Guest contributor Alex Burns studies biology at Cardiff University in the UK. Continued from Part One.
So why is titanium used at all?
Well, one of the more concerning complications is what is known as Ëœcatastrophic failure‘ with the ceramic implant. Unfortunately, being ceramic, it can crack and break much in the same way porcelain does, creating very sharp edges that could do serious internal damage so close to the femoral artery. A greater range of modern composites are conquering the problem, though it is of some concern to many orthopedic physicians. For many patients, it may not be worth the risk of it breaking and the metal implant works very well. The hope is new technology will overcome the problem entirely and provide hip replacements that outlast their owners.
Which ceramics are used?
Alumina ceramic and zirconia ceramic are the currently preferred materials, chosen for their extreme hardness (the only thing harder than aluminum oxide is diamond). They also have the advantage over the metal implant in that ceramic implants release debris of a different nature to the metal.
Not only is the amount of debris given off by an implant important, but also the type. The body reacts differently to different substances, and so leading down different biological pathways with different results. Metal debris causes loosening of the joint far quicker than ceramic debris. The metal implants’ debris is in the form of metal ions, which could be harmful to the patient or to an unborn fetus. Hence pregnant or attempting mothers are advised against metal implants.
Finally, there is a relationship between the size of the femur head and the amount of wear. A smaller head reduces wear but increases the risk of dislocation. With the ceramic implant, the surgeon is free to use a larger head and create a safer implant without worrying about the increased wear.
These developments hold out great hope for patients while the consequence for metal implant manufacturers could be far-reaching. Metal implants are an extremely lucrative industry for high-tech western metals casting and forming companies, not to mention high-quality titanium refining companies. Fortunately for primary producers, titanium’s uses are growing daily and a gradual migration of body part implants to ceramics would not be too dramatic — but for the processing firms in between, it could be a profound development.