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Supplemental Digital Content is Available in the Text., Objectives: To (1) demonstrate that the AO Spine Sacral Classification System can be reliably applied by general orthopaedic surgeons and subspecialists universally around the world and (2) delineate those injury subtypes that are most difficult to classify reliably to refine the classification before evaluating clinical outcomes. Design: Agreement study. Setting: All-level trauma centers, worldwide. Participants: One hundred seventy-two members of the AO Trauma and AO Spine community. Intervention: The AO Sacral Classification System was applied by each surgeon to 26 cases in 2 independent assessments performed 3 weeks apart. Main Outcome Measurements: Interobserver reliability and intraobserver reproducibility. Results: A total of 8097 case assessments were performed. The kappa coefficient for interobserver agreement for all cases was 0.72/0.75 (assessment 1/assessment 2), representing substantial reliability. When comparing classification grading (A/B/C) regardless of subtype, the kappa coefficient was 0.84/0.85, corresponding to excellent reliability. The kappa coefficients for interobserver reliability were 0.95/0.93 for type A fractures, 0.78/0.79 for type B fractures, and 0.80/0.83 for type C fractures. The overall kappa statistic for intraobserver reliability was 0.82 (range 0.18–1.00), representing excellent reproducibility. When only evaluating morphology type (A/B/C), the average kappa value was 0.87 (range 0.18–1.00), representing excellent reproducibility. Conclusion: The AO Spine Sacral Classification System is universally reliable among general orthopaedic surgeons and subspecialists worldwide, with substantial interobserver and excellent intraobserver reliability.

Study Design. Bibliometric Review Objective. This study aims to understand the worldwide research productivity trends in spine-related research over the past five decades. Summary of Background Data. ?? ??? Methods. We evaluated original research articles published in four prestigious journals on spine research (European Spine Journal, Journal of Neurosurgery: Spine, Spine, and The Spine Journal) from 1976 to 2020. For one year of each decade, the origin of the first and the senior author was assigned to their region of origin. For the year 2020, a detailed analysis of countries and states of origin was performed, and the number of articles was normalized by registered MDs per country (per 10,000 population). Results. We included a total of 4,436 articles and 8,776 authors for analysis. From 1976 to 2020, the percentage of publications originating from North America decreased (77% ��� 38%). In contrast, Asian contributions drastically increased (3% ��� 36%), whereas articles originating from Europe only slightly raised (20% ��� 22%). In 2020, the USA was the most productive country worldwide (34% with most articles from New York (19%), followed by China (16%) and Japan (10%). After normalization to registered MDs (per 10,000 population), the USA proved to have the highest number of articles. Besides this, India now ranked fourth and Egypt eighth in terms of the most productive countries per MDs. Conclusion. North America contributed the largest share of all articles published in the last five decades. Asia, which ranks second in 2020, has overtaken Europe. Normalization to registered MDs can be a helpful tool to reflect a country's research productivity more accurately. Level of Evidence: 3

Purpose To validate the Dutch version of AOSpine PROST (Patient Reported Outcome Spine Trauma). Methods Patients were recruited from two level-1 trauma centers from the Netherlands. Next to the AOSpine PROST, patients also filled out SF-36 for concurrent validity. Descriptive statistics were used to analyze the characteristics. Content validity was assessed by evaluating the number of inapplicable or missing questions. Also floor and ceiling effects were analyzed. Internal consistency was assessed by calculating Cronbach’s α and item-total correlation coefficients (itcc). Spearman correlation tests were performed within AOSpine PROST items and in correlation with SF-36. Test–retest reliability was analyzed using Intraclass Correlation Coefficients (ICC). Responsiveness was assessed by calculating effect sizes (ES) and standardized response mean (SRM). Factor analysis was performed to explore any dimensions within AOSpine PROST. Results Out of 179 enrolled patients, 163 (91.1%) were included. Good results were obtained for content validity. No floor or ceiling effects were seen. Internal consistency was excellent (Cronbach’s α = 0.96, itcc 0.50–0.86), with also good Spearman correlations (0.25–0.79). Compared to SF-36, the strongest correlation was seen for physical functioning (0.79; p p 1), explaining 65.4% of variance. Conclusions Very satisfactory results were obtained for reliability, validity and responsiveness of the Dutch version of AOSpine PROST. Treating surgeons are encouraged to use this novel and validated tool in clinical setting and research to contribute to evidence-based and patient-centered care.

STUDY DESIGN Cross-sectional survey. OBJECTIVE To determine the influence of surgeons' level of experience and subspeciality training on the reliability, reproducibility, and accuracy of sacral fracture classification using the Arbeitsgemeinschaft f��r Osteosynthesefragen Spine Sacral Classification System. SUMMARY OF BACKGROUND DATA A surgeons' level of experience or subspecialty may have a significant effect on the reliability and accuracy of sacral classification given various levels of comfort with imaging assessment required for accurate diagnosis and classification. METHODS High-resolution computerized tomography (CT) images from 26 cases were assessed on two separate occasions by 172 investigators representing a diverse array of surgical subspecialities (general orthopedics, neurosurgery, orthopedic spine, orthopedic trauma) and experience (20���yrs). Reliability and reproducibility were calculated with Cohen kappa coefficient (k) and gold standard classification agreement was determined for each fracture morphology and subtype and stratified by experience and subspeciality. RESULTS Respondents achieved an overall k���=���0.87 for morphology and k���=���0.77 for subtype classification, representing excellent and substantial intraobserver reproducibility, respectively. Respondents from all four practice experience groups demonstrated excellent interobserver reliability when classifying overall morphology (k���=���0.842/0.850, Assessment 1/Assessment 2) and substantial interobserver reliability in overall subtype (k���=���0.719/0.751) in both assessments. General orthopedists, neurosurgeons, and orthopedic spine surgeons exhibited excellent interobserver reliability in overall morphology classification and substantial interobserver reliability in overall subtype classification. Surgeons in each experience category and subspecialty correctly classified fracture morphology in over 90% of cases and fracture subtype in over 80% of cases according to the gold standard. Correct overall classification of fracture morphology (Assessment 1: P���=���0.024, Assessment 2: P���=���0.006) and subtype (P2���

The upper cervical spine accounts for the largest proportion of cervical range of motion afforded by a complex system of bony morphology and ligamentous stability. Its unique anatomy, however, also makes it particularly vulnerable during both low and high energy trauma. Trauma to this area, referred to as upper cervical spine trauma, can disrupt the stability of the upper cervical spine and result in a wide spectrum of injury. Numerous upper cervical injury classification systems have been proposed, each of which have distinct limitations and drawbacks that have prevented their universal adoption. In this article, we provide an overview of previous classifications, with an emphasis on the development of the new AO Spine Upper Cervical Classification System (AO Spine UCCS).

Instrumentation during metastatic spine tumor surgery (MSTS) provides stability to the spinal column in patients with pathologic fracture or iatrogenic instability produced while undergoing extensive decompression. Titanium is the current implant material of choice in MSTS. However, it hinders radiotherapy planning and generates artifacts, with magnetic resonance imaging and computed tomography scans used for postoperative evaluation of tumor recurrence and/or complications. The high modulus of elasticity of titanium (110 GPa) results in stress shielding, which may lead to construct failure at the bone-implant interface. Polyether ether ketone (PEEK), a thermoplastic polymer, is an emerging alternative to titanium for use in MSTS. The modulus of elasticity of PEEK (3.6 GPa) is close to that of cortical bone (17-21 GPa), resulting in minimal stress shielding. Its radiolucent and nonmetallic properties cause minimal interference with magnetic resonance imaging and computed tomography scans. PEEK also causes low-dose perturbation for radiotherapy planning. However, PEEK has reduced bioactivity with bone and lacks sufficient rigidity to be used as rods in MSTS. The reduced bioactivity of PEEK may be addressed by 1) surface modification (introducing porosity or bioactive coating with hydroxyapatite [HA] or titanium) and 2) forming composites with HA/titanium. The mechanical properties of PEEK may be improved by forming composites with HA or carbon fiber. Despite these modifications, all PEEK and PEEK-based implants are difficult to handle and contour intraoperatively. Our review provides a comprehensive overview of PEEK and modified PEEK implants, with a description of their properties and limitations, potentially serving as a basis for their future development and use in MSTS.

