Influence of Different Stages of Post-Traumatic Elbow Joint Capsule Healing on Pronation Movement

Purpose: In this study, animal experiments and finite element simulation was used to study pronation-supination and the mechanical environment of the elbow at different stages of joint capsule healing after injury to reveal the mechanism of mechanical factors affecting the development of the elbow contracture. Methods: The injured limbs were immobilized for 2 weeks, 4 weeks, 6 weeks and 8 weeks in animal experiments. The total ROM and joint stiffness of the limbs were tested at each time point to define the differences between different groups. The internal soft tissue stress during joint capsule healing was obtained by finite element simulation. Results: In the animal experiments, compared with the no injury group, the total ROM of the injury group was decreased and the joint stiffness of the injury group was increased. The joint capsule thickness and shear modulus increased gradually in different stages of joint capsule healing. In the simulation, the internal soft tissue stress increased at different stages of joint capsule healing. The peak stress of the capsule was 8.32 MPa, 10.5 MPa, 11.4 MPa, 11.1 MPa and 12.2 MPa, respectively. The peak stress of humerus cartilage at different stages of joint capsule healing was greater than that of ulna cartilage and 1.2 times that of ulna cartilage. Conclusion: This study revealed the evolution of stress distribution in the surrounding tissue in the process of joint capsule healing and provided a theoretical basis for the rehabilitation of the elbow contracture and the design of rehabilitation aids.