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Ask the Experts: High-flexion or conventional knee designs?
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KOLOA, Hawaii — The published literature shows similar results for high-flexion and conventional knee replacement devices. In a panel discussion at Orthopedics Today Hawaii 2011, Douglas A. Dennis, MD, asked knee replacement thought leaders to describe which device they would use to treat the knee of a 53-year-old woman, who climbs mountains, hikes and skis. She had torn her ACL skiing when she was in her 20s and has failed nonoperative care.
“There are a number of studies which show that the high-flexion knee gives you more flexion, and there is pretty much an equal matching number that show there is no difference,” Douglas began.
 Douglas A. Dennis |
“We presented our data on 93 bilateral total knee replacements in a multi-centered study, in which we put a standard knee on one side and a high-flex on the other. We found that the high-flexion knee got more flexion — only 1.35°, and in those who had stiffer knees preoperatively, they gained about 4° to 5°,” he said.
He said the high-flexion knee costs $800 to $1,000 more. “Is it worth it in this patient?”
 Panel members discuss high-flexion knees |
Wayne Paprosky, MD: I think the major advantage of using a high-flex and cutting off more bone posteriorly is if you can use a smaller incision, and it is easier to do. I’d do the high-flex knee, especially if I am doing it with a posterior stabilized design. If you believe that minimally invasive surgery is a benefit, that is certainly available. I think that is the number one reason why this has become more popular. In terms of the cost, I don’t think I could justify that.
Dennis: Certainly here the data have not shown a dramatic difference. I think maybe if there is any and you got it to 1.35°, most of them would have increased conformity and better contact in deep flexion; so if you have a patient that gets it, it might be better there. We are going to present our data at the Knee Society on the high-flex design — at 5 years the results are wonderful. But we had 44% radiolucent lines at the posterior condyle, and there are two other studies in the Asian literature that show increased loosening.
Ormonde M. Mahoney, MD: I think this is a great topic, and I agree with everything that has been said. However, one of the things that we have to remember is that “high-flex” knee is kind of a catch-all term, and they are not all the same. They are very different from one manufacturer to another. And actually, the increased flexion may be the least important benefit of what you potentially may gain by using designs that are more modern and have benefits in their size or shape. I think it is a little premature to say that these devices are beneficial.
Thomas P. Schmalzried, MD: In terms of survivorship, like Ormonde just said, taking the metal away from the front and side of the knee may be a greater benefit.
Mahoney: We looked at more than 1,000 knees comparing the standard knee and the high-flex knee, and the survivorship of the high-flex was actually higher in a 10-year study. – by Lee Beadling
Reference:
- Dennis DA, et al. Panel discussion: What technology merits additional costs of knee replacement? Presented at Orthopedics Today Hawaii 2011. Jan. 16-19. Koloa, Hawaii.
Disclosures: Dennis is a consultant and receives research grants and royalties from DePuy. Mahoney is a paid consultant for Stryker. Paprosky is a consultant for and receives royalties from Zimmer. Schmalzried is a consultant for Stryker and receives research grants from DePuy and Stryker.
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