Laird Harrison

March 30, 2015

LAS VEGAS — The risk for heterotopic ossification after hip arthroscopy is 11 times lower when the nonsteroidal anti-inflammatory drug (NSAID) naproxen is used, a new study shows.

The effect was so powerful that the Data Safety and Monitoring Board halted the trial, said James Beckmann, MD, from Stanford University in California.

"A lot of people who have been doing hip arthroscopy for a while are using NSAIDs regularly," he told Medscape Medical News. "I think this study will make it the standard of care," Dr Beckmann said here at the American Academy of Orthopaedic Surgeons 2015 Annual Meeting.

Heterotopic ossification is a common problem with hip arthroscopy, and surgeons have tried multiple methods of preventing it, including changing surgical techniques and radiation treatments.

It is believed that NSAIDs prevent heterotopic ossification by blocking signals that cause stem cells to become bone cells, Dr Beckmann explained.

However, if the NSAIDs aren't responsible for preventing the heterotopic bone, some surgeons think "it's probably bad to be giving them to everyone because there are serious and minor side effects," he said.

 
It was clear to the statisticians that there was a big difference between the groups, enough to stop the study.
 

Dr Beckmann and his team decided to put the drug to the test. They randomly assigned hip arthroscopy patients to one of two groups; 48 patients received naproxen 500 mg for 3 weeks after the surgery and 48 received placebo.

In both groups, about 69% of the patients missed fewer than five doses of their medication.

The patients underwent radiographic assessment 3 months after arthroscopy. Signs of heterotopic ossification were much less common in the naproxen group than in the placebo group (2 vs 22). The researchers had planned to enroll about twice as many patients, but stopped when they realized that the finding was already highly significant (P < .0001).

"It was clear to the statisticians that there was a big difference between the groups, enough to stop the study," Dr Beckmann explained.

The rate of adverse reactions was not significantly different in the naproxen and placebo groups (42% vs 35%; P = .45). The adverse reactions were gastrointestinal in nature, and none were serious.

The morphometric characteristics and locations of the heterotopic ossifications were also not significantly different between the two groups (average 2-dimensional ossification size, 11.6 vs 16.7 mm; P = .51).

Anti-Inflammatory Options

Naproxen is not the only NSAID being used for this purpose. In his practice, Roy Davidovitch, MD, from the Hip Center at NYU Langone Medical Center in New York City, prescribes celecoxib (Celebrex, Pfizer) 200 mg/day for 4 weeks.

"Celebrex brought my rate of heterotopic ossification down to almost zero," he told Medscape Medical News. "It's nice to know naproxen can do that."

A few questions remain, said Dr Beckmann. How much naproxen is necessary to prevent heterotopic ossification? And how much heterotopic ossification can patients safely tolerate?

In addition, there is concern that some adverse effects related to NSAIDS are going unnoticed and there is evidence that the drugs can slow healing under some circumstances.

"We don't know if it could have an effect on labral repairs or capsule repairs," Dr Beckmann said.

"In these procedures, we don't need the bone to heal, but we do need the tissues around the bone to heal," he explained. "If we're preventing one thing at the expense of getting other tissues to heal, it might not be worth it. We don't know in the end."

Dr Beckmann and Dr Davidovitch have disclosed no relevant financial relationships.

American Academy of Orthopaedic Surgeons (AAOS) 2015 Annual Meeting: Abstract 659. Presented March 26, 2015.

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