Function of revolute zygapophyses in the lumbar vertebrae of early placental mammals

The unique morphology of mammalian lumbar vertebrae allows the spine to flex and extend in the sagittal plane during locomotion. This movement increases stride length and allows mammals to efficiently breathe while running with an asymmetric gait. In extant mammals, the amount of flexion that occurs varies across different locomotor styles, with dorsostable runners relying more on movement of long limbs to run and dorsomobile runners incorporating more flexion of the back. Although long limbs and a stabilized lumbar region are commonly associated with each other in extant mammals, many "archaic" placental mammals with short limbs had lumbar vertebrae with revolute zygapophyses. These articulations with an interlocking S-shape are found only in artiodactyls among extant mammals and have been hypothesized to stabilize against flexion of the back. This would suggest that archaic placental mammals may not have incorporated dorsoventral flexion into locomotion to the same extent as extant mammals with similar proportions. We tested the relative mobility of fossil lumbar vertebrae from two early placental mammals, the creodonts Patriofelis and Limnocyon, to see how these vertebrae may have functioned. We compared range of motion (ROM) between the original vertebrae, with revolute morphology and digitally altered vertebrae with a flat morphology. We found that the revolute morphology had relatively little effect on dorsoventral flexion and instead that it likely prevented disarticulation due to shear forces on the spine. These results show that flexion of the spine has been an important part of mammalian locomotion for at least 50 million years.

The influence of lumbosacral transitional vertebrae on lumbar lordosis and the angle of pelvic incidence

Pelvic incidence and lumbar lordosis have only normative values for spines comprising five lumbar and five sacral vertebrae. However, it is unclear how pelvic incidence and lumbar lordosis are affected by the common segmentation anomalies at the lumbo-sacral border leading to lumbosacral transitional vertebrae, including lumbarisations and sacralisations. In lumbosacral transitional vertebrae it is not trivial to identify the correct vertebral endplates to measure pelvic incidence and lumbar lordosis because ontogenetically the first sacral vertebra represents the first non-mobile sacral segment in lumbarisations, but the second segment in sacralisations. We therefore assessed pelvic incidence and lumbar lordosis with respect to both of these vertebral endplates. The type of segmentation anomaly was differentiated using spinal counts, spatial relationship with the iliac crest and morphological features. We found significant differences in pelvic incidence and lumbar lordosis between lumbarisations, sacralisations and the control group. The pelvic incidence in the sacralised group was mostly below the range of the lubarisation group and the control group when measured the traditional way at the first non-mobile segment (30.2°). However, the ranges of the sacralisation and lubarisation groups were completely encompassed by the control group when measured at the ontogenetically true first sacral vertebra. The mean pelvic incidence of the sacraliation group thus increased from 30.2° to 58.6°, and the mean pelvic incidence of the total sample increased from 45.6° to 51.2°, making it statistically indistinguishable from the control sample, whose pelvic incidence was 50.2°. Our results demonstrate that it is crucial to differentiate sacralisations from lumbarisation in order to assess the reference vertebra for pelvic incidence measurement. Due to their significant impact on spino-pelvic parameters, lumbosacral transitional vertebrae should be evaluated separately when examining pelvic incidence and lumbar lordosis.

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).

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.

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.

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.

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.

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.

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.

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.

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.

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.

Anterior column reconstruction of the lumbar spine in the lateral decubitus position: anatomical and patient-related considerations for ALIF, anterior-to-psoas, and transpsoas LLIF approaches

PURPOSE

Circumferential (AP) lumbar fusion surgery is an effective treatment for degenerative and deformity conditions of the spine. The lateral decubitus position allows for simultaneous access to the anterior and posterior aspects of the spine, enabling instrumentation of both columns without the need for patient repositioning. This paper seeks to outline the anatomical and patient-related considerations in anterior column reconstruction of the lumbar spine from L1-S1 in the lateral decubitus position.

METHODS

We detail the anatomic considerations of the lateral ALIF, transpsoas, and anterior-to-psoas surgical approaches from surgeon experience and comprehensive literature review.

RESULTS

Single-position AP surgery allows simultaneous access to the anterior and posterior column and may combine ALIF, LLIF, and minimally invasive posterior instrumentation techniques from L1-S1 without patient repositioning. Careful history, physical examination, and imaging review optimize safety and efficacy of lateral ALIF or LLIF surgery. An excellent understanding of patient spinal and abdominal anatomy is necessary. Each approach has relative advantages and disadvantages according to the disc level, skeletal, vascular, and psoas anatomy.

CONCLUSIONS

A development of a framework to analyze these factors will result in improved patient outcomes and a reduction in complications for lateral ALIF, transpsoas, and anterior-to-psoas surgeries.

[Anatomical revivification of the structure of the belt vessel]

On the base of the records in Huangdi Neijing (Yellow Emperor 's Inner Classic) and relevant ancient literature, the anatomical structure of the belt vessel was revivified. The belt vessel covers the kidneys and inlays in the 14th vertebrae on the lumbar region. It joints qijie (qi street) at the groin and connects with the thoroughfare vessel, the conception vessel and the governor vessel, as well as the muscle region of foot-yangming meridian. Correspondingly, the related anatomic structure includes renal fascia and transversalis fascia. The transversalis fascia is the main part of the belt vessel structure. The superior lumbar triangle is the vulnerable spot of abdominal wall structure and also coincident with the localization of "3 cun away from the spinal column bilaterally". It is the optimal selection when stimulating the belt vessel. In late generations, "governing all of meridians" has been supplemented as the function of the belt vessel. The diaphragm extends to the transversalis fascia and renal fascia through the inferior diaphragmatic fascia and it is also the only structure that connects with the twelve meridians and five zang organs. Hence, modern acupuncture and moxibustion has actually transferred the structural center of the belt vessel from the transversalis fascia to the diaphragm.

Forensic sex estimation using the vertebrae: an evaluation on two European populations

Sex estimation is one of the primary steps for constructing the biological profile of skeletal remains leading to their identification in the forensic context. While the pelvis is the most sex diagnostic bone, the cranium and other post-cranial elements have been extensively studied. Earlier research has also focused on the vertebral column with varying results regarding its sex classification accuracy as well as the underlying population specificity. The present study focuses on three easily identifiable vertebrae, namely T1, T12, and L1, and utilizes two modern European populations, a Greek and a Danish, to evaluate their forensic utility in sex identification. To this end, 865 vertebrae from 339 individuals have been analyzed for sexual dimorphism by further evaluating the effects of age-at-death and population affinity on its expression. Our results show that T1 is the best sex diagnostic vertebra for both populations reaching cross-validated accuracy of almost 90%, while age-at-death has limited effect on its sexual dimorphism. On the contrary, T12 and L1 produced varying results ranging from 75 to 83% accuracy with the Greek population exhibiting distinctively more pronounced sexual dimorphism. Additionally, age-at-death had significant effect on sexual dimorphism of T12 and L1 and especially in the Greek female and Danish male groups. Our results on inter-population comparison suggest that vertebral sex discriminant functions, and especially those utilizing multiple measurements, are highly population specific and optimally suitable only for their targeted population. An open-source software tool to facilitate classifying new cases based on our results is made freely available to forensic researchers.

Long-term running in middle-aged men and intervertebral disc health, a cross-sectional pilot study

Purpose

To measure intervertebral disc (IVD) health parameters in middle-aged long-term runners compared to matched non-physically active controls.

