Validation of a new computer-assisted tool to measure spino-pelvic parameters

The accuracy of C-ARM in evaluating pelvic incidence and lumbar lordosis during surgery compared with EOS radiography after lumbar fixation

BACKGROUND

Achieving the global spinal alignment, especially the pelvis, in spine surgeries is considered the most important factor in the success of these surgeries, which requires an accurate evaluation of the correction angles measured during surgery. This study aimed to evaluate the accuracy of the mobile C-arm X-ray machine (C-ARM) for measuring lumbar lordosis (LL) and pelvic incidence (PI) parameters during lumbar fixation.

METHODS

In this prospective study, 59 lumbar fixation candidates who underwent surgery between 2020 and 2022 at our medical center, were examined. PI and LL parameters were measured at the fusion site with fluoroscopy, during surgery with C-ARM, and after surgery with EOS locally.

RESULTS

The mean age was 54.69 ± 17.62 years. 42 (71.2%) were female. The mean PI based on intraoperative C-ARM and post-surgery EOS findings were 54.57 ± 11.19 and 54.83 ± 11.17, respectively, which this difference was not statistically significant (P = 0.9). The mean LL estimate based on C-ARM and EOS findings was similar (P: 0.44).A significant positive linear correlation was observed for the mean PI (r: 0.97, p: 0.001) and LL (r: 0.99, p: 0.001).

CONCLUSION

The mean PI and LL angle during operation (measured with C-ARM) was similar to the mean of these parameters in EOS imaging findings after surgery. C-ARM can be used as a convenient device in the operating room with high precision to measure PI and LL values in spine surgeries.

Enabling technology in adult spinal deformity

This review analyzes enabling technology in Adult Spinal Deformity (ASD), with a focus on optimizing safety and teaching. The prevalence of ASD is rising, and recent technological advancements can empower surgeons to improve outcomes for ASD patients but also each comes with specific challenges. The paper highlights opportunities and potential obstacles in effective technology integration and assesses key enabling technologies, including surgical planning software, machine leaning, three-dimensional printing, augmented and virtual reality, patient-specific instrumentation as well as navigation and robotics.

Clarifying the impact of spine-specific sarcopenia and generalized sarcopenia on clinical features in patients with lumbar degenerative diseases

BACKGROUND

The pathogenesis of paraspinal degeneration and sarcopenia, which is characterized by the decrease in generalized muscle quality and quantity, may be different in patients with lumbar degenerative diseases (LDD). In addition, the impact of them on the clinical features of LDD and their interaction are still unclear.

PURPOSE

To investigate the impact of generalized and spine-specific sarcopenia on the clinical features of patients with LDD and further examine the mediating role of paraspinal muscles STUDY DESIGN: A retrospective analysis of a prospective, nonrandomized cohort dataset.

PATIENT SAMPLE

A total of 285 patients with LDD aged over 50 years were enrolled.

OUTCOME MEASURES

Sarcopenia was defined when low appendicular muscle mass was present in combination with low muscle strength or low physical performance, and spine-specific sarcopenia was designated below the gender median value of the total rfCSA of the MF at the L3/4-L5/S1 levels. Demographic variables and clinical features including reported outcome measures, spine sagittal parameters, paraspinal muscle parameters and imaging grading system.

METHODS

Difference analysis was used to compare the differences between groups in demographic variables and clinical features. Linear regression models were used to evaluate the association between spine-specific and generalized sarcopenia and clinical features. Additionally, mediation analysis was employed to explore the role of paraspinal muscles in the pathway through which generalized sarcopenia affects clinical features.

RESULTS

The generalized-sarcopenia patients exhibited significantly higher scores for VAS-back (p=.03), VAS-leg (p=.038), ODI (p<.001), SVA (p=.011) and tPfirrmann (p<.001), while significantly lower scores were observed for JOA (p=.001), TK (p<.001), LL (p=.005), and tDHI (p=.002). In the subsequent analysis, 36 of subjects were in the SSGS (spine-specific and generalized sarcopenia) group, 123 were in the NSSNGS (non-spine-specific and nongeneralized sarcopenia) group, 19 were in the NSSGS group and 107 were in the SSNGS group. Compared to the NSSNGS group, the SSGS group exhibited significantly lower JOA scores (p<.001), higher ODI scores (p=.003), reduced TK (p=.005), reduced LL (p=.005), increased SVA (p<.001), and a significantly higher tPfirrmann grading (p=.002). In Multiple linear regression analysis, the NSSNGS group exhibited significantly higher JOA, TK, LL, and tDHI values, with increases of 4.15 (p<.001), 8.87 (p<.001), 14.14 (p<.001), and 0.11 (p=.012) times than SSGS group, respectively, along with significantly lower ODI (B=-11.44, p=.006), SVA (B =-44.96, p<.001), and tPfirrmann grading (B=-2.29, p=.001). The mediation analysis indicated that paraspinal muscles play an important role in the association between generalized sarcopenia and LL (effect size=-1.330, 95% CI: -2.748, -0.304), as well as tPfirrmann grading (effect size=0.246, 95% CI: 0.458, 0.524).

CONCLUSIONS

Sarcopenia has an adverse impact on the clinical characteristics of LDD patients, particularly when both generalized and paraspinal degeneration coexist. It's important to highlight the significant role of paraspinal muscles, as well as the various mechanisms involved, in the relationship between sarcopenia and clinical features.

Posterolateral Fusion Versus Posterior Lumbar Interbody Fusion for Adult Low-Grade Isthmic Spondylolisthesis: Analysis of Sagittal Radiographic Parameters - A Randomized Controlled Trial

Study DesignRandomized controlled trial.ObjectivesTo compare the effect of posterolateral fusion (PLF) and posterior lumbar interbody fusion (PLIF) on sagittal radiographic parameters in patients with low-grade isthmic spondylolisthesis. Additionally, to explore the correlation between changes in these parameters and clinical outcomes.MethodsForty-six consecutive patients with single-level low-grade isthmic spondylolisthesis were initially enrolled. They were randomly assigned to undergo either PLF or PLIF. Patients were followed up for at least 24 months. Radiographic outcomes included pelvic incidence, pelvic tilt, sacral slope, lumbar lordosis, sagittal vertical axis, T1 pelvic angle, slip angle, slip degree and disc height. Clinical outcomes were assessed by the Oswestry Disability Index (ODI) and visual analogue scale (VAS).ResultsFour participants were lost to follow-up. Of the remaining 42 patients, 29 were female. The mean age was 40.23 ± 10.25 years in the PLF group and 35.81 ± 10.58 years in the PLIF group. There was a statistically significant greater correction of all radiographic parameters in the PLIF group. The ODI and VAS improved significantly in both groups, with no significant differences between the two groups. Changes in the ODI and VAS were significantly correlated with changes in disc height, slip angle and lumbar lordosis.ConclusionsIn patients with low-grade isthmic spondylolisthesis, PLIF demonstrates superior efficacy compared to PLF in correcting sagittal radiographic parameters. Nevertheless, this distinction does not seem to influence short-term clinical results. Restoring disc height, correcting the slip angle, and reestablishing normal lumbar lordosis are crucial steps in the surgical management of isthmic spondylolisthesis.

Removal versus Retention of Posterior Spinal Implants in Patients with Healed Thoracolumbar Fractures: Analysis of Clinical and Radiographic Outcomes-A Randomized Controlled Trial

Introduction

There is ongoing debate over whether to remove or retain posterior spinal implants following the successful union of thoracolumbar fractures. This study aimed to compare clinical and radiographic outcomes following removal versus retention of posterior spinal implants in patients with healed thoracolumbar fractures.

Methods

All patients who underwent posterior short segment fixation for thoracolumbar (T11-L2) fractures and presented to the outpatient clinic of our institution (level I trauma center) from October 2020 to October 2022 were enrolled in the study. The participants were randomly assigned to one of the two groups. The EQ-5D-5L was the primary outcome of the study. The secondary outcomes were the Oswestry Disability Index (ODI), loss of correction, and incidence of complications.

Results

A total of 52 patients were included in the final analysis with 26 patients in each group. During the 6-month and 1-year follow-up visits, the implant removal group had a statistically significant improvement in the EQ-Index, EQ-VAS, and ODI, while there were no significant differences in these parameters in the implant retention group. There was no significant difference between the two groups regarding loss of correction (P=0.109).

Conclusions

In patients who have undergone posterior instrumentation for thoracolumbar fractures, the removal of implants following fracture consolidation demonstrates enhanced clinical outcomes when compared to retaining the implants. Although loss of correction is marginally higher in the implant removal group than in the retention group, this disparity did not attain statistical significance, nor did it correlate with inferior clinical outcomes. Furthermore, the incidence of complications following implant removal remained minimal. These findings emphasize the favorable efficacy and safety profile of implant removal procedures within this patient population.

An update on improvement and innovation in the management of adult thoracolumbar spinal deformity

Adult spinal deformity (ASD) is a spectrum of abnormalities of the thoracic and lumbar spine and has an increasing prevalence. It is associated with significant physical and mental disability in symptomatic patients. Given the increased rates and the morbidity associated with this disease, novel innovation in the diagnosis and treatment of such deformity is required. The SRS-Schwab classification system described coronal scoliotic deformity with sagittal modifiers. Other parameters, such as the sagittal vertical axis, pelvic tilt, T1 pelvic angle, pelvic incidence and lumbar lordosis attempted to quantify global sagittal balance. More recently, a focus on more patient specific parameters has been targeted to improve patient outcomes. The Roussouly classification system attempted to predict sagittal alignment parameters based on fixed parameters of the pelvis. Others determined the parameters based on patient age. Technological advances have also enhanced our understanding of ASD. Long cassette films and automated analyses have allowed standardization of these measurements across physicians. 3D printing has been used as an adjunct for both surgical planning and implants, both generic and patient specific, to improve outcomes. With these, advances in minimally invasive approaches have allowed ASD correction with lower complications and blood loss. Intraoperative navigation and the use of robotics has allowed improved accuracy in the care of these patients. Development of complex osteotomies have allowed for correction of advanced deformity. Fusion, however, is the ultimate goal of surgical ASD correction. Advances in biologics such as the use of recombinant Human Bone Morphogenetic Protein-2 have been used to improve fusion rates and combat pseudoarthrosis. Finally, post-operative advances in ASD patient care with emphasis on enhanced recovery after surgery has allowed improvements in hospital length of stay and pain scores. ASD is becoming a more ubiquitous diagnosis for spine surgeons with an increasing aging population. Improvement in the understanding of the diagnosis, spinopelvic parameters, imaging techniques, and post operative care are all aimed toward helping patients in whom care can be extremely difficult. Further study in ASD patient care will target advanced innovation to provide optimal treatment to these patients and allow for best possible outcomes.

