AO Spine Guideline for Using Osteobiologics in Spine Degeneration project is an international collaborative initiative to identify and evaluate evidence on existing use of osteobiologics in spine degenerative diseases. It aims to formulate clinically relevant and internationally applicable guidelines ensuring evidence-based, safe and effective use of osteobiologics. The current focus is the use of osteobiologics in anterior cervical discectomy and fusion surgeries. The guideline development is planned in three phases. Phase 1- Evidence synthesis and Recommendation; Phase 2- Guideline with osteobiologics grading and Validation; Phase 3- Guideline dissemination and Development of a clinical decision support tool. The key questions formulating the guidelines for the use of osteobiologics will be addressed in a series of systematic reviews in Phase 1. The evidence synthesized by the systematic reviews will be assessed by Grading of Recommendations, Assessment, Development and Evaluations (GRADE) methodology, including expert panel discussions to formulate a recommendation. In Phase 2, osteobiologics will be graded based on evidence and the grading will be integrated with the recommendation from Phase 1, and thus formulate a guideline. The guideline will be further validated by prospective clinical studies. In the third phase, dissemination of the proposed guideline and development of a decision support tool is planned. AO-GO aims to bridge an important gap between quality of evidence and use of osteobiologics in spine fusion surgeries. With a holistic approach the guideline aims to facilitate evidence-based, patient-oriented decision-making process in clinical practice, thus stimulating further evidence-based studies regarding osteobiologics usage in spine surgeries

Introduction. This research aims to enhance the control of intricate musculoskeletal spine models, a critical tool for comprehending both healthy and pathological spinal conditions. State-of-the-art musculoskeletal spine models incorporate segments for all vertebra, each possessing 3 degrees-of-freedom (DOF). Manually defining the posture with this amount of DOFs presents a significant challenge. The prevalent method of equally distributing the spine's overall rotation among the vertebrae often proves to be an inadequate assumption, particularly when dealing with the entire spine. Method. We have engineered a comprehensive non-linear spine rhythm and the requisite tools for its implementation in widely utilized musculoskeletal modelling software (1). The rhythm controls lateral bending, axial rotation, and flexion/extension. The mathematical and implementation details of the rhythm are beyond this abstract, but it's noteworthy that the implementation accommodates non-linear rhythms. This means, for example, that one set of rhythm coefficients is used for flexion and another for extension. The rhythm coefficients, which distinguish the movement along the spine, were derived from a review of spine literature. The values for spine and vertebra range-of-motion (ROM) vary significantly in published studies, and no complete dataset was found in any single study. Consequently, the rhythm presented here is a composite, designed to provide the most consistent and average set of rhythm coefficients. Result. The novel spine rhythm simplifies the control of detailed spine models, accommodating varying amounts of input data. It allows for the specification of only the overall motion or the posture at a more detailed level (i.e., lumbar, thoracic, neck). The tools and rhythm coefficients are publicly available on GitHub. Conclusion. The innovative spine rhythm enhances the usability of cutting-edge spine models. For flexion/extension of the spine, it introduces a non-linear rhythm, exhibiting distinct behaviour between flexion and extension - a feature not previously observed in musculoskeletal spine models. 1) The AnyBody Modeling System

Infections in spine surgery are relatively common and devastating complications, a significant burden to the patient and the healthcare system. Usually, the treatment of SSIs consists of aggressive and prolonged antibiotic therapy, multiple debridements, and in chronic cases, hardware removal. Infections are correlated with worse subjective outcomes and even higher mortality. Depending on the type of spine surgery, the infection rate has been reported to be as higher as 20%. Recently silver-coated implants have been introduced in spine surgery to reduce the incidence of post-operative infections and to improve implant survivorship. The aim of the present study is to evaluate complications and outcomes in patients treated with silver-coated implants because of spine infection. All consecutive patients who had spine stabilization with a silver-coated implant from 2018 to 2021 were screened for inclusion in the study. Inclusion criteria were: (1) six months of minimum follow-up; (2) previous surgical site infection; hematogenous spondylodiscitis requiring surgical stabilization. Demographic and surgical information were obtained via chart review, all the device-related complications and the reoperation rate were also reported. A total of 57 patients were included in the present study. The mean age was 63.4 years, and there were 36 (63%) males and 21 (37%) females. Among the included cases, 57% were SSIs, 33% were spondylodiscitis, and 9% were hardware mobilization. Comorbidities such as diabetes mellitus, obesity, smoke, and oncological history were significant risk factors. In addition, the organisms cultured were Staphylococcus species in most of the cases. At six months of follow-up, 40% of patients were considered free from infection, while 20% needed multiple surgeries. The present research showed satisfactory results of silver-coated implants for the treatment of spine infection

