Assessment of a fully-parametric thoraco-lumbar spine model generator with articulated ribcage.

The present paper describes a novel user-friendly fully-parametric thoraco-lumbar spine CAD model generator including the ribcage, based on 22 independent parameters (1 posterior vertebral body height per vertebra + 4 sagittal alignment parameters, namely pelvic incidence, sacral slope, L1-L5 lumbar lordosis, and T1-T12 thoracic kyphosis). Reliable third-order polynomial regression equations were implemented in Solidworks to analytically calculate 56 morphological dependent parameters and to automatically generate the spine CAD model based on primitive geometrical features. A standard spine CAD model, representing the case-study of an average healthy adult, was then created and positively assessed in terms of spinal anatomy, ribcage morphology, and sagittal profile. The immediate translation from CAD to FEM for relevant biomechanical analyses was successfully demonstrated, first, importing the CAD model into Abaqus, and then, iteratively calibrating the constitutive parameters of one lumbar and three thoracic FSUs, with particular interest on the hyperelastic material properties of the IVD, and the spinal and costo-vertebral ligaments. The credibility of the resulting lumbo-sacral and thoracic spine FEM with/without ribcage were assessed and validated throughout comparison with extensive in vitro and in vivo data both in terms of kinematics (range of motion) and dynamics (intradiscal pressure) either collected under pure bending moments and complex loading conditions (bending moments + axial compressive force).

Anatomical Analysis of the S1 Neural Foramen Using Three-Dimensional Computed Tomography Imaging: Insights for Effective S1 Nerve Root Block.

OBJECTIVE: The first sacral nerve root block (S1 NRB) is used to diagnose and treat lumbosacral and radicular pain. This study aims to clarify the anatomy of the S1 neural foramen using three-dimensional (3D) computed tomography (CT) images and to establish the optimal fluoroscopic angle, localize the S1 neural foramen on fluoroscopy, and determine the safe puncture depth for S1 NRB. METHODS: In this single-center cohort study, 200 patients with lumbar degenerative disease who underwent preoperative CT were enrolled. Four distinct studies were conducted using the CT data. Study 1 examined the correlation of the sacral slope angle and the supine and prone positions. Study 2 analyzed the tunnel view angle (TVA) using 3D reconstruction. Study 3 ascertained the location of the S1 neural foramen in fluoroscopy images. Study 4 investigated the safe depth for performing S1 NRB. RESULTS: The regression analysis in Study 1 revealed a correlation of the sacral slope angle and the supine and prone positions. Study 2 determined an optimal fluoroscopic TVA of approximately 30° for the S1 NRB. Study 3 found that the S1 neural foramen was located caudal to the L5 pedicle 1.7 ± 0.2 times the distance between the L4 and L5 pedicles. Study 4 revealed that the depths of the S1 neural foramen and root were 27.0 ± 2.1 mm and 16.5 ± 2.0 mm, respectively. CONCLUSIONS: Our study suggests an optimal fluoroscopic angle, a simple method to locate the S1 neural foramen on fluoroscopy, and an ideal puncture depth for a safe and effective S1 NRB.

The Effect of Intraoperative Prone Position on Psoas Morphology and Great Vessel Anatomy: Consequences for Prone Lateral Approach to the Lumbar Spine.

