Total knee arthroplasty for rheumatoid arthritis patients with large tibial condyle defects.

PURPOSE To review clinical results of total knee arthroplasty (TKA) in rheumatoid arthritis (RA) patients with large bone defects of the tibial condyle. METHODS Records of 33 knees in 27 women and 3 men aged 44 to 80 (mean, 63.6) years who underwent primary TKA for RA with large tibial bone defects were reviewed. 16 knees had peripheral defects extending to the bone cortex, whereas 17 knees had central defects that did not extend to the bone cortex. The femorotibial angle (FTA) was <170º in 15 knees, 170º to 180º in 3 knees, and >180º in 15 knees. The mean duration of RA was 13.5 (range, 3-35) years. In 14 knees with severe bone defects, bone grafts (harvested from articular surfaces of knee bones and fixed without screws or Kirschner wires) and/ or metal wedges (for peripheral defects) were used to fill the defects. Clinical outcome was assessed pre- and post-operatively using Knee Society scores. RESULTS The mean follow-up duration was 6.3 (range, 2.3-13.2) years. The mean depth of tibial bone defects was 11.2 (range, 1-25) mm, whereas the mean width ratio of the bone defects was 36.5% (range, 16.4-76.9%). Mean extension and flexion (range of motion) improved from -12.5º and 113.4º to -5.1º and 115.6º, respectively. The mean Knee Society knee score improved from 35 (range, 21-59) to 85 (range, 49-95), whereas the mean Knee Society function score improved from 30 (range, 25-53) to 80 (range, 44-97) [p<0.001, Wilcoxon signed rank test]. The cruciate retention prosthesis was used in 6 knees; the posterior stabilised prosthesis was used in 27 knees; and the constrained condylar knee prosthesis was used in 3 knees. No patient had any infection or implant loosening. CONCLUSION TKA achieved favourable outcome for RA patients with large tibial bone defects. The type of prosthesis used and the use of bone grafts and/ or metal wedges were based on the depth and width ratio of the bone defects.