Comparison of 3-dimensional spinal reconstruction accuracy: biplanar radiographs with EOS versus computed tomography

Growth modulation response in vertebral body tethering depends primarily on magnitude of concave vertebral body growth

PURPOSE

There is variability in clinical outcomes with vertebral body tethering (VBT) partly due to a limited understanding of the growth modulation (GM) response. We used the largest sample of patients with 3D spine reconstructions to characterize the vertebra and disc morphologic changes that accompany growth modulation during the first two years following VBT.

METHODS

A multicenter registry was used to identify idiopathic scoliosis patients who underwent VBT with 2 years of follow-up. Calibrated biplanar X-rays obtained at longitudinal timepoints underwent 3D reconstruction to obtain precision morphological measurements. GM was defined as change in instrumented coronal angulation from post-op to 2-years.

RESULTS

Fifty patients (mean age: 12.5 ± 1.3yrs) were analyzed over a mean of 27.7 months. GM was positively correlated with concave vertebra height growth (r = 0.57, p < 0.001), 3D spine length growth (r = 0.36, p = 0.008), and decreased convex disc height (r = - 0.42, p = 0.002). High modulators (patients experiencing GM > 10°) experienced an additional 1.6 mm (229% increase) of mean concave vertebra growth during study period compared to the Poor Modulators (GM < - 10°) group, (2.3 vs. 0.7 mm, p = 0.039), while convex vertebra height growth was similar (1.3 vs. 1.4 mm, p = 0.91).

CONCLUSION

When successful, VBT enables asymmetric vertebra body growth, leading to continued postoperative coronal angulation correction (GM). A strong GM response is correlated with concave vertebral body height growth and overall instrumented spine growth. A poor GM response is associated with an increase in convex disc height (suspected tether rupture). Future studies will investigate the patient and technique-specific factors that influence increased growth remodeling.

Health technology assessment in musculoskeletal radiology: the case study of EOSedge™

OBJECTIVES

Health technology assessment (HTA) is a systematic process used to evaluate the properties and effects of healthcare technologies within their intended use context. This paper describes the adoption of HTA process to assess the adoption of the EOSedge™ system in clinical practice.

METHODS

The EOSedge™ system is a digital radiography system that delivers whole-body, high-quality 2D/3D biplanar images covering the complete set of musculoskeletal and orthopedic exams. Full HTA model was chosen using the EUnetHTA Core Model® version 3.0. The HTA Core Model organizes the information into nine domains. Information was researched and obtained by consulting the manufacturers' user manuals, scientific literature, and institutional sites for regulatory aspects.

RESULTS

All nine domains of the EUnetHTA Core Model® helped conduct the HTA of the EOSedge, including (1) description and technical characteristics of the technology; (2) health problem and current clinical practice; (3) safety; (4) clinical effectiveness; (5) organizational aspects; (6) economic evaluation; (7) impact on the patient; (8) ethical aspects; and (9) legal aspects.

CONCLUSIONS

EOS technologies may be a viable alternative to conventional radiographs. EOSedge has the same intended use and similar indications for use, technological characteristics, and operation principles as the EOS System and provides significant dose reduction factors for whole spine imaging compared to the EOS System without compromising image quality. Regarding the impact of EOS imaging on patient outcomes, most studies aim to establish technical ability without evaluating their ability to improve patient outcomes; thus, more studies on this aspect are warranted.

Estimating thoracic kyphosis without information on upper thoracic kyphosis: an observational study on 455 patients examined by EOS imaging

BACKGROUND

Physiological thoracic kyphosis (TK) allows sagittal balance of human body. Unlike lumbar lordosis (LL), TK has been relatively neglected in the literature. EOS is an imaging technique employing high-sensitivity xenon particles, featured by low-dose exposure combined with high accuracy compared to conventional radiography. The aim of this study was to investigate predictors of TK in patients with phyiological spine morphology using EOS imaging.

METHODS

EOS images of 455 patients without spinal anomalies were retrospectively assessed for TK (T1- T12), upper thoracic kyphosis (UTK, T1-T5), lower thoracic kyphosis (LTK, T5-T12), LL (L1-S1) and pelvic incidence (PI). The latter curves were measured by two researchers separately and the average of the two measurements was used for further analysis. Spearman non-parametric correlation was estimated for age, PI, LL, LTK, UTK and TK. Multiple robust linear regression analysis was employed to estimate TK, controlling for the effect of age, sex, LL and LTK.

RESULTS

The mean age of patients was 28.3 ± 19.2 years and 302 (66.4%) of them were females. The mean TK, UTK and LTK was 45.5° ± 9.3, 16 ± 7.4° and 29.7° ± 8.9, respectively. The mean UTK in people under 40 years of age was 17.0° ± 7.2, whereas for patients 40+ years old it was 13.6° ± 7.4. At univariable analysis TK positively correlated with UTK (p<0.001), LTK (p<0.001) an LL (p<0.001). At multivariable linear regression TK increased with LTK (RC = 0.67; 95%CI: 0.59; 0.75) or LL (RC = 0.12; 95%CI: 0.06; 0.18), whereas it decreased with age (RC = -0.06; 95%CI: -0.09;-0.02).

CONCLUSION

If EOS technology is available, the above linear regression model could be used to estimate TK based upon information on age, sex, LL and LTK. Alternatively, TK could be estimated by adding to LTK 17.0° ± 7.4 for patients < 40 years of age, or 13.6° ± 7.4 in patients 40 + years old. The evidence from the present study may be used as reference for research purposes and clinical practice, including spine examination of particular occupational categories or athletes.

Assessment of spinal alignment in standing position using Biplanar X-ray images and three-dimensional vertebral models

We developed two methods for three-dimensional (3D) evaluation of spinal alignment in standing position by image matching between biplanar x-ray images and 3D vertebral models. One used a Slot-Scanning 3D x-ray Imager (sterEOS) to obtain biplanar x-ray images, and the other used a conventional x-ray system and a rotating table. The 3D vertebral model was constructed from the CT scan data. The spatial position of the vertebral model was determined by minimizing the contour difference between the projected image of the model and the biplanar x-ray images. Verification experiments were conducted using a torso phantom. The relative positions of the upper vertebrae to the lowest vertebrae of the cervical, thoracic, and lumbar vertebrae were evaluated. The mean, standard deviation, and mean square error of the relative position were less than 1° and 1 mm in all cases for sterEOS. The maximum mean squared errors of the conventional x-ray system and the rotating table were 0.7° and 0.4 mm for the cervical spine, 1.0° and 1.2 mm for the thoracic spine, and 1.1° and 1.2 mm for the lumbar spine. Therefore, both methods could be useful for evaluating the spinal alignment in standing position.

Prevalence and Risk Factors of Degenerative Spondylolisthesis and Retrolisthesis in the Thoracolumbar and Lumbar Spine - An EOS Study Using Updated Radiographic Parameters

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.

3D analysis of the preoperative deformity in AIS can be used to guide surgical treatment decisions for selective thoracic fusion

PURPOSE

To identify 3D measures of scoliosis from preoperative imaging that are associated with optimal radiographic outcomes after selective thoracic fusion (STF) for adolescent idiopathic scoliosis (AIS).

METHODS

Subjects with primary thoracic curves (Lenke 1-4, B or C modifiers) fused selectively (L1 or above) who had preoperative 3D reconstructions and minimum 2 years of follow-up were included. An optimal outcome at 2 years was defined as having 4 of 5 parameters previously defined in the literature: (1) lumbar curve < 26º, (2) deformity flexibility quotient < 4, (3) C7-CSVL < 2 cm, (4) lumbar prominence < 5º and (5) trunk shift < 1.5 cm. Univariate and CART analyses were performed to identify preoperative variables associated with achieving an optimal outcome 2 years postoperatively.

RESULTS

Ninety-nine (88F, 11 M) patients met inclusion. Mean age was 15 ± 2 years. Fifty-one subjects (52%) had an optimal outcome. Seven preoperative deformity measures representing smaller thoracolumbar/lumbar deformity in the optimal group were found to be significant on univariate analysis. CART analysis identified the following variables associated with optimal outcomes: difference in apical rotation > 30° = 27% optimal outcomes, difference in apical rotation ≤ 30° and coronal vertebral wedging of lumbar apex > 3° = 46% optimal outcomes, and difference in apical rotation ≤ 30° and coronal vertebral wedging of lumbar apex ≤ 3° = 80% optimal outcomes (p < 0.05).

CONCLUSION

Optimal outcomes after STF were associated with a preoperative difference in apical vertebral rotation in the axial plane less than 30° between thoracic and lumbar curves as well as coronal plane vertebral wedging of the lumbar apical vertebra less than 3°.

Where should Scoliometer and EOS Imaging be Applied when Evaluating Spinal Rotation in Adolescent Idiopathic Scoliosis -A Preliminary Study with Reference to CT Images

STUDY DESIGN

Retrospective study.

OBJECTIVE

Our purpose was to evaluate spinal rotation measurement by scoliometer or EOS Imagings with reference to that by CT images, and to clarify their applicability in clinical practice.

METHODS

Patients with adolescent idiopathic scoliosis (AIS) who were indicated for surgery were enrolled and the informed consents were obtained. The angle of trunk rotation (ATR) was measured by the scoliometer. Apical vertebral rotation (AVR) was measured with EOS Imaging and CT images. Paired T tests were used to compare the measurements between ATR or AVR-EOS and AVR-CT. Pearson correlation analysis was performed to explore the relationship between ATR or AVR-EOS and AVR-CT. Then subgroup analysis was performed.

RESULTS

Forty-seven consecutive AIS patients with 62 curves were identified. In the whole group, the ATR, as well as AVR-EOS, was significantly smaller than the AVR-CT. Both ATR and AVR-EOS correlated with AVR-CT, although AVR-EOS correlated better. In thoracic group, there was no significant difference between ATR and AVR-CT (P = .236). A significant correlation was found between ATR and AVR-CT(r = .574, P < .001). In TL/L group, no significant difference was noted between AVR-EOS and AVR-CT (P = .414), and a significant correlation was found between AVR-EOS and AVR-CT(r = .824, P < .001).

CONCLUSION

ATR by scoliometer is numerically similar to AVR by CT and may evaluate the spinal rotation more appropriately in thoracic spine. AVR by EOS is numerically similar to AVR by CT and may be more applicable in TL/L spine. Appropriate methods could be selected according to the location of the curve.

