The radiologic anatomy of the lumbar and lumbosacral pedicles

Posterior endpoint determination of the lumbar pedicle central axis on the anterior-posterior fluoroscopic image for pedicle screw insertion

The transpedicular procedure has been widely used in spinal surgery. The determination of the best entry point is the key to perform a successful transpedicular procedure. Various techniques have been used to determine this point, but the results are variable. This study was carried out to determine the posterior endpoint of the lumbar pedicle central axis on the standard anterior-posterior (AP) fluoroscopic images. Computer-aided design technology was used to determine the pedicle central axis and the posterior endpoint of the pedicle central axis on the posterior aspect of the vertebra. The standard AP fluoroscopic image of the lumbar vertebral models by three-dimensional printing was achieved. The endpoint projection on the AP fluoroscopic image was determined in reference to the pedicle cortex projection by the measurements of the angle and distance on the established X-Y coordinate system of the radiologic image. The projection of posterior endpoint of the lumbar pedicle central axis were found to be superior to the X-axis of the established X-Y coordinate system and was located on the pedicle cortex projection on the standard AP fluoroscopic image of the vertebra. The projection point was distributed in different sectors in the coordinate system. It was located superior to the X-axis by 18° to 26° at L1, while they were located superior to the X-axis by 12° to 14° at L2 to L5. The projections of posterior endpoints of the lumbar pedicle central axis were located in different positions on the standard AP fluoroscopic image of the vertebra. The determination method of the projection point was helpful for selecting an entry point for a transpedicular procedure with a fluoroscopic technique.

Misplaced S1 screw causing L5 radiculopathy, rare and unusual presentation: a report of 2 cases

Many spine surgeons are not optimally acquainted with anatomy anterior to sacrum. Screw malposition injuring these structures can lead to unwanted lethal consequences. We report unusual cases of acute radiculopathy due to misplaced bicortical sacral screw causing L5 nerve root impingement on anterior sacrum. A 39/M patient complained of severe rest pain (VAS 9/10) post TLIF in region of L5 dermatome with sensory deficit along the right lateral leg and straight leg raise less than 30°. X-ray revealed S1 screw protruding beyond the second cortex with a straight trajectory. CT scan revealed a protrusion of 11.4mm beyond anterior cortex. The patient was taken for re-surgery and the trajectory and length of screw was revised. Sciatic pain completely disappeared immediately after surgery. A 61/M patient operated elsewhere with instrumented decompression and fusion with screws passed at L4, L5 and S1 level for lumbar canal stenosis, post-surgery patient developed new onset radicular symptoms in right lower limb. Patient was managed conservatively in the form of L5 selective nerve root block. Pain and numbness improved. Bicortical purchase of S1 screw though improves pull out strength, is associated with a risk of neurovascular complications. Surgeons should be alerted to the misplacement of S1 pedicle screws to avoid involvement not only anterior to the anteromedial neurovascular tissue, but also anterolateral to the arrangement of the L5 nerve root.

Effect of L5 spinal canal type on pedicle screw placement based on CT imaging: a retrospective clinical study

PURPOSE

The objective of this study was to investigate the optimal entry point and pedicle camber angle for L5 pedicle screws of different canal types.

METHODS

CT imaging data were processed by Mimics for simulated pedicle screw placement, and PD (Pedicle diameter), PCA (Pedicle camber angle), LD (Longitudinal distance), TD (Transverse distance), and PBG (Pedicle screw breach grade) were measured. Then they were divided into the Round group and Trefoil group according to the type of spinal canal. When comparing PD, PCA, LD, TD, and PBG, the two sides of the pedicle were compared separately, so they were first divided into the round-type pedicle group and the trefoil-type pedicle group.

RESULTS

In the round-type pedicle group (n = 134) and the trefoil-type pedicle group (n = 264), there was no significant difference in PD and LD, but there was a significant difference in PCA between the two groups (t = - 4.072, P < 0.05). A statistically significant difference in the distance of the Magerl point relative to the optimal entry point (t = - 3.792, P < 0.05), and the distance of the Magerl point relative to the optimal entry point was greater in the trefoil-type pedicle group than in the round-type pedicle group.

CONCLUSION

The optimal entry point for L5 is more outward than the Magerl point, and the Trefoil spinal canal L5 is more outwardly oriented than the Round spinal canal L5, with a greater angle of abduction during pedicle screw placement.

Morphometric measurement of lumbar pedicle in different regions: a systematic review

OBJECTIVE

To collect the data of pedicle width and height in different areas, and to investigate the difference and variation rule of pedicle width and height.

METHODS

Comprehensive search of PubMed, Ovid Medline, and Web of science databases was performed. Collected data were imported into SPSS, and one-way ANOVA test and post hoc test were used to determine whether there were statistical differences in pedicle width and height between the different regions.

RESULTS

Oceania had the largest pedicle width and height, followed by Americans. West Asian had the largest pedicle width in Asia, followed by East and Southeast Asian, and Chinese and South Asian had similar pedicle width. Different from the variation pattern of pedicle width, the pedicle height of Chinese, East and Southeast Asian and West Asian in Asian range is similar, but the pedicle height of South Asian is significantly smaller than the first three, and has statistical significance.

CONCLUSIONS

People in different regions have similar patterns of variation in pedicle width and height even though they belong to different ethnic groups. This phenomenon is particularly prominent and pronounced in populations in geographically close areas, which may be related to inter-ethnic integration due to population movement between adjacent areas. There is a relationship between the morphological characteristics of the human lumbar pedicle and geographical location.

Spinal Pedicle Morphometry using Multidetector CT—An experience from the Indian Subcontinent

Introduction For safe pedicle screws placement, knowledge of pedicle morphometry is essential, because an inconsistency between pedicle width and the screw diameter may lead to severe complications like nerve, vessel or visceral injuries.

Objectives To study the spinal pedicle width and height of lumbar spine, using multidetector CT (MDCT), among the Indian population.  To study the spinal pedicle angulation of lumbar spine, using MDCT, among the Indian population.

Method The study was conducted at a tertiary care multispecialty hospital. In the present study, a total of 321 patients were included, who underwent MDCT scan without contrast at our institution, over a period of 2 years, from May 2017 to May 2019. The study population (n = 321) was divided into different subgroups on the basis of the age. The data was taken from the workstation. Comparison was made separately between each subgroup.

Results In our subset of population, the 10 to 90 years age group, pedicle dimensions are as follow: The pedicle diameter from L1 to L5 is 4.46 to 11.92 mm. The pedicle height from L1 to L5 is 7.38 to 11.01 mm. The pedicle axial angulation from L1 to L5 is 22.27 to 36.08 degree. The pedicle lateral angulation from L1 to L5 is 16.12 to 22.47 degree.

