Orthopaedic implants can be quite complex, and the materials used to make them, called biomaterials, are highly developed. In the United States, the FDA requires extensive testing before a new material may be used in an orthopaedic implant. The materials most commonly used have a long history of clinical use with great success.
There are many different biomaterials, but there is no single biomaterial that is best for all implants and all patients. The specific requirements of an implant material vary depending on how the implant is designed to be used
An orthopaedic implant has a challenging job. As you go about your daily activities, an implant may encounter mechanical forces that tend to push on it, pull on it, bend it, scrape it, or wear against it. These forces can cause the implant to break or wear out over time. It is also subjected to the many natural chemicals inside the human body. Some of these chemicals may tend to corrode some materials. In order for an implant to perform under these conditions, it must be made from materials that can withstand these forces and chemical environment in the patient.
Whether an implant is designed to replace a joint, or help repair a fracture, several physical and biological characteristics are important when selecting the material for the implant. For example, an implant must be sufficiently strong, flexible, and resistant to wear. But that doesn’t mean the strongest material, or the most flexible material, is the best material.
The ideal implant material should have physical characteristics that match those of the bone it is replacing or reinforcing. After all, orthopaedic implants are attached to your bones, and they must work with your bones to restore function. This usually requires a balance of physical characteristics. Your bones, for example, are strong but flexible. This combination helps them withstand forces as high as several times your weight without breaking.
Obviously, physical characteristics are important to orthopaedic materials; but biological characteristics are just as important. When we talk about biological characteristics, we mean the biological effect the material has on the body, as well as the effect the body has on the material.