Conserve Plus Metal-on-Metal Hip Replacement
|X-ray of Metal-on-Metal hip repair
Sinai Hospital’s Center for Joint Preservation and Replacement is part of a six center FDA investigational study that is testing a new "metal on metal" joint replacement for the hip joint.
How is this metal on metal device different?
- Conventional total hip replacements consist of a metal ball connected to a large stem and a cup with a plastic polyethylene or metal interface. Polyethylene wear and the debris that results from this wear COULD causes osteolysis, or bone loss, around the implant. This is one of the major contributors to the early failure of the orthopedic implant.
- With the metal on metal resurfacing procedure, there is no polyethylene/metal interface. Even though there is some wear to the metal bearing surfaces, there is up to 100 or 1,000 times less wear and debris production than the traditional metal on polyethylene bearings. Because there is less wear as compared to a conventional total hip replacement, there is theoretical advantage of longer life of the prosthesis
- Less Wear: Since there is less wear and no polyethylene debris, the incidence of osteolysis decreases
- Bone Preservation: Because this is a resurfacing procedure, there is preservation of femoral bone and less of the thigh bone is actually removed. This has the advantage that in the future if there is any need for a revision or total hip replacement, this surgery will be much easier to perform
- Increase Range of Motion: With the metal on metal resurfacing procedure there is an increased range of motion post operatively. This will allow for an increased activity level and capability to perform tasks that would normally not be possible with conventional total hip replacement.
What about metal ion release? Does this cause cancer?
Over the past few years research on metal on metal hip prostheses have not conclusively proven that metal on metal hip articulations cause cancer. There has, however, been a lot of concern about the levels of these metal ions in the blood and how much the body can tolerate. Right now, there are no defined ideal levels. In a study by Visuri, over 2,000 total hip replacements were done with approximately 600 receiving metal on metal articulations. They were followed up over 16 years. Visuri compared how total hip patients compared to the general population, as far as the incidence of developing cancer. He determined that those patients who had metal on metal articulations had lower incidence of cancer than predicted by the general population. Therefore, the concern of ion release and an increased chance of cancer with metal on metal articulation is speculative.
Will the two metal surfaces bang together or cause a clicking sound? What keeps the two surfaces apart?
The synovial fluid that normally lubricates the articulating surfaces in a normal hip joint forms a barrier between the metal on metal articulating surfaces. This fluid lubricates the joint and keeps the two surfaces apart, minimizing any wear of the prosthesis.
What is the ideal age group for metal on metal resurfacing?
The ideal age group for patients receiving a metal on metal resurfacing would be the young, because of their increased activity level and longer life expectancy. However, we do implant these metal on metal resurfacings in older patients who have an active lifestyle and would benefit from the increased range of motion.
The Conserve Plus Metal on Metal hip prosthesis is not available for commercial use in the United States.
To find out more about Michael Mont, MD, the Sinai surgeon involved in this investigational study, please follow this link.