Outcomes of primary versus revision TLIF following decompression alone in degenerative spondylolisthesis: a retrospective propensity score matched study.

Background: Degenerative grade 1 spondylolisthesis is associated with lumbar instability, typically addressed with decompression and fusion to prevent iatrogenic instability. The SLIP trial indicated that decompression-only patients benefit significantly from early reoperation for instability. Yet, it's unclear how these revision patients' outcomes compare to those undergoing primary fusion.

Purpose: To evaluate whether outcomes were inferior among patients receiving revision transforaminal lumbar interbody fusion (TLIF) after prior decompression in the setting of degenerative, grade 1 spondylolisthesis when compared to those undergoing primary TLIF for grade 1 spondylolisthesis.

Study design/setting: Retrospective cohort study.

Patient sample: Patients with grade 1 spondylolisthesis at L4-L5 or L5-S1 who underwent TLIF between 2018 and 2023 and had complete 1Y clinical follow-up and 6-month (6M) patient reported outcomes(PROs) were included.

Outcome measures: PROs (ODI, PROMIS, SF-12, VAS Pain) and Clinical (Readmission and Reoperation at 6-week [6W], 6M, and 1Y).

Methods: No predictors for missing data were identified. Comparisons were made between primary fusion patients and those with prior decompression now undergoing revision TLIF. Bias was minimized via 2:1 propensity score matching (PSM) for age, comorbidities (CCI), slip percentage, slip translation, angular change, anterior and posterior disc height (ADH and PDH respectively), facet diastasis and cysts, and facet orientation-termed spondylolisthesis characteristics. Unmatched PROs and clinical outcomes were analyzed with a mixed-effects (ME) model and chi-Squared test, while matched PROs and clinical outcomes employed an ME model and conditional logistic regression.

Results: About 285 patients (55.4% female, mean age 60.80±0.73, CCI of 2.10±0.09, and 35.1% current/former smokers) were included. Spondylolisthesis slip was 13.11%±0.99% with mean translation in flexion/extension of 1.60±0.19 mm. Compared to revision patients (N=42, 14.7%), primary fusion patients (N=243, 85.3%) were younger (59.70±0.77 vs. 67.20±1.76) and had a lower prevalence of active smoking (2.48% vs. 11.90%), but showed no differences in slip percentage (p=.480), translation in flexion/extension (p=.778), ADH (p=.578), PDH (p=.991), facet diastasis (p=.132), facet cysts (p=.550), or angular change across L3-S1. Preoperatively, PROs were comparable across all domains. At 1-year postop, no differences were observed in back pain (p=.430), leg pain (p=.346), SF-12 PCS (p=.976), MCS (p=.737), PROMIS Score (p=.063), or ODI (p=.362). The PSM cohort, matched for age, CCI, and spondylolisthesis characteristics, showed standardized differences of less than 0.10 for all demographics, baseline PROs, and spondylolisthesis characteristics, aside angular change at L5-S1 (3.05 vs. 7.08, p=.062). At 1 year postop, there were no differences in back pain (2.62 vs. 2.10, p=.414), leg pain (2.15 vs. 1.48, p=.270), SF-12 PCS (43.02 vs. 43.38, p=.888), SF-12 MCS (51.31 vs. 52.80, p=.553), PROMIS Score (45.69 vs. 44.81, p=.630), and ODI (18.66 vs. 15.26, p=.375). Finally, no significant differences were found in early (6W) or long-term (6M to 1Y) complications, with 98.1% primary and 90.5% revision patients complication-free at 6W, and 93.6% versus 100.0%, respectively, from 6M to 1Y.

Conclusion: Following decompression alone for grade 1 spondylolisthesis, patients having revision TLIF after decompression exhibit patient-reported and clinical outcomes similar to those undergoing primary TLIF.