Association between obesity and pseudarthrosis risk following lumbar fusion surgery.

Background Context: Obesity is a known risk factor for various adverse health conditions and surgical complications, including in spine surgery. While obesity is associated with increased perioperative risks in lumbar fusion surgery, its impact on long-term fusion success remains controversial.

Purpose: To evaluate the effect of obesity on fusion outcomes following posterior lumbar fusion surgery, with a specific focus on the incidence of pseudarthrosis at multiple postoperative time points.

Study Design: Retrospective cohort study.

Patient Sample: Patients were identified through the TriNetX Global Collaborative Network using ICD-10-PCS and CPT codes specific to lumbar fusion procedures. After propensity score matching for demographic and comorbidity variables, 41,436 obese patients (BMI ≥ 30 kg/m) were compared with 41,436 nonobese patients (BMI < 30 kg/m).

Outcome Measures: The primary outcome was the incidence of pseudarthrosis, identified using ICD-10 code M96.0 at 6 months, 1 year, and 2 years postoperatively.

Methods: Propensity score matching (PSM) was applied to minimize confounding. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the risk of pseudarthrosis between obese and nonobese groups.

Results: The incidence of pseudarthrosis was consistently lower in the obese cohort across all postoperative time points. At 6 months postoperatively, the incidence was 9.2% in obese patients compared to 11.8% in nonobese patients (OR: 0.75, 95% CI: 0.72-0.79). At 1 year, pseudarthrosis occurred in 10.4% of obese patients versus 13.0% in nonobese patients (OR: 0.78, 95% CI: 0.74-0.81). At 2 years, rates were 11.6% in the obese group and 14.1% in the nonobese group (OR: 0.80, 95% CI: 0.76-0.83). These findings indicate a consistent and statistically significant association between obesity and lower odds of pseudarthrosis following lumbar spine fusion surgery.

Conclusions: Despite higher perioperative complication rates typically associated with obesity, our study found that obese patients experienced significantly lower rates of pseudarthrosis following lumbar spine fusion surgery.