Introduction and hypothesis Optimal choice of the lower instrumented vertebra in the management of adult spinal deformity that include lumbosacral junction is still unclear. It is therefore possible to stop fixation in S1 but also lower (S2AI or iliac screws) in order to reduce the risk of implants pullout. In such situations, mechanical solicitations can lead to secondary degradation of sacro-iliac joints. Technique and results Based on triangular pelvic fixation described for pelvic trauma, a posterior only fixation that combine S1 screws, iliac screws and sacro-iliac implants can be performed. Discussion We are describing here the operative technique of this « bedrock » fixation under fluoroscopic guidance and its preliminary results about 15 patients. Level of evidence IV.

Study Design Cross-sectional Cohort Study. Objective To determine the cervicothoracic inflection point in an asymptomatic, adult population. Introduction The cervicothoracic inflection point (CTIP) is an important sagittal marker to understand for patients with cervical deformities. We aimed to identify the CTIP and understand the relationship to other sagittal alignment markers. Methods 468 adult asymptomatic volunteers (18-80 years) from 5 countries (United States, France, Japan, Singapore, Tunisia). All volunteers underwent standing full body, low dose stereo radiographs. The CTIP was identified by measuring the cervical sagittal angle (CSA) and thoracic kyphosis maximum angle (TKMax), using the end vertebra concept. The CTIP was defined as the vertebra or disc between the lower end vertebra of the CSA and upper end vertebra of TKMax. A correlation matrix was utilized to identify the relationship between the CTIP and spinopelvic sagittal parameters of interest. Results The most common CTIP value was the T1 vertebra. CTIPs ranged from C5 to T4, respectively. CTIP showed a weak positive correlation to age (r = 0.10, P = 0.03) and negative correlation to BMI (r = −0.11, P = 0.04). Additionally, CTIP had a minor positive correlation with OC2-CL, C7 slope, T1 slope, T1PA, T1-T12 TK, and T4-T12 TK, all statistically significant. Linear regression demonstrated increased cervical lordosis and increased TK was associated with more caudal CTIP segments. Conclusion CTIP segments ranged from C5 to T4, with the most common segment being T1. Understanding the relationship of the CTIP to other sagittal variables is critical to patients with CD.

BACKGROUND CONTEXT Determining normative cervical spine alignment is crucial for guiding corrective surgery in spinal deformities. Prior studies correlate T1S-CL>17 (cervical mismatch) as a threshold for defining deformity. Staub et al proposed a T1 Slope (T1S) formula predicting cervical lordosis (CL) with 40% accuracy and MAE of 7.8. A practical classification system for the cervical spine is still needed. PURPOSE This study assesses cervical mismatch rate and predictability of Staub's CL formula (CL = T1S - 16.5°) against linear regression, in an asymptomatic adult cohort as well as a new method of classifying cervical alignment. STUDY DESIGN/SETTING Retrospective cohort study/multicenter. PATIENT SAMPLE A total of 468 asymptomatic adults (18-80 years) from 5 countries (USA, France, Japan, Singapore, Tunisia) formed the MultiEthnic Alignment Normative Study (MEANS). OUTCOME MEASURES T1S and CL (C2C7°) were measured; cervical mismatch prevalence (T1S-CL > 17) was recorded. Positive values are kyphotic, and negative values are lordotic in this study. The validity of the Staub formula was assessed. Patients were classified under a new cervical classification system and radiographic parameters of the different alignment types were compared. METHODS T1S and CL (C2C7°) were measured; cervical mismatch prevalence (T1S-CL > 17) was recorded. Positive values are kyphotic, and negative values are lordotic in this study. The validity of the Staub formula was assessed. MEANS cohort data was used for linear regression to derive a new predictive formula for comparison. A classification system was then developed using the new predictive formula and cSVA. Modifiers were added for segmental subaxial sagittal cervical alignment (SCA). CL was evaluated based on its comparison to predicted. Thresholds were set based on the average+2SD in the MEANS cohort for cSVA, and T1S. The threshold for SCA was based on the segment with the highest mean+2SD. The resulting classification system (Sardar-Miller Classification) is shown in Table 1. Radiographic parameters of the different alignment types were also compared. RESULTS Mean CL was -0.42 (12.67°), T1S was 23.0 (7.86), cSVA was 19.08 (9.75), and the highest mean SCA was 3.22(4.77) which was of segment C4/C5. T1S-CL was 22.58 (9.39) with an interquartile range of 9.5 - 35.7. Of all subjects, 71.4% exhibited cervical mismatch > 17°. Linear regression yielded CL= -1.085(T1S) +24.52 (R2=0.45, p<.0001) which was simplified to CL = 24.5 - T1S. This MEANS-derived formula predicted CL within 5° in 38.9% vs 35% with a MAE of 7.64 vs 8.99 when compared to Staub. 97% of the data was captured by Types 1A-C of the classification system, with the rest being captured by Types 2-3. Only 1% surpassed threshold for segmental kyphosis. Overall, age, CL, OC2-CL, cSVA, T1S, and TK were statistically different amongst the groups (p<.01), without significant differences in lumbar or pelvic parameters. CONCLUSIONS In this normative cohort, there was a high prevalence of cervical mismatch > 17°, suggesting that the previous definition of cervical deformity needs to be reassessed. A new classification for cervical alignment was thus developed using this normative cohort. There were significant differences in all cervical alignment parameters between groups, indicating clear distinction of cervical alignment between types. FDA Device/Drug Status This abstract does not discuss or include any applicable devices or drugs.

