The role of the joint capsule in the stability of the elbow joint.

Existing studies lack a clear understanding of the interaction of the joint capsule with surrounding tissues and the local mechanical environment. Particularly, a finite element model of human elbow joint incorporating active behavior of muscle was constructed. The simulation was performed during the elbow joint flexion movement under different injury conditions of capsule (anterior capsule, posterior capsule, medial anterior capsule, lateral anterior capsule, medial posterior capsule, and lateral posterior capsule). The stress distribution and transfer of the joint capsule, ulnar cartilage, and ligaments were obtained under different injuries and flexion angles, to explore the influence of capsule injures on the stability of the elbow joint. In medial injury posterior capsule, the peak stress of the ulnar cartilage occurred at 60° flexion and shifted from posteromedial to anteromedial. And the stress was about 1.8 times that of no injury capsule. In several cases of posterior capsule injury, the stress of capsule decreased significantly and the peak stress was 40% of that in no injury joint capsule. In the case of anterior capsular injury, the cartilage stress did not change significantly, and the stress of anterior bundle and annular ligament changed slightly in the late flexion movement. These findings provide some help for doctors to treat elbow injury and understand the interaction of tissues around the joint after trauma.

Effect of the medial collateral ligament and the lateral ulnar collateral ligament injury on elbow stability: a finite element analysis.

Ligaments are the most important stabilizer of elbow. However, the stress of ligaments is hard to measure because of the complex biomechanical environment in the elbow. Our objective was to develop a human elbow finite element model and to validate it by a comparison with previous experimental data. Then several different ligaments injury conditions and elbow flexion were simulated to analyse the elbow instability and to stress the biomechanical consequences. The computational investigation of different effects of ligament constraints of elbow was studied by means of finite element analysis. The stress of the anterior bundle was almost greater than other ligaments in all conditions, which played the most important role during the elbow flexion. The posterior bundle was the secondary stabilizer during flexion after the anterior bundle. The lateral ulnar collateral ligament (LUCL) injury could result in an increase of the ulnar cartilage stress. The anterior bundle and the LUCL were recommended to be repaired in elbow joint dislocations and fractures. This study could help understand the dynamic effects of ligaments on the joint over the entire extension by investigating the tissue stress.