Does Interbody Support at L5-S1 Matter in Long Fusions to the Pelvis?

Abstract

Study Design. Retrospective review of prospectively collected data. Objective. To determine if the addition of L5-S1 interbody support in long fusion deformity constructs is associated with superior long-term clinical and radiographic outcomes. To compare the 5-year clinical and radiographic outcomes and complications between long fusion constructs with L5-S1 interbody support versus posterolateral fusion (PLF) alone. Summary of Background Data. Cadaveric biomechanical studies have suggested that an interbody fusion at L5-S1 is beneficial in long fusion constructs with sacropelvic fixation. However, there is limited data reflecting the superiority of interbody support augmentation in optimizing arthrodesis and deformity correction relative to PLF alone. Methods. Eighty-eight consecutive adults with spinal deformity who underwent at minimum T11-pelvis posterior pedicle screw instrumentation with 5-year follow-up were included. Two cohorts were compared based on technique used at the lumbosacral junction (L5-S1): (A) no interbody (PLF; n ¼ 23), or (B) interbody support at L5-S1 (IB; n ¼ 65). Radiographic measurements and clinical outcome measures were compared at multiple time points. Complications were recorded and compared.Results. No differences in baseline patient characteristics between cohorts. One nonunion occurred at L5-S1 in the PLF group (P ¼ 0.091). Initial postop sagittal alignment was better in the IB group (PLF: 6.46 cm, IB: 2.48 cm, P ¼ 0.007); however, this was not maintained over long-term follow-up. No significant differences in proximal junctional kyphosis (PLF: 7/23, IB: 9/65, P ¼ 0.076). Proximal junctional failure was more frequent in the PLF group (PLF: 6/23, IB: 6/65, P ¼ 0.043). No significant differences in complications were found. Both cohorts had improvement from baseline pain and functional scores. Conclusion. There is no absolute long-term advantage for lumbar interbody support in adult spinal deformity patients undergoing spinal arthrodesis to the pelvis.

Revision Free Loss of Sagittal Correction > 3 Years After Adult Spinal Deformity Surgery

“…Specifically, IBF rates at L1-L4 were similar between the M and L cohorts despite the fact that the L cohort lost lordosis in this region. While this does not seem to make intuitive sense, past investigations on L5-S1 IBFs in long constructs have demonstrated similar findings 7,23 . In contrast to 1-2 level fusions, IBF may not impart as much mechanical stability in longer constructs due to how stress is distributed over a larger area 24 .…”

“…While this does not seem to make intuitive sense, past investigations on L5-S1 IBFs in long constructs have demonstrated similar findings. 7,23 In contrast to 1-2 level fusions, IBF may not impart as much mechanical stability in longer constructs due to how stress is distributed over a larger area. 24 This proposed concept is similar to the use of lag screws for simple oblique fractures versus long bridge plates for comminuted fractures.…”

What Are the Benefits of Lateral Lumbar Interbody Fusion on the Treatment of Adult Spinal Deformity: A Systematic Review and Meta-Analysis Deformity

“…Some previous studies have reported that the addition of L5-S1 interbody fusion would not significantly benefit the restoration of LL in patients with ASD who underwent long fusion to the sacrum and sacropelvic fixation. [40][41][42] Hence, the significantly greater spinopelvic correction in the LLIF+PSF group is more likely attributed to the more segmental lordosis obtained at the LLIF levels cranial to L5-S1. In addition, these superior acquisitions in regional spinopelvic parameters affected the global sagittal balance, which was reflected by the significantly greater restoration of SVA.…”