Global time-out may calm maelstrom of metal-on-metal THR

Issue: Issue 2 2012

Like a giant storm passing over the countryside, blowing down trees and destroying houses, the metal-on-metal hip bearing situation has had a damaging effect, toppling many clinicians’ decisions to use that bearing coupling and possibly marring the landscape of total hip replacement (THR) forever.

Per Kjaersgaard-Andersen

In a recent article in Lancet, British experts recommended orthopaedists stop using large-head (LH) metal-on-metal (MoM) hip prostheses because National Joint Registry of England and Wales data showed they have higher revision rates than ones with ceramic or polyethylene bearings. The authors also suggest these higher early failure rates may extend beyond the recalled ASR (DePuy Orthopaedics) resurfacing prosthesis to all LH MoM bearings.

While not the final solution, a moratorium on MoM bearings makes sense in many respects, particularly from the patient’s perspective. So until all the issues are clarified, we should support a global time-out for LH MoM THR.

The U.K. Medicines and Healthcare Products Regulatory Agency recently issued new guidelines stating patients with MoM hip replacements with head diameters of 36 mm or more should be monitored annually for the life of the THR. To manage patients with MoM hip bearings, international guidelines are needed regarding frequency of performing examinations, blood ion level tests, and ultrasound and MRI scans in symptomatic patients, and when revision is advised.

We must educate patients and the media on the effectiveness of LH MoM bearings in properly selected patients, that very few patients with those bearings will ever require a reoperation for any of the publicized problems, and the same negative effects are not reported with other types of THR bearings. Just as critical is communicating to all patients that no THR lasts forever and each device has its own risk of revision.

I suggest international health authorities partner with the European Federation of National Associations of Orthopaedics and Traumatology, the American Academy of Orthopaedic Surgeons and other groups to develop device regulations mandating that certain steps and clinical trials be completed before wide scale adoption of THR implants.

Therefore, I recommend THR implants be classified as follows:

Proven implants, ones with high 10-year survival rates in recognized national registers, may be widely released, marketed and used by trained joint replacement surgeons;
Promising implants,, those with good register results not yet at the proven implant level, may have limited, but closely observed clinical use; and
Experimental implants, which are all other THR devices, must be used on an extremely limited basis under strict observation by the authorities that originally approved them for study and use.

In time, such stratification of THR prostheses should limit the size of any “storm” arising from implant-related problems.

What implant would you choose if you needed THR today? I know what I would do — find a highly experienced surgeon who can verify that the prosthesis he or she recommends for me is a “proven implant.”

Reference:

Smith AJ, Dieppe P, Vernon K, et al. Failure rates of stemmed metal-on-metal hip replacements: Analysis of data from the National Joint Registry of England and Wales. Lancet. 2012 Mar 12. [Epub ahead of print].