Mean Canal-body Ratio among Specimens of Dried Lumbar Vertebrae in the Department of Anatomy of a Medical College: A Descriptive Cross-sectional Study

Introduction: Lumbar spinal canal stenosis is assumed to be one of the chief causative factors for low back pain. The measurement of lumbar canal and body dimensions has thus become an important tool for the diagnosis and treatment of spinal stenosis. This study aims to find out the mean canal-body ratio among specimens of dried lumbar vertebrae in a medical college. Methods: A descriptive cross-sectional study was done in a medical college from May, 2021 to July, 2021. Ethical clearance was taken from the Institutional Review Committee (Reference number: 0502202103) and whole sampling was done. Seventy-three intact dried lumbar vertebrae were studied for the dimensions of the body and canal in transverse and anteroposterior planes. The findings were recorded and the canal body ratio was calculated using the transverse diameters of the spinal canal and vertebral body. The data obtained were computed and analysed using Microsoft Excel 2013. Point estimate at 95% Confidence Interval was calculated along with mean and standard deviation for continuous data. Results: The mean canal-body ratio was observed to be 0.53±0.032. The vertebral canal-body ratio was observed to be 0.58 in L1 followed by 0.53 in L2, 0.51 in L3, 0.49 in L4 and 0.53 in L5. Conclusions: The mean canal-body ratio observed in the present study was comparable to studies done in similar settings.

Can a relatively large spinal cord for the dural sac influence severity of paralysis in elderly patients with cervical spinal cord injury caused by minor trauma?

Retrospective reviewThe degree of spinal cord compression and bony spinal canal stenosis are risk factors for the occurrence of spinal cord injury (SCI) without major fracture or dislocation, but they do not affect the severity of neurological symptoms. However, whether a relatively large spinal cord for the dural sac influences the severity of symptoms in SCI cases is unknown.The purpose of this study was to verify the influence of spinal cord size relative to dural sac on the severity of paralysis in elderly patients with cervical SCI caused by minor trauma.Subjects were 50 elderly patients with SCI caused by falls on flat ground. At 72 hours after injury, neurological assessment was performed using the Japanese Orthopaedic Association (JOA) scoring system. Bony canal anteroposterior diameters (APD) at mid C5 vertebral body were measured with computed tomography. We measured dural sac and spinal cord APD at the injured level and mid C5 with magnetic resonance imaging. Spinal cord compression ratio was calculated by dividing spinal cord at the injured level by spinal cord at mid C5. As the evaluation of spinal cord size relative to the dural sac, spinal cord/dural sac ratio was calculated at the injured level and mid C5. To clarify the factors influencing the severity of paralysis, the relationships between JOA score and those parameters were examined statistically.A significant negative correlation was observed between JOA score and spinal cord/dural sac ratio at mid C5. No clear relationship was observed between JOA score and bony canal APD or spinal cord compression ratio.In elderly patients with SCI caused by minor trauma, a relatively large spinal cord for the dural sac was shown to be a factor that influences the severity of paralysis. This result can be useful for the treatment and prevention of SCI in the elderly.

Development and evolution of the tetrapod skull-neck boundary

The origin and evolution of the vertebrate skull have been topics of intense study for more than two centuries. Whereas early theories of skull origin, such as the influential vertebral theory, have been largely refuted with respect to the anterior (pre-otic) region of the skull, the posterior (post-otic) region is known to be derived from the anteriormost paraxial segments, i.e. the somites. Here we review the morphology and development of the occiput in both living and extinct tetrapods, taking into account revised knowledge of skull development by augmenting historical accounts with recent data. When occipital composition is evaluated relative to its position along the neural axis, and specifically to the hypoglossal nerve complex, much of the apparent interspecific variation in the location of the skull-neck boundary stabilizes in a phylogenetically informative way. Based on this criterion, three distinct conditions are identified in (i) frogs, (ii) salamanders and caecilians, and (iii) amniotes. The position of the posteriormost occipital segment relative to the hypoglossal nerve is key to understanding the evolution of the posterior limit of the skull. By using cranial foramina as osteological proxies of the hypoglossal nerve, a survey of fossil taxa reveals the amniote condition to be present at the base of Tetrapoda. This result challenges traditional theories of cranial evolution, which posit translocation of the occiput to a more posterior location in amniotes relative to lissamphibians (frogs, salamanders, caecilians), and instead supports the largely overlooked hypothesis that the reduced occiput in lissamphibians is secondarily derived. Recent advances in our understanding of the genetic basis of axial patterning and its regulation in amniotes support the hypothesis that the lissamphibian occipital form may have arisen as the product of a homeotic shift in segment fate from an amniote-like condition.

Reference values for the cervical spinal canal and the vertebral bodies by MRI in a general population

Purpose

To provide population-based reference values for cervical spinal canal parameters and vertebral body (VB) width and to study their associations with sex, age, body height, body weight and body mass index (BMI) using MRI.

Methods

Cross-sectional analyses included data from 2,453 participants, aged 21–89 years, of the population-based Study of Health in Pomerania (SHIP) who underwent whole-body MRI at 1.5 Tesla between July 2008 and March 2011. A standardised reading was performed for the C2-C7 cervical spine levels at sagittal T2 TSE weighted sequences.

Results

Reference intervals for spinal canal parameters were similar in males and females, while VB width was on average 2.1–2.2 mm larger in males. Age effects were only substantial regarding VB width with a 0.5 mm per ten-year age increase. Body height effects were only substantial regarding the osseous spinal canal and VB width. Body weight and BMI effects are mostly not substantial.

Conclusions

Our study provides MRI-based reference values for the cervical spinal canal parameters in an adult Caucasian population. Except for VB width, associations with sex, age and somatometric measures are mostly small and thus have only limited clinical implications. Some available cut-off values may need a revision because they likely overestimate risks.

Current occurence of intraspinal intradural and extradural communicating branches in the spinal canal

THE AIM of this work is to point out the intraspinal anatomical current occurrence interconnections between intradural and extradural nerve roots and their possible participation in radiculopathy.

METHODS

The anatomical study was performed in 43 cadavers with a mean age of 53.7. All intradural and extradural rami communicantes between nerve roots were excised and examined histologically for the presence or absence of nervous tissue.

RESULTS

Anatomical preparations revealed intradural and extradural rami communicantes in 9 cases (20.9 %), mostly in the cervical region in 5 cases and by plexus formation variations in 5 cases. Multiple extradural rami communicantes were observed in 6 cases (13.95 %), including the simultaneous occurrence of multiple intradural and extradural ones in 5 cases (11.6 %).

CONCLUSIONS

This study allowed us to identify and describe unpublished intraspinal current occurrence intradural-extradural rami communicantes of nerve roots and their interrelationships throughout the spinal canal with their potential influence on the clinical picture (Tab. 1, Fig. 4, Ref. 25).

[The spinal dural arteriovenous fistula is an underdiagnosed vascular malformation]

The spinal dural arteriovenous fistula is the most common spinal vascular malformation, and it is severely underdiagnosed. The symptoms can mimic those of spinal stenosis. Today, the diagnosis is made by an advantageous combination of MR time-resolved imaging of contrast kinetics and digital subtraction angiography posing low risk to the patient. Treatment is primarily direct microsurgical obliteration. Early treatment is essential, since outcome is dependent on preoperative clinical status.

