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Long-term study finds a higher THR revision rate with larger femoral heads
Osteoarthritis patients with 32-mm heads had a 3.4-times greater risk vs. those with 22-mm.
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While a previous study with up to 12 years follow-up found no significant difference between the revision rates of 22-mm and 32-mm femoral heads, new, longer-term research reveals higher revision rates with larger heads.
Investigators studied more than 1,550 patients with osteoarthritis (OA), rheumatoid arthritis and femoral neck fractures who underwent total hip arthroplasty (THA) using the Scan Hip Classic I MitAB stem [MitAB; Sjöbo, Sweden] with either 22-mm or 32-mm femoral heads for up to 21 years.
Using a life table method to determine the revision rate for any component due to aseptic loosening, they found a significantly higher cumulative revision rates with 32-mm heads (P=.04).
Possible poly problem
“We’ve got the 22-mm heads showing better survival rates. [This] could be due to the polyethylene particles,” Sarunas Tarasevicius, MD, said during his presentation at the 8th European Federation of National Associations of Orthopaedics and Traumatology Congress. “It is known that the 32-mm femoral head is associated with three-times higher volumetric polyethylene wear compared to the 22-mm femoral head. In larger-diameter femoral heads, we have thicker polyethylene, and it’s also known that thickness of polyethylene inversely correlates with wear.”
Tarasevicius and his colleagues studied 1,720 THAs performed at a single institution between 1983 and 1995. They noted all revisions due to aseptic loosening before the end of 2004.
Less risk with age
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Also, for each increasing year in age, they discovered that the risk decreased by .96 times, according to their abstract.
The investigators saw similar patterns for age, gender and femoral head size when they analyzed the rates of OA patients only. “The 32-mm head had a 3.4-times greater risk of revision than the 22-mm head,” he said.
“The reason that we did not find any significant difference in cumulative revision rates when followed up to 12 years depending on head size in a previous study (Kesteris et al, 1998) may be the time it takes for particles to induce the chain of events, eventually ending up in loosening,” the investigators wrote in their abstract.
For more information:Reference:
- Sarunas Tarasevicius, MD, can be reached at Kaunas Medical University, Elveniu 2, LT-500009, Kaunas, Lithuania; e-mail: sarunas.tarasevicius@gmail.com.
- Tarasevicius S, Kesteris U, Robertsson O, et al. Femoral head diameter affects the revision rate in total hip arthroplasty: An analysis of 1,720 hip replacements with 9 to 21 years follow-up. F881. Presented at the 8th European Federation of National Associations of Orthopaedics and Traumatology Congress. May 11-15, 2007. Florence.