Adult Spine Deformity (ASD) is a degenerative condition of the adult spine leading to altered spine curvatures and mechanical balance. Computational approaches, like Finite Element (FE) Models have been proposed to explore the etiology or the treatment of ASD, through biomechanical simulations. However, while the personalization of the models is a cornerstone, personalized FE models are cumbersome to generate. To cover this need, we share a virtual cohort of 16807 thoracolumbar spine FE models with different spine morphologies, presented in an online user-interface platform (SpineView). To generate these models, EOS images are used, and 3D surface spine models are reconstructed. Then, a Statistical Shape Model (SSM), is built, to further adapt a FE structured mesh template for both the bone and the soft tissues of the spine, through mesh morphing. Eventually, the SSM deformation fields allow the personalization of the mean structured FE model, leading to generate FE meshes of thoracolumbar spines with different morphologies. Models can be selectively viewed and downloaded through SpineView, according to personalized user requests of specific morphologies characterized by the geometrical parameters: Pelvic Incidence; Pelvic Tilt; Sacral Slope; Lumbar Lordosis; Global Tilt; Cobb Angle; and GAP score. Data quality is assessed using visual aids, correlation analyses, heatmaps, network graphs, Anova and t-tests, and kernel density plots to compare spinopelvic parameter distributions and identify similarities and differences. Mesh quality and ranges of motion have been assessed to evaluate the quality of the FE models. This functional repository is unique to generate virtual patient cohorts in ASD. Acknowledgements: European Commission (MSCA-TN-ETN-2020-Disc4All-955735, ERC-2021-CoG-O-Health-101044828)

Lower back pain (LBP) is a worldwide clinical problem and a prominent area for research. Numerous in vitro biomechanical studies on spine specimens have been undertaken, attempting to understand spinal response to loading and possible factors contributing to LBP. However, despite employing similar testing protocols, there are challenges in replicating in vivo conditions and significant variations in published results. The aim of this study was to use the University of Bath (UoB) spine simulator to perform tests to highlight the major limitations associated with six degree of freedom (DOF) dynamic spine testing. A steel helical spring was used as a validation model and was potted in Wood's metal. Six porcine lumbar spinal motion segments were harvested and dissected to produce isolated spinal disc specimens. These were potted in Wood's metal, ensuring the midplane of the disc remained horizontal and then sprayed with 0.9% saline and wrapped in saline-soaked tissue and plastic wrap to prevent dehydration. A 400N axial preload was used for spinal specimens. Specimens were tested under the stiffness and flexibility protocols. Tests were performed using the UoB custom 6-axis spine simulator with coordinate axes. Tests comprised five cycles with data acquired at 100Hz. Stiffness and flexibility matrices were evaluated from the last three motion cycles using the linear least squares method. According to theory, inverted flexibility matrices should equal stiffness matrices. In the case of the spring, the matrices matched analytical solutions and inverted flexibility matrices were equivalent to stiffness matrices. Matrices from the spinal tests demonstrated some symmetry, with similarities between inverted flexibility- and stiffness matrices, though these were unequal overall. Matrix element values were significantly affected by displacements assumed to occur at disc centre. Spring tests proved that for linear, elastic specimens, the spine simulator functioned as expected. However, multiple factors limit the confidence in spine test results. Centre of rotation, displacement assumptions and rigid body transformations are known to impact the results from spinal testing, and these should be addressed going forward to improve the replication of in vivo conditions

