Patient-specific distal radioulnar joint arthroplasty Towards a novel implant design using four-dimensional computed tomography

The distal radioulnar joint (DRUJ) is vital for multiple activities of daily life. A malunited distal radius fracture or hereditary disease can lead to osteoarthritis. In this instance the last treatment where a functional joint remains is arthroplasty. During a surgical procedure the joint is replaced by an implant. Unfortunately, the most prevalent implant is suspected to change the forearm’s motion pattern. Moreover, it suffers from a high complication rate and often needs revision surgery.
In this thesis, a new approach to DRUJ arthroplasty is described where the motion pattern of the patient is defined such that it can be used to develop a patient-specific implant. To investigate the motion of the forearm, four-dimensional computed tomography (4D-CT) was used.
The methodological error of 4D-CT was first validated. Subsequently, kinematic parameters like the forearm rotation axis, radius translation along the ulna and radius rotation about its own longitudinal axis were quantified. To be able to design a patient-specific implant, a reference must be present. An obvious choice would be the contralateral forearm. A review was conducted to analyze similarity regarding geometry and function. This review was supplemented by a study comparing intraindividual kinematics in healthy forearms. Both studies revealed high bilateral symmetry. Next, a patient study was conducted to determine the kinematic changes in patients with the most prevalent implant. It was found that the implant was incapable of restoring the healthy forearm’s motion pattern. Finally, the kinematic differences were reviewed with respect to complications that occurred during patient follow-up.