Diagnostic accuracy of clinical examination to distinguish sacroiliac joint pain as a cause of chronic low back pain.

Background: Despite the availability of safe and effective surgical treatments for chronic SI joint pain, many clinicians find the diagnosis of SI joint pain challenging. Misdiagnosis can lead to misdirected surgery, which has important consequences. The study's goal was to determine whether a combination of clinical examination, joint block, and selected radiographic imaging can distinguish patients with SI joint pain from those with other causes of chronic low back pain.

Methods: Prospective diagnostic accuracy study with evaluation of 364 consecutive patients seeking advice in a neurosurgical clinic for chronic low back pain. Participating patients underwent comprehensive clinical examination (medical history items, specific physical examination manoeuvres, and selected radiographic tests) followed by SI joint block. Block was used to confirm or exclude SI joint pain. Logistic regression with LASSO (least absolute shrinkage and selection operator) penalty was used to calculate the accuracy of diagnosis when looking at (1) medical history items only, (2) medical history plus radiographic testing, and (3) medical history, radiographic testing, and physical examination testing.

Results: 150 patients had a positive response (>50% acute pain relief) to SI joint block, 214 had no response to SI joint block, and 37 had minimal (<50% improvement) in pain. Diagnostic accuracy for SI joint pain was lowest with medical history only (85-86%), slightly higher when radiographic testing was added (87%), and highest when physical examination testing was included (96%).

Conclusion: Comprehensive clinical examination (including SI joint block where relevant and selected imaging procedures) is accurate in distinguishing the SI joint from non-SI joint causes of chronic low back pain.

Trial registration: https://www.clinicaltrials.gov/study/NCT04381208.