In-Vivo Functional Evaluation Of Elbow Joint And Ulnar Collateral Ligament

Many postoperative complications are reported following elbow surgery,including joint instability,limited range of movement,etc..Understanding the in-vivo elbow biomechanics can help reduce the incidence of complications after elbow surgery.This study aimed to evaluate the in-vivo elbow kinematics and function of the ulnar collateral ligament by using a dynamic dual fluoroscopic imaging system based tracking technique.We hoped to provide some fundamental knowledge for clinical elbow trauma treatment.The main research content can be divided into the following parts.(1)The six-degree-of-freedom kinematics of normal elbow was investigated during the flexion-extension movement and pronation-supination movement.The kinematic differences between ulna and radius,and the coupling relationship between flexion angle and valgus/varus or internal/external rotation angle were analyzed.(2)The change of instant rotation axis during elbow flexion-extension movement was analyzed,and the relationship between the morphological parameters of the articular surface and the changes of rotation axis was evaluated.(3)The shortest path calculation algorithm was used to calculate the length of the ulnar collateral ligament during the elbow flexion.The effect of attachment points’ position on ligament length change was evaluated through medial collateral ligament reconstruction simulation.The main conclusions were listed as follows:(1)Humeroulnar joint decreased linearly at valgus change.It showed a nonlinear change,which rotated internally firstly and then rotated externally during flexion.The valgus angle of the humeroradial joint decreased linearly,and the internal rotation angle increased linearly during flexion.The radius gradually moved posteriorly,distally and medially relative to the ulna from pronation to supination.The valgus angle of the radioulnar joint increased at the same time.The humeroulnar joint showed increasing valgus and increasing external change from pronation to supination.The kinematics change pattern of the ulna from pronation to supination was not affected by the flexion position.(2)It showed individual movement patterns of instant rotation axis during flexion amount all subjects.The lateral trochlear size,medial trochlear size and length of trochlear were the key factors that affect the change of instantaneous rotation axis of the elbow.(3)The position of attachment points on ulna did not affect the pattern of ligament length change.When the fixed position was chosen on distal or medial of the anatomical attachment on the humerus side,the length of the ligament gradually increased as flexion angle increased.When the fixed position was chosen on the proximal or lateral of the anatomical attachment,the ligament length gradually reduced.On the humerus side,the isometric ligament length change region looked like oval shape and its long axis pointed from medial trochlear center to medial epicondyle.In this study,the in-vivo kinematics of the natural subjects’ elbow joints and the performance of the ulnar collateral ligament were analyzed.It provided fundamental biomechanical knowledge for elbow movement rehabilitation,design of artificial joint prostheses and ulnar collateral ligament reconstruction.