Above-knee amputation - an ideal' situation
G. Murdoch *
Based on a paper presented at the ISPO International Course on Above-knee Prosthetics, Rungsted, November, 1978.
The author's contribution to the course in Rungsted was intended to establish a foundation on which further discussions could be based. By agreement with the organizers it was decided that an ideal situation should be presented where thigh amputation would be discussed in the context of normal tissues.
Accordingly, this is simply a summary and reference can be made to Amputation Surgery in the Lower Extremity, Parts I and II (Murdoch 1977). In the presentation nothing about causal conditions, level and limiting factors, stump environment, pre and post-operative care or prosthetic rehabilitation was included.
The author emphasized first that the amputation should be done at as low a level as possible compatible with prosthetic fitting and, in particular, the type of knee mechanisms available. To accommodate the majority of knee mechanisms and to preserve neurovascular bundles so far as possible a distance of some 120-130 mm above the knee joint provides the longest possible stump. It was emphasized clearly that the anatomy at different levels in the thigh alters considerably, particularly in relation to the adductors.
In an ideal situation equal anterior and posterior flaps should be employed and the general rule is that the ratio of the base of the flap to its length should be as great as possible. In planning flaps one must ensure that there is adequate skin to permit suture without undue tension. The author cautioned the inexperienced to retain a sufficiency of skin in the flaps, tailoring the skin to fit the needs of the all but completed amputation at the end of the operation.
Attention was then directed to the management of the individual tissues encountered, skin, fascia, muscle, nerve, blood vessels and bone.
Skin
Further to the need to ensure a sufficiency of skin it is essential that the skin edges are handled gently and that they are closely abutted to ensure primary wound healing and a thin, strong scar.
Fascia
In general, minimal dissection between skin and deep fascia should be used.
Muscle
Management of muscle has been a matter of controversy for a very long time. The early German workers stressed the importance of attaching the divided muscle to the end of the stump securely and it would seem that their objective was to produce a muscle "pad". More recently, Dederich (1967), Burgess (1968) and Weiss (1969) have emphasized this requirement. Many benefits have been attributed to this approach, namely that it is more physiological, provides a more stable shape with less muscle wasting, better proprioception with preservation of existing neuromuscular mechanisms, more efficient vascular dynamics, etc. but few studies exist to support these contentions which all seem to be eminently sensible.
Dederich (1967) demonstrated improved vascular supply to the stump end after myoplastic revision and Hansen-Leth and Reimann (1972) demonstrated, in the laboratory rabbit, a better blood supply to the stump end when muscle stabilization is used. Condie (1973) suggested that muscle stabilization provides for better aphasie muscle activity in amputations at below-knee level on the basis of e.m.g. recordings. The author firmly believes in the secure attachment of severed muscle to the end of the stump.
Experience has demonstrated, certainly in the young adult, that simple muscle to muscle suture over the bone end is insufficient and suture of the lateral and medial hamstrings and any adductors of bulk to the bone via drill holes is advocated. These muscles are then cut flush with the bone end and the quadriceps, which has been left longer, is then drawn over the stump end to be sutured to the posterior muscles. If secure fixation is not achieved then the major muscle units work with less efficiency, causing earlier fatigue, significant distortion of the shape of the stump, and permitting lateral migration of the bone end.
Nerve
Management of the divided nerve has been a subject of controversy over many years. There now seems general acceptance of the view that a high clean cut of the nerve will ensure that the inevitable neuroma is located in such a situation that it will not become involved in distal scar tissue and thus does not interfere with prosthetic fitting or produce significant symptoms. Bone
There is some evidence that the medulla of the bone should be closed by a periosteal flap to retain normal intramedullary pressures (Askalanov and Aronov, 1959).
In the healthy young adult the periosteum is thick and is easily formed into a flap sufficient to close the medulla. It is said that this retains the normal intramedullary pressures with
improved drainage into the general circulation. Emphasis is placed on the fact that simple transection of the bone is not sufficient and that the anterior presenting edge of the cut end of the bone must be sculptured and smoothed to ease the task of the prosthetist and prevent the occurrence, albeit rare, of unwelcome bursae.
The presentation concluded with the view that in normal tissue a tourniquet should be employed, haemostasis ensured, and that closed suction drainage was highly desirable.
References:
Askalanov, I. N. and Aronov. (1959). Comparative experimental evaluation of some methods of bone revision in amputation with primary and secondary healing. Ortopediya, traumatologiya i protezi-rovanie, 20, 30-33.
Burgess, E. M. (1968). The stabilization of muscles in lower extremity amputations. J. Bone and Joint Surg., 50A, 1486-1487.
Condie, D. N. (1973). Electromyography of the lower limb amputee. Medicine and Sport, Vol. 8, Biomechanics, 3, 482-488, Karger, Basle.
Dederich, R. (1967). Technique of myoplastic amputations. Annals of the Royal College of Surgeons, 40, 222-227.
Hansen-Leth, C. and Reimann, I. (1972). Amputations with and without myoplasty on rabbits with special reference to the vascularisation. Acta Orth. Scand., 431, 68-77.
Murdoch, G. (1977). Amputation Surgery in the Lower Extremity, Part I. Pros. and Orth. Int., 1:2, 72-83.
Murdoch, G. (1977). Amputation Surgery in the Lower Extremity, Part II. Pros. and Orth. Int., 1:3, 183-192.
Weiss, M. (1969). Physiologic amputation, immediate prosthesis and early ambulation. Pros. Int., 3:8, 38-44.
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