What imaging study is best for a patient with swelling, hematoma, and pain localized to the arm after a fall?

Imaging for Arm Trauma with Swelling and Hematoma

Plain radiographs (X-rays) of the arm should be the initial imaging study for a patient who fell and hit their arm, presenting with swelling, hematoma, and pain throughout the arm. 1, 2

Initial Imaging Approach

• Standard radiographic views should include anteroposterior (AP), lateral, and oblique views to assess potential fractures, dislocations, and joint effusions 1, 2
• Radiography provides good delineation of bony anatomy to evaluate for fracture and appropriate alignment, which are primary concerns in management of acute traumatic arm pain 1
• Radiographs should be performed upright when possible, as malalignment can be underrepresented on supine radiography 1

Follow-up Imaging Based on Radiograph Results

If radiographs show fracture or dislocation:

• CT is better than radiography for characterizing complex fracture patterns and can guide surgical planning 1
• CT angiography (CTA) should be considered if there is concern for vascular compromise, especially with:
  • Presence of a non-expanding hematoma
  • Vicinity of the injury site to a main vascular axis
  • Isolated neurological deficit 1

If radiographs are normal but clinical suspicion remains high:

• MRI without contrast is the recommended next step for evaluating soft tissue injuries when radiographs are normal 1
• MRI is superior for diagnosing:
  • Muscle and tendon injuries
  • Bone marrow contusions not visible on radiographs
  • Ligament and capsular tears 1
• Ultrasound can be considered as an alternative, particularly for:
  • Evaluating hematomas and their extent 3, 4
  • Assessing for potential compartment syndrome in cases of large hematomas 4
  • Screening for rotator cuff tears if shoulder involvement is suspected 1

Special Considerations for Hematoma Evaluation

• Extensive arm hematoma after trauma requires careful evaluation for potential compartment syndrome 4, 5
• Bedside ultrasound can help rapidly identify traumatic hematomas and expedite care when there is concern for compartment syndrome 4
• For large hematomas with concern for vascular injury, CT angiography has demonstrated 96.2% sensitivity and 99.2% specificity for detecting vascular injuries 1

Common Pitfalls to Avoid

• Do not skip initial radiographs before ordering advanced imaging 2
• Remember that not all fractures are visible on initial radiographs; clinical correlation is essential 2
• Ultrasound alone may miss significant pathology - up to 40% of patients with nonspecific shoulder pain were found to have no significant pathology on ultrasound despite having symptoms 1
• Do not delay imaging if there are signs of vascular compromise or compartment syndrome 1, 4

Algorithm for Imaging Selection

1. Begin with plain radiographs (AP, lateral, oblique views) 1, 2
2. If fracture identified → CT for better characterization if needed for surgical planning 1
3. If normal radiographs but persistent symptoms → MRI without contrast 1
4. If concern for vascular injury → CT angiography 1
5. If limited access to MRI or need for rapid assessment of hematoma → Ultrasound 3, 4