Abstract
ObjectiveCartilage 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.MethodsWe 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).ResultsAmong 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.ConclusionsThe 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.
Highlights
Knee menisci play an important role in load bearing, shock absorption, and joint congruity and stability [1]
Among the 28 specimens studied (18 females) from individuals with mean age 82.8±10.2 years, cartilage and subchondral cortical plate (SCP) were thicker at the central site uncovered by the meniscus than the posterior and peripheral sites, and Cart.Vol was greater
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
Summary
Knee menisci play an important role in load bearing, shock absorption, and joint congruity and stability [1]. Their role in attenuating and distributing impact loads may be greater than that of the hyaline cartilage [2]. Contact pressures below the meniscus increased by 23% after partial meniscectomy in a knee simulator [4] and peak contact pressure by 25% with a posterior root tear in the medial meniscus of human cadaver knees [5]. Posterior root tears in the medial meniscus often lead to meniscal extrusion, which is a risk factor for osteoarthritis progression [9,10]
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