Discogenic origins of spinal instability

A Self-Polymerizing Mesh of Nano-Tethers for the Mechanical Constraint of Degraded Intervertebral Discs-A Review of 25 Years of Pre-Clinical and Early Clinical Research

Genipin polymers are self-forming tensile-load-carrying oligomers, derived from the gardenia fruit, that covalently bond to amines on collagen. The potential therapeutic mechanical benefits of a non-discrete in situ forming mesh of genipin oligomers for degraded spinal discs were first conceived in 1998. Over more than two decades, numerous studies have demonstrated the immediate mechanical effects of this injectable, intra-annular polymeric mesh including an early demonstration of an effect on clinical outcomes for chronic or recurrent discogenic low back pain. This literature review focused on articles investigating mechanical effects in cadaveric animal and human spinal discs, biochemical mechanism of action studies, articles describing the role of mechanical degradation in the pathogenesis of degenerative disc disease, initial clinical outcomes and articles describing current discogenic low back pain treatment algorithms. On the basis of these results, clinical indications that align with the capabilities of this novel injectable polymer-based treatment strategy are discussed. It is intended that this review of a novel nano-scale material-based solution for mechanical deficiencies in biologically limited tissues may provide a helpful example for other innovations in spinal diseases and similarly challenging musculoskeletal disorders.

Myofascial and discogenic origins of lumbar pain: A critical review

The purpose of this three-part narrative review is to examine the anatomy of, and the research which supports, either the lumbar myofascia or intervertebral disc (IVD) as principal sources of our patient's low back pain. A comprehensive understanding of anatomical lumbar pain generators in combination with the current treatment-based classification system will further improve and enhance clinical decision-making skills. Section I reviews the anatomy of the spinal myofascia, myofascial sources of lumbar pain, and imaging of myofascial tissues. Part II reviews the anatomy of the IVD, examines the IVD as a potential lumbar pain generator, and includes detailed discussion on Nerve Growth Factor, Inflammatory Cytokines, Vertebral End Plates and Modic change, Annular tears, and Discogenic instability. Part III looks at the history of myofascial pain, lab-based research and myofascial pain, and various levels of discogenic pain provocation research including animal, laboratory and human subjects. Our review concludes with author recommendations on developing a comprehensive understanding of altered stress concentrations affecting the posterior annulus fibrosis, neo-innervation of the IVD, inflammatory cytokines, discogenic instability, and how this knowledge can complement use of the Treatment-Based Classification System.

Defining and measuring objective and subjective spinal stiffness: a scoping review

PURPOSE

Examine and identify the breadth of definitions and measures of objective and subjective spinal stiffness in the literature, with a focus on clinical implications.

METHODS

A scoping review was conducted to determine what is known about definitions and measures of the specific term of spinal stiffness. Following the framework by Arksey and O'Malley, eligible peer-reviewed studies identified using PubMed, Ebsco health, and Scopus were included if they reported definitions or measures of spinal stiffness. Using a data abstraction form, the studies were classified into four themes: biomechanical, surgical, pathophysiological, and segmental spinal assessment. To identify similarities and differences between studies, sixteen categories were generated.

RESULTS

In total, 2426 records were identified, and 410 met the eligibility criteria. There were 350 measures (132 subjective; 218 objective measures) and 93 indicators of spinal stiffness. The majority of studies (n = 69%) did not define stiffness.

CONCLUSION

This review highlights the breadth of objective and subjective measures that are both clinically and methodologically diverse. There is no consensus regarding a standardised definition of stiffness in the reviewed literature.

Early Clinical Results of Intervertebral Joint Stabilization by Injectable Load-Sharing Polymers

Background

Genipin is a polymer-forming collagen bonding substance that can be dissolved in a buffered carrier and injected into disc annulus tissues. Therapeutic benefit is derived from the mechanical support provided by a large number of genipin polymers attached to collagen fibers in a degraded disc.

Study Design/Setting

IRB-approved prospective, multi-site, single-arm, 12-month feasibility studies were undertaken in two countries to evaluate the safety and efficacy of the genipin-based implant for treating discogenic chronic low back pain (CLBP).

Patient Sample

Twenty CLBP patients with symptomatic discs at one or two levels were enrolled in the study.

Outcome Measures

The primary safety endpoint was serious adverse events at 1 month, and the primary efficacy endpoint was reduction of pain and disability at 3 months. Secondary efficacy endpoints included reduction of pain and disability at 2 weeks, 1 month, 6 months, and 12 months; reduction of flexion-extension instability; increase in segmental lordosis and rotation; and patient satisfaction.

Methods

Fluoroscopic image-guidance was used to deliver two posterolateral injections of buffered genipin to each symptomatic disc. Flexion-extension radiographs were used to quantify joint kinematics at three time-points.

Results

Clinically meaningful improvements in pain and disability scores were reported in 80% or more of patients from 2 weeks to 1 year post-treatment. For the more severely unstable joints, treatment significantly reduced the instability score from a pre-treatment level of 2.4 standard deviations above the mean for an asymptomatic population to the asymptomatic mean at the 3-month follow-up.

Conclusion

These initial clinical data demonstrate the safety and efficacy of a genipin-based collagen tethering device capable of improving spinal joint stability while successfully addressing CLBP. This work merits additional randomized clinical studies.

Activation of Nrf2 signaling by 4-octyl itaconate attenuates the cartilaginous endplate degeneration by inhibiting E3 ubiquitin ligase ZNF598

OBJECTIVE

Cartilaginous endplate (CEP) degeneration is the main early manifestations of intervertebral disc degeneration (IVDD), and is closely related to the oxidative stress. Nrf2 (nuclear factor E2-related factor 2, NFE2L2) is a vital transcriptional factor of cellular antioxidant and anti-inflammatory responses. We aimed to illustrate whether the Nrf2 which was increased in expression by 4-octyl itaconate (4OI) could attenuate intervertebral disc degeneration through suppressing macrophage associated inflammation and catabolism of cartilaginous endplate.

METHODS

Firstly, we detected the expression of Nrf2 in human degenerative CEPs. Then, we performed in vitro, ex vivo and in vivo (a rat-tail puncture model) experiments to explore the role of 4OI in IVDD. Also, by cell co-culture experiments, we demonstrated 4OI restrained the macrophage-associated inflammatory responses. Finally, through western blotting and immunoprecipitation (IP) assay, we clarified the ZNF598-mediated ubiquitination of Nrf2.

RESULTS

We found decreased expression of Nrf2 in human degenerative CEPs. Using a rat IVDD model(n = 6), 4OI significantly ameliorated the progression of IVDD by MR images and histological analysis. Immunofluorescence results reveal that catabolism of CEPs and macrophage-associated inflammation are suppressed by 4OI treatment. Mechanistically, the 4OI increases Nrf2 expression and inhibits the secretion of inflammatory factors (IL-1β) by Lipopolysaccharide (LPS)-induced macrophages, thus preventing the inflammatory-related CEP degeneration. Meanwhile, 4OI suppresses the reactive oxygen species (ROS) production and catabolism of LPS-induced rat CEP cells. In addition, 4OI inhibits the ZNF598-dependent ubiquitination of Nrf2 in LPS-induced rat CEP cells.

CONCLUSIONS

4OI may alleviate IVDD by suppressing CEP degeneration and macrophage-associated inflammation. 4OI may be an alternative therapy for degenerative CEPs/IVDs.

Neurogenic Bladder in Dogs, Cats and Humans: A Comparative Review of Neurological Diseases

Lower urinary tract disease (LUTD) includes abnormalities in the structure and function of the bladder and the urethra. LUTD caused by neurological disease is defined neurogenic bladder (NB). The integrity of the central nervous system (CNS) and peripheral nervous system (PNS) is required to explicate normal micturition, maintaining the proper function of bladder and urethra. The location and type of neurological lesions influence the pattern of clinical manifestations, potential treatment, and prognosis. Though, in dogs and cats, spinal cord injury is considered mainly responsible for bladder and/or urethra incompetence, other disorders, congenital or acquired, involving CNS or PNS, could play a role in NB. In veterinary medicine, the information about the epidemiology, prevalence, etiopathogenesis, diagnosis and treatment of NB are scattered. The aim of this study is to provide an overview of the epidemiology, prevalence, clinical findings, diagnosis and prognosis for NB in dogs and cats compared with humans.

Even mild intervertebral disc degeneration reduces the flexibility of the thoracic spine: an experimental study on 95 human specimens

BACKGROUND CONTEXT

Intervertebral disc degeneration represents one of multiple potential trigger factors for reduced passive spinal mobility and back pain. The effects of age-related degenerative intervertebral disc changes on spinal flexibility were however mainly investigated for the lumbar spine in the past, while intervertebral disc degeneration is also highly prevalent in the thoracic spine.

