BACKGROUND CONTEXT Posterior spinal fusion (PSF) was traditionally performed freehand. Robotic-assisted navigation (RAN) allows for increased accuracy/precision of pedicle screw (PS) placement by robotically establishing/maintaining the trajectory for drilling pedicle tracts and placing screws. However, RAN presents a steep learning curve. PURPOSE This study aimed to compare the 3D accuracy/precision of PS placement between an attending surgeon with RAN experience and a 4th-year orthopaedic surgery resident who completed an adult and pediatric spine orthopedic rotation with an introduction to robotic surgery. STUDY DESIGN/SETTING Cadaveric study. PATIENT SAMPLE Two adult cadavers. OUTCOME MEASURES Systematic error, precision, and accuracy between training levels for angular deviation and translational deviation. METHODS Two cadavers were utilized, one each by attending and resident. Cadavers underwent subperiosteal exposure from T2-L5, and subsequently PS were placed using RAN from T2-L5. Preoperative CT scans were used to plan screws; plans were transposed to the robotic planning platform. A computer-vision algorithm compared the postoperative CT screw position to the preoperatively planned screw position. Laminectomies were performed to assess breach. Systematic error (signed mean error), precision (2SD), and accuracy (mean absolute error) were statistically compared between training levels for angular and translational deviation at the screw tip/tail/mid-pedicle positions in the medial-lateral (ML) and superior-inferior (SI) directions. RESULTS Fifty-seven PS were placed in two cadavers. Attending screws were more precise and accurate than the resident screws in the ML direction at the tail and mid-pedicle positions, and attending screws were more precise in the ML direction at the tip (P<0.021). Resident screws had better systematic error and accuracy than attending screws in the SI direction at the tip, tail, and mid-pedicle positions (P<0.024). There were no differences in angular deviation performance metrics. All breaches were <1mm (1 attending, 2 resident). CONCLUSIONS This cadaveric study identified that increased surgical experience may increase accuracy and precision when placing screws in the clinically important medial-lateral direction of the pedicle when using RAN. Although the fourth-year orthopedic surgery resident with a spine rotation as well as an introduction to robotic surgery rotation placed clinically safe pedicle screws using RAN without breach, this study demonstrates that 3D accuracy metrics paired with RAN can help identify specific opportunities for improvement in surgical technique for trainees. FDA Device/Drug Status This abstract does not discuss or include any applicable devices or drugs.

Objective: Severe spinal deformity results in restrictive pulmonary disease from thoracic distortions and lung-volume limitations. Though spirometry and body plethysmography are widely accepted tests for pulmonary function tests (PFTs), they are time-consuming and require patient compliance. This study investigates whether surface topographic [surface topography (ST)] measurements of body volume difference (BVD) and torso volume difference between maximum inhale and exhale correlate to values determined on PFTs. Methods: This study included patients with idiopathic scoliosis and thoracic/thoracolumbar curves ≥40 degrees. Patients received ST scans, clinical examinations, and EOS biplanar radiographs on the same day. PFTs were performed within 3 months of ST/radiographic analysis. Univariate linear regression analysis was used to examine relationships between BVD, PFT values, and mean curves. Results: Sixteen patients (14.6 ± 2.2 y, 69% females) with idiopathic scoliosis and mean thoracic/thoracolumbar curves of 62 degrees ± 15˚ degrees (45 degrees to 93 degrees) were assessed. BVD displayed statistically high-positive positive correlations with forced vital capacity ( R = 0.863, P < 0.0001), forced expiratory volume in 1 second ( R = 0.870, P < 0.001), vital capacity ( R = 0.802, P < 0.0001), and TLC ( R = 0.831, P < 0.0001. Torso volume difference showed similarly high positive correlations to forced vital capacity, forced expiratory volume in 1 second, vital capacity, and TLC, but not residual volume. No correlations emerged between the mean thoracic/thoracolumbar curve and BVD or PFT values. Conclusion: This study strongly endorses further investigation into ST scanning as an alternative to traditional PFTs for assessing pulmonary volumes. The noncontact and noninvasive nature of ST scanning presents a valuable alternative method for analyzing thoracic volume, particularly beneficial for patients unable to cooperate with standard PFTs. Level of Evidence: Level II—prognostic.