5-Year Radiographic and Functional Outcomes of Nonoperative Treatment of Completely Displaced Midshaft Clavicular Fractures in Teenagers

BACKGROUND

Optimal treatment of completely displaced midshaft clavicular fractures in adolescents remains controversial, with some favoring surgical management and others favoring a nonoperative approach. Few studies have comprehensively assessed longer-term nonoperative outcomes.

PURPOSE

To prospectively assess patient-reported outcomes (PROs) and radiographic remodeling ≥5 years after injury in teenagers undergoing nonoperative treatment of completely displaced clavicular fractures.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Adolescent patients previously enrolled in a prospective study from a single institution with nonoperatively treated, completely displaced midshaft clavicular fractures ≥5 years from injury were eligible for the study. Patients were clinically evaluated for scapular dyskinesia and strength deficits. Bilateral clavicular imaging assessed residual shortening, displacement, and angulation. PROs included the American Shoulder and Elbow Surgeons (ASES), the shortened version of the Disabilities of the Arm, Shoulder and Hand (QuickDASH), Marx Shoulder Activity Scale, cosmesis, and return to sports data.

RESULTS

A total of 24 patients were available for the follow-up, of whom 17 (71%) consented to additional imaging. The mean cohort age at the time of injury was 14.5 ± 1.1 years, with 88% being male. At a mean follow-up of 6.1 years, all fractures had healed, with no patient requiring secondary interventions. Significant remodeling was observed across all measurements, with improvements of 70% in shortening (22.8 to 6.8 mm; P < .001), 73% in superior displacement (13.4 to 3.6 mm; P < .001), and 83% in angulation (10.4° to 1.8°; P < .001). Thirteen patients (72%) had a >2-cm initial shortening, and all remodeled to <2 cm. PROs were almost universally excellent, with mean ASES, QuickDASH, and Marx activity scores of 99 ± 3, 1 ± 3, and 20 ± 1, respectively, with 79% of patients reporting perfect scores in all 3 domains. Most patients (58%) were completely satisfied with their shoulder appearance, 38% were more satisfied than not, 1 patient (4%) was neither satisfied nor dissatisfied, and no patients were dissatisfied. All patients except 1 who were interested in sports returned to sporting activities. PROs were not associated with bony remodeling (P > .05).

CONCLUSION

Teenaged patients with completely displaced clavicular fractures treated nonoperatively can expect excellent radiographic and clinical outcomes 5 years after injury.

Rotation and Asymmetry of the Axial Plane Pelvis in Cerebral Palsy: A CT-Based Study

Spinopelvic malignment is commonly seen with non-ambulatory cerebral palsy (CP). Axial plane deformation is not well described in the literature. The purpose of this study was to describe and quantify the axial plane deformity in CP using CT scans and compare it to normal controls. We retrospectively collected data using CT scans of the abdomen and pelvis of 40 patients with GMFCS IV/V CP and neuromuscular scoliosis (CPP) and normal controls (NP) matched by age and sex. Pre-operative Cobb angle was recorded for the CP patients. Pelvic anatomy was evaluated at the supra-acetabular region of bone using two angles-iliac wing angle and sacral ala angle, measured for each hemipelvis. The larger of each hemipelvis angle was considered externally rotated while the smaller angle was considered internally rotated, termed as follows-iliac wing external (IWE) and internal (IWI); sacral ala external (SAE), and internal (SAI). Differences were noted using an independent t-test while correlations with Cobb angle were performed using Pearson's correlation. Iliac wing measurements showed the externally rotated hemipelvis showed a significantly greater magnitude compared with normal controls at 47.3 ± 18.1 degrees vs. 26.4 ± 3.7 degrees in NP (p < 0.001) while no internal rotation was observed (p > 0.05). Sacral ala measurements showed greater magnitude in both external and internal rotation. SAE was 119.5 ± 9.5 degrees in CPP vs. 111.2 ± 7.7 degrees in NP (p < 0.001) while SAI was 114.1 ± 8.5 degrees in CPP vs. 107.9 ± 7.5 degrees in NP (p = 0.001). In the CP cohort, the mean Cobb angle was 61.54 degrees (n = 37/40). Cobb angle correlated with the degree of external iliac wing rotation-IWE (r = 0.457, p = 0.004) and degree of absolute difference in the rotation of the iliac wing (r = 0.506, p = 0.001). The pelvis in a patient with CP scoliosis is asymmetrically oriented exhibiting a greater external rotation of one hemipelvis relative to normal controls. The severity of neuromuscular scoliosis is related to the pelvic axial rotation in CP patients. Axial plane deformity exists in the CP pelvis and this deformity warrants consideration when considering spinopelvic instrumentation strategies and outcomes of supra-pelvic and infra-pelvic pathologies.

Weight-bearing cone-beam CT with extensive coverage for volumetric imaging in adolescent idiopathic scoliosis: system implementation and initial validation

The study aimed to introduce a novel imaging method that generates large-coverage, weight-bearing, and 3D images of the whole spine. The proposed system comprises an X-ray tube, a flat panel detector, and a standing platform. The standing platform rotates the imaged subject, allowing for the acquisition of serial fluoroscopic images from different angles which can be used to create 3D images. To increase the longitudinal coverage, we apply a segmental scanning pattern in which the imaged region is scanned in segments and stitched. To address the issue of data inaccuracy between the segments, redundant areas are set at margins of the segmental images, and registration and stitching algorithms are applied. We conducted validation experiments to evaluate radiation dose and image quality. The dose was evaluated using the volume CT dose index (CTDIvol). For image quality evaluation, we measured the low-contrast and spatial resolution. Additionally, we conducted a clinical study consisting of 30 volunteers with adolescent idiopathic scoliosis who were imaged by our method, and the images were subjectively assessed based on image noise, artifacts, anatomical coverage, diagnostic confidence, and overall quality. The CTDIvol was 1.23 mGy, and the low-contrast resolution was 0.6% at 4 mm and the spatial resolution was 8 lp/cm. The clinical images were generally of good quality, with high scores for all factors evaluated. Our method successfully generates large-coverage, weight-bearing, and 3D images of the whole spine with high image quality and low radiation dose. It shows potential for wider clinical applications for various musculoskeletal conditions.

Morphological description of sagittal lumbar spinal alignment using curve magnitude, span, and apex-the multiethnic alignment normative study (MEANS)

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.

Advances and Evolving Challenges in Spinal Deformity Surgery

BACKGROUND

Surgical intervention is a critical tool to address adult spinal deformity (ASD). Given the evolution of spinal surgical techniques, we sought to characterize developments in ASD correction and barriers impacting clinical outcomes.

METHODS

We conducted a literature review utilizing PubMed, Embase, Web of Science, and Google Scholar to examine advances in ASD surgical correction and ongoing challenges from patient and clinician perspectives. ASD procedures were examined across pre-, intra-, and post-operative phases.

RESULTS

Several factors influence the effectiveness of ASD correction. Standardized radiographic parameters and three-dimensional modeling have been used to guide operative planning. Complex minimally invasive procedures, targeted corrections, and staged procedures can tailor surgical approaches while minimizing operative time. Further, improvements in osteotomy technique, intraoperative navigation, and enhanced hardware have increased patient safety. However, challenges remain. Variability in patient selection and deformity undercorrection have resulted in heterogenous clinical responses. Surgical complications, including blood loss, infection, hardware failure, proximal junction kyphosis/failure, and pseudarthroses, pose barriers. Although minimally invasive approaches are being utilized more often, clinical validation is needed.

CONCLUSIONS

The growing prevalence of ASD requires surgical solutions that can lead to sustained symptom resolution. Leveraging computational and imaging advances will be necessary as we seek to provide comprehensive treatment plans for patients.

Three-Dimensional Spinal Evaluation Using Rasterstereography in Patients with Adolescent Idiopathic Scoliosis: Is It Closer to Three-Dimensional or Two-Dimensional Radiography?

(1) Background: Adolescent Idiopathic Scoliosis (AIS) is a three-dimensional (3D) spine deformity. The Cobb angle, evaluated with 2D radiography, is the gold standard to determine curve severity. The primary aim of this study was to evaluate the 3D spinal evaluation with rasterstereography in patients with AIS. The hypothesis was that rasterstereography reached higher accuracy than the gold standard 2D radiography. The second aim was to compare rasterstereography with 3D radiography. The hypothesis was that the rasterstereographic evaluation of patients with severe major scoliosis curves is closer to 3D radiography compared to the gold standard (2D radiography). (2) Methods: This is a prospective comparative study of a consecutive series of 53 patients, with the scoliosis curve evaluated with two 3D methods and the gold standard (2D radiography). (3) Results: The hypothesis that rasterstereography reached higher accuracy than the gold standard 2D radiography was validated for all curves. Even if all curves were highly correlated, both rasterstereography and 2D radiography scoliosis evaluation were underestimated for moderate/severe curves compared to 3D radiography. (4) Conclusions: The rasterstereographic evaluation of major curve scoliosis is not accurate enough to replace 2D radiography for moderate/severe curves. A longitudinal follow-up should be assessed in future studies to define the sensitivity of the detection of a significant change in the scoliotic mild and moderate curve (<40°).

Correcting intervertebral rotation and scoliosis simultaneously by oblique lumbar interbody fusion: a 3D analysis of EOS images

Purpose

With advancements in minimally invasive techniques, oblique lumbar interbody fusion (OLIF) has gained widespread acceptance and is now commonly performed for adult degenerative scoliosis (ADS). The objective of this research paper is to evaluate three-dimensional (3D) intervertebral motions in EOS models before and after surgery and subsequently assess the efficacy of the 3D correction achieved through staged OLIF.

Methods

In this retrospective study, 29 consecutive patients diagnosed with ADS were included, with a mean age of 63.6 years, who underwent staged OLIF surgery between 2018 and 2021. Spinopelvic parameters were assessed using EOS images, and 3D models were reconstructed to measure intervertebral motion angles (IMAs) in 70 surgical intervertebral segments, comprising wedge, lordosis, and axial rotation angles. Regression analysis was conducted to compare IMAs in different planes before and after the staged OLIF surgery.

Results

Significant three-dimensional correction was observed in 70 intervertebral segments following the first-stage OLIF. The wedge angles decreased from 5.2°± 4.2° to 2.7°± 2.4° (P < 0.001). The lordosis angles increased from 5.1°± 5.9° to 7.8°± 4.6° (P = 0.014), while the axial rotation angles decreased from 3.8°± 2.6° to 2.3°± 2.1° (P < 0.001). Linear regression analysis revealed a positive correlation between wedge angles and axial angles preoperatively (P < 0.001, r = 0.43), as well as between corrected wedge angles and corrected axial angles (P < 0.001, r = 0.42).

