title: Return of motor evoked potentials after knee flexion in the setting of high-grade spondylolisthesis.
abstract: To present a case of loss of motor-evoked potentials (MEPs) to the left foot in the supine position after a partial reduction and instrumented fusion from L4 to pelvis which was managed successfully without revision or removal of implants.
  
  
  
  We report a patient with high-grade spondylolisthesis who demonstrated loss of motor-evoked potentials after posterior spinal fusion and transfer to supine position. The patient's knees were flexed to 90° and signals were immediately restored. Systemic steroids were administered and circumferential fusion was delayed 21 days. Anterior-interbody cage was placed without complication.
  
  
  
  She was discharged on post-operative day 2. At 7 months, she is pain free and doing well with plans to return to gymnastics completely.
  
  
  
  Knee flexion can be instituted when encountering a neuromonitoring signal change following posterior spinal fusion for spondylolisthesis as a means to alleviate acute nerve stretch injury and may in some cases prevent the need to lessen the correction.
  
  
  
  IV.
authors.affiliation: Department of Orthopaedic Surgery, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
authors.forename: Justin
authors.initials: J
authors.lastname: Tilan
authors.affiliation: Children's Orthopaedic Center, Children's Hospital Los Angeles, 4650 Sunset Blvd, MS#69, Los Angeles, CA, 90027, USA.
authors.forename: Lindsay M
authors.initials: LM
authors.lastname: Andras
authors.affiliation: Department of Neurosurgery, Children's Hospital Los Angeles, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Krieger
authors.affiliation: Children's Orthopaedic Center, Children's Hospital Los Angeles, 4650 Sunset Blvd, MS#69, Los Angeles, CA, 90027, USA. dskaggs@chla.usc.edu.
authors.forename: David L
authors.initials: DL
authors.lastname: Skaggs
mesh_terms: D002648:Child; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008159:Lumbar Vertebrae / Q000503:physiopathology / Q000601:surgery; D016059:Range of Motion, Articular / Q000502:physiology*; D013123:Spinal Fusion; D013168:Spondylolisthesis / Q000145:classification / Q000503:physiopathology / Q000601:surgery*; D016683:Supine Position
keywords: Knee flexion; Neurologic deficit; Neuromonitoring change; Spondylolisthesis