Nerve Root Diameter Research Articles

Radiological cervical foraminal stenosis severity and morphology as a predictor of pre-operative function and functional surgical outcome

Background Cervical foraminal stenosis on MRI may be assessed using the Kim, modified Kim or Siller methods. This study aimed to investigate which morphological features of cervical foraminal stenosis in patients with cervical radiculopathy correlated best with pre-operative and post-operative surgical outcome following Anterior Cervical Discectomy (ACD) or a Posterior Cervical Foraminotomy (PCF). Methods Pre-operative MRIs of adults with cervical radiculopathy were assessed by six raters. The following measurements were made; uncompressed nerve root diameter, maximal compressed nerve root diameter, anterior & posterior compression, length of the neuroforaminal canal where the diameter was less than the uncompressed nerve root diameter and the distance of maximum compression from the apex of the ligamentum flavum. The Kim, modified Kim and Siller grades were calculated. Neck Disability Index (NDI) was measured pre-operatively and six weeks post-operatively. The radiological measurements and grades were compared to the pre-operative and change in NDI. Results Mean NDI was higher in female (58.2) than male patients (45.6) p = 0.05. No other baseline, operative or radiological factors where significantly associated with the pre-operative NDI. The mean [±SD] post-operative NDI was 14.3 [±22.5]. This represents a change of 37.8 (p < 0.001). The pre-operative NDI correlated strongly with the post-operative NDI but no other patient, operation or radiological factors correlated significantly. Neither pre-operative NDI or change in NDI was statistically different in those treated with ACD and those treated with PCF. Conclusion There was no association between pre-operative NDI and any of the radiological measurements or radiological grades. Furthermore, whilst surgery significantly improved NDI, for those patients with anterior compression, there was no difference in outcome between those treated with an ACD and those treated with a PCF. Current axial MRIs do not adequately assess the cervical nerve root foramina or predict surgical approach, 3D isotropic acquisition and DTI should be explored.

Correlation of age and the diameter of the cervical nerve roots C5 and C6 during the first 2years of life analyzed by high-resolution ultrasound imaging.

AimTo analyze the increase in diameter of the nerve roots C5 and C6 in early childhood.MethodsThe nerve roots of 56 children aged 0 days to 10 years (47 younger than 2 years) were examined by high‐resolution ultrasound imaging. The correlation of diameter and age was statistically tested and a logarithmic regression analysis was performed to develop a logarithmic growth model.ResultsThe increase in nerve root diameter is greatest during the first 2 years of life and then the growth rate decreases steadily. The relationship between age and diameter follows a logarithmic curve (p < 10–8).InterpretationThe main increase in the diameter of the nerve roots happens in the first 2 years of life. Comparing data from a previous study, our data also suggest that the maturation of the proximal part of the median nerve is comparable to the maturation of its distal segments. This suggests a synchronous maturation of the axons and myelin sheath for the whole extent of the nerve, from the radix to its very distal part.What This Paper AddsNormative values for the size of the cervical nerve roots C5 and C6; an insight into the maturation of the proximal parts of the peripheral nervous system; and the correlation between age and cervical root diameter.

SY3.3. Role of ultrasound in ALS

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder defined through the involvement of upper and lower motor neuronal systems. The clinical and neurophysiological investigation remains the gold standard in the diagnosis of ALS due to the lack of a definitive biomarker. Recently, a high-resolution ultrasound technique has been developed and is becoming popular in the field of the diagnosis of neuromuscular diseases. Also in the diagnosis and monitoring of ALS, neuromuscular ultrasound provides complementary information to clinical assessment and neurophysiological testing as well as insights into the underlying pathophysiology of this disease. Muscle ultrasound is used for detecting widespread fasciculations and assessing muscle atrophy. Dynamic diaphragm thickness change can be measured by ultrasound and its change correlates with respiratory function. Bulbar muscle ultrasound is also useful for the assessment of bulbar dysfunction and dysphagia. Nerve ultrasound can detect a reduction in cross-sectional area (CSA) and diameter of peripheral nerves and nerve roots in patients with ALS, reflecting nerve atrophy due to motor nerve axonal loss. These findings help us to distinguish ALS from mimicking diseases such as multifocal motor neuropathy, in which increased nerve size is observed. In addition, nerve CSA has a correlation with CSF level of progranulin which increases to maintain structure and function of neurons. Ultrasound examination is an operator-dependent and machine-dependent. However, the neuromuscular ultrasound technique is easy to learn. To have a skill of neuromuscular ultrasound is valuable to diagnose ALS accurately and to understand the pathophysiology of ALS deeper.

