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Knee replacement

MagazineSeptember 1994 (Vol. 5 Issue 6)Knee replacement

Q:I'd be grateful if you could direct me to some sources of information about knee replacement operations

Q:I'd be grateful if you could direct me to some sources of information about knee replacement operations. I have a relative who seems to be under the impression that it's like putting a new engine in a car; he'll come out of hospital with a brand

This seems rather unrealistic to me! I'd like to find out, for example, what sort of convalescent period to expect and what that involves. If the operation is successful, how tough will the new knee be (ie, will he be able to dig the garden, climb ladders, jump off machinery, etc). If the operation isn't successful, how will he be left? What percentage of operations are successful? Are there any alternative treatments to try first? V P, Enfield.


A:WDDTY recently met with California orthopedic surgeon Michael Star, who specializes in hip and joint replacements and who takes a refreshingly conservative line on orthopedic surgery. (His favorite saying is: "The safest way to practise orthopedic medicine is to stay two fads behind.")

He told us the following: "For anyone with debilitating pain from arthritis, either rheumatoid or osteoarthritis, knee replacement can have excellent results, but should only be considered in people who have tried non-surgical approaches and failed. These include restricting your activities, using non-steroidal anti-inflammatory drugs, trying physical therapy and walking with a cane. If you're still finding it difficult to walk, you may be a good candidate for knee replacement, which has now replaced virtually all forms of surgical treatment as the treatment of choice." (Some 120,000 such operations are performed every year in the US.)

"In the operation, the surgeon removes the damaged cartilage (the soft lining of the joint), plus a small amount of underlying bone. The artificial joint made of metal and polyethylene is cemented into place with acrylic cement. A patient with no complications will spend four to five days convalescing in the hospital, and a month at home. He can return to regular walking and activity over the following two to three months.

"It's important to remember this knee will not be as good as new; nothing artificial can match the versatility of a human joint," says Dr Star. "What it can do is end chronic pain and allow you to move.

"After surgery your relative should be encouraged to do non-impact activities like walking, bicycling, swimming, gardening and even climbing ladders, but avoid any sort of activity jumping, jogging skiing or tennis which can hammer the artificial joint and cause it to loosen.

"With the cemented variety of knees, studies have shown that 95 per cent of operations are successful (ie, have no complications) for a short time. According to a meta-analysis of 130 studies (JAMA, 4 May 1994) 89 per cent are successful and the knee remains functional for greater than four years." Indeed the majority of knee replacements remain functional for at least 10 years."

A small risk of complications can mean the patient is in the hospital for a longer period of time undergoing repeated operations. The above mentioned meta-analysis came up with an overall complication rate of 18 per cent among those studies which reported on complications. These included 3.9 per cent for superficial infections, 1.7 per cent for deep infections, 2 per cent for pulmonary embolism (a blockage in a vein in the lung), 6.5 per cent for deep venous thrombosis (blood clot in a vein) and 2.1 per cent for nerve damage to a limb. There are also admittedly small risks of other nerve or artery injury, permanent foot injury or the worst case scenario loss of the limb.

The overall rate of failure necessitating a "revision" in effect, replacing the knee replacement was 3.8 per cent in the JAMA study.

"The most important issue with knee replacements," cautions Dr Star, "is the patient's age when he or she undergoes the operations since with the current technology, artificial knees may only last about a decade without themselves becoming fatigued. Replacing, in effect, the knee replacement is a much more formidable operation, with much more bone loss, removal of scarred tissue, and a far lower success rate."

Because the current technology has a limited time span, since the 1980s, medical technology firms have been trying to fix artificial joints biologically to bone via little metal beads or mesh. These products, called "uncemented porous-coated" knee replacements, proved to be not as successful as the cemented variety, with higher failure rates. In one of many studies demonstrating this in the prestigious Journal of Bone and Joint Surgery (July 1991), of 96 patients undergoing 108 replacements, about a fifth had failed due to problems with the lower leg component. After seven years, more than half the replacements were recommended for revision.

"Since then the gold standard is still the cemented knee replacement. Because of their limited life span, particularly if you are under 60, it's important to opt for surgery only as a last resort."

WDDTY would only add our own view that before submitting to surgery, your relative look into a number of the dietary approaches outlined on p 3 of this month's shown Cover Story, some of which have promise clinically or in scientific trials.


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