With Minimally Invasive Hip Replacement, Less Is More

As the population ages, the number of total hip replacement surgeries steadily increases. Until recently, total hip replacement surgery involved a hospital stay of three days or more, post-operative pain and weeks of rehabilitation. That's all changing, however, with the introduction two years ago of a new minimally invasive hip replacement surgical technique. It involves a smaller incision, usually just an overnight hospital stay, far less pain and a much faster recovery time.

So now, when it comes to total hip replacement, less is more - and Froedtert & Medical College is one of the first sites in the area to offer the procedure, says James T. Ninomiya, MD, Associate Professor and Clinical Director of Research for the Medical College's Department of Orthopaedic Surgery. He is one of the first 30 surgeons trained in the new procedure. "We're now a center for training other surgeons in the technique," he says.

Smaller Incision Is Key
With the minimally invasive technique, the surgeon makes a small incision of about 7 centimeters, or approximately 2¾ inches, says Dr. Ninomiya. (Some surgeons prefer two small incisions.) That small cut compares with an incision of 8 to 12 inches in conventional hip replacement surgery. Because of this smaller incision, surgeons can operate between muscles, tendons and ligaments, rather than cutting through these soft tissues. Much of the pain associated with conventional hip replacement surgery and recovery is the result of severing these tissues, he says.

"It hurts less," says Dr. Ninomiya. "Patients can get up sooner, they walk sooner, and their rehab time is faster. They can return to their everyday activities much more quickly."

The most common cause for hip replacement is one of the scourges of growing older - osteoarthritis, which wears down joints. But it can also be a result of rheumatoid arthritis (a chronic inflammatory disease that causes joint pain, stiffness and swelling), avascular necrosis (loss of bone caused by insufficient blood supply), injury, and bone tumors that may lead to breakdown of the hip joint and require hip replacement surgery, according to the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), one of the National Institutes of Health.

Satisfied Patients
Of the more than 200 minimally invasive hip replacement procedures Dr. Ninomiya has performed over the past two years, patients overwhelmingly have been pleased with the results, he says. Patient satisfaction with the procedure has risen from 75% two years ago to 96% now, he notes. The reason: He credits both improved pain management after surgery as well as the advances in surgical techniques that have made the new procedure possible.

"Actually," Dr. Ninomiya says, "the technique itself is somewhat more complicated than conventional surgery," adding: "Although the new surgery doesn't actually take longer, there are more potential technical pitfalls due to the smaller incision. Physicians must undergo special training to use the specialized instruments. The smaller instruments used in the new procedure were developed by an Indiana company called Zimmer Inc., and the procedure is sometimes called the Zimmer Method.

Dr. Ninomiya has already trained six or seven orthopedists from Wisconsin and surrounding states in the new technique. Orthopedic surgeons who specialize in hip placements and thus are more familiar with the anatomy of the hip readily learn to perform the procedure, which is becoming popular and being widely used around the country, he says. In general, patients who undergo minimally invasive hip replacement surgery have better outcomes if the surgeon specializes in hip procedures.

Most First-Time Patients Are Eligible
Who is a candidate for the new procedure? Virtually all patients, Dr. Ninomiya says. "We can pretty much use it with all patients undergoing first-time hip replacements. Of course it depends on the anatomy and nature of arthritic deficiency." Some surgeons have ruled out using the procedure on obese patients or those with dense musculature. And hip replacement surgery is no longer limited to older patients. According to NIAMS, the surgery used to be an option primarily for people over 60 years of age, but in recent years, doctors have found that hip replacement surgery can be very successful in younger people as well.

Fewer Complications
In a report published in the November issue of the Journal of Bone and Joint Surgery, of hundreds of patients who had undergone the new minimally invasive technique, none had had any complications or needed to be readmitted for additional surgery, meaning their artificial joint remained fully attached. With traditional surgery, a small number of patients have these postoperative problems.

Other complications can include post-operative blood clots. The new procedure may help reduce that likelihood, although Dr. Ninomiya cautions that it's too early to assess the long-term results from the new technique. None of his patients has reported complications since he began using the new technique.

Growing Numbers
In 2001, approximately 165,000 total hip replacements were performed, according to data from the American Academy of Orthopaedic Surgeons, using figures from the National Center for Health Statistics. That's up from 117,000 in 1991. When all hip arthroplasties - total hip (both conventional and minimally invasive procedures), partial hip and revisions - are counted, the number performed in 2000 was 295,000. Surprisingly, perhaps, the 2001 data showed that the Midwest region had the most hip replacements in the United States, closely followed by the South and Northeast. The West lagged well behind the other regions, with 58% fewer hip procedures than the Midwest. Dr. Ninomiya said he suspected "demographics and insurance issues" might account for the difference.

Another possible reason might be that the rising rates of obesity among Americans occurred later in some western states than in other regions. Hip arthritis is more common in patients who are overweight, and weight loss tends to reduce the symptoms associated with hip arthritis.

Dr. Ninomiya, whose own research focuses on how well the body tolerates surgical implants, says the minimally invasive technique uses the same prosthetic joints used in conventional surgery. During hip replacement, the surgeon removes the diseased bone tissue and cartilage from the hip joint, leaving the healthy parts of the hip intact. Then the surgeon replaces the head and the socket of the femur (the long thigh bone) with new, artificial parts. The new hip is made of materials that allow a natural, gliding motion of the joint.

Depending on each patient's condition, the surgeon might use a special cement to bond the new parts of the hip joint to the existing, healthy bone. In other cases an uncemented procedure is called for, in which the artificial parts are made of porous material that allows the patient's own bone to grow into the pores and hold the new parts in place. Doctors might also use a hybrid replacement, consisting of a cemented femur part and an uncemented socket part.

Overall, the new procedure looks highly promising. "The smaller incision allows us to achieve results that are comparable to conventional surgery, and offer patients less pain, ability to return to everyday activities sooner, and require shorter rehabilitation therapy," Dr. Ninomiya says.

This article includes information from the National Institute of Arthritis and Musculoskeletal and Skin Diseases.

Barbara Abel
HealthLink Contributing Writer

MCW Health News presents up-to-date information on patient care and medical research by the physicians of the Medical College of Wisconsin.