Relationships between cam morphology and [¹⁸F]sodium fluoride PET uptake in asymptomatic hips

Bone deformities are linked to femoroacetabular impingement (FAI) and increased risk of hip osteoarthritis (OA) but are also common in the general population. The purpose of this study is to examine relationships between FAI-linked morphology and resting bone metabolic activity in asymptomatic hips.

This exploratory secondary analysis of hip scans from a [¹⁸F]NaF PET-MRI study on knee pain included 76 asymptomatic hips from 41 individuals (53 ± 13 years, body mass index 25.9 ± 5.1 kg/m2, 21 female/20 male). Hips were evaluated for cam, pincer, and additional morphology with the Hip Osteoarthritis MRI Scoring System. Mean and maximum PET standardized uptake values (SUV) were recorded for the femoral head-neck junction, center of the femoral head, and anterolateral acetabulum. The influence of morphology on SUV_mean and SUV_max was assessed with linear mixed effects models.

Forty-two hips had isolated cam morphology, two had isolated pincer morphology, and four had mixed-type morphology. Cam morphology or alpha angles were not associated with increased bone metabolic activity. Hips with gluteal tendinitis/trochanteric bursitis had significantly higher SUV_max in the center of the femoral head (p = 9.98e-5). No other morphological features were associated with bone metabolic activity, though the low prevalence of features such as pincer morphology limits interpretation of these findings.

In older asymptomatic hips without OA, no association was detected between cam morphology and elevated resting bone remodeling. Understanding structure-function relationships in asymptomatic hips with cam morphology may help contextualize findings associated with pain in patients with FAI or OA.