BACKGROUND: This study sought to quantify radiographic differences in psoas morphology, great vessel anatomy, and lumbar lordosis between supine and prone intraoperative positioning to optimize surgical planning and minimize the risk of neurovascular injury. METHODS: Measurements on supine magnetic resonance imaging and prone intraoperative computed tomography with O-arm from L2 to L5 levels included the anteroposterior and mediolateral proximity of the psoas, aorta, inferior vena cava (IVC), and anterior iliac vessels to the vertebral body. Psoas transverse and longitudinal diameters, psoas cross-sectional area, total lumbar lordosis, and segmental lordosis were assessed. RESULTS: Prone position produced significant psoas lateralization, especially at more caudal levels (P < 0.001). The psoas drifted slightly anteriorly when prone, which was non-significant, but the magnitude of anterior translation significantly decreased at more caudal segments (P = 0.038) and was lowest at L5 where in fact posterior retraction was observed (P = 0.032). When prone, the IVC (P < 0.001) and right iliac vein (P = 0.005) migrated significantly anteriorly, however decreased anterior displacement was seen at more caudal levels (P < 0.001). Additionally, the IVC drifted significantly laterally at L5 (P = 0.009). Mean segmental lordosis significantly increased when prone (P < 0.001). CONCLUSION: Relative to the vertebral body, the psoas demonstrated substantial lateral mobility when prone, and posterior retraction specifically at L5. IVC and right iliac vein experienced significant anterior mobility-particularly at more cephalad levels. Prone position enhanced segmental lordosis and may be critical to optimizing sagittal restoration.

Fat infiltration of the posterior paraspinal muscles is inversely associated with the fat infiltration of the psoas muscle: a potential compensatory mechanism in the lumbar spine.

BACKGROUND: The function of the paraspinal muscles and especially the psoas muscle in maintaining an upright posture is not fully understood. While usually considered solely as a hip flexor, the psoas muscle and its complex anatomy suggest that the muscle has other functions involved in stabilizing the lumbar spine. The aim of this study is to determine how the psoas muscle and the posterior paraspinal muscles (PPM; erector spinae and multifidus) interact with each other. METHODS: A retrospective review including patients undergoing posterior lumbar fusion surgery between 2014 and 2021 at a tertiary care center was conducted. Patients with a preoperative lumbar magnetic resonance imaging (MRI) scan performed within 12 months prior to surgery were considered eligible. Exclusion criteria included previous spinal surgery at any level, lumbar scoliosis with a Cobb Angle > 20° and patients with incompatible MRIs. MRI-based quantitative assessments of the cross-sectional area (CSA), the functional cross-sectional area (fCSA) and the fat area (FAT) at L4 was conducted. The degree of fat infiltration (FI) was further calculated. FI thresholds for FIPPM were defined according to literature and patients were divided into two groups (< or ≥ 50% FIPPM). RESULTS: One hundred ninetypatients (57.9% female) with a median age of 64.7 years and median BMI of 28.3 kg/m2 met the inclusion criteria and were analyzed. Patients with a FIPPM ≥ 50% had a significantly lower FI in the psoas muscle in both sexes. Furthermore, a significant inverse correlation was evident between FIPPM and FIPsoas for both sexes. A significant positive correlation between FATPPM and fCSAPsoas was also found for both sexes. No significant differences were found for both sexes in both FIPPM groups. CONCLUSION: As the FIPPM increases, the FIPsoas decreases. Increased FI is a surrogate marker for a decrease in muscular strength. Since the psoas and the PPM both segmentally stabilize the lumbar spine, these results may be indicative of a potential compensatory mechanism. Due to the weakened PPM, the psoas may compensate for a loss in strength in order to stabilize the spine segmentally.

A comparative study of the anatomy and MRI images of the lumbar foraminal ligaments at the L1-L5 levels.

PURPOSE: The purpose of this study was to evaluate the ability of MRI images to reveal foraminal ligaments at levels L1-L5 by comparing the results with those of anatomical studies. METHODS: Eighty lumbar foramina were studied. First, the best MRI scanning parameters were selected, and the transverse and sagittal axes of each lumbar foramina were scanned to identify and record the ligament-like structures in each lumbar foramen. Then, the cadaveric specimens were anatomically studied, and all ligament structures in the lumbar foramina were retained. The number, morphology and distribution of ligaments under anatomical and MRI scanning were observed. Histological staining of the dissected ligament structures was performed to confirm that they were ligamentous tissues. Finally, the accuracy of ligament recognition in MRI images was statistically analyzed. RESULTS: A total of 233 foraminal ligaments were identified in 80 lumbar intervertebral foramina through cadaveric anatomy. The radiating ligaments (176, 75.5%) were found to be attached from the nerve root to the surrounding osseous structures, while the transforaminal ligaments (57, 24.5%) traversed the intervertebral foramina without any connection to the nerve roots. A total of 42 transforaminal ligament signals and 100 radiating ligament signals were detected in the MRI images of the 80 intervertebral foramina. CONCLUSION: The MRI can identify the lumbar foraminal ligament, and the recognition rate of the transforaminal ligament is higher than that of the radiating ligament. This study provides a new method for the clinical diagnosis of the relationship between the lumbar foraminal ligament and radicular pain.

