Biomechanics of the aging spine

From Modic to Disc Endplate Bone Marrow Complex - The Natural Course and Clinical Implication of Vertebral Endplate Changes

STUDY DESIGN

Review article.

OBJECTIVES

A review of literature on the epidemiology, natural course, pathobiology and clinical implications of vertebral endplate changes.

METHODS

A literature search was performed using the Cochrane Database of Systematic Reviews, EMBASE, and PubMed. Studies published over the last 10 years were analysed. The searches were performed using Medical Subject Headings terms, and the subheadings used were "Vertebral endplate changes", "Modic changes", "Disc Endplate Bone Marrow complex".

RESULTS

The disc, endplate (EP), and bone marrow region of the spine constitute a unified morphological and functional unit, with isolated degeneration of any one structure being uncommon. Disc degeneration causes endplate defects, which result in direct communication and a constant cross-talk between the disc and the vertebral body. This may result in a persistent inflammatory state of the vertebral bone marrow, serving as a major pain generator. This review article focuses on vertebral endplate changes and how the current understanding has progressed from the Modic classification to the Disc Endplate Bone Marrow complex classification. It provides a clear portrayal of the natural course of these alterations and their clinical implications in low back pain.

CONCLUSIONS

In light of the heightened interest and current prominence of vertebral endplate changes within the spine community, we must progress beyond the Modic changes to achieve a comprehensive understanding. The DEBM complex classification will play a major part in disc degeneration research and clinical care, representing a considerable advancement in our understanding of the vertebral endplate changes over the classical Modic changes.

Dynamic in vivo 3D atlantooccipital kinematics during multiplanar physiologic motions

Normal biomechanics of the upper cervical spine, particularly at the atlantooccipital joint, remain poorly characterized. The purpose of this study was to determine the intervertebral kinematics of the atlantooccipital joint (occiput-C1) during three-dimensional in vivo physiologic movements. Twenty healthy young adults performed dynamic flexion/extension, axial rotation, and lateral bending while biplane radiographs were collected at 30 images per second. Motion at occiput-C1 was tracked using a validated volumetric model-based tracking process that matched subject-specific CT-based bone models to the radiographs. The occiput-C1 total range of motion (ROM) and helical axis of motion (HAM) was calculated for each movement. During flexion/extension, the occiput-C1 moved almost exclusively in-plane (ROM: 17.9 ± 6.9°) with high variability in kinematic waveforms (6.3°) compared to the in-plane variability during axial rotation (1.4°) and lateral bending (0.9°) movements. During axial rotation, there was small in-plane motion (ROM: 4.2 ± 2.5°) compared to out-of-plane flexion/extension (ROM: 12.7 ± 5.4°). During lateral bending, motion occurred in-plane (ROM: 9.0 ± 3.1°) and in the plane of flexion/extension (ROM: 7.3 ± 2.7°). The average occiput-C1 axis of rotation intersected the sagittal and coronal planes 7 mm to 18 mm superior to the occipital condyles. The occiput-C1 axis of rotation pointed 60° from the sagittal plane during axial rotation but only 10° from the sagittal plane during head lateral bending. These novel results are foundational for future work on upper cervical spine kinematics.

Three Stages on Magnetic Resonance Imaging of Lumbar Degenerative Spine

PURPOSES

To propose a new lumbar degenerative staging system using the current radiological classification system.

METHODS

A cross-sectional analysis of retrospective databases between January 2018 and December 2022 was performed. Total of 410 patients for Modic changes, paravertebral muscle fat infiltration, disc degeneration, articular process degeneration, vertebral endplate degeneration and other structures, and disc displacement, Spondylolisthesis, and stenosis, and grouped patients according to stage were assessed. Visual analog scale, Japanese Orthopaedic Association, and Oswestry Disability Index scores were used to assess low back pain strength, neurological function, and quality of life, respectively.

RESULTS

The lumbar degeneration staging system consists of 8 variables, which can be divided into 3 steps: early, middle and late, and the correlation between each variable is strong (P < 0.05). The later the staging, the worse the Japanese Orthopaedic Association, visual analog scale, and Oswestry Disability Index scores.

CONCLUSIONS

Patients with later stages have worse clinical scores. This staging system recommends a uniform classification to assess lumbar degeneration.

Degenerative Thoracic Myelopathy: A Scoping Review of Epidemiology, Genetics, and Pathogenesis

STUDY DESIGN

Literature Review.

OBJECTIVE

Myelopathy affecting the thoracic spinal cord can arise secondary to several aetiologies which have similar presentation and management. Consequently, there are many uncertainties in this area, including optimal terminology and definitions. Recent collaborative cervical spinal research has led to the proposal and subsequent community adoption of the name degenerative cervical myelopathy(DCM), which has facilitated the establishment of internationally-agreed research priorities for DCM. We put forward the case for the introduction of the term degenerative thoracic myelopathy(DTM) and degenerative spinal myelopathy(DSM) as an umbrella term for both DCM and DTM.

METHODS

Following PRISMA guidelines, a systematic literature search was performed to identify degenerative thoracic myelopathy literature in Embase and MEDLINE.

RESULTS

Conditions encompassed within DTM include thoracic spondylotic myelopathy, ossification of the posterior longitudinal ligament, ossification of the ligamentum flavum, calcification of ligaments, hypertrophy of ligaments, degenerative disc disease, thoracic osteoarthritis, intervertebral disc herniation, and posterior osteophytosis. The classic presentation includes girdle pain, gait disturbance, leg weakness, sensory disturbance, and bladder or bowel dysfunction, often with associated back pain. Surgical management is typically favoured with post-surgical outcomes dependent on many factors, including the causative pathology, and presence of additional stenosis.

CONCLUSION

The clinical entities encompassed by the term DTM are interrelated, can manifest concurrently, and present similarly. Building on the consensus adoption of DCM in the cervical spine and the recent proposal of degenerative cervical radiculopathy(DCR), extending this common nomenclature framework to the terms degenerative spinal myelopathy and degenerative thoracic myelopathy will help improve recognition and communication.

Stepwise reduction of bony density in patients induces a higher risk of annular tears by deteriorating the local biomechanical environment

BACKGROUND CONTEXT

The relationship between osteoporosis and intervertebral disc degeneration (IDD) remains unclear. Considering that annular tear is the primary phenotype of IDD in the lumbar spine, the deteriorating local biomechanical environment may be the main trigger for annular tears.

PURPOSE

To investigate whether poor bone mineral density (BMD) in the vertebral bodies may increase the risk of annular tears via the degradation of the local biomechanical environment.

STUDY DESIGN

This study was a retrospective investigation with relevant numerical mechanical simulations.

PATIENT SAMPLE

A total of 64 patients with low back pain (LBP) and the most severe IDD in the L4-L5 motion segment were enrolled.

OUTCOME MEASURES

Annulus integration status was assessed using diffusion tensor fibre tractography (DTT). Hounsfield unit (HU) values of adjacent vertebral bodies were employed to determine BMD. Numerical simulations were conducted to compute stress values in the annulus of models with different BMDs and body positions.

METHODS

The clinical data of the 64 patients with low back pain were collected retrospectively. The BMD of the vertebral bodies was measured using the HU values, and the annulus integration status was determined according to DTT. The data of the patients with and without annular tears were compared, and regression analysis was used to identify the independent risk factors for annular tears. Furthermore, finite element models of the L4-L5 motion segment were constructed and validated, followed by estimating the maximum stress on the post and postlateral interfaces between the superior and inferior bony endplates (BEPs) and the annulus.

RESULTS

Patients with lower HU values in their vertebral bodies had significantly higher incidence rates of annular tears, with decreased HU values being an independent risk factor for annular tears. Moreover, increased stress on the BEP-annulus interfaces was associated with a stepwise reduction of bony density (ie, elastic modulus) in the numerical models.

CONCLUSIONS

The stepwise reduction of bony density in patients results in a higher risk of annular tears by deteriorating the local biomechanical environment. Thus, osteoporosis should be considered to be a potential risk factor for IDD biomechanically.

