PhD-candidate image based implant design / School CAPHRI / Department of Orthopedic Surgery

Orthopedic surgeons employ a wide variety of surgical techniques to treat cartilage defects of the knee. Treatment algorithms provide guidance to surgeons for treatment selection, but these treatment algorithms typically only take defect size and patient functional demands (high or low) into consideration. Orthopedic surgeons increasingly recognize that other patient-specific factors need to considered and that no single treatment caters to the needs of all patients.
Orthopedic surgeons especially recognize a treatment-gap for middle-aged patients suffering from cartilage defects and desire improved treatment options and treatment selection guidance for these patients. As regenerative capacity is detrimentally affected beyond the age of 40 or after failed cartilage repair surgery, regenerative cartilage repair therapies are substantially less effective in these patient groups. On the other hand, total knee arthroplasty (TKA) is not an option for middle-aged patients, as it does not provide the demanded functional restoration. In addition, total knee implant survival is substantially lower in more active, middle-aged patients, which inevitably necessitates one or more revision procedure(s) with associated high complication rates. Joint preservation, postponing or avoiding the need for TKA, is therefore the main objective of cartilage repair surgery in the middle-aged population.
Focal knee resurfacing implants (FKRIs) have been introduced in the last 10-15 years, and thereby a new strategy of “resurfacing/restoration” has been introduced to fill the gap between “repair” and “replacement.” First generation FKRIs are fully composed of metal and the availability of limited size and curvature options only contributed to high treatment failure rates. The combination of high implant stiffness and morphological mismatch leads to super-physiological stress peaks in adjacent or opposing cartilage during articulation, which leads to further cartilage degeneration. Second generation implants rely on improving implant fit (patient-specific implants and surgical guides) or more biomimetic material properties (forgiving to morphological mismatch) to overcome these issues.

A synthetic non-degradable polymer FKRI has been developed previously in the Chemelot InSciTe public-private collaboration project “SyCap.” Avalanche Medical BV has been founded as a spin-off company from this project to continue the development of this implant. The current project is intended to help refine the indications for use, design/use considerations, and clinical implementation for this medical device and similar implants.
To generalize across all treatments options, cartilage repair treatment success is influenced by a combination of biological factors (patient demographics, regenerative capacity, catabolic or inflammatory joint condition, etc.) and biomechanical factors (defect size and location, defect fill and joint morphology restoration, repair tissue or implant mechanical properties, surgical accuracy, joint mechanical axis correction, ligamentous repair). As we transition into an era of personalized medicine, selecting the right treatment for each patient is of utmost importance, and therefore the influence of all these factors on treatment outcomes must be elucidated in order to refine treatment selection algorithms.
In this OSTASKILLS project, we aim to explore the effect of the previously mentioned factors on clinical outcomes (or proxies thereof) for various cartilage repair techniques, with a primary focus on FKRIs (medical devices). A wide variety of methods will be employed to explore the influence of biological and biomechanical factors on clinical outcomes: insights gained from ex vivo models (biomechanical testing, surgical implantation accuracy evaluation) and in silico models (finite element modelling, statistical shape models) will be combined with insights from evaluating patient records and data (patient demographics, radiological imaging, patient-reported outcomes). Early health technology assessment will also be performed to evaluate cost-effectiveness of treatments.
These activities mark the first steps towards creating digital patient-twins, to better optimize treatment outcomes.

The research will be performed in the Laboratory for Experimental Orthopedics, Maastricht University, and the Joint Preservation Clinic of Maastricht University Medical Center (MUMC+), under the supervision of dr. P. Emans, dr. ir. Alex Roth, and prof. dr. Tim Welting. Ongoing collaborations with Eindhoven University of Technology (dr. René van Donkelaar) and University of Twente (prof. dr. ir. Gabrielle Tuijthof) will be leveraged for successful completion of this project. The OSTASKILLS project (www.ostaskills.eu) is a Marie Curie COFUND project coordinated by the Dutch Arthritis Society with the objective of training 10 PhD students in translational osteoarthritis research. Intersectoral collaboration and industry exchanges are important aspects of the training.