Spinal Contour Research Articles

Mechanisms of lumbar spine "flattening" in adult spinal deformity: defining changes in shape that occur relative to a normative population.

Previous work comparing ASD to a normative population demonstrated that a large proportion of lumbar lordosis is lost proximally (L1-L4). The current study expands on these findings by collectively investigating regional angles and spinal contours. 119 asymptomatic volunteers with full-body free-standing radiographs were used to identify age-and-PI models of each Vertebra Pelvic Angle (VPA) from L5 to T10. These formulas were then applied to a cohort of primary surgical ASD patients without coronal malalignment. Loss of lumbar lordosis (LL) was defined as the offset between age-and-PI normative value and pre-operative alignment. Spine shapes defined by VPAs were compared and analyzed using paired t-tests. 362 ASD patients were identified (age = 64.4 ± 13, 57.1% females). Compared to their age-and-PI normative values, patients demonstrated a significant loss in LL of 17 ± 19° in the following distribution: 14.1% had "No loss" (mean = 0.1 ± 2.3), 22.9% with 10°-loss (mean = 9.9 ± 2.9), 22.1% with 20°-loss (mean = 20.0 ± 2.8), and 29.3% with 30°-loss (mean = 33.8 ± 6.0). "No loss" patients' spine was slightly posterior to the normative shape from L4 to T10 (VPA difference of 2°), while superimposed on the normative one from S1 to L2 and became anterior at L1 in the "10°-loss" group. As LL loss increased, ASD and normative shapes offset extended caudally to L3 for the "20°-loss" group and L4 for the "30°-loss" group. As LL loss increases, the difference between ASD and normative shapes first occurs proximally and then progresses incrementally caudally. Understanding spinal contour and LL loss location may be key to achieving sustainable correction by identifying optimal and personalized postoperative shapes.

Identifying Predictors of Neck Disability in Patients with Cervical Pain Using Machine Learning Algorithms: A Cross-Sectional Correlational Study.

(1) Background: Neck pain intensity, psychosocial factors, and physical function have been identified as potential predictors of neck disability. Machine learning algorithms have shown promise in classifying patients based on their neck disability status. So, the current study was conducted to identify predictors of neck disability in patients with neck pain based on clinical findings using machine learning algorithms. (2) Methods: Ninety participants with chronic neck pain took part in the study. Demographic characteristics in addition to neck pain intensity, the neck disability index, cervical spine contour, and surface electromyographic characteristics of the axioscapular muscles were measured. Participants were categorised into high disability and low disability groups based on the median value (22.2) of their neck disability index scores. Several regression and classification machine learning models were trained and assessed using a 10-fold cross-validation method; also, MANCOVA was used to compare between the two groups. (3) Results: The multilayer perceptron (MLP) revealed the highest adjusted R2 of 0.768, while linear discriminate analysis showed the highest receiver characteristic operator (ROC) area under the curve of 0.91. Pain intensity was the most important feature in both models with the highest effect size of 0.568 with p < 0.001. (4) Conclusions: The study findings provide valuable insights into pain as the most important predictor of neck disability in patients with cervical pain. Tailoring interventions based on pain can improve patient outcomes and potentially prevent or reduce neck disability.

Pedicle screw path planning for multi-level vertebral fixation.

For the spinal internal fixation procedures, connecting rods to the pedicle screws are commonly used in all spinal segments from the cervical to sacral spine. So far, we have only seen single vertebral screw trajectory planning methods in literatures. Joint screw placements in multi-level vertebrae with the constraint of an ipsilateral connecting rod are not considered. In this paper, a screw trajectory planning method that considers screw-rod joint system with both multi-level vertebral constraints and individual vertebral safety tolerance areproposed. The proposed method addresses three challenging constraints jointly for multi-level vertebral fixation with pedicle screws. First, a cylindrical screw safe passage model is suggested instead of a unique mathematical optimal trajectory for a single pedicle. Second, the flexible screw cap accessibility model is also included. Third, the connecting rod is modeled to accommodate the spine contour and support the needed gripping capacity. The retrospective clinical data of relative normal shape spines from Beijing Jishuitan hospital were used in the testing. The screw trajectories from the existing methods based on single vertebra and the proposed method based on multi-level vertebrae optimization are calculated andcompared. The results showed that the calculated screw placements by the proposed method can achieve 88% success rate without breaking the pedicle cortex and 100% in clinical class A quality (allow less than 2mm out of the pedicle cortex) compared to 86.1% and 99.1%, respectively, with the existing methods. Expert evaluation showed that the screw path trajectories and the connecting rod calculated by the new method satisfied the clinical implantationrequirements. The new screw planning approach that seeks an overall optimization for multi-level vertebral fixation is feasible and more advantageous for clinical use than the single vertebral approaches.

