Anatomic consideration of caudal epidural space: a cadaver study

Evaluation of sacral hiatus changes in children using ultrasound

Background and objectives

The intercornual distance in the sacral hiatus has yet to be studied precisely in children. This age-stratified, observational study aimed to clarify the changes in sacral hiatus dimensions and to quantify the correlations between the intercornual distance of the sacral hiatus and age, height, weight, and head circumference by using real-time ultrasonography.

Methods

The patients were stratified into three groups: neonates and infants, toddlers, and schoolchildren. In the operating room, the ultrasonic probe was placed at the sacral cornua to obtain a transverse view of the sacral hiatus, and the intercornual distance was measured three times in millimetres.

Results

The study included a total of 156 patients. The mean ± SD (95%CI) of intercornual distance in neonates and infants (<12 months) was 11.58 ± 1.79 (11.11-12.04) mm, 13.29 ± 1.97 (12.71-13.86) mm in toddlers (13-36 months), and 13.36 ± 2.49 (12.64-14.08) mm in schoolchildren (>36 months).The mean values of neonates and infants were different from those of toddlers and schoolchildren (p < 0.001), but it was similar between toddlers and schoolchildren (p > 0.05, 95 % CI mean difference -1.10 to 0.95).Intercornual distance was correlated with age, height, weight, and head circumference before one year of age (Spearman's R values > 0.7), but there was no correlation thereafter (Spearman's p value > 0.05).

Conclusion

In the first year after birth, the intercornual distance increases rapidly with body growth; after one year of age, the sacral hiatus dimension changes significantly. Ultrasound is superior for assessing the gradually ossified cartilage components in older children.

Effectiveness of ultrasonography-guided caudal epidural steroid injection compared to the fluoroscopic application

BACKGROUND

Caudal epidural steroid injection (CESI) has been increasingly used for treating lower back pain. However, there is still significant controversy about the efficacy and safety of different imaging techniques used to guide CESI. In this context, the objective of this study is to compare the efficacies of fluoroscopy- and ultrasonography-guided CESI in patients with chronic lower back pain.

METHODS

The population of this retrospective, observational study consisted of all consecutive patients who underwent CESI for lower back pain between 2018 and 2020. Of the 371 patients included in the study sample, 192 had undergone fluoroscopyguided CESI (Group F) and 179 ultrasonography-guided CESI (Group U). Patients' pain and functional statuses were evaluated using the visual analog scale (VAS) and Oswestry Disability Index (ODI) immediately before (baseline) and after the procedure (postintervention day 0-D0), during the second week (D15), the first month (D30), and the third month (D90) after the procedure.

RESULTS

The mean age of Group F was significantly higher than that of Group U (p < 0.001). The number of patients with lumbar dischernia was significantly higher in Group U, whereas the number of patients with spinal stenosis and lumbar disc hernia + spinal/lumbar stenosis was significantly higher in Group F (p = 0.001). The baseline and D0 ODI scores were significantly lower in Group U than in Group F (p = 0.006 and p = 0.017, respectively). There was no significant difference between the groups in other VAS and ODI scores (p > 0.05). Intragroup analyses revealed significant reductions in VAS and ODI scores over the follow-up period till D30 compared to the baseline scores in each group (p < 0.001). The decrease recorded in the ODI score between the D15 and baseline measurements was significantly higher in Group F than in Group U (p = 0.006).

DISCUSSION

The study findings indicated that ultrasound-guided CESI was as effective as fluoroscopy-guided CESI in treating chroniclower back pain.

Evaluation of the Level of Dural Sac Tip in Saudi Population: A Magnetic Resonance Imaging Study

Background For the success of procedures such as caudal block, craniospinal irradiation (CSI), and management of lower back pain and to minimize the risk of dural puncture the exact level of dural sac (DS) termination should be known. Objective The evaluation of DS tip location in the Saudi population and exploring possible significant factors that could be used as predictors in clinical prognosis. Methods A total of 200 patients' lumbar sagittal Weighted T2 Magnetic Resonance Imaging (MRI) study were randomly selected from a single-center hospital in-between 2020 and 2021. The DS tip location was determined by generating a perpendicular line from the longitudinal axis of its termination to the corresponding level. Then naming it after an intervertebral disk or a corresponding vertebrate that is divided into three thirds (upper, middle, and lower). Results In most cases, the level of DS termination is at the middle part of S2 (26.5%), followed by the upper part of S2 (25.1%), and the lower part of S2 (20%). In Saudi nationals, the DS tip was in the middle S2 level at 21.5%, upper S2 level at 19.1%, and lower S2 level at 17%. Factors such as age, sex, cause of referral, and nationality had no statistical significance in relation to DS tip location. Conclusion The DS termination level in the Saudi population ranges from disk between L5-S1 to the lower third of S3. Moreover, nationality, age, and cause of referral were not significant in determining the DS termination level. Therefore, it is still important to individualize patients' treatment by using MRI for each case that requires it.

Transverse plane ultrasound-guided caudal epidural injections: sonographic anatomy and stepwise technique

PURPOSE

The present study aims to provide a step-by-step procedural and anatomical familiarization guide for transverse plane ultrasound (US)-guided caudal epidural (CE) injection.

