Methods for Testing Meniscal Repair Using a 3D-Printed Meniscus

Abstract

Torn and damaged menisci resulting from trauma are very common knee injuries, which can cause pain and mobility limitations and lead to osteoarthritis. Meniscal injuries can require surgery to repair the tissue damage and restore mobility. Here we describe the biomechanical testing of a 3D-printed meniscus to illustrate methods to determine if it has the strength and durability to effectively repair meniscal tears and restore knee biomechanics. This work was designed to demonstrate the steps needed to test novel meniscus repair devices prior to moving toward animal testing. The first testing step determined the ability of the 3D-printed meniscus to withstand surgical fixation by measuring the suture pull-out force. We show that vertical 2/0 silk or Fiberwire sutures need an average of 1.4 or 1.8 N, respectively, to pull through the meniscus, while horizontal sutures need only 0.7 and 1.2 N, respectively. The next step measured the compressive strength of normal, damaged, and repaired porcine meniscus tissue. Here, we show that meniscectomy decreased the stiffness of meniscus tissue from 26.7 ± 0.85 N to 7.43 ± 0.81 N at 25% strain. Menisci repaired with the 3D-printed tissue restored 66% of the measured force at 25% strain. The final step measured the contact pressures and areas in an ex vivo porcine knee before and after meniscal repair was made with the 3D-printed meniscus tissue. The example 3D-printed meniscus was successfully sutured into the porcine knee joint but failed to restore normal knee contact pressures. This work demonstrates the need for an iterative biomechanical testing process of biomaterial development, 3D-printing optimization, and knee kinematics to develop a durable and functional meniscus repair device. In summary, the methods described here serve as a guide for the functional evaluation of novel meniscus repair devices.