Study Design: Systematic Review. Objective: To systematically analyze the definitions and descriptions in literature of “Spinal Posttraumatic Deformity” (SPTD) in order to support the development of a uniform and comprehensive definition of clinically relevant SPTD. Methods: A literature search in 11 international databases was performed using “deformity” AND “posttraumatic” and its synonyms. When an original definition or a description of SPTD (Patient factors, Radiological outcomes, Patient Reported Outcome Measurements and Surgical indication) was present the article was included. The retrieved articles were assessed for methodological quality and the presented data was extracted. Results: 46 articles met the inclusion criteria. “Symptomatic SPTD” was mentioned multiple times as an entity, however any description of “symptomatic SPTD” was not found. Pain was mentioned as a key factor in SPTD. Other patient related parameters were (progression of) neurological deficit, bone quality, age, comorbidities and functional disability. Various ways were used to determine the amount of deformity on radiographs. The amount of deformity ranged from not deviant for normal to >30°. Sagittal balance and spinopelvic parameters such as the Pelvic Incidence, Pelvic Tilt and Sacral Slope were taken into account and were used as surgical indicators and preoperative planning. The Visual Analog Scale for pain and the Oswestry Disability Index were used mostly to evaluate surgical intervention. Conclusion: A clear-cut definition or consensus is not available in the literature about clinically relevant SPTD. Our research acts as the basis for international efforts for the development of a definition of SPTD.

To evaluate whether a new PEEK vertebral body replacement can maintain the sagittal alignment as an anterior column reconstruction device in thoracic and lumbar spinal defects due to trauma or tumor. Retrospective review of 48 patients who underwent a corpectomy between T5 and L5 due to trauma or tumor and were stabilized with the new PEEK vertebral body replacement, between 2013 and 2017. We excluded patients who underwent a corpectomy for infection or degenerative disease and patients without complete follow-up in our institution. The primary outcome was the bi-segmental kyphotic angle (BKA). Secondary outcomes were the assessment of pedicle screw loosening, cage height, and subsidence or tilting of the cage. The clinical outcomes were assessed through the COMI-Score, EuroQol-5D, and Karnofsky indexes. Bony fusion and complications were registered. After the surgery BKA decreased by 12.1° (p

Purpose To report on the development of AOSpine CROST (Clinician Reported Outcome Spine Trauma) and results of an initial reliability study. Methods The AOSpine CROST was developed using an iterative approach of multiple cycles of development, review, and revision including an expert clinician panel. Subsequently, a reliability study was performed among an expert panel who were provided with 20 spine trauma cases, administered twice with 4-week interval. The results of the developmental process were analyzed using descriptive statistics, the reliability per parameter using Kappa statistics, inter-rater rater agreement using intraclass correlation coefficient (ICC), and internal consistency using Cronbach’s α. Results The AOSpine CROST was developed and consisted of 10 parameters, 2 of which are only applicable for surgically treated patents (‘Wound healing’ and ‘Implants’). A dichotomous scoring system (‘yes’ or ‘no’ response) was incorporated to express expected problems for the short term and long term. In the reliability study, 16 (84.2%) participated in the first round and 14 (73.7%) in the second. Intra-rater reliability was fair to good for both time points (κ = 0.40–0.80 and κ = 0.31–0.67). Results of inter-rater reliability were lower (κ = 0.18–0.60 and κ = 0.16–0.46). Inter-rater agreement for total scores showed moderate results (ICC = 0.52–0.60), and the internal consistency was acceptable (α = 0.76–0.82). Conclusions The AOSpine CROST, an outcome tool for the surgeons, was developed using an iterative process. An initial reliability analysis showed fair to moderate results and acceptable internal consistency. Further clinical validation studies will be performed to further validate the tool.

Low back pain is a prevalent socio-economic burden and is often associated with damaged or degenerated intervertebral discs (IVDs). When conservative therapy fails, removal of the IVD (discectomy), followed by intersomatic spinal fusion, is currently the standard practice in clinics. The remaining space is filled with an intersomatic device (cage) and with bone substitutes to achieve disc height compensation and bone fusion. As a complication, in up to 30% of cases, spinal non-fusions result in a painful pseudoarthrosis. Bone morphogenetic proteins (BMPs) have been clinically applied with varied outcomes. Several members of the BMP family, such as BMP2, BMP4, BMP6, BMP7, and BMP9, are known to induce osteogenesis. Questions remain on why hyper-physiological doses of BMPs do not show beneficial effects in certain patients. In this respect, BMP antagonists secreted by mesenchymal cells, which might interfere with or block the action of BMPs, have drawn research attention as possible targets for the enhancement of spinal fusion or the prevention of non-unions. Examples of these antagonists are noggin, gremlin1 and 2, chordin, follistatin, BMP3, and twisted gastrulation. In this review, we discuss current evidence of the osteogenic effects of several members of the BMP family on osteoblasts, IVD cells, and mesenchymal stromal cells. We consider in vitro and in vivo studies performed in human, mouse, rat, and rabbit related to BMP and BMP antagonists in the last two decades. We give insights into the effects that BMP have on the ossification of the spine. Furthermore, the benefits, pitfalls, and possible safety concerns using these cytokines for the improvement of spinal fusion are discussed.

Summary Objective This study aimed to characterize the mesenchymal stem cell (MSC) subpopulation migrating towards a degenerated intervertebral disc (IVD) and to assess its regenerative potential. Design Based on initial screening for migration towards C-C motif chemokine ligand 5 (CCL5), the migration potential of CD146+ and CD146- mesenchymal stem cells (MSCs) was evaluated in vitro and in a degenerated organ culture model (degeneration by high-frequency loading in a bioreactor). Discogenic differentiation potential of CD146+ and CD146- MSCs was investigated by in vitro pellet culture assay with supplementation of growth and differentiation factor-6 (GDF6). Furthermore, trypsin degenerated IVDs were treated by either homing or injection of CD146+ or CD146- MSCs and glycosaminoglycan synthesis was evaluated by Sulphur 35 incorporation after 35 days of culture. Results Surface expression of CD146 led to a higher number of migrated MSCs both in vitro and in organ culture. CD146+ and CD146- pellets responded with a similar up-regulation of anabolic markers. A higher production of sulfated glycosaminoglycans (sGAG)/DNA was observed for CD146+ pellets, while in organ cultures, sGAG synthesis rate was higher for IVDs treated with CD146- MSCs by either homing or injection. Conclusions The CD146+ MSC subpopulation held greater migration potential towards degenerative IVDs, while the CD146- cells induced a stronger regenerative response in the resident IVD cells. These findings were independent of the application route (injection vs migration). From a translational point of view, our data suggests that CD146+ MSCs may be suitable for re-population, while CD146- MSCs may represent the primary choice for stimulation of endogenous IVD cells.

