Alendronate Prevents Intervertebral Disc Degeneration Adjacent to a Lumbar Fusion in Ovariectomized Rats

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.

Protective effects of Shensuitongzhi formula on intervertebral disc degeneration via downregulation of NF-κB signaling pathway and inflammatory response

Low back pain (LBP) is a common orthopedic disease over the world. Lumbar intervertebral disc degeneration (IDD) is regarded as an important cause of LBP. Shensuitongzhi formula (SSTZF) is a drug used in clinical treatment for orthopedic diseases. It has been found that SSTZF can have a good treatment for IDD. But the exact mechanism has not been clarified. The results showed that SSTZF protects against LSI-induced degeneration of cartilage endplates and intervertebral discs. Meanwhile, SSTZF treatment dramatically reduces the expression of inflammatory factor as well as the expression of catabolism protein and upregulates the expression of anabolism protein in LSI-induced mice. In addition, SSTZF delayed the progression of LSI-induced IDD via downregulation the level of NF-κB signaling key gene RELA and phosphorylation of key protein P65 in endplate chondrocytes. Our study has illustrated the treatment as well as the latent mechanism of SSTZF in IDD.

Biomechanical effects of osteoporosis severity on the occurrence of proximal junctional kyphosis following long-segment posterior thoracolumbar fusion

BACKGROUND

Proximal junctional kyphosis is a common long-term complication in adult spinal deformity surgery that involves long-segment posterior spinal fusion. However, the underlying biomechanical mechanisms of the impact of osteoporosis on proximal junctional kyphosis remain unclear. The present study was to evaluate adjacent segment degeneration and spine mechanical instability in osteoporotic patients who underwent long-segment posterior thoracolumbar fusion.

METHODS

Finite element models of the thoracolumbar spine T1-L5 with posterior long-segment T8-L5 fusion under different degrees of osteoporosis were constructed to analyze intervertebral disc stress characterization, vertebrae mechanical transfer, and pedicle screw system loads during various motions.

FINDINGS

Compared with normal bone mass, the maximum von Mises stresses of T7 and T8 were increased by 20.32%, 22.38%, 44.69%, 4.49% and 29.48%, 17.84%, 40.95%, 3.20% during flexion, extension, lateral bending, and axial rotation in the mild osteoporosis model, and by 21.21%, 18.32%, 88.28%, 2.94% and 37.76%, 15.09%, 61.47%, -0.04% in severe osteoporosis model. The peak stresses among T6/T7, T7/T8, and T8/T9 discs were 14.77 MPa, 11.55 MPa, and 2.39 MPa under lateral bending conditions for the severe osteoporosis model, respectively. As the severity of osteoporosis increased, stress levels on SCR8 and SCR9 intensified during various movements.

INTERPRETATION

Osteoporosis had an adverse effect on proximal junctional kyphosis. The stress levels in cortical bone, intervertebral discs and screws were increased with bone mass loss, which can easily lead to intervertebral disc degeneration, bone destruction as well as screw pullout. These factors have significantly affected or accelerated the occurrence of proximal junctional kyphosis.

Establishment of an animal model of adjacent segment degeneration after interbody fusion and related experimental studies

BACKGROUND

Degenerative spine conditions are common and frequent clinical diseases, and adjacent segment disease (ASD) after spinal fusion (SF) is a common complication after spinal fusion (SF). In this study, we established an animal model of ASD after interbody fusion to observe the morphologic changes of adjacent segment (AS) disks and to determine the expression and significance of tumor necrosis factor-alpha (TNF-α) and interleukin-1beta (IL-1β) in ASD tissues to provide a good experimental basis and reference for clinical prevention and treatment of ASD after interbody fusion.

METHODS

Thirty-six male and female New Zealand rabbits weighing 2.0-2.5 kg were randomly divided into control group (group A) and experimental groups (groups B, C, and D), with 9 rabbits in each group, of which groups B, C, and D were the 4-, 8-, and 12-week groups, respectively. Autologous iliac bone grafts were used as the bone graft material. In the experimental groups, a SF was performed on the C2-C3 intervertebral space. The C3-4 adjacent segments were examined. In the experimental group, the animals were subjected to gross observation, X-ray examination, hand touch inspection, and micro-computed tomography (micro-CT) 4, 8, and 12 weeks after surgery. The micromorphologic changes of the cervical disks in the segments of the control group and experimental groups were observed under light microscopy. Immunohistochemistry and Western blotting were used to detect the expression of TNF-α and IL-1β in the AS tissues after interbody fusion in the control and experimental groups.

