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BACKGROUND Increasing kyphosis of the spine in a human is a well-recognized clinical phenomenon that has been associated with back pain, poor physical performance and disability. The pathophysiology of age-related kyphosis is complex and has been associated with physiological changes in vertebrae, intervertebral disc (IVD) and paraspinal musculature, which current cross-sectional studies are unable to demonstrate. Creating an in vivo, paraspinal myopathic animal model for longitudinal study of these changes under controlled conditions is thus warranted. PURPOSE To confirm the TSC1 gene knockout effect on paraspinal muscle musculature; to analyze the development of spinal kyphosis, IVD degeneration and vertebra structural changes in a longitudinal manner to gain insights into the relationship between these processes. STUDY DESIGN A prospective cohort study of 28 female mice, divided into 4 groups—9-month-old TSC1mKO (n=7), 9-month-old control (n=4), 12-month-old TSC1mKO (n=8), and 12-month-old controls (n=9). METHODS High resolution micro-computed tomography was used to measure sagittal spinal alignment (Cobb's angle), vertebral height, vertebral body wedging, disc height index (DHI), disc wedge index (DWI), histomorphometry of trabecular bone and erector spinae muscle cross-sectional area. Paraspinal muscle specimens were harvested to assess for myopathic features with H&E stain, muscle fiber size, density of triangular fiber and central nucleus with WGA/DAPI stain, and percentage of fibers with PGC-1α stain. Intervertebral discs were evaluated for disc score using FAST stain. RESULTS Compared to controls, paraspinal muscle sections revealed features of myopathy in TSC1mKO mice similar to human sarcopenic paraspinal muscle. While there was significantly greater presence of small triangular fiber and density of central nucleus in 9-and 12-month-old TSC1mKO mice, significantly larger muscle fibers and decreased erector spinae muscle cross-sectional area were only found in 12-month-old TSC1mKO mice compared to controls. TSC1mKO mice developed accelerated thoracolumbar kyphosis, with significantly larger Cobb angles found only at 12 months old. Structural changes to the trabecular bone in terms of higher bone volume fraction and quality, as well as vertebral body wedging were observed only in 12-month-old TSC1mKO mice when compared to controls. Disc degeneration was observed as early as 9 months in TSC1mKO mice and corresponded with disc wedging. However, significant disc height loss was only observed when comparing 12-month-old TSC1mKO mice with controls. CONCLUSIONS This study successfully shows the TSC1 gene knockout effect on the development of paraspinal muscle myopathy in a mouse which is characteristic of sarcopenia. The TSC1mKO mice is by far the best model available to study the pathological consequence of sarcopenia on mice spine. With paraspinal muscle myopathy established as early as 9 months, TSC1mKO mice developed disc degeneration and disc wedging. This is followed by kyphosis of the spine at 12 months with concomitant disc height loss and vertebral body wedging due to bone remodeling. Age-related bone loss was not found in our study, suggesting osteoporosis and myopathy-induced vertebral body wedging are likely two independent processes. CLINICAL SIGNIFICANCE This is the first study to provide key insights on the early and late consequences of paraspinal myopathy on intervertebral disc degeneration, spinal kyphosis, and vertebral body changes. With this new understanding, future studies evaluating therapies for spinal degeneration may be performed to develop time-sensitive interventions.

The purpose of this study was to investigate the affecting factors on pelvic incidence (PI) and to test the hypothesis that PI changes even after skeletal maturity probably due to hypermobility of the sacroiliac joint using a large international multi-center database.A prospective and cross-sectional healthy adult volunteers, ages 18-80 years, across 5 countries were used. Radiographic measurements included standard whole body alignment parameters. Bivariate regression analyses between PI versus demographics and spino-pelvic anatomical parameters were performed. An effect of sex on pelvic anatomical parameters was also investigated. Multivariate logistic regression with a forward stepwise procedure was performed to identify the contributing factors to PI, and an appropriate model was obtained.PI showed a significant positive correlation with age in pooled data. Divided by sex, however, there was no correlation in men, but women showed a significant higher correlation coefficient. Pelvic thickness (PTh) had a significant negative correlation with age in pooled data. Divided by sex, no correlation was found in men, but there was a significant correlation in women with higher correlation coefficient. The stepwise multivariate analysis for the factors on PI identified four significant factors: age, sex, ethnicity, and PTh.PTh, sex, ethnicity, and age affected PI. There was a positive correlation between PI and age. The tendency was more significant in woman than in man. The results support the hypothesis that PI increases with aging, but the change seems to be small and needs to be verified in a longitudinal evaluation.

To radiographically compare lateral entry point S2-alar-iliac (L-S2AI) screw with conventional S2AI (C-S2AI) and conventional iliac screw (CIS) lengths and trajectories.Twenty-five preoperative CT scans of consecutive patients undergoing adult spinal deformity realignment surgery over a random 2-year period were analysed. Maximum in-bone length, caudal and lateral trajectories of CIS, C-S2AI, and L-S2AI screws were measured and compared using One-way ANOVA with Tukey's post hoc tests. Multivariate logistic regression was performed to identify predictors of high screw length discrepancy between C-S2AI and L-S2AI.Potential screw length was longest for CIS, followed by L-S2AI, then C-S2AI (114.5 ± 8.3 mm vs 101.4 ± 9.6 mm vs 80.6 ± 5.9 mm, respectively) in all patients (p 0.001). Actual screw lengths found both CIS and L-S2AI to be longer than C-S2AI (95.3 ± 8.5 mm and 93.4 ± 7.5 mm vs 82.1 ± 7.3 mm; p = 0.008 and 0.003). Potential lateral angulation was smallest for CIS, followed by L-S2AI, then C-S2AI (21.9 ± 7.0° vs 31.9 ± 7.1° vs 40.9 ± 6.7°, respectively) in all patients (p 0.001). L-S2AI and C-S2AI had the same caudal angulation (24.9 ± 6.8°), which was smaller than CIS (30.8 ± 5.8°) in all patients (p 0.001). Univariate, but not multivariate analysis, revealed that lumbar lordosis 40° (OR 7.2, p = 0.041), diagnosis of degenerative spondylolisthesis (OR 10.5, p = 0.017), and 7 instrumented levels (OR 2.6, p = 0.049) were significantly associated with high screw discrepancies.The L-S2AI screw combines advantages of CIS and C-S2AI screws, which includes increased screw length, reduced lateral angulation, a low-profile screw head, ease of connection to proximal hardware, and the biomechanical advantage of a quadcortical purchase.

