DECOMPRESSION VERSUS DECOMPRESSION PLUS FUSION FOR STABLE DEGENERATIVE LUMBAR SPONDYLOLISTHESIS: COMPARING PATIENT OUTCOMES USING MATCHED OBSERVATIONAL DATA

Recent studies have challenged the superiority of decompression plus fusion (D+F) compared to decompression alone (D) for patients with degenerative lumbar spondylolisthesis (DLS). It is not clear if differences in outcome are generally applicable to all DLS patients or specific subgroups. Stable DLS is one such subgroup. The objective of this study was to estimate the treatment effect of D versus D+F for a stable subgroup of DLS patients using matched observational data. We also estimated the proportion of patients in each treatment group achieving a minimal clinically important improvement at 2-years. This was an analysis of data from patients with a stable DLS in the Canadian Spine Outcomes and Research Network DLS prospective cohort. A stable DLS was defined as A propensity score was estimated for each patient using a logistic regression model (0=D, 1=D+F) fitted to a range of pre-treatment covariates. Pre-treatment covariates included age, sex, body mass index, education, working status, medical comorbidities, symptom duration, medication use, back pain rating, leg pain rating, depression rating, Pfirrman disc grade, pelvic incidence and lumbar lordosis, Oswestry Disability Index (ODI), 12-Item Short Form Survey physical component score (PCS), and EuroQol Visual Analogue Scale (EQ VAS). Based on the propensity score, patients receiving D were matched 1:1 to patients receiving D+F using the genetic matching method with a caliper width equal to 0.1 of the standard deviation of the logit of the propensity score. Standardized differences Between-group differences in improvement in ODI (0 best to 100 worst), PCS (0 worst to 100 best), and EQ VAS (0 worst to 100 best) were estimated at 2-year follow-up using linear mixed models adjusted for any pre-treatment covariates that remained unbalanced after matching. We additionally examined the proportion of patients in each group achieving a minimal clinically important improvement at 2-years. A total of 228 patients were included, of which 124 were matched (62 in each treatment group). All pre-treatment covariates were balanced between groups (standardized differences 2 years; these were then included in the outcome model. No statistically significant differences between groups were found at 2-year follow-up on the ODI (mean difference −3.6; 95% CI −9.3 to 2.1), SF−12 PCS (mean difference 3.2; 95% CI −0.7 to 7.1) or EQ VAS (mean difference 1.3; 95% CI −6.1 to 8.8). The proportion achieving a clinically significant improvement at 2-year follow-up on the ODI was 67.3% in the D group versus 71.4% in the D+F group. From this well-matched study, we report no statistically or clinically significant effect in favour of D+F over D across all outcomes for stable DLS. These findings provide further real-world evidence that the addition of fusion is not necessary for DLS patients with < 5 mm of slip motion and a neutral or lordotic disc angle.