Comparing Radiographic Parameters for Single-Level L5-S1 Interbody Fusion: Anterior Lumbar (ALIF) Versus Transforaminal Lumbar Interbody Fusion (TLIF)

Abstract

Abstract INTRODUCTION The lumbosacral junction acts as a transition point between the mobile lumbar spine and the rigid pelvis. It is thereby susceptible to degenerative changes necessitating fusion at L5-S1. In this study, we compared radiographic outcomes observed from single-level anterior lumbar interbody fusion (ALIF) and transforaminal lumbar interbody fusion (TLIF) at this level. METHODS Retrospective review of single-level ALIF and TLIF with up to one level PSF at L5-S1 between May 2007 and October 2018 was undertaken. X-ray measurements were gathered for lumbar lordosis, segmental lordosis, pelvic tilt, sacral slope, pelvic incidence, pelvic incidence-lumbar lordosis mismatch, anterior/posterior disc height, and sagittal vertical axis. Computed tomography /magnetic resonance imaging was used to determine central canal area, sagittal diameter, foraminal height, and foraminal area. RESULTS A total of 47 ALIF patients and 50 TLIF patients were included. Patients averaged 53.7 ± 10.1 yr of age for ALIF and 49.4 ± 14.7 yr old for TLIF (P = .094) with significant differences (P = .0017) seen with gender as ALIF had 60.4% males and TLIF 70.0% females. Single-level ALIF led to significantly (P = .0010) more segmental lordosis (+5.75° ± 7.31°) than TLIF (+0.25° ± 6.55°), though differences in lumbar lordosis were not statistically significant (P = .52). ALIF significantly increased both anterior (+10.4 ± 4.32 mm vs +4.30 ± 3.55 mm; P < .0001) and posterior disc height (+4.33 ± 3.32 mm vs + 2.98 ± 2.07 mm; P = .043) than TLIF. Changes in sagittal vertical axis also significantly differed (P = .030) with ALIF decreasing sagittal vertical axis by 17.8 ± 26.4 mm from +60.3 mm to + 42.5 mm, and TLIF increasing by 0.95 ± 25.8 mm from 39.9 mm to 40.9 mm. Pelvic tilt, sacral slope, pelvic incidence, pelvic incidence-lumbar lordosis mismatch had no significant differences. No statistically significant differences were observed with central canal area, sagittal diameter, foraminal height or foraminal area between ALIF and TLIF. CONCLUSION At L5-S1, the ALIF approach leads to increased segmental lordosis, disc height, while also decreasing sagittal vertical axis to a significant degree than TLIF. However, these two approaches were no different with regards to pelvic parameters and measures of central canal and foraminal decompression.