Analysis of the Sagittal Balance of the Spine and Pelvis Using Shape and Orientation Parameters

Strategies for Minimizing the Effects of Observer Variability on Sagittal Parameter Measurements of the Spine

STUDY DESIGN

Exploratory-descriptive study.

OBJECTIVE

Evaluate the influence of observer variability on the measurements of both thoracic kyphosis (TK) and lumbar lordosis (LL) obtained with anatomic and functional spinal segmentation methods.

BACKGROUND

Parametric analysis for spinal surgery planning typically relies on anatomic parameters. However, incorporating functional parameters that consider the vertebrae orientation is important to minimizing surgical calculation errors.

METHODS

The authors developed parametric analysis software that integrates traditional and functional methodologies. The proposed method included functional thoracic kyphosis and functional lumbar lordosis calculated from the lines normal to the inflection points of the spine model. Using a synthetic lateral X-ray, the observer variability was computer-simulated generating 20 landmark sets that replicate the annotations of 20 observers. The analysis also included 10 clinical X-rays, annotated twice by 3 judges with a minimum 1-week interval. The spinal curvature angles were derived using the anatomic and functional methods. Statistical analysis were performed for comparison.

RESULTS

For the synthetic X-ray, the proposed method presented significantly less variability: TK (<±2.5 degrees, P=0.00023) and LL (<±5 degrees, P=0.00012). For the clinical X-rays, the interobserver reliability analysis yielded higher intraclass correlation coefficients (ICC) for functional TK (ICC>0.97) and functional LL (ICC>0.87) than for TK (ICC<0.91) and LL (ICC<0.89). Statistically significant differences were observed for both TK (P=0.001) and LL (P=0.030). Under the traditional method, observer variability led to measurement differences surpassing ±19 degrees, whereas differences with the proposed method were within ±10 degrees for both parameters.

CONCLUSION

The vertebral endplate is not the most suitable place to measure spinal sagittal curvatures. Small changes in landmark position significantly alter the measured Cobb angle. The proposed method offers a substantial advantage regarding the influence of observer variability, in addition to the more individualized analysis.

Simulative investigation of the required level of geometrical individualization of the lumbar spines to predict fractures

Injury mechanisms of the lumbar spine under dynamic loading are dependent on spine curvature and anatomical variation. Impact simulation with finite element (FE) models can assist the reconstruction and prediction of injuries. The objective of this study was to determine which level of individualization of a baseline FE lumbar spine model is necessary to replicate experimental responses and fracture locations in a dynamic experiment.Experimental X-rays from 26 dynamic drop tower tests were used to create three configurations of a lumbar spine model (T12 to L5): baseline, with aligned vertebrae (positioned), and with aligned and morphed vertebrae (morphed). Each model was simulated with the corresponding loading and boundary conditions from dynamic lumbar spine experiments. Force, moment, and kinematic responses were compared to the experimental data. Cosine similarity was computed to assess how well simulation responses match the experimental data. The pressure distribution within the vertebrae was used to compare fracture risk and fracture location between the different models.The positioned models replicated the injured spinal level and the fracture patterns quite well, though the morphed models provided slightly more accuracy. However, for impact reconstruction or injury prediction, the authors recommend pure positioning for whole-body models, as the gain in accuracy was relatively small, while the morphing modifications of the model require considerably higher efforts. These results improve the understanding of the application of human body models to investigate lumbar injury mechanisms with FE models.

Quantifying the Spinal Lordosis Ratio Unique to the Type of Spinal Sagittal Alignment in a Normal Population

STUDY DESIGN

Data collection of radiological parameters in non-pathological adult spines.

OBJECTIVES

Establishing a baseline database for measurements of the spinal lordosis ratio between upper and lower arcs of the lumbar spine unique to each type of spine described by Roussouly's classification. Illustrating the importance of correct rationing of the upper and lower arcs.

METHODS

Standardised standing true lateral plain radiographs of the spine (including base of skull and proximal femurs) from 373 adult volunteers were obtained. Exclusion criteria : any history of disease involving the spine, pelvis, hips or lower limbs. Incidental detection of any spinal deformity on radiography also excluded further participation in this study. Sacro-pelvic parameters data collected : Pelvic Incidence (PI), Pelvic Tilt (PT), Sacral Slope (SS), location of Inflection Point, number of vertebras in the spinal lordosis and type of Roussouly's spine. Values of upper arc, lower arc and spinal lordosis ratio (SLR) was determined.

RESULTS

Bivariate analysis revealed statistically significant (P < .0001) correlation between the types of sagittal spinal alignments based on Roussouly's classification and the SLR. Type 1: SLR .76 ± .17, Type 2: SLR .60 ± .18, Type 3 with anteverted pelvis: SLR .53 ± .11, Type 3: SLR .49 ± .12, Type4: SLR .41 ± .11.

CONCLUSION

With this data we are able to quantify the ratio of lumbar lordosis unique to each type of Roussouly's spine. It functions as a guide when planning lumbar spine surgeries in order to restore the SLR correctly and thus prevent post-op complications such as proximal junction kyphosis.

L1 slope: an overlooked spinal parameter

OBJECTIVE

Lumbar lordosis can be divided into two parts by a horizontal line, creating the L1 slope and the sacral slope. Despite being a major spinopelvic parameter, the L1slope (L1S) is rarely reported. However, there is some evidence that L1S is a relatively constant parameter. This study aimed to analyze the L1 slope and its relationships with other spinopelvic parameters.

METHODS

Standing lateral lumbosacral x-ray radiographies of 76 patients with low back pain and CT scans of 116 asymptomatic subjects were evaluated for spinal and spinopelvic parameters including L1 slope (L1S). The x-ray and CT groups were divided into subgroups according to mean sacral slope (SS) or pelvic incidence (PI) values. The mean values of the spinopelvic parameters and the correlations between them were investigated and compared.

RESULTS

L1S was 19.70 and 18.15 in low SS and high SS subgroups of x-ray respectively. L1S was 7.95 and 9.36 in low and high PI subgroups of CT, respectively, and the differences were insignificant statistically. L1S was the only spinal parameter that did not change as SS or PI increased in standing and supine positions. L1S was correlated with lumbar lordosis (LL) proximal lumbar lordosis (PLL) and distal lumbar lordosis (DLL) in both x-ray and CT groups. L1S was also the strongest correlated parameter with pelvic incidence lumbar lordosis mismatch (PI-LL) mismatch in supine position.

CONCLUSIONS

L1S is a relatively constant parameter and is around 16°-18° and 8°-9° in the standing and supine positions, respectively. It was significantly correlated with LL, PLL, DLL, and PI-LL. In the standing position it was nearly equal to PLL while this equality was present in low PI subgroups of CT. There is strong evidence that L1S is significantly correlated with health-related quality of life scores.

Impact of pelvic anteversion on spinopelvic alignment in an asymptomatic population: a dynamic perspective of standing and sitting

BACKGROUND CONTEXT

A subgroup of patients with pelvic anteversion can present with an unusually large degree of lumbar lordosis (LL), a highly sloped sacrum, and a relatively small pelvic incidence (PI). Prior to lumbar surgery, it can be important to consider such unique sagittal alignment. However, until now, there has been a lack of a predictive model considering different pelvic alignments. Furthermore, the dynamic characteristics of an anteverted pelvis (AP) subgroup have also been unclear.

PURPOSE

To build linear predictive formulas for LL that take pelvic anteversion into consideration and to explore the dynamic characteristics of an AP subgroup.

STUDY DESIGN

Monocentric, cross-sectional study.

PATIENT SAMPLE

Five hundred and sixty-five asymptomatic Chinese men and women between the ages of 18 and 80 years.

OUTCOME MEASURES

Sagittal parameters including LL, lumbar lordosis minus thoracic kyphosis (LL-TK), PI, pelvic tilt (PT), pelvic incidence minus lumbar lordosis (PI-LL), sacral slope (SS), sacral slope divided by pelvic incidence (SS/PI), sagittal vertical axis (SVA), thoracic kyphosis (TK), and T1 (first thoracic vertebra) pelvic angle (TPA) were measured on whole spine radiographs obtained with participants in standing and sitting positions.

METHODS

All participants underwent radiography in the standing position; 235 of them underwent additional radiography in the sitting position to allow measurement of sagittal parameters. The participants with pelvic anteversion were placed in an AP (anteverted pelvis) group. Sagittal parameters were compared between the AP group and the non-AP group, and predictive formulas for LL based on PI were created in both groups. In addition, changes in sagittal parameters from standing to sitting were compared in the AP group and a PI-matched control group.

RESULTS

Of the 565 participants, 171 (30.3%) had pelvic anteversion. In comparison with the non-AP group, the AP group presented with larger LL, a larger SS, and a smaller PT, with relatively small PI. The predictive formulas for LL were LL=0.60° × PI+21.60° (R2=0.268; p<.001) in the whole cohort, LL=0. 83×PI+18.75° (R2=0.427; p<.001) in AP group, and LL=0.79°×PI+9.66° (R2=0.451; p<.001) in the non-AP group. In moving from standing to sitting, the AP group presented with a larger decrease in SS and LL compared with the control group, indicating different patterns of spinopelvic motion.

CONCLUSIONS

In the cohort examined, 30.3% present with pelvic anteversion. Those with AP present with unique characteristics of spinopelvic alignment. In moving from standing to sitting, they exhibit different patterns of spinopelvic motion. We found that identifying the degree of anteversion in each person improves the accuracy of linear models for predicting the degree of LL, which in turn can make plans for spine surgery more accurate.

Assessment of malalignment at early stage in adolescent idiopathic scoliosis: a longitudinal cohort study

INTRODUCTION

Our objective was to assess abnormalities of the odontoid-hip axis (OD-HA) angle in a mild scoliotic population to determine whether screening for malalignment would help predict the distinction between progressive and stable adolescent idiopathic scoliosis (AIS) at early stage.

MATERIALS AND METHODS

All patients (non-scoliotic and AIS) underwent a biplanar X-ray between 2013 and 2020. In AIS, inclusion criteria were Cobb angle between 10° and 25°; Risser sign lower than 3; age higher than 10 years; and no previous treatment. A 3D spine reconstruction was performed, and the OD-HA was computed automatically. A reference corridor for OD-HA values in non-scoliotic subjects was calculated as the range [5th-95th percentiles]. A severity index, helping to distinguish stable and progressive AIS, was calculated and weighted according to the OD-HA value.

