Coracohumeral index and coracoglenoid inclination as predictors for different types of degenerative subscapularis...

To define and compare the coracohumeral index (CHI) and coracoglenoid inclination (CGI) in patients with different types of the subscapularis tendon tears.

Patients were divided into two groups: articular-sided lesion group (group A) and bursal-sided lesion group (group B). All the patients were examined using a 3.0-T magnetic resonance imaging scanner pre-operatively. The morphometric parameters of the coracoids, including the coracohumeral distance (CHD), CHI, and CGI, were measured on MRI.

There were 165 (70.2%) and 70 (29.8%) patients in groups A and B, respectively. There was no significant difference in the average CHD (7.98 ± 1.7 mm vs 7.82 ± 2.1 mm, respectively) and CGI (50.5° ± 16.6° vs 44.9° ± 17.4°, respectively; P = 0.427) between the two groups. Conversely, there was a significant difference in the CHI between them (0.32 ± 0.08 vs 0.57 ± 0.11, respectively; P = 0.0001). According to the CHI and CGI, the coracoid process was divided into three types, and nearly half of the patients (46.8%) had standard coracoids with a hook tip, which are vulnerable to injury on the articular side. However, with overlapping coracoids and hook tips, the patients (16.2%) tended to experience injury on the bursal side. There was a significant difference in the incidence of articular or bursal side tear between the two groups.

The CHI and CGI are potential valuable predictors of the types of degenerative subscapularis tendon tears. With standard hook coracoids, the lesions tend to appear on the articular side initially; otherwise, with overlapping hook coracoids, the subscapularis tendon tears are commonly seen on the bursal side.