Surface anatomical landmarks for the location of posterior sacral foramina in sacral nerve stimulation.

BACKGROUND: Sacral nerve stimulation is a common treatment for various pelvic floor disorders. It consists of the percutaneous introduction of electrodes through the posterior sacral foramina for therapeutic stimulation of the target sacral spinal nerve. The aim of our study was to determine the surface anatomical landmarks of the sacrum to facilitate identification of the posterior sacral foramina. METHODS: This study was conducted on 20 human cadavers. The cadavers were placed in a prone position, and all the soft tissues of the sacral region were removed to allow exposure of the osseous structures. Different measurements were taken in relation to the posterior sacral foramina, the posterior superior iliac spine (PSIS) and the median sacral crest (MSC). A median coefficient of variation (CV) was determined. RESULTS: The diameter of the second sacral foramen showed the greatest variability. The distances between each individual foramen and the MSC had an acceptable variability (CV < 20%). In contrast, the distance between foramina had a high variability. The distance between PSIS and the second posterior sacral foramen was also found to have an acceptable variability (CV < 20%). However, the angle formed by an horizontal line between PSIS and a line between PSIS and S2 foramina had high variability. CONCLUSIONS: We found that the distance between sacral foramina and MSC is relatively constant while the distance between foramina and the relations between foramina and PSIS is highly variable. Detailed knowledge of the anatomy may facilitate electrode placement and is complementary to the regular use of fluoroscopy.

Surface and boney landmarks for sacral neuromodulation: a cadaveric study.

INTRODUCTION AND HYPOTHESIS: Standard external landmarks have been suggested as a guide for in-office percutaneous nerve evaluation (PNE), but validity of these landmarks has not been assessed. Our objective was to determine whether the standard 9 cm from the tip of the coccyx indicates the position of the S3 sacral foramen and whether other boney landmarks and measurements improved positioning. METHODS: Measurements and distances between external boney landmarks were obtained in 22 embalmed cadavers. Spinal needles were placed 9 cm superior to the coccyx and 2 cm lateral to midline bilaterally. After dissection, internal measurements relating to sacral length, position of S3, and location of the needle in relation to S3 were recorded. Correlations among measured variables were assessed using descriptive statistics. RESULTS: Mean distance from the tip of coccyx to S3 was 9.26 cm (±0.84), from S3 to midline 2.30 cm (±0.2); from needle to S3 1.25 cm, and needle placement was as likely to be placed above or below S3; and S2-S3 and S3-S4 interforamenal distance 1.48 cm (±0.30) and 1.48 cm (±0.24), respectively. Mean distance from S3 to sacroiliac joint (SIJ) was shorter than S2 to SIJ. All associations between external measurements and length from tip of coccyx to S3 were not significant. CONCLUSION: A distance 9 cm from the tip of the coccyx is a reasonable starting landmark for in-office blind PNE. However, given the variability in coccyx length, caution should be taken; also, sensory-motor response is necessary to confirm proper placement.

A low-cost ultrasound phantom of the lumbosacral spine.

BACKGROUND AND OBJECTIVES: This report describes the production of a low-cost ultrasound phantom of the lumbosacral spine. The phantom should be a very useful tool to teach the basic skills for ultrasound-guided procedures of the lumbosacral spine. METHODS: A lumbosacral spine model is secured to the bottom of a microwave-safe container and is immersed in a concentrated gelatin solution. After the gelatin hardens, the model can be used for scanning practice as well as needle placement. The phantom can be recovered after use by melting the gelatin in a microwave to "erase" any needle track marks. RESULTS: A transparent and durable gelatin block is produced. This allows trainees to have direct visual access to the lumbosacral spine model to correlate with the ultrasound images as well as to confirm proper needle placement. Disadvantages of the model include lack of simulated soft tissue structures and an absence of simulated haptic feedback during needle placement. Metamucil can be added to the gelatin to simulate the appearance of soft tissue, although this increases the opacity and thus decreases the visual access of the gelatin. CONCLUSIONS: This teaching tool can provide trainees with an opportunity to familiarize themselves with sonoanatomy of the lumbosacral spine in addition to practicing probe handling techniques and needle placement.

Determination of the width of the presacral space on magnetic resonance imaging.