Bioenergetic dysfunction in the pathogenesis of intervertebral disc degeneration

Intervertebral disc (IVD) degeneration is a frequent cause of low back pain and is the most common cause of disability. Treatments for symptomatic IVD degeneration, including conservative treatments such as analgesics, physical therapy, anti-inflammatories and surgeries, are aimed at alleviating neurological symptoms. However, there are no effective treatments to prevent or delay IVD degeneration. Previous studies have identified risk factors for IVD degeneration such as aging, inflammation, genetic factors, mechanical overload, nutrient deprivation and smoking, but metabolic dysfunction has not been highlighted. IVDs are the largest avascular structures in the human body and determine the hypoxic and glycolytic features of nucleus pulposus (NP) cells. Accumulating evidence has demonstrated that intracellular metabolic dysfunction is associated with IVD degeneration, but a comprehensive review is lacking. Here, by reviewing the physiological features of IVDs, pathological processes and metabolic changes associated with IVD degeneration and the functions of metabolic genes in IVDs, we highlight that glycolytic pathway and intact mitochondrial function are essential for IVD homeostasis. In degenerated NPs, glycolysis and mitochondrial function are downregulated. Boosting glycolysis such as HIF1α overexpression protects against IVD degeneration. Moreover, the correlations between metabolic diseases such as diabetes, obesity and IVD degeneration and their underlying molecular mechanisms are discussed. Hyperglycemia in diabetic diseases leads to cell senescence, the senescence-associated phenotype (SASP), apoptosis and catabolism of extracellualr matrix in IVDs. Correcting the global metabolic disorders such as insulin or GLP-1 receptor agonist administration is beneficial for diabetes associated IVD degeneration. Overall, we summarized the recent progress of investigations on metabolic contributions to IVD degeneration and provide a new perspective that correcting metabolic dysfunction may be beneficial for treating IVD degeneration.

Changes in the centre of rotation and the anterior bone loss of the vertebral body in Mobi-C artificial disc replacement segments after cervical hybrid surgery: a retrospective study

OBJECTIVE

To examine the short-term efficacy and imaging results of using the Mobi-C in cervical hybrid surgery on 2-level cervical spondylolisthesis. To observe post-operative changes in the flexion-extension centre of rotation (FE-COR) and anterior bone loss (ABL) of the anterior cervical disc replacement (ACDR) segment.

METHODS

Forty-two patients (20 males and 22 females, aged 42‒67 years) who underwent cervical hybrid surgery were retrospectively analysed. Their ACDR segment used Mobi-C, and the fusion segment used ROI-C, with a follow-up of 25‒42 months (31.1 ± 4.8 months). The modified Japanese Orthopaedic Association (mJOA) score, Neck Disability Index (NDI), and visual analogue scale (VAS) were used to assess clinical outcomes. Pre-operative, 6-month post-operative, and final follow-up radiographs were collected to compare total cervical spine curvature (C2-C7), curvature of the operated segments, range of motion (ROM) in the total cervical spine, operated segmental ROM, ACDR segmental ROM, and operated adjacent segmental ROM. The height of the superior articular process (HSAP), the orientation of zygapophyseal joint spaces (OZJS), and the length of the superior articular surface (LSAS) were measured. The FE-COR of the ACDR segment was measured using the mid-plumb line method. The translation distance of the Mobi-C was measured. The degree of disc degeneration in the adjacent segment, bony fusion of the ACDF segment, and ABL of the upper and lower vertebra of the ACDR segment were observed.

RESULTS

In our group, all patients have shown improvements in their postoperative mJOA, NDI, and VAS scores. Overall cervical ROM and surgical segmental ROM decreased (P < 0.05). However, there was no significant decrease in ACDR segmental ROM and upper or lower adjacent segmental ROM compared with pre-operatively (P > 0.05). For FE-COR-X, only the last follow-up compared with pre-surgery showed statistical significance (46.74 ± 7.71% vs. 50.74 ± 6.92%, P < 0.05). For FE-COR-Y, the change was statistically significant at both 6 months post-operation and the final follow-up compared to pre-operation (45.37% ± 21.11% vs. 33.82% ± 10.87%, 45. 37% ± 21.11% vs. 27.48% ± 13.58%, P < 0.05). No significant difference in the Mobi-C translation distance was observed (P > 0.05). Moreover, the difference in HSAP was not statistically significant at each node (P > 0.05). The OZJS and LSAS were significantly different at the final follow-up compared to the pre-operative period (P < 0.05). All the ACDF segments were observed in a stable condition at the final follow-up. Furthermore, 9 of the adjacent segments showed imaging ASD (9/82, 10.98%), and all were present at the last follow-up, of which 6 were mild, and 3 were moderate. Twenty of the 42 Mobi-C segments had no significant ABL (grade 0) 6 months post-operatively (47.62%). Sixteen cases (38.10%) showed mild ABL (grade 1), and 6 cases (14.28%) showed moderate ABL (grade 2). No severe ABL occurred.

CONCLUSION

The cervical hybrid surgery using Mobi-C artificial cervical discs can achieve satisfactory results. The Mobi-C segmental FE-COR-X shows a slow forward shift trend, and FE-COR-Y drops noticeably within 6 months post-surgery before stabilizing. It's common to see mild to moderate ABL after cervical hybrid surgery using Mobi-C, and significant progression is unlikely in the short term. Furthermore, changes in the FE-COR after hybrid surgery in the Mobi-C segment might not affect clinical outcomes.

IVD fibrosis and disc collapse comprehensively aggravate vertebral body disuse osteoporosis and zygapophyseal joint osteoarthritis by posteriorly shifting the load transmission pattern

BACKGROUND

Disuse is a typical phenotype of osteoporosis, but the underlying mechanism has yet to be identified in elderly patients. Disc collapse and intervertebral disc (IVD) fibrosis are two main pathological changes in IVD degeneration (IDD) progression, given that these changes affect load transmission patterns, which may lead to disuse osteoporosis of vertebral bodies and zygapophyseal joint (ZJ) osteoarthritis (ZJOA) biomechanically.

METHODS

Clinical data from 59 patients were collected retrospectively. Patient vertebral bony density, ZJOA grade, and disc collapse status were judged via CT. The IVD fibrosis grade was determined based on the FA measurements. Regression analyses identified potential independent risk factors for osteoporosis and ZJOA. L4-L5 numerical models with and without disc collapse and IVD fibrosis were constructed; stress distributions on the bony endplate (BEP) and zygapophyseal joint (ZJ) cartilages were computed in models with and without disc collapse and IVD fibrosis.

RESULTS

A significantly lower disc height ratio and significantly greater FA were recorded in patients with ZJOA. A significant correlation was observed between lower HU values and two parameters related to IDD progression. These factors were also proven to be independent risk factors for both osteoporosis and ZJOA. Correspondingly, compared to the intact model without IDD. Lower stress on vertebral bodies and greater stress on ZJOA can be simultaneously recorded in models of disc collapse and IVD fibrosis.

CONCLUSIONS

IVD fibrosis and disc collapse simultaneously aggravate vertebral body disuse osteoporosis and ZJOA by posteriorly shifting the load transmission pattern.

Intraoperative capsule protection can reduce the potential risk of adjacent segment degeneration acceleration biomechanically: an in silico study

BACKGROUND

The capsule of the zygapophyseal joint plays an important role in motion segmental stability maintenance. Iatrogenic capsule injury is a common phenomenon in posterior approach lumbar interbody fusion operations, but whether this procedure will cause a higher risk of adjacent segment degeneration acceleration biomechanically has yet to be identified.

METHODS

Posterior lumbar interbody fusion (PLIF) with different grades of iatrogenic capsule injury was simulated in our calibrated and validated numerical model. By adjusting the cross-sectional area of the capsule, different grades of capsule injury were simulated. The stress distribution on the cranial motion segment was computed under different loading conditions to judge the potential risk of adjacent segment degeneration acceleration.

RESULTS

Compared to the PLIF model with an intact capsule, a stepwise increase in the stress value on the cranial motion segment can be observed with a step decrease in capsule cross-sectional areas. Moreover, compared to the difference between models with intact and slightly injured capsules, the difference in stress values was more evident between models with slight and severe iatrogenic capsule injury.

CONCLUSION

Intraoperative capsule protection can reduce the potential risk of adjacent segment degeneration acceleration biomechanically, and iatrogenic capsule damage on the cranial motion segment should be reduced to optimize patients' long-term prognosis.

Rotation-traction manipulation induced intradiskal pressure changes in cervical spine-an in vitro study

Objective: Evaluate the effect of rotation-traction manipulation on intradiskal pressure in human cervical spine specimen with different force and duration parameters, and compare the intradiskal pressure changes between rotation-traction manipulation and traction. Methods: Seven human cervical spine specimens were included in this study. The intradiskal pressure was measured by miniature pressure sensor implanting in the nucleus pulposus. rotation-traction manipulation and cervical spine traction were simulated using the MTS biomechanical machine. Varied thrust forces (50N, 150N, and 250N) and durations (0.05 s, 0.1 s, and 0.15 s) were applied during rotation-traction manipulation with Intradiscal pressure recorded in the neutral position, rotation-anteflexion position, preloading, and thrusting phases. Futuremore, we documented changes in intradiscal pressure during cervical spine traction with different loading forces (50N, 150N, and 250N). And a comparative analysis was performed to discern the impact on intradiscal pressure between manipulation and traction. Results: Manipulation application induced a significant reduction in intradiscal pressure during preloading and thrusting phases for each cervical intervertebral disc (p < 0.05). When adjusting thrust parameters, a discernible decrease in intradiscal pressure was observed with increasing thrust force, and the variations between different thrust forces were statistically significant (p < 0.05). Conversely, changes in duration did not yield a significant impact on intradiscal pressure (p > 0.05). Additionally, after traction with varying loading forces (50N, 150N, 250N), a noteworthy decrease in intradiscal pressure was observed (p < 0.05). And a comparative analysis revealed that rotation-traction manipulation more markedly reduced intradiscal pressure compared to traction alone (p < 0.05). Conclusion: Both rotation-traction manipulation and cervical spine traction can reduce intradiscal pressure, exhibiting a positive correlation with force. Notably, manipulation elicits more pronounced and immediate decompression effect, contributing a potential biomechanical rationale for its therapeutic efficacy.

