Acetabular dysplasia and development of hip osteoarthritis within 10 years; a nationwide prospective cohort study (check)

Purpose: Attempts to relate acetabular dysplasia (AD) to the development of hip osteoarthritis (OA) have yielded conflicting results. Previous results from the Cohort Hip and Cohort Knee (CHECK) study showed an up to 6-fold increased risk of developing hip osteoarthritis within 5 years when AD was present at both the anterior and lateral rim. We now determined the relationship between anterior and lateral AD at baseline and the risk of developing radiographic hip OA within 10 years of follow-up, using data from the prospective CHECK cohort. Methods: CHECK is a prospective, nationwide cohort study of 1002 participants (2004 hips) aged 45-65 (mean 55.9 years). Inclusion criteria were: pain or stiffness in the knee or hip, and no earlier consultation for these complaints or a first consultation with a general practitioner within 6 six months for these complaints before entry. Standardized anteroposterior (AP) and false profile (FP) pelvic radiographs were taken at baseline and at the 10-year follow-up visit. Acetabular coverage is usually only quantified on AP pelvic radiographs by the Lateral Center Edge Angle (LCEA), which determines acetabular coverage on the lateral side. However, the quantification of anterior coverage is also essential, since only considering the LCEA leads to an underestimation of AD. We therefore also quantified the anterior acetabular coverage on a false profile (FP) view using the Anterior Center Edge Angle (ACEA). AD was defined as an LCEA and/or ACEA <25° on either the AP or FP view. Sensitivity analyses were conducted using a threshold of <20° on either the AP or FP view. Development of incident hip OA was defined by Kellgren & Lawrence (K&L) grade ≥2 or total hip replacement (THR) at 10-year follow-up. End-stage OA was defined by a K&L grade ≥3 or THR). Of the initial 2004 hips, 354 hips did not have KL grading at 10 years follow-up (lost to follow-up or missing radiographs), 207 hips had a baseline K&L grade of >1 at baseline, of 176 hips AP hip views were obtained instead of AP pelvic views and on 111 baseline hips the LCEA and/or ACEA could not be reliably determined. This leaves 1156 hips for the current analyses. The associations between baseline AD and development of hip OA within 10 years were estimated using logistic regression with generalized estimating equations and expressed as odds ratios (OR). All estimates were adjusted for age, sex, BMI and baseline K&L grade (0 or 1). Results: Of the included participants (82% female), the mean age was 55.7 (±5.2) years and mean BMI 26.2 (± 4.1) at baseline. At baseline, 75% of the included hips had no signs of radiographic OA (K&L=0), whereas 25% had doubtful OA (K&L=1). Within 10 years, 496 hips (43%) developed incident OA and 61 hips (5%) developed end-stage OA. Acetabular dysplasia was not associated with either incident OA nor end-stage OA. This was true for all definitions of AD (defined on the AP view only, on the FP only and the combination of AD on both the AP and FP view) and for both the <20° and <25° threshold. Conclusions: Baseline AD was not associated with the development of hip OA at 10 years follow-up in the CHECK cohort. As previous results in the same cohort showed a consistent association between AD and development of hip OA within 5 years, it appears that AD is a risk factor for rapid development of hip OA while people might develop hip OA on a longer term due to other causes.