Impact of body mass index on surgical outcomes and complications in adult spinal deformity

Several studies have reported that overweightness and obesity are associated with higher complication rates in lumbar spine surgery. However, little is known about the effect of obesity on postoperative complications in adult spinal deformity (ASD) surgery, especially in the elderly. This study aimed to examine the effect of body mass index (BMI) on surgical outcomes and postoperative complications in elderly ASD patients undergoing surgical correction in Japan.We conducted a retrospective, multicenter, observational study of 234 consecutive patients diagnosed with ASD who underwent corrective surgery. Patients were divided into two groups according to BMI, BMI25 (153 patients, mean age 71.9 years) and BMI ≥ 25 (overweight/obese, 81 patients, mean age 73.3 years). Radiographic results and perioperative complications were compared between the two groups.Surgical complications occurred in approximately 20% of patients in each group; complications did not significantly differ between the two groups. A greater proportion of patients in the BMI ≥ 25 group experienced mechanical failure and DJK, although the difference was not significant. Preoperative mean lumbar lordosis (LL), pelvic incidence (PI) minus LL, sacral slope (SS) and sagittal vertical axis (SVA) were similar in the BMI 25 and BMI ≥ 25 groups. However, the BMI ≥25 group had lower mean LL (p = 0.015) and higher PI minus LL (p = 0.09) postoperatively. The BMI ≥25 groups also had significantly smaller LL (p = 0.026), smaller SS (p = 0.049) and higher SVA (p = 0.041) at the final follow-up, compared to the BMI 25 group.In the present study, no difference in medical or surgical complications after ASD surgery was found between overweight/obese patients (BMI ≥ 25) and those with BMI 25. However, correction of LL and SVA was smaller in patients with overweight/obese patients.