Reliability of Vertebral Pelvic Angles in Assessment of Spinal Alignment

STUDY DESIGN

Reliability analysis.

OBJECTIVES

Vertebral pelvic angles (VPA) are gaining popularity given their ability to describe the shape of the spine. Understanding the reliability and minimal detectable change (MDC) is necessary to determine how these measurement tools should be used in the manual assessment of spine radiographs. Our aim is to assess intra- and interobserver intraclass correlation coefficients (ICC) and the MDC in the use of VPA for assessing alignment in adult spinal deformity (ASD).

METHODS

Three independent examiners blindly measured T1, T4, T9, L1, and L4PA twice in ASD patients with a 4-week window after the initial measurements. Patients who had undergone hip or shoulder arthroplasty, fused or transitional vertebrae, or whose hip joints were not visible on radiographs were excluded. Power analysis calculated a minimum sample size of 19. Both intra- and interobserver ICC and MDC, which denotes the smallest detectable change in a true value with 95% confidence, were calculated.

RESULTS

Out of the 193 patients, 39 were ultimately included in the study, and 390 measurements were performed by 3 raters. Intraobserver ICC values ranged from .90 to .99. The interobserver ICC was .97, .97, .96, .95, and .92, and the MDC was 5.3°, 5.1°, 4.8°, 4.9°, and 4.1° for T1, T4, T9, L1, and L4PA, respectively.

CONCLUSION

All VPAs showed excellent intra- and interobserver reliability, however, the MDC is relatively high compared to typical ranges for VPA values. Therefore, surgeons must be aware that substantial alignment changes may not be detected by a single VPA.

Investigation of spinopelvic sagittal alignment and its correlations in asymptomatic pediatric populations

The sagittal alignment of the cervical spine and its relationship with spinopelvic parameters plays a crucial role in maintaining overall postural balance. This study aims to provide normative values for these parameters in asymptomatic pediatric subjects, aiding in the enhancement of treatment and evaluation strategies for spinal deformities and disorders. Conducted at the Third Hospital of Hebei Medical University, this retrospective study included 307 asymptomatic pediatric volunteers aged 4-18 years, screened for scoliosis from January 2021 to July 2023. Participants underwent whole-length EOS examinations following a standard protocol. Radiographic measurements of cervical and spinopelvic parameters were taken, and statistical analyses were performed using SPSS software to assess variations by age and gender. Normative values for cervical sagittal and spinopelvic parameters were established, demonstrating significant differences based on age and sex. Key findings include a strong correlation between the C2-7 Cobb angle and T1 and C7 slopes, with an observed increase in cSVA particularly pronounced in boys. Age and gender significantly influenced the normative values of these parameters, suggesting the importance of considering these factors in pediatric spinal assessments. This study establishes crucial normative values for cervical and spinopelvic parameters in a large pediatric cohort, highlighting the influence of age and sex on spinal sagittal alignment. The findings underscore the necessity of tailoring spinal assessment approaches in pediatric populations to improve the clinical evaluation and management of spinal health, providing a foundational benchmark for future research in pediatric spinal deformities and disorders.

Proximal junctional kyphosis above long spinal fusions

INTRODUCTION

Spinal deformity in adults is a major public health problem. After failure of conservative treatment, correction and fusion surgery leads to clinical and radiological improvement. However, mechanical complications and more particularly - proximal junctional kyphosis (PJK) - are common with an incidence of 10%-40% depending on the studies.

ANALYSIS

Several risk factors have been identified and can be grouped into three categories. Among the patient-related factors, advanced age, comorbidities, osteoporosis and sarcopenia play a determining role. Among the radiological factors, changes in sagittal alignment (cranial migration of thoracolumbar inflection point, over-correction of lumbar hyperlordosis, preoperative thoracolumbar kyphosis) play a key role. Finally, the fusion technique itself may increase the risk of PJK (use of screws instead of hooks) as a surgical factor.

PREVENTION

Prevention happens at each phase of treatment. A patient assessment is done preoperatively to identify those at risk of PJK. Treating osteoporosis is beneficial. The surgical strategy must also be adapted: the choice of transitional implants such as sublaminar links or hooks and the use of ligament reinforcement techniques can help minimize the risk of PJK. Finally, methodical clinical and radiological follow-up will help to detect early signs of PJK and allow a surgeon to reoperate right away.

TREATMENT

Not all PJK requires surgical revision. Radiological monitoring and functional treatment is sometimes sufficient. However, if the patient develops pain, neurological complications or instability detected by imaging (unstable fracture, spondylolisthesis, spinal cord compression), revision surgery is necessary. It may consist of proximal extension of the fusion combined with decompression of the stenosis levels at a minimum.

CONCLUSION

PJK is a major challenge for surgeons. The best treatment is prevention, with a thorough analysis of risk factors leading to a well-planned and personalized surgery. Regular postoperative follow-up is essential.

LEVEL OF EVIDENCE

Expert opinion.

Posterior instrumented correction and fusion of Scheuermann´s results in physiological reconstruction of sagittal alignment and excellent overall clinical outcome- clinical trail of 73 patients

PURPOSE

The aim was to assess the clinical outcomes after posterior spinal fusion (PSF) in patients with Scheuermann's disease (SD).

METHODS

SD undergoing PSF were retrospectively analyzed. Clinical outcome was determined using SRS-22- and Eq. 5D-questionaires preop and after 3, 12, 24 months after surgery. Whole spine x-rays were analyzed (preop, postop, after 6, 12, 24 months): sagittal and coronary Cobb angles, and pelvic parameters were evaluated; ideal lumbar lordosis (LL) was calculated using formula of le Huec (LL = 0.54*PI + 27.6). Surgical time, complications and blood loss were compared. Postop appearance of proximal (PJF) and distal junction failure (DJF) were calculated. Values were given as mean. Comparison with significance α = 0.05.

RESULTS

73 patients were included. SRS-22 total score and EQ5D showed significant increase from preop to two-year FU (each p < 0.001). Preop Thoracic kyphosis (TK) was 75.1° with significant correction to 48.5° (p < 0.001). LL showed mean correction from 68.2° to 46.7° (p < 0.001). Difference between ideal and measured LL showed improvement from - 17.2° preop to -3.3° 6 month postop, good spontaneous correction of hyperlordosis. 63% had < 10° deviation from ideal LL 6 month postoperatively, whereas only 21.4% were in this range preoperatively. No significant changes for spinopelvic parameters during FU. Complications occurred in 13,7% of cases. A low revision rate for PJF (2,7%) was necessary. Subscore mental health showed a correlation to preop TK (p < 0.05).

CONCLUSION

Physiological reconstruction of sagittal alignment could be achieved in most cases (63%). Clinical FU results were convincing with significant improvement of patient's satisfaction. Complication rate was moderate and risk of PJF after PSF low.

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.

Early Sagittal Shape of the Spine Predicts Scoliosis Development in a Syndromic (22q11.2DS) Population: A Prospective Longitudinal Study

BACKGROUND

Scoliosis is a deformation of the spine and trunk that, in its more severe forms, creates a life-long burden of disease and requires intensive treatment. For its most prevalent form, adolescent idiopathic scoliosis, no underlying condition can be defined, and the pathomechanism appears to be multifactorial; however, it has been suggested that the biomechanics of the spine play a role. For nonidiopathic scoliosis, underlying conditions can be recognized, but what drives the deformity remains unclear. In this study, we examined the early sagittal shape of the spine before the onset of scoliosis in a population with 22q11.2 deletion syndrome (22q11.2DS). This cohort was chosen since children with this syndrome have an approximately 50% chance of developing scoliosis that shares certain characteristics with idiopathic scoliosis, namely, age of onset, curve morphology, and rate of progression.

METHODS

This prospective cohort study included patients with 22q11.2DS who were followed with the use of spinal radiographs during adolescent growth. All of the children, who initially had no scoliosis while still skeletally immature (Risser stages 0 and 1), were followed at 2-year intervals until they reached skeletal maturity (Risser stages 3 to 5). We assessed the segment of the spine that has previously been shown to be rotationally unstable, the posteriorly inclined segment, to determine if it was predictive of later scoliosis development. For quantification, the area of the "posteriorly inclined triangle" (PIT), a previously described parameter that integrates both the inclination and length of the at-risk segment, was measured.

RESULTS

Of the 50 children who initially had no scoliosis (mean age at inclusion, 10.7 ± 1.7 years; mean follow-up, 4.8 ± 1.6 years), 24 (48%) developed scoliosis. Patients with an above-average PIT area (>60 cm 2 ) at inclusion showed a relative risk of 2.55 for scoliosis development (95% confidence interval [CI]:1.22 to 5.34). PIT inclination was correlated with curve type: a taller and steeper hypotenuse predicted later thoracic scoliosis, while a shorter and less steep inclination predicted the development of (thoraco)lumbar scoliosis.

