BACKGROUND:
Acromioclavicular joint (ACJ) dislocation is a common shoulder injury. In treating acute unstable ACJ dislocation, a hook plate (HP) is a straightforward and popular option for ensuring proper reduction and rigid fixation while promoting AC and coracoclavicular (CC) ligament healing. Surgeons typically remove the HP to prevent subacromial impingement and acromial osteolysis; however, concerns about redislocation after implant removal remain. Therefore, additional CC augmentation may be helpful in combination with HP fixation. The aim of this meta-analysis is to compare the outcomes and complications of HP fixation with or without additional CC augmentation for acute unstable ACJ dislocation.

METHODS:
We searched the PubMed, EMBASE, and Web of Science databases for relevant case-control studies. The primary outcomes were patient-reported outcome measures; the secondary outcomes were pain measured using a visual analog scale (VAS), CC distance (CCD), and complications. Continuous data were assessed using weighted standardized mean differences (SMDs) with 95% confidence intervals (CIs), and dichotomous data were evaluated with Mantel-Haenszel odds ratio (ORs) with 95% CIs.

RESULTS:
We analyzed one randomized control trial and four case-control studies comparing HP fixation with or without CC augmentation. A total of 474 patients with Rockwood type III or V ACJ dislocation were included. We found no differences in Constant-Murley score (SMD, - 0.58, 95% CI - 1.41 to 0.26; P = 0.18), American Shoulder and Elbow Surgeons score (SMD, 0.21, 95% CI - 0.10 to 0.52; P = 0.19), University of California at Los Angeles shoulder rating scale score (SMD, - 0.02, 95% CI - 1.27 to 1.23; P = 0.97), or VAS pain score (SMD, 0.36, 95% CI - 0.16 to 0.88; P = 0.17) between groups. The CC augmentation group had lower odds of osteolysis (OR, 0.27, 95% CI 0.10 to 0.74; P = 0.01) and a shorter CCD (SMD, - 0.29, 95% CI - 0.57 to - 0.01; P = 0.04).

CONCLUSION:
HP fixation with CC augmentation is preferable for acute unstable ACJ dislocations. Although CC augmentation did not provide additional benefits related to functional outcomes or pain, it resulted in greater reduction maintenance after implant removal and a 73% lower risk of acromial osteolysis.

TRIAL REGISTRATION:
PROSPERO ( CRD42021271118 ).





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