RESULTS

Eighty-three non-scoliotic and 205 AIS were included. The mean coronal and sagittal OD-HA angles in the non-scoliotic group were 0.2° and -2.5°, whereas in AIS values were 0.3° and -0.8°, respectively. For coronal and sagittal OD-HA, 27.5% and 26.8% of AIS were outside the reference corridor compared with 10.8% in non-scoliotic (OR = 3.1 and 3). Adding to the severity index a weighting factor based on coronal OD-HA, for thoracic scoliosis, improved the positive predictive value by 9% and the specificity by 13%.

CONCLUSION

Analysis of OD-HA suggests that AIS patients are almost three times more likely to have malalignment compared with a non-scoliotic population. Furthermore, analysis of coronal OD-HA is promising to help the clinician distinguish between stable and progressive thoracic scoliosis.

Subject-Specific Geometry of FE Lumbar Spine Models for the Replication of Fracture Locations Using Dynamic Drop Tests

For traumatic lumbar spine injuries, the mechanisms and influence of anthropometrical variation are not yet fully understood under dynamic loading. Our objective was to evaluate whether geometrically subject-specific explicit finite element (FE) lumbar spine models based on state-of-the-art clinical CT data combined with general material properties from the literature could replicate the experimental responses and the fracture locations via a dynamic drop tower-test setup. The experimental CT datasets from a dynamic drop tower-test setup were used to create anatomical details of four lumbar spine models (T12 to L5). The soft tissues from THUMS v4.1 were integrated by morphing. Each model was simulated with the corresponding loading and boundary conditions from the dynamic lumbar spine tests that produced differing injuries and injury locations. The simulations resulted in force, moment, and kinematic responses that effectively matched the experimental data. The pressure distribution within the models was used to compare the fracture occurrence and location. The spinal levels that sustained vertebral body fracture in the experiment showed higher simulation pressure values in the anterior elements than those in the levels that did not fracture in the reference experiments. Similarly, the spinal levels that sustained posterior element fracture in the experiments showed higher simulation pressure values in the vertebral posterior structures compared to those in the levels that did not sustain fracture. Our study showed that the incorporation of the spinal geometry and orientation could be used to replicate the fracture type and location under dynamic loading. Our results provided an understanding of the lumbar injury mechanisms and knowledge on the load thresholds that could be used for injury prediction with explicit FE lumbar spine models.

Relation between sagittal pelvic and thoracolumbar parameters in supine position - Pelvic parameters and their predictive value for spinal Cobb angles

Introduction

Predicting the pre-morbid sagittal profile of the spine or segmental angles could enhance the process of planning the extent of fracture reduction. There is evidence that spinopelvic parameters may be suitable for this purpose.

Research question

Is it possible to determine the inflection point and the mono- and bi-segmental endplate angles (EPA) in the thoracolumbar transition (from Th9 to L2) based on age, gender, spinopelvic parameters, and the adjacent EPA in the supine position?

Material and methods

Based on Polytrauma CT scans in the supine position, the following spinopelvic parameters were measured using non-fractured spines: pelvic incidence (PI), sacral slope (SS), lumbar lordosis (LL), and the apex of the LL.

Results

In this study, a total of 287 patients with a mean age of 42±16 years were included. Age-related changes were observed, where LL, thoracic kyphosis (TK), and PI increase with age. Gender-related comparisons showed that females had a more pronounced LL and reduced TK. Significant correlations between IP and spinopelvic parameters, with the apex of LL providing the best prediction, were found. However, the overall model quality remained low. Predicting mEPA and bEPA showed positive correlations. The prediction for mEPA L2/3 demonstrated the highest correlation. For bisegmental angles, the most caudal bEPA (L2) exhibited the highest correlation, albeit with some notable absolute differences in the values between measured and predicted values.

Discussion and conclusion

While this study highlights the complexity of the relationship between the pelvis and thoracolumbar parameters, finding a predictive tool for thoracolumbar reduction and stabilization was not possible.

Association Between Spinopelvic Parameters and Intravertebral Cleft in Osteoporosis Vertebral Compression Fractures

BACKGROUND

The high incidence of nonunion in osteoporosis vertebral compression fractures (OVCFs) among the elderly population is a significant concern. But the hypothesis about etiopathogenesis of the intravertebral cleft (IVC) is not convincing. This study aims to investigate the association between spinopelvic parameters and IVC.

METHODS

Patients with single segment IVC or healed vertebral compression fracture (HVCF) were retrospectively recruited for the study. Patients with IVC were assigned to the IVC group, the others were assigned to the HVCF group. We estimated whether IVC or HVCF locates the vertebra inflection point on lumbar lateral radiography. Distance between the sagittal line passing through the anterosuperior corner of S1and the center of the vertebra of healed fracture or with IVC (DSVA) and sacral slope (SS) were measured on lumbar lateral plain films. Intergroup spinopelvic parameters were analyzed. analysis to identify independent variables associated with IVC incidence. The receiver operating characteristics (ROC) curve was generated to identify the optimal cut-off point for statistically significant variables.

RESULTS

Sixty-five patients were included in the study. Thirty patients (mean age: 74 ± 7.16 years) had single-level IVC, and 35 patients (mean age: 67.71 ± 7.30 years) had single-level HVCF. Age, body mass index (BMI), and DSVA were statistically different between the groups (all P < 0.05). The occurrence of IVC was related to the DSVA in the multivariate logistic regression analysis (OR = 0.73, P < 0.05).

CONCLUSIONS

According to the results of this study, large DSVA was a risk factor for IVC formation in patients with OVCFs. Patients with global spinal malalignment should be actively observed during conservative treatment.

Inadequate Annotation and Its Impact on Pelvic Tilt Measurement in Clinical Practice

BACKGROUND

Accurate pre-surgical templating of the pelvic tilt (PT) angle is essential for hip and spine surgeries, yet the reliability of PT annotations is often compromised by human error, inherent subjectivity, and variations in radiographic quality. This study aims to identify challenges leading to inadequate annotations at a landmark dimension and evaluating their impact on PT.

METHODS

We retrospectively collected 115 consecutive sagittal radiographs for the measurement of PT based on two definitions: the anterior pelvic plane and a line connecting the femoral head's centre to the sacral plate's midpoint. Five annotators engaged in the measurement, followed by a secondary review to assess the adequacy of the annotations across all the annotators.

RESULTS

The outcomes indicated that over 60% images had at least one landmark considered inadequate by the majority of the reviewers, with poor image quality, outliers, and unrecognized anomalies being the primary causes. Such inadequacies led to discrepancies in the PT measurements, ranging from -2° to 2°.

CONCLUSION

This study highlights that landmarks annotated from clear anatomical references were more reliable than those estimated. It also underscores the prevalence of suboptimal annotations in PT measurements, which extends beyond the scope of traditional statistical analysis and could result in significant deviations in individual cases, potentially impacting clinical outcomes.

Predicting cervico-thoraco-lumbar vertebra positions from cutaneous markers: Combining local frame and postural predictors improves robustness to posture

Predictions of vertebra positions from external data are required in many fields like motion analysis or for clinical applications. Existing predictions mainly cover the thoraco-lumbar spine, in one posture. The objective of this study was to develop a method offering robust vertebra position predictions in different postures for the whole spine, in the sagittal plane. EOS radiographs were taken in three postures: slouched, erect, and subject's usual sitting posture, using 21 healthy participants pre-equipped with opaque cutaneous markers. Local curvilinear Frenet frames were built on a spline fitted to spinous processes' cutaneous markers. Vertebra positions were expressed as polar coordinates in these frames, defining an angle (α) and distance (d). Multilinear regressions were fitted to explain α and d from anthropometric predictors and predictors presumed to be linked to spinal posture, the predictors' effects being considered both locally and remotely. Anthropometric predictors were the main predictors for d distances, and postural predictors for α angles, with postural predictors still showing a marked influence on d distances for the cervical spine. Vertebra positions were then predicted by cross-validation. The average RMSE on vertebra positions was 11.0 ± 3.7 mm across the entire spine, 13.4 ± 4.1 mm across the cervical spine and 10.1 ± 3.1 mm across the thoraco-lumbar spine for all participants and postures, performances similar to previous models designed for a single posture. Our simple geometrical and statistical model thus appears promising for predicting vertebra positions from external data in several spinal postures and for the whole spine.

Restoration of the sagittal profile according to the Roussouly classification reduces mechanical complications and revision surgery in older patients undergoing surgery for adult spinal deformity (ASD)

PURPOSE

The mechanical complications related to ASD remain a concern due to their morbidity and associated revision surgery. Restoration of each patient's Roussouly profile may reduce these. Our aim was to examine if the restoration of the Roussouly profile reduced these complications and revision rates in older patients operated for degenerative ASD.

METHODS

Retrospective analysis of a single-centre, 2-year minimum follow-up patient database. All patients undergoing corrective surgery (≥ 4 levels) for ASD were included with analysis of demographic data, operative records, restoration of Roussouly sagittal profile, mechanical complications and revision rates. Univariate and multivariate analysis was conducted.

RESULTS

Fifty-two patients were included (mean age was 72.3 years, average follow-up 56.3 months). Twenty-six patients had a "restored" profile (50%) and 26 an "unrestored" profile (50%). The incidence of mechanical complications was 7 (27%) and 23 (88%) for the restored and unrestored groups, respectively (p < 0.001). Revision rates were 4 (15.4%) and 18 (69.2%), respectively (p < 0.000), in the restored and unrestored profiles. Univariate analysis determined that profile restoration and BMI were associated with mechanical complications and revision surgery, whilst only the profile restoration status maintained its statistical power in multivariate analysis (p = 0.002 and p = 0.002, respectively). Age was not a significant factor in univariate analysis. The relative risk for mechanical failure and revision surgery was 5.6 times (CI 1.929-16.39) and 3.08 times (CI 1.642-5.734) greater if the profile was not restored.

CONCLUSIONS

Achieving each patient's ideal Roussouly profile is associated with a reduced incidence of mechanical complications and revision rates in the older population after surgery for degenerative ASD.

Compensation from mild and severe cases of early proximal junctional kyphosis may manifest as progressive cervical deformity at two year follow-up

BACKGROUND

Postoperative reciprocal changes (RC) in the cervical spine associated with varying factors of proximal junctional kyphosis (PJK) following fusions of the thoracopelvic spine are poorly understood.