Comparison of the percentage of the C3-C7 vertebral canal occupied by the spinal cord in small-breed dogs with that in Doberman Pinschers and Great Danes with and without cervical spondylomyelopathy

OBJECTIVE To compare the percentage of the C3-C7 vertebral canal occupied by the spinal cord in small-breed dogs with that in Doberman Pinschers and Great Danes with and without cervical spondylomyelopathy (CSM). ANIMALS 30 small-breed dogs (body weight, < 15 kg), 15 clinically normal Doberman Pinschers, 15 Doberman Pinschers with CSM, 15 clinically normal Great Danes, and 15 Great Danes with CSM. PROCEDURES In a retrospective study, sagittal and transverse T2-weighted MRI images of the cervical (C3 to C7) vertebral column obtained from dogs that met study criteria and were free of extensive abnormalities that could affect the spinal cord diameter between January 2005 and February 2015 were reviewed. The area and height of the vertebral column and spinal cord were measured at the cranial and caudal aspect of each vertebra from C3 to C7, and the percentage of the vertebral canal occupied by the spinal cord at each location was calculated and compared among groups of dogs. RESULTS Mean percentage of the vertebral canal occupied by the spinal cord was greatest for small-breed dogs and lowest for Great Danes, but did not differ between Doberman Pinschers and small-breed dogs at approximately half of the locations evaluated or between Doberman Pinschers with and without CSM or between Great Danes with and without CSM. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that the percentage of the vertebral canal occupied by the spinal cord, although expected to increase with vertebral canal stenosis, may not have a primary role in the pathogenesis of CSM.

Charles Estienne (1504-1564): His Life, Work, and Contribution to Anatomy and the First Description of the Canal in the Spinal Cord

The purpose of this historic review is to summarize the life, work, and contribution to anatomy of Charles Estienne (also known by the Latin name Carolus Stephanus). Charles Estienne was an early exponent of the science of anatomy in France. Although he remained under the influence of the Galenic tradition of medicine, anatomy, and surgery throughout his distinguished career, he had a significant influence on the scientific revolution and anatomy reformation of the 16th century. Nevertheless, he cannot be placed at the same level of contribution as Vesalius, because of his lack of discipline in his work, hesitation to diverge totally from traditional beliefs, and his hesitation for a total criticism of the Galenic tradition.

Comparison of Cervical Spine Anatomy in Calves, Pigs and Humans

Background Context

Animals are commonly used to model the human spine for in vitro and in vivo experiments. Many studies have investigated similarities and differences between animals and humans in the lumbar and thoracic vertebrae. However, a quantitative anatomic comparison of calf, pig, and human cervical spines has not been reported.

Purpose

To compare fundamental structural similarities and differences in vertebral bodies from the cervical spines of commonly used experimental animal models and humans.

Study Design

Anatomical morphometric analysis was performed on cervical vertebra specimens harvested from humans and two common large animals (i.e., calves and pigs).

Methods

Multiple morphometric parameters were directly measured from cervical spine specimens of twelve pigs, twelve calves and twelve human adult cadavers. The following anatomical parameters were measured: vertebral body width (VBW), vertebral body depth (VBD), vertebral body height (VBH), spinal canal width (SCW), spinal canal depth (SCD), pedicle width (PW), pedicle depth (PD), pedicle inclination (PI), dens width (DW), dens depth (DD), total vertebral width (TVW), and total vertebral depth (TVD).

Results

The atlantoaxial (C1–2) joint in pigs is similar to that in humans and could serve as a human substitute. The pig cervical spine is highly similar to the human cervical spine, except for two large transverse processes in the anterior regions ofC4–C6. The width and depth of the calf odontoid process were larger than those in humans. VBW and VBD of calf cervical vertebrae were larger than those in humans, but the spinal canal was smaller. Calf C7 was relatively similar to human C7, thus, it may be a good substitute.

Conclusion

Pig cervical vertebrae were more suitable human substitutions than calf cervical vertebrae, especially with respect to C1, C2, and C7. The biomechanical properties of nerve vascular anatomy and various segment functions in pig and calf cervical vertebrae must be considered when selecting an animal model for research on the spine.

The Lumbar Spine as a Dynamic Structure Depicted in Upright MRI

Spinal canal stenosis is a dynamic phenomenon that becomes apparent during spinal loading. Current diagnostic procedures have considerable short comings in diagnosing the disease to full extend, as they are performed in supine situation. Upright MRI imaging might overcome this diagnostic gap.This study investigated the lumbar neuroforamenal diameter, spinal canal diameter, vertebral body translation, and vertebral body angles in 3 different body positions using upright MRI imaging.Fifteen subjects were enrolled in this study. A dynamic MRI in 3 different body positions (at 0° supine, 80° upright, and 80° upright + hyperlordosis posture) was taken using a 0.25 T open-configuration scanner equipped with a rotatable examination bed allowing a true standing MRI.The mean diameter of the neuroforamen at L5/S1 in 0° position was 8.4 mm on the right and 8.8 mm on the left, in 80° position 7.3 mm on the right and 7.2 mm on the left, and in 80° position with hyperlordosis 6.6 mm (P < 0.05) on the right and 6.1 mm on the left (P < 0.001).The mean area of the neuroforamen at L5/S1 in 0° position was 103.5 mm on the right and 105.0 mm on the left, in 80° position 92.5 mm on the right and 94.8 mm on the left, and in 80° position with hyperlordosis 81.9 mm on the right and 90.2 mm on the left.The mean volume of the spinal canal at the L5/S1 level in 0° position was 9770 mm, in 80° position 10600 mm, and in 80° position with hyperlordosis 9414 mm.The mean intervertebral translation at level L5/S1 was 8.3 mm in 0° position, 9.9 mm in 80° position, and 10.1 mm in the 80° position with hyperlordosis.The lordosis angle at level L5/S1 was 49.4° in 0° position, 55.8° in 80° position, and 64.7 mm in the 80° position with hyperlordosis.Spinal canal stenosis is subject to a dynamic process, that can be displayed in upright MRI imaging. The range of anomalies is clinically relevant and dynamic positioning of the patient during MRI can provide essential diagnostic information which are not attainable with other methods.

Automatic Segmentation of the Spinal Cord and Spinal Canal Coupled With Vertebral Labeling

Quantifying spinal cord (SC) atrophy in neurodegenerative and traumatic diseases brings important diagnosis and prognosis information for the clinician. We recently developed the PropSeg method, which allows for fast, accurate and automatic segmentation of the SC on different types of MRI contrast (e.g., T1-, T2- and T2(∗) -weighted sequences) and any field of view. However, comparing measurements from the SC between subjects is hindered by the lack of a generic coordinate system for the SC. In this paper, we present a new framework combining PropSeg and a vertebral level identification method, thereby enabling direct inter- and intra-subject comparison of SC measurements for large cohort studies as well as for longitudinal studies. Our segmentation method is based on the multi-resolution propagation of tubular deformable models. Coupled with an automatic intervertebral disk identification method, our segmentation pipeline provides quantitative metrics of the SC and spinal canal such as cross-sectional areas and volumes in a generic coordinate system based on vertebral levels. This framework was validated on 17 healthy subjects and on one patient with SC injury against manual segmentation. Results have been compared with an existing active surface method and show high local and global accuracy for both SC and spinal canal (Dice coefficients =0.91 ± 0.02) segmentation. Having a robust and automatic framework for SC segmentation and vertebral-based normalization opens the door to bias-free measurement of SC atrophy in large cohorts.