PURPOSE The purpose of this study was to investigate the type and severity of spinal injury in airborne sports, as well as patients demographics in this unique set of athletes. Paragliding is one of the most popular airborne sports in Switzerland, which thought to be no less dangerous with a high potential for spinal injury. Few studies on spinal column injuries have been performed in these high-risk athletes with only inconsistent findings. METHODS Patient charts were analyzed for all airborne sports injuries affecting the spine from 2010 to 2017 at a level-1 trauma center in Switzerland. To classify the injuries, we used the newest AOSpine classification, ASIA-grading and the injury severity score (ISS). In total, 235 patients were admitted to the emergency department due to an airborne injury. A total of 148 patients (148/235, 63.0%) which were predominantly male (125/235, 84.5%) at a mean age of 39.4 years suffered 334 spinal fractures and 5 spinal contusions. The mean ISS was 17.3, and the L1 vertebra was most commonly affected (47.6% of cases, 68/148). RESULTS A total of 78 patients (54.5% or 78/148) required spine surgery due to instability or neurological deficits (31/148 patients; 20.9%). Concomitant injuries were identified in 64.2% of cases (n = 95). CONCLUSION Due to the increasing popularity of airborne sports, age of patients and severity of injuries (ISS) increased compared with the literature. The thoracolumbal spine is at especially high risk. To prevent further complications, the treatment procedure has to be sought carefully and algorithm should be introduced in clinics to avoid delay in diagnostics and surgery. LEVEL OF EVIDENCE III, retrospective comparative study. These slides can be retrieved under Electronic Supplementary Material.

PURPOSE Factors influencing paraspinal muscle degeneration are still not well understood. Fatty infiltration is known to be one main feature of the degeneration cascade. The aim of this cross-sectional study was to illustrate the 3D cluster of paraspinal lumbar muscle degeneration on T2-weighted MRI images using our newly developed software application 'iSix'. METHODS Mono- (Mm. rotatores), multi- (Mm. multifidus) and pluri-segmental (M. erector spinae) lumbar muscles groups were segmented on T2-weighted MR sequences using a novel computer-assisted technique for quantitative muscle/fat discrimination. The degree of fatty infiltration of the three predefined muscle groups was compared on a 3-dimensional basis, with regard to segment involvement and age. General linear models were utilized for statistical comparison. RESULTS N���=���120 segments (age: 52.7; range 16-87��years) could be included. The overall relative fatty infiltration of the mono-segmental muscles was higher (21.1 14.5%) compared to the multi-segmental (16.0 8.8% p���=���0.049) and pluri-segmental muscles (8.5 8.0%; p���=���0.03). Mono-segmental muscles on the levels L4/5 (22.9��������10.2 [CI 17.6-28.2] %) and L5/S1 (27.01��������15.1 [CI 21.4-32.7] %) showed a significant higher amount of fat compared to the levels L2/3 (8.2��������6.8 [CI 2.2-14.2] %; L4/5 vs. L2/3, p���=���0.03; L5/S1 vs. L2/3, p���=���0.02) and L3/4 (13.2��������5.4 [CI 8.6-17.7]%; L4/5 vs. L3/4, p���=���0.02; L5/S1 vs. L3/4, p���

"Metastatic Spine Disease" (MSD) often requires surgical intervention and instrumentation with spinal implants. Ti6Al4V is widely used in metastatic spine tumor surgery (MSTS) and is the current implant material of choice due to improved biocompatibility, mechanical properties, and compatibility with imaging modalities compared to stainless steel. However, it is still not the ideal implant material due to the following issues. Ti6Al4V implants cause stress-shielding as their Young's modulus (110 gigapascal [GPa]) is higher than cortical bone (17-21 GPa). Ti6Al4V also generates artifacts on CT and MRI, which interfere with the process of postoperative radiotherapy (RT), including treatment planning and delivery. Similarly, charged particle therapy is hindered in the presence of Ti6Al4V. In addition, artifacts on CT and MRI may result in delayed recognition of tumor recurrence and postoperative complications. In comparison, polyether-ether-ketone (PEEK) is a promising alternative. PEEK has a low Young's modulus (3.6 GPa), which results in optimal load-sharing and produces minimal artifacts on imaging with less hinderance on postoperative RT. However, PEEK is bioinert and unable to provide sufficient stability in the immediate postoperative period. This issue may possibly be mitigated by combining PEEK with other materials to form composites or through surface modification, although further research is required in these areas. With the increasing incidence of MSD, it is an opportune time for the development of spinal implants that possess all the ideal material properties for use in MSTS. Our review will explore whether there is a current ideal implant material, available alternatives and whether these require further investigation.

Contains fulltext : 229469.pdf (Publisher’s version ) (Open Access) The aim of this study was to capture and understand the immediate recovery journey of patients following lumbar spinal fusion surgery and explore the interacting constructs that shape their journey. A qualitative study using Interpretive Phenomenological Analysis (IPA) approach. A purposive sample of 43 adult patients (≥16 years) undergoing ≤4 level instrumented fusion for back and/or leg pain of degenerative cause, were recruited pre-surgery from 4 UK spinal surgery centres. Patients completed a weekly diary expressed in their own words for the first 4 weeks following surgery to capture their life as lived. Diary content was based on previous research findings and recorded progress, recovery, motivation, symptoms, medications, healthcare appointments, rehabilitation, positive/negative thoughts, and significant moments; comparing to the previous week. To maximise completion and data quality, diaries could be completed in paper form, word document, as online survey or as audio recording. Strategies to enhance diary adherence included a weekly prompt. A framework analysis for individual diaries and then across participants (deductive and inductive components) captured emergent themes. Trustworthiness was enhanced by strategies including reflexivity, attention to negative cases and use of critical co-investigators. Twenty-eight participants (15 female; n = 18 (64.3%) aged 45-64) contributed weekly diaries (12 withdrew post-surgery, 3 did not follow through with surgery). Adherence with diaries was 89.8%. Participants provided diverse and vivid descriptions of recovery experiences. Three distinct recovery trajectories were identified: meaningful recovery (engagement in physical and functional activities to return to functionality/mobility); progressive recovery (small but meaningful improvement in physical ability with increasing confidence); and disruptive recovery (limited purpose for meaningful recovery). Important interacting constructs shaped participants' recovery including their pain experience and self-efficacy. This is the first account of immediate recovery trajectories from patients' perspectives. Recognition of a patient's trajectory may inform patient-centred recovery, follow-up and rehabilitation to improve patient outcomes.

Spinopelvic dissociation which is also called U-type or referred to H-type sacral fractures with a transverse fracture line is an infrequent injury that results mainly from high-energy accidents. This results in an osseous dissociation of the upper central segment of the sacrum and the entire spine from the lower sacral segments. The purpose was to investigate the incidence of spinopelvic fracture in general among airborne injuries. Using our electronic patient records, we retrospectively investigated all sacral fractures related to airborne sports between 2010 and 2017. All injuries were classified according to the Roy-Camille, Denis, AOSpine and the Tile classification system. During the period of interest, 44 patients (18.7%) were admitted with sacral fractures after accidents obtained from airborne sports, including 16 spinopelvic dissociations (36.4%). The majority of these injuries were obtained from paragliding (75.0%), followed by BASE jumping (21.4%) and parachuting (4%). The mean injury severity score (ISS) in the spinopelvic dissociation group was significantly higher compared with other sacral fracture group (38.1 vs. 20.0; p

