Effects of zone-specific superior labral detachment on biceps anchor stability

This study aimed to elucidate the degree of biceps anchor displacement that occurs when specific zones of the superior labrum are detached from the glenoid.

Descriptive laboratory study.

Twelve cadaveric scapulae with intact labrums were prepared by removing the surrounding musculature with the labrum, biceps anchor, and biceps tendon carefully preserved. Pulleys were used to apply traction in 3 different directions- superior, lateral, and combined posterior/superior/lateral, to simulate the "peel-back" mechanism-while a continuous 1.13 kg of traction was applied to the biceps tendon. Labral tears were created by sharp incisions in isolation and in combinations of 3 zones defined relative to the glenoid fossa: anterior, posterior, or superior. The displacement of the biceps anchor (position of the marker after the simulated lesion relative to the marker position with the labrum intact) was measured relative to a rigid reference frame.

The greatest degree of displacement occurred with the sectioning of all 3 zones, followed by the sectioning of 2 adjacent zones. Superior traction created the least displacement in all combinations, while lateral traction created maximal displacement, with one exception: in the setting of anterosuperior/superior lesions, maximal displacement was observed using the peel-back mechanism.

Biceps anchor displacement, particularly the degree and direction of displacement, is affected by the labral detachment pattern. All 3 labral zones assessed in this study have important biomechanical contributions to biceps anchor displacement.

These findings have important implications relating to the clinician's arthroscopic assessment of superior labrum anterior and posterior (SLAP) tears, as well as the determination of need for stabilization. This information is particularly useful when treating SLAP tears in certain laborers and athletes, whose activities may cause specific biceps anchor displacement patterns.