The duration of dislocation is the most important prognostic factor in chronic locked posterior shoulder dislocations treated with the modified McLaughlin surgical procedure: a multicentre study

Background: The diagnosis of posterior shoulder dislocation (PSD) is often overlooked as these injuries are not common, since clinical signs may be subtle and easily overlooked unless specifically evaluated. This study aimed to determine the factors related to clinical outcomes in patients with chronic locked PSD treated with the modified McLaughlin procedure. Methods: The study included 22 patients from 5 different clinics who were diagnosed with chronic (> 6 weeks) locked PSD and underwent the modified McLaughlin procedure. The pre- and postoperative values of shoulder forward flexion, abduction, and external rotation were recorded for each patient. At the final follow-up examination, the patient-reported clinical outcomes were evaluated through Constant-Murley Score (CMS), the Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire, and the University of California-Los Angeles (UCLA) shoulder scale. Defect depth and defect angle were measured on axial computed tomography sections. Result: Evaluation was made of 14 males and 8 females aged 25–58 years. The mean time interval between the dislocation and surgery was 18.4 ± 7.4 weeks. The postoperative scale scores were DASH mean 17.1 ± 5.6, CMS median 70.0 [35.0–83.0] and UCLA shoulder scale mean 25.5 ± 6.6. Strong to excellent correlations were determined between the functional scores and the duration of dislocation. Regardless of age, gender, depth and degree of the defect, and immobilization duration, the duration of dislocation (weeks) was associated with the DASH score (beta:0.513, 95% CI:0.931–7.528, p = 0.015), CMS (beta: -0.916, 95% CI: -1.959 to -1.293, p < 0.001), and the UCLA shoulder scale (beta: -0.899, 95% CI: 0.983 to -0.618, p < 0.001). Conclusion: In patients with locked PSD, the primary factor influencing clinical outcomes is the duration of the dislocation, rather than humeral head defect size or patient age. PSD should be suspected in patients with shoulder trauma who present with limitations in forward flexion and abduction.