title: Letters.
authors.affiliation: Comparative Effectiveness, Cost and Outcomes Research, Center, University of Washington, Seattle, WA Department of Economics, University of New Mexico, Albuquerque, NM Department of Neurology, University of California, Los Angeles, Los Angeles, CA E-mail: john.p.ney@uw.edu.
authors.forename: John P
authors.initials: JP
authors.lastname: Ney
authors.forename: David N
authors.initials: DN
authors.lastname: van der Goes
authors.forename: Marc R
authors.initials: MR
authors.lastname: Nuwer
mesh_terms: D017586:Diskectomy / Q000009:adverse effects*; D005260:Female; D006801:Humans; D007796:Laminectomy / Q000009:adverse effects*; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D016343:Monitoring, Intraoperative / Q000379:methods*; D057216:Propensity Score; D013123:Spinal Fusion / Q000009:adverse effects*