The AOSpine PROST (Patient Reported Outcome Spine Trauma) is a new disease-specific outcome instrument for spine trauma patients. Very good results were obtained for reliability and validity of the English version. It has the potential to contribute to the reduction of ongoing controversies in spine trauma care., Study Design. Multicenter validation study. Objective. The aim of this study was to translate and adapt the AOSpine PROST (Patient Reported Outcome Spine Trauma) into English, and test its psychometric properties among North-American spine trauma patients. Summary of Background Data. In the absence of an outcome instrument specifically designed and validated for traumatic spinal column injury patients, it is difficult to measure the effect size of various treatment options. The AOSpine Knowledge Forum Trauma initiated a project and developed the AOSpine PROST consisting of 19 items. Methods. Patients were recruited from two level-1 North-American trauma centers. For concurrent validity, next to AOSpine PROST also 36-item Short-Form Health Survey (SF-36) was filled out by patients. Patient characteristics were analyzed using descriptive statistics. Floor and ceiling effects as well as the number of inapplicable and missing questions were analyzed for content validity. Cronbach α and item-total correlation coefficients (ITCCs) were calculated for internal consistency. Spearman correlation tests were performed within AOSpine PROST items and in correlation to SF-36. Test-retest reliability was assessed using intraclass correlation coefficients (ICCs). Factor analysis was performed to explore any dimensions within AOSpine PROST. Results. The AOSpine PROST was translated adapted into English using established guidelines. Of 196 enrolled patients, 162 (82.7%) met the inclusion criteria and provided sufficient data. Content validity showed good results, and no floor and ceiling effects were seen. The internal consistency was excellent (Cronbach α = 0.97; ITCC 0.50–0.90) as well as test–retest reliability (ICC = 0.97). Spearman correlations were good (0.29–0.85). The strongest correlations of AOSpine PROST with SF-36 were seen with the physical components (0.69–0.82; P 1), explaining 75.7% of variance. Conclusion. The English version of AOSpine PROST showed very good validity and reliability. It is considered as a valuable tool, and has the potential to contribute to the reduction of ongoing controversies in spine trauma care. Level of Evidence: 2

Tissue engineering repair of annulus fibrosus (AF) defects has the potential to prevent disability and pain from intervertebral disc (IVD) herniation and its progression to degeneration. Clinical translation of AF repair methods requires assessment in long‐term large animal models. An ovine AF injury model was developed using cervical spinal levels and a biopsy‐type AF defect to assess composite tissue engineering repair in 1‐month and 12‐month studies. The repair used a fibrin hydrogel crosslinked with genipin (FibGen) to seal defects, poly(trimethylene carbonate) (PTMC) scaffolds to replace lost AF tissue, and polyurethane membranes to prevent herniation. In the 1‐month study, PTMC scaffolds sealed with FibGen herniated with polyurethane membranes. When applied alone, FibGen integrated with the surrounding AF tissue without herniation, showing promise for long‐term studies. The 12‐month long‐term study used only FibGen which showed fibrous healing, biomaterial resorption and no obvious hydrogel‐related complications. However, the 2 mm biopsy punch injury condition also exhibited fibrotic healing at 12 months. Both untreated and FibGen treated groups showed equivalency with no detectable differences in histological grades of proteoglycans, cellular morphology, IVD structure and blood vessel formation, biomechanical properties including torque range and axial range of motion, Pfirrmann grade, IVD height, and quantitative scores of vertebral body changes from clinical computed tomography. The biopsy‐type injury caused endplate defects with a high prevalence of osteophytes in all groups and no nucleus herniation, indicating that the biopsy‐type injury requires further refinement, such as reduction to a slit‐type defect that could penetrate the full depth of the AF without damaging the endplate. Results demonstrate translational feasibility of FibGen for AF repair to seal AF defects, although future study with a more refined injury model is required to validate the efficacy of FibGen before translation. ISSN:2572-1143

Appropriate cell sources, bioactive factors and biomaterials for generation of functional and integrated annulus fibrosus (AF) tissue analogues are still an unmet need. In the present study, the AF cell markers, collagen type I, cluster of differentiation 146 (CD146), mohawk (MKX) and smooth muscle protein 22α (SM22α) were found to be suitable indicators of functional AF cell induction. In vitro 2D culture of human AF cells showed that transforming growth factor β1 (TGF-β1) upregulated the expression of the functional AF markers and increased cell contractility, indicating that TGF-β1-pre-treated AF cells were an appropriate cell source for AF tissue regeneration. Furthermore, a tissue engineered construct, composed of polyurethane (PU) scaffold with a TGF-β1-supplemented collagen type I hydrogel and human AF cells, was evaluated with in vitro 3D culture and ex vivo preclinical bioreactor-loaded organ culture models. The collagen type I hydrogel helped maintaining the AF functional phenotype. TGF-β1 supplement within the collagen I hydrogel further promoted cell proliferation and matrix production of AF cells within in vitro 3D culture. In the ex vivo IVD organ culture model with physiologically relevant mechanical loading, TGF-β1 supplement in the transplanted constructs induced the functional AF cell phenotype and enhanced collagen matrix synthesis. In conclusion, TGF-β1-containing collagen-PU constructs could induce the functional cell phenotype of human AF cells in vitro and in situ. This combined cellular, biomaterial and bioactive agent therapy has a great potential for AF tissue regeneration and rupture repair., Editor’s note: The Scientific Editor responsible for this paper was Brian Johnstone.

Study Design: Global cross-sectional survey. Objective: To develop an injury score for the AO Spine Subaxial Cervical Spine Injury Classification System. Methods: Respondents numerically graded each variable within the classification system for severity. Based on the results, and with input from the AO Spine Trauma Knowledge Forum, the Subaxial Cervical AO Spine Injury Score was developed. Results: An A0 injury was assigned an injury score of 0, A1 a score of 1, and A2 a score of 2. Given the significant increase in severity, A3 was given a score of 4. Based on equal severity assessment, A4 and B1 were both assigned a score of 5. B2 and B3 injuries were assigned a score of 6. Unstable C-type injuries were given a score of 7. Stable F1 injuries were assigned a score of 2, with a 2-point increase for F2 injuries. Likewise, F3 injuries received a score of 5, whereas more unstable F4 injuries a score of 7. Neurologic status severity rating scores increased stepwise, with scores of 0 for N0, 1 for N1, and 2 for N2. Consistent with the Thoracolumbar AO Spine Injury Score, N3 (incomplete) and N4 (complete) injuries were given a score of 4. Finally, case-specific modifiers M1 (PLC injury) received a score of 1, while M2 (critical disc herniation) and M3 (spine stiffening disease) received a score of 4. Conclusions: The Subaxial Cervical AO Spine Injury Score is an easy-to-use metric that can help develop a surgical algorithm to supplement the AO Spine Subaxial Cervical Spine Injury Classification System.

BACKGROUND Several classification systems exist for sacral fractures; however, these systems are primarily descriptive, are not uniformly used, have not been validated, and have not been associated with a treatment algorithm or prognosis. The goal of the present study was to demonstrate the reliability of the AOSpine Sacral Classification System among a group of international spine and trauma surgeons. METHODS A total of 38 sacral fractures were reviewed independently by 18 surgeons selected from an expert panel of AOSpine and AOTrauma members. Each case was graded by each surgeon on 2 separate occasions, 4 weeks apart. Intrarater reproducibility and interrater agreement were analyzed with use of the kappa statistic (κ) for fracture severity (i.e., A, B, and C) and fracture subtype (e.g., A1, A2, and A3). RESULTS Seventeen reviewers were included in the final analysis, and a total of 1,292 assessments were performed (646 assessments performed twice). Overall intrarater reproducibility was excellent (κ = 0.83) for fracture severity and substantial (κ = 0.71) for all fracture subtypes. When comparing fracture severity, overall interrater agreement was substantial (κ = 0.75), with the highest agreement for type-A fractures (κ = 0.95) and the lowest for type-C fractures (κ = 0.70). Overall interrater agreement was moderate (κ = 0.58) when comparing fracture subtype, with the highest agreement seen for A2 subtypes (κ = 0.81) and the lowest for A1 subtypes (κ = 0.20). CONCLUSIONS To our knowledge, the present study is the first to describe the reliability of the AOSpine Sacral Classification System among a worldwide group of expert spine and trauma surgeons, with substantial to excellent intrarater reproducibility and moderate to substantial interrater agreement for the majority of fracture subtypes. These results suggest that this classification system can be reliably applied to sacral injuries, providing an important step toward standardization of treatment.

