EVALUATION OF THE ARTHROSCOPIC VALGUS INSTABILITY TEST OF THE ELBOW

Seven fresh-frozen cadaveric elbows were used to evaluate the extent t o which the medial collateral ligament must be injured before arthrosc opic evidence of valgus instability is seen, the amount of ulnohumeral joint opening that does occur after such an injury, and the elbow pos ition that maximizes visualization of this opening. While visualizing the most medial aspect of the ulnohumeral joint arthroscopically throu gh the anterolateral portal, we sequentially sectioned the medial coll ateral ligament complex until all of the medial ligamentous restraints were cut. A valgus load was applied after each incision, and the exte nt to which the ulnohumeral joint opened was measured. Ulnohumeral joi nt opening was not visualized in any specimen until complete sectionin g of the anterior bundle was performed. After the anterior bundle was released, 1 or 2 mm of joint opening was present in all specimens. Com plete release of the medial collateral ligament led to dramatic increa ses in medial joint opening in all seven specimens (4 to 10 mm). Varyi ng 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 fo und that the entire anterior bundle must be sectioned before measurabl e and reproducible medial joint opening can occur.