Acute, Traumatic Rotator Cuff Tears Have Smaller Critical Shoulder Angles Than Degenerative Tears.

Purpose: To determine whether the critical shoulder angle (CSA) in acute, traumatic rotator cuff tears (RCTs) is consistent with the previously described CSA in chronic degenerative RCTs.

Methods: We performed a multicenter retrospective analysis of 134 patients presenting to 5 surgeons fellowship trained in shoulder and elbow or sports. Preoperative imaging was used to measure the CSA and tear characteristics. Patients were included if they had acute, traumatic full-thickness RCTs documented on advanced imaging and had preoperative Grashey radiographs. Patients were excluded if they had any history of shoulder pain, injury, surgery, or treatment prior to the current episode; were overhead athletes; or had fatty infiltration greater than Goutallier grade 1 on imaging.

Results: The mean CSA was 33.5° (standard deviation, 4.1°), and 60% of tears had a CSA of less than 35°, much below the mean of 38.0° and the threshold of greater than 35° in degenerative RCTs. The mean age was 58 years, and 70% of patients were men. Overall, 60% of tears involved the subscapularis, 49% of tears occurred in patients aged 60 years or older, and 18% of patients sustained a dislocation. Older age (β = 0.316, P = .003) and male sex (β = 5.532, P = .025) were predictive of tear size, and older age (β = 0.229, P = .011) and biceps avulsion (β = 8.822, P = .012) were predictive of tear retraction.

Conclusions: Acute, traumatic RCTs have CSAs that are 5° smaller than those of degenerative tears, and the majority (60%) have CSAs that are below the threshold consistent with degenerative RCTs. The majority of traumatic tears (60%) involve the subscapularis.

Clinical Relevance: The study findings suggest that a traumatic tear is not simply the acute failure of a degenerative tendon and that it represents a distinct pathologic entity. These findings support current practice of treating traumatic RCTs differently than degenerative RCTs.