Part 15

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.

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.]

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

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.

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).