Conclusion

This study demonstrated that intervertebral motions had a correlation between coronal and axial planes in lumbar degenerative scoliosis. First-stage OLIF was efficient at correcting segmental scoliosis by inserting cages while correcting rotation deformity simultaneously, as well as improving the sagittal spinopelvic parameters.

The age-specific normative values of standing whole-body sagittal alignment parameters in healthy adults: based on international multicenter data

PURPOSE

To investigate the age-specific normative values of whole-body sagittal alignment (WBSA) including global balance parameters in healthy adults and to clarify the correlations among parameters based on the data from three international multicenter.

METHODS

Three hundred and seventeen healthy subjects (range: 20-84 y.o., mean: 43.8 ± 14.7 y.o.) were included and underwent whole-body biplanar X-ray imaging system. Spinopelvic parameters and knee flexion (KF), the center of acoustic meatus (CAM)-hip axis (HA), and C2 dentiform apophyse (OD)-HA, the cranial center (Cr)-HA were evaluated radiologically. Sub-analysis for correlation analysis between age and parameters and among parameters was performed to investigate age-specific change and compensatory mechanisms.

RESULTS

For age-related change, C2-7 angle (r = .326 for male/.355 for female), KF (r = .427/.429), and SVA (r = .234/.507) increased with age in both male and female group. For global parameters related to the center of the gravity, correlations with age were not significant (r = .120/.161 for OD-HA, r = .163/.275 for Cr-HA, r = .149/.262 for CAM-HA). Knee flexion (KF) has correlation with global parameters (i.e., SVA, OD-HA, Cr-HA, CAM-HA) and does not have correlations with local spinopelvic alignment.

CONCLUSION

While several local alignment changes with age were found, changes in global parameters related to the center of gravity were kept relatively mild by the chain of compensation mechanisms including the lower limbs. We showed the normative values for a comprehensive WBSA in standing posture from large international healthy subjects' database.

Clinical application of EOS imaging system: a scoping review protocol

OBJECTIVE

The objective of this scoping review is to examine and map the existing literature on the clinical application of the EOS imaging system and to identify related evidence gaps.

INTRODUCTION

The EOS imaging system was originally developed to conduct imaging for medical conditions, such as scoliosis and anisomelia. However, recent research suggests that the modality has other clinical uses that may benefit patients via reduced radiation dose and, thus, improve patient safety.

INCLUSION CRITERIA

This scoping review will consider all quantitative study designs, including systematic reviews and meta-analyses. Imaging phantom studies and conference abstracts will be excluded.

METHODS

Databases that will be searched include Embase, MEDLINE, CINAHL Complete, Scopus, Cochrane Library, Academic Search Premier, and OpenGrey. Relevant secondary material will be identified using citation searching (backwards and forwards) of included studies through Google Scholar. In addition, we will search by author name where more than 3 included studies from the same first author are identified. Articles published from 2003 in English, Danish, Norwegian, Swedish, French, and German will be included. Two independent reviewers will perform title/abstract screening, followed by full-text screening. Data extraction will include study type and design, age of participants, anatomical/physiological region, pathology, clinical endpoint, outcome measures, sample size, and clinical application. Data will be presented in tabular format and as a narrative summary.

REVIEW REGISTRATION NUMBER

Open Science Framework https://osf.io/yc85j/.

Influence of spinal lordosis correction location on proximal junctional failure: a biomechanical study

STUDY DESIGN

Assessment of sagittal lordosis distribution on mechanical proximal junctional failure-related risks through computer-based biomechanical models.

OBJECTIVE

To biomechanically assess how lordosis distribution influences radiographical and biomechanical indices related to Proximal Junctional Failure (PJF). The "optimal" patient-specific targets to restore the sagittal balance in posterior spinal fusion are still not known. Among these, the effect of the lumbar lordosis correction strategy on complications such as PJF remain uncertain.

METHODS

In this computational biomechanical study, five adult spinal deformity patients who underwent posterior spinal fixation were retrospectively reviewed. Their surgery, first erect posture and flexion movement were simulated with a patient-specific multibody model. Three pedicle subtraction osteotomy (PSO) levels (L3, L4, and L5) were simulated, with consistent global lordosis for a given patient and pelvic tilt adjusted accordingly to the actual surgery. Computed loads on the anterior spine and instrumentation were analyzed and compared using Kruskal-Wallis statistical tests and Spearman correlations.

RESULTS

In these models, no significant correlations were found between the lordosis distribution index (LDI), PSO level and biomechanical PJF-related indices. However, increasing the sagittal vertical axis (SVA) and thoracolumbar junction angle (TLJ) and decreasing the sacral slope (SS) increased the bending moment sustained by the rods at the proximal instrumented level (r = 0.52, 0.57, - 0.56, respectively, p < 0.05). There was a negative correlation between SS and the bending moment held by the adjacent proximal segment (r = - 0.71, p < 0.05).

CONCLUSION

Based on these biomechanical simulations, there was no correlation between the lordosis distribution and PJF-associated biomechanical factors. However, increasing SS and flattening the TLJ, as postural adjustment strategies required by a more distal PSO, did decrease such PJF-related factors. Sagittal restoration and PJF risks remain multifactorial, and the use of patient-specific biomechanical models may help to better understand the complex interrelated mechanisms.

Proximal junctional failure after surgical instrumentation in adult spinal deformity: biomechanical assessment of proximal instrumentation stiffness

STUDY DESIGN

Assessment of different proximal instrumentation stiffness features to minimize the mechanical proximal junctional failure-related risks through computer-based biomechanical models.

OBJECTIVE

To biomechanically assess variations of proximal instrumentation and loads acting on the spine and construct to minimize proximal junctional failure (PJF) risks. The use of less-stiff fixation such as hooks or tensioned bands, compared to pedicle screws, at the proximal instrumentation level are considered to allow for a gradual transition in stiffness with the adjacent levels, but the impact of such flexible fixation on the loads balance and complications such as PJF remain uncertain.

METHODS

Six patients with adult spine deformity who underwent posterior spinal instrumentation were used to numerically model and simulate the surgical steps, erected posture, and flexion functional loading in patient-specific multibody analyses. Three types of upper-level fixation (pedicle screws (PS), supralaminar hooks (SH), and sublaminar bands (SB) with tensions of 50, 250, and 350 N) and rod stiffness (CoCr/6 mm, CoCr/5.5 mm, Ti/5.5 mm) were simulated. The loads acting on the spine and implants of the 90 simulated configurations were analyzed using Kruskal-Wallis statistical tests.

RESULTS

Simulated high-tensioned bands decreased the sagittal moment at the adjacent level proximal to the instrumentation (1.3 Nm at 250 N; 2.5 Nm at 350 N) compared to screws alone (PS) (15.6 Nm). At one level above, the high-tensioned SB increased the sagittal moment (17.7 Nm-SB vs. 15.5 Nm-PS) and bending moment on the rods (5.4 Nm and 5.7 Nm vs. 0.6 Nm) (p < 0.05). SB with 50 N tension yielded smaller changes in load transition compared to higher tension, with moments of 8.1 Nm and 16.8 Nm one and two levels above the instrumentation. The sagittal moment at the upper implant-vertebra connection decreased with the rod stiffness (1.0 Nm for CoCr/6 mm vs. 0.7 Nm for Ti/5.5 mm; p < 0.05).

CONCLUSION

Simulated sublaminar bands with lower tension produced smaller changes in the load transition across proximal junctional levels. Decreasing the rod stiffness further modified these changes, with a decrease in loads associated with bone failure, however, lower stiffness did increase the rod breakage risk.

LEVEL OF EVIDENCE

N/A.

New method to apply the lumbar lordosis of standing radiographs to supine CT-based virtual 3D lumbar spine models

Standing radiographs play an important role in the characterization of spinal sagittal alignment, as they depict the spine under physiologic loading conditions. However, there is no commonly available method to apply the lumbar lordosis of standing radiographs to supine CT-based virtual 3D models of the lumbar spine. We aimed to develop a method for the sagittal rigid-body registration of vertebrae to standing radiographs, using the exact geometry reconstructed from CT-data. In a cohort of 50 patients with monosegmental spinal degeneration, segmentation and registration of the lumbar vertebrae and sacrum were performed by two independent investigators. Intersegmental angles and lumbar lordosis were measured both in CT scans and radiographs. Vertebrae were registered using the X-ray module of Materialise Mimics software. Postregistrational midsagittal sections were constructed of the sagittal midplane sections of the registered 3D lumbar spine geometries. Mean Hausdorff distance was measured between corresponding registered vertebral geometries. The registration process minimized the difference between the X-rays' and postregistrational midsagittal sections' lordoses. Intra- and inter-rater reliability was excellent based on angle and mean Hausdorff distance measurements. We propose an accessible, accurate, and reproducible method for creating patient-specific 3D geometries of the lumbar spine that accurately represent spinal sagittal alignment in the standing position.

3D Surface Topographic Optical Scans Yield Highly Reliable Global Spine Range of Motion Measurements in Scoliotic and Non-Scoliotic Adolescents

Background: Adolescent idiopathic scoliosis results in three dimensional changes to a patient’s body, which may change a patient’s range of motion. Surface topography is an emerging technology to evaluate three dimensional parameters in patients with scoliosis. The goal of this paper is to introduce novel and reliable surface topographic measurements for the assessment of global coronal and sagittal range of motion of the spine in adolescents, and to determine if these measurements can distinguish between adolescents with lumbar scoliosis and those without scoliosis. Methods: This study is a retrospective cohort study of a prospectively collected registry. Using a surface topographic scanner, a finger to floor and lateral bending scans were performed on each subject. Inter- and intra-rater reliabilities were assessed for each measurement. ANOVA analysis was used to test comparative hypotheses. Results: Inter-rater reliability for lateral bending fingertip asymmetry (LBFA) and lateral bending acromia asymmetry (LBAA) displayed poor reliability, while the coronal angle asymmetry (CAA), coronal angle range of motion (CAR), forward bending finger to floor (FBFF), forward bending acromia to floor (FBAF), sagittal angle (SA), and sagittal angle normalized (SAN) demonstrated good to excellent reliability. There was a significant difference between controls and lumbar scoliosis patients for LBFA, LBAA, CAA and FBAF (p-values < 0.01). Conclusion: Surface topography yields a reliable and rapid process for measuring global spine range of motion in the coronal and sagittal planes. Using these tools, there was a significant difference in measurements between patients with lumbar scoliosis and controls. In the future, we hope to be able to assess and predict perioperative spinal mobility changes.