Conclusion Knowledge of the pedicle morphometry (pedicle width, height and angulation) of lumbar spine will help the neurosurgeons standardize the size of pedicle screws which is required for spinal fixation surgery at various lumbar vertebra levels.

Thoracic and lumbar spine pedicle morphology in Japanese patients

PURPOSE

Pedicle morphology is important for intraoperative surgical anatomy and to define pedicle screw design and parameters. However, differences of pedicle size according to ethnicity and gender are not well studied. The purpose of this study is to investigate morphological characteristics of the pedicle in Japanese patients for determining adequate screw size and optimal surgical planning.

METHODS

We investigated thoracic and lumbar pedicle morphology in Japanese patients using computed tomography (CT) measurements and analyzed the standard size of pedicles on upper thoracic to lumbar spine CT images in 227 Japanese patients.

RESULTS

Gender had a larger impact on the shape and size of pedicles than racial differences. In the distribution of pedicle width, we calculated the ratio of values less than 4.5 mm, that in females resulted to be over 30% for the Th3-Th9 segment, and particularly high, above 60% at Th4 and Th5.

CONCLUSION

Our measurement analysis showed that pedicle morphological parameters in Japanese patients showed tendency to be smaller to those found in other studies, and particularly in female patients, they were statistically significantly smaller. Adequate transpedicular instrumentation for Japanese patients will require smaller size pedicle-related devices that will match our anatomical findings to achieve safe device placement. In addition, serving ethnically non-homogenous patient population can require further to spinal morphometric for precise device selection.

Accuracy and technical limits of percutaneous pedicle screw placement in the thoracolumbar spine

PURPOSE

The two-dimensional fluoroscopic method of percutaneous pedicle screw instrumentation has been clinically described as reliable method in the caudal thoracic and lumbosacral spine. Its accuracy has not been clearly reported in the cranial thoracic spine. The aim of this in vitro study was to investigate percutaneous pedicle screw placement accuracy according to pedicle dimensions and vertebral levels.

METHODS

Six fresh-frozen human specimens were instrumented with 216 screws from T1 to S1. Pedicle isthmus widths, heights, transversal pedicles and screws were measured on computed tomography. Pedicle cortex violation ≥ 2 mm was defined as screw malposition.

RESULTS

The narrowest pedicles were at T3-T5. A large variability between transversal pedicle axes and percutaneous pedicle screw was present, depending on the spinal level. Screw malposition rates were 36.1% in the cranial thoracic spine (T1-T6), 16.7% in the caudal thoracic spine (T7-T12), and 6.9% in the lumbosacral spine (L1-S1). The risk for screw malposition was significantly higher at cranial thoracic levels compared to caudal thoracic (p = 0.006) and lumbosacral (p < 0.0001) levels. Cortex violation ≥ 2 mm was constantly present if the pedicle width was < 4.8 mm.

CONCLUSION

Percutaneous pedicle screw placement appears safe in the caudal thoracic and lumbosacral spine. The two-dimensional fluoroscopic method has a limited reliability above T7 because of smaller pedicle dimensions, difficulties in visualizing radiographic pedicle landmarks and kyphosis.

Risk of pedicle and spinous process violation during cortical bone trajectory screw placement in the lumbar spine

Background

Previous studies have confirmed the feasibility of the cortical bone trajectory (CBT) technique. However, there are few reports on spinous process violation and screw penetration during the screw insertion. The purpose of this study was to evaluate the incidence of spinous process violation and screw penetration through the pedicle during CBT screw insertion.

Methods

Computed tomography (CT) scans with normal lumbar structures were consecutively obtained and three-dimensional (3D) reconstructions of the lumbar spine were created. Bilateral CBT screw placement was simulated on each segment using a screw diameter of 4.5 mm, 5.0 mm, or 5.5 mm. Incidences of these complications were recorded and analyzed.

Results

A total of 90 patients were enrolled. Spinous process violation was observed in 68.3, 53.3, 25.5, 1.7, and 0% from L1 to L5, respectively, using 4.5 mm screws. A significant difference was found among the five segments but this was unconnected to gender or screw diameter. The incidence of screw penetration through the inner wall decreased from L1 to L4; in turn, L1 (16.7–35.5%), L2 (12.7–34.4%), L3 (2.8–23.8%) and L4 (1.1–6.7%). This trend was reversed in L5 (6.7–16.7%). Moreover, screw penetration through the outer wall was rare. The incidence of screw penetration varied with screw size as well as lumbar level, but not with gender.

Conclusions

There are more difficulties of CBT screw fixation in upper lumbar spine. The low rate of screw penetration, using 4.5 mm screws, suggests the safety for CBT fixation in the lumbar spine. Larger screws (5.0 mm or 5.5 mm) are more recommended for use in the lower lumbar spine. Moreover, CBT fixation in L5 deserves greater attention because of the unique morphology of the pedicle.

The sacral screw placement depending on morphological and anatomical peculiarities

PURPOSE

Various pathologies of the lumbosacral junction require fusion of the L5/S1 segment. However, pseudarthroses, which often come along with sacral screw loosening, are problematic. The aim of the present investigation was to elaborate the morphological features of the L5/S1 segment to define a so-called "safe zone" for bi- or tricortical screw placement without risking a damage of the iliac vessels.

METHODS

A total of one hundred computed tomographies of the pelvis were included in this investigation. On axial and sagittal slices, pedicle morphologies, the prevertebral position of the iliac vessels, the spinal canal and the area with the largest bone density were analyzed.

RESULTS

Beginning from the entry point of S1-srews iliac vessels were located at an average angle of 7° convergence, the spinal canal at 38°. Bone density was significantly higher centrally with a mean value of 276 Hounsfield Units compared to the area of the Ala ossis sacri. The largest intraosseous screw length could be achieved at an angle of 25°. The average pedicle width was 20 mm and the pedicle height 13 mm.

CONCLUSIONS

A "safe-zone" for bicortical screw placement at S1 with regard to the course of the iliac vessels could be defined between 7° and 38° convergence. Regarding the area offering the largest bone density and the maximal possible screw length, a convergence of 25° is recommended at S1 to reduce the incidence of screw loosening. Screw diameter, as a further influence factor on screw holding, is limited by pedicle height not pedicle width.

Use of a life-size three-dimensional-printed spine model for pedicle screw instrumentation training

Background

Training beginners of the pedicle screw instrumentation technique in the operating room is limited because of issues related to patient safety and surgical efficiency. Three-dimensional (3D) printing enables training or simulation surgery on a real-size replica of deformed spine, which is difficult to perform in the usual cadaver or surrogate plastic models. The purpose of this study was to evaluate the educational effect of using a real-size 3D-printed spine model for training beginners of the free-hand pedicle screw instrumentation technique. We asked whether the use of a 3D spine model can improve (1) screw instrumentation accuracy and (2) length of procedure.