Methods

Seventeen males aged 44-62yr were included in the study: 9 runners with a running history of >10yr, averaging >50km/week, and eight matched non-physically active controls, the data from one participant had to be excluded. T2-relaxometry, diffusion weighted imaging, T1- and T2-weighted MR scanning, as well as T2 time mapping were performed. Morphological data relating to IVD were extrapolated.

Results

Compared to controls on average, runners had 20% greater IVD height (p = 0.002) and seven percentage points greater IVD-vertebral body height ratio (p = 0.001). No significant differences were observed between groups for mean(SD) IVD hydration status, as indicated by similar T2-times (runners: 94.4(11.1)ms, controls: 88.6(23.6)ms), or apparent diffusion coefficients (runners: 249.0(175.2)mm²/s, controls: 202.3(149.5)mm²/s). Average Pfirrmann score for the L5-S1 IVD was 2.2(0.7) for runners and 3.3(1.0) for controls (p = 0.026), average scores for all lumbar levels (L2-S1) were 1.9(0.2) and 2.5(0.7), respectively (p = 0.036). Anterior annulus T2-time and overall average lumbar level Pfirrmann grades were strongly correlated (r = 0.787, p = 0.021 and r = -0.704, p = 0.034, respectively) with greater distances run per week. Average lumbar level Pfirrmann grades were also strongly correlated (r = -0.823, p = 0.006) to total years of running.

Conclusion

Middle-aged long-term endurance runners exhibit less age-related decline in their lumbar IVDs. In addition, the measures of IVD morphology appeared to be better in those who had been running for a greater number of years, as well as in those who ran a greater distance per week.

A Cross-Calibration Study of GE Lunar iDXA and GE Lunar DPX Pro for Body Composition Measurements in Children and Adults

OBJECTIVE

To cross-calibrate dual energy X-ray absorptiometry machines when replacing GE Lunar DPX-Pro with GE Lunar iDXA.

METHODS

A cross-sectional study was conducted in 126 children (3-19 years) and 135 adults (20-66 years). Phantom cross calibration was carried out using aluminum phantom provided with each of the machines on both machines. Total body less head (TBLH), lumbar spine (L2-L4) and left femoral neck bone mineral density (BMD), bone mineral content (BMC), and bone area were assessed for each patient on both machines. TBLH lean and fat mass were also measured. Bland-Altman analysis, linear regressions, and independent sample t test were performed to evaluate consistency of measurements and to establish cross-calibration equations.

RESULTS

iDXA measured 0.33% lower BMD and 0.64% lower BMC with iDXA phantom as compared to DPX-Pro phantom (p < 0.001). In children, TBLH-BMC, femoral BMC and area were measured 10%-14% lesser, TBLH area was higher by 1%-2% and L2-L4 area by 10%-14% by iDXA as compared to DPX-Pro. iDXA measured higher TBLH fat [15% (girls), 31% (boys)] than DPX-Pro. In adults, TBLH-BMD (1.7%-3.4%), BMC (6.0%-10.9%) and area (4.2%-7.6%) were measured lesser by iDXA than DPX-Pro. L2-L4 BMD was higher [2.7% (men), 1.8% (women)] by iDXA than DPX-Pro. Femoral BMC was 2.11% higher in men and 4.1% lower in women by iDXA as compared to DPX-Pro. In children, R² of cross-calibration equations, ranged from 0.91 to 0.96; in adults, it ranged from 0.93 to 0.99 (p < 0.01). After the regression equations were applied, differences in BMD values between both machines were negligible.

CONCLUSION

A strong agreement for bone mass and body composition was established between both machines. Cross-calibration equations need to be applied to transform DPX-Pro measurements into iDXA measurements to avoid errors in assessment. This study documents a need for use of cross-calibration equations to transform DPX-Pro body composition data into iDXA values for clinical diagnosis.

Comparative Sacral Morphology in Spondylolisthesis Patients

STUDY DESIGN

Retrospective comparative case series.

OBJECTIVES

Evaluation of sacral morphology in spondylolisthesis patients compared with asymptomatic controls.

SUMMARY OF BACKGROUND DATA

Patients with spondylolisthesis are known to differ from asymptomatic controls in sagittal plane anatomy, but few studies examine the coronal and axial plane differences in these cohorts.

METHODS

This is a retrospective evaluation of magnetic resonance imaging of the lumbosacral spine in 29 spondylolisthesis patients and an asymptomatic cohort (n = 154). Measurements of the linear distance and angular position of L5 and sacrum were performed in the sagittal, coronal, and axial planes. Receiver operating characteristic (ROC) curve analysis quantified these associations. High- and low-grade spondylolisthesis patients were compared with two-sample t-tests. All p-values are two-sided and considered significant when p < .05.

RESULTS

Axial measurements showed the distance of the right to left anterior ala and the L5 body width did not differ between the cohorts. Sacroiliac (SI) joint angles in the spondylolisthesis cohort were closer to the true sagittal plane than in the controls 109° versus 121° (p < .001). In the sagittal plane, the linear measurement of the ratio of the midpoint anteroposterior width L5 to the sacral end plate was larger in the high-grade patients than the low-grade patients and controls. In addition, the kyphosis between S1-S2 and S2-S3 was larger in the spondylolisthesis cohort.

CONCLUSIONS

The SI joints in patients with spondylolisthesis were orientated closer to the sagittal plane than in the controls. An awareness of this positioning may be important in surgical implant insertion as well as rehabilitation of hip extensor weakness. The main anatomical differences found in this study were in the sagittal plane. Sacral end plate abnormalities were well visualized and consistent with radiographic findings in the literature.

LEVEL OF EVIDENCE

Level III, diagnostic.

Effectiveness of personalized 3D printed models for patient education in degenerative lumbar disease

OBJECTIVE

Three-dimensional printing may play an important role in patients' education. The objective of this study was to assess the effectiveness of personalized 3D printed models for increasing patient understanding of their medical condition and surgical plan.

METHODS

Forty-five patients with degenerative lumbar diseases were randomized by block design into three groups: educational program presented by CT & MRI imaging (care-as-usual), 3D reconstructions, or personalized 3D printed models. Patients' level of understanding and satisfaction were evaluated by two questionnaires one day after education.

RESULTS

Patients educated with personalized 3D printed models demonstrated an expanded level of understanding than patients educated with CT & MRI imaging (care-as-usual) (P ＜ 0.05) and 3D reconstructions (P ＜ 0.05). Personalized 3D printed models also resulted in a higher degree of patient satisfaction (P ＜ 0.05).

CONCLUSIONS

Personalized 3D printed models and 3D reconstructions can simplify and enhance understanding of lumbar anatomy, physiology, and patients' disease and surgical plan. Personalized 3D printed models also enhance patients' subjective satisfaction.

PRACTICE IMPLICATIONS

Personalized 3D printed models for patient education are feasible and could be generalized for degenerative lumbar diseases.

Bisphosphonate treatment changes regional distribution of trabecular microstructure in human lumbar vertebrae

BACKGROUND

In osteoporosis patients, antiresorptive treatments such as alendronate reduce the resorption of trabecular bone and thus minimize vertebral fracture risk. However, fracture risk reduction efficacy of antiresorptive drugs varies between skeletal sites and is highest for vertebral bone. In human vertebrae, cancellous bone is distributed heterogeneously between regions. This microstructural heterogeneity is changing with patient age and is likely to play a major role in vertebral failure mechanisms and fracture susceptibility. Whether antiresorptive treatment affects the heterogeneity of vertebral microstructure in osteoporosis has not been unraveled.

