Anatomic Differences in the Sacral Hiatus During Caudal Epidural Injection Using Ultrasound Guidance.
OBJECTIVE
The aim of this study was to clarify differences in the anatomic structure of the sacral hiatus and angle of needle insertion during caudal epidural steroid injection using ultrasound guidance in patients according to sex and age.


METHODS
A total of 237 patients with low back pain with or without sciatica were included. Sonograms of the sacral hiatus were obtained, and caudal epidural steroid injection using ultrasound guidance was performed in all patients. The intercornual distance, diameter of the sacral canal, thickness of the sacrococcygeal ligament, optimal angle for needle insertion, and actual angle of needle insertion were measured.


RESULTS
Between men and women, significant differences were observed for the intercornual distance (17.7 versus 16.5 mm; P< .01) and thickness of the sacrococcygeal ligament (4.3 versus 3.9 mm; P = .02). In all patients, the thickness of the sacrococcygeal ligament (r= 0.28) and diameter of the sacral canal (r= 0.40) were positively correlated with the optimal angle for needle insertion (P < .01). In women, the thickness of the sacrococcygeal ligament (r = -0.24), diameter of the sacral canal (r = -0.27), optimal angle for needle insertion (r = -0.29), and actual angle of needle insertion (r = -0.18) were negatively correlated with age. In men, only the diameter of the sacral canal was negatively correlated with age (r = -0.30).


CONCLUSIONS
We found that the sacral hiatus has anatomic differences between patients of different sexes and ages. Understanding these differences, especially in women, may improve the safety and reliability of caudal epidural steroid injection.
Department of Rehabilitation Medicine, Catholic University of Daegu School of Medicine, Daegu, Korea.
Gi-young
GY
Park
Department of Rehabilitation Medicine, Catholic University of Daegu School of Medicine, Daegu, Korea.
Dong Rak
DR
Kwon
Department of Rehabilitation Medicine, Catholic University of Daegu School of Medicine, Daegu, Korea.
Hee Kyung
HK
Cho
D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D000763:Anesthesia, Caudal / Q000379:methods / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012447:Sacrum / Q000002:abnormalities* / Q000000981:diagnostic imaging*; D012585:Sciatica / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000453:epidemiology; D012680:Sensitivity and Specificity; D012727:Sex Characteristics; D017678:Sex Distribution; D013256:Steroids / Q000008:administration & dosage*; D016896:Treatment Outcome; D018084:Ultrasonography, Interventional / Q000379:methods / Q000706:statistics & numerical data*
D013256:Steroids
age; caudal epidural steroid injection; musculoskeletal ultrasound; sacral hiatus; sex