Functional MR Imaging of Human Meniscus Is Associated with Histologic Degeneration

Introduction Meniscus and cartilage pathologies are closely intertwined in osteoarthritis (OA). Meniscal pathologies may predispose the joint to early OA. Our purpose was to assess human meniscus functionality (i.e., the response-to-loading patterns) ex vivo based on quantitative magnetic resonance imaging (MRI) techniques and as a function of histologic degeneration.

Material and Methods Forty-five meniscus samples of variable degeneration were harvested from the lateral meniscus body during total knee arthroplasties. Samples underwent serial high-resolution proton-density-weighted imaging and T1, T1ρ, and T2 mapping on a 3-T MRI scanner (Achieva, Philips) using validated turbo spin-echo, inversion recovery, spin-lock multi-gradient-echo, and multi-spin-echo sequences. Force-controlled loading was applied through an MRI-compatible loading device that induces compressive loading by torque. For each sample and loading position, measurements were performed unloaded (δ₀) and after loading to 2 bar (δ₁: compression force 37.1 N, torque 0.67 Nm) and to 4 bar (δ_2: 69.1 N, 1.24 Nm). Histology (Pauli classification) and biomechanics (elastic stress) served as a reference. Samples were trichotomized as normal (n = 14), mildly degenerative (n = 16), or moderate to severely degenerative (n = 15) based on histology.

Results For T1, homogeneous loading-induced decreases in all samples were found, regardless of degeneration. In the apical zones of normal samples, T1ρ values increased, whereas they decreased in degenerative samples. Changes in T2 were ambiguous.

Conclusion Meniscus functionality may be visualized using serial mapping techniques. The response-to-loading patterns of T1ρ are associated with histologic degeneration and may provide a surrogate biomarker of meniscus functionality and incipient/manifest load transmission failure to the adjacent cartilage.