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Limits imposed on glenohumeral motion by joint geometry
1Department of Orthopaedic Surgery, Loma Linda University, School of Medicine, CA 92350, USA.
Journal of Shoulder and Elbow Surgery
|July 1, 1995
Summary
Glenohumeral joint geometry limits shoulder motion. Obligate external rotation during elevation is essential for maximizing humeral cartilage articulation with the glenoid.
Area of Science:
- Orthopedic surgery
- Biomechanics
- Anatomy
Background:
- The glenohumeral joint's range of motion is influenced by its articular geometry.
- Understanding these geometric constraints is crucial for diagnosing and treating shoulder pathologies.
Purpose of the Study:
- To quantify the arcs of articular cartilage on the humeral head and glenoid in cadaveric shoulders.
- To determine the extent of uncovered cartilage in different planes of motion.
- To investigate how glenohumeral joint geometry limits shoulder movement.
Main Methods:
- Measurement and calculation of articular cartilage arcs in the frontal (coronal) and axial (transverse) planes.
- Study conducted on 50 cadaveric shoulder specimens.
Main Results:
- In the coronal plane, humeral heads had a 159° arc, with 96° covered by the glenoid, leaving 63° uncovered.
- In the transverse plane, the humeral arc was 160°, opposed by 74° of the glenoid, leaving 86° uncovered.
- Significant portions of articular cartilage remained uncovered in both planes, indicating geometric limitations.
Conclusions:
- Glenohumeral joint geometry inherently restricts motions occurring in simple arcs.
- Obligate external rotation during shoulder elevation is a biomechanical necessity to increase the articulating surface area of the humeral head cartilage.