Roger Dee, MD, Chairman, Department of Orthopaedics, holds a metal on metal artificial hip joint, one of the new generations of prosthetics.
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requiring total hip replacement surgery now have an expanded array of options for prosthesis, with newer artificial joints made of material that is longer wearing. "Wear rates are dramatically reduced, compared with techniques that were used in the 1960s and 70s," said Roger Dee, MD, Chairman of the Department of Orthopaedics at Winthrop.
An artificial hip joint is composed of
a ball and socket. Since the 1960's, joints have typically consisted of a metal ball nested inside a polyethylene socket. Physicians found that while these worked fairly well, after about 15 or 20 years they began to wear out. This made the procedure impractical for younger patients. Physically active people also experienced high wear rates.
The problem, according to Dr. Dee, was that "particles from the bearing surface would insinuate their way between the bone and the prosthesis." The result is called
osteolysis, literally an "eating away" of the bone surrounding the implant.
Newly developed manufacturing techniques have greatly reduced the problem of wear, however. By altering the molecular structure of the polyethylene during the
manufacturing process, the plastic socket is less likely to shed microscopic particles that cause osteolysis. "It is expected that a change in the molecular configuration of the polyethylene will considerably lengthen the life
of the total hip," said Dr. Dee.
These implants are being used at Winthrop in younger patients as well as those with more active lifestyles.
Dr. Dee noted that there is yet another development in total hip replacement technology available. In this version, the polyethylene socket is reinforced with a wear resistant metal liner, increasing the lifetime of the implant. The metal surfaces are lubricated by fluids naturally present in the body.
"The original metal on metal articulations did not have the polyethylene cushion," explained Dr. Dee. "As a result, stress fractures were commonly seen in patients' pelvic bones."
This new implant has a polyethylene
"sandwich" between it and the pelvic bone
to improve shock absorbency.
Winthrop orthopaedic surgeons were the first on Long Island to use the new metal/metal implants and continue to provide their patients with the most sophisticated devices available. In addition to these two new devices, they are also utilizing implants with a ceramic head and polyethylene socket. For additional information on the range of options for total joint replacement at Winthrop, call
(516) 663-2234.
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