RESULTS

The measurement data of the rabbit cervical spine bony structures indicated that the length of the vertebral body and the sagittal diameter of the lower end of the vertebral body decreased gradually from the 2nd-6th cervical vertebrae, and the difference was statistically significant (P < 0.05). The difference in the transverse diameter of the lower end of the vertebral body was not statistically significant (P > 0.05), the change in the oblique diameter of the lower end of the vertebral body fluctuated, and the difference was statistically significant (P < 0.05). The fusion rate of the cervical spine by hand touch inspection was 22.2% (2/9), 55.6% (5/9), and 88.9% (8/9) in groups B, C, and D, respectively. The differences in bone volume-to-total volume (BV/TV) and X-ray scores were statistically significant in groups B, C, and D (P < 0.05). Significant degeneration occurred in groups B, C, and D compared with group A. The expression of TNF-α and IL-1β in the intervertebral disk tissue was significantly higher in groups B, C, and D compared with group A (P < 0.05), and increased with time.

CONCLUSION

In this study, an animal model of ASD after interbody fusion fixation in rabbits was successfully established. Postoperative imaging and hand touch inspection showed a positive correlation between the amount of new intervertebral bone and the degree of fusion with time. The results of immunohistochemistry and Western blot showed that TNF-α and IL-1β were highly expressed in the AS tissues of the experimental group after interbody fusion, and the degree of disk degeneration was positively correlated with the time after interbody fusion.

The association of lumbar disc degeneration with lumbar vertebral trabecular volumetric bone mineral density in an urban population of young and middle-aged community-dwelling Chinese adults: a cross-sectional study

INTRODUCTION

Lumbar intervertebral disc degeneration (LDD) and osteoporosis (OP) are age-related conditions that induce low back pain and have an impact on quality of life. The relationship between LDD and changes in bone mineral density (BMD) is, however, contentious and ever-changing. The purpose of this study is to investigate the relationship between lumbar vertebral volumetric BMD (vBMD) and LDD in an urban population of young and middle-aged community-dwelling Chinese adults.

MATERIALS AND METHODS

719 participants were recruited from among the subjects enrolled in a 10-year longitudinal study of degeneration of the spine and knee being conducted at the Beijing Jishuitan Hospital. The severity of LDD was graded using the five-grade Pfirrmann classification, and lumbar vertebral vBMD was measured using quantitative computed tomography (QCT). The relationship between the grade of intervertebral disc degeneration and lumbar vertebral vBMD was analyzed, and multiple linear regression was performed to adjust for covariates.

RESULTS

The mean lumbar vBMD decreased as the grade of LDD increased (171.5 g/cm3, 147.8 g/cm3, and 124.3 g/cm3, respectively; P < 0.001). After adjusting for age, a higher LDD stage was associated with a lower mean L2-L4 vBMD, although a statistically significant correlation was observed only in men (standardized coefficient β = - 0.656, P = 0.004). In men, there was a negative correlation between single-vertebra vBMD and degeneration of adjacent intervertebral discs, particularly those involving the L3 vertebra (L2-3 disc: β = - 0.333, P < 0.001, L3-4 disc: β = - 0.398, P < 0.001), as well as the mean grade of the L2-4 discs (β = - 0.448, P < 0.001). However, the L5-S1 disc had a smaller correlation with age than others, and no statistically significant associations with lumbar vBMD were observed in either men (β = - 0.024, P = 0.729) or women (β = - 0.057, P = 0.396).

CONCLUSION

Our study found that the degree of LDD was negatively associated with lumbar trabecular vBMD, although (excepting the L5-S1 disc), the relationship was statistically significant only in men.

Murine models of posterolateral spinal fusion: A systematic review

BACKGROUND

Rodent models are commonly used experimentally to assess treatment effectiveness in spinal fusion. Certain factors are associated with better fusion rates. The objectives of the present study were to report the protocols most frequently used, to evaluate factors known to positively influence fusion rate, and to identify new factors.

