Artificial Limbs :: CHAPTER V

CHAPTER V

ARTIFICIAL LIMBS WITH FREE KNEE JOINT FOR AMPUTATION THROUGH THE LEG

If the leg stump is ten centimetres long, if the knee joint is freely mobile and capable of complete, or almost complete, active extension, and if there are no adherent scars around the tuberosities of the tibia, the American apparatus with free knee joint should be adopted.

Walking on the bent knee (as stated on page 63) with the "poor man's peg" may be allowed as a temporary measure, but the patient must be advised to give his knee a rest frequently in order to lessen the risk of stiffness in a flexed position.

There are two methods of fitting, corresponding with those we have described for the thigh.

1. For the ordinary amputations with bearing upon the top of the leg.

2. For amputation very low down with end bearing upon the extremity of the stump.

Fig. 102.—Limb fitted upon the patient. Note that he stands upon the toe, and that the knee is flexed.

Fig. 103.—Posterior view of the same limb.

Fig. 104.—Anterior view of the same limb.

I. Appliances with Bearing upon the Tuberosities of the Tibia

An artificial limb for amputation through the leg with a free knee joint is composed of two parts: a leg piece (with foot) which is fitted to the bony prominences around the top of the stump and supports them; and a suspensory apparatus which consists of a lacing thigh corset.

A. Leg Bucket.—The points on which the top of the bucket must be fitted are the internal tuberosity and the anterior tubercle of the tibia, and the head of the fibula, so that hollows corresponding to these must be carved out.

Pressure upon the head of the fibula is often painful, and a deep concavity is therefore carved out for it. The pressure then comes upon the external tuberosity of the tibia which, however, ordinarily bears little weight.

Whenever possible direct end bearing upon the termination of the stump should be used as an accessory to relieve the weight upon the tuberosities of the tibia; this is obtained as described on page 7. It is only possible if the scar is lateral and if there is a good thick posterior or external flap (in the upper third of the leg). An anterior flap is the least satisfactory.

It is also advisable—

That the inner surface and the anterior border of the tibia be divided obliquely, and that the fibula be divided at a higher level than the tibia.

The fibula must not take weight, it is too slender. In high amputations it has a tendency to tilt outwards, causing the double inconvenience of widening the stump and of projecting through the skin. If only 4 or 5 cms. of the fibula remain it is perhaps best to disarticulate and remove it.

With a fitting arranged in this way, we consider that the convenience of walking with a free knee can be assured to patients whose stumps measure only 10 cms. from the lower border of the patella.

These principles can be applied to a limb constructed either of wood or of leather.

The leather appliance (French method) is formed of a leather cylinder, strengthened by two laternal steels which articulate at the level of the knee joint with two similar steels in the thigh corset. Its upper edge may be strengthened anteriorly by a metal plate, but in practice the latter cannot be made to fit with precision the bony prominences enumerated above. It is actually the edge of the leather, adjusted by lacing, which supports tibial tuberosities, and therefore the precision of the fit is soon lost.

For this reason, for amputation below the knee, the American method of construction with a wooden bucket is demonstrably superior.

These limbs are infinitely more durable than the French. They may last three years, whereas the French limb used by a young and active patient is worn out at the end of the first year, and it was for this reason that a limb with a free knee joint used to be considered a luxury.[9]

[9] That is the reason that amputation at four fingers' breadth below the knee used to be called for the working class, amputation at "the seat of election," a name which is no longer applicable and which is liable to mislead the operator.

This wooden bucket is shaped very accurately to the bony prominences, and by passing the fingers over its inner surface the three hollows corresponding to the points of pressure enumerated above can be distinctly felt.

It is important to describe the shape of the upper edge of the bucket in order to guard against two points which may interfere with flexion—

I. Pinching of the tissues behind the knee.
II. The tendency of the stump, when it is short, to tilt forward in the bucket (Fig. 108).

Pinching of the flesh behind the knee in flexion takes place between the edge of the leg piece and that of the thigh corset.

If the top of the bucket is horizontal, it must inevitably occur, even if the edge of the thigh corset is well cut away (Fig. 106).

It can be avoided by cutting away these two edges into concavities opposite each other.

Figs. 105 and 106.—Limb in which the upper edge of the leg bucket is almost horizontal; in the sitting position (Fig. 106) the flesh at the back of the thigh is pinched even if the lower end of the thigh corset is well cut away.