Abstract. Objectives. Spinal disorders such as back pain incur a substantial societal and economic burden. Unfortunately, there is lack of understanding and treatment of these disorders are further impeded by the inability to assess spinal forces in vivo. The aim of this project is to address this challenge by developing and testing a novel image-driven approach that will assess the forces in an individual's spine in vivo by incorporating information acquired from multimodal imaging (magnetic resonance imaging (MRI) and biplane X-rays) in a subject-specific model. Methods. Magnetic resonance and biplane X-ray imaging are used to capture information about the anatomy, tissues, and motion of an individual's spine as they perform a range of everyday activities. This information is then utilised in a subject-specific computational model based on the finite element method to predict the forces in their spine. The project is also utilising novel machine learning algorithms and in vitro, six-axis mechanical testing on human, porcine and bovine samples to develop and test the modelling methods rigorously. Results & Discussion. MRI sequences have been identified that provide high-quality image data and information on different tissue types which will be used to predict subject-specific disc properties. In-vivo protocols to capture motion analysis, EMG muscle activity, and video X-rays of the spine have been designed with planned data collection of 15 healthy volunteers. Preliminary modelling work has evaluated potential machine learning approaches and quantified the sensitivity of the models developed to material properties. Conclusion. The development and testing of these image-driven subject-specific spine models will provide a new tool for determining forces in the spine. It will also provide new tools for measuring and modelling spine movement and quantifying the properties of the spinal tissues. Acknowledgments. Funding from the EPSRC: EP/V036602/1 (Meakin, Holsgrove & Javadi) and EP/V032275/1 (Holt & Williams). Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Introduction. Functional Spine Units (FSUs) play a vital role in understanding biomechanical characteristics of the spine, particularly bone fracture risk assessment. While established models focus on simulating axial compression of individual bones to assess fracture load, recent models underscore the importance of understanding fracture load within FSUs, offering a better representation of physiological conditions. Despite the limited number of FSU fracture studies, they predominantly rely on a linear material model with an annulus fibrosus Young's modulus set at 500 MPa, significantly higher than stiffness values (ca. 4 MPa) utilized in other FSU and spine section biomechanical models. Thus, this study aims to study the effect of varying annulus fibrosus stiffness on FSU fracture load, aiming to identify physiologically relevant biomechanical parameters. Method. Subject-specific geometry and material properties of bones were derived from computed tomography (CT) image data of five human cadaveric FSU specimens. The annulus fibrosus and nucleus pulposus were manually recreated and assigned linear elastic material properties. By subjecting the model to axial compression, the fracture load of the FSU was deduced from the peak of the force-displacement graph. To explore the effect of stiffness of the annulus fibrosus on simulated fracture load, we conducted a parameter study, varying stiffness values from the high 500 MPa to a more physiologically relevant 25 MPa, aiming to approximate values applied in FSU kinematic models while achieving bone fracture. Result. Significant reductions in fracture load were observed, ranging from 23% to 46%, as annulus stiffness decreased from 500MPa to 25MPa. Additionally, a discernible, gradual decline in fracture load was observed with a decrease in stiffness values. Conclusion. The stiffness of the annulus fibrosus significantly influences the simulated fracture load of an FSU. Future investigations should prioritize biomechanically accurate modeling of the intervertebral disc, ensuring alignment with experimental findings regarding FSU fracture load while maintaining biomechanical fidelity

Introduction. To develop an international guideline (AOGO) about use of osteobiologics in Anterior Cervical Discectomy and Fusion (ACDF) for treating degenerative spine conditions. Method. The guideline development process was guided by AO Spine Knowledge Forum Degenerative (KF Degen) and followed the Guideline International Network McMaster Guideline Development Checklist. The process involved 73 participants with expertise in degenerative spine diseases and surgery from 22 countries. Fifteen systematic reviews were conducted addressing respective key topics and evidence were collected. The methodologist compiled the evidence into GRADE Evidence-to-Decision frameworks. Guideline panel members judged the outcomes and other criteria and made the final recommendations through consensus. Result. Five conditional recommendations were created. A conditional recommendation is about the use of allograft, autograft or a cage with an osteobiologic in primary ACDF surgery. Other conditional recommendations are about use of osteobiologic for single or multi-level ACDF, and for hybrid construct surgery. It is suggested that surgeons use other osteobiologics rather than human bone morphogenetic protein-2 in common clinical situations. Surgeons are recommended to choose one graft over another or one osteobiologic over another primarily based on clinical situation, and the costs and availability of the materials. Conclusion. This AOGO guideline is the first to provide recommendations for the use of osteobiologics in ACDF. Despite the comprehensive searches for evidence, there were few studies completed with small sample sizes and primarily as case series with inherent risks of bias. Therefore high quality clinical evidence is demanded to improve the guideline