Clinical Anatomy of Human Donor C7 Nerve Roots for Surgical Transfer in Patients with Spastic Arm Paralysis

Contralateral C7 (CC7) nerve transfer has successfully restored hand function in patients with spastic hemiplegia from chronic central nervous system injuries. However, little is known about the morphology and anatomy of the donor C7 nerve root in patients undergoing this procedure. This study quantified intraoperative measurements of donor C7 nerve roots during CC7 transfer surgery for spastic hemiplegia in patients treated at a high-volume center to describe observed anatomical variations for successful direct anastomosis. A database of images from 21 patients (2 females, 19 males) undergoing CC7 surgery was searched for photographic data that contained a standard ruler measuring donor C7 nerve root length after surgical sectioning and before transfer. Two independent observers analyzed these images and recorded C7 nerve root diameter, length, and branch lengths. Mean (SD) values of donor C7 nerve measurements were length, 53.5 (8.0) mm; diameter, 5.1 (0.9) mm; branch length following surgical sectioning, 18.3 (6.3) mm. Right-sided donor C7 nerve roots yielded significantly longer branches compared with left-sided donor C7 nerve roots (P= 0.01). Other patient factors such as age, sex, or laterality of brain injury did not influence intraoperative anatomy. We report detailed intraoperative measurements of the donor C7 root during CC7 nerve transfer for spastic hemiplegia. These findings describe existing variation in surgical C7 nerve root anatomy in patients undergoing this procedure and may serve as a general reference for the expected donor C7 length in successful direct anastomosis.

Shear wave elastography evaluation of brachial plexus in multiple sclerosis.

Multiple sclerosis (MS) is a chronic neuroinflammatory disease characterized by inflammation involving the peripheral nerves. Shear wave elastography (SWE) is potentially a method of choice for detecting peripheral nerve involvement. To compare the degree of thickening and nerve elasticity of brachial plexus (BP) nerve roots and evaluate the usefulness of sonoelastography in patients with clinically diagnosed MS without brachial plexopathy. Thirty-two patients with MS and 32 controls were included in the study. Bilateral C5, C6, and C7 mean nerve root diameters, and mean elasticity values in kiloPascal (kPa) were measured in the patient and control groups. The relationship between the age, height, and weight values and nerve diameter-elasticity values of the patient and control groups was compared. The elasticity values of the C5 and C6 nerve roots were increased, and the nerve root thickness was decreased in the MS group compared to that in the control (P < 0.05). There was no difference between the C7 mean nerve root elasticity (kPa) and diameter measurements in the patient and control groups (P > 0.05). Our study showed an increase in the BP nerve root elasticity values (kPa) in patients with MS compared to that of the control group and a decrease in diameter values thought to be related to the possible chronic atrophic process. The results are consistent with the demyelinating process of the peripheral nervous system (PNS) due to MS.

Intra- and Inter-Observer Variability in Sonographic Measurement of the Cervical Nerve Roots of Healthy Volunteers

