Sacroiliac screw versus locking square plate fixation in sacroiliac joint disruption on composite bone models: A descriptive comparative biomechanical study

Abstract

Background: The aim of this study was to compare a locking square plate to a standard sacroiliac (SI) screw of the sacroiliac joint on a composite pelvic bone model to assess the ultimate load tolerated before failure of fixation and describe the mode of failure of the construct. Methods: Bilateral sacroiliac joint dislocations were created in 10 composite pelvic bone models. In this descriptive comparative study, the one SI joint was fixated using a 7.3 mm cannulated screw and the contralateral side using a 4-hole square locking plate. The pubic symphysis was not fixed. An upward vertical load was manually applied to each respective SI joint using a hook into the sciatic notch. The ultimate load to failure and the mode of failure was recorded for both groups. Results: The median load to failure for the SI screw group was 310 Newton (N) (range 280–390 N) and for the SI plate group 580 N (range 380–760 N). The ultimate load to failure was significantly lower in the SI screw group (p = 0.0002). No hardware-related failures were recorded in any of the fixations. The SI screw group had failure through a fracture of the sacrum in all the specimens. In the SI plate group, fractures of the sacrum and ilium constituted 60% and 40%, respectively. Conclusion: A locking square plate fixation is superior to a single SI screw at the ultimate load to failure when a vertical load is applied to the sacroiliac joint in a composite bone model.

Keywords

• Pelvic ring
• Pelvis trauma
• Sacroiliac joint
• SI screw
• Sacroiliac plating
• Bone models