Speer and colleagues tested how detaching the anterior inferior glenohumeral ligament and labrum from the glenoid, a simulated Bankart lesion, changes glenohumeral translation and its coupled motion in each direction.
Cadaveric study of 9 shoulders, each tested intact and again after the lesion, at three elevations and three rotations.
Methods
Model
9 fresh cadaveric shoulders from donors aged 56 to 85
Apparatus fixing the three rotations while measuring translation along three axes
Constructs
Intact shoulder
Simulated Bankart lesion: ligament and labrum detached from just above the anterior band to just behind the infraglenoid tubercle
Labral remnant excised after the lesion
Loading
50 N anterior, posterior and inferior forces applied in turn
22 N joint compression
Three elevations in the scapular plane
Anterior and posterior tests in 30° internal, neutral and 30° external rotation, inferior tests in neutral only
Outcome measures
Change in multidirectional humeral translation after simulated Bankart lesion
Coupled translation perpendicular to each applied force
Posterior band strain from a liquid‑metal strain gauge
Key Findings
The lesion increased anterior and inferior translation at every elevation, in at least one rotation, but each increase was very small.
Posterior translation rose significantly only at 90° of elevation (neutral and internal rotation, p < 0.05), with no significant change at 0° or 45°.
Coupled motion was unchanged, so the humeral head followed the same path with or without the lesion and only moved slightly farther.
Removing the thin labral remnant did not change anterior translation at 0°, 45° or 90°, which the authors linked to the small 22 N compression load.
The authors inferred that detachment from the glenoid alone does not allow dislocation, and that permanent stretching of the inferior glenohumeral ligament may also be required.
Board pearl
Detaching the anterior inferior glenohumeral ligament from the glenoid raised translation by at most 3.4 mm, so a Bankart lesion alone did not appear to allow dislocation.
Authors' conclusion
Injury to the anterior part of the inferior ligament at the level of the glenoid does not appear to be solely responsible for the increased anterior glenohumeral translation that is necessary to produce an anterior dislocation of the shoulder.
Speer and colleagues tested how detaching the anterior inferior glenohumeral ligament and labrum from the glenoid, a simulated Bankart lesion, changes glenohumeral translation and its coupled motion in each direction.
Cadaveric study of 9 shoulders, each tested intact and again after the lesion, at three elevations and three rotations.
Methods
Model
9 fresh cadaveric shoulders from donors aged 56 to 85
Apparatus fixing the three rotations while measuring translation along three axes
Constructs
Intact shoulder
Simulated Bankart lesion: ligament and labrum detached from just above the anterior band to just behind the infraglenoid tubercle
Labral remnant excised after the lesion
Loading
50 N anterior, posterior and inferior forces applied in turn
22 N joint compression
Three elevations in the scapular plane
Anterior and posterior tests in 30° internal, neutral and 30° external rotation, inferior tests in neutral only
Outcome measures
Change in multidirectional humeral translation after simulated Bankart lesion
Coupled translation perpendicular to each applied force
Posterior band strain from a liquid‑metal strain gauge
Key Findings
The lesion increased anterior and inferior translation at every elevation, in at least one rotation, but each increase was very small.
Posterior translation rose significantly only at 90° of elevation (neutral and internal rotation, p < 0.05), with no significant change at 0° or 45°.
Coupled motion was unchanged, so the humeral head followed the same path with or without the lesion and only moved slightly farther.
Removing the thin labral remnant did not change anterior translation at 0°, 45° or 90°, which the authors linked to the small 22 N compression load.
The authors inferred that detachment from the glenoid alone does not allow dislocation, and that permanent stretching of the inferior glenohumeral ligament may also be required.
Board pearl
Detaching the anterior inferior glenohumeral ligament from the glenoid raised translation by at most 3.4 mm, so a Bankart lesion alone did not appear to allow dislocation.
Authors' conclusion
Injury to the anterior part of the inferior ligament at the level of the glenoid does not appear to be solely responsible for the increased anterior glenohumeral translation that is necessary to produce an anterior dislocation of the shoulder.