Automated non-contact measurement of the spine curvature at the sagittal plane using a deep neural network

BackgroundNon-radiographical techniques have been suggested to measure the spine curvature at the sagittal plane. However, a neural network has not been used to measure the curvature. MethodsA single video camera captured images of a standing posture at the sagittal plane from twenty healthy males. Six marker positions along the spine's contour in each image were identified for measuring inclination, thoracic kyphosis, and lumbar lordosis angles. We estimated three inflection points around the neck, hip, and between the neck and hip, followed by identifying two adjacent marker positions per inflection point to compute its tangent. The angular deviation of each tangent line from the horizontal was computed to measure inclination angles. Thoracic kyphosis and lumbar lordosis angles were computed by the angular difference between the two adjacent tangents. A deep neural network was trained with 500,000 iterations using the labeled images from 18 participants (388 and 44 images for training and test set) and then evaluated using the unseen images (2 participants, 48 images; evaluation set). FindingsThe mean total training and test errors were <2 pixels (∼ 0.6 cm). The total error in the evaluation set was qualitatively comparable (∼ 3 pixels = ∼ 0.9 cm), suggesting the model performance was maintained in the unseen data. The angle values between labeled and network-predicted marker positions were similar in the evaluation set. InterpretationThe network training with a relatively small number of images was successful based on the small error values observed in the evaluation set. The model may be an affordable, automated, and non-contact measurement tool for the human spine curvature.

The Shape of the Fused Spine is Associated With Acute Proximal Junctional Kyphosis in Adult Spinal Deformity: An Assessment Based on Vertebral Pelvic Angles.

Retrospective review of prospective database. Vertebral pelvic angles (VPAs) account for complexity in spine shape by assessing the relative position of each vertebra with regard to the pelvis. This study uses VPAs to investigate the shape of the fused spine after T10-pelvis fusion, in patients with adult spinal deformity (ASD), and then explores its association with proximal junctional kyphosis (PJK). Included patients had radiographic evidence of ASD and underwent T10-pelvis realignment. VPAs were used to construct a virtual shape of the post-operative spine. VPA-predicted and actual shapes were then compared between patients with and without PJK. Logistic regression was used to identify components of the VPA-based model that were independent predictors of PJK occurrence and post-operative shape. 287 patients were included. VPA-predicted shape was representative of the true post-operative contour, with a mean point-to-point error of 1.6-2.9% of the T10-S1 spine length. At 6-weeks follow-up, 102 patients (35.5%) developed PJK. Comparison of the true post-operative shapes demonstrated that PJK patients had more posteriorly translated vertebrae from L3 to T7 (P < .001). Logistic regression demonstrated that L3PA (P = .047) and T11PA (P < .001) were the best independent predictors of PJK and were, in conjunction with pelvic incidence, sufficient to reproduce the actual spinal contour (error <3%). VPAs are reliable in reproducing the true, post-operative spine shape in patients undergoing T10-pelvis fusion for ASD. Because VPAs are independent of patient position, L3PA, T11PA, and PI measurements can be used for both pre- and intra-operative planning to ensure optimal alignment.

