susceptibility of the tendons for strain

injuries. There were significant (P < 0.01) age related differences amongst the tendons

studied. The mean value of Young` s modulus of elasticity, factor of safety and fracture

toughness did not differ (P >0.01) amongst the tendons studied, and hence these

properties appeared to be material properties. All other mechanical properties appeared

to be specimen properties. Those tendons which act as prime movers and are subjected

to high physical stresses, had higher values of tensile strength but lower values of critical

length of micro-damage and the number of fatigue cycles than their opponents. It was

therefore concluded that former tendons were more susceptible to tendon injuries than

the later ones.

INTRODUCTION

The aetiology of tendon injuries in domestic animals is, in general, rather complicated.

It is an emerging concept in musculo-skeletal pathology that cyclic over loading creates

cumulative micro-damage which ultimately results in tissue failure. Most of the

biomechanical studies have been carried out on equine tendons. The suggested factors

responsible for micro-damage of equine tendons are cross-sectional area and collagen content

(Riemersma and Schamhardt, 1985), composition of extra-cellular matrix (Jones and Boe,

1990), longitudinal heterogenecity (Smith et al.,1994), inter fibre differences (Beckeret al,.

1994) and elevation of core temperature ( Wilson and Goodship,1994 ). There are a few

reports pertaining to the biomechanical studies of the bovine tendons (Pandya, 1982, Vyas

and Vyas, 1985). However, these studies did not concern with the tendon injuries in general

and micro-damage and cyclic over loading in particular. The present work was an attempt to

_______________________________________

Part of Ph.D. thesis submitted by first author.

1Assistant professor, 2 Retd. Principal and 3Associate professor.

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compare the biomechanical properties of tendons of distal part of both the limbs of the buffalo

so that the study may be useful in understanding the tendon injuries. Emphasis was especially

so that the study may be useful in understanding the tendon injuries. Emphasis was especially

given to the transverse length of micro-damage and number of cycles, which can cause the

tendon failure.

MATERIALS AND METHODS

Fresh muscles with their tendons were obtained from cadaver fore and hind limbs of

apparently healthy six male young (6 to 10 months old) and adult ( 5 to 10 years old ) Surti

buffaloes. The mean body weight of young and adult animals were 64.54 6.74 kg and

518.84 14.55 kg respectively. The tendons were immediately kept in ice cooled normal

saline solution. The widest part of muscle belly was cut transversely then its impression was

recorded on a graph paper and subsequently its cross-sectional area (CSA in cm2) was

measured. The maximum force generated by the muscle was termed as working load (WL in

kg).The working load was calculated by multiplying the CSA of the muscle belly with 6 i.e.,

WL = 6 CSA ( Ikai and Fukunaga, 1968).

From the thinnest part of the tendon, two perpendicular diameters were taken. The

CSA was almost elliptical in shape. The tendons were then immediately subjected to study the

tensile loading at testing machine. For each tendon, a stress-strain curve was obtained to

measure the young` s modulus of elasticity (E). The ultimate tensile load (UL) at which the

tendon ruptured was also recorded. During the experiment the tendons were kept cool and

moist by applying the cold normal saline solution.

Tensile strength (TS) of a tendon was obtained by dividing the UL with its original

CSA. Factor of safety (FS) was obtained by dividing the UL with the WL. The critical length

(CL) of destructive process (the transverse length of micro-damage) was calculated as

follows:

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CL = 2 G E / (TS)2, (1)

G = Surface free energy of the tendon per unit area

The exact value of G is not known. The most probable value of G was assumed to be 0.50

10 3 J / m2 ( Pascoe 1978 and Epifanov 1979 ).

The fracture toughness (FT) was calculated as follows:

FT = (TS) ( CL)

= (2 G E)

(2)

The fatigue tensile strength (FTS) of a tendon was obtained by its minimum WL (assumed to

be equal to 4 CSA of its belly.

The number of cycles (N) of repeated loading that could produced the failure, was

calculated as follows (Pascoe 1978 ):

(d CL/dN) = C ( FTS ) n ( CL ) n/2 (3)

C = Constant.

Since CL

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cycles of fatigue failure, fracture toughness and fatigue tensile strength showed significantly

(P< 0.01) higher mean values in the adult animals than the young one.

Biomechanical properties in relation to limbs and tendons:

1. Working load and Ultimate load:

In both the age groups, the mean values of WL and UL of the tendons of hindlimb

were significantly (P< 0.05) higher than those of the forelimb. Further, the WL and UL of

tendons of cranio-lateral (tarsal flexors and digital extensors) group showed significantly (P