Methods

Twenty life-size 3D-printed lumbar spine models were made from 10 volunteers (two models for each volunteer). Two novice surgeons who had no experience of free-hand pedicle screw instrumentation technique were instructed by an experienced surgeon, and each surgeon inserted 10 pedicle screws for each lumbar spine model. Computed tomography scans of the spine models were obtained to evaluate screw instrumentation accuracy. The length of time in completing the procedure was recorded. The results of the latter 10 spine models were compared with those of the former 10 models to evaluate learning effect.

Results

A total of 37/200 screws (18.5%) perforated the pedicle cortex with a mean of 1.7 mm (range, 1.2–3.3 mm). However, the latter half of the models had significantly less violation than the former half (10/100 vs. 27/100, p < 0.001). The mean length of time to complete 10 pedicle screw instrumentations in a spine model was 42.8 ± 5.3 min for the former 10 spine models and 35.6 ± 2.9 min for the latter 10 spine models. The latter 10 spine models had significantly less time than the former 10 models (p < 0.001).

Conclusion

A life-size 3D-printed spine model can be an excellent tool for training beginners of the free-hand pedicle screw instrumentation.

Intraoperative Radiographic Technique for Visualization of Bicortical or Tricortical Anteromedial Sacral Screw Placement

The bicortical anteromedial sacral screw trajectory is the most widely used for S1 screw fixation. The assessment of anterior cortex purchase is difficult on a lateral view due to the overlapping bony anatomy of the sacrum and pelvis. We describe the intraoperative radiographic technique for a personalized pelvic inlet view that is perpendicular to the superior sacral surface to visualize sacral screw placement. This technique allows for assessment of anterior cortex purchase with anteromedial angulation in the same view.

The morphological relationship between lumbosacral transitional vertebrae and lumbosacral pedicle asymmetry

Introduction

The clinical significance of lumbosacral transitional vertebrae (LSTV) has been reported. However, the association between LSTV and lumbosacral pedicle anatomical anomaly has not been investigated. We hypothesized that LSTV might be associated with lumbosacral anatomical anomaly. The purpose of this study was to examine the morphological association between LSTV and lumbosacral pedicle asymmetry (PA) using computed tomography (CT).

Methods

A retrospective review of CT images of 347 lumbosacral degenerative disease patients was performed. We divided the subjects into two groups: the normal and LSTV groups. LSTV was classified based on Castellvi's classification. PA was defined as a difference of more than 20° between the right and left angles of the pedicle.

Results

Seventy out of 347 lumbosacral degenerative disease patients (20.17%) were diagnosed with LSTV. In the normal group, only a 0.54% incidence of PA was seen; however, with respect to the LSTV group, a 9.29% incidence of PA was seen. A significant difference in PA incidence was observed between the groups (p < 0.001). Type IIIa and Type IV in the LSTV group showed a statistically significant PA incidence rate (p = 0.004 and p = 0.039, respectively).

Conclusions

Our study demonstrated that there was a significant difference in the incidence of PA between LSTV subjects and normal subjects. Moreover, the incidence of PA was significantly higher in LSTV subjects with severe anomaly. These results suggested that lumbosacral spine anomaly might have a close relationship with the incidence of PA and lumbosacral nerve root asymmetry. Therefore, morphological evaluation of the pedicle is important for preoperative surgical management, especially in cases using pedicle screws. This information could lower the incidence of pedicle screw malposition when pedicle screws are inserted at the lumbosacral spine.

Percutaneous endoscopic lumbar discectomy for high-grade down-migrated disc using a trans-facet process and pedicle-complex approach: a technical case series

PURPOSE

The use of conventional percutaneous endoscopic lumbar discectomy (PELD) for high-grade down-migrated lumbar disc herniation medial to the pedicle via the transforaminal route can result in less favorable outcomes. We report a new PELD technique for the treatment of high-grade down-migrated lumbar disc herniation via a facet process and pedicle-complex approach.

METHODS

Three patients with high-grade down-migrated L3-4 and L4-5 disc herniation presented to our hospital. Each underwent PELD via a facet process and pedicle complex approach to remove the herniated fragment and achieve complete decompression of the nerve root.

RESULTS

Patients' symptoms were relieved. Postoperative magnetic resonance imaging showed root decompression. Follow-up 12-month computed tomography revealed no pedicle or facet fracture and healing of the pedicle complex and facet process bone tunnel.

CONCLUSION

PELD via a facet process and pedicle-complex approach may be an option for high-grade, down-migrated lumbar disc herniation with completely sequestrated nucleus pulposus.

Percutaneous pedicle screw placement under single dimensional fluoroscopy with a designed pedicle finder-a technical note and case series

BACKGROUND CONTEXT

Minimally invasive spine surgery has become increasingly popular in clinical practice, and it offers patients the potential benefits of reduced blood loss, wound pain, and infection risk, and it also diminishes the loss of working time and length of hospital stay. However, surgeons require more intraoperative fluoroscopy and ionizing radiation exposure during minimally invasive spine surgery for localization, especially for guidance in instrumentation placement. In addition, computer navigation is not accessible in some facility-limited institutions.

PURPOSE

This study aimed to demonstrate a method for percutaneous screws placement using only the anterior-posterior (AP) trajectory of intraoperative fluoroscopy.

STUDY DESIGN

A technical report (a retrospective and prospective case series) was carried out.

PATIENT SAMPLE

Patients who received posterior fixation with percutaneous pedicle screws for thoracolumbar degenerative disease or trauma comprised the patient sample.

METHOD

We retrospectively reviewed the charts of consecutive 670 patients who received 4,072 pedicle screws between December 2010 and August 2015. Another case series study was conducted prospectively in three additional hospitals, and 88 consecutive patients with 413 pedicle screws were enrolled from February 2014 to July 2016. The fluoroscopy shot number and radiation dose were recorded. In the prospective study, 78 patients with 371 screws received computed tomography at 3 months postoperatively to evaluate the fusion condition and screw positions.

RESULTS

In the retrospective series, the placement of a percutaneous screw required 5.1 shots (2-14, standard deviation [SD]=2.366) of AP fluoroscopy. One screw was revised because of a medialwall breach of the pedicle. In the prospective series, 5.8 shots (2-16, SD=2.669) were required forone percutaneous pedicle screw placement. There were two screws with a Grade 1 breach (8.6%), both at the lateral wall of the pedicle, out of 23 screws placed at the thoracic spine at T9-T12. Forthe lumbar and sacral areas, there were 15 Grade 1 breaches (4.3%), 1 Grade 2 breach (0.3%), and 1 Grade 3 breach (0.3%). No revision surgery was necessary.

