PERIPROSTHETIC BONE TURNOVER AFTER PRIMARY TOTAL HIP ARTHROPLASTY MEASURED BY SINGLE-PHOTON EMISSION COMPUTED TOMOGRAPHY

Background and Aims: Alterations in periprosthetic bone are common sequlae of prosthetic implants. This prospective 3-year study was performed to follow regional periprosthetic bone turnover after uncomplicated total hip arthroplasty (THA) using single-photon emission computed tomography (SPECT). Material and Methods: Eighteen patients (nine men, nine women: mean age 61 years, range from 50 to 73 years) with primary hip osteoarthritis underwent either uncemented or cemented THA. The SPECT measurements were taken 6, 12, and 36 months after THA. Bone mineral density (BMD) measurements were performed on the patients during follow-up. Results: The mean SPECT uptake ratios decreased significantly in the regions of interest (ROIs) during follow-up compared to baseline value, in the trochanter major (p = 0.006), the trochanter minor (p = 0.009) and the total area (p = 0.018). Despite these decreases the uptake ratios in the medial cortex (p = 0.014), tip (p = 0.002) and total area (p = 0.016) remained significantly higher in the operated side than in the contralateral side (non-operated) 3 years after THA. Changes in bone turnover in the vicinity of the implant did not correlate with changes in periprosthetic BMD. Conclusions: Local periprosthetic bone turnover decreased slowly after THA and did not recover to the level typical of non-operated hips. This led us to suggest that bone turnover around the femoral implants remains increased more than 3 years after THA even if there are no signs of failure of the prosthesis.