METHODS

Our aim was to assess whether antiresorptive treatment would have a region-dependent influence on vertebral trabecular bone. Therefore, we used high-resolution peripheral quantitative computed tomography (HR-pQCT), microcomputed tomography (microCT) and uniaxial compression testing to determine the structure and mechanical properties of trabecular bone cores from anterior and posterior regions of 22 lumbar vertebrae from elderly osteoporotic women. We analyzed age-matched ex vivo bone samples from bisphosphonate-treated female osteoporosis patients (age: 82 ± 7y, bisphosphonate treatment period: 4 ± 2 years) along treatment-naïve female controls (82 ± 7y).

RESULTS

MicroCT analysis showed a significantly lower bone volume fraction (p = 0.006) and lower trabecular number (p = 0.003) for the anterior bone cores compared to posterior bone cores in the treatment-naïve group. The bisphosphonate-treated group had a more homogeneous bone volume distribution and did not show significant regional differences in bone volume, it however also displayed significantly different trabecular numbers (p = 0.016). In bone cores of the bisphosphonate-treated group, trabeculae were thicker in comparison to treatment-naïve controls (p = 0.011). Differences in bone volume further resulted in different maximum forces during compression testing between the samples. In addition, the percental difference between BV/TV_μCT in anterior and posterior bone cores was lower in bisphosphonate-treated vertebrae when vertebrae with directly adjacent fractures (n = 3) were excluded.

CONCLUSION

In conclusion, regional trabecular bone microstructure in lumbar vertebrae of bisphosphonate-treated women was more homogeneous compared to treatment-naïve controls. Bisphosphonate treatment, which specifically targets resorption surfaces common in anterior vertebral bone, might have resulted in a region-specific preservation of vertebral microstructure and loading capacity. This could have positive implications for the reduction of wedge fracture risk and add to the explanation of the higher efficacy of fracture risk reduction in vertebrae in comparison to other fracture regions.

Modern Medical Consequences of the Ancient Evolution of a Long, Flexible Lumbar Spine

Modern human bipedality is unique and requires lumbar lordosis, whereas chimpanzees, our closest relatives, have short lumbar spines rendering them incapable of lordosis. To facilitate lordosis, humans have longer lumbar spines, greater lumbosacral angle, dorsally wedged lumbar vertebral bodies, and lumbar zygapophyseal joints with both increasingly coronal orientation and further caudal interfacet distances. These features limit modern lower lumbar spine and lumbosacral joint ailments, albeit imperfectly. The more coronal zygapophyseal orientation limits spondylolisthesis, while increasing interfacet distance may limit spondylolysis. Common back pain, particularly in people who are obese or pregnant, may result from increased lumbar lordosis, causing additional mass transfer through the zygapophyseal joints rather than vertebral bodies. Reduction in lumbar lordosis, such as in flatback syndrome from decreased lumbosacral angle, can also cause back pain. Human lumbar lordosis is necessary for placing the trunk atop the pelvis and presents a balancing act not required of our closest primate relatives.

Automatic pedicle screw planning using atlas-based registration of anatomy and reference trajectories

An algorithm for automatic spinal pedicle screw planning is reported and evaluated in simulation and first clinical studies. A statistical atlas of the lumbar spine (N  =  40 members) was constructed for active shape model (ASM) registration of target vertebrae to an unsegmented patient CT. The atlas was augmented to include 'reference' trajectories through the pedicles as defined by a spinal neurosurgeon. Following ASM registration, the trajectories are transformed to the patient CT and accumulated to define a patient-specific screw trajectory, diameter, and length. The algorithm was evaluated in leave-one-out analysis (N  =  40 members) and for the first time in a clinical study (N  =  5 patients undergoing cone-beam CT (CBCT) guided spine surgery), and in simulated low-dose CBCT images. ASM registration achieved (2.0  ±  0.5) mm root-mean-square-error (RMSE) in surface registration in 96% of cases, with outliers owing to limitations in CT image quality (high noise/slice thickness). Trajectory centerlines were conformant to the pedicle in 95% of cases. For all non-breaching trajectories, automatically defined screw diameter and length were similarly conformant to the pedicle and vertebral body (98.7%, Grade A/B). The algorithm performed similarly in CBCT clinical studies (93% centerline and screw conformance) and was consistent at the lowest dose levels tested. Average runtime in planning five-level (lumbar) bilateral screws (ten trajectories) was (312.1  ±  104.0) s. The runtime per level for ASM registration was (41.2  ±  39.9) s, and the runtime per trajectory was (4.1  ±  0.8) s, suggesting a runtime of ~(45.3  ±  39.9) s with a more fully parallelized implementation. The algorithm demonstrated accurate, automatic definition of pedicle screw trajectories, diameter, and length in CT images of the spine without segmentation. The studies support translation to clinical studies in free-hand or robot-assisted spine surgery, quality assurance, and data analytics in which fast trajectory definition is a benefit to workflow.

Musculoskeletal full-body models including a detailed thoracolumbar spine for children and adolescents aged 6-18 years

Currently available musculoskeletal inverse-dynamics thoracolumbar spine models are entirely based on data from adults and might therefore not be applicable for simulations in children and adolescents. In addition, these models lack lower extremities, which are required for comprehensive evaluations of functional activities or therapeutic exercises. We therefore created OpenSim-based musculoskeletal full-body models including a detailed thoracolumbar spine for children and adolescents aged 6-18 years and validated by comparing model predictions to in vivo data. After combining our recently developed adult thoracolumbar spine model with a lower extremity model, children and adolescent models were created for each year of age by adjusting segmental length and mass distribution, center of mass positions and moments of inertia of the major body segments as well as sagittal pelvis and spine alignment based on literature data. Similarly, muscle strength properties were adjusted based on CT-derived cross-sectional area measurements. Simulations were conducted from in vivo studies reported in the literature involving children and adolescents evaluating maximum trunk muscle strength (MTMS), lumbar disc compressibility (LDC), intradiscal pressure (IDP) and trunk muscle activity (MA). Model predictions correlated highly with in vivo data (MTMS: r ≥ 0.82, p ≤ 0.03; LDC: r = 0.77, p < 0.001; IDP: r ≥ 0.78, p < 0.001; MA: r ≥ 0.90, p < 0.001), indicating suitability for the reasonably accurate prediction of maximal trunk muscle strength, segmental loading and trunk muscle activity in children and adolescents. When aiming at investigating children or adolescents with pathologies such as idiopathic scoliosis, our models can serve as a basis for the creation of deformed spine models and for comparative purposes.

Dairy- and supplement-based calcium intake in adulthood and vertebral dimensions in midlife-the Northern Finland Birth Cohort 1966 Study

Among a representative sample of 1064 Northern Finns, we studied the association of dairy- and supplement-based calcium intake in adulthood with vertebral size in midlife. Inadequate calcium intake (< 800 mg/day) from age 31 to 46 predicted small vertebral size and thus decreased spinal resilience among women but not men.

INTRODUCTION

Small vertebral size predisposes individuals to fractures, which are common among aging populations. Although previous studies have associated calcium (Ca) intake with enhanced bone geometry in the appendicular skeleton, few reports have addressed the axial skeleton or the vertebrae in particular. We aimed to investigate the association of dairy- and supplement-based Ca intake in adulthood with vertebral cross-sectional area (CSA) in midlife.