PURPOSE

Explore reciprocal changes in the cervical spine associated with varying factors (severity, progression, patient age) of PJK in patients undergoing adult spinal deformity (ASD) correction.

PATIENTS AND METHODS

Retrospective review of a multicenter ASD database.

INCLUSION

ASD patients > 18 y/o, undergoing fusions from the thoracic spine (UIV: T6-T12) to the pelvis with two-year radiographic data. ASD was defined as: Coronal Cobb angle ≥ 20°, Sagittal Vertical Axis ≥ 5 cm, Pelvic Tilt ≥ 25°, and/or Thoracic Kyphosis ≥ 60°. PJK was defined as a ≥ 10° measure of the sagittal Cobb angle between the inferior endplate of the UIV and the superior endplate of the UIV + 2. Patients were grouped by mild (M; 10°-20°) and severe (S; > 20°) PJK at one year. Propensity Score Matching (PSM) controlled for CCI, age, PI and UIV. Unpaired and paired t test analyses determined difference between RC parameters and change between time points. Pearson bi-variate correlations analyzed associations between RC parameters (T4-T12, TS-CL, cSVA, C2-Slope, and T1-Slope) and PJK descriptors.

RESULTS

284 ASD patients (UIV: T6: 1.1%; T7: 0.7%; T8: 4.6%; T9: 9.9%; T10: 58.8%; T11: 19.4%; T12: 5.6%) were studied. PJK analysis consisted of 182 patients (Mild = 91 and Severe = 91). Significant difference between M and S groups were observed in T4-T12 Δ1Y(- 16.8 v - 22.8, P = 0.001), TS-CLΔ1Y(- 0.6 v 2.8, P = 0.037), cSVAΔ1Y(- 1.8 v 1.9, P = 0.032), and C2 slopeΔ1Y(- 1.6 v 2.3, P = 0.022). By two years post-op, all changes in cervical alignment parameters were similar between mild and severe groups. Correlation between age and cSVAΔ1Y(R = 0.153, P = 0.034) was found. Incidence of severe PJK was found to correlate with TS-CLΔ1Y(R = 0.142, P = 0.049), cSVAΔ1Y(R = 0.171, P = 0.018), C2SΔ1Y(R = 0.148, P = 0.040), and T1SΔ2Y(R = 0.256, P = 0.003).

CONCLUSIONS

Compensation within the cervical spine differed between individuals with mild and severe PJK at one year postoperatively. However, similar levels of pathologic change in cervical alignment parameters were seen by two years, highlighting the progression of cervical compensation due to mild PJK over time. These findings provide greater evidence for the development of cervical deformity in individuals presenting with proximal junctional kyphosis.

The difference in the relationship of spinal sagittal alignment between individuals with flat lumbar and normal lordosis posture based on global and regional angles

BACKGROUND

According to previous studies, the relationship between lumbar lordosis and thoracic kyphosis or that between pelvic parameters and thoracic kyphosis have been inconsistent.

OBJECTIVE

The purpose of this study was to investigate spinal sagittal alignment and its relationship to global and regional lumbar and thoracic angles, pelvic and sway angles, and C7-S1 distance measurements, followed by a detailed subgroup analysis using an inertial measurement unit system.

METHODS

A total of 51 asymptomatic volunteers stood in a comfortable posture with inertial measurement units attached to the T1, T7, T12, L3, and S2 vertebrae. T1, T7, T12, L3, and S2 sagittal angles were acquired during standing posture using the Eulerian angle coordinate system. All angles are reported as the mean of three 5-s measurements. Following the measurement of lumbar lordosis angles (T12 relative S2), participants were divided into the flat lumbar and normal lordosis groups.

RESULTS

There were different correlation patterns between groups because of spinal sagittal imbalance, which was greater in the flat lumbar group than in the normal lordosis group. In addition, sacral inclination proved the ideal parameter to evaluate reciprocal balance in lumbar lordosis, showing a stronger correlation with lower than with upper lumbar lordosis. T1 was the key element in assessing thoracic kyphosis, which showed a stronger correlation with upper than with lower thoracic kyphosis.

CONCLUSION

We suggest that when assessing posture, it is necessary to identify the global and regional angles and it is useful to classify spinal sagittal alignment into subgroups according to lumbar lordosis and evaluate the groups separately.

Digital therapeutics-based lumbar core exercise for patients with low back pain: A prospective exploratory pilot study

Objective

This study aimed to implement a digital therapeutics-based approach based on motion detection technology and analyze the clinical results for patients with chronic low back pain (LBP).

Methods

A prospective, single-arm clinical trial was conducted with 22 patients who performed mobile app-based sitting core twist exercise for 12 weeks. Clinical outcomes were assessed using the visual analog scale (VAS) for LBP, Oswestry Disability Index-Korean version (K-ODI), and EuroQol-5 dimension 5-level version (EQ-5D-5L) every 4 weeks after the initiation of treatment. Laboratory tests for factors associated with muscle metabolism, plain X-ray for evaluating sagittal balance, and magnetic resonance imaging for calculating cross-sectional area (CSA) of back muscles were performed at pretreatment and 12 weeks post-treatment.

Results

The study population included 20 female patients with an average age of 45.77 ± 15.45 years. The clinical outcomes gradually improved throughout the study period in the VAS for LBP (from 6.05 ± 2.27 to 2.86 ± 1.86), K-ODI (from 16.18 ± 6.19 to 8.64 ± 5.58), and EQ-5D-5L (from 11.09 ± 3.24 to 7.23 ± 3.89) (p < 0.001, respectively). The laboratory test results did not show significant changes. Pelvic incidence (from 53.99 ± 9.70° to 50.80 ± 9.20°, p = 0.002) and the mismatch between pelvic incidence and lumbar lordosis (from 8.97± .67° to 5.28 ± 8.57°, p = 0.027) decreased significantly. Additionally, CSA of erector spinae and total back muscles increased by 5.20% (p < 0.001) and 3.08% (p = 0.013), respectively.

Conclusions

The results of this study suggest that the efficacy of digital therapy-based lumbar core exercise for LBP is favorable. However, further large-scale randomized controlled studies are necessary.

Do Age-Related Variations Of Sagittal Alignment Rely On SpinoPelvic Organization? An Observational Study Of 1540 Subjects

STUDY DESIGN

Descriptive radiographic analysis of a prospective multi-center database.

OBJECTIVE

This study aims to provide normative values of spinopelvic parameters and their correlations according to age and pelvic incidence (PI) of subjects without spinal deformity.

METHODS

After Institutional Review Board (IRB) approval, 1540 full spine radiographs were analyzed. Subjects were divided into 3 groups of PI: low PI < 45°, intermediate PI 45-60°, high PI > 60°, and then stratified by age (20-34, 35-49, 50-64, > 65 Y.O). Pelvic and spinal parameters were measured. Statistical analysis between parameters was performed using Bayesian inference and correlation.

RESULTS

Mean age was 53.5 years (845 females, 695 males, range 20-93 years).In low PI group, lumbar lordosis (LL) decrease was mainly observed in the 2 younger age groups.In medium and high PI groups, loss of lordosis was linear during aging and occurred mainly on the distal arch of lordosis. Moderate PI group had a stable lordosis apex and thoracolumbar inflection point. High PI group had a stable thoracolumbar inflection point and a more distal lordosis apex in elderly subjects.For all subjects, kyphosis and pelvic tilt (PT) increased with age.There was a constant chain of correlation between PI and age groups. Proximal lumbar lordosis (PLL) was correlated with kyphosis and sagittal vertical axis (SVA C7), while the distal lumbar lordosis (DLL) was correlated with PI and PT.

CONCLUSION

This study provides a detailed repository of sagittal spinopelvic parameters normative values with detailed analysis of segmental kyphosis and lordosis distribution according to gender, age, and PI.

Spinopelvic Alignment: Importance in Spinal Pathologies and Realignment Strategies

Sagittal spinal malalignment can lead to pain, decreased function, dynamic imbalance, and compromise of patient-reported health status. The goal of reconstructive spine surgery is to restore spinal alignment parameters, and an understanding of appropriate patient-specific alignment is important for surgical planning and approaches. Radiographic spinopelvic parameters are strongly correlated with pain and function. The relationship between spinopelvic parameters and disability in adult spinal deformity patients is well-established, and optimal correction of sagittal alignment results in improved outcomes regarding patient health status and mechanical complications of surgery.

The Hip Center Rule Can be Used to Decide if Measured Pelvic Incidence is Accurate

STUDY DESIGN

Simulation study.

OBJECTIVE

Pelvic incidence (PI) should be considered during surgical planning. The ideal patient position with both hip centers perfectly aligned for a lateral radiograph is rarely obtained. It has been suggested that a radiograph with axial and coronal rotation up to 20° is acceptable to obtain a measured PI within 6 degrees of the actual PI. We seek to: (1) evaluate the effect of variations in PI and patient malpositioning on measured vs true PI, and (2) determine whether the presence of one hip center within the bony acetabular rim of the contralateral hip can serve as a simple clinical decision rule on the accuracy of measured PI.

METHODS

Published anthropometric three-dimensional pelvic landmark coordinates were used in this study. Radiographic projections were generated using linear algebra for combinations of axial and coronal rotation from -20° to +20°. True and measured PIs were compared.

RESULTS

Rotation to 20° cannot be uniformly accepted as decision rule. Pelvises with higher PIs are more sensitive to malpositioning with greater PI deviation with smaller amounts of rotation. Diagnostic performance of the hip center rule demonstrated a sensitivity of 25.58% and a specificity of 100.00%.

CONCLUSIONS

Rather than assessing the quality of radiographs for PI measurement by magnitude of malpositioning, we recommend clinicians use the "hip center rule." As long as at least one hip center is contained within the bony acetabular rim of the contralateral hip, there is high confidence that measured PI will be within 6° of true PI.

Correlation Between Sagittal Balance and Mechanical Distal Junctional Failure in Degenerative Pathology of the Spine: A Retrospective Analysis

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

This study aimed to investigate the failure of the caudal end of lumbar posterior fixation in terms of pre-operative and post-operative spinopelvic parameters, correction performed, demographic and clinical data.