STUDY DESIGN:Retrospective case series.OBJECTIVE:To characterize the change in angle of trunk rotation (ATR), axial vertebral rotation (AVR), and body surface rotation (BSR) in patients with adolescent idiopathic scoliosis (AIS) undergoing posterior spinal fusion (PSF) with en-bloc derotation across multiple postoperative visits.SUMMARY OF BACKGROUND DATA:Previous research has documented ATR, AVR, and BSR correction for AIS patients after surgery. However, there is a lack of evidence on the sustainability of this correction over time.METHODS:This was a retrospective study from a single-center prospective surface topographic registry of patients with AIS, age 11-20 at time of surgery, who underwent PSF with en-bloc derotation. Patients with previous spine surgery were excluded. ATR was measured with a scoliometer, AVR through EOS radiographic imaging, and BSR via surface topographic scanning, Data collection occurred at: preoperative, six-week, three-month, six-month, one-year, and two-year postoperative visits. BSR and AVR were tracked at the preoperative apical vertebral level, and the level with maximum deformity, at each respective timepoint. Generalized estimating equations models were used for statistical analysis. Covariates included age, sex, and body mass index.RESULTS:49 patients (73.4% female, mean age 14.6±2.2 years, mean preoperative coronal curve angle 57.9°±8.5, and 67% major thoracic) were evaluated. ATR correction was significantly improved at all postoperative timepoints and there was no significant loss of correction. AVR Max and AVR Apex were significantly improved at all timepoints but there was a significant loss of correction for AVR Apex between the six-week and one-year visit (P=0.032). BSR Max achieved significant improvement at the three-month visit. BSR Apex was significantly improved at the three-month and one-year visit.CONCLUSION:ATR and AVR demonstrated significant axial plane correction at two-years postoperative in patients undergoing PSF for AIS. BSR did not maintain significant improvement by the two-year visit.

BACKGROUND CONTEXT Historically, pedicle screw accuracy measurements have relied on computed tomography (CT) and expert visual assessment of the position of pedicle screws relative to preoperative plans. Proper pedicle screw placement is necessary to avoid additional complications and cost of revision procedures. PURPOSE To determine accuracy and precision of pedicle screw insertion via a novel computer vision algorithm utilizing preoperative and postoperative CT scans. STUDY DESIGN/SETTING Cadaveric controlled lab study. PATIENT SAMPLE Three adult cadaveric specimens. OUTCOME MEASURES The difference in tip, tail, and mid-pedicle screw distance (in millimeters), mean error, variance, and mean absolute error between preoperative plan and postoperative CT. METHODS Screw placement was planned in generic planning and segmentation software using standard criteria for screw planning. Two surgeons experienced in robotic workflow performed bilateral T2-L4 instrumentation using robotic-assisted navigation. Postoperative CT scans of the entire vertebral column were obtained. Automated segmentation and computer vision techniques were employed to align each postoperative vertebra with its preoperative counterpart and then compare positions along all three axes in an automated fashion. The mid-pedicle position in the anterior-posterior plane was not reported as it is not a measurable parameter. Mean error (ME), mean absolute error (MAE), and variance were calculated. Systematic error, precision, and accuracy were defined as ME, 2 standard deviations, and MAE, respectively. RESULTS Eighty-eight pedicle screws were placed. The computer algorithm showed that robotic-assisted pedicle screw placement was both accurate and precise. This study demonstrates robotic assisted pedicle screws can be placed with submillimeter accuracy in the coronal plane. Furthermore, the tip measurements showed greater precision than the tail measurements. Figure 1 shows both the numerical values and a visual representation of accuracy and precision. CONCLUSIONS This study introduces automated algorithms for determining accuracy and precision of planned pedicle screws. Our accuracy outcomes are comparable or superior to recent data from robotic-assisted in vivo studies in adult patients, as well as prior cadaver studies. This algorithmic computerized workflow establishes a standardized protocol for assessment of pedicle screw placement accuracy and precision, and provides baseline accuracy and precision for both cadaveric and in vivo comparison. FDA Device/Drug Status Medtronic Mazor X Stealth (Approved for this indication)

This study evaluates the relationship between existing radiographic measurements of shoulder asymmetry with novel surface topographic (ST) measurements, hypothesizing that these relationships will be weak. Data were gathered from a prospectively collected registry of patients who underwent ST scanning at a single tertiary care institution. Inclusion criteria were diagnosis of juvenile or adolescent idiopathic scoliosis, age 11–21, same-day ST and EOS radiographic evaluation. Twelve radiographic variables that evaluate shoulder height were measured, as well as curve magnitudes and vertebral axial rotation. ST data were collected using the 3dMDbody scanning system. Three ST measurements of shoulder symmetry were evaluated: ST-based AC angle (the angle between a line made between the surface of the AC joints and a line parallel to the ground), Shoulder Normal Asymmetry angle (the angle between the mirrored normals to the planes defined by the jugular notch, vertebral prominence, and AC joint), and Shoulder Volume Asymmetry Index (difference in volumes between the right and left shoulder). Univariate, followed by a stepwise multivariate linear regression was performed to evaluate the correlations of the radiographic measurements to the ST-based measurements. Correlation categories: weak (x < 0.4), moderate (0.4 ≤ x < 0.6), strong (0.6 ≤ x < 0.8), and very strong (x ≥ 0.8). 141 patients with idiopathic scoliosis were evaluated (65.2

