Functional Assessment of Meniscus Extrusion, Excursion, and Hoop Strain under Clinically Relevant Loaded Range of Motion Conditions in Meniscus-Intact and Meniscus Root-Deficient Knees using a Novel Biomechanical Model

The knee is meniscus-dependent, relying on the tissue's biomechanical properties to maintain joint health and function. Meniscus dysfunction has primarily been assessed by measuring tibiofemoral articular contact areas and pressures, which entail important limitations. Meniscus extrusion, excursion, and hoop strain are dynamic measures of meniscal function, which have potential advantages for clinically applicable biomechanical testing of meniscus. The objective of this study was to quantify meniscus extrusion, excursion, and hoop strain under clinically relevant loading and motion conditions in meniscus-intact and meniscus-deficient cadaveric knees using a novel model. Cadaveric knees (<i>n</i> = 8) were dynamically tested through a functional range of motion under 30 N of compressive load in a robotic testing system to determine meniscus translations at full extension and 30, 60, 90, and 100 degrees of flexion through 10 cycles. For meniscus-intact and meniscus-deficient (posterior meniscus root release) states, measurements for medial and lateral meniscus excursion, extrusion, and hoop strain were determined by calculating respective translations of fiducial tracking markers and were compared for statistically significant differences. In the meniscus-intact state, medial and lateral meniscus extrusion, excursion, and hoop strain metrics corresponded well to previously reported measurements, suggesting that this model has translational validity for assessing functional kinematics for clinical application. For both medial and lateral menisci, posterior root release was associated with significantly more meniscus extrusion and significantly less maximum meniscus hoop strain compared with the meniscus-intact status. For meniscus excursion, medial root release showed significant differences from the intact status only at a knee flexion angle of 100 degrees, whereas lateral root release differed significantly from the intact status at 60 and 90 degrees of knee flexion. Taken together, this study verifies that this model can effectively quantify meniscus extrusion, excursion, and hoop strain under clinically relevant loading and motion conditions in meniscus-intact and meniscus-deficient knees for use in preclinical studies aimed at assessing the severity of meniscus deficiency, as well as surgical interventions and postoperative management strategies intended to optimize meniscus preservation.