What imaging studies are recommended for a patient with lingering neck and buttock pain after a fall onto the lumbar spine and coccyx, with improvement over three weeks?

Imaging Recommendations for Lingering Neck and Buttock Pain After Fall

For this patient with persistent neck and buttock pain three weeks post-trauma, obtain plain radiographs of both the cervical spine (AP and lateral views) and lumbar spine/coccyx (AP and lateral views) as initial imaging, followed by MRI of the cervical spine without contrast if neck pain persists or neurological symptoms develop, and consider CT of the lumbar spine/coccyx if radiographs are inconclusive for evaluating bony injury to the coccyx.

Cervical Spine Imaging Approach

Initial Radiographic Evaluation

• Start with plain radiographs (AP and lateral views) of the cervical spine as the initial imaging modality, though recognize their significant limitations in detecting injury 1.
• Plain radiographs have low specificity and are frequently normal in the first 2-3 weeks after injury because 30-40% of bone destruction is needed before detection on radiographs 1.
• The sensitivity of plain cervical radiographs for detecting significant spinal injuries ranges from only 31-94%, with a pooled sensitivity of approximately 52% 1.

When to Advance to MRI

• If neck pain persists beyond the initial evaluation or if any neurological symptoms develop, proceed directly to MRI cervical spine without contrast 1.
• MRI is the imaging modality of choice for evaluating soft tissue injuries, ligamentous injury, disc abnormalities, and spinal cord pathology with sensitivity of 96% and specificity of 93% 1.
• At three weeks post-injury with persistent symptoms, there is sufficient clinical concern to warrant MRI evaluation even without overt neurological deficits 1.

Important Caveats for Cervical Spine

• Do not rely on negative plain radiographs alone to exclude significant cervical spine pathology in a patient with persistent symptoms 1.
• Flexion-extension views are often inadequate in the acute/subacute setting due to muscle spasm and limited motion, and should generally be reserved for later follow-up if instability remains a concern 1.
• CT cervical spine would be appropriate if there is concern for occult fracture not visualized on plain films, but MRI provides superior soft tissue evaluation 1.

Lumbar Spine and Coccyx Imaging Approach

Initial Imaging Strategy

• Obtain upright AP and lateral radiographs of the lumbar spine and coccyx as the initial imaging study 2.
• Upright positioning is essential as it provides functional information about axial loading of the spine 2.
• The lateral view must visualize the entire lumbar spine including the lumbosacral junction and coccyx 2.

Advanced Imaging Considerations

• If radiographs are normal but buttock/coccyx pain persists, CT lumbar spine/coccyx without contrast provides superior bony detail for evaluating occult fractures, particularly of the coccyx which can be difficult to assess on plain films 2.
• CT has 94-100% sensitivity for detecting thoracolumbar fractures compared to only 49-82% for plain radiographs 1.
• MRI lumbar spine without contrast would be indicated if there is concern for disc herniation, nerve root compression, or soft tissue injury contributing to buttock pain 1, 2.

Clinical Decision Points for Lumbar/Coccyx Region

• The American College of Physicians recommends prompt imaging with MRI or CT when progressive neurologic deficits are present or serious underlying conditions are suspected 1.
• For persistent low back/buttock pain without neurological symptoms at 3 weeks, radiographs followed by selective advanced imaging based on findings is appropriate 1.
• Do not obtain MRI of the lumbar spine unless radiographs show abnormalities or the patient develops radicular symptoms, as routine imaging does not improve outcomes in nonspecific low back pain 1.

Practical Algorithm Summary

1. Week 3 post-injury with persistent symptoms: Obtain plain radiographs of cervical spine (AP/lateral) AND lumbar spine/coccyx (AP/lateral upright) 1, 2

2. If cervical radiographs are negative but neck pain persists: Proceed to MRI cervical spine without contrast to evaluate for ligamentous injury, disc pathology, or soft tissue injury 1

3. If lumbar/coccyx radiographs are negative but buttock pain persists: Consider CT lumbar spine/coccyx for better bony detail, particularly for coccyx fractures 1, 2

4. If radicular symptoms develop in either region: MRI is indicated for that spinal region 1

Common Pitfalls to Avoid

• Do not assume negative plain radiographs exclude significant injury at this timeframe, especially for the cervical spine where ligamentous injuries may not be apparent 1.
• Avoid obtaining only AP radiographs—lateral views are essential for adequate evaluation 2, 3.
• Do not perform flexion-extension views in the acute/subacute period as they are often inadequate due to muscle spasm and patient guarding 1.
• Recognize that CT is superior to plain radiographs for bony injury detection but MRI is superior for soft tissue and ligamentous evaluation 1.