The Study of Displacement Changes of the Sacroiliac Joint in Unstable Pelvic Injury

Objective To determine the average articular contact area between the sacrum and ilium at the sacroiliac joint using computer analysis.Methods Thirty normal adult dry-bone sacrum and ilium specimens(left sides of pelvis) were used.Simulating all unstable pelvic injury,the sacroiliac joint was displaced in three directions by moving the ilium posteriorly,superiorly,and posterosuperioriorly.After each displacement,using Photoshop11.0 software computer analysis system to calculated the contact area between the sacrum and ilium at the sacroiliac joint.Results The data showed that the average articular surface area of the male sacroiliac joint(1138.3 mm2) was approximately 12.8% greater than the average surface area of the female sacroiliac joint(992.5 mm2)(P0.05).The average articular contact area between the sacrum and ilium at the sacroiliac joint was lowest with the ilium displaced posterosuperiorly compared to equal displacements superiorly or posteriorly(P0.05).Conclusion This study quantitatively illustrated the loss of contact surface area between the sacrum and ilium during various displacements of the ilium,thus indicating the clinical cross-section area available for open reduction and internal fixation or fusion.