Metabolic development of necrotic bone in the femoral head following resurfacing arthroplasty

BACKGROUND AND PURPOSE One concern regarding resurfacing arthroplasty is the viability of the diminished femoral head and the postoperative risk of collapse, or a femoral neck fracture. (18)F-fluoride positron emission tomography (F-PET) enables us to assess bone viability despite there being a covering metal component. By F-PET studies, we recently showed the absence of metabolism in the remaining part of femoral heads, 1-4 years after surgery in 11 of 46 consecutive cases. We now present the further development of bone metabolism in these 11 cases. PATIENTS AND METHODS 10 patients (11 chips) with previously shown loss of femoral head metabolism were evaluated by radiography and repeated F-PET scans, 3-6.5 years after surgery. The size of the area with low (18)F-fluoride PET uptake in the femoral head was compared to that in earlier PET images. RESULTS No patients had any clinical symptoms; nor was any necrotic bone area visible in plain radiographs. On F-PET scans, 2 patients showed a diminished area with low uptake, 4 were unchanged, and 5 had enlarged areas. INTERPRETATION Bone metabolism surrounding a volume of bone with no metabolic activity changes dynamically even 5 years after surgery. The presence of bone with minor uptake of F-tracer, indicating low or no bone metabolism, with further progression in 5 of 11 cases leads us to conclude that resurfacing THA should be used restrictively.