PURPOSE

To evaluate the effect of the degeneration grade on the range of motion and neutral zone of the thoracic spine.

STUDY DESIGN

Experimental study including combined radiological grading of intervertebral disc degeneration and biomechanical testing of 95 human thoracic functional spinal units (min. n=4 per level from T1-T2 to T11-T12) from 33 donors (15 female / 18 male, mean age 56 years, age range 37-80 years).

METHODS

Degeneration grades of the intervertebral discs were assessed using the validated x-ray grading scheme of Liebsch et al. (0=no, 1=mild, 2=moderate, 3=severe degeneration). Motion segments were loaded with pure moments in flexion/extension, lateral bending, and axial rotation to determine range of motion and neutral zone at 5 Nm.

RESULTS

All tested specimens exhibited degeneration grades between zero and two. Range of motion significantly decreased for grades one and two compared with grade zero in any motion direction (p<.05), showing the strongest decrease in extension comparing grade two with grade zero (-42%), while no significant differences were detected between grades one and two. Similar trends were found for the neutral zone with the strongest decrease in extension also comparing grade two with grade zero (-47%). Donor age did not significantly affect the range of motion, whereas the range of motion was significantly reduced in specimens from male donors due to the significantly higher degeneration grade in this study.

CONCLUSIONS

Even mild intervertebral disc degeneration reduces the range of motion and neutral zone of the thoracic spine in any motion plane, whereas progressing degeneration does not further affect its flexibility. This is in contrast to the lumbar spine, where a more gradual decrease of flexibility was found in prior studies, which might be explained by differences between thoracic and lumbar intervertebral disc morphologies.

CLINICAL SIGNIFICANCE

Thoracic intervertebral disc degeneration should be considered as one of multiple potential causal factors in patients showing reduced passive mobility and middle back pain.

Morphological changes of Intervertebral Disc detectable by T2-weighted MRI and its correlation with curve severity in Adolescent Idiopathic Scoliosis

Background

Our previous studies found disproportionate anteroposterior vertebral size is associated with severity of the scoliotic curves in adolescent idiopathic scoliosis (AIS) patients. Subsequent studies showed wedging of vertebral bodies (VB) had less contribution than intervertebral discs (IVD) to the anterior–posterior vertebral column length discrepancy in severe-AIS. However, the exact morphological changes of IVD were not clearly defined. This study aimed to evaluate the morphological and pathological changes of IVD and VB in AIS girls and healthy female controls.

Methods

This study included 33 age-matched female controls and 76 AIS girls with a right-sided thoracic curvature. Wedge angle, height ratio and distance ratio of VB and IVD were measured on the best midline coronal and sagittal planes from reformatted MRI spine. Volumes of VB, IVD and nucleus pulposus (NP) were also evaluated on volumetric images. One-way ANOVA with Bonferroni correction and Pearson correlation tests were used.

Results

There was significant difference in wedge angle and height ratio of VB and IVD between AIS and controls. In severe-AIS, the position of NP was significantly shifted to the convexity when compared with non-severe AIS and controls. Whereas, the volume of IVD and NP in severe-AIS was found to be significantly smaller. In addition, Cobb angle was significantly correlated with wedge angle and height ratio, and inversely correlated with the volume of NP.

Conclusions

In addition to wedging of VB and IVD, there was significantly reduced volume of IVD and NP in AIS patients with severe curve, insinuating the mechanical effect of scoliosis leads to a compression on both IVD and NP before significant disc desiccation occurs. We postulate that the compression of IVD and NP can contribute to curve progression in severe-AIS, these patients are more prone to disc degeneration in adulthood if no operative treatment is offered. Further longitudinal study on these parameters is still warranted.

Effect of a 'spine offloading' chair design on seated height and posture

A prototype chair with anterior chest and arm supports has been designed to reduce compressive spine loads. The purpose of this study was to compare the effects of this offloading design on seated height compared to a control configuration of the same chair. 20 males sat on each configuration for 1 hour. Seated height, perceived pain, spine angles, seat pressure, and participant experience were measured. Spine height loss was significantly reduced in the offloading (-0.75 ± 3.79 mm) compared to the control configuration (-6.16 ± 4.27 mm, p < 0.001), and participants sat significantly more anterior on the seat pan in the offloading (20.56 ± 1.67 cm) compared to control configuration (18.03 ± 1.92 cm, p < 0.001). There were no differences in spine angles or perceived back and gluteal pain between configurations. This design appears to be a promising approach to protecting the back during sitting when engaging in forward leaning tasks where the offloading effect of a backrest may be minimised. Practitioner summary: A prototype chair with anterior chest and arm supports designed to offload the spine was shown to significantly reduce seated height loss during 1-hour of sitting compared to a control configuration. While participants perceived the offloading design to be more supportive, no differences in perceived pain or posture were found.

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.

Unloaded Organ Culturing Has a Detrimental Effect on the Axial Mechanical Properties of the Intervertebral Disc

Healthy function of intervertebral discs (IVDs) depends on their tissue mechanical properties. Native cells embedded within IVD tissues are responsible for building, maintaining, and repairing IVD structures in response to genetic, biochemical, and mechanical signals. Organ culturing provides a method for investigating how cells respond to these stimuli in their natural architectural environment. The purpose of this study was to determine how organ culturing affects the mechanical characteristics of functional spine units (FSUs) across the entire range of axial loading, including the neutral zone (NZ), using a rat tail model. Rat tail FSUs were organ cultured at 37 °C in an unloaded state in standard culture media for either 1-day (n = 8) or 6-days (n = 12). Noncultured FSUs (n = 12) were included as fresh control specimens. Axial mechanical properties were tested by applying cyclical compression and tension. A novel mathematical approach was developed to fully characterize the relationship between load, stiffness, and deformation through the entire range of loading. Culturing FSUs for 1-day did not affect any of the axial mechanical outcome measures compared to noncultured IVDs; however, culturing for 6 days increased the size of NZ by 112% and decreased the stiffness in NZ, compressive, and tensile regions by 53%, 19%, and 15%, respectively, compared to noncultured FSUs. These results highlight the importance of considering how the mechanical integrity of IVD tissues may affect the transmission of mechanical signals to cells in unloaded organ culturing experiments.

Variation in the seventh lumbar vertebra and the lumbosacral junction morphometry associated with the sacrocaudal fusion in greyhounds

The lumbosacral joint is where the 7th lumbar vertebra (L.7) articulates within the sacrum. It is a clinically important area in the dog because of its relatively large range of motion. The current study aims to determine the possible differences in the length of the L.7 vertebra and the angle of the lumbosacral junction among greyhounds of standard and those of fused sacra, and to determine the potential association of sex, body mass and type of fused sacrum (standard and fused) on the morphology of the L.7 vertebra and the angle of the lumbosacral junction. Radiographs of 55 greyhound cadavers were used for radiographing; all radiographic images were stored and measured using X-ray acquisition software, and then analysed using descriptive statistics, multiple linear regression and logistic regression. The results of this study showed a significant increase (p < .008) in the length of the L.7 vertebra and the angle of the lumbosacral junction (p < .028) in greyhounds with fused sacra comparing with those of standard sacra, but the L.6 length was not significant (p = .431). Differences have been found in the length of L.7 vertebra and the angle of the lumbosacral junction in greyhounds. It was found that in greyhounds, any variation in the sacrum's anatomical features may alter the structure of the surrounding anatomical structures such as the L.7 vertebra and lumbosacral junction.

