Regional variation in vertebral bone morphology and its contribution to vertebral fracture strength

Slit3 by PTH-Induced Osteoblast Secretion Repels Sensory Innervation in Spine Porous Endplates to Relieve Low Back Pain

During aging, the spine undergoes degenerative changes, particularly with vertebral endplate bone expansion and sclerosis, that is associated with nonspecific low back pain (LBP). We reported that parathyroid hormone (PTH) treatment could reduce vertebral endplate sclerosis and improve pain behaviors in aging, SM/J and young lumbar spine instability (LSI) mice. Aberrant innervation noted in the vertebral body and endplate during spinal degeneration was reduced with PTH treatment in aging and LSI mice as quantified by PGP9.5+ and CGRP+ nerve fibers, as well as CGRP expression in dorsal root ganglia (DRG). The neuronal repulsion factor Slit3 significantly increased in response to PTH treatment mediated by transcriptional factor FoxA2. PTH type1 receptor (PPR) and Slit3 deletion in osteoblasts prevented PTH-reduction of endplate porosity and improvement in behavior tests, whereas PPR deletion in chondrocytes continued to respond to PTH. Altogether, PTH stimulates Slit3 to repel sensory nerve innervation and provides symptomatic relief of LBP associated with spinal degeneration.

The Expression of Toll-like Receptors in Cartilage Endplate Cells: A Role of Toll-like Receptor 2 in Pro-Inflammatory and Pro-Catabolic Gene Expression

INTRODUCTION

The vertebral cartilage endplate (CEP), crucial for intervertebral disc health, is prone to degeneration linked to chronic low back pain, disc degeneration, and Modic changes (MC). While it is known that disc cells express toll-like receptors (TLRs) that recognize pathogen- and damage-associated molecular patterns (PAMPs and DAMPs), it is unclear if CEP cells (CEPCs) share this trait. The CEP has a higher cell density than the disc, making CEPCs an important contributor. This study aimed to identify TLRs on CEPCs and their role in pro-inflammatory and catabolic gene expression.

METHODS

Gene expression of TLR1-10 was measured in human CEPs and expanded CEPCs using quantitative polymerase chain reaction. Additionally, surface TLR expression was measured in CEPs grouped into non-MC and MC. CEPCs were stimulated with tumor necrosis factor alpha, interleukin 1 beta, small-molecule TLR agonists, or the 30 kDa N-terminal fibronectin fragment. TLR2 signaling was inhibited with TL2-C29, and TLR2 protein expression was measured with flow cytometry.

RESULTS

Ex vivo analysis found all 10 TLRs expressed, while cultured CEPCs lost TLR8 and TLR9 expression. TLR2 expression was significantly increased in MC1 CEPCs, and its expression increased significantly after pro-inflammatory stimulation. Stimulation of the TLR2/6 heterodimer upregulated TLR2 protein expression. The TLR2/1 and TLR2/6 ligands upregulated pro-inflammatory genes and matrix metalloproteases (MMP1, MMP3, and MMP13), and TLR2 inhibition inhibited their upregulation. Endplate resorptive capacity of TLR2 activation was confirmed in a CEP explant model.

CONCLUSIONS

The expression of TLR1-10 in CEPCs suggests that the CEP is susceptible to PAMP and DAMP stimulation. Enhanced TLR2 expression in MC1, and generally in CEPCs under inflammatory conditions, has pro-inflammatory and pro-catabolic effects, suggesting a potential role in disc degeneration and MC.

More accurate trabecular bone imaging using UTE MRI at the resonance frequency of fat

High-resolution magnetic resonance imaging (HR-MRI) has been increasingly used to assess the trabecular bone structure. High susceptibility at the marrow/bone interface may significantly reduce the marrow's apparent transverse relaxation time (T2*), overestimating trabecular bone thickness. Ultrashort echo time MRI (UTE-MRI) can minimize the signal loss caused by susceptibility-induced T2* shortening. However, UTE-MRI is sensitive to chemical shift artifacts, which manifest as spatial blurring and ringing artifacts partially due to non-Cartesian sampling. In this study, we proposed UTE-MRI at the resonance frequency of fat to minimize marrow-related chemical shift artifacts and the overestimation of trabecular thickness. Cubes of trabecular bone from six donors (75 ± 4 years old) were scanned using a 3 T clinical scanner at the resonance frequencies of fat and water, respectively, using 3D UTE sequences with five TEs (0.032, 1.1, 2.2, 3.3, and 4.4 ms) and a clinical 3D gradient echo (GRE) sequence at 0.2 × 0.2 × 0.4 mm3 voxel size. Trabecular bone thickness was measured in 30 regions of interest (ROIs) per sample. MRI results were compared with thicknesses obtained from micro-computed tomography (μCT) at 50 μm3 voxel size. Linear regression models were used to calculate the coefficient of determination between MRI- and μCT-based trabecular thickness. All MRI-based trabecular thicknesses showed significant correlations with μCT measurements. The correlations were higher (examined with paired Student's t-test, P < 0.01) for 3D UTE images performed at the fat frequency (R2 = 0.59-0.74, P < 0.01) than those at the water frequency (R2 = 0.18-0.52, P < 0.01) and clinical GRE images (R2 = 0.39-0.47, P < 0.01). Significantly reduced correlations were observed with longer TEs. This study highlighted the feasibility of UTE-MRI at the fat frequency for a more accurate assessment of trabecular bone thickness.

Numerical evaluation of spinal reconstruction using a 3D printed vertebral body replacement implant: effects of material anisotropy

Background and objective

Artificial vertebral implants have been widely used for functional reconstruction of vertebral defects caused by tumors or trauma. However, the evaluation of their biomechanical properties often neglects the influence of material anisotropy derived from the host bone and implant's microstructures. Hence, this study aims to investigate the effect of material anisotropy on the safety and stability of vertebral reconstruction.

Material and methods

Two finite element models were developed to reflect the difference of material properties between linear elastic isotropy and nonlinear anisotropy. Their biomechanical evaluation was carried out under different load conditions including flexion, extension, lateral bending and axial rotation. These performances of two models with respect to safety and stability were analyzed and compared quantitatively based on the predicted von Mises stress, displacement and effective strain.

Results

The maximum von Mises stress of each component in both models was lower than the yield strength of respective material, while the predicted results of nonlinear anisotropic model were generally below to those of the linear elastic isotropic model. Furthermore, the maximum von Mises stress of natural vertebra and reconstructed system was decreased by 2-37 MPa and 20-61 MPa, respectively. The maximum reductions for the translation displacement of the artificial vertebral body implant and motion range of whole model were reached to 0.26 mm and 0.77°. The percentage of effective strain elements on the superior and inferior endplates adjacent to implant was diminished by up to 19.7% and 23.1%, respectively.

Conclusion

After comprehensive comparison, these results indicated that the finite element model with the assumption of linear elastic isotropy may underestimate the safety of the reconstruction system, while misdiagnose higher stability by overestimating the range of motion and bone growth capability.

Comparison of predictive value for cage subsidence between MRI-based endplate bone quality and vertebral bone quality scores following transforaminal lumbar interbody fusion: a retrospective propensity-matched study

BACKGROUND CONTEXT

Cage subsidence after lumbar fusion can lead to many adverse outcomes. Low bone mineral density (BMD) is a widely recognized risk factor for cage subsidence. Conventional methods can predict and evaluate BMD, but there are many shortcomings. Recently, MRI-based assessment of bone quality in specific parts of the vertebral body has been proposed, including scores for vertebral bone quality (VBQ) and endplate bone quality (EBQ). However, the predictive accuracy of the two scoring systems for cage subsidence after transforaminal lumbar interbody fusion (TLIF) remains unknown. Therefore, we investigated MRI-based VBQ and EBQ scores for assessing bone quality and compared their predictive value for cage subsidence after TLIF.

PURPOSE

To compare the predictive value between MRI-based VBQ and EBQ scores for cage subsidence after TLIF.

STUDY DESIGN/SETTING

A retrospective case-control study.

PATIENTS SAMPLE

Patients with degenerative lumbar diseases underwent single-level TLIF at our medical center between 2014 and 2020, all of whom had preoperative MRIs available.

OUTCOMES MEASURES

Cage subsidence, disc height, VBQ score, EBQ score, upper and lower vertebral body bone quality (UL-VBQ) score.

METHODS

Data were retrospectively examined for a consecutive sample of 346 patients who underwent TLIF at our medical center between 2014 and 2020. Patients who subsequently experienced cage subsidence or not were matched to each other based on propensity scoring, and the two matched groups (52 patients each) were compared using conditional logistic regression to investigate the association between the potential radiographic factors and cage subsidence. Scores for VBQ and EBQ were assessed for their ability to predict cage subsidence in the matched patients based on the area under the receiver operative characteristic curve (AUC).

RESULTS

Among matched patients, those who suffered cage subsidence had significantly higher VBQ score (3.7 vs 3.1, p<.001) and EBQ score (5.0 vs 4.3, p<.001), and regression linked greater risk of subsidence to higher VBQ score (OR 4.557, 95% CI 1.076-19.291, p=.039) and higher EBQ score (OR 5.396, 95% CI 1.158-25.146, p=.032). A cut-off VBQ score of 3.4 predicted the cage subsidence among matched patients with an AUC of 0.799, sensitivity of 84.6%, and specificity of 69.2%. A cut-off EBQ score of 4.7 predicted subsidence with an AUC of 0.829, sensitivity of 76.9%, and specificity of 82.7%.