PURPOSE To describe a new surgical technique for neurolysis and decompression of L4 and L5 nerve root entrapment after vertical sacral fractures via the pararectus approach for acetabular fractures, and to present four case examples. PATIENTS AND METHODS We retrospectively evaluated four patients suffering radiculopathy from entrapment of the L4 or L5 nerve root in vertical sacral fractures between January and December 2016. The mean follow-up period after surgery was 18 (range 7-27) months. All patients underwent direct decompression and neurolysis of the L4 and L5 nerve roots via the single-incision, intrapelvic, extraperitoneal pararectus approach. RESULTS In all patients, the L4 and L5 nerve root was successfully visualized and decompressed, proving feasibility of the pararectus approach for this indication. No patient presented with a neural tear. Complete neurologic recovery was present in one patient at last follow-up; two patients had incomplete recovery of their radiculopathy; and one patient had no improvement after nerve root decompression. CONCLUSIONS The pararectus approach allows for sufficient visualisation and direct decompression and neurolysis of the L4 and L5 nerve root entrapped in vertical sacral fractures. Although neurologic recovery was not achieved in all patients in this small case series, the approach may be a suitable alternative to posterior approaches and other anterior approaches such as the lateral window of the ilioinguinal approach.

Study Design: Retrospective comparative study. Objectives: To assess the effect of vertebral body lavage (VBL) on (1) systemic blood pressure, (2) heart rate, and (3) oxygen saturation following cement augmentation procedures for acute vertebral compression fractures (VCFs). Methods: A total of 145 consecutive patients undergoing cement augmentation for acute VCF (mean age 74 ± 12 years, age range 42-96 years; 70% female; 475 levels treated) were allocated to the “lavage group” (n = 61 patients; VBL prior to cement application) and to the “control group” (n = 84 patients, no VBL). Mean arterial blood pressure (MAP), heart rate, and oxygen saturation were monitored immediately prior and 3 minutes after cement injection. Logistic regression analysis was performed with ΔMAP ≥10 mm Hg before and after cement injection as the dependent outcome variable and demographic, radiographic, and procedural factors as independent variables. Results: MAP decreased by mean 3 ± 7.3 mm Hg before and after cement injection in the “lavage group” and 9 ± 10.5 mmHg in the control group ( P < .001). There were no significant differences in terms of heart rate and oxygen saturation before and after cement application within each group, or between the 2 groups. Multivariate logistic regression analyses revealed VBL as an independent factor influencing MAP (adjusted odds ratio: 3.49 [confidence interval, 1.16-10.50], P = .03). Conclusion: VBL prior to cement augmentation procedures reduces the hemodynamic response, most likely resulting from decreased amounts of bone marrow substance displaced into the circulation thereby decreasing the risk of pulmonary fat embolism syndrome.

Das internationale «Spine Tango»-Wirbelsaulenregister wurde 2002 gegrundet, um das therapeutische Bemuhen auf nationaler und internationaler Ebene vergleichen und sich in Richtung Harmonisierung und Standardisierung der Therapien bewegen zu konnen.

Le registre international du rachis «Spine Tango» a ete lance en 2002 afin de pouvoir comparer les efforts therapeutiques au niveau national et international et de tendre vers une harmonisation et une standardisation des traitements.

Supplemental Digital Content is available in the text Homing of mesenchymal stem cells (MSCs) from the endplate into the intervertebral disc (IVD) has been described as alternative intradiscal application route. Our findings indicate that the homed MSCs enhance the Tie2-positive disc progenitor cell population, prevent disc cell death, and induce a proliferative response in the IVD cells., Study Design. Experimental study with human mesenchymal stem cells (MSCs) and intervertebral disc (IVD) tissue samples. Objective. This study aimed to characterize the effect of MSC homing on the Tie2-positive IVD progenitor cell population, IVD cell survival, and proliferation. Summary of Background Data. Homing of human MSCs has been described as potential alternative to MSC injection, aiming to enhance the regenerative capacity of the IVD. IVD cells expressing Tie2 (also known as CD202b or Angiopoietin-1 receptor TEK tyrosine kinase) represent a progenitor cell population with discogenic differentiation potential. However, the fraction of Tie2-positive progenitor cells decreases with aging and degree of IVD degeneration, resulting in a potential loss of the IVD's regenerative capacity. Methods. Human MSCs, isolated from vertebral bone marrow aspirates, were labeled and seeded onto the endplate of bovine IVDs and human IVD tissue. Following MSC migration for 5 days, IVD cells were isolated by tissue digestion. The fractions of Tie2-positive, dead, apoptotic, and proliferative IVD cells were evaluated by flow cytometry and compared to untreated IVDs. For human IVDs, 3 groups were investigated: nondegenerated (organ donors), IVDs of patients suffering from spinal trauma, and degenerative IVD tissue samples. Results. MSC homing enhanced the fraction of Tie2-positive IVD cells in bovine and human IVD samples. Furthermore, a proliferative response and lower fraction of dead cells were observed after MSC homing in both bovine and human IVD tissues. Conclusion. Our findings indicate that MSC homing enhances the survival and regenerative capability of IVD cells, which may be mediated by intercellular communication. MSC homing could represent a potential treatment strategy to prevent the onset of the degenerative cascade in IVDs at risk such as IVDs adjacent to a fused segment or IVDs after herniation. Level of Evidence: N/A

PURPOSE The development of spinal implants marks a watershed in the evolution of metastatic spine tumour surgery (MSTS), which has evolved from standalone decompressive laminectomy to instrumented stabilization and decompression with reconstruction when necessary. Fusion may not be feasible after MSTS due to poor quality of graft host bed along with adjunct chemotherapy and/or radiotherapy postoperatively. With an increase in the survival of patients with spinal tumours, there is a probability of an increase in the rate of implant failure. This review aims to help establish a clear understanding of implants/constructs used in MSTS and to highlight the fundamental biomechanics of implant/construct failures. METHODS Published literature on implant failure after spine surgery and MSTS has been reviewed. The evolution of spinal implants and their role in MSTS has been briefly described. The review defines implant/construct failures using radiological parameters that are practical, feasible, and derived from historical descriptions. We have discussed common modes of implant/construct failure after MSTS to allow further understanding, interception, and prevention of catastrophic failure. RESULTS Implant failure rates in MSTS are in the range of 2-8%. Variability in patterns of failure has been observed based on anatomical region and the type of constructs used. Patients with construct/implant failures may or may not be symptomatic and present either as early ( 3months). It has been noted that not all the implant failures after MSTS result in revisions. CONCLUSION Based on the observed radiological criteria and clinical presentations, we have proposed a clinico-radiological classification for implant/construct failure after MSTS.

Intervertebral disc (IVD) repair is a high-priority topic in our active and increasingly ageing society. Since a high number of people are affected by low back pain treatment options that are able to restore the biological function of the IVD are highly warranted. Here, we investigated whether the feasibility of genetically engineered (GE)-silk from Bombyx mori containing specific growth factors to precondition human bone-marrow derived mesenchymal stem cells (hMSC) or to activate differentiated human annulus fibrosus cells (hAFC) prior transplantation or for direct repair on the IVD. Here, we tested the hypothesis that GE-silk fleece can thrive human hMSC towards an IVD-like phenotype. We aimed to demonstrate a possible translational application of good manufacturing practice (GMP)-compliant GE-silk scaffolds in IVD repair and regeneration. GE-silk with growth and differentiation factor 6 (GDF-6-silk) or transforming growth factor β3 (TGF-β3, TGF-β3-silk) and untreated silk (cSilk) were investigated by DNA content, cell activity assay and glycosaminoglycan (GAG) content and their differentiation potential by qPCR analysis. We found that all silk types demonstrated a very high biocompatibility for both cell types, that is, hMSC and hAFC, as revealed by cell activity, and DNA proliferation assay. Further, analyzing qPCR of marker genes revealed a trend to differentiation toward an NP-like phenotype looking at the Aggrecan/Collagen 2 ratio which was around 10:1. Our results support the conclusion that our GE-silk scaffold treatment approach can thrive hMSC towards a more IVD-like phenotype or can maintain the phenotype of native hAFC. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1324-1333, 2018.

