An Instrument for Matching Defect and Implant Size in Matrix-induced Autologous Chondrocyte Implantation

Cartilage defects in the knee lead to limitations in the daily life of a large group of people in the worldwide population. Research on the treatment of cartilage injuries has lead to various clinical procedures, one of them being Matrix Induced Autologous Chondrocyte Implantation (MACI). MACI surgery consist of two procedures. During the first intervention cartilage cells of the patient are first harvested from a healthy chondral area in the knee. The cells are cultivated and during the second procedure, these are implanted in the defect using a collagen scaffold. Exact fitting of the scaffold has shown to be important for the success of the surgery. Currently there is no reproducable method to match the size of the defect and the implant, without the use of overlapping scaffolds or removing excessive helathy cartilage. Objective. The objective of this study is to evaluate an instrument designed to arthroscopically create a delimited implantation site in the human knee according to a predefined shape. This shape is used to cut an equally shaped collagen implant to fit in the implantation site. Method. An electronic device, based on a movable nitinol knife that makes a rotational cut was chosen as the best solution to solve this problem. A prototype was build to test to what extent the movement of the knife can be controlled and what forces are acting on the cartilage. The amount of removed healthy cartilage was tested using a virtual test. Results: The mean amount of healthy cartilage that is removed using a predefined outline is 21% compared to an estimated 38% in current methods. The sensor and knife output partially match the prescribed paths, but the first 120 degrees of instrument rotation are not measured. Rotation of the device did not result in slipping of the tip in the cartilage. The knife blade could be inserted into the cartilage with forces lower than 3 Newtons for knife lengths up to 9.6 mm. Making a rotational cut with the instrument was not possible
Biomedical Engineering