The posterior bundle of the elbow medial collateral ligament: biomechanical study and proposal for a new reconstruction surgical technique.

BACKGROUND: The medial collateral ligament (MCL) is one of the primary elbows stabilizers. It is composed of an anterior bundle (AB), a posterior bundle (PB) and a transverse bundle. In elbow dislocations, until today MCL reconstruction has addressed the AB only. The purpose of this paper is to understand the biomechanical role of the PB of the MCL and to propose a new surgical technique for the simultaneous reconstruction of the anterior and posterior bundles, preventing the risk of recurrent posterior dislocation or posteromedial rotational instability (PMRI).
MATERIALS AND METHODS: Sixteen cadaveric elbows were subjected to a force in compression, supination valgus and pronation varus. The residual stability was evaluated in three conditions: intact MCL, sectioned AB and sectioned AB + PB. The tests were performed in collaboration with the Department of Mechanical and Aerospace Engineering of the Politecnico di Torino. In six elbows, the MCL was then reconstructed with the new technique.
RESULTS: Complete posterior elbow dislocation does not occur until the PB is sectioned. The section of the AB alone causes elbow instability in valgus stress, but not a dislocation. The reconstruction of the AB and the PB using the described technique allows a good recovery of range of motion and joint stability.
CONCLUSIONS: The PB of the MCL has a primary role in elbow stability against valgus stress, and it prevents elbow posterior dislocation at all flexion angles. The described reconstruction technique should reduce the risk of residual PMRI.