Currently there is no standard quantitative methodology for the description of Hill-Sachs defects (HSD), the size of which is important in planning surgical treatment for patients with anterior shoulder instability. The main purpose was to develop a simple imaging measurement to improve communication regarding HSDs. The secondary goal was to determine, using this new measurement, whether there was a significant difference in the size of HSDs in patients who underwent a Weber osteotomy (more invasive surgical intervention for those failing Bankart repair) compared with patients who underwent clinically successful arthroscopic Bankart repairs (the first surgical intervention for anterior shoulder instability).

HSD volume was calculated with newly developed methodology using computed tomography in ten patients who required eleven Weber osteotomies and using magnetic resonance imaging in twenty-two patients who had clinically successful arthroscopic Bankart repairs. Within the Weber cohort, regression analysis was performed to determine correlation between HSD volume and each of height, maximum depth, and width. Student's t-test analysis was used to compare HSD volume between the Weber and Bankart cohorts.

In the Weber cohort, there is a statistically significant correlation between the HSD Volume Ratio and the HSD Maximum Depth Ratio (R²=0.83). The t-test comparison of mean HSD Volumes showed statistically significant (p<0.0015) larger HSD's in the Weber cohort than the Bankart cohort.

HSD depth is a radiological indicator for HSD volume. This simple measurement may facilitate orthopaedic pre-operative planning for patients with severe recurrent anterior shoulder instability. In this preliminary study, patients who had Weber osteotomies after failed Bankart repairs had statistically significantly larger HSDs than patients with clinically successful Bankart repairs.