Effects of a novel medial meniscus implant on the knee compartments: imaging and biomechanical aspects

The altered biomechanical function of the knee following partial meniscectomy results in ongoing articular cartilage overload, which may lead to progressive osteoarthritis (OA). An artificial medial meniscus implant (NUsurface^® Meniscus Implant, Active Implants LLC., Memphis, TN, USA) was developed to mimic the native meniscus and may provide an effective long-term solution for OA patients, alleviate pain, and restore joint function. The goal of the current study was to investigate the potential effect of an artificial medial meniscus implant on the function of the lateral compartment of the knee and on the potential alterations in load distribution between the two compartments under static axial loading, using advanced piezo-resistive sensors. We used an integrated in situ/in vivo experimental approach combining contact pressure measurements of cadaveric knees with MRI joint space measurements of 72 mild OA patients. We employed this integrated approach to evaluate the mechanical consequences in both the medial (treated) and lateral knee compartments of two levels of meniscectomy and implantation of an artificial meniscus implant. Partial and subtotal meniscectomies of the medial meniscus resulted in statistically significant decrease in contact areas (p = 0.008 and p < 0.0001, respectively) and increased contact pressures in the medial compartment; however, implantation of the artificial meniscus implant restored the average contact pressure to 93 ± 14% of its pre-meniscectomy, intact value. Additionally, we found that neither the two different grades of medial meniscectomies, nor implantation of the artificial medial meniscus implant affected the lateral compartment of the knee. The MRI data from the patient cohort facilitated the integration of real-life clinical results together with the laboratory measurements from our cadaveric study, as these two approaches complement each other. We conclude that the use of the artificial medial meniscus implant may re-establish normal load distribution across the articulating surfaces of the medial compartment and not increase loading across the lateral knee compartment.