Biomechanical properties of lumbar endplates and their correlation with MRI findings of lumbar degeneration

Effect of patient-specific factors on regeneration in lumbar spine at healthy disc and total disc replacement. Computer simulation

BACKGROUND AND OBJECTIVE

Degenerative diseases of the spine have a negative impact on the quality of life of patients. This study presents the results of numerical modelling of the mechanical behaviour of the lumbar spine with patient-specific conditions at physiological loads. This paper aims to numerically study the influence of degenerative changes in the spine and the presence of an endoprosthesis on the creation of conditions for tissue regeneration.

METHODS

A numerical model of the mechanical behaviour of lumbar spine at healthy and after total disc replacement under low-energy impacts equivalent to physiological loads is presented. The model is based on the movable cellular automaton method (discrete elements), where the mechanical behaviour of bone tissue is described using the Biot poroelasticity accounting for the presence and transfer of interstitial biological fluid. The nutritional pathways of the intervertebral disc in cases of healthy and osteoporotic bone tissues were predicted based on the analysis of the simulation results according to the mechanobiological principles.

RESULTS

Simulation of total disc replacement showed that osseointegration of the artificial disc plates occurs only in healthy bone tissue. With total disc replacement in a patient with osteoporosis, there is an area of increased risk of bone resorption in the near-contact area, approximately 1 mm wide, around the fixators. Dynamic loads may improve the osseointegration of the implant in pathological conditions of the bone tissue.

CONCLUSIONS

The results obtained in the case of healthy spine and osteoporotic bone tissues correspond to the experimental data on biomechanics and possible methods of IVD regeneration from the position of mechanobiological principles. The results obtained with an artificial disc (with keel-type fixation) showed that the use of this type of endoprosthesis in healthy bone tissues allows to reproduce the function of the natural intervertebral disc and does not contribute to the development of neoplastic processes. In the case of an artificial disc with osteoporosis of bone tissues, there is a zone with increased risk of tissue resorption and development of neoplastic processes in the area near the contact of the implant attachment. This circumstance can be compensated by increasing the loading level.

Automatic Detection and Classification of Modic Changes in MRI Images Using Deep Learning: Intelligent Assisted Diagnosis System

OBJECTIVE

Modic changes (MCs) are the most prevalent classification system for describing intravertebral MRI signal intensity changes. However, interpreting these intricate MRI images is a complex and time-consuming process. This study investigates the performance of single shot multibox detector (SSD) and ResNet18 network-based automatic detection and classification of MCs. Additionally, it compares the inter-observer agreement and observer-classifier agreement in MCs diagnosis to validate the feasibility of deep learning network-assisted detection of classified MCs.

METHOD

A retrospective analysis of 140 patients with MCs who underwent MRI diagnosis and met the inclusion and exclusion criteria in Tianjin Hospital from June 2020 to June 2021 was used as the internal dataset. This group consisted of 55 males and 85 females, aged 25 to 89 years, with a mean age of (59.0 ± 13.7) years. An external test dataset of 28 patients, who met the same criteria and were assessed using different MRI equipment at Tianjin Hospital, was also gathered, including 11 males and 17 females, aged 31 to 84 years, with a mean age of 62.7 ± 10.9 years. After Physician 1 (with 15 years of experience) annotated all MRI images, the internal dataset was imported into the deep learning model for training. The model comprises an SSD network for lesion localization and a ResNet18 network for lesion classification. Performance metrics, including accuracy, recall, precision, F1 score, confusion matrix, and inter-observer agreement parameter Kappa value, were used to evaluate the model's performance on the internal and external datasets. Physician 2 (with 1 year of experience) re-labeled the internal and external test datasets to compare the inter-observer agreement and observer-classifier agreement.

RESULTS

In the internal dataset, when models were utilized for the detection and classification of MCs, the accuracy, recall, precision and F1 score reached 86.25%, 87.77%, 84.92% and 85.60%, respectively. The Kappa value of the inter-observer agreement was 0.768 (95% CI: 0.656, 0.847),while observer-classifier agreement was 0.717 (95% CI: 0.589, 0.809).In the external test dataset, the model's the accuracy, recall, precision and F1 scores for diagnosing MCs reached 75%, 77.08%, 77.80% and 74.97%, respectively. The inter-observer agreement was 0.681 (95% CI: 0.512, 0.677), and observer-classifier agreement was 0.519 (95% CI: 0.290, 0.690).