CONCLUSION

Higher VBQ and EBQ scores are associated with a greater risk of cage subsidence following TLIF, and EBQ may perform better because of greater specificity.

Methionine as a regulator of bone remodeling with fasting

Caloric restriction improves metabolic health but is often complicated by bone loss. We studied bone parameters in humans during a 10-day fast and identified candidate metabolic regulators of bone turnover. Pro-collagen 1 intact N-terminal pro-peptide (P1NP), a bone formation marker, decreased within 3 days of fasting. Whereas dual-energy x-ray absorptiometry measures of bone mineral density were unchanged after 10 days of fasting, high-resolution peripheral quantitative CT demonstrated remodeling of bone microarchitecture. Pathway analysis of longitudinal metabolomics data identified one-carbon metabolism as fasting dependent. In cultured osteoblasts, we tested the functional significance of one-carbon metabolites modulated by fasting, finding that methionine - which surged after 3 days of fasting - affected markers of osteoblast cell state in a concentration-dependent manner, in some instances exhibiting a U-shaped response with both low and high concentrations driving putative antibone responses. Administration of methionine to mice for 5 days recapitulated some fasting effects on bone, including a reduction in serum P1NP. In conclusion, a 10-day fast in humans led to remodeling of bone microarchitecture, potentially mediated by a surge in circulating methionine. These data support an emerging model that points to a window of optimal methionine exposure for bone health.

Age- and sex-related changes in vertebral trabecular bone architecture in Neolithic and Mediaeval populations from Poland

This paper investigates trabecular bone ontogenetic changes in two different Polish populations, one prehistoric and the other historical. The studied populations are from the Brześć Kujawski region in Kujawy (north-central Poland), one from the Neolithic Period (4500-4000 BC) and one from the Middle Ages (twelfth-sixteenth centuries AD), in total 62 vertebral specimens (32 males, 30 females). Eight morphometric parameters acquired from microCT scan images were analysed. Two-way ANOVA after Box-Cox transformation and multifactorial regression model were calculated. A significant decrease in percentage bone volume fraction (BV/TV; [%]) with age at death was observed in the studied sample; Tb.N (trabecular number) was also significantly decreased with age; trabecular separation (Tb.Sp) increased with advancing age; connectivity density (Conn.D) was negatively correlated with biological age and higher in the Neolithic population. These data are found to be compatible with data from the current biomedical literature, while no loss of horizontal trabeculae was recorded as would be expected based on modern osteoporosis.

Hounsfield Unit for Evaluating Bone Mineral Density and Strength: Variations in Measurement Methods

OBJECTIVE

To assess the consistency and accuracy of various measurements of the Hounsfield unit (HU) in lumbar vertebrae.

METHODS

The study reviewed lumbar spine computed tomography images of 60 postmenopausal women aged >50 years. A total of 240 vertebrae were measured and analyzed for the variations of HU values in different sections and regions. Investigated the relationship between HU values of the lumbar spine under different measurements and dual-energy X-ray absorptiometry results and the ability to identify patients with osteoporosis.

RESULTS

HU values measured in midsagittal (r = 0.763), midcoronal (r = 0.768), and midaxial (r = 0.786) sections exhibited a strong positive correlation with dual-energy X-ray absorptiometry T-scores. HU values measured in midsagittal and midaxial sections of the vertebral body were in good agreement (P > 0.1), but decreased in the midcoronal (P < 0.001). HU values in the middle of the vertebral body were significantly higher than in the near end plate (P < 0.001). HU values varied between L1 and L4 vertebrae, but all had a good ability to identify osteoporosis and did not differ significantly in screening ability (P > 0.05).

CONCLUSIONS

An averaged HU value in axial multilevel is a comprehensive assessment of vertebral bone density. Using the HU value of the lumbar spine can help identify patients with osteoporosis, and the screening ability does not differ significantly across vertebral segments.

Parathyroid hormone treatment partially reverses endplate remodeling and attenuates low back pain in animal models of spine degeneration

Low back pain (LBP) is one of the most prevalent diseases affecting quality of life, with no disease-modifying therapy. During aging and spinal degeneration, the balance between the normal endplate (EP) bilayers of cartilage and bone shifts to more bone. The aged/degenerated bony EP has increased porosity because of osteoclastic remodeling activity and may be a source of LBP due to aberrant sensory innervation within the pores. We used two mouse models of spinal degeneration to show that parathyroid hormone (PTH) treatment induced osteogenesis and angiogenesis and reduced the porosity of bony EPs. PTH increased the cartilaginous volume and improved the mechanical properties of EPs, which was accompanied by a reduction of the inflammatory factors cyclooxygenase-2 and prostaglandin E2. PTH treatment furthermore partially reversed the innervation of porous EPs and reversed LBP-related behaviors. Conditional knockout of PTH 1 receptors in the nucleus pulposus (NP) did not abolish the treatment effects of PTH, suggesting that the NP is not the primary source of LBP in our mouse models. Last, we showed that aged rhesus macaques with spontaneous spinal degeneration also had decreased EP porosity and sensory innervation when treated with PTH, demonstrating a similar mechanism of PTH action on EP sclerosis between mice and macaques. In summary, our results suggest that PTH treatment could partially reverse EP restructuring during spinal regeneration and support further investigation into this potentially disease-modifying treatment strategy for LBP.

Analysis of Influencing Factors of Vertebral Height Loss After Pedicle Screw Fixation of Thoracolumbar Fracture

STUDY DESIGN

Retrospective case-control study.

OBJECTIVE

To explore the related factors of vertebral height loss (VHL) after pedicle screw fixation of thoracolumbar fracture and to determine the optimum prediction point.

SUMMARY OF BACKGROUND DATA

With the widespread application of thoracolumbar fracture internal fixation, VHL after the operation is increasingly presented. However, there is no unified conclusion on the specific cause of VHL and how to predict it.

METHODS

A total of 186 patients were selected and divided into the loss group (n = 72) and the not-loss group (n = 114) according to whether the fractured vertebral height was lost after the operation. The two groups were compared concerning sex, age, body mass index, osteoporosis self-assessment tool for Asians (OSTA), fracture types, number of fractured vertebrae, preoperative Cobb angle and compression degree, number of screws, and extent of vertebral restore. Univariate analysis and Multivariate logistic regression analysis were performed to identify the independent factors for the VHL with the receiver operating characteristic curve and the optimal prediction value was calculated according to area under the curve.

RESULTS

Multivariate logistic regression analysis showed that OSTA ( P < 0.05) and preoperative vertebral compression ( P < 0.05) were significantly correlated with postoperative VHL, which were independent risk factors for postoperative VHL. The OSTA of 2.32 and the preoperative vertebral compression degree of 38.5% were the best prediction points for postoperative VHL based on the Youden Index analysis.

CONCLUSIONS

The OSTA and preoperative vertebral compression were independent risk factors for VHL. The risk of postoperative VHL was significantly higher when the OSTA was ≤2.32 or the preoperative vertebral compression was ≥38.5%.

LEVEL OF EVIDENCE

Level III.

Trabecular structural difference between the superior and inferior regions of the vertebral body: a cadaveric and clinical study

Background

Osteoporotic vertebral compression fractures commonly involve the superior vertebral body; however, their associated causes have not yet been clearly established. This study aimed to determine the trabecular structural differences between the superior and inferior regions of the vertebral body using cadaveric and clinical studies.

Materials and methods

First, five vertebrae were collected from three human cadavers. The trabecular structures of the superior and inferior regions of each vertebral body were analyzed using micro-computed tomography (micro-CT), finite element analysis (FEA), and biomechanical test. Based on the results of the ex vivo study, we conducted a clinical study. Second, spine CT images were retrospectively collected. Bone volume and Hounsfield unit were analyzed for 192 vertebral bodies. Finally, after sample size calculation based on the pilot study, prospectively, 200 participants underwent dual-energy X-ray absorptiometry (DXA) of the lateral spine. The bone mineral densities (BMDs) of the superior and inferior regions of each lumbar vertebral body were measured. The paired t-test and Wilcoxon signed-rank test were used for the statistical analyses, and p-value < 0.05 was considered significant.

Results

Cadaver studies revealed differences between the superior and inferior trabecular bone structures. The bone volume ratio, BMD, and various other trabecular parameters advocated for decreased strength of the superior region. Throughout the biomechanical study, the limitations of the compression force were 3.44 and 4.63 N/m2 for the superior and inferior regions, respectively. In the FEA study, the inferior region had a lower average displacement and higher von Mises stress than the superior region. In the clinical spine CT-based bone volume and BMD study, the bone volume was significantly higher in the inferior region than in the superior region. In the lateral spine DXA, the mean BMD of the superior region of vertebral bodies was significantly lower compared with that of the inferior region.

Conclusion

The superior trabecular structure of the lumbar vertebral bodies possesses more biomechanical susceptibility compared with the inferior trabecular structure, confirming its dominant role in causing osteoporotic vertebral fractures. Physicians should also focus on the BMD values of the superior region of the vertebral body using lateral spine DXA to evaluate osteoporosis.

The quantification of 3D-trabecular architecture of the fourth cervical vertebra using CT osteoabsorptiometry and micro-CT

BACKGROUND

Bone functional adaptation rationalises the inhomogeneous morphology found in bone. By means of computed tomography osteoabsorptiometry and micro-computed tomography, the mineralisation of the subchondral endplates and trabecular microstructure of vertebral bodies can be assessed to visualise the chronic loading conditions bone endures over time. In this study, we determined cancellous and compartment-specific trabecular architecture in the cervical vertebra to aid with successful integration of orthopaedic implants.

