Are Rotator Cuff Tears in Anterior Shoulder Dislocation Associated With a High Critical Shoulder Angle? A Retrospective Analysis

Aims This study aims to investigate whether the critical shoulder angle (CSA) could serve as an effective screening tool to predict acute rotator cuff tears in patients with first-time anterior glenohumeral dislocation and to assess the inter- and intra-observer reliability of CSA measurements in this cohort. Methods A review of all patients with a first-time anterior shoulder dislocation was carried out over a 17-month period at Manchester NHS Foundation Trust, across the Wythenshawe Hospital and Manchester Royal Infirmary sites. Three shoulder surgeons independently measured CSA on post-reduction radiographs, and all patients underwent imaging to assess for a traumatic rotator cuff tear (RCT). Statistical analysis was performed using unpaired t-tests and subgroup analysis based on age and rotator cuff tear presence. Inter- and intra-observer reliability was assessed using Cronbach's alpha. Results Sixty-five patients (36 female, 29 male) met the inclusion criteria. Forty-two patients (65%) had a rotator cuff tear detected on further imaging. The mean CSA for the tear group was 38.14° (SD 4.6), and for the non-tear group, it was 37.45° (SD 4.6), with no significant difference (p = 0.5598). Age was significantly higher in the tear group (64.5 years) compared to the non-tear group (58.1 years, p = 0.0225), with a positive correlation between age and the likelihood of sustaining a rotator cuff tear. Inter-observer reliability was found to be "good" (Cronbach’s alpha = 0.8519), while intra-observer reliability was "excellent" (Cronbach’s alpha ≥ 0.9282). Conclusion This study found no significant association between CSA and the incidence of rotator cuff tears following a traumatic anterior shoulder dislocation. However, increasing age was associated with a higher likelihood of sustaining a rotator cuff tear following anterior shoulder dislocation. This study has demonstrated that intra- and inter-observer reliability were excellent and good, respectively. These findings suggest that CSA may not be a reliable screening tool for rotator cuff tears following shoulder dislocation. Larger, standardised studies are needed to further explore this relationship.