Significance of spinal canal and dural sac dimensions in predicting treatment of lumbar disc herniation

This retrospective study was performed to investigate the significance of quantitative MRI measurements of spinal canal and dural sac dimensions for treatment decisions and clinical outcome of lumbar disc herniation. 182 patients (111 nonsurgical patients and 71 surgical patients) were included, while 78 nonsurgical patients and 50 surgical patients were enrolled in the final follow-up. The initial JOA score in nonsurgical patients was significantly superior to surgical patients (t-test: p < 0.001), whereas the final JOA score and the rate of improvement were not significantly different between the two groups of patients (t-test: p > 0.05). 88.46% of nonsurgical patients and 90.00% of surgical patients had a good or excellent outcome (chi-square test: p > 0.05). However, if the 16 recurrent cases were included, the proportions dropped to 75.82% and 84.90% for nonsurgical and surgical patients, respectively. Compared with nonsurgical patients, quantitative parameters, such as midsagittal diameter and available diameter of spinal canal, lateral recess width and cross-sectional areas of spinal canal and dural sac, were significantly smaller in surgical patients (t-test: p < 0.001), and was reflected in the initial JOA score (128 cases; Spearman rank correlation coefficient: r 0.01 = 0.486, 0.499, 0.493, 0.507, 0.484; p < 0.001). The spinal canal and dural sac dimensions were important predictive factors for treatment selection of lumbar disc herniation.

Hyperextension injury of the cervical spine with central cord syndrome

PURPOSE

Traumatic central cord syndrome (TCCS) is the most commonly encountered type of incomplete spinal cord injury. TCCS typically occurs in patients over the age of 50 with a narrow spinal canal and follows an acute hyperextension injury of the cervical spine. Here, we report on the demographics of TCCS patients, their clinical course and outcomes, and the factors that may have influenced these outcomes.

METHODS

We conducted a retrospective folder review of patients who presented to our facility between January 2004 and December 2008 following hyperextension injury of the cervical spine and with the clinical manifestations of a central cord syndrome. Patient details were obtained from the acute spinal cord injury register at Groote Schuur Hospital and the patient folders, radiographs and magnetic resonance imaging films were reviewed. Predetermined data points were identified, tabulated and analysed, with only information from the injury-related admission being included.

RESULTS

An ASIA motor score of ≥60 on admission or discharge correlated with an 80 % chance of being able to walk at discharge from hospital. An ASIA motor score of ≤50 on admission correlated with an 80 % chance of not walking at discharge. An ASIA motor score of ≤50 at discharge meant a patient was not only unable to walk, but required placement in a spinal injury rehabilitation centre. Further, if a patient had a cervical spinal canal diameter of ≥8 mm they had a 50 % chance of clinical improvement and nearly 80 % chance of a functional outcome.

CONCLUSION

The Groote Schuur Hospital patient population differs from the international norm, particularly with respect to age and mechanism of injury. The ASIA motor score and cervical spine canal diameter proved to be useful predictors of outcome. Within our patient group, timing of surgery did not appear to influence the outcome.

Interpars - an anatomical examination of the lumbar pars interarticulares with significance for spinal decompression

BACKGROUND

Spine procedures continue to increase significantly. As such, a more precise understanding of the anatomy, especially the pars interarticularis (PI) is critical. Current data characterizing the PI level-by-level is lacking. This study analyzed the average PI width at each level of the lumbar spine in order to elucidate statistically significant PI variations between lumbar levels.

METHODS

The interpars distance, the narrowest distance between the lateral edges of the left and right PI, was measured directly with calipers on 53 complete lumbar specimens and digitally via Fastrack measurements of 30 sets of lumbar vertebrae. For both methods, the mean interpars distances were compared moving down the lumbar spine.

RESULTS

For direct measurements, the average interpars distances increased from L2 to L5. Analysis revealed significant differences across all levels. A significant difference was noted between male and female vertebrae only at L1. For Fastrack measurements, the average interpars distances also increased from L2 to L5. An increase in spinal canal width was observed across all but L1-L2, and an increase in the interpars-to-spinal-canal-width ratio was noted at all levels except L1-L2 and L4-L5.

CONCLUSIONS

The amount of bone in the PI available for surgical removal becomes smaller moving from L5 to L1. There is a larger "margin-for-error" at L4 and L5 when decompressing the spinal canal from one side to the other than there is in the upper lumbar spine. At L1 and L2, de- compressing the entire width of the spinal canal leaves only a millimeter of remaining pars on either side. Care should be taken to use "undercutting techniques" in upper lumbar decompressions to preserve the PI.

Changes in spinal canal diameter and vertebral body height with age

PURPOSE

All structures of the spine, including the spinal canal, change continuously with age. The purpose of this study was to determine how the spinal canal of the lumbar spine changes with age. The L4/5 is the most common site of spinal stenosis and has the largest flexion-extension motion, whereas the T5/6 has the least motion. Therefore, we measured the spinal canal diameter and vertebral body height at T5, T6, L4, and L5 with age.

MATERIALS AND METHODS

This was a retrospective study of aged 40 to 77 years. We reviewed whole spine sagittal MRIs of 370 patients with lumbar spinal stenosis (LSS) (Group 2) and 166 herniated cervical disc (HCD) (Group 1). Each group was divided into four age groups, and demographic parameters (age, gender, height, weight, BMI), the mid-spinal canal diameter, and mid-vertebrae height at T5, T6, L4, L5 were compared. Within- and between-group comparisons were made to evaluate changes by age and correlations were carried out to evaluate the relationships between all parameters.

RESULTS

Height, weight, and all radiologic parameters were significantly lower in Group 2 than Group 1. Group 1 did not show any differences, when based on age, but in Group 2, height, weight, and T6, L4, and L5 height were significantly decreased in patients in their 70's than patients in their 40's, except for spinal canal diameter. Age was associated with all parameters except spinal canal diameter.

CONCLUSION

Vertebral height decreased with age, but spinal canal diameter did not change in patients with either LSS or HCD. Mid-spinal canal diameter was not affected by aging.

[Applied anatomical study on approach next to erector spinae for spinal canal decompression through intervertebral foramen]

OBJECTIVE

To observe and measure the approach next to the erector spinae in the thoracic and lumbar segments of the spine and adjacent anatomical structures by the topographic method, to clarify the positioning method and safe range so as to provide the anatomical basis of the approach for spinal canal decompression.

METHODS

Twelve formaldehyde-treated adult cadaver specimens were selected, including 6 males and 6 females with an average age of 43 years (range, 27-52 years) and with an average height of 166 cm (range, 154-177 cm). The related data of the approach at T1-S1 levels were respectively measured: the distance between the lateral edge of the erector spinae and the spinous process, the length of the approach, the angle between the approach and the horizontal plane, the size of intervertebral foramen, and the vertical distance between the segmental artery and the upper edge of the vertebrae.

RESULTS

The distance between the lateral edge of the erector spinae and the spinous process ranged from (41.75 +/- 3.29) mm to (74.54 +/- 7.08) mm. The length of the approach ranged from (66.75 +/- 10.81) mm to (97.13 +/- 13.35) mm. The angle between the approach and the horizontal plane ranged from (38.38 +/- 6.16) degrees to (53.67 +/- 4.40) degrees. The vertical distance between the segmental artery and the upper edge of the vertebrae ranged from (9.50 +/-0.60) mm to (18.30 +/- 1.56) mm. The size of foraminal was also measured. The spinal canal could reach when iliocostalis lateral edge was used as the starting point in the lumbar segments, and longissimus lateral edge as the starting point in the thoracic segments. It was confirmed that there was enough safe space for the spinal decompression without the resection of the articular process.

CONCLUSION

The approach next to the erector spinae can reach spinal canal to achieve the purpose of decompression through the intervertebral foramen. The minimally invasive approach is feasible and safe. It has the value of the operative application.

The denticulate ligament: anatomical properties, functional and clinical significance

BACKGROUND

It is widely believed that the main function of denticulate ligaments (DLs) is to stabilize the spinal cord within the vertebral canal. The aim of this study was to assess the anatomical and histological structure of the DLs and to document any regional differences.

METHODS

Five formalin-fixed adult cadavers were used. The DLs were exposed via the posterior approach, and detailed anatomy and histology of these structures were documented.

