Introduction - Arthritis is a condition causing pain, deformations and loss of motion in human joints. The surgical instruments used to place a specific unconstrained prosthesis that is used to treat an arthritic joint are difficult to use. The objective for this thesis is to improve the current placement procedure by carrying out an analysis on the procedure and by developing a novel (set of) instrument(s). Analysis - Analysis displayed which instruments used during the placement procedure fall short, and in what way. The analysis forms the basis for a list of design criteria. Concept design - A concept was generated for the part of the procedure in which the bones are prepared such that the prosthesis can be placed. Final design - One of the surgical instruments that is part of the concept was designed in detail and a prototype was made. Evaluation - An evaluation study was carried out on cadaveric joints. The efficacy of the working principle of surgical instrument was demonstrated. Discussion - It is not possible to make a statistically significant comparison between the performance of the surgical instrument and the performance of the conventional instruments used for the same procedure. Conclusion - The surgical instrument could be an improvement to the current placement procedure. A comparative study between the surgical instrument and the conventional instruments should be carried out.