Measurement of bone density around total knee arthroplasty using fan-beam dual energy X-ray absorptiometry.

The clinical survival of joint arthroplasties is clearly associated with the quality of surrounding bone environment. Bone mineral density (BMD) is an important measure of bone strength and quality. Periprosthetic BMD can be measured by using dual-energy X-ray absorptiometry (DXA) with special software algorithms. We studied short-term reproducibility of the periprosthetic BMD measurements after total knee arthroplasty (TKA) in 30 patients with primary osteoarthrosis. The operated knees and the contralateral control knees were measured twice and the results were expressed as a coefficient of variation (CV%). The average precision error was 3.1% in femoral regions of interest (ROI) and 2.9% in tibial ROIs after TKA. In the prosthesis-free control knees, CV% were similar; 3.2% and 2.5%, respectively. The best precision was found in the femoral diaphyses above the implant (1.3%), whereas the least reproducible BMD was determined in the patellar region of the TKA knees (6.9%). Our results confirm that DXA measures precisely small bone mineral changes around TKA and makes it possible to follow bone remodeling DXA and may provide a feasible method for monitoring TKA in the future.