CONCLUSION

This method avoids lateral shots of fluoroscopy during screw placement and thus decreases the operation time and exposes surgeons to less radiation. At the same time, compared with the computer-navigated procedure, it is less facility-demanding, and provides satisfactory reliability and accuracy.

Spinal fusion without instrumentation - Experimental animal study

BACKGROUND

The number and cost of instrumented spinal fusion surgeries have increased rapidly, primarily for the treatment of lumbar segmental instabilities. However, what if the organism itself is able to restore segmental stability over time? This large-animal study using sheep aimed to investigate whether the reparative response after destabilization via facetectomy and nucleotomy without instrumentation can effectively fuse the spinal segment comparable to instrumented standard fusion surgery.

METHODS

The following four surgical interventions were investigated: dorsal fixation via internal fixator, ventral fixation via cage as well as facetectomy and nucleotomy without additional instrumentation. Six months postoperatively, the animals were sacrificed, and the lumbar spines were used for biomechanical tests.

FINDINGS

Spinal stability was restored to the destabilized spinal segments at six months postoperatively and was comparable to the results of conventional surgery via screws and cages. Iatrogenic hypomobilization caused significant reductions in facet joint space and intervertebral disc height of segments at index and adjacent level. Restabilized segments after iatrogenic hypermobilzation also significantly decreased facet joint space and disc height at index level, but revealed no influence on adjacent segments.

INTERPRETATION

These findings in the sheep model question the necessity of costly instrumentation and suggest the alternative possibility of stimulating the reparative capacity of the body in human lumbar spine fusion surgery.

The radiological distance between the lumbar pedicle and laminar edges

INTRODUCTION

Lumbar foraminal inner zone herniations are challenging cases, for which there are variety of approaches. However, there is no information about the distance between these herniations and the edges of the respective lamina. The aim of this study was to measure the distance between the inferomedial aspect of lumbar pedicles and laminar edges.

MATERIALS AND METHODS

The lumbar CT images of 30 cases were reviewed. The distances between the edges of the lamina and the inferomedial aspects of the respective pedicles were measured. The study was performed on L3, L4, and L5 lumbar vertebrae on both sides.

RESULTS

The mean distance between the upper edge of the lamina and the inferomedial aspect of the respective pedicle was found to be 10.8 ± 3.5, 11.6 ± 2.4, and 14.1 ± 2.3 mm on the left side, and 11.1 ± 4.4, 12.0 ± 2.5, and 13.8 ± 3.2 mm on the right side of L3, L4, and L5 vertebrae. The mean distance between the inferior edge of the lamina and the inferomedial aspect of the respective pedicle was found to be 23.8 ± 4.2, 19.3 ± 3.5, and 11.6 ± 2.9 mm, on the left side, and 23.9 ± 3.2, 19.1 ± 3.7, and 12.4 ± 2.8 mm on the right side of L3, L4, and L5 vertebrae. There was no statistically significant difference between values of the left and right sides (p > 0.05).

CONCLUSION

This study revealed that distance between the inferomedial aspect of lumbar pedicles and the superior edge of the same lamina was shorter than the distance between the inferomedial aspect of lumbar pedicles and the inferior edge of the same lamina at L3 and L4 level. It was concluded that this shorter distance could be taken into consideration during surgery on inner zone 1 foraminal herniations.

Radiographic anatomical relationship between spinous process and pedicle in thoracolumbar and lumbar spine

Pedicle screws are widely used in spinal surgeries, but it remains technically demanding to place. There are numerous studies on the anatomy of pedicle; however, there is very little insight on the relationship between the pedicle and the spinous process, which is an important part of the spinal posterior column.The aim of the study was to investigate the radiographic anatomical relationship between spinous processes and pedicles in the thoracolumbar and lumbar spine, in order to reveal a novel entrance point for pedicle screw insertion.Sixty candidates were enrolled in this study; cases were excluded with degenerative disorders and other disorders as osteoporosis, deformity, and tumor. Radiographs and computer tomography scans between T10 and L5 were obtained on each case. The distance was measured that between the superior margin of spinous process root and the superior border, the inferior border and the axis of pedicle. In laboratory, 5 fresh cadavers were used to imitate the pedicle screw insertion.The basic reference point was supposed as the intersection between the horizontal line of superior margin of spinous process root and the central vertical line of the superior facet. For T10 to T12, the pedicle axis was 5 mm beyond the reference point. For L1 to L4, the pedicle axis was at the reference point. At L5, the pedicle axis was 5 mm beneath the reference point. In laboratory, 80 screws were all inserted into pedicles successfully according to the newly referred entrance point.The study reveals the radiographic anatomical relationship between the pedicle and the spinous process. The pedicle axis is around the horizontal line of the superior margin of spinous process root. It provides a new anatomic mark of pedicle screw entrance point.

Fluoroscopy-guided pedicle screw accuracy with a mini-open approach: a tomographic evaluation of 470 screws in 125 patients

BACKGROUND

Transpedicular screws are currently placed with open free hand and minimally invasive techniques assisted with either fluoroscopy or navigation. Screw placement accuracy had been investigated with several methods reaching accuracy rates from 71.9% to 98.8%. The objective of this study was to assess the accuracy and safety for 2-D fluoroscopy-guided screw placement assisted with electrophysiological monitoring and the inter-observer agreement for the breach classification.

METHODS

A retrospective review was performed on 125 consecutive patients who underwent minimally invasive transforaminal lumbar interbody fusion and transpedicular screws placement between the levels of T-12 and S-1. Screw accuracy was evaluated using a postoperative computed tomography by three independent observers. Pedicle breach was documented when there was a violation in any direction of the pedicle. Inter-observer agreement was assessed with the Kappa coefficient.

RESULTS

A total of 470 transpedicular screws were evaluated between the levels of T-12 and S-1. In 57 patients the instrumentation was bilateral and in 68 unilateral. A substantial degree of agreement was found between the observers AB (κ=0.769) and A-C (κ=0.784) and almost perfect agreement between observers B-C (κ=0.928). There were a total of 427.33 (90.92%) screws without breach, 39.33 (8.37%) minor breach pedicles and 3.33 (0.71%) major breach pedicles. The pedicle breach rate was 9.08% Trajectory pedicle breach percentages were as follows: minor medial pedicle breach 4.68%, minor lateral pedicle breach 3.47%, minor inferior pedicle breach 0.22%, and major medial breach 0.70%. No intraoperative instrumentation-related or postoperative clinical complications were encountered and no surgical revision was needed.

CONCLUSIONS

Our study demonstrated a high accuracy (90.2%) for 2-D fluoroscopy-guided pedicle screw using electromonitoring. Only 0.71% of the 470 screws had a major breach. Knowing the radiological spine pedicle anatomy and the correct interpretation of EMG are the key factors for this technique.

