The Below-Knee Amputation

Ernest M. Burgess, M.D.

Throughout the United States and Canada ischemia is responsible for an estimated 80 percent of all major elective civilian amputations. Almost all of these amputations involve the lower extremity. Significant improvements in below-knee prostheses and important advances in surgical and postsurgical management now allow the successful performance of below-the-knee amputation in a majority of these patients. In a consecutive series of 128 unselected cases involving major lower-extremity amputations for peripheral vascular disease between 1964 and 1968, we have been able to obtain primary healing at the below-knee level in 82 percent of the patients. Once healed, the stumps remain healed. With adequate prosthetic care, secondary breakdown will seldom occur. The distribution of our complete series of patients with below-knee amputations is shown in Table 1 .

It is difficult to overestimate the great importance of the knee in amputee rehabilitation. Especially is this true in the older, classical ischemic patient. Debility, weakness, impaired vision, poor balance, neuropathy, compromised circulation and function in the remaining lower limb, together with chronic systemic illness, all emphasize the critical need to save the knee. The older bilateral leg amputee especially needs his knees to approach the rehabilitation goal of a reasonable degree of ambulation and self-sufficiency. When coupled with below-knee amputations for conditions other than ischemia, this amputation thus becomes statistically by far the most important major elective technique.

Selection of Patients

Peripheral Vascular Disease

When acute or chronic compromise of arterial blood supply reaches a level insufficient to support tissue viability, and when reconstructive surgery and nonsurgical supportive measures fail, amputation will be required. The great achievements in surgical reconstruction of the peripheral vascular system represent a leading chapter in medical progress during the past two decades. Continuing basic and clinical research throughout the world supports the hope that an even higher percentage of limb salvage can be expected in the years ahead. As basic causes of degenerative arterial disease become better understood, prophylaxis will play an increasingly important role. Yet, despite the practical effectiveness of modern vascular reconstructive surgery and the promise of preventive measures to forestall degenerative and occlusive arterial disease, statistics indicate that amputations for ischemia are increasing both absolutely and in relation to population growth throughout the western world. Patients requiring amputation are entitled to comparable medical and surgical consideration, comparable team effort, and the same high-level rehabilitation management attending similar patients whose ischemic limbs are treated by vascular reconstruction. Too often ablative surgery does not command this high estate.

Decision to Amputate

The decision to amputate may be dictated by considerations which are simple and evident. Gross necrosis of tissue with demarcation, uncontrollable infection, pain, irreversible neuropathy, alone or in combination with the results of specific tests to assay circulation, will establish the need for amputation. When all available information poses a serious question as to the possibility of limb salvage by reconstructive surgery rather than amputation, it has been common practice to attempt such surgery, even though the procedures involved are extensive. Before questionable extensive reconstructive arterial surgery is carried out, the surgeon should critically consider the overriding probability of its failure, with mandatory amputation subsequently. Will the proposed reconstructive surgery compromise the level of amputation? Will amputee rehabilitation be additionally complicated by further deterioration of general health incident to the extensive surgical attempt at limb salvage? We have, on a number of occasions, performed below-knee amputations on ischemic patients who were being considered for possible vascular surgical treatment but on whom, after review of all available information, such surgery might well have damaged existing blood supply to a degree that an above-knee amputation would then have been required. It is important that the responsible surgeon understand the great rehabilitation value of the knee and weigh all facts relevant to rehabilitation potential.

Amputation Level

There is no single test or combination of tests now available that will specifically demonstrate the lowest effective amputation level. We have repeatedly obtained successful below-knee amputations in patients whose arteriograms indicated complete occlusion of the superficial femoral artery.

A careful physical examination is the first requisite in level determination. Tissue appearance, clinical assay of skin temperature, the presence or absence of edema after elevation, growth of hair, sensation level and acuity, together with palpation of pulses, are all important and cannot be supplanted by laboratory data. Arteriography, plethysmography, thermography, and a number of other objective determinants are useful. These additional procedures include skin mapping with inter-arterial fluorescein, the use of radioactive Xenon #133, and transcutaneous Doppler recordings. Each measure adds to the available information and assists in level determination. Old established guidelines for determining amputation level are not valid when weighed against our recent experience. Unless it is clearly evident that a through-knee or above-knee amputation will be required, the surgeon should prepare the leg for both below-knee and above-knee amputation. Incisions through the skin and muscle preparatory to below-knee surgery can then be quickly carried out. Bleeding and tissue viability can now be visualized directly and the final decision made as to the level of amputation. Only a few minutes are added to the operative time should one then elect to go to the above-knee or through-knee level.

