抄録
Objective: We performed a retrospective study of total knee arthroplasty (TKA) in rheumatoid arthritis (RA) patients with large bone defects, severe valgus deformities, or severe flexion contractures.
Methods: Between 1999 and 2010, 40 knees in 30 patients underwent primary TKA with stem extension, metal block augmentation, and/or constrained condylar knee (CCK) prosthesis at Kyushu Medical Center. The preoperative diagnosis was RA in all 27 female and three male patients. The mean age at the time of the surgery was sixty-one years old. The mean duration of follow-up was 5.9 years. Three knees received posterior-stabilized TKA (NexGen® LPS or LPS-flex, Zimmer®) with tibial stem extension, 26 knees received posterior-stabilized TKA with tibial metal block and stem extension, and 11 knees received CCK (NexGen® LCCK, Zimmer®).
Results: The average pre- and postoperative knee extension/flexion angles were −15°/111° and −1°/114°, respectively. The pre- and postoperative Japanese Orthopaedic Association scores averaged 44 and 75. According to the Knee Society roentgenographic evaluation, the average α, β, γ and δ angles were 94°, 90°, 1° and 85°, respectively. On average, a 19 mm deep peripheral tibial bone defect was treated with a 9 mm thick metal block and 11 mm thick polyethylene insert, restoring the joint line 11 mm proximal to the fibular styloid. No progressive radiolucency, and no subsidence of components or changes in alignment were observed. The complication rate was 10%. There was one early failure, consisting of a fragile supracondylar femur fracture, which was revised with a femoral stem extension. There were three late failures consisting of a case of knee instability, which required polyethylene insert revision, a case of traumatic supracondylar femur fracture which required an internal fixation, and a case of acute infection which required an intraarticular antibiotic infusion after debridement, while retaining the implant.
Conclusion: Primary TKA in patients with severe deformities due to RA demonstrated favorable clinical outcomes, but a complication rate of up to 10% can be expected at the intermediate-term follow-up.
