Stereoradiographic Images Research Articles

Understanding pelvic mobility is important to correctly diagnose and treat painful hips with positive impingement test in non-arthritic patients.

To determine repeatability of pelvic mobility, calculated as both change in sacral slope (∆SS) and pelvic tilt (∆PT), and evaluate their correlations with pelvic incidence (PI) in non-arthritic patients with hip pain and positive impingement test. The cohort comprised 82 patients aged 31.8 ± 7.4, with hip pain and positive impingement test. Stereo-radiographic images were acquired in three positions (neutral standing, neutral sitting, and flexed-forward-sitting). PI, pelvic tilt (PT), and sacral slope (SS) were measured. Repeatability was evaluated. Pelvic mobility was calculated as ΔPT and ΔSS from (i) standing to sitting, (ii) neutral to flexed-forward-sitting, and (iii) maximum to minimum values. Correlations of PI with PT, SS, ΔPT, and ΔSS were assessed. Repeatability was excellent for all pelvic mobility measurements (intraclass correlation coefficients, ICC > 0.97). ΔPT was 25.9 ± 8.3º from standing to sitting, 14.4 ± 11.2º from standing to flexed-forward-sitting, and 37.8 ± 13.7º from maximum to minimum values. ΔSS was 24.0 ± 7.6º from standing to sitting, 14.2 ± 11.6º from standing to flexed-forward-sitting, and 35.9 ± 13.7º from maximum to minimum values. PI was strongly correlated with PT in standing (r = 0.7) and SS in standing (r = 0.7), and moderately correlated with PT in sitting (r = 0.6) and SS in sitting (r = 0.5), but was not correlated with neither ΔPT nor ΔSS (r < 0.3). Pelvic mobility, calculated as ΔPT and ΔSS, has excellent repeatability, and is not correlated with PI in non-arthritic patients with hip pain. Therefore, PI is of limited value for diagnosis and treatment of painful hips with positive impingement test, as well as to distinguish hip users from spine users; pelvic mobility should be used instead. Level IV.

How is quality of life after total hip replacement related to the reconstructed anatomy? A study with low-dose stereoradiography

PurposeThe purpose of this study was to evaluate the relationships between the three-dimensional anatomy of operated hip in standing position using low-dose stereo-radiography imaging system and postoperative hip disability and osteoarthritis outcome score (HOOS) after total hip arthroplasty (THA). Material and methodsA total of 123 patients who underwent THA during a one-year period were included. There were 50 men and 73 women with a mean age of 67.3±13.6 (SD) years (range: 19–89 years). All patients underwent pre- and postoperative low-dose stereo-radiography examination and completed a HOOS form (score from 0 to 100, 100 for full satisfaction). We recorded 16 anatomical parameters before THA, and 15 after THA. After binary transformation of HOOS score using 70 as threshold value, outcome was assessed using logistic or generalised linear models. ResultsA total of 103 patients (103/123; 83.7%) had a HOOS score≥70 and were considered as the satisfied group. A significant difference in pelvic incidence (the angle between a line perpendicular to the sacral plate at its midpoint and a line connecting the same point to the centre of the bicoxofemoral axis) was found between the satisfied 56.4±10.4 (SD)° (range: 31–85°) and the unsatisfied group 48.7±8.9 (SD)° (range: 40–65) (P=0.006). The relative variation of offset (distance from the centre of rotation of the femoral head to a line bisecting the long axis of the femur) compared to the contralateral hip was −7% in the satisfied group and 7.2% in the unsatisfied group (P=0.01). ConclusionPelvic incidence, a parameter independent of the reconstructed anatomy, probably influences the quality of life of patients with THA, via pelvic compensatory capabilities. A loss of femoral offset negatively influences the satisfaction of patients.

A Novel Method for Correcting Pelvic Tilt on Anteroposterior Pelvic Radiographs.

