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Large Joints Feature

This is Damiano Pasini preparing the implant for testing with students Sajad Arabnejad and Burnett Johnston / Courtesy of Owen Egan

Porous Implant to Extend Hip Replacement Life?

Elizabeth Hofheinz, M.P.H., M.Ed. • Tue, November 15th, 2016

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An engineering researcher from Canada just may have come up with a better mousetrap, er, hip replacement. According to Damiano Pasini, Ph.D., this new design should last longer and create fewer problems for the patients than existing implants.

Dr. Pasini said in the November 2, 2016 news release, "What we've done throughout the femoral stem is to replicate the gradations of density found in a real femur by using hollowed-out tetrahedral. Despite the fact that there are spaces within the tetrahedra, these forms are incredibly strong and rigid so they're a very efficient way of carrying a load. Just think of the lattice-work in the legs of the Tour Eiffel."

Dr. Pasini, a professor of mechanical engineering at McGill University, Montreal, Quebec, Canada, added, "So because the implant loosely mimics the cellular structure of the porous part of the surrounding femur, it can ‘trick’ the living bone into keeping on working and staying alive. This means that our implant avoids many of the problems associated with those in current use."

Dr. Pasini told OTW, “Cementless porous-coated implants are the gold standard in North America for restoring hip joint function through a total hip arthroplasty (THA) procedure. All hip replacements currently available in the market are fully solid and work well, but they are much stiffer then the surrounding host bone. The difference in stiffness between the metallic hip stems and the natural host bone in which it is implanted, lead to the degradation of the femoral bone around the implant, i.e., bone resorption. The phenomenon is well-known from many decades and is known as stress shielding.”

“We developed a fully porous hip implant that has properties tailored to seamlessly match the properties of the local host bone tissue. This makes our implant mechanically biocompatible, meaning that it is capable of keeping the surround femoral bone alive, as opposed to the implants available on the market which are fully solid, much stiffer and leading to bone loss in the long term.”

“Our implant will preserve the bone tissue in the long term with two main advantages for both primary and secondary revision THA. For primary THA, serious clinical consequences, such as peri-prosthetic fractures induced by stress shielding, will disappear. The treatment of patients requiring revision THA surgery will be improved, thereby drastically dropping costs in the health care sector. Fewer revision surgeries would thus be required. For secondary THA, i.e., if revision surgery were needed, the improved bone stock would reduce the risk of complications and mortality involved with secondary THA, and the cost involved would be significantly reduced as the improved bone stock would minimize the need for expensive bone grafting and additional reinforcing elements, all necessary in revision surgery.”

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