Morphometrics of T11-L5 Vertebrae in Jordanian Population: CT Scan-Based Study / Morfometría de las Vértebras T11-L5 en una Población Jordana: Estudio Basado en Tomografía Computarizada

SUMMARY: The study will provide information on the morphometrics of the vertebrae, which can be used to guide clinicians on the appropriate size of transpedicular screws to use in spine interventions among the Jordanian population and for comparative studies with other races. A retrospective analysis of normal CT scans of the lumbar and thoracolumbar areas was done. Linear and angular measurements of 336 vertebrae were collected for 25 males and 23 females. The results were compared between right and left and between both sexes. The L5 has the longest AVBH and the shortest PVBH in both sexes, it also, had the shortest and widest pedicle in both males and females. ratio of the AVBH to PVBH showed progressive increase in both sexes from T11 to L5. Similarly, the VBW increased progressively from the top to the bottom in both sexes, but it was significantly different between both sexes. The L1 was the most cranially oriented vertebrae in males while the L2 showed the most cranial orientation in females. Both sexes L5 was the most caudally oriented vertebrae. This study provides a database for vertebral morphometrics in the Jordanian population, there are slight differences between the right and left side in the upper studied vertebrae (T11-L2) and some measurement showed significant differences between males and females. These findings need to be taken into consideration when inserting pedicle screws.

Este estudio proporciona información sobre la morfometría de las vértebras, la cual puede ser utilizada por los médicos oara determinar el tamaño adecuado de los tornillos transpediculares a utilizar en intervenciones de columna en la población jordana y para estudios comparativos con otras grupos. Se realizó un análisis retrospectivo de tomografías computarizadas normales de las áreas lumbar y toracolumbar. Se recogieron medidas lineales y angulares de 336 vértebras de 25 hombres y 23 mujeres. Los resultados se compararon entre vértebras derechas e izquierdas y entre ambos sexos. La L5 tiene el AVBH más largo y el PVBH más corto en ambos sexos, también tenía el pedículo más corto y más ancho tanto en hombres como en mujeres. La relación de AVBH a PVBH mostró un aumento progresivo en ambos sexos de T11 a L5. De manera similar, el VBW aumentó progresivamente de arriba hacia abajo en ambos sexos, pero fue significativamente diferente entre ambos sexos. La L1 fue la vértebra más orientada cranealmente en los hombres, mientras que la L2 mostró la orientación más craneal en las mujeres. En ambos sexos L5 fue la vértebra más orientada caudalmente. Este estudio proporciona una base de datos para la morfometría vertebral en la población jordana, donde existen ligeras diferencias entre el lado derecho e izquierdo en las vértebras superiores estudiadas (T11-L2). Algunas mediciones mostraron diferencias significativas entre hombres y mujeres. Estos hallazgos deben tenerse en cuenta al insertar tornillos pediculares.

Thoracolumbar transitional vertebrae: Quantitative differentiation and associated numeric variation in the vertebral column using skeletal remains.

