title: Assessment of factors affecting the difficulty of caudal epidural injections in adults using ultrasound.
abstract: BACKGROUND
  In unaided caudal epidural block (CEB), incorrect needle insertion has been reported to occur in 15% to 38% of attempts.
  
  
  OBJECTIVE
  To statistically analyze the anatomical variables affecting difficult CEB using ultrasonographic measurement.
  
  
  METHODS
  Preprocedural ultrasonography was performed and the following measurements were obtained in 146 patients: the distance from the skin to the apex of the sacral hiatus; the depth of the sacral canal at the apex of the sacral hiatus; the length of the sacrococcygeal ligament between the apex of the sacral hiatus and sacral base; the distance from the skin to the apex of the sacral cornu; and the distance between the apexes of bilateral cornua. One clinician, unaware of the ultrasonographic findings, performed the injections using the landmark technique. The procedures were videotaped and were subsequently reviewed by an independent investigator.
  
  
  RESULTS
  The means (± SDs) of the abovementioned measurements were 12.1±3.7 mm, 6.1±2.1 mm, 25.9±7.4 mm, 10.0±4.0 mm and 16.4±3.2&nbsp;mm, respectively. Injections failed in 16 (11%) patients and were defined as difficult in 21 (14.4%) patients. The depth of the sacral canal at the apex of sacral hiatus (P<0.001) and the length of the sacrococcygeal ligament between the apex of the sacral hiatus and sacral base (P=0.001) were significant predictors of difficult CEB. Of all patients, 85.7% and 75.2% were correctly classified as difficult or not difficult, respectively. The cutoff values of the depth of the sacral canal at the apex of the sacral hiatus and the length of the sacrococcygeal ligament between the apex of the sacral hiatus and the sacral base to predict a difficult CEB were 3.7 mm and 17.6 mm, respectively.
  
  
  CONCLUSIONS
  Both the depth of the sacral canal at the apex of the sacral hiatus and the length of the sacrococcygeal ligament between the apex of the sacral hiatus and sacral base are significant variables affecting the difficulty of the CEB.
authors.forename: Young Hoon
authors.initials: YH
authors.lastname: Kim
authors.forename: Hue Jung
authors.initials: HJ
authors.lastname: Park
authors.forename: Sungkun
authors.initials: S
authors.lastname: Cho
authors.forename: Dong Eon
authors.initials: DE
authors.lastname: Moon
mesh_terms: D000328:Adult; D000368:Aged; D000763:Anesthesia, Caudal; D005260:Female; D006801:Humans; D007268:Injections, Epidural / Q000379:methods*; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000000981:diagnostic imaging* / Q000188:drug therapy*; D010147:Pain Measurement; D012445:Sacrococcygeal Region / Q000000981:diagnostic imaging*; D012447:Sacrum / Q000000981:diagnostic imaging; D014463:Ultrasonography
references.citation: Pain Physician. 2009 Jan-Feb;12(1):109-35
references.pmid: 19165299
references.citation: Surg Radiol Anat. 2009 Dec;31(10):793-800
references.pmid: 19578805
references.citation: Clin Anat. 2012 Mar;25(2):158-67
references.pmid: 21739475
references.citation: Joint Bone Spine. 2010 Oct;77(5):440-4
references.pmid: 20869897
references.citation: Anesthesiology. 2004 Jul;101(1):181-4
references.pmid: 15220789
references.citation: Arch Phys Med Rehabil. 2010 Mar;91(3):358-63
references.pmid: 20298824
references.citation: Anesthesiology. 1979 Jun;50(6):549-51
references.pmid: 453583
references.citation: Pain Physician. 2004 Jan;7(1):81-92
references.pmid: 16868617
references.citation: Clin J Pain. 2004 Jan-Feb;20(1):51-4
references.pmid: 14668657
references.citation: J Ultrasound Med. 2003 Nov;22(11):1229-32
references.pmid: 14620894
references.citation: Anaesthesia. 1992 Jan;47(1):57-8
references.pmid: 1536408
references.citation: Anaesth Intensive Care. 2010 May;38(3):525-9
references.pmid: 20514963
references.citation: Anaesthesia. 2006 Oct;61(10):946-9
references.pmid: 16978308
references.citation: Clin Anat. 2009 Sep;22(6):730-7
references.pmid: 19637298
references.citation: Anesthesiology. 1999 Aug;91(2):374-8
references.pmid: 10443599