Study Design: Retrospective case series. Objective: Short posterior stabilization with vertebroplasty is one treatment option for thoracolumbar burst fractures (AO A3). Whether it avoids progression in segmental kyphosis, especially after implant removal, is unclear. In a retrospective case-control study, its stability and the effect on intervertebral discs with and without implant removal was studied. Methods: Fifty-nine consecutive patients were treated with bisegmental short posterior instrumentation and additional vertebroplasty of the fractured vertebra. Twenty-nine patients (male/female 17/12; age: 41.7 ± 15.4 years) underwent implant removal. Changes of segmental kyphosis and disc heights between both groups (with and without implant removal) were compared on lateral X-rays preoperative, postoperative, after 1 year and after implant removal. Risk factors for loss of reduction were analyzed. Results: Kyphosis increased up to 12 months after implant removal. The loss of bisegmental correction was 6.0 ± 4.2 (range 0° to 16°) 12 months after implant removal. Risk factors for loss of reduction are younger patient age, fractures of the thoracolumbar junction (Th12), and degree of traumatic kyphosis. Intervertebral discs traversed by the stabilization lose height and don’t recover within 1 year after implant removal. Without implant removal, disc height of the lower adjacent level is reduced after 24 months. Conclusions: Short posterior stabilization in combination with vertebroplasty is a treatment alternative for thoracic and lumbar AO A3 fractures. After implant removal kyphosis increases, predominantly in the segment above the augmented vertebra. Risk factors for loss of reduction include younger age, fractures of the thoracolumbar junction (T12), and higher fracture kyphosis.

Summary In vitro and in vivo studies evidenced that mesenchymal stem cells (MSCs) contribute to intervertebral disc (IVD) regeneration by differentiation towards the disc phenotype and matrix synthesis and/or by paracrine signalling to endogenous cells, thereby promoting a healthier disc phenotype in degenerative discs. The aim of this study was to investigate IVD response to human MSC (hMSC) treatment based on the disc degenerative state and hMSC carrier. Bovine caudal IVDs with endplates were cultured in a bioreactor under simulated physiological (0.1 Hz load and sufficient glucose) or degenerative (10 Hz load and limited glucose) conditions for 7 days. Discs were partially nucleotomised, restored with hMSCs in either fibrin gel or saline solution and cultured under physiological conditions for 7 days. Controls included fibrin and saline without hMSCs. Cell viability, histology, disc height, and gene expression analyses were performed to evaluate regeneration. hMSCs in fibrin were viable and homogenously distributed following 7 days of culture under dynamic loading in partially nucleotomised discs. IVD response to hMSCs was conditioned by both disc degenerative state and hMSC carrier. The effect of the regenerative treatment was stronger on simulated-degenerative discs than on simulated-physiological discs. hMSCs in fibrin induced a superior anabolic response in degenerative IVDs compared with fibrin alone, thus suggesting an added value of the cellular therapy compared with an acellular solution. When comparing fibrin and saline as a hMSC carrier, a significantly higher anabolic response was observed in IVDs treated with hMSCs in fibrin. Moreover, it was found that the degenerative state of the disc influenced hMSC differentiation. Indeed, a significantly higher expression of specific discogenic markers (ACAN and CA12) was observed in hMSCs implanted into physiological discs than in those implanted into degenerative discs. In conclusion, host disc cells and donor hMSC response depend on the degenerative state of the host disc and carrier used for hMSC delivery, and these two aspects need to be considered for a successful translation of hMSC therapies for the treatment of IVD degeneration.

Spinal fusion is hampered by the presence of remaining intervertebral disc (IVD) tissue and leads to spinal non-union. While the exact mechanism remains unknown, we hypothesise that factors preventing disc ossification, such as antagonists of the bone morphogenetic proteins (BMP), could be responsible for this process. The objective of this study was to investigate spinal non-union using an in vitro human model with a focus on the BMP signalling components and to identify factors contributing to the incomplete and delayed ossification. Human bone marrow-derived mesenchymal stromal cells (MSC) were cocultured with IVD cells in the presence of L51P, a BMP2 variant with osteoinductive potential. The ossification of MSC was evaluated by quantitative reverse transcription polymerase chain reaction (qPCR), alkaline phosphatase (ALP) activity and alizarin red staining. Endogenous expression of major BMP antagonists, namely Gremlin (GREM1), Noggin (NOG) and Chordin (CHRD) was detected in IVD-derived cells, with abundance in nucleus pulposus cells. Osteogenesis of MSC was hindered by IVD cells as shown by reduced alizarin red staining, ALP activity and qPCR. L51P, added to the cocultures, restored mineralisation, blocking the activity of the BMP antagonists secreted by IVD cells. It is possible that the BMP antagonists secreted by IVD cells are responsible for spinal non-unions. The inhibition of BMP antagonists with L51P may result in an efficient and more physiological osteoinduction rather than delivery of exogenous osteogenic factors. Therefore, L51P might represent an attractive therapeutic candidate for bone healing.

We investigated the effects of a fibrin-hyaluronic acid hydrogel (FBG&ndash, HA) and fibroblast growth factor 18 (FGF-18) for nucleus pulposus (NP) regeneration. Healthy bovine (n = 4) and human degenerated NP cells (n = 4) were cultured for 14 days in FBG-HA hydrogel with FGF-18 (∆51-mutant or wild-type) in the culture medium. Gene expression, DNA content, and glycosaminoglycan (GAG) synthesis were evaluated on day 7 and 14. Additionally, histology was performed. Human NP cells cultured in FBG-HA hydrogel showed an increase in collagen type II (COL2) and carbonic anhydrase XII (CA12) gene expression after 14 or 7 days of culture, respectively. GAG release into the conditioned medium increased over 14 days. Healthy bovine NP cells showed increased gene expression of ACAN from day 7 to day 14. Wild type FGF-18 up-regulated CA12 gene expression of human NP cells. Histology revealed an increase of proteoglycan deposition upon FGF-18 stimulation in bovine but not in human NP cells. The FBG-HA hydrogel had a positive modulatory effect on human degenerated NP cells. Under the tested conditions, no significant effect of FGF-18 was observed on cell proliferation or GAG synthesis in human NP cells.

Introduction Alpine winter sports have become increasingly popular over recent decades, with a similar increase in accident incidence. This review provides an overview of the most recent literature concerning spinal injury epidemiology, mechanisms, patterns and prevention strategies in the context of alpine winter sports. Material and methods The PubMed, Cochrane Library, and EMBASE databases were searched using the keywords spine injury, alpine injury, spine fracture, skiing injuries, snowboard injuries. 64 published studies in English and German met a priori inclusion criteria and were reviewed in detail by the authors. Results There are various mechanisms of injury in alpine winter sports (high speed falls in skiing, jumping failure in snowboarding) whilst regionality and injury severity are broadly similar. The thoracolumbar spine is the most common region for spinal injury. Spinal cord injury is relatively rare, usually accompanying distraction and rotation type fractures and is most commonly localised to the cervical spine. Disc injuries seem to occur more commonly in alpine winter sport athletes than in the general population. Discussion Despite awareness of increasing rates and risks of spinal injuries in alpine winter sports, there has been little success in injury prevention.