CONCLUSION

The model demonstrated strong performance in detecting and classifying MCs, achieving high agreement with physicians in MCs diagnosis. These results suggest that deep learning models have the potential to facilitate the application of intelligent assisted diagnosis techniques in the field of spine research.

Bone cement distribution may significantly affect the efficacy of percutaneous vertebroplasty in treating symptomatic Schmorl's nodes

PURPOSE

Percutaneous vertebroplasty(PVP) has been widely used in treating symptomatic Schmorl's nodes(SNs). However, there were still some patients with poor pain relief. At present, there is a lack of research to analyze the reasons for poor efficacy.

METHODS

Review the SNs patients treated with PVP in our hospital from November 2019 to June 2022, collect their baseline data. Reverse reconstruction software was used to calculate the filling rate of bone edema ring(R_f). NRS score was used to evaluate pain and ODI to evaluate function. The patients were divided into remission group(RG) and non remission group(n-RG) according to symptom. In addition, according to the R_f, they were divided into excellent, good and poor groups. Differences between groups were investigated.

RESULTS

A total of 26 vertebrae were included in 24 patients. When grouped according to symptoms, patients in n-RG were older, and surgical segments were tend to locate in lower lumbar spine. The proportion of Poor distribution was significantly higher. When grouped according to the cement distribution, the preoperative NRS and ODI of the three groups were comparable, but the NRS and ODI of Poor group were significantly worse than the Excellent and Good groups postoperatively and at the last follow-up.

CONCLUSIONS

The cement distribution may significantly affect the efficacy of PVP in treating symptomatic SNs. We suggest that the bone edema ring should be filled as fully as possible to ensure the efficacy. In addition, advanced age and low lumbar lesions are also adverse factors for clinical outcomes.

Analysis of the Efficacy of Percutaneous Endoscopic Interlaminar Discectomy for Lumbar Disc Herniation with Different Types/Grades of Modic Changes

Background

Percutaneous endoscopic interlaminar discectomy (PEID), one of the main techniques of spinal endoscopy, has achieved excellent results in treating lumbar disc herniation (LDH). However, its efficacy has not been systematically described in patients with LDH accompanied by Modic changes (MC).

Purpose

The purpose of this study was to observe the clinical efficacy of PEID treatment of LDH accompanied by MC.

Patients and Methods

A total of 207 patients who underwent PEID surgery for LDH were selected. According to the existence and type of MC on preoperative lumbar magnetic resonance images (MRI), they were divided into normal group (no MC, n=117), M1 group (MC I, n=23), and M2 group (MC II, n=67). According to the severity of MC, they were divided into MA group (grade A, n=45) and MBC group (grade B and C, n=45). The visual analog scale (VAS) score, Oswestry disability index (ODI) score, Disc height index (DHI), Lumbar lordosis angle (LL) and modified Macnab criteria were used to assess clinical outcomes.

Results

Postoperative back pain and leg pain VAS scores and ODI scores were significantly improved in all groups compared with preoperative scores. Patients with MC showed a deterioration in postoperative back pain VAS scores and ODI scores as time went by, and postoperative DHI decreased significantly compared with preoperative. Postoperative LL did not change significantly in each group. There was no significant difference in complications, recurrence rate and excellent rate between the groups.

Conclusion

Whether accompanied by MC or not, the efficacy of PEID for LDH was significant. However, postoperative back pain and functional status of patients with MC tend to deteriorate as time went by, especially those with type I or severe MC.

The Influence of Roussouly Type on the Prevalence, Subtype, and Distribution Characteristics of Modic Changes in Patients with Lumbar Degenerative Disc Disease

BACKGROUND

The relationship between Roussouly type and Modic changes (MC) is unknown. The aim of our study was to investigate the influence of Roussouly type on the characteristics of MC in patients with lumbar degenerative disc disease.

METHODS

This cross-sectional observational study from Huashan Hospital included 270 patients with lumbar degenerative disc disease. Subjects were divided into 4 groups according to the Roussouly classification. Prevalence, subtype, and distribution characteristics of MC from L1-L2 upper end plate to L5-S1 lower end plate were compared between 4 Roussouly types.

