Dual Osteotomy of S1 and L5 for Revision of an In-situ Fusion of a Peditric Spondyloptosis and Anatomical Consideration

Introduction: High grade pediatric spondylolisthesis and spondyloptosis require appropriate reduction and stabilization. In-situ fusion can lead to an evolving deformity, instrumentation failure and pseudoarthrosis. Here we report a complex case of a pediatric patient with an in-situ fused spondyloptosis and underwent 2 revision surgeries and developed new onset neurological deficit and severe back pain as a young adult.
A 25-year-old female with L5 spondyloptosis presented with severe back pain and left sided L5 palsy. After 3 prior surgeries starting at the age of 13, she had a L3 to pelvis instrumented in-situ fusion. Her radiographs showed 4 fractured S1 screws, two fractured pelvic screws, one TLIF cage that had migrated into the lateral recess and complete iatrogenic sacralization of L5.

Methods: A retrospective chart review was conducted of clinic notes, operative reports, and imaging studies. A literature review of the pertinent anatomy to limit the incidence of L5 palsy was performed

Results: She underwent two posterior surgeries with extension of fusion to L2 and S1 PSO across the L5-S1 disk space to include an osteotomy of L5. She had significant resolution of her left foot drop. SVA corrected from 11.2 cm to 1 cm, with reduction of her L1PA from 50° to 19°. Her thoracic spine relaxed from a 28° lordosis into kyphosis. With a 27% risk of L5 palsy following S1 PSO we did a review of the literature to describe the anatomic risk of causing a L5 palsy.

Conclusion : In-situ fused high-grade spondylolisthesis at L5-S1 can be treated with a S1 PSO with reduction of PI and correction of the sagittal deformity. Risk of L5 palsy is high but a posterior only strategy is viable and although high risk can be perfomed safely.