The accuracy of a method for printing three-dimensional spinal models

Background

To study the morphology of the human spine and new spinal fixation methods, scientists require cadaveric specimens, which are dependent on donation. However, in most countries, the number of people willing to donate their body is low. A 3D printed model could be an alternative method for morphology research, but the accuracy of the morphology of a 3D printed model has not been determined.

Methods

Forty-five computed tomography (CT) scans of cervical, thoracic and lumbar spines were obtained, and 44 parameters of the cervical spine, 120 parameters of the thoracic spine, and 50 parameters of the lumbar spine were measured. The CT scan data in DICOM format were imported into Mimics software v10.01 for 3D reconstruction, and the data were saved in .STL format and imported to Cura software. After a 3D digital model was formed, it was saved in Gcode format and exported to a 3D printer for printing. After the 3D printed models were obtained, the above-referenced parameters were measured again.

Results

Paired t-tests were used to determine the significance, set to P<0.05, of all parameter data from the radiographic images and 3D printed models. Furthermore, 88.6% of all parameters of the cervical spine, 90% of all parameters of the thoracic spine, and 94% of all parameters of the lumbar spine had Intraclass Correlation Coefficient (ICC) values >0.800. The other ICC values were <0.800 and >0.600; none were <0.600.

Conclusion

In this study, we provide a protocol for printing accurate 3D spinal models for surgeons and researchers. The resulting 3D printed model is inexpensive and easily obtained for spinal fixation research.

L5 spinal nerve injury caused by misplacement of outwardly-inserted S1 pedicle screws

PURPOSE

To evaluate L5 nerve root injuries caused by outwardly misplaced S1 pedicle screws. Pedicle screws remain the criterion standard for fixation of L5-S1 to correct lumbosacral instability. When inserting S1 pedicle screws, it is possible to injure the L5 nerve root if screws are inserted outwardly and the tip of the screw perforates the anterior cortex of the sacrum. Despite this risk, to our knowledge this type of injury has never been reported as a case series.

METHODS

We experienced 2 cases of L5 nerve root injury caused by outwardly-inserted S1 pedicle screws. In both cases, bilateral S1 pedicle screws were inserted outwardly using a free-hand technique, and on one side, screws induced severe pain by impinging on an L5 root. Computed tomography after the selective rootgraphy of the injured nerve showed the nerve compressed laterally by screw threads in Case 1 and crushed between the screw threads and the sacral body in Case 2.

RESULTS

In both cases, leg pain disappeared immediately after the infiltration of the nerve with lidocaine, but symptoms recurred within a few days in Case 1 and within an hour in Case 2. Conservative treatment of three spinal nerve infiltrations was effective in Case 1, but reinsertion of the rogue screw was necessary in Case 2.

CONCLUSIONS

Surgeons should recognize that lateral inclination of S1 pedicle screws can cause L5 nerve root injury, which may require reinsertion of the screw, especially in cases where insertion is difficult because of overlapping surrounding muscle or bony tissue.

Computed-tomography-based anatomical study to assess feasibility of pedicle screw placement in the lumbar and lower thoracic pediatric spine

PURPOSE

The anatomy of the pedicle is complex and three-dimensional; however, there are basic dimensions important for possible screw placement. There are relatively few studies examining the pedicle anatomy in children. This study was performed to evaluate the feasibility of pedicle screw placement in children aged 5-16, based on key anatomic dimensions. A case illustration is also provided.

METHODS

The CT scans of 102 consecutive children were studied. Patients with abnormal anatomy were excluded. The parameters of the pedicle isthmus width (W), estimation of screw length (L), and axial angle (A) were recorded for 1,632 pedicles from T10 through L5. Patients were divided into four age groups. Statistical analysis was performed evaluating the difference between males and females and of the particular anatomy at the thoracolumbar junction.

RESULTS

The pedicles increase in both L and W from T10-T12 and from L1-L5. L1 has a consistently smaller W compared to T12 in both genders over all age ranges. Estimating a W of 4.5 mm necessary for safe screw placement, we calculate that virtually all pedicles of T12 and L3-L5 are large enough for screw placement in both genders after age 8. L4 and L5 are large enough for screw placement in both genders in the youngest age range.

CONCLUSIONS

Most of the pedicles of the lower lumbar spine and T12 are large enough to house the smallest commercially available screw. Understanding of the anatomy at the thoracolumbar junction is important, as the W of L1 is consistently smaller than T12.

Pedicular anatomy of the first sacral segment in transitional variations of the lumbo-sacral junction

STUDY DESIGN

The study aims to investigate the dimensions and angular orientations of the pedicles of the first sacral segment at the L5-S1 junctions affected by transitional variations.

OBJECTIVE

Measurement of parameters of the S1 pedicle and its orientation in sacra with (1) Accessory L5-S1 articulations, (2) Sacralisation of the L5, and (3) Lumbarisation of the first sacral segment, and comparing data with that observed in normal sacra.

SUMMARY OF BACKGROUND DATA

Lumbosacral fusion with instrumentation and screw fixation is commonly practiced to treat unstable L5-S1 junctions caused by a host of reasons. Though morphometric data pertaining to normal S1 pedicle structure is available in literature, it is hard to find such information regarding pedicles of first sacral segments associated with transitional variations. Transitional states at the lumbosacral junctions are often linked to development of L5-S1 instability. It thus becomes imperative to investigate S1 pedicular anatomy in context of these variations to prevent inadvertent surgical injuries and optimizing effects of screw placement in such sacral variations.

METHODS

S1 pedicle dimensions were measured in normal and L5-S1 transition affected sacra. Slope of the pedicle was measured with respect to the sagittal and the horizontal planes.

RESULTS

Linear parameters were similar in the normal sacra and those with L5-S1 accessory articulations. Sacralisation reduced all dimensions including pedicle height, sagittal and transverse dimensions. Lumbarisation was associated with small length between the facet and the sacral promontory. Sacralisation reduced the sagittal angulation of the pedicles but substantially increased its downward slope. Lumbarised pedicles were more obtuse with the sagittal plane and less steep in front.

CONCLUSION

S1 pedicle morphology and angulation in the first sacral segment are different from the normal in L5-S1 transitional situations and hence should be mapped accordingly in screw placements at the region in context of such common variations.

