SEATTLE, Washington—Minimally invasive knee arthroplasty (TKA) may be appropriate for select patients when performed by an experienced surgeon. That is the main message of a vignette presented in the April 23, 2009 issue of New England Journal of Medicine.¹

In the journal, Seth S. Leopold, MD, an orthopaedic surgeon at the University of Washington School of Medicine in Seattle, tackles the case of whether a relatively healthy 65-year-old woman with diffuse and severe knee osteoarthritis who has failed medical management should undergo minimally invasive or traditional open total knee replacement. The patient has minimal joint deformity and good bone quality.

The question is whether this patient can have a minimally invasive rather than an open procedure. Dr. Leopold points out that there is really no easy answer, as no formal guidelines exist. Potential advantages include shorter recovery and less postoperative pain, but there may not be any benefits in long-term function. In fact, some surgeons fear that long-term outcomes might be inferior to those with open TKA.

Factors that favor minimally invasive TKA

So what should tip the scale in favor of choosing the minimally invasive approach? The experience of the surgeon, for one thing. A surgeon should have performed 25 to 50 minimally invasive procedures to be proficient, Dr. Leopold stressed.

Proper patient selection also plays a role. Contraindications to minimally invasive knee replacement surgery include previous open knee surgery, severe osteoporosis or rheumatoid arthritis, obesity, or increased limb girth and severe joint deformity.

“You want to choose patients who can benefit from the accelerated rehab and who are reasonably active,” added Joshua Jacobs, MD, professor and chair of orthopaedic surgery at Rush University Medical Center in Chicago.

Minimal invasion is still major surgery

Dr. Jacobs pointed out that minimally invasive total knee arthroplasty is still a major surgery with the same sized implants, and the same bone cuts. There is just a little less exposure and severing of tissues with the minimally invasive approach.

“There is no follow-up beyond 5 years with minimally invasive knee replacements, so no one knows whether or not there is a negative impact on long-term results,” he said. “Some of us are concerned that the alignment may not be as ideal as if you have a more significant exposure [of tissues] or that there may be bone cement retained in the knee which leads to wear and tear on the components,” Dr. Jacobs said.

“I worry that there will be a price to pay in long-term results,” he said.

Translating research into practice: Conversation with patient is key

Minimally invasive surgery is confusing. “Patients don’t know what it is and physicians don’t know what it is because it means different things to different people,” Dr. Jacobs said. “When we talk to patients we have to be very circumspect about what it is they think they are asking for.”

“The conversation you have is that the goal of knee replacement is to provide you with a well-functioning, very long-lasting knee that you may need for 5 to 40 years, so my emphasis is on the long-term function and results, rather than the short-term benefits,” he told MSKreport.com.

Dr. Leopold also stressed the importance of having a frank discussion with patients about the risks and benefits or both types of surgeries. He ultimately concluded that the patient may indeed be a candidate for minimally invasive knee replacement as long as she is properly informed about what she can expect in the perioperatve and immediate postoperative period.

References

1. Leopold SS. Minimally invasive total knee arthroplasty for osteoarthritis. N Engl J Med. 2009;360:1749-1758.