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

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

Cartilaginous endplates: A comprehensive review on a neglected structure in intervertebral disc research

The cartilaginous endplates (CEP) are key components of the intervertebral disc (IVD) necessary for sustaining the nutrition of the disc while distributing mechanical loads and preventing the disc from bulging into the adjacent vertebral body. The size, shape, and composition of the CEP are essential in maintaining its function, and degeneration of the CEP is considered a contributor to early IVD degeneration. In addition, the CEP is implicated in Modic changes, which are often associated with low back pain. This review aims to tackle the current knowledge of the CEP regarding its structure, composition, permeability, and mechanical role in a healthy disc, how they change with degeneration, and how they connect to IVD degeneration and low back pain. Additionally, the authors suggest a standardized naming convention regarding the CEP and bony endplate and suggest avoiding the term vertebral endplate. Currently, there is limited data on the CEP itself as reported data is often a combination of CEP and bony endplate, or the CEP is considered as articular cartilage. However, it is clear the CEP is a unique tissue type that differs from articular cartilage, bony endplate, and other IVD tissues. Thus, future research should investigate the CEP separately to fully understand its role in healthy and degenerated IVDs. Further, most IVD regeneration therapies in development failed to address, or even considered the CEP, despite its key role in nutrition and mechanical stability within the IVD. Thus, the CEP should be considered and potentially targeted for future sustainable treatments.

Osteoporosis and Vertebral Column

Background

Osteoporosis is an age-related metabolic disease which has a significant impact on bone health and overall quality of life. It is gaining importance as a major medical consideration with the rapid increase in geriatric population globally. It increases the risk of vertebral fractures, progressive spinal deformities and neurological complications, contributing significantly to morbidity and mortality. Increase in life expectancy and advancement of medical technology has led to an increase in the proportion of geriatric patients undergoing orthopaedic procedures. It is becoming vital to adequately evaluate, investigate and treat osteoporosis before planning spinal surgery, especially spinal fusions and instrumentation.

Content

Historically, osteoporosis was considered a contraindication to spine surgery adding to the burden of Disability Adjusted Life Years (DALYs) and mortality. Conversely, osteoporotic patients who underwent spine surgery were not adequately optimized, leading to an increase in failure and complication rates. Better understanding of the pathophysiology of osteoporosis and the biomechanics of an osteoporotic spine with knowledge of current standards of treatment of osteoporosis facilitate the timely and adequate management of this disease. Advances in surgical and anaesthetic techniques facilitate successful surgeries on high-risk elderly and osteoporotic patients with multiple comorbidities allowing for a significantly high predictability for long-term positive outcomes.This article discusses the biomechanics of the osteoporotic spine, the diagnosis and management of osteoporotic patients with spinal disease, and the new treatments, recommendations, surgical indications, strategies and advances in instrumentation in patients with osteoporosis who require spinal surgery.

Implications

In this article, the authors aim to provide a generalized overview for better understanding of the pathophysiological processes underlying osteoporosis in the vertebral column. This review provides a comprehensive set of guidelines for overall health and management of spine patients with pathologies, either caused by or compounded with osteoporosis. An overview of current techniques, strategies and technologies designed to address the challenges associated with spine surgery in osteoporotic patients is also outlined.

Sources

Content for this article has been sourced from routinely cited articles available via PubMed, from National Institute of Health consensus development conference, from the recommendations by World Health Organization technical report series, from previous articles by the authors and from the protocols established by the authors in their clinical practice based on experience and detailed case reviews.

The role of muscle degeneration and spinal balance in the pathophysiology of lumbar spinal stenosis: Study protocol of a translational approach combining in vivo biomechanical experiments with clinical and radiological parameters

OBJECTIVE

To describe a study protocol for investigating the functional association between posture, spinal balance, ambulatory biomechanics, paraspinal muscle fatigue, paraspinal muscle quality and symptoms in patients with symptomatic lumbar spinal stenosis (sLSS) before and 1-year after elective surgical intervention.

DESIGN

Single-centre prospective, experimental, multimodal (clinical, biomechanical, radiological) study with three instances of data collection: baseline (study visit 1), 6-month follow-up (remote) and 1-year follow-up (study visit 2). Both study visits include an in vivo experiment aiming to elicit paraspinal muscle fatigue for postural assessment in a non-fatigued and fatigued state.

EXPERIMENTAL PROTOCOL

At baseline and 1-year follow-up, 122 patients with sLSS will be assessed clinically, perform the back-performance scale assessment and complete several patient-reported outcome measure (PROMs) questionnaires regarding overall health, disease-related symptoms and kinesiophobia. Posture and biomechanical parameters (joint kinematics, kinetics, surface electromyography, back curvature) will be recorded using an optoelectronic system and retroreflective markers during different tasks including overground walking and movement assessments before and after a modified Biering-Sørensen test, used to elicit paraspinal muscle fatigue. Measurements of muscle size and quality and the severity of spinal stenosis will be obtained using magnetic resonance imaging (MRI) and sagittal postural alignment data from EOS radiographies. After each study visit, physical activity level will be assessed during 9 days using a wrist-worn activity monitor. In addition, physical activity level and PROMs will be assessed remotely at 6-month follow-up.

CONCLUSION

The multimodal set of data obtained using the study protocol described in this paper will help to expand our current knowledge on the pathophysiology, biomechanics, and treatment outcome of degenerative sLSS. The results of this study may contribute to defining and/or altering patient treatment norms, surgery indication criteria and post-surgery rehabilitation schedules.

TRIAL REGISTRATION

The protocol was approved by the regional ethics committee and has been registered at clinicaltrials.gov (NCT05523388).

Does Vitamin K2 Influence the Interplay between Diabetes Mellitus and Intervertebral Disc Degeneration in a Rat Model?

Intervertebral disc (IVD) degeneration is a common cause of low back pain in diabetes mellitus type 2 (T2DM) patients. Its pathogenesis and the vitamin (vit.) K2 influence on this disease remain unclear. Lumbar motion segments of male Zucker Diabetes Fatty (ZDF) rats (non-diabetic [control] and diabetic; fed without or with vit. K2) were used. Femur lengths and vertebral epiphyseal cross-section areas were measured. IVDs were histopathologically examined. Protein synthesis and gene expression of isolated IVD fibrochondrocytes were analyzed. T2DM rats showed histopathological IVD degeneration. Femur lengths and epiphyseal areas were smaller in T2DM rats regardless of vit. K2 feeding. Fibrochondrocytes synthesized interleukin (IL)-24 and IL-10 with no major differences between groups. Alpha smooth muscle actin (αSMA) was strongly expressed, especially in cells of vit. K2-treated animals. Gene expression of aggrecan was low, and that of collagen type 2 was high in IVD cells of diabetic animals, whether treated with vit. K2 or not. Suppressor of cytokine signaling (Socs)3 and heme oxygenase (Hmox)1 gene expression was highest in the cells of diabetic animals treated with vit. K2. Vit. K2 influenced the expression of some stress-associated markers in IVD cells of diabetic rats, but not that of IL-10 and IL-24.

Fixation-induced surgical segment's high stiffness and the damage of posterior structures together trigger a higher risk of adjacent segment disease in patients with lumbar interbody fusion operations

BACKGROUND

Adjacent segment disease (ASD) is a commonly reported complication after lumbar interbody fusion (LIF); changes in the mechanical environment play an essential role in the generation of ASD. Traditionally, fixation-induced high stiffness in the surgical segment was the main reason for ASD. However, with more attention paid to the biomechanical significance of posterior bony and soft structures, surgeons hypothesize that this factor may also play an important role in ASD.

METHODS

Oblique and posterior LIF operations have been simulated in this study. The stand-alone OLIF and OLIF fixed by bilateral pedicle screw (BPS) system have been simulated. The spinal process (the attachment point of cranial ligamentum complex) was excised in the PLIF model; the BPS system has also been used in the PLIF model. Stress values related to ASD have been computed under physiological body positions, including flexion, extension, bending, and axial rotations.

RESULTS

Compared to the stand-alone OLIF model, the OLIF model with BPS fixation suffers higher stress values under extension body position. However, there are no apparent differences under other loading conditions. Moreover, significant increases in stress values can be recorded in flexion and extension loading conditions in the PLIF model with posterior structures damage.

