No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Analysing lumbar pedicle morphometry observed via traditional and recent modalities
Abstract
Objective: The present study was conducted to collect morphometric data on the lumbar vertebrae pedicles of the
adult population from the eastern parts of India and analyse the variations, if any, with other parts of the country
and the world.
Methods: The retrospective cross-sectional study where lumbar pedicle morphometric data was obtained via dried
bone, the 3D Lumbar vertebrae images were obtained by scanning the dried lumbar vertebrae, and the 3D lumbar
vertebrae model was generated from a 1 mm thin CT scan slice of the Lumbar spine of patients who were advised
to have a CT scan of the abdomen for reasons other than related to the vertebral column. Both linear and angular
measurements in the lumbar pedicles were made bilaterally.
Results: The transverse pedicle width is widest at L3 and the narrowest at L2 vertebra bilaterally. The sagittal
pedicle width at L4 vertebrae was observed to be the widest bilaterally, while L3 had the narrowest pedicle. The
pedicular and body length along the pedicular axis is longer than the central axis at all the lumbar levels. The
linear measurement along the pedicular axis was longest at L5 bilaterally via both modes, with a range of
18.2–47.31 mm for bones and 21.03–49.28 mm for CT scan morphometry. The transverse pedicular angle on
analysis was observed to increase as one goes down the spine from L1 to L5, with a steep rise between L4 and L5.
In contrast, the sagittal pedicular angle decreased as we went caudally toward the L5 vertebrae.
Conclusion: The present study data had significant differences among the values reported in the literature from
the different populations for the parameters studied. The data obtained by this study will be highly beneficial for
the success of the free-hand technique of pedicle screw insertion.
... The planning of vertebral surgery encompasses various aspects of research, innovation, and patient education to improve surgical outcomes and enhance patient understanding. A study was conducted collecting morphometric data on lumbar vertebrae pedicles in the eastern Indian population, essential for optimizing the free-hand technique of pedicle screw insertion [15]. Focus was placed on creating personalized 3D digital models for selective dorsal rhizotomy surgeries, utilizing innovative techniques to enhance preoperative planning and surgical navigation [16]. ...
Introduction
While various 3D vertebral models have been utilized in numerous studies, there is a notable gap in the representation of pediatric lumbar vertebrae and spine. This study aimed to describe the changing shapes of lumbar vertebrae and spine with age and to develop precise 3D models.
Materials and methods
Solid-state 3D models of pediatric lumbar vertebrae and spine were created using SOLIDWORKS® Simulation software for five age groups: newborns, infants (ages 0-1), toddlers (ages 1-3), middle childhood (ages 4-7), and preadolescents (ages 8-12). Models were composed of components with varying biomechanical characteristics.
Results
Created 3D models replicate variations in the dimensions and configurations of vertebrae, taking into account osteometric analyses conducted on actual vertebral specimens. These models also include elements made of cartilage, representing various phases of vertebral growth during ontogeny. Additionally, through 3D parametric design, we developed comprehensive lumbar spine models, incorporating both the vertebrae and intervertebral disks.
Conclusion
Created pediatric solid-state vertebral 3D models can be utilized in developing virtual or augmented reality applications and for medical research. Users can interact with models, allowing virtual exploration and manipulation, enhancing learning experiences and facilitating a better understanding of spatial relationships. These solid-state 3D models allow finite element analysis and can be used for further research to calculate internal relative deformations and stress distribution under different conditions.
OBJECTIVE
The aim of this study was to design a novel lumbar cortical bone trajectory (CBT) penetrating the anterior, middle, and posterior vertebral area using imaging; measure the relevant parameters to find theoretical parameters and screw placement possibilities; and investigate the optimal implantation trajectory of the CBT in patients with osteoporosis.
METHODS
Three types of CBTs with appropriate lengths were selected to simulate screw placement using Mimics software. These CBTs were classified as the leading tip of the trajectory pointing to the posterior quarter area (original CBT [CBT-O]) and middle (novel CBT A [CBT-A]) and anterior quarter (novel CBT B [CBT-B]) of the superior endplate. The authors then measured the maximum screw diameter (MSD) and length (MSL), cephalad (CA) and lateral (LA) angles, and bone mineral density (Hounsfield unit [HU] values) of the planned novel 3-column CBT screw placements. The differences in the parameters of the novel CBTs, the percentages of successfully planned CBT screws, and the factors that influenced the successful planning of 3-column CBT screws were analyzed.
RESULTS
Three-column CBT screws were successfully designed in all segments of the lumbar spine. The success rate of the 3-column CBT planned screws was 72.25% (83.25% for CBT-A and 61.25% for CBT-B). From the CBT-O type, to the CBT-A type, to the CBT-B type, the LA, CA, and MSD of the novel CBT screws decreased with increasing trajectory length. The HU values of the three types of trajectories were all significantly higher than that of the traditional pedicle screw trajectory (p < 0.001). The main factor affecting successful planning of the 3-column CBT screw was pedicle width.
CONCLUSIONS
Moderating adjustment of the original screw parameters by reducing LAs and CAs to penetrate the anterior, middle, and posterior columns of the vertebral body using the 3-column CBT screw is feasible, especially in the lower lumbar spine.
Background The objective of this anatomical study was to perform the morphometry of dried lumbar vertebrae in human cadavers. Methods This study utilized 200 adult human cadaveric dried lumbar vertebrae. The digital Vernier calipers was used to perform the measurements. The height, antero-posterior length, transverse length of the body of the vertebrae, interpedicular distance at the lateral ends, lamina length, height and thickness, superior and inferior articular facet height and width, mid sagittal and transverse diameter of vertebral foramen, height, width and thickness of the pars inter-articularis were measured. Results The vertebral body’s anteroposterior length was more at the lower border than at the superior border ( p < 0.01). The length of lamina was higher over the right in comparison to the left (p < 0.001). The height of lamina, width of inferior articular facet, diameter of lateral recess and thickness of pars inter-articularis were greater for the left sided specimens ( p < 0.01). The statistical significance was not observed for the comparison of the remaining parameters ( p > 0.05). Conclusion This anatomical study offered several dimensions of lumbar vertebrae, which are essential in the surgical practice. The implants at the lumbar vertebrae need to be manufactured based on the anatomical dimensions of that particular sample population.
Background
Although the pedicle is routinely used as a surgical fixation site, the pedicle wall bone area fraction (bone area per unit area) and its distribution at the isthmus of the pedicle remain unknown. The bone area fraction at the pedicle isthmus is an important factor contributing to the strength of pedicle screw constructs. This study investigates the lumbar pedicle wall microstructure based on micro-computed tomography.
Methods
Six fresh-frozen cadaveric lumbar spines were analyzed. Left and right pedicles of each vertebra from L1 to L5 were resected for micro-computed tomography scanning. Data was analyzed with custom-written software to determine regional variation in pedicle wall bone area fraction. The pedicular cross-section was divided into four regions: lateral, medial, cranial, and caudal. The mean bone area fraction values for each region were calculated for all lumbar spine levels.