P48. Mechanisms of lumbar spine ‘flattening’ in adult spinal deformity: defining changes in shape that occur relative to a normative population

<h3>BACKGROUND CONTEXT</h3> Loss of lumbar curvature is often expressed as an angular regional loss. Previous work comparing adult spinal deformity (ASD) lumbar alignment to their age-and-PI adjusted normative value demonstrated that, contrary to general belief, a large proportion of the curvature is lost proximally (L1-L4). This study is a follow-up looking not only at regional angles, but also at the spinal contour collectively. <h3>PURPOSE</h3> Investigate the difference of lumbar shape between ASD and age-and-PI adjusted normative values. <h3>STUDY DESIGN/SETTING</h3> Retrospective review of an ASD registry. <h3>PATIENT SAMPLE</h3> A total of 119 asymptomatic volunteers and 362 ASD patients. <h3>OUTCOME MEASURES</h3> Sagittal alignment of the lumbar and thoracolumbar spine measures using vertebra pelvic angle from L5 to T10. <h3>METHODS</h3> Before studying ASD patients, 119 asymptomatic volunteers with full-body, free-standing radiographs were used to identify age-and-PI models of each vertebra pelvic angle (VPA) from L5 to T10, a validated methodology characterizing the detailed shape of the spine. Our study cohort was a registry of surgical primary ASD patients without coronal malalignment (SRS-Schwab Type=N). The formulas developed in the asymptomatic population were applied to the ASD group to calculate an age-and-PI normative spine shape for each patient. Loss of lumbar lordosis was defined as the offset between age-and-PI normative value and pre-operative spino-pelvic alignment. Patients were stratified into four groups by the amount of lordosis lost, ranging from "no loss" to "30° loss." Paired t-tests were performed to compare actual and normative VPA shapes within each group. <h3>RESULTS</h3> Out of 1,495 patients enrolled in this registry, 453 were primary cases, and 653 were categorized as a Schwab type N, leading to a cohort of 362 patients (age=64.4±13, 57.1% F). Pre-operative alignment demonstrated a large variability with a mean PI-LL of 15°±21, distal LL=31°±15, and PI=55°±13. Compared to their age-and-PI normative values, ASD patients demonstrated a significant lordosis loss of 17°±19 with the following distribution: 14.1% no loss (mean: 0.1±2.3), 22.9% with 10° loss (mean: 9.9±2.9), 22.1% with 20° loss (mean: 20.0±2.8), and 29.3% with 30° loss (mean:33.8±6.0). Comparison of the VPAs (and therefore the shape) between each LL group and the normative shape demonstrated that the "no loss" patients had a lumbar spine slightly anterior to the normative shape from L4 to T10 (VPA difference of 2°). The shape of the "small deformity" group (10°) superimposed on the normative one from L5 to L2 (VPA with p>0.1) and became anterior at the L1 level. As the lordosis loss increased, the offset between ASD and normative shapes began to propagate to the distal levels and became significant extending caudally to the L3 level for the "20° loss" group and further down to L4 for the more severe group. <h3>CONCLUSIONS</h3> As the deformity progresses and the loss of lordosis increases, the difference between ASD shape and normative shape happens first proximally and then progresses incrementally caudally with increasing deformity. Understanding the spinal contour and the location of this loss, in addition to regional parameters, may be key to achieving a sustainable correction by identifying optimal and personalized post-operative shape. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

Mechanical complications in adult spinal deformity and the effect of restoring the spinal shapes according to the Roussouly classification: a multicentric study

PurposeTo evaluate the incidence of mechanical complications in patients with adult spine deformity (ASD) treated by restoring the normal shape according to the Roussouly classification.MethodsThis is a retrospective multicentric study with a minimum follow-up of 2 years. Patients operated on with fusion for ASD (minimum performed fusion: L2 to sacrum) were included. Patients with a history of previous spinal fusion of more than three levels were excluded. Spinal and pelvic parameters were measured on the preoperative and the immediate postoperative follow-up. All mechanical complications were recorded.ResultsA total of 290 patients met the criteria of inclusion with a minimum follow-up of 2 years. Mechanical complications occurred in 30.4% of the cohort. The most common complication was PJK with an incidence of 18% while nonunion or instrumentation failure (rod breakage, implant failure) occurred in 12.4%. 66% of the patients were restored to the normal shape according to the Roussouly classification based on their PI and had a mechanical complication rate of 22.5%, whereas the remaining 34% of patients had a complication rate of 46.8% (p < 0.001). The relative risk for developing a mechanical complication if the algorithm was not met was 3 (CI 1.5–4.3; p < 0.001)ConclusionIn the recent literature, there are no clear guidelines for ASD correction. Restoring the sagittal spinal contour to the normal shapes of Roussouly according to the PI could serve as a guideline for ASD treatment. Ignoring this algorithm has a threefold risk of increased mechanical complications. We recommend this algorithm for treatment of ASD.Level of evidenceIV cross-sectional observational study.Graphic abstractThese slides can be retrieved under Electronic Supplementary Material.