Background: Up to 75% of patients with idiopathic scoliosis (IS) report back pain, but the exact contributors are unclear. This study seeks to assess how pain correlates with demographics, radiographic and surface topographic (ST) measurements, and patient-reported outcome measures (PROMs) in patients with IS. Methods: Patient-Reported Outcome Measurement Information System (PROMIS) Pain Interference (PI) and Scoliosis Research Society revised (SRS-22r) pain domain from an IRB approved prospectively collected registry containing patients 11 to 21 years old with IS were correlated (Spearman coefficients) with measurements from whole-body EOS radiography and ST scanning, PROMIS 1.0 PROMs, Trunk Appearance Perception Scale (TAPS), and SRS-22r domains. SRS-22r and PROMIS-PI were also compared between different sex, scoliosis severities, and primary curve locations with Mann-Whitney U or Kruskal-Wallis tests, and if significant differences were found, included with the 5 highest univariate correlated variables into stepwise multivariate linear regression models (P<0.05 to enter, P>0.1 to remove) predicting SRS-22r pain and PROMIS-PI. Results: One hundred and forty-nine patients (14.5 ± 2.0 y, body mass index 20.6 ± 4.1 kg/m2, 96 (64%) female, mean major coronal curve 40 ± 19 deg, range: 10 deg, 83 deg) reported mean PROMIS-PI of 42.2 ± 10.0 and SRS-22r pain of 4.4 ± 0.6. SRS-22r self-image was the most correlated variable with both SRS-22r pain (rho=0.519) and PROMIS-PI (rho=−0.594). Five variables, none of which were ST or radiographic measures, strongly predicted SRS pain domain (R=0.711, R2=0.505, N=138). Two variables (SRS-22r self-image and SRS-22r function) were utilized by a model correlated with PROMIS-PI (R=0.687, R2=0.463, N=124). Conclusions: SRS-22r function and self-image domains were more strongly correlated with SRS-22r pain and PROMIS-PI than any radiographic or ST measurements. Level of Evidence: Level II—retrospective study.

PurposeAdolescent idiopathic scoliosis (AIS) is a deformity of the spine that results in external asymmetry of the torso in the shoulder, waist, and rib hump. Several patient reported outcome measures (PROMS) including the Trunk Appearance Perception Scale (TAPS) and SRS-22r self-image domain are used to measure the patient's self-perception. The purpose of this study is to investigate the relationship between objective surface topographic measurements of the torso to subjective patient self-perception.Methods131 AIS subjects and 37 controls participated in this study. All subjects completed TAPS and SRS-22r PROMS followed by whole body 3d surface topographic scanning. An automated analysis pipeline was used to compute 57 measurements. Multivariate linear models were developed to predict TAPS and SRS-22r self-image using each unique combination of 3 parameters and leave one out validation where the best combinations were selected.ResultsBack surface rotation, waist crease vertical asymmetry and rib prominence volume were most predictive of TAPS. The final predicted TAPS values from leave one out cross validation was correlated to ground truth TAPS scores with an R value of 0.65. Back surface rotation, silhouette centroid deviation, and shoulder normal asymmetry were most predictive of SRS-22r self-image with a correlation of R = 0.48.ConclusionSurface topographic measurements of the torso are correlated to TAPS and SRS-22r self-image scores in AIS patients and controls, with TAPS exhibiting a stronger relationship, better reflecting the patient's external asymmetries.

Adolescent idiopathic scoliosis (AIS) patients experience structural spinal deformity, but the impact of AIS on physical activity is not widely studied. Reports of physical activity levels between children with AIS and their peers are mixed. This study sought to characterize the relationship between spinal deformity, spinal range of motion, and self-reported physical activity in AIS patients. Patients aged 11–21 completed self-reported measures of physical activity using the HSS Pedi-FABS and PROMIS Physical Activity questionnaires. Radiographic measures were obtained from standing biplanar radiographic imaging. Surface topographic (ST) imaging data was obtained using a whole-body ST scanning system. Hierarchical linear regression models analyzed the relationship between physical activity, ST, and radiographic deformity while controlling for age and BMI. 149 patients with AIS (mean age 14.5 ± 2.0 years, mean Cobb angle 39.7° ± 18.9°) were included. In the hierarchical regression predicting physical activity from Cobb angle, no factors were significant predictors of physical activity. When predicting physical activity from ST ROM measurements, age and BMI served as covariates. No covariates or ST ROM measurements were significant predictors of physical activity levels for either activity measure. Physical activity levels of patients with AIS were not predicted by levels of radiographic deformity or surface topographic range of motion. Although patients may experience severe structural deformity and range of motion limitations, these factors do not appear to be associated with decreased physical activity level utilizing validated patient activity questionnaires. Level II.