Damage to the human lumbar cartilage endplate and its clinical implications

The cartilaginous endplate (CEP) is a thin layer of hyaline cartilage, and plays an important role in the diffusion of nutrients into the intervertebral discs. Its damage may seriously affect the disc degeneration, and result in low back pain (LBP). However, the structural features of damaged CEPs have not been well characterized, and this hinders our understanding of the etiology of disc degeneration and pain. To present the structural features of micro-damaged CEPs in patients with disc degeneration and LBP that might even be regarded as an initial factor for disc degeneration, we performed a histological study of micro-damaged CEPs harvested from human lumbar intervertebral discs and analyzed its clinical implications. Human lumbar CEPs were excised from 35 patients (mean age 60.91 years) who had disc degeneration and LBP. Control tissue was obtained from 15 patients (mean age 54.67 years) with lumbar vertebral burst fractures. LBP and disability were assessed clinically, and all patients underwent anterior vertebral body fusion surgery. CEPs together with some adjacent nucleus pulposus (NP) were sectioned at 4 µm, and stained using H&E, Safranin O/Fast Green, and Alcian Blue. Immunostaining and PCR were used to identify various markers of degeneration, innervation, and inflammation. Histology demonstrated physical micro-damage in 14/35 CEPs from the disc degeneration group. Six major types of damage could be distinguished: fissure, traumatic nodes, vascular mimicry, incorporation of NP tissue within the CEP, incorporation of bone within the CEP, and incorporation of NP and bone within the CEP. Pain and disability scores (ODI: p = 0.0190; JOA: p = 0.0205; JOABPEQ: p = 0.0034) were significantly higher in those with micro-damaged CEPs (N = 14) than in those with non-damaged CEPs (N = 21). CEP damage was significantly associated with elevated MMP3 (p = 0.043), MMP13 (p = 0.0191), ADAMTS5 (p = 0.0253), TNF-α (p = 0.0011), and Substance P (p = 0.0028), and with reduced Sox9 (p = 0.0212), aggrecan (p = 0.0127), and type II collagen (p = 0.0139). In conclusion, we presented a new classification of human lumbar micro-damaged CEPs. Furthermore, we verify disc degeneration, innervation, and discogenic pain in micro-damaged CEPs.

Factors important in bone union after posterior lumbar interbody fusion using the cortical bone trajectory technique

Background

The cortical bone trajectory (CBT) technique has developed as an alternative to the traditional pedicle screw fixation technique due to its minimum invasiveness for screw insertion and rigid fixation for posterior lumbar interbody fusion (PLIF). However, the factors contributing to bone union after CBT-PLIF is a controversial subject. The aim of this study was to investigate factors important to bone union after CBT-PLIF.

Methods

We analyzed 69 consecutive patients who underwent single-level CBT-PLIF from October 2011 to December 2016 and were followed for over two years. Bone union was evaluated using computed tomography (CT) and dynamic assessment in the radiograph within two years after CBT-PLIF. The following factors that may influence bone union were investigated: age, gender, bone mineral density (BMD), cage materials [polyether-ether-ketone (PEEK) or titanium (Ti)], vertebral-slip (neutral), translational motion (flexion/extension), angular motion (flexion/extension), screw depth into the vertebral body (% depth), interval of bilateral screw heads, and cage position.

Results

The bone union rate at the two-year follow-up was 88.4% (61/69). A univariate analysis revealed that variables with values of P<0.20 were age (P<0.01), gender (P=0.07), cage material (P=0.18), vertebral slip (neutral) (P=0.14), % depth (P=0.086), and cage position (P<0.01). Multiple logistic regression analyses revealed that factors related to bone union were young age (P<0.01), Ti cage (P<0.01), small vertebral slip (neutral) (P<0.01), high % depth (P<0.01), and anterior cage position (P<0.01).

Conclusions

For CBT-PLIF, deeper screw insertion into the vertebral body, anterior cage placement, and Ti cage usage may be important surgical techniques to achieve a successful bone union.

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

PURPOSES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Cyclin-Dependent Kinase 9 (CDK9) Inhibitor Atuveciclib Suppresses Intervertebral Disk Degeneration via the Inhibition of the NF-κB Signaling Pathway

Intervertebral disk degeneration (IVDD) is a spinal disk condition caused by an inflammatory response induced by various proinflammatory cytokines, such as interleukin (IL)-1β and tumor necrosis factor (TNF)-α. cyclin-dependent kinase 9 (CDK9) is a transcriptional regulator and potential therapeutic target for many diseases, especially in regulating the activation of primary inflammatory response genes. Our study investigated a highly selective CDK9 inhibitor, atuveciclib, which protects nucleus pulposus (NP) cells from proinflammatory stimuli-induced catabolism. The effects of CDK9 inhibition were determined in human and rat NP cells treated with IL-1β in the presence or absence of atuveciclib or small interfering RNA target CDK9. Inhibition of CDK9 led to the attenuation of inflammatory response. In addition, rat intervertebral disk (IVD) explants were used to determine the role of CDK9 inhibition in extracellular matrix degradation. The rat IVDD model also proved that CDK9 inhibition attenuated IVDD, as validated using magnetic resonance imaging and immunohistochemistry. Taken together, CDK9 is a potential therapeutic target to prevent IVDD.

The degenerative lumbar disc: not a disease, but still an important consideration for OMPT practice: a review of the history and science of discogenic instability

BACKGROUND

A recent AAOMPT position paper was published that opposed the use of the term 'degenerative disc disease' (DDD), in large part because it appears to be a common age-related finding. While common, there are significant physiologic and biomechanical changes that occur as a result of discogenic degeneration, which are relevant to consider during the practice of manual therapy.

METHODS

A narrative review provides an overview of these considerations, including a historical perspective of discogenic instability, the role of the disc as a pain generator, the basic science of a combined biomechanical and physiologic cycle of degeneration and subsequent discogenic instability, the influence of rotation on the degenerative segment, the implications of these factors for manual therapy practice, and a perspective on an evidence-based treatment approach to patients with concurrent low back pain and discogenic degeneration.

CONCLUSIONS

As we consider the role of imaging findings such as DDD, we pose the following question: Do our manual interventions reflect the scientifically proven biomechanical aspects of DDD, or have we chosen to ignore the helpful science as we discard the harmful diagnostic label?

Three-Dimensional Spinal Position With and Without Manual Distraction Load Increases Spinal Height

OBJECTIVE

The purpose of this study was to investigate if spinal height increases using 3-dimensional (3-D) spinal position with and without manual distraction load and to assess the correlation between spine height changes and degrees of trunk rotation.

METHODS

Fifty-six participants were randomly placed in one of two groups: (1) 3-D spinal position with manual distraction load, and (2) without manual distraction load. Spinal height was measured before and after the interventions using a stadiometer. For the statistical analysis, we used a 2 (Loading status: pre- versus post-intervention height) X 2 (3-D spinal position: with versus without manual distraction load) repeated measures Analysis of Variance (ANOVA) was used to identify significant interaction and main effects. Paired t-tests were used to calculate differences in spinal height changes between the two interventions. Pearson correlation coefficient was used to measure correlations between changes in spinal heights and degrees of trunk rotation.

RESULTS

Mean spinal height increase with 3-D spinal position with and without manual distraction load was 6.30 mm (±6.22) and 5.69 mm (±4.13), respectively. No significant interaction effect was present between loading status and 3-D spinal position but a significant main effect in loading status was. Paired t-tests revealed significant differences in spinal heights between pre-and post-3-D spinal position with and without manual distraction load. No significant correlation was measured between trunk rotation and spinal height changes.

CONCLUSION

3-D spinal position with or without distraction load increased spinal height. This suggests that 3-D spinal positioning without manual distraction could be used in home settings to help maintain intervertebral disc (IVD) health.

Recurrent disc herniation following percutaneous endoscopic lumbar discectomy preferentially occurs when Modic changes are present

Objective

To investigate the relationship between Modic changes (MCs) and recurrent lumbar disc herniation (rLDH) and that between the herniated disc component and rLDH following percutaneous endoscopic lumbar discectomy (PELD).

Methods

We included 102 (65 males, 37 females, aged 20–66 years) inpatients who underwent PELD from August 2013 to August 2016. All patients underwent CT and MRI preoperatively. The presence and type of Modic changes were assessed. During surgery, the herniated disc component of each patient was classified into two groups: nucleus pulposus group and hyaline cartilage group. The association of herniated disc component with Modic changes was investigated. The incidence of rLDH was assessed based on a more than 2-year follow-up.

Results

In total, 11 patients were lost to follow-up; the other 91 were followed up during 24–60 months. Of the 91 patients, 99 discs underwent PELD; 28/99 (28.3%) had MCs. Type I and II MCs were seen in 9 (9.1%) and 19 (19.2%), respectively; no type III MCs were found. Among 28 endplates with MCs, according to the herniated disc component, 18/28 (64.3%) showed evidence of hyaline cartilage in the intraoperative specimens, including 6/9 and 12/19 endplates with type I and II MCs, respectively. Among 71 endplates without MCs, 14/71 (19.7%) showed evidence of hyaline cartilage in the intraoperative specimens. Hyaline cartilage was more common in patients with MCs (P < 0.05). We found 2 cases of rLDH in the non-MC group (n = 71); 6 cases of rLDH were found in the MC group (n = 28), including 2 and 4 cases for types I and II, respectively. There was no significant difference between types I and II (P > 0.05). rLDH was more common in patients with MCs (P < 0.05). We found 5 rLDH cases in the hyaline cartilage group (n = 32); 3 rLDH cases were found in the nucleus pulposus group (n = 67). rLDH was more common in the hyaline cartilage group (P < 0.05).

