Force and time recording for validating the sacroiliac distraction test

Objective. The present aim was to investigate whether applied force and time interval of force exposure during the sacroiliac distraction test could discriminate subjects with sacroiliitis pain from healthy subjects. Design. The study was a methodological one using force plates sensing three orthogonal forces. Background. Studies evaluating the validity of sacroiliac joint tests show conflicting results. To our knowledge, no previous studies have evaluated force recording combined with pain reports. Methods. Eleven subjects with sacroiliitis and 11 healthy subjects were examined with distraction test once by each of three physiotherapists. The subjects indicated any pain by pressing a button giving a mark in the data collection. Results. The magnitude of the total force vector was significantly smaller (P<0.05) and the time interval was significantly shorter (P<0.05) in the sacroiliitis group, although almost 20 s could elapse before pain was provoked. The sensitivity of the test was 0.55 calculated for all physiotherapists involved, and varied between them, range 0.55–0.82. The specificity was 1.0. Conclusions. The results support the advantage of force and time recording during the distraction test as a technique for evaluating pain. Further investigation is needed on whether the velocity of force application, the ability to maintain the same pressure and the bilateral distribution of force on the sacroiliac joints influence the sensitivity.