Introduction et hypothèse Le choix du niveau de fixation distal lors de la réalisation d’une arthrodèse vertébrale pontant la charnière lombo-sacrée reste toujours sujet à discussion. Il est ainsi possible de se fixer au sacrum (S1) ou d’y associer une fixation pelvienne (vis iliaques ou S2AI) afin de limiter les risques d’arrachement du matériel. Cela pose toutefois la question du risque de dégradation secondaire des articulations sacro-iliaques. Technique et résultats Basée sur les montages en triangulation utilisés en traumatologie du bassin, une fixation associant des vis S1, des vis iliaques et des implants d’arthrodèse sacro-iliaques par un abord postérieur unique est réalisable. Discussion Nous décrivons ici la technique opératoire de cette fixation de type « bedrock » réalisée sous contrôle scopique et ses résultats préliminaires à propos de 15 patients. Niveau de preuve IV.

STUDY DESIGN:Multi-Ethnic Alignment Normative Study (MEANS) cohort: prospective, cross-sectional, multicenter. OBJECTIVE:To analyze the distribution of GAP scores in the MEANS cohort and compare the spinal shape via stratification by GAP alignment category, age, and country. SUMMARY OF BACKGROUND DATA:The GAP score has been used to categorize spinal morphology and prognosticate adult spinal deformity surgical outcomes and mechanical complications. We analyzed a large, multiethnic, asymptomatic cohort to assess the distribution of GAP scores. METHODS:Four hundred sixty-seven healthy volunteers without spinal disorders were recruited in five countries. Sagittal radiographic parameters were measured via the EOS imaging system. The GAP total and constituent factor scores were calculated for each patient. Kruskal-Wallis rank sum test was performed to compare variables across groups, followed by the post hoc Games-Howell test. Fisher exact test was used to compare categorical variables. The significance level was set to P <0.05. RESULTS:In the MEANS cohort, 13.7% (64/467) of volunteers were ≥60 years old, and 86.3% (403/467) were <60 years old. 76.9% (359/467) was proportioned, 19.5% (91/467) was moderately disproportioned, and 3.6% (17/467) was severely disproportioned. There was no significant difference in the frequency of proportioned, moderately, or severely disproportioned GAP between subjects from different countries ( P =0.060). Those with severely disproportioned GAP alignment were on average 14.5 years older ( P =0.016), had 23.1° lower magnitude lumbar lordosis (LL) ( P <0.001), 14.2° higher pelvic tilt ( P <0.001), 13.3° lower sacral slope ( P <0.001), and 24.1° higher pelvic-incidence (PI)-LL mismatch ( P <0.001), 18.2° higher global tilt ( P <0.001) than those with proportioned GAP; thoracic kyphosis and PI were not significantly different ( P >0.05). CONCLUSIONS:The GAP system applies to a large, multiethnic, asymptomatic cohort. Spinal alignment should be considered on a spectrum, as 19.5% of the asymptomatic volunteers were classified as moderately disproportioned and 3.6% severely disproportioned. Radiographic malalignment does not always indicate symptoms or pathology. LEVEL OF EVIDENCE:3.

