Benefits of less-invasive knee replacement surgery

The benefits of less-invasive knee replacement surgery may not be as dramatic as some direct-to-consumer advertising may claim, but the procedure has resulted in less scarring, diminished pain and faster recoveries for select patients.

At a panel briefing of the American Academy of Orthopaedic Surgeons' 73rd Annual Meeting, experts discussed the pros and cons of the increasingly popular procedure, how orthopaedic surgeons are attempting to meet patients' growing demand for shorter incisions, and whether the less-invasive approach will ever totally take the place of traditional knee replacement surgery.

"Minimally invasive surgery (MIS) is no longer just about making smaller incisions," said Robert E. Booth, Jr., MD, chief of orthopaedic surgery at Pennsylvania Hospital in Philadelphia. "The procedure now includes a range of precise techniques to control pain, get people back on their feet and back to work more quickly."

Less-invasive knee replacement surgery involves an incision of three to four inches as opposed to the eight- to 10-inch incision required for traditional surgery. Surgeons attempt to reach the knee without cutting into tendons, muscles and other tissues around the knee.

Minimizing pain in the days and weeks after surgery is a primary goal of the procedure. Patients are given anti-inflammatory medicine and local anesthesia before surgery, and pain medications after the operation. Patients also receive counseling about what to expect from the surgery, the length of the recovery process and how much pain they may experience.

"Often times if you tell patients beforehand that taking medication will reduce their discomfort, they will, indeed, feel less pain," Dr. Booth explained.

Like the traditional surgery, the less-invasive approach has many of the same risks like infection and blood clots. But smaller incisions mean surgeons have to operate in a more compact area with a reduced field of vision.

"Any time surgery is performed with a smaller incision, the surgeon has fewer visual clues to guide them on techniques, such as the appropriate placement of the implant," said Mark W. Pagnano, MD, associate professor of orthopedics at the Mayo Clinic College of Medicine in Rochester, Minn. "Particular care must be taken during surgery not to damage tissue around the knee."

Computer-assisted navigation systems make the procedure safer when visibility is compromised. The length of the incision, however, is the least important factor in the successful outcome of the procedure. Smaller incisions necessitate more force on the tissues that may inhibit wound healing.

The other major risk is that less-invasive surgeries can take two- to three-times longer to perform than traditional operations. The protracted surgery may increase the risk of infections, blood clots and other complications. Thus far these additional risks have not been a problem, according to Dr. Booth, though he emphasized the need for more evidence-based data on the efficacy of less-invasive surgery to determine if the procedure has long-term benefits for patients.

While medical device companies are fueling the demand for the procedure by advertising directly to patients, both experts agreed that smaller is not always better across the board. "Not every patient is right for the procedure," stressed Dr. Pagnano. "Patients who are obese, have a very stiff knee or a high degree of knee damage are not candidates for less-invasive knee replacement."

However Dr. Booth mentioned one positive outcome of the direct-to-consumer advertising is that patients are coming in earlier to get surgery; this can translate into a more successful operation. The experts concluded that while the less-invasive approach has many advantages, it may never completely replace the traditional method.

"Certainly not in the foreseeable future, as long as you have people who are overweight or who have already undergone multiple operations on their knee," said Dr. Pagnano. "But as techniques improve and evolve, we hope to make this type of surgery available to a wider range of patients."

"Regardless of whether you call it less invasive or minimally invasive, almost every surgeon these days is making smaller incisions," concluded Dr. Booth. "The art of knee surgery has been significantly advanced because MIS is out there."

While no current estimates exist, Dr. Booth predicted that within the next decade, "I think about half of all patients will be getting MIS operations on their knees."