Biomechanical Investigation of Elbow Dislocation: Comparative Analysis Using Papio anubis Baboon and Human Cadaver Models

Samer Kork^1*Karim Youssef¹Sherif Said¹Taha Beyrouthy¹Farid Amirouche²Edward Abraham²

• ¹College of Engineering and Technology, American University of the Middle East, Kuwait City, Kuwait
• ²University of Illinois at Chicago, Chicago, Illinois, Department of Orthopaedic Surgery, Chicago, United States

This study investigates the biomechanical mechanisms underlying elbow dislocation, 3 emphasizing the role of flexion angle and forearm rotation on joint stability. Simulating realistic 4 fall dynamics and injury conditions remains a major challenge in experimental biomechanics, 5 and this work addresses that gap through controlled in vitro testing and computational modeling. 6 Seventy Papio anubis (baboon) and twenty-one human cadaveric arms were tested under axial 7 and hyperextension loading conditions to evaluate dislocation thresholds and ligament failure 8 sequences. These trials indicate that maintaining bone integrity and soft-tissue support may 9 restore elbow stability through severalnonsurgical strategies. Across both models, dislocation 10 resistance increased with elbow flexion and was significantly greater in pronation compared to 11 supination. The results demonstrate that maintaining bony congruence and soft-tissue integrity 12 substantially enhances stability and that complete dislocation typically requires combined ligament 13 rupture and bony failure. Across 0◦–45◦of flexion, Stage III dislocation thresholds reached 14 approximately 1.9–2.2 kN in pronation versus 0.8–1.0 kN in supination for Papio anubis, closely 15 matching the human mean of 1.94 kN.. Finite-element simulations confirmed these patterns, 16 revealing stress localization at the coronoid process and radial head consistent with early-17 stage dislocation. The results highlight the translational relevance of the baboon model for 18 studying human elbow instability and provide a validated framework for future surgical and 19 rehabilitation strategies. These findings advance the mechanical understanding of elbow instability 20 and emphasize how forearm orientation and flexion angle influence load distribution, ligament 21 strain, and the sequence of failure.