RESULTS

The main findings were: (1) each DL is composed of a single narrow fibrous strip that extends from the craniovertebral junction to T12, and each also features 18-20 triangular extensions that attach to the dura at their apices; (2) the triangular extensions are smaller and more numerous at the cervical levels, and are larger and less numerous at the thoracic levels; (3) the apices of the extensions attach to the dura via fibrous bands at cervical levels (each band 3-5 mm long) and lower thoracic levels (21-26 mm long), whereas they attach directly to the dura at upper thoracic levels; (4) the narrow fibrous strip of the DL features longitudinally oriented collagen fibers, whereas the triangular extensions are composed of transverse and obliquely oriented collagen fibers. The collagen fibers are thicker and more abundant at the cervical than at the thoracic levels.

CONCLUSION

DL histology and anatomy are strongly correlated with the function of this structure at different spinal levels. It is important to have accurate knowledge about DLs as these structures are relevant for clinical procedures that involve the spinal cord or craniovertebral junction.

Lumbosacral intrathecal nerve roots: an anatomical study

BACKGROUND

The lumbosacral intrathecal anatomy is complex because of the density of nerve roots in the cauda equina. Space-occupying lesions, including disc herniation, trauma and tumor, within the spinal canal may compromise the nerve roots, causing severe clinical syndromes. The goal of this study is to provide spinal surgeons with a detailed anatomical description of the intrathecal nerve roots and to emphasize their clinical importance.

METHOD

Ten formalin-fixed male cadavers were studied. They were dissected with the aid of a surgical microscope, and measurements were performed.

RESULTS

The number of dorsal and ventral roots ranged from one to three. The average diameter of roots increased from L1 to S1 (0.80 mm for L1 and 4.16 for S1), respectively. Then their diameter decreased from S1 to S5 (4.16 mm for S1, 0.46 mm for S5). The largest diameter was found at S1 and the smallest at S5. The average number of rootlets per nerve root increased from L1 to S1, then decreased (3.25 for L1, 12.6 for S1, and 1.2 for S5), respectively. The greatest rootlet number was seen at S1, and the fewest were observed at S5. The average diameter of the lateral recess gradually decreased from L1 to L4 (9.1 mm for L1; 5.96 mm for L4) and then increased at L5 level (6.06 mm); however, the diameter of the nerve root increased from L1 to L5. The midpoint of distance between the superior and inferior edge of the intradural exit nerve root was 3.47 mm below the inferior edge of the superior articular process at the L1 level, while the origin of the L5 exit root was 5.75 mm above the inferior edge. The root origin gradually ascended from L1 to L5.

CONCLUSIONS

The findings of this study may be valuable for understanding lesions compressing intradural nerve roots and may be useful for intradural spinal procedures.

Three-dimensional magnetic resonance image of structures enclosed in the spinal canal relevant to anesthetists and estimation of the lumbosacral CSF volume

Three-dimensional (3D) image-reconstruction of structures inside the spinal canal certainly produces relevant data of interest in regional anesthesia. Nowadays, all hospital MRI equipment is designed mainly for clinical diagnostic purposes. In order to overcome the limitations we have produced more accurate images of structures contained inside the spinal canal using different software, validating our quantitative results with those obtained with standard hospital MRI equipment. Neuroanatomical 3D reconstruction using Amira software, including detailed manual edition was compared with semi-automatic 3D segmentation for CSF volume calculations by commonly available software linked to the MR equipment (MR hospital). Axial sections from seven patients were grouped in two aligned blocks (T1 Fast Field Eco 3D and T2 Balance Fast Field Eco 3D-resolution 0,65 x 0,65 x 0,65 mm, 130 mm length, 400 sections per case). T2 weighted was used for CSF volume estimations. The selected program allowed us to reconstruct 3D images of human vertebrae, dural sac, epidural fat, CSF and nerve roots. The CSF volume, including the amount contained inside nerve roots, was calculated. Different segmentation thresholds were used, but the CSF volume estimations showed high correlation between both teams (Pearson coefficient = 0.98, p = 0.003 for lower blocks; Pearson 0.89, p = 0.042 for upper blocks). The mean estimated value of CSF volume in lower blocks (L3-S1) was 15.8 + 2.9 ml (Amira software) and 13.1 +/- 1.9 ml (software linked to the MR equipment) and in upper blocks (T11-L2) was 21 +/- 4.47 ml and 18.9 +/- 3.5 ml, respectively. A high variability was detected among cases, without correlation with either weight, height or body mass index. Aspects concerning the partial volume effect are also discussed. Quick semi-automatic hospital 3D reconstructions give results close to detailed neuroanatomical 3D reconstruction and could be used in the future for individual quantification of lumbosacral CSF volumes and other structures for anesthetic purposes.

[The anatomic study of transferring thoracic nerve roots to lumbar nerve root inside the spinal canal of paraplegia]

OBJECTIVE

To study the fundamental anatomy of transferring T(9-12) nerve roots to L(2-4) nerve root for the quadriceps function recovery inside the spinal canal of paraplegia.

METHODS

Thoracic and lumbar spinal canal and spinal dura mater of 5 adult cadavers (male 2 and female 3) were opened and explored. Investigated including: the position which T₉-L₄ nerve root generated from spinal cord; the relation between the position which T₉-L₄ nerve root generated from spinal cord and T₁₂ vertebrae and L₁ vertebrae; The length beginning part of T₉-L₄ nerve root inside the spinal canal. The diameter of T₉-L₄ nerve root. The distance between the T₉-L₄ nerve root separately. The distance between the position which T(9-12) nerve root separately generated from dura mater and the middle of L₂ vertebrae.

RESULTS

T₉ nerve root generated from the middle part of T₉ vertebrae; L₄ nerve root generates from middle part of L₂ vertebrae. The average length of T₉-L₄ nerve root inside the spinal canal separately was 16.12, 22.97, 30.43, 43.47, 56.02, 70.03, 88.70 and 113.65 mm. The average diameter of T₉-L₄ nerve root separately was 2.45, 2.04, 1.96, 2.18, 2.32, 2.56, 3.10 and 3.26 mm. The average distance between the beginning part of T₉-L₄ nerve root separately was 22.87, 25.08, 28.47, 27.38, 29.78, 31.93 and 31.00 mm. The average distance between the position which T(9-12) nerve root separately generated from dura mater and the middle of L₂ vertebrae was 118.69, 95.82, 70.74, and 42.27 mm.

CONCLUSIONS

T(9-12) nerve root can be used as donor nerve for repair L(2-4) nerve root. The level of L₂ vertebrae can be anastomose site of the recipient nerve.

Effect of lumbar angular motion on central canal diameter: positional MRI study in 491 cases

BACKGROUND

Lumbar spinal stenosis is a common problem that is receiving attention with the advent of novel treatment procedures. Prior positional MRI studies demonstrated lumbar canal diameter changes with flexion and extension. There have not been any studies to examine the amount of spinal canal diameter change relative to the amount of angular motion. The purpose of this study was to evaluate the correlation between the lumbar canal diameter change and the angular motion quantitatively.

METHODS

Positional MRI (pMRI) images for 491 patients, including 310 males and 181 females (16 years-85 years of age), were obtained with the subjects in sitting flexion 40 degree, upright, and with extension of 10 degrees within a 0.6 T Positional MRI scanner. Quantitative measurements of the canal diameter and segmental angle of each level in the sagittal midline plane were obtained for each position. Then the diameter change and angular motion were examined for correlation during flexion and extension with linear regression analysis.

RESULTS

The lumbar segmental angles were lordotic in all positions except L1-2 in flexion. The changes of canal diameters were statistically correlated with the segmental angular motions during flexion and extension (P < 0.001). The amount of canal diameter change correlated with the amount of angular change and was expressed as a ratio.