STUDY DESIGN Retrospective cohort study on prospectively implemented EOS protocol. OBJECTIVE This study aims to audit and compare existing radiological definitions of gaze direction-chin brow vertical angle (CBVA), McGregor slope (McGS), slope of line of sight (SLS), orbital-internal occipital protuberance (OIOP) slope angle, and Tangent to the hard palate (THP) in a neutral, healthy, and asymptomatic cohort. SUMMARY OF BACKGROUND DATA The ability to accurately define direction of gaze is the first step when striving for horizontal gaze restoration in any affected individual with rigid sagittal deformity. Yet, the radiological definition of gaze direction remains poorly standardized. METHODS Hundred healthy subjects who could achieve horizontal gaze underwent whole-body standing EOS radiographs taken under a strictly standardized protocol. Radiographic measurements of global spinal sagittal parameters and surrogate measures of horizontal gaze were analyzed and compared. RESULTS The mean age was 45 ± 15.9 years, with a balanced male-to-female-ratio. Their C7 SVA was -7.7 mm ± 24.8 mm, PI was 51.0o ± 11.4o, PI-LL was -0.9o ± 13.0o and T1-slope was 21.2o ± 9.2o. Measured horizontal gaze parameters were as follows: CBVA (1.07o ± 5.48o), McGS (-3.23o ± 5.63o), SLS (0.45o ± 5.34o), OIOP (5.03o ± 4.66o), THP (-0.17o ± 6.27o). CBVA correlated strongly with McGS (r = 0.679, P

Ossification of the posterior longitudinal ligament (OPLL) is a progressive, debilitating disease most commonly affecting the cervical spine. When compared to other degenerative pathologies, OPLL procedures carry a significantly higher risk of complications owing to increased case complexity and technical difficulties. Most previous studies have focused on functional outcomes and few have reported on risk factors for postoperative complications in OPLL patients.To identify clinical and radiological risk factors of surgical complications following treatment for cervical OPLL STUDY DESIGN: Retrospective review PATIENT SAMPLE: One hundred thirty-one patients with cervical myelopathy secondary to OPLL who underwent surgical decompression with complete 2-year follow-up.Surgical and medical postoperative complications were analyzed. Revision surgery rates and mortality rates were recorded.Clinical, surgical, and radiological characteristics were collected for each patient. Complications within 30 days were identified. Univariate and multivariate analysis were performed to identify risk factors for surgical complications.There were 39 (29.8%) surgical complications in the cohort, which included C5 palsy (7.6%), dural tear (3.1%), surgical site infection (3.1%), and epidural hematoma (1.5%). 2-year revision and mortality rates were 4.6% and 2.3%, respectively. Univariate analysis revealed that blood loss ≥750mL (OR 3.42, p=0.028), operative duration ≥5.5 hours (OR 3.16, p=0.008), hill-type OPLL (OR 3.08, p=0.011), K-line (-) OPLL (OR 5.39, p0.001), and presence of a double-layer sign (OR 3.79, p=0.002) were significant risk factors. In multivariate analysis, only hill-type OPLL (OR 2.61, p=0.048) and K-line (-) OPLL (OR 2.98, p=0.031) were found to be significant. Patients with both hill-type and K-line (-) OPLL had a 3.5 times risk of developing surgical complications (p=0.009).Patients with OPLL have a higher risk of perioperative surgical complications if they had a hill-shaped OPLL and K-line (-) OPLL on preoperative imaging studies. To the best of the authors' knowledge, this study is the first to link hill-type and K-line (-) OPLL morphology as risk factors for perioperative surgical complications.

In a population of asymptomatic volunteers across 5 countries, we sought to: (a) establish normative values of the Odontoid-Central Sacral Vertical Line (OD-CSVL) across patient factors, and (b) assess correlations of OD-CSVL with other radiographic parameters. A prospective, cross-sectional study of asymptomatic adult volunteers, ages 18–80 years, were enrolled across 5 countries (France, Japan, Singapore, Tunisia, United States) forming the Multi-Ethnic Alignment Normative Study (MEANS) cohort. Included volunteers had no known spinal disorder(s), no significant neck/back pain (VAS ≤ 2; ODI ≤ 20), and no significant scoliosis (Cobb ≤ 20°). Radiographic measurements included commonly used coronal alignment parameters (mm) and angles (°). OD-CSVL was defined as the difference between the odontoid plumb line (line from the tip of the odontoid vertically down) and the CSVL (vertical line from the center of the sacrum). Chi-square, student’s t tests, Kruskal–Wallis, Wilcoxon rank-sum, linear regression, and Pearson’s correlation were used with significance at p