Carbon fibre reinforced polyether ether ketone (CFR-PEEK) is a suitable material to replace metal implants in orthopaedic surgery. The radiolucency of CFR-PEEK allows an optimal visualisation of the bone and soft tissue structures. We aimed to assess the performance and radiological and clinical outcomes of anterior cervical discectomy and fusion (ACDF) with CFR-PEEK anterior cervical plating (ACP) under first use clinical conditions. We retrospectively studied the prospectively-collected data of 42 patients who underwent ACDF with CFR-PEEK ACP between 2011 and 2016. We assessed clinical outcome (Odom&rsquo, s criteria, complications) and radiological parameters (global and segmental cervical lordosis, Bridwell score for fusion, adjacent segment degeneration) preoperatively, immediately post-operatively, and after a 12-month follow-up period. Patients&rsquo, satisfaction was excellent, good, fair, and poor in 12, 19, 3, and 1 patients, respectively. Two patients developed dysphagia. No hardware failure occurred. Compared with preoperative radiographs, we observed a gain of global cervical lordosis and segmental lordosis (7.4 &plusmn, 10.1 and 5.6 &plusmn, 7.1 degrees, respectively) at the 12-month follow-up. Bridwell IF grades I, II, and III were observed in 22, 6, and 7 patients, respectively. The 12-month adjacent segment degeneration-free and adjacent segment disease-free survival rates were 93.1% and 96.3%, respectively. We observed a dysphagia rate of 5.7% and a reoperation rate of 4.8%. In conclusion, CFR-PEEK ACP shows positive outcomes in terms of implant safety, restoration of cervical lordosis, and functional recovery, and is suitable for ACDF.

Carbon fibre reinforced polyetheretherketone (CFR-PEEK) is a suitable material to replace metal implants in orthopaedic surgery. The radiolucency allows optimal visualization of bone and soft tissue. We aimed to assess performance and radiological and clinical outcomes of anterior cervical discectomy and fusion (ACDF) with CFR-PEEK anterior cervical plating (ACP) under first use clinical conditions. We retrospectively studied data of 42 patients undergoing ACDF with CFR-PEEK ACP between 2011 and 2016. We assessed clinical and radiological parameters preoperatively, immediately post-operative and after a 12-month follow-up period. Patients’ satisfaction was excellent, good, fair and poor in 12, 19, 3, and 1 respectively. 2 patients developed dysphagia. No hardware failure occurred. Compared to preoperative radiographs, we observed a gain of global cervical lordosis and segmental lordosis (7.4±10.1 and 5.6±7.1 degrees respectively) at 12-month follow-up. Bridwell interbody fusion grades I, II, and III were observed in 22, 6, and 7 Pts respectively. The 12-month adjacent segment degeneration-free and adjacent segment disease-free survival rates were 93.1% and 96.3% respectively. In conclusion, CFR-PEEK ACP shows positive outcomes in terms of implant safety, radiological outcomes and functional recovery and is suitable for ACDF in trauma, degenerative disease and tumours. Radiolucency and the absence of imaging artefacts enable precise radiological follow-up.

Study Design: Narrative review. Objectives: To provide an updated overview of the management of acute traumatic central cord syndrome (ATCCS). Methods: A comprehensive narrative review of the literature was done to identify evidence-based treatment strategies for patients diagnosed with ATCCS. Results: ATCCS is the most commonly encountered subtype of incomplete spinal cord injury and is characterized by worse sensory and motor function in the upper extremities compared with the lower extremities. It is most commonly seen in the setting of trauma such as motor vehicles or falls in elderly patients. The operative management of this injury has been historically variable as it can be seen in the setting of mechanical instability or preexisting cervical stenosis alone. While each patient should be evaluated on an individual basis, based on the current literature, the authors’ preferred treatment is to perform early decompression and stabilization in patients that have any instability or significant neurologic deficit. Surgical intervention, in the appropriate patient, is associated with an earlier improvement in neurologic status, shorter hospital stay, and shorter intensive care unit stay. Conclusions: While there is limited evidence regarding management of ATCCS, in the presence of mechanical instability or ongoing cord compression, surgical management is the treatment of choice. Further research needs to be conducted regarding treatment strategies and patient outcomes.

Objective Sheep are used as a large animal model for intervertebral disc research. However, for the ovine ventral surgical approach to the cervical disc, limited descriptions exist. We, therefore, give a detailed in vivo anatomical description of this approach in sheep for the use in intervertebral disc regeneration and degeneration models to increase the reproducibility of such interventions. Materials and Methods Eighteen female Swiss white alpine sheep, with an age range of 2 to 4 years, were used. A ventral surgical access was performed to establish defined intervertebral disc punch defect from cervical levels C3/4 to C5/6. Cervical levels C2/3 and C6/7 were used as negative controls. Intraoperative findings, radiographical controls and postoperative clinical follow-up were documented and collected for this clinical report. Results All sheep recovered rapidly from the surgical intervention. Two sheep developed wound seroma, which resorbed spontaneously. Two further sheep showed wound dehiscence within 3 days after surgery, which had to be revised. No clinical wound infections occurred and all sheep healed well and did not show any side effects related to the surgical procedure. Conclusion The ventral surgical access to the ovine cervical spine is a safe and reliable procedure. The advantage of the cervical intervertebral disc is the easier surgical access and the increased disc height compared to the sheep lumbar spine. Since the ovine cervical intervertebral disc shows a high grade of similarities (e.g. molecular characteristics) compared to human discs, it is a promising degeneration and regeneration model for disc diseases.

Study Design:Narrative review.Objectives:To describe the current AOSpine Trauma Classification system for spinal trauma and highlight the value of patient-specific modifiers for facilitating communication and nuances in treatment.Methods:The classification for spine trauma previously developed by The AOSpine Knowledge Forum is reviewed and the importance of case modifiers in this system is discussed.Results:A successful classification system facilitates communication and agreement between physicians while also determining injury severity and provides guidance on prognosis and treatment. As each injury may be unique among different patients, the importance of considering patient-specific characteristics is highlighted in this review. In the current AOSpine Trauma Classification, the spinal column is divided into 4 regions: the upper cervical spine (C0-C2), subaxial cervical spine (C3-C7), thoracolumbar spine (T1-L5), and the sacral spine (S1-S5, including coccyx). Each region is classified according to a hierarchical system with increasing levels of injury or instability and represents the morphology of the injury, neurologic status, and clinical modifiers. Specifically, these clinical modifiers are denoted starting with M followed by a number. They describe unique conditions that may change treatment approach such as the presence of significant soft tissue damage, uncertainty about posterior tension band injury, or the presence of a critical disc herniation in a cervical bilateral facet dislocation. These characteristics are described in detail for each spinal region.Conclusions:Patient-specific modifiers in the AOSpine Trauma Classification highlight unique clinical characteristics for each injury and facilitate communication and treatment between surgeons.