Study Design: Prospective, cross-sectional study. Objective: In a geographically diverse population of asymptomatic volunteers, we sought to report the incidence of pelvic obliquity (PO), establish normative values of PO across patient factors, and assess the correlation of PO with radiographic parameters. Summary of Background Data: PO is defined as the misalignment of the pelvis and can be assessed through several anatomic landmarks. Significant PO, whether caused by leg-length discrepancy or not, can lead to coronal malalignment which causes severe pain and disability. Significant emphasis has been placed on achieving appropriate sagittal alignment in recent decades; however, a greater understanding of coronal alignment is needed, and PO is a crucial aspect of evaluating the coronal plane in adult spinal deformity patients. Methods: Asymptomatic adult volunteers, ages 18–80 years, enrolled patients from 5 countries (France, Japan, Singapore, Tunisia, and the United States) in the “multiethnic alignment normative study” cohort (IRB 201812144). The included volunteers had no known spinal disorder(s), no significant neck or back pain (Visual Analog Scale: ≤2; Oswestry Disability Index: ≤20), and no abnormal alignment (Cobb ≤20°). PO was measured in the frontal plane as the distance between the highest points of each acetabulum, calculated along the vertical axis in millimeters (mm). The incidence of PO was defined as PO ≥10 mm. Kruskal-Wallis, Wilcoxon rank-sum, Pearson correlation, and linear regression were used. Results: A total of 467 patients were included, and PO values by age, sex, body mass index, and country were provided. The overall incidence of PO ≥10 mm was 4.3%, and a nonsignificant trend toward increased PO with age was seen ( P = 0.077). No significant differences were seen in PO between sex, ethnicity, or body mass index groups. No significant correlation existed between PO and other commonly used coronal radiographic measurements. Conclusion: PO ≥10 mm occurred in 4.3% of asymptomatic volunteers. Despite the importance of recognizing PO in preventing coronal malalignment, PO did not seem to be associated with other radiographic and demographic information, which underscores the importance of intentionally assessing for any PO before surgery. These results in an asymptomatic population provide a foundation for studying PO in patients with spinal pathology.

Assess normative values of sagittal spinal and lower extremity alignment in asymptomatic volunteers of three difference races. 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. Volunteers were grouped into three main races; Asian (A), Arabo-Bèrbère (B), and Caucasian (C). The Asian volunteers included in this study were from Japan and Singapore. There were statistical differences in the Age, ODI, and BMI of the volunteers from the three different races. Asian volunteers had the lowest age (A: 36.7, B: 45.5, C: 42.0) and BMI (A: 22.1, B: 27.1, C: 27.3). Pelvic morphology including pelvic incidence (A: 51.0, B: 52.0, C: 52.5, p = 0.37), pelvic tilt (A: 11.9, B: 12.3, C: 12.9, p = 0.44), and sacral slope (A: 39.1, B: 39.7, C: 39.6, p = 0.77) were similar amongst the 3 races. Regional spinal alignment was different between the groups. Thoracic Kyphosis (A: 32.9, B: 43.3, C: 40.0, p < 0.0001) and Lumbar lordosis (A: − 54.2, B: − 60.4, C: − 59.6, p < 0.0001) were lower in Asians compared to Caucasian and Arabo-Bèrbère volunteers despite having similar pelvic incidence. Volunteers in the Asian group had lower lumbar lordosis and thoracic kyphosis when compared to the Arabo-Bèrbère and Caucasian groups while all groups had similar pelvic morphology. Thoracic Kyphosis had no correlation with Pelvic Incidence, while Lumbar Lordosis correlated well with both Thoracic Kyphosis and Pelvic Incidence. Thoracic kyphosis may be an independent variable in establishing adequate lumbar lordosis and varies based on an individual’s race.

