Quantitative analysis of radiophosphate uptakes in asymptomatic porous-coated hip endoprostheses

A quantitative analysis of the uptake of radiophosphate adjacent to the femoral component of a porous-coated cementless prosthesis was undertaken in asymptomatic patients in order to establish normal temporal changes. The group consisted of 55 patients with 62 arthroplasties of 1.6-49-mo duration. Ratios of the stem, stem tip, greater trochanter, lesser trochanter and calcar, and normal femur to the reference sacroiliac joint were obtained, as well as tip-to-stem, and stem-to-normal femur in unilateral arthroplasties. The ratios remained stable at 12 months and beyond, except for the tip and lesser trochanter. Tip-to-stem and tip-to-sacroiliac joint ratios decreased by 24% and 33%, respectively, between 12 and 49 mo. There was also a decrease in the relative uptakes at the lesser trochanter and calcar in the same time interval. Evidence is given that different designs of prostheses may not have the same normal temporal uptakes of radiophosphate.