METHODS

The study cohort consisted of 23 chronic low back pain patients (23-67 years old) previously unresponsive to conservative management. A transverse plane US-guided CE injection was performed, with each procedure step documenting and emphasizing sonographic anatomy. Several Thiel's method fixed cadaveric specimen dissections were also performed to demonstrate relevant CE injection-related anatomy.

RESULTS

The sacral hiatus location can be estimated by visually forming an equilateral triangle between the posterior superior iliac spines and the sacral apex (trigonum sacrale). Follow-up palpation locates the sacral cornua, guiding transducer placement visualizing over the paired cornua 'bull frog's eye's appearance, with the epidural space visualized as a hypoechoic line, between the eyes. Then, 2-3 ml of 1% lidocaine is injected subcutaneously at the mid-point between the sacral cornua and superficial to the posterior sacrococcygeal ligament (SCL). Although keeping the cornua, superficial posterior SCL and epidural space in view, the needle is slowly advanced to the epidural space at around a 20 degree cephalad angle till the tip becomes visible. Expansion of the epidural space is monitored under the transverse sacral ligament as the injectant is slowly introduced.

CONCLUSION

The present study demonstrated the anatomical landmarks necessary for the transverse ultrasound caudal epidural technique and that the cornua, superficial posterior SCL, CE space, and other relevant sacral hiatal anatomy are well visualized with this technique.

A Morphometric and Radiological Study of Sacral Hiatus in Human Adult Sacra and Its Clinical Relevance in Caudal Epidural Anaesthesia

Background: The knowledge of sacral hiatus anatomy is crucial in clinical situations requiring caudal epidural block for various diagnostic and therapeutic procedures of the lumbosacral spine to avoid complications and failure rate. This study was undertaken to compare morphometric characteristics of sacral hiatus in human dry sacra and pelvic radiographs for placing the needle more accurately in the sacral hiatus landmarks to permit correct, painless, and uncomplicated caudal epidural accesses. Materials and methods: The present study was done on 138 human adult dry sacra and 110 anteroposterior lumbosacral spine radiographs of the North Karnataka region of India. Sacral hiatus was evaluated in each sacrum based on its shape, level of its apex, and base according to sacral and coccygeal vertebrae, length, anteroposterior diameter at its apex, and transverse width at its base. Results:The mean length of sacral hiatus in men and women was 27.81+1.17 mm and 24.73+2.21 mm, respectively. The mean anteroposterior diameter of the sacral hiatus at the apex was 6.24+2.73 mm in males and 6.63+2.81 mm in females. The transverse width of the sacral hiatus at the base was 17.56+1.81 mm in males and 17.92+2.59 mm in females. The location of the apex of sacral hiatus was the highest in number at the level of the fourth sacral vertebra (23.63%). The location of apex in radiographs of all lumbosacral spine S3 showed 49.09% maximum. The location of the base of the sacral hiatus was observed in the dry sacra at the level of the fifth sacral vertebra (64.54%). In the present study, different shapes of the sacral hiatus were recorded. The most common shape in males and females was inverted U shape (42.02%), followed by inverted V shape (26.08%) and dumbbell shape (12.31%). The least common shape was observed in the bifid sacra (5.07%). In 2.17% of cases, sacral hiatus was absent. Percentage of absence, agenesis, irregular, and bifid shapes were found rather in female than male sacra. An anteroposterior view of spine radiograph showed sacral hiatus agenesis in both females (7.81%) and males (4.34%). The anatomical knowledge of sacral hiatus and its variations are important in caudal epidural anesthesia, and it may improve the success rate of caudal epidural anesthesia.

Sacral hiatus corticosteroid injection in the management of radicular pain in adults

Radicular pain is a common reason for patients to consult at back pain clinics. While epidural steroid injections are widely done, some aspects are still controversial. The epidural space can be accessed via a transforaminal approach, an interlaminar route or by passing through the sacral hiatus. The aim of this article is to describe the epidural injection technique through the sacral hiatus that our team uses and to report our experience with it. Beyond the treatment effect, sacral hiatus corticosteroid injection can be useful as a diagnostic test or as an interim solution. Image-guided injection is recommended to ensure optimal positioning of the needle below S3. Sacral hiatus corticosteroid injection is a relevant alternative for treating lumbar radiculopathy in adults.

Imaging anatomy of the vertebral canal for trans-sacral hiatus puncture of the lumbar cistern

A standard lumbar puncture may be impossible for many anatomic or technical reasons. Previous accounts of caudal epidural anesthesia and other procedures via the sacral hiatus prompted us to test if image-guided percutaneous trans-sacral hiatus access to the lumbosacral subarachnoid cistern would be anatomically feasible. To study vertebral canal morphometry and curvature, we analyzed midsagittal computed tomography-myelogram images of 40 normal subjects and digitally measured sacral curvatures between S1 to S5 and S2 to S4 using two methods whereby a lower angle signifies a straighter sacrum. We measured midsagittal vertebral canal area, hiatus width, dural sac termination levels, and distance from sacral hiatus to the dural sac tip (needle distance). Subjects were F:M = 25:15, with a mean age of 44.9 years. The two S1-S5 full sacral curvature mean angles were 57.3° and 60.4°. Almost all sacral hiatuses were at S4, and dural sac terminations were at S1-S2. The mean S2-S4 sacral curvature was 25.1°, and the mean needle distance was 57.7 mm. Using two-way analysis of variance, there were significant sex differences for needle distances (p = .001), and full and limited sacral curvatures (p = .02, and p = .046, respectively). There were no significant linear regression correlations between age and sacral curvature, needle distance, canal area, or hiatus width. Therefore, despite a frequently prominent full sacral curvature, the combination of S1-S2 dural sac termination plus a relatively straight trajectory of the lower vertebral canal between S2 and S4 support the theoretical feasibility of percutaneous trans-sacral hiatus and vertebral canal access to the lumbosacral cistern using a standard spinal needle.