METHODS

The lumbar, thoraco-lumbar and lumbo-sacral posterior fixations performed with pedicle screws and rods in 2017-2019 were retrospectively analyzed. As 81% failures occurred within 4 years, an observational period of 4 years was chosen. The revision surgeries due to the failure in the caudal end were collected in the junctional group. Fixations which have not failed were gathered in the control group. The main spinopelvic parameters were measured for each patient on standing lateral radiographs with the software Surgimap. Demographic and clinical data were extracted for both groups.

RESULTS

Among the 457 patients who met the inclusion criteria, the junctional group included 101 patients, who required a revision surgery. The control group collected 356 primary fixations. The two most common causes of revision surgeries were screws pullout (57 cases) and rod breakage (53 cases). SVA, PT, LL, PI-LL and TPA differed significantly between the two groups (P = .021 for LL, P < .0001 for all the others). The interaction between the two groups and the pre-operative and post-operative conditions was significant for PT, SS, LL, TK, PI-LL and TPA (P < .005). Sex and BMI did not affect the failure onset.

CONCLUSIONS

Mechanical failure is more likely to occur in patients older than 40 years with a thoraco-lumbar fixation where PT, PI-LL and TPA were not properly restored.

The Thoracolumbar Inflection Point in a Population of Asymptomatic Volunteers: A Multi-Ethnic Alignment Normative Study Cohort Study

STUDY DESIGN

Prospective cohort study.

OBJECTIVES

To show population variance in the Inflection Point (IP) and its role in defining maximum Thoracic Kyphosis (TK) and Lumbar Lordosis (LL).

METHODS

468 asymptomatic adult volunteers were included in the Multi-Ethnic Normative Alignment Study (MEANS). To find parameters correlating with IP, the vertebrae and discs were numbered such that C7 was 0, T1 was 1, with T1-T2 disc being 1.5, etc. Statistical analysis was performed by a correlation matrix for IP and the 9 other selected parameters along with linear regressions.

RESULTS

The overall mean IP was 12.44 approximately corresponding to T12-L1 disc with the median being 12.50, range was T8-L4. The cohort was then stratified by sex and ethnicity, but there was no significant difference in IP between groups. IP in younger subjects was 13 (L1), compared to 12.5 (T12-L1 disc) in older subjects (P < .05). IP was moderately correlated with the TK apex (r = .66). No strong correlation was found between IP and LL magnitude or apex, TK magnitude, sacral slope, or Pelvic Incidence (PI). In terms of other sagittal parameters, PI and LL demonstrated a significant positive correlation. PI and TK did not have a strong association.

CONCLUSIONS

The mean IP was at the T12-L1 disc, however IP ranged from T8 to L4. Older subjects tended to have a relatively more cephalad IP. No radiographic variable was found to be a strong predictor of the IP. TK apex was found to have a moderate correlation.

From the Spinopelvic Parameters to Global Alignment and Proportion Scores in Adult Spinal Deformity

In the last 20 years, sagittal alignment and balance of the spine have become one of the most important issues in the field of spine surgery. Recent studies emphasize that sagittal balance and alignment are more important for health-related quality of life. The understanding of normal and abnormal sagittal alignment of the spine is necessary for the diagnosis and appropriate treatment of adult spinal deformity (ASD), and we will discuss the currently used classification of ASD, the parameters of sagittal alignment that are essential for the diagnosis of spinal deformity, compensatory actions to maintain sagittal balance, and the relationship between sagittal alignment and clinical symptoms. Furthermore, we will also discuss the recently introduced Global Alignment and Proportion scores. The Korean Spinal Deformity Society is publishing a series of review articles on spinal deformities to help spine surgeons better understand spinal deformities.

Sagittal realignment: surgical restoration of the global alignment and proportion score parameters: a subgroup analysis. What are the consequences of failing to realign?

INTRODUCTION

The Global Alignment and Proportion (GAP) score incorporates three domains directly modified with surgery (relative pelvic version-RPV, relative lumbar lordosis-RLL, lumbar distribution index-LDI) and one indirectly restored (relative spinopelvic alignment-RSA). We analyzed our surgical realignment performance and the consequences of domain-specific realignment failure on mechanical complications and PROMs.

MATERIALS AND METHODS

From an adult spinal deformity prospective multicenter database, we selected patients: fused to pelvis, upper instrumented vertebra at or above L1, and 2 years of follow-up. Descriptive, univariate and multivariate analyses were employed.

RESULTS

The sample included 333 patients. RLL-6w showed the highest success rate (58.3% aligned), but 16.5% of patients were classified in the "Severe hypolordosis" and "Hyperlordosis" subgroups. RPV-6w was the most challenging to realign, with 51.6% moderate or severe retroversion. Regarding RSA-6w, 21.9% had severe positive malalignment. Correct alignment of RPV-6w (p = 0.025) and RSA-6w (p = 0.002) proved to be protective factors against the development of mechanical complications. Severe pelvic retroversion (p = 0.026) and severe positive malalignment (p = 0.007) were risk factors for mechanical complications. RSA-6w "Severe positive malalignment" was associated with less improvement in PROMs: ∆ODI (8.83 vs 17.2; p = 0.011), ∆SRS-22 total (0.54 vs 0.87; p = 0.007), and ∆SF-36PCS (3.47 vs 7.76; p = 0.04); MCID for ODI (37.0 vs 55.5%; p = 0.023), and SRS-22 (40.8 vs 60.1%; p = 0.015); and PASS for ODI (17.6 vs 31.7%; p = 0.047).

CONCLUSIONS

RPV was the most underperformed modifiable parameter. Severe pelvic retroversion and severe positive malalignment influenced the occurrence of mechanical complications. Severe positive malalignment affected PROMs improvement.

Spino-pelvic radiological parameters: Comparison of measurements obtained by radiologists using the traditional method versus spine surgeons using a semi-automated software (Surgimap)

Background

Spinopelvic balance measurement is a key point to get an appropriate diagnosis and treatment in a group of spine pathologies; thus, it seems necessary the evaluation of different methods for obtaining the most reliable values. For that reason, different automatic and semi-automatic computer-assisted tools have been developed, and one example of them is Surgimap.

Purpose

To demonstrate that the sagittal balance measurements with Surgimap are equal and more time-efficient than with Agfa-Enterprise.

Material and Methods

Retrospective-prospective study. Biased comparative analysis of radiographic measurements performed on two different occasions (96 h interval), between two spine surgeons using Surgimap and two radiologists using the traditional Cobb method (TCM) with the Agfa-Enterprise program in 36 full spine lateral X-ray, determining inter- and intra-observer reliability and the mean time required to obtain the measurements.

Results

Measurements with both methods demonstrated an excellent intra-observer correlation (Surgimap: PCC 0.95 [0.85-0.99]; TCM: PCC 0.90 [0.81-0.99]). Inter-observer correlation also demonstrated an excellent relationship (PCC >0.95). Thoracic kyphosis (TK) demonstrated the lowest levels of inter-observer correlation (PCC: 0.75). The average time in seconds with TCM was 154.6, while with the Surgimap it was 41.8 s.

Conclusion

Surgimap proved to be equally reliable and 3.5 times faster. Therefore, in consistency with the available literature, our results would allow us to promote the use of Surgimap as a clinical diagnostic tool considering precision and efficiency.

Downward-Growing Neural Networks

A major issue in the application of deep learning is the definition of a proper architecture for the learning machine at hand, in such a way that the model is neither excessively large (which results in overfitting the training data) nor too small (which limits the learning and modeling capabilities of the automatic learner). Facing this issue boosted the development of algorithms for automatically growing and pruning the architectures as part of the learning process. The paper introduces a novel approach to growing the architecture of deep neural networks, called downward-growing neural network (DGNN). The approach can be applied to arbitrary feed-forward deep neural networks. Groups of neurons that negatively affect the performance of the network are selected and grown with the aim of improving the learning and generalization capabilities of the resulting machine. The growing process is realized via replacement of these groups of neurons with sub-networks that are trained relying on ad hoc target propagation techniques. In so doing, the growth process takes place simultaneously in both the depth and width of the DGNN architecture. We assess empirically the effectiveness of the DGNN on several UCI datasets, where the DGNN significantly improves the average accuracy over a range of established deep neural network approaches and over two popular growing algorithms, namely, the AdaNet and the cascade correlation neural network.

Reliability Analysis of Vertebral Landmark Labelling on Lumbar Spine X-ray Images

Vertebral landmark labelling on X-ray images is important for objective and quantitative diagnosis. Most studies related to the reliability of labelling focus on the Cobb angle, and it is difficult to find studies describing landmark point locations. Since points are the most fundamental geometric feature that can generate lines and angles, the assessment of landmark point locations is essential. The aim of this study is to provide a reliability analysis of landmark points and vertebral endplate lines with a large number of lumbar spine X-ray images. A total of 1000 pairs of anteroposterior and lateral view lumbar spine images were prepared, and 12 manual medicine experts participated in the labelling process as raters. A standard operating procedure (SOP) was proposed by consensus of the raters based on manual medicine and provided guidelines for reducing sources of error in landmark labelling. High intraclass correlation coefficients ranging from 0.934 to 0.991 verified the reliability of the labelling process using the proposed SOP. We also presented means and standard deviations of measurement errors, which could be a valuable reference for evaluating both automated landmark detection algorithms and manual labelling by experts.

New Onset Sacroiliac Joint Pain After Transforaminal Interbody Fusion: What Are the Culprits?

STUDY DESIGN

A retrospective case-control study.

OBJECTIVE

Only a few studies have studied the incidence of new-onset SI joint pain following lumbar spine fusion surgery. We aimed to explore the association between new-onset SI joint pain following Transforaminal Lumbar Interbody Fusion (TLIF) for degenerative spine disorders and changes in spinopelvic parameters.

METHODS

A retrospective review of hospital records and imaging database of a tertiary care institute was done for patients who underwent TLIF from October 2018 to October 2019. The 354 patients who satisfied the eligibility criteria were divided into 2 groups(Group A, new-onset SI joint pain group, n = 34 and Group B, normal controls, n = 320). Symptomatic relief (>70% reduction in the VAS [Visual Analogue Scale] score) after 15 minutes of SI joint injection was considered diagnostic of SI joint pain. Clinical and radiological spinopelvic parameters were compared between the 2 groups.

