Body Mass Index Affects Proximal Femoral but Not Acetabular Morphology in Adolescents Without Hip Pathology

Abstract

Higher BMI percentile was associated with increased alpha angle, reduced head-neck offset and epiphyseal extension, and a more posteriorly tilted epiphysis with decreased tilt angle and increased epiphyseal angle. This morphology resembles a mild slipped capital femoral epiphysis deformity and may increase the shear stress across the growth plate, increasing the risk of slipped capital femoral epiphysis development in obese adolescents. BMI percentiles had no association with measurements of acetabular morphology. Further studies will help to clarify whether obese asymptomatic adolescents have higher prevalence of a subclinical slip deformity and whether this morphology increases the risk of slipped capital femoral epiphysis and femoroacetabular impingement development.

Acetabular Retroversion and Decreased Posterior Coverage Are Associated With Sports-related Posterior Hip Dislocation in Adolescents

“…However, higher BMI has been associated with cam morphology resembling a mild slipped capital femoral epiphysis deformity [18] and decreased femoral retroversion [10]. Notably, BMI has been shown to have no impact in the morphology of the acetabulum [18]. We believe that is unlikely that BMI difference observed between the groups would be related to the morphology of the acetabulum and to a higher risk of dislocation in the study group [18].…”

“…Despite our efforts to match patients by BMI, BMI was slightly higher (p = 0.005) in the control group (23 6 2 kg/m 2 ) compared with the study group (19 6 2 kg/m 2 ). Although the difference in BMI could influence the femoral morphology and be a factor indirectly associated with the risk of a dislocation, BMI has no impact on the development of the acetabular morphology [18]. With the numbers available, no difference (p = 0.157) in skeletal maturity assessed by the status of the triradiate cartilage was observed between the groups.…”

“…Although we attempted to match patients based on BMI, BMI was slightly higher in the control group compared with the study group. However, higher BMI has been associated with cam morphology resembling a mild slipped capital femoral epiphysis deformity [18] and decreased femoral retroversion [10]. Notably, BMI has been shown to have no impact in the morphology of the acetabulum [18].…”

“…Notably, BMI has been shown to have no impact in the morphology of the acetabulum [18]. We believe that is unlikely that BMI difference observed between the groups would be related to the morphology of the acetabulum and to a higher risk of dislocation in the study group [18]. Third, our study included a wide range of ages (10-19 years old) to be compliant with the definition of adolescent age by the World Health Organization [29] with a risk of assessing patients with different stages of skeletal maturity.…”

To Explain or to Predict: Important Aspect to Consider Also in Orthopaedics: Letter to the Editor

“…Previous literature has described well that these measures are related to BMI and gender. 3,5 Again, while using alpha angle as an exposure, gender is a confounding variable. But when exposure is gender, alpha angle is a mediator, and this may result in bias when the interest is a single regression coefficient.…”