Pros and cons of mini-incisions for THA debated

Patient demand and peer pressure push surgeons to decrease the length of their incisions.

Issue: Issue 3 2003

NEW ORLEANS — The use of a mini-incision for total hip arthroplasty is appropriate for some patients and may be associated with faster recovery and greater patient satisfaction. Whether such an approach compromises the long-term results of arthroplasty was the subject of debate here at the American Academy of Orthopaedic Surgeons 70th Annual Meeting.

Thomas P. Sculco, MD, director of orthopaedic surgery at the Hospital for Special Surgery, New York, is an advocate of the mini-incision approach and has been using it for the past six and a half years. William J. Maloney, MD, professor of orthopaedic surgery at Washington University in St. Louis, U.S.A., and chief of the orthopaedic surgery service at Barnes-Jewish Hospital, St. Louis, pointed out numerous concerns with the technique and disputed any long-term benefit associated with it.

Most of Sculco’s incisions are approximately 8 cm. Sculco said that the mini-incision is not for every patient, and it is not for every surgeon. Patients who are severely obese, very muscular (particularly men), and those undergoing complex revision surgery are not appropriate candidates for the technique. A thin patient is the ideal candidate for a mini-incision, he said.

Surgeons who undertake the mini-incision approach must be experienced arthroplasty surgeons, Sculco said. Those who want to use the mini-incision should “start with your standard incision and then gradually reduce it in size until you find a level where you are comfortable with the approach.”

Facilitating the technique

Sculco has developed customized instrumentation to facilitate the technique. He recommends having experienced assistance in the OR. Although not necessary, he finds that using a monoblock socket eliminates the need to engage the liner into the shell and makes the procedure easier. He also uses epidural hypotensive anesthesia “so the fields are essentially bloodless.”

Explaining the rationale for the mini-incision, Sculco said, “We felt that there would be less morbidity, faster rehabilitation, a reduced length of stay. We felt the patients would be more satisfied.”

Of greatest concern, he said, was whether the arthroplasty was being compromised. He cited the results of two studies, which he said suggest that it is not. In the first study, 22 patients were randomized to an 8-cm incision and 24 patients to a 15-cm incision. The surgical time, about 80 minutes, was similar for the two groups. Patients in the smaller incision group used less pain medicine, and their blood loss was significantly less.

“Rehabilitation in terms of limp and progression off a cane was faster with a smaller incision. Radiographically, the results indicated that the lateral abduction angles were about the same. Cement grades were A and B for most of the patients in both groups. And so we felt that it did not increase surgical morbidity,” Sculco said.

The second study, which is underway, includes 484 patients who have been followed for up to six years. Their average incision length was 8.2 cm. The average lateral abduction angle was 42º (range 28º-59º), 95% of patients had Barrack cement grades of A or B, 93% had neutral femoral alignment, and there was a 5% incidence of dome gap, which Sculco said was similar to his results before using the smaller incision. Problems included four dislocations and two neuropraxias.

Maloney questioned whether Sculco’s results with the mini-incision were better than his results with a conventional incision. He also challenged the importance of a shorter scar, faster recovery and the long-term benefit of the procedure.

“The length of the scar is only an issue to a small percentage of patients and is not nearly as important as what you do once you make the skin incision and how you handle the muscular tissue underneath the skin incision. The last time I checked, wounds healed side to side,” he said.

Noting that the length of stay was similar in patients receiving either length incision, Maloney pointed out that Sculco did not show any data related to recovery time. “I challenge this issue of faster recovery. The people that are being done with a mini-incision are a highly motivated group of patients,” he said.

“You have to question whether it’s the patient or the incision,” he said. “I suspect that if you took the same group of patients with conventional incisions you could send them home on postop day one as well. I think it’s clearly related to patients’ expectations and preoperative counseling.”

Maloney said there is increased risk of short-term complications. “You’re going to have dislocations, you’re going to break some femurs, and early on everyone who has used the two-incision technique that I’m aware of has broken at least one femur. There’s an increased risk of superficial infection and nerve injury.”

Referring to Sculco’s range of 28º to 59º in abduction angle of sockets, Maloney said, “I suspect in his conventional incisions that he does a little bit better than that.” His other concerns with the mini-incision technique include component malposition and failure to restore hip mechanics in terms of offset and leg length.

“Most modern cementless stems are extremely sensitive to rotational alignment,” Maloney said. “The problem with a mini-incision and a two-incision technique is that you have limited visualization of the calcar and it’s hard to tell if you’ve got the rotation right. If you put them in rotationally incorrect, you’re going to break some femurs.”

He linked the increased rate of superficial skin infection related to aggressive skin retraction despite the use of customized instruments and experienced assistance.

Nerve injury

Maloney said he believed Sculco’s two transient nerve injuries were related to “blind replacement of retractors and aggressive retraction.” He said, “It’s probably a higher incidence of nerve injuries than he’s had in his standard operation.”

Sculco said nerve injury may result from the use of excessive posterior tension. If a surgeon is having problems with exposure, he recommends reducing posterior retraction, extending the incision, and releasing the quadratus femoris and the gluteus maximus tendon if necessary.

Mini-incision THAs are a long-term experiment, Maloney said. “If you don’t get these in stable, if there’s more than 50 µm of micromotion, you’re going to a fibrous interface. That will do clinically well for five, six, seven, eight years. At that point in time, you’re going to see clinical failures. … We don’t know that these implants are actually rigidly stable.

“What I’ve done is just what Tom suggested. I’ve continued to shorten my incision, and I’ve used a small single incision for some patients who are in the appropriate category to have this type of surgery,” Maloney said, adding that he has not used the two-incision technique.

“One thing we’ve done now with all of our cementless implants is let the patients weight bear as tolerated,” Maloney explained.

“[Of] the first six patients who were allowed to weight bear as tolerated at six weeks, five were already walking without a cane and back to regular activities. So again, I’m not sure we’re really going to achieve much in terms of faster recovery with this technique.”

Sculco said, “It’s not for everybody. If you’re doing 10 or 20 hips a year, it’s probably not for you. But for most surgeons who are accomplished, it’s a very useful technique.”

For your information:

Sculco TP. Why I use a mini-incision in some patients. Presented at the American Academy of Orthopaedic Surgeons 70th Annual Meeting. Feb. 5-9, 2003. New Orleans.

Maloney WJ. Why I prefer a conventional incision. Presented at the American Academy of Orthopaedic Surgeons 70th Annual Meeting. Feb. 5-9, 2003. New Orleans.