Sliding Anterior Thigh Flap for Below-Knee Amputation

JAMES R. URBANIAK, M.D. BERT R. TITUS, C.P.O.


When amputation is inevitable following severe trauma of the lower extremity, maximal efforts should be directed toward salvaging as much length as possible. This preservation of maximal stump length is important in patients of all ages. However, in the young patient who has healthier soft tissues with greater elasticity and blood supply, greater diversification is possible in the reconstructive procedures which may be applied in attempting to maintain useful length in the amputated limb. This paper presents a method used to obtain a below-knee stump in a teenager when it initially appeared that an above-knee amputation would result from a severe compound fracture of the extremity with subsequent gas gangrene.

Case History

The patient was a 16-year-old male who was involved in a motorcycle accident and sustained a severe compound fracture of the midshaft of the right tibia and fibula with extensive soft tissue and vascular damage. The initial management included debridement with a residual six-inch below-knee amputation stump. In an effort to salvage the below-knee stump, a loose primary closure of a long anterior flap of skin over drains was effected by the surgeon. Six days postoperatively, the patient developed gas gangrene and was transferred to Duke University Medical Center for further management.

On arrival at the Medical Center the boy was alert and did not appear toxic. His temperature was 38 deg. C. Examination revealed a six-inch, below-knee stump with necrotic skin extending to the knee joint ( Fig. 1 ). Purulent, foul, fruit-smelling material was exuding from the posterior flap. Subcutaneous crepitation was present above the knee and x-rays revealed the presence of gas in the extremity, extending above the knee joint. Gram stains and cultures revealed Clostridia perfringes. The patient was given intravenous penicillin G and Kanamycin. He was immediately placed in the hyperbaric chamber for two hours under 100 per cent oxygen at 3 atmospheres of pressure. After the hyperbaric oxygenation, the wound was thoroughly debrided and irrigated. It was necessary to excise two more inches of skin and bone and nearly all the muscle below the knee, except the insertions of the hamstrings. A long posterior thigh incision, extending nearly to the ischial tuberosity, and shorter medial and lateral thigh incisions were made. No muscle above the knee was excised. All wounds were left open and the patient had five additional two-hour treatments with the hyperbaric chamber over the next 48-hour period.

Following three debridements in the operating room with postoperative stockinette skin traction, a three-inch below-knee stump resulted. This stump consisted of tibial bone only (the fibula having been excised), healthy granulation tissue posteriorly, no posterior skin below the femoral condyles, and only one inch of skin anteriorly below the knee joint. Seventeen days after the injury, a sliding full-thickness anterior thigh flap was advanced distally to cover the end of the tibia. A transverse, five-inch, "V"-shaped incision extending to the muscle fascia at the anterior midthigh was made ( Fig. 2 ), The area from the incision distally was undermined to the fascia to permit advancement of three inches of the flap. The proximal incision was then closed by further proximal undermining.

A tibial pin was inserted to prevent knee-flexion contractures and split-thickness skin was applied posteriorly. All wounds eventually healed with complete skin coverage of the stump. Full-thickness skin covered the anterior and end-bearing portion of the stump, and split-thickness skin covered the posterior portion ( Fig. 3 ). Skeletal traction was maintained for three weeks postoperatively, and the boy obtained 100 deg. of flexion and full extension of the knee joint.

Three months after the final grafting, the split-thickness graft posteriorly was thought to be durable enough for prosthetic tolerance. The patient was fitted with a standard PTS socket with a soft insert ( Fig. 4-A and Fig. 4-B ). He has been ambulating with a satisfactory gait for several months without pain, limp, or skin breakdown

Discussion

It is not the purpose of this paper to discuss the prevention and management of gas gangrene. However, this case clearly emphasizes the always present hazard of closing compound wounds primarily. It is a strict policy of the Orthopaedic Service at Duke Medical Center to leave all compound fractures or traumatic amputations open, and follow with delayed primary closure as the condition of the wound dictates. Hyperbaric-chamber therapy was of unquestionable value in the salvaging of this boy's below-knee stump. The remaining muscle tissue of the stump appeared more viable after each treatment.

The stockinette skin traction after each debridement prevented skin retraction, but gave no additional length in this particular case. Approximately three inches of valuable full-thickness skin was gained by the sliding advancement of the anterior thigh flap. Without this full-thickness skin anteriorly and distally, we feel a functional BK stump capable of tolerating weight-bearing in a prosthesis could not have been achieved. The amount of advancement after the relaxing incision was determined by the blanching of the skin. We had initially planned to close the proximal defect of the thigh with split-thickness graft, but were able to close it primarily by undermining the proximal subcutaneous tissue. The tibial pin was of utmost importance in preventing knee-flexion contractures and in permitting open care of the split-thickness graft on the posterior aspect of the stump.

The prosthetic fitting was delayed until the split-thickness graft was thought to be mature enough to withstand the socket. A standard PTS socket was prescribed because of: (1) the thin split-thickness graft over a large area of the stump, (2) limited knee motion, (3) the need for minimal pistoning action between the socket and the stump during ambulation, and (4) the advantage that the patient could slip the insert on the stump prior to the placement of the stump in the socket and, therefore, decrease tension on the skin and end of the stump.

We feel that this type of socket has been ideal for this particular stump although it is emphasized that socket revisions will undoubtedly be necessary from time to time to maintain the perfect fit essential to the prevention of any stump breakdown.

In conclusion, this patient's youth was undoubtedly a major factor in the successful outcome. The amount of healthy full-thickness skin for the sliding anterior flap, the excellent knee function, and the ability of the posterior split-thickness skin to withstand a socket probably could not have been obtained in an older individual.

Duke University Medical Center Durham, North Carolina