By the way, doctor: Minimally invasive knee replacement

By Donald Reilly, M.D.
Content provided by the Faculty of the Harvard Medical School

Q. I need a knee replacement and am trying to decide between a minimally invasive operation and a traditional one. What do you think?

A. The traditional operation involves an incision that's about eight to 10 inches long that goes down the front of the knee and leg. With the minimally invasive operation, the incision is about half as long, and some of the operations use a "lateral" approach that involves making the incision on the outside of the knee. But the traditional and the minimally invasive operations have more in common than not. The surgeon still cuts away portions of the femur (thighbone) and the tibia (shin bone) that form the knee, and it still involves replacing them with a prosthesis that is designed to restore movement and decrease pain.

Some people find minimally invasive surgery appealing for cosmetic reasons — and it does result in a smaller scar. But the main selling points are less pain after the operation and a speedier recovery, so the benefits of knee replacement are experienced sooner. Minimally invasive surgery should be able to deliver on these promises: a smaller incision does mean less tissue damage. And proponents of the operations can point to some studies that have shown some advantages, such as shorter hospital stays and less blood loss.

But replacing a knee isn't like taking out a gall bladder. A device has to be implanted into the body. The jury is still very much out whether replacements done through smaller incisions will last as long and be as stable as those done through the larger incision. As a surgeon who has done thousands of knee replacements the traditional way, I think the view — the direct visualization — that the surgeon gets of the joint through the larger incision is important to proper placement of the prostheses and avoiding surgical complications. And there are other ways to reduce postoperative pain and speed recovery besides making a smaller incision. They range from injections of long-acting painkillers into the joint and surrounding tissues, to cold wraps around the joint, to "constant passive motion" machines that can be used in the days right after surgery to exercise the knee gently, keeping down swelling and stiffness. I don't think minimally invasive surgery is the kind of "disruptive technology" that is going to revolutionize total knee replacement, which is already a safe, effective, time-tested operation. The gains, if any, are likely to be marginal, and I think these other approaches to postoperative care can probably match them.

A couple of general points about new surgical procedures. Surgeons have learning curves. You don't want to be a patient on the steep part. It's important, therefore, to ask how many of these procedures a surgeon has done. And surgical techniques aren't like medications that go through clinical trials and FDA approvals before they are on the market.

It's great that there's innovation. The recovery from knee replacement is painful — and always requires a lot of hard work. Anything that makes it easier for patients is welcome.

But joint replacement is a big money maker that engenders a lot of competition for patients among surgeons and hospitals. Touting minimally invasive surgery before it has proven its value is a way of drumming up business. So my advice to you is pick a skillful surgeon who does a large number of knee replacements, in a hospital that does the same.

— Donald T. Reilly, M.D. New England Baptist Hospital

Last Annual Review Date: 2008-05-01T00:00:00-06:00 Copyright: Copyright Harvard Health Publications

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