Influence of T-shift capsulorrhaphy on rotation and translation of the glenohumeral joint: An experimental study.

To evaluate changes in the response of capsuloligamentous restraints to translatory forces and rotation torques caused by experimental capsulorrhaphy (T-shift modification of Bankart repair), eight cadaveric shoulders were tested. Measurements were taken in intact and vented specimens, after severance of the anterior capsule at the glenoid rim (creating an artificial Bankart lesion), T-shaped incision of the anterior capsule, and refixation of the capsule (with a standard Bankart procedure) combined with tightening by T-shift. Rotation torques and translatory forces were applied in different positions of abduction with a specifically designed mounting apparatus that had four degrees of freedom. Dynamic and static measurements were performed with a tracking sysem that had six degrees of freedom. T-shift capsulorrhaphy restored the resistance of the capsuloligamentous restraints to translatory forces in all directions. This restoration was confirmed when we compared these results with data obtained from intact joints. No significant alteration of the centering mechanism resulting from rotation torques was observed, although the extent of external and internal rotation was remarkably decreased. This T-shift modification seems to produce a symmetric reduction of the volume of the capsule without significant displacement of the humeral head.