Quantitative bone scanning after asymptomatic Charnley arthroplasty

To establish the normal pattern of postoperative tracer uptake we performed 73 99mtechnetium methylene diphosphonate scans following primary Charnley hip replacements for arthrosis in 68 patients without clinical, hematological and radiographic complications. The patients were divided into 7 subgroups according to the period, 6-24 months, between surgery and scan. There were 10-12 patients in each subgroup. A high-resolution gamma camera with a large field of view was used. Ratios of uptake in each of 10 peri-prosthetic zones to normal bone were calculated. Femoral uptake was found to decrease in linear fashion from 6 to 12 months after surgery. Thereafter the uptake remained unaltered at levels nearly twice the normal ones in the greater trochanter and nearly 1.5 times in the lesser trochanter, returning to almost normal levels in other zones. Acetabular uptake remained elevated throughout.