Rapid Detection of Scoliosis Based on Digital Image Processing

To design a rapid scoliosis detection system for general survey. The camera was used to take the upright image of human back, and then the region of interest was extracted. After image preprocessing, the feature points of human back spine were extracted. The feature points were fitted into the spine contour curve. Finally, the Cobb angle of scoliosis was calculated according to the contour curve, and the scoliosis degree was judged. The outline curve of the spine can be obtained by this method, and the Cobb angle of scoliosis can be calculated. It can detect scoliosis quickly, effectively and accurately. Compared with the traditional methods, the digital image processing method can achieve rapid and non-destructive detection of scoliosis, save a lot of manpower and material resources, and is of great significance to the national survey of adolescent scoliosis.

Automatic measurement algorithm of scoliosis Cobb angle based on deep learning

Aiming at the subjective experience of the physician, the high measurement error in the Cobb angle measurement of scoliosis X-ray images and the X-ray image of spine is difficult to segment. A deep learning based scoliosis Cobb angle measurement algorithm which can automatically calculate Cobb angle without the physician’s manual definition is proposed. A DU-Net detection and segmentation network is proposed in this paper to remove the unrelated regions and to segment the spine contour in the spine X-ray image. The aggregated channel features in pedestrian detection algorithm is introduced to scoliosis image to realize the spine region detection. And the DU-Net network is training to segment spine contour. Therefore, the spine curve can be fitted by the spine contour and the Cobb angle can be automatically measured by the tangent line of spine curve. As a result, the Cobb angle measure methods yields an average error of 2.9° to reference Cobb angle which are measured manually by special orthopaedist. The detection algorithm in this paper yields an average precision of 98.5% and a recall of 99.5%. Moreover, the DU-Net reach an average Dice coefficient to reference segmentation of 90.28%, an IOU of 82.29% and a precision of 86.30%.

Spinal sagittal alignment and trapezoidal deformity in patients with degenerative cervical spondylolisthesis

Degenerative cervical spondylolisthesis (DCS) is a cervical deformity arising from regressive changes where trapezoidal deformity characterized by hypertrophic osteophytes of spinal elements is often observed. There is a paucity of literature about the spinal contour of DCS and trapezoidal vertebrae. We conducted this research to clarify the relationship between spinal sagittal alignment and trapezoidal deformity in DCS. Total seventy-nine patients with cervical spondylosis were enrolled. Twenty-four patients who exhibited cervical spondylolisthesis were classified into DCS group. Other patients were classified into a control group. Measurements of radiographic parameters and trapezoidal deformity were made. DCS was found mostly in C3-C4 and C4-C5 (16 and 10 cases, respectively). T1S and T1-T4 TK was larger in the DCS group than in the control (T1S: 29.9 ± 2.3° vs. 23.7 ± 1.5°, T1-T4 TK: 14.9 ± 2.1° vs. 9.0 ± 1.4°). C2-C7A was smaller in DCS (3.5 ± 3.6° vs. 11.9 ± 2.3°). Trapezoidal deformity was apparent in the vertebra below the slipped segment. Among sagittal parameters, T1S and T1-T4 TK were positively correlated with DCS (r = 0.523 and r = 0.438, respectively). For these correlations with DCS, both logistic and linear regression models predicted threshold values of approximately 30° for T1S and 15° for T1-T4 TK responsible for DCS. DCS was mostly found in the middle cervical region. Among sagittal parameters, enlarged T1S and T1-T4 TK, which were strongly correlated with amount of slippage, was considered affected to DCS. Cervical kyphosis and trapezoidal deformity also exhibited strong correlations with DCS, and were considered responsible for clinical instability.