Abstract. Introduction. Back pain affects 80% of the population at some stage in their life with significant costs to society. Mechanisms and causes of pain have been investigated by studying the behaviour of functional spinal units (FSUs) subjected to displacement- or load control protocols in 6 degrees of freedom (DOF). Load control allows specimens to move physiologically in response to applied loads whereas displacement control constrains motion to individual axes. The displacement control system of the Bath University six-axis spine simulator has been validated and the load control system is in the process of iterative development. Objectives. The objective was to build a computational model of the spine simulator to develop a complete 6 DOF load control system to enable accurate specimen testing under load control. Methods. SolidEdge part files of the simulator assembly exported to MATLAB Simulink® were used to generate a full model of the simulator. Results from displacement tests using a helical spring specimen in the simulator were used to validate the performance of the simulator model in displacement control. The model was then used to develop a 6 DOF load control system including matrix transformations to ensure correct load tracking. Results. Model results for displacement control matched the physical test data within 12% and replicated coupling loads. The developed load control model demonstrated good control in all 6 axes, maintaining zero-commanded loads. Furthermore, peak-to-peak errors in non-zero-commanded loads and moments were below 10% and 15% respectively. Conclusions. The computational model proved a valuable tool in understanding the assembly and functioning of the spine simulator. The in-silico development and validation of the 6 DOF load control system will allow seamless implementation of load control within the spine simulator. The ultimate outcome of this will be the ability to assess the behaviour of FSUs subjected to biofidelic loading conditions

Abstract. Objective. This study assesses the prevalence of major and minor discordance between hip and spine T scores using Radiofrequency Echographic Multi-spectrometry (REMS). REMS is a novel technology that uses ultrasound and radiofrequency analysis to measure bone density and bone fragility at the hip and lumbar spine. The objective was to compare the results with the existing literature on Dual-Energy X-ray Absorptiometry (DEXA) the current “gold standard” for bone densitometry. REMS and DEXA have been shown to have similar diagnostic accuracy, however, REMS has less human input when carrying out the scan, therefore the rates of discordance might be expected to be lower than for DEXA. Discordance poses a risk of misclassification of patients’ bone health status, causing diagnostic ambiguity and potentially sub-optimal management decisions. Reduction of discordance rates therefore has the potential to significantly improve treatment and patient outcomes. Methods. Results from 1,855 patients who underwent REMS investigations between 2018 and 2022 were available. Minor discordance is defined as a difference of one World Health Organisation (WHO) diagnostic classification (Normal / Osteopenia or Osteopenia / Osteoporosis). Major discordance is defined as a difference of two WHO diagnostic classifications (Normal / Osteoporosis). The results were compared with reported DEXA discordance rates. Results. 1,732 individuals had both hip and spine T scores available for analysis. There were 267 cases of discordance. No instances of major discordance were observed. The minor discordance rate was 15.4%. 6.5% of the REMS scans with minor discordance showed > 1.0 standard deviation (SD) difference between the T scores of the hip and spine. 19.4% had differences of between 0.6 SD and 1.0 SD while 73.9% had ≤ 0.5 SD or less. In 24.5% of the cases of REMS discordance the hip T scores were greater than the spine and in 75.5% of cases the spine T score was greater than the hip. Conclusions. The current analysis is the largest of its kind. It demonstrates that REMS has an overall lower rate of discordance than reported DEXA rates. Major discordance rates with DEXA range from 2–17%, but REMS avoids many of the positioning problems and post-processing errors inherent in DEXA scanning, which might account for the absence of major discordance. Rates of minor discordance in DEXA scans range between 38–51%. The REMS minor discordance rate being much lower than these rates suggests that it has the potential to enhance diagnostic accuracy considerably. Most REMS discordance results showed ≤ 0.5 SD variance between the T scores of the two sites, indicating close correlation in the bone densitometry analysis. Most studies of DEXA discordant results confirm that spinal T scores are more often higher than at the hip. The REMS results concur with this observation. Considering the comparable accuracy rates that have been shown between REMS and DEXA, with its much lower discordance rate, REMS can potentially improve current medical practice and enhance patient care. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Mental disorders in particular depression and anxiety have been reported to be prevalent among patients with spinal pathologies. Goal of the current study was to analyze the relationship of Zung pre- and post-op score to other PROs and length of stay. Secondary outcomes included revision surgery and post-operative infections. Data from the international multicenter prospective spine degenerative surgery data repository, DegenPRO v1.1 (AO Spine Knowledge Forum Degenerative) were utilized. Patients undergoing cervical or lumbar procedure were included. Patient's demographics, Charlson Comorbidity Index, surgical information, Zung score, NDI, pain related PROs and EQ-5D, and complications at surgery and at various post-op time periods. Except for hospital duration, data were analyzed, using multivariable mixed linear models. A robust linear regression model was used to assess the association between Zung score and hospital duration. All models were adjusted for gender and age. 42 patients had Zung score administered. Among those patients 22 (52%) were within normal range, 18 (43%) were mildly and 2 (5%) severely depressed. 62% of the patients had a lumbar pathology with fusion procedures being the most common. Median EQ-5D (3L) score at surgery was significantly higher (0.7, IQR: 0.4-0.7) for patients within normal range than for those with mild (0.4, IGR: 0.3-0.7) or severe depression (0.3, IQR: 0.3-0.3, p-value: 0.05). Compared to patients within normal Zung range, mixed models, indicated lower EQ-5D (3L) score values and higher values for neck and arm pain at surgery with both PROs and EQ-5D (3L) improving in patients with depression over the follow-up time. No association was found between Zung score and hospital length of stay. The initial analysis showed that 43% of the patients were mildly depressed and mainly male patients. Zung score was correlated with post-operative improvements in EQ-5D and arm and neck pain PROs

