This article is more than 5 years old. Information may no longer be current.
National registries show differences in use, outcomes of THA articulation choices
Metal-on-metal hips may have lower revision rates for dislocation but higher rates of lysis and pain.
Click Here to Manage Email Alerts
Orthopaedists currently have a plethora of articulation choices for total hip arthroplasty. While older Scandinavian national registries report good results with metal-on-polyethylene bearings, data from newer registries may indicate problems with alternative bearing combinations.
“Nations with long-standing registries are very cautious with the introduction of alternative bearings,” Michael J. Dunbar, MD, FRCSC, PhD, said during his presentation at the 9th Annual Current Concepts in Joint Replacement Spring Meeting. “Despite this, their cumulative revision rates are decreasing, and I believe that this is related to standardization.”
Sweden
Although the Swedish national hip arthroplasty registry contains data from as far back as 1979, Dunbar noted that all of the information is on conventional metal-on-ultra-high molecular weight polyethylene (UHMWPE) constructs.
He theorized that the lack of data on alternative bearings in the registry stems from a philosophical difference between North American and European orthopaedists that occurred with the introduction of the term “cement disease” when North American orthopaedists abandoned cemented stems. This paradigm shift led to a focus on product innovation in North America and an emphasis on procedural standardization in Europe.
He noted that Scandinavian countries using only conventional metal-on-polyethylene bearings have seen a decrease in their cumulative revision rates for every 5-year period during the last 20 years.
Data from the Norwegian national registry shows that nearly 90% of total hip arthroplasties (THAs) are performed with UHMWPE. “There is no experience per se with the crosslinked polyethylene or the alternative bearings that are exploding,” he said.
|
|
North America
However, data from newer national registries are shedding light on the use and outcomes of alternative bearings.
“I would submit that, unfortunately in North America ... the introduction of these bearings is an irrational process,” Dunbar said.
Information from the Canadian Joint Replacement Registry shows that more surgeons have switched from using standard polyethylene (PE) to highly crosslinked PE during the last 4 years, with a three-to-one ratio of procedures now involving highly crosslinked PE.
Canada also reports twice as many metal-on-metal procedures and ceramic-on-ceramic procedures than Norway, and a 10-fold increase in the use of ceramic bearing combinations compared to metal-on-PE constructs between provinces.
“The patients are not that different from province to province and the surgeons are certainly not that different from province to province,” Dunbar said. “So, this represents an irrational introduction.”
Australia
Dunbar also cited early, unpublished research by Stephen E. Graves, DPhil (Oxon), and colleagues that examined the outcomes of different articulation choices using data from the Australian Orthopaedic Association National Joint Replacement Registry. The investigators found no significant differences in the 4-year survivorship between metal-on-metal and non-metal-on-metal bearings.
“Their conclusions were that there were no overall differences with all comers; that there were reduced revisions for dislocation with metal-on-metal, but increased revisions for loosening, pain and lysis; and that 30- to 40-mm heads increased revision at 4 years,” Dunbar said. Longer-term outcomes are uncertain, but already there is some concern with metal-on-metal bearings through this registry.”
Dunbar also stressed the importance of registries and called for a U.S. registry. “I would make a plea and a note to our American colleagues and friends in terms of [registries]: What are you waiting for?” he said. “Get on board with a registry. I guarantee you with the innovation in your country and a comprehensive registry, yours will be the premiere data in the world and it will tell us what to do for the future.”
For more information:
- Michael J. Dunbar, MD, FRCSC, PhD, associate professor, Department of Surgery, Division of Orthopaedics, and clinical research scholar, Dalhousie University, can be reached QE II Health Sciences Centre Suite 4822, 1796 Summer St., Halifax, Nova Scotia, Canada; +1-902-473-7337; e-mail: michael.dunbar@dal.ca. He receives institutional or research support from Stryker and Zimmer, and owns less than $10,000 stock in both companies.
References:
- Dunbar MJ. Articulation Choices: What do the registries tell us? Presented at the 9th Annual Current Concepts in Joint Replacement Spring 2008 Meeting. May 18-21, 2008. Las Vegas.
- Graves SE, Davidson D, Ingerson L, et al. The Australian Orthopaedic Association National Joint Replacement Registry. Med J Aust. 2004;180(5 Suppl): S31-34.