MRI rules change but still useful in knees

As Medicare tightens up on ordering MRIs of the knee, new research has found MRI-detected osteophytes are a clinically relevant marker of early osteoarthritis.

Results from the Tasmania Older Adult Cohort study have previously shown that MRI-detected osteophytes (OPs) were common – found in about 85% of 50-80 years olds in the community compared to just 10% when using two-dimensional plain X-rays.

MRI follow-up after a mean of 2.6 years from baseline showed the osteophytes could be a precursor of cartilage degradation and bone marrow lesions (BMLs).

The latest findings from the study provide more insight into the natural history of osteophytes including progression.

More than half (51%) of participants had an increase in total MRI-detected osteophyte size from baseline, 48% were stable and only 1% demonstrated some regression.

“These [and other] findings indicate that early OP formation on radiographs can be used as an early marker of initiation of disease process and when identified by primary healthcare provider, should warrant further action,” the study said.

The study found baseline BMLs, cartilage defects, meniscal extrusion, presence of IPFP abnormality and effusion-synovitis were associated with worsening MRI-detected osteophytes over time.

“On the other hand, it should be noted that MRI-detected OPs were also found to consistently and independently predict changes in knee cartilage, BMLs and cartilage volume, and the need to undergo total knee replacement (TKA).”

Coauthor Professor Graeme Jones, from the University of Tasmania, told the limbic it was difficult to decipher what came first when the observed structural abnormalities were so interlinked

“I used to think osteophytes were a consequence rather than a cause of osteoarthritis but this study, and some of the others we have done, suggest that it is a cause.”

Theoretically then, MRI-detected osteophytes could, in the future, help with targeting therapy for osteoarthritis. The dilemma was the current lack of evidence for any early or disease modifying treatment.

“There is a push Australia-wide to stop GPs and probably even specialists from ordering MRIs. Our argument has been that if you have therapies that make a difference, and this remains to be shown for osteophytes, then MRI is very useful.”

“The current philosophy appears to be that we haven’t got treatments that make much difference so let’s not investigate anyone. Let’s just tell them to lose weight and exercise, which may be the best for the group as a whole.”

“However if we are going to move the osteoarthritis field forward we are going to need precision medicine.”

“It’s reasonable to cut back [on MRIs] at this point in time while we await further research looking at targeted therapies,” he said.

Following recommendations from the MBS Review in relation to knee imaging, and effective from November 1, GPs will not be able to request knee MRIs for patients aged 50 years and over.

In other changes, patients under 16 years of age will not be required to have an x-ray of the knee prior to receiving a MRI scan.

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