Thumb base osteoarthritis (OA) constitutes a significant burden of disease in our society, affecting up to one third of post-menopausal women. After conservative measures have failed, the current management is trapeziectomy or removal of the trapezium, the bone at the base of the thumb. Many prosthetic trapezium implants have been tested, brought to market to ultimately fail. None were based on the shape or volume of the patient’s own hand or trapezium. Ultimately, using 3-D printing, we aim to produce a model trapezium prosthesis which is volume appropriate to the patient and includes structural elements to enhance tendon interposition and ligament reconstruction. This project aims to identify what may predict the trapezium implant size and shape for each patient. This is a collaborative project with the Monash Institute of Medical Engineering which has provided seed-funding.