The Incidence of Heterotopic Ossification After Hip Arthroscopy

Background: Minimally invasive techniques to treat femoroacetabular impingement (FAI), snapping hip syndrome, and peritrochanteric space disorder (PSD) were developed to reduce complications and recovery time. Although a multitude of studies have reported on the incidence of heterotopic ossification (HO) after open procedures of the hip, there is little known about the rate of HO after hip arthroscopy.

Hypotheses: The incidence of HO after hip arthroscopy is comparable with that after open surgical dislocation of the hip and can be reduced with the addition of indomethacin to an existing nonsteroidal anti-inflammatory medication prophylaxis protocol.

Study Design: Cohort study; Level of evidence, 3.

Methods: Between July 2008 and July 2010, 616 primary hip arthroscopies were performed to treat FAI and PSD. In July 2009, indomethacin was added in the acute postoperative period to an existing HO prophylactic protocol of naproxen administered for 30 days postoperatively. Postoperative radiographs were reviewed to detect the presence and classify the size and location of HO. Odds ratios and logistic regression explored predictor variables and their relationships with HO, with P < .05 defined as significant.

Results: Twenty-nine (21 male, 8 female) of 616 (4.7%) hip procedures developed HO postoperatively. Brooker classification of HO was 18 grade I, 4 grade II, 6 grade III, and 1 grade IV. Mean follow-up was 13.2 months (range, 2.9-26.5 months). Rate of HO for cases with and without indomethacin for prophylaxis was 1.8% (6/339) and 8.3% (23/277), respectively. This difference was statistically significant (P < .05), and patients who underwent protocol 1 were 4.36 times more likely to develop HO postoperatively than those who had protocol 2. The majority of cases of HO (72.4%) occurred in male patients, and all cases occurred in the setting of osteoplasty performed for symptomatic FAI. We were not able to demonstrate statistically significant clinical risk factors that were predictive for the development of postoperative HO. However, the data clearly demonstrate that the performance of arthroscopic osteoplasty with a capsular cut in male patients represented the majority of cases, who are likely the group at highest risk. Seven cases (~1%) required revision procedures to excise HO. There were no cases of recurrence of HO after excision, whether it was performed open or arthroscopically.

Conclusion: The addition of indomethacin is effective in reducing the incidence of HO after hip arthroscopy and should be especially considered in male patients who undergo osteoplasty for correction of symptomatic FAI.