Summary

Evaluating and grading the hip morphology of patients with borderline dysplasia is crucial since the clinical outcomes differ among the various clusters. Hip arthroscopy produces excellent results for stable anterolateral and lateral deficiency borderline hips.

Abstract

Purpose

The aim of this study was to analyze a cohort with borderline dysplastic hips who were treated by hip arthroscopy to classify specify hip morphology subtypes according to radiographic abnormalities and to report the short-term clinical outcomes of these different clusters.

Methods

Patients with a lateral center-edge angle (LCEA) between 18° and 25° who underwent hip arthroscopy between January 2015 and December 2016 were examined. According to the radiographic parameters, including the LCEA, Femoro-Epiphyseal Acetabular Roof (FEAR) index, anterior and posterior wall index (AWI and PWI), Tönnis angle, alpha angle and femoral neck-shaft angle, a hierarchical cluster analysis was performed to identify the hip morphology subtypes. In addition, the International Hip Outcome Tool-12 (iHOT-12) and a pain visual analog scale (VAS) were applied preoperatively and at follow-up and compared among the different clusters.

Results

A total of 40 patients with an LCEA between 18° and 25° who underwent hip arthroscopy between January 2015 and December 2016 were identified. Thirty-six patients were available for evaluation at a mean follow-up of 43.8 months. In total, 4 different sex-independent clusters with different patterns of hip morphology were identified: cluster 1: the unstable anterolateral deficiency cluster; cluster 2: the stable anterolateral deficiency cluster; cluster 3: the stable lateral deficiency cluster; and cluster 4: the stable posterolateral deficiency cluster. At follow-up, all groups had significantly improved iHOT-12 (p<0.0001) and pain VAS scores (p=0.0001). Within the individual clusters, clusters 2 and 3 showed highly significant improvements, cluster 1 showed significant improvements, and cluster 4 showed no significant improvements.

Conclusion

Evaluating and grading the hip morphology of patients with borderline dysplasia is crucial since the clinical outcomes differ among the various clusters. Hip arthroscopy produces excellent results for stable anterolateral and lateral deficiency borderline hips. In contrast, borderline dysplastic hips with additional acetabular retroversion showed no improvement after arthroscopic therapy.