CONCLUSIONS

This prospective study identified the pre-scoliotic sagittal shape of the spine as a risk factor for the later development of scoliosis in the population of children with 22q11.2DS.

LEVEL OF EVIDENCE

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

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.

Performance evaluation of a deep learning-based cascaded HRNet model for automatic measurement of X-ray imaging parameters of lumbar sagittal curvature

PURPOSE

To develop a deep learning-based cascaded HRNet model, in order to automatically measure X-ray imaging parameters of lumbar sagittal curvature and to evaluate its prediction performance.

METHODS

A total of 3730 lumbar lateral digital radiography (DR) images were collected from picture archiving and communication system (PACS). Among them, 3150 images were randomly selected as the training dataset and validation dataset, and 580 images as the test dataset. The landmarks of the lumbar curve index (LCI), lumbar lordosis angle (LLA), sacral slope (SS), lumbar lordosis index (LLI), and the posterior edge tangent angle of the vertebral body (PTA) were identified and marked. The measured results of landmarks on the test dataset were compared with the mean values of manual measurement as the reference standard. Percentage of correct key-points (PCK), intra-class correlation coefficient (ICC), Pearson correlation coefficient (r), mean absolute error (MAE), mean square error (MSE), root-mean-square error (RMSE), and Bland-Altman plot were used to evaluate the performance of the cascade HRNet model.

RESULTS

The PCK of the cascaded HRNet model was 97.9-100% in the 3 mm distance threshold. The mean differences between the reference standard and the predicted values for LCI, LLA, SS, LLI, and PTA were 0.43 mm, 0.99°, 1.11°, 0.01 mm, and 0.23°, respectively. There were strong correlation and consistency of the five parameters between the cascaded HRNet model and manual measurements (ICC = 0.989-0.999, R = 0.991-0.999, MAE = 0.63-1.65, MSE = 0.61-4.06, RMSE = 0.78-2.01).

CONCLUSION

The cascaded HRNet model based on deep learning algorithm could accurately identify the sagittal curvature-related landmarks on lateral lumbar DR images and automatically measure the relevant parameters, which is of great significance in clinical application.

Deep learning algorithm for fully automated measurement of sagittal balance in adult spinal deformity

AIM

Deep learning (DL) algorithms can be used for automated analysis of medical imaging. The aim of this study was to assess the accuracy of an innovative, fully automated DL algorithm for analysis of sagittal balance in adult spinal deformity (ASD).

MATERIAL AND METHODS

Sagittal balance (sacral slope, pelvic tilt, pelvic incidence, lumbar lordosis and sagittal vertical axis) was evaluated in 141 preoperative and postoperative radiographs of patients with ASD. The DL, landmark-based measurements, were compared with the ground truth values from validated manual measurements.

RESULTS

The DL algorithm showed an excellent consistency with the ground truth measurements. The intra-class correlation coefficient between the DL and ground truth measurements was 0.71-0.99 for preoperative and 0.72-0.96 for postoperative measurements. The DL detection rate was 91.5% and 84% for preoperative and postoperative images, respectively.

CONCLUSION

This is the first study evaluating a complete automated DL algorithm for analysis of sagittal balance with high accuracy for all evaluated parameters. The excellent accuracy in the challenging pathology of ASD with long construct instrumentation demonstrates the eligibility and possibility for implementation in clinical routine.

Automatic 3D pelvimetry framework in CT images and its validation

In the field of spinal pathology, sagittal balance of the spine is usually judged by the spatial structure and morphology of pelvis, which can be represented by pelvic parameters. Pelvic parameters, including pelvic incidence, pelvic tilt and sacral slope, are therefore essential for the diagnosis and treatment of spinal disorders, however, it is a time-consuming and laborious procedure to measure these parameters by traditional methods. In this paper, an automatic measurement framework for pelvic CT images was proposed to calculate three-dimensional (3D) pelvic parameters with the support of deep learning technology. Pelvic images were first preprocessed, and 3D reconstruction was then performed to obtain 3D pelvic model by the Visualization Toolkit. DRINet was trained to segment the femoral head region in the pelvic images, and 3D sphere fitting was performed to locate the femoral heads. In addition, VGG16 was adopted to recognize images containing superior sacral endplate, and the plane growth algorithm was used to fit the plane so that the midpoint and normal vector of the superior sacral endplate could be obtained. Finally, 3D pelvic parameters were automatically calculated, and compared with manual measurements for 15 patients. The proposed framework automatically generated 3D pelvic models, and calculated two-dimensional (2D) and 3D pelvic parameters from continuous CT images. Experiments demonstrated that the framework can greatly speed up the calculation of pelvic parameters, and these parameters are accurate when compared with the manual measurements. In conclusion, the proposed framework demonstrates good performance on automatic pelvimetry measurement by incorporating deep learning technology, and can well replace the traditional methods for pelvic parameter measurement.

Analysis of the reliability of KEOPS version 2 for the measurement of coronal and sagittal parameters in spinal deformity

BACKGROUND

The purpose of the study is to evaluate the updated version of this software in patients with various spinal deformity.

METHODS

Sixty patients were included in this study and were divided into three categories: 20 patients with AIS, 20 patients with ASD, and 20 patients having undergone corrective surgery for spinal deformity. The measurements were performed by two senior and two junior orthopedic surgery residents, and were done at two points in time separated by a 3-week interval with the cases being randomized every time to reduce the risk of memory bias. Measured parameters included coronal, sagittal, global alignment parameters, and pelvic parameters.

RESULTS

When assessing the inter- and intra-observer reliability across all the groups of patients, none of the coefficients was smaller than 0.8 with a very high level of agreement. The standard error ranged from 0.7° to 1.5° demonstrating a high level of accuracy. Fairly similar results were seen when the groups were divided into the three categories except for the post-operative groups where a strong and not perfect level of agreement was reported.

CONCLUSION

This is the first study to assess the reproducibility of the new version of KEOPS, showing a very high agreement in all measurements. In the post-operative group, although it showed a strong agreement, the lower performance can be explained by the presence of surgical material making it harder to identify the anatomical landmarks accurately. Nevertheless, we can recommend the usage of this software in a clinical setting.

A Geometrical Explanation for Change in Pelvic Tilt (or Lack of Change) Following Long Spinal Fusions

STUDY DESIGN

Retrospective cohort.

OBJECTIVE

Examine the relationship between compensatory pelvic retroversion, positive sagittal imbalance (measured by C2 tilt), and the C2 pelvic angle (C2PA) in patients before long spinal fusions; and to determine the association between changes in C2PA and pelvic tilt (PT) following long spinal fusions.

BACKGROUND

Adult spinal deformity surgical goals often include a PT target, yet patients frequently demonstrate persistent compensatory pelvic retroversion following surgery.

METHODS

Adults above 18 years old undergoing long spinal fusions (>4 levels) with standing preoperative and postoperative radiographs were included. To examine drivers of preoperative sagittal balance, regression models were fit to estimate the association between preoperative C2PA and pelvic incidence with preoperative PT and C2 tilt. To predict postoperative change in PT, multivariable regression was used to estimate change in PT, adjusting for change in C2PA and preoperative C2 tilt.

RESULTS

Among the 80 patients identified, the median age was 61 (IQR: 45-72) and 46 (58%) were female. The median number of levels fused was 10 (IQR: 8-13) and 55 (69%) were instrumented to the sacrum/pelvis. Preoperative C2PA had a significant nonlinear association with preoperative PT ( r2 =0.81, P <0.001) and preoperative C2 tilt ( r2 =0.41, P =0.002). Postoperative change in PT was strongly associated with change in C2PA (β=0.81; P <0.001) and preoperative C2 tilt (β=0.55; P <0.001).

CONCLUSIONS

Following long spinal fusions, change in PT (or lack thereof) can be reliably predicted based on change in C2PA and preoperative C2 tilt. In patients with normal preoperative C2 tilt, the change in C2PA is nearly equivalent to the change in PT, but in patients with more positive C2 tilt (sagittal imbalance), a greater change in C2PA will be required to achieve an equivalent change in PT.

LEVEL OF EVIDENCE

3.

Influence of cranium orientation on cervical sagittal alignment during radiographic examination: a radiographic analysis

BACKGROUND CONTEXT

During the radiographic examination, the cranium orientation varies not only individually but also within the same subject, in different imaging sessions. Knowing how changes in the orientation of the cranium influences cervical sagittal alignment during the radiographic examination of the cervical spine can aid clinicians in the accurate evaluation for cervical sagittal alignment in clinical practice.

PURPOSE

To radiographically examine the influence of cranium orientation on cervical sagittal alignment during radiographic examination in an asymptomatic cohort.

STUDY DESIGN

A prospective radiographic study.

PATIENT SAMPLE

Eighty asymptomatic volunteers (mean age, 40.4 years; 50.0% male) were enrolled.

OUTCOME MEASURES

Cervical sagittal parameters including the regional slope (C1 slope, C2 slope, C5 slope, C7 slope, and T1 slope), Cobb angle (O-C1 angle, C1-C2 angle, C2-C5 angle, C5-C7 angle, and C7-T1 angle), and cranial/cervical offset (sella turcica tilt [ST tilt] and C2 tilt).

METHODS

In all participants, standing lateral radiographs of the cervical spine were taken in 3 forward-gazing positions: anteverted-cranium (AC) position; neutral-cranium (NC) position; and retroverted-cranium (RC) position. Cervical sagittal parameters, including the regional slope, Cobb angle, and cranial/cervical offset, in these 3 positions were statistically compared.

RESULTS

The C1 and C2 slopes were anteverted and retroverted in the AC and RC positions, respectively, compared to those in the NC position. The C5 slope, C7 slope, and T1 slope were constant among the 3 positions. In O-C2 and C2-C5, statistically significant differences in the regional Cobb angles were identified among the 3 positions; however, there were no significant differences in the C5-C7 or C7-T1 segments. Cranial and cervical offsets of ST tilt and C2 tilt increased and decreased when the cranium was anteverted and retroverted, respectively.

