This study assesses the relative importance of the radial collateral ligament (RCL) and the lateral ulnar collateral ligament (LUCL) to posterolateral rotatory instability of the elbow. 12 fresh frozen cadaveric arms were fixed to a base plate and a serial sectioning study was performed on the origin of the RCL or LUCL followed by complete sectioning of the lateral collateral ligament (LCL) complex. The arm was then placed in a valgus gravity loaded orientation, varus gravity loaded orientation, and neutral position, with one examiner moving the elbow passively through a full range of flexion while maintaining the forearm in either pronation or supination. With the arm in a vertical position, a pivot shift test was performed by the same clinician. It should be noted that the anterior capsule was incised and the lateral extensor tendon origin was released from the epicondyle and not repaired for the mechanical testing. An electromagnetic tracking device was used to determine the orientation of the ulna relative to the humerus. They found that an intact RCL or LUCL with an intact annular ligament were able to prevent lateral rotatory instability. However, release of both of these structures did result in rotatory instability. There was a trend toward greater varus-valgus and rotational stability provided by the LUCL than by the RCL. However, this was not statistically significant secondary to the small study size.
The results of this biomechanical cadaveric study suggests that lateral rotatory instability of the elbow occurs secondary to rupture of the entire lateral collateral ligament including the RCL and LUCL. When O’Driscoll et. al. first described the pathomechanics of posterolateral rotatory instability, it was suggested that rupture of the LUCL was primarily responsible for this instability pattern. However, clinical findings and recent biomechanical studies have suggested that there are multiple components to lateral elbow stability, including the lateral ligament structures and multiple tendons crossing the lateral side of the elbow. This study confirms that the LUCL is not solely the stabilizer for posterolateral rotatory instability and that disruption of both the RCL and LUCL is required for rotational instability. This model was performed in cadavers with release of the extensor origin, but with an intact annular ligament. Therefore, it did not assess all components of lateral joint stability. The authors suggest that operative exposures to the elbow or injuries that compromise only one portion of the lateral ligament structures should not result in posterolateral rotatory instability.
Journal of Bone and Joint Surgery