Technique for Below-Knee Amputation in Ischemia

No tourniquet is used. The leg is draped free with the patient supine. Open and infected areas are walled off and shielded by sterile adherent plastic drapes prior to skin preparation. The level of amputation is three and one-half to five inches below the knee, i.e., a short below-knee stump is the goal. We routinely use long posterior and short anterior skin flaps. It has been recognized for many years that the skin over the posterior leg has a better blood supply than that over the anterior and anterolateral aspects. A long anterior flap or even anterior and posterior flaps that are of equal length should be avoided. Using the long posterior flap, the resulting anterior scar presents no problem in fitting a prosthesis. It is our policy in fact to place the scar wherever it will heal most advantageously. The modern total-contact below-knee prosthetic socket can accept a stump with scar placement in any position, provided it is nontender, nonadherent and well healed.

The anterior skin flap is fashioned at approximately the level of anticipated tibial section. The posterior flap must then be five to six inches longer to provide proper skin coverage without undue tension (Sketch A. ).

After outlining the skin flaps, dissection is carried down through the deep fascia to tibia. Periosteum is incised and stripped proximally one inch. The anterolateral muscles are divided down to the intermuscular septum; blood vessels and nerves are appropriately ligated and severed; then the tibia and fibula are sectioned, preferably with a power saw. The fibula is cut no more than three-eighths to one-half inch above the level of the tibia. Soft tissues are dissected from the posterior aspect of the tibia and fibula down to the level of the posterior transverse division of skin. The leg is then separated and removed. The tibia is very carefully rounded with a short bevel over its anterior and medial aspects. It is important that no rough bone areas or ridges remain. A long bevel is specifically avoided. Nerves are pulled down and sectioned high with a sharp knife.

They are not injected, crushed, or cauterized. The major nerves are ligated with fine suture prior to division and just above the site. The encircling suture controls oozing from the blood supply accompanying the nerve. It also appears to localize neuroma formation and lessen overgrowth and adherence to adjacent structures. The posterior muscle mass consisting of the gastrocnemius-soleus and deep flexor group is now beveled and tailored to permit the entire muscle flap to come forward and be sewn anteriorly to the deep fascia of the anterolateral muscle group and to the reflected periosteum over the anterior tibia. Medial and lateral contouring and trimming of the gastrocnemius muscle give a smooth musculo-fascial flap stabilized over the end of the bones. The skin is then brought up and closed without subcutaneous suture (Sketch B. ). Medial and lateral "dog ears" are contoured moderately. They should not be taken back sufficiently to disturb skin circulation. The immediate postsurgical socket rapidly shapes the stump, including moderate skin irregularities at the medial and lateral angles. The wound is drained deep to the muscle flap, i.e., to bone. Through-and-through drain or suction drainage may be used. An immediate postsurgical rigid dressing and prosthesis is then applied.

Postoperative Management

Drains are removed 48 hours following surgery. If the patient's general condition permits, ambulation with guarded weight-bearing is begun 24 to 48 hours following surgery. Touchdown weight-bearing only is allowed until the initial cast change. Weight in the initial prosthesis should not exceed 25 pounds until the cast is changed. Personnel who ambulate the patient should be carefully instructed as to their responsibility in preventing the patient from bearing excessive weight or falling. However, the advantages of upright activity with limited stance and gait are obvious.

Postoperative pain is generally of a diffuse aching type. The postsurgical management with an immediate prosthesis has resulted in much less pain than previously encountered. Localized complaints of pain would indicate abnormal pressures which require stump inspection and possibly a socket change. Unless complications develop, i.e., evidence of infection, excessive loosening of the prosthetic cast, or severe pain, the initial rigid dressing should be left intact until the time of anticipated suture removal, usually two to two and one-half weeks following surgery. Without anesthesia, but with sedation, the cast is removed, the wound inspected, sutures removed if indicated, and a new temporary prosthesis applied. By this time the patient is usually ready for unsupported crutch ambulation and discharge from the hospital. A temporary prosthesis is worn continuously until the definitive limb is fitted. Ordinarily the final limb can be fabricated, fitted, and worn four to five weeks following below-knee amputation.

Necrosis of skin flaps can result from either inadequate blood supply or undue pressure. If judgment as to amputation level at the time of surgery was faulty and the available blood supply was insufficient to support a below-knee amputation, this failure will be evident at the initial cast change. The decision to amputate at a higher level should then be made promptly. In our series the reamputation rate from below-the-knee to through-the-knee or above has been 9.4 percent over the four-year period. As experience and techniques have improved with the below-knee amputation for ischemia, our reamputation rate has continued to decrease. The surgeon would, of course, like to avoid any reamputations. However, salvage of the knee is of such paramount importance that an occasional reamputation may be required on the basis of our present inadequate means of diagnosis for level of determination.