STUDY DESIGN A retrospective, radiographic comparative study conducted in a single academic institution. OBJECTIVE This study aims to compare fulcrum extension with conventional extension imaging to determine maximum "hip lordosis" (HL), an important novel patient-specific parameter in spinal realignment surgery, as well as understand the extension capabilities of the lower lumbar spine, which together, are key contributors to whole-body balancing. SUMMARY OF BACKGROUND DATA Recent literature recognizes the hip as an important contributor to whole-body lordosis beyond a compensator for spinal imbalance. METHODS Patients >45 years' old with mechanical low back pain due to degenerative spinal conditions were included and grouped based on the imaging performed-fulcrum or conventional extension. All imaging was performed using EOS under standardized instructions and visual aids. Radiographic parameters include global lumbar angle (GLA), inflexion-S1 (Inf-S1) angle, segmental lumbar angles, pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), femoral alignment angle (FAA), HL and spinocoxa angle (SCA). Unpaired t test was used to compare between radiographic parameters. RESULTS One hundred patients (40 males and 60 females, mean age 63.0 years) underwent either fulcrum or conventional extension EOS® imaging. Both groups had comparable baseline radiographic parameters. Fulcrum extension gave a larger mean GLA (-60.7° vs. -48.5°, P = 0.001), Inf-S1 angle (-58.8° vs. -48.8°, P = 0.003), SCA (-36.5° vs. -24.8°, P < 0.001), L4/5 and L5/S1 lordosis (-20.7° vs. -17.7°, P = 0.041, and -22.3° vs. -17.1°, P = 0.018, respectively), compared to conventional extension. PI, SS, PT, FAA, and HL were similar between both extension postures. CONCLUSION Fulcrum extension, compared to conventional extension, is better at generating lordosis in the lower lumbar spine, thus improving preoperative assessment of stiffness or instability of the lumbar spine. Both extension methods were equally effective at determining the patient-specific maximum HL to assess the flexibility and compensation occurring at the hip, potentially guiding surgical management of patients with degenerative spines.Level of Evidence: 3.

Interbody cages are commonly used to augment interbody fusion. Commonly used materials include titanium (Ti) and polyetheretherketone (PEEK), with their inherent differences. The aim of this study is to perform a systematic review and meta-analysis to compare between the various clinical and radiological outcomes of Ti and PEEK interbody spinal cages. A systematic review and meta-analysis comparing clinical and radiological outcomes between Ti and PEEK interbody cages in patients undergoing spinal fusion was performed. PubMed, Scopus, Web of Science, Embase, and Cochrane Central Register of Controlled Trials database were searched. All studies that compared the clinical and radiological outcomes of patients who underwent Ti and PEEK cages were included. Subgroup analyses was performed to differentiate between patients who had cervical and lumbar interbody fusion. A total of 11 articles were identified, with a total of 743 patients. Spinal fusion rates at final follow-up did not differ between Ti and PEEK cages (OR 1.50, 95% CI 0.57–3.94, P = 0.41), although in patients undergoing lumbar fusion, Ti cages demonstrated superior fusion (OR 2.12, 95% CI 1.05–4.28, P = 0.04). In patients with non-infective etiologies, Ti cages had a higher rate of cage subsidence (RR 2.17, 95% CI 1.13–4.16, P = 0.02). Both types of cages had similar operating time, postoperative hematoma formation, neuropathic pain, segmental angle correction and postoperative clinical outcome improvement. In non-infective lumbar spine conditions, Ti cage may be the superior option due to the higher fusion rate. III.

Introduction During the Coronavirus disease 2019 outbreak, while healthcare systems and hospitals are diverting their resources to combat the pandemic, patients who require spinal surgeries continue to accumulate. The aim of this study is to describe a novel hospital capacity versus clinical justification triage score (CCTS) to prioritize patients who require surgery during the “new normal state” of the COVID-19 pandemic. Methodology A consensus study using the Delphi technique was carried out among clinicians from the Orthopaedic Surgery, Neurosurgery, and Anaesthesia departments. Three rounds of consensus were carried out via survey and Webinar discussions. Results A 50-points score system consisting of 4 domains with 4 subdomains was formed. The CCTS were categorized into the hospital capacity, patient factors, disease severity, and surgery complexity domains. A score between 30 and 50 points indicated that the proposed operation should proceed without delay. A score of less than 20 indicates that the proposed operation should be postponed. A score between 20 and 29 indicates that the surgery falls within a grey area where further discussion should be undertaken to make a joint justification for approval of surgery. Conclusion This study is a proof of concept for the novel CCTS scoring system to prioritize surgeries to meet the rapidly changing demands of the COVID-19 pandemic. It offers a simple and objective method to stratify patients who require surgery and allows these complex and difficult decisions to be unbiased and made transparently among surgeons and hospital administrators.