Results
The lateral region showed lower bone area fraction than the medial region at all spinal levels. Bone area fraction in the medial region was the highest at all levels except for L4, and the median values were 99.8% (95.9–100%). There were significant differences between the lateral region and the caudal region at L1, L2 and L3, but none at L4 and L5. The bone area fraction in the lateral region was less than 64% at all spinal levels and that in the caudal region was less than 67% at the L4 and L5 levels.
Conclusions
This study provides initial detailed data on the lumbar pedicle wall microstructure based on micro-computed tomography. These findings may explain why there is a higher incidence of pedicle screw breach in the pedicle lateral and caudal walls.
The aim of this study was to compare pedicle dimensions in degenerative lumbar spinal stenosis (DLSS) with those in the general population. A retrospective computerized tomography (CT) study for lumbar vertebrae (L1 to L5) from two sample populations was used. The first included 165 participants with symptomatic DLSS (age range: 40-88 years, sex ratio: 80 M/85 F), and the second had 180 individuals from the general population (age range: 40-99 years, sex ratio: 90 M/90 F). Both males and females in the stenosis group manifested significantly greater pedicle width than the control group at all lumbar levels (P < 0:05). In addition, pedicle heights for stenosis females were remarkably smaller on L4 and L5 levels compared to their counterparts in the control group (P < 0:001). Males have larger pedicles than females for all lumbar levels (P < 0:001). Age and BMI did not demonstrate significant association with pedicle dimensions. Our outcomes indicate that individuals with DLSS have larger pedicle widths than the control group. More so, pedicle dimensions are gender-dependent but independent of age and BMI.
Study design:
Retrospective chart review.
Purpose:
We sought to determine the differences in pedicle diameter (PD) in the lumbar spine between various races: 'Asian,' 'Black,' 'White,' and 'Other.' These data could aid in perioperative planning during instrumented spinal fusion.
Overview of literature:
Recent literature underscores the importance of understanding diverse pedicle isthmus morphology to perform successful transpedicular procedures. These studies suggest that more detailed and reliable measurements of pedicles should be undertaken. However, none of the current literature comprehensively compares average PDs between diverse racial populations with a standardized study design.
Methods:
Coronal cuts of 5,060 lumbar spine pedicles were inspected to obtain their transverse outer cortical PD as measured through the isthmus at L1-L5. Data were collected and categorized on the basis of patient-reported race. We examined average PD and PD range at each level for each race. To determine the significance, we used a mixed analysis of variance and a post hoc analysis.
Results:
The Asian cohort consistently had a significantly smaller PD at L1-L5 than Blacks or Whites (p<0.001), as did the 'Other' group compared with Blacks (p<0.001) and Whites (p=0.032). At L1-L2, the 'Other' group showed the least variability in PD. At L3-L5, the Asian population showed the smallest range, and the Black population had the largest variability in PD except at L5. There was a significant difference in PD between the various races.
Conclusions:
The Asian population consistently has significantly smaller pedicles in the lumbar spine than the Black or White populations. This information could prove useful for surgical planning. We suggest using preoperative computed tomography for pedicle screw templating as a safe method for pedicle screw instrumentation with the highest pullout strength given the wide range of PD in the Black population and the variability of PD between races.
Pedicle screws are an established method for spinal segmental fixation. To pursue high accuracy and minimally invasive, various different guidance techniques have developed. However, the preoperative screw position plans are determined by manual selection which demands complex operations and costs a lot of time. In addition, the current paths planning only consider the position, without taking the postoperative screws retention into consideration. In order to solve the problems, a new method was proposed to plan the lumbar pedicle screw placement automatically. Firstly, identify pedicle area and establish initial path based on the current vertebrae segmentation technology. After that, optimize path via the improved boundary limited Nelder–Mead simplex algorithm, and get the highest firmness path in theory. We considered that both the accuracy of position and the firmness of postoperative screws, achieved a fully automatic optimal path planning, which can effectively assist operators, improve the firmness of screw placement.
Pedicle screw instrumentation has been used to stabilize the thoracolumbar spine for several decades. Although pedicle screws were originally placed via a free-hand technique, there has been a movement in favor of pedicle screw placement with the aid of imaging. Such assistive techniques include fluoroscopy guidance and stereotactic navigation. Imaging has the benefit of increased visualization of a pedicle's trajectory, but can result in increased morbidity associated with radiation exposure, increased time expenditure, and possible workflow interruption. Many institutions have reported high accuracies with each of these three core techniques. However, due to differing definitions of accuracy and varying radiographic analyses, it is extremely difficult to compare studies side-by-side to determine which techniques are superior. From the literature, it can be concluded that pedicles of vertebrae within the mid-thoracic spine and vertebrae that have altered morphology due to scoliosis or other deformities are the most difficult to cannulate. Thus, spine surgeons would benefit the most from using assistive technologies in these circumstances. All other pedicles in the thoracolumbar spine should theoretically be cannulated with ease via a free-hand technique, given appropriate training and experience. Despite these global recommendations, appropriate techniques must be chosen at the surgeon's discretion. Such determinations should be based on the surgeon's experience and the specific pathology that will be treated.
Single-center prospective randomized controlled study.
To evaluate the accuracy of robot-assisted (RO) implantation of lumbar/sacral pedicle screws in comparison with the freehand (FH) conventional technique.
SpineAssist is a miniature robot for the implantation of thoracic, lumbar, and sacral pedicle screws. The system, studied in cadaver and cohort studies, revealed a high accuracy, so far. A direct comparison of the robot assistance with the FH technique is missing.
Patients requiring mono- or bisegmental lumbar or lumbosacral stabilization were randomized in a 1:1 ratio to FH or RO pedicle screw implantation. Instrumentation was performed using fluoroscopic guidance (FH) or robot assistance. The primary end point screw position was assessed by a postoperative computed tomography, and screw position was classified (A: no cortical violation; B: cortical breach <2 mm; C: ≥2 mm to <4 mm; D: ≥4 mm to <6 mm; E: ≥6 mm). Secondary end points as radiation exposure, duration of surgery/planning, and hospital stay were assessed.
A total of 298 pedicle screws were implanted in 60 patients (FH, 152; RO, 146). Ninety-three percent had good positions (A or B) in FH, and 85% in RO. Preparation time in the operating room (OR), overall OR time, and intraoperative radiation time were not different for both groups. Surgical time for screw placement was significantly shorter for FH (84 minutes) than for RO (95 minutes). Ten RO screws required an intraoperative conversion to the FH. One FH screw needed a secondary revision.
In this study, the accuracy of the conventional FH technique was superior to the RO technique. Most malpositioned screws of the RO group showed a lateral deviation. Attachment of the robot to the spine seems a vulnerable aspect potentially leading to screw malposition as well as slipping of the implantation cannula at the screw entrance point.