METHODS

We examined the micro-computed tomography scans of seven prospectively healthy C4 vertebrae, evaluated their microstructure parameters (bone volume fraction (BV/TV), bone surface density (BS/BV), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), trabecular number per volume (Tb.N), connectivity density (Conn.D), structure model index (SMI), and degree of anisotropy (DA), and compared the trabecular architecture in twelve predefined volumes of interest: the cranial and caudal 0-10%, 10-15%, and 25-50% in both the ventral and dorsal half. Using computed tomography osteoabsorptiometry, the subchondral bone mineralisation of the subchondral endplates of nine C4 vertebrae was also evaluated.

RESULTS

Highest mineralisation is located dorsally at the endplates. Tb.Sp and Tb.N were the only two parameters that displayed significant differences in averaged values of VOI. Nonetheless, distinct, consistent ventral-dorsal modulations were seen in matched sample ventral-dorsal comparison in the BV/TV, BS/BV, and SMI overall levels, as well as in Tb.Th in the three caudal levels. To simplify, the vertebra was split into ventral-cranial, dorsal-cranial, ventral-caudal, and dorsal-caudal equal quarters. The ventral quarters display lower BV/TV, respectively, higher BS/BV and SMI than their sample paired dorsal quarters. The ventral-cranial quarter shows the lowest BV/TV and the highest BS/BV and SMI, describing spacious cancellous bone with rod-like trabeculae. In contrast, the dorsal-caudal quarter exhibits the highest BV/TV and Tb.Th and the lowest BS/BV and SMI, illustrating thicker, denser, and more plate-like trabeculae. The dorsal-cranial and ventral-caudal quarters are comparable and represent intermediate characteristics.

CONCLUSIONS

CT-OAM and µCT demonstrate the interdependence of compact and trabecular bone in response to long-term loading conditions. Results show highest mineralisation in the dorso-caudal part of the C4 vertebra. Recommended placement of orthopaedic implants should be positioned dorsally with screws anchored in the dorsal-caudal region.

Stiffness and Strain Properties Derived From Digital Tomosynthesis-Based Digital Volume Correlation Predict Vertebral Strength Independently From Bone Mineral Density

Vertebral fractures are the most common osteoporotic fractures, but their prediction using standard bone mineral density (BMD) measurements from dual energy X-ray absorptiometry (DXA) is limited in accuracy. Stiffness, displacement, and strain distribution properties derived from digital tomosynthesis-based digital volume correlation (DTS-DVC) have been suggested as clinically measurable metrics of vertebral bone quality. However, the extent to which these properties correlate to vertebral strength is unknown. To establish this relationship, two independent experiments, one examining isolated T11 and the other examining L3 vertebrae within the L2-L4 segments from cadaveric donors were utilized. Following DXA and DTS imaging, the specimens were uniaxially compressed to fracture. BMD, bone mineral content (BMC), and bone area were recorded for the anteroposterior and lateromedial views from DXA, stiffness, endplate to endplate displacement and distribution statistics of intravertebral strains were calculated from DTS-DVC and vertebral strength was measured from mechanical tests. Regression models were used to examine the relationships of strength with the other variables. Correlations of BMD with vertebral strength varied between experimental groups (R2adj = 0.19-0.78). DTS-DVC derived properties contributed to vertebral strength independently from BMD measures (increasing R2adj to 0.64-0.95). DTS-DVC derived stiffness was the best single predictor (R2adj = 0.66, p < 0.0001) and added the most to BMD in models of vertebral strength for pooled T11 and L3 specimens (R2adj = 0.95, p < 0.0001). These findings provide biomechanical relevance to DTS-DVC calculated properties of vertebral bone and encourage further efforts in the development of the DTS-DVC approach as a clinical tool.

Biomechanical evaluation of position and bicortical fixation of anterior lateral vertebral screws in a porcine model

Although an anterior approach with anterior lateral screw fixation has been developed for stabilizing the thoracolumbar spine clinically, screw loosening still occurs. In this novel in vitro study, we attempted to elucidate the optimal screw position in the lateral lumbar vertebra and the effect of bicortical fixation. A total of 72 fresh-frozen lumbar vertebrae from L1-6 were harvested from 12 mature pigs and randomly assigned to two modalities: bicortical fixation (n = 36) and unicortical fixation (n = 36). Six groups of screw positions in the lateral vertebral body in each modality were designated as central-anterior, central-middle, central-posterior, lower-anterior, lower-middle, and lower- posterior; 6 specimens were used in each group. The correlations between screw fixation modalities, screw positions and axial pullout strength were analyzed. An appropriate screw trajectory and insertional depth were confirmed using axial and sagittal X-ray imaging prior to pullout testing. In both bicortical and unicortical fixation modalities, the screw pullout force was significantly higher in the posterior or middle position than in the anterior position (p < 0.05), and there was no significant differences between the central and lower positions. The maximal pullout forces from the same screw positions in unicortical fixation modalities were all significantly lower, decreases that ranged from 32.7 to 74%, than those in bicortical fixation modalities. Our study using porcine vertebrae showed that screws in the middle or posterior position of the lateral vertebral body had a higher pullout performance than those in the anterior position. Posteriorly positioned lateral vertebral screws with unicortical fixation provided better stability than anteriorly positioned screws with bicortical fixation.

Morphological features of basivertebral foramen among different age groups: Recognition in spine

Background

Basivertebral foramen (BF) is a vessel and nerve passage in the posterior wall of vertebral body (VB). Our goal was to report BF's morphological characteristics in different age groups of mainland Chinese adults and to evaluate the relationship between BF's morphology and factors such as age, gender, heavy work, size and level of VB.

Methods

We enrolled 300 adults among persons who came to our hospital for health examination. We measured BFs and VBs' parameters on T1 weighted sagittal lumbar spine MR images. We also assessed following potential predictors: gender, body height, body weight, body mass index, alcohol use, habits of smoking and drinking, type of work (physical work or non-physical work). A stepwise multivariate linear regression analysis was conducted to identify predictors of BF's height.

Results

People above 60 have significantly bigger BFHr than those in young adulthood and in the middle ages at all five levels, while they have shallowest BFs, especially at L3. Multiple linear regression resulted in a formula that accounted for 30.1% of the variability in the height of basivertebral foramen. Significant predictors included: gender, age, level, vertebral height and heavy work.

Conclusion

Age is the highest weight in all factors on the height of BF. BF is closer to the upper endplate. The BF was relatively higher and deeper in the female lumbar spine. Heavywork results in lower BF. Last but not the least, as we supposed, BF gets shallower and higher compare to VB with age.

Level of evidence

Prognostic level III. See instructions for authors for a complete description of levels of evidence.

Selected mechanical properties of human cancellous bone subjected to different treatments: short-term immersion in physiological saline and acetone treatment with subsequent immersion in physiological saline

Background

Physiological saline (0.9% NaCl) and acetone are extensively used for storage (as well as hydration) and removal of bone marrow, respectively, of cancellous bone during preparation and mechanical testing. Our study aimed to investigate the mechanical properties of cancellous bone subjected to short-term immersion in saline and acetone treatment with subsequent immersion in saline.

Methods

Cylindrical samples (Ø6 × 12 mm) were harvested from three positions (left, middle, and right) of 1 thoracic vertebral body, 19 lumbar vertebral bodies, and 5 sacral bones, as well as from 9 femoral heads. All samples were divided into two groups according to the different treatments, (i) samples from the left and middle sides were immersed in saline at 4℃ for 43 h (saline-immersed group, n = 48); (ii) samples from the respective right side were treated with a combination of acetone and ultrasonic bath (4 h), air-dried at room temperature (21℃, 15 h), and then immersed in saline at room temperature (21℃, 24 h) (acetone and saline-treated group, n = 38). All samples were subjected, both before and after treatment, to a non-destructive compression test with a strain of 0.45%, and finally destructive tests with a strain of 50%. Actual density (ρ_act), initial modulus (E₀), maximum stress (σ_max), energy absorption (W), and plateau stress (σ_p) were calculated as evaluation indicators.

Results

Based on visual observation, a combination of acetone and ultrasonic bath for 4 h failed to completely remove bone marrow from cancellous bone samples. The mean values of ρ_act, σ_max, W, and σ_p were significantly higher in the femoral head than in the spine. There was no significant difference in E₀ between non-treated and saline-immersed samples (non-treated 63.98 ± 20.23 vs. saline-immersed 66.29 ± 20.61, p = 0.132). The average E₀ of acetone and saline-treated samples was significantly higher than that of non-treated ones (non-treated 62.17 ± 21.08 vs. acetone and saline-treated 74.97 ± 23.98, p = 0.043).

Conclusion

Short-term storage in physiological saline is an appropriate choice and has no effect on the E₀ of cancellous bone. Treatment of cancellous bone with acetone resulted in changes in mechanical properties that could not be reversed by subsequent immersion in physiological saline.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-022-03265-4.