MINI: This is a long-term prospective cohort study comparing the radiographic outcomes of anterior versus posterior instrumentation for Lenke 5 adolescent idiopathic scoliosis. Both approaches were comparable in terms of radiographic outcomes up to 10 years. The posterior approach is more prone to developing proximal junctional kyphosis.Prospective cohort study.To compare the long-term, radiographic coronal and sagittal outcomes of these two approaches at 10-year follow-up.Both anterior and posterior instrumented fusions have been found to be safe and effective treatments for Lenke 5 adolescent idiopathic scoliosis with up to 2 to 5 years of follow-up. Few studies follow patients beyond this duration.36 patients who underwent anterior (n = 25) or posterior instrumented spinal fusion (n = 11) for Lenke 5 adolescent idiopathic scoliosis over a 4-year period were recruited and followed for 10 years. Preoperative clinical data include patient's age and age of menarche. Operative data included instrumented levels, duration of surgery, and surgical blood loss. Postoperative data included duration of hospital stay, duration of intensive care unit stay, and complications. Pre- and postoperative radiographic data collected include coronal Cobb angles for structural thoracolumbar/lumbar curves, and sagittal angles-sagittal vertical axis, thoracic kyphosis, global lumbar angle, pelvic incidence, pelvic tilt, sacral slope, and upper and lower end vertebrae.Posterior surgery had a shorter operative time (P 0.010) and hospital stay (P 0.010). Coronal plane deformity improved by a mean of 74% in the anterior group and 71% in the posterior group. There was no significant change at 10 years in both groups (anterior P = 0.455 and posterior P = 0.325). Sagittal parameters remained unchanged. There was a higher incidence of proximal junctional kyphosis in the posterior (45%) compared to the anterior (16%) group (P 0.010).Both anterior and posterior instrumentation and fusion are successful surgeries after 10 years of follow-up. They are comparable with regards to their ability to achieve and maintain good correction of scoliotic deformities and have a low rate of pseudoarthrosis and instrument failure. Ideal sagittal parameters are maintained up to 10 years of follow-up.3.Prospective cohort study. To compare the long-term, radiographic coronal and sagittal outcomes of these two approaches at 10-year follow-up. Both anterior and posterior instrumented fusions have been found to be safe and effective treatments for Lenke 5 adolescent idiopathic scoliosis with up to 2 to 5 years of follow-up. Few studies follow patients beyond this duration. 36 patients who underwent anterior (n = 25) or posterior instrumented spinal fusion (n = 11) for Lenke 5 adolescent idiopathic scoliosis over a 4-year period were recruited and followed for 10 years. Preoperative clinical data include patient's age and age of menarche. Operative data included instrumented levels, duration of surgery, and surgical blood loss. Postoperative data included duration of hospital stay, duration of intensive care unit stay, and complications. Pre- and postoperative radiographic data collected include coronal Cobb angles for structural thoracolumbar/lumbar curves, and sagittal angles—sagittal vertical axis, thoracic kyphosis, global lumbar angle, pelvic incidence, pelvic tilt, sacral slope, and upper and lower end vertebrae. Posterior surgery had a shorter operative time (P 0.010) and hospital stay (P 0.010). Coronal plane deformity improved by a mean of 74% in the anterior group and 71% in the posterior group. There was no significant change at 10 years in both groups (anterior P = 0.455 and posterior P = 0.325). Sagittal parameters remained unchanged. There was a higher incidence of proximal junctional kyphosis in the posterior (45%) compared to the anterior (16%) group (P 0.010). Both anterior and posterior instrumentation and fusion are successful surgeries after 10 years of follow-up. They are comparable with regards to their ability to achieve and maintain good correction of scoliotic deformities and have a low rate of pseudoarthrosis and instrument failure. Ideal sagittal parameters are maintained up to 10 years of follow-up. Level of Evidence: 3.

Instrumentation of the cervical spine with cervical pedicle screws (CPS) is beneficial in patients with various types of spinal pathology. Despite posing greater technical challenges, CPS instrumentation confers better fixation outcomes when compared to lateral mass screws. While developments in technology have augmented the accuracy of CPS insertion, mastery in freehand CPS insertion allows the aforementioned technologies to reach their full potential in improving patient outcomes. The aim of this article is to discuss freehand CPS insertion techniques as established in the current literature while sharing our experience in this context. A comprehensive literature search was performed using the following electronic databases: PubMed, Medline, and EMBASE. Full-text articles focusing on clinical studies with description of freehand techniques were included. Articles which were on cadaveric studies, drill jig, navigation or robotic technology were excluded. Thirteen primary references comprising 1,480 patients were included in this review. Majority of studies reported utilizing the cranial margin of lamina for C2 level as a landmark for entry point, as well as lateral to centre of the articular mass, and just medial to the lateral border of the superior articular process for C3–7 levels. Method of tracking and facilitation of trajectory was reported in multiple studies, with use of instruments ranging from curved pedicle probes to high-speed burrs. Limited studies reported specific trajectories of CPS insertion. Most studies noted testing pedicle wall integrity at various checkpoints, with pedicle screw repositioning or conversion to lateral screw mass following detection of perforation or screw malpositioning. Success in CPS insertion rests on meticulous preoperative planning to identify the ideal screw entry point and trajectory. Patient-specific drill jigs, navigation and robotic technologies, while beneficial to progress in the field of cervical spine surgery and patient outcomes, should serve primarily to augment good expertise in freehand CPS insertion technique.

Multicenter Cohort.Assess normative values of sagittal spinal and lower extremity alignment in asymptomatic volunteers stratified by age and gender.Our understanding of ideal sagittal alignment is still evolving. The Multiethnic Alignment Normative Study (MEANS) investigated skeletal alignment of the largest multiethnic cohort of asymptomatic adult volunteers. We aim to assess normative values of sagittal spinal and lower extremity alignment in asymptomatic volunteers stratified by age and gender.Asymptomatic volunteers between the ages of 18-80 years were enrolled prospectively and then analyzed retrospectively from six different centers. Volunteers included reported no significant neck or back pain, nor any known spinal disorder(s). All volunteers underwent a standing full-body or full-spine low-dose stereoradiograph.MEANS consisted of 468 volunteers with a mean age of 40.4±14.8 years. Thoracic kyphosis (TK) from T4 to T12 showed a mean of 37.4±10.9°. The average L1-S1 lumbar lordosis (LL) was -57.4±11.3°. LL did not show significant differences across the five age groups. TK showed a significant difference based on age ( P0.0001). Sagittal vertical axis increased across age groups from -14.2 mm in young adults to 17.0 mm in patients64. Similar trend was seen for T1 pelvic angle with a mean of 5.0° in young adults and 13.7° in those older than age 64. Knee flexion increased across age groups without a significant change in odontoid-knee distance which is a surrogate for the center of the head aligned over the knees.In asymptomatic volunteers, sagittal alignment parameters showed a slow and steady change across age groups exemplified by an increase in TK. However, LL did not show a significant decrease across age groups. Volunteers used compensatory mechanisms such as slight pelvis retroversion, knee flexion, and neck extension to maintain an aligned sagittal posture with their head centered over their knees (odontoid-knee).3.