RESULTS

Of 270 patients, 65 (24.1%) were Roussouly type I, 115 (42.6%) were Roussouly type II, 55 (20.4%) were Roussouly type III, and 35 (13.0%) were Roussouly type IV. MC were present in 45.9% (n = 270) of patients, 12.7% (n = 2700) of end plates, and 11.8% (n = 1350) of intervertebral discs. The prevalence rate of MC by subtype and intervertebral disc among the 4 Roussouly types was statistically different (P < 0.05), and the prevalence rate of MC by intervertebral disc in Roussouly type I was statistically higher than the other 3 Roussouly types. In Roussouly types I and IV, the prevalence rate of MC at L4-L5 level showed no significant differences compared with those at upper lumbar levels, while in Roussouly types II and III, the prevalence rate of MC at L4-L5 level was significantly higher than those at upper lumbar levels.

CONCLUSIONS

Roussouly types can influence prevalence, subtype, and distribution characteristics of MC in patients with lumbar degenerative disc disease.

Development of a Computational Model of the Mechanical Behavior of the L4-L5 Lumbar Spine: Application to Disc Degeneration

Degenerative changes in the lumbar spine significantly reduce the quality of life of people. In order to fully understand the biomechanics of the affected spine, it is crucial to consider the biomechanical alterations caused by degeneration of the intervertebral disc (IVD). Therefore, this study is aimed at the development of a discrete element model of the mechanical behavior of the L4-L5 spinal motion segment, which covers all the degeneration grades from healthy IVD to its severe degeneration, and numerical study of the influence of the IVD degeneration on stress state and biomechanics of the spine. In order to analyze the effects of IVD degeneration on spine biomechanics, we simulated physiological loading conditions using compressive forces. The results of modeling showed that at the initial stages of degenerative changes, an increase in the amplitude and area of maximum compressive stresses in the disc is observed. At the late stages of disc degradation, a decrease in the value of intradiscal pressure and a shift in the maximum compressive stresses in the dorsal direction is observed. Such an influence of the degradation of the geometric and mechanical parameters of the tissues of the disc leads to the effect of bulging, which in turn leads to the formation of an intervertebral hernia.

The effects of lumbar fusion and non-fusion surgery on the development of Modic changes

Background

The aim of this study was to investigate the influence of lumbar fusion and non-fusion surgery on the postoperative development of Modic changes (MCs).

Methods

A total of 270 patients who underwent lumbar fusion, microsequestrectomy, microdiscectomy, and microdecompression, and who were examined by pre- and postoperative magnetic resonance imaging during the period of January 2012 to December 2018, were included in this retrospective study. The incidence of new postoperative MCs and the change of volume of preexisting MCs after surgery were investigated.

Results

The total incidence of new MCs following lumbar surgical procedures was 36.3%. Lumbar fusion showed a tendency towards a lower postoperative incidence of new MCs than the other three lumbar surgical procedures. The first postoperative year seems to be the most active phase for the development of new MCs. The postoperative volumes of MCs in patients who underwent lumbar non-fusion procedures were significantly greater than those before surgery (P < 0.01). However, no significant difference was detected between pre- and postoperative volumes of MCs in patients with lumbar fusion (P > 0.05).

Conclusion

Lumbar surgical procedures contribute to the development of new MCs, particularly non-fusion surgeries. However, further studies are needed to confirm the clinical relevance of these findings.

Automatic detection and voxel‐wise mapping of lumbar spine Modic changes with deep learning

Background

Modic changes (MCs) are the most prevalent classification system for describing magnetic resonance imaging (MRI) signal intensity changes in the vertebrae. However, there is a growing need for novel quantitative and standardized methods of characterizing these anomalies, particularly for lesions of transitional or mixed nature, due to the lack of conclusive evidence of their associations with low back pain. This retrospective imaging study aims to develop an interpretable deep learning‐based detection tool for voxel‐wise mapping of MCs.

Methods

Seventy‐five lumbar spine MRI exams that presented with acute‐to‐chronic low back pain, radiculopathy, and other symptoms of the lumbar spine were enrolled. The pipeline consists of two deep convolutional neural networks to generate an interpretable voxel‐wise Modic map. First, an autoencoder was trained to segment vertebral bodies from T₁‐weighted sagittal lumbar spine images. Next, two radiologists segmented and labeled MCs from a combined T₁‐ and T₂‐weighted assessment to serve as ground truth for training a second autoencoder that performs segmentation of MCs. The voxels in the detected regions were then categorized to the appropriate Modic type using a rule‐based signal intensity algorithm. Post hoc, three radiologists independently graded a second dataset with the aid of the model predictions in an artificial (AI)‐assisted experiment.

