Uptake of Tc-99m-MDP after uncemented hip arthroplasty - A quantitative analysis of findings around the femoral component in asymptomatic patients

We studied the pattern of Tc-99m-methylene diphosphonate uptake around uncemented femoral components in 44 asymptomatic hip arthroplasties, performing isotope scans at intervals from 4 to 48 months after operation, We used phase-HI images obtained with a high-resolution gamma camera and measured the activity in various zones using a specially designed computer program, The components studied at 4, 6, 9 and 12 months were coated with hydrogyapatite (HA) and those studied at 18, 24, 36 and 48 months were not coated. We found a statistically significant fall in activity between four and six months around HA-coated prostheses in all five femoral periprosthetic zones, After six months activity was relatively uniform, but remained higher than that in normal femoral bone at 48 months in non-coated prostheses, We discuss the application of these patterns in the evaluation of painful cementless hip arthroplasties.