Transitional vertebrae at the thoracolumbar region are called thoracolumbar transitional vertebrae (TLTV) and retain physical features from the thoracic and lumbar regions. Since TLTV were first classified 40 years ago, there has been much discrepancy regarding its features, identification and clinical relevance. Vertebral body levels are used in the medical field as a frame of reference to locate specific organs, vessels, nerves or landmarks. Any numeric variation or deviation in the vertebral column may lead to clinical errors. Previous findings have suggested a high association between numeric variation and the presence of TLTV. Therefore, the aim of this study was to identify the types of TLTV observed and to identify any possible associated numeric variation in the vertebral column. This study also aimed to validate the established technique to quantitatively differentiate TLTV from T12 and L1 at the thoracolumbar junction using skeletal remains from a South African population group. Skeletal remains (n = 187) remains from the Pretoria bone collection were assessed. Measurements were taken of the angle of the superior zygapophyseal processes of the last thoracic vertebra (T12), the first lumbar (L1), and identified TLTV. The results indicate a TLTV prevalence of 35% (n = 66/187). The results show that each vertebral type (T12, L1, TLTV) fall into independent confidence intervals: T12 is 188° ± 9.22 (CI: 187° < µ < 189.6°), 110° ± 7.52 (CI: 109.2° < µ < 111.3°) in L1, and 135° ± 24.51 (CI: 130.4° < µ < 139.1°) in the TLTV. This study observed that 70% of cases with TLTV was associated with numeric variation in the spine, both homeotic and meristic and that TLTV has a 35% prevalence. The results clearly show that quantitative morphometric analysis can effectively differentiate TLTV from other vertebral types at the thoracolumbar junction in skeletal remains.

Evolution of vertebral numbers in primates, with a focus on hominoids and the last common ancestor of hominins and panins.

The primate vertebral column has been extensively studied, with a particular focus on hominoid primates and the last common ancestor of humans and chimpanzees. The number of vertebrae in hominoids-up to and including the last common ancestor of humans and chimpanzees-is subject to considerable debate. However, few formal ancestral state reconstructions exist, and none include a broad sample of primates or account for the correlated evolution of the vertebral column. Here, we conduct an ancestral state reconstruction using a model of evolution that accounts for both homeotic (changes of one type of vertebra to another) and meristic (addition or loss of a vertebra) changes. Our results suggest that ancestral primates were characterized by 29 precaudal vertebrae, with the most common formula being seven cervical, 13 thoracic, six lumbar, and three sacral vertebrae. Extant hominoids evolved tail loss and a reduced lumbar column via sacralization (homeotic transition at the last lumbar vertebra). Our results also indicate that the ancestral hylobatid had seven cervical, 13 thoracic, five lumbar, and four sacral vertebrae, and the ancestral hominid had seven cervical, 13 thoracic, four lumbar, and five sacral vertebrae. The last common ancestor of humans and chimpanzees likely either retained this ancestral hominid formula or was characterized by an additional sacral vertebra, possibly acquired through a homeotic shift at the sacrococcygeal border. Our results support the 'short-back' model of hominin vertebral evolution, which postulates that hominins evolved from an ancestor with an African ape-like numerical composition of the vertebral column.

Female Sex and Supine Proximal Lumbar Lordosis Are Associated With the Size of the LLIF "Safe Zone" at L4-L5.

STUDY DESIGN: Retrospective chart review. OBJECTIVE: Identify demographic and sagittal alignment parameters that are independently associated with femoral nerve position at the L4-L5 disk space. SUMMARY OF BACKGROUND DATA: Iatrogenic femoral nerve or lumbar plexus injury during lateral lumbar interbody fusion (LLIF) can result in neurological complications. The LLIF "safe zone" is the anterior half to two third of the disk space. However, femoral nerve position varies and is inconsistently identifiable on magnetic resonance imaging. The safe zone is also narrowest at L4-L5. METHODS: An analysis of patients with symptomatic lumbar spine pathology and magnetic resonance imaging with a visibly identifiable femoral nerve evaluated at a single large academic spine center from January 1, 2017, to January 8, 2020, was performed. Exclusion criteria were transitional anatomy, severe hip osteoarthritis, coronal deformity with cobb >10 degrees, > grade 1 spondylolisthesis at L4-L5 and anterior migration of the psoas.Standing and supine lumbar lordosis (LL) and its proximal (L1-L4) and distal (L4-S1) components were measured. Femoral nerve position on sagittal imaging was then measured as a percentage of the L4 inferior endplate. A stepwise multivariate linear regression of sagittal alignment and LL parameters was then performed. Data are written as estimate, 95% CI. RESULTS: Mean patient age was 58.2±14.7 years, 25 (34.2%) were female and 26 (35.6%) had a grade 1 spondylolisthesis. Mean femoral nerve position was 26.6±10.3% from the posterior border of L4. Female sex (-6.6, -11.1 to -2.1) and supine proximal lumbar lordosis (0.4, 0.1-0.7) were independently associated with femoral nerve position. CONCLUSIONS: Patient sex and proximal LL can serve as early indicators of the size of the femoral nerve safe zone during a transpsoas LLIF approach at L4-L5.

