An Australian case series suggests a single injection of hyaluronic acid in the setting of hip joint OA is both safe and efficacious, but rheumatologists say RCTs are needed.

The 87 patients had symptomatic OA, categorised as mild to moderate disease on x-ray. All patients had previously received conservative management in the form of physiotherapy.

The study, published in BMC Musculoskeletal Disorders, found evidence of a short term improvement in pain and function with the mean modified Harris Hip Score (mHHS) increasing from 58.47 at baseline to 71.30 at six weeks (p < 0.01).

“This was greater than the minimal clinically important difference (MCID) of 10 for clinical improvement at 6 weeks,” the study said.

The only adverse events were minor injection site pain lasting less than 24 hrs, requiring either no treatment or mild analgesia.

The authors, Victorian sports physicians Dr David Long and Dr Jane Fitzpatrick, acknowledged the limitations of an open label study and the potential for placebo effects.

They also said the evidence was inconsistent and therefore controversial, and that confirmation in RCTs was required.

In another recently published study, Victorian sports physicians followed 623 patients who had received the intra-articular hyaluronic acid (Durolane) for osteoarthritis in a variety of joints.

They found patients experienced symptomatic pain relief for about 15 months from an initial treatment, and that this was sustained for subsequent injections. However the study was also uncontrolled.

The study was funded by Bioventus.

Commenting on the studies, Professor Chris Maher told the limbic that there was a clear reason for controlled trials.

“In those particular studies where there is no control group, we are not able to distinguish what is responsible for the person’s improvement … part of the response might be placebo but my thoughts are it is likely to be small … the biggest thing I think is the natural history of the condition.”

“Things improve over time. Even for something like arthritis, people usually seek care when it is bad and if you just do nothing, it will improve anyway because OA tends to fluctuate.”

Professor Maher, director of the Institute for Musculoskeletal Health, Sydney, said we’ve known for centuries that you need a control group in clinical trials.

“It’s a bit odd that people are doing those sorts of studies.”

Rheumatologist Professor Graeme Jones, head of the Musculoskeletal Research Group at the Menzies Institute for Medical Research, also agreed that cases series were not a suitable way to demonstrate efficacy.

OARSI guidelines include a conditional recommendation for the use of intra-articular hyaluronic acid in knee OA but not in hip OA.

Professor David Hunter, chair of the Institute of Bone and Joint Research at the University of Sydney, said there were adequately powered RCTs showing no effects of hyaluronic acid in hip OA over placebo.

“Because of the large contextual/ placebo effects I don’t see how case series can add to our knowledge base of efficacy or safety,” he told the limbic.

“When we know there are associated  harms and not insignificant costs I don’t think these case studies would change the current recommendations.”