Conclusions

rLDH following PELD preferentially occurs when MCs or herniated cartilage are present.

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.

Human Disc Nucleotomy Alters Annulus Fibrosus Mechanics at Both Reference and Compressed Loads

Nucleotomy is a common surgical procedure and is also performed in ex vivo mechanical testing to model decreased nucleus pulposus (NP) pressurization that occurs with degeneration. Here, we implement novel and noninvasive methods using magnetic resonance imaging (MRI) to study internal 3D annulus fibrosus (AF) deformations after partial nucleotomy and during axial compression by evaluating changes in internal AF deformation at reference loads (50 N) and physiological compressive loads (∼10% strain). One particular advantage of this methodology is that the full 3D disc deformation state, inclusive of both in-plane and out-of-plane deformations, can be quantified through the use of a high-resolution volumetric MR scan sequence and advanced image registration. Intact grade II L3-L4 cadaveric human discs before and after nucleotomy were subjected to identical mechanical testing and imaging protocols. Internal disc deformation fields were calculated by registering MR images captured in each loading state (reference and compressed) and each condition (intact and nucleotomy). Comparisons were drawn between the resulting three deformation states (intact at compressed load, nucleotomy at reference load, nucleotomy at compressed load) with regard to the magnitude of internal strain and direction of internal displacements. Under compressed load, internal AF axial strains averaged -18.5% when intact and -22.5% after nucleotomy. Deformation orientations were significantly altered by nucleotomy and load magnitude. For example, deformations of intact discs oriented in-plane, whereas deformations after nucleotomy oriented axially. For intact discs, in-plane components of displacements under compressive loads oriented radially outward and circumferentially. After nucleotomy, in-plane displacements were oriented radially inward under reference load and were not significantly different from the intact state at compressed loads. Re-establishment of outward displacements after nucleotomy indicates increased axial loading restores the characteristics of internal pressurization. Results may have implications for the recurrence of pain, design of novel therapeutics, or progression of disc degeneration.

Changes in the macroscopic morphology of hip muscles in low back pain

Low back pain is a major health issue affecting the lumbopelvic muscles. Morphological changes in hip muscles, such as alterations in the muscle cross-sectional area and muscle volume, may occur in patients with low back pain. This systematic review was conducted to investigate whether patients with low back pain have macroscopic changes in their hip muscle morphology compared with asymptomatic, healthy individuals, based on current evidence. The electronic databases of PubMed/Medline, Ovid, Scopus, Embase^® , and Google Scholar were searched from the inception to August 31, 2018. We only included full texts of original studies regarding macroscopic morphological alterations, including atrophy and fat infiltration, in hip muscles of patients with low back pain compared with asymptomatic controls. The quality of the included studies was determined using an assessment tool based on the Newcastle-Ottawa Scale. The scale was modified for the purposes of this study. Sixteen comparative observational studies were found eligible to be included in this review. Eleven were classified as high quality and four as moderate quality. The morphological changes in the psoas major, gluteus maximus, gluteus medius, gluteus minimus, and piriformis muscles were assessed in the primary studies. All selected studies were considered B level of evidence studies. The strength of conclusions for the psoas major, gluteal, and piriformis muscles was moderate. The results revealed that there is substantial controversy about the morphological changes in hip muscles in patients with low back pain; however, the majority of high-quality studies concluded that atrophy of hip muscles is evident in patients with low back pain. The psoas major muscle was the most commonly investigated hip muscle for morphological changes. Major methodological limitations of the included studies were identified and discussed. The present systematic review does not include a formal meta-analysis because of very significant differences in the primary studies in terms of study populations and methodologies. Finally, in clinical practice, it is recommended that physical therapists develop exercise programs to improve hip muscle function in patients with low back pain.

Motor Control Changes in Low Back Pain: Divergence in Presentations and Mechanisms

Compared to healthy individuals, patients with low back pain demonstrate differences in all aspects of trunk motor control that are most often studied as differences in muscle activity and kinematics. However, differences in these aspects of motor control are largely inconsistent. We propose that this may reflect the existence of 2 phenotypes or possibly the ends of a spectrum, with "tight control" over trunk movement at one end and "loose control" at the other. Both may have beneficial effects, with tight control protecting against large tissue strains from uncontrolled movement and loose control protecting against high muscle forces and resulting spinal compression. Both may also have long-term negative consequences. For example, whereas tight control may cause high compressive loading on the spine and sustained muscle activity, loose control may cause excessive tensile strains of tissues. Moreover, both phenotypes could be the result of either an adaptation process aimed at protecting the low back or direct interference of low back pain and related changes with trunk motor control. The existence of such phenotypes would suggest different motor control exercise interventions. Although some promising data supporting these phenotypes have been reported, it remains to be shown whether these phenotypes are valid, how treatment can be targeted to these phenotypes, and whether this targeting yields superior clinical outcomes. J Orthop Sports Phys Ther 2019;49(6):370-379. Epub 12 Jun 2018. doi:10.2519/jospt.2019.7917.

Controlled immobilization-traction based on intervertebral stability is conducive to the regeneration or repair of the degenerative disc: an in vivo study on the rat coccygeal model

BACKGROUND CONTEXT

Previous studies have shown the potential for intervertebral disc tissue regeneration is very limited. While in vivo and in vitro studies have shown that traction can restore disc height and internal pressure, in many clinical studies it was shown that axial mechanical traction for the treatment of low back pain is ineffective.

PURPOSE

The aim of this study was to identify how the disc could be distracted, how to define the state of traction, and to further examine the feasibility of regenerating or restoring the degenerative disc by means of traction.

STUDY DESIGN

A macro- and microlevel structural analysis of degenerative discs of rat tail before and after controlled immobilization-traction.

METHODS

In this study, 49 6-month-old male Sprague-Dawley rats were randomly assigned to one of seven groups. Group A was the sham control group in which caudal vertebrae were instrumented with K-wires only. In Group B (model group), caudal vertebrae were immobilized using a custom-made external device to fix four caudal vertebrae (Co7-Co10) and Co8-Co9 underwent 4 weeks of compression to induce moderate disc degeneration. In Group C, vertebrae Co8-Co9 underwent 4 weeks of compression to induce moderate disc degeneration, followed by removal of the external apparatus. Rats in the other four groups (Groups D-G), Co8-Co9 underwent 4 weeks of compression to induce moderate disc degeneration followed by 2 weeks, 4 weeks, 6 weeks, and 8 weeks of distraction, respectively. Caudal vertebrae were harvested and disc height, T2 signal intensity of the discs, disc morphology, total glycosaminoglycan content of the nucleus pulposus and the structure of the Co8-Co9 end plate were evaluated.

RESULTS

After 4 weeks of compression, the intervertebral height and T2 signal intensity of Co8-Co9 vertebrae of rats in Groups B to G were significantly reduced compared with Group A (sham group, all p<.0001). Histological scores of rats in Group B averaged 10.14 and the total glycosaminoglycan (GAG) of nucleus pulposus averaged 238.21μg GAG/ng DNA. The bony end plate structure showed significant changes in comparison with the control Group. After 2 weeks to 8 weeks of traction, the disc space and T2 signal intensity of Co8-Co9 vertebrae in Group E were significantly recovered compared to that of rats in Group B (p<.0001), and the intervertebral height of the Co8-Co9 in Group D, Group F, and Group G when compared with Group B (p<.0001). Meanwhile, the T2 signal intensity of Co8-Co9 in Group D, F, and G when compared with Group B (p<.001). Histological scores dropped from an average of 10.14 in Group B to 5.57 in Group E, and 5.86 in Group F (all p<.0001). Furthermore, the total GAG content of the nucleus pulposus increased from an average of 238.21μg GAG/ng DNA in Group B to 601.02μg GAG/ng DNA in Group E (p<.0001). The number of pores of end plates in rats in Groups D and E both were significantly increased when compared to that of rats in Group B (Groups D vs Groups B, p<.05; Groups E vs Groups B, p<.0001).

CONCLUSIONS

A mechanical degenerative model was successfully established by using a custom-made device. We demonstrated that disc degeneration is a cascade of biochemical, mechanical, and structural changes mediated by cells in an abnormal mechanical environment. Not all levels of disc degeneration can be regenerated or repaired. Regeneration or recovery of disc degeneration requires specific conditions. Based on the immobilization-traction mode, the cascade cycle of disc degeneration is interrupted. Traction of 2 to 6 weeks is a sensitive period for regeneration of the degenerative disc. Moreover, the duration and extent of the traction loading must be moderately controllable, and beyond the limits that can lead to significant degeneration. These data may help improve our understanding of the pathogenesis of clinical disc degeneration and how to optimize the use of traction devices for possible regeneration.

