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.