Background:

Heterotopic ossification (HO) is a known complication of hip arthroscopy. Our objective was to determine the effect of postoperative naproxen therapy on the development of HO following arthroscopic surgery for femoroacetabular impingement.

Methods:

Between August 2011 and April 2013, 108 eligible patients were enrolled and randomized to take naproxen or a placebo for three weeks postoperatively. Radiographs were made at routine follow-up visits for one year following surgery. The primary outcome measure was the development of HO, as classified with the Brooker criteria and two-dimensional measurements on radiographs made at least seventy-five days postoperatively (average, 322 days). The primary analysis, performed with a Fisher exact test, compared the proportion of subjects with HO between the treatment and control groups. A single a priori interim analysis was planned at the midpoint of the study.

Results:

Our data safety and monitoring board stopped this study when the interim analysis showed that the stopping criterion had been met for demonstration of efficacy of the naproxen intervention. The prevalence of HO was 46%(twenty-two of the forty-eight in the final analysis) in the placebo group versus 4%(two of forty-eight) in the naproxen group (p< 0.001). Medication compliance was 69% overall, but it did not differ between the naproxen and placebo groups. Minor adverse reactions to the study medications were reported in 42% of the patients taking naproxen versus 35% of those taking the placebo (p= 0.45).

Conclusions:

In this trial, prophylaxis with naproxen was effective in reducing the prevalence of HO without medication-related morbidity.

Level of Evidence:

Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.