• Alexander Von Glinski, Clifford Pierre, Sven Frieler, Jonathan M Mahoney, Jonathan A Harris, Dhara B Amin, May Allall, Brandon S Bucklen, Thomas A Schildhauer, Rod J Oskouian, and Jens R Chapman.
• Swedish Neuroscience Institute, Swedish Medical Center, Seattle, Washington, USA; University Hospital Bergmannsheil, Bochum, Germany. Electronic address: Alexandervonglinski@icloud.com.
• World Neurosurg. 2021 Oct 1; 154: e481-e487.

ObjectiveTraditional iliac (TI) screws require extensive dissection, involve offset-connectors, and have prominent screw heads that may cause patient discomfort. S2 alar-iliac (S2AI) screws require less dissection, do not need offset connectors, and are less prominent. However, the biomechanical consequences of S2AI screws crossing the alar-iliac joint is unknown. The present study investigates the fixation strength of a modified iliac (MI) screw, which has a more medial entry point and reduced screw prominence, but does not cross the alar-iliac joint.MethodsEighteen sacropelvic spines were divided into 3 groups (n = 6): TI, S2AI, and MI. Each specimen was fixed unilaterally with S1 pedicle screws and pelvic fixation according to its group. Screws were loaded at ±10 Nm at 3Hz for 1000 cycles. Motion of each screw and rod strain above and below the S1 screw was measured.ResultsToggle of the S1 screw was lowest for the TI group, followed by the MI and S2AI groups, but there were no significant differences (P = 0.421). Toggle of the iliac screw relative to the pelvis was also lowest for the TI group, followed by the MI group, and was greatest for the S2AI group, without significant differences (P = 0.179). Rod strain was similar across all groups.ConclusionsNo statistically significant differences were found between the TI, S2AI, and MI techniques with regard to screw toggle or rod strain. Advantages of the MI screw include its lower profile and a medialized starting point eliminating the need for offset-connectors.Published by Elsevier Inc.

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