Risk factors for persistent numbness following decompression surgery for lumbar spinal stenosis

Objective: Decompression surgery is a mainstay of surgical treatment for lumbar spinal stenosis (LSS). However, up to 30% of patients have low satisfaction due to residual symptoms. In the clinical setting, improvements in leg pain are more significant than those in leg numbness. Residual numbness could be related to the relatively low satisfaction rate. However, few studies have focused on numbness; thus, elucidating the risk factors and rate of residual numbness would benefit surgeons and patients. This study aimed to clarify the risk factors for and rate of residual numbness after decompression surgery. Patients and Methods: We retrospectively reviewed prospectively collected data from consecutive patients who underwent lumbar decompression without fusion for LSS at a single institution between January 2014 and March 2016. Patients were included if preoperative and final follow-up questionnaires and radiographs were available. A minimum one-year follow-up was required. We evaluated the Numeric Rating Scale (NRS) scores of low back pain, leg pain, and leg numbness preoperatively and at the final follow-up visit. Residual numbness was defined as a postoperative NRS >= 1, whereas persistent numbness was defined as a postoperative NRS >= 5. We compared the clinical data of patients with or without residual numbness to those of patients with or without persistent numbness. Multivariate logistic regression analysis was performed to identify risk factors for residual and persistent numbness. Results: A total of 116 patients (73 men, 43 women) were included. Of them, 60% had residual numbness with a mean follow-up period of 25 months. Only durotomy differed significantly between patients with and those without residual numbness. However, the significance did not persist after logistic regression analysis. A total of 16% had persistent numbness. Diabetes mellitus, intraoperative durotomy, and preoperative NRS of numbness were identified as risk factors. There were no differences in smoking status, presence of spondylolisthesis or scoliosis, or severity of stenosis. Conclusions: We found three risk factors for persistent numbness following decompression surgery for LSS; diabetes mellitus and durotomy were modifiable, whereas preoperative numbness was not. Our findings would help surgeons minimize the incidence of persistent numbness by adequately controlling diabetes and avoiding durotomy during surgery. Providing information about the potential for residual numbness during the informed consent process is important to ensuring realistic patient expectations.