Get ‘hip’ to joint replacement

By R. DAVID METZ

VIEW ON HEALTH

According to the American Academy of Orthopaedic Surgeons, total knee replacement surgery was the most common procedure for musculoskeletal-related hospitalizations in 2004 at 478,000 while total hip replacement ranked third on the list at 324,000. With the number of hip and knee joint replacement surgeries more than doubling in the last decade -- the stereotype that only the aged and inactive undergo the procedure is now being challenged.

WHAT IS JOINT REPLACEMENT?

Joint replacement surgery, otherwise known as arthroplasty, is considered one of the most successful treatments for patients with osteoarthritis, according to the National Institute of Arthritis and Musculoskeletal and Skin Diseases. The two most common joints are the knee and hip. The surgery is done on patients whose joints have become damaged by disease or injury.

Joints are formed by two ends of bone connected by a soft, protected cushion called cartilage. If the cartilage tissue becomes damaged, it does not allow the joints to move in a smooth manner. Initially, the inflammation of the tissue causes pain, but as the cartilage wears away the bones begin to rub against one another and cause even more pain.

Sometimes surgeons may be able to replace or repair just damaged parts of the joint, but when the entire joint is injured a total joint replacement is necessary. When this procedure is done, the doctor removes the diseased and damaged portions of the joint and replaces them with implants.

There are various prosthetic options, which are all regulated by the Food and Drug Administration. The most commonly used prostheses for hips and knees are made of metal and plastic, however, there are also other options. Usually the metal is titanium or a mix of chromium and cobalt, and the plastic is a polyethylene. According to the FDA, the doctor considers the patient's gender, age, weight, anatomy, general health, activity level and medical history when choosing the right prosthesis.

The AAOS reports the average length of stay for patients who underwent total hip replacement surgery was about four days and had a price tag of approximately $35,000 in 2003. Knee arthroplasty patients stayed the same amount of time in the hospital, but paid less at $31,000.

It is also important to consider that surgery is only the first hurdle for knee and hip replacements. Afterwards, much rehabilitation is necessary to fully enjoy the new joint.

WHO HAS JOINT REPLACEMENT SURGERY?

Though the number of knee replacement patients under the age of 60 has increased in recent years, the average age of patients in 2004 was about 67, according to the National Hospital Discharge Survey. Surprisingly, the average age of hip replacement patients was a year younger, at about 66 years. While the stereotype that joint replacement surgery is for the elderly, rock star Eddie Van Halen joined a growing number of younger adults who are undergoing the surgery when he had his hip replaced in 1999 at the age of 43.

John J. Callaghan, MD, Professor of the Departments of Orthopaedic Surgery and Biomedical Engineering at the University of Iowa College of Medicine and spokesperson for the American Academy of Orthopaedic Surgeons said people are getting joint replacement surgery because the cartilage is worn out and is seeing mostly older people, but sometimes sees younger people with severe trauma.

Not only is age a factor, but gender also seems to play a role. Women account for approximately two-thirds of knee and hip joint replacement surgeries. This is because women are more prone to conditions that require the procedure and on average they live longer than men.

WHAT ARE COMMON PROBLEMS ASSOCIATED WITH JOINT SURGERY?

Despite the growing number of success stories associated with the surgery, there are still a few drawbacks. Complications associated with the surgery, such as blood clots can occur. In addition, the knee or hip replacements don't always hold up throughout the patient's lifetime. About 80 percent of implants last at least 20 years, according to the AAOS. When they fail, revision surgery is then necessary.

In spite of many technological advancements in the area, the AAOS reports the proportion of knee revision replacement surgeries to primary procedures has continued to hover around 8 percent over recent years. Revision hip procedures account for about one in every six hip replacement surgeries, according to the National Hospital Discharge Survey.

Hip and knee surgery can take from one and half to two hours, depending on the surgery, Callaghan said.

The success of the joint replacement surgery depends on several factors: the age of the patient at the time of the surgery, the lifestyle and activity of the patient and whether the patient experienced any complications as a result of the surgery.

Complications can include infection, blood clots in the veins of the leg (venous thromboembolism), joint dislocation, loosening of the implant, nerve damage and the formation of normal bone in the soft tissues (heterotopic ossification). While most of these complications are relatively rare, doctors take many precautions directly after surgery and during rehabilitation to avoid them.

Callaghan agrees that one area of concern is infection.

"If an infection forms on the metal surface, the implant will have to be removed to get rid of the infection. An infection scares everybody," he added.

The second concern with surgery is blood clots. Patients will take blood thinners for about 28 days in hip surgeries and 10 days in knee surgeries.

WHAT'S NEW IN JOINT REPLACEMENT TECHNOLOGY?

When it comes to hip replacement surgery, much progress has been made in the last ten years thanks to "minimally invasive surgery" or MIS. Though not all patients qualify for MIS, those who do have fewer complications, have less pain and recover faster. With this new procedure, there is only one scar measuring about two inches in comparison to the large incisions of open surgery that can be up to six inches in length. However, the downfall is that doctors trained in MIS estimate that only about 17 to 20 percent of hip replacement candidates are eligible for the procedure despite the high demand from patients.

Callaghan warns MIS is not the perfect surgery for all patients.

"It is very important that we have the good surgical candidates with correct fixation of the parts in hip replacement surgery," Callaghan said.

Obese patients are not good candidates. In addition, because of the nature of the surgery, it takes more time and therefore, more anesthesia. Unfortunately, the surgery also has more incidences of need for surgical revisions due to problems associated with the original surgery, Callaghan said. This is due to the increased restriction on the visual field imposed by MIS techniques.

For knee replacement, there has been a technological advance called computer-assisted total knee replacement surgery that allows for greater durability of the replaced joints. The surgery uses image-guided technology to perfectly align the knee implant. The computer-assisted procedure does not use the intramedullary rod necessary in the standard surgery. This reduced the risk of acute respiratory distress caused by fat embolization and allows surgeons to experience the same success with smaller incisions.

Dr. Daniel J. Berry, professor and chairman of Orthopedics at the Mayo Clinic said the new procedure is making great progress and has a high level of success with those experience with the surgery.

"Current efforts are focused on making the process simpler, more efficient, and more cost effective," Berry said. "As these methods evolve, it seems likely some form of computer assistance will eventually become a routine part of total knee arthroplasty."

Because the surgery is still quite new, computer-assisted total knee replacement is more difficult and takes extra time for the surgeon.

Another type of replacement surgery that has made a resurgence according is partial-knee replacement as well as hip resurfacing.

"It's really exciting to see the partial knee replacements," Callaghan said. "I have patients tell me that they know that in a complete knee replacement that the knee isn't theirs, but with the partial they feel that it's their own knee. The artificial parts are no where near as good as what you were born with."

He explained that in a partial they don't have to detach all the ligaments and that really helps the process. Another exciting area he sees is the rotating platform, with less wear and stress on the joint.

Callaghan believes that with machining getting more precise doctors are able to offer more options with metal on metal, plastic and ceramic. The implants are fitting the patient better and lasting longer.

"They won't wear out as quickly. And the second surgery is never as good as the first. Data is showing that there is an 85 percent chance the knee or hip will last about 20 years," he said.

When does a person know they should have the surgery? Callaghan said he tells patients that waiting doesn't really matter on the surgery end, but that if the pain is stopping them from pursuing the activities they enjoy in life they should consider it. Modern surgical procedures are very successful at pain relief.

"They shouldn't be sitting on the couch avoiding activities," Callaghan said.