Advantages of Hip Resurfacing
- Femoral head is preserved.
- Femoral canal is preserved and no associated femoral bone loss with future revision. Also, the risk of microfracture of femur with uncemented stem implantation is eliminated.
- Larger size of implant "ball" reduces the risk of dislocation significantly.
- Stress is transferred in a natural way along the femoral canal and through the head and neck of the femur. With the standard THR, some patients experience thigh pain as the bone has to respond and reform to less natural stress loading.
- Use of metal rather than plastic reduces osteolysis and associated early loosening risk.
- Use of metal has low wear rate with expected long implant lifetime.
Special Risks of Hip Resurfacing
- Lack of long-term track record. Current device has only been used for about 7 years. Despite known low wear rate, longevity and longterm effects of wear debris are unknown.
- For some surgeons, the procedure has a longer surgical time. The procedure requires somewhat more skill of surgeon.
Special Requirements of Resurfacing Patients
- Solid bone in femoral head to hold resurfacing component. A few cysts or slight AVN collapse may be acceptable.
- Healthy kidneys to process any bloodborne metal ions from debris products.
Hip Resurfacing Frequently Asked Questions
 What are the major differences among the hip resurfacing implants?
What made you stop waiting and go ahead with surgery?
Did you do anything special to prepare for surgery?
What physical restrictions do you have after surgery?
Is there a tendency for the femoral head to die under the resurfacing implant?
Does the resurfacing implant remove more bone from the pelvis than a
standard total hip replacement?
What was the key factor in your deciding for the resurfacing?
What are the major differences among the hip resurfacing implants?
The primary difference lies in the backing of the acetabular component. The BHR (Midland Medical Technology) uses a cast porous surface with a hydroaxiphate (HA) coating to promote bone ingrowth. The Wright Conserve Plus using a sintering process to affix cobalt chrome beads to the back surface. The Corin Cormet device has a plasma sprayed titanium backing with an HA coating.
MidMedtech asserts that the heating of the device in the sintering or plasma spray process weakens the metal integrity. It has been shown in laboratory tests however, that when the machining tolerances are identical, the wear rate is not affected by the heat treatment.
A patient might ask, then, what are the machining tolerances of the various manufacturers. To date, they are protecting that information for competitive reasons.
What made you stop waiting and go ahead with surgery?
For me I was having significant pain in certain situations more than 4 years before I had surgery. I waited until it had advanced to where I had severe pain and joint stiffness after any exertion (such as doing yardwork or a lot of walking). My range of motion had been affected so much that climbing stairs was a problem and I could no longer ride a bike. The decision came down to one of quality of life -- in order to avoid situations with a lot of standing or walking I was passing up a lot of activities to the point I felt my life had become one of only avoiding pain. Although I wasn't in pain all the time, it was enough that at times I felt it was affecting my personality.
Did you do anything special to prepare for surgery?
If you have time you can do what you can to be in the best shape you can be by your surgery date. I did some upper body work (home gym) to lose a few extra pounds (nothing serious in my case) that I had gained because I had a period of less physical activity due to hip pain avoidance. The upper body strength then helped when I had to move myself in/out of bed using mostly my arms and also helped somewhat with the crutches.
What physical restrictions do you have after surgery?
I will not be allowed to jog or play basketball for recreation. I think downhill skiing on groomed trails will be allowed, but I don't think I'll risk that.
The lifetime of any implant would better be described in terms of "miles" than years. Or a better measure would be number of cycles times the force of each (combination of the patient's weight and the vigor of the step, walking vs. jogging). So, regardless of what is "OK'ed", one still has to be aware of the wear factors.
Is there a tendency for the femoral head to die under the resurfacing implant?
This is a common misconception as it was once thought to be the reason some previous attempts at resurfacing were not successful. Here is a copy the abstract of a recent study on the question.
J Arthroplasty 2000 Jan;15(1):120-2Viability of femoral heads treated with resurfacing arthroplasty.
Campbell P, Mirra J, Amstutz HC." There is a general conception that resurfacing arthroplasty causes femoral head osteonecrosis and subsequent failure of the implant. This study histologically analyzed 25 resurfaced femoral heads up to 12 years postoperatively and found that osteonecrosis was not induced by the procedure."
Does the resurfacing implant remove more bone from the pelvis than a standard total hip replacement?
Because the head is significantly larger than that of the standard total hip replacement, one might think that more bone would need to be removed on the pelvis side, but this is generally not true. The outside diameter of the acetabular component is similar in size to the typical modular total hip replacemet acetabular cup. This is because the resurfacing implant has a single part acetabular cup, the two-part nature of the shell-and-drop-in-liner style modular component ads to the thickness of the THR component. If this is a concern in your case, you should verify the outside diameters of the components that you are considering.
What was the key factor in your deciding for the resurfacing?
For me it came down to this: the surface replacements offered an excellent short term result (less chance of dislocation, less thigh pain compared to the standard stemmed hip replacement), with the chance they could last as long or longer than the stem device. Should they not last too long, at least I gave it a shot, and I still have nearly-intact femur bones. If I went for an implant with a stem, I could never "go-back" to resurfacing if they became the widely-accepted treatment.
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