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This Article Full Text Full Text (PDF) All Versions of this Article: 32/5/1197    most recent 0363546503262643v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Request Reprints Citing Articles Citing Articles via ISI Web of Science (2) Citing Articles via Google Scholar Google Scholar Articles by Shepard, M. F. Articles by Andrews, J. R. Search for Related Content PubMed PubMed Citation Articles by Shepard, M. F. Articles by Andrews, J. R. Related Collections Shoulder Biomechanics

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

Michael F. Shepard, MD^*,, Jeff R. Dugas, MD, Nigel Zeng, PhD and James R. Andrews, MD

From the Orthopaedic Specialty Institute, Orange, California, and the American Sports Medicine Institute, Birmingham, Alabama

^* Address correspondence to Michael F. Shepard, Orthopaedic Specialty Institute, 280 S. Main Street, Suite 200, Orange, CA 92868 (e-mail: moshepard72{at}yahoo.com).

Background: The pathogenesis of superior labral anterior posterior lesions remains controversial.

Hypothesis: The biceps anchor is more vulnerable to loading with a posterior vector as opposed to an in-line pull.

Study Design: Controlled laboratory study.

Methods: Eight pairs of cadaveric shoulders were dissected, and the biceps tendon was loaded to failure in 1 of 2 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 significantly increased ultimate strength with in-line loading (group A, 508 N) as opposed to posterior loading (group B, 262 N, P <.001). 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.

Conclusions: Direction of biceps loading resulted in significant differences in the ultimate strength of the biceps anchor and the generation of superior labral anterior posterior lesions. The biceps anchor was significantly weaker when loaded with a posterior vector.

Relevance: The superior labrum may be most vulnerable to injury in late cocking. The reproducible generation of type II superior labral anterior posteriorlesions may have applications as a biomechanical model.

Key Words: superior labral anterior posterior (SLAP) lesion • biceps • labrum • instability