A novel tool to quantify in vivo lumbar spine kinematics and 3D intervertebral disc strains using clinical MRI.

Medical imaging modalities that calculate tissue morphology alone cannot provide direct information regarding the mechanical behaviour of load-bearing musculoskeletal organs. Accurate in vivo measurement of spine kinematics and intervertebral disc (IVD) strains can provide important information regarding the mechanical behaviour of the spine, help to investigate the effects of injuries on the mechanics of the spine, and assess the effectiveness of treatments. Additionally, strains can serve as a functional biomechanical marker for detecting normal and pathologic tissues. We hypothesised that combining digital volume correlation (DVC) with 3T clinical MRI can provide direct information regarding the mechanics of the spine. Here, we have developed a novel non-invasive tool for in vivo displacement and strain measurement within the human lumbar spine and we used this tool to calculate lumbar kinematics and IVD strains in six healthy subjects during lumbar extension. The proposed tool enabled spine kinematics and IVD strains to be measured with errors that did not exceed 0.17 mm and 0.5%, respectively. The findings of the kinematics study identified that during extension the lumbar spine of healthy subjects experiences total 3D translations ranging from 1 mm to 4.5 mm for different vertebral levels. The findings of strain analysis identified that the average of the maximum tensile, compressive, and shear strains for different lumbar levels during extension ranged from 3.5% to 7.2%. This tool can provide base-line data that can be used to describe the mechanical environment of healthy lumbar spine, which can help clinicians manage preventative treatments, define patient-specific treatments, and to monitor the effectiveness of surgical and non-surgical interventions.

Deep learning in sex estimation from a peripheral quantitative computed tomography scan of the fourth lumbar vertebra-a proof-of-concept study.

Sex estimation is a key element in the analysis of unknown skeletal remains. The vertebrae display clear sex discrepancy and have proven accurate in conventional morphometric sex estimation. This proof-of-concept study aimed to investigate the possibility to develop a deep learning algorithm for sex estimation even from a single peripheral quantitative computed tomography (pQCT) slice of the fourth lumbar vertebra (L4). The study utilized a total of 117 vertebrae from the Terry Anatomical Collection. There were 58 male and 59 female cadavers, all of the white ethnicity, with the average age at death 49 years and a range of 24 to 77 years. A coronal pQCT scan was taken from the midway of the L4 corpus. Sex estimation was performed in a total of 19 neural network architectures implemented in the AIDeveloper software. Of the explored architectures, a LeNet5-based algorithm reached the highest accuracy of 86.4% in the test set. Sex-specific classification rates were 90.9% among males and 81.8% among females. This preliminary finding advances the field by encouraging and directing future research on artificial intelligence-based methods in sex estimation from individual skeletal traits such as the vertebrae. Combining quickly obtained imaging data with automated deep learning algorithms may establish a valuable pipeline for forensic anthropology and provide aid when combined with traditional methods.

The anatomical feasibility of anterior intra- and extra-bifurcation approaches to L5-S1: an anatomic study based on lumbar MRI.

