Functional Pet-Mri in Symptomatic Cam Femoroacetabular Impingement Examining the Crosstalk Between Bone and Cartilage

Cam morphology of the hip may predispose to Femoroacetabular Impingement (FAI) and osteoarthritis (OA). Understanding the biological and functional changes in FAI may provide insight into the early stages of OA and allow for the development of a predictive biomarker. Magnetic Resonance Imaging (MRI) T1ρ mapping gives information on proteoglycan content in hyaline cartilage, while Positron Emission Tomography (PET) allows for functional imaging of bone turnover. In this study, Positron Emission Tomography and Magnetic Resonance Imaging (PET-MRI) were performed simultaneously to analyze bone and cartilage in hips with cam impingement and controls. 3T PET-MRI was used to study two groups: symptomatic cam morphology (n = 24), and healthy controls (n = 18). MRI T1ρ maps were acquired as measures of cartilage proteoglycan content, and 18F-NaF-PET Standard Uptake Values (SUVs) were acquired as measures of bone turnover in the acetabulum and femoral head-neck junction (FHNJ). Patient reported outcome measures (PROMs) were collected using Hip Disability and Osteoarthritis Outcome Score (HOOS), EQ-5D-5L, and the International Hip Outcome Tool (iHOT-33). Kruskal–Wallis, pairwise Wilcoxon tests, and Spearman correlations were used to compare measures between groups. For the symptomatic group, significant positive correlations were observed between T1ρ anterior medial and full anterior cartilage with maximum SUV in several regions of acetabulum and FHNJ, although not strong (−0.6 Increased T1ρ in the symptomatic group indicates early stages of cartilage degeneration in FAI patients. Increased SUV in the symptomatic group indicates active bone remodeling occurring in symptomatic presentations of FAI. The positive correlation between T1ρ and SUV suggest an association of cartilage degeneration and bone remodeling in the symptomatic group. Both measures are associated with worsening pain and quality of life, as demonstrated through the PROMs results. PET-MRI allows simultaneous analysis of bone and cartilage and may be a useful tool for FAI and OA research.