March 2012

MIS adventures: Minimal approach rivals standard TKA

In the moment: Surgery #16259863

By Emily Delzell

Several studies presented in February found few differences in outcomes for minimally invasive total knee arthroplasty (TKA) and traditional TKA.

Minimally invasive surgery (MIS) for TKA involves a shorter incision than open TKA (4 in vs 8 in). Previous studies have reported some benefits for MIS TKA in terms of postoperative pain, hospitalization time, and return of knee function, said Seth S. Leopold, MD, a professor in the Department of Orthopaedics & Sports Medicine at the University of Washington, Seattle.

Leopold’s recent study, presented at the annual meeting of the American Academy of Orthopaedic Surgeons (AAOS) in San Francisco, CA, reported on four-year outcomes of 50 patients who underwent traditional TKA and 100 who had quadriceps-sparing MIS TKA. Leopold and colleagues found no significant differences in Knee Society Score (KSS) or in risk of reoperation/revision between the groups.

“In a study of this same group of patients published in 2007 [The Journal of Bone and Joint Surgery] we observed less postoperative pain, shorter inpatient hospital stays, and a much increased likelihood of the patient being able to go straight home after the short inpatient stay [than patients who underwent traditional TKA],” Leopold said. “The study presented at AAOS this year showed these benefits appear to accrue without an increased revision risk.”

A randomized controlled trial (RCT), also presented at the AAOS meeting reported no substantial gait or strength benefits for MIS versus standard TKA. A surgeon experienced with both MIS and traditional TKA performed both procedures, which were done at the Mayo Clinic in Rochester, MN, a high-volume center for both approaches.

At two months and at two years, KSS improved significantly in all 40 patients, as did gait parameters (particularly knee kinematics and kinetics) during level walking and stair climbing; quadriceps strength also increased significantly at two months. Investigators found no differences in the two groups except for a higher speed during stair ascent at two months in the MIS group.

Investigators concluded that in a high-volume center with advanced pain management and rapid rehabilitation there is no substantial additive benefit for MIS TKA over traditional surgery.

An RCT presented at the American Physical Therapy Association (APTA) Combined Sections Meeting in Chicago compared early (four and 12 weeks postsurgery) clinical outcomes in patients randomized to traditional or MIS TKA. Investigators evaluated isometric quadriceps and hamstring strength, quadriceps activation, functional performance, and knee active range of motion and pain. At four weeks, the MIS group had greater hamstring and quadriceps strength, but no differences in other measures; at 12 weeks investigators found no clinically meaningful differences in the two groups.

“Minimally invasive surgery is kind of a misnomer here because whatever the approach, TKA is still the most invasive knee surgery one can do, involving complete resurfacing of all joint surfaces and removal of one or even two ligaments,” said Michael Bade, PT, MPT, a PhD candidate at University of Colorado at Denver who reported the findings at the APTA meeting.

He also points out that the study involved one surgeon whose experience with MIS TKA enables him to perform that technique as quickly as standard TKA, but this may not be the case for the majority of surgeons.

“The learning curve means that most MIS TKA procedures are going to involve longer operative time, longer time under anesthesia, and longer tourniquet time,” he said. “I think surgical techniques should evolve to be as least traumatizing as possible, but it’s important to note that with MIS, you’re basically trying to build a ship through a bottle. Potential TKA patients should consider surgical experience in procedure selection.”


  1. Daines BK, Stamper D, White JKK, et al. MIS TKA Does Not Improve Patient Outcomes Compared to Traditional TKA at Intermediate Term. Presented at Annual Meeting of American Academy of Orthopaedic Surgeons, San Fran­cisco, February 2012.
  2. King J, Stamper DL, Schaad DC, Leopold SS. Minimally invasive total knee arthroplasty compared with traditional total knee arthroplasty: Assessment of the learning curve and postoperative recuperative period. J Bone Joint Surg 2007;89(7):1497-1503.
  3. Pagnano MW, Wegrzyn J, Parratte S, et al. A randomized clinical trial of minimally invasive TKA: Comprehen­sive gait and strength testing outcomes. Presented at Annual Meeting of American Academy of Orthopaedic Surgeons, San Francisco, February 2012.
  4. Stevens-Lapsley JE, Bade MJ, Shulman, BC, et al. Minimally invasive total knee arthroplasty improves early knee strength but not functional perfor­mance: a randomized controlled trial. Presented at American Physical Ther­apy Association Combined Sections Meeting, Chicago, February 2012.

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