Comparative Study of the Acromioglenoid Angle and Critical Shoulder Angle in Assessing the Role of Scapular Morphology in Primary Glenohumeral Osteoarthritis

Introduction Glenohumeral osteoarthritis (GHOA) is a common degenerative shoulder disorder. Individual scapular morphology, including glenoid inclination and acromial extension, has been implicated in shoulder biomechanics and disease risk. This study was conducted to assess the comparative efficacy of acromioglenoid angle (AGA) and critical shoulder angle (CSA) as radiological parameters for predicting GHOA. Methods A cross-sectional observational study was conducted at All India Institute of Medical Sciences, Rajkot, involving 277 shoulder radiographs in true anteroposterior (AP) view. Participants were divided into GHOA and non-GHOA groups based on radiographic findings. Both CSA and AGA were measured independently by two observers using standardized methodology. Statistical analysis included the intraclass correlation coefficient (ICC) for reliability, Pearson correlation for association analysis, and logistic regression for predictive value determination. Results Among 277 shoulders analysed, 158 showed radiographic evidence of GHOA (mean age 65.3 ± 12.4 years; 91 males, 67 females) and 119 were non-GHOA group (mean age 52.1 ± 10.8 years; 62 males, 57 females). Mean CSA was significantly lower in the GHOA group (32.5° ± 2.8°) compared to the non-OA group (36.9° ± 2.3°; t = 13.95, p < 0.001). Similarly, mean AGA was significantly reduced in GHOA patients (44.4° ± 2.7°) versus the non-OA group (50.1° ± 2.8°; t = 17.1, p < 0.001). Strong positive correlation existed between AGA and CSA in both GHOA (r = 0.530, p < 0.001) and non-GHOA groups (r = 0.703, p < 0.001). Conclusions Both AGA and CSA are useful radiological measures for predicting GHOA, and there are statistically significant correlations between them. When measuring from the midglenoid reference point, AGA is a useful addition to CSA for clinical assessment and surgical planning for individuals with GHOA.