Aim: The aim of our study is to determine the normal values of mean cervical (C) nerve root diameter in millimeters (mm) in healthy volunteers and to show its relationship to age, gender, height, weight, body mass index (BMI), and the dominant hand.Material and Method: Two observers measured the mean nerve root diameter of the bilateral C5, C6, and C7 nerve of all volunteers. Before the procedure, the age, sex, height, weight, BMI, and the dominant hand of all the participants were noted. Two measurements were taken by each of the two observers without one knowing about the other’s noted values. The intraclass correlation coefficient (ICC) test was used to analyze intra-and inter-observer reliability.Results: There was no statistically significant relationship between gender and dominant hand, and mean nerve root diameter. Moreover, when we compared the mean nerve root diameter for the nerves in the right and left sides of each participant, no significant statistical differences were identified. The mean diameter of the C6 nerve root was higher than that of C7, which was higher than that of C5 on both sides (p &amp;lt; 0.001). The ICC values for intra- and inter-observer were good or excellent for all diameter measurements (ICC &amp;gt; 0.8).Conclusions: The normal range of cervical nerve root diameters should be determined to distinguish pathological conditions. In our study, the measurement of mean nerve root diameters of C5, C6, and C7 nerves is highly reproducible with excellent intra-observer and inter-observer agreement. Therefore, the measurement of nerve root diameter can be confidently performed in daily clinical practice.

Foraminal Origin of the Dorsal Scapular Nerve: An Anatomical Study

Although distal dorsal scapular nerve (DSN) anatomy has been well characterized, a paucity of literature exists detailing its proximal origin. To our knowledge, this is the first study examining DSN origin and its anatomy relative to the C5 nerve root, which may help localize pathology and provide insight into timing of DSN or C5 nerve root clinical and electrophysiological recovery. Eighteen cadaveric dissections were performed using a posterior-midline approach. Calipers were used for DSN branching and course characterization with statistical analysis completed for the following measurements: DSN diameter, C5 nerve root diameter, distance of DSN branch-point from the C5 ganglion, dural edge, and posterior foraminal tubercle (intra-vs. extraforaminal origin), as well as C5 root-SC branch-point distance. Average/mean measurements (standard error) were as follows: DSN diameter: 3.7 mm (0.3 mm), C5 nerve root diameter: 6.2 mm (0.5 mm), DSN origin to C5 DRG: 12.4 mm (1.9 mm) distal, DSN origin to dural edge: 19. 6mm (1.8 mm), DSN origin to C5 root origin: 23.3 mm (2.2 mm), DSN origin to the posterior foraminal tubercle: 2.3 mm (2.5 mm) proximal/intraforaminal (first branch from C5 in all cases, and the majority [12 of 18, 67%] of DSNs originating from the C5 spinal nerve root within the foramen). The C5 nerve root contributed to the DSN in all specimens that originated from the proximal, intraforaminal, C5 nerve root in the majority of specimens. As the first C5 nerve branch, surgeon knowledge of this proximal DSN pattern will help localize lesional pathology, as well as may help monitor clinical and electrophysiological recovery.

MRI quantifies lumbosacral nerve root and sciatic nerve hypertrophy in chronic inflammatory demyelinating polyradiculoneuropathy

PurposeChronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is a treatable, immune-mediated condition characterised by progressive or relapsing motor and sensory neurological deficits. The diagnosis is based on a combination of clinical, neurophysiological and supportive criteria, but can be challenging. In this study, we quantified the diameter and cross-sectional area of the lumbosacral nerve roots, and explored the imaging characteristics of the sciatic nerves, in patients with CIDP versus healthy controls using MRI. MethodsMRI of the lumbosacral plexus and both thighs was performed at 3 T. Orthogonal diameter and cross-sectional area of the lumbosacral nerve roots were measured, along with sciatic nerve cross-sectional area at the mid-thigh level. The MRI appearance of the sciatic nerves was also evaluated qualitatively. All measurements were performed by an observer blinded to the diagnosis. Results10 patients with CIDP and 10 healthy controls (age and sex-matched) were studied. Lumbosacral nerve root diameter and cross-sectional area were significantly increased in patients with CIDP compared to controls (mean diameter 6.0 ± 1.1 mm vs 4.8 ± 0.3 mm; p = 0.006), with a high sensitivity (89 %) and specificity (90 %) on ROC analysis. Sciatic nerve cross sectional area was also significantly increased in the CIDP group, and was accompanied by qualitative MRI changes. ConclusionsQuantitative MRI reveals significant hypertrophy of the lumbosacral nerve roots and sciatic nerves in patients with CIDP compared to controls. This study provides further evidence for the inclusion of lumbosacral nerve root and sciatic nerve hypertrophy on MRI as a supportive feature in the diagnostic criteria for CIDP.