METHODS

A sample of 1064 individuals from the Northern Finland Birth Cohort 1966 had undergone lumbar magnetic resonance imaging at the age of 46, and provided self-reported data on diet and Ca intake (dairy consumption and use of Ca supplements) at the ages of 31 and 46. We assessed the association between Ca intake (both continuous and categorized according to local recommended daily intake) and vertebral CSA, using generalized estimating equation and linear regression models with adjustments for body mass index, diet, vitamin D intake, education, leisure-time physical activity, and smoking.

RESULTS

Women with inadequate Ca intake (< 800 mg/day) over the follow-up had 3.8% smaller midlife vertebral CSA than women with adequate Ca intake (p = 0.009). Ca intake among men showed no association with vertebral CSA.

CONCLUSIONS

Inadequate Ca intake (< 800 mg/day) from the age of 31 to 46 predicts small vertebral size and thus decreased spinal resilience among middle-aged women. Future studies should confirm these findings and investigate the factors underlying the association of low Ca intake in women but not in men with smaller vertebral size.

Physical Performance Variables and Bone Parameters in a Group of Young Overweight and Obese Women

The aim of this study was to explore the relationships between physical performance variables and bone parameters such as bone mineral density (BMD), bone mineral content, hip geometry indices, and trabecular bone score in a group of young overweight and obese adult women. Sixty-eight overweight/obese (body mass index ≥25 kg/m²; 25.5-42.4 kg/m²) young women whose ages range from 18 to 35 yr participated in this study. Body composition and bone outcomes were measured by dual-energy X-ray absorptiometry. Maximum oxygen consumption (VO₂ max, in liter per minute) was determined indirectly using a progressive shuttle run test. One-repetition-maximum half-squat was directly measured. Vertical jump was measured and maximum power (P max) of the lower limbs was calculated. Lean mass was positively correlated to whole body (WB) BMD, total hip BMD, femoral neck (FN) BMD, femoral neck cross-sectional area (FN CSA) and femoral neck cross sectional moment of inertia (FN CSMI) (p < 0.05). VO₂ max (in liter per minute) and muscle power were positively correlated to WB BMD, total hip BMD, FN BMD, FN CSA, and FN CSMI (p < 0.05). One-repetition-maximum half-squat was positively correlated with lumbar spine trabecular bone score, WB BMD, FN BMD, FN CSA and FN CSMI (p < 0.05). This study suggests that lean mass, vertical jump, VO₂ max (liter per minute), muscle power and one-repetition-maximum half squat are positive determinants of BMD and hip geometry indices in young overweight and obese women.

Analysis of Radiographic Parameters of Sagittal Spinopelvic Alignment: Polish Nomenclature and Clinical Implications

Over the last 30 years, many authors have suggested that the shape of the human spine in the sagittal plane is helpful in understanding its physiology and pathology. This paper presents the current views and Polish no-men-clature used for the assessment of the morphology and position of the pelvis in the sagittal plane. The va-lues of particular radiographic parameters are presented for healthy individuals and for patients with selected spinal pathologies. Moreover, the paper discusses the practical application of the radiographic parameters that describe the shape and position of the pelvis in the sagittal plane.

Performance evaluation of the X-sight spine tracking system for abdominal tumors distal to spine: A 2D dosimetric analysis

The X-sight spine tracking system was integrated with Cyberknife unit to deliver radiosurgery treatments for spinal tumors without fiducial placement. However the tracking system can also be used for the treatment of abdominal tumors located in a certain distance from the spine. The aim of our study is to evaluate the tracking performance of the X-sight spine system for abdominal tumors distal to spine based on the 3 factors: tumor distance from the reference vertebra, the angle of tumor with the vertebra, and the amplitude of tumor motion due to respiration. An experimental setup was designed mainly with ovine lumbar vertebrae and the BrainLab ExacTrac gating phantom. Planning Target Volume (PTV) structures were delineated at different vertical distances from the reference vertebra. The dosimetric measurements were taken with GafChromic EBT3 film placed between slab phantoms so that they corresponded to centers of the target volumes. Dosimetric comparisons were performed based on dose-volume parameters and the gamma analysis. The measurements were then repeated for the same experimental conditions by using the Synchrony system to compare tracking performances. Using the X-sight system, percentage differences between the dose-volume parameters of the Treatment Planning System (TPS) calculations and the EBT3 film readings went up to 12% for the motion amplitude of 8 mm. The differences decreased with small motions while angles and vertical distances of the lesion locations did not induce major changes in dose discrepancies. Percentages of pixels passing gamma analysis were found to be below the acceptance threshold of 95%. Using the Synchrony system, the measured dose distributions had more similar patterns with those of the TPS system such that the percentage differences in the dose parameters were less than 4% and the gamma passing rates were found to be higher than 95%. Our results showed that the X-sight spine system should not be chosen for tracking abdominal tumors distal to the spine or osseous structures because of the effect of diaphragmatic motion on entire abdominal region. The fiducial-based Synchrony tracking system can be preferred for these tumors.

Anatomical analysis of the human ligamentum flavum in the thoracic spine: Clinical implications for posterior thoracic spinal surgery

BACKGROUND

Knowledge of the ligamentum flavum anatomy is important for posterior spinal surgery. However, only a few studies have evaluated the relationship between the thoracic ligamentum flavum and its surrounding structures. This study aimed to clarify the anatomy of the thoracic ligamentum flavum.

METHODS

The entire spines from 20 human embalmed cadavers were harvested in an en bloc fashion. All pedicles were vertically cut using a thread bone saw, and the ligamentum flavum from T1-T2 to T12-L1 was painted using a contrast agent containing an iron powder. Computed tomography was performed, and the ligamentum flavum shape (width and height) and its relationship with the spinal bony structures (lamina and foramen height percentage covered by the ligamentum flavum) were analyzed using a three-dimensional analyzing software.

RESULTS

The thoracic ligamentum flavum height and width gradually increased from T1-T2 to T12-L1. The caudal lamina height ventrally covered by the ligamentum flavum also increased gradually from the upper (T1-T2: 31.7%) to the lower levels (T12-L1: 41.7%); however, the cranial lamina height dorsally covered by the ligamentum flavum decreased from the upper (12.6%) to the lower levels (4.3%). The neural foramen was covered by the ligamentum flavum in all thoracic spines, except for T1-T2. Between T2-T3 and T12-L1, approximately 50% of the cranial part of the foramens was covered by the ligamentum flavum; however, the caudal part was not covered.

CONCLUSIONS

This study using contrasted ligamentum flavum and reconstructed CT provided information on the thoracic ligamentum flavum shape and its relationship with the bony structures. The ventral ligamentum flavum coverage of the cranial lamina increase from cranial to caudal, and the cranial half of the neural foramen is covered by the ligamentum flavum below T2-T3 but not in T1-T2. These findings would help spine surgeons to design and perform safe and adequate posterior thoracic spinal surgeries.

Comparison of Measurements of Bone Mineral Density in Young and Middle-Aged Adult Women in Relation to Dietary, Anthropometric and Reproductive Variables

The objective of this study was to compare current measurements of bone mineral density (BMD) of the lumbar spine (LS), femoral neck (FN), and total femur (TF) regions with initial values recorded 12 years ago in women from Northwest Mexico, and evaluate their correlation with dietary, anthropometric, and reproductive variables. BMD was assessed by Dual-energy X-ray absorptiometry. Participants were grouped as follows: Nulliparous (G1); women who were mothers 12 years ago (G2); and women who were nulliparous 12 years ago, but are now mothers (G3). In all three groups, current LS BMD was higher than initial (p ≤ 0.05) and current TF BMD in G2 was higher than initial values (p ≤ 0.05). When comparing current FN and TF BMD among the three groups, G2 had higher values than G3 (p ≤ 0.05). G2 also showed higher LS BMD than G1 and G3 (p = 0.006). Age at menarche was inversely-correlated with FN and TF BMD in G1 (p < 0.01), while the body mass index (BMI) correlated positively with all three bone regions in G2 (p < 0.05). This study shows that in women without and with children, age at menarche, BMI, and age were factors associated to BMD in healthy subjects in reproductive age.

