Age / Sex : 18 / M

Myositis Ossificans

Discussion

Findings:

 CT : about 2.8cm sized soft tissue density mass with peripheral rim calcification in right paraspinal muscle, T4/5 level

 MRI : T2 hyperintense, T1 slightly hyperintense mass in right paraspinal muscle

      extensive peritumoral edema in adjacent soft tissue

      heterogeneous contrast enhancement

Differential Diagnosis:

 Heterotopic ossification(Myositis ossificans)

 Soft tissue sarcoma such as extraskeletal osteosarcoma

Diagnosis:  

Heterotopic ossification(Myositis ossificans) in right paraspinal muscle

Discussion:

• Benign, localized, self-limiting, extraskeletal formation of heterotopic bone and cartilage in soft tissues


• Location – anterior muscles of extremities
  
  
  
  • lower extremity - quadriceps femoris (m/c)
  
  
  • upper extremity – brachialis muscle (m/c)
    
    
    
    • usually involves  arm, shoulder, elbow, hand,  neck, head
    
    
    
    
  
  
  
  

• occur after trauma (60%-75%, myositis ossificans circumscripta)


• Radiography, CT




• soft tissue swelling, faint peripheral calcification




• MR




• Intramuscular nodule, swelling




• isointense T1, Hyperintense T2


• peripheral or diffuse enhancement


• faint low SI foci or rim à small calcification




• markedly edematous muscle




• no bone abnormality, periostitis, BM edema 

References:

u  Philippa Tyler et al : The Imaging of Myositis Ossificans, SEMINARS IN MUSCULOSKELETAL RADIOLOGY/VOLUME 14, NUMBER 2 2010

u  Dong-Geun Lee, MD et al : Myositis ossificans in the paraspinal muscles of the neck after acupuncture: a case report, The Spine Journal 13 (2013)