Risk factors for neurophysiological events related to intraoperative halo-femoral traction in spinal deformity surgery

Purpose: This study identifies risk factors for neurophysiological events caused by intraoperative halo-femoral traction (IOHFT) in patients with adolescent idiopathic scoliosis (AIS), and neuromuscular scoliosis (NMS). Methods: Neurophysiological integrity was monitored using motor evoked potentials (MEPs). IONM event was defined as a decreased MEP amplitude of more than 80% of baseline in, at least, one muscle. Time between application of IOHFT and event, affected muscles, surgical stage, and time between removal of IOHFT and recovery of MEPs were described. Characteristics (age, height, weight, diagnosis, Cobb angle, and flexibility of the curve) of patients with and without IOHFT-events were compared using analysis of variance. Binary logistic regression analyses were performed to identify predictors. Results: The study included 81 patients (age 15.6 ± 2.4 years, 53 females, AIS: n = 47, NMS n = 34). IOHFT-events occurred in 11 patients (13%; AIS n = 4, NMS n = 7). IOHFTevents affecting all limbs occurred pre-incision in NMS. Events affecting only the legs occurred during all stages of surgery. Patients with IOHFT-events were smaller (p = 0.009) and had stiffer curves (p = 0.046). Height was a predictor (odds ratio, 0.941; 95% confidence interval = 0.896–0.988). All MEPs recovered after removing IOHFT. Conclusion: Neurophysiologic events due to IOHFT were common, with the majority in patients with NMS. A shorter stature was a risk factor, and larger Cobb angle and stiffer curve were associated with IOHFT-events. Events occurred at any stage of surgery and involved upper and lower limbs. With an adequate response on IOHFT events, none of the patients had postoperative neurological impairments due to IOHFT.