Due to the presence of megakaryocytes, platelets and clotting factors, bone marrow aspirate (BMA) tends to coagulate. For the first time, starting from our previous studies on mesenchymal vertebral stem cells, it has been hypothesized that coagulated BMA represents a safe and effective autologous biological scaffold for bone regeneration in spinal surgery. The present research involved advanced preclinical in vitro models and the execution of a pilot clinical study. Evaluation of cell morphology, growth kinetics, immunophenotyping, clonogenicity, trilineage-differentiation, growth-factors and HOX and TALE gene expression were analyzed on clotted- and un-clotted human V-BMA. In parallel, a pilot clinical study on ten patients with degenerative spine diseases submitted to instrumented posterior arthrodesis, is ongoing to assess the ability of clotted-V-BMA to improve spinal fusion at 6- and 12-months follow-up. Results demonstrated that clotted-V-BMA have significantly higher growth-factor expression and mesenchymal stem cell (MSCs) viability, homogeneity, clonogenicity, and ability to differentiate towards the osteogenic phenotype than un-clotted-V-BMA. Clotted-V-BMA also highlighted significant reduced expression of PBX1 and of MEIS3 genes negatively involved in osteoblast maturation and differentiation. From December 2020, eight patients have already been enrolled with first promising results that will be finally evaluated in the next two months. The application of V-BMA-clot as carrier of progenitors and cytokines and as natural scaffold with a structural texture represents a point-of-care orthobiologic product to improve spinal fusion. Clinical application seems to be efficacy, and we will confirm and strengthen these data with the final results of the pilot clinical study

Introduction and Objective. Over the past few years, a reorganization of the educational pathways has been promoted with the purpose of optimizing the acquisition of competences and their assessment, so as to reduce the risks to both health care professionals and end users. Virtual reality (VR) has been repeatedly tested, initially as a positive reinforcement for more traditional educational pathways and, more recently, as their potential substitute. The aim of this study was to demonstrate the potentiality of VR simulation training in spine surgery. Materials and Methods. The VR simulator reproduced the lateral lumbar access to the spine. The simulation included a tutorial, the preoperative settings, and the surgical session with different levels of procedural complexity. A total of 10 users were recruited for this study: 3 senior surgeons (group A) and 7 orthopedic residents or junior orthopedic surgeons (group B). Each user completed the simulation twice. Results. The user's age or previous experience with VR technology did not show any relevance. On average, the entire simulation was completed in 24 minutes and 36 seconds. Group B showed an improvement between the 2 attempts in both sessions, the preoperative settings and the surgical simulation. The number of major errors dropped from an average of 5.2 to 1.8 and from an average of 4 (1–6) to 1.4, respectively. The simulation was never interrupted because of technical bugs or adverse effects related to the technology. Conclusions. VR-based training pathways might promote a high standard of care. Our preliminary experience suggests an effective implementation of the traditional coaching process

