Should a Lumbar MRI for back pain routinely include the sacro-iliac joint?

BACKGROUND Back pain is a common problem and has been shown to affect approximately 85% of the adult population at any one time. The source of this pain can be difficult to identify and the sacroiliac joint (SIJ) has been proposed as a possible pain source. Its percentage contribution to lower back pain is controversial. Clinical provocative tests for SIJ pathology have been developed but these have high intra and inter-observer variability and the significant of positive findings is unclear. This study proposes that the SIJ should not be imaged as part of a routine MRI lumbar spine series. METHODS We retrospectively reviewed the images of 353 patients who had MRI lumbar spine scans. 130 had the SIJ imaged. We recorded the clinical findings and diagnosis at referral. We reviewed the images and documented the radiological findings. RESULTS SI joint pathology was most frequently identified when clinical suspected. Overall SIJ pathology found on MRI in only 0.02% of patients. CONCLUSIONS We conclude that routinely imaging the SIJ in MRI lumbar spine series is not cost-effective or a useful use of resources. The SIJ should be imaged only if significant clinical findings are demonstrated.