CONCLUSIONS

Positional MRI demonstrated the amount of spinal canal diameter change that was statistically correlated with the segmental angular motion of the spine during flexion and extension. These results may be used to predict the extent of canal diameter change when interspinous devices or positional changes are used to treat spinal stenosis and the amount of increased canal space may be predicted with the amount of angular or positional change of the spine. This may correlate with symptomatic relief and allow for improved success in the treatment of spinal stenosis.

Comparison of cervical spinal canal diameter between younger and elder generations of Japanese

BACKGROUND

Cervical myelopathy is more common among Japanese than Westerners. The shorter anteroposterior diameter of the cervical spinal canals (AP diameter) is its probable cause. In recent years, builds of younger Japanese have become larger and been approaching those of Westerners. The purpose of this study was to investigate whether the cervical spinal canal had enlarged in the younger Japanese as well as any cross-sectional improvement in their builds.

METHODS

The subjects included 300 men and 300 women who were healthy and without symptoms related to the cervical spine. They were divided into six age groups at 10-year intervals from the twenties to the seventies. Height, body weight, and arm span were measured as physical factors. Using lateral dynamic radiographs of the cervical spine, the AP diameter from C3 to C6 in the neutral position and Penning's jaw diameter in extension (jaw diameter) from C2/3 to C5/6 were measured. The number of trapezoid-shaped vertebral bodies with a thickened posterior margin were also counted as such thickening might be one of the causes of spinal canal narrowing. Statistical analysis was performed for the following associations in both sexes: (1) age and physical factors; (2) age and the AP diameter; (3) age and jaw diameter; and (4) the difference of the AP diameter of the canal within and outside the trapezoid-shaped deformity of the vertebral body.

RESULTS

In both men and women, the younger generations statistically had a larger height, arm span, and AP diameter. Older generations showed a significantly narrower jaw diameter at all measured spinal levels in both sexes. Trapezoid-shaped vertebral bodies were found in 3.5% of the men and in 1.3% of the women in their fifties, sixties, and seventies, which statistically had no effect on the AP diameter being wider in the younger generations.

CONCLUSIONS

Younger generations had larger builds and a wider canal of the cervical spine. A narrow spinal canal is a fundamental risk factor for cervical myelopathy. Therefore, cervical myelopathy might be expected to decrease in Japan in the near future when the present younger generations have aged.

Clinical implications of epidural fat in the spinal canal. A scanning electron microscopic study

BACKGROUND AND OBJECTIVES

This review of articles summarizes recent developments in relation to fat located in the epidural space and also in dural sleeves of spinal nerve roots in order to improve our understanding of the clinical effects of the epidural blockade.

METHOD

Medline search was carried cross-matching of the following words: "epidural fat", "epidural space", "adipose tissue" and "fat cells" from 1966 to 2008 in which articles referring to different pathologies that alter the epidural fat were also reviewed. Techniques used by different authors included the use of samples from dissections, cryomicrotome sections, as well as light and electron microscopy.

RESULTS

Fat in the epidural space has a metameric distribution along the spinal canal that can be altered in some pathological conditions. Epidural fat is not evenly distributed. At cervical level fat is absent while in the lumbar region, fat in the anterior and posterior aspects of the epidural space forms two unconnected structures. Fat cells are found also in the thickness of dural sleeves enveloping spinal nerve roots but not in the region of the dural sac. Epidural lipomatosis is characterized by an increase in epidural fat content. When a patient has a combination of kyphosis and scoliosis of the spine, the epidural fat distributes asymmetrically. Spinal stenosis is frequently accompanied by a reduction in the amount of epidural fat around the stenotic area.

CONCLUSIONS

The epidural space contains abundant epidural fat that distributes along the spinal canal in a predictable pattern. Fat cells are also abundant in the dura that forms the sleeves around spinal nerve roots but they are not embedded within the laminas that form the dura mater of the dural sac. Drugs stored in fat, inside dural sleeves, could have a greater impact on nerve roots than drugs stored in epidural fat, given that the concentration of fat is proportionally higher inside nerve root sleeves than in the epidural space, and that the distance between nerves and fat is shorter. Similarly, changes in fat content and distribution caused by different pathologies may alter the absorption and distribution of drugs injected in the epidural space.

[Sagittal diameters measurements on MR of the cervical spinal cord in normal subjects]

OBJECTIVE

To offer normal reference of diameter of the cervical spinal cord and available diameter of cervical spinal canal and to screen scientific radiographic criteria to define and quantify cervical spinal cord disease.

METHODS

The magnetic resonance images of 120 normal people had been measured. The data of diameters of cervical spinal cord, CSF, M, the ratio of diameters of cord and CSF, and the ratio of diameters of cord and M had been collected and statistical analysis was made. And the relationships between the data above and each of gender, the length of C-spine and age were evaluated. In addition, the ratio of diameters of cord and CSF, and the ratio of diameters of cord and M was evaluated.

RESULTS

The study showed that in healthy people, the diameters of cervical spinal cord, CSF and M was larger in the males than in the females, decreased with age, and increased with the length of C-spine but the diameter of CSF. And the ratio of diameters of cord and CSF increased with age and not affected by the length of C-spine. However, the ratio of diameters of cord and M was not affected by age and the length of C-spine.

CONCLUSION

The ratio of diameters of cord and M is not affected by individual variation and can be used to evaluate cervical spinal cord atrophy, compression and impaired in patients with cervical myelopathy and can be important information in looking for clinically critical points.

Five-level one-piece laminoplasty for extensive tumors of the lumbar spine

The authors describe the surgical method and results of nonexpansive one-piece multivel laminoplasty of the whole lumbar spine, for microsurgical resection of extensive spinal tumors. This technique allows a very comfortable approach to the dura and intradural content, as well as a perfect replacement of the posterior spinal arch with supporting elements and an optimal reconstruction of the spinal anatomy. A nonexpansive whole lumbar one-piece laminoplasty was performed for resection of extensive multilevel lumbar tumors. The authors report an illustrative case of a patient who initially presented with a three-year history of numbness on both legs and progressive difficulty in walking. Two months before admission, he complained of bilateral sciatica and rectourinary dysfunction. A spinal magnetic resonance imaging (MRI) documented an intradural tumor extending from L2 to S1. The patient underwent a nonexpansive whole lumbar one-piece laminoplasty and microsurgical removal of the intradural lesion. The postoperative course was uneventful, the sensory disturbances and bilateral sciatica early recovered while rectourinary disturbance gradually improved up to a complete resolution at one year follow-up. The authors believe that multilevel laminoplasty rather than laminectomy is the technique of choice as a posterior procedure for extensive lumbar spinal tumors. With this technique, it is possible to obtain a very confortable approach to the dura and intradural content, as well as a perfect replacement of the posterior spinal arch with supporting elements and an optimal reconstruction of the normal spine. Moreover, this method prevents postoperative instability and deformity and avoids the so called post-laminectomy epidural membrane.

Sectioning of filum terminale externum using a rigid endoscope through the sacral hiatus. Cadaver study

AIM

Tethered cord syndrome (TCS) is a stretch-induced functional disorder of the spinal cord, which is directly related to filum fixation. Classic surgical approaches to the filum involve open surgery and include varying amounts of spinal bone removal. In an effort to reduce the morbidity and mortality of these procedures, the authors explored a less invasive method. They evaluated the ability, safety and feasibility for endoscopic sectioning of the filum terminale externum by performing upward orientated navigation in the extradural sacral spinal canal through the sacral hiatus using a rigid endoscope.

METHODS

Four adult, phenol-formalin embalmed cadavers were used for endoscopic section of the filum terminale externum at the tip of thecal sac. After preparing the anatomical area of sacral hiatus, a rigid endoscope (Storz, of 3.8 mm external diameter with two working channels, of 1 mm each, one for suction-irrigation and one as working) was inserted into the extradural sacral spinal canal and the filum terminale externum was identified and cut easily at the distal end of thecal sac at the level of S2. In all cases, it was possible to manipulate the rigid endoscope and inspect the full length of the extradural sacral spinal canal, especially at the S1-S2 level.

