Design of a customizable implant for thumb arthroplasty

Abstract

Osteoarthritis (OA) is a degenerative joint disease, i.e. “wear and tear” arthritis. Approximately 1,2 million people were known to have the disease in the year 2015. Although most joints affected by osteoarthritis have a eminent treatment, the treatments for OA in the trapeziometacarpal joint (TMC) aren’t proven superior to one another. Because there isn’t a superior total joint replacement for the TMC joint, various implants are on the market, based on different techniques and kinematics. For this reason, Reinier de Graaf Hospital feels compelled to develop a new implant to meet the requirements and design an implant that has a similar durability as current hip and knee replacement. Therefore the main assignment was to design a customizable implant for TMC joint replacement, that restores the anatomical and biomechanical functions of the TMC joint. The process of this graduation project was divided over three phase: the analysis phase, the concept development phase and the concept evaluation phase. To find the parameters to build a customizable implant, the variation of the trapezium, the metacarpal and the trapeziometacarpal joint were analyzed. Statistical shape modelling seemed to be a proper method. During this project a statistical shape model was acquired in cooperation with to Marco Schneider and Ju Zhang, whom developed a Statistical Shape model for the trapeziometacarpal joint. Furthermore, the kinematic characteristics were analyzed in cooperation with the Academic Medical Centre in Amsterdam. 4D CT technology, can visualize the motion of bones in-vivo after segmentation. The TMC joints of three healthy subjects were investigated. The transformation matrices found in this research, could be used to evaluate the concepts afterwards. During the conceptualization phase a customizable implant was designed in Rhinoceros in combination with the Grasshopper Plug-in to generate personalized implants, that resurface the trapezium. The method accurately mimics the trapezium articular surface, but failed to mimic the kinematical characteristics. Further proposals for the concept were made solve this issue.