PREVALENCE OF ACETABULAR DYSPLASIA IN 6-YEAR-OLDS IN A GENERAL POPULATION

Abstract

INTRODUCTION

Acetabular dysplasia (AD) is an important risk factor for early hip OA in adults. In Europe, infants are screened for developmental hip dysplasia. However, AD can also develop during skeletal maturation and these cases often remain unrecognized. Potentially, AD could be influenced prior to the closure of the hip growth plates. Understanding AD development during growth is crucial to prevent future joint degeneration. Different definitions are used to measure AD, depending on the stage of skeletal maturation. More knowledge of the prevalence of AD in the general population is required to understand its development during growth.

OBJECTIVE

1) To estimate the prevalence of AD in 6-year-olds from the general population, and 2) to compare different AD definitions in this age group.

METHODS

Data from The Generation R Study, a population-based study examining growth and health from fetal life to adulthood, was used. All participants aged 6 years, with high-resolution dual-energy x-ray absorptiometry (DXA) anteroposterior image of the right hip available were included. The hip shape was outlined with 70 landmarks using BoneFinder®. Using these landmarks, the acetabular index (AI), a measurement of acetabular roof inclination, was calculated to assess AD (AI>20°). While AI is commonly used in children, the lateral center-edge angle (LCEA), as indicator for acetabular roof coverage of the femoral head, was also calculated. Mean LCEA and prevalence of AD (LCEA<15°) were compared to measures using AI.

RESULTS

In total, 3,270 participants were included with a mean age of 6.2 (SD 0.6) years, and 51% was female. The mean AI was 11.3° (SD 5.0°) and the mean LCEA was 19.5° (SD 5.9°). The distribution for both AD definitions is shown in Figure 1. An AI>20° was found in 124 participants, indicating a AD prevalence of 3.8% (95%CI, 3.1% - 4.5%). Based on the LCEA, the AD prevalence was 21.3% (95%CI, 19.9% - 22.7%).

CONCLUSION

The prevalence of AD in 6-year-olds is 3.8%, based on the AI. The LCEA classifies more hips as dysplastic in 6-year-olds. The validity of the LCEA in this age group and clinical relevance of these newly classified dysplastic hips need to be determined. A better understanding of the development of AD is important, as recovery during growth may be feasible and could contribute to the prevention of OA.