Heterotopic Ossification

Ovid: 5-Minute Orthopaedic Consult

Editors: Frassica, Frank J.; Sponseller, Paul D.; Wilckens, John H.
Title: 5-Minute Orthopaedic Consult, 2nd Edition
> Table of Contents > Heterotopic Ossification

Heterotopic Ossification
Constantine A. Demetracopoulos BS
Frank J. Frassica MD
  • Pathologic bone formation as a consequence of direct trauma or central nervous system injuries
  • Bone formed in heterotopic locations such as muscle, subcutaneous tissues, or nerves
  • Most commonly occurs at the hip, elbow, and shoulder joints (1).
Less common in children than in adults, and more common in males than in females (1)
Occurs in 10–20% of patients with central nervous system or traumatic injuries, with an average onset of 2 months after injury (1).
Risk Factors (2)
  • Central nervous system injury
  • Osteoarthrosis
  • Osteophyte formation
  • Surgical approach
  • Previous surgical procedures
  • Trochanteric osteotomy
  • AS
No genetic link can successfully predict patient susceptibility to heterotopic ossification.
  • Traumatic brain injury
  • Spinal cord injury
  • Trauma
Associated Conditions
  • Fibrodysplasia ossificans progressiva
  • Primary osteoma cutis
Signs and Symptoms
  • Unexplained increase in pain, spasticity, or muscle guarding
  • Decreased ROM
  • Stiffness
  • Radiographic evidence of ectopic bone
Physical Exam
  • Limited ROM is the most common and earliest sign (1).
  • Erythema, swelling, and signs of inflammation also may be noted.
  • Serum alkaline phosphatase levels are elevated.
    • Value begins to rise 2–3 weeks after injury (1).
    • Although nonspecific and not absolute, elevated serum alkaline phosphatase may be the earliest test for detection.
  • On plain radiographs, new bone formation
    may be 1st visible at 3–6 weeks; but radiographs generally are not
    confirmatory until 3 months.
  • Bone scans allow for earlier detection and show intense uptake.
  • CT may be used for preoperative planning and to show the zonal pattern: Mineralized in the periphery and lucent in the center.
Pathological Findings
  • Initially, an intense inflammatory response occurs with myofibroblasts and osteoblasts.
  • Such a high degree of cellular activity occurs that the inflammatory response can be mistaken for a neoplasm.
Differential Diagnosis
  • Septic joint
  • Thrombophlebitis
  • Neoplasm in the soft tissues
General Measures
  • Joint motion is maintained to allow normal functioning.
  • Most patients are treated successfully with nonoperative measures, including physical therapy, analgesics, and NSAIDs.
  • Few patients require surgical excision.
Special Therapy
  • Radiation therapy is ineffective once heterotopic ossification has been documented.
    • When used for prophylaxis, it must be delivered within 72 hours (2).
Physical Therapy
Use ROM exercises and treatment modalities that are designed to increase joint mobility.
First Line
  • Anti-inflammatories are used to prevent
    or to lessen the amount of heterotopic ossification formation after the
    initial insult and to prevent recurrence after surgical excision.
    • Indomethacin, naproxen, or other NSAIDs for 6 weeks (3)


  • Surgery is indicated to restore joint motion or to correct contractures in disabled patients.
  • Heterotopic ossification should not be resected earlier than 6 months after injury.
  • Excision after 2 years increases the likelihood of permanent contractures.
  • After resection of heterotopic
    ossification, patients are treated with low doses of irradiation (must
    be delivered within 72 hours) (2).
  • Some patients elect to take NSAIDs (e.g., indomethacin) for 6 weeks after resection.
    • For effective prophylaxis, the medications must be taken.
    • Gastric intolerance prevents 10–20% of patients from taking these medications (3).
  • Prognosis varies, depending on the location of heterotopic ossification and its cause.
  • Most patients with nonneurogenic heterotopic ossification maintain reasonable function and do not require surgical intervention.
  • Loss of mobility
  • Ankylosis
Patient Monitoring
Serial radiographs are obtained at 1–3-month intervals for 6 months.
1. Garland DE. A clinical perspective on common forms of acquired heterotopic ossification. Clin Orthop Relat Res 1991;263:13–29.
2. Ayers DC, Pellegrini VD Jr, Evarts CM. Prevention of heterotopic ossification in high-risk patients by radiation therapy. Clin Orthop Relat Res 1991;263: 87–93.
3. Kjaersgaard-Andersen
P, Schmidt SA. Total hip arthroplasty. The role of antiinflammatory
medications in the prevention of heterotopic ossification. Clin Orthop Relat Res 1991;263: 78–86.
Additional Reading
McCarthy EF, Sundaram M. Heterotopic ossification: a review. Skeletal Radiol 2005;34:609–619.
Pape HC, Marsh S, Morley JR, et al. Current concepts in the development of heterotopic ossification. J Bone Joint Surg 2004;86B:783–787.
728.89 Heterotopic ossification
Patient Teaching
  • Joint motion should be encouraged.
  • Immobilization is not recommended and can worsen the prognosis.
Patients are encouraged to use involved joints.
Heterotopic ossification can be prevented in at-risk patients (e.g., trauma patients) with external beam irradiation or NSAIDs.
Q: Which patients are at greatest risk for heterotopic ossification?
A: Patients who have substantial heterotopic ossification from a previous arthroplasty and patients who have AS (20–50% risk).

Q: Why are patients with a neurologic injury, such as head or spinal trauma, at such high risk?
Patients with a severe closed head injury or a spinal cord injury have
a high risk of heterotopic ossification of the hip, shoulder, and
elbow. Unfortunately, the cause of the heterotopic bone formation is

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