Dupuytren’s fasciectomy requires precise separation of diseased cords from adjacent neurovascular structures, yet conventional scalpels offer no intrinsic tissue selectivity and depend entirely on surgeon skill. This thesis presents Fascinex, a handheld oscillation-assisted cutting device built on a commercially available actuator (Dragonhawk X8) and equipped with custom blade geometries designed to exploit stiffness-dependent mechanical response for selective cutting. Multilayer anatomical phantoms were developed for evaluation, and clinicians compared Fascinex (6025 and 9000 RPM) with a scalpel in skin-incision and nerve-extraction tasks. While the scalpel remained superior in cutting speed and edge smoothness, Fascinex exhibited characteristic mechanical selectivity: stiff cord-like structures were incised reliably, whereas softer tissues deformed and remained preserved. At 9000 RPM, cutting deviations approached those of the scalpel, with no damage to simulated nerves or vessels. These results demonstrate proof-of-concept feasibility for stiffness-based tissue discrimination under oscillatory loading and highlight directions for improving blade design, vibration control, and ergonomics.

The thumb finger is indispensable for an independent daily life. Implant replacement, which aims to restore joint mobility and functionality, is one of the surgical treatments for patients with osteoarthritis at the thumb-base. However, current designs and the biomechanical understanding of the thumb-base joint are inadequate. Small bone size, deep location, and high degree-of-freedom challenge the investigation on this exquisite joint. Taking advantage of 4D CT scanning, this dissertation examined bone shape, joint contact, and the active motion boundary of the thumb-base joint among participants without signs of joint degeneration. In detail, the analysis compared the joint movement between females and males for the etiology of thumb-base osteoarthritis. The deeper insights gained into the structure and mechanics of the asymptomatic thumb-base joints provide the baseline understanding of the thumb-base joints, which can help researchers and healthcare professionals improve and develop more effective treatments for patients with thumb-base osteoarthritis. Furthermore, the exploration of connecting information between the skeletal and skin systems opens up possibilities for future research perspectives.

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.