Hill-sachs lesions in shoulders with traumatic anterior instability: evaluation using computed tomography with 3-dimensional reconstruction

Background: In patients with traumatic anterior shoulder instability, a large Hill-Sachs lesion is a risk factor for postoperative recurrence. However, there is no consensus regarding the occurrence and enlargement of Hill-Sachs lesions.

Purpose: To investigate the influence of the number of dislocations and subluxations on the prevalence and size of Hill-Sachs lesions evaluated by computed tomography (CT) with 3-dimensional reconstruction.

Study design: Cohort study (diagnosis); Level of evidence, 2.

Methods: The prevalence and size of Hill-Sachs lesions were evaluated preoperatively by CT in 142 shoulders (30 with primary instability and 112 with recurrent instability) before arthroscopic Bankart repair. First, the prevalence of Hill-Sachs lesions was compared with the arthroscopic findings. Then, the size of Hill-Sachs lesions confirmed by arthroscopy was remeasured using the previous CT data. In addition, the relationship of Hill-Sachs lesions with the number of dislocations and subluxations was investigated.

Results: Hill-Sachs lesions were detected in 90 shoulders by initial CT evaluation and were found in 118 shoulders at arthroscopy. The Hill-Sachs lesions missed by initial CT were 15 chondral lesions and 13 osseous lesions. However, all 103 osseous Hill-Sachs lesions were detected by reviewing the CT data. In patients with primary subluxation, the prevalence of Hill-Sachs lesions was 26.7%, and the mean length, width, and depth of the lesions (calculated as a percentage of the diameter of the humeral head) were 9.0%, 5.3%, and 2.1%, respectively, while the corresponding numbers for primary dislocation were 73.3%, 27.7%, 14.8%, and 7.0%, all showing statistically significant differences. Among all 142 shoulders, the corresponding numbers were, respectively, 56.3%, 20.7%, 11.2%, and 4.8% in patients who had subluxations but never a dislocation; 83.3%, 33.4%, 19.1%, and 7.6% in patients with 1 episode of dislocation; and 87.5%, 46.8%, 22.2%, and 10.2% in patients with ≥2 episodes, all showing statistically significant differences. There were no differences in lesion measurements in relation to the number of subluxations.

Conclusion: Computed tomography is a useful imaging modality for evaluating Hill-Sachs lesions except for purely cartilaginous lesions. Hill-Sachs lesions were more frequent and larger when the primary episode was dislocation than when it was subluxation. Among patients with recurrent episodes of complete dislocation, the prevalence of Hill-Sachs lesions is increased, and the lesions are larger.