METHOD

A systematic literature search of PubMed and Web of Science found 139 experimental studies of posterolateral lumbar spinal fusion in rodent models. Data for level and location of fusion, animal strain, sex, weight and age, graft, decortication, fusion assessment and fusion and mortality rates were collected and analyzed.

RESULTS

The standard murine model for spinal fusion was male Sprague Dawley rats of 295g weight and 13 weeks' age, using decortication, with L4-L5 as fusion level. The last two criteria were associated with significantly better fusion rates. On manual palpation, the overall mean fusion rate in rats was 58% and the autograft mean fusion rate was 61%. Most studies evaluated fusion as a binary on manual palpation, and only a few used CT and histology. Average mortality was 3.03% in rats and 1.56% in mice.

CONCLUSIONS

These results suggest using a rat model, younger than 10 weeks and weighing more than 300 grams on the day of surgery, to optimize fusion rates, with decortication before grafting and fusing the L4-L5 level.

Preclinical in vivo animal models of intervertebral disc degeneration. Part 1: A systematic review

Intervertebral disc degeneration (IVDD), a widely recognized cause of lower back pain, is the leading cause of disability worldwide. A myriad of preclinical in vivo animal models of IVDD have been described in the literature. There is a need for critical evaluation of these models to better inform researchers and clinicians to optimize study design and ultimately, enhance experimental outcomes. The purpose of this study was to conduct an extensive systematic literature review to report the variability of animal species, IVDD induction method, and experimental timepoints and endpoints used in in vivo IVDD preclinical research. A systematic literature review of peer-reviewed manuscripts featured on PubMed and EMBASE databases was conducted in accordance with PRISMA guidelines. Studies were included if they reported an in vivo animal model of IVDD and included details of the species used, how disc degeneration was induced, and the experimental endpoints used for analysis. Two-hundred and fifty-nine (259) studies were reviewed. The most common species, IVDD induction method and experimental endpoint used was rodents(140/259, 54.05%), surgery (168/259, 64.86%) and histology (217/259, 83.78%), respectively. Experimental timepoint varied greatly between studies, ranging from 1 week (dog and rodent models), to >104 weeks in dog, horse, monkey, rabbit, and sheep models. The two most common timepoints used across all species were 4 weeks (49 manuscripts) and 12 weeks (44 manuscripts). A comprehensive discussion of the species, methods of IVDD induction and experimental endpoints is presented. There was great variability across all categories: animal species, method of IVDD induction, timepoints and experimental endpoints. While no animal model can replicate the human scenario, the most appropriate model should be selected in line with the study objectives to optimize experimental design, outcomes and improve comparisons between studies.

Adjacent segment disease after minimally invasive transforaminal lumbar interbody fusion for degenerative lumbar diseases: incidence and risk factors

Study design

Retrospective study.

Objectives

To explore the incidence and risk factors for symptomatic adjacent segment disease (ASD) in patients enveloped in degenerative lumbar diseases after minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF).

Methods

Data were retrospectively analyzed on 744 patients who underwent MIS-TLIF for degenerative lumbar diseases in our hospital from October 2012 to December 2018. The patients were divided into the ASD group and non-ASD (N-ASD) group on the basis of developing ASD at follow-up, and then the incidence of ASD was calculated. Clinical and radiological risk factors were assessed over time to determine their association with ASD by excluding less important factors.

Results

Data were missing for 26 patients, while a total of 718 patients were successfully monitored after MIS-TLIF. Of the 718 individuals participated in the study, 34 (4.7%) patients plagued by ASD required surgical intervention. The average onset time of ASD was 62.7 ± 15.1 months. Univariate analysis results shows that age, bone mineral density (BMD), body mass index (BMI), preoperative adjacent intervertebral disc height and preoperative adjacent segment disc degeneration were significantly different between the ASD and N-ASD groups (p < 0.05). The logistic regression analysis results demonstrated that BMD (p = 0.039, OR = 0.986, 95% CI 0.899–1.115), BMI (p = 0.041, OR = 1.119, 95% CI 1.103–2.397), and preoperative adjacent intervertebral disc degeneration (p = 0.023, OR = 1.215, 95% CI 1.015–1.986) may be seen as risk factors for ASD after MIS-TLIF.

