P148. Treatment of the fractional curve with interbody fusion L4-S1 versus posterior fusion alone: impact on surgical outcomes and complications

Abstract

<h3>BACKGROUND CONTEXT</h3> The fractional curve is the curve below the major curve of a lumbar or thoracolumbar scoliosis, and while it is often the primary driver of the adult spinal deformity patient's decision to proceed with surgery, a treatment strategy to identify and address the fractional curve is not widely examined. There is a paucity of data evaluating the ideal strategy to correct the lumbosacral fractional curve in ASD surgery. <h3>PURPOSE</h3> We sought to evaluate the impact of interbody fusion at L4-L5 and/or L5-S1 compared with posterior fusion alone on fractional curve correction, and rate of instrumentation related complications at the lumbosacral junction. <h3>STUDY DESIGN/SETTING</h3> Retrospective review of prospectively collected single center database. <h3>PATIENT SAMPLE</h3> A total of 592 ASD patients (Age: 48 ± 23 y; mFI: .4 ± .7; Levels fused: 10.3 ± 4.1). <h3>OUTCOME MEASURES</h3> Outcomes evaluated were fractional curve correction, overall deformity correction and rates of revision surgery for pseudarthrosis or rod fracture at the lumbosacral junction. <h3>METHODS</h3> A total of 592 ASD patients (Age: 48 ± 23 y; mFI: .4 ± .7; Levels fused: 10.3 ± 4.1), lumbosacral fractional curve > 10°, mean followup 39.5 months, were divided into 2 groups: PSF alone (PSF, n=382) and interbody fusion (IBF, n=210; ALIF: 31, TLIF: 179). Outcomes evaluated were fractional curve correction, overall deformity correction and rates of revision surgery for pseudarthrosis or rod fracture at the lumbosacral junction. <h3>RESULTS</h3> A significantly greater number of patients in the IB cohort had underlying osteoporosis (63% versus 33%, p < 0.001); otherwise, there were no significant difference in patient comorbidities. There was significantly greater EBL (2.3 L vs. 1.3 L, p < 0.0001), intraoperative pRBCs transfused (2.3 U vs. 1.3 U, p < 0.001), and longer operative time (7.1 vs. 6.3 hours, p < 0.0001) in the IBF group compared with PSF. Both groups had similar magnitude of fractional curve correction (7.0 ±7.1° in IB vs. 6.3 ± 6.9° in PSF, p=0.26) and final coronal alignment (23.5 mm vs. 19.8 mm, p=0.08). Patients in the IBF group had a higher magnitude of SVA change (−30.6 mm vs -19.5 mm, p < 0.05) and increase in lumbar lordosis (11.5° vs 5.6°, p < 0.001). There was no difference in the rate of revision surgery at minimum 2-year followup for rod fracture, pseudarthrosis, or any instrumentation related complication. Sub-analysis demonstrated that there were no significant differences in magnitude of fractional curve correction, or improvement in lumbar lordosis, coronal, or sagittal alignment in the ALIF group compared to the TLIF group. There was no significant impact of number of levels at which a lumbar interbody fusion was performed on the degree of fractional curve correction. <h3>CONCLUSIONS</h3> At minimum 2-year followup, patients had comparable fractional curve and coronal alignment correction when treated with interbody fusion at L4-S1 versus posterior fusion alone. There was no difference in rod fracture and pseudarthrosis rates at 2-year followup. These data suggest that utilization of interbody technique at the lumbosacral junction is not clearly superior to posterior fusion alone for treatment of the fractional curve. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.