Heterotopic Ossification

By admin On Jan 28, 2024

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

Basics

Description

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).

Epidemiology

Less common in children than in adults, and more common in males than in females (1)

Incidence

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

Genetics

No genetic link can successfully predict patient susceptibility to heterotopic ossification.

Etiology

Traumatic brain injury
Spinal cord injury
Trauma

Associated Conditions

Fibrodysplasia ossificans progressiva
Primary osteoma cutis

Diagnosis

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.

Tests

Lab

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.

Imaging

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

Treatment

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

Radiotherapy

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.

Medication

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)

P.177

Surgery

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).

Follow-up

Prognosis

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.

Complications

Loss of mobility
Ankylosis

Patient Monitoring

Serial radiographs are obtained at 1–3-month intervals for 6 months.

References

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.

Miscellaneous

Codes

ICD9-CM

728.89 Heterotopic ossification

Patient Teaching

Joint motion should be encouraged.
Immobilization is not recommended and can worsen the prognosis.

Activity

Patients are encouraged to use involved joints.

Prevention

Heterotopic ossification can be prevented in at-risk patients (e.g., trauma patients) with external beam irradiation or NSAIDs.

FAQ

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?

A:
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
unknown.