CT analysis of the posterior anatomical landmarks of the scoliotic spine

AIM

To use computed tomography (CT) to assess the validity and reliability of the posterior landmarks, spinous processes (SP), transverse processes (TP), and centre of lamina (COL), as compared to the Cobb angle to assess the curve severity and progression of adolescent idiopathic scoliosis (AIS).

MATERIALS AND METHODS

A consecutive series of CT examinations of severe AIS patients were included retrospectively. SP, TP, and COL angles were measured for all curves and compared to the Cobb angle.

RESULTS

One hundred and five patients were included. The mean Cobb versus SP, TP, and COL angles were, 54° versus 37°, 49°, and 51° in the thoracic curves and 34° versus 26°, 31°, and 34° in the (thoraco)lumbar curves. Intraclass correlation coefficient values for intra-rater measurements of the SP, TP, and COL angles were 0.93, 0.97, and 0.95 and 0.70, 0.90, and 0.88 for inter-rater measurements. The correlations between the Cobb angle and SP, TP, and COL angles in thoracic and (thoraco)lumbar curves were 0.79 and 0.66, 0.87 and 0.84, and 0.80 and 0.70.

CONCLUSIONS

The posterior spinal landmarks can be used for assessment of scoliosis severity in AIS; however, they show a systematic underestimation, but a strong correlation with the coronal Cobb angle. TP and COL angles had the highest validity.

The Adolescent Spine

Adolescent idiopathic scoliosis (AIS) is the most characteristic disorder of the adolescent spine. It is a three-dimensional (3D) disorder that occurs from 10 years of age and comprises 90% of all idiopathic scolioses. Imaging plays a central role in the diagnosis and follow-up of patients with AIS. Modern imaging offers 3D assessment of scoliosis with less radiation exposure. Imaging helps rule out occult conditions that cause spinal deformity. Various imaging methods are also used to assess skeletal maturity in patients with AIS, thus determining the growth spurt and risk of progression of scoliosis. This article provides a brief overview of the pathophysiology, biomechanics, clinical features, and modern imaging of AIS relevant to radiologists in clinical settings.

Intraoperative stitched fluoroscopic images: effect of parallax on angular measurements of the spine

BACKGROUND CONTEXT

Intraoperative stitched O-arm images are commonplace during spinal deformity correction surgeries; however, the accuracy of stitched images for measuring angular measures is unknown.

PURPOSE

To examine the effect of radiographic parallax effect of stitched O-arm images by assessing the regional curve agreement with measurements from computed tomography (CT).

STUDY DESIGN/SETTING

Experimental radiographic study.

PATIENT SAMPLE

Four whole body cadavers (age: 81±14, sex: 2M/2F) and two fabricated spine model phantoms from surgical cases, one with extreme scoliosis and one normal spine, were utilized.

OUTCOME MEASURES

The limits of agreement for angular measures between CT (gold-standard) and intraoperative stitched fluoroscopic images were calculated. Further, intra- and inter-rater reliability was measured.

METHODS

A series of adjacent anterior-posterior and lateral images were acquired cranial to caudal using an O-arm in three table configurations (standard position, off-axis in the coronal plane, and reverse Trendelenburg) and stitched manually. Regional angular measures were extracted, and the limits of agreement were calculated between each table position and CT using a Bland-Altman approach.

RESULTS

The observers displayed excellent inter-rater reliability across table positions (range: 0.944-0.989) and intra-rater reliability (0.979-0.995). The limits of agreement results showed a similar and better agreement was observed for the Standard and Reverse Trendelenburg than the Off-Axis position.

CONCLUSIONS

This work shows reliable regional curvature measurements can be calculated with good agreement with CT in common table positions, but care should be taken to ensure the patient is perpendicular to the X-rays, particularly in the lateral view.

Assessment of the axial plane deformity in subjects with adolescent idiopathic scoliosis and its relationship to the frontal and sagittal planes

PURPOSE

Investigate the axial plane deformity in the scoliotic segment and its relationship to the deformity in the frontal and sagittal planes.

METHODS

Two hundred subjects with AIS (Cobb ≥ 20°) underwent low dose biplanar X-rays with 3D reconstruction of the spine and pelvis. All structural curves were considered and were distributed as follows: 142 thoracic (T), 70 thoracolumbar (TL), and 47 lumbar curves (L). Common 3D spino-pelvic and scoliosis parameters were collected such as: frontal Cobb; torsion index (TI); hypokyphosis/lordosis index (HI). Parameters were compared between each type of curvature and correlations were investigated between the 3 planes.

RESULTS

Frontal Cobb was higher in all T (45 ± 19°) and TL (41 ± 15°) curves compared to L curves (35 ± 14°, p = 0.004). TI was higher in T curves when compared to TL and L curves (TI: 15 ± 8°, 9 ± 6°, 7 ± 5°, p < 0.001). HI was similar between curve types. T curves showed significant correlations between the 3 planes: Cobb vs. TI (r = 0.76), Cobb vs. HI (r = - 0.54) and HI vs. TI (r = - 0.42). The axial plane deformity was related to the frontal deformity and the type of curvature (adjusted-R² = 0.6).

CONCLUSION

Beside showing the most severe deformity frontally and axially compared to TL and L curves, the T curves showed strong correlations between the 3 planes of the deformity. Moreover, this study showed that the axial plane deformity cannot be fully determined by the frontal and sagittal deformities, which highlights the importance of 3D assessment in the setting of AIS.

Three-Dimensional Assessment of Vertebral Derotation in Adolescent Idiopathic Scoliosis: Review of a Surgical Technique and Its Success in Achieving Derotation in the Instrumented and Uninstrumented Spine

BACKGROUND

Three-dimensional (3D) imaging represents a novel way to assess surgical derotation maneuvers in adolescent idiopathic scoliosis (AIS).

OBJECTIVE

To assess the following in patients with AIS undergoing derotation surgery with Lenke type 1/2 curves using 3D imaging: (1) the primary outcome of thoracic apical vertebral rotation (T-AVR) and (2) secondary outcomes of thoracic kyphosis (TK), lumbar AVR (L-AVR), and rotation of each thoracic/lumbar vertebrae.

METHODS

A retrospective, pilot study of type 1/2 AIS patients from 2017 to 2018 was performed. All patients received posterior pedicle screw/rod constructs with consistent direct vertebral derotational maneuvers and received full length SterEOS imaging with 3D reconstruction. The primary outcome of interest was T-AVR. Secondary outcomes included TK, L-AVR, and rotation at each thoracic/lumbar vertebrae.

RESULTS

Fifteen patients (mean age 15.7 ± 1.2 years, 67.0% female) were studied. The mean preoperative/postoperative Cobb angle of the major curve was 51.8° ± 14.9° (range 39.8-62.0) and 11.0° ± 5.1° (range 3.7-20.7). Mean level fused was 10.5 ± 1.2. The primary outcome of T-AVR showed significant improvement (13.8° ± 12.5° vs 9.2° ± 8.6°, P = .015) after surgery, along with secondary outcome of TK (T1-12/T4-12, P = .008/.027). Significant spontaneous rotational improvement was seen in L-AVR (P = .016). Significant improvement was also seen in 11 of 17 (64.7%) individual vertebrae (T3-8/T11-L3) (P < .05).

CONCLUSION

In Lenke Type 1/2 AIS patients undergoing surgical derotation and fusion, 3D imaging techniques captured improvements in rotation. Significant postoperative improvement was seen in T-AVR, TK, L-AVR, and rotation of the individual vertebrae T3-8/T11-L3. These pilot results warrant the study of 3D imaging in all patients with AIS and other scoliosis populations.

An analysis on the determinants of head to pelvic balance in a Chinese adult population

BACKGROUND

Balanced global spinopelvic balance is important in the maintenance of the physiological alignment of all body segments above the pelvis with minimum energy expenditure. The key determinants affecting the 3D index-odontoid-hip axis (OD-HA) angle, and in particular its alterations, have not been clearly defined. The aim of this study is to identify the determinants of the 3D OD-HA angle in maintaining global spinopelvic balance in a large Chinese adult cohort of different gender and age groups.

METHODS

A total of 516 asymptomatic adults were enrolled in this study. Biplanar radiographies were performed to reconstruct the subject's inter-acetabular axis and C2 odontoid process. The 3D angle formed by the vertical and the line between odontoid and mid-interacetabular axis (OD-HA angle) was computed and projected in the subject's sagittal and coronal planes. Thoracic kyphosis (TK), lumbar lordosis (LL), T1 pelvic angle (TPA) and sagittal vertical axis (SVA) were measured.

RESULTS

The mean values of sagittal and coronal OD-HA were -0.2°±2.5° and 0.2°±1.1°, respectively. Both sagittal and coronal OD-HA had significant correlation with age (r=0.265 and r=-0.143, P<0.01, respectively), sagittal OD-HA showed increment from 20s to 80s (-1.3° to 0.8° for female, -0.3° to 1.5° for male) and a significant difference between male and female from 20 to 69 years old. Further analysis showed that sex, weight, TK, PT, SVA, TPA and ODI were determinants of OD-HA.

CONCLUSIONS

3D OD-HA angle showed physiological stability with little variability from young to elderly adults, with SD of 2.45° and 1.06° in sagittal and coronal planes, respectively. OD-HA angle confirms the hypothesis that the head tends to remain above the pelvis in a small cone of stability. This study provides an analysis of the determinants of OD-HA and the reference range of the head-pelvis balance in each decade and gender based on a large-scale asymptomatic population.

