TKA surgeons get similar results after switching to MIS

Half of the surgeons preferred the mini procedure following five practicecases.

Issue: June 2005

WASHINGTON — Learning minimally invasive surgery and getting good results may not take as long as you think.

In a multicenter study evaluating the safety of mini operations, researchers found comparable Knee Society scores, functional outcomes and adverse events between minimally invasive surgery (MIS) and traditional TKA. What’s more, the six surgeons performing the procedures had limited MIS training, which consisted of one site visit and five practice cases. “This minimally invasive surgical technique does in fact appear to be safe for the small learning curve of five cases and one observation,” said Frank R. Kolisek, MD, a surgeon with Orthopaedics Indianapolis, during his presentation at the American Academy of Orthopaedic Surgeons 72nd Annual Meeting.

Kolisek and his five co-authors learned a mini midvastus approach from the Bonutti Clinic founder, Peter M. Bonutti, MD, FACS, and performed it on 40 patients. An independent reviewer compared the results to 40 patients the surgeons operated on with standard methods. The investigators found the mean Knee Society score for the MIS group was 83 vs. 86 for the standard cohort three months postoperatively, they wrote in their abstract. Tibial subsidence occurred in both groups and operative time increased in the MIS group by 10 minutes, Kolisek said. “And surprisingly, the length of stay was the same [and the] intraoperative blood loss was the same,” he said.

A crash course in mini surgery

Bonutti’s success and experience with more than 500 mini knees intrigued the surgeons, Kolisek said. “And so we wanted to know if it is something he worked really hard on and was able to accomplish,” he said. “And would it be safe for five other surgeons besides himself to try some of these MIS techniques or would we be doing patients a disservice?” Kolisek said.

In the IRB approved study, Kolisek and colleagues observed Bonutti, a Stryker Howmedica consultant, perform his technique. The surgeons practiced on five cases using the Scorpio knee system (Stryker Corp.) and cemented implants, Kolisek said.

In the real MIS cases, surgeons made less than 13-inch incisions and 2- to 2.5-cm vastus splits, Kolisek said. They visualized components using mobile windows and maneuvered knees with Stryker MIS instruments, he said. All surgeons avoided patella eversion.

Parallel outcomes

“The good news is all knees in both groups were within 3° of both AP and lateral alignment goals for both the femoral and tibial components.”
— Frank R. Kolisek

Intraoperatively, the researchers noted that the average MIS incision was 6 cm shorter (9 cm vs. 15 cm), while the surgery was longer (69 minutes vs. 59 minutes), Kolisek said. In a radiographic evaluation, they discovered that changing techniques did not affect surgical accuracy. “The good news is all knees in both groups were within 3° of both AP and lateral alignment goals for both the femoral and tibial components,” Kolisek said.

Both groups had similar medical problems, he said. “We had a femoral fracture following manipulation under anesthesia in the MIS group and four superficial wound problems that resolved without needing further surgery,” Kolisek said. In the standard cohort, one patient had a superficial wound infection that later healed. Another sustained a tibia fracture in a car accident, he said.

Kolisek said that the short-term success may be due to an early learning curve “and it also could be that some of our regular techniques are so ‘close’ to minimally invasive that we didn’t see a big clinical difference.”

A surgeon’s preference

More surgeons in the study, three out of six, clearly favored the MIS technique. “One surgeon had no preference which approach he or she did, and two other surgeons preferred their standard technique over the MIS approach,” Kolisek said.

The study findings may foreshadow future MIS use, he said. “And this may be [that] it’s basically a surgeon’s choice to deal with their own patients, depending on how they feel [and being] comfortable with their own surgical techniques and skills,” Kolisek said.

For more information:

Kolisek FR, Bonutti PM, Hozack WJ, et al. Multi-center study: comparison of standard to minimally invasive total knee arthroplasty. #70. Presented at the American Academy of Orthopaedic Surgeons 72nd Annual Meeting. Feb. 23-27, 2005. Washington.