Study design Single centre, cross-sectional study. Objectives The objective is to report the prevalence of spondylolisthesis and retrolisthesis, analyse both conditions in terms of the affected levels and severity, as well as identify their risk factors. Methods A review of clinical data and radiographic images of consecutive spine patients seen in outpatient clinics over a 1-month period is performed. Images are obtained using the EOS® technology under standardised protocol, and radiographic measurements were performed by 2 independent, blinded spine surgeons. The prevalence of both conditions were shown and categorised based on the spinal level involvement and severity. Associated risk factors were identified. Results A total of 256 subjects (46.1% males) with 2304 discs from T9/10 to L5/S1 were studied. Their mean age was 52.2(± 18.7) years. The overall prevalence of spondylolisthesis and retrolisthesis was 25.9% and 17.1% respectively. Spondylolisthesis occurs frequently at L4/5(16.3%), and retrolisthesis at L3/4(6.8%). Majority of the patients with spondylolisthesis had a Grade I slip (84.3%), while those with retrolisthesis had a Grade I slip. The presence of spondylolisthesis was found associated with increased age ( P < .001), female gender (OR: 2.310; P = .005), predominantly sitting occupations (OR:2.421; P = .008), higher American Society of Anaesthesiology grades ( P = .001), and lower limb radiculopathy (OR: 2.175; P = .007). Patients with spondylolisthesis had larger Pelvic Incidence ( P < .001), Pelvic Tilt ( P < .001) and Knee alignment angle ( P = .011), but smaller Thoracolumbar junctional angle ( P = .008), Spinocoxa angle ( P = .007). Retrolisthesis was associated with a larger Thoracolumbar junctional angle ( P =.039). Conclusion This is the first study that details the prevalence of spondylolisthesis and retrolisthesis simultaneously, using the EOS technology and updated sagittal radiographic parameters. It allows better understanding of both conditions, their mutual relationship, and associated clinical and radiographic risk factors.

This is a cross-sectional cohort.The aim was to describe sagittal plane alignment and balance in a multinational cohort of nondegenerated, asymptomatic adults.Current sagittal alignment targets were developed using correlations between radiographic and quality-of-life measures in spinal deformity patients, rather than disease-free samples leading to relatively poor accounting for variance within a population.Sagittal balance was defined using vertebral body tilt and spinopelvic alignment was defined as the vertebral pelvic angles from C2 to L5 (vertebral pelvic angle=vertebral tilt+pelvic tilt). Associations with pelvic incidence (PI) were assessed using linear regression. Multivariable linear regression was used to estimate a normal L1-S1 lordosis, adjusting for PI and the L1 pelvic angle (L1PA). Correlation between the L1 and T4 pelvic angles was assessed to define a normal thoracic alignment conditioned on lumbar alignment.Among 320 volunteers from 4 continents, median age was 37% and 60% were female. C2 tilt was independent of PI with minimal variation. PI was inadequate for estimating a normal lumbar lordosis (L1-S1, r2 =0.3), but was strongly associated with the lumbar pelvic angles (L1PA, r2 =0.58). Defining lumbar lordosis as a function of PI and L1PA resulted in high explained variance ( R2 =0.74) and the T4 pelvic angle had near perfect correlation with the L1PA ( r =0.9).We defined normal sagittal balance and spinopelvic alignment in a disease-free international volunteer cohort. Four parameters are either fixed or directly modifiable in surgery and can define a normal thoracic and lumbar alignment: the L1-S1 lordosis defined as a function of PI and the L1PA; and the T4 pelvic angle is nearly equivalent to the L1PA, aligning the T4-L1-hip axis.

A radiographic comparative study.To investigate the influence of radiographic lower limb-spinal length proportion on sagittal radiographic parameters.Although lordotic realignment of the lumbar spine is a well-established surgical strategy, its ideal target has not been fully understood. The widely used pelvic incidence-lumbar lordosis discrepancy (PI-LL) method to guide lordotic restoration of the lumber spine in the standing posture, may be further refined using the novel, radiographic lower limb-spinal length proportion parameter in selected subjects.A 100 healthy subjects were imaged in the standing posture using EOS imaging to obtain whole-body lateral radiographs for the measurement of sagittal radiographic parameters. Univariate analyses were performed to compare radiographic parameters between groups with different radiographic lower limb-spinal length proportion. Multivariate analyses were performed to identify the associations between lower limb-spinal length proportions and other radiographic parameters.Regardless of lower limb-spinal length proportion (mean = 1.4), global lumbar angle (GLA) differed from spinal lordosis (SL), with the absolute means of SL and GLA larger and smaller than pelvic incidence (PI) respectively. Univariate analysis showed that patients with proportionately larger lower limb-spinal length proportion are more likely to have larger mean T1-slope, global thoracic angle (GTA), spinal kyphosis (SK), GLA, and SL. Multivariate analysis showed that a larger lower limb length-spinal length proportion is predictive of larger GLA is less than -47.69° (Odds Ratio (OR) 2.660, P = 0.026), and larger T1-slope of more than 18.84° (OR 3.695, P = 0.012).Larger radiographic lower limb-spinal length proportion results in naturally accentuated spinal curves. These patients balance with a larger lumbar lordosis that is closer to the PI and a higher T1-slope which should be considered for spinal realignment. SL differs from GLA and should be separately assessed.Level of Evidence: 3.

