Summary

A biomechanical cadaveric study of acromioclavicular joint dislocation in clavicle-scapular specimens investigated horizontal and vertical motion in five conditions: intact, disruption, CC loops, AC repair and AC augmentation, demonstrating comparable restoration of native horizontal stability in both AC repair and augmentation procedures despite distinct failure mechanisms, while vertical transla

Abstract

Background

Acromioclavicular (AC) joint dislocation commonly results from a direct fall on the ipsilateral arm, necessitating effective treatment to restore joint stability and function. Various stabilization techniques, including repair, reconstruction, and augmentation, have been proposed for horizontal stabilization, but the optimal treatment remains controversial. This study aims to evaluate the horizontal motion between repair and augmentation techniques.

Method

Eight clavicle-scapula specimens with intact AC, coracoclavicular (CC), and coracoacromial (CA) ligaments were subjected to biomechanical testing under five conditions: intact, disruption (resection of AC and CC ligaments), CC loops (with suture tape), AC repair (CC loops and AC repair with suture anchor), and AC augmentation (CC loops and AC augmentation with figure-of-eight fiber tape suture configuration). Each condition was tested for posterior rotation, anterior rotation, and vertical translation. Anterior displacement, posterior displacement, and rotational stiffness were then calculated. Data were presented with median and interquartile range (IQR) for statistical analysis.

Result
Both the AC repair and AC augmentation groups effectively restored anterior and posterior rotation comparable to the native stage (Intact group: anterior rotation 5.71°, IQR [3.10 – 8.49], posterior rotation 5.53°, IQR [3.83 - 9.52]; Repair group: anterior rotation 12.75°, IQR [10.13 - 23.91], P=0.494, posterior rotation 14.60°, IQR [10.13 - 23.91], P=0.419; Augmentation group: anterior rotation 19.44°, IQR [5.28 – 25], P=0.55, posterior rotation 18.94°, IQR [5.28 – 25], P=0.641). In contrast, the CC loops group alone did not achieve this condition (anterior rotation 25°, IQR [25], P<0.006, posterior rotation 25°, IQR [25], P=0.0). Vertical translation was effectively restored in all groups. The Intact group showed a median vertical translation of 2.48 mm (IQR [1.25 – 4.20]). The CC loops group alone achieved 5.83 mm (IQR [4.77 – 5.83], P=0.157), while the combination of CC loops with AC repair resulted in 3.59 mm (IQR [2.78 – 6.63], P=1). Similarly, the AC augmentation group achieved 4.18 mm (IQR [3.00 – 6.09], P=1).

Conclusion

Both anchor suture repair and suture tape augmentation techniques provide horizontal stability comparable to the native stage. However, different modes of failure might be a potential limitation of each technique. Vertical stability could be restored by either CC loops alone or additional AC repair procedures.

Keywords: acromioclavicular joint dislocation, acromioclavicular ligament augmentation, acromioclavicular ligament repair, horizontal motion, vertical motion