Spinal Enumeration by Morphologic Analysis of Spinal Variants: Comparison to Counting in a Cranial-To-Caudal Manner

Objective

To compare the spinal enumeration methods that establish the first lumbar vertebra in patients with spinal variants.

Materials and Methods

Of the 1446 consecutive patients who had undergone computed tomography of the spine from March 2012 to July 2016, 100 patients (62 men, 38 women; mean age, 47.9 years; age range, 19-88 years) with spinal variants were included. Two radiologists (readers 1 and 2) established the first lumbar vertebra through morphologic analysis of the thoracolumbar junction, and labeled the vertebra by counting in a cranial-to-caudal manner. Inter-observer agreement was established. Additionally, reader 1 detected the 20th vertebra under the assumption that there are 12 thoracic vertebra, and then classified it as a thoracic vertebra, lumbar vertebra, or thoracolumbar transitional vertebra (TLTV), on the basis of morphologic analysis.

Results

The first lumbar vertebra, as established by morphologic analysis, was labeled by each reader as the 21st segment in 65.0% of the patients, as the 20th segment in 31.0%, and as the 19th segment in 4.0%. Inter-observer agreement between the two readers in determining the first lumbar vertebra, based on morphologic analysis, was nearly perfect (κ value: 1.00). The 20th vertebra was morphologically classified as a TLTV in 60.0% of the patients, as the first lumbar segment in 31.0%, as the second lumbar segment in 4.0%, and as a thoracic segment in 5.0%.

Conclusion

The establishment of the first lumbar vertebra using morphologic characteristics of the thoracolumbar junction in patients with spinal variants was consistent with the morphologic traits of vertebral segmentation.

Sex Specific Sacroiliac Joint Biomechanics During Standing Upright: A Finite Element Study

STUDY DESIGN

The comparison of sacroiliac joint (SIJ) angular motions, pelvis ligaments strain, load sharing, and stress distribution across the joint for male and female spine-pelvis-femur models using finite element analysis.

OBJECTIVE

To quantify biomechanical parameters at SIJ for all motions for both male and female models.

SUMMARY OF BACKGROUND DATA

SIJ has been recognized as a main source of pain in 13% to 30% of patients with low back pain. It is shown that the SIJ rotation and translation in different planes are not exceeding 2° to 3° and 2 mm, respectively. Due to limitation of in vivo and in vitro studies, it is difficult to quantify certain biomechanical parameters such as load-sharing and stress distribution across the joint. Finite element analysis is a useful tool which can be utilized to understand the biomechanics of the SIJ.

METHODS

The validated finite element models of a male and a female lumbar spine-pelvis-femur were developed from computer tomography (CT) scans. The models were used to simulate spine physiological motions. The range of motion, ligament strains, load sharing, and stress distribution across the left and right SIJs were compared between male and female models.

RESULTS

Motions data at SIJs demonstrated that female model experienced 86% higher mobility in flexion, 264% in extension, 143% in left bending, and 228% in right bending compared with the male model. The stresses and loads on SIJs were higher on the female model compared with the male model. Female model ligaments underwent larger strains compared with the male model ligaments.

CONCLUSION

Female SIJ had higher mobility, stresses, loads, and pelvis ligament strains compared with the male SIJ which led to higher stress across the joint, especially on the sacrum under identical loading conditions. This could be a possible reason for higher incidence of SIJ pain and pelvic stress fracture in females.

LEVEL OF EVIDENCE

N/A.

Cortical Thinning and Structural Bone Changes in Non-Human Primates after Single-Fraction Whole-Chest Irradiation

Stereotactic body radiation therapy (SBRT) is associated with an increased risk of vertebral compression fracture. While bone is typically considered radiation resistant, fractures frequently occur within the first year of SBRT. The goal of this work was to determine if rapid deterioration of bone occurs in vertebrae after irradiation. Sixteen male rhesus macaque non-human primates (NHPs) were analyzed after whole-chest irradiation to a midplane dose of 10 Gy. Ages at the time of exposure varied from 45-134 months. Computed tomography (CT) scans were taken 2 months prior to irradiation and 2, 4, 6 and 8 months postirradiation for all animals. Bone mineral density (BMD) and cortical thickness were calculated longitudinally for thoracic (T) 9, lumbar (L) 2 and L4 vertebral bodies; gross morphology and histopathology were assessed per vertebra. Greater mortality (related to pulmonary toxicity) was noted in NHPs <50 months at time of exposure versus NHPs >50 months ( P = 0.03). Animals older than 50 months at time of exposure lost cortical thickness in T9 by 2 months postirradiation ( P = 0.0009), which persisted to 8 months. In contrast, no loss of cortical thickness was observed in vertebrae out-of-field (L2 and L4). Loss of BMD was observed by 4 months postirradiation for T9, and 6 months postirradiation for L2 and L4 ( P < 0.01). For NHPs younger than 50 months at time of exposure, both cortical thickness and BMD decreased in T9, L2 and L4 by 2 months postirradiation ( P < 0.05). Regions that exhibited the greatest degree of cortical thinning as determined from CT scans also exhibited increased porosity histologically. Rapid loss of cortical thickness was observed after high-dose chest irradiation in NHPs. Younger age at time of exposure was associated with increased pneumonitis-related mortality, as well as greater loss of both BMD and cortical thickness at both in- and out-of-field vertebrae. Older NHPs exhibited rapid loss of BMD and cortical thickness from in-field vertebrae, but only loss of BMD in out-of-field vertebrae. Bone is sensitive to high-dose radiation, and rapid loss of bone structure and density increases the risk of fractures.

Low-cost three-dimensional printed phantom for neuraxial anesthesia training: Development and comparison to a commercial model

METHODS

Anonymized CT DICOM data was segmented to create a 3D model of the lumbar spine. The 3D model was modified, placed inside a digitally designed housing unit and fabricated on a desktop 3D printer using polylactic acid (PLA) filament. The model was filled with an echogenic solution of gelatin with psyllium fiber. Twenty-two staff anesthesiologists performed a spinal and epidural on the 3D printed simulator and a commercially available Simulab phantom. Participants evaluated the tactile and ultrasound imaging fidelity of both phantoms via Likert-scale questionnaire.

RESULTS

The 3D printed neuraxial phantom cost $13 to print and required 25 hours of non-supervised printing and 2 hours of assembly time. The 3D printed phantom was found to be less realistic to surface palpation than the Simulab phantom due to fragility of the silicone but had significantly better fidelity for loss of resistance, dural puncture and ultrasound imaging than the Simulab phantom.

CONCLUSION

Low-cost neuraxial phantoms with fidelity comparable to commercial models can be produced using CT data and low-cost infrastructure consisting of FLOS software and desktop 3D printers.

