Evaluation of the arthroscopic valgus instability test of the elbow.

Seven fresh-frozen cadaveric elbows were used to evaluate the extent to which the medial collateral ligament must be injured before arthroscopic evidence of valgus instability is seen, the amount of ulnohumeral joint opening that does occur after such an injury, and the elbow position that maximizes visualization of this opening. While visualizing the most medial aspect of the ulnohumeral joint arthroscopically through the anterolateral portal, we sequentially sectioned the medial collateral ligament complex until all of the medial ligamentous restraints were cut. A valgus load was applied after each incision, and the extent to which the ulnohumeral joint opened was measured. Ulnohumeral joint opening was not visualized in any specimen until complete sectioning of the anterior bundle was performed. After the anterior bundle was released, 1 or 2 mm of joint opening was present in all specimens. Complete release of the medial collateral ligament led to dramatic increases in medial joint opening in all seven specimens (4 to 10 mm). Varying the angle of elbow flexion from 15 degrees to 120 degrees revealed that visualization of the medial joint opening was best at 60 degrees to 75 degrees. Finally, forearm pronation increased ulnohumeral joint opening and supination decreased joint opening in all specimens. We found that the entire anterior bundle must be sectioned before measurable and reproducible medial joint opening can occur.