Sacral anatomical interspace landmark for lumbar puncture in pregnancy: A randomized trial

OBJECTIVE

To determine whether the sacral anatomical interspace landmark (SAIL) technique is more accurate than the classic intercristal line (ICL) technique in pregnant patients and to assess the percentage of clinical determinations above the third lumbar vertebra.

METHODS

In this prospective, randomized, open-label trial, there were 110 singleton pregnant patients with gestational age greater than 37 weeks included. Selection procedure was a convenience sample of pregnant patients who presented for office visits or vaginal or cesarean delivery between March 15 and July 31, 2018, at a single-center obstetric tertiary care university hospital. Both techniques were evaluated by 2 physicians independently assessing each method. Before data collection, we hypothesized that the SAIL technique would be more accurate than the ICL technique in determining the L4-L5 interspace, and that the SAIL technique would produce more estimations below the third lumbar vertebra than the ICL technique. Therefore, the primary outcome was accuracy in identifying the L4-L5 lumbar interspace with SAIL vs ICL. The secondary outcome was difference in clinical assessments above the third lumbar vertebra. Both outcomes were measured via ultrasonography.

RESULTS

Patients were 31 ± 5 years of age (mean ± SD) and had body mass index of 31.8 ± 5.7 kg/m² and gestational age of 38.8 ± 1.1 weeks. A total of 110 patients were analyzed. SAIL correctly identified the L4-L5 interspace 49% of the time vs 8% using ICL (p < 0.0001). Estimations above L3 were 1% for SAIL vs 31% for ICL (p < 0.0001).

CONCLUSIONS

Our study shows improved accuracy in identifying intervertebral space using the SAIL technique; this may prevent direct mechanical trauma to the conus medullaris when lumbar punctures are performed in pregnancy.

CLINICALTRIALSGOV IDENTIFIER

NCT03433612.

Bolus epidural infusion improves spread compared with continuous infusion in a cadaveric porcine spine model

BACKGROUND

The administration of epidural anesthesia during labor is a common technique used to reduce the pain of childbirth. We sought to compare standard infusion strategies of continuous epidural infusions (CEI) with programmed intermittent epidural bolus (PIEB) to assess the length of spread in terms of vertebral body length. Based on previous clinical data in humans, the PIEB was associated with improved pain control and decreased total dose of local anesthetic. We hypothesized that the PIEB was associated with increased spread when compared with CEI.

METHODS

Thirty female Yorkshire-cross swine cadavers were used to compare three infusion strategies, continuous infusion (CEI) 10 mL/hour programmed continuously, multiple bolus (MB) 2 mL given every 12 min for 10 mL total and 10 mL delivered in a single bolus (SB). Radiographs were used to identify the spread of the radiopaque contrast dye, and a number of vertebral bodies covered were measured to assess spread.

RESULTS

Overall, the CEI had an average spread of 5.6 levels, MB 7.9 and SB 10.4. The differences between SB and MB (p=0.011), SB and CEI (p<0.001) and MB and CEI (p=0.028) were all found to be significant.

CONCLUSIONS

We demonstrated increased spread of epidural contrast with programmed intermittent bolus strategies. This supports previous evidence of improved patient outcomes with PIEB strategy compared with CEI, and encourages the use of PIEB in the appropriate patient population.

Morphological evaluation of the coccyx with multidetector computed tomography

PURPOSE

This study aims to evaluate the morphology of the coccyx in adults with multidetector computed tomography and to contribute to the classification of the coccyx using intercoccygeal and sacrococcygeal angle measurements.

METHODS

The pelvic computed tomography images of 224 patients were retrospectively evaluated. The multiplanar reconstruction and 3D volume rendering images of the coccyx were obtained from all patients at sagittal and coronal planes. The morphology of the coccyx, number of bone segments, the presence of scoliosis, and presence of sacrococcygeal and intercoccygeal fusion were evaluated. After the measurement of coccygeal length, width, and thickness, intercoccygeal and sacrococcygeal angles were also calculated in all patients.

RESULTS

The morphological classification showed that 136 patients (60.7%) had type 1, 65 patients (29%) had type 2, and 17 patients (7.6%) had type 3 coccyx. The intercoccygeal angle was zero degree in five patients (type 0) and one patient had retroverted coccyx (type 5). The coccyx had four segments in 155 patients (69.2%), three segments in 52 patients (23.2%), five segments in 15 patients (6.7%), two segments in one patient (0.4%), and one segment in one patient (0.4%).

CONCLUSION

We determined patients with an intercoccygeal angle of zero degree, which is not mentioned in the literature before, and we propose to use the term "type 0" for these patients in the classification of coccyx. The coccygeal measurements and classification will be instructive for the radiologists and have a guiding role for the future studies.