Reproduction triggers adaptive increases in body size in female mole-rats

In social mole-rats, breeding females are larger and more elongated than non-breeding female helpers. This status-related morphological divergence is thought to arise from modifications of skeletal growth following the death or removal of the previous breeder and the transition of their successors from a non-breeding to a breeding role. However, it is not clear what changes in growth are involved, whether they are stimulated by the relaxation of reproductive suppression or by changes in breeding status, or whether they are associated with fecundity increases. Here, we show that, in captive Damaraland mole-rats (Fukomys damarensis), where breeding was experimentally controlled in age-matched siblings, individuals changed in size and shape through a lengthening of the lumbar vertebrae when they began breeding. This skeletal remodelling results from changes in breeding status because (i) females removed from a group setting and placed solitarily showed no increases in growth and (ii) females dispersing from natural groups that have not yet bred do not differ in size and shape from helpers in established groups. Growth patterns consequently resemble other social vertebrates where contrasts in size and shape follow the acquisition of the breeding role. Our results also suggest that the increases in female body size provide fecundity benefits. Similar forms of socially responsive growth might be more prevalent in vertebrates than is currently recognized, but the extent to which this is the case, and the implications for the structuring of mammalian dominance hierarchies, are as yet poorly understood.

Magnetic resonance morphometry of the adult normal lumbar intervertebral space

PURPOSE

This study aims to: (a) quantify and evaluate normal relationships between neighboring spinal units using MR imaging indices, (b) propose an easy-to-apply-and-reproduce method of estimating the correct amount of distraction when surgically restoring a collapsed intervertebral disc, based on individualized measurements.

METHODS

This is a retrospective cross-sectional MR imaging study of 119 adult subjects, aged 18-54, asymptomatic for low back pain. Each of the examinees should demonstrate two or more consecutive intervertebral discs classified as Pfirrmann grade I or II to be included. We measured and studied the relationships of disc height index, Dabbs index, Farfan index, disc convexity index and mean and posterior disc height per spinal level using multiple regression analysis. All measurements were tested for intra- and interobserver agreement by two raters.

RESULTS

DHI, Dabbs, Farfan, and mean disc height had a statistically significant correlation with the spinal level and age. Our results were highly reproducible, with excellent inter- and intraobserver agreement and reliability between two raters (ICC = 0.992 and 0.994, respectively). Furthermore, we expressed each intervertebral space as a percentage of its adjacent space, introducing the coefficient α factor for every intervertebral space.

CONCLUSIONS

Our results suggest that a normal values' database to refer during preoperative planning of correction of a degenerated intervertebral disc is feasible. Our study offers new anatomical and radiological insight in terms of spinal measurements and their potential correlation with current surgical techniques. A new approach for calculating disc space as an expression of its adjacent disc has been introduced with various potential applications.

Pulsed electromagnetic fields (PEMF) attenuate changes in vertebral bone mass, architecture and strength in ovariectomized mice

Pulsed electromagnetic fields (PEMF) has been investigated as a noninvasive alternative method to prevent bone loss for postmenopausal osteoporosis (OP), and the bone tissue involved in these studies are usually long bones such as femur and tibia in OP patients or rat models. However, few studies have investigated the effects of PEMF on the vertebral bone in mice with OP. This study aimed to investigate whether PEMF preserve lumbar vertebral bone mass, microarchitecture and strength in ovariectomized (OVX) mouse model of OP and its associated mechanisms. Thirty 3-month-old female BALB/c mice were randomly divided into three groups (n=10): sham-operated control (Sham), ovariectomy (OVX), and ovariectomy with PEMF treatment (OVX+PEMF). The OVX+PEMF group was exposed to 15Hz, 1.6 mT PEMF for 8h/day, 7days/week. After 8weeks, the mice were sacrificed. The OVX+PEMF group showed lower body weight gain of mice induced by estrogen deficiency compared with OVX group. Biochemical analysis of serum demonstrated that serum bone formation markers including bone specific alkaline phosphatase (BALP), serum osteocalcin (OCN), osteoprotegerin (OPG) and N-terminal propeptide of type I procollagen (P1NP) were markedly higher in OVX+PEMF group compared with OVX group. Besides, serum bone resorption markers including tartrate-resistant acid phosphatase 5b (TRAP-5b) and C-terminal crosslinked telopeptides of type I collagen (CTX-I) were markedly lower in OVX+PEMF group compared with OVX group. Biomechanical test observed that OVX+PEMF group showed higher compressive maximum load and stiffness of the lumbar vertebrae compared with OVX group. Micro-computed tomography (μCT) and histological analysis of lumbar vertebrae revealed that PEMF partially prevented OVX-induced decrease of trabecular bone mass and deterioration of trabecular bone microarchitecture in lumbar vertebrae. Real-time PCR showed that the canonical Wnt signaling pathway of the lumbar vertebrae, including Wnt3a, LRP5 and β-catenin were markedly up-regulated in OVX+PEMF group compared with OVX group. Moreover, the mRNA expressions of RANKL and OPG were markedly up-regulated in OVX+PEMF group compared with OVX group, whereas no statistical difference in RANKL/OPG mRNA ratio was found between OVX+PEMF group and OVX group. Besides, our study also found that the RANK mRNA expression was down-regulated in OVX+PEMF group compared with OVX group. Taken together, we reported that long-term stimulation with PEMF treatment was able to alleviate lumbar vertebral OP in postmenopausal mice through a combination of increased bone formation and suppressed bone resorption related to regulating the skeletal gene expressions of Wnt3a/LRP5/β-catenin and OPG/RANKL/RANK signaling pathways.

Development and Involution of the Notochord in the Human Spine

The availability of a collection of fetal and embryonic spines made possible a review of the involution of the notochord. Results of this histological, histochemical and immunohistochemical study are in accord with the dominant view in the literature that the notochord does not contribute materially to the adult nucleus pulposus. It is also consonant with the expectation that, normally, all chordal cells have disappeared during early childhood, but is not sufficiently detailed to assess the possibility of occasional survivors.

The change of volume of the lumbar vertebrae along with aging in asymptomatic population: a preliminary analysis

INTRODUCTION

Previous studies have demonstrated that the length of the lumbar spine is decreasing with age. Despite considerable research based on sagittal measurements, little is known about the changes in the volume of vertebrae. The objective of this study was to evaluate the changes in the volume of either column of the spine with age.

MATERIALS AND METHODS

Computed tomography scans of 62 asymptomatic subjects, performed for thoracolumbar trauma evaluation were used to create virtual 3D models. At least 10 patients were assigned to every decade of life from third to eight. We used a novel technique to measure the volume of anterior column (AC) and posterior column (PC) per each segment (a total of 310 segments). Midline sagittal images were used to measure disc height (DH) and vertebral body height (VH).

RESULTS

With age, both DH increases, whereas the VH decreases. The overall length of lumbar segment of the spine decreases with age. The volumetric measurements performed on same subjects showed that volume of both AC and PC does not change with age in females. In males, there is a weak but statistically significant correlation between AC volume and age and no change in the volume of PC. The ratio of PC:AC volume does not change with age in women, although it decreases slightly but significantly (in favor of AC) with age in males.

CONCLUSIONS

The overall length of lumbar spine decreases with age. This process is not a result of mere changes in the volume of either AC or PC.