ISSLS PRIZE IN BIOENGINEERING SCIENCE 2019: biomechanical changes in dynamic sagittal balance and lower limb compensatory strategies following realignment surgery in adult spinal deformity patients

STUDY DESIGN

A longitudinal cohort study.

OBJECTIVE

To define a set of objective biomechanical metrics that are representative of adult spinal deformity (ASD) post-surgical outcomes and that may forecast post-surgical mechanical complications. Current outcomes for ASD surgical planning and post-surgical assessment are limited to static radiographic alignment and patient-reported questionnaires. Little is known about the compensatory biomechanical strategies for stabilizing sagittal balance during functional movements in ASD patients.

METHODS

We collected in-clinic motion data from 15 ASD patients and 10 controls during an unassisted sit-to-stand (STS) functional maneuver. Joint motions were measured using noninvasive 3D depth mapping sensor technology. Mathematical methods were used to attain high-fidelity joint-position tracking for biomechanical modeling. This approach provided reliable measurements for biomechanical behaviors at the spine, hip, and knee. These included peak sagittal vertical axis (SVA) over the course of the STS, as well as forces and muscular moments at various joints. We compared changes in dynamic sagittal balance (DSB) metrics between pre- and post-surgery and then separately compared pre- and post-surgical data to controls.

RESULTS

Standard radiographic and patient-reported outcomes significantly improved following realignment surgery. From the DSB biomechanical metrics, peak SVA and biomechanical loads and muscular forces on the lower lumbar spine significantly reduced following surgery (- 19 to - 30%, all p < 0.05). In addition, as SVA improved, hip moments decreased (- 28 to - 65%, all p < 0.05) and knee moments increased (+ 7 to + 28%, p < 0.05), indicating changes in lower limb compensatory strategies. After surgery, DSB data approached values from the controls, with some post-surgical metrics becoming statistically equivalent to controls.

CONCLUSIONS

Longitudinal changes in DSB following successful multi-level spinal realignment indicate reduced forces on the lower lumbar spine along with altered lower limb dynamics matching that of controls. Inadequate improvement in DSB may indicate increased risk of post-surgical mechanical failure. These slides can be retrieved under Electronic Supplementary Material.

Changes in Spinal Height After Manual Axial Traction or Side Lying: A Clinical Measure of Intervertebral Disc Hydration Using Stadiometry

OBJECTIVES

The purpose of this study was to determine the immediate effects of a manual therapy technique consisting of axial traction compared with side lying on increased spine height after sustained loading.

METHODS

Twenty-one asymptomatic participants were included. Participants either received manual therapy technique consisting of manual axial traction force for 2 consecutive rounds of 3 minutes or sustained side lying for 10 minutes. Spine height was measured using a commercially available stadiometer. Spinal height change was determined from measurements taken after loaded walking and measurements taken after manual therapy. A paired t test was performed to determine if a manual therapy technique consisting of axial traction increased spinal height after a period of spinal loading.

RESULTS

A significant increase in height was found after both manual therapy technique and sustained side lying (P < .0001). The mean height gain was 8.60 mm using 3-dimensional axial separation.

CONCLUSION

This study is an initial attempt at evaluating the biomechanical effects of manual therapy technique consisting of axial traction. Both manual axial traction force and sustained side-lying position were equally effective for short-term change in spine height after a loaded walking protocol among healthy asymptomatic individuals. This study protocol may help to inform future studies that evaluate spine height after loading.

Percutaneous transforaminal endoscopic discectomy in the treatment of senior patients with lumbar degenerative disc disease

The aim of the current study was to analyze the efficacy of percutaneous transforaminal endoscopic discectomy (PTED) in the treatment of lumbar degenerative disc disease for senior patients. The clinical and follow-up data of senior patients were retrospectively reviewed. Patients were divided into a PTED group and an open surgery group. Parameters were analyzed, including surgery time, intraoperative fluoroscopy time, intraoperative blood loss, postoperative complications, visual analog scale (VAS) and Japan Orthopedic Association (JOA) scores. Compared with the open surgery group, the surgery time and intraoperative blood loss were decreased, while the intraoperative fluoroscopy time was increased, in the PTED group (P<0.001). Significant improvements in VAS and JOA scores were identified within both groups from preoperative to 12 months following surgery (P<0.001). VAS and JOA scores were significantly improved in the PTEN group compared with the open surgery group at 1 week after surgery (P<0.001), but there was no significant difference between groups prior to and at 12 months following surgery. The incidence of venous thrombosis of the lower extremities in the PTED group was decreased compared with the open surgery group (P<0.05). In the open surgery group, patients suffered from multiple postoperative complications, including constipation, urinary system infection, wound infection, gastrointestinal hemorrhagic stress ulcer, pneumonia, pulmonary embolism, mortality following myocardial infarction, mortality following cerebral infarction, and hemiplegia following cerebral hemorrhage. By contrast, patients in the PTED group did not experience any of these complications. In conclusion, PTED resulted in reduced trauma and a lower incidence of severe complications compared with open surgery, which suggests that PTED is a safe and effective minimally invasive surgery for senior patients with lumbar degenerative disc disease.

Strong association between vertebral endplate defect and Modic change in the general population

Modic change (MC) is considered an independent risk factor for low back pain (LBP) but its aetiology remains unclear. In this cross-sectional, large-scale population-based study we sought to characterise associations between endplate defect (ED) and MC in a population sample of broad age range. The study population consisted of 831 twin volunteers (including 4155 discs and 8310 endplates) from TwinsUK. Lumbar T2-weighted MR images were coded for ED and MC. Total endplate (TEP) score was calculated at each intervertebral disc while receiver operating curves (ROC) were calculated to define critical endplate values predictive of MC. MC was detected in 32.1% of the subjects, with a significantly higher prevalence at lower lumbar levels (3.5% at L1/2-L3/4 vs. 15.9% at L4/5-L5/S1, p < 0.001). TEP score was strongly and independently associated with MC at each lumbar level (risk estimates from 1.49 to 2.44; all p ≤ 0.001) after adjustment for age, sex, BMI and twin pairing. ROC analysis showed a TEP score cut-off of 6 above which there was a significantly higher prevalence of MC. In conclusion, ED were strongly associated with MC at every lumbar level. These findings support the hypothesis that endplate defect is a major initiating factor for the cascade of events that may include disc degeneration (DD) and MC.

Bone-Preserving Decompression Procedures Have a Minor Effect on the Flexibility of the Lumbar Spine

Objective

To mitigate the risk of iatrogenic instability, new posterior decompression techniques able to preserve musculoskeletal structures have been introduced but never extensively investigated from a biomechanical point of view. This study was aimed to investigate the impact on spinal flexibility caused by a unilateral laminotomy for bilateral decompression, in comparison to the intact condition and a laminectomy with preservation of a bony bridge at the vertebral arch. Secondary aims were to investigate the biomechanical effects of two-level decompression and the quantification of the restoration of stability after posterior fixation.

Methods

A universal spine tester was used to measure the flexibility of six L2–L5 human spine specimens in intact conditions and after decompression and fixation surgeries. An incremental damage protocol was applied : 1) unilateral laminotomy for bilateral decompression at L3–L4; 2) on three specimens, the unilateral laminotomy was extended to L4–L5; 3) laminectomy with preservation of a bony bridge at the vertebral arch (at L3–L4 in the first three specimens and at L4–L5 in the rest); and 4) pedicle screw fixation at the involved levels.

Results

Unilateral laminotomy for bilateral decompression had a minor influence on the lumbar flexibility. In flexion-extension, the median range of motion increased by 8%. The bone-preserving laminectomy did not cause major changes in spinal flexibility. Two-level decompression approximately induced a twofold destabilization compared to the single-level treatment, with greater effect on the lower level. Posterior fixation reduced the flexibility to values lower than in the intact conditions in all cases.

Conclusion

In vitro testing of human lumbar specimens revealed that unilateral laminotomy for bilateral decompression and bone-preserving laminectomy induced a minor destabilization at the operated level. In absence of other pathological factors (e.g., clinical instability, spondylolisthesis), both techniques appear to be safe from a biomechanical point of view.

A Mouse Intervertebral Disc Degeneration Model by Surgically Induced Instability

STUDY DESIGN

An experimental study to develop a mouse model of lumbar intervertebral disc degeneration (IDD).

OBJECTIVE

The aim of this study was to develop a mouse lumbar IDD model using surgically induced instability and to compare the findings of this model to those in human IDD.

SUMMARY OF BACKGROUND DATA

Previously, various kinds of inducers have been used to reproduce IDD in experimental animals; however, there is yet no standard mouse lumbar IDD model without direct injury to intervertebral disc.