Fluoroscopic evaluation of the influence of needle gauge on epidural spread in caudal block

Caudal block has limited injectate distribution to the desired lumbar level due to the relatively long distance from the injection site and reduction in the volume of injectate due to leakage into the sacral foramen. The objective of this study was to investigate the influence of needle gauge on fluoroscopic epidural spread and to assess the correlation between the spread level and analgesic efficacy in patients undergoing caudal block. We retrospectively analyzed data from 80 patients who received caudal block for lower back and radicular pain. We categorized patients based on the epidural needle gauge used into group A (23 gauge), group B (20 gauge), and group C (17 gauge). Fluoroscopic image of the final level of contrast injected through the caudal needle and pain scores before the block and 30 minutes after the block recorded using a numerical rating scale, were evaluated. Of the 80 patients assessed for eligibility, 7 were excluded. Thus, a total of 73 patients were finally analyzed. Age, sex, body mass index, diagnosis, lesion level, lesion severity, and duration of pain did not differ among the 3 groups. All patients showed cephalic spread of contrast. Contrast spread beyond L5 was seen in 26.9% of patients in group A, 41.7% in group B, 39.1% in group C, and 35.6% overall; there was no significant difference among the groups (P = .517). Analgesic efficacy was not significantly different among the groups (P = .336). The needle gauge did not influence the level of epidural spread or analgesic efficacy in caudal block.

Prospective comparison of the efficacy of caudal versus periprostatic nerve block, both with intrarectal local anesthesia, during transrectal ultrasonography-guided prostatic needle biopsy

OBJECTIVE

The aim of this study was to compare the effectiveness of caudal block (CB) versus periprostatic nerve block (PPNB), both with intrarectal local anesthesia (IRLA), in reducing pain during transrectal ultrasonography (TRUS)-guided prostatic biopsy.

MATERIALS AND METHODS

This study included 532 patients: 266 patients received CB with IRLA and 266 patients PPNB with IRLA. A visual analogue scale (VAS) was applied to prospectively evaluate pain (1) at induction of anesthesia, (2) at insertion of the TRUS probe, (3) at needle penetration to the prostate, and (4) throughout the biopsy procedure. Pain scores were compared to evaluate differences between groups. The secondary endpoint of serious complication rate was also evaluated. As a subanalysis, the pain scores were compared in patients with high body mass index (BMI ≥25 kg/m²).

RESULTS

Overall, the pain score in the PPNB group was significantly lower than in the CB group at induction of anesthesia (mean ± SD: 2.0 ± 1.9 vs 2.9 ± 2.1, p = .0001) but higher at insertion of the TRUS probe (2.7 ± 2.5 vs 1.9 ± 1.7, p = .009). The pain score did not differ significantly between groups at needle penetration or throughout the biopsy. Univariate analyses indicated no significant association between VAS scores and patient demographics. Overall rates of serious complications did not differ between the two groups (5.6% vs 5.3%, p = .85). In patients with high BMI, the pain score was significantly lower in the PPNB group than in the CB group throughout the procedure (2.5 ± 2.0 vs 3.5 ± 2.5, p = .03).

CONCLUSIONS

Both procedures were equally effective in reducing pain, and the incidence of serious complications was similar. PPNB with IRLA may be more applicable than CB with IRLA in obese patients.

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

PURPOSE

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.

MATERIALS AND METHODS

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.

RESULTS

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 ± 7.1 mm, the average distance of the intercornual distance was 13.48 ± 2.69 mm, the average of the apex of SH and S2 sacral foramen was 34.68 ± 7.09 mm. 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 7.25 mm which suggested that it would not be safe to push the needle beyond 7 mm into the sacral canal so as to avoid dural puncture. In 8.77% cases, the depth of hiatus was less than 3 mm.

CONCLUSIONS

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 3 mm 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.

Caudal Epidural Block: An Updated Review of Anatomy and Techniques

Caudal epidural block is a commonly used technique for surgical anesthesia in children and chronic pain management in adults. It is performed by inserting a needle through the sacral hiatus to gain entrance into the sacral epidural space. Using conventional blind technique, the failure rate of caudal epidural block in adults is high even in experienced hands. This high failure rate could be attributed to anatomic variations that make locating sacral hiatus difficult. With the advent of fluoroscopy and ultrasound in guiding needle placement, the success rate of caudal epidural block has been markedly improved. Although fluoroscopy is still considered the gold standard when performing caudal epidural injection, ultrasonography has been demonstrated to be highly effective in accurately guiding the needle entering the caudal epidural space and produce comparative treatment outcome as fluoroscopy. Except intravascular and intrathecal injection, ultrasonography could be as effective as fluoroscopy in preventing complications during caudal epidural injection. The relevant anatomy and techniques in performing the caudal epidural block will be briefly reviewed in this article.

Ultrasonographic Evaluation of Anatomic Variations in the Sacral Hiatus: Implications for Caudal Epidural Injections

STUDY DESIGN

Prospective study OBJECTIVE.: The aim of this study was to evaluate variations in the sacral hiatus based on ultrasonographic images.

SUMMARY OF BACKGROUND DATA

Caudal epidural injection is commonly used for the treatment of lower back pain, but blind injections commonly lead to mistakes made at the injection site due to anatomic variations in the sacral hiatus.