CONCLUSIONS

Fixation-induced surgical segment's high stiffness and the damage of posterior soft tissues together trigger a higher risk of ASD in patients with LIF operations. Optimizing BPS fixation methods and pedicle screw designs and reducing the range of posterior structures excision may be an effective method to reduce the risk of ASD.

Avoiding Spinal Implant Failures in Osteoporotic Patients: A Narrative Review

STUDY DESIGN

Narrative review.

OBJECTIVES

With an aging population, the prevalence of osteoporosis is continuously rising. As osseous integrity is crucial for bony fusion and implant stability, previous studies have shown osteoporosis to be associated with an increased risk for implant failure and higher reoperation rates after spine surgery. Thus, our review's purpose was to provide an update of evidence-based solutions in the surgical treatment of osteoporosis patients.

METHODS

We summarize the existing literature regarding changes associated with decreased bone mineral density (BMD) and resulting biomechanical implications for the spine as well as multidisciplinary treatment strategies to avoid implant failures in osteoporotic patients.

RESULTS

Osteoporosis is caused by an uncoupling of the bone remodeling cycle based on an unbalancing of bone resorption and formation and resulting reduced BMD. The reduction in trabecular structure, increased porosity of cancellous bone and decreased cross-linking between trabeculae cause a higher risk of complications after spinal implant-based surgeries. Thus, patients with osteoporosis require special planning considerations, including adequate preoperative evaluation and optimization. Surgical strategies aim towards maximizing screw pull-out strength, toggle resistance, as well as primary and secondary construct stability.

CONCLUSIONS

As osteoporosis plays a crucial role in the fate of patients undergoing spine surgery, surgeons need to be aware of the specific implications of low BMD. While there still is no consensus on the best course of treatment, multidisciplinary preoperative assessment and adherence to specific surgical principles help reduce the rate of implant-related complications.

Biomechanical responses of the human lumbar spine to vertical whole-body vibration in normal and osteoporotic conditions

BACKGROUND

The prevalence of osteoporosis is continuing to escalate with an aging population. However, it remains unclear how biomechanical behavior of the lumbar spine is affected by osteoporosis under whole-body vibration, which is considered a significant risk factor for degenerative spinal disease and is typically present when driving a car. Accordingly, the objective of this study was to compare the spine biomechanical responses to vertical whole-body vibration between normal and osteoporotic conditions.

METHODS

A three-dimensional finite-element model of the normal human lumbar spine-pelvis segment was developed using computed tomographic scans and was validated against experimental data. Osteoporotic condition was simulated by modifying material properties of bone tissues in the normal model. Transient dynamic analyses were conducted on the normal and osteoporotic models to compute deformation and stress in all lumbar motion segments.

FINDINGS

When osteoporosis occurred, vibration amplitudes of the vertebral axial displacement, disc bulge, and disc stress were increased by 32.1-45.4%, 25.7-47.1% and 23.0-42.7%, respectively. In addition, it was found that for both the normal and osteoporotic models, the response values (disc bugle and disc stress) were higher in L4-L5 and L5-S1 intervertebral discs than in other discs.

INTERPRETATION

Osteoporosis deteriorates the effect of whole-body vibration on lumbar spine, and the lower lumbar segments might have a higher likelihood of disc degeneration under whole-body vibration.

Quantitative Study of Vertebral Body and Paravertebral Muscle Degeneration Based on Dual-Energy Computed Tomography: Correlation With Bone Mineral Density

OBJECTIVES

This study aimed to quantify the degeneration of the vertebral body and paravertebral muscles using dual-energy computed tomography (DECT) and study its relationship with osteoporosis.

METHODS

A total of 130 patients with chronic low back pain were included in this study, and DECT scanning of the lumbar region was undertaken prospectively. By placing a standard quantitative computed tomography corrected phantom under the waist during the DECT procedure, bone mineral density (BMD) and the following quantitative parameters were obtained: calcium density (CaD), vertebral fat fraction (VFF), psoas major area, psoas major fat fraction, erector spinalis area, and erector spinalis fat fraction (ESFF). Independent sample t test and 1-way analysis of variance were used between different age-BMD groups. Pearson test was applied to determine correlations for all measurements, and a mathematical model of BMD was established through regression analysis.

RESULTS

Calcium density, VFF, psoas major area, psoas major fat fraction, erector spinalis area, and ESFF were significantly different among the age-BMD groups (P < 0.05), and BMD was significantly correlated with these parameters (P < 0.05). Calcium density, VFF, and ESFF were included in the BMD regression equation: BMD = 69.062 + 11.637 × CaD - 1.018 × VFF - 0.726 × ESFF (R2 = 0.860, F = 125.979, P < 0.001).

CONCLUSIONS

Degeneration of the vertebral body and paravertebral muscles can be quantitatively analyzed using DECT, and CaD, VFF, and ESFF were independent influencing factors of BMD.

Stepwise reduction of bone mineral density increases the risk of cage subsidence in oblique lumbar interbody fusion patients biomechanically: an in-silico study

BACKGROUND

Cage subsidence causes poor prognoses in patients treated by oblique lumbar interbody fusion (OLIF). Deterioration of the biomechanical environment initially triggers cage subsidence, and patients with low bone mineral density (BMD) suffer a higher risk of cage subsidence. However, whether low BMD increases the risk of cage subsidence by deteriorating the local biomechanical environment has not been clearly identified.

METHODS

OLIF without additional fixation (stand-alone, S-A) and with different additional fixation devices (AFDs), including anterolateral single rod screws (ALSRs) and bilateral pedicle screws (BPSs) fixation, was simulated in the L4-L5 segment of a well-validated finite element model. The biomechanical effects of different BMDs were investigated by adjusting the material properties of bony structures. Biomechanical indicators related to cage subsidence were computed and recorded under different directional moments.

RESULTS

Overall, low BMD triggers stress concentration in surgical segment, the highest equivalent stress can be observed in osteoporosis models under most loading conditions. Compared with the flexion-extension loading condition, this variation tendency was more pronounced under bending and rotation loading conditions. In addition, AFDs obviously reduced the stress concentration on both bony endplates and the OLIF cage, and the maximum stress on ALSRs was evidently higher than that on BPSs under almost all loading conditions.

CONCLUSIONS

Stepwise reduction of BMD increases the risk of a poor local biomechanical environment in OLIF patients, and regular anti-osteoporosis therapy should be considered an effective method to biomechanically optimize the prognosis of OLIF patients.

Species variation in the cartilaginous endplate of the lumbar intervertebral disc

Backgrounds

Cartilaginous endplate (CEP) plays an essential role in intervertebral disc (IVD) health and disease. The aim was to compare the CEP structure of lumbar IVD and to reveal the detailed pattern of integration between the CEP and bony endplate (BEP) from different species.

Methods

A total of 34 IVDs (5 human, 5 goat, 8 pig, 8 rabbit, and 8 rat IVDs) were collected, fixed and midsagittally cut; in each IVD, one‐half was used for histological staining to observe the CEP morphology, and the other half was used for scanning electron microscopy (SEM) analysis to measure the diameters and distributions of collagen fibers in the central and peripheral CEP areas and to observe the pattern of CEP‐BEP integration from different species.

Results

The human, pig, goat, and rabbit IVDs had the typical BEP‐CEP structure, but the rat CEP was directly connected with the growth plate. Human CEP was the thickest (896.95 ± 87.71 μm) among these species, followed by pig, goat, rat, and rabbit CEPs. Additionally, the mean cellular density of the rabbit CEP was the highest, which was 930 ± 202 per mm², followed by the rat, goat, pig, and human CEPs. In all the species, the collagen fiber diameter in the peripheral area was much bigger than that in the central area. The collagen fiber diameters of CEP from the human, pig, goat, and rat were distributed between 35 nm and 65 nm. The BEP and CEP were connected by the collagen from the CEP, aggregating into bundles or cross links with each other to form a network, and anchored to BEP.

Conclusions

Significant differences in the thickness, cellular density, and collagen characterization of CEPs from different species were demonstrated; the integration of BEP‐CEP in humans, pigs, goats, and rabbits was mainly achieved by the collagen bundles anchoring system, while the typical BEP‐CEP interface did not exist in rats.

Defining age-adjusted spinopelvic alignment thresholds: should we integrate BMI?

PURPOSE

To develop age- and BMI-adjusted alignment targets to improve patient-specific management and operative treatment outcomes.