New methods for diagnosing lumbar foraminal stenosis using dynamic digital tomosynthesis radiculography

The symptoms of lumbar radiculopathy, in particular foraminal stenosis, often exacerbated when the patient is upright. However, it is difficult to detect the compression of nerve roots while the patient is upright using conventional MRI. In this study, we analyzed the compression of lumbar nerve roots using dynamic digital tomosynthesis radiculography (DTRG) in patients diagnosed with lumbar radiculopathy. And we determined the relationship between leg pain and nerve compression while the patients are either prone or upright. We evaluated 30 patients with unilateral leg pain diagnosed as lumbar radiculopathy by physical examination and MRI. The patients were divided in two groups, one with foraminal stenosis (17 patients) and the other with canal stenosis (13 patients), based on MRI findings. All patients underwent DTRG to determine the diameter of their nerve roots in the foramen while prone and upright. Pain while prone or upright was assessed using a 100-point visual analogue scale (VAS) questionnaire. The VAS for leg pain while upright was significantly higher in the foraminal stenosis group (58 ± 24.7) than it was in the canal stenosis group (19.6 ± 13.2; p = 0.0002)). The nerve root diameter while prone or upright was significantly smaller in the foraminal stenosis group (1.2 ± 0.2 mm) than it was in the canal stenosis group (0.2 ± 0.1 mm; p < 0.0001). DTRG has the potential to visualize nerve compression while the patient is upright to reveal the relevance of foraminal stenosis to clinical findings. DTRG is useful for diagnosis of lumbar foraminal stenosis.

Magnetic resonance imaging of the cervical spinal cord in spinal muscular atrophy.

ObjectiveIn this study we investigated the potential value of magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) in characterizing changes in the cervical spinal cord and peripheral nerve roots in vivo in patients with spinal muscular atrophy (SMA).MethodsWe developed an MRI protocol with 4 sequences to investigate the cervical spinal cord and nerve roots on a 3 Tesla MRI system. We used 2 anatomical MRI sequences to investigate cross-sectional area (CSA) at each spinal segment and the diameter of ventral and dorsal nerve roots, and two diffusion tensor imaging (DTI) techniques to estimate the fractional anisotropy (FA), mean (MD), axial (AD) and radial diffusivity (RD) in 10 SMA patients and 20 healthy controls.ResultsThere were no significant differences in CSA (p > .1), although an 8.5% reduction of CSA in patients compared to healthy controls was apparent at segment C7. DTI data showed a higher AD in grey matter of patients compared to healthy controls (p = .033). Significantly lower MD, AD and RD values were found in rostral nerve roots (C3-C5) in patients (p < .045).ConclusionsWe showed feasibility of an advanced 3 T MRI protocol that allowed differences to be determined between patients and healthy controls, confirming the potential of this technique to assess pathological mechanisms in SMA. After further development and confirmation of findings in a larger sample, these techniques may be used to study disease course of SMA in vivo and evaluate response to survival motor neuron (SMN) augmenting therapy.

The Relationship amongst Intervertebral Disc Vertical Diameter, Lateral Foramen Diameter and Nerve Root Impingement in Lumbar Vertebra

Introduction: The vertical diameter of the foramen is dependent upon the vertical diameter of the corresponding intervertebral disc. A decrease in disc vertical diameter has direct anatomic consequences to the foraminal diameter and area available for the nerve root passing through it. This study is to establish the relationship amongst the intervertebral disc vertical diameter, lateral foramen diameters and nerve root compression in the lumbar vertebra.Materials and Methods: Measurements of the study parameters were performed using sagittal MRI images. The parameters studied were: intervertebral disc vertical diameter (DVD), foraminal vertical diameter (FVD), foraminal transverse diameter (FTD) and nerve root diameter (NRD) of both sides. The relationship between the measured parameters were then analyzed.Results: A total of 62 MRI images were available for this study. Statistical analysis showed moderate to strong correlation between DVD and FVD at all the lumbar levels except at left L23 and L5S1 and right L3L4 and L4L5. Correlation between DVD and FTD were not significant at all lumbar levels. Regression analysis showed that a decrease of 1mm of DVD was associated with 1.3, 1.7, 3.3, 3.3 and 1.3mm reduction of FVD at L1L2, L2L3, L3L4, L4L5 and L5S1 respectively.Conclusion: Reduction of DVD was associated with reduction of FVD. However, FVD was relatively wide for the nerve root even with complete loss of DVD. FTD was much narrower than the FVD making it more likely to cause nerve root compression at the exit foramina. These anatomical details should be given consideration in treating patients with lateral canal stenosis.

