Three-dimensional Patterns of Early Acetabular Cartilage Damage in Hip Dysplasia; a High-resolutional CT Arthrography Study

Objective: The purpose of this study was to examine the three-dimensional (3D) progression patterns of early acetabular cartilage damage in hip dysplasia using high-resolutional computed tomography (CT) arthrography.

Design: Thirty-two dysplastic hips of 26 Japanese symptomatic females including 21 hips in pre-stage of osteoarthritis (Kellgren-Lawrence (K-L) grade 0; mean patient age, 32.0 years) and 11 hips in early stage of osteoarthritis (K-L grade 1 or 2; mean patient age, 32.8 years) were examined. Isotropic high-resolutional CT arthrography with an image resolution of 0.5 mm in any orthogonal direction was performed. A 3D acetabular cartilage model was generated and we evaluated distribution of cartilage thickness in 12 zones after dividing the weight-bearing area of the hip joint in radial and lateral/medial directions.

Results: In pre-stage of osteoarthritis, significant differences in cartilage thickness were observed between the lateral and medial zones in all radial regions, most prominently in the antero-superior region. In early stage of osteoarthritis, no significant differences in cartilage thickness were observed, except in the most posterior region. The lateral-medial (LM) ratio was defined as cartilage thickness in the lateral zone divided by that in the medial zone, and hips with the LM ratio in the antero-superior region of <1.4 had significantly more extensive involvement of labral tears than hips with the LM ratio of ≥1.4.

Conclusions: In hip dysplasia, acetabular cartilage damage was probably occurred in the antero-superior lateral area. The LM ratio may be a sensitive index to quantify early cartilage damage associated with extent of labral disorders.