Effects of acromioclavicular and coracoclavicular ligament stability on acromioclavicular joint dislocation: insights from a cadaveric study.

BACKGROUND

Acromioclavicular (AC) joint (ACJ) dislocation can lead to superior clavicular instability when the AC and coracoclavicular (CC) ligaments are torn. No previous study has assessed the effects of combined AC-CC ligament resections in fresh-frozen cadavers with preserved soft tissues around the thorax and shoulder girdle. This study aimed to develop such an ACJ dislocation model and evaluate stability following ligament resections.

METHODS

Nine fresh-frozen cadaver shoulders (mean age, 86.6 years) without clavicular fractures or ACJ osteoarthritis were used. Each specimen included the thoracic spine, scapula, clavicle, and shoulder. Biomechanical testing was performed with a customized system to assess displacement and evaluate superior and posterior stability. Three conditions were compared: intact ligaments, AC ligament resection, and AC-CC ligament resection.

RESULTS

Superior translations were 0.0 mm (intact), 1.1 mm (AC resection), and 9.6 mm (AC-CC resection). Posterior translations were 0.0 mm, 3.2 mm, and 9.0 mm, respectively. The AC-CC resection group showed significantly increased translations compared to the intact and AC resection groups. No significant difference was observed between the intact and AC resection groups in superior translation. Posterior translation increased progressively from intact to AC and then AC-CC resection.

CONCLUSIONS

This is the first study to assess both superior and posterior ACJ stability using cadavers with preserved soft tissues. Our findings demonstrate the importance of the AC and CC ligaments in maintaining ACJ stability. Notably, the AC ligament contributes to posterior stability, indicating the need for reconstruction to achieve overall joint stability. Level of evidence: Controlled laboratory study.