METHODS

Retrospective review of a single-center stereographic database. ASD patients receiving operative or non-operative treatment, ≥ 18y/o with complete baseline (BL) ODI scores and radiographic parameters (PT, SVA, PILL, TPA) were included. Patients were stratified by age consistent with US-Normative values (norms) of SF-36(< 35, 35-55, 45-54, 55-64, 65-74, ≥ 75y/o), and dichotomized by BMI (Non-Obese < 30; Obese ≥ 30). Linear regression analysis established normative age- and BMI-specific radiographic thresholds, utilizing previously published age-specific US-Normative ODI values converted from SF-36 PCS (Lafage et al.), in conjunction with BL age and BMI means.

RESULTS

486 patients were included (Age: 52.5, Gender: 68.7%F, mean BMI: 26.2, mean ODI: 32.7), 135 of which were obese. Linear regression analysis developed age- and BMI-specific alignment thresholds, indicating PT, SVA, PILL, and TPA to increase with both increased age and increased BMI (all R > 0.5, p < 0.001). For non-obese patients, PT, SVA, PILL, and TPA ranged from 10.0, - 25.8, - 9.0, 3.1 in patients < 35y/o to 27.8, 53.4, 17.7, 25.8 in patients ≥ 75 y/o. Obese patients' PT, SVA, PILL, and TPA ranged from 10.5, - 7.6, - 7.1, 5.8 in patients < 35 y/o to 28.3, 67.0, 19.15, 27.7 in patients ≥ 75y/o. Normative SVA values in obese patients were consistently ≥ 10 mm greater compared to non-obese values, at all ages.

CONCLUSION

Significant associations exist between age, BMI, and sagittal alignment. While BMI influenced age-adjusted alignment norms for PT, SVA, PILL, and TPA at all ages, obesity most greatly influenced SVA, with normative values similar to non-obese patients who were 10 years older. Age-adjusted alignment thresholds should take BMI into account, calling for less rigorous alignment objectives in older and obese patients.

Deterioration of the fixation segment’s stress distribution and the strength reduction of screw holding position together cause screw loosening in ALSR fixed OLIF patients with poor BMD

The vertebral body’s Hounsfield unit (HU) value can credibly reflect patients’ bone mineral density (BMD). Given that poor bone-screw integration initially triggers screw loosening and regional differences in BMD and strength in the vertebral body exist, HU in screw holding planes should better predict screw loosening. According to the stress shielding effect, the stress distribution changes in the fixation segment with BMD reduction should be related to screw loosening, but this has not been identified. We retrospectively collected the radiographic and demographic data of 56 patients treated by single-level oblique lumbar interbody fusion (OLIF) with anterior lateral single rod (ALSR) screw fixation. BMD was identified by measuring HU values in vertebral bodies and screw holding planes. Regression analyses identified independent risk factors for cranial and caudal screw loosening separately. Meanwhile, OLIF with ALSR fixation was numerically simulated; the elastic modulus of bony structures was adjusted to simulate different grades of BMD reduction. Stress distribution changes were judged by computing stress distribution in screws, bone-screw interfaces, and cancellous bones in the fixation segment. The results showed that HU reduction in vertebral bodies and screw holding planes were independent risk factors for screw loosening. The predictive performance of screw holding plane HU is better than the mean HU of vertebral bodies. Cranial screws suffer a higher risk of screw loosening, but HU was not significantly different between cranial and caudal sides. The poor BMD led to stress concentrations on both the screw and bone-screw interfaces. Biomechanical deterioration was more severe in the cranial screws than in the caudal screws. Additionally, lower stress can also be observed in fixation segments’ cancellous bone. Therefore, a higher proportion of ALSR load transmission triggers stress concentration on the screw and bone-screw interfaces in patients with poor BMD. This, together with decreased bony strength in the screw holding position, contributes to screw loosening in osteoporotic patients biomechanically. The trajectory optimization of ALSR screws based on preoperative HU measurement and regular anti-osteoporosis therapy may effectively reduce the risk of screw loosening.

Overexpression of Aquaporin-3 Alleviates Hyperosmolarity-Induced Nucleus Pulposus Cell Apoptosis via Regulating the ERK1/2 Pathway

Intervertebral disc degeneration (IDD) is closely related to osmolarity, which fluctuates with daily activities, and hyperosmolarity may be a contributor to nucleus pulposus (NP) cells apoptosis. Aquaporin-3 (AQP-3) belongs to the family of aquaporins and mainly transports water and other small molecular proteins, which is reduced with the aging of the intervertebral disc. ERK1/2 pathway is one type of mitogen-activated protein kinase (MAPK) and is associated with cellular apoptosis. This study was aimed to investigate the effects of AQP-3 on NP cells apoptosis induced by a hyperosmolarity and focused on the role of the ERK1/2 signaling pathway. We found that NP apoptosis could be induced by hyperosmolarity (550 mOsm/kg), and downregulation of AQP-3 and inhibition of ERK1/2 could be simultaneously observed. Therefore, lentivirus was used to enhance the expression of AQP-3 to compare apoptosis between AQP-3-overexpressed NP cells and the control NP cells. The results showed that apoptosis could be alleviated by overexpression of AQP-3 and the activity of ERK1/2 could also be promoted. Furthermore, we found that the inhibitor U0126 could partly aggravate apoptosis of the AQP-3-overexpressed NP cells. In summary, our results suggested that overexpression of AQP-3 could protect against hyperosmolarity-induced NP cell apoptosis via promoting the activity of the ERK1/2 pathway. This study may shed light on a better understanding of the pathologic mechanism of IDD and bring AQP-3 into the therapeutic approaches for IDD treatment.

The Mismatch Between Bony Endplates and Grafted Bone Increases Screw Loosening Risk for OLIF Patients With ALSR Fixation Biomechanically

The mismatch between bony endplates (BEPs) and grafted bone (GB) triggers several complications biomechanically. However, no published study has identified whether this factor increases the risk of screw loosening by deteriorating the local stress levels. This study aimed to illustrate the biomechanical effects of the mismatch between BEP and GB and the related risk of screw loosening. In this study, radiographic and demographic data of 56 patients treated by single segment oblique lumbar interbody fusion (OLIF) with anterior lateral single rod (ALSR) fixation were collected retrospectively, and the match sufficiency between BEP and GB was measured and presented as the grafted bony occupancy rate (GBOR). Data in patients with and without screw loosening were compared; regression analyses identified independent risk factors. OLIF with different GBORs was simulated in a previously constructed and validated lumbosacral model, and biomechanical indicators related to screw loosening were computed in surgical models. The radiographic review and numerical simulations showed that the coronal plane’s GBOR was significantly lower in screw loosening patients both in the cranial and caudal vertebral bodies; the decrease in the coronal plane’s GBOR has been proven to be an independent risk factor for screw loosening. In addition, numerical mechanical simulations showed that the poor match between BEP and GB will lead to stress concentration on both screws and bone-screw interfaces. Therefore, we can conclude that the mismatch between the BEP and GB will increase the risk of screw loosening by deteriorating local stress levels, and the increase in the GBOR by modifying the OLIF cage’s design may be an effective method to optimize the patient’s prognosis.

Single-Cell RNA-Seq Analysis Reveals Macrophage Involved in the Progression of Human Intervertebral Disc Degeneration

Intervertebral disc degeneration (IDD) has been considered as the primary pathological mechanism that underlies low back pain. Understanding the molecular mechanisms underlying human IDD is imperative for making strategies to treat IDD-related diseases. Herein, we report the molecular programs, lineage progression patterns, and paths of cellular communications during the progression of IDD using single-cell RNA sequencing (scRNA-seq) on nucleus pulposus (NP) cells from patients with different grades of IDD undergoing discectomy. New subtypes of cells and cell-type-specific gene signatures of the metabolic homeostatic NP cells (Met NPC), adhesive NP cells (Adh NPC), inflammatory response NP cells (IR NPC), endoplasmic reticulum stress NP cells (ERS NPC), fibrocartilaginous NP cells (Fc NPC), and CD70 and CD82+ progenitor NP cells (Pro NPC) were identified. In the late stage of IDD, the IR NPC and Fc NPC account for a large proportion of NPC. Importantly, immune cells including macrophages, T cells, myeloid progenitors, and neutrophils were also identified, and further analysis showed that significant intercellular interaction between macrophages and Pro NPC occurred via MIF (macrophage migration inhibitory factor) and NF-kB signaling pathways during the progression of IDD. In addition, dynamic polarization of macrophage M1 and M2 cell subtypes was found in the progression of IDD, and gene set functional enrichment analysis suggested a significant role of the macrophage polarization in regulating cell metabolism, especially the Pro NPC. Finally, we found that the NP cells in the late degenerative stage were mainly composed of the cell types related to inflammatory and endoplasmic reticulum (ER) response, and fibrocartilaginous activity. Our results provided new insights into the identification of NP cell populations at single-cell resolution and at the relatively whole-transcriptome scale, accompanied by cellular communications between immune cells and NP cells, and discriminative markers in relation to specific cell subsets. These new findings present clues for effective and functional manipulation of human IDD-related bioremediation and healthcare.

