Older age and BMI not necessarily contraindications for joint replacement

Old age and BMI over 40 should not necessarily be regarded as contraindications for joint surgery, a rheumatologist has told the conference.

Speaking during a session called Joint Replacement in OA: Friend or Foe Dr Lisa Mandl from the Weill Cornell Medicine Centre in New York said, in general, total hip and knee replacements were extremely successful procedures that gave people with end stage arthritis significant improvements in pain, function, and quality of life.

“But as we all know these rates are due to skyrocket over the coming decades and they are expensive,” she said.

The annual US hospital charges were estimated to be about $17 billion for primary hip and about $40 billion for primary knee.

“These procedures have been shown to be cost effective and associated with substantial savings in arthritis attributable costs.”

“But even if a small number of these patients don’t do well that’s going to result in a large number of people who are unhappy – and a lot of cost.

“It’s therefore really important to be able to identify patients who are most likely to have poor outcomes after athroplasty,” she said.

Is older age a risk factor for poor outcomes after arthroplasty?

According to Dr Mandl the issue of age is important because an ageing population will increase the demand for total joint replacement (TJR) procedures.

For example, it is estimated that half of all US adults will develop OA in at least one knee by the time they are 85. And half of them are predicted to get a knee replacement.

More than half of all referring physicians believe that patients over the age of 80 have an increased risk of poor outcomes.

However this view didn’t necessarily marry up with the facts.

For example morality rates for TJR were about 4 to 5 percent in the over 80s – a figure  similar to the per annum age specific mortality rates in the United States.

Survival rates in TJR for people over 80 were also in line with expected values of people their age.

“And  we know TJR is more cost effective for the elderly than putting them into nursing homes,” Dr Mandl said.

She suggested that markers of frailty rather than absolute age were important when assessing patients.

Studies had shown that patients with more than two chronic diseases do worse rather than absolute age.

“So I think the take home message is that older age is not a major risk factor for poor outcomes, she told the audience.

“These people are having elective surgery to improve their quality of life and I think, in appropriately selected patients, they can do very well.”

“It is very appropriate to talk to patients about the risks and let them make the decision,” she said.

 What about BMI?

Dr Mandl noted that obesity was one of the strongest modifiable factors for developing knee OA.

“Obesity is increasing and not going away anytime soon…However over 90 percent of referring physicians believe obesity increases the likelihood of poor outcomes after TJR” she said.

Although patients who are obese may have worse functional outcomes than non-obese they have similar total improvements.

And even when obesity was associated with less functional improvement patients still improved significantly over their baseline, she said.

In a study from her institution patients with a lower BMI had a trend towards better functional outcomes and less pain.

The average difference in WOMAC scores at two years between the average weight and the morbidly obese was 5.

“It’s absolute versus relative risk,” she said.

Looking at the risk data she said a BMI over 40 should not be considered a contraindication to total joint replacement.

But a BMI over 50 appears to be associated with a significant increase in complications, she added.

“It’s really important when you’re discussing obesity that you present risk factors in a clinically meaningful way. “

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