Introduction Vertebroplasty (VP) is a cost-efficient alternative to kyphoplasty; however, regarding safety and vertebral body (VB) height restoration, it is considered inferior. We assessed the safety and efficacy of VP in alleviating pain, improving quality of life (QoL) and restoring alignment. Methods In a prospective monocenter case series from May 2007 until July 2008, there were 1,408 vertebroplasties performed during 319 interventions in 306 patients with traumatic, lytic and osteoporotic fractures. The 249 interventions in 233 patients performed because of osteoporotic vertebral fractures were analyzed regarding demographics, treatment and radiographic details, pain alleviation (VAS), QoL improvement (NASS and EQ-5D), complications and predictors for new fractures requiring a reoperation. Results The osteoporotic patient sample consisted of 76.7% (179) females with a median age of 80 years. A total of 54 males had a median age of 77 years. On average, there were 1.8 VBs fractured and 5 VBs treated. The preoperative pain was assessed by the visual analog scale (VAS) and decreased from 54.9 to 40.4 pts after 2 months and 31.2 pts after 6 months. Accordingly, the QoL on the EQ-5D measure (−0.6 to 1) improved from 0.35 pts before surgery to 0.56 pts after 2 and to 0.68 pts after 6 months. The preoperative Beck Index (anterior height/posterior height) improved from a mean of 0.64 preoperative to 0.76 postoperative, remained stable at 2 months and slightly deteriorated to 0.72 at 6 months postoperatively. There were cement leakages in 26% of the fractured VBs and in 1.4% of the prophylactically cemented VBs; there were symptoms in 4.3%, and most of them were temporary hypotension and one pulmonary cement embolism that remained asymptomatic. The univariate regression model revealed a tendency for a reduced risk for new or refractures on radiographs (OR = 2.61, 95% CI 0.92–7.38, p = 0.12) and reoperations (OR = 2.9, 95% CI 0.94–8.949, p = 0.1) when prophylactic augmentation was performed. The final multivariate regression model revealed male patients to have an about three times higher refracture risk (radiographic) (OR = 2.78, p = 0.02) at 6 months after surgery. Patients with a lumbar index fracture had an about three to five times higher refracture/reoperation risk than patients with a thoracic (OR = 0.33/0.35, p = 0.009/0.01) or thoracolumbar (OR = 0.32/0.22, p = 0.099/0.01) index fracture. Conclusion If routinely used, VP is a safe and efficacious treatment option for osteoporotic vertebral fractures with regard to pain relief and improvement of the QoL. Even segmental realignment can be partially achieved with proper patient positioning. Certain patient or fracture characteristics increase the risk for early radiographic refractures or new fractures, or a reoperation; a consequent prophylactic augmentation showed protective tendencies, but the study was underpowered for a final conclusion.

Spinal fusion is a common surgical procedure to address a range of spinal pathologies, like damaged or degenerated discs. After the removal of the intervertebral disc (IVD), a structural spacer is positioned followed by internal fixation, and fusion of the degenerated segment by natural bone growth. Due to their osteoinductive properties, bone morphogenetic proteins (BMP) are applied to promote spinal fusion. Although spinal fusion is successful in most patients, the rates of non-unions after lumbar spine fusion range from 5% to 35%. Clinical observations and recent studies indicate, that the incomplete removal of disc tissue might lead to failure of spinal fusion. Yet, it is still unknown if a secretion of BMP antagonists in intervertebral disc (IVD) cells could be the reason of inhibition in bone formation. In this study, we co-cultured human primary osteoblasts (OB) and IVD cells i.e., nucleus pulposus (NPC), annulus fibrosus (AFC) and cartilaginous endplate cells (CEPC), to test the possible inhibitory effect from IVD cells on OB. Although we could see a trend in lower matrix mineralization in OB co-cultured with IVD cells, results of alkaline phosphatase (ALP) activity and gene expression of major bone genes were inconclusive. However, in NPC, AFC and CEPC beads, an up-regulation of several BMP antagonist genes could be detected. Despite being able to show several indicators for an inhibition of osteoinductive effects due to IVD cells, the reasons for pseudarthrosis after spinal fusion remain unclear.

Comparison of two annulus fibrosus injury models that mimic intervertebral disc (IVD) herniation, enabling the study of IVD behaviour under three loading regimes in a bovine organ culture model. An injury was induced by custom-designed cross-incision tool or a 2-mm biopsy punch in IVDs. Discs were cultured for 14 days under (1) complex (compression and torsion), (2) static, and (3) no load. Disc height, mitochondrial activity, DNA and glycosaminoglycan (GAG) contents, and disc stiffness under complex load were determined. Further, gene expression and histology analysis were performed. While both injury models did not change the compressional stiffness of IVDs, cross-incision decreased disc height under complex load. Moreover, under complex load, the biopsy punch injury induced down-regulation of several anabolic, catabol ic, and inflammatory genes, whereas cross-incision did not significantly differ from control discs. However, DNA and GAG contents were in the range of the healthy control discs for both injury models but did show lower contents under no load and static load. Injury side and contralateral side of the IVD showed a similar behaviour on the biochemical assays tested. Compressional stiffness, GAG and DNA contents, did not differ between injury models under complex load. This behaviour was partially attributed to the positive influence of complex loading on matrix regeneration and cell viability. However, disc height was reduced for the cross-incision. Relative gene expression changes of the inflammatory and anabolic genes for the biopsy punch approach might indicate that induced damage was too intense to trigger any inflammatory or repair response. These slides can be retrieved under Electronic Supplementary Material.

IntroductionThere has been a 65% increase in lumbar spinal fusion surgery (LSFS) worldwide over the last 13 years, with costs of £26 million to the UK National Health Service annually. Patient dissatisfaction with outcome and persistent pain and disability incurs further costs. Three trials provide low-quality evidence for the role of physiotherapy. Our UK surveys investigating physiotherapy/surgeon practice concluded rehabilitation should be tailored to the individual patient owing to considerable clinical heterogeneity. This study will explore the perceptions of patients who undergo LSFS to inform precision rehabilitation.Methods and analysisA qualitative study, using interpretive phenomenological analysis, will recruit a purposive sample (n=40) to ensure patterns of similarity and difference in their journeys can be explored. In-depth semistructured interviews will be undertaken following discharge from hospital and at 12 months postsurgery. Patients’ preoperative and postoperative experiences, underlying attitudes and beliefs towards the surgical intervention, facilitators and barriers to recovery, adherence to advice and physiotherapy, experiences of rehabilitation and return to normal function/activity/work will be explored. A 12-month patient diary will provide real time access to patient data, capturing a weekly record of life as lived, including symptoms, medication, experiences of stages of recovery, rehabilitation adherence, healthcare professional appointments, attitudes, their feelings and experiences throughout their journey. Data will be analysed in a number of stages in accordance with interpretive phenomenological analysis, supported using NVivo software. Analysis of the first interviews and patient diaries will afford a rich density of data to build an overall understanding of the patients’ lived experiences, informing the 12-month interview. Strategies (eg, reflexivity) will ensure trustworthiness.Ethics and disseminationThe study has ethical approval (IRAS 223283). Findings will ensure that patient-driven data inform precision rehabilitation by understanding the patient journey. Findings will be disseminated through peer-reviewed journals and conferences.

(1) Background: Intervertebral disc (IVD) repair represents a major challenge. Using functionalised biomaterials such as silk combined with enforced hydrogels might be a promising approach for disc repair. We aimed to test an IVD repair approach by combining a genipin-enhanced fibrin hydrogel with an engineered silk scaffold under complex load, after inducing an injury in a bovine whole organ IVD culture, (2) Methods: Bovine coccygeal IVDs were isolated from ~1-year-old animals within four hours post-mortem. Then, an injury in the annulus fibrosus was induced by a 2 mm biopsy punch. The repair approach consisted of genipin-enhanced fibrin hydrogel that was used to fill up the cavity. To seal the injury, a Good Manufacturing Practise (GMP)-compliant engineered silk fleece-membrane composite was applied and secured by the cross-linked hydrogel. Then, IVDs were exposed to one of three loading conditions: no load, static load and complex load in a two-degree-of-freedom bioreactor for 14 days. Followed by assessing DNA and matrix content, qPCR and histology, the injured discs were compared to an uninjured control IVD that underwent the same loading profiles. In addition, the genipin-enhanced fibrin hydrogel was further investigated with respect to cytotoxicity on human stem cells, annulus fibrosus, and nucleus pulposus cells, (3) Results: The repair was successful as no herniation could be detected for any of the three loading conditions. Disc height was not recovered by the repair DNA and matrix contents were comparable to a healthy, untreated control disc. Genipin resulted being cytotoxic in the in vitro test but did not show adverse effects when used for the organ culture model, (4) Conclusions: The current study indicated that the combination of the two biomaterials, i.e., genipin-enhanced fibrin hydrogel and an engineered silk scaffold, was a promising approach for IVD repair. Furthermore, genipin-enhanced fibrin hydrogel was not suitable for cell cultures, however, it was highly applicable as a filler material.