Influence of meniscus on cartilage and subchondral bone features of knees from older individuals: A cadaver study

<div><p>Objective</p><p>Cartilage and subchondral bone form a functional unit. Here, we aimed to examine the effect of meniscus coverage on the characteristics of this unit in knees of older individuals.</p><p>Methods</p><p>We assessed the hyaline cartilage, subchondral cortical plate (SCP), and subchondral trabecular bone in areas covered or uncovered by the meniscus from normal cadaver knees (without degeneration). Bone cores harvested from the medial tibial plateau at locations uncovered (central), partially covered (posterior), and completely covered (peripheral) by the meniscus were imaged by micro-CT. The following were measured on images: cartilage volume (Cart.Vol, mm³) and thickness (Cart.Th, mm); SCP thickness (SCP.Th, μm) and porosity (SCP.Por, %); bone volume to total volume fraction (BV/TV, %); trabecular thickness (Tb.Th, μm), spacing (Tb.Sp, μm), and number (Tb.N, 1/mm); structure model index (SMI); trabecular pattern factor (Tb.Pf); and degree of anisotropy (DA).</p><p>Results</p><p>Among the 28 specimens studied (18 females) from individuals with mean age 82.8±10.2 years, cartilage and SCP were thicker at the central site uncovered by the meniscus than the posterior and peripheral sites, and Cart.Vol was greater. SCP.Por was highest in posterior samples. In the upper 1–5 mm of subchondral bone, central samples were characterized by higher values for BV/TV, Tb.N, Tb.Th, and connectivity (Tb.Pf), a more plate-like trabecular structure and lower anisotropy than with other samples. Deeper down, at 6–10 mm, the differences were slightly higher for Tb.Th centrally, DA peripherally and SMI posteriorly.</p><p>Conclusions</p><p>The coverage or not by meniscus in the knee of older individuals is significantly associated with Cart.Th, SCP.Th, SCP.Por and trabecular microarchitectural parameters in the most superficial 5 mm and to a lesser extent the deepest area of subchondral trabecular bone. These results suggest an effect of differences in local loading conditions. In subchondral bone uncovered by the meniscus, the trabecular architecture resembles that of highly loaded areas.</p></div

Correlations among SCP and SBT measurements (STB_{1–5 mm}) and (STB_6–10mm).

<p>Correlations among SCP and SBT measurements (STB_{1–5 mm}) and (STB_6–10mm).</p

Micro-architectural changes of the STB by sample site and depth for all knees (n = 28).

<p>Micro-architectural changes of the STB by sample site and depth for all knees (n = 28).</p

Subchondral trabecular bone (STB) architectural variables by sample site and gender and depth (1–5 and 6–10 mm below the SCP).

<p>Subchondral trabecular bone (STB) architectural variables by sample site and gender and depth (1–5 and 6–10 mm below the SCP).</p

Depth-dependence of morphological variables below the SCP at the three sampling sites.

<p>(CENT) central, uncovered; (PER) peripheral, fully covered; (POST) posterior, partially covered. Comparisons were by ANOVA for normally distributed variables and Kruskal-Wallis test otherwise. Data are mean±SD. BV/TV, bone volume fraction (mineralized bone volume/total bone volume); Tb.Th, trabecular thickness; Tb.N, trabecular number; Tb.Pf, trabecular pattern factor; SMI, structure model index; DA, degree of anisotropy, POST, posterior sampling site (partially covered); CENT, central sampling site (uncovered); PER, peripheral sampling site (fully covered).</p

Mean score of cartilage lesion of the tibial plateaus in knees with/without meniscal calcifications, hyaline cartilage calcifications and CT-assessed osteoarthritis.

<p>Mean score of cartilage lesion of the tibial plateaus in knees with/without meniscal calcifications (MC+/MC<b>−</b>), hyaline cartilage calcifications (HCC+/HCC<b>−</b>) and CT-assessed osteoarthritis (CT-OA+/CT-OA<b>−</b>). The percentage of knees is calculated out of the 29 left knees analyzed after dissection and ink staining.</p

Computed tomographic scans of the same knee showing osteoarthritis in the medial femoro-tibial compartment on a coronal reformation (A) and in the proximal tibio-fibular joint on a sagittal reformation (B).

<p>Osteoarthritic changes are consistent with multiple osteophytes (white arrows) and subchondral cysts (arrow heads). Articular calcifications are visible in the femoro-tibial compartment.</p

Detection of meniscal calcifications, hyaline cartilage calcifications and CT-assessed osteoarthritis in femoro-tibial and proximal tibio-fibular joints.

<p>Detection of meniscal calcifications, hyaline cartilage calcifications and CT-assessed osteoarthritis in femoro-tibial joints and proximal tibio-fibular joints expressed by subjects, knees and femoro-tibial compartments when applicable (<i>N/A</i>: not applicable). Osteoarthritis was considered for CT-assessed Kellgren and Lawrence (KL) grade ≥2.</p

Computed tomography scans of the same knee demonstrating calcifications within the hyaline cartilage (black arrows, arrow heads) and the meniscal segments (white arrows) in the femoro-tibial joint on a sagittal (A) and coronal (B–C) reformations, and in the proximal tibio-fibular joint on a sagittal reformation (D).

<p>Computed tomography scans of the same knee demonstrating calcifications within the hyaline cartilage (black arrows, arrow heads) and the meniscal segments (white arrows) in the femoro-tibial joint on a sagittal (A) and coronal (B–C) reformations, and in the proximal tibio-fibular joint on a sagittal reformation (D).</p

Distribution of calcifications in the hyaline cartilage of the femoral condyles.

<p>Each condyle was divided into inner, middle and outer thirds for analysis.</p