RESULTS

Patients with postoperative SI joint pain (Group A) had significantly less preoperative and postoperative lumbar lordosis (p < 0.001) compared to the other group. Most of the patients in Group A had a cephalad migration of the apex postoperatively (30/34 patients) whereas majority of patients in group B had either predominant caudal migration (44/320 patients) or no migration of the lumbar apex (272/320 patients).

CONCLUSIONS

The preoperative and postoperative lumbar lordosis are significantly less and the postoperative pelvic tilt is significantly high in patients with new-onset SI joint pain compared to the control group. The cephalad migration of the lumbar apex is significantly associated with new-onset SI joint pain.

Total knee arthroplasty in patients with lumbar spinal fusion leads to significant changes in pelvic tilt and sacral slope

BACKGROUND

The knee-hip-spine syndrome has been well elucidated in the literature in recent years. The aim of this study was to evaluate the effect of total knee arthroplasty (TKA) on spinopelvic sagittal alignment in patients with and without pre-TKA lumber spinal fusion.

METHODS

This is a retrospective cohort study of 113 patients who underwent TKA for primary osteoarthritis. Patients were stratified into the following three groups: (1) patients who had pre-TKA spinal fusion (SF, n = 19), (2) patients who had no spinal fusion but experienced pre-TKA flexion contracture (FC, n = 20), and (3) patients without flexion contracture or spinal fusion before TKA (no SF/FC, n = 74). Spinopelvic sagittal alignment parameters, including pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), thoracic kyphosis (TK), and plumb line-sacrum distance (SVA) were measured preoperatively and 3 months postoperatively on lateral standing full-body low-dose images.

RESULTS

TKA resulted in significant pre- to postoperative changes in pelvic tilt (average ∆ PT = - 8.6°, p = 0.018) and sacral slope (average ∆ SS = 8.6°, p = 0.037) in the spinal fusion (SF) group. Non-significant changes in spinopelvic sagittal alignment parameters (PT, SS, LL, TK, SVA) were noted postoperatively in all patients in the FC and the no SF/FC groups.

CONCLUSIONS

TKA can lead to meaningful changes in spinopelvic alignment in patients with prior lumbar fusion compared to those without spinal fusion. Patients with spinal fusion who are candidates for both hip and knee replacements should consider undergoing TKA first since changes in spinopelvic sagittal alignment can increase the risk of future complications.

LEVEL III EVIDENCE

Retrospective Cohort Study.

The Effect of Cervical Fusion on Functional Sagittal Spinal Alignment Based on the Inflection Point: Case Series Study

STUDY DESIGN

A retrospective radiologic study.

OBJECTIVE

The inflection point is the disc space between a lordotic and kyphotic segment of spine. To our knowledge, there has been no study evaluating changes in functional sagittal alignment determined by inflection points after cervical fusion surgery. The purpose is to identify changes in functional sagittal alignment after cervical fusion as determined by functional segments between cervicothoracic and thoracolumbar inflection points.

METHODS

Standing radiographs of the sagittal whole spine were taken in 62 patients who underwent cervical fusion procedures. We identified cervicothoracic and thoracolumbar inflection points in the sagittal plane and measured Cobb angles of resulting "functional" cervical, thoracic, and lumbar segments. We also measured the C2 and T1 sagittal vertical axis (SVA) distance to S1 and the anatomic cervical lordosis, thoracic kyphosis, lumbar lordosis, spinopelvic parameters, and T1 sagittal slope. We compared the pre- and post-op values.

RESULTS

The functional cervical segment and T1 sagittal slope increased postoperatively. C2 and T1 SVA distance to S1 decreased postoperatively. In patients with a single level fusion or lower instrumented vertebra (LIV) proximal or equal to C6, functional cervical segment, and anatomic cervical lordosis increased postoperatively. In those with multiple level fusion or LIV distal or equal to C7, the C2 SVA distance to S1 decreased postoperatively.

CONCLUSIONS

After cervical fusion surgery, functional cervical sagittal parameters determined by the inflection point improve without changes in the anatomic sagittal parameters. Postoperative changes in functional sagittal parameters were affected by the number of fused levels and LIV.

Effects of cycling on the morphology and spinal posture in professional and recreational cyclists: a systematic review

The aim was to know if cycling affects spinal morphology in postures off the bicycle, such as adapting the spinal curvatures on the bicycle depending on the handlebar type and position on the handlebars. A systematic review was conducted following the PRISMA guidelines. The studies selected met the following criteria: a) the study design was cross-sectional or longitudinal (experimental or cohorts); b) the study evaluated the sagittal morphology of the spine on the bicycle; c) the study included healthy and trained participants without injuries or cyclists reporting low back pain. Fifteen studies reported that a greater pelvic tilt was observed that when the handlebar was in a lower position. Sixteen studies found that lumbar kyphosis was greater when the handlebar grip was lower and farther from the saddle. Twelve studies reported that a tendency towards greater thoracic flexion as the time spent pedalling on the bicycle increased. In conclusion, the practice of cycling produces adaptations in the morphology of the spine of the cyclist compared to non-cyclists, such as an increase in pelvic tilt and a greater capacity for lumbar flexion in trunk flexion positions, and a greater thoracic kyphosis in the standing position.

How to make a more optimal surgical plan for Lenke 5 adolescent idiopathic scoliosis patients: a comparative study based on the changes of the sagittal alignment and selection of the lowest instrumented vertebra

BACKGROUND

The treatment of patients with Lenke 5 adolescent idiopathic scoliosis (AIS) is closely related to the pelvic because the spine-pelvis is an interacting whole. Besides, the choice of fusion segment is a significant issue; with the optimal choice, there will be fewer complications and restoring the pelvic morphology to some extent. This study aims to analyze the impact of changes in sagittal parameters and selection of the lowest instrumented vertebra (LIV) on spine and pelvic morphology for better surgical strategy.

METHOD

Ninety-four patients with Lenke 5 AIS who underwent selective posterior thoracolumbar/lumbar (TL/L) curve fusion were included in the study and grouped according to pelvic morphology and position of LIV. Spinopelvic parameters were measured preoperatively, postoperatively, and at the latest follow-up. The patient's preoperative and last follow-up quality of life was assessed with the MOS item short-form health survey (SF-36) and scoliosis research society 22-item (SRS-22).

RESULT

Patients being posterior pelvic tilt had the oldest mean age (P = 0.010), the smallest lumbar lordosis (LL) (P = 0.036), the smallest thoracic kyphosis (TK) (P = 0.399) as well as the smallest proximal junctional angle (PJA) while those being anterior pelvic tilt had the largest PJA. The follow-up TK significantly increased in both groups of anterior and normal pelvic tilt (P < 0.039, P < 0.006) while no significant changes were observed in the posterior pelvic tilt group. When LIV is above L4, the follow-up PJA was larger than other groups (P = 0.049, P = 0.006). When LIV is below L4, the follow-up TK and PT were larger and LL was smaller than other groups(P < 0.05). The SF-36 and SRS-22 scores were better in the LIV = L4 group than in other groups at the last follow-up (P < 0.05).

CONCLUSION

The correction of TK and LL after surgery can improve pelvic morphology. Besides, LIV is best set at L4, which will facilitate the recovery of TK, the improvement of symptoms, and the prevention of complications and pelvic deformities. Level of evidence Level III.

The dynamic sagittal balance: Definition of dynamic spino-pelvic parameters using a method based on gait analysis

Introduction

Evaluation of sagittal balance parameters is a standard assessment before spine surgery. However, these parameters can change during walking. We aimed to describe the behavior of spino-pelvic parameters during walking in healthy subjects.

Material and methods

Analyses were performed in 60 healthy subjects. Static spinal sagittal balance parameters were assessed. We performed gait analysis and we used SMART-DX 500® to analyze parameters aimed at defining dynamic sagittal balance, including pelvic tilt angle (PTA), sagittal trunk shift (STS), and trunk angle (TA). We considered rotational and obliquity movements of the pelvis, flexo-extension movements of the hip, trunk, and knees. Analyses were performed in a standing posture and during walking.

Results

PTA-cycle, PTA-stance, PTA-swing, STS-cycle, STS-stance, and STS-swing showed good-to-excellent internal reliability (ICC = 0.867; ICC = 0.700; ICC = 0.817, respectively). The parameters with the lowest variability were radiographic PI (CV = 16.53%), PTA-stance (CV = 9.55%), and PTA-swing (CV = 17.22%). PT was directly related to PTA-cycle (r = 0.534, p = .027). PI was inversely correlated with trunk flexo-extension range of motion (r = -0.654, p = .004) and dynamic PT (r = -0.489, p = .047). LL and SS were directly related to knee flexo-extension (r = 0.505, p = .039; r = 0.493, p = .045, respectively). SVA was correlated with the trunk obliquity in dynamics (r = 0.529, p = .029). PTA-cycle was directly related to trunk obliquity (r = 0.538, p = .049). STS and TA in the three phases of step were related to the kinematic parameters of the pelvis. TA was related to flexo-extension of the hip and knee.

Conclusions

Variations of dynamic spino-pelvic parameters occur during walking and modify sagittal balance from a static to a dynamic condition.

Crossing the Bridge From Degeneration to Deformity: When Does Sagittal Correction Impact Outcomes in Adult Spinal Deformity Surgery?

BACKGROUND

Patients with less severe adult spinal deformity (ASD) undergo surgical correction and often achieve good clinical outcomes. However, it is not well understood how much clinical improvement is due to sagittal correction rather than treatment of the spondylotic process.

PURPOSE

Determine baseline thresholds in radiographic parameters that, when exceeded, may result in substantive clinical improvement from surgical correction.

STUDY DESIGN

Retrospective.

MATERIALS AND METHODS

ASD patients with BL and two-year data were included. Parameters assessed: sagittal vertical axis, pelvic incidence-lumbar lordosis mismatch, pelvic tilt, T1 pelvic angle, L1 pelvic angle, L4-S1 lordosis, C2-C7 sagittal vertical axis, C2-T3, C2 slope. Outcomes: Good Outcome (GO) at two years: [meeting either: (1) Substantial Clinical Benefit for Oswestry Disability Index (change >18.8), or (2) Oswestry Disability Index <15 and Scoliosis Research Society Total>4.5]. Binary logistic regression assessed each parameter to determine if correction was more likely needed to achieve GO. Conditional inference tree run machine learning analysis generated baseline thresholds for each parameter, above which, correction was necessary to achieve GO.