With the advances and improvement of computer-assisted surgery devices, computer-guided pedicle screws insertion has been applied to the lumbar, thoracic and cervical spine. The purpose of the present study was to perform a systematic review of all available prospective evidence regarding pedicle screw insertion techniques in the thoracic and lumbar human spine.
We considered all prospective in vivo clinical studies in the English literature that assessed the results of different pedicle screw placement techniques (free-hand technique, fluoroscopy guided, computed tomography (CT)-based navigation, fluoro-based navigation). MEDLINE, OVID, and Springer databases were used for the literature search covering the period from January 1950 until May 2010.
26 prospective clinical studies were eventually included in the analysis. These studies included in total 1,105 patients in which 6,617 screws were inserted. In the studies using free-hand technique, the percentage of the screws fully contained in the pedicle ranged from 69 to 94%, with the aid of fluoroscopy from 28 to 85%, using CT navigation from 89 to 100% and using fluoroscopy-based navigation from 81 to 92%. The screws positioned with free-hand technique tended to perforate the cortex medially, whereas the screws placed with CT navigation guidance seemed to perforate more often laterally.
In conclusion, navigation does indeed exhibit higher accuracy and increased safety in pedicle screw placement than free-hand technique and use of fluoroscopy.
The results and complications of pedicle screw plate (PSP) stabilizations were investigated in lumbar fresh fractures, malunions, lumbar metastases, primary tumors, lumbosacral fusions, and highgrade spondylolisthesis. The low incidence of neurologic complications of PSP is noteworthy, and a reason for recommending the method.
Utilization of thoracic pedicle screws is controversial, especially in the treatment of scoliosis. We present a case of a 15-year-old girl seen 6 months after her initial surgery for scoliosis done elsewhere. She complained of persistent epigastric pain, tremor of the right foot at rest, and abnormal feelings in her legs. Clinical examination revealed mild weakness in the right lower extremity, a loss of thermoalgic discrimination, and a forward imbalance. A CT scan revealed at T8 and T10 that the right pedicle screws were misplaced by 4 mm in the spinal canal. At the time of the revision surgery the somatosensory evoked potentials (SSEP) returned to normal after screw removal. The clinical symptoms resolved 1 month after the revision. The authors conclude that after pedicle instrumentation at the thoracic level a spinal cord compression should be looked for in case of subtle neurologic findings such as persistent abdominal pain, mild lower extremity weakness, tremor at rest, thermoalgic discrimination loss, or unexplained imbalance.
This paper details the quantitative three-dimensional anatomy of lumbar vertebrae L1-L5 from Asian (Singaporean) subjects based on 60 lumbar vertebrae from 12 cadavers. The purpose of the study was to measure the dimensions of the various parameters of the lumbar vertebrae and thereafter to compare the data with a study performed on Caucasian specimens. Measurements were taken with the aid of a three-dimensional digitiser. The means and standard errors for linear, angular and area dimensions of the vertebral body, spinal canal, pedicle, and spinous and transverse processes were obtained for each lumbar vertebra. From this comparison, it was found that the dimensions of the vertebral body of the Asian subjects are slightly larger, with a maximum average difference of 8% for the posterior vertebral body height. The dimensions of the spinal canal, pedicle, and spinous and transverse processes of Asian subjects are smaller. The greatest difference can be found in the spinal canal area and pedicle width, which are smaller by an average of 30% and 20%, respectively. With the exception of the spinal canal depth, spinal canal area and pedicle width, all other parameters compared show a similar trend. The findings can provide more accurate modelling for analysis and spinal implant design and also allow more precise clinical diagnosis in sub-Asian groups.
Analysis of morphometric data obtained from computed tomography scans in relation to the lower thoracic, lumbar, and S1 pedicle in patients from the Indian subcontinent.
To record the surgically relevant parameters of transverse pedicle isthmus width, transverse pedicle angle, and depth to anterior cortex along the midline axis and the pedicle axis and to compare the results with those of similar studies in literature.
Most studies reported are for white populations. Considerable differences are documented in the few reports in Oriental populations compared with Western populations. To the authors' knowledge, no similar study has been published for patients from the Indian subcontinent.
Computed tomography scans of the lower thoracic and lumbosacral spine of patients from the Indian subcontinent were reviewed. We selected and analyzed 86 vertebrae in 31 patients. Parameters recorded were transverse pedicle isthmus width, transverse pedicle angle, and depth to anterior cortex along the midline axis and the pedicle axis.
The mean transverse pedicle isthmus width was least at the T9 level (5.02 mm). Of the pedicles at T9, 46.15% had a diameter of less than 5 mm, followed by T10 (12.5%), T11 (11.11%), and L1 (11.11%). Of the pedicles at T9, 76.92% had a diameter of less than 6 mm, followed by T11 (33.33%), L1 (33.33%), T10 (25%), T12 (25%), L2 (20%), and L3 (5.56%). The mean transverse pedicle angle faced laterally at T11 (-2.97 degrees ) and T12 (-3.00 degrees ), being least at T12. The depth to the anterior cortex was more along the pedicle axis at all levels except T11 and T12, consistent with the laterally facing pedicles at these levels.
Significant differences exist between the pedicles of Indian and white populations. It is suggested that preoperative computed tomography scans of the patients must be evaluated to choose the appropriately sized implant and avoid inadvertent complications. Preparation of the pedicle intraoperatively should take into account the orientation of the transverse pedicle angle.
Pedicle screw construct have become one of the most practiced procedure in spinal surgery. Despite commonly used, questions remain about their safety especially for the thoracic spine and in deformity where difficulty in positioning can lead to pedicle breach and adjacent structures injury. Misplacement rates have been reported to be from 5 to 41% in the lumbar spine and from 3 to 55% in the thoracic spine. Hence, various procedures have been described in order to improve pedicle screw insertion accuracy. Aim of this study is to evaluate current concepts on pedicle screws placement techniques to better understand recent attitude and clarify some doubts when selecting the most proper method.
Study design:
Cadaveric in vitro computed tomography (CT) imaging study.
Objective:
To examine minimum pedicle diameter from transverse and coronal CT reconstructions of thoracolumbar spine specimens and compare their degree of disparity, if any. Pedicle angulation in coronal and transverse planes was measured and their contribution to the disparity in minimum pedicle diameter was assessed.
Summary of background data:
Spinal minimum pedicle diameter can be obtained from both transverse and coronal CT reconstructions; however, the degree of disparity in these measurements has not been described previously. Angulation of the pedicle in transverse and coronal planes may contribute to a disparity in minimum pedicle diameter acquired from reconstructions. This also has not been described previously. This study examined whether the disparity could be predicted by spinal level, as pedicle angulations vary in both coronal and transverse planes.
