The coracoclavicular ligament (CC ligament) has two distinct components: the conoid ligament (medial, cone-shaped, attaches to the coracoid root and the clavicle conoid tubercle) and the trapezoid ligament (lateral, quadrilateral, attaches from the coracoid superior surface to the clavicle trapezoid line). The conoid ligament is the primary restraint to vertical displacement; the trapezoid ligament is the primary restraint to horizontal displacement and clavicle rotation.
The conoid ligament primarily prevents superior clavicular displacement; the trapezoid ligament primarily prevents horizontal (anteroposterior) and rotational clavicular displacement. Together they maintain the scapulothoracic relationship.
AC joint separation grading (Rockwood classification) correlates with CC ligament integrity: Grade III involves CC ligament disruption with 25-100% vertical clavicle displacement; Grade IV involves posterior clavicle displacement into trapezius from trapezoid disruption; Grades V and VI involve complete disruption. Surgical reconstruction of Grade III-V AC separations recreates both CC ligament components. Anatomic CC reconstruction with two separate grafts (conoid and trapezoid reconstructions) reduces rotational instability compared to single-loop techniques that only address vertical displacement.
Rockwood Grade III AC separation with complete CC ligament disruption produces 25-100% vertical clavicle displacement; surgical intervention is considered for Grade III separations in overhead athletes and for all Grade IV-VI injuries, with anatomic dual-bundle CC reconstruction restoring both conoid and trapezoid functions.
