Shape Of Hiatus Research Articles

Morphometric Study of Sacral Hiatus in Dry Adult Human Sacra: Its Clinical Relevance in Caudal Epidural Block.

Correct localization of the sacral hiatus is essential for administering a successful caudal epidural block. The present study was undertaken to find out the anatomical variations of sacral hiatus by a metrical method so that it could help anaesthesiologists in the clinical field. The study was performed on 140 (83 male and 57 female) adult human sacra. Various parameters of the sacrum studied were as follows: the shape of the hiatus, length of the sacral hiatus, transverse width at the base and anteroposterior diameter at the level of the apex. For each parameter, the mean value (calculated in mm), standard deviation, range and percentage of bones identified correctly were calculated. Various shapes of sacral hiatuswere observed, including inverted "U" in 73 (52.14%), inverted "V" in 33 (23.57%), irregular in 10 (7.14%), elongated in 10 (7.14%) and dumbbell-shaped in 12 (8.57%). Absent sacral hiatus was observed in two (1.43%) specimens. The mean value for the length of sacral hiatus from the apex to the midpoint of the base was found to be 23.26 mm in males and 22.38 mm in females. However, the parameter was found to be statistically not significant. The mean value for transverse width at the base of hiatus was found to be 14.19 mm in males and 13.54 mm in females. The mean value for the anteroposterior diameter of the sacral canal at the apex was found to be 4.57 mm in males and 4.32 mm in females. Both the above parameters were found to be statistically not significant. The anatomical knowledge of sacral hiatus and its variations are important in caudal epidural anaesthesia, and it may improve the success rate of caudal epidural anaesthesia.

Anatomy of the sacral hiatus and its clinical relevance in caudal epidural block.

Caudal epidural anesthesia (CEB) is widely used for the prevention of chronic lower back pain, the control of intraoperative analgesia such as genitourinary surgery and labor pain cases in sacral epidural space approach for the implementation of analgesia. CEB is an anesthetic solution used into the sacral canal via sacral hiatus (SH). For optimal access into the sacral epidural space, detailed anatomical landmarks of SH are required. This study aims at exploring the anatomical structures and differences of the SH by using the sacral bone as a guide point to failure criteria for reviewing the caudal epidural anesthesia and improving the criteria for success in practice. Detailed morphometric measurements of orientation points of the SH were taken in 87 sacral bones. The measurements were taken using digital calipers and calculated with photogrammetric methods using Image J program. Most commonly encountered shape of the SH was inverted U (33.33%), while 6.9% 3.45% often lack SH and bifida shape were found. The average length of the SH was 28.7 ± 7.1mm, the average distance of the intercornual distance was 13.48 ± 2.69mm, the average of the apex of SH and S2 sacral foramen was 34.68 ± 7.09mm. There was no statistically significant difference determined in bilateral measurements (p > 0.05). Apex and base of SH were most commonly observed against S4 and S5 vertebrae, respectively. The level of maximum curvature of sacrum was S3 in 62.07% and S4 in 28.78%. Findings of spina bifida level were found 16.13% often in L5-S1 segment. Sacral cornua were marked by their bilateral presence in 55.26% and impalpable in 21.05% cases. Minimum distance between the S2 and the apex of the SH was 7.25mm which suggested that it would not be safe to push the needle beyond 7mm into the sacral canal so as to avoid dural puncture. In 8.77% cases, the depth of hiatus was less than 3mm. Single bony landmark may not help in locating the SH because of the anatomical variations. Important anatomical landmarks of the CEB are the sacral cornu, lateral sacral crests, the apex of the SH, the base of the SH, the top portion of the median sacral crest, anteroposterior distance of the sacral canal, intercornual distance, distance of the apex of the SH to the S2 foramina. Depth of hiatus less than 3mm may be one of the causes for the failure of needle insertion. Surrounding bony irregularities, different shapes of hiatus and defects in dorsal wall of sacral canal should be taken into consideration before undertaking CEB so as to avoid its failure. This guide can be done by considering the points and securing a successful venture.

Anatomical study of sacral hiatus in South Indian population and its clinical significance in caudal epidural anaesthesia

Abstract Background: Caudal anaesthesia is administered into the epidural space through Sacral Hiatus(SH). Hence reliability and success of caudal epidural anaesthesia depends upon the anatomical knowledge of sacral hiatus. Aim: The aim is to study the morphological measurements and variations of structures around the sacral hiatus and to identify possible anatomical reasons for failure of caudal epidural anaesthesia (CEA). Materials and methods: Fifty three dry adult sacral bones of both sexes were measured using Vernier Caliper, scale and divider. The shape of sacral hiatus (SH) was observed and its length and breadth were measured. The measurements were focused on sacral hiatus and its relation with surrounding bony projections. Results: The shape of the sacral hiatus showed a maximum occurrence of inverted 'V' and 'U' shapes with 35.85% and 26.42% respectively. The level of apex of SH was maximum at S4 foramen level in 68.63% cases followed by S5 and S3 level. In 62.26%, the level of base was observed at S5 level . The average length of the sacral hiatus was 23.02(± 8.95 mm), APdiameter was 5.49 (±l.44 mm) and base of SH was 14.6 (± 3.99 mm). The distance from apex and base of SH to S2 foramen level was 31.07 mm and 52.86 mm respectively. Conclusion: The anatomical knowledge of SH is very much necessary to increase the reliability and success of CEA. Surrounding bony irregularity, different shapes of hiatus and defect in dorsal wall of sacral canal should be taken into consideration before undertaking CEA so as to avoid its failure.