Abstract. OBJECTIVES. Bone health deterioration is a major public health issue. General guidelines for the limitation of bone loss prescribe a healthy lifestyle and a minimum level of physical activity. However, there is no specific recommendation regarding targeted activities that can effectively maintain lumbar spine bone health. To provide a better understanding of such influencing activities, a new predictive modelling framework was developed to study bone remodelling under various loading conditions. METHODS. The approach is based on a full-body subject-specific musculoskeletal model [1] combined with structural finite element models of the lumbar vertebrae. Using activities recorded with the subject, musculoskeletal simulations provide physiological loading conditions to the finite element models which simulate bone remodelling using a strain-driven optimisation algorithm [2]. With a combination of daily living activities representative of a healthy lifestyle including locomotion activities (walking, stair ascent and descent, sitting down and standing up) and spine-focused activities involving twisting and reaching, this modelling framework generates a healthy bone architecture in the lumbar vertebrae. The influence of spine-focused tasks was studied by adapting healthy vertebrae to an altered loading scenario where only locomotion activities were performed. RESULTS. The spine-focused activities were responsible for 57% of the overall bone mechanical stimulus of the five lumbar vertebrae. Cortical bone maintenance was more influenced by these activities in the superior vertebrae than in the inferior ones, with a stimulus degradation of 74% in L1 against 24% in L5 when adapted to the altered loading scenario. Trabecular bone stimulus degradation varied between 53% and 68%. CONCLUSION. The study suggests that locomotion activities are insufficient to maintain lumbar spine bone health. When appropriate, larger spine movements should be recommended as part of the minimum daily physical activities. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Abstract. Objectives. to evaluate the efficacy and safety of topically applied tranexamic acid (TXA) in thoracolumbar spinal tuberculosis surgery, posterior approach. Methods. Thoracolumbar spine tuberculosis patients who requiring debridement, pedicle screw fixation and fusion surgery were divided into two groups. In the TXA group (n=50), the wound surface was soaked with TXA (1 g in 100 mL saline solution) for 3 minutes after exposure, after decompression, and before wound closure, and in the control group (n=116) using only saline. Intraoperative blood loss, drain volume 48 hours after surgery, amount of blood transfusion, transfusion rate, the haemoglobin, haematocrit after the surgery, the difference between them before and after the surgery, incision infection and the incidence of deep vein thrombosis between the two groups. Results. EBL for the control group was 783.33±332.71 mL and for intervention group 410.57±189.72 mL (p<0.001). The operative time for control group was 3.24±0.38 hours and for intervention group 2.99±0.79 hours (p<0.695). Hemovac drainage on days1 and 2 for control group was 167.10±53.83mL and 99.33±37.5 mL, respectively, and for intervention group 107.03±44.37mL and 53.38±21.99mL, respectively (p<0.001). The length of stay was significantly shorter in the intervention group (4.8±1.1 days) compared to control group (7.0±2.3 days). There was bo different in incision side infection and DVT. Conclusions. Topical TXA is a viable, cost-effective method of decreasing perioperative blood loss in major spine surgery with fewer overall complications than other methods. Further studies are required to find the ideal dosage and timing

Background. Finite element (FE) models have become a standard pre-clinical tool to study biomechanics of spine and are used to simulate and evaluate different strategies in scoliosis treatment: examine their efficacy as well as the effect of different implant design parameters. The goal of this study is to investigate, in a system of rods and laminar wires, the effect of the number of wires and their pre-stress on whole spine stiffness. Methods. A generic FE model was developed to represent a full human spine, including vertebrae, intervertebral discs, ligaments, facet and costovertebral joints, and ribcage. Intervertebral discs were modeled with 3D rebar elements with linear elastic material properties. Vertebrae, ribs, sternum, facet joints, cartilage and endplates were modeled with brick elements, and costal muscles with shell elements with linear elastic properties. Furthermore, ligaments were modeled with truss elements with nonlinear hypo-elastic properties. The spine model was instrumented from T7 to T12 with rods and wires modeled as titanium. Nonlinear contact properties were defined for rib neck-vertebra, transverse processes-rib and facet joint sets. The FE model was loaded in flexion and the whole spine instantaneous stiffness was calculated for different wire pre-stressing levels (0.1 to 2 MPa). Similar analyses were performed with changed numbers of wires and whole spine stiffness was calculated. Results. The results show that with increasing the pre-stress level the whole spine instantaneous stiffness increases by up to 6%. Reducing the number of wires decreases the whole spine stiffness almost linearly by 5%. These changes also alter center of rotation of the spine. The results suggest that pre-stressing and number of wires have an effect on whole spine stiffness. Conclusions. In summary, the develop FE model can be used to simulate different treatment strategies and to improve implant designs used in surgical treatment of scoliosis. Level of evidence. FEA study

