BACKGROUND: Limb salvage in the treatment of bone sarcomas requires wide resection and reconstruction of bone and soft tissues. Wound healing problems can lead to hardware exposure, subsequent prosthesis infection with eventual amputation. It is essential to have viable soft tissue coverage of the prosthesis. In the pediatric population, this can be challenging to achieve without significant morbidity and one that maximizes growth. This is the largest series of pediatric knee sarcoma resection and reconstruction with endoprothesis and primary flap coverage.
METHODS: This is a prospective review of all sarcoma patients with primary gastrocnemius and soleus muscle flap coverage of customized knee endoprosthesis over the 10-year period, 1997 to 2007. Ten patients (9 male, 1 female) with an average age of 14 years (range 10 to 17) underwent resection of the knee joint including proximal tibia and skin. Pathology included osteosarcoma (n=8), Ewings (n=1), and spindle cell (n=1). After resection of the knee joint and proximal tibia to clear margins, the bony defect is reconstructed with an endoprosthesis. Because all of the patients had resection of the skin, primary closure would have been under tension or impossible in some patients. Any wound dehiscence would have resulted in exposure and potential infection of the endoprosthesis. The soleus is rotated medially to cover the inferior portion of the prosthesis, and the medial gastrocnemius is then rotated anteriorly to cover the upper portion of the prosthesis as well as the patellar tendon.
RESULTS: Average follow-up was 31.2 months (range, 1 to 91 months). Patients had endoprosthetic coverage by gastrocnemius and soleus flaps; four patients had additional split-thickness skin graft over the gastrocnemius. Average length of tibial osteotomy from the knee joint was 17cm. Mean soft tissue mass resected with bone was 171cm2. There was one flap failure that was reconstructed with a rectus abdominis free flap. There was no limb loss or hardware exposure or infection. All wounds healed well. All patients achieved ambulation. Functionally, all patients attained excellent passive and active range of motion at the knee joint, and motor and sensory function was preserved. Two patients had foot drop. Leg length discrepancy was found in three patients who underwent opposite limb epiphysiodesis.
CONCLUSIONS: Results of this study support the use of gastrocnemius and soleus flaps as dependable coverage for knee endoprosthesis in the pediatric population. It provides well-vascularized soft tissue that prevents wound complications and hardware exposure.