METHODS

A total of 339 patients with low back pain or sciatica were studied using a linear-array ultrasound transducer. The transducer was placed at the sacral cornua and the distance between the bilateral cornua and the width of the sacrococcygeal ligament between the bilateral cornua were measured in the transverse view. The transducer was also placed between the two cornua and the distance between the skin and posterior sacral bony surface was measured, including the depth of the subcutaneous fat, in the longitudinal view. The surface distance was then measured from the natal cleft to the apex of the sacral hiatus.

RESULTS

The mean distance between the bilateral cornua was 18.1 ± 3.2 mm and mean width of the sacrococcygeal ligament was 10.5 ± 2.6 mm. The mean diameter of the sacral canal was 6.8 ± 2.5 mm but 6 of 339 patients (1.8%) found less than 2 mm. The mean surface distance from the natal cleft to the apex of the sacral hiatus was 29.3 ± 12.3 mm. The distance between the sacral hiatus and the natal cleft ranged from -2.0 to 75.0 mm.

CONCLUSION

We believe that the variations found in the surface distance from the natal cleft to the sacral hiatus are significant for caudal epidural injection. However, the other measurements may also have clinical importance in this area.

LEVEL OF EVIDENCE

3.

Fluoroscopically guided tunneled trans-caudal epidural catheter technique for opioid-free neonatal epidural analgesia

Epidural analgesia confers significant perioperative advantages to neonates undergoing surgical procedures but may be very technically challenging to place using a standard interlaminar loss-of-resistance to saline technique given the shallow depth of the epidural space. Thoracic epidural catheters placed via the caudal route may reduce the risk of direct neural injury from needle placement, but often pose higher risks of infection and/or improper positioning if placed without radiographic guidance. We present a detailed method of placing a fluoroscopically guided, tunneled transcaudal epidural catheter, which may reduce both of these risks. The accuracy and precision of this technique often provides adequate analgesia to allow for opioid-free epidural infusions as well as significant reductions in systemic opioids through the perioperative period. Opioid-free analgesia using a regional anesthetic technique allows for earlier extubation and reduced perioperative sedation, which may have a less deleterious neurocognitive effect on the developing brain of the neonate.

Anatomic Differences in the Sacral Hiatus During Caudal Epidural Injection Using Ultrasound Guidance

OBJECTIVES

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.

A Comparison of Two Techniques for Ultrasound-guided Caudal Injection: The Influence of the Depth of the Inserted Needle on Caudal Block

Background

Caudal epidural injections have been commonly performed in patients with low back pain and radiculopathy. Although caudal injection has generally been accepted as a safe procedure, serious complications such as inadvertent intravascular injection and dural puncture can occur. The present prospective study was designed to investigate the influence of the depth of the inserted needle on the success rate of caudal epidural blocks.

Methods

A total of 49 adults scheduled to receive caudal epidural injections were randomly divided into 2 groups: Group 1 to receive the caudal injection through a conventional method, i.e., caudal injection after advancement of the needle 1 cm into the sacral canal (n = 25), and Group 2 to receive the injection through a new method, i.e., injection right after penetrating the sacrococcygeal ligament (n = 24). Ultrasound was used to identify the sacral hiatus and to achieve accurate needle placement according to the allocated groups. Contrast dyed fluoroscopy was obtained to evaluate the epidural spread of injected materials and to monitor the possible complications.

Results

The success rates of the caudal injections were 68.0% in Group 1 and 95.8% in Group 2 (P = 0.023). The incidences of intravascular injections were 24.0% in Group 1 and 0% in Group 2 (P = 0.022). No intrathecal injection was found in either of the two groups.

Conclusions

The new caudal epidural injection technique tested in this study is a reliable alternative, with a higher success rate and lower risk of accidental intravascular injection than the conventional technique.

Assessment of factors affecting the difficulty of caudal epidural injections in adults using ultrasound

Caudal epidural block is used to treat pain in the lower back and lower extremities. The procedure can be difficult to perform, particularly when a blind technique is being used. The authors of this study aimed to identify variables affecting the difficulty of caudal epidural blocks performed using a blind technique by measuring relevant anatomical variables using ultrasonography.

BACKGROUND:

In unaided caudal epidural block (CEB), incorrect needle insertion has been reported to occur in 15% to 38% of attempts.

OBJECTIVE:

To statistically analyze the anatomical variables affecting difficult CEB using ultrasonographic measurement.

METHODS:

Preprocedural ultrasonography was performed and the following measurements were obtained in 146 patients: the distance from the skin to the apex of the sacral hiatus; the depth of the sacral canal at the apex of the sacral hiatus; the length of the sacrococcygeal ligament between the apex of the sacral hiatus and sacral base; the distance from the skin to the apex of the sacral cornu; and the distance between the apexes of bilateral cornua. One clinician, unaware of the ultrasonographic findings, performed the injections using the landmark technique. The procedures were videotaped and were subsequently reviewed by an independent investigator.

RESULTS:

The means (± SDs) of the abovementioned measurements were 12.1±3.7 mm, 6.1±2.1 mm, 25.9±7.4 mm, 10.0±4.0 mm and 16.4±3.2 mm, respectively. Injections failed in 16 (11%) patients and were defined as difficult in 21 (14.4%) patients. The depth of the sacral canal at the apex of sacral hiatus (P<0.001) and the length of the sacrococcygeal ligament between the apex of the sacral hiatus and sacral base (P=0.001) were significant predictors of difficult CEB. Of all patients, 85.7% and 75.2% were correctly classified as difficult or not difficult, respectively. The cutoff values of the depth of the sacral canal at the apex of the sacral hiatus and the length of the sacrococcygeal ligament between the apex of the sacral hiatus and the sacral base to predict a difficult CEB were 3.7 mm and 17.6 mm, respectively.

