Differences in the Ultimate Strength of the Biceps Anchor and the Generation of Type II Superior Labral Anterior Posterior Lesions in a Cadaveric Model

Zhepard MF, Dugas JR, Zheng N, Andrews JR. Differences in the ultimate strength of the biceps anchor and the generation of Type II superior labral anterior posterior lesions in cadaveric models. The American Journal of Sports Medicine 32(5):1197-1201, 2004

The pathogenesis of superior labral anterior posterior lesions remains controversial. The study hypothesized that the biceps anchor was more vulnerable to loading with a posterior vector as opposed to an in-line pull.

Methods

Eight pairs of cadaveric shoulders were dissected, and the biceps tendon was loaded to failure in one of two loading patterns. Loading pattern A was meant to simulate the eccentric load of the biceps in the deceleration phase of throwing. Loading pattern B was meant to simulate the posterior biceps load of the late cocking phase.

Results

The biceps anchor demonstrated increased ultimate strength with in-line loading (group A, 508 N) as opposed to posterior loading (group B, 262 N). All group B specimens failed at the biceps anchor, resulting in a Type II superior labral anterior posterior lesion. Specimens in group A did not create a superior labral anterior posterior lesion. The results suggested that the biceps anchor was significantly weaker when loaded with a posterior vector and the superior labrum may be most vulnerable to injury in late cocking phase.