RESULTS

The results indicate that the tested transhiatal approach for upward orientated extradural endoscopy represents a minimally invasive procedure that provides an appropriate and feasible route to the extradural sacral spinal canal.

CONCLUSION

Such approach is an attractive alternative for filum terminale externum sectioning in cases where tethered cord syndrome is not accompanied by any other pathology. Moreover if filum terminale internum sectiong is indicated, it can be performed in second stage.

Endoscopic anatomy of the thecal sac using a flexible steerable endoscope

In this study the ability for upward-orientated endoscopic visualization of thecal subarachnoid space using a flexible steerable endoscope was evaluated in order to compare endoscopic anatomical findings with the already known macroscopic ones of the incontained structures and to test the approach for clinical employment. For this purpose, four adult phenol-formalin embalmed cadavers were used and the approach selected was through a laminectomy window at the S1-S2 level. The dura mater was opened and a flexible steerable endoscope (Storz, of 2.8 mm external diameter with one working channel) was inserted subarachnoidally for upward-orientated observation of the content of thecal sac. By using this approach filum terminale, lower lumbar, sacral and coccygeal nerve rootlets were identified and observed in detail. By moving the endoscope even more upwards, inspection of the upper part of the thecal subarachnoid space and conus medullaris was also possible. The findings collected from the study indicate that this approach for upward-orientated intradural subarachnoid endoscopy gives an appropriate working and inspecting window to the lower, as well as to the upper part of the thecal subarachnoid space and even of the conus medullaris. Furthermore, inspection and identification of lower lumbar, sacral and coccygeal nerve rootlets is possible and efficient and the endoscopic anatomical observations coincide with the already known gross-anatomical ones.

Lumbar retrodiscal transforaminal injection

BACKGROUND

Spinal injections are commonly used to treat lumbar radiculitis and back pain. Delivery of medication to specific targeted pathology is considered important for a successful therapeutic outcome. A variety of routes of injection have been devised for epidural injection of corticosteroid.

OBJECTIVES

The author demonstrates a variation of the transforaminal injection technique. The radiographic spread of contrast is described using a more oblique and ventral caudad approach in the epidural space "retrodiscal." It is suggested that the radiographic findings of this technique for discogenic causes of induced radiculitis and/or back pain may yield more precise targeting of putative pathologic sources of radiculopathy and back pain in selected patients.

METHODS

In patients with disc pathology and radiculitis, the anatomy of the lumbar epidural space is reviewed for its potential effect on the flow of injectate. Contrast spread was documented for lumbar transforaminal injection using a needle placement more oblique and behind the disc rather than in the cranial portion. Comparison is made to a typical contrast spread of an infra-pedicular placed transforaminal injection.

RESULTS

Retrodiscal contrast injection results in reliable coverage of the retrodiscal region, the exiting nerve at that foraminal level and the proximal portion of the transiting segmental neural sleeve.

CONCLUSIONS

The radiographic findings demonstrate a difference between classic infra-pedicular versus retrodiscal transforaminal epidural contrast injection patterns, particularly at relatively low volumes. The clinical advantage of one technique versus the other should be established in randomized prospective studies.

The anatomy of the thoracic spinal canal investigated with magnetic resonance imaging (MRI)

BACKGROUND AND OBJECTIVES

Anesthesiologists are reluctant to consider higher levels for spinal anesthesia, largely due to direct threats to the spinal cord. The goal of this study is to investigate, with magnetic resonance imaging (MRI), the distances between the relevant structures of the spinal canal (spinal cord, thecal tissue, etc.) to determine modal anatomical positions for neuraxial anesthesia.

METHOD

A group of 19 patients were imaged with an MRI scanner in supine position. Medial sagittal slices of the thoracic and lumbar spine were measured for the relative distances between anatomical structures, including epidural space, dura, and spinal cord.

RESULTS

The posterior dura - spinal cord distance is significantly greater in the middle thoracic region than at upper and lower thoracic levels (e.g. T6 9.5 +/- 1.8 mm, T12 3.7 +/- 1.2 mm, p < 0.001, T1 4.7 +/- 1.7 mm, p < 0.001). There is variation in modal distances between the structures important for neuraxial anesthesia, at different levels of the spinal canal.

CONCLUSIONS

The spinal cord tends to follow the straightest line through the imposed geometry of the spine. Considering the necessary angle of entry of the needle at mid-thoracic levels, there is relatively (more than at upper thoracic and lumbar levels) substantial separation of cord and surrounding thecal tissue. Anesthesiologists perform spinal blockades up to the L2-L3 interspace, but avoid higher levels for fear of neurological damage. The information that there is substantially more space in the dorsal subarachnoid space at thoracic level, might lead to potential applications in regional anesthesia. In contrast, the cauda equina sits more dorsally in the lumbar region.

Computed tomography study of implantation corridors in canine vertebrae

OBJECTIVES

To define the characteristics of optimum implantation corridors in vertebral bodies C2 to C7 and T10 to S1, using computed tomography examination.

METHODS

Measurements were taken from 207 vertebrae from 35 different adult dogs.

RESULTS

Implantation corridors of the cervical vertebrae are narrow. The width preserving the transverse hole is less than 2.5 mm in 68.6 per cent of the 86 vertebrae C2 to C6. Dorsal implantation corridors of the last four thoracic vertebrae are narrow, and major anatomical structures are very close to their emergence point. In 63 per cent of the 40 thoracic vertebrae, the right azygos vein is at a distance less than or equal to 1 mm from the vertebral body. The first six lumbar vertebrae have broader corridors. Furthermore, vascular structures are far from the emergence point. The last lumbar vertebra and the sacrum have a broad pedicle, which provides an alternative site for implant placement.

CLINICAL SIGNIFICANCE

For the vertebrae L1 to S1, the dorsal implantation can be performed. For the cervical vertebrae, the risk of laceration of the vertebral artery is high. For the last four thoracic vertebrae, the dorsal implantation should not be used.

The BiP Test: a modified loss of resistance technique for confirming epidural needle placement

BACKGROUND

Correct identification of the epidural space minimizes complications and ensures successful epidural blockade. The loss of resistance technique is the most common technique used for identification of the epidural space. However, sometimes loss of resistance occurs when the needle is not actually in the epidural space. The injection in this instance will result in the medication not being deposited in the epidural space. At other times, loss of resistance is not definitive. Further advancement of the needle may predispose to a wet tap.

METHODS

A simple manual technique was devised using pressure applied with two fingers (bi-digital pressure test; BiP Test).

RESULTS

The technique helps distinguish true loss of resistance from a false loss of resistance.

CONCLUSION

This technique adds a useful confirmatory test to the already well-known loss of resistance technique used to verify the position of the epidural needle.

Morphometric analysis of the roots and neural foramina of the lumbar vertebrae

BACKGROUND

There have been few anatomic studies on the foramina and roots of the lumbar region, and those available in human specimens are usually based on computed tomography and magnetic resonance imaging methods.

METHODS

Using the recent breakthroughs in microscopic anatomic dissections, the roots and vertebral foramina of the lumbar region were examined in 15 cadavers. Morphometric analysis of the roots and vertebral foramina of 80 lumbar vertebral objects was conducted.

RESULTS

The transverse and sagittal diameters of the lumbar intervertebral foramina were measured at each vertebral level. The median diameter of the lumbar neural foramina was 8.8 +/- 1.7 mm for the transverse and 19.4 +/- 2.7 mm for the sagittal planes. The widest median diameter of roots was 3.9 mm in the L4 root, and the narrowest was 3.3 mm in the L1 root.

