Prediction of Hip Development Using Femoral Head Cartilage and Acetabular Cartilage Diameters on MRI Images.

BACKGROUND

Acetabular dysplasia may persist in developmental dysplasia of the hip (DDH), leading to an increased risk of early hip degeneration. This study aimed to identify predictive factors for residual acetabular dysplasia (RAD) in children aged 2 to 5 years using magnetic resonance imaging (MRI).

METHODS

A retrospective study was conducted on 67 hips from 34 patients. The diameters of the femoral head and acetabular cartilages were measured on T2-weighted coronal images, and the difference and ratio of the cartilage diameters were calculated. The outcome measure was the Severin classification at the final follow-up. Patients were divided into 3 groups based on their age at the time of MRI, for additional evaluations.

RESULTS

The mean age at the final follow-up was 13.4 (6.2 to 23.5) years, and the mean age at the MRI was 3.8 (2.4 to 5.9) years. The good and poor outcome groups comprised 48 (72%) and 19 (28%), respectively. The good outcome group had a smaller cartilage diameter difference (4.6±0.9 vs. 6.4±1.4 mm; P <0.05), and larger cartilage diameter ratio (86±3 vs. 82±3%; P <0.05). A cartilage diameter difference of ≥5.5 mm and a cartilage diameter ratio of ≤85% were associated with poor acetabular growth. The difference and ratio of the cartilage diameters was significantly different at all ages at which the MRI was performed. Combining cartilage diameter measurements with radiographic parameters improved predictive accuracy.

CONCLUSIONS

Cases in which the acetabular cartilage diameter was larger than the femoral head cartilage diameter (difference ≥5.5 mm, ratio ≤85%) showed poor subsequent acetabular development. Cartilage evaluation using MRI during childhood, particularly between 3 and 5 years of age, is useful for predicting acetabular development.

LEVEL OF EVIDENCE: Level III-retrospective comparative study.