Conclusions

The incidence of ASD was about 4.7% in patients suffer from degenerative lumbar diseases after MIS-TLIF. BMD, BMI and preoperative adjacent intervertebral disc degeneration might be the risk factors for the occurrence of ASD after MIS-TLIF. Our research also suggested that patients with lower BMD, higher BMI and disc preoperative adjacent segment disc degeneration were more likely to develop ASD after MIS-TLIF.

Hounsfield Unit as a Predictor of Adjacent-Level Disease in Lumbar Interbody Fusion Surgery

BACKGROUND

Bone density has been associated with a successful fusion rate in spine surgery. Hounsfield units (HUs) have more recently been evaluated as an indirect representation of bone density. Low preoperative HUs may be an early indicator of global disease and chronic process and, therefore, indicative of the need for future reoperation.

OBJECTIVE

To assess preoperative HUs and their association with future adjacent segment disease requiring surgical intervention through retrospective study.

METHODS

Patients who underwent lumbar interbody fusion at a single institution between 2007 and 2016 were retrospectively reviewed. Hounsfield unit values were measured from preoperative computed tomography (CT) using sagittal images, encircling cancellous portion of the vertebral body. Patient charts were reviewed for follow-up data and adjacent-level disease development.

RESULTS

A total of 793 patients (age: 56.1 ± 13.7 years, 54.4% female) were included in this study. Twenty-two patients required surgical intervention for adjacent segment disease. Patients who underwent lumbar interbody fusion and did not subsequently require surgical intervention for adjacent-level disease were found to have a higher mean preoperative HU than patients who did require reoperation (180.7 ± 70.0 vs 148.4 ± 8.1, P = .032). Preoperative CT HU was a significant independent predictor for the requirement of adjacent-level surgery after spinal arthrodesis (odds ratio = 0.891 [0.883-0.899], P = .029).

CONCLUSION

Patients who underwent lumbar interbody fusion that did not require reoperation for adjacent-level degeneration were found to have a higher mean preoperative HU than patients who did require surgical intervention. Lower preoperative CT HU was a significant independent predictor for the requirement of adjacent-level surgery after spinal arthrodesis.

The Proteolysis of ECM in Intervertebral Disc Degeneration

Intervertebral disc (IVD) degeneration (IDD) is a pathological process that commonly occurs throughout the human life span and is a major cause of lower back pain. Better elucidation of the molecular mechanisms involved in disc degeneration could provide a theoretical basis for the development of lumbar disc intervention strategies. In recent years, extracellular matrix (ECM) homeostasis has received much attention due to its relevance to the mechanical properties of IVDs. ECM proteolysis mediated by a variety of proteases is involved in the pathological process of disc degeneration. Here, we discuss in detail the relationship between the IVD as well as the ECM and the role of ECM proteolysis in the degenerative process of the IVD. Targeting ECM proteolysis-associated proteases may be an effective means of intervention in IDD.

Role of the Lumbosacral Transition Vertebra and Vertebral Lamina in the Pathogenesis of Lumbar Disc Herniation

OBJECTIVE

To investigate the prevalence of lumbosacral transition vertebrae (LSTVs) in both the normal population and the lumbar disc herniation (LDH) population and to determine the risk factors for LDH.

METHODS

Between January 2019 and September 2020, all patients aged 18-39 years and underwent an anteroposterior (AP) X-ray of the lumbar vertebrae were retrospective reviewed in our institution. Those patients who were diagnosed with LDH were eligible for inclusion in the LDH group. During the same period, those patients admitted to our hospital who underwent an anteroposterior X-ray of the lumbar spine and had not been diagnosed with LDH were included in the control group. Those patients with disease that might affect the lumbar anatomy were excluded from both groups. The type of LSTV was classified according to the Castellvi classification. The height of the lumbar vertebral lamina was evaluated through the h/H index. The inter- and intra-observer reliability was evaluated by one senior radiologist and one senior orthopedist using intraclass correlation coefficient (ICC). The association between the LSTV and the herniation level was also investigated. Binary logistic regression was used to explore the association of different factors between the LDH group and the control group.

