Biomedical Engineering Reference
In-Depth Information
availablewillallowforoptimizationofconditionsneededforengi-
neering articular cartilage with functional zonal variations, with a
final goal of treating a wide range of cartilage conditions.
36.1 Introduction
Normal articular cartilage is an avascular, aneural, alymphatic tis-
sue with a zonal structure that allows for e
cient low-friction
load bearing in synovial joints. The noncalcified cartilage is com-
monly described as having three zones with distinct features and
functions (Fig. 36.1). The superficial zone is soft in compression,
allowing for even stress distribution, and the resident chondro-
cytes secrete a lubricant molecule, proteoglycan 4 (PRG4), which
adheres to the surface and is abundant in the synovial fluid to aid
in low-friction articulations.
1
,
2
The middle zone is stiffer in com-
pression, due largely to the abundance of sulfated glycosaminogly-
cans. The deep zone integrates with the calcified cartilage and stiff
subchondral bone through aligned collagen fibrils to maintain the
integrityof the osteochondral junction.
Figure 36.1.
Zonal organization of articular cartilage. Differences are evi-
dentincellmorphologyandfunction,aswellasextracellularmatrixcontent
and organization with depth from the articular surface.
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