Dunn View Alpha Angle More Useful Than Femoral Head-Neck Offset to Predict Acetabular Cartilage Damage in Patients With Femoroacetabular Impingement Syndrome Undergoing Hip Arthroscopy

Abstract

Purpose: To identify radiographic measurements and demographics that are predictive of acetabular cartilage damage in patients with femoroacetabular impingement syndrome (FAIS) undergoing hip arthroscopy. More specifically, to compare the predictive value of alpha angle and femoral head-neck offset, as measured on Dunn view radiographs, in determining the preoperative likelihood and severity of acetabular cartilage damage.

Methods: Patients were included if they underwent primary hip arthroscopy for FAIS between February 2008 and June 2020. Exclusion criteria were prior ipsilateral hip conditions, Tönnis grade of osteoarthritis >1, unwilling to participate, missing intraoperative, demographic or radiographic variables of interest, and lateral center-edge angle (LCEA) >40° or ≤25°. Fourteen variables were assessed in a bivariate comparison and analyzed in a multivariate logistic model. The Acetabular Labrum Articular Disruption (ALAD) and Outerbridge (OB) classifications were used to define acetabular cartilage defects. Those without damage or those with mild acetabular cartilage damage belonged to the ALAD/OB ≤2 group and those with severe damage belonged to the ALAD/OB ≥ 3 group.

Results: A total of 1485 patients were analyzed, including 1038 patients with ALAD/OB ≤2 and 447 patients with ALAD/OB ≥3. There was a greater proportion of males in the ALAD/OB ≥3 group (64.21% vs 25.82%; P <.001). The multivariate logistic regression selected age, sex, anterior center-edge angle (ACEA), and alpha angle. Every additional degree in the alpha angle was associated with a 6% increase in the odds of severe acetabular cartilage damage (odds ratio [OR], 1.06 [95% confidence interval [CI], 0.12-8.11]). The multivariate analysis did not identify femoral head-neck offset as a predictor. The odds of severe acetabular cartilage damage were 3.73 times higher in males than females (OR, 3.73 [95% CI, 0.01-1705.96]). Higher age was found to increase the likelihood of ALAD/OB ≥3 (OR, 1.04 [95% CI, 0.13-7.75]).

Conclusions: In a multivariate analysis, factors identified as preoperative predictors of acetabular cartilage damage in patients with FAIS were age, sex, ACEA, and alpha angle. Femoral head-neck offset was not predictive, suggesting that Dunn view alpha angle may take precedence as a predictor of acetabular cartilage damage.

Level of evidence: Level III, cohort study.