Diagnostic Approach for CRPS Patients with Chronic Foot Pain

Initial Diagnostic Approach

The American College of Radiology recommends plain radiographs of the foot as the first imaging study for any chronic foot pain, including CRPS, to rule out other causes of pain such as fractures, osteoarthritis, or other osseous abnormalities 1, 2
Weight-bearing radiographs are recommended for optimal evaluation of foot structures 1
Although radiographs have limited sensitivity for diagnosing CRPS specifically, they are essential to exclude other pathologies 1, 2

A 3-phase bone scan is highly recommended with a sensitivity of 78% and specificity of 88% for diagnosing CRPS type I, and an excellent negative predictive value (88%) 1, 2
MRI foot without IV contrast is also appropriate with high specificity (91%) but lower sensitivity (35%) for CRPS type I, and is particularly useful for CRPS type II due to its ability to visualize nerves and detect muscle denervation 1, 2
Contrast-enhanced MRI may improve diagnostic accuracy in some cases 3

The American College of Radiology recommends starting with foot radiographs (weight-bearing if possible) 2
If radiographs are negative or equivocal, a 3-phase bone scan is preferred for CRPS type I suspicion due to higher sensitivity 1
For CRPS type II suspicion (likely in crush injury), MRI without contrast is preferred due to ability to visualize nerve damage and muscle denervation 1, 2

Ultrasound with power Doppler may be considered with a sensitivity of 73% and specificity of 92% for detecting increased blood flow in CRPS type I, and ability to assess nerve structures in CRPS type II 1, 2
CT is not recommended for CRPS evaluation as there is no relevant literature supporting its use 1, 2