Impact of obesity on adult spinal deformity (ASD) long-segment spinal fusion radiographic and clinical outcomes

Study design: Retrospective chart review of patients receiving long -segment fusion during a five-year period. Objective: To determine whether obese patients receive comparable benefits when receiving long -segment fusion compared to non -obese patients and to identify factors that may predict hardware failure and post -surgical complications among obese patients. Methods: Demographic, spinopelvic radiographic, patient -reported outcome measures (PROMs), and complications data was retrospectively collected from 120 patients who underwent long -segment fusion during a five-year period at one tertiary care medical center. Radiographic measurements were pelvic incidence, pelvic tilt (PT), lumbar lordosis, L4 -S1 lordosis, thoracic kyphosis, sagittal vertical axis, PI -LL mismatch, and proximal junction cobb angle at upper instrumented vertebrae + 2 (UIV+2). PROMs were Oswestry disability index, numeric rating scale (NRS) Back Pain, NRS Leg Pain, RAND SF -36 pain, and RAND SF -36 physical functioning. Included patients were adults and had at least 2 -years of postoperative follow-up. Descriptive and multivariate statistical analysis was performed with alpha = 0.05. Results: Patients with a BMI >= 30 (n=63) and patients with a BMI < 30 (n=57) demonstrated comparable improvements (P>0.05) for all spinopelvic radiographic measurements and PROMs. Each cohort demonstrated significant improvements from pre -assessment to post -assessment on nearly all spinopelvic radiographic measurements and PROMs (P<0.05), except PT and L4 -S1 lordosis where neither group improved (p=0.95 and 0.58 for PT and P=0.23 and 0.11 for L4 -S1 lordosis fornon-obese and obese cohorts respectively) and SF -36 physical functioning where the non -obese cohort not statistically improve (P=0.08). Patients with a BMI >= 30 demonstrated an increased incidence of cardiovascular complications (P=0.0293), acute kidney injury (P=0.0241), rod fractures (P=0.0293), and reoperations (P=0.0241) when compared to patients with a BMI < 30. Conclusion: This study adds to a growing body of evidence linking demographic factors with risks of hardware failure. Further, this data challenges the assumption that obese patients may not receive sufficient benefit to be long -segment surgical candidates. However, given their elevated risk for post -operative and delayed hardware complications, obese patients should be appropriately counseling before undergoing surgery.