WASHINGTON — Growing public demand for minimally invasive hip and knee replacement—and increasing hype over small incisions—is driving a wedge in the orthopedic community, exciting some surgeons and fueling anxiety and anger among others.
At the annual meeting of the American Academy of Orthopaedic Surgeons, discussions of minimally invasive joint replacement and “mini” incisions drew crowds. Physicians shared surgical techniques, reported outcomes, described learning curves, and discussed what most—if not everyone—agreed are a lack of long-term effectiveness data, a paucity of randomized controlled studies, and unrealistically high public expectations fueled by direct-to-patient advertising.
“Surgeons have readily adapted these techniques despite the lack of evidence to support better outcomes,” said Jay Lieberman, M.D., of the University of California, Los Angeles. “We've all done this because of patient interest, the potential for improved function and cosmetics, and, though we don't like to admit it, the fear of lost income and market share.”
There are no commonly accepted definitions for “minimally invasive” total joint replacement surgery. Published studies define the incisions for less invasive knee replacement surgery as approximately one-half the length of traditional incisions.
Most single-incision techniques for less invasive hip replacement allow for surgery through an incision that's one-half or less of the 10- to 12-inch length of a traditional total hip incision. A newer two-incision technique, the one technique that completely spares the muscles, utilizes incisions that are about 2-4 inches in length.
Potential Advantages
The promise of the minimally invasive techniques is that reduced trauma—to the skin, soft tissue, and muscle, for example—can lead to quicker recoveries, shorter hospital stays, less pain, and less blood loss. The potential risks, physicians said, include malposition or instability of the prostheses, skin necrosis and maceration, fracture, and nerve palsy. So far, none of the claims have been substantiated in prospective, randomized, long-term trials.
Nearly 250,000 hip replacements and 300,000 knee replacements are done annually—increasingly in younger, active patients—according to the AAOS.
“Several years ago, when less invasive approaches were introduced, many surgeons felt it was a foolish idea,” said Aaron Rosenberg, M.D., of Rush University Medical Center in Chicago. “Ask today how many are doing small incisions, and everybody raises their hands.
Scar appearance “is real for patients, and early recovery is real, and if you provide that, patients will line up at your door,” Dr. Rosenberg said.
In its 2004 “physician advisory statement” on minimally invasive joint replacement surgery, the American Association of Hip and Knee Surgeons said that “most positive results have been demonstrated by a small number of [high-volume] total joint centers in selected patient populations.”
Two Incisions Better Than One?
At the AAOS meeting, orthopedic surgeons spoke of positive results at their own institutions.
Richard A. Berger, M.D., reported that all of his patients undergoing two-incision hip replacement at Rush University Medical Center in Chicago now leave for home the same day of surgery, with no risk of readmission or postdischarge complications.
“There's nothing magic about two incisions. That's just the only way we could figure out how to do it without disturbing any muscles or tendons. … It's a completely muscle-sparing approach,” said Dr. Berger, who, according to the AAOS, was the first surgeon to perform total hip replacements and knee replacements as outpatient procedures.
Rather than making a single smaller incision using either a posterior or anterolateral approach, Dr. Berger makes one 4- to 5-cm incision directly over the femoral neck, which allows for preparation and placement of the femoral component of the hip prosthesis. The acetabular component is placed through a second incision, also 4-5 cm. Unique instruments and fluoroscopic guidance help ensure accurate component position and alignment.
In a presentation on “learning curve complications,” Alan E. Gross, M.D., who also uses the two-incision technique, said the technique represents “a dramatic paradigm shift” from traditional approaches and thus has a steep learning curve. It takes about 50 cases to perform the procedure successfully.
A single-incision “mini” operation uses the “same technique as traditional (surgery) except that it's a shorter incision with less muscle dissection,” said Dr. Gross of Mt. Sinai Hospital in Toronto. The learning curve, he said, is “probably about 10 cases.”
An important difference between the two techniques is that “the bail-out with the single-incision mini is easy. You just make the incision longer,” he said.
“The bail-out with the two-incision mini is very stressful and very difficult,” Dr. Gross said. “Basically, you have to close up and start all over again.”
Positive Outcomes
Lawrence D. Dorr, M.D., of the Arthritis Institutes in Los Angeles and Inglewood, Calif., said that his mini-incision total hip replacements result in improved gait analysis results 6 weeks postoperatively and improved patient pain scores. “These operations as I perform them now are the best hip replacements I've ever done,” he said.