Abstract
Introduction
This study aims to determine how the acetabular version changes during the key developmental stage of adolescence, and what contributes to this change. In addition, we examined whether patient factors (BMI, activity levels) or the femoral-sided anatomy contribute to any observed changes.
Patients/Materials & Methods
This prospective longitudinal cohort study included 19 volunteers (38 healthy hips). The participants underwent clinical examination (BMI, range of movement assessment), MRIs of both hips at recruitment and at follow-up (6 ± 2 years) and HSS Paediatric Functional Activity Brief Scale (Pedi-FABS) questionnaire. MRI scans were assessed at both time points to determine change of the tri-radiate cartilage complex (TCC), the acetabular anteversion, the degree of anterior, posterior, and superior femoral head coverage by the acetabulum, and anterior and antero-superior alpha angles. We investigated if the change in anteversion and sector angles was influenced by the BMI, range of movement measurements, the Pedi-FABS or the alpha angle measurements.
Results
At the baseline MRI, all hips had a Grade I (open) TCC; the TCC was Grade III (closed) by follow-up MRI in all of the hips. The acetabular anteversion increased moving caudally further away from the roof for both time-points. The mean anteversion increased from 7.4° ± 3.8 to 12.2° ± 4 (p < 0.001). The increase in version occurred universally on the acetabulum but was greatest at the rostral ¼ of the acetabulum. The change in version did not correlate with any of the patient factors tested (p = 0.1–0.6).
Discussion
The native acetabulum orientation changes around adolescence, with the version significantly increasing as a result of a reduction of the femoral head coverage anteriorly. Disturbance of this process would lead to pathology contributing to pincer or retroversion FAI.
Conclusion
Further study of greater power is needed to provide further insight into association between version and patient factors.