METHODS

A total number of 59 C57BL/6J male mice at 8 weeks old were used. Instability of lumbar spine was induced by surgical resection of posterior elements, including facet joints, supra- and interspinous ligaments. We then analyzed time course changes in radiographical (n = 17) and histological analyses (n = 42), and compared these findings with those in human IDD.

RESULTS

Radiographical analyses showed that the disc height began to decrease in the first 2 weeks after the surgery, and the decrease continued throughout 12 weeks. Bone spurs at the vertebral rims were observed in the late stage of 8 and 12 weeks after the surgery. Histological analyses showed that the disorder of the anterior anulus fibrosus (AF) was initially obvious, followed by posterior shift and degeneration of the nucleus pulposus (NP). Proteoglycan detected in inner layer of AF and periphery of NP was decreased after 8 weeks. Immunohistochemistry displayed the increase of type I and X collagen, and matrix metalloproteinase 13 in the anterior AF.

CONCLUSION

Surgical resection of posterior elements of mouse lumbar spine resulted in reproducible IDD. Because the present procedure does not employ direct injury to intervertebral disc and the radiological and histological findings are compatible with those in human IDD, it may contribute to further understanding of the native pathophysiology of IDD in future.

LEVEL OF EVIDENCE

N/A.

Radiologic Analysis of Kinematic Characteristics of Modic Changes Based on Lumbar Disc Degeneration Grade

OBJECTIVE

The kinematic characteristics of Modic changes (MCs) in the lumbar spine have rarely been reported; furthermore, the effect of disc degeneration (DD) on segmental motion has not been considered in analyzing the motion characteristics of MCs. Therefore, this study was designed to evaluate the kinematic characteristics of MCs based on different DD grades.

METHODS

894 patients with 4470 lumbar segments were reviewed, and those with MCs were selected for segmental motion evaluation. MC type was defined as 0, I, II, and III, and DD grade was classified into 5 groups from grade A to grade E. Segmental angular and translational motion were calculated from X-ray images in positions of flexion and extension, and the absolute values of the differences were recorded.

RESULTS

MCs were observed in 308 segments from 260 patients. No MC was found in DD grade A, and MC III was not observed in DD grade B. MC I was found to significantly increase angular motion in the DD grade E group, and MC II could enlarge translational motion in the DD grade D group (all P < 0.05); MC III had the lowest segmental motion in both angular and translational motion; There was no statistical difference in angular and translational motion between MC I and II in all DD grade groups (all P > 0.05).

CONCLUSIONS

MC III indicates the final stable phase of segmental motion. MC I might increase angular motion, and MC II would increase certain translational motions in the segments that were believed to be stable.

Fifty top-cited spine articles from mainland China: A citation analysis

Objective To identify the 50 top-cited spine articles from mainland China and to analyze their main characteristics. Methods Web of Science was used to identify the 50 top-cited spine articles from mainland China in 27 spine-related journals. The title, year of publication, number of citations, journal, anatomic focus, subspecialty, evidence level, city, institution and author were recorded. Results The top 50 articles had 29-122 citations and were published in 11 English-language journals; most (32) were published in the 2000s. The journal Spine had the largest number of articles and The Lancet had the highest impact factor. The lumber spine was the most discussed anatomic area (18). Degenerative spine disease was the most common subspecialty topic (22). Most articles were clinical studies (29); the others were basic research (21). Level IV was the most common evidence level (17). Conclusions This list indicates the most influential articles from mainland China in the global spine research community. Identification of these articles provides insights into the trends in spine care in mainland China and the historical contributions of researchers from mainland China to the international spine research field.

Sensory nerve ingrowth, cytokines, and instability of discogenic low back pain: A review

Introduction

Many patients suffer from discogenic low back pain. However, the mechanisms, diagnosistic strategy, and treatment of discogenic low back pain all remain controversial. The purpose of this paper was to review the pathological mechanisms of discogenic low back pain.

Methods

Many authors have investigated the pathological mechanisms of discogenic low back pain using animal models and examining human patients. Central to most investigations is understanding the innervation and instabilities of diseased intervertebral discs and the role of inflammatory mediators. We discuss three pathological mechanisms of discogenic low back pain: innervation, inflammation, and mechanical hypermobility of the intervertebral disc.

Results

Sensory nerve fibers include C-fibers and A delta-fibers, which relay pain signals from the innervated outer layers of the intervertebral disc under normal conditions. However, ingrowth of these sensory nerve fibers into the inner layers of intervertebral disc occurs under disease conditions. Levels of neurotrophic factors and some cytokines are significantly higher in diseased discs than in normal discs. Stablization of the segmental hypermobility, which can be induced by intervertebral disc degeneration, suppresses inflammation and prevents sensitization of sensory nerve fibers innervating the disc.

Conclusions

Pathological mechanisms of discogenic low back pain include sensory nerve ingrowth into inner layers of the intervertebral disc, upregulation of neurotrophic factors and cytokines, and instability. Inhibition of these mechanisms is important in the treatment of discogenic low back pain.

Increased spinal height using propped slouched sitting postures: Innovative ways to rehydrate intervertebral discs

BACKGROUND

Upright and slouched sitting are frequently adopted postures associated with increased intradiscal pressure, spinal height loss and intervertebral disc pathology.

OBJECTIVES

To examine the effects of two sustained propped slouched sitting (PSS) postures on spinal height after a period of trunk loading.

METHODS

Thirty-four participants without a history of low back pain (LBP) were recruited (age 24.4 ± 1.6 years). Subjects sat in (1) PSS without lumbar support and (2) PSS with lumbar support for 10 min, after a period of trunk loading. Spinal height was measured using a stadiometer.

RESULTS

Mean spinal height increase during PSS without lumbar support was 2.94 ± 3.63 mm and with lumbar support 4.74 ± 3.07 mm.

CONCLUSIONS

Both PSS with and without lumbar support significantly increased spinal height after a period of trunk loading (p < 0.001). Such PSS postures can provide a valuable alternative to upright sitting and may be recommended for recovering spinal height in the working environment following periods of loading.

Instability in Thoracolumbar Trauma: Is a New Definition Warranted?

STUDY DESIGN

Review of the articles.

OBJECTIVE

The objective of this study was to review all articles related to spinal instability to determine a consensus statement for a contemporary, practical definition applicable to thoracolumbar injuries.

SUMMARY OF BACKGROUND DATA

Traumatic fractures of the thoracolumbar spine are common. These injuries can result in neurological deficits, disability, deformity, pain, and represent a great economic burden to society. The determination of spinal instability is an important task for spine surgeons, as treatment strategies rely heavily on this assessment. However, a clinically applicable definition of spinal stability remains elusive.

MATERIALS AND METHODS

A review of the Medline database between 1930 and 2014 was performed limited to papers in English. Spinal instability, thoracolumbar, and spinal stability were used as search terms. Case reports were excluded. We reviewed listed references from pertinent search results and located relevant manuscripts from these lists as well.

RESULTS

The search produced a total of 694 published articles. Twenty-five articles were eligible after abstract screening and underwent full review. A definition for spinal instability was described in only 4 of them. Definitions were primarily based on biomechanical and classification studies. No definitive parameters were outlined to define stability.

CONCLUSIONS

Thirty-six years after White and Panjabi's original definition of instability, and many classification schemes later, there remains no practical and meaningful definition for spinal instability in thoracolumbar trauma. Surgeon expertise and experience remains an important factor in stability determination. We propose that, at an initial assessment, a distinction should be made between immediate and delayed instability. This designation should better guide surgeons in decision making and patient counseling.

Paraspinal Muscle Passive Stiffness Remodels in Direct Response to Spine Stiffness: A Study Using the ENT1-Deficient Mouse

STUDY DESIGN

Basic science study of the relationship between the structural properties of the spine and its surrounding musculature.

OBJECTIVE

To determine whether an increase in spine stiffness causes an inverse compensatory change in the passive stiffness of the adjacent paraspinal muscles.

SUMMARY OF BACKGROUND DATA

Intervertebral disc degeneration causes an increase in multifidus passive stiffness; this was hypothesized to compensate for a decrease in spine stiffness associated with disc degeneration. Mice lacking equilibrative nucleoside transporter 1 (ENT1) develop progressive ectopic calcification of the fibrous connective tissues of the spine, which affects the lumbar spine by 6 months of age and likely creates a mechanically stiffer spine.

