[Biomechanical evaluation of anterior instability of shoulder joint after glenoid osseous defect]

To evaluate the role of glenoid osseous structure on anterior stability of shoulder so as to provide the biomechanical basis for clinical treatment.

Ten fresh shoulder joint-bone specimens were collected from 10 adult males cadavers donated voluntarily, including 4 left sides and 6 right sides. The displacements of the specimens were measured at 0 degrees and 90 degrees abduction of shoulder joint by giving 50 N posterior-anterior load under the conditions as follows: intact shoulder joint, glenoid lip defect, 10% of osseous defect, 20% of osseous defect, and repairing osseous defect.

For intact shoulder joint, glenoid lip defect, 10% of osseous defect, 20% of osseous defect, and repairing osseous defect, the displacements were (10.73 +/- 2.93), (11.43 +/- 3.98), (13.58 +/- 4.86), (18.53 +/- 3.07), and (12.77 +/- 3.13) mm, respectively at 0 degrees abduction of shoulder joint; the displacements were (8.41 +/- 2.10), (8.55 +/- 2.28), (9.06 +/- 2.67), (12.49 +/- 2.32), and (8.55 +/- 2.15) mm, respectively at 90 degrees abduction of shoulder joint. There was no significant difference between intact shoulder joint and others (P > 0.05) except between intact shoulder joint and 20% of osseous defect (P < 0.05).

When shoulder glenoid lip defects or the glenoid osseous defect is less than 20%, the shoulder stability does not decrease obviously, indicating articular ligament complex is not damaged or is repaired. When glenoid osseous defect is more than 20%, the shoulder stability decreases obviously even if articular ligament complex is not damaged or is repaired. Simultaneous repair of glenoid osseous defect and articular ligament complex can recover the anterior stability of the shoulder.