EVALUATION OF PERIPROSTHETIC BONE USING DUAL-ENERGY X-RAY ABSORPTIOMETRY - PRECISION OF THE METHOD AND EFFECT OF OPERATION ON BONE-MINERAL DENSITY

To assess the perioperative bone loss of femur during total hip arthro plasty (THA), periprosthetic bone mineral density (BMD) of the seven r egions of interests (Gruen zones) was determined with dual-energy x-ra y absorptiometry (DXA) preoperatively in both proximal femurs and post operatively in the involved side in 53 patients with degenerative hip osteoarthrosis. The mean (standard deviation, SD) precision error (coe fficient of variation percent, CV%) in various regions of interest (RO Is) based on two consecutive measurements (n = 16), were 2.3 (0.8)%, 2 .5 (1.5)%, and 2.8 (1.6)% for uncemented stems, cemented stems, and co ntrol sides, respectively. Furthermore, the mean variability caused by the rotation of femur was 3.5 (1.4)%. The most significant perioperat ive bone loss (13.5-19.2%) was found in the calcar area (zone 7) after noncemented THA, Zone 4, representing the bone below the prosthesis, also showed BMD decreases. These decreases suggest perioperative bone loss owing to rasping and seaming the calcar and bone canal. However, after cemented THA, highly significant BMD increases were found in all the lateral zones. The calcar area was the only site where significan t perioperative bone loss was detected (12.8%). Tn conclusion, DXA is a precise method for quantifying bone mass and density changes in the follow-up of THA. However, when interpreting the results, the preopera tive BMD, differences between the femurs and the effect of operation o n bane mass should be taken into account. We suggest that the best ref erence for BMD follow-up is the periprosthetic BMD of the involved sid e measured soon after the THA.