Methods:
Five thoracolumbar specimens (T1-L5, age 48-59 yrs, male) were CT scanned utilizing clinical protocols. Minimum pedicle diameters and pedicle angulations were acquired in transverse and coronal reconstructions. Disparities between minimum pedicle diameters were measured and the correlation between this disparity and spinal level was characterized.
Results:
A significant difference (P < 0.001) in minimum pedicle diameter existed between measures from coronal and transverse reconstructions. There was a significant correlation (P < 0.001) between the difference in minimal pedicle diameter and the transverse pedicle angle as well as the coronal pedicle angle.
Conclusion:
An overestimation of minimum pedicle diameter in the transverse reconstruction occurs when the coronal pedicle angulation increases, and in the coronal reconstruction when the transverse pedicle angulation increases. Therefore, pedicle angle should be determined using both coronal and transverse reconstructions and utilized to reduce the risk of overestimation of the true pedicle diameter.
Level of evidence:
NA.
Study Design. An anatomic study of pedicle dimensions was performed for lumbar vertebrae from American subjects.
To quantify the dimensions of the lumbar pedicles and to better define the demographic factors that could ultimately govern the caliber selection of pedicle screws.
Transpedicular screw fixation allows for segmental instrumentation into multiple vertebrae across multilevel fusion area, offering considerable biomechanical advantage over the conventional hook and lateral mass fixation. Large variations in morphology from previous studies may be related to differences in demographics, sample size, and methodology.
For this study, L1-L5 vertebrae from 503 American human cadavers were directly measured with a digital caliper. Examiner measured each vertebra to determine medial-lateral pedicle width (PW) and cranial-caudal pedicle height (PH). Demographic information regarding age, sex, and race, as well as body height and weight, was available for all 503 subjects.
PH decreased in size caudally down the lumbar spine, but PW increased in size. The largest PH was at the L1 level with a mean of 15.75 mm. The widest PW was at the L5 level with a mean of 18.33 mm. Males have larger pedicles than females for all lumbar levels. The tallest and heaviest groups generally had larger pedicles than the shorter and lighter groups, respectively. Age and race did not consistently affect pedicle dimension in a statistically significant manner.
Our large-scale study of American specimens characterized the relationship between pedicle dimensions and a variety of demographic factors such as age, sex, body height and weight. With substantial statistical power, the current study showed that male, taller, and heavier individuals had larger lumbar pedicles.
This study details the quantitative three-dimensional surface anatomy of human lumbar vertebrae based on a study of 60 vertebrae. The two lower vertebrae (L4 and L5) appeared to be transitional toward the sacral region, whereas the upper two vertebrae (L1 and L2) were transitional toward the thoracic region. Means and standard errors of the means for linear, angular, and area dimensions of vertebral bodies, spinal canal, pedicle, pars interarticularis, spinous and transverse processes were obtained for all lumbar vertebrae. This information provides a better understanding of the spine, and allows for a more precise clinical diagnosis and surgical management of spinal problems. The information is also necessary for constructing accurate mathematical models of the human spine.
Study Design. A computer‐assisted planning and visualization system (the Orthopaedic Surgery Planning System) was tested for pedicle screw insertion in vivo. Objectives. To evaluate the system's applicability for regular intraoperative use and its accuracy for pedicle screw placement in vivo. Summary of Background Data. Pedicle screw placement poses considerable anatomic and biomechanical risks. The reported rates of screw misplacement with conventional insertion techniques are unacceptably high. It previously has been shown in vitro that computer assistance offers the potential to decrease the number of screws perforating the pedicular cortex. Methods. The accuracy of 162 pedicle screws inserted with the Orthopaedic Surgery Planning System was assessed by means of postoperative computed tomography evaluation. Reconstructions of the horizontal, frontal, and sagittal planes were analyzed. Cortex perforations were graded in steps of 2 mm. Results. The cortex was perforated in 2.7% of pedicles. Complete preoperative computed tomography scanning of the levels to be operated on is essential to allow for a precise image reconstruction. Initial difficulties in applying the system contribute to the malplacements. A learning curve for general handling of the Orthopaedic Surgery Planning System was observed. Conclusions. The system provides a safe and reproducible technique for pedicle screw insertion. Other applications in the field of spine surgery are under evaluation.
Abastract: Lumbar Pedicles from an important part of lumbar spine. They also have the quality of playing an important role in transmission of weight in lumbar spine. The Present study was conducted on 60 adult lumbar vertebrae in dept. of Anatomy, M.P. Shah Medical College, Jamnagar. Out of 60 vertebrae studied, 45 were of males & 15 were of females. The Height and Width of Lumbar pedicles were measured with the help of Sliding Vernier Caliper. The observations showed that there is always an increase in width of lumbar pedicles proceeding from L1 to L5 levels and the width being maximum at L5 level to enable in weight transmission. The observations also showed that the height of lumbar pedicles decreases as we move from L3 to L5 levels i.e. at the lower lumbar levels to enable the transmission of weight through thoracolumbar region.
The classification of vascular bone tumors remains challenging, with considerable morphological overlap spanning across benign to malignant categories. The vast majority of both benign and malignant vascular tumors are readily diagnosed based on their characteristic histological features, such as the formation of vascular spaces and the expression of endothelial markers. However, some vascular tumors have atypical histological features, such as a solid growth pattern, epithelioid change, or spindle cell morphology, which complicates their diagnosis. Pathologically, these tumors are remarkably similar, which makes differentiating them from each other very difficult. For this rare subset of vascular bone tumors, there remains considerable controversy with regard to the terminology and the classification that should be used. Moreover, one of the most confusing issues related to vascular bone tumors is the myriad of names that are used to describe them. Because the clinical behavior and, consequently, treatment and prognosis of vascular bone tumors can vary significantly, it is important to effectively and accurately distinguish them from each other. Upon review of the nomenclature and the characteristic clinicopathological, radiographic and genetic features of vascular bone tumors, we propose a classification scheme that includes hemangioma, hemangioendothelioma, angiosarcoma, and their epithelioid variants.
