Biomechanical Rationale for Development of Anatomical Reconstructions of Coracoclavicular Ligaments after Complete Acromioclavicular Joint Dislocations

Abstract

Background Surgical treatments of complete acromioclavicular joint dislocations replace or reconstruct the coracoclavicular ligaments with a single structure and do not account for the anatomical variance of each ligament in the design. Purpose To evaluate the cyclic behavior and structural properties of an anatomic tendon reconstruction of the coracoclavicular ligament complex after a simulated acromioclavicular joint dislocation. Study Design Controlled laboratory study. Methods Cyclic loading followed by a load-to-failure protocol (simulated dislocation) of the normal coracoclavicular ligament complex was performed and repeated after an anatomic reconstruction on the same specimen (n = 9). The anatomical reconstruction consisted of a semitendinosus tendon that replicated the direction and orientation of both the trapezoid and conoid ligaments. Results The coracoclavicular ligament and anatomical reconstruction complexes had clinically insignificant (<3 mm) permanent elongation after cyclic loading. The stiffness and ultimate load of the coracoclavicular ligament complex (60.8 ± 12.2 N/mm and 560 ± 206 N) were significantly greater than for the anatomical reconstruction complex (23.4 ± 5.2 N/mm and 406 ± 60 N), respectively (P < .05). Further analysis of the complexes revealed a 40% decrease in the bending stiffness of the clavicle after the simulated dislocation and failure of the normal coracoclavicular ligament complex (P < .05), which contributed to the diminished properties of the anatomic reconstruction. Conclusions The low level of permanent elongation after cyclic loading suggests that the anatomic reconstruction complex could withstand early rehabilitation; however, the decrease in the structural properties and stiffness of the clavicle should be considered in optimizing the anatomic reconstruction technique. Clinical Relevance Despite the differences compared to the normal coracoclavicular ligament complex, the anatomical reconstruction complex more closely approximates the stiffness of the coracoclavicular ligament complex than current surgical constructs, and the incorporation of biological tissue could improve the overall structural properties with healing.