Duration of Indomethacin for Myositis Ossificans
Indomethacin should be administered at 25 mg three times daily for 6 weeks starting on the first postoperative day (or immediately after diagnosis in non-surgical cases) to prevent heterotopic ossification in myositis ossificans. 1, 2
Evidence-Based Dosing Regimen
Standard protocol: Indomethacin 25 mg orally three times daily (total 75 mg/day) for 6 weeks represents the most extensively studied and validated regimen for preventing heterotopic ossification. 1, 3
Timing of initiation: Begin treatment on the first postoperative morning (or immediately upon diagnosis in traumatic myositis ossificans without surgery). 1
Minimum effective duration: At least 3 weeks of treatment is required for effectiveness, though 6 weeks provides optimal prophylaxis against severe heterotopic ossification. 1
Shorter courses may be considered: Some evidence suggests that treatment periods shorter than 6 weeks may be equally effective in preventing the most severe degrees of heterotopic ossification, though 6 weeks remains the standard recommendation. 1
Clinical Context and Supporting Evidence
The 6-week duration is derived primarily from orthopedic surgery literature studying heterotopic ossification prevention after total hip arthroplasty and acetabular fracture repair, which represents the same pathophysiologic process as traumatic myositis ossificans. 1, 2, 3
In a randomized trial of 72 patients with acetabular fractures, indomethacin 25 mg three times daily for 6 weeks was equally effective as radiation therapy in preventing heterotopic ossification, with no significant complications. 2
A study of 74 high-risk patients receiving indomethacin 75 mg daily for 6 weeks showed only 4% developed mild (grade IIA) heterotopic ossification, with no patients developing more severe forms. 3
Combined therapy with indomethacin (25 mg daily for 4 weeks) plus low-dose radiation proved highly effective, with 44 of 54 fractures showing no heterotopic ossification. 4
Practical Implementation
Start immediately: Do not delay initiation beyond the first postoperative day; delays up to 5 days may still be effective, but earlier is better. 1
Complete the full course: Approximately one-third of patients discontinue treatment early due to gastrointestinal side effects or other adverse reactions, which limits overall effectiveness. 3
Ossification timeline: The final extent of heterotopic ossification is typically already present by 6 weeks in patients who develop it, supporting the 6-week treatment duration. 2
Case Report Evidence
A pediatric case of severe bridging myositis ossificans after supracondylar humerus fracture successfully used indomethacin postoperatively after surgical excision of the ossified mass, with no recurrence at 2-year follow-up. 5 While this case did not specify exact duration, it demonstrates the principle of using indomethacin to suppress bone proliferation after myositis ossificans treatment.
Important Contraindications and Monitoring
Screen for contraindications: Active peptic ulcer disease, significant renal impairment, aspirin-sensitive asthma, bleeding disorders, and pregnancy are contraindications to indomethacin use. 1, 3
Monitor for adverse effects: Gastrointestinal upset (most common), renal dysfunction, and bleeding complications require vigilance throughout the 6-week course. 1, 3
No impact on bone healing: Treatment with indomethacin in the immediate postoperative weeks does not increase the incidence of implant-bone interface radiolucencies, aseptic loosening, or revisions when evaluated one year after surgery. 1
Alternative Considerations
If indomethacin cannot be tolerated or is contraindicated, other NSAIDs have been reported effective for heterotopic ossification prophylaxis, though indomethacin has the most robust evidence base. 1 Single-dose radiation therapy (700-800 cGy) is an alternative but is approximately 200 times more expensive than indomethacin. 2