By James F. Holtzclaw, M.D.

Millions of Americans with disabling arthritis of the hip or knee have experienced excellent outcomes following hip or knee replacement surgery. Advances in technology and instrumentation now allow surgeons to perform hip and knee replacement procedures through smaller incisions with less soft tissue and muscle detachment. In many cases this will translate into shorter hospital stays and rehabilitation with a more rapid return of function. Not all MIS (minimally invasive surgery) procedures are the same. This article will describe what makes a hip or knee replacement minimally invasive and why it may be a good option for patients with advanced arthritis of the hip or knee.

MIS Hip Replacement

Most hip replacement procedures in North America are done through a 10-12 inch skin incision over the back of the hip. Some of the muscles, tendons and the posterior hip capsule are detached from the bone in order to dislocate the hip and carry out the arthroplasty procedure. These muscles and tendons are typically not repaired. Numerous long term studies of over 20 years have shown this procedure to be reliable with excellent long term outcomes.

The standard posterior ap- proach can also be carried out with a skin incision as small as 6-8 inches in thin patients. Even though the skin incision is smaller, I would not con- sider this minimally invasive as it requires detachment of the same muscles and tendons as the standard posterior ap- proach.

The mini-anterior approach is carried out through a 3-4 inch skin incision over the front of the hip. The approach is done without detachment of any muscles or tendons from the bone. The anterior hip capsule is opened to dislocate the hip and carry out the arthroplasty (surgery to relieve pain and restore range of motion by realigning or reconstructing a joint) procedure. The anterior hip capsule is then repaired after hip replacement is done. A special operating table greatly assists in exposure of the hip. This table allows the procedure to be done in the supine position (patient is lying on his/her back). With the patient in this position, the table allows the hip prosthesis to be placed under fluoroscopic guidance to assure satisfactory position of components and to check for leg length equality.

MIS Knee Replacement

Total knee replacements are typically done through a skin incision of 8-10 inches over the front of the knee. The main tendon (quadriceps tendon) over the front of the thigh is divided and then repaired with suture after the knee has been re-placed. Long term outcome studies of over 15-20 years have shown this procedure to have excellent outcomes for millions of Americans with advanced arthritis of the knee.

The goal of a minimally invasive knee replacement is to leave the quadriceps tendon intact. The MIS approach is carried out through a skin incision of 3-4 inches without dividing the quadriceps tendon. With the quadriceps tendon intact, patients can usually begin active straight leg raises the day following surgery. Length of hospital stays can be as short as 24-48 hours.

Correct placement of femoral and tibial components is more difficult when using a smaller skin incision. Computer assisted navigation systems have been developed using infrared sensors to help assure correct alignment of prosthetic components. There will soon be electromagnetic sensors incorportated in the bone cutting blocks which will make the procedure even easier to perform. This technology should result in similar or better long term outcomes since studies have shown that poorly aligned components have worse long term outcomes.

Summary

Advances in technology and instrumentation now allow traditional procedures to be carried out in a less invasive manner. MIS hip and knee procedures can lead to shorter hospital stays and a more rapid return of function. If you are considering hip or knee replacement surgery, ask your Orthopaedic Surgeon if a minimally invasive procedure may be right for you.

James F. Holtzclaw, M.D. can be contacted at Chatham Orthopaedic Associates, P.A., 4425 Paulsen Street, Savannah, GA 31405; 912-355-6615 or visit chathamorthopaedics.com.