[Prospective study on natural evolution of 99mTc-MDP bone scan in asymptomatic total hip arthroplasty]

Natural history of bone scan in forty three patients (55 joints) with asymptomatic total hip arthroplasty was evaluated. Bone uptake of 99mTc-MDP in regions of the acetabulum and femoral shaft, except the marginal acetabulum, became normal on one year post-operation. Radiographic detection of clear zone between bone and cement interface was common and increased with time after the arthroplasty. The post-operative natural change observed by radiography and scintigraphy at the site of the roof of acetabulum was statistically significant (p less than 0.01) by the chi-square test. This may imply that differentiation of true mechanical loosening from asymptomatic natural change at the site of the acetabulum in total hip arthroplasty is difficult. Our results presented here may help diagnosis of delayed complications in total hip replacement by bone scan.