Elbow medial ulnar collateral ligament insufficiency alters posteromedial olecranon contact.

BACKGROUND The effect of elbow medial ulnar collateral ligament injury on posteromedial compartment contact is unknown. HYPOTHESIS Medial ulnar collateral ligament injury causes altered contact area and pressure in the posteromedial compartment of the elbow. STUDY DESIGN Controlled laboratory study. METHODS Seven elbow cadaveric specimens were tested in an apparatus that positioned the elbow at 30 degrees and 90 degrees of flexion. Partial and full tears were simulated by releasing the medial ulnar collateral ligament. Pressure-sensitive film was placed in the posteromedial compartment for each condition. Valgus torques of 1.25 and 2.0 N.m were applied for each ligament condition, and kinematic data were obtained at each flexion angle using a 3-dimensional digitizer. RESULTS Both ligament condition and valgus load had significant effects on contact area and pressure (P<.05). For a given load and flexion angle, the contact area decreased and the pressure increased with increasing medial ulnar collateral ligament insufficiency. Within these trends, statistical significance was found at 30 degrees of elbow flexion for both area and pressure (P<.05); at 90 degrees of elbow flexion, increasing medial ulnar collateral ligament insufficiency did not significantly affect contact area or pressure (P>.05). DISCUSSION Medial ulnar collateral ligament insufficiency alters contact area and pressure between the posteromedial trochlea and olecranon and helps explain the development of posteromedial osteophytes.