STUDY DESIGN.: Prospective, computer aided pedicle morphometric data measurements obtained from computed tomography (CT) scan of lower thoracic (T9-T12) and lumber vertebrae in a large group of Indian population. OBJECTIVES.: Measurement on CT scan of the surgically relevant parameters of transverse pedicle isthmus width, transverse pedicle angle, and depth to anterior cortex along the midline axis and the pedicle axis by Computer software aid in a large sample of Indian population. To compare the results with those of similar studies of Western and Indian population in literature by other methods and to deduce safety parameters for pedicular screw placements in these areas. SUMMARY OF BACKGROUND DATA.: Although differences have been reported in literature between various ethnic groups, most studies reported are for white populations and Indian studies are few. The Indian studies have had small sample size, and been done on patients with preexisting spinal disorder or cadavers and by manual data measurements. To the authors' knowledge, the present study is the largest published for patients from the Indian subcontinent and only using computer software aided measurements. METHODS.: CT scans of the lower thoracic and lumbosacral spine of patients free from spinal disorders from the Indian subcontinent were reviewed. We analyzed a total of 450 vertebrae in 50 consecutive patients. Parameters recorded were transverse pedicle isthmus width, transverse pedicle angle, and depth to anterior cortex along the midline axis and the pedicle axis with help of computer software. RESULTS.: The mean transverse pedicle isthmus width was least at the T9 level (5.65 mm). Majority of pedicles at thoracic level had diameter over 5 mm T9 (94%), T10 (100%), T11 (96%), T12 (100%). At lumber all had diameters over 7 mm with wide range at upper levels. The mean transverse pedicle angle faced laterally at thoracic vertebrae with exception of T9. In lumber area, all were medially directed with maximum at L5 and least at L1. The depth to the anterior cortex was more along the pedicle axis at all levels except T11 and T12. CONCLUSION.: Significant differences exist between the pedicles of Indian and white populations. It is suggested that preoperative software-based morphometric data should be collected if possible for preoperative planning of pedicle implant placement and sizes to avoid inadvertent complications. Further, data from study can be used as a guide for implant size, intraoperative placement trajectory at lower thoracic and lumber vertebrae pedicles.
This study details the quantitative three-dimensional surface anatomy of human lumbar vertebrae based on a study of 60 vertebrae. The two lower vertebrae (L4 and L5) appeared to be transitional toward the sacral region, whereas the upper two vertebrae (L1 and L2) were transitional toward the thoracic region. Means and standard errors of the means for linear, angular, and area dimensions of vertebral bodies, spinal canal, pedicle, pars interarticularis, spinous and transverse processes were obtained for all lumbar vertebrae. This information provides a better understanding of the spine, and allows for a more precise clinical diagnosis and surgical management of spinal problems. The information is also necessary for constructing accurate mathematical models of the human spine.
Extensive development of spinal instrumentation has occurred recently, benefitted by improved biomechanical knowledge. Reviewed here are various devices and the major biomechanical issues relevant to them. The devices are categorized by site of attachment. The major emphasis is on the most recently developed category: devices attached by transpedicular screws. Aspects of this last category reviewed here include screw design, screw placement, longitudinal linking devices (rods, plates), and transverse connectors (cross-linking). Emphasis is placed not only on current knowledge, but also on unresolved issues.
The pedicles of lumbar vertebrae were measured both directly and radiographically to determine the differences between the sexes and the accuracy of radiographic measurement. The lumbar pedicles of cadavera of forty-nine patients--twenty-four men and twenty-five women--who died between the ages of sixty and ninety-eight years were measured directly and on radiographs. The pedicles of lumbar vertebrae from fifty-one patients--twenty-three men and twenty-eight women--between the ages of twenty and fifty years who had low-back problems were measured on radiographs and computerized tomographic scans. Comparison revealed that the average transverse and sagittal diameters of the pedicles and the distance from the posterior aspect of the laminar cortex to the anterior aspect of the cortex of the vertebral body along the central axis of the pedicles were 5 to 20 per cent greater in men, but the transverse and sagittal angles of the pedicle did not differ significantly between the sexes. Measurements on radiographs and computerized tomographic scans of the transverse angles of the pedicles and of the distances from the posterior aspect of the laminar cortex to the anterior aspect of the cortex of the vertebral body from the second to the fifth lumbar vertebra were greater than direct measurements, even without magnification. Direct measurements of the diameters of the transverse and sagittal diameters of the pedicle of the fifth lumbar vertebra, however, were greater than the radiographic measurements.
The accuracy of pedicular screw placement was assessed in 40 consecutive patients treated with the AO "Fixateur Interne." Postoperative CT scans were used to measure canal encroachment from the medial border of the pedicle, the angle of insertion and the point of entry. Eighty-one percent of the screws were placed within 2 mm of the medial border of the pedicle and 6% had 4-8 mm of canal encroachment with two patients developing minor neurological complications that spontaneously resolved. Four percent were inserted lateral to the pedicle. The parameters linked to satisfactory screw placement include entry point, angle of insertion and pedicular isthmus widths. Improvement in accuracy was noted in the latter 25% of screw insertions, reflecting the learning curve associated with this technique.
The geometric properties of 380 vertebral pedicles, ranging from T6 to L5, were analysed. Measurement were made directly from the specimens as well as from roentgenograms. The parameters considered were the horizontal and vertical pedicle diameters, pedicle angles in the transverse and sagittal planes, and the transverse and anteroposterior widths of the spinal canal and vertebral body. In addition, the length of the pedicle and the length of the pedicle including the vertebral body to the anterior cortex were measured along the pedicle axis and in a line parallel to the midline of the vertebral body. The smallest horizontal and vertical pedicle diameters were found at vertebral levels from T6 to T10. The correlation between pedicle widths and screw dimensions is obvious. In the transverse plane, the pedicle angle diverged from the vertebral body at all levels, except at T12. In the sagittal plane, the pedicles were angled cephalad from T6 to L3 and slightly caudally at L5. Knowledge of the length of the pedicle to the anterior vertebral body cortex is very important for safe screw purchase. At all levels, with the exception of T12, this length was found to be significantly greater along the pedicle axis than along a line parallel to the midline of the vertebral body.
A total of 2,905 pedicle measurements were made from T1-L5. Measurements were made from spinal computerized tomography (CT) scan examinations and individual vertebral specimen roentgenograms. Parameters considered were the pedicle isthmus width in the transverse and sagittal planes, pedicle angles in the transverse and sagittal planes, and the depth to the anterior cortex in a line parallel to the midline of the vertebral body and along the pedicle axis. There was no significant difference between data obtained from CT scans and specimen roentgenograms. Pedicles were widest at L5 and narrowest at T5 in the transverse plane. The widest pedicles in the sagittal plane were seen at T11, the narrowest at T1. Due to the oval shape of the pedicle, the sagittal plane width was generally larger than the transverse plane width. The largest pedicle angle in the transverse plane was at L5. The posterolateral to anterolateral pedicle axis orientation in the transverse plane, seen at other levels throughout the thoracolumbar spine, reversed at T12. In the sagittal plane, the pedicles angled caudally at L5 and cephaladly from L3-T1. The depth to the anterior cortex was significantly longer along the pedicle axis than along a line parallel to the midline of the vertebral body at all levels with the exception of T12 and T11.
The results of a morphometric study of selected human vertebrae undertaken to provide data for implant design are presented in this report. Twenty-seven dimensions were measured from thoracic (T2, T7, T12) and lumbar (L1-L5) vertebrae using prepared spinal columns from 30 skeletons belonging to the Hamann-Todd Osteological Collection. Maximum and minimum pedicle dimensions indicated that the pedicles are less symmetric cephalad than they are caudal. Vertebral body height increases caudally except posteriorly where, after an initial increase, it decreases in the lower lumbar region. Major and minor body diameters and the major spinal canal diameter slightly increase caudally, whereas minor spinal canal diameter exhibits little or no change.
