Posterior acetabular uptake on ¹⁸F-fluoride positron emission tomography/computed tomography reveals a putative contrecoup region in patients with femoroacetabular impingement.

Abstract

The pathology of the posterior acetabular lesions, so-called "contrecoup regions", in femorocacetabular impingement (FAI) has not been elucidated fully. ¹⁸F-fluoride positron emission tomography/computed tomography (PET/CT) can visualize abnormal uptake caused by impingement. Therefore, we aimed to evaluate posterior acetabular uptake on PET/CT in FAI patients. Patients with FAI who underwent ¹⁸F-fluoride PET/CT between October 2014 and October 2016 were retrospectively evaluated. The maximum standardized uptake value (SUV_max) in the posterior acetabulum was evaluated. The mean SUV_max of FAI with cam morphology (the cam group) was compared with that of FAI with pincer morphology (the pincer group). In addition, the numbers of cases with SUV_max ≥ 6 and SUV_max < 6 in each group were evaluated. The entire study cohort was also grouped according to SUV_max, and the mean <i>α</i> and center edge angles were evaluated. In total, 41 hips were analyzed (34 hips in the cam group and 7 in the pincer group). The mean SUV_max of the cam group (11.2 ± 7.4) was significantly higher than that of the pincer group (4.9 ± 1.9) (<i>p</i> < 0.01). The incidence of cases with SUV_max ≥ 6 in the cam group was significantly high (<i>p</i> < 0.01). In the overall cohort, the mean <i>α</i> angle of the SUV_max ≥ 6 group was significantly higher than that of the SUV_max < 6 group (<i>p</i> < 0.01). Evaluation of posterior acetabular uptake suggests an association between cam morphology and increased posterior acetabular uptake.