 
Many patients present to the Emergency Department for low back pain. Determining whether these patients have a red-flag diagnosis can be difficult. Red flag diagnoses include:
- Fracture
- Cauda equina syndrome/ spinal cord compression
- Spinal infection
- Vertebral malignancy
Almost all patients presenting with back pain, whether it be a muscle spasm or a spinal epidural abscess, will have back tenderness to some extent. So, how can you better differentiate benign from dangerous etiologies?
Trick of the trade
Spine percussion
Percussion is an easy physical exam technique that can be used to risk-stratify patients that you suspect may have serious back pathology. Classically, percussion of the thoracic and lumbar spine should trigger pain in patients with serious back pain pathology, such as vertebral malignancy or a spinal infection. Because bone conducts vibration extremely well, percussion irritates deep space pathology. In contrast, percussion should not exacerbate discogenic pain, back strain, or muscular spasm.
Technique
Position your finger over the spinous process, and percuss using your other hand. Repeat this for each vertebral level. With significant focal spine tenderness to percussion, the clinician should be more suspicious for worrisome pathology.
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