Mini mid-vastus approach may speed return of function vs. standard-incision TKA

Avoiding patella eversion proves the key part of the procedure and also prevents postop patella baja.

The mini mid-vastus approach may resolve the problems of postoperative pain and function found with standard medium parapatellar incisions, but the technique is not for all patients.

In his experience using the mini technique for nearly 400 total knee replacements (TKR), Richard S. Laskin, MD, of the Hospital for Special Surgery (HSS) in New York, found better short-term results. “They acquire less pain postoperatively,” Laskin said.

“Their range of motion comes back faster, but equalizes as you go further on out. The tourniquet time is not particularly longer [and] they get their functional milestones back much more quickly than the patients in [which] we used the larger incision and twisted the patella upside down,” he said during his presentation at the 7th Annual Current Concepts in Joint Replacement Spring 2006 Meeting.

Knees well-balanced postop

Laskin also found that the knees were well-balanced postoperatively and that the procedure decreased the chance for patella baja.

“The components are coming out in the right position, our Knee Society scores are good, [and] more important, our balancing scores are good,” he said. “We’re not misbalancing these knees. We found that by not everting the patella, we decreased the prevalence of patella baja, and patella baja definitely leads to decreased flexion.”

Despite these advantages, Laskin said that the procedure may not be feasible for patients with markedly limited preoperative motion or who had previous open knee surgery. He also noted that despite some improper direct-to-consumer advertising, the approach is not pain-free, and no knee replacement performed through any approach will result in a knee equivalent to what the patient had prior to developing arthritis.

“But, if you can do a knee replacement and decrease the amount of pain, increase their rate of getting their motion back, enable them to return to functional activities quicker, but still do it safely by putting the components in the proper position, balancing the soft tissues, protecting the vital tissues and not extending the surgical time, the question is, ‘Why wouldn’t you consider doing it?’” Laskin asked.

Surgical technique

Laskin performs the procedure with the knee slightly flexed and makes his initial incision across the medial third of the patella. He makes the capsular incision 2 cm into the vastus medialis and approaches the medium parapatella distally.

After putting the leg in additional extension, he inserts a PCL retractor. The most crucial part of the procedure is avoiding patella eversion.

“I then just push the patella to the side, but I don’t twist it 180° on itself,” Laskin said. “I think that that’s going to be the most important part of doing this operation.”

Using smaller instruments during the procedure may also prove safe. In more than 750 replacements done at HSS by several surgeons using miniaturized tools, there have been no femoral condyle fractures. Laskin also pointed out that the length of the incision does not prove to be important. In actuality, “The length of the skin incision is related to the width of the femoral condyles, to the height of the patient and the girth of the legs,” Laskin said.

Detractors of the mini mid-vastus approach claim the procedure carries a high failure rate and has limited long-term advantages, but Laskin disagrees. “From all the studies and in our experience, we didn’t malposition them,” he said. “We did balance the knees. We didn’t get infected and we used the same implant that everyone else used, so there’s no reason to think that they’ll fail in the long term. It doesn’t change the long-term results. However, by one year they look alike. They just got there a little bit easier.”

Editors note: This article is taken from the August 2006 issue of Orthopedics Today, page 26.

For more information:
Laskin RS. Choosing the surgical approach. #37. Presented at the 7th Annual Current Concepts in Joint Replacement Spring 2006 Meeting. May 21-24, 2006. Las Vegas.