Accuracy of the Free-hand Placement of Pedicle Screws in the Lumbosacral Spine Using a Universal Entry Point: Clinical Validation.

Abstract

Retrospective radiographic study. To evaluate the accuracy of the free-hand placement of pedicle screws (PSs) using a new method of localization of entry points. The PSs are essential in modern spinal surgery but their placement can be technically demanding. To improve this accuracy, numerous aids have been developed, some of them technologically advanced. Despite advances in technology the free-hand technique is still very popular. A simple geometric method of localization of entry points is proposed, designed to improved anatomic orientation. The radiographic and clinical data of 92 consecutive patients who underwent primary placement of PS in the lumbar spine were retrospectively analyzed. Postoperative computed tomography scans were used to assess the accuracy of screw placement using both quantitative and anatomic criteria. A total of 85 patients with 410 screws were included in the study. Twenty screws were malpositioned, thus the overall accuracy was 95.12%. Of all levels instrumented the breach rate for the L1 level was highest (21.43%) and the difference was statistically significant. Two screws in 2 patients were symptomatic, causing radicular pain. Both underwent successful revisions. The proposed method of PS placement is safe and reliable for all levels from L2 to S1, with the accuracy similar to image-guided navigation systems.