The hip: An essential articulation

Isabelle Catelas

“One day, thanks to tissue engineering and regenerative medicine, we may be able to regenerate joints within the human body itself, thereby eliminating the need for artificial implants, for the greater good of the patients.”

– Isabelle Catelas

With the aging of the population and the growing number of younger patients, more and more Canadians will need joint replacements. Thankfully, scientists, like Professor Isabelle Catelas of the Department of Mechanical Engineering and the Faculty of Medicine, are looking out for our well-being.

People who talk about untreatable joints or show defeatism when faced with aging and the wearing down of our bodies have evidently never heard scientists like Isabelle Catelas speak about their work. Spend some time listening to this professor and you will want to fund her research in order to be able to benefit from her results when you eventually need them!

Professor Catelas holds the Canada Research Chair in Bioengineering in Orthopedics. Her research includes developing therapeutic approaches to extend the lifespan of joint implants, and in particular hip implants. According to the Canadian Joint Replacement Registry, over 30,000 hip replacements were performed in Canada in 2008–2009, and approximately 35% of the recipients were under the age of 65. Although joint replacements are very effective at eliminating pain and restoring joint function, unfortunately they do not last indefinitely and many patients eventually need to have their implant replaced.

Hip implant failures are often due to bone loss around the implant, which is caused primarily by an inflammatory response to small particles breaking off as the implant wears down. “Each implant replacement becomes increasingly complex, because the patient has less and less bone left. Extending the lifespan of the implants would improve patients’ quality of life and result in lower healthcare costs,” explains the researcher, who hesitated between studies in engineering and medicine and whose work in the field of biomaterials now places her at the intersection of these two disciplines. “There are many ways to achieve this. The industry is working on improving implant materials and designs, while my team and I are working with the surgeons to better understand the reasons for failures. We retrieve and analyze the implants and samples of tissues from patients who are getting their implant replaced.” Understanding the biological mechanisms responsible for implant failures would allow this scientist to develop new therapeutic approaches—using molecules capable of controlling these mechanisms—and thus extend the lifespan of the joint replacements.

An important part of this research program focuses on hip implants with a metal head and a metal cup. Hip implants currently available on the market can be made of various combinations of metal, ceramic and polyethylene, each with its own advantages and disadvantages. “Metal-on-metal hip implants are resistant to wear, but, in some cases, they may cause hypersensitivity reactions that we still don’t fully comprehend. We are trying to understand these reactions in order to improve the implants and develop new methods for diagnosing patients more prone to developing such a reaction.”

Logically, a second important aspect of Professor Catelas’ research is bone regeneration, a field in which she had worked during her time with healthcare giant Baxter and at the University of California, Los Angeles (UCLA). “Patients getting their implant replaced or those suffering from a complex bone fracture, for example, suffer from bone loss. Bone is a vascularized tissue, so it often regenerates on its own,” explains the researcher. “However, when the bone loss is too great, the bone can’t overcome the loss on its own. We then need a substitute that will reconnect and regenerate the bone. If the substitute is biodegradable, it will be gradually replaced by the regenerated bone.”

In order to improve bone regeneration, Professor Catelas and her research team are developing new bone substitutes that will be mineralized and vascularized like the natural bone. To do so, they are using biomaterials such as fibrin (the protein-based natural polymer responsible for clot formation). “We will be using fibrin as our starting matrix, along with other biomaterials, to grow stem cells and endothelial cells. The stem cells will produce bone cells, resulting in mineralization, while the endothelial cells will promote vascularization. In fact, we have just acquired a bioreactor that we will be using to develop our bone substitutes.” These approaches will make it possible to offer new treatments for patients suffering from bone loss.

“Ultimately, the goal of our research is to improve the quality of life of patients with joint problems. This improvement is generally huge. I also saw this in my personal life, because my mother could no longer walk before she received hip implants. One day, thanks to tissue engineering and regenerative medicine, we may be able to regenerate joints within the human body itself, thereby eliminating the need for artificial implants, for the greater good of the patients.”


by Martine Batanian

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