Is lesser tuberosity morphology related to subscapularis tears and anterior shoulder instability?

Although the morphological relationship of the scapula and the humeral head has been claimed to be related to shoulder pathologies, few studies examined the relationship between subscapularis (Ssc) tears and lesser tuberosity (LT)-humeral head (HH) and between Ssc tears and HH-glenoid. This study aims to evaluate the relationship of LT with HH and glenoid in patients with Ssc tears and anterior shoulder instability (ASI). We hypothesized that the glenoid, HH, and their combined relationship with LT may impact Ssc tears and ASI.

The study included 34 patients with ASI, 28 patients with isolated Ssc tears, and 40 patients as the control group. The radius of HH (Hr), the distance between the center of HH and LT (LTr), and the glenoid radius (Gr) were measured in shoulder magnetic resonance (MR) images. The LTr to Hr (LTr/Hr) ratio was defined as the lesser tuberosity-humeral head index (LTHHI), whereas the LTr to Gr (LTr/Gr) ratio was defined as the lesser tuberosity-glenoid index (LTGI). The three groups were compared regarding LTHHI, LTGI, LTr, Hr, and Gr.

There was a significant difference between each group concerning LTGI (p < 0.001). LTGI values below 1.99 showed 93.1% sensitivity and 93.3% specificity for Ssc tears, while values above 2.24 showed 86.7% sensitivity and 86.2% specificity for ASI. Also, there was a significant difference when the groups were compared for LTHHI (p < 0.001). This rate was lowest for Ssc tears, and LTHHI values below 1.17 showed 82.8% sensitivity and 80.1% specificity.

LTGI may be a new predictive factor showing 93.1% sensitivity and 93.3% specificity for Ssc tears and 86.7% sensitivity and 86.2% specificity for ASI. In addition, LTHHI may be a new predictive factor showing 82.8% sensitivity and 80.1% specificity for Ssc tears.

III retrospective comparative study.