In the French limbs made of leather it is usual to make the leg piece very high in front, i.e. as high as the middle of the patella. This is quite useless. The posterior border is cut down to a depth of two fingers' breadth below the axis of the joint. Pinching is thus avoided, but the posterior support is insufficient, the stump tilts forward as described above and the bucket gapes in front (Fig. 108). If the top of the bucket is horizontal—as in certain American limbs—there is, as we have already said, pinching of the popliteal tissues and compression of the popliteal vessels and nerves (Fig. 106). A concavity is therefore necessary, but one reaching to one finger's breadth below the axis of the joint is sufficient. In front the edge of the bucket reaches up to the joint line, this is quite sufficient to enclose the bony prominences (Fig. 109).

The posterior concavity of the leg piece is combined with a concavity in the thigh piece varied in accordance with the thickness of the popliteal soft parts.

Figs. 107 and 108.—If the leg bucket is hollowed out too much at the back, the stump is tilted obliquely forward (Fig. 108), the knee loses contact with the bucket, and the flesh at the back of the thigh is pinched.

To diminish further the tendency of the stump to tilt forward the posterior edge of the bucket is flattened so that the shape of the top of the bucket is triangular with curved sides and angles much rounded (the anterior angle over the tuberosity of the tibia being obtuse). This is the natural shape of a section of the top of the calf. In this way the posterior muscles are flattened and no longer tend to escape from the bucket when the knee is flexed. In figures 110 and 111 are shown two ways in which this flattened posterior margin may be shaped.

Fig. 109.

Figs. 110 to 111.

B. Suspension Apparatus.—The leg is attached (a) by a thigh corset taking its hold on the femoral condyles, and (b) by braces over the shoulders.

(a) The thigh corset is made of leather laced in front. Two lateral steels curving in sharply against the upper part of the condyles (Fig. 112) form the most effective part of the support. At their lower ends they are articulated with two steels passing up from the top of the leg to which they are attached. The joint (Fig. 113) is composed of a nut, A, into which fits a screw. Around the nut is a copper ring made to move with the femoral steel by means of a stop-notch. When the knee flexes and extends the wear comes upon this copper ring. The steels remain intact. If the joint works loose it is sufficient to renew the ring.

Fig. 112.—The thigh steels, curved in above the condyles, hold the limb on very securely.[10]

Fig. 113.—Details of the joint at the knee.

[10] In this illustration the joints are placed too low. They should be opposite the centre of rotation of the knee joint, i.e. a transverse line passing through the femoral condyles. (Ed.)

(b) The braces are a very useful addition which French orthopÆdists should employ systematically. They increase the stability of the limb and allow the thigh piece to be laced less tightly, so that contraction of the thigh muscles is facilitated.

Figs. 114 and 115.

Support may be given by a strap from a waist belt as shown in figure 117, but proper braces are better. These braces pass over the shoulder of the sound side and are attached either to the thigh corset or to the leg piece of the artificial limb. Attachment to the thigh corset is made by a single strap either in front and behind (Fig. 114) or on either side of the front lacing, the ends of the strap crossing in front of the groin (Fig. 115). It is a simple matter to add to the brace an extending strap, such as we have described for the artificial limb for amputation through the thigh (page 44). It is only necessary to terminate the brace in a strap from which two branches pass down in an inverted V and are fixed to the sides of the front of the leg piece (Figs. 116 and 117). This is unnecessary if the stump is long, for its leverage will then be good. It is, however, very useful for short stumps which give little power to the action of the quadriceps. In the case of patients with a long stump an attempt has been made to abolish the thigh piece and suspend the limb exclusively by braces. This method, we believe, is inadequate even if it is completed by a transverse band above the knee (Figs. 118 and 119).

Figs. 116 and 117.

Figs. 118 and 119.

C. The Foot.—The foot, usually articulated, is fixed in exactly the same way as in a limb for an amputation through the thigh, i.e. it is mounted in the equinus position. But in this case, however, precautions must be taken against stretching of the posterior ligaments of the knee joint, because the equinus mechanically produces hyperextension of the knee, and a genu recurvatum may result. For this reason a strap must be fixed posteriorly between the thigh corset and the leg piece to prevent full extension of the knee (popliteal check cord). This means that we make the patient stand and walk with slight flexion of the knee and with a corresponding elevation of the heel of the shoe (2-3 centimetres).