The feasibility study of extradural nerve anastomosis technique for canine bladder reinnervation after spinal cord injury

Objective: Intradural nerve anastomosis for bladder innervation has been demonstrated to be useful. However, its clinical application remains limited because of the complex surgery, its complications and extensive bony destruction. The purpose of the current study was to demonstrate the feasibility of extradural spinal root anastomosis for bladder innervation in canines.Methods: Ten beagle dogs were used. The length of the extradural segment of the nerve root, upper nerve root outlet (the point at which it emerges from the spinal dura mater) to S2 (dS2), the S3 (dS3) nerve root outlet distance, and the diameters of the extradural spinal roots were measured. The numbers of nerve fibers from L6 to S3 ventral roots were calculated using immunohistochemical staining.Results: The extradural spinal roots could be divided into a ventral root (VR) and a dorsal root (DR) before the ganglionic enlargement of the dorsal root, and the extradural motor nerve roots situate ventrally to their corresponding sensory nerve roots. The extradural nerve root lengths of S1 and parts of L7 were longer than the corresponding dS2. The numbers of nerve and motor nerve fibers, and the diameters of extradural nerve roots, were gradually descending from L6 to S3.Conclusion: The S1 VRs and parts of the L7 VRs can be extradurally anastomosed to the S2 nerves without tension. A nerve graft was needed for extradural anastomosis of L6 VRs and parts of L7 VRs to S2 VRs. This study demonstrated the feasibility of extradural spinal nerve anastomosis for treating neurogenic bladder in canines.

Sensory neuronopathy involves the spinal cord and brachial plexus: a quantitative study employing multiple-echo data image combination (MEDIC) and turbo inversion recovery magnitude (TIRM)

Sensory neuronopathy (SNN) is a distinctive subtype of peripheral neuropathies, specifically targeting dorsal root ganglion (DRG). We utilized MRI to demonstrate the imaging characteristics of DRG, spinal cord (SC), and brachial plexus at C7 level in SNN. We attempted multiple-echo data image combination (MEDIC) and turbo inversion recovery magnitude (TIRM) methods in nine patients with sensory neuronopathy and compared with those in 16 disease controls and 20 healthy volunteers. All participants underwent MRI for the measurement of DRG, posterior column (PC), lateral column, and spinal cord area (SCA) at C7 level. DRG diameters were obtained through its largest cross section, standardized by dividing sagittal diameter of mid-C7 vertebral canal. We also made comparisons of standardized anteroposterior diameter (APD) and left-right diameters of SC and PC in these groups. Signal intensity and diameter of C7 spinal nerve were assessed on TIRM. Compared to control groups, signal intensities of DRG and PC were higher in SNN patients when using MEDIC, but the standardized diameters were shorter in either DRG or PC. Abnormal PC signal intensities were identified in eight out of nine SNN patients (89%) with MEDIC and five out of nine (56%) with T2-weighted images. SCA, assessed with MEDIC, was smaller in SNN patients than in the other groups, with significant reduction of its standardized APD. C7 nerve root diameters, assessed with TIRM, were decreased in SNN patients. MEDIC and TIRM sequences demonstrate increased signal intensities and decreased area of DRG and PC, and decreased diameter of nerve roots in patients with SNN, which can play a significant role in early diagnosis.

