Minimally Invasive Surgery (MIS): Who is a Candidate for MIS Total Knee Replacement

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.