Functional anatomy of the lateral collateral ligament complex of the elbow: configuration of Y and its role

A previous anatomic study has revealed that the lateral collateral ligament (LCL) complex of the elbow has a Y-shaped configuration, which consists of a superior, an anterior, and a posterior band. The LCL complex, including the annular ligament, functions as a 3-dimensional (3D) Y-shaped structure. On the basis of this concept, joint laxity after transection of the anterior band was studied in 5 normal, fresh-frozen cadaver elbows with a 3D kinematic testing apparatus. Cutting the anterior band produced significant laxity to varus torque with a mean 5.9 degree at 10 degree of elbow flexion and caused significant laxity to torque in external rotation with a mean 8.5 degree at 40 degree of flexion. No significant laxity was observed during application of valgus or internal rotational torque. Further transection of the posterior band resulted in gross instability with dislocation of the ulnohumeral joint. The laxity occurring after severance of the anterior band suggests that these fibers play a role in preservation of elbow stability against varus and external rotational torque. These results indicate that the LCL functions as a complex with a Y structure and not as an isolated linear ligament. A concept of conjoint point is hypothesized for the function of the LCL complex to restrain posterolateral rotatory instability.