title: Ultrasound as a screening tool for performing caudal epidural injections.
abstract: BACKGROUND
  The caudal approach to the epidural space has been used for decades to treat low back pain caused by lumbosacral root compression. The use of fluoroscopy during epidural steroid injection is the preferred method for placing the needle more accurately in the sacral hiatus, but it carries the risk of radiation hazard.
  
  
  OBJECTIVE
  The aim of the study was to assess the anatomical structure of the sacral hiatus and the feasibility of caudal epidural injections under ultrasound guidance.
  
  
  METHODS
  Two hundred and forty patients (male = 100, female = 140) with low back pain and sciatica who were candidates for caudal epidural injection were enrolled into this study. Ultrasound images of the sacral hiatus and bilateral cornua were obtained by a real-time linear array ultrasound transducer. The distance between bilateral cornua and the anterior and posterior wall of the sacrum were measured at the base (sacral hiatus). Under the guide of ultrasonography, we defined the injection successful if turbulence of medication fluid was observed in the sacral canal, but correct placement of the needle and injectant was confirmed on fluoroscopic view as the gold standard technique.
  
  
  RESULTS
  The epidurogram showed that the injection was successful in 230 of the 240 patients (95.8%). In eight patients, the injection was not in the correct place in the sacral canal. The sacral hiatus could not be identified by ultrasound images in only two patients who had a closed sacral hiatus identified by fluoroscopy. The mean distance of the sacral hiatus was 4.7 ± 1.7 mm and the mean distance between bilateral cornua was 18.0 ± 2.8 mm. The mean duration of the procedure was 10.8 ± 6.8 minutes. No major complication was observed in the next month.
  
  
  CONCLUSIONS
  In conclusion, ultrasound could be used as a safe, fast and reliable modality to observe the anatomic variation of the sacral hiatus and to perform caudal epidural injections.
authors.affiliation: Department of Anesthesiology, Hamadan University of Medical Sciences, Hamedan, Iran.
authors.forename: Mahshid
authors.initials: M
authors.lastname: Nikooseresht
authors.affiliation: Department of Anesthesiology, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Masoud
authors.initials: M
authors.lastname: Hashemi
authors.affiliation: Department of Anesthesiology, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Seyed Amir
authors.initials: SA
authors.lastname: Mohajerani
authors.affiliation: Department of Radiology, Akhtar Hospital, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Farideh
authors.initials: F
authors.lastname: Shahandeh
authors.affiliation: Department of Anesthesiology, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
authors.forename: Mahvash
authors.initials: M
authors.lastname: Agah
keywords: Anesthesia, Caudal; Low Back Pain; Ultrasonography