Interactive biomechanical effects between medial meniscus anterior horn transverse tears and osteoarthritic degeneration: a finite element simulation analysis

Abstract

BACKGROUND: Meniscus injury, as a significant contributing factor to knee joint degeneration, can accelerate the progression of osteoarthritis through anterior horn tears that alter joint stress distribution. Existing studies primarily focus on biomechanical changes in normal bone conditions, while the regulatory role of different bone conditions on the injury mechanism remains unclear. OBJECTIVE: To investigate the effect of medial meniscus anterior horn transverse tears on the biomechanical differences of knee joints with varying bone conditions. METHODS: Imaging data of the lower limb from a healthy adult were used to construct a normal knee joint model in Mimics 2017. The model was further optimized and assembled using Geomagic Studio 2017 and SolidWorks 2017, and a medial meniscus anterior horn transverse tear model was established. Material properties were assigned in Ansys Workbench 2017, and three finite element models were created to simulate normal bone, reduced bone mass, and osteoporosis conditions. The models were validated using anterior drawer and axial loading tests. With the femur constrained and the distal tibia fixed, a 1000 N axial compressive load was applied to calculate stress peaks and strain distributions. RESULTS AND CONCLUSION: (1) Under static standing conditions, both normal and injured medial meniscus models showed significantly higher joint stress loads in reduced bone mass and osteoporosis groups compared to normal bone mass group. (2) The medial meniscus anterior horn transverse tear model exhibited a progressive increase in stress loads on femoral cartilage and both menisci compared to the normal model, while stress on tibial cartilage surfaces decreased with bone mass reduction. In the meniscus injury model, stress concentrated at the tear edges. (3) Subchondral bone regions showed elevated stress levels under reduced bone mass conditions, especially after medial meniscus injury, with significantly increased strain distribution range and equivalent stress peaks (P < 0.05). (4) These findings suggest that medial meniscus anterior horn transverse tears under reduced bone density exacerbate joint contact area reduction and local stress concentration, potentially leading to increased local strain in tibial subchondral bone, indicating an interactive biomechanical effect between bone degeneration and meniscus injury. This provides a reference for meniscus repair strategies considering bone quality differences.

1. Introduction

The meniscus is a crucial biomechanical structure of the knee joint, primarily responsible for shock absorption, load transmission, joint lubrication, and improving the congruity between the femur and tibia [1-2]. Its core function is to distribute gravitational loads over a larger articular cartilage surface, thereby reducing excessive stress on the cartilage. Additionally, it limits hyperextension and hyperflexion of the knee, promotes synovial circulation, and enhances joint stability [3-4]. Meniscus tears are common structural injuries of the knee, with medial meniscus injuries occurring more frequently than lateral ones [5]. The ability of the meniscus to transmit axial loads depends on the integrity of the knee joint structures [6-7]. When a complete tear occurs, the meniscus's capacity to convert axial loads into hoop stresses is significantly diminished, leading to joint pain, reduced stability [8], and an increased risk of moderate-to-severe cartilage damage in the medial femoral condyle. Research has confirmed that this pathological change is a key mechanism in the progression of osteoarthritis [9].

Current studies have found that osteoarthritis and osteoporosis often exhibit a synergistic trend, with certain correlations in pathological mechanisms and clinical manifestations [10]. Osteoporosis leads to reduced bone mass and disruption of trabecular bone architecture, thereby decreasing joint stability and load-bearing capacity. This change may further affect the stress distribution on articular cartilage, accelerating the onset and progression of osteoarthritis [11]. Existing research indicates that osteoporosis not only exacerbates degenerative changes in osteoarthritis but also makes patients with medial meniscus posterior root tears more susceptible to osteonecrosis complications [12]. Notably, this risk is particularly pronounced in spontaneous osteoporosis cases, suggesting that osteoporosis may play a significant role in the disease outcome after meniscus injury.

Human finite element models are three-dimensional simulation models based on medical imaging data and anatomical details. Through finite element analysis, these models can non-invasively provide and reproduce human biomechanical data and visualize tissue stress distributions.