STUDY DESIGN Cross-sectional radiographic comparison study. OBJECTIVE The aim of this study was to understand whole-body balancing in directed and natural standing postures, through comparison of kypholordotic ratios on whole-body radiographs of young, healthy subjects. SUMMARY OF BACKGROUND DATA Recent studies highlighted the importance of understanding whole-body balancing, proposing the use of the more physiological natural standing posture, together with the conventional directed standing posture, for imaging. METHODS Sixty healthy, 21-year-old subjects (36 males, 24 females) were recruited. EOS whole-body radiographs of subjects in directed and natural standing postures were obtained. Radiographic parameters compared include C2-sagittal vertical axis (C2-SVA), C7-SVA, C2-7-SVA, global cervical angles (C0-T1 and C2-C7), regional cervical angles (C0-C2, C2-C4, C4-C7), T1-slope, global thoracic angles (T1-T12 and T1-inflection vertebra [Inf]), thoracolumbar angle (T11-L2), global lumbar angles (T12-S1 and Inf-S1), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), spinocoxa angle (SCA), and femoral alignment angle (FAA). Kypholordotic ratios of T1-12/T12-S1, T1-Inf/Inf-S1, Tl-Inf/SCA, and (T1-Inf + FAA)/(T1-slope + SCA) were calculated and compared. RESULTS Compared to directed standing, natural standing has greater C2-SVA and C7-SVA, more lordotic global and regional cervical angles (except C0-2 angle), higher T1-slope, larger T1- T12 and T1-Inf kyphotic angles, smaller T12-S1 and Inf-S1 lordotic angles, larger PT, more lordotic SCA, and smaller SS and FAA angles. T1-12/T12-S1 and T1-Inf/Inf-S1 ratios in natural standing, and (Tl-Inf + FAA)/(T1-slope + SCA) ratio in both postures approximate 1. There were significant differences between postures for Tl-l2/Tl2-Sl, Tl-Inf/Inf-Sl and Tl-Inf/SCA ratios. CONCLUSION Whole-body balancing requires understanding of the balance between kyphosis and lordosis, which varies with the posture of patients. Analysis of kypholordotic ratios obtained in this study allude to the importance of performing whole-body imaging in the directed standing posture, and whole-spine or whole-body imaging in the natural standing posture, so as to fully understand spinal and whole body balancing for spinal realignment surgeries.Level of Evidence: Level 3.

Cross-sectional, epidemiological study.This study aims to describe the prevalence, risk factors, disability, and quality of life (QoL) burden of neck pain.Neck pain is an increasingly common symptom that results in significant disability and loss of QoL to the individual, and imposes a considerable economic burden to developed countries.A cross-sectional, questionnaire-based study was conducted via multistage random sampling of public households in Singapore on individuals aged 21 and older. Questionnaires were administered face-to-face by trained interviewers. Data analyzed included the prevalence and characteristics of neck pain, its relationship with sociodemographic factors, and its association on QoL and disability via validated questionnaires: EQ5D questionnaire and Neck Disability Index (NDI), respectively.A total of 626 individuals with a median age of 52.0 years (interquartile range 37.0-67.0), and even sex distribution of males (54.0%) and females (46.0%) were included in this study. A total of 144 individuals reported neck pain over the past 6 months, giving a 6-month period prevalence of 23.0%. Among them, nine (6.3%) had chronic, whereas 12 (8.3%) had severe neck pain. Female sex was the only significant risk factor for neck pain on multivariate analysis, with a risk ratio of 1.34 (95% confidence interval [CI] 1.00-1.80, P = 0.049). Individuals with neck pain had mean raw NDI scores of 4.91 ± 6.25, with higher disability seen with increasing pain duration and intensity (P 0.001 and P = 0.002 respectively). Compared to individuals without neck pain, those with neck pain had poorer QoL with lower EQ5D-Index scores (0.84 ± 0.25 vs. 0.93 ± 0.15; 95% CI 0.046-0.132, P 0.001) and EQ5D-VAS scores (68.76 ± 14.59 vs. 73.86 ± 13.64; 95% CI 2.510-7.697, P 0.001).Our findings show that neck pain is a prevalent condition with chronicity and severity of symptoms associated with reduced QoL and increased disability. Population sample health scores can serve as potential reference targets in disease management and aid national health care policy-making.Level of Evidence: 3.

To understand the pathophysiology of L5-S1 loss of lordosis and retrolisthesis by comparing 2 commonly assumed physiological weight-bearing postures.This was a prospective comparative study of whole-body standing and slump sitting EOS radiographs in clinic patients presenting with back pain or lower limb radicular pain. Patients with prior spinal intervention, malignancy, trauma, inflammatory diseases, transitional lumbosacral vertebra, pregnancy, and L5-S1 retrolisthesis or spondylolisthesis from nondegenerative causes were excluded. C7 sagittal vertical axis, global cervical angle, global thoracic angle, global lumbar angle, thoracolumbar angle, T1-slope, pelvic incidence, pelvic tilt, sacral slope, L5-S1 angle, L5-S1 vertebral translation, L5-S1 disc height, and presence of L4-5 vertebral translation were measured. Univariate and multivariate analyses were performed to identify predictors of L5-S1 lordosis loss and retrolisthesis.L5-S1 loss of lumbar lordosis (7.02 ± 9.90°, P0.001), retrolisthesis (0.07 ± 0.411 cm, P0.001), and loss of disc height (0.10 ± 0.23 cm, P0.001) occurred when changing from standing to slump sitting along with other sagittal profile changes (P0.001). Taller L5-S1 disc height (odds ratio [OR] 2.57, P = 0.04), larger lumbar range-of-motion change (OR 3.82, P = 0.012), lower sacral slope on sitting (OR 2.50, P = 0.043), and presence of L4-5 spondylolisthesis (OR 2.75, P = 0.032) were predictive of larger L5-S1 lordosis loss (7°) on multivariate analysis, while larger lumbar range-of-motion change (OR 2.21, P = 0.050) and presence of L4-5 spondylolisthesis (OR 3.08, P = 0.023) were predictive of greater L5-S1 retrolisthesis (0.07 cm).Degenerative L5-S1 loss of lordosis and retrolisthesis likely result from long-standing lower lumbar spine bending forces against the posterior ligamentous complex with slump sitting, predisposed by a negatively sloped sacrum and increased lumbar flexibility.

