Biomedical Engineering Reference
In-Depth Information
Chapter 5
The Bone-Cartilage Interface
Virginia L. Ferguson and Rachel C. Paietta
5.1
Introduction
Bone-cartilage interfaces in the body anchor together stiff bone and compliant
cartilage in a thin (
100's of microns) [
1
] region that progressively calcifies with
aging. This bone-cartilage, or osteochondral, interface is of critical importance in
articular joints and the spine due to the significant occurrence and health detriments
of osteoarthritis and intervertebral disc (IVD) degeneration [
2
]. In 2008, 27 million
individuals in the U.S. suffered from clinical osteoarthritis [
3
]. A separate analysis
showed that as many as 40% of adults experience herniated discs in the lumbar
spine which require surgical repairs [
4
]. One potential solution for repair of
damaged cartilage or IVD is to replace the soft tissue with a synthetic replacement,
yet engineered cartilage implants often fail due to a lack of mechanical anchoring
[
5
]. Another solution, total joint replacement, is destructive to the surrounding
tissue [
6
,
7
], has a limited lifetime (~15 years for femoral head replacements),
and is not a viable option for young patients needing successive replacements.
Instead, recent efforts have focused on integrating engineered tissues and devices
into the osteochondral interface or underlying bone [
5
,
8
-
14
]. Synthetic grafts are
improving in functionality for repair of joints and entheses (i.e., the bone-tendon
attachment); however, such engineered solutions have yet to succeed, possibly
because they lack equivalent material properties and functionality as compared to
the native, healthy tissue.
One common approach to designing artificial osteochondral interfaces is to
adhere or form a continuum between stiff, bone-like and soft, cartilage-like
materials [
5
,
14
,
15
]; however, such solutions have not yet shown efficacy in the
harsh loading environment of the osteochondral region [
14
]. The natural
mechanisms for functional grading of hard-soft tissue interfaces are considered
V.L. Ferguson (
*
) R.C. Paietta
Department of Mechanical Engineering, University of Colorado, Boulder, CO, USA
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