Apex Of Hiatus Research Articles

An Anatomical Study of Variations of Sacral Hiatus and Its Clinical Correlation.

Sacrum is a triangular bone formed by fusion of five sacral vertebrae (S1-S5). It forms the lower part of vertebral column. The opening present at the lower end of sacral canal is known as sacral hiatus. It is formed by failure of fusion of lamina of fifth sacral vertebra in midline. Shape and extent of the sacral hiatus is variable. So our study is directed to find out such variations. The remnants of the inferior articular process of S5 elongates downward on both sides of the sacral hiatus. These two bony process are known as sacral cornua (horns). It is very important landmark to locate the sacral hiatus during caudal epidural anaesthesia and analgesia. In our present study we have summarised the variations in the sacral hiatus according to its shape and extent. Sacrum is a large triangular bone formed by fusion of five sacral vertebrae and forms the lower part of vertebral column. Cranially it articulates with lumbar vertebra and caudally it articulates with coccyx. Vertebral foramina of sacrum is known as sacral canal. It contains cauda equine, spinal meninges, sacral and coccygeal nerve roots. The opening present at the lower end of the sacral canal is known as sacral hiatus.Its shape is variable but generally it is triangular in shape with apex upward and base downward. It contains fifth pair of sacral nerve, coccygeal nerve and filum terminale. Sacral hiatus is formed due to failure of fusion of lamina of fifth (sometimes fourth) sacral vertebrae. It is located inferior to fourth (or3 rd ) fused sacral spines or lower end of median sacral crest. If the lamina of the higher sacral vertebrae are not fused then hiatus will be seen at a higher level .Sometimes non fusion of all the five lamina of sacrum is observed posteriorly which will present a midline gap. This condition is observed in spina bifida. Spina bifida is a developmental defect of vertebral column in which the laminae of one or more vertebrae fail to fuse. It is of two types spina bifida occulta and spina bifida cystica. Spina bifida cystica is again of two types meningocele and myelomeningocele. Sometimes spina bifida with myeloschisis is also seen. Most common site of spina bifida is lumber and sacral region. The remnants of inferior articular process of fifth sacral vertebra projects downward on both sides of sacral hiatus which is known as sacral cornua (horn). It is very important landmark to locate the sacral hiatus during caudal epidural anaesthesia. Caudal epidural anaesthesia is most popular regional anaesthesia used in children. Caudal approach of epidural anaesthesia is done through sacral hiatus. Lots of variations are found in anatomy of sacral hiatus which leads to failure of caudal epidural block. Tsui et al studied that caudal epidural block has 25% failure rate. So awareness of the anatomical variation like absence of sacral hiatus and narrowing of sacral canal is needed for successful anaesthetic procedures. Caudal epidural block is used for anaesthesia and analgesia below umbilicus in young ages and in urgent procedures like incarcerated hernia, perineal procedure, lower limb surgery and in superficial operations such as skin grafting. Material and methods: The study was conducted in department of anatomy, Aiims, Patna. We studied over 42 sacra with undetermined sex and age. Damaged bones were excluded from study. We studied different features of sacrum like the shape and extent of sacral hiatus. Level of apex and base of sacral hiatus were noted and photographs were taken for variable findings of the sacrum. Then we summarised our study. Observation: In our present study we found a lots of variation in shape and extent of sacral hiatus. All our findings are disused under following headings. Apex of sacral hiatus: In all the sacra the level of sacral hiatus was noted. Many variations in the level of apex were found. The apex of sacral hiatus extends between 2 nd to 5 th sacral vertebra. In present study one (2.3%) sacrum (fig 1) was found in which all the lamina was unfused leading to an open sacral canal (spina bifida). None of sacrum have apex of hiatus at the level of S2.In one specimen (fig 2) lamina of S1 was unfused and lamina of S2 was fused and below that all the lamina was unfused. So in this specimen apex of sacral hiatus was at S3 level. In (fig 3) level of apex of sacral hiatus was found at level of S3 , thus in 2 (4.76%)specimens

The caudal space in fetuses: an anatomical study

The caudal epidural space is a popular site for analgesia in pediatrics. High variation in blind needle placement is common during caudal epidurals, increasing the risk of intravascular and intrathecal spread. Knowledge of safe distances and angles for accessing the caudal epidural space in premature infants can improve the safety of caudal epidural blocks. Thirty-nine fetuses with crown-heel length between 33 and 50cm, corresponding to gestational age of 7-9months, were included. The dorsal surface of the sacrum from the fourth lumbar vertebra to the tip of the coccyx was dissected, following which measurements were taken on dorsal surface and midsagittal sections. The angle of depression of the needle was measured using a goniometer following the two-step method of needle insertion. Right and left sacral cornua were palpable in 23 of 39 fetuses (58.97%). Termination of dural sac was at S2 in most of the fetuses (53.84%), whereas the apex of the sacral hiatus was at S3 in most (58.97%). The distance from the apex of the hiatus to the termination of dura ranged from 3 to 13mm; the anteroposterior distance of the canal at the apex of the hiatus ranged from 1.72 to 4.38mm. All sacral parameters correlated with crown-heel length except inter-cornual distance, depth of canal at hiatus, and height of sacral hiatus. Distances and angles for accessing the caudal epidural space in fetuses do not provide all parameters for safe performance of caudal epidural blocks in premature and low birth weight infants because the apex of the sacral hiatus and the termination of the dura show wide variation in location.