BACKGROUND CONTEXT: The anterior approach at L5-S1 has many advantages, however, vascular complications are challenging for spinal surgeons who may not be familiar with the variability of vascular anatomy. There are three different anterior approaches (intra-bifurcation approach and extra-bifurcation: left-, and right-sided prepsoas approaches) described in previous studies to respond to the variability of anterior vascular anatomy for reduction in vascular injury, while no guidance for the choice of approach preoperatively. PURPOSE: To analyze the anatomical feasibility of three anterior approaches to access the L5-S1 disc space according to a practical framework. STUDY DESIGN: Retrospective study. PATIENT SAMPLE: Lumbar magnetic resonance imaging (MRI) from patients who visited our outpatient clinic were reviewed, with 150 cases meeting the inclusion criteria. OUTCOME MEASURES: The following radiographic parameters were measured on axial T2-weighted MRI at the lower endplate of L5 and the upper endplate of S1: width of the vascular corridor, position of the left and right common iliac vein (CIV), and presence of perivascular adipose tissue (PAT). Moreover, we designed a safe line to evaluate the feasibility of left- and right-sided prepsoas approaches. Cases of lumbosacral transitional vertebrae were identified. METHODS: The feasibility of the intra-bifurcation approach was determined by the width of the vascular corridor, presence of PAT, and the position of the CIV. The feasibility of the prepsoas approach was determined by the relative position of the CIV to the safe line, presence of PAT, and the intersection point of the CIV and vertebral body. RESULTS: Sixty-eight percent, 64.7%, and 75.3% cases allowed the intra-bifurcation, left-, and right-sided prepsoas approach to L5-S1, respectively. The cases in this study had at least one of three anterior approaches to access L5-S1 disc space, and 74% of cases had more than one anatomical feasibility of anterior approach. The right-sided prepsoas approach was feasible in the majority of cases because of the vertical course of the right CIV with a significantly higher proportion of presence of PAT. Patients with lumbosacral transitional vertebrae (24 cases) may prefer the prepsoas approaches, and only six cases (25.0%) were determined to be feasible for the intra-bifurcation approach. CONCLUSIONS: Our study proposes a practical framework to determine whether the three different anterior approaches are feasible access at L5-S1. According to the framework, all cases had the anatomical feasibility of using an anterior approach to access L5-S1, and three-fourths of cases had a replaceable anterior approach when encountering intraoperative difficulties.

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.

Anatomy and morphology of iliolumbar ligament.

PURPOSE: To address limited amount of available data and contradictory statements in published works 60 Iliolumbar ligaments extracted from 30 cadavers were examined to describe their insertions and morphology. METHODS: The ligaments were removed during the standard autopsy procedures with a use of an oscillating saw, a chisel and a scalpel. The specimens were photographed before the extraction and measured alongside their anterior margin. Next, they were preserved in formaldehyde, stripped of other soft tissues and then examined, photographed and described. RESULTS: The mean length of the ligaments was 31.7 mm. 44 specimens were described as single-banded, 13 as double-banded and 3 as other. In 24 cases costal process of LV has been fixed to the iliac plate by short ligamentous bands. In 38 cases there was a thick fibrous membrane connected to the ligament. No legitimate insertions on LIV vertebra were observed. CONCLUSIONS: Typical iliolumbar ligament consists of a single ligamentous band. Most common variability of the ligament consist of two bands. In approximately 40% of cases the costal process of LV can be additionally stabilized to the iliac plate by short, strong ligamentous bands. In 63% of cases a connection between the iliolumbar ligament and a fibrous membrane placed in the frontal plane, superiorly to the ligament, has been observed. There seems to be no convincing proof of existence of the insertion of the iliolumbar ligament on the LIV vertebra.

Deep learning and morphometric approach for Sex determination of the lumbar vertebrae in a Thai population.

Sex determination is a fundamental step in biological profile estimation from skeletal remains in forensic anthropology. This study proposes deep learning and morphometric technique to perform sex determination from lumbar vertebrae in a Thai population. A total of 1100 lumbar vertebrae (L1-L5) from 220 Thai individuals (110 males and 110 females) were obtained from the Forensic Osteology Research Center, Faculty of Medicine, Chiang Mai University, Thailand. In addition, two linear measurements of superior and inferior endplates from the digital caliper and image analysis were carried out for morphometric technique. Deep learning applied image classification to the superior and inferior endplates of the lumbar vertebral body. All lumbar vertebrae images are included in the dataset to increase the number of images per class. The accuracy determined the performance of each technique. The results showed the accuracies of 82.7%, 90.0%, and 92.5% for digital caliper, image analysis, and deep learning techniques, respectively. The lumbar vertebrae L1-L5 exhibit sexual dimorphism and can be used in sex estimation. Deep learning is more accurate in determining sex than the morphometric method. In addition, the subjectivity and errors in the measurement are decreased. Finally, this study presented an alternative approach to determining sex from lumbar vertebrae when the more traditionally used skeletal elements are incomplete or absent.