Radiological Outcome of Cotrel-Dubousset Instrumentation in Nineteen Patients with Adolescent Idiopathic Scoliosis

Objective: Adolescent idiopathic scoliosis is a progressive type of scoliosis that may lead to permanent deformity unless prevented and treated effectively. To present radiological outcome of patients with adolescent idiopathic scoliosis treated with the Cotrel-Dubousset (CD) instrumentation in our clinic. Methods: This was a prospective follow-up study of 19 patients (8 males, 11 females; mean age 18.5 years; age range 12-43 years) who underwent CD instrumentation for late onset idiopathic scoliosis. The CD instrumentation and posterior spinal fusion was performed using the standard technique through either anterior or posterior approach. On average, 13.52 vertebrae (range, 8-16) were included in the spinal fusion. The mean postoperative follow-up duration was 18 months (2-32 months). Results: Cobb angle on frontal plane was corrected 47.74%±21.73% at thoracic region and 34.52%±15.96% at lumbar region. On sagittal plane, the percentage of correction was 28.61%±20.91% on thoracic kyphosis angle and 38.96%±29.73% lumbar lordosis angle. In general, physiological sagittal contour of spine was obtained in 49.2% of patients after CD instrumentation. The most common postoperative complications were hook dislocation (n=8), bending and dislocation of screw (n=7), broken lamina and pedicule (n=5), and infection (n=3), all of which were effectively treated. Conclusio n: CD instrumentation effectively corrects the late onset idiopathic scoliosis if it is performed after a proper preoperative planning.

3D rod shape changes in adolescent idiopathic scoliosis instrumentation: how much does it impact correction?

Flattening of rods is known to reduce the correction capability of the instrumentation, but has not been studied in 3D. The aim is to evaluate the rods shape 3D changes during and immediately after instrumentation, and its effect on 3D correction. The 5.5mm CoCr rods of 35 right thoracicadolescent idiopathic scoliosis patients were measured from rod tracings prior to insertion, and reconstructed in 3D from bi-planar radiographs taken intra-operatively after the correction maneuvers and 1week post-operatively. The rod bending curvature, maximal deflection and orientation of the rod's plane of maximum curvature (RPMC) were computed at each stage. The relation between rod contour, kyphosis and apical vertebral rotation (AVR) was assessed. Main thoracic Cobb angle was corrected from 58°±10° to 15°±8°. Prior to insertion, rods were more bent on the concave side (curvature/deflection: 39°±8°/25±6mm) than the convex side (26°±5°/17±3mm). Only the concave rod shape changed after the correction maneuvers execution (flattening of 21°±9°/13±7mm; p<0.001) and stayed unchanged post-operatively. After instrumentation, the RPMC was deviated from the sagittal plane (concave side: 27°±19°/convex side: 15°±12°). There was a significant association between kyphosis change and the relative concave rod to spine contour (rod curvature-pre-operative kyphosis) (R 2=0.58) and between AVR correction and initial differential concave/convex rods deflection (R 2=0.28). Correction maneuvers induce a significant change of the concave rod profile. Both rods end in a plane deviated from the sagittal plane which is representative of the spinal curvature 3D orientation. Differential rod contouring technique has a significant impact on the resulting thoracic kyphosis and transverse plane correction.

Contour and Angle-Function Based Scoliosis Monitoring: Relaxing the Requirement on Image Quality in the Measurement of Spinal Curvature.