The causes of spine disease are often biomechanical ones (e.g. disc degeneration, vertebral fracture). Currently, a deep investigation of the spine biomechanics is missing, due to the high complexity of the spine system (Fung 1980, Brandolini, Cristofolini et al. 2014): vertebrae and intervertebral discs. Recently, the Digital Image Correlation allowed measuring in vitrothe displacement and strain on the surface of soft and hard tissues, upon a specific non-invasive preparation of their surface with a speckle pattern (Palanca, Tozzi et al. 2016). The aim of this explorative work was to evaluate the deformation on spine segments, being able to distinguish between hard and soft tissue in the elastic regime and up to fracture. Segment of four vertebrae were extracted from porcine spines. All ligaments and muscles were removed, without damaging the spine segment (vertebrae and intervertebral discs). A suitable non-conventional white-on-black speckle pattern was prepared on the surface with airbrush airgun to track the movements of the specimen with DIC (Lionello, Sirieix et al. 2014). The endplates of the extreme vertebrae were potted in poly-methyl-methacrylate. The spine segments were tested in pure axial loading with cycles of increasing magnitude, up to fialure. A commercial 3D-DIC (Dantec Dynamics, Denmark) was used. In the present configuration, it allowed a resolution of 30 micrometers. It was used to measure the displacements and strains in a full-field and contactless way on the frontal surface of the spine segments. DIC allowed measuring with success the displacement and strain during the entire test, in the elastic regime and up to failure. The displacements and strains could be measured on the entire specimen, both in the vertebrae (hard tissue) and in the intervertebral discs (soft tissue). The axial strain evaluated prior to failure was close to 10’000 microstrain on the vertebral body surface and exceed 70’000 microstrain on the intervertebral discs, where failure was localized. The pattern, prepared in a dedicated way showed its suitability for both the bone and the disc. The evaluated failure strains were in agreement with the literature (Bayraktar, Morgan et al. 2004) (Spera, Genovese et al. 2011). To the authors' best knowledge, this kind of measurement including strain on soft and hard tissue simultaneously has never been performed before. This work showed the capability of DIC in providing full-field measures on the surface with complex geometry, such as the spine. The assertion of these potentialities could open the way to further application of DIC to study the behaviour of human spines, including improvement of spinal fixation devices

Recent clinical studies on targeting nerve growth factor (NGF) in chronic low back pain and knee osteoarthritis have demonstrated efficient pain reduction in a short-term treatment regimen. However, the increased risk for the development of rapid progressive osteoarthritis at the required high drug dose remains a serious concern and prompts thorough analysis of the tissue distribution and role of NGF in degenerative musculoskeletal disorders. Here, we sought to investigate tissue distribution of NGF, its high affinity receptor TrkA and CD68-positive macrophages in human facet joint osteoarthritis of the lumbar spine. Facet joint specimens (n=10) were harvested by facetectomy from patients undergoing elective lumbar intervertebral spine fusion. Facet joint osteoarthritis and presence of synovitis was graded using preoperative magnetic resonance imaging. Tissue distribution of NGF, TrkA and CD68 was determined using immunohistochemistry. Tissue degradation was graded on safranin-O-stained tissue sections. Association between imaging parameters and tissue distribution was determined using Pearson correlation analysis. Synovitis was present in 6 cases and facet joints displayed moderate to severe radiological osteoarthritis (median Weishaupt grade; 2 [1.5–3]). NGF was expressed in 8 of 10 specimens. NGF was expressed in connective tissue, articular and fibrocartilage, but not bone tissue. Cartilaginous NGF expression was predominantly found in the extracellular matrix of superficial cartilage tissue with complete loss of proteoglycans, chondrocyte death and structural damage (fissures). Loss of cartilage proteoglycan staining alone did not display NGF immunoreactivitiy. NGF expression was not correlated with radiological osteoarthritis severity or presence of synovitis. NGF high affinity receptor TrkA was exclusively expressed in bone marrow tissues. Differential grades of bone marrow infiltration by CD68-positive macrophages were observed, yet these were not associated with NGF expression. Targeting NGF in chronic low back pain and/or facet joint osteoarthritis might affect pathomechanisms in cartilaginous tissues and NGF signalling in the bone marrow compartment

