WASHINGTON, DC (Feb. 25) – Two studies presented at the 72nd Annual Meeting of the American Academy of Orthopaedic Surgeons on Thursday suggest that minimally invasive (MIS) total knee replacement (TKR) produces less postoperative pain and better functional recovery than long incision TKR,1,2 though concerns remain about the potential for complications associated with the procedure.  "This is controversial.  It's very difficult and only experienced surgeons should be looking at it," says an author of one of the studies, Peter M. Bonutti, MD, of the Bonutti Clinic of St. Anthony's Memorial Hospital in Effingham, Illinois.

But patients may not have the patience to wait for surgeons to speed the learning curve and perfect MIS procedures. Some orthopaedic surgeons blame direct-to-consumer (DTC) advertising for generating pressure to change to MIS procedures, even though supportive data are sparse and many surgeons do not have adequate experience.

Improved recovery with MIS arthroplasty

In one retrospective, matched-pair study that compared open versus MIS TKR, 25 patients (32 knees) received the standard long incision of 10 to 22 cm and 25 patients (32 knees) received a small incision of 6 to 10 cm.  In this study, only the technique was changed, while length of hospital stay and other variables were held constant.

The MIS procedure took 56 minutes to perform, compared with 51 minutes for the standard long incision surgery. In addition, there were subtle differences in postoperative pain and function, including knee society scores (KSS) and radiographic alignment, that favored the MIS group. Patients who had the MIS procedure lost 318 cc of blood, compared with 371 cc in the open group. Moreover, 45% of patients in the MIS group were using narcotic analgesics up to 3 months after surgery. By contrast, 78% in the standard incision group were using narcotic analgesics up to 12 months after their procedure.

There were also differences in functional recovery. At 2 weeks after surgery, 59% of patients in the standardized long incision group were using a walker, compared with just 16% in the MIS group. It took 8 weeks for those patients who received the long incision to walk without the use of a cane, compared with 3.5 weeks in the MIS group.

William J. Maloney, MD, professor and chairman of the Department of Orthopaedic Surgery at Stanford University School of Medicine in Stanford, California, suggested that the real question is whether surgeons who do not perform many minimally invasive procedures can produce the same type of results. When asked how surgeons can best adapt to the new technology, Dr. Bonutti responded that they can take their cue from this study and do so "gradually, in an evolutionary fashion." He suggested that "you can't make radical changes, and instead must change one variable at a time—such as slightly change the incision—and learn to use the new instrumentation gradually," he says. "If you do that, the average surgeon can improve soft tissue trauma and overall functional results."

First ever lateral incision MIS TKR study

Another study reported results of the first 26 patients (30 knees) who underwent a lateral incision approach to MIS TKR. During this procedure, surgeons make a 10 cm incision from the lateral side of the knee, and the instrumentation goes through the iliotibial band only.

After the surgery, patients had minimal anterior knee pain and 23 of 26 could execute a straight leg raise immediately following surgery, compared with 14 of 47 patients who had the standard incision. In addition, the lateral incision patients had better functional recovery at early time points, and a mean KSS of 97 versus 91 for the standard group.

Lateral MIS patients also showed a normal gait pattern. "These are some of the best knees ever done," study author and chief surgeon Michael A. Mont, MD, director of the Center for Joint Preservation and Reconstruction at Sinai Hospital in Baltimore, Maryland said. "We never get a normal gait pattern."

He urged caution however, given that four serious complications occurred in the 30 lateral incision knees.  Specifically, there were two knees that loosened and required revision arthroplasty, one patient developed peroneal nerve palsy that required a peroneal nerve release, and one patient developed a wound problem that required 2 weeks of care. The procedure may not be ready for widespread use, Dr. Mont says, "but we should still be pushing the envelope. There is tremendous potential for all these [MIS] procedures, but we need to be careful."

Douglas A. Dennis, MD, medical director of Rocky Mountain Musculoskeletal Research Laboratory in Denver, Colorado, is less optimistic. "Four potentially significant complications is pretty hard for me to swallow," he said. "It is not yet known if this is an incredible approach." Dr. Mont remains enthusiastic, however.  "There is a tremendous possible upside with this procedure," he adds. "The patients who did great, did great, and the patients who did poorly were disasters."

Pressure driven by DTC advertising

A week after pharmaceutical firms were chastised for DTC advertising by a US Food and Drug Advisory panel reviewing the safety of coxibs, orthopaedic surgeons speaking at the meeting also criticized the practice, suggesting that it stimulates patients to pressure them for procedures that are not adequately supported by available data.

"This sensationalistic type of marketing is a very bad thing for the overall care of the patient," agrees Dr. Dennis. For example, a recent promotion by golfer Jack Nicklaus has created patient demand for the latest but not necessarily the most widely studied implants and surgical procedures.

Besides DTC advertising, surgeon self-promotion also plays a role in the creation of potentially unreasonable patient expectations. "A surgeon should be in the paper three times in his life," Dr. Maloney says, "when he is born, when he opens up his own practice, and when he dies."

References

1.        Bonutti  PM, McMahon M, Mont MA, Ragland P. Limited approach total knee arthroplasty: a comparison study. Poster No 139 presented at:  The 72nd Annual Meeting of the American Academy of Orthopaedic Surgeons; February 23–27, 2005; Washington, DC.

2.        Mont MA, Bezwada H, Ragland P, et al. Minimally invasive lateral approach to total knee arthroplasty. Paper No 071 presented at: The 72nd Annual Meeting of the American Academy of Orthopaedic Surgeons; February 23–27, 2005; Washington, DC.