RESULTS

We included 431 ASD patients. There were 223 (50%) that achieved a GO by two years. Binary logistic regression analysis demonstrated, with increasing baseline severity in deformity, sagittal correction was more often seen in those achieving GO for each parameter(all P <0.001). Of patients with baseline T1 pelvic angle above the threshold, 95% required correction to meet GO (95% vs. 54%, P <0.001). A baseline pelvic incidence-lumbar lordosis >10° (74% of patients meeting GO) needed correction to achieve GO (odds ratio: 2.6, 95% confidence interval: 1.4-4.8). A baseline C2 slope >15° also necessitated correction to obtain clinical success (odds ratio: 7.7, 95% confidence interval: 3.7-15.7).

CONCLUSIONS

Our study highlighted point may be present at which sagittal correction has an outsized influence on clinical improvement, reflecting the line where deformity becomes a significant contributor to disability. These new thresholds give us insight into which patients may be more suitable for sagittal correction, as opposed to intervention for the spondylotic process only, leading to a more efficient utility of surgical intervention for ASD.

Changes in health-related quality of life measures associated with degree of proximal junctional kyphosis

PURPOSE

To explore the changes in health-related quality of life parameters observed in patients experiencing varying degrees of proximal junctional kyphosis following corrective adult spinal deformity fusions.

METHODS

Inclusion: adult spinal deformity patients > 18 y/o, undergoing spinal fusion. PJK: ≥ 10° measure of the sagittal Cobb angle between the inferior endplate of the UIV and the superior endplate of the UIV + 2. Severe PJK: > 28° PJK. Mild PJK: ≥ 10^oand ≤ 28°. ANOVA, followed by ANCOVA, compared the change in HRQoLs between time points (BL, 1Y, 2Y) among PJK groups. Correlation-related change in PJK and change in HRQoL for mild and severe groups.

RESULTS

969 patients (age: 64.5 y/o,75% F, posterior levels fused:12.3) were studied. 59% no PJK, 32% mild PJK, 9% severe PJK. No differences in HRQoLs were seen between no PJK and PJK groups at baseline, one year, and 2 years. Adjusted analysis revealed Severe PJK patients improved less in SRS-22 Satisfaction (NoPJK: 1.6, MildPJK: 1.6, SeverePJK: 1.0; p = 0.022) scores at 2 years. Linear regression analysis only found clinical improvement in SRS-22 Satisfaction to correlate with the change of the PJK angle by 2 years (R = 0.176, P = 0.008). No other HRQoL metric correlated with either the incidence of PJK or the change in the PJK angle by one or 2 years.

CONCLUSIONS

These results maintain that patients presenting with and without proximal junctional kyphosis report similar health-related qualities of life following corrective adult spinal deformity surgery, and SRS-22 Satisfaction may be a clinical correlate to the degree of PJK. Rather than proving proximal junctional kyphosis to have a minimal clinical impact overall on HRQoL metrics, these data suggest that future analysis of this phenomenon requires different assessments.

LEVEL OF EVIDENCE

Level of evidence: III.

Posterior Pelvic Tilt in the Standing Position Might Be Associated with Collapse Progression in Post-Collapse Stage Osteonecrosis of the Femoral Head

OBJECTIVE

Excessive pelvic tilt has been reported to impair the biomechanical loading of the hip joint. However, the influence of pelvic tilt in osteonecrosis of the femoral head (ONFH) remains unclear. This study aims to assess whether sagittal pelvic posture in the standing position correlates with progression of femoral head collapse in post-collapse stage ONFH.

METHODS

This is a single-center retrospective study. We investigated 107 patients (107 hips; 73 males and 34 females; mean age, 48 years) diagnosed with Association of Research Circulation Osseous (ARCO) stage III ONFH at the first visit and who subsequently underwent surgical treatment in our institution from July 2016 to December 2020. The sagittal pelvic posture in the standing position before surgery was quantified as the angle formed by the anterior pelvic plane and the vertical z-axis in the sagittal view (APP angle). An APP angle <0° indicated posterior pelvic tilt. Progression of femoral head collapse was calculated as collapse speed. The following factors potentially associated with collapse speed were evaluated by exploratory data analysis followed with multiple linear regression analysis: sex, age, BMI, etiology, pelvic incidence, contralateral hip condition, time interval between the first visit and surgery, size of necrotic lesion, location of necrotic lesion, and APP angle.

RESULTS

As ONFH progressed from ARCO stage IIIA to stage IV, APP angle decreased significantly and continuously (stage IIIA, -0.2° ± 5.5°; stage IIIB, -3.7° ± 5.8°; stage IV, -7.1° ± 6.4°). The factors significantly associated with collapse speed were size of necrotic lesion (p = 0.0079), location of necrotic lesion (p = 0.0190), and APP angle (p < 0.0001). APP angle showed a negative correlation with collapse speed (r = -0.40, p < 0.0001). After stratifying by size of necrotic lesion (<50% and ≥50% involvement) and location of necrotic lesion (JIC type C1 and C2), a significant negative correlation was observed between APP angle and collapse speed in each group (JIC type C1 with <50% involvement, r = -0.69, p < 0.0001; JIC type C1 with ≥50% involvement, r = -0.58, p = 0.0475; JIC type C2 with <50% involvement, r = -0.51, p = 0.0124; JIC type C2 with ≥50% involvement, r = -0.39, p = 0.0286).

CONCLUSIONS

Our results suggest that posterior pelvic tilt in the standing position occurred as ONFH progressed from ARCO stage IIIA to stage IV, which might be associated with progression of femoral head collapse in ONFH.

Spinal stability analysis of lumbar interbody fusion according to pelvic type and cage angle based on simplified spinal model with various pelvic indices

Recently, the objectives of lumbar interbody fusion (LIF) have been extended to include the correction of broader/relative indications in addition to spinal fixation. Accordingly, LIF must be optimized for sagittal alignment while simultaneously achieving decompression. Therefore, a representative model classified into three pelvic types, i.e., neutral pelvis (NP), anterior pelvis (AP), and retroverted pelvis (RP), was selected according to the pelvic index, and LIF was performed on each representative model to analyze Lumbar lordosis (LL) and the corresponding equivalent stress. The finite element (FE) model was based on a sagittal 2D X-ray image. The calculation efficiency and convergence were improved by simplifying the modeling of the vertebral body in general and its posterior portion in particular. Based on the position of the pelvis, according to the pelvic shape, images of patients were classified into three types: AP, RP, and NP. Subsequently, representative images were selected for each type. The fixation device used in the fusion model was a pedicle screw and a spinal rod of a general type. PEEK was used as the cage material, and the cage shape was varied by using three different cage angles: 0°, 4°, and 8°. Spinal mobility: The pelvic type with the highest range of motion (ROM) for the spine was the NP type; the AP type had the highest LL. Under a combination load, the NP type exhibited the highest lumbar flexibility (LF), which was 2.46° lower on average compared to the case where a pure moment was applied. Equivalent stress on the spinal fixation device: The equivalent stress acting on the vertebrae was lowest when cage 0 was used for the NP and AP type. For the RP type, the lowest equivalent stress on the vertebrae was observed when cage 4 was used. Finally, for the L5 upper endplate, the stress did not vary significantly for a given type of cage. In conclusion, there was no significant difference in ROM according to cage angle, and the highest ROM, LL and LF were shown in the pelvic shape of NP type. However, when comparing the results with other pelvic types, it was not possible to confirm that LF is completely dependent on LL and ROM.

Spinal sagittal alignment and postoperative adding-on in patients with adolescent idiopathic scoliosis after surgery

INTRODUCTION

Surgery for patients with adolescent idiopathic scoliosis (AIS) may change spinal sagittal alignment, and postoperative adding-on may affect spinal sagittal balance after reconstruction. This study was to investigate the effect of surgery on spinal sagittal alignment and the relationship between postoperative adding-on and spinal sagittal balance in patients with AIS.

HYPOTHESIS

The hypothesis of this study was that the effect of surgery on AIS was associated with recovery of the spinal sagittal plane and that presence of postoperative adding-on might affect the spinal sagittal balance. Materials and methods This retrospective study enrolled 22 patients who received surgical treatment. Clinical, imaging and follow-up data were analyzed.

RESULTS

After surgery, T1 slope (T1S) and thoracic kyphosis (TK) were significantly (P<0.05) lower in patients with postoperative adding-on (16.73°±6.12° for T1S and 28.95°±11.3° for TK) than those without adding-on (24.82°±8.59° for T1S and 40.29°±12.08° for TK). At the last follow-up, cervical lordosis (CL), T1S, and TK were significantly (P<0.05) lower in patients with adding-on (3.05°±11.41° for CL, 22.12°±3.68° for T1S, and 37.89°±8.97° for TK) than those without adding-on (15.94°±°13.6 for CL, 28.86°±4.26° for T1S, and 47.64°±7.1° for TK). The Cobb angle was significantly (19.65°±8.69° vs. 50.66°±11.46°; P<0.001) decreased after compared with that before surgery. At the final follow-up, the Cobb angle (26.48°±9.61° vs. 19.65°±8.69°, P<0.001), T1S (24.87°±5.11° vs. 20.04°±8.13°), and TK (41.88°±9.45° vs 33.53°±12.71°) all significantly (P<0.01) increased compared with those immediately after surgery. The Cobb angle significantly (26.48°±9.61° vs. 50.66°±11.46°, P<0.001) decreased while CL, T1S, and TK all significantly (8.32°±13.67° vs 2.47°±14.42° for CL, T1S 24.87°±5.11° vs. 21.28°±5.88° for T1S, and 41.88°±9.45° vs. 33.13°±10.97° for TK, P<0.05) increased at the final follow-up compared with those before surgery.

DISCUSSION

Surgery affects spinal sagittal alignment, and postoperative adding-on may affect spinal sagittal balance after reconstruction. Surgery as the ultimate approach for AIS has good effects but may result in some side effects.

LEVEL OF PROOF

III, retrospective cohort study.

Age and Gender Based Spinopelvic and Regional Spinal Alignment in Asymptomatic Adult Volunteers: Results of the Multi-Ethnic Alignment Normative Study (MEANS)

BACKGROUND

Spinal alignment can have a significant impact on a patient's overall quality of life. Predicting the ideal sagittal spinal alignment of a specific individual is still a difficult task. The Multi-Ethnic Alignment Normative Study (MEANS) investigated skeletal alignment, including the spine and lower extremities, of the largest multi-ethnic cohort of asymptomatic adult volunteers. In this analysis, the authors aim to assess normative values of spinopelvic parameters and the regional cervical, thoracic, and lumbar spinal alignment in asymptomatic volunteers stratified by age and sex.

