Hip Shape as a Predictor of Osteoarthritis Progression in a Prospective Population Cohort.

OBJECTIVE: Hip morphology plays a significant role in the incidence and progression of hip osteoarthritis (OA). We hypothesized that hip shape would also be associated with other key factors and tested this in a longitudinal community-based cohort combining radiographic, magnetic resonance imaging (MRI), dual-energy x-ray absorptiometry (DXA), and clinical data. METHODS: Baseline DXA images of the left hip of 831 subjects from the Tasmanian Older Adult Cohort were analyzed using an 85-point statistical shape model. Hip pain was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index, and muscle strength was measured using a dynamometer. Hip structural changes were assessed using MRI and radiographic OA using plain radiographs. RESULTS: Six shape modes accounted for 68% of shape variation. At baseline, modes 1, 2, 4, and 6 were associated with radiographic hip OA; modes 1, 3, 4, and 6 were correlated with hip cartilage volume; and all except mode 2 were correlated with muscle strength. Higher mode 1 and lower mode 3 and mode 6 scores at baseline predicted hip pain at followup and higher mode 1 and mode 2 scores were associated with hip effusion-synovitis. Higher scores for mode 2 (decreasing acetabular coverage) and lower scores for mode 4 (nonspherical femoral head) at baseline predicted 10-year total hip replacement (THR), while mode 4 alone was correlated with bone marrow lesions (BMLs), effusion-synovitis, and increased cartilage signal. CONCLUSION: Hip shape is associated with radiographic OA, THR, hip pain, effusion-synovitis, BMLs, muscle strength, and hip structural changes. These data suggest that different shape modes reflect multiple facets of hip OA.

Correlates of Hip Cartilage Defects: A Cross-sectional Study in Older Adults.

OBJECTIVE: Knee cartilage defects are a key feature of osteoarthritis (OA) but correlates of hip defects remain unexplored. The aims of this cross-sectional study were to describe the correlates of hip cartilage defects. METHODS: The study included 194 subjects from the Tasmanian Older Adult Cohort who had right hip short-tau inversion recovery magnetic resonance imaging (MRI). Hip cartilage defects were assessed and categorized as grade 0 = no defects, grade 1 = focal blistering or irregularities on cartilage or partial thickness defect, and grade 2 = full thickness defect. Hip pain was determined by Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Hip structural changes were measured on MRI, and hip radiographic OA (ROA) was assessed. Leg strength and physical activity were assessed using dynamometer and pedometers, respectively. Data were analyzed using log binomial and linear regression. RESULTS: Of 194 subjects, 24% (n = 48) had no defects, 34% (n = 66) had grade 1, and 41% (n = 80) had grade 2. In multivariable analyses, any hip defects were associated with greater hip pain [prevalence ratio (PR) 1.20, 95% CI 1.02-1.35] and lower mean leg strength (men; mean ratio 0.83, 95% CI 0.67-0.98). Grade 1 defects were associated with hip bone marrow lesions (BML; PR 1.42, 95% CI 1.03-1.96) and high cartilage signal (men; PR 1.84, 95% CI 1.27-2.70), but not with hip pain or other structural findings. Grade 2 defects were associated with greater hip pain (PR 1.40, 95% CI 1.09-1.80), hip BML (PR 1.45, 95% CI 1.15-1.85), hip effusion cross-sectional area (PR 1.14, 95% CI 1.01-1.30), hip ROA (men; PR 1.60, 95% CI 1.13-2.25), and steps/day (PR 0.97, 95% CI 0.96-0.99). CONCLUSION: Grade 2 defects in both sexes and grade 1 defects (mostly in men) are associated with clinical, demographic, and structural factors relevant for OA. Damage to the hip cartilage could be one of the major causes of rapid disease progression and pathophysiology of hip defects. The topic needs further study.