The paradox of lumbopelvic alignment in anterolateral and posterolateral phenotypes of symptomatic hip dysplasia

Purpose

The relationship between sagittal lumbopelvic alignment and the bony pathomorphology of hip dysplasia is currently at the forefront of clinical and scientific interest. The aim of this study was to determine whether there is a compensatory lumbopelvic aspect associated with the two major acetabular phenotypes in dysplastic hips.

Methods

From September 2022 to March 2024, a total of 145 patients with symptomatic bilateral hip dysplasia were included in the study. Hips were categorized into either anterolateral or posterolateral morphologies based on anteroposterior pelvic x-rays. Additionally, the lumbopelvic sagittal alignment was determined radiographically. Furthermore, a multivariable linear regression analysis was conducted to assess the association of lumbopelvic sagittal alignment with additional independent factors.

Results

Pelvic tilt (PT) significantly differed between the anterolateral and posterolateral phenotypes of hip dysplasia (16.84° ± 8.75° vs. 11.51° ± 6.63°, respectively; p < 0.001). Similar significant findings were observed for pelvic incidence (57.19° ± 12.96° vs. 50.75° ± 13.1°, respectively; p < 0.001). A PT of >14.5° was identified as the most likely factor associated with anterolateral dysplasia.

Conclusions

The results of this study reveal a paradox in the hip–spine association in hip dysplasia. Contrary to previous theories, it seems that PT constitutes a component of the corresponding phenotype of dysplastic pathology, rather than functioning as a compensatory tilt.

Level Evidence

Level III.