CONCLUSIONS:

Both the depth of the sacral canal at the apex of the sacral hiatus and the length of the sacrococcygeal ligament between the apex of the sacral hiatus and sacral base are significant variables affecting the difficulty of the CEB.

A review of the surface and internal anatomy of the caudal canal in children

The anatomy of the sacral hiatus and caudal canal is prone to significant variation, yet studies assessing this in the pediatric population remain limited. Awareness of the possible anatomical variations is critical to the safety and success of caudal epidural blocks, particularly when image guidance is not employed. This systematic review analyzes the available evidence on the clinical anatomy of the caudal canal in pediatric patients, emphasizing surface anatomy and internal anatomical variations. A literature search using three electronic databases and standard pediatric and anatomy reference texts was conducted yielding 24 primary and seven secondary English-language sources. Appreciating that our current landmark-guided approaches to the caudal canal are not well studied in the pediatric population is important for both clinicians and researchers.

Morphologic diversities of sacral canal in children; three-dimensional computed tomographic study

BACKGROUND

Caudal block is a common technique in children for reducing postoperative pain, and there have been several reports on the variations of the sacral canal in children. However, previous studies have mainly focused on the needle trajectory for caudal block, and there is limited information on the structural variations of the sacrum in children. The purpose of this study was to analyze the anatomic variations of sacral canals in children.

METHODS

Three-dimensional computed tomographic images were analyzed. The data from the images included ① fusion of the sacral vertebral laminae and the sacral intervertebral space ② existence of the sacral cornua and ③ the types of sacral hiatus. The types of sacral hiatus were classified into 3 groups: group I (fusion of S3 or S4 vertebral laminae), group II (unfused vertebral arch with the distance of the S3 and S4 vertebral laminae < 50% of the distance between the cornua), and group III (unfused vertebral arch with the distance of the S3 or S4 vertebral laminae ≥ 50% of the distance between the cornua).

RESULTS

A total of 143 children were included in this study. All of the sacral vertebral arches were not fused in 22 children (15.4%). Cornua were not identified bilaterally in 5 (3.5%) and unilaterally in 6 (4.2%) children. In the sacral hiatus, group II and group III were identified in 22 (15.4%) and 31 (21.7%) children, respectively.

CONCLUSIONS

The sacral canal has various anatomical variations in children. Careful attention must be paid to identify the correct anatomic landmark.

Ultrasound as a screening tool for performing caudal epidural injections

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.

Objectives:

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.

Patients and 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.

Where is the apex of the sacral hiatus for caudal epidural block in the pediatric population? A radio-anatomic study

PURPOSE

Caudal epidural block (CEB), administered through the sacral hiatus, is a regional anesthetic technique commonly used in children. To facilitate and optimize pediatric CEB, morphometric data that may be important for the sacral hiatus have been obtained using multidetector computed tomography (MDCT).

METHODS

This study is the first radio-anatomic study designed to address this topic in children. Images of 79 children (39 girls and 40 boys between 1 and 9 years old) were divided into three groups according to age [group I (ages 1-3), group II (ages 4-6), and group III (ages 7-9)] and were retrospectively examined. Data were gathered via 3D volume-rendered images. Measurements included the height and width of the sacral hiatus, S2-S4 (sacral vertebra) distance, the distances between the poles of the unfused spinous process of each sacral vertebra, and the dimensions of an imaginary triangle formed between the right and left posterior superior iliac spines (PSIS) and the apex of the sacral hiatus.

RESULTS

The most frequently fused spinous process was at S2 level. The mean S2-S4 distance was 1.36 cm for group I, 1.78 cm for group II, and 2.17 cm for group III. There was not the imaginary equilateral triangle used in the method of finding the sacral hiatus for CEB, and the apex of this triangle did not occur at the standard level (S4) in most of the children. It was observed that the apex deriving from the most distal fused spinous process was at the level of S2 in one of two children.

CONCLUSION

Dural puncture is inevitable for CEB applied at the S2 level. Consequently, CEB should be applied below this level (range, 1.36-2.17 cm) from the midpoint of the interspinous distance between the PSIS (at the same level with S2) in children aged 1-9 years.

The anatomy of the sacrococcygeal cornual region and its clinical relevance

There has been no systematic study of the anatomy of the region between the sacral and coccygeal cornua. Reference texts describe an intercornual ligament connecting these structures. The aim of this study was to investigate the anatomy of this region, which may be relevant to unexplained cases of coccygeal pain (coccydynia) and local nerve blocks. The bony anatomy of the sacrococcygeal (SC) cornual region was analyzed in 33 CT scans obtained from supine adults of mostly European origin with no known SC pathology, 7 μCT scans of cadaver SC specimens, and 105 Asian Indian adult skeletons. A further five cadaver SC specimens were examined histologically. SC cornual fusion was seen in 45% of CT/μCT scans (mean age 67 years, 20 males) and in 20% of adult skeletons (78 males); there was no association with age or sex. In the absence of SC fusion, the mean intersacrococcygeal cornual gap was 7.1 ± 2.4 mm; this was bridged by an intercornual ligament composed of parallel vertical collagen fibers reinforced by elastin fibers on its anterior surface. Small nerve branches were observed adjacent to the ventral aspect of the intercornual ligament and, in one case, traversing the ligament. Ipsilateral sacral and coccygeal cornua are therefore normally bridged by an intercornual ligament that is probably innervated. The cornua are fused on one or both sides in 20-45% of adults. These findings may have implications for some cases of coccydynia and for anesthetists performing local nerve blocks.