Results

The model successfully identified the presence of changes in 85.7% of samples in the unseen test set with a sensitivity of 0.71 (±0.072), specificity of 0.95 (±0.022), and Cohen's kappa score of 0.63. In the AI‐assisted experiment, the agreement between the junior radiologist and the senior neuroradiologist significantly improved from Cohen's kappa score of 0.52 to 0.58 (p < 0.05).

Conclusions

This deep learning‐based approach demonstrates substantial agreement with radiologists and may serve as a tool to improve inter‐rater reliability in the assessment of MCs.

Biomechanical comparison of vertebral augmentation and cement discoplasty for the treatment of symptomatic Schmorl's node: a finite element analysis

Percutaneous vertebral augmentation (PVA) and percutaneous cement discoplasty (PCD) are two relatively new minimally invasive surgeries for symptomatic Schmorl's reported in recent decade. However, the clinical evidence for the effectiveness of these two surgeries is insufficient. The purpose of this study was to compare the biomechanical benefits and risks of the two surgeries in order to analyze their biomechanical differences and effectiveness. We reconstructed Five lumbar finite element models via computed tomography data, including control model, PVA-ideal model, PVA-nonideal model, PCD-ideal model, and PCD-nonideal model. The stress and strain of Schmorl's nodes, bone marrow edema zone (BMEZ), affected endplate, and the overall stability of segment were analyzed and compared. The validity of our models was confirmed. As a result, the PVA-ideal model can significantly reduce the stress of Schmorl's node and the strain of BMEZ, while this effect is inappreciable in PVA-nonideal model. The PCD-ideal model significantly reduced the strain of Schmorl's nodes and BMEZ, and significantly improve segmental stability, but also resulted in a significant increase in the stress of Schmorl's nodes, BMEZ and endplates. The PCD-nonideal model not only lacks blocking effect, but also sharply increases the strain of Schmorl's nodes and BMEZ. Thus, We recommend that both PVA and PCD surgeries in ideal distribution facilitated a more stable paranodular biomechanical microenvironment. However, due to the possibility of poor biomechanical outcomes caused by the non-ideal cement distribution, the non-ideal distribution of bone cement needs to be remedied in practice.

Comparison of Percutaneous Transforaminal Endoscopic Decompression and Transforaminal Lumbar Interbody Fusion in the Treatment of Single-Level Lumbar Disc Herniation with Modic Type I Changes

Background

Modic changes (MC) are generally considered to be related to degenerative disc disease, and there is no uniform standard for surgical methods for lumbar disc herniation (LDH) accompanied by Modic type I changes (MC I). The purpose of this study was to observe the clinical results of percutaneous transforaminal endoscopic decompression (PTED) and transforaminal lumbar interbody fusion (TLIF) for treatment of LDH accompanied by MC I.

Methods

Of the 53 consecutive patients included, 29 underwent PTED and 24 underwent TLIF. All patients were followed up for at least 24 months. Preoperative demographic characteristics, perioperative outcomes, and clinical outcomes were recorded. Visual analog scale (VAS) scores, Oswestry disability index (ODI) scores, and modified Macnab criteria were used to assess clinical results.

Results

The mean age was 53.7±9.2 years in the PTED group and 53.6±9.6 years in the TLIF group. The scores of VAS legs, VAS back and ODI in the two groups after operation were significantly improved compared with those before operation (P<0.05). Notably, the VAS back pain score and ODI in the PTED group showed an increasing trend with time. And the VAS back pain scores and ODI of the two groups were statistically different at 1 year and 2 years postoperatively (P<0.05). In addition, compared with the TLIF group, the PTED group showed less operation time, blood loss, and postoperative hospital stay (P<0.05). At the final follow-up, the excellent rates were 91.7% and 86.2% in the fusion and PTED groups, respectively.

Conclusion

Both PTED and TLIF procedures significantly improved the clinical symptoms of single-level LDH patients with MC I. Compared with TLIF, MC I may affect the improvement of low back pain and functional status after PTED.

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.

Lumbar Vertebral Endplate Defects on Magnetic Resonance Imaging in Degenerative Spondylolisthesis: Novel Classification, Characteristics, and Correlative Factor Analysis

BACKGROUND

Endplate defects are commonly seen in patients with lumbar degenerative disease. However, little is known about the presence of endplate defects in patients with degenerative spondylolisthesis (DS). In the present study, we have introduced a classification system for endplate defects in patients with DS using routine magnetic resonance imaging findings and explored the correlative factors.