BackgroundAnteroposterior (AP) pelvic radiographs remain the standard for pre- and postoperative imaging during total hip arthroplasty (THA), despite the known limitation of plain films, including the inability to adequately account for distortion caused by variations in pelvic orientation such as pelvic tilt. The purpose of this study was to develop a reliable method for correcting pelvic tilt on AP pelvic radiographs in patients undergoing THA.MethodsCT scans from 20 patients/cadaver specimens (10 male, 10 female) were used to create 3D renderings, from which synthetic radiographs of each pelvis were generated. For each pelvis, 13 synthetic radiographs were generated, showing the pelvis at between -30° and 30° of pelvic tilt, in 5° increments. On each image, eight unique parameters/distances were measured to determine the most appropriate parameters for the calculation of pelvic tilt. The most reliable and accurate of these parameters was determined via regression analysis and used to create gender-specific nomograms from which pelvic tilt measurements could be calculated. The accuracy and reliability of the nomograms and correction method were subsequently validated using both synthetic radiographs (n=50) and stereoradiographic images (n=58).ResultsOf the eight parameters measured, the vertical distance between the superior margin of the pubic symphysis and the transischial line (PSTI) was determined to be the most reliable (r=-0.96, ICC=0.94). Using that parameter and applying the associated nomograms to 50 synthetic radiographs of random pelvic tilt, the mean difference between the actual pelvic tilt and that calculated using the correction method was 0.1°±5.1° (p=0.98, r=0.96). In 58 stereoradiographic images, the mean difference between actual and measured pelvic tilt was -0.2°±6.4° (p=0.74, r=0.77). The pooled results indicate no significant difference between actual (2.2°±13.9°) and measured pelvic tilt (2.1°±14.3°, p=0.93, r=0.91). No significant differences were noted based on gender.ConclusionsOur method of correcting for pelvic tilt using the vertical distance from the pubic symphysis to the transischial line provides a reliable method for correcting for pelvic tilt on AP pelvic radiographs.

The Link Between the 3D Spino-pelvic Alignment and Vertebral Body morphology in Adolescent Idiopathic Scoliosis

BackgroundVertebral anterior overgrowth has been suggested as part of the etio-pathogenesis of adolescent idiopathic scoliosis (AIS). However, the link between 3D spinopelvic alignment and the vertebral anteroposterior height asymmetry in different scoliotic curves types and whether it deviates from the non-scoliotic controls, has not been studied. PurposeWe aimed to retrospectively describe the link between the anteroposterior vertebral height differences (ΔAPVH) measured in the true sagittal plane of each vertebra and the spinopelvic parameters in three anatomical planes. Methods30 AIS cases with primary thoracic curves, 28 with thoracolumbar/lumbar curves, and 20 non-scoliotic controls were included. All subjects had 3D reconstruction of the spine, generated from low-dose upright stereoradiography images. Pelvic incidence (PI), thoracic and lumbar coronal and sagittal curve measurements, and vertebral axial rotation were measured. The association between the spinopelvic parameters and ΔAPVH were compared between the two AIS and control groups. ResultsΔAPVH at the apex of the curve was significantly different between the two AIS groups, as well as between both AIS groups and the controls and was related to the vertebral apical rotation (p < 0.05). Kyphosis and lordosis measurements were significantly related to the sum of the ΔAPVH in thoracic and lumbar regions respectively in AIS group but not in non-scoliotic controls (p < 0.05). ConclusionsThe ΔAPVH depended on the scoliotic curve type and was significantly different from the controls only at the apical levels. Morphological changes in the scoliotic vertebrae, measured as anterior-posterior differences in the vertebral height, are related to the sagittal spinal profile suggesting the morphology of the vertebra contributes to the sagittal curvatures of the spine in AIS; nonetheless, such relationship between the vertebral morphology and the sagittal profile was not evident in non-scoliotic controls.