Magnetic resonance imaging of childhood Guillain–Barre syndrome

To describe the spinal magnetic resonance imaging (MRI) features in children with Guillain-Barre syndrome (GBS) and to investigate the correlation with the clinical/laboratory findings. Clinical/laboratory findings of 40 children (mean age 5.7 years; range, 3 months-15 years) who had a final diagnosis of GBS were retrospectively reviewed. Clinical severity was graded according to Hughes classification. Electromyogram and cerebrospinal fluid analysis of the patients were recorded. All patients had a contrast-enhanced spinal MRI. The contrast enhancement pattern was determined, and the diameters of anterior and posterior spinal nerve roots were measured. The clinical/laboratory findings were correlated with the MRI findings. Twenty-eight patients had an electromyogram examination, and 25 of them revealed findings consistent with GBS. Cerebrospinal fluid analysis of 37 out of 40 patients showed albumino-cytologic dissociation. All but two patients had thickening and contrast enhancement of the nerve roots and cauda equina on spinal MRI. The most common MRI finding was enhancement of both the anterior and the posterior nerve roots of cauda equina which was prominent anteriorly. The mean anteroposterior diameter of the anterior nerve roots was 2.19 mm (range, 1.38-3.30 mm) and the posterior nerve root was 1.80 mm (range, 1.07-2.97 mm). Spinal MRI is a reliable imaging method for the diagnosis of GBS as it was positive in 38 of 40 patients. The severity on MRI does not correlate with severity of the clinical condition. MRI can be used as a supplementary diagnostic modality to clinical and laboratory findings of GBS.

Morphological changes in the cervical intervertebral foramen dimensions with unilateral facet joint dislocation

Background Many investigators have conducted studies to determine the biomechanics, causes, complications and treatment of unilateral facet joint dislocation in the cervical spine. However, there is no quantitative data available on morphological changes in the intervertebral foramen of the cervical spine following unilateral facet joint dislocation. These data are important to understand the cause of neurological compromise following unilateral facet joint dislocation. Methods Eight embalmed human cadaver cervical spine specimens ranging from level C1-T1 were used. The nerve roots of these specimens at C5-C6 level were marked by wrapping a 0.12 mm diameter wire around them. Unilateral facet dislocation at C5-C6 level was simulated by serially sectioning the corresponding ligamentous structures. A CT scan of the specimens was obtained before and after the dislocation was simulated. A sagittal plane through the centre of the pedicle and facet joint was constructed and used for measurement. The height and area of the intervertebral foramen, the facet joint space, nerve root diameter and area, and vertebral alignment both before and after dislocation were evaluated. Results The intervertebral foramen area changed from 50.72 ± 0.88 mm 2 to 67.82 ± 4.77 mm 2 on the non-dislocated side and from 41.39 ± 1.11 mm 2 to 113.77 ± 5.65 mm 2 on the dislocated side. The foraminal heights changed from 9.02 ± 0.30 mm to 10.52 ± 0.50 mm on the non-dislocated side and 10.43 ± 0.50 mm to 17.04 ± 0.96 mm on the dislocated side. The facet space area in the sagittal plane changed from 6.80 ± 0.80 mm 2 to 40.02 ± 1.40 mm 2 on the non-dislocated side. The C-5 anterior displacement showed a great change from 0 mm to 5.40 ± 0.24 mm on the non-dislocated side and from 0 mm to 3.42 ± 0.20 mm on the dislocated side. Neither of the nerve roots on either side showed a significant change in size. Conclusions The lack of change in nerve root area indicates that the associated nerve injury with unilateral facet joint dislocation is probably due to distraction rather than due to direct nerve root compression.

Spinal Nerve Root Hypertrophy on MRI: Clinical Significance in the Diagnosis of Chronic Inflammatory Demyelinating Polyradiculoneuropathy