Attempts at segmental correction and fixation of the vertebral column usually result in biomechanical instability, defined as an alteration of any two of the longitudinal mechanical columns. This leads to a system that involves all three columns to restore stability to the spine. The use of specially-designed interpeduncular screws bilaterally and segmentally permits firm attachment of each vertebra through the pedicle and into the vertebral body, thus covering all three biomechanical columns. By attaching coupling screw drivers to each set of transpedicular screws, lordosis, kyphosis, and rotation can be corrected segmentally within the tolerance of disc elasticity. The correction of lateral deviation is accomplished in a segmental manner. As a preliminary report, 20 cases are presented between the ages of 15 and 55 years with a variety of spine pathology. All were treated with interpeduncular screw fixation (ISF) and arthrodesis. The average follow-up period is 15 months, so no conclusion of the rate of pseudoarthrosis can be made. The correction of pathology is 80% with balance and maintenance of physiologic saggital curves. There have been no complications in this group of patients.
Measurements of the subarachnoid space at myelography were carried out in three groups of patients, one group with stenosis of the lumbar spinal canal, one group without stenosis, and one intermediate group. Although spinal canal stenosis is most prominent at disc levels, the results demonstrate decreased sagittal diameter at mid-vertebral body level as well. The mean transverse diameters did not differ in three groups. This points towards congenital or developmental factors as the basic abnormality in the majority of patients with stenosis of the lumbar spinal canal.
The horizontal and vertical diameters of the pedicles of the lumbar vertebrae were measured from plain anteroposterior radiographs of the lumbar spines of male and female subjects aged from 10 to 65 y. The results showed that there were significant differences between the pedicle diameters of males and females. Horizontal diameters ranged from 7.4 to 13.6 mm in females and from 7.5 to 14.2 mm in males. Female vertical diameters ranged from 14.2 to 18.2 mm whilst male vertical diameters ranged from 14.8 to 20.7 mm. Generally, there was a cephalocaudal increase of diameters in both sexes. Significant age-related variations of pedicle diameters were noted at all segmental levels. Within the adolescent group (10-19.9 y), the diameters of the 10-14.9 y group and 15-19.9 y group differed significantly (P < 0.001). When the pedicle diameters of the individual age groups were compared, the pedicles of the 10-19.9, 20-29.9, 30-34.9, 40-49.9, and 50+ y groups were found to be significantly different from each other. The evidence suggests that pedicle diameters undergo continuous change throughout the age range studied. The changes are characterised by increase of diameters in some age groups and decrease in others, but there was an overall increase of both vertical and horizontal diameters as the age groups were followed from the youngest to the oldest. The pattern of variation with age differed for horizontal and vertical diameters. After the 5th decade, female horizontal and vertical diameters showed a tendency to increase while male diameters decreased.
The lumbar pedicles of 100 adult Chinese patients were studied with computed tomography to provide data on their dimensions and angular alignment. Data obtained were compared with published measurements of spines from white patients to determine similarities and differences between the lumbar spines.
The age range of the patients was 18 to 60 years. There were 63 men and 37 women. There was no demonstrable sex difference for dimensions or angular alignment of the pedicles.
The method of scanning and measurement was standardized. Levels considered abnormal by the radiologist were excluded from the study, and a single observer was used to avoid inter-observer errors. The data obtained were statistically analyzed using Student's t test to determine differences between men and women and left and right sides. Age differences were analyzed using the F statistic test. The pedicle inclination angle (transverse angle) and the pedicle dimensions were compared with published data of whites.
The pedicles of Asians, when compared with those of whites, showed a similar pattern of changes with vertebral level. However, Asian pedicles had a larger pedicle inclination angle (transverse angle) from L1 to L4 (L1 = 16 degrees, L2 = 16 degrees, L3 = 19 degrees, L4 = 23 degrees), whereas L5 (29 degrees) was similar to many series of whites.
There are differences between the lumbar pedicles of Asians and whites. Such differences need to be considered when posterior pedicle screw fixation of the spine is performed.
Knowledge of pedicle diameter and surface landmarks is crucial for safe placement of screws. Little attention has been paid to variations of entrance points for pedicle screws, differentiation of male and female pedicle sizes and pedicle size differences in nonwhite populations. Forty thoracolumbar spinal columns from T9 to L5 were measured using vernier calipers. Cephalad-caudad and medial-lateral diameter of the pedicle, length of the pedicle from posterior cortex to anterior cortex at the midline and parallel to midline was measured. Relation of the centre of the pedicle to the transverse process (TP) and to the superior facet joint was noted. Twenty-five male and 15 female specimens were measured. Average pedicle width in the female was 5.2 mm at T9 (SD 0.9) to 13 mm at L5 (SD 2.7) and in the male 6.0 mm at T9 (SD 1.1) to 12.8 mm at L5 (SD 2.7). Cephalad caudad diameter was 12.5 mm (SD 1.2) at T9 to 20.5 mm (SD 3.6) at L5 in the male and in the female 12.2 mm (SD 1.3) at T9 to 18.7 mm (SD 3.9) at L5. All specimens had starting points cephalad to the midpoint of the TP at T9. At L5, 37 of 40 specimens had starting points at the midpoint of the TP. Starting points were parallel to the middle or lateral third of the superior facet joint at T9. At L5 starting points were at least one third of the facet joint lateral to the lateral border of the facet. Female pedicle width was smaller than male at T9 (P = 0.03) and T12 (P = 0.04).(ABSTRACT TRUNCATED AT 250 WORDS)
The location of pedicle screws (n = 42) in four human specimens of the lumbar spine and in 30 patients (n = 131 screws) after lumbar spinal fusion was assessed using computed tomography.
To determine the accuracy of pedicle screw placement in lumbar vertebrae and the reproducibility and repeatability of the computed tomography examination.
Failures in the placement of transpedicular screws for lumbar fusion are reported. The evaluation of such screws using computed tomography examination has not been investigated.
After surgery, the specimens were dissected in transversal slices to observe macroscopically the location of the pedicle screw and to correlate these observations with the computed tomography images. All patients were examined by one observer. To determine the reproducibility and repeatability of the computed tomography examination, two observers studied computed tomography images of 12 patients (n = 58 screws) twice within 3 months.