CONCLUSIONS

The current study suggests that the adjustment of the cranium orientation when taking cervical spine radiographs is mainly controlled at the upper cervical spine of the O-C2 segment in an asymptomatic cohort. On radiograph, alignment in the upper cervical segment of O-C2 changes; accordingly, the middle cervical segment of C2-C5 can change during the adjustment of cranium orientation. However, alignment in the lower cervical segment of C5-C7 and the cervicothoracic junction of C7-T1 remains constant. Further, cranial/cervical offset increases and decreases when the cranium is anteverted and retroverted, respectively. Our results can help the accurate evaluation of cervical sagittal alignment on plain radiographs in clinical practice.

Reliability of the Biomechanical Assessment of the Sagittal Lumbar Spine and Pelvis on Radiographs Used in Clinical Practice: A Systematic Review of the Literature

Background: Biomechanical analysis of the sagittal alignment of the lumbar spine and pelvis on radiographs is common in clinical practices including chiropractic, physical therapy, scoliosis-related thoraco-lumbo-sacral orthosis (TLSO) management, orthopedics, and neurosurgery. Of specific interest is the assessment of pelvic morphology and the relationship between angle of pelvic incidence, sacral slope, and lumbar lordosis to pain, disability, and clinical treatment of spine conditions. The current state of the literature on the reliability of common methods quantifying these parameters on radiographs is limited. Methods: The objective of this systematic review is to identify and review the available studies on the reliability of different methods of biomechanical analysis of sagittal lumbo-pelvic parameters used in clinical practice. Our review followed the recommendations of the preferred reporting items for systematic reviews and meta-analyses (PRISMA). The design of this systematic review was registered with PROSPERO (CRD42023379873). Results: The search strategy yielded a total of 2387 articles. A total of 1539 articles were screened after deduplication and exclusion by automation tools, leaving 473 full-text articles that were retrieved. After exclusion, 64 articles met the inclusion criteria. The preponderance of the evidence showed good to excellent reliability for biomechanical assessment of sagittal lumbo-pelvic spine alignment. Conclusions: The results of this systematic review of the literature show that sagittal radiographic analysis of spinal biomechanics and alignment of the human lumbo-pelvic spine is a reliable tool for aiding diagnosis and management in clinical settings.

Global sagittal angle and spinopelvic sagittal alignment: a step toward investigation of sagittal plane deformity in upper lumbar disc herniation

BACKGROUND AND OBJECTIVES

Understanding the biomechanical relationship between the spine and the pelvis is important for the management of symptomatic lumbar disease. There are several different metrics that may be used to evaluate the spine in the sagittal plane. The aim of this study is to compare spinopelvic parameters and global sagittal angle (GSA) in a cohort of patients with upper lumbar disc herniations (ULDH) to identify a correlation between the pelvic incidence (PI) and GSA with ULDH.

MATERIAL AND METHODS

Eighty-six patients with ULDH and 86 asymptomatic control group underwent whole body biplanar stereographs- and magnetic resonance imaging. The spinopelvic parameters and GSA were measured.

RESULTS

PI, sacral slope (SS), lumbar lordosis (LL), and thoracic kyphosis (TK) were all significantly lower than in the control group (p < 0.01) but there was no difference in the pelvic tilt (PT). The two groups were divided into subgroups. PI in the T12-L1 and L1-L2 level groups were significantly smaller than in the control group (p < 0.05). Also, there was a significant difference in TK and LL between the L3-L4 level and control group (p < 0.05), but there was no statistically significant difference in PT between all levels and the control group.

CONCLUSION

This study demonstrated a unique correlation between several spinopelvic parameters and GSA and the occurrence of ULDH. Lower PI, SS, and LL in T12-L1 and L1-L2 levels indicates a flat lumbar spine which may increase mechanical stress at these levels, thereby leading to disc herniation.

The Impact of Unplanned Reoperation Following Adult Spinal Deformity Surgery: A Prospective Longitudinal Cohort Study with 5-Year Follow-up

BACKGROUND

The long-term impact of reoperations following adult spinal deformity (ASD) surgery is still poorly understood. Our aim was to identify the relationship between unplanned reoperation and health-related quality of life (HRQoL) gain at 2 and 5 years of follow-up.

METHODS

We included patients enrolled in a prospective ASD database who underwent surgery ≥5 years prior to the start of the study and who had 2 years of follow-up data. Adverse events (AEs) leading to an unplanned reoperation, the time of reoperation occurrence, invasiveness (blood loss, surgical time, hospital stay), and AE resolution were assessed. HRQoL was measured with use of the Oswestry Disability Index, Scoliosis Research Society-22, and Short Form-36. Linear models controlling for baseline data and index surgery characteristics were utilized to assess the relationships between HRQoL gain at 2 and 5-year follow-up and the number and invasiveness of reoperations. The association between 5-year HRQoL gain and the time of occurrence of the unplanned reoperation and that between 5-year HRQoL gain and AE resolution were also investigated.

RESULTS

Of 361 eligible patients, 316 (87.5%) with 2-year follow-up data met the inclusion criteria and 258 (71.5%) had 5-year follow-up data. At the 2-year follow-up, 96 patients (30.4%) had a total of 165 unplanned reoperations (1.72 per patient). At the 5-year follow-up, 73 patients (28.3%) had a total of 117 unplanned reoperations (1.60 per patient). The most common cause of reoperations was mechanical complications (64.9%), followed by surgical site infections (15.7%). At the 5-year follow-up, the AE that led to reoperation was resolved in 67 patients (91.8%). Reoperation invasiveness was not associated with 5-year HRQoL scores. The number of reoperations was associated with lesser HRQoL gain at 5 years for all HRQoL measures. The mean associated reduction in HRQoL gain per unplanned reoperation was 41% (range, 19% to 66%). Reoperations resulting in no resolution of the AE or resolution with sequelae had a greater impact on 5-year follow-up HRQoL scores than reoperations resulting in resolution of the AE.

CONCLUSIONS

A postoperative, unplanned reoperation following ASD surgery was associated with lesser gain in HRQoL at 5 years of follow-up. The association did not diminish over time and was affected by the number, but not the magnitude, of reoperations. Resolution of the associated AE reduced the impact of the unplanned reoperation.

LEVEL OF EVIDENCE

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

Auto-CA: Automated Cobb Angle Measurement Based on Vertebrae Detection for Assessment of Spinal Curvature Deformity

An accurate identification and localization of vertebrae in X-ray images can assist doctors in measuring Cobb angles for treating patients with adolescent idiopathic scoliosis. It is useful for clinical decision support systems for diagnosis, surgery planning, and spinal health analysis. Currently, publicly available annotated datasets on spinal vertebrae are small, making deep-learning-based detection methods that are highly data-dependent less accurate. In this article, we propose an algorithm based on convolutional neural networks that can be trained to detect vertebrae from a small set of images. This method can display critical information on a patient's spine, display vertebrae and their labels on the thoracic and lumbar, calculate the Cobb angle, and evaluate the severity of spinal deformities. The proposed achieved an average accuracy of 0.958 and 0.962 for classifying spinal deformities (i.e., C-shaped, S-shaped type 1, and S-shaped type 2) and severity of Cobb angle (i.e., normal, mild, moderate, and severe), respectively. The Cobb angle measurement had a median difference of less than 5° from the ground-truth with SMAPE of 5.27% and an error on landmark detection of 19.73. In addition, Lenke classification is used to analyze spinal deformities as types A, B, and C, which have an average accuracy of 0.924. Physicians can use the proposed system in clinical practice by providing X-ray images via the user interface.

Publication Trends in the Pelvic Parameter Related Literature between 1992 and 2022 : A Bibliometric Review

OBJECTIVE

This study aimed to conduct a bibliometric analysis on pelvic parameter related research over the last 30 years, analyzing trends, hotspots, and influential works within this field.

METHODS

A comprehensive Web of Science database search was performed. The search yielded 3249 results, focusing on articles and reviews published from 1992 to 2022 in English. Data was analyzed using CiteSpace and VOSviewer for keyword, authorship, and citation burst analysis, co-citation analysis, and clustering.

RESULTS

The number of publications and citations related to pelvic parameters has increased exponentially over the last 30 years. The USA leads in publication count with 1003 articles. Top publishing journals include the European Spine Journal, Spine, and Journal of Neurosurgery: Spine, with significant contributions by Schwab, Lafage V, and Protoptaltis. The most influential articles were identified using centrality and sigma values, indicating their role as key articles within the field. Research hotspots included spinal deformity, total hip arthroplasty, and sagittal alignment.

CONCLUSION

Interest in pelvic parameter related research has grown significantly over the last three decades, indicating its relevance in modern orthopedics. The most influential works within this field have contributed to our understanding of spinal deformity, pelvic incidence, and their relation to total hip arthroplasty. This study provides a comprehensive overview of the trends and influential research in the field of pelvic parameters.

[Translated article] How do I plan adolescent idiopathic scoliosis surgery? Systematization of a preoperative planning method

Preoperative planning is essential in adolescent idiopathic scoliosis (AIS) surgery to determine the fusion levels and to perform the procedure with greater precision and diligence. However, the protocolized performance of such planning is not as widespread among specialists in training. The aim of this article is to describe in detail the preoperative planning method for AIS used in a specialised paediatric and adolescent spine unit of a referral centre, as well as the logistics and the tactics, supported a free semi-automatic digital measurement and planning software. Three representative cases of different vertebral deformities, treated by posterior spinal fusion after preoperative planning according to the method, are shown. This method is highly suitable for the trainee surgeon as it combines the advantages of traditional and modern methods, and is simple, low-cost, accessible, reproducible and with an educational character.