Comparison of radiographic and computed tomographic measurement of pedicle and vertebral body dimensions in Koreans: the ratio of pedicle transverse diameter to vertebral body transverse diameter

This study was designed to investigate the characteristics of pedicle transverse diameters (PD), vertebral body transverse diameters (VBD), especially the ratios of PD/VBD (CT ratio), which has never been discussed, in Koreans using computed tomography (CT) scans and to evaluate the possibility of obtaining more accurate estimations of PD from plain radiographs using the CT ratios in each spine level. The T1-L5 vertebrae of 50 participants were analyzed prospectively with CT scans (CT-VBD and CT-PD), and the T9-L5 vertebrae of the same participants were investigated with plain radiographs (X-VBD and X-PD). The CT ratio had a higher correlation with the CT-PD (r2 = 0.630) from T1 to L5, especially in the lower thoracic and lumbar spine (T9-L5, r2 = 0.737). The correlation of VBDs between the two radiologic tools (r2 = 0.896) was higher than that of the PDs (r2 = 0.665). Based on the data, equations for the estimation of a more accurate PD from plain radiographs were developed as follows: estimated PD = estimated VBD × [1.014 × (X-VBD) + 0.152] × the mean CT ratio at each spinal level. The correlation between the estimated PD and the CT-PD (r2 = 0.852) was improved compared with that (r2 = 0.665) between the X-PD and the CT-PD. In conclusion, the CT ratio showed a very similar changing trends to CT-PD from T1 to L5 regardless of sex and body mass, and the measurement error of PD from only plain radiographs could be minimized using estimated VBD and the mean CT ratio at each spinal level.

Standard fluoroscopic views in cadavers for determining the entry point and depth of a guide needle for use in transpedicular procedures of the thoracolumbar spine

The purpose of this study was to determine the entry point and the depth of a guide needle in a transpedicular procedure of the lower thoracic and lumbar spine on standard fluoroscopic views. Ten human cadaveric thoracolumbar spines (T9-L5) were anatomized into single vertebrae. The transpedicular puncturing needle was inserted and placed under the anterior cortex of the vertebrae along the center axis of the pedicle. The projection of the pedicle was divided into 12 sectors ("clock measurement") on the standard posterior-anterior (PA) view. We found that the ratio of the needle depth to the width of the vertebrae on the standard lateral view varied from 71.53%+/-5.72% to 93.28%+/-3.72% (mean+/-standard deviation). The entry point was located at the 9 o'clock to 11 o'clock position on the left pedicle projection and at the 1 o'clock to 3 o'clock position on the right pedicle projection on the PA view.

In vivo three-dimensional morphometric analysis of the lumbar pedicle isthmus

STUDY DESIGN

In vivo noninvasive study.

OBJECTIVE

To properly quantify pedicle anatomic parameters, using subject-based CT three-dimensional models and compare the data from 2-dimensional transverse-CT images.

SUMMARY OF BACKGROUND DATA

Accurate measurement of morphometric parameters of pedicle isthmus is important for transpedicular procedures. Anatomically, the lumbar pedicle is known to be elliptical cross-sectionally and slightly inclined in the vertical plane in the lower lumbar levels. Therefore, measurement of the pedicle isthmus may be overestimated when transverse images are used. More accurate measurement of the 3-dimensional geometry of the pedicle is therefore needed. To the best of our knowledge, 3-dimensional geometry of the pedicle has not been reported as the literature values are based on 2-dimensional image data.

METHODS

In vivo measurements of the lumbar pedicle isthmus were performed on the 3-dimensional subject-based CT models, using custom-developed software in 89 volunteers.

RESULTS

The least axis of pedicle, the longest axis of pedicle and the transverse plane width were largest at L5 in both genders. The isthmus angle declined in the lower levels. The ratio of the transverse plane width to the least axis of pedicle was largest at L5.

CONCLUSION

Our results showed that the least axis of pedicle, the longest axis of pedicle and the transverse plane width peaked at L5, and the transverse plane width became approximately twice as long in the lower levels compared to the upper levels. The ratio of the transverse plane width to the least axis of pedicle increased by about 40% at L5. These findings highlight the fact that measuring the isthmus width from CT transverse images leads to overestimation, especially in the lower lumbar spine. Therefore, a 3-dimensional inclination of the least axis of the pedicle should be taken into account for the determination of the pedicle diameter in the lower lumbar vertebrae.

An anatomical study of the mid-lateral pars relative to the pedicle footprint in the lower lumbar spine

STUDY DESIGN

An anatomic study that describes the relationship of the pedicle center to the mid-lateral pars (MLP) in the lower lumbar spine as a guide to pedicle screw placement.

OBJECTIVE

Describe morphometric data of the lower lumbar pedicles, the unique coronal pedicle footprints of L4 and L5, and their impact on the relationship of the pedicle center to the MLP.

SUMMARY OF BACKGROUND DATA

Traditional medial-lateral starting points for lumbar pedicle screws use the facet as an anatomic reference for all lumbar levels. The facet is often a difficult landmark to use secondary to degenerative changes and the desire to minimize damage to the facet capsule in the most cephalad level. These techniques can also result in pedicle violation particularly in the lower lumbar spine. Use of the nonarthritic MLP is proposed in this study as an alternative anatomic reference point for the pedicle center.

METHODS

Seventy-two pedicles (L3-S1) from embalmed cadaveric spines were used. Linear and angular dimensions of the pedicle were measured, including the degree of coronal pedicle tilt of L4 and L5. The center of the pedicle relative to the MLP and relative to the midline of the base of the transverse process was measured. The axial superior facet angle and angle of pedicle screw insertion were also measured.

RESULTS

The minimum pedicle width was 10.9 and 12.4 mm and the coronal pedicle tilt was 36 degrees and 55 degrees for L4 and L5, respectively. A classification of 2 types of L5 pedicles relevant to pedicle center location was developed. In the medial-lateral direction, the pedicle center is 2.9 mm lateral to the MLP at L3 and L4. At L5, it is 1.5 and 4.5 mm lateral to the MLP for a type I and type II pedicle, respectively. In the superior-inferior direction, the pedicle center is 1 mm superior to the midline of the transverse process base for all lower lumbar levels. Significant differences between a type I and II L5 pedicle were a larger pedicle width and distance of the pedicle center to the MLP for a type II pedicle. The difference between the axial pedicle screw insertion angle and anatomic superior facet angles was 8 degrees from L4-S1.

CONCLUSION

The MLP is a reliable anatomic reference point for the center of the pedicle in the lower lumbarspine. Consideration needs to be taken when inserting pedicle screws at L4 and L5 because of the degree of their coronal tilts and unique pedicle footprints. It is important to distinguish a type I from type II L5 pedicle as a type II pedicle is wider, has a more lateral pedicle center relative to the MLP, and has the potential for lateral screw placement while still remaining within the pedicle.

