Biomechanical comparison of a modified Weaver-Dunn and a free-tissue graft reconstruction of the acromioclavicular joint complex.

BACKGROUND

Most surgical reconstructions of the separated acromioclavicular joint do not address the injured ligaments and capsule of the acromioclavicular joint.

PURPOSE

This study was undertaken to compare the biomechanical characteristics of a modified Weaver-Dunn reconstruction and an intramedullary acromioclavicular joint reconstruction that uses a free-tissue graft for reconstruction of both the coracoclavicular and acromioclavicular ligaments.

STUDY DESIGN

Controlled laboratory study.

METHODS

Each pair of 6 matched pairs of cadaveric shoulders was randomly selected for a modified Weaver-Dunn reconstruction on 1 side and the contralateral side was used for free-tissue graft reconstruction of the coracoclavicular and acromioclavicular ligamentous complexes. Anterior-posterior and superior-inferior acromioclavicular joint translation (in millimeters) was measured with acromioclavicular joint compressions of 10, 20, and 30 N, and with translational loads of 10 and 15 N both before and after acromioclavicular joint reconstruction. Load-to-failure testing was then performed for each construct. Repeated-measures analysis of variance (translational testing) and Wilcoxon signed rank test (load-to-failure testing), both with P = .05, were used for statistical analysis.

RESULTS

Mean anterior-posterior and superior-inferior translation of the intramedullary acromioclavicular joint reconstruction was significantly less than that of the modified Weaver-Dunn under all loading conditions (P < .001 and P = .001, respectively), but was not significantly different from that of the intact state (P = .656 and P = .173, respectively). Although the mean ultimate and yield loads and linear stiffness for the intramedullary acromioclavicular reconstruction were greater than that of the modified Weaver-Dunn reconstruction, this did not reach statistical significance (P = .625, P = .625, and P = .625, respectively).

CONCLUSION

Acromioclavicular joint reconstruction with free-tissue graft for both the coracoclavicular and acromioclavicular ligamentous complexes demonstrates initial stability significantly better than a modified Weaver-Dunn and similar to that of intact specimens.

CLINICAL RELEVANCE

This acromioclavicular joint reconstruction provides the surgeon with a relatively nondestructive option.