We report the results of a transplantation of a free flap that included the vascularized calcaneus and associated soft tissues in an attempt to obtain greater function after a below-the-knee amputation by providing sensate skin for prosthetic weight-bearing.
*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. No funds were received in support of this study.
†Department of Orthopaedic Surgery, Harvard Medical School, Children's Hospital, 300 Longwood Avenue, Boston, Massachusetts 02115. Please address requests for reprints to Dr. Waters.
An eleven-year-old boy slipped and fell while trying to board a slow-moving train. The left leg was caught in the train tracks, and the train continued to move over it. He was taken to a nearby hospital for initial evaluation and then was transferred to our institution. The initial duration of ischemia was six hours. He had a devascularizing and degloving injury of the leg, which was rotated 360 degrees, was cold, was without a pulse, and was without motor function distal to the knee. There was only a six-millimeter-wide flap of dorsal skin attaching the knee to the foot. There was a segmental defect of muscle, bone, and neurovascular tissue that extended from the proximal to the distal tibial metaphysis. The tibia and the fibula were completely shattered. The zone of injury to the skin extended to the level of the distal femoral metaphysis. There were no associated injuries, and the patient was hemodynamically stable. He had a history of melorheostosis for which he had had a quadricepsplasty to improve flexion of the knee.
The severe segmental defects of soft tissue and bone made replantation impossible and amputation inevitable. We decided to salvage the extremity by creating a below-the-knee amputation stump that would permit weight-bearing and preserve the extensor mechanism. A microvascular free flap was fashioned, with use of the plantar skin, the calcaneus, and the subcutaneous plantar and calcaneal heel pad, based on the posterior tibial arterial system with its calcaneal, lateral, and medial branches. After isolation of the neurovascular structures, débridement of the flap, and preservation of the calcaneus and the plantar skin, the flap was placed on ice in gauze that had been soaked in saline solution. The excised dorsal skin of the foot and skin from the diaphyseal region of the tibia were defatted to be used as a full-thickness skin graft.
The distal portion of the femur and the proximal portion of the tibia were explored beyond the apparent zone of injury to determine if there were additional injuries. The proximal portion of the fibula was comminuted and was therefore removed. All non-viable muscle, including a major portion of the soleus, was debrided. The medial and lateral heads of the gastrocnemius were viable and were preserved to be used as pedicle flaps9. The proximal neurovascular structures in the popliteal fossa were isolated and clamped. The osteocutaneous flap then was brought up and secured into the proximal tibial metaphysis with smooth, large Steinmann pins that passed through the calcaneus, through the proximal portion of the tibia, and across the knee joint into the femur. The wound was thoroughly irrigated. Radiographs showed good apposition and alignment of the extremity. Administration of dextran was begun before the microvascular anastomosis of the proximal, popliteal artery to the distal, transplanted posterior artery. Two venous anastomoses then were performed. The posterior tibial nerve was repaired to provide sensation to the flap. The medial and lateral gastrocnemius muscles were rotated as pedicle flaps into the anterior defect of the junction of the proximal tibial metaphysis with the calcaneus. The exposed muscle was covered with the meshed skin graft obtained from the amputated leg and foot. Instantaneous capillary refill of the flap was maintained. The patient was extubated and transferred to the intensive-care unit. Postoperatively, dextran and antibiotics were given for five days.
The wound was debrided and the dressing was changed with the patient under general anesthesia on the second and fifth postoperative days. On the seventh postoperative day, another split-thickness skin graft was applied. There were no problems with the viability of the flaps. Six weeks postoperatively, the pins were removed and the patient was fitted for a prosthesis. At nine weeks, the skin graft and the free flap had healed and the patient was walking with the prosthesis. At four months, the calcaneus and tibia had fused (Figs. 1-A and 1-B). At five months, the active range of motion of the knee was 0 to 105 degrees, with normal strength in the quadriceps. This was better than the arc of knee flexion of 95 degrees that had been measured before the injury by his previous orthopaedic surgeon. The patient had returned to playing competitive basketball while wearing the prosthesis. At the time of the latest follow-up examination, there was no change in the melorheostosis. Four years after the procedure, he had normal strength in the quadriceps, a good range of motion of the knee, and no problems with overgrowth of the stump or breakdown of the skin despite a high level of sports activity.
The treatment of severe injuries of the lower extremity in the presence of extensive damage of the skin, muscles, bones, nerves, and blood vessels and loss of large segments of the extremity is complex, making it difficult to choose between salvage and amputation. When the preoperative findings consist of absent pedal pulses, severe loss of soft tissue, and osseous and neural injuries, amputation is the procedure of choice8. Jupiter et al., Frykman and Jobe, and Dubert et al. outlined the benefits of amputation with salvage of what they termed spare parts, which helps to preserve the length of the limb by resurfacing the stump with undamaged tissues from the amputated leg and foot. Microvascular technique has made this possible4,6. The concept of spare-parts operations is becoming more common in trauma surgery7. In our patient, the level and extent of injury suggested the need for a disarticulation at the knee or an above-the-knee amputation. The use of a primary free osteocutaneous flap made it possible to create a below-the-knee amputation stump and thus facilitate the rapid return to a normal level of activity4,8.
The guiding principle in amputations has been to maintain length for better prosthetic support and function. A functioning knee joint makes prosthetic fitting easier5,11, although advances in prosthetic fitting and manufacture have made it less necessary to adhere rigidly to the principle of maintaining length. There is 5 to 15 per cent less energy expenditure with a below-the-knee amputation than with an above-the-knee amputation11. The soft-tissue transfer and the nerve repair in our patient provided a sensate weight-bearing surface. Plantar skin, anatomically ideal for weight-bearing, functioned as the primary contact tissue with the prosthesis (Figs. 2-A and 2-B). The overgrowth of the stump and the breakdown of tissue that can be seen after diaphyseal amputations in children may have been prevented by the calcaneus acting as a biological cap, allowing the stump to behave like a disarticulation1,10. The result in this patient encourages us to recommend the use of tissue flaps from the amputated segment to preserve function.
NOTE: The authors thank Dr. Julian Pribaz for his inspiring surgical work that fostered the thoughts behind this case.