Factors affecting postoperative pulmonary function deterioration in adolescent idiopathic scoliosis: A prospective study using 3-dimensional image reconstruction by biplanar stereoradiography

This study aimed both to evaluate rib cage parameters in patients with adolescent idiopathic scoliosis (AIS) by three-dimensional (3D) image reconstruction using biplanar stereoradiography (EOS) (EOS Imaging, Paris, France) and identify factors associated with postoperative pulmonary function deterioration (PFD). A total of 67 patients with Lenke type 1 or 2 AIS (59 females and 8 males; mean age, 14.4 years) undergoing posterior corrective fusion with a rod rotation maneuver based on segmental pedicle screw fixation were recruited. 3D images and pulmonary function test results were analyzed preoperatively and at 2 years postoperatively. The following parameters were measured: maximum thickness, maximum width, thoracic index, rib hump, rib cage volume (RCV), spinal penetration index (SPI), endothoracic hump ratio (EHR), vertebra-sternum angle (VSA), rib-vertebra angle difference, vertebral lateral decentering (VLD), forced vital capacity (FVC), and percent predicted FVC (%FVC). PFD was defined as a postoperative %FVC decline of 5% or greater. Patients were divided into two groups, namely PFD and non-PFD. FVC increased from 2.62 L to 2.73 L, while %FVC decreased from 88.7% to 82.7%. The maximum width diminished postoperatively in the PFD group. Patients in the PFD group exhibited a significantly smaller increase in RCV and VLD as well as a significantly smaller decrease in SPI, EHR, and VSA than those in the non-PFD group. The rib cage parameters quantified on 3D images reconstructed using EOS are useful in identifying factors affecting PFD in patients with AIS.

Reconstruction of three-dimensional lumbar vertebrae from biplanar x-rays

Objective. Vertebrae models from computer tomographic (CT) imaging are extensively used in image-guided surgical systems to deliver percutaneous orthopaedic operations with minimum risks, but patients may be exposed to excess radiation from the pre-operative CT scans. Generating vertebrae models from intra-operative x-rays for image-guided systems can reduce radiation exposure to the patient, and the surgeons can acquire the vertebrae's relative positions during the operation; therefore, we proposed a lumbar vertebrae reconstruction method from biplanar x-rays.Approach. Non-stereo-corresponding vertebral landmarks on x-rays were identified as targets for deforming a set of template vertebrae; the deformation was formulated as a minimisation problem, and was solved using the augmented Lagrangian method. Mean surface errors between the models reconstructed using the proposed method and CT scans were measured to evaluate the reconstruction accuracy.Main results. The evaluation yielded mean errors of 1.27 mm and 1.50 mm inin vitroexperiments on normal vertebrae and pathological vertebrae, respectively; the outcomes were comparable to other template-based methods.Significance. The proposed method is a viable alternative to provide digital lumbar to be used in image-guided systems, where the models can be used as a visual reference in surgical planning and image-guided applications in operations where the reconstruction error is within the allowable surgical error.

Systematic Review of Reciprocal Changes after Spinal Reconstruction Surgery : Do Not Miss the Forest for the Trees

The purpose of this review was to synthesize the research on global spinal alignment and reciprocal changes following cervical or thoracolumbar reconstruction surgery. We carried out a search of PubMed, EMBASE, and Cochrane Library for studies through May 2020, and ultimately included 11 articles. The optimal goal of a truly balanced spine is to maintain the head over the femoral heads. When spinal imbalance occurs, the human body reacts through various compensatory mechanisms to maintain the head over the pelvis and to retain a horizontal gaze. Historically, deformity correction has focused on correcting scoliosis and preventing scoliotic curve progression. Following substantial correction of a spinal deformity, reciprocal changes take place in the flexible segments proximal and distal to the area of correction. Restoration of lumbar lordosis following surgery to correct a thoracolumbar deformity induces reciprocal changes in T1 slope, cervical lordosis, pelvic shift, and lower extremity parameters. Patients with cervical kyphosis exhibit different patterns of reciprocal changes depending on whether they have head-balanced or trunk-balanced kyphosis. These reciprocal changes should be considered to in order to prevent secondary spine disorders. We emphasize the importance of evaluating the global spinal alignment to assess postoperative changes.

Microdose protocol stereoradiography has similar reliability to standard low-dose protocol during concurrent Sanders skeletal maturity staging

PURPOSE

Decreasing radiation exposure is important for scoliosis patients who require serial imaging. Microdose protocol stereoradiography is now increasingly utilized. Previous studies have reported similar reliability of concurrent Sanders skeletal maturity staging based on standard low-dose stereoradiography and standard hand radiographs. The purpose of our study was to investigate the reliability and radiation exposure of concurrent Sanders staging using microdose protocol compared to a standard protocol for adolescent idiopathic scoliosis. We hypothesized that surgeon-performed Sanders staging would have similar reliability when comparing microdose and standard-dose imaging protocols.

METHODS

A randomized survey of 30 hand images using standard protocol spinal stereoradiography and an equal number from microdose protocol were distributed to six experienced pediatric orthopaedic spine surgeons. Images were graded by each surgeon according to the Sanders skeletal maturity grading system. Items were again randomized and graded after a 2-week interval. Fleiss' weighted kappa for inter and intraobserver reliability was calculated and an unpaired t test was used to test for significance.

RESULTS

Interobserver reliability for all modalities was in the strong to almost perfect agreement (average weighted κ > 0.8) range. For the microdose protocol, κ was 0.82 and 0.84 for each separate round of grading. Standard low-dose protocol κ was 0.83 and 0.79. Intraobserver κ was 0.86 for microdose and 0.82 for standard. Average radiation for microdose was significantly less radiation (82.6%) than standard stereoradiography (0.3 ± 0.1 mGy vs. 1.9 ± 0.4 mGy, p < 0.001).

CONCLUSIONS

Sanders staging reliability of a well-positioned hand during scoliosis stereoradiography was similarly excellent for both microdose and standard low-dose protocol. Microdose protocol used less radiation while still preserving the reliability of Sanders staging.

Investigation of in vivo three-dimensional changes of the spinal canal after corrective surgeries of the idiopathic scoliosis

OBJECTIVE

To determine the three-dimensional (3D) changes of the spinal canal length (SCL) after corrective surgeries and their association with the radiographic and clinical outcomes of idiopathic scoliosis patients. The length of the spinal cord has been demonstrated to be strongly correlated with the SCL. Understanding the changes in SCL could help determine the morphologic changes in the spinal cord to prevent spinal cord injury.

METHODS

Twenty-seven scoliotic patients' 3D spinal canal were investigated using computed tomography images. The SCL between the upper and lower end vertebrae (U/L-EV) was measured at five locations. The radiographic parameters of each patient and the patient-reported outcomes (PROs) scores were also collected. The correlations of the changes of the SCLs with the other factors were analyzed.

RESULTS

The SCL between the U/L-EV changed non-uniformly at different locations. The post-operative SCLs were significantly elongated by 7.5 ± 3.5 mm (6.0 ± 2.5%, P < .001) at the concave side and compressed by -2.6 ± 2.6 mm (-1.9 ± 1.9%, P < .001) at the convex side. The elongations of the SCL at the concave and posterior locations were correlated with the radiographic parameters including the pre-operative main Cobb angles (r = .511, P = .006; r = .613, P = .001) and apical vertebral translation (AVT) (r = .481, P = .011; r = .684, P = .000). No PRO scores were found to correlate with the SCL changes.

CONCLUSION

The corrective surgeries elongated the spinal canal mainly at the concave side and compressed at the convex side. The main thoracic Cobb angle, the changes of AVT, and Cobb angles were moderately associated with the changes of the SCLs, but no PRO score was found to associate with the changes of the SCLs. The data could be instrumental for the improvement of corrective surgeries that are aimed to maximize the correction of scoliosis and minimize the negative effect on the spinal cord to prevent neurological complications.

Credibility assessment of patient-specific biomechanical models to investigate proximal junctional failure in clinical cases with adult spine deformity using ASME V&V40 standard

Computational models are increasingly used to assess spine biomechanics and support surgical planning. However, varying levels of model verification and validation, along with characterization of uncertainty effects limit the level of confidence in their predictive potential. The objective was to assess the credibility of an adult spine deformity instrumentation model for proximal junction failure (PJF) analysis using the ASME V&V40:2018 framework. To assess model applicability, the surgery, erected posture, and flexion movement of actual clinical cases were simulated. The loads corresponding to PJF indicators for a group of asymptomatic patients and a group of PJF patients were compared. Model consistency was demonstrated by finding PJF indicators significantly higher for the simulated PJF vs. asymptomatic patients. A detailed sensitivity analysis and uncertainty quantification were performed to further establish the model credibility.

Clinical assessment and management of Bertolotti Syndrome: a review of the literature

Bertolotti Syndrome is a diagnosis given to patients experiencing pain caused by the presence of a lumbosacral transitional vertebra (LSTV), which is characterized by enlargement of the L5 transverse process(es), with potential pseudoarticulation or fusion with the sacrum. The Castellvi classification system is commonly utilized to grade LSTVs based on the degree of contact between the L5 transverse process(es) and the sacrum. LSTVs present a diagnostic dilemma to the treating clinician, as they may remain unidentified on plain x-rays and even advanced imaging; additionally, even if the malformation is identified, patients with a LSTV may be asymptomatic or have nonspecific symptoms, such as low back pain with or without radicular symptoms. With low back pain being extremely prevalent in the general population; it can be difficult to implicate the LSTV as the source of this pain. Care should be taken however, to exclude Bertolotti Syndrome in patients under 30 years old presenting with persisting low back pain given its congenital origin. If a LSTV is identified, typically with acquisition of a MRI or CT scan of the lumbosacral spine, and there is an absence of a more compelling or obvious source for the patient's symptoms, a conservative, step-wise management plan is recommended. This may include assessing for improvement in symptoms with injections prior to proceeding with surgical intervention. Additional concerns arise from the biomechanical alterations that a LSTV induces in adjacent spinal levels, predisposing this patient population to a more rapid-onset of adjacent segment disease, raising the question as to the most appropriate surgery (resection of LSTV pseudoarticulation with or without fusion). Postoperative outcome data for patients undergoing surgical treatment is limited in the literature with promising, but variable, results. More large-scale, controlled studies must be performed to gain further insight into the ideal work-up and management of this pathology.

Emerging Technologies in Spinal Surgery: Ultra-Low Radiation Imaging Platforms

BACKGROUND

Spine surgery has seen tremendous growth in the past 2 decades. A variety of safety, practical, and market-driven needs have spurred the development of new imaging technologies as necessary tools for modern-day spine surgery. Although current imaging techniques have proven satisfactory for operative needs, it is well-known that these techniques have negative consequences for operators and patients in terms of radiation risk. Several mitigating techniques have arisen in recent years, ranging from lead protection to radiation-reducing protocols, although each technique has limits. A hitherto-problematic barrier has been the fact that efforts to diminish radiation emission come at the cost of reduced image quality.