Study design: Descriptive radiographic analysis of a prospective multi-center database. Objective: This study aims to provide normative values of spinopelvic parameters and their correlations according to age and pelvic incidence (PI) of subjects without spinal deformity. Methods: After Institutional Review Board (IRB) approval, 1540 full spine radiographs were analyzed. Subjects were divided into 3 groups of PI: low PI < 45 degrees, intermediate PI 45-60 degrees, high PI > 60 degrees, and then stratified by age (20-34, 35-49, 50-64, > 65 Y.0). Pelvic and spinal parameters were measured. Statistical analysis between parameters was performed using Bayesian inference and correlation. Results: Mean age was 53.5 years (845 females, 695 males, range 20-93 years). In low PI group, lumbar lordosis (LL) decrease was mainly observed in the 2 younger age groups. In medium and high PI groups, loss of lordosis was linear during aging and occurred mainly on the distal arch of lordosis. Moderate PI group had a stable lordosis apex and thoracolumbar inflection point. High PI group had a stable thoracolumbar inflection point and a more distal lordosis apex in elderly subjects. For all subjects, kyphosis and pelvic tilt (PT) increased with age. There was a constant chain of correlation between PI and age groups. Proximal lumbar lordosis (PLL) was correlated with kyphosis and sagittal vertical axis (SVA C7), while the distal lumbar lordosis (DLL) was correlated with PI and PT. Conclusion: This study provides a detailed repository of sagittal spinopelvic parameters normative values with detailed analysis of segmental kyphosis and lordosis distribution according to gender, age, and PI.

STUDY DESIGN:Prospective cohort study. OBJECTIVES:To show population variance in the Inflection Point (IP) and its role in defining maximum Thoracic Kyphosis (TK) and Lumbar Lordosis (LL). METHODS:468 asymptomatic adult volunteers were included in the Multi-Ethnic Normative Alignment Study (MEANS). To find parameters correlating with IP, the vertebrae and discs were numbered such that C7 was 0, T1 was 1, with T1-T2 disc being 1.5, etc. Statistical analysis was performed by a correlation matrix for IP and the 9 other selected parameters along with linear regressions. RESULTS:The overall mean IP was 12.44 approximately corresponding to T12-L1 disc with the median being 12.50, range was T8-L4. The cohort was then stratified by sex and ethnicity, but there was no significant difference in IP between groups. IP in younger subjects was 13 (L1), compared to 12.5 (T12-L1 disc) in older subjects (P < .05). IP was moderately correlated with the TK apex (r = .66). No strong correlation was found between IP and LL magnitude or apex, TK magnitude, sacral slope, or Pelvic Incidence (PI). In terms of other sagittal parameters, PI and LL demonstrated a significant positive correlation. PI and TK did not have a strong association. CONCLUSIONS:The mean IP was at the T12-L1 disc, however IP ranged from T8 to L4. Older subjects tended to have a relatively more cephalad IP. No radiographic variable was found to be a strong predictor of the IP. TK apex was found to have a moderate correlation.

Study design Descriptive radiographic analysis of a prospective multi-center database. Objective This study aims to provide normative values of spinopelvic parameters and their correlations according to age and pelvic incidence (PI) of subjects without spinal deformity. Methods After Institutional Review Board (IRB) approval, 1540 full spine radiographs were analyzed. Subjects were divided into 3 groups of PI: low PI < 45°, intermediate PI 45–60°, high PI > 60°, and then stratified by age (20–34, 35–49, 50–64, > 65 Y.O). Pelvic and spinal parameters were measured. Statistical analysis between parameters was performed using Bayesian inference and correlation. Results Mean age was 53.5 years (845 females, 695 males, range 20–93 years). In low PI group, lumbar lordosis (LL) decrease was mainly observed in the 2 younger age groups. In medium and high PI groups, loss of lordosis was linear during aging and occurred mainly on the distal arch of lordosis. Moderate PI group had a stable lordosis apex and thoracolumbar inflection point. High PI group had a stable thoracolumbar inflection point and a more distal lordosis apex in elderly subjects. For all subjects, kyphosis and pelvic tilt (PT) increased with age. There was a constant chain of correlation between PI and age groups. Proximal lumbar lordosis (PLL) was correlated with kyphosis and sagittal vertical axis (SVA C7), while the distal lumbar lordosis (DLL) was correlated with PI and PT. Conclusion This study provides a detailed repository of sagittal spinopelvic parameters normative values with detailed analysis of segmental kyphosis and lordosis distribution according to gender, age, and PI.