Human lumbar sympathetic blockade: An anatomical study to address potential block failure.

The lumbar sympathetic block is often used to treat complex regional pain syndrome, but it seems to have a high failure rate. This study seeks anatomical explanations for this apparent failure in order to refine our block procedure. Two simulated sympathetic trunk blocks were carried out on four fresh, cryopreserved unembalmed human cadavers under fluoroscopic control at the L2 vertebral body level, followed by two further simulated blocks at the L4 vertebral body level on the other side. Dye was injected, and the areas were dissected following a specific protocol. We then describe the anatomy and the spread of the dye compared to the spread of the contrast medium on fluoroscopy. The ganglia were differently located at different vertebral levels, and differed among the cadavers. Following this anatomical clarification, we now prefer to perform lumbar sympathetic blocks at the fourth lumbar vertebra level, using an extraforaminal approach at the caudal end of ​​the vertebra, avoiding the anterolateral margin of the vertebral body at the midpoint.

The association between paraspinal muscle parameters and vertebral pedicle microstructure in patients undergoing lumbar fusion surgery.

PURPOSE: Lumbar fusion surgery has become a standard procedure in spine surgery and commonly includes the posterior placement of pedicle screws. Bone quality is a crucial factor that affects pedicle screw purchase. However, the relationship between paraspinal muscles and the bone quality of the pedicle is unknown. The aim of the study was to determine the relationship between paraspinal muscles and the ex vivo bony microstructure of the lumbar pedicle. METHODS: Prospectively, collected data of patients undergoing posterior lumbar fusion for degenerative spinal conditions was analyzed. Pre-operative lumbar magnetic resonance imaging (MRI) scans were evaluated for a quantitative assessment of the cross-sectional area (CSA), functional cross-sectional area (fCSA), and the proportion of intramuscular fat (FI) for the psoas muscle and the posterior paraspinal muscles (PPM) at L4. Intra-operative bone biopsies of the lumbar pedicle were obtained and analyzed with microcomputed tomography (µCT) scans. The following cortical (Cort) and trabecular (Trab) bone parameters were assessed: bone volume fraction (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), connectivity density (CD), bone-specific surface (BS/BV), apparent density (AD), and tissue mineral density (TMD). RESULTS: A total of 26 patients with a mean age of 59.1 years and a mean BMI of 29.8 kg/m2 were analyzed. fCSAPPM showed significant positive correlations with BV/TVTrab (ρ = 0.610; p < 0.001), CDTrab (ρ = 0.679; p < 0.001), Tb.NTrab (ρ = 0.522; p = 0.006), Tb.ThTrab (ρ = 0.415; p = 0.035), and ADTrab (ρ = 0.514; p = 0.007). Cortical bone parameters also demonstrated a significant positive correlation with fCSAPPM (BV/TVCort: ρ = 0.584; p = 0.002; ADCort: ρ = 0.519; p = 0.007). FIPsoas was negatively correlated with TMDCort (ρ = - 0.622; p < 0.001). CONCLUSION: This study highlights the close interactions between the bone microstructure of the lumbar pedicle and the paraspinal muscle morphology. These findings give us further insights into the interaction between the lumbar pedicle microstructure and paraspinal muscles.

L4/5 accessibility for extreme lateral interbody fusion (XLIF): a radiological study.