Mechanical and morphometric characterization of custom-made trabecular bone surrogates

Synthetic bones for biomechanical testing and surgeon training have become more important due to their numerous advantages compared to human bones. Several bone models are already available on the market, but most of them do not reflect the full range of versatile properties that characterize human bone like population-level influences, size, stiffness, bone-implant-interface or morphometry. Thus, the objectives of this study were to develop synthetic trabecular bone surrogates from polyurethane and varying additives and to determine their elastic and plastic mechanical compressive and additionally morphometric properties. Another aim was to investigate the influence of varying additives on aforementioned properties and finally compare the results with published data from human trabecular bone. Additives used were blowing agents to create a porous structure, mineral fillers to manipulate the basic polyurethane resin, and cell stabilizers to achieve an open porous composition. Mechanical properties were obtained from static compression tests until failure while morphometric analysis was carried out using microcomputed tomography. Thereby, the blowing agent showed the strongest influence on mechanical and morphometric properties with mean Young's moduli ranging from 627 ± 37 MPa (0% blowing agent) to 154 ± 15 MPa (0.25% blowing agent) while the variation of mineral filler content resulted in small standard deviations of approximately 10-20 MPa with a constant proportion of blowing agent. The achieved mechanical properties of the developed synthetic bones, such as the Young's modulus, ultimate stress and yield stress were in accordance with human trabecular bone, while yield strain for all groups was noticeably higher compared to human trabecular bone. Additionally, morphometric analysis showed results indicating similar morphometry of the custom-made synthetic bone and human cancellous bone. Although recreating bone structures in physiological conditions is not simple, the results of the current study show the possibility of developing synthetic bone materials with characteristics like human trabecular bone.

Measuring the thickness of vertebral endplate and shell using digital tomosynthesis

The vertebral endplate and cortical shell play an important structural role and contribute to the overall strength of the vertebral body, are at highest risk of initial failure, and are involved in degenerative disease of the spine. The ability to accurately measure the thickness of these structures is therefore important, even if difficult due to relatively low resolution clinical imaging. We posit that digital tomosynthesis (DTS) may be a suitable imaging modality for measurement of endplate and cortical shell thickness owing to the ability to reconstruct multiplanar images with good spatial resolution at low radiation dose. In this study, for 25 cadaveric L1 vertebrae, average and standard deviation of endplate and cortical shell thickness were measured using images from DTS and microcomputed tomography (μCT). For endplate thickness measurements, significant correlations between DTS and μCT were found for all variables when comparing thicknesses measured in both the overall endplate volume (R² = 0.25-0.54) and when measurements were limited to a central range of coronal or sagittal slices (R² = 0.24-0.62). When compared to reference values from the overall shell volume, DTS thickness measurements were generally nonsignificant. However, when measurement of cortical shell thickness was limited to a range of central slices, DTS outcomes were significantly correlated with reference values for both sagittal and coronal central regions (R² = 0.21-0.49). DTS may therefore offer a means for measurement of endplate thickness and, within a limited sagittal or coronal measurement volume, for measurement of cortical shell thickness.

Focal osteoporosis defect is associated with vertebral compression fracture prevalence in a bone mineral density-independent manner

Introduction

Focal osteoporosis defect has shown a high association with the bone fragility and osteoporotic fracture prevalence. However, no routine computed tomography (CT)-based vertebral focal osteoporosis defect measurement and its association with vertebral compression fracture (VCF) were discussed yet. This study aimed to develop a routine CT-based measurement method for focal osteoporosis defect quantification, and to assess its association with the VCF prevalence.

Materials and Methods

A total of 205 cases who underwent routine CT scanning, were retrospectively reviewed and enrolled into either the VCF or the control group. The focal bone mineral content loss (focal BMC loss), measured as the cumulated demineralization within bone void space, was proposed for focal osteoporosis defect quantification. Its scan-rescan reproducibility and its correlation with trabecular bone mineral density (BMD) and apparent microarchitecture parameters were evaluated. The association between focal BMC loss and the prevalence of VCF was studied by logistic regression.

Results

The measurement of focal BMC loss showed high reproducibility (RMSSD = 0.011 mm, LSC = 0.030 mm, ICC = 0.97), and good correlation with focal bone volume fraction (r = 0.79, P < 0.001), trabecular bone separation (r = 0.76, P < 0.001), but poor correlation with trabecular BMD (r = 0.37, P < 0.001). The focal BMC loss was significantly higher in the fracture group than the control (1.03 ± 0.13 vs. 0.93 ± 0.11 mm; P < 0.001), and was associated with prevalent VCF (1.87, 95% CI = 1.31-2.65, P < 0.001) independent of trabecular BMD level.

Discussion

As a surrogate measure of focal osteoporosis defect, focal BMC Loss independently associated with the VCF prevalence. It suggests that focal osteoporosis defect is a common manifestation that positively contributed to compression fracture risk and can be quantified with routine CT using focal BMC Loss.

Using Statistical Shape and Appearance Modelling to characterise the 3D shape and material properties of human lumbar vertebrae: A proof of concept study

Patient variation affects the outcomes of a range of spinal interventions, from disc replacement to vertebral fixation and vertebroplasty. Statistical Shape and Appearance Modelling (SSAM) can be used to describe anatomical variation and pathological differences within the population. To better understand how bone density and shape variation affect load transfer with respect to surgical treatments, Finite Element (FE) models can be generated from a SSAM. The aim for this study is to understand whether geometric and density variation as well as multiple vertebral levels can be incorporated into a single SSAM and whether this can be used to investigate the relationships between, and effects of, the various modes of variation. FE models of 14 human lumbar vertebrae that had been μCT imaged and validated through experimental testing were used as input specimens for a SSAM. The validity of the SSAM was evaluated by using principal component analysis to identify the primary modes of geometric and bone density variation and comparing to those in the input set. FE models were generated from the SSAM to examine the response to loading. The mean error between the input set and generated models for volume, mean density and FE compressive stiffness were 10%, 3% and 10% respectively. Principal Component (PC) 1 captured the majority of the bone density variation. The remaining PCs described specific geometric variation. The FE models generated from the SSAM showed the variations in vertebral stiffness as a result of complex relationships between bone density and shape. The SSAM created has limited data for its input set, however, it acts as a proof of concept for the novel combination of material and shape variation into a single shape model. This approach and the tools developed can be applied to wider patient groups and treatment scenarios to improve patient stratification and to optimise treatments.

Regional distribution of computed tomography attenuation across the lumbar endplate

The vertebral endplate forms a structural boundary between intervertebral disc and the trabecular bone of the vertebral body. As a mechanical interface between the stiff bone and resilient disc, the endplate is the weakest portion of the vertebral-disc complex and is predisposed to mechanical failure. However, the literature concerning the bone mineral density (BMD) distribution within the spinal endplate is comparatively sparse. The objective of this study is to investigate the three-dimensional (3D) distribution of computed tomography (CT) attenuation across the lumbosacral endplate measured in Hounsfield Units (HU). A total of 308 endplates from 28 cadaveric fresh-frozen lumbosacral spines were used in this study. Each spine was CT-scanned and the resulting DICOM data was used to obtain HU values of the bone endplate. Each individual endplate surface was subdivided into five clinically-relevant topographic zones. Attenuation was analyzed by spinal levels, sites (superior or inferior endplate) and endplate region. The highest HU values were found at the S1 endplate. Comparisons between the superior and inferior endplates showed the HU values in inferior endplates were significantly higher than those in the superior endplates within the same vertebra and the HU values in endplates cranial to the disc were significantly higher than those in the endplates caudal to the disc within the same disc. Attenuation in the peripheral region was significantly higher than in the central region by 32.5%. Regional comparison within the peripheral region showed the HU values in the posterior region were significantly higher than those in the anterior region and the HU values in the left region were significantly higher than those in the right region. This study provided detailed data on the regional HU distribution across the lumbosacral endplate, which can be useful to understand causes of some endplate lesions, such as fracture, and also to design interbody instrumentation.

The Correlation of Regional Microstructure and Mechanics of the Cervical Articular Process in Adults

Purpose: Using micro-CT and finite element analysis to establish regional variation microarchitectures and correlation with mechanical properties of cervical articular facet trabecular bone to predict cervical spine security and material properties. Methods: A total of 144 cervical articular processes (each articular was separate to four region of interest (ROI), superior-anterior (SA), superior-posterior (SP), inferior-anterior (IA), and inferior-posterior (IP) regions) specimens with a volume of 5 × 5 × 5 mm³ were scanned by micro-CT, and allowable stress and other mechanical properties parameters in each region were calculated after mechanical testing, then the effectiveness was verified of finite element models by ABAQUS software. Results: Maximum and minimum values of C2–C7 articular processes and regions are C5 and C7 level, SA and SP regions for bone volume fraction (BV/TV) and trabecular thickness (Tb.Th), whose variation tendency is similar to the Young’s modulus, allowable stress, BMD, maximum force and strain. Between Young’s modulus and all microstructure parameters, especially between BV/TV, bone mineral density (BMD) and Tb.Th, had higher linear regression coefficients R² = 0.5676, 0.6382, 0.3535, respectively. BMD and yield strength, BV/TV, and allowable stress also had better regression coefficients, R² = 0.5227, 0.5259, 0.5426, respectively. Conclusions: The contribution of the microstructure and mechanical properties of the C2–C7 cervical spine to the movement of the cervical spine is different and has a good correlation and the effectiveness of the finite element model is also verified that we can correctly calculate the microstructure and mechanical properties of the cervical articular process to evaluate the stability and injury risk of cervical vertebrae by the established model.

