Diagnostic Imaging
Core approach
Diagnostic imaging should answer a specific clinical question. Select the modality based on the suspected tissue and urgency: radiography for bone alignment and gross pathology, CT for complex bone trauma, MRI for soft tissue and neurologic detail, and ultrasound for selected soft-tissue or vascular questions. Apply ALARA and consider whether the result will change management.
Concepts to know
Know common indications for imaging in spine and extremity complaints, including trauma, suspected fracture, infection, malignancy, progressive neurologic deficit, and failure to improve. Understand limitations: early fractures may be radiographically occult, and degenerative changes are common in asymptomatic people. Contrast agents carry risks, including renal and allergic considerations.
Question traps
Do not order imaging before a focused examination unless red flags demand it. Avoid treating incidental degenerative findings as the pain generator. Beware pseudofracture lines, overlapping shadows, and normal variants. Also remember that a normal radiograph does not exclude serious soft-tissue or neurologic disease.
Worked example
A healthy 28-year-old with acute nonspecific low back pain and no red flags does not routinely need lumbar radiographs. Initial care is conservative with reassessment. By contrast, new back pain with fever, cancer history, significant trauma, or progressive neurologic deficit warrants urgent imaging and escalation. Rule of thumb: image to answer a question, not to reassure by habit.
Documentation
State the clinical question, findings, limitations, and plan. Follow up abnormal or inconclusive results.