OBJECTIVE

To describe new ultra-low radiation imaging modalities that have the potential to drastically reduce radiation risk and minimize unacceptable adverse effects.

METHODS

A literature review was performed of articles and studies that used either of 2 ultra-low radiation imaging modalities, the EOS system (EOS-Imaging S.A., Paris, France) and LessRay (NuVasive, San Diego, CA).

RESULTS

Both ultra-low radiation imaging modalities reduce radiation exposure in the preoperative and perioperative settings. EOS provides 3-dimensional reconstructive capability, and LessRay offers intraoperative tools that facilitate spinal localization and proper visual alignment of the spine.

CONCLUSION

These novel radiation-reducing technologies diminish patient and surgeon exposure, aid the surgeon in preoperative planning, and streamline intraoperative workflow.

Changes in peri-apical vertebral body and intervertebral disc shape in both the sagittal and coronal planes correlate with scoliosis severity: a 3D study of 397 patients

PURPOSE

To evaluate associations between vertebrae and disc shape asymmetry and adolescent idiopathic scoliosis (AIS) curve severity.

METHODS

Analysis included normal screening referrals and patients with right, main thoracic AIS who underwent upright, biplanar radiographs with 3D reconstruction at a single institution from 2010 to 2015. Peri-apical anterior, posterior, right, and left vertebral body heights (aVBH, pVBH, rVBH, lVBH) and intervertebral disc heights (DH) were measured, and ratios of these measurements were calculated in sagittal and coronal planes. Correlations were performed between curve severity and height measurements. Sagittal and coronal plane components of these measurements were compared between normal controls with coronal curve measurements < 11° and patients with moderate (11°-49°) and severe curves (≥ 50°), with tolerance intervals established for the normal controls.

RESULTS

The analysis included a total of 397 patients. Patients with AIS had coronal curve measurements ranging from 11° to 101°. Greater coronal curve severity strongly correlated with smaller pVBH relative to aVBH and moderately correlated with smaller pDH relative to aDH (r = - 0.643, r = - 0.305, respectively). aVBH was greater for larger curves; pVBH remained stable. Scoliosis severity strongly correlated with right relative to left VBH and DH ratios (r = 0.919, r = 0.865 respectively). In comparison of normal controls to severe curves, severe curves had significantly greater aVBH and aDH, while pVBH was not significantly different and pDH was significantly less. Nearly half (46.9%) of the severe curves were below the range of normal for PA vertebral height ratio.

CONCLUSION

In right, main thoracic AIS, greater main thoracic curve severity is associated with greater sagittal and coronal plane asymmetry of both the vertebral bodies and the discs. Severity more strongly correlates with vertebral changes in symmetry than with disc changes, though both are present.

3D ultrasound imaging provides reliable angle measurement with validity comparable to X-ray in patients with adolescent idiopathic scoliosis

BACKGROUND & OBJECTIVE

The application of ultrasound imaging for spine evaluation could minimize radiation exposure for patients with adolescence idiopathic scoliosis (AIS). A customized three-dimensional (3D) ultrasound imaging system has been demonstrated to provide reliable and valid coronal curvature measurements. However, these measurements were using the spinous processes as anatomical reference, leading to a predictable underestimation of the traditionally used Cobb angles. An alternative 3D ultrasound image reconstruction method was applied to create coronal images with more lateral features for angle measurement. The objective of this study was to test the reliability and the validity of this angle, the ultrasound curve angle (UCA), and compare the UCA with the Cobb angles on X-ray images of patients with AIS.

MATERIALS AND METHODS

This study was divided into: 1) Investigation of intra- and inter-reliability between two raters for measuring the UCA and two operators for acquiring ultrasound images; 2) Investigation of the validity between the radiographic Cobb angle and the UCA. Fifty patients and 164 patients with AIS, were included in the two stages, respectively. Patients underwent bi-planar X-ray and 3D ultrasound scanning on the same day. The proposed UCA was used to measure the coronal curvature from the ultrasound coronal images, which were formed using a newly customized volume projection imaging (VPI) method. The intra-rater/operator and inter-rater and operator reliability of the UCA were tested by intra-class correlation coefficient (ICC) (3,1) and (2,1), respectively. The validity of UCA measurements as compared to radiographic Cobb angles was tested by inter-method ICC (2,1), mean absolute difference (MAD), standard error of measurement (SEM), Pearson correlation coefficient and Bland-Altman statistics. The level of significance was set as 0.05.

RESULTS

Excellent intra-rater and intra-operator (ICC (3,1)≥0.973) and excellent inter-rater and inter-operator reliability (ICC (2,1)≥0.925) for UCA measurement, with overall MAD and SEM no more than 3.5° and 1.7° were demonstrated for both main thoracic and (thoraco)lumbar curvatures. Very good correlations were observed between UCA and Cobb angle for main thoracic (R 2 =0.893) and (thoraco)lumbar (R 2 =0.884) curves. The mean (SD) measurements in terms of radiographic Cobb and UCA were 27.2 ​± ​11.6° and 26.3 ​± ​11.4° for main thoracic curves; and 26.2 ​± ​11.4° and 24.8 ​± ​9.7° for (thoraco)lumbar curve respectively. One hundred sixty-four subjects (33 male and 131 female subjects; 11-18 years of age, mean of 15.1 ​± ​1.9 years) were included for the validity session. Excellent inter-method variations (ICC (2,K) ≥0.933) with overall MAD and SEM no more than 3.0° and 1.5° were demonstrated for both main thoracic and (thoraco)lumbar curvatures. In addition, Bland-Altman plots demonstrated an acceptable agreement between ultrasound and radiographic Cobb measurements.

CONCLUSION

In this study, very good correlations and agreement were demonstrated between the ultrasound and X-ray measurements of the scoliotic curvature. Judging from the promising results of this study, patients with AIS with different severity of curves can be evaluated and monitored by ultrasound imaging, reducing the usage of radiation during follow-ups. This method could also be used for scoliosis screening.The Translational potential of this article: Ultrasound curve angle (UCA) obtained from 3D ultrasound imaging system can provide reliable and valid evaluation on coronal curvature for patients with AIS, without the need of radiation.

Visualization of the Cervicothoracic Junction With EOS Imaging Is Superior to Conventional Lateral Cervical Radiographs

STUDY DESIGN

Single-center retrospective review.

OBJECTIVES

The cervicothoracic junction (CTJ) is typically difficult to visualize using traditional radiographs. Whole-body stereoradiography (EOS) allows for imaging of the entire axial skeleton in a weightbearing position without parallax error and with lower radiation doses. In this study we sought to compare the visibility of the vertebra of the CTJ on lateral EOS images to that of conventional cervical lateral radiographs.

METHODS

Two fellowship-trained spine surgeons evaluated the images of 50 patients who had both lateral cervical radiographs and EOS images acquired within a 12-month period. The number of visible cortices of the vertebral bodies of C6-T2 were scored 0-4. Patient body mass index and the presence of spondylolisthesis >2 mm at each level was recorded. The incidence of insufficient visibility to detect spondylolisthesis at each level was also calculated for both modalities.

RESULTS

On average, there were more visible cortices with EOS versus XR at T1 and T2, whereas visible cortices were equal at C6 and C7. Patient body mass index was inversely correlated with cortical visibility on XR at T2 and on EOS at T1 and T2. There was a significant difference in the incidence of insufficient visibility to detect spondylolisthesis on EOS versus XR at C7-T1 and T1-2, but not at C6-7.

CONCLUSIONS

EOS imaging is superior at imaging the vertebra of the CTJ. EOS imaging deserves further consideration as a diagnostic tool in the evaluation of patients with cervical deformity given its ability to produce high-quality images of the CTJ with less radiation exposure.

Don't forget the pelvis: accounting for pelvic rotation in the preoperative assessment of adolescent idiopathic scoliosis

Background

Accurate radiographic assessment of adolescent idiopathic scoliosis (AIS) is crucial to achieving surgical correction, yet pelvic rotation may alter measurements. In Lenke Type 1/2 AIS patients, we conducted a pilot study to assess how pelvic rotation (i.e., the patient's position in the X-ray scanner) affected sagittal, coronal, and rotational measurements.

Methods

A retrospective, pilot study of Type 1/2 AIS patients was undertaken. Demographics and three-dimensional (3D) SterEOS imaging were obtained. Measurements were compared between two scenarios: (I) radio plane-patient's natural position in the scanner; and (II) patient plane-patient's position after correcting to the transverse plane. Sagittal, coronal, and rotational measurements were compared, including: thoracic kyphosis (TK), lumbar lordosis (LL), main thoracic (MT) and thoracolumbar/lumbar (TL-L) Cobb, and apical vertebral rotation (AVR) in the proximal thoracic (PT), MT, and TL/L regions.

Results

Of 15 patients, average age was 15.7 years and 67% were female. Average baseline pelvic obliquity was 4.0 mm and pelvis rotation was 5.1°. Significant differences were seen between the radio vs. patient plane, respectively, in the following three measurements: TK, LL, and AVR: (I) TK (T1-12: 36.5° vs. 32.8°, P=0.003; T4-12: 28.4° vs. 22.7°, P<0.001); (II) LL (L1-5: 46.6° vs. 42.8°, P=0.002; L1-S1: 58.2° vs. 55.1°, P=0.003); (III) AVR (PT-AVR: 4.0° vs. 8.2°, P=0.003; MT-AVR: -14.8° vs. -10.5°, P=0.004; TL/L-AVR: (4.5° vs. 8.7°, P=0.003). No significant differences were seen in coronal cobb angles.

Conclusions

After accounting for pelvic rotation, sagittal and rotational measurements were significantly altered. These results have implications for measurement accuracy, surgical decision-making, and postoperative monitoring.

Incidental extraspinal imaging findings on adult EOS full body radiographs: prevalence and clinical importance

Purpose

The purpose of this study was to review our institutional experience with the EOS machine in order to identify the incidence and clinical significance of incidental extraspinal findings (IESF) in an adult spinal deformity population.

Methods

Our institutional database was queried for all full-length standing radiographs generated by the EOS machine. Dictations were reviewed and the number of incidental extraspinal findings were classified using a previously described system. All findings related to the spine were excluded. A subset of electronic medical records were reviewed to determine further workup for individual findings of suspected clinical significance.

