Christopher A. Browne, MD
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Patient Education: Computer-Assisted Knee Surgery

The Stryker® Knee Navigation System

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 prevents 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 in which 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 polyethylene, 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 shinbone. 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 minimally invasive surgical techniques and joint implant materials are making TKR safer and more effective 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

Now, advanced computer-assisted surgical monitoring with the Stryker Knee 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 served them…and their patients…well.

It is now understood 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. Armed 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.

1. Data on file at Howmedica Osteonics

For More Information Please Visit the Stryker Navigation Website >>

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Last Modified: July 2, 2018