Posterior epidural intervertebral disc migration and sequestration: A systematic review

Posterior epidural intervertebral disc migration and sequestration (PEIMS) is a rare and debilitating complication of degenerative disc disease. Radiological differential diagnosis is often challenging, complicating the accurate planning of appropriate treatment strategies. We systematically reviewed the literature on PEIMS, focusing on clinical-radiological features and available treatments. PubMed, Scopus, Web of Science, and Cochrane were searched to include studies reporting clinical data of patients with PEIMS. Clinical characteristics, treatment strategies, and functional outcomes were analyzed. We included 82 studies comprising 157 patients. Median age was 54 years (range, 19-91). PEIMSs occurred spontaneously (49.7%) or acutely in patients with underlying progressive degenerative disc disease (50.3%). The most common symptoms were lower-back pain (77.1%) and radiculopathy (66.2%), mainly involving the L5 nerve root (43.8%). PEIMSs were mostly detected at MRI (93%) and/or CT (7%), frequently located in the lumbar spine (81.5%). Median maximum PEIMS diameter was 2.4 cm (range, 1.2-5.0). Surgical debulking was completed in 150 patients (95.5%), sometimes coupled with decompressive laminectomy (65%) or hemilaminectomy (19.1%). Median follow-up time was 3 months (range, 0.5-36.0). Post-treatment symptomatic improvement was reported in 153 patients (97.5%), with total recovery in 118 (75.2%). All 7 patients (4.5%) who received conservative non-surgical management had total clinical recovery at ≤ 3 months follow-ups. PEIMS is a challenging entity that may severely quality-of-life in patients with degenerative disc disease. Surgical removal represents the gold standard to improve patient's functional status. Spine fusion and conservative strategies proved to be effective in some cases.

Thoracolumbar flexion dysfunction and thoracolumbar compression fracture in postmenopausal women: a single-center retrospective study

OBJECTIVE

To investigate whether thoracolumbar flexion dysfunctions increase the risk of thoracolumbar compression fractures in postmenopausal women.

METHODS

The records of postmenopausal women with thoracolumbar vertebral compression fractures and without vertebral compression fractures were surveyed. Demographic data, clinical data, and quantitative computed tomography (QCT) findings were compared between the groups. Chi-squared tests, unpaired t-tests, Spearman, and Mann-Whitney U were used to assess the group characteristics and proportions. The relationship between the risk of fracture and the difference of Cobb's angle of thoracolumbar segment (DCTL) was evaluated by logistic regression. DCTL was calculated by subtracting thoracolumbar Cobb's angles (TLCobb's) from thoracolumbar hyperflexion Cobb's angles (TLHCobb's). Quantitative computed tomography (QCT) values and spinal osteoarthritis (OA) of postmenopausal women in the two groups were compared.

RESULTS

102 of 312 were enrolled to the study group of postmenopausal women with the fracture, and 210 of 312 were enrolled to the control group of postmenopausal women without the fracture. There were significant differences in QCT values and spinal OA including disc narrowing (DSN) and osteophytes (OPH) between the two groups (p < 0.001 for all four). The risk of thoracolumbar compression fractures in the postmenopausal women with DCTL ≤ 8.7° was 9.95 times higher (95% CI 5.31-18.64) than that with > 8.7° after adjusting for age, BMI, and QCT values.

CONCLUSION

Low DCTL may be a risk factor of thoracolumbar compression fractures in postmenopausal women, and a DCTL ≤ 8.7° can be a threshold value of thoracolumbar compression fractures.

Effect of different attributes of the mimic human lumbar spine biomechanics material structure change by finite element analysis

In this study, we compared stress changes and quantity effect relationships from 3D finite element models of normal and degenerative lumbar segments. We further defined the mechanisms causing alterations in mechanical stability the control of normal and degenerative lumbar segments using traditional Chinese medicine. The characteristics of the stress change and the quantity effect relationships of the three-dimensional finite element model of normal and degenerative lumbar segments were compared. The mechanism(s) leading to changes in mechanical stability and the intervention and balance between normal and degenerative lumbar segments of the traditional Chinese medicine was analyzed. The change trend of stress and strain was compared with the three dimensional finite element model under different motion states of normal lumbar vertebrae. A 3D-FEM of degenerative lumbar segments L4 ~ 5 of the human spine was established to simulate the physiological and pathological changes of the lumbar spine in response to flexion, extension, lateral bending and torsion. The stress changes in the normal and degenerative lumbar vertebrae were assessed through external force interventions and the response to TCM. Stress in the degenerative lumbar vertebrae changed according the external load. Stress and strain were compared in the FEM model under a range of motion states. Components of the human lumbar vertebrae including the cortical vertebrae, cancellous bone, endplates, fibrous rings, and facet articular processes were investigated. The elastic modulus of the nerve roots and the posterior marginal structures of the vertebral body increased with lumbar degeneration. Under stress trends in normal lumbar and different degrees of degenerative lumbar structures including cortical bone, loose bone, terminal plate, fiber ring, nucleus, small articular processes, nerve roots and posterior structures. In normal lumbar spine, 20%, 50%, 70% lumbar degeneration, 106 different lumbar anterior flexion 30 and posterior extension with different external forces showed that ANOVA F was between 3.623 and 11.381 and P changed between 0.001 and 0.05.It is clear that in the lumbar movement segments under different pressure intervention, the changes in the degree of degeneration are significantly different from each constituent structure, among which the trend of expected change between the constituent structures of the lumbar anterior flexion 30 is particularly obvious. The stress distribution in the intervertebral discs were influenced by TCM, and the space in the spinal canal enlarged so that nerve root stress decreased, vertebral body stress increased, and facet processes and pedicle stress in the posterior regions exceeded those of the anterior flexion position. The internal stress of the intervertebral disc increased in the flexion compared to the extension position, gradually increasing from top to bottom. The stress concentration point of the degenerative lumbar disc is significantly greater than the stress in the normal lumbar disc stress distribution area, and increases with the degree of degeneration. Compared with the load capacity of normal lumbar and mild (15% reduction), moderate (40% reduction) lumbar disc protrusion model in bending, extension, axial rotation, lateral bending, the results found that the load transmission of lumbar disc degeneration model to different degrees has also changed, so its compression stiffness, strain distribution and size are also different. TCM can improve and treat lumbar disc disease through its ability to regulate the mechanical environment of degenerative lumbar vertebrae. Compared to the FEM models of the lumbar vertebrae, lumbar degenerative changes could be assessed in response to alterations in the biomechanical environment. These findings provide a scientific basis for the popularization and application of TCM to prevent and treat spinal degenerative disease.

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.

Is Preexisting Cervical Degeneration a Risk Factor for Poor Prognosis in Whiplash-Associated Disorder?

BACKGROUND

The term whiplash describes the acceleration-deceleration mechanism of injury to the cervical spine. Whiplash injuries present with a variety of clinical and psychological manifestations, collectively termed as whiplash-associated disorders (WADs). Although largely self-limiting, some patients may experience long-lasting symptoms. This review aimed to summarize the current literature regarding the predictive value of cervical degeneration in the prognosis of patients with WAD.

METHODS

A comprehensive search of the literature was performed. Nine studies were identified, including 894 patients, with an age range between 16 and 76 years.

RESULTS

A statistically significant association was found between moderate facet joint degeneration and nonrecovery. Although no association was established between isolated disc degeneration and nonrecovery, total cervical degeneration (facet joint + disc degeneration) was shown to correlate with nonrecovery.All included studies demonstrated the lack of correlation between preexisting disc degeneration and clinical outcomes. Four studies showed a significant correlation between cervical degeneration and poor prognosis following whiplash injury. A significantly higher proportion of patients who remained symptomatic at 2 years following a whiplash injury had preexisting degenerative changes.

CONCLUSIONS

This review highlights the presence of significant variability in the existing literature concerning WAD in terms of study methodology, definitions of cervical degeneration, and outcome measures. Degenerative changes of the facet joint lead to alterations in its biomechanics. Several cadaveric, biomechanical, and clinical studies have demonstrated facet joints as a source of pain in patients with chronic WAD. We present moderate evidence to suggest that preexisting facet joint degeneration is a negative prognostic indicator for long-lasting symptoms in WAD. Conversely, preexisting disc degeneration is not associated with chronicity of WAD symptoms. We propose facet joint instability due to facet joint capsule rupture as a potential mechanism for nonrecovery. Further studies are needed to inform our knowledge of the long-term sequelae of WAD among patients with preexisting cervicalspine degeneration.