METHODS

Endplate defects were classified into 3 major categories (rim defects, focal defects, and erosive defects) and 5 subtypes (anterior type, posterior type, arc type at the anterior rim, notch type, and Schmorl's nodes). The incidence rates of the endplate defects were compared between the slippage and nonslippage levels. The correlations between the endplate defects and age, sex, disc degeneration, Modic changes (MCs), body mass index, slippage segment, and slippage degree were analyzed.

RESULTS

Endplate defects were present in 47.43% of the endplates in DS. The most common endplate defects were rim defects. The occurrence of endplate defects, especially anterior defects, was more common at the slippage levels. Endplate defects were associated with age and closely related to MCs and the severity of disc degeneration. The slippage degree, slippage segment, body mass index, and sex differences were not associated with endplate defects in our study. The results obtained using this novel classification system were stable and consistent.

CONCLUSIONS

The results from the present study have shown that the novel radiological classification system of endplate defects is reliable. Endplate defects were associated with slippage but not with the slippage degree or slippage segment differences in DS. The correlation between endplate defects and age and between MCs and disc degeneration were important features on the magnetic resonance imaging scans of patients with DS.

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.

Analysis of the Relationship Between Modic Change and Spinopelvic Parameters in the Sagittal Plane

Background

This study explored relationship between Modic change and spinopelvic parameters in the sagittal plane.

Material/Methods

We divided 80 patients into 4 groups: 60 subjects diagnosed with Modic changes (MC) were enrolled in the MC groups (MC1, MC2, and MC3) with each MC type consisting of 20 subjects, and 60 healthy subjects were enrolled in the control group. Spinopelvic parameters in the sagittal plane were calculated to assess their associations with MC. Multivariate logistic regression was used to explore possible risk factors for MC.

Results

PI and LL in the MC groups were significant smaller than in the control group (p<0.05). PI, SS, and PT were significantly correlated with LL with a correlation coefficient of 0.75_PI, 0.71_SS and 0.69_PT (p<0.05). Multivariate logistic regression of the significant variables showed that PI (less than 43.2°) is an independent significant risk factor for MC. ROC analysis showed that moderate diagnostic value was obtained for the significant variable, with an area under the curve (AUC) of 0.80 (p>0.05).

Conclusions

We concluded that PI is risk factor for MC, and smaller PI is associated with higher incidence of MC.

A new lever reduction technique for the surgical treatment of elderly patients with lumbar degenerative Spondylolisthesis

BACKGROUND

Proper reduction method for Lumbar degenerative spondylolisthesis (LDS) is still controversial. The aim of this study was to determine the safety and effectiveness of lever reduction combined with traditional elevating-pull reduction technique for the treatment of elderly patients with LDS.

METHODS

From May 2015 to December 2017, 142 elderly patients (≥65 years) diagnosed with LDS were enrolled in this study with a mean follow-up of 25.42 ± 8.31 months. All patients were operated using lever reduction combined with traditional elevating-pull reduction technique. Patient age, sex, body mass index, bone mineral density, preoperative comorbidities, surgical duration, blood loss, and surgical complications were collected form patient charts. Clinical data as visual analog scale (VAS), Oswestry Disability Index (ODI), and 36-Item Short Form Health Survey (SF-36) were collected preoperatively, 1 month postoperatively, and at the final follow-up. Radiographic evaluation included slip percentage, slip angle (SA), lumbar lordosis (LL), and fusion status.

RESULTS

The clinical parameters of VAS_back, VAS_leg, ODI, and SF-36 had significantly improved at both follow-ups after surgery. A significant improvement was indicated for slippage reduction at both follow-ups, showing no significant correction loss after surgery. SA significantly increased after surgery and was well maintained at the final follow-up. LL was not affected by the surgery. At the final follow-up, complete fusion was obtained in 121 patients (85.2%) and partial fusion in 21 (14.8%). Revision surgery was performed for one patient. Screw loosening was observed in 3 (2.11%) cases. No nerve root injury or adjacent segment disease was observed.

CONCLUSIONS

This new lever reduction combined with traditional elevating-pull reduction technique for the surgical treatment of elderly patients with LDS is both safe and effective. Satisfactory correction and fusion rates were achieved with acceptable correction loss and reduction-related complications.

