Acromioclavicular joint biomechanics: a systematic review.

Background: The aim of this systematic review was to investigate the available literature on the biomechanical characteristics of the acromioclavicular (AC) joint to identify trends in translational parameters and contributions of the various ligamentous structures supporting the joint.

Methods: A comprehensive literature search was conducted in the Web of Science, Scopus, and PubMed databases until October 2023 to identify articles reporting on the biomechanical characteristics of the AC joint. Non cadaveric or projects involving reconstruction were excluded. Consistent parameters evaluated were anterior, posterior, superior, and inferior translation. The data were extracted from the included articles and summarized.

Results: 11 biomechanical papers were reviewed from six different countries - United States (n = 6), France (n = 1), Austria (n = 1), Thailand (n = 1), United Kingdom (n = 1), and Japan (n = 1). The total number of specimens included across the reviewed papers was 141. All 11 papers reported the data on an intact model (coracoclavicular and AC ligaments intact). Seven papers assessed the translational results of the AC sectioned condition, finding a greater increase in anterior-posterior (AP) laxity relative to SI. 3 papers evaluated coracoclavicular ligament sectioning, finding increased superior-inferior laxity relative to AP. Only one study involved ligament sectioning isolating the anterior-inferior bundle of the AC joint.

Conclusion: This review highlights the key AP and superior-inferior constraints of both the intact and ligament sectioned AC joint. The inconsistency of AC joint testing parameters and the lack of thorough translation studies indicate a necessity for increased attention in the overall assessment of shoulder stability to close the gap in the foundational biomechanical research.