Sacral hiatus (SH) is a significant landmark during caudal epidural block (CEB) which is employed for analgesia and anaesthesia during a wide range of clinical conditions. This requires a thorough knowledge of morphometric characteristics of SH and surrounding landmarks, but variability in morphometric dimensions exists among different populations.
Aim: The aim of this study is to examine measure and record the morphometry of sacral hiatus in order to study the anatomical variations of sacral hiatus which will be useful for administration of caudal epidural block and improve its reliability and success rate.
Materials and Methods: The study is done in the Department of Anatomy, Osmania Medical College, and in various other medical colleges in and around Hyderabad. The 200 dry sacra are collected from Department of Anatomy of Osmania Medical College, and in various other medical colleges in and around Hyderabad, during the period January 2011 - December 2012.
Results: Inverted U shape is the most common shape seen in 91 sacra (45.5%) and M shape is the rarest finding seen in 2 sacra (1%) in this study. Levels of apex vary from upper of second sacral vertebra to middle of fifth sacral vertebra. It is most commonly located at the level of fourth sacral vertebra in 106 sacral bones (56.99%) and it is least common at level of second sacral vertebra in 2 sacra (1.08%). Levels of base vary from middle of fourth sacral vertebra to middle of coccygeal vertebra. It is most commonly located at the level of fifth sacral vertebra in 150 sacral bones (80.65%) and is least common at level of 4th sacral vertebra in 11 sacral bones (5.91%). The length of sacral hiatus ranges from 5.75 mm to 49.5 mm with arithmetic mean of 24.804mm with median of 23.86mm. Standard deviation is found to be 9.415mm. Length is most commonly found in range of 20 – 30 mm in 77 sacra (41.10%) followed by 11 – 20 mm in 54 sacra (29.03%), Transverse diameter in the range of 5.54mm to 21.92mm with arithmetic mean of 13.861mm and median of 13.955mm. Standard deviation is found to be 2.520mm. In 89.25% (166) sacra the transverse diameter is found to be in range of 11mm to 20mm. Anteroposterior diameter is in the range of 1 mm to 10.96mm with arithmetic mean of 4.445 mm and median of 4.410 mm. Standard deviation is found to be 1.627 mm. Most of sacra that is in about 118 sacra (63.44%) the AP diameters are found to be between 4mm to 6mm.The presented study results coincided with majority of studies in other regions and it contributes to the available literature.
Conclusion: Multiple bony landmarks and their morphometric dimensions should be considered to locate the SH during CEB. Values for various morphometric parameters of SH are less in Indians in comparison to other populations, which should be contemplated during caudal epidural injections and trans-sacral the caloscopy.