Synonyms

• Heterotopic ossification
• myositis ossificans progressiva (MOP)

Category

Bone and soft tissue

Behaviour

Benign

Gender

Both equally

Tissue of Origin

Other

Epidemiology

• Benign ectopic Bone formation in soft tissues
• Post-traumatic form most common
• MOP form is rare genetic condition

Clinical Features

• Swelling and pain in affected soft tissue
• Progressive stiffness and limitation of motion
• Mass palpable with induration

Location

• THigh (post-traumatic most common)
• Hip
• Shoulder
• Can occur anywhere (MOP)

Imaging

• Plain radiograph: progressive heterotopic Bone formation
• CT: characterises maturity of ossification
• MRI: early stages show soft tissue edema before ossification

Pathology

• Mature Bone in soft tissue
• Early: myofibroblasts and inflammatory cells
• Late: mature lamellar Bone

Genetics

ACVR1 mutations in MOP (progressive form)

Treatment

• Observation and NSAIDs (indomethacin) for prevention
• Surgical excision only after maturation

Prognosis

• Benign - ossification eventually matures
• Prognosis depends on extent and functional impact

Key Points

• Benign heterotopic ossification
• Wait for maturation before surgical excision
• NSAIDs helpful for prevention

Workup - Blood Tests

No routine blood tests

Workup - Local Imaging

• Plain radiograph - assess maturity of ossification
• CT - confirm nature of lesion

Workup - Biopsy

Rarely needed if imaging typical

Workup - Staging

No staging required