title: Sonoanatomy of the lumbar spine in patients with previous unintentional dural punctures during labor epidurals.
abstract: OBJECTIVE
  Preprocedural lumbar ultrasound is a valuable tool to assess anatomical landmarks and predict the depth of the epidural space. Variations of the ligamentum flavum sonoanatomy are occasionally observed; however, no literature is available as to their incidence or clinical significance. We hypothesize that abnormal sonoanatomy of the lumbar spine detected by ultrasound can be associated with an increase in unintentional dural punctures. This study was undertaken to determine if the sonoanatomy of the lumbar spine of patients who had documented unintentional dural punctures differs from that of patients with a history of uneventful epidural placement for labor analgesia.
  
  
  METHODS
  Ultrasound of the entire lumbar spine was performed on 18 patients with a documented history of unintentional dural punctures, and 18 volunteers with a history of uneventful labor epidurals. At each interspace, we studied the quality of the ligamentum flavum (normal or abnormal), the symmetry of the bony structures (symmetric or asymmetric), and the distance from the skin to the ligamentum flavum. These parameters were compared in both groups.
  
  
  RESULTS
  The incidence of asymmetric sonoanatomy and the distance from the skin to the ligamentum flavum was similar in both groups. The incidence of abnormal ligamentum flavum sonoanatomy was higher in the dural puncture group (overall odds ratio for the 5 interspaces was 8.21, 95% confidence interval 3.07-22.0, P < .0001).
  
  
  CONCLUSIONS
  Abnormal sonoanatomy of the ligamentum flavum may represent anatomical variations of this structure, which may be related to an increased incidence of unintentional dural punctures during epidural placements.
authors.affiliation: Department of Anesthesia and Pain Management, Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Yung
authors.initials: Y
authors.lastname: Lee
authors.forename: Motoshi
authors.initials: M
authors.lastname: Tanaka
authors.forename: Jose C A
authors.initials: JC
authors.lastname: Carvalho
mesh_terms: D000328:Adult; D016362:Analgesia, Obstetrical / Q000009:adverse effects*; D000767:Anesthesia, Epidural / Q000009:adverse effects*; D016022:Case-Control Studies; D004388:Dura Mater / Q000000981:diagnostic imaging / Q000293:injuries*; D005260:Female; D006801:Humans; D015994:Incidence; D017843:Ligamentum Flavum / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D008159:Lumbar Vertebrae / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D016602:Needlestick Injuries / Q000000981:diagnostic imaging / Q000209:etiology*; D011247:Pregnancy; D014463:Ultrasonography