What is a hip resurfacing made of?
Almost all resurfacings are metal-on-metal devices, both sides of which are made from an alloy known as cobalt-chromium-molybdenum. There is, however, at least one device that has a metal on plastic bearing. Currently there are no ceramic hip resurfacings available, but several companies and research institutions are working on their development.
How is the resurfacing held in place?
The pelvic socket (acetabulum) is press-fit. This means it is wedged into place. The body’s own bone then grows into it over several months providing a long lasting hold. The ball is cemented in place on the peg that is shaped from the ball at the top of the thigh bone. There are no FDA approved press-fit femoral components in the USA.
Is the surgery bone conserving?
On the socket side, no. On the femoral side, yes.
Is the surgery easier than a total hip replacement?
No. A total hip resurfacing is a technically more demanding operation than a total hip replacement. Fixation of the socket is more difficult for a variety of reasons. On the femoral side, as the ball has to be placed on the femoral head, errors in positioning can occur.
Will my insurance pay for it?
In May 2006, the FDA granted approval for Smith & Nephew to market the Birmingham Hip Resurfacing. Most insurance companies will cover the procedure under CPT code 27130. For those who wish, negotiated private pay rates are also available. Please contact us for further information.
How long will it last?
Unfortunately, it is impossible to know this in any individual situation. Additionally, these devices have not been around for more than 10 years and we only have clinical results for 8 years or less. The data that has been collected so far, however, encouragingly suggests that there is a 95% chance that the device will last 8 years. This compares to about 90% for a total hip replacement in the same age range.
Is the revision surgery easier if the resurfacing loosens?
We do not really know the answer to this as very few surgeons have had the opportunity to revise large numbers of these devices. This is because relatively few of the metal-on-metal resurfacings have so far failed. In our experience here at The NYCHR, the revision procedures have proven to be significantly easier than a standard revision hip replacement, however.
What are the metal ions and are they to be worried about?
Current resurfacings are made of a cobalt-chromium alloy that create a ball and socket joint. When a patient walks, the metal rubs on the metal as it was designed to do so. Although lubricated by the body's own joint fluid, some abrasion occurs and metal particles are released into the body which then are corroded by the body to release metal ions (charged atoms). These Ions travel through the body and are eventually excreted by the kidneys.
We know that all metal implants release metal ions. Metal-on-metal bearing hip replacements and resurfacings clearly release more than most due to the abrasive action of the bearing and large number of particles created. The long-term effect of metal ions is unknown but is an area of intense research and observation.
Am I a candidate for hip resurfacing?
Most patients who are poor candidates for hip replacements are also poor candidates for a hip resurfacing. In addition, there are certain persons/conditions that may not be best suited for a hip resurfacing procedure and a hip replacement may be a better alternative. Although there are exceptions and decisions are made on an individual basis , these typically include:
• Older patients (males over 70 and females over 60). This is because of the risk of osteopenia and osteoporosis which are bone thinning conditions that place the patient at higher risk of fracture of the neck; a risk that is not present with total hip replacement.
• Osteopenia and Osteoporosis in younger patients. Any condition that weakens the bone would make the decision to resurface a more risky one.
• Severe avascular necrosis (AVN). Patients with a badly destroyed femoral head may not be candidates for resurfacing as the ball needs good quality bone to fix to. You do not want to build a house on mud…….
• Young females who intend to become pregnant. This is an area of controversy and relates to the release of metal ions, as they are thought to be able to cross the placenta. There are, however, anecdotal reports of healthy babies being born to mothers with hip resurfacings, but the area is not well studied.
• Significant kidney and liver failure. If the body cannot the excrete the metal ions that the prosthesis produces, they accumulate in the body and may become toxic.
How long will I be in the hospital ?
Typically, a patient who has had a hip resurfacing will be in hospital for 2 to 3 days.
When do I need to come back?
The typical follow-up regimen is 2 weeks, 6 weeks, 3 months, 6 months, 1 year and then annually thereafter. Patients who do not live close by may follow-up with a medical professional in their area, but should check with their office beforehand.
Is the risk of dislocation lower?
Dislocation is the separation of the ball and socket when the leg is placed in an extreme position. Although the risk of dislocation is related to many factors, it does appear that hip resurfacings overall have a lower risk of dislocation (<1%) when compared to hip replacement.
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