What are the recommended imaging studies for a patient with lingering neck and buttock pain in the lumbar, sacrum, and coccyx area after a fall?

Imaging Recommendations for Post-Fall Neck and Buttock Pain

For lingering neck and buttock pain involving the lumbar, sacrum, and coccyx area after a fall, start with plain radiographs of both the cervical spine and lumbosacral spine/pelvis as your initial imaging, then proceed to MRI without contrast if red flags are present or pain persists beyond 4-6 weeks.

Initial Imaging Strategy

Cervical Spine (Neck Pain)

• Plain radiographs of the cervical spine are the appropriate first-line imaging for post-traumatic neck pain, even when symptoms are lingering 1
• A detailed clinical history and physical examination should focus on identifying "red flag" symptoms including: risk for fracture, malignancy, constitutional symptoms (fever, weight loss), infection, neurological deficits, or coagulopathy 1, 2
• If radiographs are negative but pain persists beyond 4-6 weeks or red flags are present, proceed directly to MRI cervical spine without contrast 1

Lumbosacral Spine and Pelvis (Buttock/Sacral/Coccyx Pain)

• Plain radiographs of the lumbosacral spine and pelvis are the initial imaging of choice for post-fall buttock and lower back pain 1, 3
• The pelvis radiograph is particularly important because patients with suspected sacral or coccyx injuries often have concomitant pelvic fractures that may be missed if only focused views are obtained 3
• For suspected sacral or coccyx fractures with negative radiographs, CT without contrast is more appropriate than MRI as it provides superior bone detail 1

When to Advance to MRI

Critical Red Flags Requiring Urgent MRI 2

• Progressive neurological deficits (motor weakness, sensory changes, bowel/bladder dysfunction)
• Constant pain or night pain lasting ≥4 weeks
• Abnormal neurological examination
• Fever with elevated inflammatory markers (suggesting infection)
• History of cancer (suggesting metastatic disease)
• Unexplained weight loss

MRI Protocol Selection

• MRI without contrast is sufficient for most post-traumatic evaluations including occult fractures, ligamentous injuries, and disc pathology 1, 3
• MRI without AND with IV contrast is reserved for suspected infection (discitis, osteomyelitis, epidural abscess) or malignancy 1, 2

Special Considerations for Sacroiliac Joint Pain

If inflammatory sacroiliac symptoms are suspected (morning stiffness, pain improving with activity):

• Start with plain radiographs of the sacroiliac joints 1
• If radiographs are negative or equivocal, MRI sacroiliac joints without contrast (or with and without contrast) is rated as usually appropriate 1
• CT without contrast may be helpful for identifying subtle erosions, especially in patients unable to undergo MRI 1

Common Pitfalls to Avoid

• Do not obtain MRI as initial imaging in the absence of red flags - approximately 50% of asymptomatic patients have abnormalities on cervical spine MRI that are not clinically relevant 1
• Do not rely solely on negative radiographs to exclude fracture - approximately 10% of proximal femoral and pelvic fractures are not visible on initial radiographs 3
• Do not obtain isolated hip or sacral views without including the entire pelvis - this misses associated fractures that can alter treatment decisions 3
• Recognize that delays in diagnosis of occult fractures are associated with increased complications, length of stay, and mortality 3

Timeline for Imaging Decisions

• Immediate imaging (radiographs): Any post-fall pain with inability to bear weight or point tenderness over bone 1, 3
• Urgent advanced imaging (MRI within 24-48 hours): Progressive neurological deficits, suspected cauda equina syndrome, or signs of infection 2
• Delayed advanced imaging (4-6 weeks): Persistent pain without red flags that fails conservative management 1, 4

What NOT to Order Initially

• CT with IV contrast adds no value for post-traumatic evaluation 1
• Bone scan with SPECT/CT lacks specificity and spatial resolution for acute trauma evaluation 1
• MRI with contrast alone (without pre-contrast sequences) is never appropriate 1