A novel cadaveric model for anterior-inferior shoulder dislocation using forcible apprehension positioning

Area of Science:

• Orthopedics
• Biomechanics
• Anatomy

Background:

• Anterior-inferior shoulder dislocation is a common injury.
• Understanding the in vivo mechanism is crucial for effective treatment.
• Existing cadaveric models may not fully replicate the dynamic forces involved.

Purpose of the Study:

• To develop and validate a novel cadaveric model for anterior-inferior shoulder dislocation.
• To simulate the in vivo mechanism of injury using a custom testing device.
• To analyze the biomechanical forces leading to dislocation and associated capsulolabral lesions.

Main Methods:

• Utilized 14 cadaveric upper limbs, fixing scapulae to a custom shoulder-testing device.
• Simulated rotator cuff and deltoid muscles using a pneumatic system with pulleys and cables.
• Positioned the glenohumeral joint in apprehension and applied horizontal abduction to induce dislocation, measuring forces with load cells.

Main Results:

• The cadaveric model successfully produced anterior-inferior dislocations in all specimens.
• Six dislocations resulted in avulsion of the capsulolabrum from the glenoid bone; eight showed capsulolabral stretching.
• Pectoralis major muscle force at dislocation (609.6 N) was comparable to the joint compression force (569.6 N).

Conclusions:

• A novel cadaveric model accurately simulates anterior-inferior shoulder dislocation via forcible apprehension positioning.
• The model effectively replicates in vivo capsulolabral lesions, including avulsion and stretching.
• This model serves as a valuable tool for studying shoulder instability biomechanics and injury patterns.