How do I plan adolescent idiopathic scoliosis surgery? Systematization of a preoperative planning method

Preoperative planning is essential in adolescent idiopathic scoliosis (AIS) surgery to determine the fusion levels and to perform the procedure with greater precision and diligence. However, the protocolized performance of such planning is not as widespread among specialists in training. The aim of this article is to describe in detail the preoperative planning method for AIS used in a specialized pediatric and adolescent spine unit of a referral center, as well as the logistics and the tactics, supported a free semi-automatic digital measurement and planning software. Three representative cases of different vertebral deformities, treated by posterior spinal fusion after preoperative planning according to the method, are shown. This method is highly suitable for the trainee surgeon as it combines the advantages of traditional and modern methods, and is simple, low cost, accessible, reproducible and with an educational character.

Sagittal trunk excursion and lumbar repositioning error between female and male patients with patellofemoral pain syndrome

Background

Patellofemoral pain syndrome (PFPS) is a challenging clinical problem affecting adults, adolescents, and physically active populations. PFPS impacts the patient's trunk kinematics in the frontal plane. Previous studies have found gender-based biomechanical differences in patients with PFPS; however, sagittal trunk kinematics during mini-squats and lumbar proprioception in PFPS have not been studied previously.

Objectives

To investigate sagittal trunk excursion (It is defined as the sagittal trunk flexion angle from the start to the end of the mini squat) during mini-squats as well as lumbar repositioning error between individuals with and without PFPS, and determine gender differences in the outcome variables.

Methods

A sample of 56 participants aged 18-25 years was enrolled; 30 with PFPS (13 males, 17 females) and 26 asymptomatic controls (11 males, 15 females). The sagittal trunk excursion during mini-squats was examined by two-dimensional (2D) photographic analysis using Surgimap software. Active lumbar flexion repositioning error was assessed using an isokinetic dynamometer.

Results

For sagittal trunk excursion, no significant main effect of group was observed (p = 0 . 136 ). On the other hand, the main effect was significant for gender (p = 0 . 005 ), as was the interaction effect. Compared to the control group, the PFPS group showed significantly (p = 0 . 01 ) lower sagittal trunk excursion in females than in males during mini-squats. For active lumbar flexion repositioning error, no evidence was found for significant main or interaction effects (p > 0 . 05 ).

Conclusion

Females with PFPS exhibit a more erect sagittal trunk posture than males during mini-squats. Trunk posture should be considered during weight-bearing activities in PFPS, and gender-specific assessment protocols should be developed.

How does the correction in lumbar lordosis affect the spinopelvic realignments in degenerative lumbar scoliosis underwent scoliosis surgery?

BACKGROUND

To evaluate the effects of correction in lumbar lordosis (LL) that have on full-body realignments in patients with degenerative lumbar scoliosis (DLS) who had undergone long sacroiliac fusion surgery.

METHODS

A multi-center retrospective study including 88 DLS patients underwent the surgical procedure of long sacroiliac fusion with instrumentations was performed. Comparisons of radiographic and quality-of-life (QoL) data among that at the pre-operation, the 3rd month and the final follow-up were performed. The correlations between the LL correction and the changes in other spinopelvic parameters were explored using Pearson-correlation linear analysis and linear regression analysis. The correlation coefficient (r) and the adjusted r2 were calculated subsequently.

RESULTS

All radiographic and QoL data improved significantly (P < 0.001) after the surgical treatments. The LL correction correlated (P < 0.001) with the changes in the sacral slope (SS, r = 0.698), pelvic tilt (PT, r = -0.635), sagittal vertical axis (SVA, r = -0.591), T1 pelvic angle (TPA, r = -0.782), and the mismatch of pelvic incidence minus lumbar lordosis (PI-LL, r = -0.936), respectively. Moreover, LL increased by 1° for each of the following spinopelvic parameter changes (P < 0.001): 2.62° for SS (r2 = 0.488), -4.01° for PT (r2 = 0.404), -4.86° for TPA (r2 = 0.612), -2.08° for the PI-LL (r2 = 0.876) and -15.74 mm for SVA (r2 = 0.349). Changes in the thoracic kyphosis (r = 0.259) and pelvic femur angle (r = 0.12) were independent of the LL correction, respectively.

CONCLUSIONS

LL correction correlated significantly to the changes in spinopelvic parameters; however, those independent variables including the thoracic spine and hip variables probably be remodeled themselves to maintain the full-body balance in DLS patients underwent the correction surgery.

PreOperative Planning for Adult Spinal Deformity Goals: Level Selection and Alignment Goals

Adult Spinal Deformity (ASD) is a complex pathologic condition with significant impact on quality of life, including pain, loss of function, and fatigue. Achieving realignment goals is crucial for long-term results. Reliable preoperative planning strategies, including nomograms, measurement tools, and level selection, are key to maximizing the likelihood of achieving a good outcome following ASD corrective surgery. This review covers recent literature on such strategies, including review of the different targets for realignment and their association with outcomes (both patients-reported outcomes and complications), selection of upper and lower instrumented vertebrae, and the latest innovation in preoperative planning for deformity surgery.

Spinal‑pelvic sagittal imbalance and paraspinal muscle degeneration in patients with degenerative lumbar spinal stenosis: A monocentric, prospective and observational study

Degenerative lumbar spinal stenosis (DLSS) is a condition in which the body is held in a poor posture for a long period of time, resulting in a change in the stress structure of the lumbar spine that causes degenerative changes in the muscles of the spine. The sagittal balance of the spine and pelvis and the degeneration of the paravertebral muscles have been the focus of recent research. To explore the relationship between paraspinal muscle degeneration and changes in spine-pelvic sagittal parameters in patients with DLSS, 95 patients with DLSS (experimental group) and 70 healthy volunteers (control group) hospitalized in the Ordos Central Hospital between January 2020 and January 2022 were included as study subjects. All patients underwent lumbar magnetic resonance imaging and spinal X-ray using uniform criteria. The correlation between paravertebral muscle parameters and sagittal-pelvic sagittal parameters in patients with DLSS was obtained from two imaging examinations, and the data were organized and grouped in order to explore the correlation between these parameters. There was no significant difference in the general data between the two groups (P>0.05). In the L4-5 DLSS patient group, the ratio of fat infiltration in the right erector spinae (ES) muscle was negatively correlated with thoracic kyphosis (TK) (r=-0.536; P<0.05) but not significantly in the left side. The relative cross-sectional area of the left multifidus muscle (MF RCSA) was positively correlated with TK (r=0.685; r=0.615; P<0.05) but not significantly in the right side. In the L5-S1DLSS patient group, the right MF RCSA and right ES RCSA were significantly positively correlated with TK (r=0.685; r=0.615; P<0.05) but not significant in the left side. Thus, paravertebral muscle parameters were correlated with spinal-pelvic sagittal parameters in patients with DLSS.

Internal Chain of Correlation of Sagittal Cervical Alignment in Asymptomatic Subjects

STUDY DESIGN

Cross-sectional observational study in a prospective cohort.

OBJECTIVE

To analyze the cervical alignment characteristics and their chain of correlation in a sample of asymptomatic individuals.

METHODS

Asymptomatic adults who had full spinal radiographs performed. Cervical radiographic parameters were measured, including upper cervical curvature (McGregor line-C2), lower cervical curvature (C2-C7), McGregor slope, and sagittal vertical axis from C2-C7 (CSVA) and T1-slope (T1S). Subjects were stratified by age into 3 groups (18-39 years, 40-59 years, and >60 years), and radiographic parameters were compared across age groups and based on sex.

RESULTS

102 asymptomatic subjects (mean age, 50 years) were included. The T1S significantly increased with age, accompanied by an increase in C2-C7 lordosis. The cervical sagittal alignment, represented by CSVA, did not significantly differ based on age. There was a close correlation among the cervical sagittal parameters, such that the CSVA may be predicted based on the T1S and C2-C7 lordosis. Comparisons of the normative values identified in the present study with those reported in previous studies demonstrate variability in what constitutes normal in different populations.

CONCLUSION

This analysis of cervical alignment in a sample of asymptomatic volunteers revealed that with increasing age there is an observed increase in the sagittal inclination of the base of the cervical spine (T1S) that is accompanied by an increase in cervical lordosis as a means of maintaining cervical sagittal alignment (CSVA). The variability in what constitutes normal values for cervical parameters suggests that further study is warranted using standardized methodologies across diverse populations.

Height Gain Following Correction of Adult Spinal Deformity

BACKGROUND

Height gain following a surgical procedure for patients with adult spinal deformity (ASD) is incompletely understood, and it is unknown if height gain correlates with patient-reported outcome measures (PROMs).

METHODS

This was a retrospective cohort study of patients undergoing ASD surgery. Patients with baseline, 6-week, and subanalysis of 1-year postoperative full-body radiographic and PROM data were examined. Correlation analysis examined relationships between vertical height differences and PROMs. Regression analysis was utilized to preoperatively estimate T1-S1 and S1-ankle height changes.

RESULTS

This study included 198 patients (mean age, 57 years; 69% female); 147 patients (74%) gained height. Patients with height loss, compared with those who gained height, experienced greater increases in thoracolumbar kyphosis (2.81° compared with -7.37°; p < 0.001) and thoracic kyphosis (12.96° compared with 4.42°; p = 0.003). For patients with height gain, sagittal and coronal alignment improved from baseline to postoperatively: 25° to 21° for pelvic tilt (PT), 14° to 3° for pelvic incidence - lumbar lordosis (PI-LL), and 60 mm to 17 mm for sagittal vertical axis (SVA) (all p < 0.001). The full-body mean height gain was 7.6 cm, distributed as follows: sella turcica-C2, 2.9 mm; C2-T1, 2.8 mm; T1-S1 (trunk gain), 3.8 cm; and S1-ankle (lower-extremity gain), 3.3 cm (p < 0.001). T1-S1 height gain correlated with the thoracic Cobb angle correction and the maximum Cobb angle correction (p = 0.002). S1-ankle height gain correlated with the corrections in PT, PI-LL, and SVA (p < 0.001). T1-ankle height gain correlated with the corrections in PT (p < 0.001) and SVA (p = 0.03). Trunk height gain correlated with improved Scoliosis Research Society (SRS-22r) Appearance scores (r = 0.20; p = 0.02). Patient-Reported Outcomes Measurement Information System (PROMIS) Depression scores correlated with S1-ankle height gain (r = -0.19; p = 0.03) and C2-T1 height gain (r = -0.18; p = 0.04). A 1° correction in a thoracic scoliosis Cobb angle corresponded to a 0.2-mm height gain, and a 1° correction in a thoracolumbar scoliosis Cobb angle resulted in a 0.25-mm height gain. A 1° improvement in PI-LL resulted in a 0.2-mm height gain.