BACKGROUND CONTEXT:Current definition of lumbar lordosis uses the L1-S1 angle. Prevailing classification of sagittal spinal morphology, derived from a young adult population, classifies the spine into four subtypes defined by their sacral slope (SS) and curve morphology. PURPOSE:To describe physiological sagittal alignment of the lumbar spine across age groups using three main parameters that dictate the lumbar curve: angular magnitude, span, and apex. STUDY DESIGN:A large, multicenter, cross-sectional radiographic comparison study. PATIENT SAMPLE:Four hundred sixty-eight healthy, asymptomatic subjects aged 18 to 80 years from five countries (184 males, 284 females; 98 France, 119 Japan, 79 Singapore, 80 Tunisia, 92 USA, mean age 40.61±14.99 years). OUTCOME MEASURES:Sagittal lumbar profile subtypes clustered based on lumbar curve angular magnitude (ie, Cobb angle of the lumbar lordosis), span, and apex, and described by sagittal radiographic parameters. METHODS:Subjects underwent whole-body low-dose EOS stereoradiographs. Comparisons between conventional L1-S1 lumbar lordosis (cLL) and true lumbar lordosis (tLL, defined by the inflection-S1 angle) were conducted. Using the K-means clustering algorithm, lumbar curve angular magnitude, span and apex were used to classify sagittal spinal morphology into subtypes, stratified across age groups. Further univariate and multivariate analyses were conducted to compare radiographic parameters across subtypes, and identify predictors for the lumbar curve's angular magnitude, span and apex. RESULTS:Mean cLL was -57.27±11.37°, and tLL was -62.62±10.76°. Using tLL, instead of cLL, to describe sagittal spinal morphology, we found significant differences in terms of angular magnitude of the lumbar curve, the median thoracolumbar inflection vertebral level and pelvic incidence-lumbar lordosis mismatch Multivariate analysis found a larger SS, more positive T9 tilt, and more kyphotic T4-T12 predictive for a more lordotic tLL, while a larger overhang distance predicted for a less lordotic tLL (p-values<.001). In addition, a larger T9 tilt, less lordotic L1-L5 and smaller PT were predictors of a more caudal thoracolumbar inflection and lumbar apical vertebral levels (p-values<.001). Sagittal lumbar profiles of subjects age<30 years, 30≤age<60 years and age≥60 years, could be classified into 4, 6, and 3 subtypes, respectively. CONCLUSIONS:Sagittal lumbar profile subtypes vary across age groups, with more homogenous morphologies at the extremes of ages. Improved understanding of the morphological evolution of sagittal spinal profiles with age in asymptomatic individuals will help guide future individualized surgical treatment.

Purpose Adult spinal deformity (ASD) surgery gives good clinical outcomes but has a high rate of mechanical complications (MC). In 2016, Lafage described the age-adjusted alignment thresholds (AAAT) to adapt the correction in relation to patient’s age proposing less aggressive corrections for the elderly population. The aim of this review was to clarify the effectiveness of AAAT to achieve good health-related quality of life (HRQoL) and their relationship with post-operative MC. Materials and methods We performed a review of the literature, including articles reporting data on post-operative HRQoL and MC rates in relation to the AAAT. Data were stratified according to whether they matched the AAAT, dividing the population in undercorrected (U), matched (M) and overcorrected (O). The quality of the included studies was assessed using the GRADE and MINORS systems. Results S ix articles reporting data from 1,825 patients were included. The different categories (U, M and O) had homogeneous pre-operative sagittal parameters ( p > 0.05) that became statistically different after surgeries ( p < 0.05). Proximal junctional kyphosis (PJK) was more frequent in the O group compared to U ( p = 0.05). Post-operative HRQoL parameters were similar in the 3 groups ( p > 0.05). The quality of the included studies was generally low with a high bias risk. Conclusion The results extrapolated from this review are interesting, as for the same HRQoL the U group had a lower MC rate. Unfortunately, the results are inconsistent, mainly because of the low quality of the included studies and the lack of reporting of some important patient- and surgery-related factors.