Presacral space enlargement may be the first sign of certain diseases. The normal width of the presacral space has not been widely investigated and in all previous studies was calculated from lateral radiographs obtained at barium enema examination. Our study determined the normal width of the presacral space on MRI and investigated a possible difference between men and women. The width of the presacral space was measured retrospectively from sagittal T2-weighted MR images of 193 patients (87 males; 106 females, aged 18-83 years). Presacral space width was measured separately for S1, S2, and S3 vertebral levels from the anterior surface of the vertebral bodies to the closest part of the posterior wall of the rectum. Differences between male and female subjects were analyzed by t-tests. Normal mean widths of the presacral space in men and women were 16.2 mm and 11.9 mm for S1, 14.9 mm and 11.2 mm for S2, and 13.0 mm and 10.6 mm for S3, respectively. Measurements of the presacral space width in men were significantly larger than in women at all three levels (P < 0.001 for S1, P < 0.001 for S2, P = 0.006 for S3). In summary, the presacral space width measured on MRI was found to be significantly larger in the male than in the female population.

Relaçöes anatômicas do ponto B-32 (Ciliao) localizado no segundo forame sacral / Anatomic relations of point B-32 (Ciliao) located on the second sacral foramen

O ponto B-32 (Ciliao) é utilizado no tratamento de afecções geniturinárias, lombalgias, lombociatalgias, dores genitais e pélvicas. O presente estudo visa determinar a profundidade e o ângulo de inserção do ponto B-32 (Ciliao) e sua relação com outras estruturas anatômicas; espinha ilíaca póstero-superior, forames sacrais posteriores, linha mediana posterior. Material - Foram estudados 30 cadáveres adultos masculinos e femininos fixados e conservados em solução aquosa de formol a 10 por cento. Método - Foram medidas as distâncias do forame S-2 à linha mediana posterior aos forames sacrais posteriores S-1, S-3, S-4, à espinha ilíaca póstero-superior. Foi traçada uma linha entre os dois forames S-2 e prolongada até a EIPS. Foi determinado o ângulo de inserção com o plano delimitado entre as espinhas ilíacas póstero-superiores e a margem superior do hiato sacral e a profundidade de inserção foi medida a partir do forama S2. Resultados - O teste t de Student não mostrou diferença significante entre os valores do lado direito e esquerdo. As distâncias médias entre o forame S-2 e a linha mediana posteior, aos formaes sacrais posteriores S-1, S-3, S-4, e a espinha ilíaca póstero-superior, foram de 1 tsun (1,9 cm), 0,8 tsun (1,8cm), 0,7 tsun (1,7cm), 1,4 tsun (3,0cm), 0,7 tsun (1,5cm), respectivamente. A localização do forame S-2 coincidiu com o nível da EIPS em 5 cadáveres (16,6 por cento) e foi inferior em 25 cadáveres (83,3 por cento). A profundidade média foi de 0,8 tsun (1,76cm). A média do ângulo com o plano delimitado foi de 53§. Conclusão - O ponto B-32 (Ciliao) localiza-se no formae S-2 do sacro de esqueleto humano adulto, a 1 tsun (1,9cm) da linha mediana posterior 0,8 tsun (1,8cm) abaixo de S-1, 0,7 tsun (1,7cm) acima de S-3, 1,4 tsun (3,0cm) acima de S-4, e 0,7 tsun (1,5cm) da espinha ilíaca póstero superior (83,3 por cento abaixo da EIPS, e 16,6 por cento no mesmo nível), a uma profundidade de 0,8 tsun (1,76cm) e com uma angulação de 53§ com o plano delimitado entre as espinhas ilíacas póstero-superiores e a margem superior do hiato sacral.

Distribution of hypothalamic neurons projecting to the thoracic and sacral spinal segments in the cat.

The distribution of hypothalamic neurons participating in hypothalamo-spinal projections (hypothalamo-spinal HSP neurons) to the thoracic and sacral segments was studied using the technique of retrograde axonal transport. Horseradish peroxidase (HRP) and nuclear yellow (NY) were injected into various thoracic and/or sacral spinal cord segments. The retrogradely labeled cells were distributed in a continuous crescent-shaped field in the posterior, dorsolateral and lateral regions of the hypothalamus: starting from the ventral tegmental area (VTA), through the posterior hypothalamic nucleus (PH), the supramammillary nucleus (SM), the dorsal- and lateral hypothalamic area (AH1) and LH), the dorsomedial nucleus (DM) as well as in the paraventricular nucleus (PV). Neurons in all of the above hypothalamic nuclei project as caudally as to the sacral segments. The projection is bilateral and the contralaterally projecting fibres cross the midline at or near their termination site. Projection to thoracic segments is mainly ipsilateral. HSP neurons projecting to upper thoracic and sacral segments showed different patterns of distribution. A sacral injection resulted in most labeled neurons in the SM and LH and less labeled neurons in the PV, than a thoracic injection of comparable size and locations. Experiments with two tracer substances suggested that some of HSP neurons had divergent axon collaterals terminating both in thoracic and sacral spinal segments.