A histological study of the medial meniscus posterior root tibial insertion

Abstract

Purpose: The functions of the meniscus are stabilizing the knee joint and controlling the complex biomechanics of the knee, such as tension, compression, and shear stress. The meniscal roots are important anchoring structures for normal meniscal function. Disruption of the medial meniscus (MM) posterior root leads to altered biomechanics, resulting in degeneration of the knee cartilage. Transtibial pullout repair technique is recommended to restore the MM function in patients with MM posterior root tear. Previous studies have investigated anatomical position of the MM posterior root. However, these studies are based on macroscopic findings. The aim of this study was to evaluate true attachment area of the MM posterior root tibial insertion (MMPI) using a histological analysis. Methods: Tibial surface samples were obtained from the osteoarthritic knees of 7 patients who underwent total knee arthroplasty. Among the study participants, three were men and four were women, with a mean age of 75 years. Patients with intact MMPI on macroscopic observation were selected. Patients with severe morphological bone changes and severe degenerated MM were excluded. Samples were divided into 4 regions (Fig. 1, 2 mm thickness) in a medial-to-lateral direction. Histological measurements were performed using safranin O-stained sagittal sections. The attachment of the MMPI was determined as the width of ligamentous fibers stained by safranin O dye. We determined the width of insertion area by referring the edge of ligamentous fibers. Results: Safranin O-stained insertional structure of the MMPI was observed in slice 1, slice 2, and slice 3. The widest MMPI was observed in the slice 2. Deposition of safranin O-stained proteoglycan was higher in the anterior one-third of the MMPI than in the central-to-posterior area on slice 2 (Fig. 2). The posterior cruciate ligament was detected on slice 3 and slice 4. Conclusions: This study demonstrated that the MMPI was placed on the area between the medial tibial eminence and PCL. Furthermore, the insertional structure of the MMPI mainly localized at the anterior one-third of the MM posterior root attachment. There were several limitations in this study. First, the tissue samples were obtained from elderly patients who underwent total knee arthroplasty. Second, this study was performed using a small sample size. Our results can help to create an accurate tibial bone tunnel within the dense MMPI during transtibial pullout repair of the MM posterior root tear.View Large Image Figure ViewerDownload Hi-res image Download (PPT)View Large Image Figure ViewerDownload Hi-res image Download (PPT)