Review Question - QID 219166

In the setting of acetabular fracture fixation, there are surgical techniques that may or may not help prevent the incidence of heterotopic ossification, such as gluteus minimus debridement. Only radiation therapy (700-800 cGy within 72 hours post-op) has been clearly shown to prevent its occurrence in the postoperative period, whereas indomethacin lacks definitive clinical utility and increases the risk for nonunion with prolonged use (Answer 4).

Heterotopic ossification (HO) is commonly encountered within the first year after acetabular fracture fixation. The majority of cases are asymptomatic and seldom cause pain (~85% of cases). However, approximately 15% may develop debilitating stiffness affecting activities of daily living. HO is generally characterized by utilizing the Brooker classification system (Illustration A). Debridement of nonviable muscle and the gluteus minimus at the index fracture fixation procedure has been shown to prevent the formation and severity of HO but has been questioned recently. While post-operative oral NSAID prophylaxis (i.e. indomethacin) has been shown to be effective in other areas of HO formation, it has not been shown to be clinically effective in the setting of acetabular fractures. Rather, prolonged NSAID prophylaxis has only been shown to increase the rate of nonunion. Targeted post-op radiation therapy (700-800 cGy) within 72 hours post-op is the only post-operative protocol shown to clearly decrease the risk for HO formation after acetabular fracture fixation. Its use is limited secondary to resource availability, cost, and the multi-disciplinary coordination required. Once formed, only surgical debridement can resolve the stiffness associated with HO. This may be performed early, particularly in the setting of sciatic nerve compression, with a relatively low risk for symptomatic recurrence despite the lack of HO maturation. Treating surgeons should be aware of the hypervascularity of the surrounding HO tissue and expect higher-than-average blood loss.

Fitoozabadi and colleagues provided a comprehensive review article on the diagnosis and management of HO after acetabular fracture surgery. The authors discuss that the risk for HO has been related to the operative approach, fracture pattern, operative delay, and associated craniocerebral trauma. They further review the Brooker classification, mentioning that Brooker stages I/II may go unnoticed by patients, whereas Brooker stages III/IV have a significant functional impact. The authors conclude by reviewing prophylactic and reactive treatment options, urging that advances in prophylaxis are needed.

Rath and colleagues retrospectively reviewed 21 patients at their institution in which any necrotic gluteus minimus musculature was debrided at the time of acetabular fracture fixation (via Kocher-Langenbeck approach). The authors’ justification for specific gluteus minimus debridement was that HO typically forms along its anatomic course. They reported that only 10% of patients had resultant clinically significant HO formation (Brooker III/IV). The authors concluded that resection of necrotic gluteus minimus musculature diminishes HO formation compared to other reported series.

Sagi and colleagues performed a randomized, prospective control trial comparing various durations of indomethacin (75mg PO daily) use after acetabular fracture fixation and the resultant risk for HO formation. They found that a 6-week course was associated with a significantly increased risk of posterior wall segment nonunion. On posthoc analysis, they found that 1 week of post-operative indomethacin may decrease the volume and incidence of HO formation, however, a higher power was needed and this finding may be attributable to sampling error. The authors concluded that further investigations are required to confirm or refute their findings in larger clinical trials.

Figure A demonstrates an AP radiographic image with right-sided Brooker IV periacetabular HO formation tracking along the gluteus medius musculature. Illustration A demonstrates the Brooker classification.

Incorrect Answers:
Answer 1: Most patients who develop HO after acetabular ORIF procedures are generally asymptomatic (~85%) and therefore seldom require HO excision.
Answer 2: Debridement specifically of the gluteus MINIMUS during index ORIF surgery may or may not help decrease the risk of HO. Further, generous debridement of the gluteus medius is discouraged as it may result in an iatrogenic Trendelenburg gait.
Answer 3: As discussed, only radiation therapy has shown definitive clinical benefit in the prevention of HO formation after posterior acetabular fracture fixation.
Answer 5: While the risk of technical recurrence can be notable (~30%), it is always considerably less in quantity and symptom severity. Even in the setting of early excision (<2 years of HO maturation) due to sciatic nerve compression, the few case series available reported no symptomatic recurrence at the final follow-up.