Anatomic and Biomechanical Evaluation of Ulnar Tunnel Position in Medial Ulnar Collateral Ligament Reconstruction.

BACKGROUND: Although numerous techniques of reconstruction of the medial ulnar collateral ligament (mUCL) have been described, limited evidence exists on the biomechanical implication of changing the ulnar tunnel position despite the fact that more recent literature has clarified that the ulnar footprint extends more distally than was appreciated in the past.

PURPOSE: To evaluate the size and location of the native ulnar footprint and assess valgus stability of the medial elbow after UCL reconstruction at 3 ulnar tunnel locations.

STUDY DESIGN: Controlled laboratory study.

METHODS: Eighteen fresh-frozen cadaveric elbows were dissected to expose the mUCL. The anatomic footprint of the ulnar attachment of the mUCL was measured with a digitizing probe. The area of the ulnar footprint and midpoint relative to the joint line were determined. Medial elbow stability was tested with the mUCL in an intact, deficient, and reconstructed state after the docking technique, with ulnar tunnels placed at 5, 10, or 15 mm from the ulnotrochlear joint line. A 3-N·m valgus torque was applied to the elbow, and valgus rotation of the ulna was recorded via motion-tracking cameras as the elbow was cycled through a full range of motion. After kinematic testing, specimens were loaded to failure at 70° of elbow flexion.

RESULTS: The mean ± SD length of the mUCL ulnar footprint was 27.4 ± 3.3 mm. The midpoint of the anatomic footprint was located between the 10- and 15-mm tunnels across all specimens at a mean 13.6 mm from the joint line. Sectioning of the mUCL increased elbow valgus rotation throughout all flexion angles and was statistically significant from 30° to 100° of flexion as compared with the intact elbow ( P < .05). mUCL reconstruction at all 3 tunnel locations restored stability to near intact levels with no significant differences among the 3 ulnar tunnel locations at any flexion angle.

CONCLUSION: Positioning the ulnar graft fixation site up to 15 mm from the ulnotrochlear joint line does not significantly increase valgus rotation in the elbow.

CLINICAL RELEVANCE: A more distal ulnar tunnel may be a viable option to accommodate individual variation in morphology of the proximal ulna or in a revision setting.