Biomechanical Study of the Osteoporotic Spine Fracture: Optical Approach

Background and objectives: Osteoporotic spine fractures represent a significant factor for decreasing quality of life in the elderly female population. Understanding the mechanisms involved in producing these fractures can improve their prevention and treatment. This study presents a biomechanical method to produce a vertebral fracture, conducted on a human spine segment, observing the displacements and strains in the intervertebral disc, endplate, and vertebral body. Materials and Methods: We performed two tests, one corresponding to an extension loading, and the second to an axial loading. Results: The maximum displacement in the target vertebral body presented higher values in the case of the extension as compared to the axial strain where it mainly occurred after the fracture was produced. The strains occurred simultaneously on both discs. In the case of the axial strain, due to the occurrence of the fracture, the maximum value was recorded in the spine body, while in the case of the extensions, it occurred in the neural part of the upper disc. The advantage of this method was that the entire study was an experiment, using optical methods, increasing the precision of the material data input. Conclusions: The research method allowed recording in real time of a larger amount of data from the different components of the spine segment. If there was an extension component of the compression force at the moment of the initial loading, part of this load was absorbed by the posterior column with higher mechanical resistance. After the maximum capacity of the absorption was reached, in both situations the behavior was similar.

Structure-function relationships of the human vertebral endplate

BACKGROUND

Although deformation and fracture of the vertebral endplate have been implicated in spinal conditions such as vertebral fracture and disc degeneration, few biomechanical studies of this structure are available. The goal of this study was to quantify the mechanical behavior of the vertebral endplate.

METHODS

Eight-five rectangular specimens were dissected from the superior and/or inferior central endplates of human lumbar spine segments L1 to L4. Micro-computed tomography (μCT) imaging, four-point-bend testing, and ashing were performed to quantify the apparent elastic modulus and yield stress (modulus and yield stress, respectively, of the porous vertebral endplate), tissue yield stress (yield stress of the tissue of the vertebral endplate, excluding pores), ultimate strain, fracture strain, bone volume fraction (BV/TV), bone mineral density (BMD), and various measures of tissue density and composition (tissue mineral density, ash fraction, and ash density). Regression was used to assess the dependence of mechanical properties on density and composition.

RESULTS

Wide variations in elastic and failure properties, and in density and tissue composition, were observed. BMD and BV/TV were good predictors of many of the apparent-level mechanical properties, including modulus, yield stress, and in the case of the inferior vertebral endplate, failure strains. Similar values of the mechanical properties were noted between superior and inferior vertebral endplates. In contrast to the dependence of apparent stiffness and strength on BMD and BV/TV, none of the mechanical properties depended on any of the tissue-level density measurements.

CONCLUSION

The dependence of many of the mechanical properties of the vertebral endplate on BV/TV and BMD suggests possibilities for noninvasive assessment of how this region of the spine behaves during habitual and injurious loading. Further study of the nonmineral components of the endplate tissue is required to understand how the composition of this tissue may influence the overall mechanical behavior of the vertebral endplate.

Diagnostic Role of Magnetic Resonance Imaging in Low Back Pain Caused by Vertebral Endplate Degeneration

Low back pain (LBP) is a common health issue worldwide with a huge economic burden on healthcare systems. In the United States alone, the cost is estimated to be $100 billion each year. Intervertebral disc degeneration is considered one of the primary causes of LBP. Moreover, the critical role of the vertebral endplates in disc degeneration and LBP is becoming apparent. Endplate abnormalities are closely correlated with disc degeneration and pain in the lumbar spine. Imaging modalities such as plain film radiography, computed tomography, and fluoroscopy are helpful but not very effective in detecting the causes behind LBP. Magnetic resonance imaging (MRI) can be used to acquire high-quality three-dimensional images of the lumbar spine without using ionizing radiation. Therefore, it is increasingly being used to diagnose spinal disorders. However, according to the American College of Radiology, current referral and justification guidelines for MRI are not sufficiently clear to guide clinical practice. This review aimed to evaluate the role of MRI in diagnosing LBP by considering the correlative contributions of vertebral endplates. The findings of the review indicate that MRI allows for fine evaluations of endplate morphology, endplate defects, diffusion and perfusion properties of the endplate, and Modic changes. Changes in these characteristics of the endplate were found to be closely correlated with disc degeneration and LBP. The collective evidence from the literature suggests that MRI may be the imaging modality of choice for patients suffering from LBP. LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY STAGE: 3.

Relationship between diffuse idiopathic skeletal hyperostosis and fragility vertebral fracture: a prospective study in older men

OBJECTIVE

To analyse the risk of incident vertebral and non-vertebral fracture in men with DISH.

METHODS

In 782 men ages 50-85 years, DISH was diagnosed using Resnick's criteria. In men followed prospectively for 7.5 years, a radiographic incident vertebral fracture was defined by a decrease of ≥20% or ≥4mm in any vertebral height vs baseline. Self-reported incident non-vertebral fractures were confirmed by medical records.

RESULTS

Men with DISH had higher BMD at the lumbar spine (P < 0.05), but not at other skeletal sites. After adjustment for confounders including disc space narrowing (DSN) and endplate irregularity, the risk of vertebral fracture was higher in men with DISH vs men without DISH [10/164 (6.1%) vs 16/597 (2.7%), P < 0.05; odds ratio (OR) 2.89 (95% CI 1.15, 7.28), P < 0.05]. DISH and low spine BMD were each associated with a higher vertebral fracture risk. The vertebral fracture risk was higher in men who had both DISH and severe DSN. DISH and endplate irregularities (EIs) were each associated with higher vertebral fracture risk. DISH, DSN and EIs define the intervertebral space dysfunction, which was associated with higher vertebral fracture risk [OR 3.99 (95% CI 1.45, 10.98), P < 0.01]. Intervertebral space dysfunction improved the vertebral fracture prediction (ΔAUC = +0.111, P < 0.05), mainly in men with higher spine BMD (>0.9 g/cm2; ΔAUC = +0.189, P < 0.001). DISH was not associated with the risk of non-vertebral fracture.

CONCLUSION

DISH is associated with higher vertebral fracture risk, independently of other risk factors. Assessment of the intervertebral space dysfunction components may improve the vertebral fracture prediction in older men.

The Influence of Axial Compression on the Cellular and Mechanical Function of Spinal Tissues; Emphasis on the Nucleus Pulposus and Annulus Fibrosus: A Review

In light of the correlation between chronic back pain and intervertebral disc (IVD) degeneration, this literature review seeks to illustrate the importance of the hydraulic response across the nucleus pulposus (NP)-annulus fibrosus (AF) interface, by synthesizing current information regarding injurious biomechanics of the spine, stemming from axial compression. Damage to vertebrae, endplates (EPs), the NP, and the AF, can all arise from axial compression, depending on the segment's posture, the manner in which it is loaded, and the physiological state of tissue. Therefore, this movement pattern was selected to illustrate the importance of the bracing effect of a pressurized NP on the AF, and how injuries interrupting support to the AF may contribute to IVD degeneration.

Vertebral pneumaticity is correlated with serial variation in vertebral shape in storks

Birds and their ornithodiran ancestors are unique among vertebrates in exhibiting air-filled sinuses in their postcranial bones, a phenomenon called postcranial skeletal pneumaticity. The factors that account for serial and interspecific variation in postcranial skeletal pneumaticity are poorly understood, although body size, ecology, and bone biomechanics have all been implicated as influencing the extent to which pneumatizing epithelia invade the skeleton and induce bone resorption. Here, I use high-resolution computed-tomography to holistically quantify vertebral pneumaticity in members of the neognath family Ciconiidae (storks), with pneumaticity measured as the relative volume of internal air space. These data are used to describe serial variation in extent of pneumaticity and to assess whether and how pneumaticity varies with the size and shape of a vertebra. Pneumaticity increases dramatically from the middle of the neck onwards, contrary to previous predictions that cervical pneumaticity should decrease toward the thorax to maintain structural integrity as the mass and bending moments of the neck increase. Although the largest vertebrae sampled are also the most pneumatic, vertebral size cannot on its own account for serial or interspecific variation in extent of pneumaticity. Vertebral shape, as quantified by three-dimensional geometric morphometrics, is found to be significantly correlated with extent of pneumaticity, with elongate vertebrae being less pneumatic than craniocaudally short and dorsoventrally tall vertebrae. Considered together, the results of this study are consistent with the hypothesis that shape- and position-specific biomechanics influence the amount of bone loss that can be safely tolerated. These results have potentially important implications for the evolution of vertebral morphology in birds and their extinct relatives.

Trabecular Architecture and Mechanical Heterogeneity Effects on Vertebral Body Strength

PURPOSE OF REVIEW

We aimed to synthesize the recent work on the intra-vertebral heterogeneity in density, trabecular architecture and mechanical properties, its implications for fracture risk, its association with degeneration of the intervertebral discs, and its implications for implant design.

RECENT FINDINGS

As compared to the peripheral regions of the centrum, the central region of the vertebral body exhibits lower density and more sparse microstructure. As compared to the anterior region, the posterior region shows higher density. These variations are more pronounced in vertebrae from older persons and in those adjacent to degenerated discs. Mixed results have been reported in regard to variation along the superior-inferior axis and to relationships between the heterogeneity in density and vertebral strength and fracture risk. These discrepancies highlight that, first, despite the large amount of study of the intra-vertebral heterogeneity in microstructure, direct study of that in mechanical properties has lagged, and second, more measurements of vertebral loading are needed to understand how the heterogeneity affects distributions of stress and strain in the vertebra. These future areas of study are relevant not only to the question of spine fractures but also to the design and selection of implants for spine fusion and disc replacement. The intra-vertebral heterogeneity in microstructure and mechanical properties may be a product of mechanical adaptation as well as a key determinant of the ability of the vertebral body to withstand a given type of loading.

