Risk factors for screw breach and iatrogenic nerve injury in percutaneous posterior pelvic ring fixation.

Background: Percutaneous screw fixation of the posterior pelvic ring is technically demanding and can result in cortical breach. The purpose of this study was to examine risk factors for screw breach and iatrogenic nerve injury.

Methods: A retrospective review at a single level-one trauma center identified 245 patients treated with 249 screws for pelvic ring injuries with postoperative computed tomography (CT) scans. Cortical screw breach, iatrogenic nerve injury, and associated risk factors were evaluated.

Results: There were 86 (35%) breached screws. The breach rate was similar between screw types (33% S1-iliosacral (S1-IS), 44% S1-transsacral (S1-TS), 31% S2-IS, and 30% S2-TS) and was not associated with patient characteristics, Tile C injuries, or corridor size or angle. The overall rate of screw revision for screw malpositioning was 1.2% (3/249). Iatrogenic nerve injuries occurred in 8 (3.2%) of the 249 screws. Screws that caused iatrogenic nerve injuries had greater screw breach distances (5.4 vs. 0 mm, MD 5, CI 2.3 to 8.7, p < 0.0001), were more likely to be S1-IS screws (88% vs. 47%, PD 40%, CI 7 to 58%, p = 0.006), more likely to be placed in Tile C injuries (75% vs. 44%, PD 31%, CI -3 to 55%, p = 0.04), and there was a trend for having a screw corridor size <10 mm (75% vs. 47%, PD 28, CI -6 to 52%, p = 0.06). Of the 7 iatrogenic nerve injuries adjacent to screw breaches, two nerve injuries recovered after screw removal, three recovered with screw retention, and two did not recover with screw retention.

Conclusion: Screw breaches were common and iatrogenic nerve injuries were more likely with S1-IS screws. Surgeons should maintain a high degree of caution when placing these screws and consider removal of any breached screw associated with nerve injury.