MATERIALS AND METHODS

Asymptomatic volunteers between ages 18 and 80 years were enrolled prospectively from centers in France, Japan, Singapore, Tunisia, and the United States. Volunteers included reported no significant neck or back pain (Visual Analog Scale ≤2), nor any known spinal disorder(s). All volunteers underwent a standing full-body or full-spine low-dose stereoradiograph.

RESULTS

MEANS consisted of 468 volunteers with a mean age of 40.4±14.8 years. Mean cervical lordosis from C2 to C7 was -0.4±12.7°. The T1-slope averaged 23.0±7.9° and showed strong correlation ( r =0.87) with the C7-slope mean of 19.8±8.6°. Thoracic kyphosis (TK) from T4 to T12 showed a mean of 37.4±10.9°. Average L1-S1 lumbar lordosis (LL) was -57.4±11.3°. The mean pelvic incidence (PI) measured 52.0±10.7° and pelvic tilt was 12.5±7.3°. Sacral slope averaged 39.5±8.2°. The average PI-LL was -5.4±10.7°. Approximately 60% of volunteers met the PI-LL criteria within ±10°, 8.3% were ≥10°, while 32.1% were ≤-10°. LL showed moderate correlation with PI ( r =0.53) and TK ( r =0.50), while there was no correlation between TK and PI. Multiple linear regression including PI, TK, and age resulted in the following equation LL=14.6+0.57 (PI)+0.57 (TK)-0.2 (age) ( r =0.75).

CONCLUSIONS

LL did not change with increasing age in asymptomatic volunteers. However, TK did increase with age leading to an increase in T1-slope and a compensatory increase in cervical lordosis. TK did not correlate with PI and was an independent variable in the prediction of LL.

LEVEL OF EVIDENCE

Level II-prospective cohort study.

Age- and Gender-based Global Sagittal Spinal Alignment in Asymptomatic Adult Volunteers: Results of the Multiethnic Alignment Normative Study (MEANS)

STUDY DESIGN

Multicenter Cohort.

OBJECTIVE

Assess normative values of sagittal spinal and lower extremity alignment in asymptomatic volunteers stratified by age and gender.

SUMMARY OF BACKGROUND DATA

Our understanding of ideal sagittal alignment is still evolving. The Multiethnic Alignment Normative Study (MEANS) investigated skeletal alignment of the largest multiethnic cohort of asymptomatic adult volunteers. We aim to assess normative values of sagittal spinal and lower extremity alignment in asymptomatic volunteers stratified by age and gender.

MATERIALS AND METHODS

Asymptomatic volunteers between the ages of 18-80 years were enrolled prospectively and then analyzed retrospectively from six different centers. Volunteers included reported no significant neck or back pain, nor any known spinal disorder(s). All volunteers underwent a standing full-body or full-spine low-dose stereoradiograph.

RESULTS

MEANS consisted of 468 volunteers with a mean age of 40.4±14.8 years. Thoracic kyphosis (TK) from T4 to T12 showed a mean of 37.4±10.9°. The average L1-S1 lumbar lordosis (LL) was -57.4±11.3°. LL did not show significant differences across the five age groups. TK showed a significant difference based on age ( P <0.0001). Sagittal vertical axis increased across age groups from -14.2 mm in young adults to 17.0 mm in patients >64. Similar trend was seen for T1 pelvic angle with a mean of 5.0° in young adults and 13.7° in those older than age 64. Knee flexion increased across age groups without a significant change in odontoid-knee distance which is a surrogate for the center of the head aligned over the knees.

CONCLUSIONS

In asymptomatic volunteers, sagittal alignment parameters showed a slow and steady change across age groups exemplified by an increase in TK. However, LL did not show a significant decrease across age groups. Volunteers used compensatory mechanisms such as slight pelvis retroversion, knee flexion, and neck extension to maintain an aligned sagittal posture with their head centered over their knees (odontoid-knee).

LEVEL OF EVIDENCE

3.

Introduction of a Novel “Segmentation Line” to Analyze the Variations in Segmental Lordosis, Location of the Lumbar Apex, and Their Correlation with Spinopelvic Parameters in Asymptomatic Adults

Study Design

Cross-sectional study.

Purpose

This study aimed to understand the sagittal spinopelvic parameters, segmental lumbar parameters, and lumbar apex location in asymptomatic adults and analyze their correlations with each other.

Overview of Literature

Roussouly and his colleagues reported that pelvic incidence (PI) influences the lower arc of lumbar lordosis, whereas Pesenti and his colleagues reported that PI influences only the proximal part of lordosis and not the distal part. Both studies have their shortcomings.

Methods

One hundred asymptomatic adult volunteers (mean age, 29.1±7.9 years; 69 males, 31 females) who satisfied the selection criteria were enrolled in this study. Standing antero-posterior and lateral whole spine and pelvis X-rays were performed, and the radiographic parameters were analyzed. We introduced a “segmentation line” bisecting the apical vertebra/disk to divide the upper arc of lumbar lordosis (ULL) and lower arc of lumbar lordosis (LLL).

Results

The mean PI was 48.02°, ULL 29.12°, LLL 16.02°, total lumbar lordosis (TLL) 45.14°, lumbar tilt angle 4.73°, and location of the apex of lumbar lordosis (LLA) 4.11°. The location of the lumbar apex moved higher as the PI increased. The PI was strongly positively correlated with the LLL (r =0.582, p <0.001) and TLL (r =0.579, p <0.001) but not with the ULL (r =0.196, p =0.05). The LLA was strongly positively correlated with the ULL (r =0.349, p <0.001), negatively with the LLL (r =−0.63, p <0.001), and not correlated with the TLL (r =−0.177, p =0.078).

Conclusions

The PI influences the location of the lumbar apex, the LLL, and the TLL but not the ULL. The location of the lumbar apex significantly influences the segmental lordosis but not the TLL.

Sagittal Balance Using Position and Orientation of Each Vertebra in an Asymptomatic Population

STUDY DESIGN

A monocentric, retrospective radiographic study with 99 asymptomatic volunteers.

OBJECTIVE

The authors performed the postural analysis commonly scheduled when evaluating sagittal balance in a vertebra-by-vertebra manner by enrolling an asymptomatic population. They measured the position and angulation of each vertebra to reveal those for which the spatial positioning could be relevant during spinal surgeries.

SUMMARY OF BACKGROUND DATA

Several recent publications detailed the sagittal alignment parameters and focus on global analysis parameters. Some patients with identical commonly evaluated spinal parameters have exhibited very different profiles, with notable differences in vertebral positions and orientations. Therefore, a fine segmental analysis of position of each vertebra could be interest to gain understanding of spine alignment.

MATERIALS AND METHODS

The authors obtained full-spine EOS x-rays of 99 volunteers in the standard free-standing position. We used a validated three-dimensional reconstruction technique to extract current spinal parameters and the positions and angulations of all vertebrae and lumbar discs. Particular attention was paid to the positions and angulations of the apical and transitional vertebrae in the general population and in subgroups according to pelvic incidence (PI).

RESULTS

T1 was the most common transitional cervicothoracic vertebra (in 89.9% of subjects) and was oriented downwards by an average of 22.0° (SD=7.3°, minimum=2.3°, maximum=40.1°). The thoracic apex trio of T5 (22.2%), T6 (28.3%), and T7 (36.4%) were equally found. The transitional thoracolumbar vertebrae were L1 (39.4%) and T12 (33.3%). The lumbar apex was usually the L3-L4 disc (36.4%). T1 seemed to be the transitional vertebra (90%) irrespective of the PI. For the other relevant vertebrae, the greater the PI, the more cranial the vertebra.

CONCLUSIONS

We performed a detailed three-dimensional assessment of overall spinal balance using positional and rotational parameters. The positions and orientations of all vertebrae were specified, particularly the apical and transitional vertebrae.

LEVEL OF EVIDENCE

Level 3.

Automatic recognition of whole-spine sagittal alignment and curvature analysis through a deep learning technique

PURPOSE

Artificial intelligence based on deep learning (DL) approaches enables the automatic recognition of anatomic landmarks and subsequent estimation of various spinopelvic parameters. The locations of inflection points (IPs) and apices (APs) in whole-spine lateral radiographs could be mathematically determined by a fully automatic spinal sagittal curvature analysis system.

METHODS

We developed a DL model for automatic spinal curvature analysis of whole-spine lateral plain radiographs by using 1800 annotated images of various spinal disease etiologies. The DL model comprised a landmark localizer to detect 25 vertebral landmarks and a numerical algorithm for the generation of an individualized spinal sagittal curvature. The characteristics of the spinal curvature, including the IPs, APs, and curvature angle, could thus be analyzed using mathematical definitions. The localization error of each landmark was calculated from the predictions of 300 test images to evaluate the performance of the landmark localizer. The interrater reliability among a senior orthopedic surgeon, a radiologist, and the DL model was assessed using the intraclass correlation coefficient (ICC).

RESULTS

The accuracy of the landmark localizer was within an acceptable range (median error: 1.7-4.1 mm), and the interrater reliabilities between the proposed DL model and each expert were good to excellent (all ICCs > 0.85) for the measurement of spinal curvature characteristics.

CONCLUSION

The interrater reliability between the proposed DL model and human experts was good to excellent in predicting the locations of IPs, APs, and curvature angles. Future applications should be explored to validate this system and improve its clinical efficiency.

A Influência dos nódulos de Schmorl no equilíbrio sagital de adultos jovens

Objectives  The present study aims to characterize the spinal balance (SB) in young adults with Schmorl nodes (SN).

Methods  A cross-sectional study was conducted on a sample of 47 young adults. Lumbar magnetic resonance imaging (MRI) was used to divide the patients into an SN group and a control group. Standing full spine radiographs were used to compare the spinopelvic SB parameters between groups: sagittal vertical axis, thoracic kyphosis, lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS).

Results  The LL and SS values were significantly lower in patients with SN when compared with the control group (54.5° versus 64.3°; 36.2° versus 41.4°, respectively). No significant differences were observed for the other parameters. Significant correlations were found in both groups between LL and SS; PI and PT; and PI and SS.

