Cam morphology and the risk of developing radiographic hip osteoarthritis within 8 years: an individual participant data meta-analysis from the world coach consortium
Jinchi Tang, Fleur Boel, Michiel M. van Buuren, Noortje S. Riedstra, Myrthe A. van den Berg, Harbeer Ahedi, Vahid Arbabi, Nigel Arden, Sita Bierma-Zeinstra, Cindy Boer, Flavia Cicuttini, Timothy F. Cootes, Kay M. Crossley, David Felson, Willem Paul Giellis, Josh Heerey, Graeme Jones, Stefan Kluzek, Nancy E. Lane, Claudia Lindner, John A. Lynch, Joyce v. Meurs, Andrea Mosler, Amanda E. Nelson, Michael Nevitt, Edwin Oei, Jos Runhaar, Harrie Weinans, Rintje Agricola
DOI: https://doi.org/10.1016/j.joca.2024.02.386
Purpose (the aim of the study):
Bony hip morphology has been identified as an important risk factor for the development of hip osteoarthritis (HOA). One of the strongest bone shape related risk factors for radiographic HOA (RHOA) is cam morphology. This bony prominence at the anterolateral aspect of the femoral head–neck junction results in a non-spherical femoral head shape. However, current knowledge of cam morphology and HOA development comes from single cohort studies. Limiting generalizability to the broader population. This study aims to assess the strength of the association between cam morphology at baseline and the risk of incident RHOA development within 8 years follow-up, using individual participant data from the Worldwide Collaboration on OsteoArthritis prediCtion for the Hip (World COACH consortium).
Methods:
The World COACH consortium is an international collaboration comprising nine prospective cohort studies worldwide. For the present study we included cohorts with anteroposterior (AP) radiographs (of hip, pelvis or full-limb) both at baseline and follow-up visit between 4-8 years. Baseline cam morphology was classified by the alpha angle with a common and widely accepted threshold value of ≥60°. The alpha angle was uniformly calculated using in-house built software through a set of automatically placed landmark points using BoneFinder software (Figure 1). Among the cohorts included, radiological indices for RHOA included the Kellgren and Lawrence (KL) classification, the Croft classification, and the atlas of individual radiographic features in osteoarthritis (OARSI atlas). We harmonized these scores into “definitely no OA” (any score 0), “doubtful OA” (any score 1), or “definite OA” (any score≥2 or total hip replacement) and only included hips with definitely no OA (score of 0) at baseline and excluded those with doubtful OA at follow-up. The association between baseline cam morphology and incident definite RHOA development at follow-up was estimated by a logistic regression model with generalized mixed effects with three levels: hip side (left/right), individual, and cohort. The results are expressed as odds ratios (OR), adjusted for age, sex, and body mass index (BMI) at baseline.
Results:
In total, 23,206 hips from seven cohorts were included in this study (Table 1). The participants had a mean age of 61.9 ± 8.8 years and a mean BMI of 27.4 ± 4.5 kg/m2. The prevalence of cam morphology was 10.5% at baseline and the incidence of RHOA was 1.9% within a maximum of 8 years follow-up. Cam morphology was significantly associated with incident radiographic hip OA with an adjusted OR of 1.56 (95% CI 1.07-2.27).
Conclusions:
The odds of developing RHOA within 8 years are 1.56 times higher in hips with baseline cam morphology than in those without. Identifying such high-risk subgroups through a simple measurement on AP radiographs has the potential to better target treatment and prevention of RHOA. Within the World COACH consortium, we plan to further investigate if the observed effect is different in subgroups (e.g., stratified by age and biological sex).