Patient absorbed dose comparison in CT and Stereoradiography (EOS) imaging during lower limb torsion evaluation using in-vivo and in-vitro dosimetry methods

Introduction: Accurate evaluation of femoral and tibial torsion is essential for children or adult with legs deformity, becuse incorrect legs morphogenesis can lead to pathological situation. CT scan is commonly used for the measurement of skeletal bone parameters. But, disability in imaging from standing and sitting posture and absorb dose of patients are deficits of this method. EOS method overcome this dificits. Likewise some paper have reported decrease of EOS dose rather than dose level in CT, this project aim to measure amount of dose reduction and to verify reduction of EOS dose level in compare to CT. Materials and Methods: For EOS and CT invitro dosimetry, a pencil ionization chamber was used. Computed tomography dose index volume (CTDIvol) was mesuered, using this dosimeter and standard tissue equivalent CT phantom. DLP of both imaging methods was compared for acquisition of adult hip. With radiothermoluminescent detectors (TLD) in vivo dosimetry enterans skin dose for 30 patients was measuered, which 15 of them were underwented CT scan and the other were underwented EOS imaging. Results: The reading of dosimeters level and therefor enterans skin doses, in EOS system was significantly lower than CT scan. Patient dose in AP, RT and LT fields of CT scan was respectively 24, 41.5 and 9 times more than EOS. Enterans skin dose in CT scan was 18 times more than EOS on average. Also, in invitro dosimetry CT scan dose was 47 times more than EOS dose. Conclusion: Elimination of scatter radiation and high quantum efficiency of detector lead to minimum dose for an optimum qulity scan with EOS system than CT scan. Stereoradiography imaging modality will impose less doses of CT scan imaging modality in similar imaging views from the lower limbs.

Comparison of entrance skin dose in the hip region in the imaging of the lower extremity by CT scan and EOS

Introduction: Increasing in refer to computed tomography (CT-scan) imaging causes to increase in cumulative dose. Stereoradiography (EOS) is an X-ray imaging technology that, by eliminating scattering radiation, reduces patient's absorption dose and improves image quality. Materials and Methods: This cross-sectional study was carried out in a hospital with two different types of imaging apparatus, EOS Biospace Instruments and CT TOSHIBA MDCT Alexion. 15 patients were selected randomly for each Imaging method. Prior to irradiation, three thermoluminescence dosimeters (TLDs) were installed on the target area in three AP, RT and LT views. The 85 kVp and 110 kVp were used for EOS and CT respectively. The TLDs were read and the statistical analysis was performed using one-way ANOVA. Results: The mean reading of TLD dosimeters in EOS imaging of the lower regions with AP, RT and LT views were 57.88 ± 14.73, 19.84 ± 16.5 and 98.98 ± 19.59 (nc) respectively. These values with similar views in CT scan images were 1369.88 ± 585.18, 824.179 ± 35.22 and 785.66 ± 304 nc. According to the results of statistical analysis, the mean reading of TLDs in all EOS imaging views was significantly lower than the CT imaging method for estimating the entrance skin dosing. Conclusion:Stereoradiography imaging modality will impose less doses of CT scan imaging modality in similar imaging views from the lower limbs.

A Comparison of the In Vivo Contact Pressure at the Tibiotalar Joint During Walking and Running

Category: Ankle Introduction/Purpose: Knowledge of cartilage pressure distribution in healthy ankle joints during gait is important for understanding the loading environment of articular cartilage and for providing a basis for comparison to evaluate how ankle pathology and surgical procedures affect cartilage loading. Finite element models of the ankle have been developed to examine in vitro loads at the tibiotalar joint during simulated standing in healthy and injured ankle joints [1, 2]. However, there are currently no in vivo studies of tibiotalar cartilage pressure during dynamic loading activities. The goal of this study was to develop a subject-specific finite element model of the tibiotalar joint to estimate contact pressure during walking and running. Methods: Informed consent was obtained from one healthy male, age 23 yrs., BMI 27 kg/m2). Synchronized biplane radiographs of the ankle were acquired at 100 and 150 frames per second during the support phase of overground walking and running, respectively, at a self-selected pace (1.5 m/s and 3.0 m/s, respectively). CT-based bone models of the tibia and talus were matched to the stereoradiographic images to precisely track the three-dimensional bone movement [3]. Six degrees-of-freedom joint kinematics were calculated for each bone model, and used to position bone models in the finite element analysis. Cartilage volumes for the distal tibia and proximal talus were created in Geomagic software by extruding the articulating bone surface. Bones were modeled as rigid bodies and cartilage was modeled as deformable bodies with uniform thickness of 1.3 mm [4-7]. Simulations were performed using FEBio software. The primary outcome parameter was peak cartilage pressure in the tibiotalar joint. Results: On average, peak tibiotalar cartilage pressure was approximately 25% greater during the midstance phase of running in comparison to walking (Figure 1). During walking, peak contact pressure occurred on the lateral-central region of the tibiotalar cartilage throughout the entire stance phase. During the early support phase of running, the location of peak contact pressure was also on the lateral-central region of the tibiotalar cartilage. During running push-off, pressure increased in the medial-central cartilage region and the overall peak cartilage pressure increased. Conclusion: A novel finding of this study is that the peak pressure in tibiotalar cartilage moves from the lateral to medial side of the joint during running, but remains on the lateral side throughout the support phase of walking. This suggests that the location and magnitude of the loads seen by tibiotalar joint cartilage are activity dependent, even in the healthy ankle joint. Future work will investigate cartilage loading in pathologic ankles before and after surgical intervention, as well as during other common athletic activities.