Proper animal experimental designs for preclinical research of biomaterials for intervertebral disc regeneration

Low back pain is a vital musculoskeletal disease that impairs life quality, leads to disability and imposes heavy economic burden on the society, while it is greatly attributed to intervertebral disc degeneration (IDD). However, the existing treatments, such as medicines, chiropractic adjustments and surgery, cannot achieve ideal disc regeneration. Therefore, advanced bioactive therapies are implemented, including stem cells delivery, bioreagents administration, and implantation of biomaterials etc. Among these researches, few reported unsatisfying regenerative outcomes. However, these advanced therapies have barely achieved successful clinical translation. The main reason for the inconsistency between satisfying preclinical results and poor clinical translation may largely rely on the animal models that cannot actually simulate the human disc degeneration. The inappropriate animal model also leads to difficulties in comparing the efficacies among biomaterials in different reaches. Therefore, animal models that better simulate the clinical charateristics of human IDD should be acknowledged. In addition, in vivo regenerative outcomes should be carefully evaluated to obtain robust results. Nevertheless, many researches neglect certain critical characteristics, such as adhesive properties for biomaterials blocking annulus fibrosus defects and hyperalgesia that is closely related to the clinical manifestations, e.g., low back pain. Herein, in this review, we summarized the animal models established for IDD, and highlighted the proper models and parameters that may result in acknowledged IDD models. Then, we discussed the existing biomaterials for disc regeneration and the characteristics that should be considered for regenerating different parts of discs. Finally, well-established assays and parameters for in vivo disc regeneration are explored.

Measurement of Three-Dimensional Internal Dynamic Strains in the Intervertebral Disc of the Lumbar Spine With Mechanical Loading and Golden-Angle Radial Sparse Parallel-Magnetic Resonance Imaging

BACKGROUND

Noninvasive measurement of internal dynamic strain can be potentially useful to characterize spine intervertebral disc (IVD) in the setting of injury or degenerative disease.

PURPOSE

To develop and demonstrate a noninvasive technique to quantify three-dimensional (3D) internal dynamic strains in the IVD using a combination of static mechanical loading of the IVD using a magnetic resonance imaging (MRI)-compatible ergometer.

STUDY TYPE

Prospective.

SUBJECTS

Silicone gel phantom studies were conducted to assess strain variation with load and repeatability. Mechanical testing was done on the phantoms to confirm MR results. Eight healthy human volunteers (four men and four woman, age = 29 ± 5 years) underwent MRI using a rest, static loading, and recovery paradigm. Repeatability tests were conducted in three subjects.

FIELD STRENGTH/SEQUENCE

MRI (3 T) with 3D continuous golden-angle radial sparse parallel (GRASP) and compressed sensing (CS) reconstruction.

ASSESSMENT

CS reconstruction of the images, motion deformation, and Lagrangian strain maps were calculated for five IVD segments from L1/L2 to L5/S1.

STATISTICAL TESTS

Ranges of displacement and strain in each subject and the resulting mean and standard deviation were calculated. Student t-tests were used to calculate changes in strain from loading to recovery. The correlation coefficient (CC) in the repeatability study was calculated.

RESULTS

The most compressive strain experienced by the IVD segments under loaded conditions was in the L4/L5 segment (-7.5 ± 2.9%). The change in minimum strain from load to recovery was the most for the L4/L5 segment (-7.5% to -5.0%, P = 0.026) and the least for the L1/L2 segment (-4.4% to -3.9%, P = 0.51). In vivo repeatability in three subjects shows strong correlation between scans in subjects done 6 months apart, with CCs equal to 0.86, 0.94, and 0.94 along principal directions.

DATA CONCLUSION

This study shows the feasibility of using static mechanical loading with continuous GRASP-MRI acquisition with CS reconstruction to measure 3D internal dynamic strains in the spine IVD.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY STAGE: 1.

Long versus Short Segment Instrumentation in Osteoporotic Thoracolumbar Vertebral Fracture

Study Design

Retrospective comparative study.

Purpose

This study aimed to compare clinical and radiological data and rate of mechanical complications in elderly patients treated with short segment (SSS) or long segment stabilization (LSS) for thoracolumbar junction osteoporotic vertebral fractures (OVFs).

Overview of Literature

A fervent debate is now focused on the treatment of OVF using SSS or LSS. High rate of complications is associated with pedicle screw fixation because of poor bone quality.

Methods

Patients over 65 years old with a T-score of <−2.5, affected by (T10–L2) vertebral fracture treated with LSS or SSS pedicle screw fixation, with at least 24 months of follow-up were evaluated. All patients were analyzed with conventional X-ray to evaluate bisegmental kyphotic angle (BKA) and clinically with Visual Analog Scale (VAS), Oswestry Disability Index (ODI), and rate of mechanical complications at 2, 6, 12, and 24 months. Data were expressed as mean±standard deviation. Student t-test was used to compare clinical scores between populations. Mann-Whitney U-test was used to analyze clinical and radiological variable, whereas Fisher’s exact test was used to identify differences in the rate of complications between groups.

Results

A total of 37 patients met the inclusion criteria. Mean follow-up was 33.97±9.26 months. For both groups, ODI and VAS significantly decreased over time with good results (p<0.00001). At the final follow-up, no significant differences were found in terms of ODI and VAS. There was no difference in correction of BKA between groups; however, a significant difference was found in LSS group between pre- and postoperative BKA (p=0.046), whereas no difference was found in SSS group. A significant difference in the rate of mechanical complications was found between groups (p=0.011).

Conclusions

Both treatments showed good clinical and radiological results; however, LSS group showed better BKA correction and lower mechanical complications than SSS group.

Reciprocal relationship between multifidus and psoas at L4-L5 level in women with low back pain

Background Low back pain (LBP) may originate from different sources such as intervertebral disc degeneration (IVDD), end-plate and paraspinal muscle changes. Our aim is to explore the relevance of paraspinal muscles' fat-infiltration in women with LBP and its association with IVDD and Modic changes.Methods Consecutive female patients presenting with chronic LBP to the outpatient clinics were included. Patients were evaluated in terms of IVDD, vertebral end-plate changes, and fatty infiltration in the paraspinal muscles at all lumbar levels on lumbar spine magnetic resonance imaging (MRI). Visual Analogue Scale (VAS) scores were recorded using our prospectively collected database.Results Patients with higher VAS scores were significantly more likely to have more fatty infiltration in the multifidus and less fatty infiltration in the psoas at L4-L5 level when compared to those with lower VAS scores (69.1 vs. 31.8%, p = 0.003). To predict LBP, fatty infiltration in the multifidus and psoas had odds ratio (OR) of 4 (p = 0.010), and 0.3 (p = 0.013), respectively; whereas disc degeneration had an OR of 0.5 (p = 0.028).Conclusion This is the first clinical cross-sectional study suggested that women with chronic low back pain could have less fat-infiltrated psoas to compensate more fat-infiltrated multifidus at L4-L5 disc level.

Measuring the neutral zone of spinal motion segments: Comparison of multiple analysis methods to quantify spinal instability

PURPOSE

Neutral zone (NZ) parameters in spinal biomechanics studies are sensitive to spinal instability, disc degeneration, and repair. Multiple methods in the literature quantify NZ, yet no consensus exists on applicability and comparability of methods. This study compares five different NZ quantification methods using two different load-deflection profiles.

METHODS

Rat caudal and lumbar motion segments were tested in axial rotation to generate load-deflection curves with profiles exhibiting prominent distinction between elastic and NZ regions (ie, triphasic) and profiles that did not (ie, viscoelastic). NZ was quantified using five methods: trilinear, double sigmoid (DS), zero load, stiffness threshold (ST), and extrapolated elastic zone. Absolute agreement and consistency of NZ parameters were assessed using intraclass correlation (ICC), Bland-Altman analyses, and analysis of variance.

RESULTS

For triphasic profiles, NZ magnitude exhibited high consistency (methods correlate but differ in absolute values), and only some methods exhibited agreement. For viscoelastic profiles, NZ magnitude showed limited consistency and no absolute agreement. NZ stiffness had high agreement and consistency across most methods and profiles. For triphasic profiles, the linear NZ regions for all methods were not well-described by a linear fit yet for viscoelastic profiles all methods characterized a linear NZ region.

CONCLUSION

This NZ comparison study showed surprisingly limited agreement and consistency among NZ parameters with approximately 5% to 100% difference depending on the method and load-deflection profile. Nevertheless, the DS and ST methods appeared to be most comparable. We conclude that most NZ quantification methods cannot be applied interchangeably, highlighting a need to clearly state NZ calculation methods. Future studies are required to identify which methods are most sensitive to disc degeneration and repair in order to identify a "best" method.

Effects of Corrective Exercise for Thoracic Hyperkyphosis on Posture, Balance, and Well-Being in Older Women: A Double-Blind, Group-Matched Design

BACKGROUND AND PURPOSE

The purpose of this study was to identify the effects of a corrective exercise for thoracic hyperkyphosis on posture, balance, and well-being in Korean community-dwelling older women.