Approach for epiduroscopic laser neural decompression in case of the sacral canal stenosis

Epiduroscopy is very useful in the treatment of not only low back pain caused by failed back surgery syndrome, epidural scar or herniated disc but also by chronic refractory low back pain which does not respond to interventional conservative treatment including fluoroscopically-directed epidural steroid injections and percutaneous adhesiolysis. Because cauterization using a laser fiber has become recently available, a wider opening is required to enter into the sacral canal in the case of epiduroscopic laser neural decompression (ELND). However, in a few patients, it is difficult to insert a device into the epidural space due to stenosis around the opening, and there is no alternative method. Herein, we report a case where a hiatus rasp specially designed for such patients was used to perform the operation.

Caudal epidural blockade in adolescents

BACKGROUND

Various options are available for the provision of analgesia following major surgical procedures including systemic opioids and regional anesthetic techniques. Regional anesthetic techniques offer the advantage of providing analgesia while avoiding the deleterious adverse effects associated with opioids including nausea, vomiting, sedation and respiratory depression. Although used commonly in infants and children, there is a paucity of experience with the use of caudal epidural blockade in adolescents.

METHODS

We retrospectively reviewed the perioperative care of adolescents undergoing major urologic or orthopedic surgical procedures for whom a caudal epidural block was placed for postoperative analgesia.

RESULTS

The cohort for the study included 5 adolescents, ranging in age from 13 to 18 years and in weight from 42 to 71 kilograms. Caudal epidural analgesia was accomplished after the induction of anesthesia and prior to the start of the surgical procedure using 20-25 mL of either 0.25% bupivacaine or 0.2% ropivacaine with clonidine (1 μg/kg). The patients denied pain the recovery room. The time to first request for analgesia varied from 12 to 18 hours with the patients requiring 1-3 doses of analgesic agents during the initial 24 postoperative hours.

CONCLUSIONS

Our preliminary experience demonstrates the efficacy of caudal epidural block in providing analgesia following major urologic and orthopedic surgical procedures. The applications of this technique as a means of providing postoperative analgesia are discussed.

Inadvertent Dural Puncture during Caudal Approach by the Introducer Needle for Epidural Adhesiolysis Caused by Anatomical Variation

There have been reports of abnormalities in the lumbosacral region involving a lower-than-normal termination of the dural sac, which is caused by disease or anatomical variation. Inadvertent dural puncture or other unexpected complications can occur during caudal epidural block or adhesiolysis in patients with these variations, but only a small number of case reports have described this issue. We report a case of dural puncture by the introducer needle before attempting caudal epidural adhesiolysis, which occurred even though the needle was not advanced upward after penetrating the sacrococcygeal ligament. Dural puncture was caused by a morphological abnormality in the lumbosacral region, with no pathological condition; the dural sac terminal was located more distally than normal. However, dural puncture could have been prevented if we had checked for such an abnormality in the magnetic resonance imaging (MRI) taken before the procedure.

Morphometric study of sacral hiatus in adult human Egyptian sacra: Their significance in caudal epidural anesthesia

Background:

The reliability and success of caudal epidural anesthesia depends on anatomic variations of sacral hiatus (SH) as observed by various authors. SH is an important landmark during caudal epidural block (CEB).The purpose of the present study was to clarify the morphometric characteristics of the SH in human Egyptian dry sacra and pelvic radiographs and identification of nearest ony landmarks to permit correct and uncomplicated caudal epidural accesses.

Methods:

The present study was done on 46 human adult Egyptian dry sacra. The maximum height, midventral curved length, and maximum breadth of each sacrum were measured and sacral and curvature indices were calculated. According to sacral indices, sacra were divided into 2 groups (22 male and 24 female sacra). SH was evaluated in each sacrum according to its shape, level of its apex, and base according to sacral and coccygeal vertebrae, length, anteroposterior (AP) diameter at its apex, and transverse width at its base. Linear distances were measured between the apex of SH and second sacral foramina, right and left superolateral sacral crests. The distance between the 2 superolateral sacral crests also was measured.

Results:

The most common types of SH were the inverted U and inverted V (in male) and inverted V and dumbbell shaped (in female). Absent SH was observed in male group only. The most common location of SH apex was at the level of S4 in all groups of dry sacra and S3 in all groups of lumbosacral spine radiographs, whereas S5 was the common level of its base. The mean SH length, transverse width of its base, and AP diameter of its apex were 2.1±0.80, 1.7±0.26, and 0.48±0.19 cm. Female sacra showed narrower SH apex than male. The distance between the S2 foramen and the apex of the SH was 4.1±1.14, 3.67±1.21, and 4.48±1.01 cm in total, female and male sacra, respectively.