METHODS

Experiments were conducted on four groups of mice (n = 8 mice/group): wild-type (WT) and ENT1 knockout (KO) at 2 or 8 months of age. Lumbar spines were removed and tested in cyclic axial compression to determine neutral zone length and stiffness. Single muscle fibers and bundles of fibers were isolated from lumbar multifidus and erector spinae, as well as tibialis anterior (a non-spine-related control) and tested to determine elastic modulus (passive stiffness).

RESULTS

At 2 months of age, neither spine nor muscle stiffness was different between KO and WT. At 8 months of age, compared with WT the lumbar spines of ENT1 KO mice had a stiffer and shorter neutral zone, and the paraspinal muscle fibers were less stiff; however, fiber bundles were not different. In addition, tibialis anterior was not different between KO and WT.

CONCLUSION

This work has confirmed that calcification of spinal connective tissues in the ENT1 KO mouse results in a stiffened spine, whereas the concurrent decrease in muscle fiber elastic modulus in the adjacent paraspinal muscles suggests a direct compensatory relationship between the stiffness of the spine and the muscles that are attached to it.

LEVEL OF EVIDENCE

N/A.

Uneven intervertebral motion sharing is related to disc degeneration and is greater in patients with chronic, non-specific low back pain: an in vivo, cross-sectional cohort comparison of intervertebral dynamics using quantitative fluoroscopy

PURPOSE

Evidence of intervertebral mechanical markers in chronic, non-specific low back pain (CNSLBP) is lacking. This research used dynamic fluoroscopic studies to compare intervertebral angular motion sharing inequality and variability (MSI and MSV) during continuous lumbar motion in CNSLBP patients and controls. Passive recumbent and active standing protocols were used and the relationships of these variables to age and disc degeneration were assessed.

METHODS

Twenty patients with CNSLBP and 20 matched controls received quantitative fluoroscopic lumbar spine examinations using a standardised protocol for data collection and image analysis. Composite disc degeneration (CDD) scores comprising the sum of Kellgren and Lawrence grades from L2-S1 were obtained. Indices of intervertebral motion sharing inequality (MSI) and variability (MSV) were derived and expressed in units of proportion of lumbar range of motion from outward and return motion sequences during lying (passive) and standing (active) lumbar bending and compared between patients and controls. Relationships between MSI, MSV, age and CDD were assessed by linear correlation.

RESULTS

MSI was significantly greater in the patients throughout the intervertebral motion sequences of recumbent flexion (0.29 vs. 0.22, p = 0.02) and when flexion, extension, left and right motion were combined to give a composite measure (1.40 vs. 0.92, p = 0.04). MSI correlated substantially with age (R = 0.85, p = 0.004) and CDD (R = 0.70, p = 0.03) in lying passive investigations in patients and not in controls. There were also substantial correlations between MSV and age (R = 0.77, p = 0.01) and CDD (R = 0.85, p = 0.004) in standing flexion in patients and not in controls.

CONCLUSION

Greater inequality and variability of motion sharing was found in patients with CNSLBP than in controls, confirming previous studies and suggesting a biomechanical marker for the disorder at intervertebral level. The relationship between disc degeneration and MSI was augmented in patients, but not in controls during passive motion and similarly for MSV during active motion, suggesting links between in vivo disc mechanics and pain generation.

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.

Assessment of Lumbar Spine Height Following Sustained Lumbar Extension Posture: Comparison Between Musculoskeletal Ultrasonography and Stadiometry

OBJECTIVES

The purpose of this study was to correlate sitting height measured by stadiometry with lumbar spine height (LSH) modifications measured by musculoskeletal ultrasonography (MSU).

METHODS

Eighteen healthy young adults were recruited for this study (mean age: 21.5 ± 1.5 years). All subjects were tested in the following sequence: (1) lying supine for 10 minutes, (2) sitting under loaded (9.5 kg) and unloaded conditions for 5 minutes each, (3) lying supine for 15 minutes with passive lumbar extension, and (4) sitting unloaded for 5 minutes. Both stadiometry and MSU measurements were taken after each step of the testing sequence.

RESULTS

Following the loaded sitting step, sitting height (measured by stadiometry) decreased by 3.4 ± 1.6 mm, whereas following sustained lumbar extension, sitting height increased by 5.4 ± 3.5 mm (P < .05). Following loaded sitting and sustained lumbar extension, LSH decreased by 3.8 ± 1.7 mm and increased by 6.2 ± 4.1 mm, respectively (P < .05). On the basis of the mean differences (between the different steps of the testing sequence), the mean correlation coefficient and the mean coefficient of determination between stadiometry and MSU measurements were calculated at 0.93 ± 0.07 and 0.88 ± 0.13, respectively, and no statistical differences were observed (P > .05).

CONCLUSIONS

In vivo measurements of sitting height changes, measured using stadiometry, were strongly correlated with LSH changes, measured using ultrasonography.

Paraspinal muscle, facet joint, and disc problems: risk factors for adjacent segment degeneration after lumbar fusion

BACKGROUND CONTEXT

Adjacent segment degeneration (ASD) is one of the major complications after lumbar fusion. Several studies have evaluated the risk factors of ASD. Although the paraspinal muscles play an important role in spine stability, no study has assessed the relationship between paraspinal muscle atrophy and the incidence of ASD after lumbar fusion.

PURPOSE

In the present study, we aimed to verify the known risk factors of ASD, such as body mass index (BMI), preoperative adjacent facet joint degeneration, and disc degeneration, and to assess the relationship between paraspinal muscle atrophy and ASD.

STUDY DESIGN

This is a retrospective 1:1 pair analysis matched by age, sex, fusion level, and follow-up period.

PATIENT SAMPLE

To calculate the appropriate sample size for the study, we performed a pre-study analysis of the paraspinal muscle cross-sectional area (CSA), and estimated that at least 35 cases would be needed for each group. Among the 510 patients who underwent posterior lumbar fusion for degenerative lumbar disease between January 2009 and October 2009, a total of 50 patients with ASD after surgery were selected. Another group of 50 matched patients with degenerative lumbar disease without ASD after spinal fusion were selected as the control group. Each patient in the ASD group was matched with a control patient according to age, sex, fusion level, and follow-up period.

OUTCOME MEASURES

Radiographic measurements and demographic data were reviewed.

METHODS

The risk factors considered were higher BMI, preoperative adjacent segment disc and facet degeneration, and preoperative paraspinal muscle atrophy and fatty degeneration. The radiographic data were compared between the ASD and control groups to determine the predictive factors of ASD after posterior lumbar fusion by using logistic regression analysis. The study was not externally funded. The authors have no conflict of interest to declare.

RESULTS

Multivariate logistic regression analysis indicated that higher BMI (odds ratio [OR]: 1.353, p=.008), preoperative facet degeneration on computed tomography examination (OR: 3.075, p=.011), disc degeneration on magnetic resonance imaging (MRI) (OR: 2.783, p=.003), fatty degeneration (OR: 1.080, p=.044), and a smaller relative CSA of the paraspinal muscle preoperatively (OR: 0.083, p=.003) were significant factors for predicting the development of ASD.

CONCLUSIONS

The occurrence of radiological ASD is most likely multifactorial, and is associated with a higher BMI, preexisting facet and disc degeneration on preoperative examination, and a smaller preoperative relative CSA of the paraspinal muscle on MRI.

Incorporating Six Degree-of-Freedom Intervertebral Joint Stiffness in a Lumbar Spine Musculoskeletal Model-Method and Performance in Flexed Postures

Intervertebral translations and rotations are likely dependent on intervertebral stiffness properties. The objective of this study was to incorporate realistic intervertebral stiffnesses in a musculoskeletal model of the lumbar spine using a novel force-dependent kinematics approach, and examine the effects on vertebral compressive loading and intervertebral motions. Predicted vertebral loading and intervertebral motions were compared to previously reported in vivo measurements. Intervertebral joint reaction forces and motions were strongly affected by flexion stiffness, as well as force-motion coupling of the intervertebral stiffness. Better understanding of intervertebral stiffness and force-motion coupling could improve musculoskeletal modeling, implant design, and surgical planning.

