| Research Abstract |
We performed this experimental study to investigate the mechanism of inferior capsular shift procedure to stabilize the shoulder with multidirectional instability.
We used 10 fresh previously-frozen cadaveric shoulders. All the muscles were removed from the shoulder, and the scapula was stabilized to the custom-made shoulder fixator. The position of the humeral head relative to the glenoid was measured using plain roentgenograms. The humerus was loaded inferiorly with 0 kg, 0,5 kg, and 1.0 kg load. The capsular conditions were 1) intact, 2) anteroinferior capsule imbricated using a clamp, 3) posteroinferior capsule imbricated in the same fashion. The Intraarticular pressure was measured using a pressure sensor attached to the catheter filled with saline.
The negative value of intraarticular pressure increased with the increase of the load in a linear fashion. This was also observed after imbrication of anterior and posterior capsule. There was no significant difference between the capsular conditions. The position of the humeral head translated less than 5 mm when the Intraarticular pressure was intact regardless of capsular conditions. When the Intraarticular pressure was vented, the humeral head dislocated inferiorly. After the imbrication of anterior and posterior capsule, the humeral head was still inferiorly subluxated.
In conclusion, the major stabilizing mechanism of the inferior capsular shift procedure is to maintain the intraarticular pressure by reducing the joint volume.
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