Purpose: We sought to qualitatively and quantitatively describe characteristics of Hill-Sachs lesions (HSL) in a cohort of anterior shoulder instability patients using advanced 3-dimensional (3-D) modeling software and assess the impact of various HSL parameters on the HSL volume, location, and orientation in patients with anterior shoulder instability.
Methods: A total of 100 recurrent anterior instability patients with evidence of HSL with a mean age of 27.2 years (range = 18 to 43 years) were evaluated. Three-dimensional models of unilateral proximal humeri were reconstructed from CT scans, and 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) angle in order to classify the level and location of potential humeral head engagement. Mann-Whitney U test assessed the relationship between measured parameters.
Results: By volume, larger HSL had greater humeral head surface area (HH SA) loss (P = .001), HSL width (P = .001), were more medial (P = .015), and more inferior (P = .001). Additionally, more medial lesions had greater HSLr angles (P = 0.001). The mean depth, width, and volume of HSLs were 3.3 mm (range = 1.2-7.1 mm), 16.0 mm (range = 6.2-30.4 mm) and 449.2 mm3 (range = 62.0-1365.6 mm3), respectively. The medial border of the HSL extended to 17.2 ± 4.4 (range = 9.3-28.3 mm) off the most medial edge of the HH cartilage margin (medialization). The mean HSLr was 29.3 ± 10.5°.
Conclusion: There was a statistically significant association between HSL medialization and HSL volume, position, and orientation. More medialized HSL have larger volume, greater width, more SA loss and higher lesion angles and are more inferior in the humeral head. As it has been established that more medialized lesions have poorer clinical outcomes, this study highlights that HS lesions have varying angles and medialization, which may portend eventual treatment and outcomes.
Level of evidence: IV, case series.
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