The Nonischemic Below-Knee Amputation

The optimum level for a below-knee amputation in the presence of adequate blood supply is at the junction of the middle and lower third of the leg. This somewhat longer stump can be fitted very satisfactorily with a total-contact prosthesis and provides excellent leverage for strong limb control. Often, the level of amputation will be determined by the causal pathology, including infection, the degree of scarring of the tissues, and related factors. The surgeon should save all effective length down to optimum level and consistent with providing a comfortable, nontender stump.

Plastic and Reconstructive Surgery

The elective amputation must be considered plastic and reconstructive in nature. We have repeatedly emphasized the need to create a dynamic and sensory motor end-organ. The below-knee stump no longer hangs suspended in an open-end socket. Total contact with variable degrees of pressure and weight-bearing over the entire stump surface enhances the surgeon's opportunity to fashion a functional terminal end-organ. Stump strength created by surgical muscle stabilization, pliable, sensitive, but nontender skin and scar, adequate soft tissue coverage of bone ends and other pressure-sensitive areas, high ligation and division of nerves to remove neuromata from pressure zones, meticulous rounding and tailoring of bone surfaces, all contribute to an ideal organ for substitute limb reception. As this stump matures, the profound shrinkage previously considered desirable is avoided. The atrophic, wasted, bony below-knee stump so commonly encountered in years past is no longer acceptable. Stump muscle stabilization, i.e., the attachment of sectioned muscles under appropriate tension to bone (myodesis) or to opposing muscles (myoplasty), is a prime requisite for dynamic stump activity. Muscle stabilization is especially needed in the through-knee and above-knee amputee. Our experience also justifies its routine use in below-knee amputation. Muscle-to-bone suture does add operative handling of tissues, and encircling sutures carry the potential of local muscle constriction. For these reasons we do not now use myodesis in the below-knee amputation for vascular disease. The technique described, which utilizes the long posterior myofascial flap sewn anteriorly to anterolateral deep fascia and tibial periosteum, provides a reasonable degree of muscle fixation without risk of strangulation. Muscle-to-bone suture is reserved for the nonischemic patient.

In addition to established physical measures of rehabilitation the therapist must specifically stress exercises for the stump musculature. Isometric exercises of the stump muscles sectioned at amputation level and surgically stabilized should be encouraged. A cylindrical stump shape is desired. For the purposes of teaching we direct the surgeon's thinking to the concept of producing a foot-like organ at below-knee level. The total-contact socket is the "shoe on the foot." Just as plastic surgical techniques are required in operating on the hand and foot, the same techniques of gentleness in skin and other tissue handling are applicable to amputation surgery. When viewed in this light, the amputation becomes a surgical challenge instead of a distressing surgical exercise. Immediate postsurgical prosthetic fitting not only supports and augments the dynamic approach to rehabilitation, but offers certain physical advantages, i.e., immobilization, appropriate continuous pressure relationships, and comfort. These benefits further justify its incorporation into the overall management of the below-knee amputee.

Case Presentations

Case #1 was a 68-year-old white male who had severe chronic peripheral vascular disease without diabetes. A complete vascular review indicated that no reconstructive vascular surgery was indicated-the patient had no peripheral pulses distal to the femoral pulse and had an occlusion of the superficial femoral artery with poor collateral circulation and extensive small-artery disease. A chronic osteomyelitis of the second metatarsal was present and was unresponsive to surgery.

The preoperative condition of the leg is shown in Fig 1A . Salient features of the surgical procedures are indicated in Fig. 1B , Fig. 1C , Fig. 1D , Fig. 1E ,Fig. 1F and Fig. 1G . The appearance of the stump at closure, at suture removal and at time of delivery of the definitive prosthesis are presented Fig. 1H , Fig. 1I and Fig. 1J .

Case #2 was a 73-year-old white female with severe chronic peripheral vascular disease without diabetes. Two attempts at femoral popliteal bypass graft had been made in the three weeks prior to "breakdown" of the graft operative sites. Progressive gangrene of the foot had ensued with demarcation just above the ankle level.

Fig. 2A shows the appearance of the leg prior to amputation. A short below-knee level of amputation was selected and a long posterior musculocutaneous flap developed (Fig. 2B and 2C). The appearance of the stump at closure following surgery is shown in Fig. 2D . A plastic drape, used to cover the infected popliteal bypass graft at the time of surgery can be seen in this illustration, while the infected area itself is shown in Fig. 2E . The appearance of the below-knee stump at 19 and 29 days following surgery is indicated in Fig. 2F and Fig. 2G . The definitive prosthesis was fitted on the 32nd postoperative day.

