Coracoid clavicular tunnel angle is related with loss of reduction in a single-tunnel coracoclavicular fixation using a dog bone button in acute acromioclavicular joint dislocation.

PURPOSE: Despite the high failure rates of techniques used to maintain the reduction of single-tunnel coracoclavicular (CC) fixation, analyses of the etiology of loss of reduction related to surgical techniques are limited. Therefore, it was hypothesized that the initial coracoclavicular tunnel angle was related to loss of reduction in the single-tunnel technique for AC joint dislocation. This study aimed to evaluate the clinical and radiological outcomes of arthroscopic single-tunnel CC suture button fixation according to the initial coracoclavicular tunnel angle.
METHODS: Thirty-two consecutive patients who underwent arthroscopic single-tunnel CC suture button fixation for AC joint dislocation from 2014 to 2018 were enrolled. The tunneling-first technique was used in the first 11 patients, while the reduction-first technique was used in the remaining 22 consecutive patients. For clinical assessments, the American Shoulder and Elbow Surgeons (ASES) score and Korean Shoulder Score (KSS) were recorded. For radiological evaluation, coracoclavicular distance ratio, coracoclavicular tunnel angle, coracoid, and clavicular tunnel widths were measured.
RESULTS: The ASES score did not differ significantly between the two groups (n.s.). However, the KSS was significantly better in the reduction-first group (p = 0.031). No significant intergroup differences were observed in the pre- and postoperative coracoclavicular distance ratio. However, at the last follow-up, loss of coracoclavicular distance ratio was significantly smaller in the reduction-first group (p < 0.001). At the final follow-up, loss of the coracoclavicular distance ratio was positively correlated with the postoperative coracoclavicular tunnel angle (p < 0.001, Spearman's rho correlation coefficient = 0.602). The final follow-up clavicular tunnel width was also significantly smaller in the reduction-first group (p = 0.002). Finally, the last follow-up clavicular tunnel width was positively correlated with the postoperative coracoclavicular tunnel angle (p = 0.008, Spearman's rho correlation coefficient = 0.459).
CONCLUSION: The reduction-first technique showed better clinical and radiological outcomes than the tunneling-first technique in single-tunnel CC fixation for AC joint dislocation. A large postoperative coracoclavicular tunnel angle was associated with loss of reduction and clavicular tunnel widening. Therefore, obtaining a straight coracoclavicular tunnel angle is crucial for achieving better outcomes and minimizing loss of reduction. LEVEL OF EVIDENCE: III.