RESULTS

Two hundred LDH patients (115 male and 85 female) and 200 individuals (108 male and 92 female) were investigated retrospectively. The prevalence of LSTVs was 71.5% (n = 143) in the LDH group and 34.0% (n = 68) in the control group. The most frequent LSTV types were type Ib and type IIa. The inter- and intra-observer ICCs of the measurement of "h/H" index and the classification of LSTV were all "excellent" (ICC > 0.90). The median h/H index in the control group was significantly higher than that in the LDH group (0.28 (0.26, 0.31) vs 0.34 (0.31, 0.37), P = 0.000). The distribution of the Castellvi classification in the L4/5 and L5/S1 herniation patients was significantly different (P = 0.048). LSTVs, BMI and the h/H index were closely associated with LDH, with odds ratios of 3.06 (95% CI: 2.12-4.43), 1.23 (95% CI: 1.13-1.33) and 0.09 (95% CI: 0.05-0.15), respectively. The incidence of L4/5 disc herniation in patients with an LSTV was significantly more common than that in patients with L5/S1 disc herniation (P = 0.048).

CONCLUSION

The prevalence of LSTVs was 34.0% in the control group and 71.5% in the LDH group; LSTVs and BMI were positively correlated with LDH, and h/H was negatively correlated with LDH.

3D assessment of intervertebral disc degeneration in zebrafish identifies changes in bone density that prime disc disease

Back pain is a common condition with a high social impact and represents a global health burden. Intervertebral disc disease (IVDD) is one of the major causes of back pain; no therapeutics are currently available to reverse this disease. The impact of bone mineral density (BMD) on IVDD has been controversial, with some studies suggesting osteoporosis as causative for IVDD and others suggesting it as protective for IVDD. Functional studies to evaluate the influence of genetic components of BMD in IVDD could highlight opportunities for drug development and repurposing. By taking a holistic 3D approach, we established an aging zebrafish model for spontaneous IVDD. Increased BMD in aging, detected by automated computational analysis, is caused by bone deformities at the endplates. However, aged zebrafish spines showed changes in bone morphology, microstructure, mineral heterogeneity, and increased fragility that resembled osteoporosis. Elements of the discs recapitulated IVDD symptoms found in humans: the intervertebral ligament (equivalent to the annulus fibrosus) showed disorganized collagen fibers and herniation, while the disc center (nucleus pulposus equivalent) showed dehydration and cellular abnormalities. We manipulated BMD in young zebrafish by mutating sp7 and cathepsin K, leading to low and high BMD, respectively. Remarkably, we detected IVDD in both groups, demonstrating that low BMD does not protect against IVDD, and we found a strong correlation between high BMD and IVDD. Deep learning was applied to high-resolution synchrotron µCT image data to analyze osteocyte 3D lacunar distribution and morphology, revealing a role of sp7 in controlling the osteocyte lacunar 3D profile. Our findings suggest potential avenues through which bone quality can be targeted to identify beneficial therapeutics for IVDD.

Denosumab alleviates intervertebral disc degeneration adjacent to lumbar fusion by inhibiting endplate osteochondral remodeling and vertebral osteoporosis in ovariectomized rats

Background

Although adjacent segmental intervertebral disc degeneration (ASDD) is one of the most common complications after lumbar fusion, its exact mechanism remains unclear. As an antibody to RANKL, denosumab (Dmab) effectively reduces bone resorption and stimulates bone formation, which can increase bone mineral density (BMD) and improve osteoporosis. However, it has not been confirmed whether Dmab has a reversing or retarding effect on ASDD.

Methods

Three-month-old female Sprague-Dawley rats that underwent L4–L5 posterolateral lumbar fusion (PLF) with spinous-process wire fixation 4 weeks after bilateral ovariectomy (OVX) surgery were given Dmab 4 weeks after PLF surgery (OVX+PLF+Dmab group). In addition, the following control groups were defined: Sham, OVX, PLF, and OVX+PLF (n=12 each). Next, manual palpation and X-ray were used to evaluate the state of lumbar fusion. The bone microstructure in the lumbar vertebra and endplate as well as the disc height index (DHI) of L5/6 was evaluated by microcomputed tomography (μCT). The characteristic alterations of ASDD were identified via Safranin-O green staining. Osteoclasts were detected using tartrate-resistant acid phosphatase (TRAP) staining, and the biomechanical properties of vertebrae were evaluated. Aggrecan (Agg), metalloproteinase-13 (MMP-13), and a disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS-4) expression in the intervertebral disc were detected by immunohistochemistry and real-time polymerase chain reaction (RT-PCR) analysis. In addition, the expression of CD24 and Sox-9 was assessed by immunohistochemistry.

