Who is a Candidate for Minimally Invasive Surgery?

Here in the Phoenix – Scottsdale, Arizona area I am frequently asked by patients “Can you perform Minimally Invasive (MIS) Total Knee Replacement (TKR) on my knee?”

My answer is I can perform Minimally Invasive Total Knee Replacement on most any patient but I choose to use the technique on the large subset of patients that benefit most from the technique. It is a surgical procedure that is more technically demanding and more time consuming than traditional Total Knee Replacement so I am somewhat selective on choosing patients for this method. By analogy, I would not buy a new Basketball for my 90 year old mother in law but I would for my teenage son who is on the high school basketball team. She would never use the basketball and he would use it frequently.

I always perform Minimally Invasive Surgery on the healthy, motivated, energetic patients who will recover fast because of their good health and motivation to get well fast. I rarely perform Minimally Invasive Surgery on unhealthy patients with multiple co morbidities (Diabetes combined with cardiac or respiratory disease combined with high Body Mass Index is a typical patient profile that comes to mind). The first example patient would take full advantage of having had this technique by discharging from the hospital in 1-2 days, be walking freely without a walker in 5-10 days, be driving in 10 days -3 weeks, be back to work in 2-4 weeks and be golfing or hiking in the beautiful Arizona desert in 4-8 weeks. The second example patient would recover but take 1-3 months to reach similar milestones.

Body mass index is sometimes a factor since some patients with high BMI have low energy. BMI alone is not a reason not to perform MIS Total Knee surgery.

A normal BMI is under 30 and defined as a six foot tall man weighing 215 pounds or less or a five foot six inch woman weighing 182 pounds or less.
Obesity (BMI 30-40) is the six foot man between 215 and 285 pounds or the five foot six woman between 182 and 240 pounds. Morbid obesity (BMI above 40) is above 285 pounds for the six foot man and above 240 pounds for the five foot six inch woman. (BMI tables are available online to calculate your own BMI). Minimally Invasive Surgery can be performed on the higher BMI patients. It always requires a skin incision 2-4 times longer than the incision in under 30 BMI patients. The longer skin incision allows the surgeon to “convert” the high BMI patient into a low BMI patient by retracting away the “extra” skin and subcutaneous tissue. However, the definition of Minimally Invasive Surgery Knee Replacement and the key factor allowing for faster recovery is not the size of the skin incision but the size of the deep or Capsular incision that allows the surgeon into the knee joint proper. Therefore high BMI patient can have Minimally Invasive Total Knee Replacement Surgery and enjoy the benefits of a faster recovery.

Returning to the question posed at the beginning of this post: Who is a candidate for Minimally Invasive Total Knee Replacement Surgery? The answer is that most people are good candidates for MIS TKR as long as they are healthy, have a good energy level and are motivated to recover quickly.

Minimally Invasive Knee Replacement is Safe/Better: Refuting the Wall Street Journal

The October 14, 2008 edition of the Wall Street Journal published an article entitled “New Doubts About Popular Joint Surgery”. The following excerpt from the WSJ raises issues concerning Minimally Invasive Joint Replacement surgery (MIS).

“But patients aren’t always told that minimally invasive surgery is more difficult to perform than a traditional operation. Because of the smaller incision, surgeons have a harder time seeing what they are doing. And because minimally invasive surgery has grown so fast, many doctors don’t have extensive experience performing the complicated procedure.”

As an experienced MIS Knee Replacement Surgeon I completely agree with the above quoted comments. However, the other side to the story is that experienced surgeons using computer surgical navigation have patients with consistently excellent outcomes and complication rates as low or lower than traditional joint replacement surgeons.

I would like to address the three issue raised. First, “minimally invasive surgery is more difficult that a tradition joint replacement”. There is a known “learning curve” of approximately 25 cases, after which most surgeons will have mastered the MIS technique. I have been performing MIS Total Knee Replacement since 2004 and to date have over 500 cases experience. The transition to MIS replacement will occur with time and can be compared to the transition in sports medicine from open “traditional” knee and shoulder surgery in the past to current arthroscopic treatment for most knee and shoulder injuries.

Secondly, “because of the smaller incision, surgeons have a harder time seeing what they are doing”. Using Computer surgical navigation intraoperatively or computer generated surgical cutting blocks preoperatively provides the Minimally Invasive Joint surgeon with the information needed to accurately place the new hip or knee joint using the smaller incision. Computer technology more than overcomes the exposure issue raised in this second point. I personally do not perform MIS Total Knee Replacement unless I have computer navigation or computer generated cutting blocks.

Third, “because minimally invasive surgery has grown so fast, many doctors don’t have extensive experience performing the complicated procedure”. Every major city and some smaller towns have compentent, experienced minimally invasive joint replacement surgeons. As a patient, do your research and find the well trained, experienced minimally invasive joint replacement surgeon and you will often times be rewarded by a faster recovery and a less painful experience while getting all the long term benefits of traditional total joint replacement.

Minimally Invasive Total Knee Replacement Facilitates Recovery

An article appeared in the July, 2007 Journal of Bone and Joint Surgery entitled “Minimally Invasive Total Knee Arthroplasty Compared With Traditional Total Knee Arthroplasty“. The main author is Seth S. Leupold, M.D. from the Department of Orthopedic Surgery at the University of Washington in Seattle.

The conclusion of the article is that minimally invasive Total Knee Replacement seems to facilitate recovery after this operative procedure. The patients who had the minimally invasive approach demonstrated significantly better clinical outcomes with respect to shorter length of hospital stay, higher percentage of patients discharged to home instead of inpatient rehabilitation facility, less narcotic use at 2 and 6 weeks post-operatively and less need for assistive devices to walk at two weeks after surgery.

The Journal of Bone and Joint Surgery is one of the most respected and credible orthopedic surgery publications. The journal was founded in 1903 and is the official journal of the American Association of Orthopedic Surgery. The guiding principle of the JBJS is excellence through peer review. There are high standards, professional review and rigid criteria that have to be met before an article is accepted for publication. This is one of the first unbiased articles to appear in a prestigious orthopedic journal confirming the benefits of minimally invasive Total Knee Replacement. Therefore I believe the appearance of this article in the JBJS is highly significant.

Like the author of this article, I began performing MIS Total Knee Replacement in 2004. And just as the author discusses in the quoted article there is a learning curve of at least 25 cases to become more familiar with the technique. Like the author I perform a number of these operations on a monthly basis so that I got the over the learning process in a 3 month period. Over the last 3 years I have performed Minimally Invasive Knee Replacement on most of the patients I treat surgically for knee arthritis.

The components that are implanted are the same for MIS and Traditional Knee Replacement. I always use Surgical Computer Navigation as I believe this improves the accuracy in component position.

In my experience 1 in 4 patients are discharged home after one night in the hospital and most of the remaining patients go home after 2 nights. It is less common for a patient to be hospitalized 3 nights or to be discharged to an inpatient rehab facility. Similarly 25 % of patients are walking without assist in a week and the 70 % are walking without assist at 2 weeks. Most patients are driving in 2-3 weeks.

The results with respect to mobility, knee motion, pain relief and function for activities of daily life after MIS and Traditional Knee Replacement seem to merge around 3-12 months after surgery, however the return of quadriceps strength seems to occur sooner in MIS patients.

In conclusion I found the publication of the article highly significant and supportive of the beliefs of my colleagues who are currently performing minimally invasive Knee Replacement. Surgeons using minimally invasive techniques for Joint Replacement do so because of the greater patient benefits with this procedure.