Abstract. Objectives. Impingement in total hip replacements (THRs), including bone-on-bone impingement, can lead to complications such as dislocation and loosening. The aim of this study was to investigate how the location of the anterior inferior iliac spine (AIIS) affected the range of motion before impingement. Methods. A cohort of 25 CT scans (50 hips) were assessed and nine hips were selected with a range of AIIS locations relative to the hip joint centre. The selected CT Scans were converted to solid models (ScanIP) and THR components (DePuy Synthes) were virtually implanted (Solidworks). Flexion angles of 100⁰, 110⁰, and 120⁰ were applied to the femur, each followed by internal rotation to the point of impingement. The lateral, superior and anterior extent of the AIIS from the Centre of Rotation (CoR) of the hip was measured and its effect on the range of motion was recorded. Results. There was found to be a significant (p<0.05) inverse relationship between the ROM of the THR and the lateral measure of the AIIS. Of the three measures, the lateral AIIS measure showed the strongest relationship with ROM to impingement (R=0.73) with the anterior and superior measures resulting in R values of 0.41 and 0.56 respectively. For every millimetre lateral the AIIS location, there was typically a loss of 1.2° of range of motion. With increasing lateralisation, the AIIS was positioned more directly over the femur, thereby reducing the ROM in the THR during high flexion positions. No soft tissue was included in the models which would have affected the ROM. Conclusions. The results from this study have shown that the lateral measure of the AIIS could be a predictor for bone-on-bone impingement. To build confidence, wider study of AIIS location variation is needed, as well as analysis under impingement prone activities of daily living. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Summary. Our meta-analysis showed that pooled mean blood loss during spinal tumour surgeries was 2180 ml. Standardised methods of calculating and reporting intra-operative blood loss are needed as it would be beneficial in the pre-operative planning of blood replenishment during surgery. Introduction. The vertebral column is the commonest site of bony metastasis, accounting for 18,000 new cases in North America yearly. Patients with spinal metastasis are often elderly, have compromised cardiovascular status, poor physiological reserve and altered immune status, all of which render them more susceptible to the complications of intra-operative blood loss and associated transfusion. Currently no consensus exists regarding the expected volume of blood lost during metastatic spine tumour surgery with various papers quoting anywhere between 1L to 6L. Knowledge of the expected blood loss prior to surgery however is important as it facilitates pre-operative planning, intra- and post-operative management of fluid balance and blood transfusion. We conducted a meta-analysis of published literature on spine tumour surgery to answer the question: “What is the expected blood loss in major spinal tumour surgery for metastatic spinal disease?”. Methods. A comprehensive online search of the English literature using Medline, Embase, and the Cochrane Central Register of Controlled Trials was performed. We included articles published from 31 January 1992 until 31 January 2012. This initial online search yielded 98 relevant articles. Two senior investigators independently reviewed all abstracts. The full text of articles that were deemed eligible for further consideration obtained and reviewed. Eighty five articles were excluded at this stage, largely due to lack of clear blood loss data, leaving 13 eligible articles. A hand search of the reference lists of relevant articles yielded 5 more articles. A total of 18 articles were included in the final meta-analysis of blood loss data. Disagreements regarding eligibility of articles for analysis were resolved by consensus. Selected articles for final analysis were independently graded according to the Centre for Evidence-Based Medicine (CEBM) Levels of Evidence. We evaluated the possibility of publication bias by obtaining a funnel plot (created by plotting the sample size against the effect estimate). The Egger's regression asymmetry test was used to assess the existence of publication bias. Results. Eighteen selected articles had a total of 785 patients who had undergone major spine tumour surgery for metastatic spinal disorders. The pooled estimate of the blood loss occurring during spinal tumour surgeries was calculated to be 2180ml (95%CI: 1805–2554ml). Apart from two studies which reported significant mean blood loss of more than 5500 ml, the resulting funnel plot suggested absence of publication bias. This was confirmed by Egger's test which did not show any small-study effects (p=0.119). However, there was strong evidence of heterogeneity between studies with I2=90% (p<0.001). Conclusions. The expected blood loss of a patient undergoing major surgery for spinal tumour constitutes more than a third of the circulating blood volume in a typical cancer patient with significantly impaired physiological reserve. Moreover, cases of catastrophic blood loss exceeding 5L exist in almost every series evaluated in this paper, with some reaching as much as 17–18L. Blood loss is a significant problem during spine tumour surgery and concerted effort is needed to address it