In vitro evaluation of shoulder external rotation after a Bankart reconstruction

The Bankart procedure is a commonly performed anterior shoulder reconstruction that may shorten the anterior capsule. In this study, biomechanical testing was performed to evaluate the effect of the classic Bankart reconstruction on external rotation of the shoulder, The procedure was performed on six fresh-frozen cadaveric specimens that were free of intraarticular pathologic changes. With the arm in 0 degrees of abduction, resisting torques about the vertical axis were measured while the humerus was externally rotated. The intact specimens demonstrated a nonlinear load displacement behavior in which little resisting torque was measured until a moderate amount of external rotation was applied. Shortening the capsule by 2 mm resulted in a 40% decrease in the low-tension zone of external rotation, and shortening the capsule an additional 5 mm resulted in a 67% decrease in the low-tension zone. This study demonstrates that the normal shoulder capsule is quite sensitive to anterior capsular shortening and suggests that care must be exercised when performing a Bankart reconstruction to avoid overtightening this structure.