Arthroscopically assisted acromioclavicular joint stabilization leads to significant clavicular tunnel widening in the early post-operative period

Purpose: Arthroscopically assisted acromioclavicular joint (ACJ) stabilization techniques use bone tunnels in the clavicle and coracoid process. The tunnel size has been shown to have an impact on the fracture risk of clavicle and coracoid. The aim of the present study was to radiographically evaluate the alterations of the clavicular tunnel size in the early post-operative period. It was hypothesized that there would be a significant increase of tunnel size. Methods: Twenty consecutive patients with acute high-grade ACJ (Rockwood type IV–V) injury underwent arthroscopic-assisted ACJ stabilization. The median age of the patients was 40 (26–66) years. For all patients, a single tunnel button–tape construct was used along with an additional ACJ tape cerclage. Radiologic measurements were undertaken on standardized Zanca films at two separate time points, immediate post-operative examination (IPO) and at late post-operative examination (> 4 months; LPO). The LPO radiographs were taken at a median follow-up period of 4.5 (3–6) months. Clavicular tunnel width (CT) and coracoclavicular distance (CCD) were measured using digital calipers by two independent examiners and the results are presented as median, range, and percentage. Results: The median CCD increased significantly from 9.5 (8–13) mm at IPO to 12 (7–20) mm at LPO (p < 0.05). Median tunnel size showed significant difference from 3 (3–4) mm at IPO to 5 (4–7) mm at LPO (p < 0.05). Despite a significant increase of 2 mm (66.6%) of the initial tunnel size, there was no correlation between tunnel widening and loss of reduction. Conclusion: Arthroscopic ACJ stabilization with the use of bone tunnels led to a significant increase of clavicular tunnel size in the early post-operative period. This phenomenon carries a higher fracture risk, especially in high-impact athletes, which needs to be considered preoperatively. Level of evidence: IV.