Morphological features of the acetabulum with coxa profunda in women: a retrospective observational study

TL;DR

This study examines the acetabular morphology in women with coxa profunda, revealing differences in acetabular structure that suggest a link to acetabular dysplasia rather than pincer-type hip issues.

Contribution

The study reclassifies coxa profunda as a sign of acetabular dysplasia, impacting hip arthroplasty approaches.

Findings

Coxa profunda is associated with increased acetabular anteversion and thinner acetabular walls.

The ilioischial line is positioned more posteriorly in coxa profunda cases.

Findings suggest coxa profunda reflects acetabular dysplasia rather than excessive coverage.

Abstract

The morphology of coxa profunda remains inadequately understood. However, knowledge about the characteristics of the acetabulum in coxa profunda can help to predict pelvic morphology in three dimensions based on radiographic findings, as well as help to diagnose and predict hip pathologies. Therefore, this study aimed to investigate the relationship between the morphological characteristics of the pelvis and coxa profunda.

We conducted a retrospective analysis including women who had undergone unilateral total hip arthroplasty. Only those with normal hip joint morphology on the opposite side, as evidenced by anteroposterior pelvic radiography showing a distance of ≥ 2 mm between the ilioischial line and acetabular floor, were included. Five parameters related to acetabular anteversion, thickness, and the position of the ilioischial line were measured using axial computed tomography at the central hip joint. The coxa profunda group (n = 39) and control group (n = 34) were compared.

The mean acetabular anteversion angle was 12.5° ± 4° in the control group and 22.3° ± 5.6° in the coxa profunda group. The mean thickness from the acetabular fossa to the medial wall was 7.5 ± 1.7 mm in the control group and 3.9 ± 1.2 mm in the coxa profunda group. Furthermore, the bony region representing the ilioischial line was positioned more posteriorly in the coxa profunda group than it was in the control group.

Our findings suggest that coxa profunda in women is associated with anterior acetabular dysplasia and a thin acetabulum, in contrast to previous interpretations of excessive coverage. This insight suggests a conversion of coxa profunda from a finding of pincer-type femoroacetabular impingement to a finding of acetabular dysplasia, a revelation that also draws attention to cup positioning for total hip arthroplasty.

The online version contains supplementary material available at 10.1186/s12891-024-07540-9.

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