Results

Manual palpation showed clear evidence of the fused segment’s immobility. Compared to the OVX+PLF group, more new bone formation was observed by X-ray examination in the OVX+PLF+Dmab group. Dmab significantly alleviated ASDD by retaining disc height index (DHI), decreasing endplate porosity, and increasing vertebral biomechanical properties and BMD. TRAP staining results showed a significantly decreased number of active osteoclasts after Dmab treatment, especially in subchondral bone and cartilaginous endplates. Moreover, the protein and mRNA expression results in discs (IVDs) showed that Dmab not only inhibited matrix degradation by decreasing MMP-13 and ADAMTS-4 but also promoted matrix synthesis by increasing Agg. Dmab maintained the number of notochord cells by increasing CD24 but reducing Sox-9.

Conclusions

These results suggest that Dmab may be a novel therapeutic target for ASDD treatment.

Chlorogenic Acid retards cartilaginous endplate degeneration and ameliorates intervertebral disc degeneration via suppressing NF-κB signaling

AIMS

Intervertebral Disc Degeneration (IDD) is a key factor involved in low back pain (LBP) which affects approximately 540 million individuals worldwide. Chlorogenic Acid (CGA), a natural compound, exerts anti-inflammatory property in several diseases. Here, we aim to investigate the biological effect of CGA on IDD and explore the underlying mechanism.

MATERIALS AND METHODS

Lumbar spine instability (LSI) model in mice was utilized to mimic process of IDD. The effects of CGA in response to LSI were evaluated by luminescent imaging, micro-CT, histomorphology, and immunohistochemistry in vivo. Besides, the cytotoxicity of CGA on chondrocytes was detected by cell counting kit-8 (CCK-8) and the biological effects were assessed by polymerase chain reaction (PCR) in vitro.

KEY FINDINGS

We found that CGA treatment dramatically suppressed the NF-κB activity in LSI mice. Moreover, administration of CGA mitigated cartilaginous endplate degeneration and postponed IDD development accompanying a decrease of inflammatory and catabolic mediators. Specifically, CGA ameliorated endplate degeneration might be related to its protective effects against endplate chondrocytes apoptosis and trans-differentiation. We further elucidated that CGA exerted these biological effects mainly by repressing NF-κB signaling in cartilage endplate.

SIGNIFICANCE

Our study has illustrated, for the first time, the curative effects as well as the latent mechanism of CGA in IDD and our results suggested that CGA administration might be used as an alternative therapy for IDD.

Effects of menopausal state on lumbar decompression and fusion surgery

Menopause leads to fluctuations in androgenic hormones which directly affect bone metabolism. Bone resorption, mineralization, and remodeling at fusion sites are essential in order to obtain a solid and biomechanically stable fusion mass. Bone metabolic imbalance seen in the postmenopausal state may predispose to fusion related complications. The aim of this study was to investigate fusion outcomes in lumbar spinal fusion surgery in women based on menopausal status. A retrospective analysis of all female patients who underwent posterior lumbar decompression and fusion at a single institution from 2013 to 2017 was performed. A total of 112 patients were identified and stratified into premenopausal (n = 25) and postmenopausal (n = 87) groups. Clinical and radiographic data was assessed at 1 year follow up. Postmenopausal patients had a higher rates of pseudarthrosis (11.63% vs 0%, p = 0.08), PJK (15.1% vs 4%, p = 0.14), and revision surgery (3.5% vs 0%, p = 0.35). The number of levels fused was associated with increased risk of pseudarthrosis (OR 1.4, p = 0.02); however, there was no association between age, hormonal use, prior tobacco use, or T-score. Age was associated with increased risk of developing PJK (OR = 1.11, p = 0.01); however, PJK was not associated with menopause, hormonal use, prior tobacco use, or T-score. Revision surgery was not associated with age, hormonal use, prior tobacco use, or T-score. This study suggests that postmenopausal women may be prone to have higher rates of pseudarthrosis, PJK and revision surgery, although our results were not statistically significant. Larger studies with longer follow up will help elucidate the true effects of menopause in spine surgery.