Conclusion:

Sacrum and SH showed morphometric variations in adult Egyptians. The equilateral triangle is an important guide to detect SH easily and increases the success rate of CEB. Insertion of a needle into the SH for caudal block is suggested to be done at its base to avoid the anatomic variations of its apex.

Spinal anesthesia or caudal anesthesia for anorectal surgery: An analysis of 74 cases

AIM: To observe the clinical effect of spinal anesthesia and caudal anesthesia in anorectal surgery.

METHODS: Seventy-four patients who underwent anorectal surgery between September 2009 and May 2012 were reviewed retrospectively. The patients were divided into spinal anesthesia group (n = 36) and caudal anesthesia group (n = 38). There were no significant differences in age, sex, illness, and operation time between the two groups. Anesthesia effect, onset time, cardiovascular complication, urinary retention, and time to sensory recovery were compared between the two groups.

RESULTS: The rate of satisfaction with anesthesia effect was 95% in the spinal anesthesia group and 79% in the caudal anesthesia group (P < 0.05). The morbidity of cardiovascular complication was 30.6% in the spinal anesthesia group and 5.3% in the caudal anesthesia group (P < 0.01). The mean onset time was 1.98 min in the spinal anesthesia group and 8.99 min in the caudal anesthesia group (P < 0.01). Urinary retention occurred in 4 cases in the spinal anesthesia group and in 3 cases in the caudal anesthesia group (P > 0.05). Mean time to sensory recovery was 324 min in the spinal anesthesia group and 288 min in the caudal anesthesia group (P > 0.05).

CONCLUSION: Spinal anesthesia has better clinical effect than caudal anesthesia when used in anorectal surgery, but the blood pressure and heart rate must be closely monitored and cardiovascular changes must be handled on time.

The caudal space in fetuses: an anatomical study

PURPOSE

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.

METHODS

Thirty-nine fetuses with crown-heel length between 33 and 50 cm, corresponding to gestational age of 7-9 months, 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.

RESULTS

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 13 mm; the anteroposterior distance of the canal at the apex of the hiatus ranged from 1.72 to 4.38 mm. All sacral parameters correlated with crown-heel length except inter-cornual distance, depth of canal at hiatus, and height of sacral hiatus.

CONCLUSION

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.

The evaluation of upper leg traction in lateral position for pediatric caudal block

PURPOSE

A well-functioning caudal block is an excellent adjunct to general anesthesia, but misplaced injection results in poor analgesia as well as possibility of serious morbidity. Therefore, the purpose of this study was to evaluate the effectiveness of leg traction on success rate of caudal block in lateral position in children.

METHODS

Two hundred children, age 2 months to 6 years, ASA I and II, who underwent lower abdominal surgeries were randomized in prospective controlled clinical trial study in two groups. After induction of General anesthesia, the caudal block was performed in the lateral position with upper leg traction (L-T-) or with the standard position (S-P) (leg flexed 90°). Hemodynamicchanges, movement of lower extremity in response to surgical stimulus were evaluated.

RESULTS

There was no significant difference in caudal block's success rate between two groups at first attempt (P=0.25). In group (S-P) the procedure was successful in 60% of cases at first attempt, 25% at second,10% at third attempt and 5% failure of caudal block, whereas in the first group it was 75%, 20%, 1% and 4% of cases respectively. There were no significant differences in heart rate and blood pressure changes between two groups (P>0.05).

CONCLUSION

The success rate of pediatric caudal block in upper leg traction did not differ from that of the standard position.

Ultrasound as a screening tool for proceeding with caudal epidural injections

OBJECTIVE

To study the anatomical structure of the sacral hiatus using ultrasound. Based on the sonographic images of the sacral hiatus, the feasibility of caudal epidural injection can then be assessed.

DESIGN

Case-controlled study.

SETTING

Rehabilitation outpatient clinic in a tertiary medical center.

PARTICIPANTS

Patients (N=47; 20 women, 27 men) with low back pain and sciatica who were to receive caudal epidural injection treatments were recruited into this study.

INTERVENTIONS

Sonographic images of the sacral hiatus were obtained from all the patients. An ultrasound machine capable of examining musculoskeletal tissues with real-time linear-array ultrasound transducer was used to measure the distance between the anterior wall and posterior wall of the sacral hiatus (diameter of the sacral hiatus) and the distance between bilateral cornua.

MAIN OUTCOME MEASURES

Diameter of the sacral canal and distance between bilateral cornua measured in millimeters.

RESULTS

The mean diameter of the sacral canal was measured to be 5.3+/-2.0 mm in our recruited patients. The mean distance between bilateral cornua was measured to be 9.7+/-1.9 mm. Caudal epidural injections failed in 7 patients. In these 7 patients, 4 had very small diameter of the sacral canal (1.6, 1.2, 1.4, and 1.5 mm). In 1 man, sonographic images revealed a closed sacral hiatus (no sacral canal diameter can be measured). Two patients revealed flow of fresh blood into the syringe while checking for the escape of cerebrospinal fluid after the needles were inserted into the sacral canal. For safety reasons, steroid injections were not performed in these 2 patients.

CONCLUSIONS

Ultrasound may be used as an effective screening tool for caudal epidural injections. Anatomic variations of the sacral hiatus can be clearly observed using ultrasound. Sonographic images indicating a closed sacral canal and sacral diameters ranging from 1.2 to 1.6mm may suggest a higher failure rate in caudal epidural injection.