A method for measuring spinal curvature that provides a useful analog to the Cobb angle and is tolerant of degraded image quality is proposed. Conventional methods require a higher standard of discernibility for vertebra features and suffer high variability. Assumption is made that the natural representation of the spine for the purpose of scoliosis monitoring is that of a continuous curved contour rather than a series of discrete vertebral bodies with individual orientations. The angle that a tangent line to this contour makes with the vertical, expressed as a continuous function of height, is proposed as a metric for characterization of the curve. The Cobb angle can be approximated as the difference between the extrema of this function, and details of the function shape can provide additional markers for tracking curve variation and evolution. A method for deriving the angle function from coronal images of the spine is proposed, and both manual and automatic variants of the procedure are described. The method is applied to conventional coronal radiographs and to magnetic resonance (MR) coronal views derived from volumetric acquisitions of the spine. Included in the latter category is an image exhibiting poor discrimination of vertebra features due to motion artifacts. The method permits extraction of the curve and Cobb angles in all cases. Because the spine contour is discernible even in low quality images where vertebral endplates may be obscured or poorly contrasted from surrounding tissue, the approach offers improved reliability, applicability across imaging modalities, and, in the case of x-rays, the possibility of a reduced radiation dose. Moreover, since it relies on larger image features and exploits the continuity of the spine, the contour-based approach is expected to reduce the variability associated with Cobb angle measurement.

Generation of a Patient-Specific Model of Normal Sagittal Alignment of the Spine

Study DesignMathematical modeling of normal sagittal spinal alignment. ObjectiveTo create a patient specific 3-dimensional (3D) model of normal adolescent spinal shape and alignment. Summary of Background DataRecreating normal sagittal balance is a key goal in spinal deformity surgery. Because of the variation in normal sagittal alignment based on inherent pelvic parameters, it is difficult to know what is normal for a given patient who presents with spinal deformity. MethodsSimultaneous biplanar 2-dimensional digital radiographs were taken for pediatric patients with no known spinal disease using the EOS system. Three-dimensional reconstructions were produced using sterEOS and imported into custom MATLAB software. The researchers defined relationships to approximate orientations and positions of the vertebral bodies from patients' pelvic incidence (PI). The predicted spinal contour was then calculated to optimize congruence to patients' sagittal T1–sacrum offset, sagittal curve inflection point location, and predicted vertebral body orientations and positions. ResultsA total of 75 patients (26 male and 49 female) were included, mean age 14.5 ± 2.6 years. Baseline measurements were PI 46.7° ± 10.2°, sacral lope 40.2° ± 8.9°, T1–T12 kyphosis 39.8° ± 8.8°, and L1–L5 lordosis −37.1° ± 11.2°. Average difference in vertebral position in the anteroposterior direction between actual spines and their predicted models was 1.2 ± 1.2 mm and varied from an absolute minimum of 0.2 mm (T3) to an absolute maximum of 3.7 mm (L2). ConclusionsThis model uses an adolescent patient's PI to predict the normal sagittal alignment that best matches that patient's native sagittal curve. The model was validated on patients with no spinal deformity; average difference between actual sagittal positions of each vertebra and those predicted by the model was less than 5 mm at each vertebral level. This model may be useful in adolescent scoliotic patients with altered sagittal alignment to determine the magnitude of 3D deformity (compared with predicted normal values) and the completeness of 3D correction.

Basic principles of kinesiotherapy in patients with degenerative spinal deformities (part 1)

Degenerative lumbar spondylolisthesis (DLS) causes the develop­ment of sagittal spinal-pelvic imbalance with accompanying muscle imbalance in lumbar-pelvic area which is not able to be eliminated spontaneously and worsens the functional results of conservative and surgical treatment. Objective: To develop a method of correct­ing selective kinesiotherapy (KSP) for the patients with DLS for correction of muscle imbalance and to test it in long-term period after instrumented lumbar spine fusion. Methods: We used clinical, radiological (with radiometry), biomechanical (including comput­erized electromechanical goniometry), and statistical methods. As material we applied surveys from 10 men with LIV DLS aged from 46 to 65 years (prior to surgery, after 3 and 6 months, 1 year) which were randomly divided into groups: Vosn — we used a new technique of KSC (pat. 83739, Ukraine), Vkontr — we used a stan­dard program of postisometric relaxation. Results: In all patients in the preoperative period we found degenerative deformity «flat back», infringement of kinematics of the spine and myofixation of the torso, moderate pain intensity according to VAS and high indexes of disabilitation according to Oswestry scale, kineziofobia according to Tampa scale, dismay and anxiety related to the expec­tation of pain, and according to PASS scale. Despite on surgical correction of sagittal spinal contour there were not detected any significant decreasing of indexes of disabilitation, elimination of myotonic reactions and muscle imbalances in lumbar-pelvic area. In the closest terms of using of KSC technique there also were no any significant differences between the studied groups of patients in none of the clinical signs. We traced a tendency to improvement in endurance of extensor and flexor muscles of the spine, pelvis and hips, PASS, VAS and ODI indexes in the Vosn group. Conclusion: There were proven an efficiency and an opportunity of using a de­veloped KSC technique at all stages of rehabilitation in patients with degenerative spinal deformities and muscle imbalance.