CONCLUSIONS

Most patients undergoing ASD surgery experienced height gain following deformity correction, with a mean full-body height gain of 7.6 cm. Height gain can be estimated preoperatively with predictive ratios, and height gain was correlated with improvements in reported SRS-22r appearance and PROMIS scores.

LEVEL OF EVIDENCE

Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Effect of the type of brace on head to pelvis sagittal alignment of adolescents with Scheuermann's kyphosis

The aim of this study was to determine the effects of the Milwaukee brace and thoracolumbosacral orthosis (TLSO) on head to pelvis sagittal alignment in adolescents with Scheuermann's kyphosis (SK). A total of 52 adolescents with SK who were under brace treatment were studied. They underwent biplanar radiography of the head to pelvis (EOS Imaging, Paris, France) before and 6 months after the beginning of bracing. We measured T1 slope, neck tilt (NT), cervical sagittal vertical axis (cSVA), thoracic inlet angle (TIA), C0-C2 lordosis, C2-C7 lordosis, thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), sagittal vertical axis (SVA) and T1 spinopelvic inclination (T1SPi). There were no significant differences in baseline values of TIA, PT, SS, PI, SVA, TK, cSVA, NT and T1 slope between the two groups (p > 0.05). There were significant differences between the baseline and final measurements of T1 slope, cSVA, TK, LL, T1SPi and TIA in both groups (p < 0.05). The results imply that brace treatment can significantly affect head to pelvis sagittal parameters of adolescents with SK. However, there are no significant differences in the values of head to pelvis sagittal parameters when comparing short-term effect of TLSO and the Milwaukee brace.

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.

Automatic Spine Segmentation and Parameter Measurement for Radiological Analysis of Whole-Spine Lateral Radiographs Using Deep Learning and Computer Vision

Radiographic examination is essential for diagnosing spinal disorders, and the measurement of spino-pelvic parameters provides important information for the diagnosis and treatment planning of spinal sagittal deformities. While manual measurement methods are the golden standard for measuring parameters, they can be time consuming, inefficient, and rater dependent. Previous studies that have used automatic measurement methods to alleviate the downsides of manual measurements showed low accuracy or could not be applied to general films. We propose a pipeline for automated measurement of spinal parameters by combining a Mask R-CNN model for spine segmentation with computer vision algorithms. This pipeline can be incorporated into clinical workflows to provide clinical utility in diagnosis and treatment planning. A total of 1807 lateral radiographs were used for the training (n = 1607) and validation (n = 200) of the spine segmentation model. An additional 200 radiographs, which were also used for validation, were examined by three surgeons to evaluate the performance of the pipeline. Parameters automatically measured by the algorithm in the test set were statistically compared to parameters measured manually by the three surgeons. The Mask R-CNN model achieved an average precision at 50% intersection over union (AP50) of 96.2% and a Dice score of 92.6% for the spine segmentation task in the test set. The mean absolute error values of the spino-pelvic parameters measurement results were within the range of 0.4° (pelvic tilt) to 3.0° (lumbar lordosis, pelvic incidence), and the standard error of estimate was within the range of 0.5° (pelvic tilt) to 4.0° (pelvic incidence). The intraclass correlation coefficient values ranged from 0.86 (sacral slope) to 0.99 (pelvic tilt, sagittal vertical axis).

Initial study on an expert system for spine diseases screening using inertial measurement unit

In recent times, widely understood spine diseases have advanced to one of the most urgetn problems where quick diagnosis and treatment are needed. To diagnose its specifics (e.g. to decide whether this is a scoliosis or sagittal imbalance) and assess its extend, various kind of imaging diagnostic methods (such as X-Ray, CT, MRI scan or ST) are used. However, despite their common use, some may be regarded as (to a level) invasive methods and there are cases where there are contraindications to using them. Besides, which is even more of a problem, these are very expensive methods and whilst their use for pure diagnostic purposes is absolutely valid, then due to their cost, they cannot rather be considered as tools which would be equally valid for bad posture screening programs purposes. This paper provides an initial evaluation of the alternative approach to the spine diseases diagnostic/screening using inertial measurement unit and we propose policy-based computing as the core for the inference systems. Although the methodology presented herein is potentially applicable to a variety of spine diseases, in the nearest future we will focus specifically on sagittal imbalance detection.

The Impact of Global Spinal Alignment on Standing Spinopelvic Alignment Change After Total Hip Arthroplasty

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

The interactions between hip osteoarthritis (OA) and spinal malalignment are poorly understood. The purpose of this study was to assess the influence of total hip arthroplasty (THA) on standing spinopelvic alignment.

METHODS

In this retrospective cohort study, patients undergoing THA for OA with pre-and postoperative full-body radiographs were included. Standing spinopelvic parameters were measured. Contralateral hip was graded on the Kellgren-Lawrence scale. Pre-and postoperative alignment parameters were compared by paired t-test. The severity of preoperative thoracolumbar deformity was measured using TPA. Linear regression was performed to assess the impact of preoperative TPA and changes in spinal alignment. Patients were separated into low and high TPA (<20 or >/=20 deg) and change in parameters were compared between groups by t-test. Similarly, the influence of K-L grade, age, and PI were also tested.

RESULTS

95 patients were included (mean age 58.6 yrs, BMI 28.7 kg/m2, 48.2% F). Follow-up radiographs were performed at mean 220 days. Overall, the following significant changes were found from pre-to postoperative: SPT (14.2 vs. 16.1, P = 0.021), CL (-8.9 vs. -5.3, P = .001), TS-CL (18.2 vs. 20.5, P = .037) and SVA (42.6 vs. 32.1, P = .004). Preoperative TPA was significantly associated with the change in PI-LL, SVA, and TPA. High TPA patients significantly decreased SVA more than low TPA patients. There was no significant impact of contralateral hip OA, PI, or age on change in alignment parameters.

CONCLUSION

Spinopelvic alignment changes after THA, evident by a reduction in SVA. Preoperative spinal sagittal deformity impacts this change. Level of evidence: III.

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.

Outcome of Conservative Therapy of Adolescent Idiopathic Scoliosis (AIS) with Chêneau-Brace

Chêneau-brace (C-Brace) is a potential tool for the treatment of adolescent idiopathic scoliosis (AIS) with a Cobb angle between 20° and 45° for the primary curve. The aim of the present study was (1) to estimate study cohorts with C-brace therapy success and therapy failure and (2) to analyze possible factors that influence the therapy outcome. Seventy-eight patients with AIS were assessed before the initiation of C-brace treatment. Each patient underwent radiography examinations before the brace, in-brace, and at the therapy end. Cobb angle was considered as increased when the value at the end of therapy was increased more than 5° (Δ > 5°), unchanged—when the value was unchanged within ± 5° and decreased- when the value was decreased more than 5° (Δ < −5°). The study cohort was stratified due to curve topography in the thoracic, thoracolumbar, and lumbar scoliosis groups. Global analysis revealed no statistically significant modification of the Cobb angle (Cobb angle pre-brace vs. Cobb angle post-brace: 30.8° ± 8.2 vs. 29.3° ± 15.2, p = 0.26). However, at the end of C-brace therapy, the primary Cobb angle was decreased by more than 5° in 27 patients (35%), unchanged (Δ within the range of ±5°) in 36 patients (46%), and increased more than 5° in 15 patients (19%). Sub-group analysis due to curve topography and skeletal maturity has shown higher rates of brace therapy failure in thoracic curves and in younger patients (Risser grade 0). Patients with higher Cobb angle correction with C-brace had lower rates of therapy failure. The C-brace can be useful for the prevention of scoliotic curve progression in patients with AIS. However, many factors influence the therapy effect.

Accuracy of Rod Contouring to Desired Angles With and Without a Template: Implications for Achieving Desired Spinal Alignment and Outcomes

STUDY DESIGN

Biomechanical Study.

OBJECTIVE

The search for optimal spinal alignment has led to the development of sophisticated formulas and software for preoperative planning. However, preoperative plans are not always appropriately executed since rod contouring during surgery is often subjective and estimated by the surgeon. We aimed to assess whether rods contoured to specific angles with a French rod bender using a template guide will be more accurate than rods contoured without a template.

METHODS

Ten experienced spine surgeons were requested to contour two 125 × 5.5 mm Ti64 rods to 40°, 60° and 80° without templates and then 2 more rods using 2D metallic templates with the same angles. Rod angles were then measured for accuracy and compared.

RESULTS

Average angles for rods bent without a template to 40°, 60° and 80° were 60.2°, 78.9° and 97.5°, respectively. Without a template, rods were overbent by a mean of 18.9°. When using templates of 40°, 60° and 80°, mean bend angles were 41.5°, 59.1° and 78.7°, respectively, with an average underbend of 0.2°. Differences between the template and non-template groups for each target angle were all significant (p < 0.001).

CONCLUSIONS

Without the template, surgeons tend to overbend rods compared to the desired angle, while surgeons improved markedly with a template guide. This tendency to overbend could have significant impact on patient outcomes and risk of proximal junctional failure and warrants further research to better enable surgeons to more accurately execute preoperative alignment plans.

