HIP MORPHOLOGY DEVELOPMENT FROM CHILDHOOD TO YOUNG ADULTHOOD

Hip morphology is marked as important risk factor for the development of hip OA in relatively young individuals. There may be unknown morphological factors that provide insight into the development of specific hip morphologies and, in the long term, contribute to the prevention of hip OA since limited effective preventative strategies currently exist. A step towards understanding hip morphology development and related risk factors is to create growth models to quantify morphological development.

This study aimed to create a growth model for hip morphology from childhood to young adulthood in males and females separately.

Data from the Generation R Study were used, a population-based cohort of participants examined around ages 6, 9, 13 and 18 years. We selected participants with high-resolution anteroposterior (AP) dual-energy x-ray absorptiometry (DXA) of the right hip at three or four timepoints. In total, 1610 participants were included. Hip shape was described with 36 landmarks outlining the acetabular roof, teardrop, femoral head and neck using the software Bonefinder®. The radiological landmarks could be identified at all timepoints. With the same software, the statistical shape model (SSM) was created to quantify hip morphology in the population. Linear mixed-effects models were used to describe the longitudinal changes in shape related to sex assigned at birth and age. All shape modes explaining at least 2% of the total variation in shape within our population were analyzed.

A total of 5141 observations were included, of which 3881 from participants with three timepoints, and 1260 from participants with four timepoints. Six shape modes explained 85% of the total variation and were analyzed. All shape modes showed a relationship with age and linear mixed-effects models improved by incorporating interaction with sex assigned at birth. Shape modes 1 - 3 (SM1, SM2, SM3) were highlighted in Figure 1. The first shape mode shows the largest change (in SDs) over time and could be partially interpreted as calcification of the femoral head over time (Fig. 1: SM1). Shape mode 2 shows the femoral head sphericity, possibly related to the calcification, and relative femoral head size compared to the acetabulum (Fig. 1: SM2). Shape mode 3 shows variation in the coverage and lateral neck junction shape (Fig. 1: SM3).

This exploratory study provides insight into the morphological development of the hip joint from childhood to young adulthood, describing the development of the entire hip joint with age. The model could be used to identify potential developmental risk factors related to hip morphology, which may be relevant for the early detection and prevention of hip morphologies related to hip OA.