Experimental justification of reconstruction of coracoclavicular ligaments in chronic instability of the acromioclavicular joint

Chronic posttraumatic instability of the acromioclavicular joint is often accompanied by pain and dysfunction of the limb. Known methods of surgical treatment of this pathology have their advantages and disadvantages. A relatively simple and accessible method of stabilizing the acromioclavicular joint in chronic cases is the reconstruction of the coracoclavicular ligaments with a loop encircling the coracoid process of the scapula and the clavicle, using a tendon graft reinforced with a synthetic tape. This surgical treatment method does not involve the formation of holes in the bones, which increase the risk of pathological fractures in the postoperative period. Aim. To assess the horizontal and vertical stability of the acromioclavicular joint when it is fixed with a loop of synthetic tape encircling the coracoid process of the scapula and the clavicle, and a half-loop with two-bundle transosseous fixation to the clavicle. Materials and methods. In a biomechanical experiment on 14 acromioclavicular joints in 7 cadavers, the displacement of the acromial end of the clavicle in the anterior, posterior and superior directions was determined under a load of 70 N. The measurements were performed sequentially: with an intact ligamentous apparatus, after crossing the acromioclavicular ligament, after crossing the coracoclavicular ligaments with stabilization of the acromial end of the clavicle with the studied encircling loop, then with a half-loop with transosseous fixation to the clavicle at the attachment sites of the trapezoid and conoid ligaments. A synthetic tape “FiberTape” folded in two was used as a model of a reinforced tendon graft. Results. The intersection of the acromioclavicular ligament resulted in a significant increase in the displacement of the acromial end of the clavicle under load superior by 3,3 mm (61,4%), posterior by 1,5 mm (24,5%) and anterior by 1,9 mm (24,6%). Stabilization with a encircling loop, as well as a half-loop with transosseous fixation to the clavicle restored the anterior and superior stability of the acromioclavicular joint to the initial level. The residual posterior displacement exceeded the initial one by 0,5 mm (8,4%) and 0,4 mm (7,1%), respectively. When comparing the fixation methods, no significant differences in stability were found. Conclusions. In case of complete failure of the ligamentous apparatus of the acromioclavicular joint, isolated reconstruction of the coracoclavicular ligaments restores vertical and horizontal stability by more than 90% of the original. Reconstruction of the coracoclavicular ligaments with a loop encircling the coracoid process of the scapula and the acromial end of the clavicle is not inferior in its effectiveness to the use of a half-loop with a two-bundle transosseous fixation to the clavicle.