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A Closer Look at the Knee
The knee is the largest joint in the body and is central to nearly every routine activity.
The knee joint is formed by the ends of 3 bones: the lower end of the thighbone
(femur), the upper end of the shinbone (tibia), and the kneecap (patella).
Thick, tough tissue bands called ligaments connect the bones and stabilize
the joint. A smooth, plastic-like lining called cartilage covers the ends
of the bones and pre-vents them from rubbing against each other, allowing
for flexible and nearly frictionless movement. Cartilage also serves as
a shock absorber, cushioning the bones from the forces between them. Finally,
a soft tissue called synovium lines the joint and produces a lubricating
fluid that reduces friction and wear.
Arthritis - The Leading Cause of Knee Pain
One of the most common causes of knee pain and loss of mobility is the
wearing away of the cartilage lining. When this happens, the bones rub
together causing significant pain and swelling - a condition known as
osteoarthritis. Trauma and direct injury to the knee can also cause osteoarthritis.
Conservative treatments such as steroidal and nonsteroidal anti-inflammatory
drugs, physical therapy, and cortisone injections may effectively relieve
pain and restore mobility. However, more severe pain and disability frequently
require knee "resurfacing" surgery.
Total Knee Replacement - A New Lease on Joint Life
Total knee replacement (TKR) is a surgical procedure inwhich the arthritic or
damaged surfaces of the joint are removed and replaced with an artificial
joint called a prosthesis. The artificial joint is designed to move just
like a healthy human joint.
In total knee replacement, the prosthesis is composed of strong metal
alloy, to replace diseased bone, and high-density polyethyl-ene, to replace
diseased cartilage .
One part is attached to the end of the thighbone where diseased bone
has been removed, and another is anchored to the shin-bone. The replacement
may also include a circular piece of plastic that attaches to the kneecap
to replace cartilage or diseased bone. Cement may or may not be used to
anchor the prosthesis into place.
Total knee replacement has been performed for nearly 40 years and has
enabled millions of Americans suffering from severe knee pain and stiffness
to return to active and rewarding lives. Recent advances in joint implant
materials are making TKR safer and more e ffective than ever. They also
have the potential to significantly increase the longevity of the implants
- an important benefit, especially for younger, more active patients.
The Stryker® Knee Navigation System
Helping to make total knee replacement even better...
Now, advanced computer-assisted surgical monitoring with the Stryker®
Navigation System also promises to help enhance the longevity of
knee replacements. To better appreciate this technological advance in
orthopedic surgery, let us first consider the critical role of proper
mechanical alignment in total knee replacement.
Precise Alignment Critical to TKR
As with any moving part, alignment is key to smooth movement and long-term
wear, just as wheel alignment affects the life of automobile tires. This
is also the case with knee replacement. For years, surgeons have used
X-rays, specialized instrumentation, operative technique, and experience
to ensure a tight fit and proper alignment of the knee implant to the
hip joint. And these have serv d them - and their patients - well. It is
now under-stood that to obtain the best possible outcomes in TKR, accuracy
to within 1 to 2 degrees and 1 to 2 millimeters is extremely important.1
The Stryker Knee Navigation System was designed to assist the surgeon
in achieving this degree of precision - routinely and consistently.
Science Made Simple
While the medical and computer science behind the Knee Navigation System
is extremely complex, the system's instrumentation and functions are relatively
easy for the surgeon to use. Minimally invasive wireless "pointers" and
"trackers" send data pertaining to knee movement (kinematics) to the Knee
Navigation System computer. These data are translated into real-time images
that provide the surgeon with a comprehensive understanding of the knee
mechanics... before any bone is cut. A rmed with this information, the
surgeon can make pre- and intra-operative adjustments to within a fraction
of a degree, helping to ensure the best possible fit and placement of
the knee prosthesis. Once the implant is in place, the System can also
provide post-operative outcomes assessment data.
To obtain the best possible outcomes in TKR, accuracy to within 1 to
2 degrees and 1 to 2 millimeters is extremely important.1 The
Stryker Knee Navigation System was designed to assist the surgeon in achieving
this degree of precision ... routinely and consistently.
Learn more about new technologies in image guided surgery
1. Data on file at Howmedica Osteonics.
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