Acromioclavicular (AC) capsular ligaments are known to be the primary restraints that provide horizontal stability for the AC joint, whereas the coracoclavicular (CC) liga-ments prevent vertical translation. However, biomechani-cal investigations have demonstrated that the soft tissues that support the AC joint provide stability in a more com-plex manner.6,9,13 Four components of the AC capsular lig-aments contribute to stability respectively when a load is applied to the joint. Of these, the superior capsular liga-ment, reinforced by the deltoid and trapezius muscle, is important because of its primary role in posterior transla-tion.13 Serial ligament cutting experiments also revealed that 2 components of the CC ligaments have different func-tions according to the direction and magnitudes of the forces applied.5,16 The trapezoid ligament provides the major support against compressive loads applied along the clavicle axis and acts as a secondary restraint to supe-rior translation. On the other hand, the conoid ligament contributes to both superior and anterior stability.9,17 The ideal surgical treatment for complete AC dislocation is considered to be restoring separately each ligament sup-porting the AC joint to achieve functionally optimal out-comes. Surgical procedural improvements depend on a comprehensive understanding of the contribution made by each surrounding ligament to overall AC joint function
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