Evaluating Outcomes of Spinopelvic Fixation for Patients Undergoing Long Segment Thoracolumbar Fusion with a Prior Total Hip Arthroplasty

INTRODUCTION

Understanding the relationship between spinal fusion and its effects on relative spinopelvic alignment in patients with prior total hip arthroplasty (THA) is critical. However, limited data exist on the effects of long spinal fusions on hip alignment in patients with a prior THA. Our objective was to compare clinical outcomes and changes in hip alignment between patients undergoing long fusion to the sacrum versus to the pelvis in the setting of prior THA.

METHODS

Patients with a prior THA who underwent elective thoracolumbar spinal fusion starting at L2 or above were retrospectively identified. Patients were placed into one of two groups: fusion to the sacrum or pelvis. Preoperative, six-month postoperative, one-year postoperative, and delta spinopelvic and acetabular measurements were measured from standing lumbar radiographs.

RESULTS

A total of 112 patients (55 sacral fusions, 57 pelvic fusions) were included. Patients who underwent fusion to the pelvis experienced longer length of stay (LOS) (8.31 vs. 4.21, P < 0.001) and less frequent home discharges (30.8% vs. 61.9%, P = 0.010), but fewer spinal revisions (12.3% vs. 30.9%, P = 0.030). No difference was observed in hip dislocation rates (3.51% vs. 1.82%, P = 1.000) or hip revisions (5.26% vs. 3.64%, P = 1.000) based on fusion construct. Fusion to the sacrum alone was an independent predictor of an increased spine revision rate (odds ratio: 3.56, P = 0.023). Patients in the pelvic fusion group had lower baseline lumbar lordosis (LL) (29.2 vs. 42.9, P < 0.001), six-month postoperative LL (38.7 vs. 47.3, P = 0.038), and greater 1-year ∆ pelvic incidence-lumbar lordosis (-7.98 vs. 0.21, P = 0.032).

CONCLUSION

Patients with prior THA undergoing long fusion to the pelvis experienced longer LOS, more surgical complications, and lower rate of spinal revisions. Patients with instrumentation to the pelvis had lower LL preoperatively with greater changes in LL and pelvic incidence-lumbar lordosis postoperatively. No differences were observed in acetabular positioning, hip dislocations, or THA revision rates between groups.

Anterior Lumbar Interbody Fusion (ALIF) or Transforaminal Lumbar Interbody Fusion (TLIF) for Fusion Surgery in L5/S1 - What Is the Best Way to Restore a physiological Alignment?

STUDY DESIGN

A retrospective single center cohort study with prospective collected data from an institutional spine registry.

OBJECTIVES

To determine whether restoration of lordosis L5/S1 is possible with both anterior lumbar interbody fusion (ALIF) and transforaminal lumbar interbody fusion (TLIF) and to find out which technique is superior to recreate lordosis in L5/S1.

METHODS

Seventy-seven patients with ALIF and seventy-nine with TLIF L5/S1 were included. Operation time, estimated blood loss), and complications were evaluated. Segmental lordosis L5/S1 and L4/5, overall lordosis, and proximal lordosis (L1 to L4) were measured in X-rays before and after surgery. Oswesery disability index and EQ-5D were assessed before surgery, and 3 and 12 months after surgery.

RESULTS

Mean operation time was 176.9 minutes for ALIF and 195.7 minutes for TLIF (p = 0.048). Estimated blood loss was 249.2 cc for ALIF and 362.9 cc for TLIF (p = 0.005). In terms of complications, only a difference in dural tears were found (TLIF 6, ALIF none; p = 0.014). Lordosis L5/S1 increased in the ALIF group (15.8 to 24.6°; p < 0.001), whereas no difference was noted in the TLIF group (18.4 to 19.4°; p = 0.360). Clinical results showed significant improvement in the Oswesery disability index (ALIF: 43 to 21.9, TLIF: 45.2 to 23.0) and EQ-5D (ALIF: 0.494 to 0.732, TLIF: 0.393 to 0.764) after 12 months in both groups, without differences between the groups.

CONCLUSION

ALIF and TLIF are comparable methods for performing fusion at L5/S1, with good clinical outcomes and comparable rates of complications. However, there is only a limited potential for recreating lordosis at L5/S1 with a TLIF.

Novel artificial intelligence algorithm: an accurate and independent measure of spinopelvic parameters

OBJECTIVE

The analysis of sagittal alignment by measuring spinopelvic parameters has been widely adopted among spine surgeons globally, and sagittal imbalance is a well-documented cause of poor quality of life. These measurements are time-consuming but necessary to make, which creates a growing need for an automated analysis tool that measures spinopelvic parameters with speed, precision, and reproducibility without relying on user input. This study introduces and evaluates an algorithm based on artificial intelligence (AI) that fully automatically measures spinopelvic parameters.

METHODS

Two hundred lateral lumbar radiographs (pre- and postoperative images from 100 patients undergoing lumbar fusion) were retrospectively analyzed by board-certified spine surgeons who digitally measured lumbar lordosis, pelvic incidence, pelvic tilt, and sacral slope. The novel AI algorithm was also used to measure the same parameters. To evaluate the agreement between human and AI-automated measurements, the mean error (95% CI, SD) was calculated and interrater reliability was assessed using the 2-way random single-measure intraclass correlation coefficient (ICC). ICC values larger than 0.75 were considered excellent.

RESULTS

The AI algorithm determined all parameters in 98% of preoperative and in 95% of postoperative images with excellent ICC values (preoperative range 0.85-0.92, postoperative range 0.81-0.87). The mean errors were smallest for pelvic incidence both pre- and postoperatively (preoperatively -0.5° [95% CI -1.5° to 0.6°] and postoperatively 0.0° [95% CI -1.1° to 1.2°]) and largest preoperatively for sacral slope (-2.2° [95% CI -3.0° to -1.5°]) and postoperatively for lumbar lordosis (3.8° [95% CI 2.5° to 5.0°]).

CONCLUSIONS

Advancements in AI translate to the arena of medical imaging analysis. This method of measuring spinopelvic parameters on spine radiographs has excellent reliability comparable to expert human raters. This application allows users to accurately obtain critical spinopelvic measurements automatically, which can be applied to clinical practice. This solution can assist physicians by saving time in routine work and by avoiding error-prone manual measurements.

Segmental cervical instability does not drive the loss of cervical lordosis after laminoplasty in patients with cervical spondylotic myelopathy

BACKGROUND/CONTEXT

Kyphotic deformity after cervical laminoplasty (CLP) often leads to unfavorable neurological recovery due to insufficient indirect decompression of the spinal cord. Existing literature has described that segmental cervical instability is a contraindication for CLP because it is a potential risk factor for kyphotic changes after surgery; however, this has never been confirmed in any clinical studies.

PURPOSE

To confirm whether segmental cervical instability was an independent risk factor for postoperative kyphotic change and to examine whether segmental cervical instability led to poor neurological outcomes after CLP for cervical spondylotic myelopathy (CSM).

STUDY DESIGN/SETTING

A retrospective study PATIENT SAMPLE: Patients who underwent CLP for CSM between January 2013 and January 2021 with a follow-up period of ≥1 year were enrolled.

OUTCOME MEASURES

Cervical radiographic measurements including C2-C7 lordosis (C2-7 angle), cervical sagittal vertical axis, C7 slope, flexion range of motion (fROM) and extension ROM (eROM) were assessed using neutral and flexion-extension views. Segmental cervical instability was classified into anterolisthesis (AL) of ≥2 mm displacement, retrolisthesis (RL) of ≥2 mm displacement, and translational instability (TI) of ≥3 mm translational motion. The amount of C2-7 angle loss at the follow-up period compared to the preoperative measurements was defined as cervical lordosis loss (CLL). Neurological outcomes were assessed using the recovery rate of the Japanese Orthopedic Association score (JOA-RR).

METHODS

CLL was compared among patients with and without segmental cervical instability. Further, multiple linear regression model for CLL was built for the evaluation with adjustment of the reported risks, including cervical sagittal vertical axis, C7 slope, fROM, eROM, and patient age together with AL, RL, and TI, as independent variables. The JOA-RR was also compared between patients with and without segmental cervical instability.

RESULTS

A total of 138 patients (mean age, 68.7 years; 65.9% male) were included in the analysis. AL, RL, and TI were found in 12 (8.7%), 33 (23.9%), and 16 (11.6%) patients, respectively. Comparisons among the groups showed that AL led to greater CLL; however, RL and TI did not. Multiple linear regression analysis revealed that greater CLL is significantly associated with greater fROM and smaller eROM (regression coefficient [β]=0.328, 95% confidence interval: 0.178 to 0.478, p<.001; β=-0.372, 95% confidence interval: -0.591 to -0.153, p=.001, respectively). However, there were no significant statistical associations in the AL, RL, and TI. Whereas, patients with AL tended to exhibit lower JOA-RR than those without AL (37.8% vs. 52.0%, p=.108).

CONCLUSIONS

Segmental cervical instability is not the definitive driver for loss of cervical lordosis after CLP in patients with CSM; thus, is not a contraindication in and of itself. However, it is necessary to consider the indications for CLP, according to individual cases of patients with AL on baseline radiograph, which is a sign of poor neurological recovery.

