What is the best diagnostic approach for a patient with hip and back pain who prefers a computed tomography (CT) scan over a magnetic resonance imaging (MRI) scan?

Diagnostic Imaging for Hip and Back Pain When Patient Prefers CT Over MRI

Start with plain radiographs of the pelvis/hip and lumbar spine first, then proceed to CT of the targeted area if radiographs are negative or nondiagnostic—CT is an acceptable alternative to MRI for evaluating osseous pathology, fractures, and spondylolysis, though it has significant limitations for soft tissue evaluation. 1

Initial Imaging Approach

• Plain radiographs are mandatory as the first-line test for both hip and back pain evaluation, regardless of the patient's preference for subsequent imaging 1
• Radiographs can establish the diagnosis in up to 24% of cases and guide selection of additional imaging 1
• For hip pain, obtain pelvis and proximal femur views rather than isolated hip views 1
• For back pain, anteroposterior views of the symptomatic region are typically sufficient 1

When CT Is Acceptable After Radiographs

CT without IV contrast can serve as the next imaging step in several specific scenarios:

For Back Pain:

• CT has increased sensitivity for detecting nondisplaced fractures and spondylolysis compared to radiographs 1
• CT provides excellent bone detail and can evaluate osseous pathology when MRI is not feasible 1
• CT is superior to radiography for detecting mineralized matrix and evaluating bony architecture 1
• Recent dual-energy CT technology can even evaluate bone marrow edema, partially bridging the gap with MRI 1

For Hip Pain:

• CT excels at detecting hardware complications, occult fractures, and bone tumors 2
• CT has 94% sensitivity and 100% specificity for occult hip fractures 2
• CT is useful for evaluating calcifications and bony impingement 1

Critical Limitations of CT You Must Understand

MRI remains superior for soft tissue evaluation, and CT has significant diagnostic blind spots:

• CT is suboptimal for evaluating intraspinal contents and paraspinal soft tissues 1, 3
• CT is less sensitive for detecting stress injuries of the pars interarticularis without complete lysis—a common finding in back pain 1
• CT cannot adequately visualize disc herniation (only 55% sensitivity), disc signal changes, or Modic changes 4
• For hip pain, CT misses labral tears, tendon pathology (abductor tears, iliopsoas issues), bursitis, and muscle injuries 1, 5
• Soft tissue pathology is usually not evaluated with CT because MRI has superior soft tissue resolution 1

When You Must Insist on MRI Despite Patient Preference

If clinical red flags are present, MRI is strongly preferred over CT:

Red Flags Requiring MRI Consideration:

• Suspected infection (discitis, osteomyelitis, epidural abscess) 1
• Suspected tumor or neoplasm 1
• Neurologic deficits or radicular symptoms 1
• Night pain, fever, unintentional weight loss 1
• Suspected labral tear or femoroacetabular impingement in hip pain 1
• Suspected tendon tears or soft tissue injury 1, 5

In these scenarios, CT may miss life-threatening or surgically correctable pathology 1, 3

Practical Algorithm for Your Patient

1. Order plain radiographs first (pelvis/hip and lumbar spine) 1

2. If radiographs are negative/nondiagnostic:

   • For primarily osseous concerns (fracture, spondylolysis, bone tumor): CT without contrast of the targeted area is acceptable 1
   • Add IV contrast only if infection or soft tissue abscess is specifically suspected 1

3. If CT is negative but pain persists or worsens:

   • Strongly reconsider MRI as CT may have missed soft tissue pathology 2, 3
   • MRI detects additional pathology in 38% of cases when CT is negative 2

Addressing Patient Concerns About MRI

If claustrophobia or anxiety is the barrier:

• Offer sedation for the MRI procedure [@general medical knowledge@]
• Consider open MRI or extremity MRI units if available [@general medical knowledge@]
• Explain that MRI has near 100% sensitivity for occult fractures and soft tissue injury 2

Document clearly if the patient refuses MRI after counseling about CT's limitations, as this affects medicolegal risk and diagnostic accuracy [@general medical knowledge@]

Common Pitfalls to Avoid

• Never skip radiographs to go directly to CT—this violates standard imaging algorithms 1
• Do not add IV contrast unnecessarily to CT—it adds cost and risk without benefit for most osseous pathology 1, 2
• Delaying appropriate cross-sectional imaging increases morbidity by missing complications that could be treated earlier 2
• Relying solely on CT to rule out spinal pathology will lead to missed diagnoses of disc herniations, nerve compression, and soft tissue masses 3, 4