Unipedicular vertebroplasty for osteoporotic compression fracture using an individualized needle insertion angle

OBJECTIVES

In the classic transpedicular vertebroplasty, second needle placement is routinely required at the same level. However, each patient requires a different needle insertion angle (NIA) at each site. Therefore, precise NIA is required for each fractured vertebral body. In this study, we performed a unipedicular approach through an individualized NIA that had been evaluated with axial magnetic resonance imaging before vertebroplasty.

METHODS

We performed percutaneous vertebroplasty (PVP) on 103 vertebrae in 63 consecutive patients (50 women, 13 men; mean age, 70.4 y; range, 56 to 87 y). Before PVP, we measured the NIA for each pedicle. If leakage occurred without midline cement crossover, the unipedicular approach was stopped and changed to a bipedicular approach.

RESULTS

PVPs were performed from T7 to L5. We considered a successful outcome of a unipedicular approach to be when the center of vertebral body was filled with cement. Successful unipedicular PVPs were performed in 93 (90.3%) of 103 cases. Fifty-six of 63 patients were included for the pain evaluation. There was a statistically significant difference (P<0.0001) between pre-visual analog scale (VAS) (84) and post-VAS (postoperatively at 1 d-VAS: 32, postoperatively at 1 mo-VAS: 34, and postoperatively at 3 mo-VAS: 37). No statistically significant difference was found between pre-NIAs and post-NIAs. A positive correlation was found between pre-NIAs and post-NIAs.

DISCUSSION

Unipedicular PVP can be performed safely, provided the operator has a thorough knowledge of the bony landmarks and the anatomy of the pedicle. A unipedicular approach could be considered first using individualized NIA at each vertebral level.

Pedicle screw placement accuracy: a meta-analysis

STUDY DESIGN

A meta-analysis of the published literature was conducted specifically looking at accuracy and the postoperative methods used for the assessment of pedicle screw placement in the human spine.

OBJECTIVES

This study specifically aimed to identify postoperative methods used for pedicle screw placement assessment, including the most common method, and to report cumulative pedicle screw placement study statistics from synthesis of the published literature.

SUMMARY OF BACKGROUND DATA

Safety concerns have driven specific interests in the accuracy and precision of pedicle screw placement. A large variation in reported accuracy may exist partly due to the lack of a standardized evaluation method and/or the lack of consensus to what, or in which range, is pedicle screw placement accuracy considered satisfactory.

METHODS

A MEDLINE search was executed covering the span from 1966 until 2006, and references from identified papers were reviewed. An extensive database was constructed for synthesis of the identified studies. Subgroups and descriptive statistics were determined based on the type of population, in vivo or cadaveric, and separated based on whether the assistance of navigation was employed.

RESULTS

In total, we report on 130 studies resulting in 37,337 total pedicle screws implanted, of which 34,107 (91.3%) were identified as accurately placed for the combined in vivo and cadaveric populations. The most common assessment method identified pedicle screw violations simply as either present or absent. Overall, the median placement accuracy for the in vivo assisted navigation subgroup (95.2%) was higher than that of the subgroup without the use of navigation (90.3%).

CONCLUSIONS

Navigation does indeed provide a higher accuracy in the placement of pedicle screws for most of the subgroups presented. However, an exception is found at the thoracic levels for both the in vivo and cadaveric populations, where no advantage in the use of navigation was found.

Comparative assessment of pedicle morphology of the lumbar spine in various degenerative diseases

Measurement of the morphological dimensions of the pedicles of the lumbar spine was conducted using computed tomography (CT) to clarify the difference in pedicle morphology among different lumbar degenerative diseases. The subjects were 136 patients with lumbar spinal disorders who underwent myelography followed by CT scans. They were divided into four groups, that is a group of 25 patients with degenerative spondylolisthesis (DS group), a group of 54 patients with lumbar canal stenosis (LCS group), a group of 42 patients with lumbar disc herniation (LDH group), and a control group of 15 patients with spinal cord tumor in cervicothoracic region but without lumbar diseases (control group). Measurements of the transverse diameter, axial length, and axial angle of the pedicles were performed on CT slices obtained at the middle of the pedicle. The transverse diameter was the width of the isthmus, the axial length was the distance between the anterior of the vertebral body and the posterior of the vertebral arch on a line perpendicular to the line bisecting the isthmus, and the axial angle was the angle between the line perpendicular to the line bisecting the isthmus and the midline of the vertebral body. While there were no significant differences in the mean transverse diameter or axial length among the four groups, the mean axial angle was significantly smaller in the DS and LCS groups when compared to that in the LDH and control groups. In the DS and LCS groups, the pedicles were more sagitally oriented than in the LDH and control groups. Such difference in the axial angle of the pedicles in different lumbar diseases should be taken into consideration when placing at the insertion of pedicle screws, because precise orientation of screw insertion would scarcely allow penetration of the pedicle wall.

Morphometric analysis of the thoracic and lumbar spine in Japanese on the use of pedicle screws

The pedicle screw and hook have become popular instruments in treating spinal deformity and disease. This study gathered morphological data on thoracic and lumbar spines in a Japanese population that should serve as useful reference for posterior instrumentation surgery. One hundred and three dry bones were used to investigate the morphology of pedicle and facet in thoracic and lumbar spines. Measurements included the diameter and axial length of pedicle from T8 to L5, height and width of facets and thickness of articular processes from T1 to T12, and axial angle of pedicle from T1 to L5. The diameter and axial length of pedicle were smallest at T8, diameter was largest at L5 and axial length was largest at L3. Height of facets and thickness of articular processes were largest at T12. Men tended to have larger pedicles and facets than women. Transverse angle of pedicle was smallest at T12. These precise data may provide useful information when performing posterior instrumentation surgery and when developing new spinal implant systems for Asians.

Open versus endoscopic lumbar pedicle screw fixation and posterolateral fusion in a sheep model: a feasibility study

BACKGROUND CONTEXT

Conventional open procedures for lumbar pedicle screw instrumentation are often associated with significant morbidity resulting in longer postoperative recovery and hence have led to the advent of less invasive techniques of spinal instrumentation and fusion.

PURPOSE

This study compares lumbar pedicle screw fixation and posterolateral fusion using endoscopic and open techniques in a sheep model.

STUDY DESIGN

Endoscopic and open techniques of lumbar pedicle screw instrumentation and posterolateral fusion are compared in a sheep model (12 sheep in each group). The safety and fusion outcome are assessed by postoperative computed tomography (CT) scans performed at 6 months.

METHODS

Twelve sheep underwent bilateral L4-L5 pedicle screw fixation and posterolateral fusion by means of endoscopic instrumentation and another 12 sheep by means of conventional open technique. For posterolateral fusions, an autologous iliac crest bone or bone graft substitute (Healos/MP52; Orquest, Mountain View, CA) was used on either the animal's left or right side. The animals were euthanized 6 months after surgery and the lumbar spines were harvested. Pedicle dimensions and screw insertion angles were measured and the two techniques were compared using CT and image analysis software. Pedicle screw misplacement was detected by means of direct inspection and CT scan, and fusions were evaluated by CT scans.