Statistical shape modelling of hip and lumbar spine morphology and their relationship in the MRC National Survey of Health and Development

The anatomical shape of bones and joints is important for their proper function but quantifying this, and detecting pathological variations, is difficult to do. Numerical descriptions would also enable correlations between joint shapes to be explored. Statistical shape modelling (SSM) is a method of image analysis employing pattern recognition statistics to describe and quantify such shapes from images; it uses principal components analysis to generate modes of variation describing each image in terms of a set of numerical scores after removing global size variation. We used SSM to quantify the shapes of the hip and the lumbar spine in dual-energy x-ray absorptiometry (DXA) images from 1511 individuals in the MRC National Survey of Health and Development at ages 60-64 years. We compared shapes of both joints in men and women and hypothesised that hip and spine shape would be strongly correlated. We also investigated associations with height, weight, body mass index (BMI) and local (hip or lumber spine) bone mineral density. In the hip, all except one of the first 10 modes differed between men and women. Men had a wider femoral neck, smaller neck-shaft angle, increased presence of osteophytes and a loss of the femoral head/neck curvature compared with women. Women presented with a flattening of the femoral head and greater acetabular coverage of the femoral head. Greater weight was associated with a shorter, wider femoral neck and larger greater and lesser trochanters. Taller height was accompanied by a flattening of the curve between superior head and neck and a larger lesser trochanter. Four of the first eight modes describing lumbar spine shape differed between men and women. Women tended to have a more lordotic spine than men with relatively smaller but caudally increasing anterior-posterior (a-p) vertebral diameters. Men were more likely to have a straighter spine with larger vertebral a-p diameters relative to vertebral height than women, increasing cranially. A weak correlation was found between body weight and a-p vertebral diameter. No correlations were found between shape modes and height in men, whereas in women there was a weak positive correlation between height and evenness of spinal curvature. Linear relationships between hip and spine shapes were weak and inconsistent in both sexes, thereby offering little support for our hypothesis. In conclusion, men and women entering their seventh decade have small but statistically significant differences in the shapes of their hips and their spines. Associations with height, weight, BMI and BMD are small and correspond to subtle variations whose anatomical significance is not yet clear. Correlations between hip and spine shapes are small.

Coronal plane trunk asymmetry is associated with whole-body sagittal alignment in healthy young adolescents before pubertal peak growth

PURPOSE

To investigate coronal plane trunk asymmetry (TA) and its association with sagittal postural alignment in healthy subjects before pubertal peak growth.

METHODS

In this cross-sectional baseline study, 1190 healthy pre-peak growth velocity subjects were included. Coronal plane TA was evaluated using back surface topography. Whole-body sagittal alignment (previously validated and objectively classified as neutral, sway-back or leaning-forward) and sagittal spinopelvic profile (trunk lean, lumbar lordosis, thoracic kyphosis, sacral inclination and length of the posteriorly inclined thoracolumbar segment) were determined, as were height, proportion of trunk to body length, body mass index, generalized joint laxity, and handedness.

RESULTS

Logistic regression analysis yielded overall sagittal posture class to be independently associated with coronal plane TA: having a leaning-forward posture associated with a nearly three times higher odds of coronal TA (p < 0.001) compared to neutrals. A sway-back was 2.2 times more likely to show TA (p = 0.016) than a neutral, yet only in boys. Significant associations with coronal TA were also found for trunk lean, thoracic kyphosis and body mass index. These correlations, however, were gender and posture class specific. The spinal region where asymmetry is seen, varies according to the whole-body sagittal alignment type: primary thoracic curves were the most frequent in leaning-forwards, whereas primary curves in the lumbar or declive thoracolumbar segment were the most common in sway-backs.

CONCLUSIONS

In immature spines without known scoliosis, coronal plane TA is associated with whole-body sagittal alignment. It is more often seen in non-neutral than neutral sagittal posture types. Whether adolescent idiopathic scoliosis is related with postural characteristics before pubertal growth peak, should be addressed in future prospective studies.

A novel finite element model of the ovine lumbar intervertebral disc with anisotropic hyperelastic material properties

The Ovine spine is an accepted model to investigate the biomechanical behaviour of the human lumbar one. Indeed, the use of animal models for in vitro studies is necessary to investigate the mechanical behaviour of biological tissue, but needs to be reduced for ethical and social reasons. The aim of this study was to create a finite element model of the lumbar intervertebral disc of the sheep that may help to refine the understanding of parallel in vitro experiments and that can be used to predict when mechanical failure occurs. Anisotropic hyperelastic material properties were assigned to the annulus fibrosus and factorial optimization analyses were performed to find out the optimal parameters of the ground substance and of the collagen fibers. For the ground substance of the annulus fibrosus the investigation was based on experimental data taken from the literature, while for the collagen fibers tensile tests on annulus specimens were conducted. Flexibility analysis in flexion-extension, lateral bending and axial rotation were conducted. Different material properties for the anterior, lateral and posterior regions of the annulus were found. The posterior part resulted the stiffest region in compression whereas the anterior one the stiffest region in tension. Since the flexibility outcomes were in a good agreement with the literature data, we considered this model suitable to be used in conjunction with in vitro and in vivo tests to investigate the mechanical behaviour of the ovine lumbar disc.

The Decussating Fibers of the Lumbar Thoracolumbar Fascia: A Landmark for Identifying the L5 Spinous Process?

BACKGROUND

The thoracolumbar fascia (TLF) has been well studied and is known to have crisscrossing fibers. Based on surgical experience, we hypothesized that the decussating fibers of the TLF may indicate a specific vertebral level and performed an anatomic study.

METHODS

Twenty adult fresh frozen cadavers aged 72-84 years at death were placed in the prone position, and the skin of the lumbar and upper sacrum was removed. Careful attention was given to the TLF and any fibers of it that grossly crossed the midline to interdigitate with its contralateral counterpart. Once such decussations were identified, a metal wire was laid on them at their center, and fluoroscopy was performed to verify the vertebral level.

RESULTS

Decussating fibers of the TLF were found on all but 1 specimen (95%). The central part of the decussation on the midline corresponded to the spinous process of L5 in 17/19 (89%) of specimens and the lower edge (L4-L5 interspace) of the spinous process of L4 in the remaining 2 specimens (11%). No specimens were found to have previous surgery in the area dissected or congenital anomalies of the spine.

CONCLUSIONS

In our cadaveric study, the decussating fibers of the TLF in the lumbar region helped predict the L5 spinous process in 89% of specimens and the L4 spinous process in 11% of specimens. This anatomic landmark might be used as an adjunct to palpation and intraoperative imaging during surgical exploration of the lower lumbar region.

The Neandertal vertebral column 2: The lumbar spine

Here we provide the most extensive metric and morphological analysis performed to date on the Neandertal lumbar spine. Neandertal lumbar vertebrae show differences from modern humans in both the vertebral body and in the neural arch, although not all Neandertal lumbar vertebrae differ from modern humans in the same way. Differences in the vertebral foramen are restricted to the lowermost lumbar vertebrae (L4 and L5), differences in the orientation of the upper articular facets appear in the uppermost lumbar vertebrae (probably in L1 and L2-L3), and differences in the horizontal angle of the transverse process appear in L2-L4. Neandertals, when compared to modern humans, show a smaller degree of lumbar lordosis. Based on a still limited fossil sample, early hominins (australopiths and Homo erectus) had a lumbar lordosis that was similar to but below the mean of modern humans. Here, we hypothesize that from this ancestral degree of lumbar lordosis, the Neandertal lineage decreased their lumbar lordosis and Homo sapiens slightly increased theirs. From a postural point of view, the lower degree of lordosis is related to a more vertical position of the sacrum, which is also positioned more ventrally with respect to the dorsal end of the pelvis. This results in a spino-pelvic alignment that, though different from modern humans, maintained an economic postural equilibrium. Some features, such as a lower degree of lumbar lordosis, were already present in the middle Pleistocene populations ancestral to Neandertals. However, these middle Pleistocene populations do not show the full suite of Neandertal lumbar morphologies, which probably means that the characteristic features of the Neandertal lumbar spine did not arise all at once.

