Page 3 - KNEETA

Total Knee Arthroplasty - A History

In knee replacements,

the prosthetic components must work in concert with existing The theory states that the knee joint is a particularly sophisticated
ligaments and provide normal kinematics and function in cases kind of four-bar link, because the cruciate ligaments are not rigid
and have to be kept taut by the rolling action of the bones.
important to maintain the function provided by the posterior cru-
ciate ligament (PCL). This can be achieved either by retaining the
ligament or by substituting for it using a post and cam mechanism FEMUR
or a raised anterior lip.
Knee replacements have made leaps and bounds from their PCL ACL
inception and continue to surpass previous designs.
How did we get where TIBIA

we are now?

The history of total knees may be traced back as far as 1860,
when Gluck fashioned a crude total knee of ivory that featured
a simple hinge. The device allowed only a limited angle of
rotation and motion in a single direction. Gluck’s hinge yielded
great strength, but was not biocompatible. Over the next 100
years, the knee was thought to behave according to this simple
hinge design. It was not until the mid 1960s when researchers
and surgeons again turned their attention to total knee replace-
ments. During this time, the kinematic assumptions in knees had
changed; no longer did researchers believe the knee was a simple
hinge. As the knee has many critical geometrical characteristics,
researchers thought the two cruciate ligaments and the two leg
bones formed a very sophisticated and precise mechanism, called
a four-bar link. Many total knee designs were based around this
rationale. This four-bar link mechanism of the knee is shown at
various stages of rotation in FIGURE 1.
FIGURE 1 | Four-Bar Link Theory
One important feature of the four-bar link theory is that the
instantaneous center of rotation coincides with the cross-over
point of the cruciate ligaments. This cross-over point moves as the It was not until the release of the ICLH Knee, which was designed
by Drs. Freeman and Swanson, that the four-bar link was
rotation that is found in a simple hinge joint. discredited. Their implant relied heavily on component geometry,

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