Abstract Purpose To compare the biomechanical behavior of vertebrae with vertebral compression fractures (VCF) treated by a novel system with pedicular anchorage (dowelplasty) versus balloon kyphoplasty. Methods Four cadaveric spines (T12‐L5) were harvested, cleaned from soft tissues, and separated into vertebrae. Axial compressive loads were applied to each vertebra until a VCF was generated. Half of the vertebrae (n = 11) were instrumented using the “dowelplasty” system, consisting of a hollow titanium dowel anchored into the pedicle, through which a cannulated titanium nail is inserted and locked and through which cement is injected. The other half (n = 11) were instrumented using balloon kyphoplasty. Axial compressive loads were re‐applied to each vertebra until fracture. Fracture load and fracture energy were calculated from load–displacement data for the pre‐ and post‐treatment states. Results Compared to balloon kyphoplasty, dowelplasty granted greater net change in fracture load (373N; 95%CI,‐331–1076N) and fracture energy (755Nmm; 95%CI,‐563–2072Nmm). A sensitivity analysis was performed without L4 and L5 vertebrae from the dowelplasty group, since the length of the cannulated nails was too short for these vertebrae: compared to balloon kyphoplasty, dowelplasty granted an even greater net change in fracture load (680N; 95%CI,‐96–1457N) and fracture energy (1274Nmm; 95%CI,‐233–2781Nmm). Conclusion Treating VCFs with dowelplasty grants increased fracture load and fracture energy compared to the pre‐treatment state. Furthermore, dowelplasty grants greater improvement in fracture load and fracture energy compared to balloon kyphoplasty, which suggests that dowelplasty may be a good alternative for the treatment of VCF. Level of evidence level IV.

Purpose:To report accuracy, repeatability, and agreement of Cobb angle measurements on radiographs and/or stereo-radiographs (EOS) compared against one another or against other imaging modalities. Methods:This review follows Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines. A literature search was conducted on 21 July 2021 using Medline, Embase, and Cochrane. Two researchers independently performed title/abstract/full-text screening and data extraction. Studies were eligible if they reported Cobb angles, and/or their repeatability and agreement, measured on radiographs and/or EOS compared against one another or against other imaging modalities. Results:Of the 2993 records identified, 845 were duplicates and 2212 were excluded during title/abstract/full-text screening. Two more relevant studies were identified from references of eligible studies, leaving 14 studies for inclusion. Two studies compared Cobb angles from EOS vs CT, while 12 compared radiographs vs other imaging modalities: EOS, CT, MRI, digital fluoroscopy, or dual-energy x-ray absorptiometry. Angles from standing radiographs tended to be higher than those from supine MRI and CT, and angles from standing EOS tended to be higher than those from supine or prone CT. Correlations across modalities were strong (R = 0.78-0.97). Inter-observer agreement was excellent for all studies (ICC = 0.77-1.00), except one (ICC = 0.13 radiographs and ICC = 0.68 for MRI). Conclusion:Differences of up to 11º were found when comparing Cobb angles across combinations of imaging modalities and patient positions. It is not possible, however, to determine whether the differences observed are due to the change of modality, position, or both. Therefore, clinicians should be careful when utilizing the thresholds for standing radiographs across other modalities and positions for diagnosis and assessment of scoliosis.

Study Design. Prospective, cross-sectional cohort study. Objective. To determine the relationship between lumbar shape and sagittal parameters. Summary of Background Data. Understanding the lumbar shape is vital for deformity surgery. Normative sagittal parameters and spine shape remain unstudied in large, multiethnic, asymptomatic cohorts. Materials and Methods. A prospective, cross-sectional cohort of 468 asymptomatic volunteers between 18 and 80 years was enrolled across 5 countries. Demographic data and radiographic parameters such as pelvic incidence (PI) were collected. Pearson correlation test and linear regression were used to find the relationship between lumbar lordosis (LL) and other parameters. One-way analysis of variance and Welch 2-sample t test were performed to compare lumbar shape across such categories as PI and lumbar apex followed by post hoc Bonferroni correction if needed. Results. PI was moderately correlated with proximal lumbar lordosis (pLL) (r = −0.54) and weakly correlated with distal lumbar lordosis (dLL) (r = −0.16). Thoracic kyphosis (T1–T12) was moderately correlated with pLL (r = −0.35) and dLL (r = −0.29). dLL was moderately correlated with LL (r = 0.64). 2.6% (12/468) of subjects had lumbar apex at L2, 40.2% (188/468) at L3, 56.6% at L4 (265/468), and 0.6% (3/468) at other levels. Mean PI was different between volunteers with the apex at L3 and L4. A lower mean PI was associated with the apex at L4 (49.0°), whereas a higher mean PI was associated with the apex at L3 (55.8°). The mean PI−LL mismatch for volunteers was −5.4° with a range from −35° to 39.7°. PI−LL mismatch increased from a mean of −10.1° in volunteers with low PI to a mean of 2.2° in volunteers with high PI. Age was not correlated with LL (P = 0.84). Conclusions. In asymptomatic adult volunteers, pLL showed a moderate correlation with PI and increased with PI, whereas dLL showed a weak correlation. The lumbar apex migrated proximally with increasing PI. Segmental lordosis and apex position instead of solely global lordosis should be emphasized. Level of Evidence. Level III.