Mechanics and Biology Interact in Intervertebral Disc Degeneration: A Novel Composite Mouse Model

The aim of this study was to distinguish the characteristics of intervertebral disc degeneration (IVDD) originating from mechanics imbalance, biology disruption, and their communion, and to develop a composite IVDD model by ovariectomy combined with lumbar facetectomy for mimicking elderly IVDD with osteoporosis and lumbar spinal instability. Mice were randomly divided into four groups and subjected to sham surgery (CON), ovariectomy (OVX), facetectomy (mechanical instability, INS) or their combination (COM), respectively. Radiographical (n = 4) and histological changes (n = 8) of L4/5 spinal segments were analyzed. Tartrate-resistant acid phosphatase (TRAP) staining was conducted to detect osteoclasts, and expression of osterix (OSX), type I collagen (Col I), type II collagen (Col II) and vascular endothelial growth factor (VEGF) were evaluated by immunochemistry. OVX affected the body's metabolism but INS did not, as the body weight increased and uterus weight decreased in OVX and COM mice compared to CON and INS mice. OVX, INS, and COM caused IVDD in various degrees at 12 weeks after surgery. However, the major pathogeneses of OVX- and INS-induced IVDD were different, which focused on endplate (EP) remodeling and annulus fibrosus (AF) collapse, respectively. OVX induced osteopenia of vertebra. In contrast, INS promoted the stress-adaptive increase of subchondral bone trabeculae. The COM produced a reproducible severe IVDD model with characteristics of sparse vertebral trabeculae, cartilaginous EP ossification, subchondral bone sclerosis, fibrous matrix disorder, angiogenesis, disc stiffness, as well as space fusion. Additionally, all groups had elevated bone and cartilage turnover compared with CON group, as the quantity of trap + osteoclasts and the osteogenic OSX expression increased in these groups. Likewise, the VEGF expression levels were similar, accompanied by the altered matrix expression of disc, including the changed distribution and contents of Col II and Col I. The findings suggested that the composite mouse model to some extent could effectively mimic the interactions of biology and mechanics engaged in the onset and natural course of IVDD, which would be more compatible with the IVDD of elderly with vertebral osteoporosis and spinal instability and benefit to further clarify the complicated mechanobiological environment of elderly IVDD progression.

Biomechanical role of osteoporosis affects the incidence of adjacent segment disease after percutaneous transforaminal endoscopic discectomy

Study design

Variation in the biomechanical characteristics of intervertebral discs adjacent to the segment disc after undergoing percutaneous transforaminal endoscopic discectomy (PTED) in models with normal and abnormal bone mineral density (BMD) was estimated using the finite element method.

Objective

The study investigated the change in the incidence of adjacent segment disease (ASD) after PTED in patients without and with osteoporosis.

Backgrounds

PTED has been widely used for treating lumbar disc herniation (LDH); changes in BMD will affect biomechanical characteristics, possibly leading to changes in the incidence of ASD after PTED. However, this issue remains largely unclear.

Methods

A non-linear, lumbosacral finite element model was reconstructed based on imaging data and validated using compared values computed by the current model from published and well-validated, in vitro biomechanical experiment studies. Corresponding PTED models with normal and abnormal BMDs were also reconstructed. Shear and von Mises stresses on the annulus fibrosis, the von Mises stress on the endplates in L5–S1 segment discs, and the total deformation of current lumbosacral models were computed in different body positions by changing loading conditions, including flexion, extension, left and right lateral bending, and axial rotation.

Results

In most loading conditions, biomechanical characteristics of the lumbosacral segment discs with normal BMDs after PTED slightly increased. However, in the PTED model with osteoporosis, most of the biomechanical characteristics dramatically increased.

Conclusion

Osteoporosis leads to the deterioration of biomechanical characteristics in the adjacent segment disc after PTED; this variation may also result in an increase in the incidence of ASD. However, further studies on the interactions between pathological changes are warranted.

Osteoporosis therapies might lead to intervertebral disc degeneration via affecting cartilage endplate

Osteoporosis and intervertebral disc degeneration (IDD) are both age-related diseases of the musculoskeletal system. With the average life expectancy longer than ever, the morbidity caused by these two diseases is increasing. Nowadays, treatment strategies for osteoporosis are mainly aimed at increasing the mineral density of the bone. Some of these therapies, including vitamin D, calcium, bisphosphonates, Wnt signal activators and parathyroid hormone regulators, have been suggested to be capable of causing calcification of the cartilage endplate in the intervertebral disc. This alteration could block nutrient and oxygen transportation to the center part of the disc, thus lead to intervertebral disc degeneration. Consequently, we hypothesize that osteoporosis therapies might be a potential risk for IDD. This assumption indicates that we should take the alterations of the cartilage endplate into consideration in further osteoporosis treatment to avoid IDD in the patient.