Development of artificial intelligence for automated measurement of cervical lordosis on lateral radiographs

Cervical sagittal alignment is an essential parameter for the evaluation of spine disorders. Manual measurement is time-consuming and burdensome to measurers. Artificial intelligence (AI) in the form of convolutional neural networks has begun to be used to measure x-rays. This study aimed to develop AI for automated measurement of lordosis on lateral cervical x-rays. We included 4546 cervical x-rays from 1674 patients. For all x-rays, the caudal endplates of C2 and C7 were labeled based on consensus among well-experienced spine surgeons, the data for which were used as ground truth. This ground truth was split into training data and test data, and the AI model learned the training data. The absolute error of the AI measurements relative to the ground truth for 4546 x-rays was determined by fivefold cross-validation. Additionally, the absolute error of AI measurements was compared with the error of other 2 surgeons’ measurements on 415 radiographs of 168 randomly selected patients. In fivefold cross-validation, the absolute error of the AI model was 3.3° in the average and 2.2° in the median. For comparison of other surgeons, the mean absolute error for measurement of 168 patients was 3.1° ± 3.4° for the AI model, 3.9° ± 3.4° for Surgeon 1, and 3.8° ± 4.7° for Surgeon 2. The AI model had a significantly smaller error than Surgeon 1 and Surgeon 2 (P = 0.002 and 0.036). This algorithm is available at (https://ykszk.github.io/c2c7demo/). The AI model measured cervical spine alignment with better accuracy than surgeons. AI can assist in routine medical care and can be helpful in research that measures large numbers of images. However, because of the large errors in rare cases such as highly deformed ones, AI may, in principle, be limited to assisting humans.

Reliability and Validity Analysis of Pelvic Sagittal Inclination Calculated by Inverse Cosine Function Method on Pelvic Anteroposterior Radiographs

Objective

Evaluation of sagittal pelvic tilt is significant for hip surgeons. However, the accurate measurement of pelvic sagittal inclination (PSI) is still a challenge. The objective of this study is to propose a new method for measurement of PSI from pelvic anteroposterior radiograph based on the inverse cosine function obtained from individualized pelvic model.

Methods

Collecting the imaging data of 30 patients with both pelvic CT and full‐length spine radiographs. Establishing pelvic model by customized 3D reconstruction software. The length of three groups of longitudinal and transverse line segments (A′p and B′) were measured from full‐length spine anteroposterior radiographs. The corresponding anatomical parameters, including A, B, b, ∠α, ∠γ, were measured and calculated on the same patient's pelvic model. The estimated PSI (ePSI) based on three groups of anatomical landmarks, including ePSI‐1, ePSI‐2, and ePSI‐3, were calculated by equation, ePSI=arccosA′pb*B′−∠α, and compared with the actual PSI (aPSI) measured by Surgamap software. For the reliability and validation evaluation, three observers measured these parameters in two rounds. Intra‐class correlation and inter‐class correlation were both calculated. Bland–Altman method was used to evaluate the consistency between the estimated PSI (ePSI) and the actual PSI (aPSI).

Results

ePSI‐1 and ePSI‐2 showed excellent intra‐observer reliability (0.921–0.997, p < 0.001) and inter‐observer reliability (0.801–0.977, p < 0.001). ePSI‐3 had a fair inter‐observer reliability (0.239–0.823, p < 0.001). ePSI‐1 showed the strongest correlation with aPSI (r = 0.917, p < 0.001). Mean (maximum) absolute difference of ePSI‐1, ePSI‐2, and ePSI‐3 is 2.62° (7.42°), 4.23° (13.78°), and 7.74° (31.47°), respectively. The proportion of cases with absolute difference less than 5° in three groups were 86.7% (ePSI‐1), 66.7% (ePSI‐2), 56.7% (ePSI‐3).

Conclusion

This new method based on inverse cosine function has good reliability and validity when used in the evaluation of PSI on pelvic anteroposterior radiographs.

Defining age-adjusted spinopelvic alignment thresholds: should we integrate BMI?

PURPOSE

To develop age- and BMI-adjusted alignment targets to improve patient-specific management and operative treatment outcomes.

METHODS

Retrospective review of a single-center stereographic database. ASD patients receiving operative or non-operative treatment, ≥ 18y/o with complete baseline (BL) ODI scores and radiographic parameters (PT, SVA, PILL, TPA) were included. Patients were stratified by age consistent with US-Normative values (norms) of SF-36(< 35, 35-55, 45-54, 55-64, 65-74, ≥ 75y/o), and dichotomized by BMI (Non-Obese < 30; Obese ≥ 30). Linear regression analysis established normative age- and BMI-specific radiographic thresholds, utilizing previously published age-specific US-Normative ODI values converted from SF-36 PCS (Lafage et al.), in conjunction with BL age and BMI means.

RESULTS

486 patients were included (Age: 52.5, Gender: 68.7%F, mean BMI: 26.2, mean ODI: 32.7), 135 of which were obese. Linear regression analysis developed age- and BMI-specific alignment thresholds, indicating PT, SVA, PILL, and TPA to increase with both increased age and increased BMI (all R > 0.5, p < 0.001). For non-obese patients, PT, SVA, PILL, and TPA ranged from 10.0, - 25.8, - 9.0, 3.1 in patients < 35y/o to 27.8, 53.4, 17.7, 25.8 in patients ≥ 75 y/o. Obese patients' PT, SVA, PILL, and TPA ranged from 10.5, - 7.6, - 7.1, 5.8 in patients < 35 y/o to 28.3, 67.0, 19.15, 27.7 in patients ≥ 75y/o. Normative SVA values in obese patients were consistently ≥ 10 mm greater compared to non-obese values, at all ages.

CONCLUSION

Significant associations exist between age, BMI, and sagittal alignment. While BMI influenced age-adjusted alignment norms for PT, SVA, PILL, and TPA at all ages, obesity most greatly influenced SVA, with normative values similar to non-obese patients who were 10 years older. Age-adjusted alignment thresholds should take BMI into account, calling for less rigorous alignment objectives in older and obese patients.

Spinopelvic measurements of sagittal balance with deep learning: systematic review and critical evaluation

PURPOSE

To summarize and critically evaluate the existing studies for spinopelvic measurements of sagittal balance that are based on deep learning (DL).

METHODS

Three databases (PubMed, WoS and Scopus) were queried for records using keywords related to DL and measurement of sagittal balance. After screening the resulting 529 records that were augmented with specific web search, 34 studies published between 2017 and 2022 were included in the final review, and evaluated from the perspective of the observed sagittal spinopelvic parameters, properties of spine image datasets, applied DL methodology and resulting measurement performance.

RESULTS

Studies reported DL measurement of up to 18 different spinopelvic parameters, but the actual number depended on the image field of view. Image datasets were composed of lateral lumbar spine and whole spine X-rays, biplanar whole spine X-rays and lumbar spine magnetic resonance cross sections, and were increasing in size or enriched by augmentation techniques. Spinopelvic parameter measurement was approached either by landmark detection or structure segmentation, and U-Net was the most frequently applied DL architecture. The latest DL methods achieved excellent performance in terms of mean absolute error against reference manual measurements (~ 2° or ~ 1 mm).

CONCLUSION

Although the application of relatively complex DL architectures resulted in an improved measurement accuracy of sagittal spinopelvic parameters, future methods should focus on multi-institution and multi-observer analyses as well as uncertainty estimation and error handling implementations for integration into the clinical workflow. Further advances will enhance the predictive analytics of DL methods for spinopelvic parameter measurement.

LEVEL OF EVIDENCE I

Diagnostic: individual cross-sectional studies with the consistently applied reference standard and blinding.

Factors Related to Preoperative Coronal Malalignment in Degenerative Lumbar Scoliosis: An Analysis on Coronal Parameters

Objectives

Recently the effects of coronal malalignment (CM) in degenerative lumbar scoliosis (DLS) have been reported, however, there was few studies on the correlated parameters of coronal alignments at pre‐operation. The aims of this current study were to investigate the associations of coronal parameters with scoliosis and coronal alignment, and to explore the relationships between the coronal pelvic tilt and coronal alignment in DLS.

Methods

One hundred and sixty‐one DLS patients in our hospital from May 2016 to December 2020 were reviewed and documented. The coronal balance distance (CBD, the offset between the center of C7 and the plumb line drawn from the center of S1), major Cobb (MC), fractional Cobb (FC), L4 coronal tilt, L5 coronal tilt, coronal pelvic tilt, apical rotation, and the vertebras in major curve were measured and documented. CM was considered if the CBD ≥ 30mm. All of those participants were assigned into group A (CBD ≥ 30 mm) and group B (CBD < 30 mm). Comparisons of demographic and radiographic data were performed between groups A and B. Pearson correlation and further multiple regression with stepwise method analysis were used to investigate those coronal parameters correlated to MC and CBD, respectively.

Results

Thirty‐one patients suffering from CM were assigned into group A, and the rest of 130 patients were assigned to group B accordingly. Then the incidence of CM was about 19.3% (31/161). Patients in group A had less vertebras in the main curve (P = 0.009), however, the apical rotation (P < 0.001) and the L4 coronal tilt (P = 0.007) were much larger. Although the MC (P = 0.426) and FC (P = 0.06) had no difference between the two groups, the match between MC and FC was much smaller (p = 0.021) in group A. The coronal pelvic tilt correlated significantly with FC (r = 0.552, p < 0.001), but mildly with MC (r = −0.366, p < 0.001), L4 coronal tilt (r = 0.348, p < 0.001), and L5 coronal tilt (r = 0.351, p < 0.001), respectively. The CBD correlated strongly with L4 coronal tilt (r = −0.471, p < 0.001) and L5 coronal tilt (r = −0.468, p < 0.001), respectively, but mildly with FC (r = −0.255, p = 0.016). Further multiple regression analysis revealed that only L4 coronal tilt was the independent factor for MC (r² = 0.549, p < 0.001) and CBD (r² = 0.221, p < 0.001), respectively.

Conclusions

The prevalence of CM in DLS patients is about 19% at pre‐operation. With similar major Cobb, the less the vertebras in the major curve, the larger the CBD. L4 coronal tilt may correlate significantly to scoliosis and CBD. Coronal pelvic tilt may be just one of the compensations for the scoliosis deformity but effects CBD directly.