Human Modelling and Design of Custom-Made Knee Implants: Definition of an Automatic Procedure

Total knee arthroplasty (TKA) is the surgical procedure of choice for end-stage osteoarthritis. Even if it is widely performed, there is still dissatisfaction with the surgical procedure in about 20-30% of patients. Factors such as malalignment of the implant and the size of the components have been reported as the most common reasons for post-operative complaints. Custom-made prostheses have been introduced to replicate each individual joint geometry and kinematics. In this study, a novel approach is proposed to automate custom-made knee implant design. The aim is to create a pipeline, where customized implants can be designed automatically for a large number of patients, reducing the time for design. Firstly, a manual procedure for designing the implant is defined. The lower part of the femur is extruded with a thickness that matches with the natural anatomy of the patient and cut planes are used to design the customized femoral implant. Then, an automatic procedure is developed. For the purpose, a statistical shape model of femur, based on 33 patients, is created and employed. The procedure is tested with 5 study cases showing the potential of the methodology. Results will be furtherly validated on a larger scale.