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Scapular Morphology and Posterior Shoulder Stability: Biomechanical Evidence From an Advanced Cadaveric Shoulder
Bettina Hochreiter1, Justine Fleurette2, Mohammad Haddara2
1Department of Orthopaedics, Balgrist University Hospital, University of Zurich, Zurich, Switzerland.
The American Journal of Sports Medicine
|February 6, 2026
Summary
Combined glenoid and acromial malalignment significantly increases posterior shoulder translation. Complete correction of both deformities is essential for restoring normal shoulder kinematics and stability.
Area of Science:
- Orthopedic surgery
- Biomechanics
- Shoulder anatomy
Background:
- Static posterior shoulder subluxation (SPSL) is linked to glenoid retroversion and acromial morphology.
- The biomechanical role of acromial anatomy in SPSL is not fully understood.
Purpose of the Study:
- To investigate the combined effect of acromial and glenoid malalignment on posterior humeral head translation.
- To evaluate the efficacy of targeted corrections in restoring posterior shoulder stability.
Main Methods:
- Controlled laboratory study using a 6-DoF, 8-muscle actuated cadaveric shoulder simulator.
- Tested seven conditions: intact, posterior labral detachment, isolated glenoid malalignment, isolated acromial malalignment, combined malalignment, and combined malalignment with posterior acromial bone graft (PABG).
- Measured humeral head translation during simulated active elevation.
Main Results:
- Isolated glenoid malalignment increased posterior translation by 29%; isolated acromial malalignment by 31%.
- Combined malalignment resulted in a significant 54% increase in posterior translation.
- Glenoid correction with PABG partially reduced translation but did not restore native kinematics.
Conclusions:
- Both glenoid and acromial malalignment contribute to pathological posterior humeral head translation.
- Combined malalignment has additive effects, significantly worsening posterior translation.
- Complete anatomic correction of both deformities is necessary for restoring normal posterior shoulder kinematics.
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