In the specimens, 10 screws were observed to penetrate the medial wall of the pedicle. This correlated fully with the images. In the patients' group, 40% of all screws penetrated the cortex of the vertebra. Of all screws, 29% penetrated the medial wall of the pedicle. From the computed tomography images, it appeared that a deviation of more than 6 mm medially was a high risk for nerve root damage. Three months after his first examination, Observer 1 documented a different position in three of 58 screws (kappa = 0.90). Observer 2 found a different position in eight screws (kappa = 0.65). The comparison between the reviews of the two observers showed a different opinion for the first evaluation, four disagreements (2-4 mm) and 17 disagreements (0-2 mm; kappa = 0.34), and for the second evaluation, four disagreements (2-4 mm) and 12 disagreements (0-2 mm; kappa = 0.43).
Correct placement of transpedicular screws for spinal fusion seems to be more difficult than it looks. The computed tomography scanning is useful for differential diagnosis of postoperative radicular syndromes after lumbar transpedicular fixation.
This study defined the projection point of the lumbar pedicle on its posterior aspect and its relation to a reliable landmark and reported pedicle dimensions based on 50 lumbar spines.
To establish the best starting point for a pedicle screw for passing the screw down the center (axis) of the pedicle; to describe quantitatively the relations of the pedicle projection point to a reliable landmark; and to evaluate the linear and angular dimensions of the lumbar pedicle.
Posterior transpedicular screw fixation has been most widely used for management of the unstable lumbar spine. Several studies of pedicular anatomy exist, but little quantitative data regarding the location of the lumbar pedicle axis for each level have been reported.
Fifty dry lumbar specimens (250 lumbar vertebrae) were obtained for study of the lumbar pedicle. Anatomic evaluation focused on determination of the projection point of the lumbar pedicle axis on the junction of the superior facet and the transverse process and measured the distance from the projection point to the midline of the transverse process for each level of the lumbar vertebrae. Pedicle dimensions, including linear and angular, also were measured.
Differences in dimensions between men and women were not found to be statistically significant. The average distance from the projection point to the midline of the transverse process consistently changed from L1 to L5. Above L4, the projection point for men and women averaged 3.9 mm for L1, 2.8 mm for L2, and 1.4 mm for L3 superior to the midline of the transverse process, respectively. At L4, the projection point was close to the midline of the transverse process (0.5 mm inferior). At L5, the projection point was an average of 1.5 mm inferior to the midline of the transverse process.
The average distance from the projection point of the lumbar pedicle axis to the midline of the transverse process consistently varied at different levels. This information may prove helpful in the placement of screws into the lumbar pedicle.
A computer-assisted planning and visualization system (the Orthopaedic Surgery Planning System) was tested for pedicle screw insertion in vivo.
To evaluate the system's applicability for regular intraoperative use and its accuracy for pedicle screw placement in vivo.
Pedicle screw placement poses considerable anatomic and biomechanical risks. The reported rates of screw misplacement with conventional insertion techniques are unacceptably high. It previously has been shown in vitro that computer assistance offers the potential to decrease the number of screws perforating the pedicular cortex.
The accuracy of 162 pedicle screws inserted with the Orthopaedic Surgery Planning System was assessed by means of postoperative computed tomography evaluation. Reconstructions of the horizontal, frontal, and sagittal planes were analyzed. Cortex perforations were graded in steps of 2 mm.
The cortex was perforated in 2.7% of pedicles. Complete preoperative computed tomography scanning of the levels to be operated on is essential to allow for a precise image reconstruction. Initial difficulties in applying the system contribute to the malplacements. A learning curve for general handling of the Orthopaedic Surgery Planning System was observed.
The system provides a safe and reproducible technique for pedicle screw insertion. Other applications in the field of spine surgery are under evaluation.
Comparison of the radiation dose between the traditional fluoroscopic approach and computed tomography (CT)-based computer-assisted surgery for pedicle screw placement was determined.
To evaluate the radiation dose delivered by fluoroscopy-controlled pedicle screw placement versus insertion guided by computer. To define the CT computer-assisted protocol, involving lower radiation exposure for the patient, that still provides acceptable image quality.
There are no published data describing the dose delivered in CT-based image-guided surgery, and there are few studies in which the organ dose and the effective dose delivered during pedicle screw insertion that is performed traditionally with fluoroscopic control are described.
Dose measurements were performed on two types (REMAB and RANDO) of anthropomorphic phantoms. Thermoluminescent dosimeters were used to measure the organ dose. Both phantoms were exposed to the fluoroscopic x-ray beam. The representative intraoperative scenario was determined by observation of 20 consecutive surgical interventions featuring pedicle screw implantation. For the CT dose measurement only, the REMAB phantom was used with two types of CT scanners. Three scanning protocols were evaluated: sequential, spiral optimized, and sequential optimized. Optimization of the scanning protocol included changes of anode current. The CT images were subsequently processed to achieve three-dimensional reconstruction of the lumbar spine for the computer-assisted intervention.
Organ and effective doses were higher in any of the CT examinations than in the fluoroscopic procedure. There was a slight difference between doses registered during optimized spiral scanning and doses in the calculated optimized sequential CT protocol. Optimized sequential scanning was associated with an effective dose 40% lower than that in nonoptimized sequential scanning. The small anatomic structures of the spine could be easily recognized on each of the three-dimensional reconstructions, and all of them were suitable for use in computer-assisted surgery.
Percutaneous pedicle screw insertion in the lumbar region of the spine, performed using fluoroscopic control, requires a lower radiation dose than do CT scans necessary for computer-assisted surgery. The CT radiation dose can be significantly decreased by optimization of the scanner settings for computer-assisted surgery. The advantages of computer-assisted surgery justify CT scans, when based on correctly chosen indications.
This article provides a perspective on the development of pedicle-screw fixation in the lumbar spine, the biomechanics of its application, the possible complications, and the scientific evidence that supports specific applications in selected disorders. The overall goal is to objectify the debate currently surrounding the use of these devices. Lumbar-pedicle fixation devices are currently considered class III med-ical devices. According to the Food and Drug Administration, such devices are investigational or experimental, have not been proved safe and effective, and may potentially pose a risk to patients.
An experimental model to assess radiation exposure during lumbar pedicle screw insertion.
To measure skin (patient) and scatter (surgeon) doses of radiation during lumbar spine fluoroscopy to assess safety of the procedure for both the surgeon and patient and determine best practice.
Fluoroscopy assists with accuracy of pedicle screw placement, yet the optimal technique of C-arm use and risk to both patient and operating room staff from radiation exposure are unknown.
Entry- and scatter-dose recordings were made using a digital dosimeter while screening an anthropomorphic phantom prone on a radiolucent operating table. The source was positioned both superiorly and inferiorly with the height varied in the latter orientation to create a working space under the C-arm. The senior author's fluoroscopy records were reviewed in 140 consecutive cases.
In a series of 140 patients who underwent pedicle screw fixation, the fluoroscopy time was 1.4 minutes per case or 0.33 minutes per screw. In the source-superior position, the effective dose received by the patient was approximately 2.3 mSv per case. In the source-inferior position with a working space of 300 mm, the effective dose was 6.8 mSv. Scatter dose to the surgeon was higher in the source-superior position but was still less than 10% of recommended limits for the hand, thyroid, and eyes.