Conclusions  Young adults with SN have associated SB modifications, particularly lower LL and SS values, when compared with a control group. This flatter profile resembles that observed in patients with lower back pain and early disc pathology. We believe that SNs are relevant clinical findings that should prompt the study of the SB of a patient, as it may uncover variations associated with early disc degeneration.

Level of Evidence III

Impacto dos parâmetros espinopélvicos pré-operatórios na correção de lordose segmentar após fusão intersomática lombar por via lateral de um nível

Objectives  The present study aimed to assess whether preoperative spinopelvic parameters can influence the gain of segmental lordosis after one level of lateral lumbar interbody fusion.

Methods  The following radiological parameters were measured in the X-rays: pelvic incidence, lumbar lordosis, pelvic tilt, L4S1 lordosis, index level segmental lordosis, intraoperative index segmental lordosis, pelvic mismatch (IP-LL), distal lordosis proportion, delta segmental lordosis, Pelvic Titlt (PT) > 20, actual sacral slope, and ideal sacral slope, and the correlation of these variables with the gain of segmental lordosis was investigated. Afterwards, an exploratory cluster analysis was performed to identify common characteristics between patients and segmental lordosis gain.

Results  The sample of the present study comprised 104 patients, of which 76% presented segmental lordosis gain. The most correlated parameters with the segmental lordosis gain were preoperative segmental lordosis (−0.50) and delta intraoperative lordosis (0.51). Moreover, patients in the high PI groups had a trend to gain more segmental lordosis ( p  < 0.05) and a reduced risk of losing segmental lordosis (Odds 6.08).

Conclusion  Patients with low-medium PI profiles presented higher odds of loss of segmental lordosis. However, the preoperative spinopelvic parameters alone do not seem to play a significant role in the fate of segmental lordosis gain.

Change in sagittal alignment after decompression alone in patients with lumbar spinal stenosis without significant deformity: a prospective cohort study

OBJECTIVE

The authors' objective was to investigate whether sagittal balance improves in patients with spinal stenosis after decompression alone.

METHODS

This prospective longitudinal cohort study compared preoperative and 6-month postoperative 36-inch full-length radiographs in patients aged older than 60 years. Patients underwent decompression alone for central lumbar spinal stenosis with either a minimally invasive bilateral laminotomy for central decompression, unilateral laminectomy as an over-the-top procedure for bilateral decompression, or traditional wide laminectomy with removal of the spinous processes on both sides. The following radiographic parameters were measured: sagittal vertical axis (SVA), lumbar lordosis (LL), pelvic tilt (PT), pelvic incidence (PI), PI-LL mismatch, coronal Cobb angle, and sacral slope (SS). Patient-reported outcome measures (PROMs) were collected, including scores on the Oswestry Disability Index (ODI), visual analog scale (VAS) for leg and back pain, and EQ-5D.

RESULTS

Forty-five patients (24 males) with a mean ± SD age of 71.8 ± 5.6 years were included. Sagittal balance showed statistically significant improvement, with the mean SVA decreasing from 52.3 mm preoperatively to 33.9 mm postoperatively (p = 0.0001). The authors found an increase in LL, from mean -41.5° preoperatively to -43.9° postoperatively, but this was not statistically significant (p = 0.055). A statistically significant decrease in PI-LL mismatch from mean 8.4° preoperatively to 5.8° postoperatively was found (p = 0.002). All PROM scores showed significant improvement after spinal decompression surgery. The correlations between SVA and all PROMs were statistically significant at both preoperative and postoperative time points, although most correlations were weak except for those between preoperative SVA and ODI (r = 0.55) and between SVA and VAS for leg pain (r = 0.58).

CONCLUSIONS

Sagittal balance and PROMs show improvement at short-term follow-up evaluations in patients who have undergone decompression alone for lumbar spinal stenosis.

Modifications of the locomotor system in habitually quadrupedal humans

The acquisition of habitual bipedal locomotion, which resulted in numerous modifications of the skeleton was a crucial step in hominid evolution. However, our understanding of the inherited skeletal modifications versus those acquired while learning to walk remains limited. We here present data derived from X-rays and CT scans of quadrupedal adult humans and compare the morphology of the vertebral column, pelvis and femur to that of a bipedal brother. We show how a skeleton forged by natural selection for bipedal locomotion is modified when used to walk quadrupedally. The quadrupedal brother is characterised by the absence of femoral obliquity, a very high anteversion angle of the femoral neck, a very high collo-diaphyseal angle and a very reduced lordosis. The differences in the pelvis are more subtle and complex, yet of functional importance. The modification of the ischial spines to an ischial ridge and the perfectly rounded shape of the sacral curvature are two unique features that can be directly attributed to a quadrupedal posture and locomotion. We propose a functional interpretation of these two exceptional modifications. Unexpectedly, the quadrupedal brother and sister show a greater angle of pelvic incidence compared to their bipedal brother, a trait previously shown to increase with learning to walk in bipedal subjects. Moreover, the evolution from an occasional towards a permanent bipedality has given rise to a functional association between the angle of pelvic incidence and the lumbar curvature, with high angles of incidence and greater lumbar curvature promoting stability during bipedal locomotion. The quadrupedal brother and sister with a high angle of incidence and a very reduced lordosis thus show a complete decoupling of this complex functional integration.

Correlation analysis of the PI-LL mismatch according to the pelvic incidence from a database of 468 asymptomatic volunteers

PURPOSE

Previous studies on adults with degenerative scoliosis (ADS) have been fixed the threshold of PI-LL mismatch less than 10° for achieving good clinical outcomes. Recent studies discussed that PI-LL mismatch should consider individual pelvic incidence (PI) and should be set first in a normal population. The purpose of this study is to assess the variability of PI-LL mismatch according to PI in an asymptomatic population.

METHODS

Full-body low dose stereoradiographic evaluation was done in a multi-ethnic cohort of 468 asymptomatic adult volunteers. Patients were clustered in three groups depending on individual PI values: PI < 45°, 45° < PI < 60° and PI > 60°. 3D measurements were performed using a commercially available 2D/3D modeling software to establish a correlation of PI with other spinopelvic parameters. ANOVA and Tukey's HSD for post-hoc analysis were used to determine the differences between the three groups.

RESULTS

In our asymptomatic population, the mean value of PI-LL mismatch is - 5.4° ± 10.7°. Clusterization of the population reveals significant differences in the distribution of L1S1 lordosis, pelvic tilt and PI-LL with positive linear correlation according to PI values. As an interestingly result, PI-LL mismatch is equal to 0° when PI is around 64°.

CONCLUSIONS

The present study demonstrated that PI-LL mismatch is negative in an asymptomatic population (- 5.4° ± 10.7°) and the value should be customized to each patient to be able to restore the appropriate lordosis in ADS. The PI-LL mismatch is given by the formula PI-LL = - 28.5 + 0.44 × PI.

The Association Between Sagittal Spinopelvic Alignment and Persistent Low Back Pain After Posterior Lumbar Interbody Fusion for Treatment of Mild L5-S1 Spondylolisthesis: A Retrospective Study

Introduction

The aim of this study was to explore the association between sagittal spinopelvic alignment and persistent low back pain (PLBP) following posterior decompression and instrumented fusion for mild L5-S1 spondylolisthesis.

Methods

By retrieving medical records from January 2015 to April 2020, 200 patients following PLIF for mild L5-S1 spondylolisthesis were retrospectively reviewed. Patients were divided into two groups: PLBP group and non-PLBP group. The baseline characteristics and radiographic parameters were analyzed and compared between groups.

Results

The PLBP group comprised 26 patients, and the non-PLBP group comprised 174 patients. No significant differences in preoperative spinopelvic parameters were found between the two groups (p > 0.05). There were statistically significant differences between the preoperative and postoperative variations of LL, SL, LSA, SD, and HOD spinopelvic parameters, regardless of group (p < 0.05). Postoperative PT and SS differed significantly between the PLBP group and non-PLBP group (p < 0.05). In the PLBP group, there were no significant differences between preoperative and postoperative PT; the same applied to SS. However, significant differences were found for the variations in preoperative and postoperative PT and SS between the two groups. The ΔPT was found as an independent risk factor for postoperative PLBP.

Conclusion

Patients with mild L5-S1 spondylolisthesis with PLBP after posterior lumbar spinal fusion had decreased SS and increased PT.

Anterior Pelvic Plane: A Potentially Useful Pelvic Anatomical Reference Plane in Assessing the Patients' Ideal Pelvic Parameters Without the Influence of Spinal Sagittal Deformity

STUDY DESIGN

Observational study.

OBJECTIVE

This study was aimed at investigating the reliability of anterior pelvic plane (APP) as an anatomical reference plane for assessing the patients' pelvic incidence in patients with ankylosing spondylitis kyphosis deformity.

METHODS

The globe kyphosis (GK), lumber lordosis (LL), thoracolumbar kyphosis (TLK), thoracic kyphosis (TK), anatomical cervical 7 sacrum angle (aC7SA), and cervical 7 sacrum angle (C7SA) were measured on full-length spine radiography imagines. The pelvic incidence (PI), anatomical pelvic tilt (aPT), and anatomical sacral slope (aSS) were measured on the pelvic synthesized 2D lateral radiography imagines. Because the angle between APP and vertical line was about 4°, Angle1 and tPT were calculated using the following formulas: Angle1 = aC7SA - 4; PT = aPT + 4. According to the study conducted by Vialle, traditional PT (tPT) was calculated using the following widely accepted formula: tPT = PI * 0.37 - 7. Measured PT (mPT) was also measured on the full-length spine radiography imagines.

RESULTS

The data analysis showed that PI, mPT, aSS, aPT, and APPA were 50.83 ± 13.44°, 32.52 ± 4.64°, 41.36 ± 9.46°, 8.56 ± 6.80°, and 23.95 ± 5.17°, respectively. There was no significant difference between the PT and tPT (12.56 ± 6.80, 11.49 ± 4.73; P = .152). So, the results demonstrated that the PT could play the equivalent effect as tPT did for making surgical plans in patients with kyphosis deformity.

CONCLUSION

The pelvic anatomical reference plane had potential to be used in assessing the patients' ideal pelvic incident without the influence of spinal sagittal deformity. The aPT+4 may represent patients' postoperative ideal PT.