KNEE

Minimally Invasive Knee Replacement

Minimally invasive total knee arthroplasty is one method of performing a knee replacement, which is the resurfacing of the worn out surfaces of the knee. A surgeon replaces lost cartilage with metal and plastic through an incision down the center of the knee. This incision averages 8 inches to 10 inches long. However, minimally invasive total knee arthroplasty is a different way of performing the surgery. It uses an incision that is only 4 inches to 6 inches long, which means that potentially there will be less damage to the tissue around the knee.

Causes

Knees wear out for a variety of reasons. These include inflammation from arthritis, injury, or simple wear and tear. Arthritis can also run in families. Most knee arthritis is due to a lifetime of wear and tear. Nobody knows why some people get severe arthritis, while others don't or why one knee in the same person gets arthritis, while the other does not. Previous injury and obesity are other known causes of arthritis.

Symptoms

Typical symptoms include:

  • Pain during activity.
  • Pain while resting.
  • Difficulty going up or down stairs, walking distances, or getting up from low seats.
  • Swelling, stiffness, or a feeling of looseness.

Treatment

The first steps in treating knee arthritis are activity modification, a program of regular exercise, and weight loss. The muscles around the knee protect it during activity, however, every step puts several times your body weight through your knee. Improved strength and decreased body weight will prolong the life of your knee. Soft knee braces and modifications of your shoe can sometimes help, as well as medications like Tylenol® or anti-inflammatories (NSAIDs), and some dietary supplements. You may need to use a cane or walker.

The next step is injections. Steroids may be used to decrease inflammation, or a lubricant may be used to improve the function of the knee. They can be repeated from time to time if they help.

Surgery is the final step in the treatment of knee arthritis if the steps above have failed and the pain from the arthritis is limiting your lifestyle and activities. A knee replacement can help to eliminate most of the pain from arthritis. Surgical options include knee arthroscopy (although this is rarely used just for arthritis), partial knee replacement, and total knee replacement.

Total knee replacement can be performed in the traditional method (8 inch to 10 inch incision), or it can be performed using newer techniques (4 inch to 6 inch incision). The goal of knee replacement is to provide a pain-free knee that allows relatively normal activities and lasts for as long as possible. Using the current techniques, 90 percent to 95 percent of knee replacements should last 15 years or longer.

The minimally invasive knee replacement technique attempts to accomplish all of this through a smaller incision. With the smaller incision comes the potential benefits of a shorter hospital stay, a shorter recovery and a better looking scar. Although there is no question that a knee can be put in through a smaller incision, it is still unknown whether it can be done as well.

Several early studies of minimally invasive knee surgery have shown some benefits such as less blood loss, shorter hospital stays, and better motion, while others have shown a higher rate of complications, suboptimal positioning of the knee implants, and no real difference in the recovery. Unfortunately, we won't know if these new techniques affect the long-term function and durability of the knee replacement for 10 to 15 years. Long-term durability is much more important than whether you were in the hospital for two days or four days after surgery.

Research on the Horizon 
Advocates of minimally invasive knee replacement are working to address concerns about accurate positioning of the knee replacement. They are combining the small incision with computer-guided instruments. The potential benefits, risks, and costs of this are not yet established.

Reproduced with permission Fischer S., (interim ed): Your Orthopaedic Connection. Rosemont, Illinois. Copyright American Academy of Orthopaedic Surgeons.