The source-superior position is the preferred position for pedicle screw screening if a working space is required. Patient exposure is minimized, and surgeon dose is well within current recommendations.
New techniques to stabilize and correct the thoracic and lumbar spine have been developed in recent years. In view of the wide variety and complexity of fixation devices, the optimum configuration of spinal instrumentation systems needs to be defined. Linear and angular measurements of both vertebral pedicles were made in ten complete thoracic and lumbar cadaveric spines using callipers and a goniometer. The vertical interpedicular distance gradually increased along the spine up to L5. The transverse interpedicular distance was larger at both ends of the spine. Pedicular height gradually increased from T1 to L5, plateauing between T3 and T9, being widest at the thoracolumbar junction. Pedicular width was greatest at the three junctional regions of the spine. The sagittal pedicular angle decreased along the length of the spine to zero at L5. The transverse pedicular angle decreased from T1 to T12 and then increased to L5. Of the pedicular measurements only width limits the diameter of fixation screws. The vertical interpedicular distance determines the distance between the holes of plates, while the length of the transfixator is related to the transverse interpedicular distance. The pedicular angles enable triangulation of screws and determine the stability of the fixation.
A morphometric study of lumbar vertebral pedicular parameters in cadavers and comparison with previous studies in the literature was conducted.
To suggest dimensions for pedicular implants in the Indian population, and to improve the pedicular screw placement technique.
Detailed knowledge of pedicle morphometry is critical for proper placement of a transpedicular screw. The size and shape of the vertebral pedicle vary between different races. Morphometric studies have been conducted in white and nonwhite populations (e.g., Chinese, Koreans).
The vertebral pedicles at L1-L5 were studied in 20 cadavers by direct roentgenographic and computerized tomographic scan methods. The following parameters were studied: transverse diameter, transverse angle, sagittal diameter, sagittal angle, chord length, interpedicular distance, medial and lateral cortical thickness.
Transverse diameter was largest at L5 (16.19 mm) and smallest at L1 (7.05 mm). The transverse angle was largest at L5 (29 degrees) and smallest at L1 (9 degrees). The pedicles were directed cranially in the sagittal plane at all lumber levels except L5. The sagittal angle was largest at L5 (29 degrees) and smallest at L1 (9 degrees). Chord length was largest at L2 (47.5 mm) and smallest at L1 (46.01 mm). The values of linear measurements were smaller in females at all levels.
On the basis of this limited study in a subset of the Indian population, it appears that the transverse diameter and pedicle entrance point differ from those in the white population. The results suggest that a 5-mm screw would be safer in the upper lumbar levels (L1, L2), and 6-mm screw in the lower lumbar levels (L3-L5). The pedicle entrance point migrates laterally for lower lumbar levels, especially at L5. The medial pedicle cortex can be safely sounded while the pedicle is probed.
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.
The aim of this study is to understand the magnitude of the pedicle's diameters for the use of pedicle screw fixation in spinal instrumentation. Pedicle dimensions from T1 to L5 were measured in 16 whole human cadaver spines (eight women and eight men). The mean age at the time of death was 67.2 (range: 59-84 years). The external transverse, the external sagittal, and the internal transverse diameter pedicle widths were measured with electronic calipers both on the right and left pedicles. The widest external transverse diameter was at the L5 level with a mean of 13.61 mm (range: 10.29-16.20 mm). The narrowest external transverse pedicle diameter was at the T5 level with a mean of 5.09 mm (range: 4.10-6.88 mm). The widest external sagittal pedicle diameter was at the T11 level with a mean of 17.02 mm (range: 14.84-19.57 mm), while the narrowest one was at T1 level with a mean of 8.90 mm (range: 7.18-11.37 mm). The maximum internal transverse pedicle diameter was at the L5 level with a mean 8.95 mm (range: 7.10-11.21 mm), while the minimum was at the T5 level with a mean 3.90 mm (range: 3.10-4.82 mm). Statistical significant greater pedicle dimensions were found in males at multiple levels. Pedicle dimensions at the levels from T3 to T8 need preoperative evaluation with computed tomography before the insertion of pedicle screws with diameter more than 5 mm. Pedicles at T12 to L5 levels may accommodate screws of 7 mm diameter.
Cadaver study.
To evaluate with direct observation the errors made when novice resident surgeons place thoracic pedicle screws. To determine how many specimens need to be instrumented to assure an improvement in accuracy to currently published levels.
Thoracic pedicle screw instrumentation has been shown to provide numerous benefits in spinal deformity surgery including 3 column fixation of the spinal elements, decreased need for thoracoplasty or anterior thoracic release and decreased operative time and blood loss.
Three orthopaedic residents inexperienced in pedicle screw placement received an introductory teaching session. Intact thoracic vertebral body specimens were harvested from 15 cadaver spines. Each vertebral body was mounted on a clear Plexiglas frame with only the posterior surface anatomy visible to the surgeon. Each resident surgeon instrumented 5 thoracic spines verbalizing all perceived pedicle wall violations as they occurred. An observer recorded the accuracy of the gearshift probe, flexible probe, tap, and screw placement. Critically perforated screws were defined as a greater than 2 mm breach of the pedicle wall.
Two hundred ninety-seven pedicles in 149 intact vertebral body specimens were instrumented. Eighty-five (29%) screws were not fully within the pedicle. Sixty-three (74%) were noncritical violations and 22 (26%) were critical violations. There were 18 (21%) screw violations not perceived by the surgeon to be outside the pedicle. There was a decrease in the proportion of total screw violations by the third cadaver (P < 0.001) and in critical screw violations by the fourth cadaver (P = 0.01).
Novice resident surgeons placing thoracic pedicle screws in cadavers were able to significantly improve by the fourth cadaver to accuracy levels documented in the literature. Surgeons in training shouldpractice these skills in the laboratory before proceeding to the operating room.
Biomechanics of thoracolumbar spinal fixation. A review
- Krag
Radiation dose for pedicle screw insertion. Fluoroscopic method versus computer-assisted surgery
- Slomczykowski
Morphometric study of width and height of lumbar pedicles in population of Haryana
- S Tyagi
- S Chhabra
- R Narayan
Tyagi S, Chhabra S, Narayan R. Morphometric study of width and height of lumbar
pedicles in population of Haryana. Int J Appl Decis Sci. 2017;3:78-81. https://www.
semanticscholar.org/paper/Morphometric-study-of-width-and-height-of-lumbar-i
n-Tyagi-Chhabra/87298e1eb13a1129a53e71bf3070fdab840deeb3.
Accuracy of robot-assisted placement of lumbar and sacral pedicle screws: a prospective randomized comparison to conventional freehand screw implantation
- Ringel
Morphometric study of width and height of lumbar pedicles in population of Haryana
- Tyagi