To investigate the clinical usefulness of measuring diameters of spinal nerve roots on magnetic resonance imaging (MRI) in patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) with regard to the diagnosis and estimation of neurofunctional impairment. Fourteen patients with CIDP (mean age, 38.9+/-19.2 years) and 10 controls were enrolled in this study. Diameters of cervical and lumbosacral spinal nerve roots were determined on the short tau inversion recovery image of MRI. Correlations between these diameters and clinical indices, including the conduction velocity of median and tibial nerves, were examined. Mean diameters of cervical and lumbosacral spinal nerve roots in CIDP patients were 6.0 to 6.8 mm and 7.3 to 10.4 mm, respectively. CIDP patients showed higher values of the diameter in C5 (p<0.05), C6 (p<0.05), C7 (p<0.005) and C8 (p<0.01) than controls. C7 and C8 showed significantly negative correlations between diameters of spinal nerve roots and the F-wave conduction velocity (FWCV) (p<0.05). In the lumbosacral region, L3, L4 and S1 showed significantly negative correlations between diameters of spinal nerve roots and FWCV (p<0.005, p<0.0005 and p<0.005, respectively). The latency-time difference between F- and M-waves increased with diameters of spinal nerve roots, and there were significantly positive correlations between them in L3 (p<0.05) and L4 (p<0.005). Hypertrophy of spinal nerve roots shown on MRI may be useful as a clue to the diagnosis of CIDP and also as a clinical marker suggesting impairment of peripheral nerve conduction, particularly FWCV.

Mechanical properties of spinal nerve roots subjected to tension at different strain rates

An understanding of the biomechanical and physiological properties of spinal nerve roots, particularly in response to tension, is critical in understanding the pathomechanisms of pain and nerve root injury and subsequent management of related injuries. Biomechanical properties of dorsal nerve roots at the lumbar and sacral levels were evaluated at various strain rates. Nerve roots were stretched at two different rates, 0.01 mm/s (Group A, quasistatic) and 15 mm/s (Group B, dynamic). Load, displacement and digital video data were obtained as the nerve roots were stretched until failure. Maximum stress, strain at maximum stress and modulus of elasticity ( E ) were calculated from the load–displacement measurements. Comparison of mechanical properties and failure patterns of nerve roots at two different rates revealed significant differences. Maximum load, maximum stress and E values of 5.7±2.7 gm, 257.9±111.3 kPa and 1.3±0.8 MPa were observed for Group A and 13.9±7.5 gm, 624.9±306.8 kPa and 2.9±1.5 MPa were observed for Group B, respectively. Higher maximum load, maximum stress and E values occurred at the dynamic stretch rate as compared to the quasistatic stretch rate, illustrating the strain-rate dependency of spinal nerve roots. No differences were observed in the strain values. Differences in mechanical behavior of nerve roots were also observed among the four root levels (L4–S1). A significant interaction effect was observed between nerve root diameter and stretch rates. Overall, results from the present study demonstrate viscoelastic material properties of spinal nerve roots and provide better insight on the tensile properties of nerve roots at different strain rates.

Lumbar pedicle: surgical anatomic evaluation and relationships.

Although several clinical applications of transpedicular screw fixation in the lumbar spine have been documented for many years, few anatomic studies concerning the lumbar pedicle and adjacent neural structures have been published. The lumbar pedicle and its relationships to adjacent neural structures were investigated through an anatomic study. Our objective is to highlight important considerations in performing transpedicular screw fixation in the lumbar spine. Twenty cadavers were used for observation of the lumbar pedicle and its relations. After removal of whole posterior bony elements including spinous processes, laminae, lateral masses, and inferior and superior facets, the isthmus of the pedicle was exposed. Pedicle width and height (PW and PH), interpedicular distance (IPD), pedicle-inferior nerve root distance (PIRD), pedicle-superior nerve root distance (PSRD), pedicle-dural sac distance (PDSD), root exit angle (REA), and nerve root diameter (NRD) were measured. The results indicated that the average distance from the lumbar pedicle to the adjacent nerve roots superiorly, inferiorly and to the dural sac medially at all levels ranged from 2.9 to 6.2 mm, 0.8 to 2.8 mm, and 0.9 to 2.1 mm, respectively. The mean PH and PW at L1-L5 ranged from 10.4 to 18.2 mm and 5.9 to 23.8 mm, respectively. The IPD gradually increased from L1 to L5. The mean REA increased consistently from 35 degrees to 39 degrees. The NRD was between 3.3 and 3.9 mm. Levels of significance were shown for the P < 0.05 and P < 0.01 levels. On the basis of this study, we can say that improper placement of the pedicle screw medially and inferiorly should be avoided.

