Combined S-1 and S-2 sacral alar-iliac screws as a salvage technique for pelvic fixation after pseudarthrosis and lumbosacropelvic instability

Lumbosacropelvic pseudarthrosis after long spinal fusions for treatment of adult degenerative scoliosis remains a challenging condition. Moreover, although pelvic fixation with iliac screws is widely used in deformity surgery to provide a biomechanically strong distal anchor for long thoracolumbar constructs, there are very few options available after failed pelvic fixation with iliac screws. The authors conducted a retrospective review of the surgical charts and imaging findings of patients subjected to revision surgery for lumbosacropelvic pseudarthrosis from August 2011 to August 2012. This review identified 5 patients in whom a salvage technique combining both S-1 and S-2 sacral alar-iliac (SAT) screws had been performed. In this technical note, the authors present a detailed anatomical discussion and an appraisal of the sequential intraoperative steps of this new technique involving a combination of S-1 and S-2 SAI screws. The discussion is illustrated with a surgical case in which this technique was used to treat a patient with pseudarthrosis that had developed after fixation with classic iliac screws. In conclusion, although S-2 SAI screws have previously been reported as an interesting alternative to classic iliac wing screws, this report is the first on the use of combined S-1 and S-2 SAI screws for pelvic fixation as a salvage technique for lumbosacropelvic instability. According to the reported experience, this technique provides a biomechanically robust construct for definitive pelvic fixation during revision surgeries in the challenging scenarios of pseudarthrosis and instability of the lumbosacropelvic region.