Myths about Resurfacing and Hip Replacement

Table of Contents

"Ceramic-on-ceramic resurfacing is the answer."

Ceramic-on-ceramic hip resurfacing will have a difficult time outperforming the current gold standard, uncemented metal-on-metal hip resurfacing which has a 99% 15-year implant survivorship. There are not yet any published data on the trials with ceramic-ceramic.

The main reason to pursue these new bearings is to take advantage of their superior wear characteristics. Ceramic-on-ceramic have the lowest benchtop laboratory wear rates, they are the only bearing better than metal-on-metal, the current gold standard. But metal-on-metal already has such a low wear rate that it can never wear out in anyone’s lifetime.

But metal-on-metal has an Achilles heel. If the socket is malpositioned in too steep or anteverted a position, a small percentage (5% of these) will suffer edge-loading mechanics and start releasing large amounts of metal debris. How often does this happen? I have published several papers on this topic. The first showed a 1% 10-year failure due to metallosis before the time we were aware of proper cup positioning. The second paper outlines a safe zone for socket positioning (RAIL: relative acetabular inclination limit) to avoid metallosis. In the third paper, we validate the safe zone. We evaluate a subsequent cohort of patients where we were able to place 100% of cups within the safe zone and experienced no cases with excessive ion levels or metallosis. I have not had a single case of metallosis in over 5000 cases since 2009.

The problem with metallosis has been solved in metal-on-metal bearings. The only remaining problem is one of perception and misinformation. The diagnosis of a metallosis failure is very straightforward. But many surgeons who do not perform hip resurfacing are quick to diagnose this problem without meeting the diagnostic criteria. The problem comes when a patient has residual unexplained pain. In a THR, where this occurs in 20% of cases, nobody suggests metal allergy as a cause, in hip resurfacing, where this occurs much less commonly, a presumptive diagnosis of metal allergy or excess ions is frequently made by uninformed surgeons evaluating an unhappy patient with hip resurfacing. A small residual fluid collection is seen in 30% of well-functioning THR and hip resurfacing cases. This is a normal postoperative finding. In a painful THR this may be misdiagnosed as a trunion failure, in a hip resurfacing it could erroneously be called a metallosis case.

Revision for unexplained pain carries a very low success rate. Far less than 50% of patients are satisfied. After all, if you don’t understand the problem, you can’t really expect to fix it, but sometimes you get lucky. I sometimes offer my own patients with unexplained pain a revision with this proviso, but I do not recommend it. I do not offer this option to others.

If we had a ceramic-on-ceramic hip resurfacing that otherwise worked as well as the current gold standard metal-on-metal variety, this problem with misdiagnosing unexplained pain would go away. It would be great to rid ourselves of this thorny problem.

But ceramic-on-ceramic may not be as good for several reasons. First, the early fracture/head collapse rate may be higher due to a smaller supporting stem. Second thin shells of ceramic (4mm) may fracture with repetitive high impact. Third, squeaking may be a problem. Finally, the porous titanium coating may detach from the ceramic cup after many years. I have published my experience with this problem with the Corin metal-on-metal system which had titanium coating that debonded from a cobalt substrate between 8-10 years postop. On the other hand, the ZB Magnum cup with the same type of coating that I have used for the last 17 years has not had that problem. Will titanium remain adhered to a ceramic shell over the long run in highly active patients? This is my main concern.

Having said this, I would welcome the opportunity to offer patients this option if they desired. I personally would have a metal-on-metal. Ceramic-on-ceramic is unlikely to beat 99% of 17-year KM implant survivorship in over 5000 cases.

Phone Consultation

If you are interested in determining if you are a candidate for surgery, please mail your completed new patient forms to the office and include a digital x-ray.

Dr. Gross will call you back to discuss your options.

Download New Patient Forms

Located in South Carolina

Irmo Office

1013 Lake Murray Blvd.
Irmo, SC 29063

  Get Directions
Columbia Office

1910 Blanding St.
Columbia, SC 29201

  Get Directions