Biomedical Engineering Reference
In-Depth Information
10
Hard Tissue Replacements
10.1 Long Bone Repair ...........................................................................
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Wires and Cables • Pins • Screws • Plates • Intramedullary Nails
10.2 Joint Replacements .........................................................................
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Implant Fixation Methods
10.3 Total Joint Replacements .............................................................
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Hip Joint Replacement • Knee Joint Replacement • Ankle
Joint Replacement • Shoulder Joint Replacement • Elbow Joint
Replacement • Finger Joint Replacement (Metacarpophalangeal
and Interphalangeal Joints) • Prosthetic Intervertebral
Disk • Prostheses for Limb Salvage
Defining Terms .........................................................................................
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References ..................................................................................................
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Sang-Hyun Park
Orthopedic Hospital
University of California,
Los Angeles
Adolfo Llinás
Fundacion Cosme and
Damián
Universidad de los Andes
Vijay K. Goel
University of Toledo
The use of biomaterials to restore the function of traumatized or degenerated connective tissues and thus
to improve the quality of life of a patient has become widespread. In the past, implants were designed
with insufficient cognizance of biomechanics. Accordingly, the clinical results were not very encourag-
ing. An upsurge of research activities into the mechanics of joints and biomaterials has resulted in better
designs with better
in vivo
performance. The improving long-term success of total joint replacements for
the lower limb is testimony to this. As a result, researchers and surgeons have developed and used fixa-
tion devices for the joints, including artificial spine disks. A large number of devices are also available
for the repair of the bone tissue. This chapter provides an overview of the contemporary scientific work
related to the use of biomaterials for the repair of bone (e.g., fracture) and joint replacements ranging
from a hip joint to a spine.
10.1 Long Bone Repair
The principal functions of the skeleton are to provide a frame to support the organ systems and to
determine the direction and range of body movements. Bone provides an anchoring point (insertion),
for most skeletal muscles and ligaments. When the muscles contract, long bones act as levers, with the
joints functioning as pivots, to cause body movement.
Bone is the only tissue able to undergo spontaneous regeneration and to remodel its micro- and mac-
rostructure. This is accomplished through a delicate balance between
osteogenic
(bone-forming) and
osteoclastic
(bone-removing) processes (Brighton 1984; Kakar and Einhorn 2009). Bone can adapt to a
new mechanical environment by changing the equilibrium between osteogenesis and osteoclasis. These
processes will respond to changes in the static and dynamic stress applied to bone; that is, if more stress
than the physiological is applied, then the equilibrium tilts toward more osteogenic activity. Conversely,
if less stress is applied, then the equilibrium tilts toward osteoclastic activity (it is known as the Wollf 's
law of bone remodeling) (Wolff 1986).
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