Degeneration Affects Three-Dimensional Strains in Human Menisci: In situ MRI Acquisition Combined With Image Registration

Abstract

Degenerative changes of menisci contribute to the evolution of osteoarthritis in the knee joint, because they alter the load transmission to the adjacent articular cartilage. Identifying alterations in the strain response of meniscal tissue under compression that are associated with progressive degeneration may uncover links between biomechanical function and meniscal degeneration. Therefore, the goal of this study was to investigate how degeneration effects the three-dimensional (3D; axial, circumferential, radial) strain in different anatomical regions of human menisci (anterior and posterior root attachment; anterior and posterior horn; pars intermedia) under simulated compression. Magnetic resonance imaging (MRI) was performed to acquire image sequences of 12 mild and 12 severe degenerated knee joints under unloaded and loaded [25%, 50% and 100% body weight (BW)] conditions using a customized loading device. Medial and lateral menisci as well as their root attachments were manually segmented. Intensity-based rigid and non-rigid image registration were performed to obtain 3D deformation fields under the respective load levels. Finally, the 3D voxels were transformed into hexahedral finiteelement models and direction-dependent local strain distributions were determined. The axial compressive strain in menisci and meniscal root attachments significantly increased on average from 3.1% in mild degenerated joints to 7.3% in severe degenerated knees at 100% BW (p ≤ 0.021). In severe degenerated knee joints, the menisci displayed a mean circumferential strain of 0.45% (mild: 0.35%) and a mean radial strain of 0.41% (mild: 0.37%) at a load level of 100% BW. No significant changes were observed in the circumferential or radial directions between mild and severe degenerated knee joints for all load levels (p > 0.05). In conclusion, high-resolution MRI was successfully combined with image registration to investigate spatial strain distributions of the meniscus and its attachments in response to compression. The results of the current study highlight that the compressive integrity of the meniscus decreases with progressing tissue degeneration, whereas the tensile properties are maintained.

Acute repair of meniscus root tear partially restores joint displacements as measured with MRI and loading in a porcine knee

“…There is a clear improvement in our images and images from similar studies to achieve more signal from the meniscus while maintaining higher resolution and/or shorter scan times [13], [14], [20]- [22]. This study is not without limitations.…”

“…To our knowledge, we are the first to utilize T 1 VIBE in the knee specifically for meniscus imaging. There is a clear improvement in our images and images from similar studies to achieve more signal from the meniscus while maintaining higher resolution and/or shorter scan times [13], [14], [20]–[22].…”

“…Then, a partial segmentation of the tibia was made using ITK-SNAP's active contour semi-automatic segmentation tool [32]. The tibia coordinate system and segmentation were created in the Intact Low Load image, and the five other images (Intact High Load, Tear Low and High Load, and Repair Low and High Load) were aligned to this coordinate system by rigid registration of the tibia, using the segmentation as a registration mask [20], [21], [33]. All registrations were visually checked to confirm alignment of the tibia across all 6 conditions.…”

“…Two studies have utilized MRI to measure meniscus protrusion/extrusion at various flexion angles in healthy, uninjured subjects or in patients with OA, but not following a diagnosed meniscus injury [18], [19]. Other work used MRI to measure 3D strains in the meniscus at various degeneration levels, but either did not report femur or meniscus displacements or only studied healthy joints [20]- [22]. Additional work has measured cartilage deformations under loading using MRI-compatible loading devices or exercise, but meniscus findings were not reported [23]- [25].…”

Knee Joint Menisci Are Shock Absorbers: A Biomechanical In-Vitro Study on Porcine Stifle Joints

“…Normal menisci have a highly anisotropic structure that is mainly composed of water (75%), collagen (23%), water-binding glycosaminoglycans (1%), and other matrix components leading to a time-dependent viscoelastic behavior ( Herwig et al, 1984 ; Pereira et al, 2014 ; Seitz et al, 2021 ). While under static equilibrium conditions ( Tibesku et al, 2004 ; Martin Seitz et al, 2013 ; Schwer et al, 2020 ) and repetitive loading ( Kessler et al, 2006 ), the menisci exhibit considerable axial deformation, high impact, or shock loads, as seen, e.g., during jump landings, leading to an increase in their stiffness, and thus, to a decrease in the ability to reduce the transmitted stresses. Therefore, we hypothesize that the menisci contribute significantly to knee joint shock absorption during repetitive loads, while under impact loads, this shock absorption potential is absent.…”