Patients with Modic type 2 change have a severe radiographic representation in the process of lumbar degeneration: a retrospective imaging study

Background

There are few studies to investigate changes in imaging parameters of Modic changes (MCs). The imaging studies examining the distinctions in the lumbar sagittal parameters between MCs and lumbar disc degeneration (LDD) are still lacking. The purpose of this study was to identify the differences in the lumbar sagittal parameters among patients for LDD with/without Modic type 2 change (MII).

Methods

A total of 208 patients with lumbar degenerative disease from January 2017 to August 2018 volunteered for this study. Sixty-two patients with MII were used as the MC group. The other 146 patients served as the disc degeneration (DD) group. The DD scores and sagittal parameters were measured on magnetic resonance imaging (MRI) and X-ray by using Surgimap software.

Results

The prevalence of MII for patients with degenerative lumbar diseases in this study was 29.81%, primarily located at L5/S1. There were significant differences in lumbar lordosis (LL) and sacral slope (SS) between these two groups (P < 0.05). Similarly, the significant decrease in intervertebral height index (IHI) was found at L3-S1 in the MC group, compared with the DD group (P < 0.05). However, a significant difference in intervertebral angle (IVA) was observed only at L5/S1 (P < 0.05). The MC group had the smaller endplate concave angle (ECA) than the DD group from L3 caudal endplate to S1 cranial endplate (P < 0.05).

Conclusions

MII has a severe radiographic representation in the process of lumbar degeneration than patients without MII, and the overconcentration of load caused by the smaller LL, SS, and IVA may be a reasonable explanation to answer why MCs are more common at the L5/S1.

The Relationship Between Endplate Pathology and Patient-reported Symptoms for Chronic Low Back Pain Depends on Lumbar Paraspinal Muscle Quality

STUDY DESIGN

Cross-sectional cohort study of chronic low back pain (CLBP) patients and matched controls.

OBJECTIVE

To explore the interplay between vertebral endplate damage and adjacent paraspinal muscle (PSM) quality, and to test their association in a cohort of patients with CLBP and matched controls.

SUMMARY OF BACKGROUND DATA

Nonspecific CLBP is challenging to diagnose, in part, due to uncertainty regarding the source of pain. Delineating interactions among potential CLBP mechanisms may enhance diagnosis and treatment customization.

METHODS

We collected advanced MRI imaging on 52 adult subjects, including 38 CLBP patients and 14 age- and sex-matched asymptomatic control subjects. Mean multifidus and erector spinae fat fraction (FF) was measured throughout the spine using an IDEAL MRI sequence. Presence of cartilage endplate (CEP) defects was determined at each disc level using UTE MRI. Logistic regression was used to test association of PSM FF, CEP defects, modic changes (MC), disc degeneration, and their interplay.

RESULTS

We observed that CEP defects were the strongest predictor of nonspecific CLBP (OR: 14.1, P < 0.01) even after adjusting for MC and disc degeneration (OR: 26.1, P = 0.04). PSM quality did not independently distinguish patient and control groups, except for patients with high self-reported disability.At specifically L4L5, CEP damage was most prevalent and CEP damage was significantly associated with CLBP (OR: 3.7, 95% CI: 1.2-21.5, P = 0.03). CEP damage at L4L5 was predictive of CLBP when adjacent to PSMs with greater FF (MF, OR 14.7, P = 0.04; ES, OR: 17.3, P = 0.03), but not when PSM FF was lower and comparable to values in control, asymptomatic subjects.

CONCLUSION

These results demonstrate the clinically important reciprocity between passive and dynamic spinal stabilizers, and support the notion that therapies targeting the PSMs may provide clinical benefit even in the presence of other spinal pathologies.

LEVEL OF EVIDENCE

4.

New insights into the natural course and clinical relevance of Modic changes over 2 years following lumbar limited discectomy: analysis of prospective collected data

PURPOSE

Few retrospective studies have addressed Modic changes (MC) following lumbar spine surgery, though it is usually assumed that MC increase in grade and incidence. To test this conventional wisdom, we investigated the natural course of MC following primary lumbar limited discectomy with two-year follow-up. In addition, a possible clinical relevance to those changes was assessed.

METHODS

The data of the control group (278 subjects) of a prospective randomized, controlled trial (RCT) were evaluated retrospectively.

