Distraction test of the posterior superior iliac spine (PSIS) in the diagnosis of sacroiliac joint arthropathy

BACKGROUND The sacroiliac joint (SIJ) is a frequently underestimated cause of lower back (LBP). A simple clinical test of sufficient validity would be desirable. The aim of this study was to evaluate the diagnostic value of a new PSIS distraction test for the clinical detection of SIJ arthropathy and to compare it to several commonly used clinical tests. METHODS Consecutive patients, where a SIJ pathology had been confirmed by an SIJ infiltration were enrolled (case group, 61 SIJs in 46 patients). Before infiltration, patients were tested for pain with PSIS distraction by a punctual force on the PSIS in medial-to-lateral direction (PSIS distraction test), pain with pelvic compression, pelvic distraction, Gaenslen test, Thigh Thrust, and Faber (or Patrick's) test. In addition, these clinical tests were applied to both SIJs of a population of individuals without history of LBP (control group, 64 SIJs in 32 patients). RESULTS Within the investigated cohort, the PSIS distraction test showed a sensitivity of 100% and a specificity of 89% for SIJ pathology. The accuracy of the test was 94%, the positive predictive value (PPV) was 90% and the negative predictive value (NPV) was 100%. Pelvic compression, pelvic distraction, Gaenslen test, Thigh Thrust, and Faber test were associated with a good specificity (> 90%) but a poor sensitivity (< 35%). CONCLUSIONS Within our population of patients with confirmed SIJ arthropathy the PSIS distraction test was found to be of high sensitivity, specificity and accuracy. In contrast, common clinical tests showed a poor sensitivity. The PSIS distraction test seems to be an easy-to-perform and clinically valuable test for SIJ arthropathy.