Loading and kinematic profiles for patellofemoral durability testing.

Patellar complications after total knee replacement (TKR), such as maltracking, fracture, wear, and loosening, can lead to implant failure and revision surgery. However, few in vitro patellofemoral durability tests for the implanted joint have been developed. Existing standards for patellofemoral loading profiles (ISO 14243-5, draft) are generic (not implant-specific) and do not include patient variability. The goal of this study was to derive implant-specific loading profiles to simulate a motor task that reaches high knee flexion and include patient variability. In vivo data, including motion capture and stereo-radiographic images at the knee, were collected for eleven rotating platform TKR patients performing a single-leg lunge activity. Quadriceps forces during the activity were estimated for each patient from marker data and ground forces with a musculoskeletal model. Patellofemoral contact forces were estimated with patient-specific finite element models of the implanted knees. Stereo-radiography patellofemoral kinematics and estimated contact loads were combined to derive seven loading profiles that span the observed inter-patient variability. The loading profiles were experimentally evaluated in a 6-degree-of-freedom testing machine and worst-case loading profiles were identified. The two profiles that generated the highest stresses in the patellar button (43% and 46% of the volume surpassed yield stress, respectively) included the largest internal (4.4°) and external (13.0°) patellar rotation, and greater medio/lateral contact forces (up to 915 N). The same profiles were also tested in a finite element model of the experimental simulator, which was able to adequately replicate location and magnitude of the peak deformations measured in the prostheses after the experiment. The kinematic and loading profiles developed in this study simulated a high-demand motor task and incorporated inter-patient variability, capturing worst-case patellofemoral configurations, and can be utilized for pre-clinical testing of new patellar designs.

Two for One: A Change in Hand Positioning During Low-Dose Spinal Stereoradiography Allows for Concurrent, Reliable Sanders Skeletal Maturity Staging

Study DesignProspective survey. ObjectivesTo evaluate the reliability of low-dose stereoradiography compared to standard hand bone age films for assessing Sanders skeletal maturity stage in patients with idiopathic scoliosis. Summary of Background DataThe Sanders skeletal maturity staging system is a valuable tool in the care of juvenile and adolescent spine scoliosis, but obtaining dedicated hand films adds additional time, radiation, and expense to the clinic visit. A change in patient hand positioning for routine full-length PA spine low-dose stereoradiography may offer a viable alternative. MethodsA survey consisting of 30 standard bone age hand films and 26 posteroanterior spine low-dose stereoradiography images (magnified view of hands only) was created in REDCap and distributed to two pediatric spine surgeons and two fellows. The graders were asked to classify the images according to the Sanders skeletal maturity classifications. Images were graded in two trials conducted one week apart. Inter- and intraobserver reliability was assessed using the mean linearly weighted kappa to provide an overall index of agreement. ResultsIn Trial 1, the interobserver reliability was similar for both the standard bone age films (κ = 0.82) and for the low-dose stereoradiography films (κ = 0.79) (p = .501). In Trial 2, reliability was similar between imagine modalities and slightly improved for both standard bone age films (κ = 0.85) and low-dose stereoradiography films (κ = 0.82) (p = .192). Intraobserver reliability was strong for both standard films (κ=0.89) and low-dose stereoradiography films (κ = 0.86) (p = .446). ConclusionA simple change in patient hand positioning for low-dose stereoradiography allows clinicians to simultaneously assess a patient’s spinal deformity and skeletal maturity with excellent reliability. Given the frequency of scoliosis surveillance visits, this simple change could lead to significant savings of time, money, and radiation exposure for the growing child. Level of EvidenceLevel III.

