To 1) qualitatively and quantitatively analyze the interplay between Hill-Sachs lesions (HSL) and glenoid bone loss (GBL) in a cohort of anterior instability patients using 3-dimensional (3-D) imaging software and 2) assess significant relationship between amount of GBL and HSL characteristics.
A cohort of 100 anterior shoulder instability patients presenting with evidence of both HSL and GBL confirmed on computed tomography (mean age: 27.9, range = 18 – 43 years) were identified. 3-D models of the unilateral proximal humeral head and en face sagittal oblique view of the glenoid were reconstructed using MIMICS (Materialise NV, Leuven, Belgium) software. The volume, surface area (SA), width, and depth of identified HSLs were quantified along with their location (medial, superior, and inferior extent). Multiple angular orientation measures of HSLs were recorded, including Hill-Sachs rim [HSLr] and Hill-Sachs center [HSLc] angles in order to classify the level and location of potential engagement. Glenoid bone loss, surface area (SA), width, defect length, and glenoid track width were quantified. Analysis of variance was computed to analyze significant differences (p < 0.05) between severity of GBL (0-10%, 11-20%, 21 – 30%, and 31 – 40%) and HSL parameters.
GBL width, percent glenoid width loss, defect length, and glenoid track width significantly differed across the four GBL groups (0-10%, 11-20%, 21 – 30%) (p < .03). Greater GBL was significantly associated with greater average HSL width (p = .001) and depth (p = .002), as well as maximum HSL width (p = 0. 002). Patients presenting with greater GBL presented with greater humeral head SA loss (p = .006). Patients with 0-10% GBL had significantly narrower (average and max width) (p < .03) and deeper (p < .03) HSL’s than all other GBL groups.
HSL’s present with significantly different characteristics depending on extent of GBL. Larger amounts of GBL have HSL’s that are wider, and shallower due to a larger surface area of glenoid-humerus interaction, while smaller glenoid defect size is associated with narrower and deeper HSL’s likely as a result of the hardness of the glenoid bone producing deeper, more localized defects on the humeral head. While additional work is needed to validate clinical outcomes, this study sheds important light on how HSL’s present with increasing amounts of GBL that may present clinically useful.