MIS Knee Replacement May be Linked to Early Failure?

A high incidence of failures performed using a Minimal Incision Surgery (MIS) technique was noted in a paper presented at the 2009 annual meeting of the American Academy of Orthopaedic Surgeons (AAOS). 1

In total knee replacement, the worn ends of the bones that make up the knee joint are resurfaced with metal and plastic implants. The surgeon must carefully align the implants relative to the bones and must restore the proper alignment of the bones to one another. If proper alignment is not achieved, excessive wear and premature loosening of the implants may result.

In “Minimal Incision” or “Minimally Invasive” Surgery, exposure of the surgical site is limited. Often the landmarks used in standard total knee replacement surgery may be obscured. The surgeon must rely on experience and sophisticated instruments to properly align the components. Although MIS knee replacement has grown in popularity in recent years, the possibility of issues arising due to the limited exposure has remained a primary concern.

In their paper, Dr. Derek Miller et. al. examined a series of revision cases performed by five surgeons at three different centers between 2004 and 2006. Excluding revisions due to infection and re-revisions, 236 first time revisions were recorded. Of those, 43 were originally performed via MIS, and 193 were revisions of implants first implanted using a “standard” knee replacement technique. In comparing the two groups of revisions, the findings were dramatic. On average, the time to revision was 14.8 months in the MIS group compared to 80 months for the standard group. Thirty-seven percent of the MIS group were failures less than 12 months after surgery compared to only 5% in the standard group. More than eight out of ten of the MIS revisions were in total knee replacement patients that had their implant in for less than two years.

Although MIS knee replacement may lead to quicker recovery and less scarring, this study suggests that the long-term performance of these procedures may be compromised. It remains to be seen whether continued advances in the technique and surgeon experience can counteract this trend.

1 Miller DW, Barrack RL, Barnes CL, Clohisy, JC, Maloney WJ, “Minimal Incision Surgery As A Risk Factor For Early Failure Of Total Knee Arthroplasty?” 2009 AAOS Annual Meeting, Podium No. 272

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Minimally Invasive Knee Replacement

Surgeons and the developers of knee implants have begun to market an alternative to standard knee replacement surgery that has been termed “Minimally Invasive Surgery” or “MIS” . This should really be termed “Less Invasive” since a significant (although reduced) incision is still required, the entire joint and bones are still exposed and “standard” implants are still used. What makes it less invasive is the exposure that the surgeon chooses to work with. Often this means less visibility for the surgeon and a more difficult procedure.

The possible benefits to the patient are:

  • The potential for less scaring
  • Possibly more rapid recovery since the surrounding muscles and tissue are left more intact.

However, this procedure can be quite challenging for the surgeon that is less experienced or new to this type of operation. The surgeon must rely on landmarks which are less visible and must use smaller instrumentation to position and align the implant components. This is important to note because malalignment of implants is one of the key short-term failure mechanisms in Total Knee Replacement (although newer designs are more “forgiving” than older versions).

For more information on Minimally Invasive Knee Replacement, you can visit some of the company sponsored sites.

Stryker: http://www.miknee.com

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