Medical optimization of lumbar fusion in the osteoporotic patient

PURPOSE

In patients undergoing lumbar fusion, osteoporosis has been shown to lead to poorer outcomes and greater incidence of fusion-related complications. Given the undesirable effect of osteoporosis on lumbar fusion surgery, a number of medications have been proposed for use in the peri- and postoperative period to mitigate risks and enhance outcomes. The purpose of this review was to summarize and synthesize the current literature regarding medical management of osteoporosis in the context of lumbar fusion surgery.

METHODS

A literature search of PubMed, Embase, and Web of Science was conducted in October 2016, using permutations of various search terms related to osteoporosis, medications, and lumbar fusion.

RESULTS

Teriparatide injections may lead to faster, more successful fusion, and may reduce fusion-related complications. Bisphosphonate therapy likely does not hinder fusion outcomes and may be useful in reducing certain complications of fusion in osteoporotic patients. Calcitonin and selective estrogen receptor modulator therapy show mixed results, but more research is necessary to make a recommendation. Vitamin D deficiency is associated with poor fusion outcomes, but evidence for supplementation in patients with normal serum levels is weak.

CONCLUSIONS

Overall, the current body of research appears to support the use of teriparatide therapy to enhance lumbar fusion outcomes in the osteoporotic patient, although the extent of research on this topic is limited. Additionally, very little evidence exists to cease any of the mentioned osteoporosis treatments prior to lumbar fusion.

Impact of prenatal hypoxia on fetal bone growth and osteoporosis in ovariectomized offspring rats

Prenatal hypoxia causes intrauterine growth retardation. It is unclear whether/how hypoxia affects the bone in fetal and offspring life. This study showed that prenatal hypoxia retarded fetal skeletal growth in rats, inhibited extracellular matrix (ECM) synthesis and down-regulated of insulin-like growth factor 1 (IGF1) signaling in fetal growth plate chondrocytes in vivo and in vitro. In addition, ovariectomized (OVX) was used for study of postmenopausal osteoporosis. Compared with the control, OVX offspring in prenatal hypoxic group showed an enhanced osteoporosis in the femurs, associated with reduced proteoglycan and IGF1 signaling. The results indicated prenatal hypoxia not only delayed fetal skeletal growth, but also increased OVX-induced osteoporosis in the elder offspring probably through down-regulated IGF1 signaling and inhibition of ECM synthesis, providing important information of prenatal hypoxia on functional and molecular bone growth and metabolism in fetal and offspring.

Characterization of a novel caudal vertebral interbody fusion in a rat tail model: An implication for future material and mechanical testing

Background

Of the proposed animal interbody fusion models, rat caudal discs have gained popularity in disc research due to their strong resemblance to human discs with respect to geometry, composition and mechanical properties. The purpose of this study is to demonstrate an efficient, repeatable and easily accessible animal model of interbody fusion for future research into mechanical testing and graft materials.

Methods

Twelve 12-week-old female Sprague–Dawley (SD) rats underwent caudal interbody fusion of the third and fourth coccygeal vertebrae of the tail. Serial radiological evaluation, and histological evaluation and manual palpation after sacrifice were performed to assess the fusion quality. Mechanical testing of functional units (FUs) of non-operated and operated segments was compared using a three-point bending test.

Results

At postoperative 12 weeks, callus formation was observed at the fusion sites in all rats, with the mean radiological evaluations of 2.75/3 according to the Bransford classification. Newly formed bone tissue was also observed in all rats with the mean histological score of 5.85/7, according to the Emery grading system. No palpable gaps and obvious change of bending stiffness was observed in the operated segments. The mean bending stiffness of the FUs was statistically higher than that of the control FUs (26.57 ± 6.71 N/mm vs. 12.45 ± 3.21 N/mm, p < 0.01).

Conclusion

The rat caudal disc interbody fusion model proved to be an efficient, repeatable and easily accessible model. Future research into adjuvant treatments like growth factor injection and alternative fusion materials under conditions of osteoporosis using this model would be worthwhile.