CONCLUSION

Quantitative measurements of the diameters of the neural foramina and roots of the lumbar region in anatomic dissection models may provide a deeper understanding about the pathologies of this region and influence the success of surgical interventions.

Morphological Study of the Spinal Canal Content for Subarachnoid Endoscopy

STUDY DESIGN AND OBJECTIVE

This study was designed to examine the morphology of the spinal dural sac and contents, using magnetic resonance imaging in order to define the inner geometrical dimensions that confine the manoeuvre of an endoscope inserted in the lumbar region and along the thoracic and cervical spine.

BACKGROUND

The morphology of the spine has been studied since the development of myelography. However, most studies have measured the diameters of the spinal cord only, not the size of the subarachnoid space. In addition, the few studies available on the subarachnoid space have focused on the cervical spine, leaving a near-complete dearth of data on the subarachnoid space dimensions along the thoracic spine.

METHODS

Based on MRI images of the spine from 42 patients, the dimensions of the spinal cord, dural sac, and subarachnoid space were measured at mid-vertebral and inter-vertebral disc levels.

RESULTS

It was found that at each selected transverse level, the subarachnoid space tends to be symmetrical on the right and left sides of the cord, and measures 2.5 mm on average. However, the posterior and anterior segments, measured on the mid-sagittal plane, are generally asymmetrical and vary widely in size, ranging from 1 to 5 mm. These measurements match those found in previous studies, where these are available. The coefficient of variance for the dimensions of the subarachnoid space is as high as 42.4%, while that for the dimensions of the spinal cord is 10-15%.

CONCLUSIONS

The findings presented here expand our knowledge of the spinal canal's morphology, and show that an endoscope designed to travel within the subarachnoid space must be smaller than 2.5 mm in diameter.

Accuracy of Pedicle Screw Placement for Lumbar Fusion using Anatomic Landmarks versus Open Laminectomy: A Comparison of Two Surgical Techniques in Cadaveric Specimens

OBJECTIVE:

We determined whether the accuracy of lumbar pedicle screw placement is optimized by performing a laminectomy before screw placement with screw entry point and trajectory being guided by pedicle visualization and palpation (Technique 1). This technique was compared with a technique using anatomic landmarks for pedicle screw placement (Technique 2). The biomechanical stability of the instrumented constructs, in the absence and presence of a laminectomy, was also compared.

METHODS:

Twelve L1–L3 specimens were harvested from fresh cadavers. The intact laminectomy and instrumented spines were biomechanically tested in flexion and extension, lateral bending, and axial rotation. Laminectomies were performed in six of the 12 specimens before pedicle screw placement using Technique 1. The remaining six specimens underwent pedicle screw and rod fixation using Technique 2. Computed tomographic images were obtained for all instrumented specimens. Deviation of the screws from the ideal entry point or trajectory was analyzed to quantitatively compare the two techniques.

RESULTS:

Computed tomographic analysis of the specimens showed that all screw placements were within the pedicles. Scatter plot analysis demonstrated that screws placed using Technique 2 were more likely to have the combination of entry points and trajectories medial to the ideal entry point and trajectory. Laminectomy did not weaken the final pedicle screw and rod-fixated constructs.

CONCLUSION:

All screw placements were grossly within the confines of the pedicles, regardless of technique, as evidenced by computed tomographic analysis. Furthermore, the anatomic landmark technique and the open laminectomy technique yielded biomechanically equivalent pedicle screw and rod-fixated constructs.

Dynamic Canal Encroachment of Ligamentum Flavum

OBJECTIVE

In extension of the cervical spine, the ligamentum flavum (LF) may bulge and intrude into the vertebral canal and cause symptoms of myelopathy and/or radiculopathy in patients with canal stenosis. Knowledge of the relationship between the extension angle and the physiologic changes of the LF is important for a better understanding of the clinical symptoms. The current study was designed to demonstrate the dynamic correlativity of canal intrusion of the LF bulge with the extension angle of the cervical spine.

METHODS

With a novel method, the probe of the electrical resistance strain gauge was put into the cervical canals of 14 cadaveric specimens. The LF bulge distance of six segments (C2-C3 to C7-T1) and corresponding extension angles of every 5 degrees from 0 degrees to 45 degrees were collected. Angle-bulge curves were drawn.

RESULTS

In overextension (45 degrees ), C5-C6 had the biggest canal intrusion depth (3.478+/-0.527 mm), whereas the upper and lower segments declined gradually (C5-C6>C4-C5>C6-C7>C3-C4>C7-T1>C2-C3). The curves in all segments were sigmoidal, which demonstrated the dynamic change of LF, that is, during the process of extension, LF shortened and contracted first, after the original length was reached, it began to bulge and burst into the canal.

CONCLUSION

The current study has provided a method to measure inner canal kinematic changes in intact spinal specimens.

Specializations in the lumbosacral vertebral canal and spinal cord of birds: evidence of a function as a sense organ which is involved in the control of walking

Birds are bipedal animals with a center of gravity rostral to the insertion of the hindlimbs. This imposes special demands on keeping balance when moving on the ground. Recently, specializations in the lumbosacral region have been suggested to function as a sense organ of equilibrium which is involved in the control of walking. Morphological, electrophysiological, behavioral and embryological evidence for such a function is reviewed. Birds have two nearly independent kinds of locomotion and it is suggested that two different sense organs play an important role in their respective control: the vestibular organ during flight and the lumbosacral system during walking.

Idiopathic normal pressure hydrocephalus: Theoretical concept of a spinal etiology

Normal pressure hydrocephalus (NPH) is an adult syndrome characterised by a combination of gait disturbance, varying degrees of cognitive decline, urinary incontinence, ventricular enlargement and normal mean intracranial pressure. Since this syndrome was first described, its pathophysiology has been a matter of great debate, although it is now considered that NPH could be divided into two groups: cases with unknown etiology (idiopathic normal pressure hydrocephalus, or INPH) and those which develop from several known causes (such as trauma, meningitis or subarachnoid haemorrhage). The pathophysiology of INPH is still unclear and a matter of debate. In this manuscript, the current pathophysiological conditions of INPH are analysed and the authors put forward the theory that the disease is a dynamic syndrome which occurs in patients who have suffered a significant loss of spinal compliance over time. Consequently, intracranial pressure increases more during systole in INPH patients because it cannot be compensated for by the escape of CSF into the spinal canal as effectively, due to the reduced volume or lack of distension of the spinal canal. This leads to an increase in ventricular size and causes cumulative brain damage over a long period of time and accounts for the slow, progressive nature of NPH. The loss of spinal compliance with age is fundamental to the proposed theory which provides a theoretical justification for studying the spinal canal in INPH and investigating the relationship between the progressive narrowing of the spinal canal and the compensating ability of the craniospinal system.

The posterior longitudinal ligament and peridural (epidural) membrane

The posterior longitudinal ligament (PLL) is described as having deep and superficial layers, though recent studies have suggested that there may be three layers. Additional membranous structures have been reported, although there is no consensus as to their presence or morphology. The vertebral canal and dural sac were opened and the spinal nerve roots and spinal cord removed. The anterior dural ligaments were sectioned at their attachment to the PLL and the dura mater freed from the posterior surface of the vertebral bodies. The borders of the PLL were identified and the superficial and deep layers separated. The PLL is a wide band in the cervical region becoming more denticulate inferiorly, the widest parts being attached to the intervertebral discs (IVD) and adjacent vertebral body where the superficial and deep layers could not be separated. A continuous well developed peridural membrane attaching to the pedicles was present anterior to the deep PLL as well as a separate, thin, incomplete layer in 6 of 18 cadavers, covering the posterior surface of the superficial PLL.