Importance of the epiphyseal ring in OLIF stand-alone surgery: a biomechanical study on cadaveric spines

PURPOSES

To explore the function of endplate epiphyseal ring in OLIF stand-alone surgery using a biomechanical model to reduce the complications of endplate collapse and cage subsidence.

METHODS

In total, 24 human cadaveric lumbar function units (L1-2 and L3-4 segments) were randomly assigned to two groups. The first group was implanted with long fusion cages which engaged with both inner and outer regions of epiphyseal ring (Complete Span-Epiphyseal Ring, CSER). Those engaged with only the inner half of epiphyseal ring were the second group (Half Span-Epiphyseal Ring, HSER). Each group was divided into two subgroups [higher cage-height (HH) and normal cage-height (NH)]. Specimens were fixed in testing cups and compressed at approximately 2.5 mm/s, until the first sign of structural failure. Trabecular structural damage was analyzed by Micro-CT, as well as the difference of bone volume fraction (BV/TV), trabecular thickness (Tb.Th) et al. in different regions.

RESULTS

Endplate collapse was mainly evident in the inner region of epiphyseal ring, where trabecular injury of sub-endplate bone was most concentrated. Endplate collapse incidence was significantly higher in HSER than CSER specimens (P = 0.017). A structural failure occurred at a lower force in HSER (1.41 ± 0.34 KN) compared with CSER (2.44 ± 0.59 KN). HH subgroups failed at a lower average force than NH subgroups. Micro-CT results showed a more extensive trabecular fracture in HSER specimens compared to CSER specimens, especially in HH subgroup.

CONCLUSIONS

Endplate collapse is more likely to occur with short half span cages than complete span cages, and taller cages compared with normal height cages. During OLIF surgery, we should choose cages matching intervertebral disc space height and place the cages spanning over the whole epiphyseal ring to improve support strength.

Distribution of Young's modulus at various sampling points in a human lumbar spine vertebral body

BACKGROUND CONTEXT

Mathematical modeling for creating computer spine models is one of the basic methods underlying many scientific publications. The accuracy of strength parameters of tissues introduced into such models translates directly into the reliability of obtained results. Experimental determination of Young's modulus (E) in various areas of spongy bone tissue seems to be crucial for creating a reliable spine model without excessive simplifications in the form of a single E value for the whole vertebral body.

PURPOSE

The aim of the study was to determine Young's modulus in different parts of the lumbar vertebral column for samples subjected to compression and bending.

STUDY DESIGN

Cylindrical spongy bone tissue samples were subjected to bending and compression strength tests.

METHODS

The study included 975 pathologically unchanged samples of spongy bone tissue harvested from the lumbar vertebrae of 15 male donors. The samples were subjected to compression or bending strength tests and then Young's modulus was determined for each sample depending on its location in the vertebral body. The samples were tested differently between given locations within one vertebra as well as between vertebrae.

RESULTS

Compressed specimens are characterized by highly significantly different Young's modulus values depending on the location in the vertebral body. Samples No. 7 and No. 9 in the anterior part of the vertebral body have highly significantly higher Young's modulus values compared to those in the posterior part of the vertebral body for all lumbar vertebrae. Samples subjected to bending showed significant differences (p<.05) between samples located closer to the vertebral canal (No.16, No.17) and samples located further away (No.14, No.15) with higher values for the samples located in the posterior part of the vertebral body.

CONCLUSIONS

Accommodating the anisotropic structure of spongy bone in computer models and the application of different Young's module values for areas within one vertebral body will allow one to obtain realistic results of computer simulations used.

CLINICAL SIGNIFICANCE

Determining the exact strength parameters of spongy bone tissue within one vertebra and changes in these properties in subsequent vertebrae will allow to create more accurate computer models of the lumbar spine and the whole spine. This, in turn, will translate into more reliable computer simulations used, among others, to determine the risk of fractures or osteoporotic changes, or simulation of the procedure of spinal fusion.

Local and global microarchitecture is associated with different features of bone biomechanics

Purpose

Beside areal bone mineral density (aBMD), evaluation of fragility fracture risk mostly relies on global microarchitecture. However, microarchitecture is not a uniform network. Therefore, this study aimed to compare local structural weakness to global microarchitecture on whole vertebral bodies and to evaluate how local and global microarchitecture was associated with bone biomechanics.

Methods

From 21 human L3 vertebrae, aBMD was measured using absorptiometry. Parameters of global microarchitecture were measured using HR-pQCT: trabecular bone volume fraction (Tb.BV/TV_global), trabecular number, structure model index and connectivity density (Conn.D). Local minimal values of aBMD and Tb.BV/TV were identified in the total (Tt) or trabecular (Tb) area of each vertebral body. “Two dimensional (2D) local structural weakness” was defined as Tt.BMD_min, Tt.BV/TV_min and Tb.BV/TV_min. Mechanical testing was performed in 3 phases: 1/ initial compression until mild vertebral fracture, 2/ unloaded relaxation, and 3/ second compression until failure.

Results

Initial and post-fracture mechanics were significantly correlated with bone mass, global and local microarchitecture. Tt.BMD_min, Tt.BV/TV_min, Tb.BV/TV_min, and initial and post-fracture mechanics remained significantly correlated after adjustment for aBMD or Tb.BV/TV_global (p < 0.001 to 0.038). The combination of the most relevant parameter of bone mass, global and local microarchitecture associated with failure load and stiffness demonstrated that global microarchitecture explained initial and post-fracture stiffness, while local structural weakness explained initial and post-fracture failure load (p < 0.001).

Conclusion

Local and global microarchitecture was associated with different features of vertebral bone biomechanics, with global microarchitecture controlling stiffness and 2D local structural weakness controlling strength. Therefore, determining both localized low density and impaired global microarchitecture could have major impact on vertebral fracture risk prediction.

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Global and local microarchitecture were associated with different features of bone biomechanics.

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Localized low density and/or impaired microarchitecture regions could have major impact on bone mechanical behavior.

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Global microarchitecture determined initial and post-fracture vertebral stiffness.

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Local microarchitecture determined initial and post-fracture vertebral failure load.

Association of vertebral endplate microstructure with bone strength in men and women

Epidemiological and biomechanical evidence indicates that the risk of vertebral fracture differs between men and women, and that vertebral fracture frequently involves failure of the endplate region. The goal of this study was to compare the bone microstructure of the endplate region-defined as the (bony) vertebral endplate and underlying subchondral trabecular bone-between sexes and to determine whether any such sex differences are associated with vertebral strength. The bone density (volume fraction, apparent density and tissue mineral density) of the superior-most 2 mm of the vertebra, and the bone density and trabecular architecture of the next 5 mm were quantified using micro-computed tomography in human T8 (12 female, 16 male) and L1 (13 female, 12 male) vertebrae. Average density of the vertebra (integral bone mineral density (BMD)) was determined by quantitative computed tomography and compressive strength by mechanical testing. Few differences were found between male and female vertebrae in the density of the endplate region; none were found in trabecular architecture. However, whereas endplate volume fraction was positively correlated with integral BMD in male vertebrae (r = 0.654, p < .001), no correlation was found in the female vertebrae (r = 0.157, p = .455). Accounting for the density of the endplate region improved predictions of vertebral strength (p < .034) and eliminated sex-specificity in the strength prediction that was based on integral BMD alone. These results suggest that the density of the endplate region influences vertebral fracture and that non-invasive assessment of this region's density can contribute to predictions of vertebral strength in men and women.

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.

Evaluation and Prediction of Human Lumbar Vertebrae Endplate Mechanical Properties Using Indentation and Computed Tomography

Current implant materials and designs used in spinal fusion show high rates of subsidence. There is currently a need for a method to predict the mechanical properties of the endplate using clinically available tools. The purpose of this study was to develop a predictive model of the mechanical properties of the vertebral endplate at a scale relevant to the evaluation of current medical implant designs and materials. Twenty vertebrae (10 L1 and 10 L2) from 10 cadavers were studied using dual-energy X-ray absorptiometry to define bone status (normal, osteopenic, or osteoporotic) and computed tomography (CT) to study endplate thickness (μm), density (mg/mm3), and mineral density of underlying trabecular bone (mg/mm3) at discrete sites. Apparent Oliver-Pharr modulus, stiffness, maximum tolerable pressure (MTP), and Brinell hardness were measured at each site using a 3 mm spherical indenter. Predictive models were built for each measured property using various measures obtained from CT and demographic data. Stiffness showed a strong correlation between the predictive model and experimental values (r = 0.85), a polynomial model for Brinell hardness had a stronger predictive ability compared to the linear model (r = 0.82), and the modulus model showed weak predictive ability (r = 0.44), likely due the low indentation depth and the inability to image the endplate at that depth (≈0.15 mm). Osteoporosis and osteopenia were found to be the largest confounders of the measured properties, decreasing them by approximately 50%. It was confirmed that vertebral endplate mechanical properties could be predicted using CT and demographic indices.

Differences in Trabecular Bone, Cortical Shell, and Endplate Microstructure Across the Lumbar Spine

Background

The quality of the vertebral body structures such as endplate, cortex, and trabecular bone is important for understanding the performance of implants, particularly at the bone-implant interface. Although vertebral body structures have been analyzed separately in the literature, there is no comprehensive study to assess these anatomical measurements along with their interrelationships in the lumbar spine. Therefore, the purpose of this study was to assess variations in trabecular microstructure, vertebral endplate thickness and concavity, and vertebral body cortex thickness within the lumbar spine.

