Effect of knee flexion angle on the direction and magnitude of tensile force in complete lateral meniscus radial tears: A porcine biomechanical study.

Purpose: The effect of the knee flexion angle on the direction and magnitude of tensile force on the meniscus during flexion and extension under a load is unknown. This study aimed to clarify this effect on repair sutures in a lateral meniscus radial tear of the midbody under knee-joint conditions during flexion and extension. Methods: This study was performed using 10 porcine knees, a robotic system with six degrees of freedom and a load cell. Meniscal repairs were performed using horizontal sutures, with a single stitch between the central and peripheral regions at (1) the inner third position and (2) the outer third position, each meniscus sequentially. The suture of the posterior segment was drawn tangentially anteriorly, whereas the suture of the anterior segment was drawn tangentially posteriorly. The suture of the posterior segment was connected to an anterior load cell to measure the tensile force applied to the suture in the posterior direction. Subsequently, the suture of the anterior segment was connected to a posterior load cell to measure the tensile force applied in the anterior direction. A valgus load of 5 N m was applied for three cycles at 30°, 60° and 90° flexion. Results: The tensile forces exerted anteriorly on the repair sutures at the inner and outer sides in the anterior segment at 30°, 60° and 90° flexions were 13.7/13.3 N (inner/outer), 7.6/7.3 N and 3.4/3.5 N, respectively. The tensile forces exerted posteriorly on the repair sutures in the posterior segment at 30°, 60° and 90° flexions were 1.8/1.5, 10.6/9.7 and 16.2/16.4 N, respectively. Conclusions: Tensile force was exerted on the repair sutures of complete lateral meniscus radial tears of the midbody, anteriorly in the anterior segment at 30° flexion and posteriorly in the posterior segment at 90° flexion. Level of Evidence: N/A.