Acromioclavicular reconstruction techniques after acromioclavicular joint injuries: A systematic review of biomechanical studies

Background: Residual horizontal instability after surgical treatment for acromioclavicular joint injuries is seen as a potential cause of suboptimal clinical outcomes. Biomechanical studies have demonstrated that the acromio-clavicular capsule/ligaments are the primary restraints for anteroposterior translation. However, limited studies have addressed the biomechanics of a reconstruction of the acromioclavicular capsule/ligaments. The aim of this systematic review was to evaluate the biomechanical role of acromioclavicular capsule/ligament reconstruction techniques after an acromioclavicular joint injury.Methods: A search was carried out on the databases Medline and EMBASE, and was conducted according to the PRISMA guidelines. Biomechanical studies addressing horizontal and vertical displacement or joint stiffness after reconstructing the acromioclavicular capsule/ligament with or without coracoclavicular ligament reconstruc-tion, were included.Findings: Nineteen studies were included in this review after screening and eligibility assessment. Five of them investigated different sole acromioclavicular capsule/ligament reconstruction techniques. In 10 studies, a sole coracoclavicular ligament reconstruction was compared to a coracoclavicular ligament reconstruction with additional acromioclavicular capsule/ligament reconstruction. The remaining 4 studies compared different acromioclavicular capsule/ligament with coracoclavicular reconstruction techniques with each other.Interpretation: Several testing protocols to evaluate acromioclavicular capsule/ligament reconstruction have been described and can make it difficult to compare the results of the different studies. Acromioclavicular capsule/ ligament reconstruction may provide increased anteroposterior and rotational stability but an optimal recon-struction technique, which mimics all biomechanical characteristics of the native joint is not yet available.