Finite-element optimization of clavicular tunnel positioning improves short-term outcomes of single-button AC joint stabilization.

Abstract

Finite element analysis was used to estimate the ideal clavicular tunnel position for treating acromioclavicular joint dislocation by single-loop cortical knob fixation on a single-name healthy East Asian male model. This information was then converted into precise surgical placement techniques. In order to evaluate short-term safety and serve as a foundation for later large-sample and long-term follow-up investigations, the early imaging and clinical results of 17 individuals 12 months following surgery were reported. A finite-element model of the acromioclavicular joint stabilized with a single-strap plate was created using 3D CT data from a single healthy volunteer. Ten 5-mm-spaced tunnel sites (0-50 mm) were assessed for AC/CC distance and stress distribution during physiological loading using the coracoclavicular ligament's anatomical insertion (42.68 ± 6.34 mm from the AC joint surface) as a reference. A precise surgical landmark was then created using this biomechanical optimization. We present the short-term (12-month) radiological (AC/CC distance) and clinical (Constant-Murley score, complications) results of 17 patients with Rockwood type II-III dislocations who were fixed at the determined best site between September 2023 and October 2024. The best attachment site, according to finite element analysis, is 40 mm distal to the acromioclavicular joint surface, exhibiting balanced biomechanical performance (ACdistance: 8.39 mm; CCdistance: 3.89 mm; peak cortical bone stress: 48.76 MPa; peak cancellous bone stress: 35.78 MPa). A 12-month clinical follow-up revealed a notable improvement: The Constant-Murley score rose from 30.82 ± 6.02 to 93.48 ± 3.01 (P < 0.001), the AC distance dropped from 21.18 ± 4.29 mm to 10.12 ± 0.70 mm (P < 0.001), and the CC distance decreased from 18.43 ± 4.24 mm to 11.50 ± 0.95 mm (P < 0.001). There were no documented postoperative complications (0/17, 95% CI 0-19.5%). Fixation at 40 mm proximal to the acromioclavicular joint surface produced excellent reduction and function in this short-term (12-month) observation; however, larger cohorts with following long-term follow-up are needed to demonstrate durability.