Minimally Invasive Lumbopelvic Fixation for Unstable U-Type Sacral Fractures

Multi-planar transverse, U-type, and vertical sacral fractures occur from high energy trauma or as pathologic fractures and often have associated neurologic and extremity injuries. Modern treatment algorithms fall into two broad categories: 1) percutaneous posterior pelvic fixation (iliosacral or transiliac-transsacral screws) or 2) lumbopelvic fixation. Posterior pelvic screw fixation is minimally invasive but typically requires restricted weight bearing until fracture union. In many cases, lumbopelvic fixation allows for a closed reduction and provides stability to allow full weight bearing immediately after surgery; however, this fixation is often removed in a second surgery after fracture healing. Lumbopelvic fixation was originally described as an open procedure, minimally invasive lumbopelvic fixation is a recent variation and has shown promising results with less morbidity. We present a case series of unstable U-type sacral fractures treated with minimally invasive lumbopelvic fixation with staged hardware removal to illustrate the advantages and complications associated with this new technique. Ten patients with U-type sacral fractures underwent minimally invasive lumbopelvic fixation from 2016 to 2019. Six patients underwent scheduled hardware removal an average of 3.5 (range 1.9-5.5) months after index surgery. Two patients did not undergo hardware removal due to short life expectancy and diagnosis of pathologic fractures. One patient was lost to follow-up. One patient had failed fracture reduction and went on to sacral malunion that required a late sacral extension osteotomy to restore her ability to stand upright. Final disposition of all nine patients with follow-up was normal standing upright posture and normal ambulation without assistive device. There were no late displacements on postoperative upright radiographs. Complex sacral fractures are a challenging injury that can be treated with percutaneous posterior pelvic or lumbopelvic fixation. Lumbopelvic fixation offers the advantages of closed reduction to restore pelvic incidence and immediate weight bearing but has greater surgical morbidity than percutaneous posterior pelvic fixation and often requires hardware removal. The morbidity of lumbopelvic fixation may be reduced with minimally invasive techniques. Minimally invasive lumbopelvic fixation is a treatment option to be considered for complex sacral fractures.