Preliminary experience with SpineEOS, a new software for 3D planning in AIS surgery.

Preoperative planning of scoliosis surgery is essential in the effective treatment of spine pathology. Thus, precontoured rods have been recently developed to avoid iatrogenic sagittal misalignment and rod breakage. Some specific issues exist in adolescent idiopathic scoliosis (AIS), such as a less distal lower instrumented level, a great variability in the location of inflection point (transition from lumbar lordosis to thoracic kyphosis), and sagittal correction is limited by both bone-implant interface. Since 2007, stereoradiographic imaging system is used and allows for 3D reconstructions. Therefore, a software was developed to perform preoperative 3D surgical planning and to provide rod's shape and length. The goal of this preliminary study was to assess the feasibility, reliability, and the clinical relevance of this new software. Retrospective study on 47 AIS patients operated with the same surgical technique: posteromedial translation through posterior approach with lumbar screws and thoracic sublaminar bands. Pre- and postoperatively, 3D reconstructions were performed on stereoradiographic images (EOS system, Paris, France) and compared. Then, the software was used to plan the surgical correction and determine rod's shape and length. Simulated spine and rods were compared to postoperative real 3D reconstructions. 3D reconstructions and planning were performed by an independent observer. 3D simulations were performed on the 47 patients. No difference was found between the simulated model and the postoperative 3D reconstructions in terms of sagittal parameters. Postoperatively, 21% of LL were not within reference values. Postoperative SVA was 20mm anterior in 2/3 of the cases. Postoperative rods were significantly longer than precontoured rods planned with the software (mean 10mm). Inflection points were different on the rods used and the planned rods (2.3 levels on average). In this preliminary study, the software based on 3D stereoradiography low-dose system used to plan AIS surgery seems reliable for preoperative planning and precontoured rods. It is an interesting tool to improve surgeons' practice, since 3D planning is expected to reduce complications such as iatrogenic malalignment and to help for a better understanding of the complications, choosing the location of the transitional vertebra. However, further work is needed to improve thoracic kyphosis planning. These slides can be retrieved under Electronic Supplementary Material.

Considerations in sagittal evaluation of the scoliotic spine.

To predict the sagittal spinal parameters as measured in a 3D model of the spine using the 2D radiographic measurements. Bi-planar low-dose stereoradiography images of 73 right thoracic AIS patients were processed to generate 3D models of the spine and pelvis. T1-T12 kyphosis, L1-S1 lordosis, and pelvic rotation were calculated using these 3D models. With the same X-rays, T1-T12 kyphosis, L1-S1 lordosis, thoracic and lumbar frontal curves, and pelvic rotation (calculated from the frontal and sagittal distances between the femoral heads) were manually measured on the X-rays by two independent observers. 3D sagittal parameters were predicted from only 2D sagittal parameters (simple regression) and from 2D sagittal parameters, 2D frontal parameters, and pelvic rotation (multiple regression). The simple and multiple regression models were compared for efficiency and accuracy of prediction. Comparing single and multiple regression models, multiple regression improved the prediction of the 3D sagittal parameters for kyphosis (R2 = 0.78-0.86) and lordosis (R2 = 0.88-0.92) measurements when compared to simple regression. The impact of pelvic rotation was significant when 2D kyphosis was higher than 40° and thoracic curve was less than 60° or 2D kyphosis was less than 40° and thoracic curve was higher than 60°, p < 0.05. Lordosis of 60° and higher were more prone to measurement error when pelvic rotation was present, p < 0.05. Both pelvic rotation and frontal deformity affect the accuracy of the 2D sagittal measurements of the scoliotic spine. We suggest the importance of the 3D considerations in sagittal evaluation of AIS.

Radiological and functional outcomes of high-grade spondylolisthesis treated by intrasacral fixation, dome resection and circumferential fusion: a retrospective series of 20 consecutive cases with a minimum of 2years follow-up.

