Aim Obesity and tall stature at skeletal maturity are associated with an increased risk of hip joint replacement, suggesting that skeletal growth and maturation may influence hip joint structure and function in adult life potentially by increasing the risk of acetabular dysplasia. We examine associations between growth in early life and acetabular dysplasia at skeletal maturity in a unique prospective study with follow up from newborn to adult life.
Methods We report data from a population-based prospective follow-up of a two-stage sample of 11,925 newborns recruited to a randomised study of ultrasound imaging to screen for developmental hip dysplasia. Of 4,507 invited 2,338 (51.9%) attended follow-up at age 18 years including an erect pelvic anteroposterior radiograph, 1,846 (79.0%) with at least one previous anthropometric measurement. Radiographic features of hip dysplasia included the acetabular depth-width ratio (ADR). Birth weight and length were obtained from the national birth registry and height and weight measured at ages two, four and seven years from child health clinic records. Body Mass Index (BMI) and sex and age-specific z-scores were calculated. Weighted multivariable regression models were used to evaluate associations between anthropometric distances and velocity z-scores at birth, 2, 4, 7 and 18 years and ADR at 18 years.
Findings For girls (n=1079) higher BMI at maturity was associated with a lower ADR (more acetabular dysplasia): regression coefficient (95% CI) −2.64 (−4.69; −0.59) for one BMI z-score increase. An interaction between birth weight and BMI at maturity (p<0.05) was observed, with the effect of BMI at maturity greater for girls of low birth weight. In multivariable analyses a one z-score increase in BMI between birth and two years and between four years and skeletal maturity were associated with a lower ADR: regression coefficients −3.77 (−6.66; −0.87) and −2.44 (−4.78; −0.10) respectively.
Interpretation Body size growth in childhood is associated with radiologically-defined acetabular dysplasia at skeletal maturity in girls, especially in those of lower birth weight, suggesting an effect on skeletal maturation of early and late catch-up growth. These preliminary findings need confirmation by sensitivity analyses and independent replication in other populations.
Funding Arthritis Research UK ref. 18196; UK Medical Research Council ref GO400546