INTRODUCTION: Potential advantages of the Extreme Lateral Interbody Fusion (XLIF) approach are smaller incisions, preserving anterior and posterior longitudinal ligaments, lower blood loss, shorter operative time, avoiding vascular and visceral complications, and shorter length of stay. We hypothesize that not every patient can be safely treated at the L4/5 level using the XLIF approach. The objective of this study was to radiographically (CT-scan) evaluate the accessibility of the L4/5 level using a lateral approach, considering defined safe working zones and taking into account the anatomy of the superior iliac crest. METHODS: Hundred CT examinations of 34 female and 66 male patients were retrospectively evaluated. Disc height, lower vertebral endplate (sagittal and transversal), and psoas muscle diameter were quantified. Accessibility to intervertebral space L4/5 was investigated by simulating instrumentation in the transverse and sagittal planes using defined safe zones. RESULTS: The endplate L5 in the frontal plane considering defined safe zones in the sagittal and transverse plane (Zone IV) could be reached in 85 patients from the right and in 83 from the left side. Through psoas split, the safe zone could be reached through psoas zone II in 82 patients from the right and 91 patients from the left side. Access through psoas zone III could be performed in 28 patients from the right and 32 patients from the left side. Safe access and sufficient instrumentation of L4/5 through an extreme lateral approach could be performed in 76 patients of patients from the right and 70 patients from the left side. CONCLUSION: XLIF is not possible and safe in every patient at the L4/5 level. The angle of access for instrumentation, access of the intervertebral disc space, and accessibility of the safe zone should be taken into account. Preoperative imaging planning is important to identify patients who are not suitable for this procedure.

Spinal Morphometry As A Novel Predictor For Recurrent Lumbar Disc Herniation Requiring Revision Surgery: Results of A Case Control Study.

Introduction: There is conflicting data on the risk factors for recurrent lumbar disc herniation (rLDH). Most of the predictors for rLDH identified so far are acquired risk factors or radiological factors at the level of the herniation. Whole lumbar spine (WLS) morphometry has not been evaluated as a possible predictor of rLDH. Objectives: We aimed to evaluate if preoperative spinal morphometry can predict the occurrence of rLDH requiring revision surgery. Methods: This retrospective case-control study on 250 patients included 45 patients operated for rLDH, 180 controls without rLDH who had previously undergone microdiscectomy for a single level lumbar disc prolapse, and a holdout validation set of 25 patients. Morphometric variables related to the WLS were recorded in addition to previously identified predictors of rLDH. Logistic regression (LR) analysis was performed to identify independent predictors of rLDH. Results: LR yielded four predictors of which two were WLS morphometric variables. While increasing age and smoking positively predicted rLDH, increasing WLS interfacet distance and WLS dural-sac circumference negatively predicted rLDH. The LR model was statistically significant, χ2 (4) =15.98, P = 0.003, and correctly classified 80.3% of cases. On validation, the model demonstrated a fair accuracy in predicting rLDH (accuracy: 0.80, AUC: 0.70). Conclusions: Larger mean lumbar bony canals and dural sacs protect from the occurrence of symptomatic rLDH. These WLS morphometric variables should be included in future risk stratification algorithms for lumbar disc disease. In addition to the previously recognized risk factors, our study points to an underlying developmental predisposition for rLDH.

Development and Validation of a Whole Human Body Finite Element Model with Detailed Lumbar Spine.

OBJECTIVE: Investigations showed that low back pain of occupational drivers might be closely related to the whole-body vibration. Restricted by ethical concerns, the finite element method had become a viable alternative to invasive human experiments. Many mechanical behaviors of the human spine inside of the human body were unclear; therefore, a human whole-body finite element model might be required to better understand the lumbar behavior under whole-body vibration. METHODS: In this study, a human whole-body finite element model with a detailed lumbar spine segment was developed. Several validations were performed to ensure the correctness of this model. RESULTS: The results of anthropometry and geometry validation, static validation, and dynamic validation were presented in this study. The validation results showed that the whole human body model was reasonable and valid by comparing with published data. CONCLUSIONS: The model developed in this study could reflect the biomechanical response of the human lumbar spine under vibration and could be used in further vibration analysis and offer proposals for protecting human body under whole-body vibration environment.