Conversion of failed unicompartmental knee arthroplasty to TKA.

UNLABELLED: As the number of unicompartmental knee arthroplasties performed continues to rise, so too will the number of failures. In order to justify its continued use, conversion to total knee arthroplasty must be evaluated. From 1993-2004, 22 consecutive knees from 18 patients with a failed unicondylar knee arthroplasty underwent conversion to total knee arthroplasty. The most common modes of failure were polyethylene wear (12 patients), loosening of the femoral (4 patients) or tibial component (3 patients), and osteoarthritis progression (3 patients). All patients were converted to primary cruciate retaining components. Twenty-seven percent of patients had contained defects on the femoral condyle that required bone graft. No femoral stems or metal augmentation were required. Forty-five percent of patients had contained defects on the tibia that required bone graft. Metal wedge augmentation was required in five knees (23%), and stems were used in two patients. Sixteen of 22 knees (73%) were followed for an average of 64.5 months. Knee Society knee scores and functional scores at latest followup were 93 and 78, respectively. Conversion of a failed unicondylar knee arthroplasty to a total knee arthroplasty is technically demanding, but may be done successfully with careful preoperative planning and possible need for revision techniques. LEVEL OF EVIDENCE: Therapeutic study, level IV (case series). See the Guidelines for Authors for a complete description of levels of evidence.