Axial twisting of the spine has been previously shown to be affected by scoliosis with decreased motion and asymmetric twisting. Existing methods for evaluating twisting may be cumbersome, unreliable, or require radiation exposure. In this study, we present an automated surface topographic measurement tool to evaluate global axial rotation of the spine, along with two measurements: twisting range of motion (TROM) and twisting asymmetry index (TASI). The aim of this study is to evaluate the impact of scoliosis on axial range of motion. Adolescent idiopathic scoliosis (AIS) patients and asymptomatic controls were scanned in a topographic scanner while twisting maximally to the left and right. TROM was significantly lower for AIS patients compared to control patients (69.1° vs. 78.5°, p = 0.020). TASI was significantly higher for AIS patients compared to control patients (29.6 vs. 19.8, p = 0.023). After stratifying by scoliosis severity, both TROM and TASI were significantly different only between control and severe scoliosis patients (Cobb angle > 40°). AIS patients were then divided by their major curve region (thoracic, thoracolumbar, or lumbar). ANOVA and post hoc tests showed that only TROM is significantly different between thoracic AIS patients and control patients. Thus, we demonstrate that surface topographic scanning can be used to evaluate twisting in AIS patients.

Purpose This study introduces a novel surface-topographic scanning system capable of automatically generating a suite of objective measurements to characterize torso shape. Research Question: what is the reliability of the proposed system for measurement of trunk alignment parameters in patients with adolescent idiopathic scoliosis (AIS) and controls? Methods Forty-six adolescents (26 with AIS and 20 controls) were recruited for a prospective reliability study. A series of angular, volumetric, and area measures were computed from topographic scans in each of three clinically relevant poses using a fully automated processing pipeline. Intraclass correlation coefficients (ICC(2,1)) were computed within (intra-) and between (inter-) raters. Measurements were also performed on a torso phantom. Results Topographic measurements computed on a phantom were highly accurate (mean RMS error 1.7%) compared with CT. For human subjects, intra- and inter-rater reliability were both high (average ICC > 0.90) with intrinsic (pose-independent) measurements having near-perfect reliability (average ICC > 0.98). Conclusion The proposed system is a suitable tool for topographic analysis of AIS; topographic measurements offer an objective description of torso shape that may complement other imaging modalities. Further research is needed to compare topographic findings with gold standard imaging of spinal alignment, e.g., standing radiography. Conclusion: clinical parameters can be reliably measured in a fully automated system, paving the way for objective analysis of symmetry, body shape pre/post-surgery, and tracking of pathology without ionizing radiation.

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

The proliferation of 3D scanning technology has driven a need for methods to interpret geometric data, particularly for human subjects. In this paper we propose an elegant fusion of regression (bottom-up) and generative (top-down) methods to fit a parametric template model to raw scan meshes. Our first major contribution is an intrinsic convolutional mesh U-net architecture that predicts pointwise correspondence to a template surface. Soft-correspondence is formulated as coordinates in a newly-constructed Cartesian space. Modeling correspondence as Euclidean proximity enables efficient optimization, both for network training and for the next step of the algorithm. Our second contribution is a generative optimization algorithm that uses the U-net correspondence predictions to guide a parametric Iterative Closest Point registration. By employing pre-trained human surface parametric models we maximally leverage domain-specific prior knowledge. The pairing of a mesh-convolutional network with generative model fitting enables us to predict correspondence for real human surface scans including occlusions, partialities, and varying genus (e.g. from self-contact). We evaluate the proposed method on the FAUST correspondence challenge where we achieve 20% (33%) improvement over state of the art methods for inter- (intra-) subject correspondence.

The EOS(R) scanner is a radiographic system that captures PA and lateral images in standing posture. The system is widely used in diagnosis and assessment of scoliosis, as it provides a low-dose alternative to traditional X-ray and can capture full-body images. Furthermore, spacial calibration between the two imaging views is implemented in hardware, facilitating 3D reconstruction of imaging targets. In this paper, a brief description of the system is followed by an explanation of the geometric relationship between 3D space and radiographic image space.

Spine shape can be reconstructed from stereoradiography, but often requires specialized infrastructure or fails to account for subject posture. In this paper a protocol is presented for stereo reconstructions that integrates surface recordings with radiography and naturally accounts for variations in patient posture. Low cost depth cameras are added to an existing radiographic system to capture patient pose. A statistical model of human body shape is learned from public datasets and registered to depth scans, providing 3D correspondence across images for stereo reconstruction of radiographic landmarks. A radiographic phantom was used to validate these methods in vitro with RMS 3D landmark reconstruction error of 2.0 mm. Surfaces were automatically and reliably registered, with SD 12 mm translation disparity and SD .5° rotation. The proposed method is suitable for 3D radiographic reconstructions and may be beneficial in compensating for involuntary patient motion.