Results

Original database query based on radiology reports returned a total of 1857 EOS studies. Duplicate studies, studies without the entire body, and patients with more than 1 study during the search period were excluded. 503 patient studies (55.5% female, mean age 59-years-old, range 18 to 91-years-old) met inclusion criteria. The overall rate of incidental extraspinal findings in our study was 60.4% (304 findings in 503 patients). Most findings were classified as Minor. The rate of Major and Moderate findings was 4.8%. The final rate of clinically significant incidental extraspinal findings was 0.8% and included 3 presumed metastatic lesions in long bones and 1 pulmonary nodule.

Conclusion

To our knowledge this is the first study that reports the rate of incidental extraspinal findings on full body EOS studies. We report a low rate (0.8%) of clinically significant incidental extraspinal findings which is lower than that of CT or MRI. Further research is warranted in comparing EOS and standard radiography.

Adolescent idiopathic scoliosis 3D vertebral morphology, progression and nomenclature: a current concepts review

PURPOSE

There has been a recent shift toward the analysis of the pathoanatomical variation of the adolescent idiopathic scoliosis (AIS) spine with the three dimensions, and research of level-wise vertebral body morphology in single anatomical planes is now replete within the field. In addition to providing a precise description of the osseous structures that are the focus of instrumented surgical interventions, understanding the anatomical variation between vertebral bodies will elucidate possible pathoaetiological mechanisms of the onset of scoliotic deformity.

METHODS

This review aimed to discuss the current landscape of AIS segmental vertebral morphology research and provide a comprehensive report of the typical patterns observed at the individual vertebral level.

RESULTS

We have detailed how these vertebrae are typically characterised by lateral wedging to the convexity, have a marked degree of anterior overgrowth, are rotated towards the convexity, have inherent gyratory mechanical torsion created within them and are associated with pedicles on the concave side being narrower, longer and more laterally angled. For the most part, these findings are most pronounced at and around the apex of a scoliotic curve, with these deformations reducing towards junctional vertebrae. We have also summarised a nomenclature defined by the Scoliosis Research Society, highlighting the need for more consistent reporting of these level-wise dimensional anatomical changes.

CONCLUSION

Finally, we emphasised how a marked degree of heterogeneity exists between the included investigations, namely in scoliotic curve-type inclusion, imaging modality and timepoint of analysis within scoliosis' longitudinal development, and how improvement in these study design characteristics will enhance ongoing research.

How do spine instrumentation parameters influence the 3D correction of thoracic adolescent idiopathic scoliosis? A patient-specific biomechanical study

BACKGROUND

Patient-specific models promises to support the surgical decision-making process, particularly in adolescent idiopathic scoliosis. The present computational biomechanical study investigates how specific instrumentation parameters impact 3D deformity correction in thoracic scoliosis.

METHODS

1080 instrumentation simulations of a representative patient were run. The independent instrumentation parameters were: screw pattern, upper and lower instrumented vertebrae, rod curvature and rod stiffness. ANOVA and correlation analyses analyzed how the instrumentation parameters influenced the 3D correction.

FINDINGS

Coronal plane correction was affected by the lower instrumented vertebra and rod stiffness (explaining 84% and 11%, respectively, of its overall variance). The sagittal profile was controlled by rod curvature and the upper vertebra (56% and 36%). The transverse plane vertebral rotation was influenced by lower, upper instrumented vertebra and screw pattern (35%, 32% and 19%). The Cobb angle correction was strongly correlated with the number of fused vertebrae, particularly when grouped by the upper instrumented vertebra (r = -0.91) and rod stiffness (r = -0.73). Thoracic kyphosis was strongly correlated with the number of fused vertebrae grouped by rod curvature (r = 0.84). Apical vertebral rotation was moderately correlated with the number of fused vertebrae grouped by upper/lower instrumented vertebra (r = 0.55/0.58), although variations were minimal.

INTERPRETATION

Instrumenting the last vertebra touching the central sacral vertical line improves 3D correction. A trade-off between a more cranial vs. caudal upper instrumented vertebra, respectively beneficial for coronal/sagittal vs. transverse plane correction, is required. High rod stiffness, differential rod contouring, and screw pattern were effective for coronal correction, thoracic kyphosis, and axial vertebral derotation, respectively.

Image Distortion in Biplanar Slot Scanning: Part 2 Technology-specific Factors

BACKGROUND

Biplanar digital slot scanning technology has become the standard of care in the treatment of scoliosis. Yet, the amount of distortion and reproducibility of this type of imaging modality has yet to be fully investigated. In our paper "Image distortion in biplanar slot scanning: part 1 patient-specific factors" we found that there was potentially clinically impactful interimage distortion. The purpose of this study was to evaluate the degree to which this image distortion was secondary to the image acquisition process.

METHODS

Four 25 mm radio-opaque markers were placed at C3, T1, T12, and L5 on a full-length skeleton model. The skeleton was imaged in 10 different positions within the scanner. Five posteroanterior and 5 lateral images were obtained in each position. Two orthopaedic attending physicians and 3 orthopaedic resident physicians measured the markers for a total of 3200 measurements. Intraclass correlation coefficients (ICCs) and 95% confidence intervals were used to examine image distortion.

RESULTS

Average marker size was 24.77, with a standard error of measurement of 0.00493. Image distortion and standard error of measurement accounted for ∼0.5% to 1.5% of total the measurement. Overall, there was good reliability and consistency when looking at markers in different views (ICC 0.790), planes, and locations within the image. Horizontal measurements were found to be more consistent and have better reliability (ICC 0.881) than vertical measurements (ICC 0.386). Position within the scanner had minimal impact on the accuracy of the measurements.

CONCLUSIONS

This study demonstrates that there is minimal error due to image acquisition and measurement when using a biplanar slot scanner. Biplanar slot scanning technology tended to underestimate the size of the marker; however, the least accurate measurements only erred by 1.5% from the true length. This indicates that unlike traditional radiographs the sources of error in biplanar slot scanning images are not due to parallax and are likely due to patient-specific factors and rather than the technology itself.

Predictors of spontaneous lumbar curve correction in thoracic-only fusions: 3D analysis in AIS

PURPOSE

To evaluate how 3D parameters of the instrumented thoracic spine relate to the uninstrumented lumbar spine following thoracic-only fusion (TOF) for adolescent idiopathic scoliosis (AIS) and determine the factors predictive of lumbar correction.

METHODS

A multi-center retrospective review was conducted of AIS patients with Lenke 1-4 B or C curves undergoing fusion of their thoracic spine only with minimum 2-year follow-up and 3D spine reconstructions from biplanar radiography. Pre-operative to 2-year post-operative differences were evaluated. Pearson's correlations were used to identify 3D coronal, sagittal and axial relationships at 2 years post-operative. Multivariate linear regression was used to identify variables most predictive of lumbar curve correction.

RESULTS

Eighty-four AIS patients met inclusion (54 B modifiers, 30 C modifiers). Average pre-operative thoracic and lumbar curves were 54 ± 9° and 41 ± 7° and corrected to 19 ± 7° and 21 ± 7°, respectively. 3D T5-T12 thoracic kyphosis increased from 6 ± 13° to 26 ± 8°. Thoracic and lumbar apical rotation decreased from - 14 ± 6° to -5 ± 6° and 13 ± 5° to 11 ± 6°, respectively. Thoracic curve correction correlated with lumbar curve correction (r = 0.67, p = 0.001) and decreased LIV tilt correlated with smaller residual lumbar curve magnitude (r = 0.63, p < 0.001). Increasing 3D kyphosis of the instrumented segment correlated with increased percentage lumbar curve correction (r = 0.29, p = 0.009). Multivariate linear regression showed LIV tilt and thoracic curve magnitude as the most predictive variables of post-operative residual lumbar curve magnitude, and percent correction of the thoracic curve and change in 3D instrumented kyphosis as most predictive of percent correction of the lumbar curve.

CONCLUSIONS

Analysis of 3D data highlights several considerations for AIS patients undergoing TOF. Maximizing thoracic curve correction, leveling the LIV, and to a lesser extent, restoring kyphosis in the instrumented segment are the factors most likely to result in greater correction of the instrumented lumbar curve following thoracic-only fusions in Lenke 1-4 B and C curves.

Three-Dimensional Analysis of Preoperative and Postoperative Rib Cage Parameters by Simultaneous Biplanar Radiographic Scanning Technique in Adolescent Idiopathic Scoliosis: Minimum 2-Year Follow-Up

STUDY DESIGN

Prospective study.

OBJECTIVE

This study aimed to investigate the changes in rib cage deformity in adolescent idiopathic scoliosis (AIS) by comparing the preoperative and postoperative three-dimensional (3D) reconstruction images using simultaneous biplanar radiographic scanning technique (EOS) (EOS Imaging, Paris, France).

SUMMARY OF BACKGROUND DATA

EOS data are limited for the analyses of preoperative and postoperative rib cage deformity.

METHODS

A total of 67 Lenke type 1 or 2 AIS patients who underwent surgery (59 females and 8 males) were enrolled in this study. The mean patient age was 14.4 years (range: 11-17 yr). In all patients, posterior corrective fusion was performed with a rod rotation maneuver based on segmental pedicle fixation. Spinal parameters (scoliosis and kyphosis) and rib cage parameters (max thickness, thoracic index (TI), rib hump (RH), surface spinal penetration index (sSPI), end thoracic hump ratio, vertebra-sternum angle, rib vertebral angle difference at the apex, and vertebral lateral decentering), were measured. 3D images were assessed preoperatively and postoperatively at 2-year follow-up.

RESULTS

Both main thoracic (MT) and proximal thoracic scoliosis were significantly corrected (51° to 15°, 30° to 17°, P < 0.0001). The rotation of MT apical vertebrae was also significantly corrected (12° to 5°, P < 0.0001). Thoracic kyphosis (T4-T12) significantly increased (13° to 18°, P < 0.0001). Besides, max thickness, TI, and RH demonstrated significant differences between preoperative and postoperative images (P < 0.01). T8-10 sSPI and end thoracic hump ratio decreased significantly postoperatively (P < 0.05). Although surgery significantly decreased vertebra-sternum angle (P < 0.0001), no significant difference was observed between the preoperative and postoperative rib vertebral angle difference (P = 0.32). Following the surgery, vertebral lateral decentering and rib cage volume were significantly increased (P < 0.0001).

CONCLUSIONS

3D reconstruction of the rib cage using biplanar standing stereoradiography is useful to evaluate preoperative and postoperative rib cage deformity in patients with AIS.Level of Evidence: 2.