Major concern during surgery for high-grade spondylolisthesis (HGS) is to reduce lumbosacral kyphosis and restore sagittal alignment. Despite the numerous methods described, lumbosacral fixation in HGS is a challenging technique associated with high complication rate. Few series have described outcomes and most of the results are limited to lumbosacral correction without global sagittal alignment analysis. This study aims at analyzing clinical and radiological outcomes of HGS patients treated with intrasacral rods on full spine radiographs. HGS patients (Meyerding III or higher) operated between 2004 and 2014 were reviewed. All patients underwent full spine stereoradiographic images. After L5 and S1 decompression, reduction and circumferential fusion with intrasacral rod fixation and fusion up to L4 were performed under fluoroscopy. The entry points for S1 screws were located 3-5mm above and 5mm lateral to the first sacral hole, toward the promontory. The two short distal fusion rods were then positioned into the sacrum guided by anteroposterior fluoroscopy using Jackson's technique. Then, sacral dome resection was performed and a PEEK cage was impacted in L5S1 after reduction. Postoperatively, the hip and knee were kept flexed at 45° for 1week and extended progressively. Preoperative, 3months postoperative and last follow-up (>2years minimum) clinical and radiographic data were collected. Sagittal parameters included lumbosacral angle (LSA), olisthesis, T1 spinopelvic inclination (T1SPi) and spinopelvic parameters. 20 HGS patients were included (8 ptosis, 5 Meyerding IV). The mean age was 14years. At final FU (7.2years±3), LSA kyphosis and olisthesis were reduced (65°±14 vs 99°±11, p<0.001 and 81%±19 vs 45%±18, p<0.001, respectively). While L1L5 lordosis decreased, T1T12 kyphosis increased. At FU, global alignment with T1SPi was -6°±3. No significant loss of correction was observed. Regarding complications, ten patients presented transient L5 motor deficit that occurred when patients were put in standing position. However, all recovered before 3months postoperatively. Intrasacral rod fixation appears to be an effective technique to correct LSA kyphosis, compensatory hyperlordosis and restore global sagittal alignment with a postoperative T1SPi corresponding to the value of the asymptomatic subject and achieve fusion. However, it remains a demanding technique with high risk of transient neurologic complications.

Application of Low-dose Stereoradiography in In Vivo Vertebral Morphologic Measurements: Comparison With Computed Tomography.

Though computed tomography (CT) and 3 dimensional (3D) reconstruction of the spine and ribcage are powerful techniques for detailed monitoring of spinal growth and surgical planning of patients, drawbacks can arise. We explored the application of low-dose stereoradiography of the spine to calculate distinct morphologic parameters of the vertebral body in a juvenile patient population with early-onset scoliosis or congenital scoliosis. This study compares the 3D vertebral morphology measurements using low-dose stereoradiography with the currently accepted imaging modality for such measurements, CT scans. A total of 86 vertebrae of 6 patients with early-onset scoliosis and 3 patients with congenital scoliosis, age ranged between 7.8 and 12.5 years, who had both thoracic spine CT scan and low-dose stereoradiography of the spine were included. 3D reconstructions of CT and low-dose stereoradiography were generated. Using previously validated image processing techniques, vertebral anterior (A), posterior (P), left (L), and right (R) heights, superior and inferior endplates depth and width (S-D, I-D, S-W, I-W) were measured on the CTs' 3D reconstructions and were compared with the same parameters measured on low-dose stereoradiography reconstructions using a postprocessing custom code. The agreement between the 2 techniques in measurement of the vertebral morphology was assessed using the Bland-Altman plots. No significant difference was observed in the A, P, L, R, S-W, and I-W between the stereoradiography and CT measurements (P>0.05). S-D and I-D were significantly greater in low-dose stereoradiography measurements P<0.05. Bland-Altman plots showed an agreement between the stereoradiography and CT techniques in vertebral height measurements (A, P, L, R); however, larger measurement bias and greater limits of agreement in S-D, I-D, S-W, and I-W measurements were shown. In vivo measurements of the vertebral heights using low-dose stereoradiography 3D reconstructions were comparable with CT measurements except for the superior and inferior vertebral depths. The low-dose stereoradiography imaging modality and the postprocessing platform can be used for assessment of the vertebral heights and monitoring asymmetric growth in patients undergoing growth-sparing treatment except for the vertebral levels with congenital deformities. Level IV.

