Hip replacement is most commonly recommended for patients with osteoarthritis, according to the Arthritis Research UK. However, people with inflammatory diseases such as rheumatoid arthritis or ankylosing spondylitis may also need hip replacement surgery at some point in their lives. A surgeon may also recommend replacement hip surgery for fractures of the hip. The hip joint is known as a ball-and-socket joint. Inflammatory disease such as rheumatoid arthritis damages the surface of the joint, which hinders mobility. The aim of hip replacement surgery is to replace the damaged surfaces with artificial implants. Implants can be made of metal, ceramic, or plastic.
Metal-on-Metal
In metal-on-metal hip replacement, both the ball and the cup component of the hip joint are resurfaced with metal. Metal-on-metal hip replacement allows a good range of movement, and may have lower dislocation rates than other types of implants. However, concerns have been raised that metal-on-metal implants produce high blood serum levels of cobalt and chromium, the metals found in metal-on-metal implants. In an article published in "The Journal of Arthoplasty," lead author, J.H. Dumbleton states, "Biological effects from metal ions remain a concern. Patients with both first- and second-generation metal-on-metal hips have higher levels of cobalt and chromium in their blood and urine than either patients with metal-on-polyethylene devices or unoperated patients."
Metal-on-Plastic
In the 1960's, Sir John Charnley from Wigan, England developed metal-on-plastic hip replacement. According to Mr. J.N. O'Hara, consultant orthopedic surgeon at the Hip Clinic, metal-on-plastic implants do not last well in younger patients. He adds, that the weakest point of the metal-on-plastic hip is that the plastic does wear away. Eventually just enough plastic dust accumulates to cause a rejection reaction by the body, and this undermines and loosens the hip replacement. This typically takes 12 or 15 years in older people, but in younger, more vigorous and active people, the rate of wear will provoke earlier loosening. The rejection reaction can sometimes seriously compromise the surgeon's ability to re-do the operation.
Ceramic-on-Ceramic
The Food and Drug Administration first approved ceramic-on-ceramic implants in 2003. Ceramic-on-ceramic implants consists of a ceramic ball bearing that slots into a ceramic-coated socket. According to David Blaha who performed one of the first two ceramic-on ceramic hip implants in the U.S. in 2003, this type of implant allows the young or the young at heart to function normally. He adds that ceramic has proven to be a very strong material, which means there is a very small chance that patients will need another hip replacement.
Ceramic-on-Metal
In ceramic-on-metal hip replacement, the ball is made of ceramic and the cup component of the hip joint is resurfaced with metal. Ceramic-on-metal implants may improve a patient's range-of-motion. According to a 2007 article published in "Orthopaedics Today International," ceramic-on-metal implants may produce less friction than metal-on-metal hip replacements, and may also leak less metal ions into the bloodstream. Research by Dr. John Fisher from the University of Leeds, England, has shown that there is a reduction of more than 50 percent of cobalt and chromium ions in the blood of patients with ceramic-on metal-hips compared to metal-on-metal hips.
References
- Arthritis Research UK: Hip surgery
- Total Joints: Metal-on-Metal Total Hips
- "The Journal of Arthoplasty": Metal-on-metal hip resurfacing: advantages and disadvantages
- "The Journal of Arthoplasty": Metal-on-Metal total hip replacement: what does the literature say?
- The Hip Clinic: Total Hip Replacement - THR
