Development of a Biomechanical Model for Sacroiliac Range of Motion

In the last seven years, increasing interest has been shown in the sacroiliac (SI) joint. Recent evidence has shown that more than 22% of lower back pain cases are caused by SI joint instability. Sacroiliac joint problems mimic discogenic and/or radicular low back pain, leading to many misdiagnoses (Weksler 2007). Over the last decade, SI fusion devices have been developed and have achieved clinical success (Wise 2008). However, there is no standard biomechanical testing procedure for SI fusion devices, although such a protocol would benefit further product development and comparison testing. The goal of our study is to develop a biomechanical model of sacroiliac range of motion. This study puts forth two methods of producing SI ROM: one model simulating a single leg stance and the second model simulating double leg stance. Our hypothesis was that the single leg stance model would produce ROM similar to what has been observed in vivo; the double leg stance model would produce ROM significantly lower. We aimed to test this hypothesis through comparison of ROM for both models and in vivo results obtained from the literature.