Sources of Sacroiliac Region Pain: Insights Gained From a Study Comparing Standard Intra-Articular Injection With a Technique Combining Intra- and Peri-Articular Injection

Objectives: To present evidence supporting the existence of extra-articular sources for sacroiliac region pain and to present evidence that intra-articular anesthetic blockade may underestimate the true prevalence of sacroiliac region pain. Design: Retrospective review of 2 large case series comparing patient responses to intra-articular injection versus combined intra-articular and peri-articular injection of anesthetic and corticosteroid. Setting: Private practice chronic pain clinic set in a hospital outpatient clinic. Participants: Patients (N=120) sequentially enrolled from practice billing records. Inclusion criteria included pain in the low back below L4 and in the buttock, thigh, groin, or lower leg. If disk herniation, lumbar stenosis, or facet syndrome was previously treated with appropriately chosen injections, response to treatment had to be negative. Patients failed to respond to treatment with physical therapy. Exclusion criteria included records with an incomplete database, patients increasing pain medication use greater than 15% for pain not related to the sacroiliac region, severe psychiatric illness, and nonspecific anesthetic blockade. One hundred sixty-seven records were reviewed to obtain the 120 study subjects. Interventions: Intra-articular injection was done according to the standard technique described by Fortin. Peri-articular injection was done by a slight modification of the procedure described by Yin. Main Outcome Measures: Percentage change in visual analog scale (VAS) pain scores at 3 weeks and 3 months postinjection; patients' self reported activities of daily living (ADLs) improvement at 3 weeks and 3 months postinjection; and percentage change in VAS pain score within I hour of injection. Results: For intra-articular injection alone, the rate of positive response at 3 months was 12.50% versus 31.25% for the combined injection (P=.025). Positive response was defined as greater than 50% drop in VAS pain score or patients describing ADLs as "greatly improved." Anesthetic response rates were higher in the combined injection group (62.5% vs 42.5%; P=.037). Conclusions: Significant extra-articular sources of sacroiliac region pain exist. Intra-articular diagnostic blocks underestimate the prevalence of sacroiliac region pain.