The kinematic elbow axis as a parameter to evaluate total elbow replacement: A cadaver study of the iBP elbow system

Malpositioning of prosthetic implants leads to biomechanical changes, often resulting in deteriorating functional outcome. This emphasizes the relevance of evaluating the surgical process of inserting the prostheses. This study tested to what extent the iBP elbow prosthesis and its alignment tools enabled a surgeon to reconstruct normal joint kinematics. It demonstrates the use of the kinematic elbow axis as an evaluation tool. An electromagnetic tracking device registered controlled passive elbow flexion of 10 embalmed upper extremities. The position and direction of the preoperative and postoperative kinematic elbow axes were established with the use of helical axes and compared. The postoperative position of the elbow axis differed from the preoperative axis because of limitations of the alignment tools. Suggestions for adjustment of the alignment tools are made. The direction of the imposed resection plane was correct; therefore, the direction of the postoperative elbow axis corresponded with the direction of the preoperative axis.