Bone scintigraphy in femoroacetabular impingement: a preliminary report.

Femoroacetabular impingement (FAI) has recently been recognized as a cause of hip pain, labral tears, and cartilage damage in young adults. We determined the sensitivity and specificity of bone scans in diagnosing FAI and describe its findings on nuclear imaging. We prospectively followed 25 patients with hip pain (four bilateral) of greater than 6 months' duration and a positive impingement sign (IS). All patients had plain radiographs and a three-phase bone scan followed by single-photon emission computed topographic (SPECT) images of both hips. We presumed patients had FAI if they had all three of the following findings: hip pain, positive IS, and diagnostic radiographs. Forty-six of the 50 hips had bony abnormalities on radiographs and 26 hips were diagnosed with FAI according to our criteria. Twenty-two of these 26 hips showed an increased uptake on SPECT representing true-positives. There were four false-positives, nine false-negatives, and 15 true-negatives. Sensitivity of bone SPECT was 84.7%, specificity 62.5%, positive predictive value 71%, and negative predictive value 78.9%. Focal uptake was localized to the superolateral acetabular rim and/or anterolateral femoral head-neck junction consistent with the reported intra-articular cartilage hip damage seen in FAI.