RESULTS

We did not observe a simple increase in MC with regard to grade. There is variable activity observed in Type 2 (at 12 months) and in Type 1 (at 24 months). Conversion from one grade to another may occur and may be upward or downward. The incidence of MC increased slightly over time, as after surgery a decreasing percentage of the study group remained without MC over two years (1 year: 34% (85/250); 2 years: 30% (72/237)). Radiological parameters (rotation, translation, and spondylolisthesis) had no significant correlation to MC or MC subtypes. Lastly, we found that neither the different MC types nor their changes were correlated with clinical parameters (VAS back, VAS leg, ODI score) preoperatively or during follow-up.

CONCLUSION

The pattern of Modic changes following lumbar limited discectomy is complex, not simply increasing. There is variable activity in MC Types 1 and 2 at the different time points of follow-up, and conversion from a higher grader to a lower one or vice versa is possible. These slides can be retrieved under Electronic Supplementary Material.

Defects of the vertebral end plate: implications for disc degeneration depend on size

BACKGROUND CONTEXT

Bony vertebral end plates must be porous to allow metabolite transport into the disc, and yet strong to resist high intradiscal pressure (IDP). End plate defects may therefore have nutritional and mechanical consequences for the disc, depending on their size and type. We hypothesize that broad, diffuse defects are more closely associated with disc decompression and degeneration than are focal Schmorl's node-type defects.

PURPOSE

This study aimed to determine how the size and type of end plate defects are related to decompression and degeneration in the adjacent intervertebral disc.

STUDY DESIGN

Mechanical, histologic, and micro-computed tomographic investigations were carried out in cadaver spines.

METHODS

The study involved 40 motion segments (T8-T9 to L4-L5) dissected from 23 cadavers aged 48-98 years. Intradiscal stresses were measured, under 1 kN compression, by pulling a pressure transducer along the disc's midsagittal diameter. The resulting "stress profiles" revealed nucleus pressure (IDP) and maximum stresses in the anterior and posterior annulus. Micro-computed tomography was then used to examine all 40 discs, with 5 mm of adjacent bone on either side, so that end plate defects could be characterized at a resolution of 35 µm. Cross-sectional area (in the transverse plane), volume, location, and morphologic type were determined for all bony defects in the 80 end plates. Finally, discs from each motion segment (with hyaline cartilage and bone attached) were sectioned (undecalcified) at 7 µm for histology to allow degeneration to be assessed.

RESULTS

Substantial defects were identified in 24 of 40 specimens (35 of 80 end plates). Of these, 83% was centrally located, and 17% was laterally located. Defects occurred more frequently in male than female specimens (p=.043), and were more common in thoracic than lumbar end plates (p=.002), although lumbar defects were greater in volume (p=.05). Defect area and volume increased with decreasing IDP, with decreasing peak stress in the annulus, and with increasing tissue degeneration. Stepwise multiple regression showed that average defect area depended most strongly on IDP, whereas maximum defect area and volume depended most strongly on peak stress in the anterior annulus. Multiple end plate defects were associated with lower values of IDP and higher degeneration scores when compared with erosions and Schmorl's nodes.

CONCLUSIONS

Disc degeneration has a stronger association with large or multiple end plate defects than with small or single defects (of any type). Large end plate defects probably allow greater volume changes within the disc, leading to greater nucleus decompression.

Biomechanics of the human intervertebral disc: A review of testing techniques and results

Many experimental testing techniques have been adopted in order to provide an understanding of the biomechanics of the human intervertebral disc (IVD). The aim of this review article is to amalgamate results from these studies to provide readers with an overview of the studies conducted and their contribution to our current understanding of the biomechanics and function of the IVD. The overview is presented in a way that should prove useful to experimentalists and computational modellers. Mechanical properties of whole IVDs can be assessed conveniently by testing 'motion segments' comprising two vertebrae and the intervening IVD and ligaments. Neural arches should be removed if load-sharing between them and the disc is of no interest, and specimens containing more than two vertebrae are required to study 'adjacent level' effects. Mechanisms of injury (including endplate fracture and disc herniation) have been studied by applying complex loading at physiologically-relevant loading rates, whereas mechanical evaluations of surgical prostheses require slower application of standardised loading protocols. Results can be strongly influenced by the testing environment, preconditioning, loading rate, specimen age and degeneration, and spinal level. Component tissues of the disc (anulus fibrosus, nucleus pulposus, and cartilage endplates) have been studied to determine their material properties, but only the anulus has been thoroughly evaluated. Animal discs can be used as a model of human discs where uniform non-degenerate specimens are required, although differences in scale, age, and anatomy can lead to problems in interpretation.