Thoracic pedicle: surgical anatomic evaluation and relations.

This anatomic study investigated the thoracic pedicle and its relations. The objective was to emphasize the importance of the thoracic pedicle for transpedicular screw fixation to avoid complications during surgery. Twenty cadavers were used to observe the cervical pedicle and its relations. The isthmus of the pedicle was exposed after removal of whole-posterior bony elements, including spinous processes, laminas, lateral masses, and the inferior and superior facets. The pedicle width and height, interpedicular distance, pedicle-inferior nerve root distance, pedicle-superior nerve root distance, pedicle-dural sac distance, root exit angle, and nerve root diameter were measured. There was no distance between the pedicle and dural sac in eight specimens. There was, however, a short distance in 12 remaining specimens in the upper and lower thoracic regions. The distances between the thoracic pedicle and the adjacent nerve roots ranged from 1.5 to 6.7 mm and 0.8 to 6.0 mm superiorly and inferiorly at all levels. The mean pedicle height and width at T1-T12 ranged from 2.9 to 11.4 mm and 6.2 to 21.3 mm, respectively. The interpedicular distance decreased gradually from T1 to T5 and then increased gradually to T12. The mean root exit angle decreased consistently from 104 degrees to 60 degrees. The nerve root diameter was between 2.3 and 2.5 mm at the T1-T5 level and then increased consistently from 2.5 to 3.7 mm. All significant differences were noted at p < 0.05 and p < 0.01. The following suggestions are made based on these results. 1) More care should be taken when a transpedicular screw is placed in the horizontal plane. 2) Improper medial placement of the pedicle screw, especially in the middle thoracic spine, should be avoided, and the anatomic variations between individuals should be considered. 3) Because of substantial variations in the size of thoracic pedicles, utmost attention should be given to the findings of a computed tomographic evaluation before thoracic transpedicular fixation is begun.

Surgical anatomic evaluation of the cervical pedicle and adjacent neural structures.

Although several clinical applications of transpedicular screw fixation in the cervical spine have been documented recently, few anatomic studies concerning the cervical pedicle are available. This study was designed to evaluate the anatomy and adjacent neural relationships of the middle and lower cervical pedicle (C3-C7). The main objective is to provide accurate information for transpedicular screw fixation in the cervical region and to minimize complications by providing a three-dimensional orientation. Twenty cadavers were used to observe the cervical pedicle and its relationships. After removal of the posterior bony elements, including spinous processes, laminae, lateral masses, and inferior and superior facets, the isthmus of the pedicle was exposed. Pedicle width, pedicle height, interpedicular distance, pedicle-inferior nerve root distance, pedicle-superior nerve root distance, pedicle-dural sac distance, medial pedicle-dural sac distance, mean angle of the pedicle, root exit angle, and nerve root diameter were measured. The results indicate that there was no distance between the pedicle and the superior nerve root and between the pedicle and the dural sac in 16 specimens, whereas there was a slight distance in the lower cervical region in the 4 other specimens. The mean distance between the pedicle and the inferior nerve root for all specimens ranged from 1.0 to 2.5 mm. The mean distance between the medial pedicle and the dural sac increased consistently from 2.4 to 3.1 mm. At C3-C7, the mean pedicle height ranged from 5.2 to 8.5 mm, and the mean pedicle width ranged from 3.7 to 6.5 mm. Interpedicular distance ranged from 21.2 to 23.2 mm. The mean root exit angle ranged from 69 to 104 degrees, with the largest angle at C3 and the smallest at C6. The mean angle of the pedicle ranged from 38 to 48 degrees. The nerve root diameter increased consistently from 2.7 mm at C3 to 3.8 mm at C6 and then decreased to 3.7 mm at the C7 level. Differences in measurements were considered statistically significant at levels ranging from P < 0.05 to P < 0.01. This study indicates that improper placement of the pedicle screw medially and superiorly in the middle and lower cervical spine should be avoided and that the anatomic variations between individuals should be established by measurement.