Tridimensional Analysis of Rotatory Subluxation and Sagittal Spinopelvic Alignment in the Setting of Adult Spinal Deformity

Study DesignRetrospective single-center. ObjectiveTo investigate rotatory subluxation (RS) in adult spinal deformity (ASD) with three-dimensional (3D) stereoradiographic images and analyze relationships between RS, transverse plane parameters, spinopelvic parameters, and clinical outcomes. BackgroundRecent research has demonstrated that sagittal plane malalignment and listhesis correlate with ASD patient-reported outcomes. However, there is still a lack of knowledge regarding the clinical impact of 3D evaluation and rotatory subluxation. Recent developments in stereoradiography allow clinicians to obtain full-body standing radiographs with low-dose radiation and 3D reconstruction. MethodsOne hundred thirty lumbar ASD patients underwent full-spine biplanar radiographs (EOS Imaging, Paris, France). Clinical outcomes were recorded. Using sterEOS software, spinopelvic parameters and lateral listhesis were measured. 3D transverse plane parameters included apical axial vertebral rotation, axial intervertebral rotation (AIR), and torsion index (sum of AIR in the curve). ASD patients were divided in three groups: AIR <5°, 5°< AIR <10°, AIR >10°. Groups were compared with respect to radiographic and clinical data. Correlations were performed between the transverse and sagittal plane parameters and clinical outcomes. ResultsPatients with AIR >10° were significantly older, with larger Cobb angle (39.5°) and greater sagittal plane deformity (pelvic incidence–lumbar lordosis mismatch 11.7° and pelvic tilt 22.6°). The AIR >10° group had significantly greater apical vertebra axial rotation apex (24.8°), torsion index (45°), and upper-level AIR (21.5°) than the two other groups. Overall, 27% of AIR patients did not have two-dimensional (2D) lateral listhesis. Patients with AIR >10° had significantly worse Oswestry Disability Index and more low back pain. ConclusionFor patients in which lateral listhesis was unreadable in 2D imaging, rotatory subluxation was revealed using stereoradiography and at an earlier disease stage. Moreover, different 3D transverse plane parameters are related to different patient-reported outcomes. Therefore, axial rotation can be considered in evaluation of lumbar degenerative scoliosis severity and prognosis. Level of EvidenceLevel III.

Erratum to: Stereoradiography imaging motion artifact: does it affect radiographic measures after spinal instrumentation?

Erratum to: Stereoradiography imaging motion artifact: does it affect radiographic measures after spinal instrumentation?

Stereoradiography imaging motion artifact: does it affect radiographic measures after spinal instrumentation?

Stereoradiography imaging (SRI) is an accurate and reliable low-dose radiographic method. However, patients must remain motionless during image acquisition. Motion artifacts are frequently noted. The aims of the study were to determine the incidence of the SRI motion artifact and assess if motion during SRI acquisition affects radiographic measurements. In this retrospective study, 198 patients with spinal instrumentation had biplanar SRI radiographs performed, of whom 39 had concomitant conventional radiographs. Eight coronal and sagittal spinal parameters were independently measured on SRI and conventional radiographs for the 39 patients by 2 observers. Inclusion criteria were: presence of spinal instrumentation of more than six levels and an SRI motion artifact identified on the coronal and/or the sagittal views on either the spinal rods or on the limbs. Means were compared between both types of radiographs using the Student's t test; intraclass correlation coefficients (ICCs) were used for intraobserver reproducibility and interrater reliability. A motion artifact was identified in 19.7% (n=39, mean age 19.5±1.7years) of the cases. There were no differences in any of the coronal or sagittal plane measurements between SRI and X-rays. Intraobserver reliability and interrater reproducibility was high (range 0.81-0.98). Motion artifact during full-spine stereoradiography imaging acquisition is frequent, but does not affect spinal measurements. SRI with a motion artifact can be used to produce reliable measurements of the sagittal and coronal parameters. Some SRI images with a motion artifact may suggest loss of fixation or bending of the rods. However, after becoming familiar with the appearance of the motion artifact, repeat radiographs are rarely indicated. 14-004872. Level IV.

