Background

Hip dysplasia is characterized by joint instability and progression to osteoarthritis. The lateral center-edge angle (LCEA) is a radiographic measure of acetabular coverage where <18 is diagnostic of dysplasia and 18-25 indicates borderline dysplasia. Borderline hip dysplasia is difficult for hip preservation surgeons because some patients have hip instability that requires periacetabular osteotomy (PAO) for treatment, whereas others have impingement that can be treated with arthroscopy alone. No single standard exists to determine whether borderline dysplastic patients should undergo arthroscopy or PAO.

Objective

To describe new measures of acetabular wall intersection with the sorcil – anterior (WiSA) and – posterior (WiSP) and identify whether these measures predicted surgical management of patients with borderline dysplasia upon retrospective review of prospectively collected registry data.

Methods

This retrospective study consisted of 256 hips (n=241 arthroscopy, n=15 PAO) with borderline dysplasia that were surgically treated between October 2017 and June 2022. LCEA (red), acetabular wall intersection with the sorcil – anterior (WiSA; yellow) and – posterior (WiSP; cyan) were measured on preoperative AP pelvis radiographs. Univariate logistic regressions estimated the predictive power of the measures for surgical management using odds ratios and ROC curves.

Results

Compared to arthroscopy patients, average LCEA, WiSA, and WiSP were lower in the PAO cohort (p<0.0001; p=0.0004; p=0.0131). A 1 increase in WiSA decreased the odds of PAO by 17% (OR=0.83; 95% CI, 0.75-0.93). A 1 increase in WiSP decreased the odds of PAO by 10% (OR=0.90; 95% CI, 0.82-0.98). LCEA and WiSA were strong discriminators between the arthroscopy and PAO cohorts (AUC=0.851 and 0.789 respectively).

Conclusions

WiSA and WiSP measured retrospectively on preoperative radiographs predicted whether the patient underwent hip arthroscopy or PAO. WiSA and WiSP are novel measurements that can further delineate the gray area of borderline dysplasia and help determine whether an arthroscopy or PAO is the preferred treatment.