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Elbow subluxation and dislocation. A spectrum of instability
S W O'Driscoll1, B F Morrey, S Korinek
1Department of Orthopaedic Surgery, Mayo Clinic, Rochester, Minnesota.
Clinical Orthopaedics and Related Research
|July 1, 1992
Summary
Posterior elbow dislocations result from posterolateral rotation and valgus moments. The anterior medial collateral ligament (AMCL) remains intact during these injuries, guiding reduction and rehabilitation strategies.
Area of Science:
- Orthopedic Surgery
- Biomechanics
- Anatomy
Background:
- Elbow dislocations are complex injuries often involving multiple ligamentous structures.
- Understanding the sequential stages and mechanisms of elbow instability is crucial for effective treatment.
Purpose of the Study:
- To investigate the biomechanical mechanism of posterior elbow dislocations.
- To determine the role of the anterior medial collateral ligament (AMCL) in elbow instability.
- To correlate pathoanatomy with the degree of instability in sequential stages.
Main Methods:
- Sequential release of elbow ligaments and capsules in fresh autopsy specimens.
- Application of external rotation, valgus moments, and axial forces.
- Measurement of kinematic displacements using a 3D electromagnetic tracking device.
- Testing of valgus stability during simulated active flexion.
Main Results:
- Posterior dislocations occurred in 12 of 13 specimens with the AMCL intact.
- Dislocation involved 34-50 degrees posterolateral rotation and 5-23 degrees valgus at 80 degrees flexion.
- The AMCL origin-to-insertion distance did not increase beyond normal during dislocation.
- No significant increase in valgus laxity was observed after reduction compared to intact specimens.
Conclusions:
- Posterior elbow dislocation is the final stage of instability from posterolateral rotation, progressing from lateral to medial soft-tissue disruption.
- The AMCL remains intact during posterior dislocation, indicating its importance in stability.
- Reduction of posterior dislocations should be performed in supination.
- Immediate rehabilitation in a hinged cast-brace in full pronation is feasible if valgus stability is present in pronation, suggesting AMCL integrity.