The relationship between postoperative results and bone dynamics in RA patients who underwent cementless Ortholoc II TKA: histomorphometric study

Abstract

We previously reported a histomorphometric study of iliac bone obtained at the time of cementless total knee arthroplasty (TKA) in patients with rheumatoid arthritis (RA). In this paper, we further extended our analysis to investigate the postoperative results and radiographs after TKA in association with bone metabolism. All the patients were female, ranging in age from 38 to 68 years (mean, 56.8 years). Histomorphometric results demonstrated that bone volume and trabecular thickness were decreased, whereas bone absorption and bone formation rate (BFR) were increased. The bone in patients with mutilating disease (MUD) showed remarkably increased bone turnover and osteoporosis compared with those of the more erosive subset (MES) patients. Sixteen out of the 20 patients were alive at the time of follow-up (follow-up period between 5 years 10 months and 8 years 11 months). Among them, 10 patients could be further examined. Radiolucent lines (RLL) were assessed by the modified Knee Society evaluation (scoring) system. The number of RLL (N-RLL) were correlated with BFR in morphometric examination. In addition, the weight-bearing zones in the N-RLL were more significantly correlated with BFR. The Japanese Orthopedic Association (JOA) score and pain score negatively correlated with eroded bone surface. The present study indicated that bone dynamics, rather than the bone volume at the time of TKA, were involved in the presence of RLL and in pain after surgery for TKA.