Natural progress of a bone scan after cementless hydroxyapatite-coated total hip arthroplasty

To establish the natural progress pattern of postoperative bone uptake, a p eriprosthetic quantitative technetium-99m methylene diphosphonate scintisca n was done on 80 asymptomatic hips (62 patients) with uncomplicated cementl ess hydroxyapatite-coated total hip arthroplasties and 20 healthy control h ips (10 subjects) without previous surgery. The patients were studied in ei ght groups at scheduled intervals of 1 to 48 months. There were 10 hips in each group. The measurement of bone uptake in the healthy untreated control group indicated that the uptake ratio in the proximal femur was physiologi cally higher in the metaphyseal area than in the diaphyseal area and the up take ratio in the acetabulum. appeared to be much higher than that of the p roximal femur. In the patient group, the uptake ratio around the femoral st em area and the acetabular cup area showed a statistically significant decr ease between 1 and 3 months after surgery and changed little after 3 months . Comparing the result of the patient group with that of the healthy untrea ted control group, the uptake ratio decreased much faster in the hydroxyapa tite-coated metaphyseal zone than in the noncoated diaphyseal zone of the f emoral stem area. In the acetabular cup area, the uptake ratio decreased fa st, as in the hydroxyapatite-coated metaphyseal zone of the femoral stem ar ea. Based on these clinical results, a quantitative bone scan may be a help ful diagnostic procedure for evaluating postoperative progress when used in conjunction with clinical symptoms and radiologic examinations.