3. small Anim. Pract. (1970) 11, 723-726

Compensatory mechanisms in a dog after hind leg amputation

L E O N A R D B L A C K

Department of Veterinary Clinical Studies, Liverpool University, Liverpool

A B S T R A C T

A dog was observed for 2 years after hind leg amputation and the com- pensatory mechanisms adopted by it are described. Most weight was taken by the front legs which were placed well under the body. When stationary, stability was achieved by leaning the rump toward the intact side and turning the hind leg inward from the hip. Propulsion was effected mainly by flexion-extension of the back and hip while the stifle and hock were held relatively unbending. The tail was also used to aid in balance.

I N T R O D U C T I O N

Rehabilitation in human amputees has often been described (Sokolow et al., 1962; Ganger el al., 1964; Kohn & Gordon, 1965) b u t nothing on this subject could be found in veterinary literature. An opportunity arose for observing the behaviour of a 2-year 9-month-old three-legged Retriever-type dog weighing 20 kg. The right hind leg had been amputated 5 cm below the femoral neck when the animal was 9 months old.

E N V I R O N M E N T A L F A C T O R S

The dog was kept on a small country estate together with a Yellow Labrador about twice his weight. I n spite of the discrepancy in their sizes he was sometimes able to outstrip his companion and gave as good as he took in their tussles. With regard to daily exercise, the dog was walked for about I f - miles, and in addition, he roamed the countryside on his own for 2-3 hr. This wanderlust may have been the result of his unusual appearance which made him something of a celebrity in the neighbourhood.

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724 L E O N A R D B L A C K

P H Y S I C A L A D A P T I O N

Stance and gait Most of the weight was taken on the front legs which were placed well under

the body. This was especially noticeable during urination when the only hind leg was sometimes cocked and the dog stood balanced on the front legs only. This could be accomplished without raising the hind quarters and with the body more or less horizontal. Fig. 1 shows the dog stepping off a front leg before replacing the hind leg to the ground after urination and all weight is borne on one leg only.

FIG. 1. The only hind leg is cocked during urination. Note that balance is achieved by placing the front legs beneath the centre of the body rather than by raising the hind quarters out of the horizontal. Balance is adapted to the extent that the dog was able to step off his front leg before replacing the hind leg to the ground, and the photograph

shows him standing on one fore leg only.

When stationary, stability was achieved by placing the back leg beneath the

(1) Inclining the rump toward the intact side so that the axis of the leg formed

(2) Lateral bending of the spine (scoliosis) away from the amputated side. (3) Rotating the hind leg inward from the hip downwards so that the stifle and

toe pointed roughly in the direction of the opposite foreleg. When walking, propulsion was achieved mainly by flexion-extension of the hip

and spine while the stifle and hock were held relatively unbending. With each step the back was strongly arched and straightened as the body was pushed forward.

At a run the disability was less obvious and at a distance an observer might well overlook the fact that the dog had only three legs. The remarkable features were:

(a) The extent to which propulsion was effected by flexion-extension of the spine.

centre of gravity of the hind quarters (Fig. 2). This was achieved by:

an angle of about 80" to the ground when viewed from behind.

H I N D L E G A M P U T A T I O N A N D C O M P E N S A T O R Y M E C H A N I S M S 725

FIG. 2. Position adopted when standing. Note: (a) leaning over of the rump toward the intact side. The hind leg forms a slightly inclined angle with the ground, rather than a vertical. (b) Scoliosis of the spine away from the amputated side. (c) The inward

rotation of the hind toe.

FIG. 3. At a slow run the back is flexed and the hind leg brought further forward than one would expect in an intact animal. The crossing of the front and hind legs is a reflection both of the degree of spinal flexion and of the fact that the front legs are

habitually carried well under the body.

726 L E O N A R D B L A C K

(b) The hind foot was brought further both forward and backward than might have been expected in the normal dog. This was especially noticeable at a slow trot (Fig. 3) and also at a walk.

(c) The hind leg was kicked diagonally outwards rather than straight back- wards. This in turn was an expression of the inward rotation of the stifle and toe noted previously.

The tail, which was thick and muscular, appeared to aid balance to some extent. When sitting it was placed flat on the floor toward the defective side and seemed to stabilize the seat.

D I S C U S S I O N

Quantitative assessments of adaptive behaviour are difficult (Hoberman & Springer, 1958; Kelman & Willner, 1962) and in the description of an isolated case such as this, the assessment of features as abnormal was of necessity subjective. For example, although it was concluded after careful observation that the tail assisted with balance, objective criteria were lacking. Likewise, the marked flexion-extension of the lumbar spine at slow pace led to its classification as an adaptive mechanism although this feature is usual in dogs moving at speed.

A C K N O W L E D G M E N T

It is a pleasure to thank the late Mr J. H. Sears, ARPS, for his painstaking photography.

R E F E R E N C E S GANGER, A.B., BROWNELL, W.M., RUSSEL, W.W. & RETTER, R.W. (1964) Archs phys. Med. 45,

HOBERMAN, M. & SPRINGER, C.F. (1958) Archsphys. Med. 39, 235. KELMAN, H.R. & WILLNER, A. (1962) Archsphys. Med. 43, 172. KOHN, K.H. & GORDON, E.E. (1965) Archsphys. Med. 46, 427. SOKOLOW, J., SILSON, J.E., TAYLOR, E. J., ANDERSON, E.T. & RUSK, H.A. (1962) 3. chron. Dis.

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15, 105.

RCsumi. Observation d’un chien de z ans qui a subi l’amputation d’une patte de derritre et description des mtcanismes de compensation adoptts par I’animal. La plus grande partie d u poids est supportte par les membres anttrieurs qui sont placts immbdiatement sous le tronc. Lorsque la stabilitt A l’ttat immobile a tt6 acquise par deviation d u tronc vers le c6tC intact et rotation du rnernbre posttrieur restant vers la ligne mtdiane par rapport A la hanche, la pro- pulsion etait effectute surtout par les mouvements de flexion et extension du dos et de la hanche, alors que le grasset et le jarret Ctaient maintenus dans une position relativement fixe. La queue a t t t tgalement utiliste pour assurer l’tquilibre.

Zusammenfassung. Ein Hund wurde 2 Jahre nach einer Hinterbeinamputation beobachtet und die von ihrn entwickelten kompensatorischen Mechanismen beschrieben. Das Hauptgewicht wurde von den Vorderbeinen iibernommen, die weit unter den Korper gesetzt wurden. Im Stehen wurde die Stabilitat dadurch erreicht, dass der Rumpf nach der intakten Seite gelehnt und das Hinterbein von der Hiifte nach innen gedreht wurde. Die Vorwartbewegung wurde hauptsachich durch Kriimmung und Streckung von Riicken und Hufte erreicht, wahrend Kniegelenk und -sehne relativ unbeweglich blieben. Der Schwanz wurde auch als Balancier- hilfe benutzt.