Is intervertebral disc pressure linked to herniation?: An in-vitro study using a porcine model

Approximately 40% of low back pain cases have been attributed to internal disc disruption. This disruption mechanism may be linked to intradiscal pressure changes, since mechanical loading directly affects the pressure and the stresses that the inner annulus fibrosus experiences. The objective of this study was to characterize cycle-varying changes in four dependent measures (intradiscal pressure, flexion-extension moments, specimen height loss, and specimen rotation angle) using a cyclic flexion-extension (CFE) loading protocol known to induce internal disc disruption. A novel bore-screw pressure sensor system was used to instrument 14 porcine functional spinal units. The CFE loading protocol consisted of 3600 cycles of flexion-extension range of motion (average 18.30 (SD 3.76) degrees) at 1Hz with 1500N of compressive load. On average, intradiscal pressure and specimen height decreased by 47% and 62%, respectively, and peak moments increased by 102%. From 900 to 2100 cycles, all variables exhibited significant changes between successive time points, except for the specimen posture at maximum pressure, which demonstrated a significant shift towards flexion limit after 2700 cycles. There were no further changes in pressure range after 2100 cycles, whereas peak moments and height loss were significantly different from prior time points throughout the CFE protocol. Twelve of the 14 specimens showed partial herniation; however, injury type was not significantly correlated to any of the dependent measures. Although change in pressure was not predictive of damage type, the increase in pressure range seen during this protocol supports the premise that repetitive combined loading (i.e., radial compression, tension and shear) imposes damage to the inner annulus fibrosus, and its failure mechanism may be linked to fatigue.

Clinical and Radiological Characteristics of Lumbosacral Lateral Disc Herniation in Comparison With Those of Medial Disc Herniation

Lateral disc herniation (foraminal and extra foraminal) has clinical characteristics that are different from those of medial disc herniation (central and subarticular), including older age, more frequent radicular pain, and neurologic deficits. This is supposedly because lateral disc herniation mechanically irritates or compresses the exiting nerve root or dorsal root ganglion inside of a narrow canal more directly than medial disc herniation. The purpose of this study was to investigate clinical and radiological characteristics of lateral disc herniation in comparison with medial disc herniation. The 352 subjects diagnosed with localized lumbosacral disc herniation and followed up for at least 12 months after completion of treatment were included and divided into medial and lateral disc herniation groups, according to the anatomical location of the herniated disc in axial plain of magnetic resonance image. Clinical and radiological data were obtained and compared between the two groups. The lateral group included 74 (21%) patients and the medial group included 278 (79%). Mean age of the lateral group was significantly higher than that in the medial group. The lateral group showed a significantly larger proportion of patients with radiating leg pain and multiple levels of disc herniations than the medial group. No significant differences were found in terms of gender, duration of pain, pretreatment numeric rating scale, severity of disc herniation (protrusion and extrusion), and presence of weakness in leg muscles. The proportion of patients who underwent surgery was not significantly different between the 2 groups. However, the proportion of patients who accomplished successful pain reduction after treatment was significantly smaller in the lateral than in the medial group. In conclusion, patients with lateral disc herniation were older and had larger proportion of radiating leg pain than those with medial disc herniation. Lateral disc herniation was more associated with multiple disc herniations and worse clinical outcomes after treatment than medial disc herniation.

Needle puncture in rabbit functional spinal units alters rotational biomechanics

STUDY DESIGN

An in vitro biomechanical study for rabbit lumbar functional spinal units (FSUs) using a robot-based spine testing system.

OBJECTIVE

To elucidate the effect of annular puncture with a 16 G needle on mechanical properties in flexion/extension, axial rotation, and lateral bending.

SUMMARY OF BACKGROUND DATA

Needle puncture of the intervertebral disk has been shown to alter mechanical properties of the disk in compression, torsion, and bending. The effect of needle puncture in FSUs, where intact spinal ligaments and facet joints may mitigate or amplify these changes in the disk, on spinal motion segment stability subject to physiological rotations remains unknown.

METHODS

Rabbit FSUs were tested using a robot testing system whose force/moment and position precision were assessed to demonstrate system capability. Flexibility testing methods were developed by load-to-failure testing in flexion/extension, axial rotation, and lateral bending. Subsequent testing methods were used to examine a 16 G needle disk puncture and No. 11 blade disk stab (positive control for mechanical disruption). Flexibility testing was used to assess segmental range-of-motion (degrees), neutral zone stiffness (N m/degrees) and width (degrees and N m), and elastic zone stiffness before and after annular injury.

RESULTS

The robot-based system was capable of performing flexibility testing on FSUs-mean precision of force/moment measurements and robot system movements were <3% and 1%, respectively, of moment-rotation target values. Flexibility moment targets were 0.3 N m for flexion and axial rotation and 0.15 N m for extension and lateral bending. Needle puncture caused significant (P<0.05) changes only in flexion/extension range-of-motion and neutral zone stiffness and width (N m) compared with preintervention. No. 11 blade-stab significantly increased range-of-motion in all motions, decreased neutral zone stiffness and width (N m) in flexion/extension, and increased elastic zone stiffness in flexion and lateral bending.

CONCLUSIONS

These findings suggest that disk puncture and stab can destabilize FSUs in primary rotations.

A New CT Method for Assessing 3D Movements in Lumbar Facet Joints and Vertebrae in Patients before and after TDR

This study describes a 3D-CT method for analyzing facet joint motion and vertebral rotation in the lumbar spine after TDR. Ten patients were examined before and then three years after surgery, each time with two CT scans: provoked flexion and provoked extension. After 3D registration, the facet joint 3D translation and segmental vertebral 3D rotation were analyzed at the operated level (L5-S1) and adjacent level (L4-L5). Pain was evaluated using VAS. The median (±SD) 3D movement in the operated level for the left facet joint was 3.2 mm (±1.9 mm) before and 3.5 mm (±1.7 mm) after surgery and for the right facet joint was 3.0 mm (±1.0 mm) before and 3.6 mm (±1.4 mm) after surgery. The median vertebral rotation in the sagittal plane at the operated level was 5.4° (±2.3°) before surgery and 6.8° (±1.7°) after surgery and in the adjacent level was 7.7° (±4.0°) before and 9.2° (±2.7°) after surgery. The median VAS was reduced from 6 (range 5–8) to 3 (range 2–8) in extension and from 4 (range 2–6) to 2 (range 1–3) in flexion.

Comparative role of disc degeneration and ligament failure on functional mechanics of the lumbar spine

Understanding spinal kinematics is essential for distinguishing between pathological conditions of spine disorders, which ultimately lead to low back pain. It is of high importance to understand how changes in mechanical properties affect the response of the lumbar spine, specifically in an effort to differentiate those associated with disc degeneration from ligamentous changes, allowing for more precise treatment strategies. To do this, the goals of this study were twofold: (1) develop and validate a finite element (FE) model of the lumbar spine and (2) systematically alter the properties of the intervertebral disc and ligaments to define respective roles in functional mechanics. A three-dimensional non-linear FE model of the lumbar spine (L3-sacrum) was developed and validated for pure moment bending. Disc degeneration and sequential ligament failure were modelled. Intersegmental range of motion (ROM) and bending stiffness were measured. The prediction of the FE model to moment loading in all three planes of bending showed very good agreement, where global and intersegmental ROM and bending stiffness of the model fell within one standard deviation of the in vitro results. Degeneration decreased ROM for all directions. Stiffness increased for all directions except axial rotation, where it initially increased then decreased for moderate and severe degeneration, respectively. Incremental ligament failure produced increased ROM and decreased stiffness. This effect was much more pronounced for all directions except lateral bending, which is minimally impacted by ligaments. These results indicate that lateral bending may be more apt to detect the subtle changes associated with degeneration, without being masked by associated changes of surrounding stabilizing structures.

Lumbar paraspinal muscle transverse area and symmetry in dogs with and without degenerative lumbosacral stenosis

OBJECTIVES

To investigate whether dogs with degenerative lumbosacral stenosis have decreased lumbar paraspinal muscle transverse area and symmetry compared with control dogs.

MATERIALS AND METHODS

Retrospective cross-sectional study comparing muscles in transverse T2-weighted magnetic resonance images for nine dogs with and nine dogs without degenerative -lumbosacral stenosis. Mean transverse area was measured for the lumbar multifidus and sacrocaudalis dorsalis lateralis muscles bilaterally and the L7 vertebral body at the level of the caudal endplate. Transverse areas of both muscle groups relative to L7 and asymmetry indices were compared between study populations using independent t tests.

RESULTS

Mean muscle-to-L7 transverse area ratios were significantly smaller in the degenerative lumbosacral stenosis group compared with those in the control group in both lumbar multifidus (0·84 ±0·26 versus 1·09 ±0·25; P=0·027) and sacrocaudalis dorsalis lateralis (0·5 ±0·15 versus 0·68 ±0·12; P=0·005) muscles. Mean asymmetry indices were higher for both muscles in the group with degenerative lumbosacral stenosis than in the control group, but highly variable and the difference was not statistically significant.

CLINICAL SIGNIFICANCE

These findings suggest that dogs with degenerative lumbosacral stenosis have decreased lumbar paraspinal muscle mass that may be a cause or consequence of the -syndrome. Understanding altered paraspinal muscle characteristics may improve understanding of the -pathophysiology and management options for degenerative lumbosacral stenosis.