RESULTS

The endoscopic group's screw insertion angle was more convergent, corresponded more closely to the human pedicle angle and was less variable than in the open technique. Three of the endoscopic group's 48 screws were misplaced medially, whereas in the open technique, 5 screws were misplaced laterally. Posterolateral bone fusion masses were palpable 6 months after surgery for both the autologous bone grafts and graft substitutes. There were no complications. The ratio of screw to pedicle diameter was approximately 0.6, greater than in human studies.

CONCLUSIONS

Despite differences between pedicle dimensions and screw angles, most screws could be inserted into the sheep pedicle using endoscopic or open techniques. Bone fusion was successful in both groups. Thus, minimally invasive, endoscopic transpedicular screw-plate fixation and posterolateral fusion is feasible, and as effective as the conventional open technique.

Closed posterior superior iliac spine impeding pediculocorporeal S-1 screw insertion

OBJECT

Placement of pedicle screws into S-1 is difficult. In cases in which there is a closed posterior superior iliac spine (PSIS), its medial situation prevents lateral oblique placement of the screw inserter sleeve and directing the screw to the anteromedial aspect of S-1. In the present study, the authors discuss anatomical variations of the PSIS and sacrum, and they describe a safe and effective S-1 screw insertion technique.

METHODS

The relation of 50 PSISs obtained from 25 dry pelvises (15 male and 10 female cadavers) was examined. The distance from the inferolateral aspect of the S-1 superior articular facet to its promontory was estimated. The relation between the point of anterior penetration of the "screw line" and "safe zone" was analyzed. Penetration of screw lines into the S-1 body was also measured. (An illustrative case of closed PSIS is presented with pre- and postoperative computerized tomography [CT] scan findings.) The authors found that that PSIS was situated in 28% of the specimens. When screws were directed anteromedially, the screw lines failed to penetrate the S-1 body in 24% of the male and in 15% of female specimens. The screw lines deviated from the safe zone anteriorly in 34% of the male and in 20% of the female specimens. When the PSIS was medial to the line that connects the inferolateral aspect of the S-1 superior articular facet to the promontory, a classification of closed PSIS was assigned.

CONCLUSIONS

The accuracy of the placement of the screws and their pullout strength are increased when using the present technique. Preoperative CT scanning should be performed to determine the presence of a closed PSIS; in cases in which a closed PSIS is found, the ilium should be resected to enable a greater anteromedial trajectory for placement of S-1 pedicle screws.

Measurements of the lumbar pedicles in the Eastern Anatolian population

Pedicle screw fixation of the spine has become one of the most stable and versatile methods of spine fixation, and knowledge of pedicle morphology is crucial for the safe application of these systems. We undertook this study because only a few reports have investigated Eastern populations. Lumbar pedicle anatomy, i.e., pedicle width (PW) and pedicle height (PH), transverse and sagittal pedicle angles (TPA, SPA), and pedicle length (PL), were assessed in the following two groups: (1) computed tomography scans of 29 normal adults, and (2) 16 dried lumbar spines obtained from the Anatomy Department. Interpedicular distance was different in each group. PW ranged from 4 mm to 14 mm. In both groups, the narrowest PH was 8.2 mm, the widest 19.7 mm. TPA ranged from 6(o) to 19(o) and increased from L1 to L5. In the sagittal plane, the pedicles angled caudally at L5. PL was longest at L1 and shortest at L5. In conclusion, pedicle dimensions and angles may show individual and structural differences. Our data were not significantly different from previous reported data. A detailed knowledge of these relationships is important for any surgery involving screw purchase via a pedicle, to prevent screw cutout and failure of fixation or neurological injury. Selection of the proper diameter of screw is an important issue for safe placement. Knowledge of the pedicle axis length is essential in choosing screw lengths but should always be checked intraoperatively with fluoroscopic control during screw insertion.

Anatomy based research in neurosurgery

The Anatomy Based Research in Neurosurgery is an important part of Applied Neuroanatomy that mainly concerns neurosurgical procedures and related problems, namely neuroimaging, brain mapping and surgical techniques. This includes a wide variety of research fields such as 2-D and 3-D structure visualization and referencing (stereotaxy), intraoperative imaging cartography and targeting (neuronavigation), as well as microsurgical, functional and endoscopic anatomy. The methods involved in this investigation regard predominantly microsurgical proceedings and morphological variability studies, both on living or post-mortem material (the strict neuroimaging techniques remaining a main tool for radiologists). The present paper provides an overview of the main techniques of neuroanatomical research applied to neurosurgery. Their major indications and requirements are described and discussed. Special attention is paid to some anatomical techniques such as microdissection and serial sectioning as well as 2-D and 3-D image procedures that are explained in detail.

Lumbar pedicle morphology in the immature spine: a three-dimensional study using spiral computed tomography

STUDY DESIGN

A cross-sectional study was conducted.

OBJECTIVE

To investigate the pediatric pedicle morphology with the help of modern computed tomography technology.

SUMMARY OF BACKGROUND DATA

The use of pedicular screws recently has gained popularity because of their ability to provide three-dimensional correction of spinal deformity. Extensive work has been published on the pedicle morphology of the adult and adolescent thoracolumbar spine. Less is known about the pedicle morphology of children.

METHODS

A total of 21 patients ages 5 to 10 years underwent standard spiral computed tomography of the abdomen. The patients were grouped according to age: Group 1 (5 to 8 years of age) and Group 2 (9 to 10 years of age). Images were reformatted, and multiplanar reconstructions were used to attain images of lumbar pedicles on sagittal, coronal, and transverse planes. The measurements included the inner and outer pedicle diameters on the transverse plane, the pedicle angle on both the transverse and sagittal planes, and pedicle length.

RESULTS

The smallest pedicle lengths were 24 mm for Group 1 and 25 mm for Group 2. When the average values were considered, the smallest lengths were at L5 and the longest at L3. The smallest diameter was at L1 (2.3 mm for Group 1 and 3 mm for Group 2), whereas L5 had the largest diameter (6.17 mm for Group 1 and 8.72 mm for Group 2). In the transverse plane, the pedicle angle increased from L1 to L5 in both groups. In the sagittal plane, the angulations followed an opposite trend.

CONCLUSIONS

The inner transverse diameter of the lumbar pedicle, particularly in young children, is smaller than previously reported. Insertion of screws currently available commercially screws seems to be safe in the L4-L5 pedicles of children ages 5 to 8 years, and in the L3-L5 pedicles of older children. Custom-made screws might be considered for upper levels for safe application.