How is 3D imaging impacting orthopedic treatments?

We have not experienced great evolutions in the field of orthopedic surgery during the last decade. We have reached a threshold in terms of devices such as joint replacements, screws and nails. However, the business continues and each orthopedic brand claims to achieve better results than the others. Objectively, designs are equivalents and we no longer are surprised when opening the boxes of an ancillary; maybe companies do not want surprises either and are slowing down their RD we need help in making the right decision and evaluating what we do. From my point of view, 3D imaging in the standing position is the main evolution that will impact planning and e valuation of orthopedics treatments. Biplanar stereoradiography was initially developed for analysis of spine deformities. In the early 1980s, Perdriolle [1], Graf and Dubousset [2] first described adolescent idiopathic scoliosis (AIS) as a 3D deformity. Then clinicians and engineers worked hand in hand to improve stereoradiography imaging systems in the standing position. But we had to wait for the 21st century and the work of Georges Charpak (who received the 1992 Nobel Prize in Physics) to reach technologies such as EOS (EOS-imaging). EOS is a low-dose imaging system that performs simultaneous full-spine or full-body antero-posterior (AP) and lateral views. With special software, a 3D reconstruction of the spine and lower limbs is possible. 3D is available routinely, but now that we have 3D, we have to learn how to use it. It is a very new way to see the body from the inside, and since every orthopedic surgeon has learned their profession on 2D x-rays, we need to build novel references.

Tibio-femoral joint constraints for bone pose estimation during movement using multi-body optimization

When using skin markers and stereophotogrammetry for movement analysis, bone pose estimation may be performed using multi-body optimization with the intent of reducing the effect of soft tissue artefacts. When the joint of interest is the knee, improvement of this approach requires defining subject-specific relevant kinematic constraints. The aim of this work was to provide these constraints in the form of plausible values for the distances between origin and insertion of the main ligaments (ligament lengths), during loaded healthy knee flexion, taking into account the indeterminacies associated with landmark identification during anatomical calibration.Ligament attachment sites were identified through virtual palpation on digital bone templates. Attachments sites were estimated for six knee specimens by matching the femur and tibia templates to low-dose stereoradiography images. Movement data were obtained using stereophotogrammetry and pin markers. Relevant ligament lengths for the anterior and posterior cruciate, lateral collateral, and deep and superficial bundles of the medial collateral ligaments (ACL, PCL, LCL, MCLdeep, MCLsup) were calculated. The effect of landmark identification variability was evaluated performing a Monte Carlo simulation on the coordinates of the origin-insertion centroids. The ACL and LCL lengths were found to decrease, and the MCLdeep length to increase significantly during flexion, while variations in PCL and MCLsup length was concealed by the experimental indeterminacy.An analytical model is given that provides subject-specific plausible ligament length variations as functions of the knee flexion angle and that can be incorporated in a multi-body optimization procedure.

Effects of quantum noise and binocular summation on dose requirements in stereoradiography

In the case of a quantum-noise limited detector, signal detection theory suggests that stereoradiographic images can be acquired with one half of the per-image dose needed for a standard radiographic projection, as information from the two stereo images can be combined. Previously, film-screen stereoradiography has been performed using the same per-image dose as in projection radiography, i.e., doubling the total dose. In this paper, the assumption of a possible decrease in dose for stereoradiography was tested by a series of contrast-detail experiments, using phantom images acquired over a range of exposures. The number of visible details, the effective reduction of the dose, and the effective decrease in the threshold signal-to-noise ratio were determined using human observers under several display and viewing conditions. These results were averaged over five observers and compared with multiple readings by a single observer and with the results of an additional observer with limited stereoscopic acuity. Experimental results show that the total dose needed to produce a stereoradiographic image pair is approximately 1.1 times the dose needed for a single projection in standard radiography, indicating that under these conditions the human visual system demonstrates almost ideal binocular summation.