E4721. Skeletal Surprises: Cracking the Case of Nontraumatic Musculoskeletal Emergencies
  1. Sungmee Park; University of California, Irvine School of Medicine
  2. Thomas Duong; University of California, Irvine School of Medicine
  3. Anthony Wu; University of California, Irvine School of Medicine
  4. Saman Andalib; University of California, Irvine School of Medicine
  5. Chang Shu; University of California, Irvine School of Medicine
  6. Roozbeh Houshyar; University of California, Irvine School of Medicine
  7. Maryam Golshan Momeni; University of California, Irvine School of Medicine
Musculoskeletal pain, the etiology and management of which can vary widely, is one of the most common reasons for emergency department visits in the US. Imaging plays a crucial role in diagnosis, and knowledge of characteristic findings is vital to guiding management.

Educational Goals / Teaching Points
This exhibit will review the risk factors and imaging features of important nontraumatic musculoskeletal emergencies.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Necrotizing fasciitis is a rapidly progressive soft tissue infection often affecting diabetics and the immunosuppressed. Imaging findings overlap with those of cellulitis, with the addition of deep fascial thickening, fluid collections, and intermuscular edema. Although diagnosis is ultimately made clinically and/or surgically, a characteristic finding (which is not always seen) is soft tissue gas. Septic arthritis is a destructive arthropathy resulting from synovial infection. High-risk populations include the immunosuppressed and IV drug users. The knee, hip, and ankle are most commonly affected. Findings include joint effusions, bony erosions, and soft tissue swelling. Arthrocentesis is crucial to diagnosis and often yields purulent synovial fluid. Bone marrow edema can be visualized on MRI. Osteomyelitis is an infection of the medullary cavity often seen with diabetes, bacteremia, and trauma. Diagnosis is based on clinical, imaging, and pathologic findings. Although radiography has low sensitivity early on, bony erosions, periosteal reaction, and soft tissue swelling may be seen. CT is more sensitive for diagnosis, but MRI is superior with characteristically decreased T1 and increased T2 signal. Osteonecrosis is ischemic bone death, most often idiopathic or related to steroids, alcohol, or trauma. Any bone can be involved, but the femoral and humeral heads are most commonly affected. Radiographs and CT show a serpentine sclerotic rim that can progress to subchondral fracture (the “crescent sign”) and eventual articular collapse. MRI is the gold standard. Pathologic fractures occur secondary to an underlying bone tumor or infection. Common locations include the vertebral bodies, femur, and humeral head. Of note, avulsion fractures of the lesser trochanter in adults should be considered pathologic until proven otherwise. Imaging typically shows a lytic lesion with cortical breakthrough and periosteal reaction.

Knowledge of the risk factors and specific imaging features of nontraumatic musculoskeletal emergencies is key for accurate diagnosis, guiding management, and improving outcomes.