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Degenerative spondylolisthesis (DS) with lumbar spinal stenosis (LSS) is commonly treated with decompression and fusion. The LimiFlex Dynamic Sagittal Tether (DST) is an investigational stabilization device for patients with DS and LSS. The purpose of this study is to assess the clinical and radiographic outcomes of decompression and DST compared to transforaminal lumbar interbody fusion (TLIF) for patients with DS and LSS. Multicenter prospective concurrently controlled study. Patients undergoing treatment (decompression and DST or TLIF stabilization) of Grade I Meyerding lumbar degenerative spondylolisthesis. Patients undergoing treatment (decompression and DST or TLIF stabilization) of Grade I Meyerding lumbar degenerative spondylolisthesis. Patients with single-level Grade I DS with LSS were enrolled in the FDA-IDE study (NCT03115983) comparing decompression with DST and decompression with TLIF. Clinical and radiographic outcomes were assessed at baseline and 6-week, 3, 6, 12 and 24-month follow-up. All propensity score (PS) selected patients who had 24-month follow-up were included in this interim analysis. Summary statistics are reported, as well as paired t-tests to assess within-group changes. At 24 months, 228 PS-selected patients (129DST/99TLIF) had clinical follow-up and 197 (117DST/80TLIF) had radiographic follow-up. Mean characteristics of DST and TLIF groupswere: age 65.5/64.1 yrs; BMI 28.1/30.5; CCI 0.43/0.41, respectively. Mean perioperative outcomes for DST/TLIF were: procedure time 112/189 min; EBL 53/232 mL; LOS 0.7/3.2 nights. A significant reduction at 24 months for mean VAS-leg/hip (79.5 to 22.9), VAS-back (66.8 to 19.0) and ODI (52.8 to 13.2) was reported for DST patients (all p < 0.01) with 91% achieving 15-point ODI improvement. TLIF patients demonstrated similar improvements for VAS-leg (80.6 to 24.4), VAS-back (68.1 to 26.1) and ODI (52.3 to 20.9) (all p < 0.01), with 80% achieving 15-point ODI improvement. While there was no difference at baseline, the DST group had lower ODI at all postoperative timepoints. Within the 24 months, 9% of each group had additional surgery at the index or adjacent level. At 24 months, the DST group had mean reductions of 1.7° ROM and 0.4mm translation in flexion/extension images compared to 3.8° and 1.0mm reductions in the TLIF group. Considering the index and adjacent segments together (IAS), the index segment accounted for 30% of IAS ROM at baseline and 27% at 24 months in the DST group compared to 29% at baseline and 13% at 24 months in the TLIF group. These results suggest that decompression with DST stabilization for spondylolisthesis can achieve significant clinical improvement as is expected with fusion, without an increase in reoperations during the 24 months postoperative period. Similarly, statistically significant improvements in patient-reported outcomes were demonstrated in each group, with lower disability scores in the DTB group at all postoperative timepoints. Imaging demonstrated no increased instability in the DST group with maintained distribution of motion between the index and adjacent segments. While these groups were PS-selected, further analyses should include quantitative comparison between groups with PS-adjusted differences per the predefined composite clinical success criteria for a definitive comparison of outcomes. LimiFlex Dynamic Sagittal Tether (Investigational/Not Approved). [ABSTRACT FROM AUTHOR]