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.

The objective is to analyse peri-operative blood loss (BL) and hidden blood loss (HBL) rates in spinal deformity complex cases surgery, with a focus on the strategies to prevent major bleeding. We retrospectively analysed surgical and anaesthesiologic data of patients who had been operated for adolescent idiopathic scoliosis (AIS) or adult spinal deformities (ASD) with a minimum of five levels fused. A statistical comparison among AIS, ASD without a pedicle subtraction osteotomy (PSO) (ASD-PSO( −)) and ASD with PSO (ASD-PSO( +)) procedures was performed with a view to identifying patient- and/or surgical-related factors affecting peri-operative BL and HBL. One-hundred patients were included with a mean 9.9 ± 2.8 fused vertebrae and a mean 264.2 ± 68.3 minutes operative time (OT) (28.3 ± 9 min per level). The mean perioperative BL was 641.2 ± 313.8 ml (68.9 ± 39.5 ml per level) and the mean HBL was 556.6 ± 381.8 ml (60.6 ± 42.8 ml per level), with the latter accounting for 51.5% of the estimated blood loss (EBL). On multivariate regression analysis, a longer OT (p < 0.05; OR 3.38) and performing a PSO (p < 0.05; OR 3.37) were related to higher peri-operative BL, while older age (p < 0.05; OR 2.48) and higher BMI (p < 0.05; OR 2.15) were associated to a more significant post-operative HBL. With the correct use of modern technologies and patient management, BL in major spinal deformity surgery can be dramatically reduced. Nevertheless, it should be kept in mind that 50% of patients estimated losses are hidden and not directly controllable. Knowing the per-level BL allows anticipating global losses and, possibly, the need of allogenic transfusions.

Background. 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. Materials and Methods. 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. Results. 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). Conclusions. 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 of Evidence. Level II—prospective cohort study.

Background Patient radiation exposure associated with the use of computed tomography (CT) navigation during spinal surgeries was widely compared with other intraoperative imaging techniques. The aim of this study is to explore the use of navigation with regard to current spinal surgery practices and the technical limitations of such imaging systems. Methods Dosimetric data from 101 patients who underwent intraoperative, CT-navigated spine surgery were retrospectively collected. The study population was divided into 3 groups according to the primary surgical indication. The number of CT image acquisitions per patient, the field length, and the time of exposure per acquisition during a single surgery were compared as well as the radiation dose emitted to patients. Results Dose-length products (DLP) per acquisition were 678.52, 656.8, and 649.36 mGy·cm with no significant difference for spinal deformity (SD), degenerative disease (DD), and vertebral fracture (VF) procedures, respectively. Analyzing the number of CT image acquisitions per patient revealed that repeated intraoperative scans were often performed for patients who were suffering from an SD due to technical limitations of the navigation. As a consequence, the cumulative dose was higher in the SD group (DLP total = 1175 mGy·cm) than in the DD (DLP total = 762.74 mGy·cm) and VF (DLP total = 649.36 mGy·cm) groups. Conclusions CT navigation is an efficient intraoperative imaging technique that reduces the rate of surgical complications, but its technical limitations lead to an increased risk of patient radiation exposure, especially for complex surgeries where multiple scanning acquisitions are needed. Clinical Relevance To avoid patient’s overexposure, spine surgeons should minimize the number of intraoperative acquisitions while considering the complexity of the surgery and the limitations of the guidance system. The use of dual guidance systems has also to be considered according to the benefit-risk balance between patient’s outcomes and radiation dose exposure. Level of Evidence 4.