Mild and Severe Obesity Reduce the Effectiveness of Lumbar Fusions: 1-Year Patient-Reported Outcomes in 8171 Patients.

Abstract

Elevated body mass index (BMI) is a well-known risk factor for surgical complications in lumbar surgery. However, its effect on surgical effectiveness independent of surgical complications is unclear. To determine increasing BMI's effect on functional outcomes following lumbar fusion surgery, independent of surgical complications. We retrospectively analyzed a prospectively built, patient-reported, quality of life registry representing 75 hospital systems. We evaluated 1- to 3-level elective lumbar fusions. Patients who experienced surgical complications were excluded. A stepwise multivariate regression model assessed factors independently associated with 1-yr Oswestry Disability Index (ODI), preop to 1-yr ODI change, and achievement of minimal clinically important difference (MCID). A total of 8171 patients met inclusion criteria: 2435 with class I obesity (BMI 30-35kg/m2), 1328 withclass II (35-40kg/m2), and 760 with class III (≥40kg/m2).IncreasingBMI wasindependently associated with worse 12-mo ODI(t=8.005, P <.001) and decreased likelihood of achievingMCID (odds ratio [OR]=0.977,P <.001). One year after surgery, mean ODI, ODIchange,and percentage achieving MCID worsened withclass I, class II, and class III vsnonobese cohorts (P <.001) in stepwise fashion. Increasing BMI is associated with decreased effectiveness of 1- to 3-level elective lumbar fusion, despite absence of surgical complications. BMI≥30kg/m2 is, therefore, a risk factor for both surgical complication and reduced benefit from lumbar fusion.