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

Abstract

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° at 10° of elbow flexion and caused significant laxity to torque in external rotation with a mean 8.5° at 40° 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. (J Shoulder Elbow Surg 2002;11:53-9.)

Introduction

The anatomy and kinematics of the lateral collateral ligament (LCL) of the elbow have been discussed for several years and are still controversial.2, 4, 5, 9, 13, 14, 16, 17 The ulnar part of the LCL (lateral ulnar collateral ligament [LUCL]) was believed by some authors to be the key stabilizer of the elbow to posterolateral rotatory stress.7, 8, 9, 10, 11 Others have recently suggested, on the basis of serial sectioning studies, that the LCL complex comprising the LCL and the annular ligament was the restraint to posterolateral rotatory laxity.2, 13 The anatomic descriptions of the structure of the LCL complex have varied in the literature as well.2, 4, 5, 9, 13, 14, 16, 17

A previous anatomic study, which included 15 macroscopically normal elbow specimens, suggested that the LCL complex has a Y-shaped structure and that the whole Y structure was the constraint against rotatory laxity.¹⁵ The observation of the 3 bands of the Y structure made us question whether the LCL complex functions as a 3D Y-shaped structure (including the annular ligament) and not only as a linear structure connecting the lateral epicondyle of the humerus to the supinator crest of the ulna.

A previous ligament-sectioning study by Olsen et al¹³ revealed laxity produced by sectioning at the posterior insertions of both the annular ligament and LUCL. Those structures comprised the posterior portion of the Y structure.

The purpose of this study was to investigate joint laxity after severance of the anterior portion of the Y structure and to clarify the importance of the Y structure concept. In this study the 3 bands of the Y structure were named the superior, the anterior, and the posterior bands (Figure 1).