Total knee replacement: who should and who shouldn’t?

AUSTRALIANS are having total knee arthroplasty (TKA) at almost twice the rate of people in comparable countries, say researchers who have outlined the importance of selecting the patients most likely to have good outcomes and optimising those patients before surgery.

A narrative review, published by the MJA, noted that in 2016 the rate for all TKA procedures in Australia was 242 per 100 000 population, with most procedures (70%) performed in the private sector. The average in all Organisation for Economic Co-operation and Development (OECD) nations was 126 per 100 000 population, the authors reported.

Dr Christopher Vertullo, a Gold Coast-based orthopaedic surgeon specialising in knees, said Australians were not only more obese than people in most other OECD countries, but also had one of the highest rates of knee injury in the world.

“That’s a dangerous combination,” Dr Vertullo told InSight+.

Dr Vertullo said access to TKA was also better in Australia than in many other OECD nations, and increasing rates also reflected improved surgical outcomes with innovations in prosthesis design and improvements in surgical expertise.

The MJA authors wrote that the minimum requirements for TKA were significant, prolonged symptoms with supporting clinical and radiological signs. They noted that non-operative treatments, including medications, exercise and weight loss were unlikely to reverse radiographic changes, but they may improve symptoms and delay the need for surgery.

The review noted that factors such as mental health and obesity affected both the level of symptomatic improvement after surgery and the risks of surgery. However, they said, neither had been identified as contraindications to TKA because significant health benefits could still be achieved.

The average age of patients undergoing TKA was 69 years, and the authors reported that TKA was thought to be contraindicated in patients aged under 50 years or over 90 years.

However, in an InSight+ podcast, Narrative Review co-author Associate Professor Justine Naylor, from the South Western Sydney Clinical School of UNSW, said TKAs need not be ruled out in younger and older patients.

“TKA is widely regarded as one of the best operations we have,” Associate Professor Naylor said, “so, it doesn’t make sense to limit access if someone can potentially benefit from the surgery, and we do know that even the very young or the relatively older patient can still gain quite large functional and symptomatic improvements from knee arthroplasty, similar to other patients.”

She noted, however, that it was important to consider the specific risks associated with younger and older patient cohorts.

“If you are a younger patient, then you’re going to have a higher lifetime risk of revision and that’s simply because you are going to live longer, so you are going to be more likely to wear out the prostheses,” she said.

Older patients have a higher early mortality (about 8 per 1000 at 30 days post-surgery in patients aged over 90 years) than younger patients (1 per 1000 in those aged under 80 years), but Professor Naylor said the mortality risks were still low at less than 1%.

“If the symptoms and signs warrant the surgery, then this should be discussed with the patient … but there really is no strong age cut-off,” she said.

Dr Vertullo said the Narrative Review highlighted the importance of shared clinical decision making in determining patients who would do well after TKA.

“There’s no magic formula to decide. Everybody wants to be told whether or not they have to have a TKA, but the reality is, it needs to be a shared decision between the GP, the surgeon, the patient and the patient’s family,” he said.

“As a clinician, it’s really important not only to look at the x-ray and say, ‘you need a knee replacement’, but to delve into that individual’s clinical status, the level of symptoms, the expectations around what they want, and, before we do decide to proceed, the maximisation of their non-operative management.”

In addition to selecting the right patients, Dr Vertullo said it was also crucial to select the right prosthesis. He pointed to two recent studies (here and here), of which he is lead author, which found that prosthesis choice affected the risk of infection and revision.

Dr Vertullo said most patients presenting for TKA had not been optimised.

“They haven’t lost weight, they haven’t done a rehabilitation program, they are not adequately taking analgesia,” he said.

Funding was key, he said.

“There is a lack of governmental funding for non-operative rehabilitation for people with musculoskeletal disease even though it’s a massive drain on the Australian gross domestic product,” he said, noting a lack of funding for obesity management programs in primary care.

“Infection is now the number one risk for implant failure, so it’s really important that we maximise a patient’s [management of diabetes]. We also need to make sure they are not colonised with Staphylococcus aureus, which affects about 20–25% of patients. And a patient’s weight is important; the more obese you are, the higher risk the risk of complications.”

The MJA authors found limited evidence to support a role for “prehabilitation” in improving TKA outcomes, and routine programs were not recommended at this time.

Dr Vertullo said there was certainly a role for exercise in non-operative management but acknowledged that there had been mixed results in studies investigating prehabilitation.

“We have done studies on bike riding, showing that pedalling on an exercise bike is highly beneficial to people with osteoarthritis, their [quadriceps] are stronger, and it helps their pain,” he said.

“But for many people, when they get to the point of knee replacement, they are in agony. So, when they get on a bike, it can be [unbearable],” he said. “I say to patients, ride a bike before the surgery if it doesn’t hurt too much, but don’t hurt yourself because it’s more important after the surgery.”

Dr Vertullo said his research group will soon publish a randomised controlled trial showing that patients with TKA who participated in a simple, self-directed pedalling program had superior pain scores at Days 2 and 14 post-knee replacement than patients who had participated in the standard, in-hospital physiotherapy program.