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Mar 16, 2012Science and Technology
Artificial implants may be ineffective and unsafe, but are avoidable

A replaced hipJust like cars, our parts wear out over time.  Our vision and hearing deteriorates, necessitating glasses and hearing aides, and our joints weaken or fail us, leading to a need for new hips or knees.  But as with any artificial substance we put in our bodies, there is a risk of unintended side effects from these synthetic materials. 

We saw this issue with BPA, a widely used strengthening substance used in plastics and composite materials, which was discovered to be leaching into people’s systems through baby bottles, food containers and dental fillings, leading to cancer, diabetes and heart disease.  Now the same is being found in hip prostheses.

Total hip replacement (THR) is a very common procedure.  But some prostheses used are failing, particularly in younger patients.  These failures are often due to wear, dislocation and loosening.  In response to these issues, surgeons attempted to create a more durable hip prosthetic by implanting large diameter metal-on-metal (MoM) bearing surfaces. The National Joint Registry of England and Wales conducted an efficacy study on these purportedly improved hips, but found that the MoM THRs were failing at very high rates, with the larger heads deteriorating the fastest.  Based on their data, these researchers concluded that surgeons should stick to ceramic-on-ceramic implants.

It turns out that MoM hip implants cause more problems attendant to wearing out.  In fact, hundreds of thousands of patients worldwide may have been exposed to dangerously high levels of toxic metals from failing hip implants. Cobalt and chromium ions were found to be leaking from MoM implants, seeping into the surrounding tissues and causing local reactions that destroy bone and muscle, and leaving some patients with long term disability.  The metal ions can also leach into the patient’s blood stream, spreading to the lymph nodes, liver and kidneys before leaving the body in urine. This metal ion leakage also raises concerns over chromosomal damage leading to unintended genetic alterations. 

An x-rayIn the field of dental implants, doctors have attempted to improve artificial tooth durability by coating the titanium prostheses in a drug usually used to treat osteoporosis. The drug allows the bone surrounding the implant to rapidly become denser and stronger, thereby improving the implant’s efficacy. 

But rather than focusing on adjusting these artificial implants, perhaps scientists should be looking to more biologically natural solutions for bone weakening.  For example, the injectable bone healing composite patented by Drexel University scientists is a real-life Skele-gro that may be used to repair vertebral fractures by injecting the hydrogel into the vicinity of the fracture. It may also be used to reinforce vertebral bone structures in patients with a higher risk of fracture, for example those with osteoporosis, trauma, or certain types of cancer. Furthermore, the hydrogel may be used to resurface articulating joints by providing a bearing surface that can bond to the underlying bone tissue, as in a knee joint. 

Knowing that joint weakening and bone fractures are imminent as people are living longer and their bodies are wearing out, doctors could take preemptive action to strengthen the predicted problem areas, rather than waiting to replace them after they break.  In this way, the problems associated with artificial implants could be avoided all together.  As they say, the time to fix the roof is when the sun is shining.

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