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Posts Tagged ‘cement disease’


Collaboration that corrected a major problem in Hip Replacement Surgery

Reporter:Irina Robu, PhD

British orthopedic surgeon, John Charnley performed an operation that almost miraculously restored pain-free movement and active lives to patients whose hip-joint damage had made even the simple act of walking across the room difficult.

However, with the advance in materials Charnley removed the damaged joint and replaced it with one made of Teflon. He cut off the top of the thigh bone and inserted the end of a rod like metal implant into its center, cementing it in place. The round head of the implant fits perfectly into the Teflon hip socket. The procedure seemed to work, but within some year complications arose. The routine movement of the balls in the sockets made the Teflon wear quickly, loosening the implants. Charnley was required to operate on nearly 300 patients after they developed an infection around the implant.
Charnley filled that need with a more-resistant material called high-density polyethylene, which he began using in a new version of the artificial hip joint in 1962. In 1974, a noted orthopedic surgeon at Massachusetts General Hospital had a patient who had replaced surgery but his X-ray showed that a large portion of his thigh bone had been eaten away. Even after further tests, it was confirmed that the patient was cancer free. Harris saw three similar cases that year and many more over the years and it was defined as a new disease, periprosthetic osteolysis.

The condition led not just to implant failures, hip fractures, femur fractures, and complex reoperations to install new implants. It would take decades to devise a solution, in the form of a new material , highly crosslinked polyethylene invented in the labs of Harris and his Massachusetts Institute of Technology collaborator, Edward Merrill. A few years after Harris described the condition, in 1976, another separate research effort drawn its cause to tiny particles of the cement that secured the metal thigh implant inside the femur. Those particles caused a massive immune reaction that in turn triggered osteoclasts, the only cell in the body capable of destroying bone.

The discovery led to the condition being called “cement disease,” warning the development in the early 1980s of porous-metal implants that allowed the bone to grow into the implant and hold it in place in the thigh bone. Further research displayed that particles were still there, but of the polyethylene that made up the hip socket. Nevertheless, the polyethylene was far more durable than Teflon, the even motion of the ball in the socket caused wear, producing particles that set off the same destructive immune reaction.

By that discovery, researchers finally understood what was happening in the body. With so many hip replacement surgeries ongoing around the world, what was needed was a material more durable as polyethylene. Harris had asked patients to donate implants for study after they died, and he worked with lab members to examine them under a scanning electron microscope. The long, skinny molecules of high-density polyethylene, which normally curl had become aligned in the direction of the back-and-forth motion of the joint.

Harris worked with Merrill who mentioned that he can created polyethylene into a new form: highly crosslinked polyethylene. Meanwhile in 1998, the first artificial hips using highly crosslinked polyethylene were put in patients and it shows a huge progress.

SOURCE
https://news.harvard.edu/gazette/story/2018/03/harvard-surgeon-publishes-vanishing-bone-conquering-a-stealth-disease-caused-by-total-hip-replacements/?utm_source=SilverpopMailing&utm_medium=email&utm_campaign=Daily%20Gazette%2020180306

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