The development of inter-strain variation in cortical and trabecular traits during growth of the mouse lumbar vertebral body

How cortical and trabecular bone co-develop to establish a mechanically functional structure is not well understood. Comparing early postnatal differences in morphology of lumbar vertebral bodies for three inbred mouse strains identified coordinated changes within and between cortical and trabecular traits. These early coordinate changes defined the phenotypic differences among the inbred mouse strains.

INTRODUCTION

Age-related changes in cortical and trabecular traits have been well studied; however, very little is known about how these bone tissues co-develop from day 1 of postnatal growth to establish functional structures by adulthood. In this study, we aimed to establish how cortical and trabecular tissues within the lumbar vertebral body change during growth for three inbred mouse strains that express wide variation in adult bone structure and function.

METHODS

Bone traits were quantified for lumbar vertebral bodies of female A/J, C57BL/6J (B6), and C3H/HeJ (C3H) inbred mouse strains from 1 to 105 days of age (n = 6-10 mice/age/strain).

RESULTS

Inter-strain differences in external bone size were observed as early as 1 day of age. Reciprocal and rapid changes in the trabecular bone volume fraction and alignment in the direction of axial compression were observed by 7 days of age. Importantly, the inter-strain difference in adult trabecular bone volume fraction was established by 7 days of age. Early variation in external bone size and trabecular architecture was followed by progressive increases in cortical area between 28 and 105 days of age, with the greatest increases in cortical area seen in the mouse strain with the lowest trabecular mass.

CONCLUSION

Establishing the temporal changes in bone morphology for three inbred mouse strains revealed that genetic variation in adult trabecular traits were established early in postnatal development. Early variation in trabecular architecture preceded strain-specific increases in cortical area and changes in cortical thickness. This study established the sequence of how cortical and trabecular traits co-develop during growth, which is important for identifying critical early ages to further focus on intervention studies that optimize adult bone strength.

Differences in bone quality and strength between Asian and Caucasian young men

This is a cross-sectional study to assess differences in bone quality in young Asian and Caucasian (n = 30/group) men between 25 and 35 years. We found that Asians had smaller bones, thicker and denser cortices, and more plate-like trabeculae, but stiffness did not differ between groups.

INTRODUCTION

We conducted a cross-sectional study to assess differences in bone quality in young Asian and Caucasian (n = 30/group) men between 25 and 35 years.

METHODS

We measured bone mineral density (BMD) at the spine, total hip (TH), femoral neck (FN), and forearm by dual energy X-ray absorptiometry (DXA), and bone geometry, density, microarchitecture, and mechanical competence at the radius and tibia by high-resolution peripheral quantitative computed tomography (HR-pQCT) with application of individual trabecula segmentation (ITS) and trabecular and whole bone finite element analysis (FEA). We measured load-to-strength ratio to account for differences in bone size and height, respectively. We used Wilcoxon rank sum and generalized linear models adjusted for height, weight, and their interaction for comparisons.

RESULTS

Asians were 3.9 % shorter and weighed 6.5 % less than Caucasians. In adjusted models: by DXA, there were no significant race-based differences in areal BMD; by HR-pQCT, at the radius, Asians had smaller total and trabecular area (p = 0.003 for both), and denser (p = 0.01) and thicker (p = 0.04) cortices at the radius; by ITS, at the radius Asians, had more plate-like than rod-like trabeculae (PR ratio p = 0.01), greater plate trabecular surface (p = 0.009) and longer rod length (p = 0.002). There were no significant race-based differences in FEA or the load-to-strength ratio.

CONCLUSIONS

Asians had smaller bones, thicker and denser cortices, and more plate-like trabeculae, but biomechanical estimates of bone strength did not differ between groups. Studies are needed to determine whether these differences persist later in life.

Elastic constants influence on the L4-L5-S1 annuli fibrosus behavior, a probabilistic finite element analysis

PURPOSE

A probabilistic finite element (FE) analysis of the L4-L5 and L5-S1 human annulus fibrosus (AF) was conducted to obtain a better understanding of the biomechanics of the AF and to quantify its influence on the range of motion (ROM) of the L4-L5 and L5-S1 segments.

METHODS

The FE models were composed of the AF and the upper and lower endplates. The AF was represented as a continuous material composed of a hyperelastic isotropic Yeoh matrix reinforced with two families of fibers described with an exponential energy function. The caudal endplate was fully restricted and 8 Nm pure moment was applied to the cranial endplate in flexion, extension, lateral flexion and axial rotation. The mechanical constants were determined randomly based on a normal distribution and average values reported.

RESULTS

Results of the 576 models show that the ROM was more sensitive to the initial stiffness of the fibers rather than to the stiffening coefficient represented in the exponential function. The ROM was more sensitive to the input variables in extension, flexion, axial rotation and lateral bending. The analysis showed an increased probability for the L5-S1 ROM to be higher in flexion, extension and axial rotation, and smaller in lateral flexion, with respect to the L4-L5 ROM.

CONCLUSIONS

An equation was proposed to obtain the ROM as a function of the elastic constants of the fibers and it may be used to facilitate the calibration process of the human spine segments and to understand the influence of each elastic constant on the ROM.

Evaluation of functional and structural changes affecting the lumbar spine in professional field hockey players

PURPOSE

The aim of this study was to evaluate functional and structural changes in the lumbar spine which occurred as a consequence of playing field hockey.

METHODS

The research group consisted of 20 male professional field hockey players. Computed tomography scans were collected to define the radiological density of the vertebral bodies and to calculate Young's modulus. An electrogoniometer was used to measure the range of movement. Geometric parameters, such as Lumbar Lordosis Angle, Index of Lumbar Lordosis, Whitmann-Ferguson Angle and Anterior Pelvic Tilt, were also measured.

RESULTS

The values describing lumbar lordosis increased linearly with years of training and were significantly greater than those reported in the literature. Field hockey players displayed a larger range of flexion, side bending and rotation to the right. An analysis of radiological density discovered significantly high values. An analysis of Young's modulus showed that the vertebral bodies become more fragile.

CONCLUSIONS

The results show that overuse changes in the lumbar spine of field hockey players are severe and highly correlated with years of training.

Patient-Specific Templating of Lumbar Total Disk Replacement to Restore Normal Anatomy and Function

The purpose of this study was to develop a tool to determine optimal placement and size for total disk replacements (TDRs) to improve patient outcomes of pain and function. The authors developed a statistical shape model to determine the anatomical variables that influence the placement, function, and outcome of lumbar TDR. A patient-specific finite element analysis model has been developed that is now used prospectively to identify patients suitable for TDR and to create a surgical template to facilitate implant placement to optimize range of motion and clinical outcomes. Patient factors and surgical techniques that determine success regarding function and pain are discussed in this article.

The Cervical and Lumbar Vertebrae — An Anthropometric Model

An anthropometric model for human vertebrae in the mid-sagital plane is described, using parameters which were measured from lateral X-rays of the cervical and lumbar regions in normal, healthy men. The data was processed statistically and results are presented. The findings reported are new in the literature. They can be used in many ways, including modelling of the spine, and orthopaedics. Clinically significant parameters are the heights of the vertebral bodies and the intervertebral spacings. The relations between these parameters are presented and discussed.