Case 48: Knee Fusion and Lengthening for Failed Total Knee Replacement and Bone Loss

Abstract

A 64 year old woman underwent total knee arthroplasty of the right knee. The knee developed a chronic recurrent infection with exposed hardware and no extensor mechanism. The prosthesis and components were removed. The infection was treated, and her knee was fused with the insertion of an antibiotic cement-coated intramedullary rod. She presented to our clinic with persistent pain that was primarily located at the distal interlocking screws. The right limb had a 3-cm limb length discrepancy (LLD). Radiographs showed persistent nonunion of the right knee. At the time of surgery, the patient underwent simultaneous treatment of the nonunion and LLD. The antibiotic cement-coated rod was not removed. She underwent resection of the nonunion and implantation of bone graft harvested from the left femur with the Reamer/Irrigator/Aspirator (RIA) system (Synthes, West Chester, PA). BMP-2 was used to augment healing. The distal tibial interlocking screws were then removed, and proximal tibial and fibular osteotomies were performed. A two-incision technique (anterolateral and posteromedial) was used for the tibial osteotomy to cut around the rod. The knee fusion rod was always locked proximally, and the external fixator controlled the entire tibial segment (proximal and distal) with respect to rotation. An Orthofix external fixator (Lewisville, TX) was applied to the tibia. Distraction began 1 week after surgery (four 1/4 turns per day). The patient received physical therapy for the ankle to prevent equinus contracture. The tibia was distracted 3 cm over a 30-day period. She remained non-weight bearing throughout the distraction phase. After achieving correction, the external fixation was locked in place for 1 month. The patient then returned to surgery for insertion of distal interlocking screws and frame removal. After surgery, the patient attended physical therapy sessions and was partial weight bearing as tolerated. Eight weeks after external fixation removal, the patient achieved full weight-bearing status with a cane.