Minimal-incision total knee arthroplasty found to be a risk factor for early failure

LAS VEGAS — Minimally invasive total knee arthroplasty was found to have a significantly higher rate of early failures in a multicentered review investigation.

“Despite the excellent long-term survival of traditional total knee arthroplasty, there has been interest in a minimally invasive approach,” Derek W. Miller, DO, said at the American Academy of Orthopaedic Surgeons 76th Annual Meeting.

“A number of short-term studies have appeared in the literature noting advantages of minimally invasive knee replacement over standard incision, including less narcotic use, a shorter length of stay, and earlier or better motion, at least in the short therm. Most of the studies, however, are authored either by the designers or advocates of the systems being evaluated. They are total knee specialists; they have high-volume experience,” he said.

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The problem now, Miller said, is that minimally invasive surgery (MIS) is being promoted for widespread use and is frequently being performed far beyond the surgeons who performed the early studies.

To compare the revision rates of the MIS and traditionally performed total knee arthroplasty (TKA), Miller and colleagues reviewed a series of revision knees from three referral centers, performed by five surgeons over a 3-year period from 2004 and 2006.

For the evaluation, MIS surgery was defined as using an incision length less than 14 cm that could be confirmed by operative records.

The researchers found 236 first-time revisions; 193 had been performed through the standard approach and 43 were MIS. They noted that the MIS knees were more likely to be in the younger patients and women.

“The most striking finding was that the average time to revision was 14.8 months for the MIS knees and it was 80 months for knees using the traditional approach,” Miller said. “MIS knees were more likely to fail at less than 12 months and less than 24 months.””

The MIS knees also showed a trend toward having an incidence of loosening as a cause of failure, according to the study abstract.

“This only represents the subset of patients whose symptoms were severe enough to require early revision surgery,” Miller said. “The question is, is this just the tip of the iceberg? It is possible, if not likely, that there is a far greater number of patients with suboptimal knees, experiencing compromised clinical results and are at risk for mid-term failure?”

Reference:

• Miller DW. Minimal incision surgery as a risk factor for early failure of total knee replacement. Paper #272. Presented at the American Academy of Orthopaedic Surgeons 76th Annual Meeting. Feb. 25-28, 2008. Las Vegas.