Abstract
IntroductionThe mechanism by which obesity increases the risk of hip osteoarthritis is unclear. One possibility may be by mediating abnormalities in bony geometry, which may in turn be associated with early structural abnormalities, such as cartilage defects and bone marrow lesions.MethodsOne hundred and forty one older adults with no diagnosed hip osteoarthritis had weight and body mass index measured between 1990 and 1994 and again in 2009 to 2010. Acetabular depth and lateral centre edge angle, both measures of acetabular over-coverage, as well as femoral head cartilage volume, cartilage defects and bone marrow lesions were assessed with 3.0 T magnetic resonance imaging performed in 2009 to 2010.ResultsCurrent body mass index, weight and weight gain were associated with increased acetabular depth and lateral centre edge angle (all P ≤ 0.01). For every 1 mm increase in acetabular depth, femoral head cartilage volume reduced by 59 mm3 (95% confidence interval (CI) 20 mm3 to 98 mm3, P < 0.01). Greater acetabular depth was associated with an increased risk of cartilage defects (odds ratio (OR) 1.22, 95% CI 1.03 to 1.44, P = 0.02) and bone marrow lesions (OR 1.29, 95% CI 1.01 to 1.64, P = 0.04) in the central region of the femoral head. Lateral centre edge angle was not associated with hip structure.ConclusionsObesity is associated with acetabular over-coverage. Increased acetabular depth, but not the lateral centre edge angle, is associated with reduced femoral head cartilage volume and an increased risk of cartilage defects and bone marrow lesions. Minimising any deepening of the acetabulum (for example, through weight management) might help to reduce the incidence of hip osteoarthritis.
Highlights
The mechanism by which obesity increases the risk of hip osteoarthritis is unclear
Increasing acetabular depth was associated with increased body mass index (BMI) (β = 0.22 mm, 95% confidence interval (CI) 0.05 to 0.38 mm, P < 0.01) and body weight (β = 0.08 mm, 95% CI 0.02 to 0.14 mm, P = 0.01) after adjusting for potential confounders
We have demonstrated that increased weight and BMI, as well as weight gain, are associated with acetabular over-coverage, as measured by both acetabular depth and the lateral centre edge angle (LCEA)
Summary
The mechanism by which obesity increases the risk of hip osteoarthritis is unclear. The exact mechanism by which obesity mediates OA at weight-bearing joints such as the hip is unclear. FAI occurs when either a non-spherical femoral head compacts the acetabular rim (cam deformity) [15], or acetabular over-coverage limits the range of movement of the hip joint Teichtahl et al Arthritis Research & Therapy (2015) 17:112 deformity) [9] or when cam and pincer deformities coexist. In these instances, abnormal bone geometry between the femoral head and acetabulum is thought to mechanistically account for cartilage damage [16,17]. Whether the association between obesity and risk of hip OA might be partly explained by an influence on bone geometry has not previously been examined
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