A biomechanical evaluation of the role of labrum on anterior/posterior translation of shoulders at different degrees of abduction.

The objective of the study was to investigate the effects of anterior and posterior labrums on the anterior/posterior translations of shoulders. Thirteen cadaver shoulders were arthroscopically evaluated and nine were selected based on the absence of any pathological findings. These shoulders were tested intact, vented and after sequential arthroscpoic incision of the anterior and posterior labrums. The anterior/posterior translations were measured in a specially designed apparatus. The loads vs. displacement curves were obtained. The loads vs. displacement curves of the shoulders before and after labrum incision did not show any appreciable differences. Moreover the measured loads at 6 mm displacement did not show any statistically significant differences due to labrum incision. It was concluded that both anterior and posterior labrum incisions of the shoulders did not show any appreciable differences in anterior/posterior laxity. An arthroscopic technique was successfully developed to isolate the effect of labrum on the shoulder laxity.