MIS: Why mess with excellence? Although it may have benefits, MIS does not have data to warrant its widespread use.

Link http://www.orthosupersite.com/view.asp?rID=25529

By Robert L. Barrack, MD
ORTHOPEDICS TODAY 2008; 28:61
January 2008

Minimally invasive surgery is probably the only topic that outpaces the gender issue in orthopedics in terms of interest and media attention. In fact, if you look at the Internet, there�s about a half-million sites that address MIS; only a handful of which have any data. If you look at the medical literature, there are a little over one-hundred articles and only 20 or so of them have any outcomes data. That gives us a ratio of promotion to science of about 13,000:1.

This was generated by a tremendous amount of hype and has resulted in patient expectations that are often out of sight, maybe even unrealistic. If you ask patients what they expect following an MIS knee, they think they are having an arthroscopy. They don�t expect to have much pain, and they certainly don�t expect any increase in complications. So, the real questions are: Do we get better results and is this associated with a higher risk of complications?

Best representatives?
There is some literature support for some advantage, including evidence that in 3 months it might be better than traditional total knee arthroplasty (TKA), but this is very controversial. Most investigators have not shown much difference. The problem with most studies is that they are usually from designers or proponents of the systems utilized, so they are prone to a lot of selection and observer bias. Many times data are from very experienced, high volume-surgeons who have performed thousands of knees before their first MIS. Therefore, the results may not be representative of the results that most surgeons can expect.

Recently a randomized controlled trial was published in Journal of Arthroplasty in which MIS-total knee demonstrated no improvement over a standard approach. There was a 10% incidence of delayed wound healing in the MIS group, even with experienced surgeons. The downsides included: a longer tourniquet time; there were more radiographic outliers early on; and a higher complication rate, some of which were serious.

Early failure
If you look in the literature, some well-known, experienced knee surgeons describe serious complications. That leads us to ask: Is MIS leading to early failures compared to standard knee replacement?

At Barnes Jewish Hospital we looked at all of our revisions over about a 3-year period and we had almost 200, excluding infections and second and third time revisions, there were about 90 cases. In recent years, MIS makes up about 16% of our revisions, usually for failure of fixation, instability, or malalignment. The problem is that the time of failure for these MIS cases is dramatically shorter � 13 months to failure or to revision compared to almost 80 months following a standard incision.

The complications we are seeing include: malrotation of the components, particularly the tibial component; improper tensioning of the knee; and failure of fixation.

The long term results of TKA have been excellent and with improvements in perioperative management we are really going to be hard pressed to improve on these excellent results. MIS does hold some promise in reducing perioperative morbidity and possibly improving short-term outcomes, but the data is not compelling enough to establish a clear advantage over standard TKA at present. The advantages reported currently may be due to selection and observer bias and the level of skill of the reporting surgeons.

In the hands of many, if not most, surgeons the complication rates will increase and that substantial increase in complication rates is really not warranted based on the modest improvements and outcomes reported even in the most optimistic studies at the present time.

For more information:
Robert L. Barrack, MD, can be reached at Washington University School of Medicine, 660 S. Euclid Ave., Campus Box 8233, Department of Orthopedic Surgery, St. Louis, MO 63110; 314-727-2562; e-mail: [email protected]. He is a consultant for Smith & Nephew and is also a member of the company�s advisory committee/review panel.
Reference:

Barrack RL. MIS: A risk factor for early failure � Affirms. Paper #32. Presented at Current Concepts in Joint Replacement Spring 2007. May 20-23, 2007. Las Vegas.