What is the diagnosis and management for left arm pain following a vehicular accident?

Diagnosis and Management of Left Arm Pain Following Vehicular Accident

Begin with plain radiographs (AP, lateral, and oblique views) of the left arm as the initial imaging study to assess for fractures, dislocations, and joint effusions, followed by CT if fractures are complex or CT angiography if vascular injury is suspected based on clinical findings. 1

Initial Clinical Assessment

Obtain a focused history documenting:

• Exact pain location and radiation pattern (proximal vs distal arm, specific regions involved) 1
• Mechanism of injury (direction of impact, patient position, restraint use) 2
• Timing of symptom onset (immediate vs delayed within 1 week) 3
• Associated symptoms: numbness, tingling, weakness, swelling, or hematoma 1, 4
• Presence of neurological deficits in specific dermatomal distributions 4

Physical examination priorities:

• Assess for signs of vascular compromise (diminished pulses, expanding hematoma, pallor) 1
• Evaluate for compartment syndrome (severe pain, tense compartments, pain with passive stretch) 1
• Document neurological function (motor strength, sensation, reflexes) 4
• Examine for visible deformity, swelling, or ecchymosis 1

Imaging Algorithm

Step 1: Initial Radiography

Plain radiographs are the mandatory first imaging study for all patients with post-traumatic arm pain, providing good delineation of bony anatomy to evaluate for fractures and alignment. 1 Obtain standard views including anteroposterior, lateral, and oblique projections, performed upright when possible as malalignment can be underrepresented on supine radiography. 1

Step 2: Advanced Imaging Based on Radiograph Results

If fractures are identified:

• CT without contrast is recommended for characterizing complex fracture patterns to guide surgical planning, offering superior visualization of fracture complexity compared to radiography 1

If vascular injury is suspected (large hematoma, proximity to major vessels, isolated neurological deficit):

• CT angiography should be obtained promptly, demonstrating 96.2% sensitivity and 99.2% specificity for detecting vascular injuries 1
• Do not delay imaging if signs of vascular compromise or compartment syndrome are present 1

If radiographs are normal but clinical suspicion remains high:

• MRI without contrast is recommended for evaluating soft tissue injuries, nerve compression, or occult fractures 1

Differential Diagnoses to Consider

Musculoskeletal injuries (most common):

• Fractures (humerus, radius, ulna) - visible on initial radiographs 1
• Soft tissue contusions and hematomas - may require MRI if extensive 1
• Joint dislocations or subluxations - evident on radiographs 1

Peripheral nerve injuries:

• Nerve entrapment syndromes can develop after motor vehicle collisions, with sudden onset of compression symptoms typically within 1 week of injury 3
• Common patterns include carpal tunnel syndrome, cubital tunnel syndrome, and radial sensory nerve entrapment, occurring in 25% bilaterally 3
• The typical mechanism involves the driver with hands on steering wheel during frontal or rear impact 3

Vascular injuries:

• Arterial dissection or laceration - requires urgent CT angiography if suspected 1
• Expanding hematoma with potential compartment syndrome 1

Cervical radiculopathy (if pain radiates from neck):

• Nerve root compression from disc herniation or osteophytes causing neuropathic pain radiating into shoulder and arm 4
• Requires cervical spine MRI without contrast if clinical examination supports radiculopathy 4

Common Pitfalls to Avoid

• Never skip initial radiographs before ordering advanced imaging, as this can lead to missed diagnoses or inappropriate management 1
• Not all fractures are visible on initial radiographs - clinical correlation is essential and repeat imaging or MRI may be needed if symptoms persist 1
• Do not assume pain is simply "muscle tension" without ruling out structural pathology, particularly if neurological symptoms are present 4
• Ultrasound alone may miss significant pathology - up to 40% of patients with pain may have no significant findings on ultrasound despite symptoms 1
• Do not delay imaging if vascular compromise or compartment syndrome is suspected, as these are surgical emergencies 1

Pain Management Considerations

Recognize that persistent pain is common:

• 67.4% of motor vehicle collision patients experience moderate or severe pain at 8 weeks post-injury 5
• Pain severity in the emergency department predicts persistent pain development 5
• Axial pain distribution (neck, back) causes the greatest interference with life function, though arm pain significantly contributes to overall disability 6

Early intervention is critical:

• The first several days after trauma may dictate recovery trajectories 5
• Peritraumatic stress symptoms (distress and dissociation) influence both acute pain and the transition to persistent pain 5
• Early recognition and treatment of nerve compression may improve outcomes 3