Arthroscopic retrograde disimpaction of reverse Hill-Sachs lesions in acute posterior shoulder dislocation type A2 leads to good clinical outcome and close to anatomic reconstruction of the articular surface of the humeral head

Background: Posterior shoulder dislocation frequently results in a centrally located impression fracture of the anterior humeral head, known as reverse Hill-Sachs lesion (RHSL). Depending on its size and location, the RHSL can lead to engagement with the posterior glenoid rim and subsequently redislocation of the shoulder joint. The objective of this study was to present the clinical and radiologic outcomes of anatomic reconstruction of the humeral articular surface using arthroscopically assisted disimpaction in patients with acute posterior shoulder dislocation and an engaging RHSL. Methods: As part of a retrospective analysis, 9 shoulders in 9 patients (1 female, 8 males) with engaging RHSL following acute posterior shoulder dislocation (type A2 according to the ABC classification) who underwent arthroscopically assisted disimpaction of the RHSL between 2016 and 2023 were identified. Eight patients were included, because 1 patient refused to participate. In all patients, a radiologic analysis of the RHSL was accomplished on preoperative and postoperative cross-sectional imaging including the alpha, beta, and gamma angle as well as depth measurements. The clinical examination included an assessment of the active range of motion, instability tests, and patient-reported outcome measures, such as the Western Ontario Shoulder Instability (WOSI) Index, the Constant Score, and the Subjective Shoulder Value (SSV). Results: The mean follow-up period for all 8 patients was 34.4 +/- 38 months (range: 6-102 months). The mechanisms of injury included falls (n = 6), traffic accident (n = 1), and convulsive episode (n = 1). The average time from injury to surgery was 6.8 +/- 4.7 days (range: 2-16). Patient-reported outcomes at the final follow-up indicated an average WOSI Index of 77.8% +/- 17%, a mean Constant Score of 88.3 +/- 11 points, and a mean SSV of 87% +/- 16%. None of the patients experienced recurrent dislocations during the follow-up period. Post-traumatically, the mean absolute defect depth was 8.4 +/- 2.2 mm and the mean gamma angle was 115.8 degrees +/- 13 degrees. In the radiologic follow-up, the RHSL depth measurements showed a significant reduction in the mean defect depth from 8.4 +/- 2 mm to 1.2 +/- 1 mm resulting in an average reduction of the RHSL by 7.1 mm (P < .001). In 3 of the 8 patients (37.5%), the RHSL was not identifiable any more at follow-up and in 5 patients barely identifiable. Conclusion: Arthroscopically assisted disimpaction of acute RHSLs leads to close to anatomic reduction of RHSL, achieving a stable shoulder and good clinical outcomes. Level of evidence: Level IV; Case Series; Treatment Study (c) 2024 The Author(s). This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).