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Background and purpose One of the main concerns regarding resurfacing arthroplasty is the viability of the remaining part of the femoral head, and the postoperative risk of a femoral neck fracture or collapse. In contrast to radiographic methods, positron emission tomography using the radiotracer [18F]-fluoride (Fluoride-PET) enables us to visualize the viability of bone in the remaining part of the head, despite the presence of the covering metal component.Patients and methods This is preliminary prospective study of 14 patients who underwent an ASR resurfacing arthroplasty. Apart from clinical and radiographic analyses, all patients were analyzed by PET scan 1 week, 4 months, and 1 year after surgery.Results 1 patient had a minor region of osteonecrosis on PET scan at 1 week and at 4 months. After 1 year, the necrosis had increased to include most of the head. 2 other patients, normal at 4 months, had developed equally large osteonecrosis at 1 year. A fourth patient had a minor osteonecrosis at 1 year. None of the patients had clinical symptoms, and the necrotic areas were not visible on plain radiographs.Conclusions We found Fluoride PET to be a sensitive and useful method for evaluation of bone metabolism at resurfacing arthroplasty. 3 of the 14 patients had developed osteonecrosis, involving most of the head at 1 year. The late onset of the phenomenon does not support the hypothesis of surgically damaged vascularity. The presence of this complication together with the lack of visibility on plain radiographs gives reason for concern.

Hip resurfacing (HR) carries attendant risks of avascular necrosis (AVN) and femoral neck fracture. We used fluoride positron emission tomography (PET) scans to analyze bone metabolism 2-5 years after surgery in 35 cases. Three of the patients had been clinical failures. Using PET scans in the remaining 32 cases, 7 were found to have an area of non-viable bone in the femoral head. This was seen following both posterior and antero lateral approaches. Fluoride PET is a sensitive and useful method for evaluating bone metabolism following HR.

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. 18F-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 18F-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.