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Finite-element optimization of clavicular tunnel positioning improves short-term outcomes of single-button AC joint
Huanhuan Sun1,2, Zhipeng Yang1,2, Peijie Zhao1,2
1First School of Clinical Medicine, Ningxia Medical University, Yinchuan, 750004, China.
Objective:
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.
Methods:
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.
Results:
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%).
Conclusion:
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.