Anatomic consideration of caudal epidural space: A cadaver study

The knowledge of sacral hiatus anatomy is imperative in clinical situations requiring caudal epidural block for various diagnostic and therapeutic procedures of the lumbosacral spine to avoid failure and dural injury. In this study, a detailed anatomic study of the sacral region was carried out on 49 male adult Indian cadavers. Dorsal surface of sacral region was dissected to study sacral cornua, sacral hiatus, and the dimensions of triangle formed by the right and left posterosuperior iliac spines with apex of the hiatus. Midsagittal sections were subjected for various anatomical measurements. The angle of needle insertion and the depth of caudal space were noted. Cornu was not palpable bilaterally in 7 (14.3%) and palpable unilaterally in 12 (24.5%) specimens. Mean (standard deviation) distance between apex of hiatus and coccyx tip was 57.5 (8.7) mm and length of sacrococcygeal ligament was 34.2 (7.4) mm. The dimensions of the triangle were found to be interchangeable in 25 cadavers. Once the needle is introduced into the canal after penetrating the sacrococcygeal ligament, it should not be advanced >5 mm to prevent dural puncture. The level of maximum curvature of sacrum was S3 in 34 (69.4%) of cases. The dural sac was found to terminate at S2 in 41 (83.6%). The mean (SD) angle of depression of the needle was 65.7 (5.5) (range 58-78). The measurements described for the identification of the sacral hiatus, optimal angle of depression, and depth of the needle may improve the safety and reliability of a caudal epidural block.

Morphometry of sacral hiatus and its clinical relevance in caudal epidural block

Sacral approach to epidural space produces reliable and effective block of sacral nerves. It is necessary to have a detailed knowledge of sacral hiatus (SH) for optimal access into sacral epidural space. This study was undertaken to evaluate various landmarks of SH. One hundred and fourteen adult dry human sacral bones were examined for morphometric analysis using vernier caliper. SH was categorized on the basis of shape. Most commonly encountered shape of hiatus was inverted U (40.35%). Its apex and base were most commonly observed against fourth and fifth sacral vertebrae, respectively. Various defects in dorsal wall of sacral canal were recorded. Height and anteroposterior depth at the apex of hiatus were ranged 4.30-38.60 and 1.90-10.40 mm, respectively. Mean intercornual distance at base was 11.95 +/- 2.78 mm. The triangle formed by right and left posterior superior iliac spines and apex of SH was found equilateral in 45% cases only. Sacral cornua were marked by their bilateral presence in 55.26% and impalpable in 21.05% cases. Minimum distance between S2 and apex was 7.25 mm which suggested that it would not be safe to push the needle beyond 7 mm into sacral canal so as to avoid dural puncture. In 8.77% cases, depth of hiatus was less than 3 mm. Single bony landmark may not help in locating SH because of anatomical variations. Depth of hiatus less than 3 mm may be one of the causes for 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 caudal epidural block so as to avoid its failure.

The short esophagus: Intraoperative assessment of esophageal length

To define the frequency and predictors of short esophagus in a case series of patients undergoing antireflux surgery. An observational prospective study from September 10, 2004, to October 31, 2006, was performed at 8 centers. The distance between the esophagogastric junction as identified by intraoperative esophagoscopy and the apex of the diaphragmatic hiatus was measured intraoperatively before and after esophageal mediastinal dissection; a distance of 1.5 cm was arbitrarily determined to categorize cases as long (>1.5 cm) or short (<or=1.5 cm). One hundred eighty patients were enrolled; the mean age of patients was 49.3 +/- 15.3 years. At the first measurement (after isolation of the esophagogastric junction), the median distance between the esophagogastric junction and the apex of the hiatus was equal to or shorter than 1.5 cm in 68 (37.7%) patients; at the second measurement (after full mediastinal isolation), the measurement of the distance was still shorter than 1.5 cm in 34 (18.8%) patients and between 1.5 and 2.5 cm in 24 (13.4%) patients. The median length of the mediastinal esophageal dissection was 6 cm (range 1-12 cm). An esophageal lengthening procedure was performed in 26 (14.4%) patients. The duration of symptoms (P = .047), the General Health domain of the SF-36 questionnaire (P = .001), and an x-ray barium swallow (P = .000) are predictive factors for a "true" short esophagus. True short esophagus is present in about 20% of patients undergoing routine antireflux surgery. Radiology, severity, and duration of symptoms are predictors of true foreshortening.