Methods

A total of 80 lumbar vertebrae (L1-L5) were dissected from 16 human cadaver specimens and imaged with microcomputed tomography to determine trabecular microstructure, vertebral cortex thickness, endplate thickness, and maximum endplate concavity depth. A paired t test and regression analysis were used to determine significant differences (P < .05) between different vertebral levels and correlations between the analyzed anatomical parameters.

Results

L1 vertebra had significantly better (P < .02) trabecular bone microstructure (eg, trabecular bone volume fraction) than all other lumbar vertebrae. However, L1 vertebra also had significantly thinner (P ≤ .02) anterior, left, and right cortices compared to all other vertebral levels. Within L3-L5 intervertebral disc spaces, cranial endplates had significantly greater (P ≤ .03) thickness and maximum concavity depth compared to their respective caudal endplates. No strong correlations were observed between trabecular bone microstructure, maximum endplate concavity depth, vertebral cortex, and endplate thickness parameters.

Conclusions

Detailed reference data of these anatomical parameters for each lumbar vertebral body can aid in improved understanding of bone quality, particularly when assessing different implant designs and fixation approaches. Moreover, such anatomical knowledge may help clinicians with optimal implant design selection and surgical placement of these devices into their respective locations.

Subregional areal bone mineral density (aBMD) is a better predictor of heterogeneity in trabecular microstructure of vertebrae in young and aged women than subregional trabecular bone score (TBS)

BACKGROUND

Currently, bone densitometry fails to identify nearly half of those elderly patients at immediate fracture risk. To improve clinical assessment of vertebral fracture risk, we aimed to determine how the DXA-based 2D parameter Trabecular Bone Score (TBS) relates to subregional variability in 3D trabecular microstructure in young and elderly women compared to aBMD.

METHODS

T12 vertebrae from 29 women (11 young: 32 ± 6 years, 18 aged: 71 ± 5 years) were DXA-scanned ex vivo in anterior-posterior (AP) and lateral projection providing vertebral aBMD and TBS. Additionally, aBMD and TBS were measured for three horizontal (superior, mid-horizontal, inferior) and three vertical subregions (anterior, mid-vertical, posterior) and related to 3D microstructure indices, i.e. bone volume per tissue volume (BV/TV), trabecular number and thickness (Tb.N, Tb.Th), based on HRpQCT.

RESULTS

Subregional high-resolution tomography showed significant differences in trabecular parameters for both age groups: In horizontal subregions, BV/TV was lowest superiorly, Tb.Th was highest mid-horizontally, and Tb.N was lowest mid-horizontally and highest inferiorly. Correspondingly, aBMD varied between horizontal subregions, with differences depending on projection direction. TBS varied only in lateral projections of the aged group, with lower values for the mid-horizontal subregion. In vertical subregions, BV/TV, Tb.N, and aBMD were highest posteriorly for both groups. TBS did not differ between vertical subregions. Regression analysis showed aBMD as a predictor explained more of the variance in subregional 3D microstructure compared to TBS. Stepwise multi-regression analysis revealed only three combinations of subregion, projection, and group where aBMD and TBS were both significant predictors.

CONCLUSIONS

Subregional aBMD reflects variations in trabecular bone microstructure better than subregional TBS for trisected regions. Specifically, lateral aBMD identifies microstructural heterogeneities independent of age and may improve prediction of vertebral strength and susceptibility to specific fracture types.

Digital Tomosynthesis and Fractal Analysis Predict Prevalent Vertebral Fractures in Patients With Multiple Myeloma: A Preliminary In Vivo Study

OBJECTIVE. The objective of this study was to investigate the association of fractal-derived bone microstructural parameters with vertebral fracture status using in vivo digital tomosynthesis images of the spine. MATERIALS AND METHODS. Digital tomosynthesis images of the thoracic and lumbar spine from T1 to L5 were acquired from 36 patients with newly diagnosed multiple myeloma or monoclonal gammopathy of uncertain significance (age range, 39-85 years old). Scans were performed with patients in the supine position with reconstructed planes formed in the coronal direction. Bone mineral density (BMD) was recorded for 10 patients who had recently undergone dual x-ray absorptiometry. Vertebral fracture and lytic lesion status was determined by a radiologist from digital radiographs. Radiologist interpretation was reviewed to identify levels with a minimum number of fractures or lesions. For fractal analysis, the largest possible cuboid volume of interest within the cancellous bone was cropped from T7 and T11 images. Mean and SD of fractal variables between slices of fractal dimension (FD, a measure of self-similarity in the texture), mean lacunarity (λ, a measure of heterogeneity) and the slope of lacunarity versus box size relationship (S_λ, a measure of sensitivity of heterogeneity to size scale) were calculated using a box-counting method. A generalized estimating equation (GEE) platform was used to examine fractal variables as predictors of fracture status. RESULTS. Fracture status was not significantly associated with sex, race, age, stage of myeloma, presence of lesion in the spine, or BMD. In light of these results, no correction was made for these variables in further analyses of fractal variables. No interaction was found between vertebral level and any of the fractal variables (p = 0.12-0.77). Therefore, vertebral level was not considered further as an independent variable. Logistic regression analysis within GEE indicated that probability of fracture decreased with increasing mean FD (p = 0.02). In contrast, probability of fracture increased with increasing mean λ (p = 0.03). Although not to a statistically significant degree, probability of fracture increased with increasing mean S_λ (p = 0.08), SD of FD (p = 0.07), SD of λ (p = 0.07), and SD of S_λ (p = 0.06). CONCLUSION. We found FD and lacunarity calculated within the cancellous centrum of T7 and T11 vertebrae to be significantly associated with the presence of a vertebral fracture in this cohort. The decreased probability of fracture with increasing fractal dimension and increased probability of fracture with increasing lacunarity are consistent with the idea that cancellous bone with a better organized trabecular architecture is mechanically more competent. To our knowledge, this is the first in vivo evidence that fractal analysis of vertebral bone from tomosynthesis images may be useful in assessing vertebral fracture risk in patients with multiple myeloma.

Normal trabecular vertebral bone is formed via rapid transformation of mineralized spicules: A high-resolution 3D ex-vivo murine study

At birth, mouse vertebrae have a reticular fine spongy morphology, yet in the adult animal they exhibit elaborate trabecular architectures. Here, we characterize the physiological microstructural transformations in growing young female mice of the widely used C57BL/6 strain. Extensive architectural changes lead to the establishment of mature cancellous bone in the spine. Vertebrae were mapped in 3D by high resolution microcomputed tomography (µCT), backed by conventional histology. Three different phases are observed in the natural bony biomaterial: In a prenatal templating phase, early vertebrae are composed of foamy, loosely-packed mineralized spicules. During a consolidation phase in the first 7 days after birth, bone material condenses into struts and forms primitive trabeculae accompanied by a significant (>50%) reduction in bone volume/tissue volume ratio (BV/TV). After day 7, the trabeculae expand, reorient and increase in mineral density. Swift growth ensues such that by day 14 the young lumbar spine exhibits all morphological features observed in the mature animal. The greatly varied micro-morphologies of normal trabecular bone observed in 3D within a short timespan are typical for rodent and presumably for other mammalian forming spines. This suggests that fully structured cancellous bone emerges through rapid post-natal restructuring of a foamy mineralized scaffold. STATEMENT OF SIGNIFICANCE: Cancellous bone develops in stages that are not well documented. Using a mouse model, we provide an observer-independent quantification of normal bone formation in the spine. We find that within 14 days, the cancellous bone transforms in 3 phases from a scaffold of spicules into well organized, fully mineralized trabeculae in a functional spine. Detailed knowledge of the physiological restructuring of mineralized material may help to better understand bone formation and may serve as a blueprint for studies of pharmaceuticals effects, tissue healing and regeneration.

The Effects of Bone Microstructure on Subsidence Risk for ALIF, LLIF, PLIF, and TLIF Spine Cages

Several approaches (anterior, posterior, lateral, and transforaminal) are used in lumbar fusion surgery. However, it is unclear whether one of these approaches has the greatest subsidence risk as published clinical rates of cage subsidence vary widely (7–70%). Specifically, there is limited data on how a patient's endplate morphometry and trabecular bone quality influences cage subsidence risk. Therefore, this study compared subsidence (stiffness, maximum force, and work) between anterior (ALIF), lateral (LLIF), posterior (PLIF), and transforaminal (TLIF) lumbar interbody fusion cage designs to understand the impact of endplate and trabecular bone quality on subsidence. Forty-eight lumbar vertebrae were imaged with micro-ct to assess trabecular microarchitecture. micro-ct images of each vertebra were then imported into image processing software to measure endplate thickness (ET) and maximum endplate concavity depth (ECD). Generic ALIF, LLIF, PLIF, and TLIF cages made of polyether ether ketone were implanted on the superior endplates of all vertebrae and subsidence testing was performed. The results indicated that TLIF cages had significantly lower (p < 0.01) subsidence stiffness and maximum subsidence force compared to ALIF and LLIF cages. For all cage groups, trabecular bone volume fraction was better correlated with maximum subsidence force compared to ET and concavity depth. These findings highlight the importance of cage design (e.g., surface area), placement on the endplate, and trabecular bone quality on subsidence. These results may help surgeons during cage selection for lumbar fusion procedures to mitigate adverse events such as cage subsidence.

