Standalone Anterior Lumbar Interbody Fusion Without Supplementary Posterior Fixation Is Effective for Treatment of Symptomatic Grade 1 Isthmic Spondylolisthesis

<h3>Background</h3> There is a paucity of data examining anterior lumbar interbody fusion (ALIF) with pedicle-screw fixation (ALIF-PSF) or without (standalone, sa-ALIF) for the treatment of low-grade isthmic spondylolisthesis (IS). Treating pathology with sa-ALIF reduces costs, operative times, and posterior access morbidity. This study aimed to investigate the clinical and radiographic outcomes of sa-ALIF for the management of low-grade IS compared with an ALIF-PSF cohort. <h3>Methods</h3> Retrospective analysis of prospectively collected data. Consecutive patients from 1 senior spine surgeon performing sa-ALIF or ALIF-PSF for management of low-grade IS. Patient-reported outcome measures (PROMs) were collected at baseline, then postoperatively at 6 weeks, 6 months, 12 months, and a final follow-up timepoint. Computed tomography was conducted at 6 months, 12 months, or until interbody fusion was confirmed. <h3>Results</h3> Two cohorts comprised 51 patients (sa-ALIF 22 and ALIF-PSF 29). Both cohorts’ PROMs improved from baseline to 12 months postoperatively. There were no significant differences (<i>P</i> = 0.05) in PROMs between the 2 cohorts at 6 months postoperatively, 12 months postoperatively, or at a final follow-up timepoint. There were no significant differences in mean fusion rates 12 months postoperatively (sa-ALIF 82% and ALIF-PSF 88%). Compared with preoperative measurements in sa-ALIF and ALIF-PSF cohorts, listhesis and segmental lordosis showed no significant changes, while disc height significantly increased (<i>P</i> = 0.0001). There were no significant differences in disc L5/S1 radiographic measurements between the cohorts at 12 months. There were 12 complications (sa-ALIF 2 and ALIF-PSF 10). Only 1 patient in the ALIF-PSF cohort required revision surgery. <h3>Conclusions</h3> In appropriately selected patients with normal bone density, sacral slope &lt;40°, and a body mass index &lt;35, sa-ALIF is a safe and effective treatment option for grade I IS. The additional morbidity and cost of PSF may not be justified given the satisfactory clinical and radiographic outcomes of sa-ALIF for grade I IS. <h3>Clinical Relevance</h3> Clinically, this research continues to suggest that sa-ALIF is a safe and effective method of treatment for low grade IS. <h3>Level of Evidence</h3> 4.