Does Interbody Support at L5-S1 Matter in Long Fusions to the Pelvis? A 5 Year Analysis

2019

Summary

Current literature has not definitively shown that the use of interbody support is better than posterior correction alone in deformity surgery. This study compared the 5yr clinical and radiographic outcomes between PSF alone and interbody support. This study demonstrates that compared to posterior spinal fusion alone, interbody fusion at L5-S1 results in superior short-term sagittal alignment and lower rates of revision for proximal junctional failure in adult deformity patients undergoing long fusions to the pelvis.

Hypothesis

When compared to PSF alone, interbody support at L5-S1 is not associated with superior clinical or radiographic outcomes at 5yr followup.

Design

Retrospective cohort study of prospectively collected data from a single surgical spine practice

Introduction

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 actual clinical benefit of interbody use to assist with deformity correction relative to PSF. This study will compare the 5yr clinical and radiographic outcomes and complications between long fusion constructs with L5-S1 interbody support vs. PSF alone.

Methods

88 consecutive adults with spinal deformity who underwent at minimum T10-pelvis PSF and had 5yr follow-up were included. Two cohorts were created based on technique used at the lumbosacral junction (L5-S1): 1) No interbody (PSF; n=23) or 2) ALIF or TLIF (I; n=65). Radiographic measurements and clinical outcome measures (VAS,ODI) were compared preop, postop and at 5 years. Complications including hardware failure, nonunion, seroma, infection, and revision surgery were recorded.

Results

There were no differences in baseline patient characteristics between cohorts. Initial postop sagittal alignment (SVA) was better in the interbody group (PSF: 6.46cm, I:2.48cm, p=0.007). At 5yr follow-up there was no significant difference in coronal balance or SVA (PSF: 6.53cm, I:5.86, p=0.753). One nonunion occurred at L5-S1 in the PSF group (p=0.091). No significant differences in proximal junctional kyphosis (PJK) (PSF:7/23, I:9/65, p=0.076). However, proximal junctional failure requiring revision surgery (PJF) was more frequent in the PSF only group (PSF:6/23, I:6/65, p=0.043). No significant differences in complications including: rod fracture (PSF:5, I: 8, p=0.201), infection (PSF:1, I:2, p=0.714), or overall revision surgery (PSF:10, I:29, p=0.810). At final follow-up there were no significant differences in VAS or ODI between cohorts; all cohorts had improvement from baseline scores.

Conclusion

Compared to PSF alone, interbody fusion at L5-S1 results in superior short-term sagittal alignment and lower rates of revision for PJF in adult deformity patients undergoing long fusions to the pelvis.