Obturator inlet and iliac oblique technique for safe, convenient, and reliable iliac screw placement.

BACKGROUND: There are many described techniques for the placement of posterior iliac screws for extension of lumbar posterior spinal instrumentation to the pelvis. However, each one has its limitations. We describe our technique for fluoroscopic guidance of iliac screw placement utilizing the obturator inlet and iliac oblique views as well as a detailed review of how to obtain and interpret these views for safe iliac screw placement.

METHODS: Retrospective chart review of patients undergoing iliac screw placement utilizing the obturator inlet and iliac oblique views as part of spine instrumentation between January 2019 and March 2022. Screw length and bony breaches are reported utilizing this technique.

RESULTS: Twelve patients underwent posterior lumbopelvic fixation with a total of 23 screws placed via either open or percutaneous technique. The mean screw length was 96.5 mm (Range 80-110, standard dev 7.75). There were no recorded breaches or recannulation attempts.

CONCLUSIONS: We show how this technique is a much more convenient alternative to the placement of iliac screws under the obturator outlet oblique ("teardrop" view) which necessitates that the C-arm is in line with the instruments being placed. These described views can be used to place screws with either open or percutaneous techniques and with either the posterior superior iliac spine (PSIS) or S2 alar iliac (S2AI) starting points.