Surgeons discuss ‘good, bad, and ugly’ aspects of MIS THA

Surgeons discuss ‘good, bad, and ugly’ aspects of MIS THA

In the last 10 years, public and press attention have focused on “minimally invasive surgery” (MIS) for total hip arthroplasty (THA). During a media briefing yesterday, four orthopaedic surgeons discussed the “good, bad, and ugly” of MIS THA, in advance of a symposium on the subject scheduled for Sunday, Feb. 18, (10:30 a.m., Room 6A, San Diego Convention Center).

John J. Callaghan, MD, and colleagues Steven T. Woolson, MD; Lawrence D. Dorr, MD; and Thomas P. Sculco, MD, reviewed the use of MIS THA in the United States and discussed patient selection criteria, complications, and the use of computer navigation.

Although there is a high demand from patients for minimally invasive surgery, only about one in five patients is a candidate for MIS THA, according to the panel. In fact, according to Dr. Sculco, “The phrase seems like a misnomer, in that hip replacement surgery requires considerable alteration of anatomy, regardless of the exposure or technique. The term ‘less invasive’ is a more accurate description of what these procedures encompass.”

Are there advantages?

According to Dr. Woolson, none of the studies on MIS THA shows any clinically significant advantages to the procedure, and two studies show higher complication rates and/or more component malpositioning. MIS THA takes more time than the conventional surgery, requires more anesthesia, and can cause more muscle damage than the traditional “open” surgery. Other studies have shown “suboptimal positioning of the knee implants” and virtually no difference in recovery time.

Dr. Sculco, on the other hand, believes that his data indicate that “the advantages of these more limited procedures are real and include more rapid rehabilitation, less blood loss, and better cosmesis.”

Complicating factors

The size of some patients presents a challenge for MIS THA. Although the numbers of individuals considered overweight or obese is increasing, obese patients are not good candidates for hip replacement surgery. According to Dr. Sculco, the ideal patient for an MIS THA would have a body mass index of less than 30. “As body weight and obesity increase, more extensive exposures are necessary,” he pointed out.

“It is very important that we have good surgical candidates with correct fixation of the parts in hip replacement surgery,” cautioned Dr. Callaghan. “I do not want to see this procedure go ‘backwards.’”

Dr. Callaghan also expressed his concern about the number of surgical “revisions”—MIS procedures that have to be redone due to problems with the first surgery. “At the present time,” he said, “there are many more revision procedures performed in the United States than in Sweden.”

The restricted visual field may be one reason for the increased number of revisions. “A surgeon is inserting devices through a very small incision when performing MIS THA. It is critical that the components are in the right position, and this is difficult to ensure with such a small incision,” explained Dr. Callaghan.

Computer assistance may help

According to Dr. Dorr, “computer technology provides both qualitative and quantitative knowledge for the surgeon for the placement of the components. One great advantage of the computer is that the tilt of the pelvis is known, enabling the surgeon to adjust the acetabular position to give better coverage of the femoral component in different positions.”

In the final analysis, long-term durability of the hip replacement is more important than the length of the patient’s hospital stay. “Even though patients want a small incision, surgeons should only use the smallest incision that allows them to do a good job,” said Dr. Woolson. “Until there is convincing evidence of the benefits and safety of MIS THA, standard-incision THA remains the ‘gold standard.’”

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