To report the perioperative complication rates in elderly patients undergoing lumbar arthrodesis and to analyze the risk factors. Between Sep 2015 and Jun 2018, 215 patients aged 70 or more underwent posterior lumbar arthrodesis with pedicle screw fixation. Demographic data including age, gender, smoking status, body mass index (BMI) and preoperative comorbidities were collected. Operative records as the number of levels fused, estimated blood loss, time of surgery, and the occurrence of perioperative complications were reviewed. Risk factors of perioperative complications were determined by logistic regression analysis. The total perioperative complication rate in all patients was 30.2%, of which major complications occurred in 24 patients (11.2%) and minor complications occurred in 41 patients (19.1%). Two risk factors of perioperative complications (major or minor) were chosen: BMI (cut-off value 24.32) and surgical level (≥3). Longer surgical level (≥3) and smaller BMI were risk factors of perioperative minor complication, while major complication was only affected by surgical level (≥3). The risk factor of perioperative complication in elderly patients following lumbar arthrodesis was fusion segment (≥3), while BMI was a protective factor. Elderly patients with BMI less than 24.32 are more likely to have perioperative complications after lumbar arthrodesis. Copyright ? 2019. Published by Elsevier Inc.