Disc degeneration promotes regional inhomogeneity in the trabecular morphology of loaded rat tail vertebrae

Background

There is a close relationship between the vertebral trabecular morphology and the condition of the associated disc.

Objective

The relationship between disc degeneration and vertebral trabecular inhomogeneity is unclear. This study aimed to analyse the regional changes of vertebral trabecular morphology after disc degeneration.

Methods

Thirty male Sprague–Dawley rats were randomly assigned to five groups. Group 1 served as an experimental group for the assessment of disc degeneration induced by needle puncture. Group 2 served as a sham group for trabecular morphology analysis. In Group 3, rats had their tail bent between the eighth and tenth coccygeal vertebrae. In Group 4, the tail of rats was bent with a compression load of 4.5 N. In Group 5, rats first underwent disc degeneration induced by a needle puncture before their tail was bent with a compressive load of 4.5 N. Magnetic resonance imaging was performed on all groups, and histological examination was performed on rodents from Group 1. The ninth coccygeal vertebrae of rats from Groups 2–5 were scanned by Micro-computed tomography. Trabecular morphologic changes were assessed in the concave and convex regions by bone volume fraction, trabecular number, trabecular thickness and trabecular separation.

Results

Vertebral trabecular morphology in the concave region improved significantly, whereas the convex region was of significantly lower trabecular morphologic parameters with disc degeneration. The difference in trabecular morphologic parameters between the convex and concave regions increased significantly after disc degeneration.

Conclusion

Disc degeneration promotes regional inhomogeneity in the vertebral trabecular morphology, with the convex region of the vertebrae having the worse trabecular bone morphology than the concave region.

The translational potential of this article

Our study indicates that disc degeneration promotes regional inhomogeneity in the vertebral trabecular morphology. Regional variations in trabecular microarchitecture are helpful to predict vertebral fragility. This may help to elucidate the mechanisms by which disc degeneration contributes to vertebral fracture.

Variation in human vertebral body strength for vertebral body samples from different locations in segments L1-L5

BACKGROUND

The human spine, in particular the lumbar spine, is subject to significant compressive and bending stresses, which affect the structure of the bone tissue of the vertebrae. The more heterogeneous the structure of the spongy bone tissue, the less resistant the whole vertebral body. It is therefore necessary to establish variations in bone strength parameters within one particular vertebral body.

METHODS

The research material comprised human L1-L5 lumbar vertebrae sampled from 15 donors aged 29-35. A total of 975 samples prepared from the collected material were subjected to compressive and bending strength tests. The samples for the tests were collected from carefully selected locations in order to discover the strength properties of various parts of the vertebral body.

FINDINGS

In the case of sample 2 (located in the posterior part of the vertebra, at mid-height) the stress values were the lowest and there were statistically significant differences compared to other samples. Moreover the value of compressive force in this case was lower for vertebrae with higher numbers. Top and bottom samples demonstrated statistically significant higher mean values of destructive stress. In terms of the bending strength test, the mean value of destructive stress in all lumbar vertebrae for all samples increased for vertebrae with higher numbers.

INTERPRETATION

The spongy tissue in healthy vertebral bodies has a very heterogeneous structure. This may be due to the presence of the nutrient canal and the arc structure allowing more springy movement and improved transfer of loads by the vertebral body.

Long term prognosis of Scheuermann's disease: The association with fragility fracture - The MINOS cohort

The aim was to assess the association of Scheuermann's disease (SCD) with fracture risk (vertebral, peripheral) and bone mineral density (BMD) in older men. SCD was assessed on the baseline lateral spine radiographs using the Berlin criteria in 766 men aged 50-85. We evaluated the association of SCD and its diagnostic criteria with incident fracture (vertebral over 7.5 years, peripheral over 10 years) and BMD (baseline). SCD prevalence was 25.2%. SCD and its criteria showed inconsistent associations with BMD at different skeletal sites. Eighty-four men had incident fractures. After adjustment for age, weight, spine BMD, prevalent vertebral fractures, prior falls and score of disc space narrowing due to osteoarthritis (DSN-OA), SCD was not associated with vertebral fracture risk. Vertebral endplate irregularities (EI), one of its diagnostic criteria, were associated with higher vertebral fracture risk (OR = 3.26, 95% CI: 1.34-7.94, p < 0.01). Vertebral fracture risk was higher in men with EI and low spine BMD vs. men without these characteristics (OR = 12.84, 95% CI: 3.12-52.83, p < 0.005). EI was associated with higher vertebral fracture risk in men without severe DSN-OA and without prevalent vertebral fractures. Peripheral fracture risk was lower in men with SCD (HR = 0.39, 95% CI: 0.18-0.83, p < 0.02) and EI. Peripheral fracture risk was higher in men without SCD who had low femoral neck BMD vs. men with SCD and normal BMD (HR = 4.68, 95% CI: 1.09-20.03, p < 0.05). In conclusion, EI were associated with high vertebral fracture risk. SCD and EI were associated with lower peripheral fracture risk. The associations of SCD and its criteria with BMD were inconsistent.

Dynamic adaptation of vertebral endplate and trabecular bone following annular injury in a rat model of degenerative disc disease

BACKGROUND CONTEXT

Degenerative disc disease (DDD) is associated with longitudinal remodeling of paravertebral tissues. Although chronic vertebral changes in advanced stages of DDD are well-studied, very little data exists on acute vertebral bone remodeling at the onset and progression of DDD.

PURPOSE

To longitudinally characterize bony remodeling in a rodent model of disc injury-induced DDD.

STUDY DESIGN

In vivo animal study involving a rat annulus fibrosus injury model of DDD.

METHODS

Eight female Lewis rats were assigned to intervertebral disc (IVD) injury (Puncture) or sham surgery (Sham). All rats underwent anterior, transperitoneal approach to the lumbar spine, and Puncture rats underwent annulus fibrosus injury at the L3-L4 and L5-L6 IVDs (n = 8 per group). Live micro computed tomography imaging (10-μm voxel size) was performed 1 week before surgery and postoperatively at 2-week intervals up to a 12-week endpoint. Bone morphology and densitometry of the cranial vertebral body and bony endplate were analyzed and reported with respect to the preoperative baseline scan. Sagittal Safranin-O/Fast-Green and Toluidine Blue histology evaluated using the Rutges IVD score and a custom vertebral endplate score.

RESULTS

Vertebral trabecular tissue mineral density (TMD), vertebral trabecular spacing, endplate TMD, and endplate apparent bone mineral density were all significantly greater in Puncture compared with Sham at 4 weeks and each subsequent timepoint. Puncture rats exhibited marginally lower endplate total volume. Anterior endplate osteophyte formation and central physeal ossification were observed in Puncture rats. Endpoint histological analysis demonstrated moderate evidence of IVD degeneration, indicating that vertebral bone adaptation occurs in the acute phases of DDD onset and progression.

CONCLUSIONS

Annulus injury-induced DDD leads to acute and progressive changes to the morphology and densitometry of bone in the adjacent vertebral bodies and endplates.

Therapeutic effects of new-type hydraulic delivery vertebroplasty, balloon kyphoplasty and conventional pusher-type vertebroplasty on single segmental osteoporotic vertebral compression fracture

This study aims to evaluate safety and practicality in clinical application for better guidance of single segmental osteoporotic vertebral compression fractures treatment. From May 2012 to September 2013, a total of 188 cases of patients with fractures, who received different treatment, were incorporated in the study and then divided into: group A (n=59), conventional pusher-type vertebroplasty; group B (n=54), balloon kyphoplasty; group C (n=60), new-type hydraulic delivery vertebroplasty treatment. The overall follow-up rate was 92.02%. Postoperative visual analogue scale (VAS) and Oswestry disability index (ODI) scores were significantly improved more than those of the preoperative scores in the three groups. Bone cement injection volumes in group A were significantly lower than those in group B and group C. Vertebral height recovery rates among groups were obviously different, showing statistical significance. After a year of follow-up, the vertebral height recovery outcome in group A was obviously poorer than that in group B and group C. A poorer outcome in group B was also found when compared with group C. In addition, the vertebral height restoration had a certain degree of loss, with the loss rate of 20.5, 14.0 and 7.5% in the three groups, respectively. Three operation methods have equivalent effects in the improvement of symptoms and functional recovery. Therefore, the new-type hydraulic delivery vertebroplasty provides a relatively more concise operation and shorter operation time, displaying more outstanding performance of clinical efficacy in spinal reconstruction and reduction of complications risks by evaluating the diffusion of the bone cement, vertebral height restoration rate and postoperative complications.

Contribution of the endplates to disc degeneration

Purpose of review

The endplates form the interface between the rigid vertebral bodies and compliant intervertebral discs. Proper endplate function involves a balance between conflicting biomechanical and nutritional demands. This review summarizes recent data that highlight the importance of proper endplate function and the relationships between endplate dysfunction, adjacent disc degeneration, and axial low back pain.

Recent findings

Changes to endplate morphology and composition that impair its permeability associate with disc degeneration. Endplate damage also associates with disc degeneration, and the progression of degeneration may be accelerated and the chronicity of symptoms heightened when damage coincides with evidence of adjacent bone marrow lesions.

Summary

The endplate plays a key role in the development of disc degeneration and low back pain. Clarification of the mechanisms governing endplate degeneration and developments in clinical imaging that enable precise evaluation of endplate function and dysfunction will distinguish the correlative vs. causative nature of endplate damage and motivate new treatments that target pathologic endplate function.