Case #3 was an 80-year-old white male with severe arteriosclerotic peripheral vascular disease. A preoperative lumbar sympathectomy was performed two weeks prior to amputation of the leg. A transmetatarsal amputation (Fig. 3A ) had been done nine days prior to the below-knee amputation.

The appearance of the stump two months and 11 months following amputation is shown in Fig. 3B , Fig. 3C and 3D . The definitive prosthesis was delivered on the 34th postoperative day at which time the patient was ambulant and had been returned to his home.

Case #4 was a 92-year-old white male having a diagnosis of arteriosclerotic peripheral vascular disease without diabetes. The appearance of the leg prior to amputation is shown in Fig. 4A . A below-knee amputation was performed using the long posterior musculocutaneous flap technique with through-and-through drainage (Fig. 4B and 4C ). The stump was well healed by the 23rd postoperative day when the sutures were removed (Fig. 4D ) and the appearance of the stump at the time of definitive limb fitting on the 37th postoperative day is indicated in Fig. 4E .

Case #5, a 50-year-old white female, was a severe brittle diabetic with infected moist gangrene of the foot, lymphangitis, and lymphadenitis. Her opposite leg had previously been amputated below the knee. Fig. 5A shows the appearance of the foot prior to below-knee amputation on the left leg. By the 15th postoperative day the patient was ambulating in a below-knee prosthesis on the right and an immediate postsurgical prosthesis on the left (Fig. 5B ). The appearance of the stump at the 28th and 45th postoperative days is shown in Fig. 5C and 5D . The definitive prosthesis had been fitted on the 38th postoperative day.

Case #6 was a 47-year-old patient having a diagnosis of arteriosclerotic peripheral vascular disease with acute iliac thrombosis. Iliac thromboendarterectomy had been performed and some improvement in circulation obtained. Later the circulation became increasingly compromised and subsequent studies including arteriography demonstrated complete occlusion of the superficial femoral artery and no visible popliteal artery. Further arterial reconstructive surgery was not considered to be feasible.

[popup30 indicates the condition of the foot prior to amputation. Following the below-knee amputation (Fig. 6A and 6B ) pressure transducers were located about the stump in order to record the pressure relationships between the stump and the postsurgical rigid dressing. These pressure relationships were measured both immediately following surgery and during ambulation in the immediate postsurgical prosthesis. The stump was healed by the 34th postoperative day (Fig. 6C and 6D ) at which time the definitive prosthesis was fitted. The condition of the stump at the 73rd postoperative day is shown in Fig. 6C and 6D .

Case #7, a 69-year-old white male, had multiple difficulties consisting of arteriosclerosis obliterans with complete right superficial femoral occlusion, diabetes mellitus, arteriosclerotic heart disease with mitral insufficiency and coronary occlusion. No reconstructive vascular surgery was considered to be feasible. The preoperative condition of his foot is indicated in Fig. 7A . Good stump healing was achieved by the 25th postoperative day (Fig. 7B and Fig. 7C ). The definitive prosthesis was applied on the 28th postoperative day (Fig. 7D ).

Case #8 was a 27-year-old white male who sustained a crushing injury to the right lower extremity with compound fractures of the lower tibia and fibula extending into the ankle joint. The case is presented to illustrate the below-knee amputation for nonischemic disease and to demonstrate the reconstructive nature of amputation surgery.

For three months after the injury, multiple reconstructive procedures were tried (Fig. 8A ) before amputation was decided upon. A primary closed amputation through the tibia was done, even though the wound was still open and covered with infected granulation tissue. The stump was closed with drainage (Fig. 8B ) and an immediate postsurgical prosthesis was applied and primary healing achieved by the 35th postoperative day (Fig. 8C ) at which time the definitive limb was fitted.

Summary and Conclusions

Below-knee amputation is statistically the most important major amputation used today. The vast majority of lower-extremity amputations performed for ischemia will heal primarily and remain healed at the below-knee level. The below-knee amputation for ischemia provides a stump which is short in length; the posterior skin and myofascial flaps are fashioned long, and the technique is precise. The resulting stump is cylindrical in shape, well-padded, comfortable, and easy to fit with modern below-knee prostheses of the total-contact-type. An immediate postsurgical prosthesis is an integral part of the overall below-knee amputee management program in both the ischemic and nonischemic patient. Restoration of function and rehabilitation of the below-knee amputee, both unilateral and bilateral, has improved in almost spectacular fashion when the guidelines and management procedures described are followed.


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*Also, Principal Investigator, Prosthetics Research Study, Seattle, Washington. This study was conducted under Contract No. V5261P-438 with the Veterans Administration.

Ernest M. Burgess, M.D. is associated with the Child Amputee and Congenital Deficiency Clinic Children's Orthopedic Hospital Seattle, Washington