In the 16th century, broken bones were physically manipulated back to the correct orientation by a bone setter. Failing that, the local blacksmith would step in. Advances in medical treatments mean we no longer need to worry about a blacksmith fixing our broken bones.
Here, Matt Parkes, Senior Medical Development Engineer at Renishaw and currently working on a collaborative project with Western University in Ontario, Canada, discusses how smart implants are changing the way bone diseases and injuries are treated.
Since the early 1900s, surgeons have been using metal implants in healthcare, typically to treat bone diseases including osteoarthritis and inflammatory rheumatoid arthritis, as well as in reconstruction therapy. Though a long-established technology, traditional implants often cause challenges for patients and surgeons. One area currently being developed is smart implants, which improve patient outcomes, bringing the technology into the modern age.
Implants can be smart in two ways, either by being additively manufactured to produce patient specific implants (PSIs) from computed tomography (CT) data, or by incorporating sensors. Still in the early phases of development, inbuilt sensors could collect patient-specific data, enabling surgeons and other healthcare professionals to tailor treatment to the needs of individual patients.
The challenges with traditional implants
One of the key challenges that traditional implants present is loosening. Particularly common following joint replacement procedures, loosening can be a result of poor osseointegration — the structural and functional connection of the implant with the patient’s bone. This can occur due to wearing over time and is exacerbated by factors including infection and poor compliance with advised physiotherapy regimes.
Another limitation of traditional metal implants is that they are only manufactured in a discrete number of shapes and sizes. Therefore, it’s unlikely patients will receive an implant that fits them accurately. This can cause poor physical function and contribute to loosening.
Poor physical function can also occur because of stress shielding — the process whereby metal implants remove stress from the patient’s bone. The bone responds by reducing in density and therefore becomes weaker.
The increasing incidence of obesity is one reason joint replacements are becoming more common in young people. This poses longevity issues as implants can reach their maximum lifespan and need replacing several times during the patient’s lifetime.
To combat these issues, researchers and engineers have been developing implants in new ways, using techniques such as additive manufacturing (AM). The technology aims to improve the form, fit and function of implants.
Image Credit: RENISHAW