Analysis of the stress-strain state of the suprahumeral-clavicular joint in case of damage to the coracoclavicular ligament and various methods of fixation

Background. There are two main methods to fix the acromial end of the clavicle with the help of metal structures: a hook plate, and the Weber’s method. Each of them has advantages and disadvantages. When using the Weber’s method, they are a violation of the integrity of the wire and spikes, destruction of the acromion process and the acromial end of the clavicle, migration of the spikes. When using a hook plate, this is a pain in the shoulder, destruction of bone tissue in the area of the acromion process, and subacromial conflict. Purpose: to conduct a comparative analysis of the fixation of the acromial end of the clavicle according to Weber, with hook plate and the proposed construction by studying the stress-strain state of the suprahumeral-clavicular joint with a combined injury of the lig.conoideum and lig.trapezoideum and various methods of fixation. Materials and ­methods. The finite element model of the suprahumeral-clavicular joint was built, which consisted of the scapula, clavicle, and ligaments of the suprahumeral-clavicular and coracoclavicular complexes. A combined injury of the ligaments of the suprahumeral-clavicular joint was modeled, namely lig.conoideum and lig.trapezoideum, with three methods of fixation: according to the Weber, hook plate and the proposed construction. Results. It was found that all types of fixators allow obtaining approximately the same level of stress in the bone elements of the model. An exception is Weber’s fixation, in which the stress on the acromial end of the clavicle and on the acromion process increases several times and even exceeds the strength limit of the cortical bone, which can be the cause of bone tissue destruction. The stresses in the wire itself can even exceed the strength limit of surgical steel and cause its break. A hook plate does not provide a sufficient stress reduction in the intact ligaments of the acromial-clavicular joint. The stress on the plate itself can approach the strength limit of surgical steel, which can cause its damage. The hinge-type fixator provides the best stress distribution, both in the bone elements of the model, and a fairly low level of stress in the intact ligaments. According to the criterion of minimizing the amount of relative deformations in the ligaments of the clavicle-scapular joint, the best results were shown by the hinge-type fixator. The largest relative deformations in the ligaments occur during fixation with a hook plate. Conclusions. Fixation of the acromial end of the clavicle according to Weber does not ensure its reliable fixation. The level of stresses in the wire during abduction of the limb approaches the strength limit of surgical steel, and stresses in the intact ligaments may even exceed the strength limit of cortical bone. All this can be the cause of complications such as breaking of the wire and destruction of bone tissue in the place of contact with it. The hook plate fixator does not provide sufficient stress reduction in the intact ligaments of the acromial-clavicular joint. The stresses on the plate itself can approach the strength limit of surgical steel, which can cause its damage. The fixator of the proposed design provides the best balance, in terms of both stress distribution in the model elements and the magnitude of relative deformations in the intact connections.