II. Appliances with End Bearing only

These appliances are suitable for certain amputations very low down in the leg which we must first define.

The orthopÆdist should consider the following operations as very low amputations of the leg, allowing of walking with end bearing only, and suitable for the same type of appliance:—

Supra-malleolar amputation.[11]
Disarticulation at the ankle joint.
Sub-astragaloid amputation.
Osteoplastic amputations through the os calcis (or amputation in which the os calcis is retained entire after removal of the astragalus).

[11] In England, of course, this is always called Syme's amputation. It constitutes the type par excellence of the end-bearing stump. Upon a good Syme stump a patient may be able to walk ten miles without an artificial foot, wearing simply an "elephant boot." Amputations above the Syme level are not end bearing, however long the stump may be. The other amputations in this region seen in English war surgery are the various types of osteoplastic amputations in which a part of the os calcis is retained (Pirogoff's amputation, etc.). These have the following defects:—

(1) There is often sepsis between the tibia and the os calcis, necessitating re-amputation. Osteoplastic amputations are unsuitable for septic surgery.

(2) Ankylosis between the os calcis and the tibia is often imperfect so that the bulbous end of the stump is unstable.

(3) The stump is too long to allow of the fixation of a good artificial ankle joint beneath it. A Syme's amputation leaves two to two and a half inches clearance between it and the ground.

I have not yet seen a sub-astragaloid amputation in war surgery, and only once a disarticulation through the ankle joint, the latter could not bear pressure and it was necessary to convert it into a Syme's amputation. In fact, in this region there is Syme's amputation and a number of other far inferior amputations which should never be considered when a Syme's amputation is possible. (Ed.)

Certain limb makers consider these operations are bad for the same two reasons that we have already refuted in connection with amputation through the condyles of the femur, viz.—

(1) The stump being enlarged at its lower end will not fit into a wooden bucket.

(2) The stump is too long to allow an artificial foot to be fixed below it.

From this it simply follows: 1. That complete enclosure of the stump in a wooden bucket is impossible; 2. That pressure must be placed directly and exclusively upon the end of the stump.

The latter condition is only possible if the state of the soft parts allows the cutting of a thick plantar flap to cover the cut surface of the bone and if care be taken to resect the posterior tibial nerve in the flap.

We therefore draw special attention to the excellent elliptical supra-malleolar amputation with posterior flap (Guyon's method) in which it is sufficient to retain a bare finger's breadth of skin from the plantar surface in front of the point of the heel. It bears direct pressure well, perfectly if a layer of the os calcis is cut with the scissors from the area adjacent to the tendo-Achillis and applied under the cut end of the tibia.

For all these amputations the anterior flap is bad. The thin dorsal skin of the foot is incapable of withstanding the direct pressure which is indispensable for this method of fitting.

Even if it were true that under these long stumps it is impossible to insert an artificial foot for lack of space, the operations which we have enumerated above should be recommended if the flap can be cut in the way we have indicated.

Figs. 120 and 121.

Their great advantage—and the reason for retaining as much length of bone as possible—is that they allow walking directly on the stump without an apparatus. It is sufficient to have a circular shoe made by any shoemaker consisting of a heel more or less thickened surmounted by a lacing gaiter reaching halfway up the leg. Guyon's amputation constitutes the limit up to which this "elephant boot" is possible.

It is an unsightly apparatus, but its simplicity and cheapness should be taken into consideration, for it is quite possible that a manual labourer, especially a countryman, to whom an artificial foot and an "elephant boot" are given, will reserve the former for Sunday and use the other for his daily work.

Appliances with Artificial Foot.—The wooden piece which partly encloses the stump consists of a block carved to the shape of the stump and padded with felt, it is prolonged in front by an instep reaching to the level of the middle of the metatarsus, and above by a grooved piece which reaches halfway up the leg and encloses the anterior half of the latter. A leather gaiter is fixed at the sides and back and extends up the leg, being laced in front over the wooden piece as a field boot is laced over the leather tongue. The foot may be mounted at right angles to the leg, but it is better mounted slightly in equinus.

The sole and toes are of rubber as described on page 35.

In studying figures 120 and 121 the following should be noted:—

1. The shape of the leg bucket in which an aperture behind permits the introduction of the stump which is enlarged at its lower end.

2. The mechanism by which the posterior gaiter laced in front fixes this leg bucket.

3. The articulation of the foot on a transverse axis.

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