Accuracy of EOS Imaging Technology in Comparison to Computed Tomography in the Assessment of Vertebral Rotational Orientation in Instrumented Spines in Adolescent Idiopathic Scoliosis

STUDY DESIGN

Retrospective radiographic reliability study.

OBJECTIVE

The aim of this study was to assess the validity of EOS 3D imaging technology in the determination of vertebral rotations in the spine of patients with previous instrumentation.

SUMMARY OF BACKGROUND DATA

There is a lack of evidence on the accuracy of vertebral rotational measurement using EOS 3D morphological analysis in the instrumented spine.

METHODS

A retrospective review of 31 patients with adolescent idiopathic scoliosis (AIS) who underwent instrumented fusion and postoperative computed tomography (CT) scans of the spine was performed. Vertebral rotations of the apex vertebra, the uppermost (UIV) and lowermost (LIV) instrumented vertebra, the noninstrumented vertebra one level cranial to the UIV (UIV + 1) and one level caudal to LIV (LIV + 1) were determined using EOS 3D reconstruction. The vertebral rotation was also measured using reformatted CT axial images. Relative vertebral rotational difference (VRD) were calculated for UIV to apex, UIV + 1 to apex, LIV to apex, LIV + 1 to apex, UIV to LIV and UIV + 1 to LIV + 1. Paired t tests were used to compare the VRD measured using the two different imagining modalities. For values where P > 0.05, the Bland-Altman plot was used to assess the agreement between the measures. Interclass correlation (ICC) was used to determine interobserver and intraobserver reliabilities of EOS and CT measurements.

RESULTS

EOS analysis of relative VRD was found to be significantly different from that of CT for UIV to apex (P = 0.006) and UIV + 1 to apex (P = 0.003). No significant differences were found for LIV to apex (P = 0.06), LIV + 1 to apex (P = 0.06), UIV to LIV (P = 0.59) and UIV + 1 to LIV + 1 (P = 0.64). However, Bland-Altman plots showed that agreement was poor, and variance was beyond acceptable. ICC showed good interobserver and good to very good intraobserver reliability for EOS.

CONCLUSION

EOS 3D morphological analysis of VRD in the instrumented levels of the spine demonstrated significant difference and unacceptable variance in comparison to CT measurement.Level of Evidence: 4.

Brace Effectiveness Is Related to 3-Dimensional Plane Parameters in Patients with Adolescent Idiopathic Scoliosis

BACKGROUND

Although scoliosis is a 3-dimensional (3D) deformity, little research has been performed on the use of 3D imaging in brace curve correction. The purpose of the present study was to determine the effect of axial-plane parameters on the outcomes of bracing with a thoracolumbosacral orthosis for adolescent idiopathic scoliosis.

METHODS

This prospective longitudinal cohort study included patients with adolescent idiopathic scoliosis who fulfilled the criteria for bracing according to the Scoliosis Research Society, and was conducted from the time the patient began wearing the brace through a minimum follow-up of 2 years or until a surgical procedure was performed. Radiographs made with use of an EOS Imaging System were used to reconstruct 3D images of the spine at the pre-brace, immediate in-brace, 1-year in-brace, and latest follow-up out-of-brace stages. Univariate and multiple linear regressions were performed to determine the association between axial rotation correction and curve progression at the time of the latest follow-up. Logistic regressions were performed to model the probability of risk of progression.

RESULTS

Fifty-three patients were enrolled, and 46 patients were included in the analysis. At the time of the latest follow-up, 30 patients did not experience curve progression and 16 patients had curve progression. There was no difference in baseline demographic characteristics between groups. For the transverse-plane parameters, there was a significant difference between non-progression and progression groups in pre-brace apical vertebral rotation (4.5° ± 11.2° compared with -2.4° ± 9.8°, respectively; p = 0.044) and in 1-year in-brace apical vertebral rotation correction velocity (2.0° ± 5.0°/year compared with -1.7° ± 4.4°/year, respectively; p = 0.016). Logistic regression analysis showed that pre-brace apical vertebral rotation (odds ratio, 1.063; 95% confidence interval, 1.000 to 1.131; p = 0.049) and 1-year in-brace apical vertebral rotation correction velocity (odds ratio, 1.19; 95% confidence interval, 1.021 to 1.38; p = 0.026) were associated with an increased risk of curve progression. There was no difference in Scoliosis Research Society 22-Item scores between patients who experienced curve progression and those who did not.

CONCLUSIONS

In this prospective study, we demonstrated that axial-plane parameters and the correction of these parameters during bracing are related to the successful use of the brace.

LEVEL OF EVIDENCE

Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

In silico patient-specific optimization of correction strategies for thoracic adolescent idiopathic scoliosis

BACKGROUND

With modelling and simulation (or in silico) techniques, patient-specific optimization algorithms represent promising tools to support the surgical decision-making process, particularly in 3D correction of adolescent idiopathic scoliosis, where the best intraoperative instrumentation strategy and the correction goals are debated.

METHODS

1080 biomechanical intraoperative simulations of a representative pediatric thoracic curve were run according to a full-factorial design approach. Widely accepted instrumentation configurations (5 screw patterns, 4 upper and 3 lower instrumented vertebrae, 6 rod curvatures and 3 rod stiffnesses) were analyzed, assuming concave rod rotation and en bloc derotation as main correction maneuvers. Results in terms of 3D correction and mobility were rated using an objective function for thoracic scoliosis also including surgeon-dependent correction objectives. An extensive sensitivity analysis on correction objectives was performed.

FINDINGS

Multiple optimal strategies were identified, depending on the selected correction objective. They provided significantly better coronal (67% vs. 55%) correction, using comparable instrumented levels (9.9 ± 1.6 vs. 10.7 ± 2.1), screw patterns and significantly higher implant density (1.6 ± 0.3 vs. 1.4 ± 0.2 screws/vertebra) compared to worst ones. Optimal strategies typically included the neutral and the last touching vertebrae in the construct and high stiffness (CoCr, 6 mm) differentially/highly contoured rods.

INTERPRETATION

The computerized algorithm determined the best instrumentation parameters to achieve optimal correction for the considered thoracic case. Multiple clinically equivalent strategies may be used, as supported by the variety of considered correction objectives. The current approach could be translated to any scoliotic curves, including surgeon preferences in terms of instrumentation parameters, intraoperative correction maneuvers and correction objectives.

Associations between three-dimensional measurements of the spinal deformity and preoperative SRS-22 scores in patients undergoing surgery for major thoracic adolescent idiopathic scoliosis

STUDY DESIGN

Retrospective study.

OBJECTIVE

To analyze the relationships between three-dimensional (3D) measurements of spinal deformity and Scoliosis Research Society-22 (SRS-22) scores in preoperative patients with major thoracic adolescent idiopathic scoliosis (AIS). Previous studies reported 2D measurements were not or only weakly correlated with preoperative SRS-22 scores. However, 2D measures do not always accurately represent the 3D deformity.

METHODS

A multicenter prospective registry of surgically treated AIS patients was reviewed for patients with right major thoracic AIS (Lenke type 1-4) who underwent biplanar radiography and completed the SRS-22 questionnaire preoperatively. For the 3D measurements, two reference frames were utilized: global (gravity/patient-based) and local (vertebra/disc-based). To obtain regional measurements, the individual segments in the appropriate reference plane were summed between the levels of interest. Patients were divided into two groups for each SRS-22 domain according to their scores: low (< 4) and high (≥ 4) score groups. Group differences and correlations with SRS-22 scores were analyzed with p < 0.01 as the threshold for significance.

RESULTS

There were 405 eligible patients (mean age, 14.4 years). The mean 3D thoracic curve was 59° (45°-115°). The only significant group difference of 3D measurements occurred in the local lumbar lordosis (LL) with a small mean difference (- 3.4°, p = 0.008) in the mental health domain. In the correlation analyses, global and local thoracic kyphosis (TK) and TK/LL ratio demonstrated significant, but weak, correlations with function and total scores (|r|< 0.2, p < 0.01).

CONCLUSION

3D measurements of scoliosis severity have only weak associations with preoperative SRS-22 scores, which might indicate a limit to the discriminative capacity of the SRS-22 within surgical range major thoracic AIS curves. Interestingly, the sagittal plane was the principle 3D plane in which significant correlations existed.

LEVEL OF EVIDENCE

II, prognostic.

More severe thoracic idiopathic scoliosis is associated with a greater three-dimensional loss of thoracic kyphosis

STUDY DESIGN

Retrospective.

OBJECTIVES

Utilize three-dimensional (3D) measurements to assess the relationship between thoracic scoliosis severity and thoracic kyphosis in a large, multicenter cohort, and determine impact of 3D measurements on adolescent idiopathic scoliosis (AIS) curve classification. Research has demonstrated differences in two-dimensional (2D) and 3D assessment of the sagittal plane deformity in AIS. A prior smaller, single-institution study demonstrated an association between scoliosis severity and loss of 3D thoracic kyphosis.

METHODS

Data included retrospective compilation of prospectively enrolled bracing candidates and prospectively enrolled surgical candidates with thoracic AIS. Analysis included two groups based on thoracic curve magnitude: moderate (20-45°) and severe (> 45°). Imaging was performed using 2D radiographs. 3D thoracic kyphosis was calculated using a 2D to 3D conversion formula. Kyphosis was categorized according to the Lenke classification sagittal plane modifier.

RESULTS

Analysis included 3032 patients. 2D kyphosis was significantly less in the moderate group (21 ± 12 vs 23 ± 14, p = 0.028). However, estimated 3D kyphosis was significantly greater in the moderate group (13 ± 10 vs 5 ± 12, p < 0.001). In the moderate group, the rate of normokyphosis was 78% with 2D measures and 61% with 3D measures of T5-T12 kyphosis. In the severe group, this rate changed from 72 to 32% with use of 2D and 3D measures, respectively. In the moderate group, 16% of patients were classified as hypokyphotic using 2D measures while this rate increased 38% with 3D measures (p < 0.001). In the severe group, this rate changed from 18 to 68% using 2D and 3D measures, respectively (p < 0.001).

CONCLUSIONS

Increased coronal curve severity was associated with decreased thoracic kyphosis. Hypokyphosis was more pronounced in 3D. 2D radiographs increasingly underestimate kyphosis with increasing coronal severity. Assessment of sagittal alignment from 2D radiographs can be improved with a 2D-3D conversion formula. Findings indicate potential for classification system improvement with use of 3D sagittal plane measurements.

LEVEL OF EVIDENCE

IV.