Variation in the human cervical neural canal

BACKGROUND CONTEXT

The dimensions of the cervical spinal canal can impact the likelihood of an individual suffering longtime effects from a spinal neck injury as well as influence recovery time. Most studies have used radiographic studies to compare differences in the neural canal, but few have examined skeletal populations to determine variation in the neural canal dimensions without the presence of soft tissue.

PURPOSE

To analyze variation seen in the cervical neural canal (anterior-posterior and transverse diameters) with respect to sex and ancestry and to define cervical canal narrowing in the sample.

STUDY DESIGN

Observational.

METHODS

Measurements of the anterior-posterior (sagittal) (CAP) and transverse (CTR) diameters were taken from 321 individual skeletons. Comparisons were made between males and females and individuals belonging to different ancestral (racial) groups.

RESULTS

CAP was narrowest at the C4 level for African-Americans and at C6 for Caucasians. CTR was narrowest at the C2/C3 level for all groups. Statistical analyses indicated that significant differences in cervical canal dimensions are due first to sexual dimorphism and then to ancestry.

CONCLUSIONS

Significant variation in cervical canal dimensions precludes usage of universal definitions to determine spinal stenosis in individuals; definitions should be according to sex and ancestry.

Morphometry of the sacrum for clinical use

Degenerative disease and instability in the lower lumbar spine may necessitate fusion and stabilization supplemented by instrumentation to the sacrum. However, screw placement in a reasonable position is more difficult to achieve because of the unique anatomy of the first sacral (S1) vertebra. Therefore, this study has been conducted to evaluate sacrum anatomy of the Western Anatolian population in terms of morphometric measurements and make a comparison with previous studies as well as giving a guidance to the surgeons. In this study, 60 dry adult sacrums (30 male and 30 female) were assessed for morphometric analysis. The measurement data for the sacrum and S1 vertebra revealed that there was no significant difference between both sexes except the sacral width and sacral canal width (p<0.05). In the present study, the ratio of S1 corpus' width to sacral width was lower in females compared with males. A detailed knowledge of the morphometric data about sacrum is very important for spinal surgery, as pedicle screw insertion is crucial in spinal instrumentation in order to prevent neurological injury and/or fixation failure.

[Surgical anatomy of the lumbar spine]

The success and risks of spinal surgery depend on a correct diagnosis and detailed knowledge of anatomy. This report provides information on relevant structures of the lumbar spine and possible surgical complications. Anatomical topography and different surgical approaches are described step by step.

Objective assessment of reduced invasiveness in MED. Compared with conventional one-level laminotomy

Microendoscopic discectomy (MED) has been accepted as a minimally invasive procedure for lumbar discectomy because of the small skin incision and short hospital stay required for this surgery. However, there are few objective laboratory data to confirm the reduced systemic responses in the early phase after this procedure. In order to substantiate the reduced invasiveness of MED compared to microdiscectomy (MD) or procedures involved in one-level unilateral laminotomy, the invasiveness of each surgical procedure was evaluated by measuring serum levels of biochemical parameters reflective of a post-operative inflammatory reaction and damage to the paravertebral muscles. Thirty-three patients who underwent lumbar discectomy or one-level unilateral laminotomy (MED in 15 cases, MD in 11 cases and one-level unilateral laminotomy in 7 cases with lumbar spinal canal stenosis) were included in this study. The serum levels of C-reactive protein (CRP) and creatine phosphokinase (CPK) were measured at 24 h after operation. Interleukin-6 (IL-6) and Interleukin-10 (IL-10) were measured at 2, 4, 8 and -24 h following the surgery to monitor the inflammatory response to the respective surgery. The post-operative serum CRP levels from both the MD and MED groups were significantly lower than those from the open laminotomy group. However, there was no significant difference in these serum levels between the MED and MD groups. The levels of IL-6 and IL-10 in the MED group during the first post-operative day were also significantly lower than those in the laminotomy group. When the MED and MD groups were compared, the IL-6 levels in the MED group were lower than in MD group at 2, 4 and 8 h after surgery, but the differences were not statistically significant. However, the level was significantly lower in the MED group at 24 h after surgery. In terms of IL-10, no significant difference was noted between the MED and MD groups over the study period. The changes in serum levels of post-operative inflammatory: markers (CRP, IL-6 and IL-10) in the early phase indicated reduced inflammatory reactions in MED as well as in MD when compared with classical open unilateral laminotomy. These data draw a direct link between the lower level of the inflammatory response and reduced invasiveness of MED. However, an indicator for muscle damage (CPK) appeared not to be affected by the type of surgical procedure used to correct disc herniation.

Normal values of the sagittal diameter of the lumbar spine (vertebral body and dural sac) in children measured by MRI

BACKGROUND

The definition of normal values is a prerequisite for the reliable evaluation of abnormality in the lumbar spine, such as spinal canal stenosis or dural ectasia in patients with Marfan syndrome. Values for vertebral body diameter (VBD) and dural sac diameter (DSD) for the lumbar spine have been published in adults. In children, normal values have been established using conventional radiography or myelography, but not by MRI.

OBJECTIVE

To define normal values for the sagittal diameter of the vertebral body and dural sac, and to calculate a dural sac ratio (DSR) in the lumbosacral spine (L1-S1) in healthy children using MRI.

MATERIALS AND METHODS

A total of 75 healthy children between 6 years and 17 years of age were examined using a sagittal T2-weighted sequence. Sagittal VBD and DSD were measured and a DSR was calculated. This was a retrospective and cross-sectional study.

RESULTS

With increasing age there is a significant increase of VBD, a slight increase of DSD, and a slight decrease of DSR. There is no significant sex difference. DSR in healthy children is higher than in healthy adults.

CONCLUSIONS

MRI is a reliable method demonstrating the natural shape of the lumbosacral spine and its absolute values. These normal values compare well with those established by conventional radiological techniques. Our data may serve as a reference for defining dural ectasia in children with Marfan syndrome.

Combined intra-extracanal approach to lumbosacral disc herniations with bi-radicular involvement. Technical considerations from a surgical series of 15 cases

Large lumbosacral disc herniations effacing both the paramedian and the foraminal area often cause double radicular compression. Surgical management of these lesions may be difficult. A traditional interlaminar approach usually brings into view only the paramedian portion of the intervertebral disc, unless the lateral bone removal is considerably increased. Conversely, the numerous far-lateral approaches proposed for removing foraminal or extraforaminal disc herniations would decompress the exiting nerve root only. Overall, these approaches share the drawback of controlling the neuroforamen on one side alone. A combined intra-extraforaminal exposure is a useful yet rarely reported approach. Over a 3-year period, 15 patients with bi-radicular symptoms due to large disc herniations of the lumbar spine underwent surgery through a combined intra-extracanal approach. A standard medial exposure with an almost complete hemilaminectomy of the upper vertebra was combined with an extraforaminal exposure, achieved by minimal drilling of the inferior facet joint, the lateral border of the pars interarticularis and the inferior margin of the superior transverse process. The herniated discs were removed using key maneuvers made feasible by working simultaneously on both operative windows. In all cases the disc herniation could be completely removed, thus decompressing both nerve roots. Radicular pain was fully relieved without procedure-related morbidity. The intra-extraforaminal exposure was particularly useful in identifying the extraforaminal nerve root early. Early identification was especially advantageous when periradicular scar tissue hid the nerve root from view, as it did in patients who had undergone previous surgery at the same site or had long-standing radicular symptoms. Controlling the foramen on both sides also reduced the risk of leaving residual disc fragments. A curved probe was used to push the disc material outside the foramen. In conclusion, specific surgical maneuvers made feasible by a simultaneous extraspinal and intraspinal exposure allow quick, safe and complete removal of lumbosacral disc herniations with paramedian and foraminal extension.