Unintended Change of Physiological Lumbar Lordosis and Pelvic Tilt After Posterior Spinal Instrumentation and Fusion for Adolescent Idiopathic Scoliosis: How Much Is Too Much?

Study DesignRetrospective review of prospective multicenter adolescent idiopathic scoliosis (AIS) database. ObjectivesTo investigate the effect of decreased lumbar lordosis (LL) on measured pelvic tilt (PT) after posterior spinal instrumentation and fusion for AIS and to test the hypothesis that lumbar spinal fusion resulting in mismatched LL is associated with increased PT. Summary of Background DataInteraction between the spine and pelvis highly influences global sagittal alignment (GSA). In adults, correlation between health-related quality of life measures and LL proportional to a patient-specific pelvic incidence (PI) has been established, although the implications of poor sagittal alignment are less well-defined in AIS. This observation warrants further examination of regional spine contour and its relation to the pelvis in AIS. MethodsThe authors queried a prospective multicenter database for AIS patients who underwent posterior spinal instrumentation and fusion with lowest instrumented vertebra between L2 and L5 and identified 155 patients with minimum 2 years' follow-up. Lumbar lordosis (T12–S1), LL within fusion, LL below fusion, GSA, PT, and PI were measured preoperatively and at 2 years. Change in PT was compared between patients with matched or mismatched LL based on a common clinical definition (LL = PI + 10) and a research-driven model (LL = 0.56 PI + 33.43). ResultsThirty-eight percent of patients had decreased LL from before surgery to 2 years after surgery. These patients had significantly higher rates of increased PT (73%) than patients without decreased LL (40%). Multivariate regression demonstrated that change in LL, LL within fusion, and GSA had a significant predictive effect on PT (p < .001). Using either definition of LL, patients with LL less than 2 standard deviations from predicted values were more likely to have increased PT. ConclusionsIatrogenic loss of LL commonly occurs in spine fusion for AIS and is associated with a reciprocal increase in PT. As such, spinal fusion in AIS can have unintended effects on sagittal alignment with currently uninvestigated potential consequences in the future.

WE-F-16A-04: Micro-Irradiator Treatment Verification with High-Resolution 3D-Printed Rodent-Morphic Dosimeters

Purpose: Pre-clinical micro-radiation therapy studies often utilize very small beams (∼0.5-5mm), and require accurate dose delivery in order to effectively investigate treatment efficacy. Here we present a novel high-resolution absolute 3D dosimetry procedure, capable of ∼100-micron isotopic dosimetry in anatomically accurate rodent-morphic phantoms Methods: Anatomically accurate rat-shaped 3D dosimeters were made using 3D printing techniques from outer body contours and spinal contours outlined on CT. The dosimeters were made from a radiochromic plastic material PRESAGE, and incorporated high-Z PRESASGE inserts mimicking the spine. A simulated 180-degree spinal arc treatment was delivered through a 2 step process: (i) cone-beam-CT image-guided positioning was performed to precisely position the rat-dosimeter for treatment on the XRad225 small animal irradiator, then (ii) treatment was delivered with a simulated spine-treatment with a 180-degree arc with 20mm x 10mm cone at 225 kVp. Dose distribution was determined from the optical density change using a high-resolution in-house optical-CT system. Absolute dosimetry was enabled through calibration against a novel nano-particle scintillation detector positioned in a channel in the center of the distribution. Results: Sufficient contrast between regular PRESAGE (tissue equivalent) and high-Z PRESAGE (spinal insert) was observed to enable highly accurate image-guided alignment and targeting. The PRESAGE was found to have linear optical density (OD) change sensitivity with respect to dose (R2 = 0.9993). Absolute dose for 360-second irradiation at isocenter was found to be 9.21Gy when measured with OD change, and 9.4Gy with nano-particle detector- an agreement within 2%. The 3D dose distribution was measured at 500-micron resolution Conclusion: This work demonstrates for the first time, the feasibility of accurate absolute 3D dose measurement in anatomically accurate rat phantoms containing variable density PRESAGE material (tissue equivalent and bone equivalent). This method enables precise treatment verification of micro-radiation therapies, and enhances the robustness of tumor radio-response studies. This work was supported by NIH R01CA100835.

