Why Abduction and External Rotation Should Be Avoided After Anterior Shoulder Dislocation Reduction
After reducing an anterior shoulder dislocation, abduction and external rotation positioning should be avoided because this position can lead to redislocation by placing the shoulder in the same vulnerable position that caused the initial dislocation. 1
Mechanism of Injury and Redislocation Risk
The anterior shoulder dislocation typically occurs when the arm is forced into abduction and external rotation, creating anterior instability. 1 Placing the shoulder back into this position after reduction:
- Recreates the mechanism of injury, stressing the already-damaged anterior capsulolabral structures 1
- Applies excessive translational forces on the humeral head against the glenoid, with internal rotation torques up to 67 N-m that must be resisted by compromised static stabilizers 1
- Increases horizontal abduction angle during movement, which promotes anterior shoulder instability with repetitive stress 1
Post-Reduction Positioning Concerns
The ACR specifically warns that care should be taken with positioning after shoulder reduction because certain positions may lead to redislocation. 1 The axillary lateral view positioning, which requires abduction and external rotation, may be particularly painful and risky for patients who have just had their shoulders reduced. 1
Biomechanical Rationale
During the arm cocking phase of shoulder motion (which involves abduction and external rotation):
- Maximum external rotation creates the greatest internal rotation torque, occurring near the time of maximum external rotation 1
- Shear forces combined with rapid rotation can lead to physeal or labral injury in the already-compromised joint 1
- The static stabilizers are weakened after dislocation, making them unable to adequately resist the translational forces in this position 1
Practical Clinical Implications
Avoid overhead pulleys during rehabilitation, as these encourage uncontrolled abduction that can worsen instability. 2, 3 Instead:
- Immobilize the shoulder in a position that does not stress the anterior structures 4, 5, 6, 7
- Focus rehabilitation on restoring range of motion gradually while maintaining proper alignment 2
- Progress external rotation and abduction slowly only after adequate healing and strengthening 2
Common Pitfall
The most critical error is returning the shoulder to positions of abduction and external rotation too early in the recovery process, before the damaged capsulolabral structures have healed and before adequate dynamic stabilization has been restored through rehabilitation. 2, 3