Previous studies on adults with degenerative scoliosis (ADS) have been fixed the threshold of PI-LL mismatch less than 10° for achieving good clinical outcomes. Recent studies discussed that PI-LL mismatch should consider individual pelvic incidence (PI) and should be set first in a normal population. The purpose of this study is to assess the variability of PI-LL mismatch according to PI in an asymptomatic population.Full-body low dose stereoradiographic evaluation was done in a multi-ethnic cohort of 468 asymptomatic adult volunteers. Patients were clustered in three groups depending on individual PI values: PI 45°, 45° PI 60° and PI 60°. 3D measurements were performed using a commercially available 2D/3D modeling software to establish a correlation of PI with other spinopelvic parameters. ANOVA and Tukey's HSD for post-hoc analysis were used to determine the differences between the three groups.In our asymptomatic population, the mean value of PI-LL mismatch is - 5.4° ± 10.7°. Clusterization of the population reveals significant differences in the distribution of L1S1 lordosis, pelvic tilt and PI-LL with positive linear correlation according to PI values. As an interestingly result, PI-LL mismatch is equal to 0° when PI is around 64°.The present study demonstrated that PI-LL mismatch is negative in an asymptomatic population (- 5.4° ± 10.7°) and the value should be customized to each patient to be able to restore the appropriate lordosis in ADS. The PI-LL mismatch is given by the formula PI-LL = - 28.5 + 0.44 × PI.

Spinal alignment can have a significant impact on a patient's overall quality of life. Predicting the ideal sagittal spinal alignment of a specific individual is still a difficult task. The Multi-Ethnic Alignment Normative Study (MEANS) investigated skeletal alignment, including the spine and lower extremities, of the largest multi-ethnic cohort of asymptomatic adult volunteers. In this analysis, the authors aim to assess normative values of spinopelvic parameters and the regional cervical, thoracic, and lumbar spinal alignment in asymptomatic volunteers stratified by age and sex.Asymptomatic volunteers between ages 18 and 80 years were enrolled prospectively from centers in France, Japan, Singapore, Tunisia, and the United States. Volunteers included reported no significant neck or back pain (Visual Analog Scale ≤2), nor any known spinal disorder(s). All volunteers underwent a standing full-body or full-spine low-dose stereoradiograph.MEANS consisted of 468 volunteers with a mean age of 40.4±14.8 years. Mean cervical lordosis from C2 to C7 was -0.4±12.7°. The T1-slope averaged 23.0±7.9° and showed strong correlation ( r =0.87) with the C7-slope mean of 19.8±8.6°. Thoracic kyphosis (TK) from T4 to T12 showed a mean of 37.4±10.9°. Average L1-S1 lumbar lordosis (LL) was -57.4±11.3°. The mean pelvic incidence (PI) measured 52.0±10.7° and pelvic tilt was 12.5±7.3°. Sacral slope averaged 39.5±8.2°. The average PI-LL was -5.4±10.7°. Approximately 60% of volunteers met the PI-LL criteria within ±10°, 8.3% were ≥10°, while 32.1% were ≤-10°. LL showed moderate correlation with PI ( r =0.53) and TK ( r =0.50), while there was no correlation between TK and PI. Multiple linear regression including PI, TK, and age resulted in the following equation LL=14.6+0.57 (PI)+0.57 (TK)-0.2 (age) ( r =0.75).LL did not change with increasing age in asymptomatic volunteers. However, TK did increase with age leading to an increase in T1-slope and a compensatory increase in cervical lordosis. TK did not correlate with PI and was an independent variable in the prediction of LL.Level II-prospective cohort study.

In a population of asymptomatic volunteers across 5 countries, we sought to: (a) establish normative values of the Odontoid-Central Sacral Vertical Line (OD-CSVL) across patient factors, and (b) assess correlations of OD-CSVL with other radiographic parameters.A prospective, cross-sectional study of asymptomatic adult volunteers, ages 18-80 years, were enrolled across 5 countries (France, Japan, Singapore, Tunisia, United States) forming the Multi-Ethnic Alignment Normative Study (MEANS) cohort. Included volunteers had no known spinal disorder(s), no significant neck/back pain (VAS ≤ 2; ODI ≤ 20), and no significant scoliosis (Cobb ≤ 20°). Radiographic measurements included commonly used coronal alignment parameters (mm) and angles (°). OD-CSVL was defined as the difference between the odontoid plumb line (line from the tip of the odontoid vertically down) and the CSVL (vertical line from the center of the sacrum). Chi-square, student's t tests, Kruskal-Wallis, Wilcoxon rank-sum, linear regression, and Pearson's correlation were used with significance at p 0.05.467 volunteers were included with normative OD-CSVL values by age decade, gender, BMI, and country. Mean ± SD OD-CSVL was 8.3 mm ± 6.5 mm and 31 (6.6%) volunteers were almost perfectly aligned (OD-CSVL 1 mm). A linear relationship was seen between OD-CSVL with both age (p 0.001) and BMI (p = 0.015). Significant variation was seen between OD-CSVL and 5 different ethnicities (p = 0.004). OD-CSVL correlated best with other coronal radiographic parameters, C7-CSVL (r = 0.743, p 0.001), OD-knee (r = 0.230, p 0.001), CAM-knee (r = 0.612, p 0.001), and regional TL cobb angle (r = 0.4214, p = 0.005).Among asymptomatic volunteers, increased OD-CSVL was significantly associated with increased age, increased BMI, and ethnicity, but not gender. OD-CSVL correlated strongest with C7-CSVL, TL cobb angle, OD-knee, and CAM-knee. OD-CSVL. These results support further study of OD-CSVL in symptomatic adult spine deformity patients.