Simulation of Spinal Loading: Importance of Subject-Specific Posture and Motion Patterns

IntroductionMechanical factors play an important role in the development of spinal disorders (e.g., fracture, disc degeneration). The overall objective of our research is to develop simulation mode...

Current concepts and controversies on adolescent idiopathic scoliosis: Part II

A new era in the surgical treatment of adolescent idiopathic scoliosis (AIS) opened with the introduction of pedicle screw instrumentation, which provides 3-column vertebral fixation and allows major deformity correction on the coronal, sagittal, and axial planes. A steep learning curve can be expected for spinal surgeons to become familiar with pedicle screw placement and correction techniques. Potential complications including injury to adjacent neural, vascular, and visceral structures can occur due to screw misplacement or pull-out during correction maneuvers. These major complications are better recognized as pedicle screw techniques become more popular and may result in serious morbidity and mortality. Extensive laboratory and clinical training is mandatory before pedicle screw techniques in scoliosis surgery are put to practice. Wider application, especially in developing countries, is limited by the high cost of implants. Refined correction techniques are currently developed and these utilize a lesser number of pedicle anchors which are strategically positioned to allow optimum deformity correction while reducing the neurological risk, surgical time, and blood loss, as well as instrumentation cost. Such techniques can be particularly attractive at a time when cost has major implications on provision of health care as they can make scoliosis treatment available to a wider population of patients. Pedicle screw techniques are currently considered the gold standard for scoliosis correction due to their documented superior biomechanical properties and ability to produce improved clinical outcomes as reflected by health-related quality-of-life questionnaires. Ongoing research promises further advances with the future of AIS treatment incorporating genetic counseling and possibly fusionless techniques.

Current concepts and controversies on adolescent idiopathic scoliosis: Part I

Adolescent idiopathic scoliosis is the most common spinal deformity encountered by General Orthopaedic Surgeons. Etiology remains unclear and current research focuses on genetic factors that may influence scoliosis development and risk of progression. Delayed diagnosis can result in severe deformities which affect the coronal and sagittal planes, as well as the rib cage, waistline symmetry, and shoulder balance. Patient's dissatisfaction in terms of physical appearance and mechanical back pain, as well as the risk for curve deterioration are usually the reasons for treatment. Conservative management involves mainly bracing with the aim to stop or slow down scoliosis progression during growth and if possible prevent the need for surgical treatment. This is mainly indicated in young compliant patients with a large amount of remaining growth and progressive curvatures. Scoliosis correction is indicated for severe or progressive curves which produce significant cosmetic deformity, muscular pain, and patient discontent. Posterior spinal arthrodesis with Harrington instrumentation and bone grafting was the first attempt to correct the coronal deformity and replace in situ fusion. This was associated with high pseudarthrosis rates, need for postoperative immobilization, and flattening of sagittal spinal contour. Segmental correction techniques were introduced along with the Luque rods, Harri-Luque, and Wisconsin systems. Correction in both coronal and sagittal planes was not satisfactory and high rates of nonunion persisted until Cotrel and Dubousset introduced the concept of global spinal derotation. Development of pedicle screws provided a powerful tool to correct three-dimensional vertebral deformity and opened a new era in the treatment of scoliosis.