Distal Junctional Failure Following Lumbosacral Spinal Fusion: A Novel Classification System

Introduction: While traditional literature examining mechanical complications has revolved around proximal junctional kyphosis/failure, distal junctional failure (DJF) consisting of constructs ending at the sacrum as well those with supplemental pelvic fixation and/or concomitant sacroiliac joint fusion remains less explored.

Methods: A prior review study was completed identifying all types of distal complications for lumbosacral fusions, and a panel of twenty-five senior spinal deformity surgeons used a modified Delphi approach with thee rounds of review to create a classification system. Ten deformity surgeons then reviewed a representative series of 14 de-identified cases to assess the inter-rater reliability of the classification system, with use of the intraclass correlation coefficient (ICC).

Results: Complications were classified as acute ( < 90 days of surgery) or chronic (within ≥3 months of surgery). Acute failures included mechanical failure of the screws and screw-rod interface, such as pelvic set plug dissociation (open vs. closed), tulip head dissociation (open vs. closed), and fracture of the pelvic screw at any point along its trajectory. Fractures of the rod (proximal vs. distal to S1) and distal bony anatomy (sacrum vs. pelvis) were included, as was failure of the offset connector. Chronic failures also consisted of pseudarthrosis at distal levels, sacroiliac joint (SIJ) pain, screw halo formation (symptomatic vs. asymptomatic), and painful screw prominence. The ICC for classifying DJF with this scheme was 0.98, demonstrating very high interrater reliability.

Conclusion : These data provide a comprehensive and systematic classification scheme of distal complications following lumbosacral fusion, and will hopefully improve the consistency of reporting surgical outcomes following lumbosacral fusion with or without supplemental pelvic fixation and/or concomitant sacroiliac joint fusion. This classification scheme resulted in outstanding interrater reliability.