METHODS

Fifty women 65 years of age and older, recruited from 2 senior centers, participated in this study. Participants were assigned to either the experimental group (EG) or the control group (CG) on the basis of convenience of location, and 22 in each were analyzed. Participants in the EG underwent a thoracic corrective exercise program 1 hour each session, twice per week for 8 weeks (a total of 16 sessions), which consisted of specific exercises to enhance breathing, thoracic mobility and stability, and awareness of thoracic alignment. The CG received education on the same thoracic corrective exercise program and a booklet of the exercises. Outcome measures included the extent of postural abnormality (angle of thoracic kyphosis, kyphosis index calculated both in relaxed- and best posture using flexicurve, the ratio of the kyphosis index calculated best posture/relaxed posture, craniovertebral angle, and tragus-to-wall distance), balance (Short Physical Performance Battery and limit of stability), and well-being (Geriatric Depression Scale Short Form and the 36-Item Short Form Health Survey [SF-36]). All data were collected by 6 blinded assessors at baseline, at 8 weeks after the completion of intervention, and at 16 weeks for follow-up.

RESULTS AND DISCUSSION

For participants of the EG, means of all parameters showed significant improvements over time (P < .05), with improved values both in comparison of baseline to postintervention and baseline to follow-up. Means of CG parameters were significantly improved in only the angle of thoracic kyphosis and the tragus-to-wall distance (P < .05). Furthermore, in all parameters, percent change between baseline and postintervention data was significantly (P < .05) higher for the EG than that for the CG, except for the limit of stability and SF-36 which improved but not significantly. All parameters between baseline and follow-up data were significantly (P < .05) higher for the EG than those for the CG, except for the limit of stability.

CONCLUSIONS

The findings of this study suggest that a well-designed exercise program may be beneficial to improve spinal posture, balance, and well-being in older women with thoracic hyperkyphosis. We recommend the use of the therapeutic strategies utilized in this study to enhance thoracic posture, balance, and well-being of older women with thoracic hyperkyphosis. Future research is needed to apply this exercise protocol on a larger and more diverse population.

Lumbar stability following graded unilateral and bilateral facetectomy: A finite element model study

BACKGROUND

Excision of excessive amount of facet joint during lumbar discectomy or decompression can cause segmental instability of the lumbar spine. This study was performed to assess the segmental instability, facet joint loading and intradiscal pressure following graded lumbar facetectomy. This biomechanical study was performed using a verified and validated L3-S1 finite element model.

METHODS

Nine scenarios were analysed. Intact model as control, 30%, 45%, 60% and complete facet joint excision in unilateral and bilateral setting. The effect of progressive graded facetectomy of L4-L5 on the segmental mobility, facet loading and intradiscal pressure was assessed.

FINDINGS

In comparison with control 30% excision of the facet joint mainly caused increase in mediolateral mobility. With 45% excision of the facet joint there was increase in both anteroposterior and mediolateral mobility, this was worse in bilateral and unilateral models respectively. This worsened with larger facet excision scenarios. Facet load increased significantly on extension with excision of 45% & 60% unilaterally and 100% bilaterally. Flexion produced rise in intradiscal pressure in all scenarios.

INTERPRETATION

The increased spinal mobility, facet loading and intradiscal pressure with more than 30% facetectomy highlights the importance of preserving the facets during decompression thereby safeguarding accelerated degeneration of these segments and iatrogenic segmental instability. The findings from this study could also potentially explain the correlation between spinal instability, disc degeneration and facet joint arthrosis as noted in clinical studies.

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

Purpose

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

Methods

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

Results

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

Conclusion

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

Degenerative cervical myelopathy - update and future directions

Degenerative cervical myelopathy (DCM) is the leading cause of spinal cord dysfunction in adults worldwide. DCM encompasses various acquired (age-related) and congenital pathologies related to degeneration of the cervical spinal column, including hypertrophy and/or calcification of the ligaments, intervertebral discs and osseous tissues. These pathologies narrow the spinal canal, leading to chronic spinal cord compression and disability. Owing to the ageing population, rates of DCM are increasing. Expeditious diagnosis and treatment of DCM are needed to avoid permanent disability. Over the past 10 years, advances in basic science and in translational and clinical research have improved our understanding of the pathophysiology of DCM and helped delineate evidence-based practices for diagnosis and treatment. Surgical decompression is recommended for moderate and severe DCM; the best strategy for mild myelopathy remains unclear. Next-generation quantitative microstructural MRI and neurophysiological recordings promise to enable quantification of spinal cord tissue damage and help predict clinical outcomes. Here, we provide a comprehensive, evidence-based review of DCM, including its definition, epidemiology, pathophysiology, clinical presentation, diagnosis and differential diagnosis, and non-operative and operative management. With this Review, we aim to equip physicians across broad disciplines with the knowledge necessary to make a timely diagnosis of DCM, recognize the clinical features that influence management and identify when urgent surgical intervention is warranted.

Quantifying deformations and strains in human intervertebral discs using Digital Volume Correlation combined with MRI (DVC-MRI)

Physical disruptions to intervertebral discs (IVDs) can cause mechanical changes that lead to degeneration and to low back pain which affects 75% of us in our lifetimes. Quantifying the effects of these changes on internal IVD strains may lead to better preventative strategies and treatments. Digital Volume Correlation (DVC) is a non-invasive technique that divides volumetric images into subsets, and measures strains by tracking the internal patterns within them under load. Applying DVC to MRIs may allow non-invasive strain measurements. However, DVC-MRI for strain measurements in IVDs has not been used previously. The purpose of this study was to quantify the strain and deformation errors associated with DVC-MRI for measurements in human IVDs. Eight human lumbar IVDs were MRI scanned (9.4 T) for a 'zero-strain study' (multiple unloaded scans to quantify noise within the system), and a loaded study (2 mm axial compression). Three DVC methodologies: Fast-Fourier transform (FFT), direct correlation (DC), and a combination of both FFT and DC approaches were compared with subset sizes ranging from 8 to 88 voxels to establish the optimal DVC methodology and settings which were then used in the loaded study. FFT + DC was the optimal method and a subset size of 56 voxels (2520 µm) was found to be a good compromise between errors and spatial resolution. Displacement and strain errors did not exceed 28 µm and 3000 microstrain, respectively. These findings demonstrate that DVC-MRI can quantify internal strains within IVDs non-invasively and accurately. The method has unique potential for assessing IVD strains within patients.

Corrigendum to how to define an osteoporotic vertebral fracture

[This corrects the article DOI: 10.21037/qims.2019.09.10.].

Three-Dimensional Morphometric Analysis of Lumbar Vertebral End Plate Anatomy

BACKGROUND

Information on the three-dimensional (3D) shape of vertebral end plates is lacking. Previous studies have analyzed two-dimensional shape; however, 3D data are important because they may help improve our understanding of how differences in shape are related to age, gender, race, size, and other parameters, which may subsequently help improve device design for interbody prosthesis.

OBJECTIVE

To study the 3D shape of lumbar vertebral end plates from normal adult lumbar spines and correlate them with age, gender, spinal/end plate level, end plate surface area, concave depth, and size.

METHODS

An in vivo analysis was undertaken of lumbar vertebral end plate 3D shape. A total of 136 patients' computed tomography scans were used to create 3D models of the lumbar spine for each patient, which were subsequently analyzed.

RESULTS

The shape of the superior end plates is different compared with inferior end plates. Across the lumbar spine (L1-S1), the shape of inferior end plates is similar; however, the shape of the superior end plate varies between spinal levels significantly. There was no clear relationship between age and principal component (PC) shapes but there was a strong correlation between end plate concave depth and end plate PC shape scores.

CONCLUSIONS

Future interbody (disc replacement and fusion) device designs could use the findings that inferior end plate shape is similar throughout the length of the lumbar spine, whereas superior end plate shape changes. Further, future implants could be level-specific because the present study shows that end plate shape varies through the length of the lumbar spine.

How to define an osteoporotic vertebral fracture?

A vertebral deformity (VD) is not always a vertebral fracture (VF). Because of lack of a completely satisfactory "gold standard", there is no consensus on the exact definition of a VF. Therefore, it may sometimes be difficult, especially in mild cases, to discriminate the prevalent VF from a non-fracture deformity or short vertebral height (SVH). A combined standardized approach based on qualitative and semiquantitative (SQ) vertebral assessment may be the most option to correctly identify a VD as a VF. However this visual approach for VF identification is subjective, therefore it is mandatory an adequate training and experience of radiologist to reach a good sensitivity and specificity. Vertebral morphometry, objective and reproducible method, could be used only to evaluate the severity of VFs but requires the availability of reference values of vertebral height ratios. There is actually an evidentiary basis for suggesting that a qualitative approach by expert radiologists to morphological vertebral assessment, combined SQ and morphometric methods seem to be the preferred option for the correct diagnosis of VF as endplate or/and cortex fracture (ECF) or severe vertebral height loss.