Low back pain is a disabling condition that imposes an enormous socioeconomic burden. Intervertebral disc (IVD) regeneration strategies are ideal goals aiming to provide a better solution. While regeneration occurs with tensile loading of degenerated IVDs, no long-term longitudinal data exists to show the sustained impact of tensile loading under physiological conditions. The aim of this study is to develop an MRI-compatible rabbit IVD distraction model to enable longitudinal monitoring of nutrient supply and regeneration process of degenerated discs. Rabbits were divided into two groups. (1) IVD stabbing, no treatment (2) IVD stabbing, distractor implant on 6 weeks post-stabbing, treated by 120 N tensile force. Under C-arm guidance, L4-5 IVD was stabbed by bone marrow aspirate needle to induce disc degeneration. At 6 weeks post stabbing, baseline IVD degeneration was verified by MRI. Under C-arm guidance, path was created by stainless steel k-wire on L4-5 vertebra and replaced by zirconia k-wire. Distractor was connected to k-wire and 120 N force was applied on rabbit spine. Rabbit disc health was evaluated by MRI at 7, 11- and 15-weeks post distractor implant. Rabbit was euthanized after the last MRI scan. From T2 STIR MRI, disc distraction can arrest the progression of disc degeneration in treated group but further deteriorate in control. Post-contrast MRI showed the improvement of nutrient flow in distracted disc. The development of MRI compatible distractor will allow a longitudinal study of the degenerated disc regeneration process under tensile distraction.

The Cervical Spine Research Society (CSRS) is dedicated to advancing the care of patients with cervical spine pathology. The authors present here highlights of the 2019 CSRS-Asia Pacific Traveling Fellowship.

Study design A cross-sectional study on a randomly selected prospective cohort of patients presenting to a single tertiary spine center. Objective The aim of this study was to describe the clinical and radiographic parameters of patients with S- and C-shaped thoracolumbar sagittal spinal profiles, and to identify predictors of these profiles in a natural, relaxed sitting posture. Summary of background data Sagittal realignment in adult spinal deformity surgery has to consider the sitting profile to minimize the risks of junctional failure. Persistence of an S-shaped sagittal profile in the natural, relaxed sitting posture may reflect a lesser need to accommodate for this posture during surgical realignment. Methods Consecutive patients with low back pain underwent whole body anteroposterior and lateral radiographs in both standing and sitting. Baseline clinical data of patients and radiographic parameters of both standing and sitting sagittal profiles were compared using χ, unpaired t tests, and Wilcoxon rank-sum test. Subsequently, using stepwise multivariate logistic regression analysis, predictors of S-shaped curves were identified while adjusting for confounders. Results Of the 120 patients included, 54.2% had S-shaped curves when sitting. The most common diagnoses were lumbar spondylosis (26.7%) and degenerative spondylolisthesis (26.7%). When comparing between patients with S- and C-shaped spines in the sitting posture, only diagnoses of degenerative spondylolisthesis (odds ratio [OR], 5.44; P = 0.01) and degenerative scoliosis (OR, 2.00; P = 0.039), and pelvic incidence (PI) >52.5° (OR, 5.48; P = 0.008), were predictive of an S-shaped sitting sagittal spinal alignment on multivariate analysis. Conclusion Stiffer lumbar curves (e.g., patients with degenerative spondylolisthesis and degenerative scoliosis) or those who have a predilection for an S-shaped standing sagittal profile when sitting (e.g., high PI) may be more amenable to fusion in accordance with previously studied sagittal realignment targets. In contrast, more flexible curves may benefit from less aggressive lordotic realignment to prevent potential junctional failures. Level of evidence 3.

Cervical spine pathology is becoming increasingly prevalent with an aging world population and is associated with significant morbidity, affecting all areas of the world. This review was undertaken to provide a global perspective on cervical spine pathology, including epidemiology, burden of disease, access to care, and plan of care in both developed and developing low- and middle-income countries (LMICs). We found that epidemiology, access to care, plan of care, and health outcomes were relatively similar between nations with similar economies. However, these aspects change dramatically when comparing developing nations to LMICs, with LMICs displaying substantial barriers to care and subsequently higher rates of morbidity and mortality. There is currently a need for large-scale, global, prospective multicenter studies that analyze not only the epidemiology and treatment of cervical spine pathology, but also consider patient outcomes.

Study Design: Retrospective cohort study.Purpose: To study the incidence, onset, underlying mechanism, clinical course, and factors leading to asymptomatic construct failure (AsCF) after metastatic spinal tumor surgery (MSTS).Overview of Literature: The reported incidence rates for implant and/or construct failure after MSTS are low (1.9%–16%) and based on clinical presentations and revisions required for symptomatic failures (SFs). AsCF after MSTS has not been reported.Methods: We conducted a retrospective analysis of 288 patients (246 for final analysis) who underwent MSTS between 2005–2015. Data collected were demographics and peri/postoperative clinical and radiological features. Early and late radiological AsCF were defined as presentation before and after 3 months, respectively. We analyzed patients with AsCF for risk factors and survival duration by performing competing risk regression analyses where AsCF was the event of interest, with SF and death as competing events.Results: We observed AsCF in 41/246 patients (16.7%). The mean time to onset of AsCF after MSTS was 2 months (range, 1–9 months). Median survival of patients with AsCF was 20 and 41 months for early and late failures, respectively. Early AsCF accounted for 80.5% of cases, while late AsCF accounted for 19.5%. The commonest radiologically detectable AsCF mechanism was angular deformity (increase in kyphus) in 29 patients. Increasing age (p