Biplanar Radiographs Research Articles

Assessment of micro-dose biplanar radiography in lower limb measurements in children.

To evaluate in children microdose protocol compared with low dose for lower limb alignment (LLA) measurements on biplanar radiography. Children 6 years or older were included. Height, weight and hip width were measured prior to imaging. Hip width allowed classifying children into morphotype M1 (width <25 cm), M2 (25-35 cm) or M3 (>35 cm) corresponding to predefined acquisition parameters (kV, mA, tube speed). Micro- and low-dose protocols were used alternately, with simultaneous acquisition of frontal and lateral radiographs. LLA measurements were performed by two independent observers (n = 526). In 15 children per morphotype, a third observer performed measurements twice (n = 180). Intraclass correlation coefficients and the dose (delivered, absorbed) were calculated. 100 girls and 160 boys (mean age = 11.7 years) were investigated: 74 M1 (mean BMI, 15.7kg/m2), 149 M2 (19.8 kg/m2) and 40 M3 (30.2 kg/m2). With microdose, inter- and intra-observer agreement was >0.90 for lengths whatever the morphotype, 0.75-0.90 (M1) and >0.90 (M2, M3) for valgus/varus and flexion/hyperextension deviations. Dose reduction reached a factor of 8.5 and 5.4 for the delivered and absorbed dose respectively. Microdose could be used for LLA measurements in children and permits a significant dose reduction. • Lower limb lengths of children can be evaluated with microdose biplanar radiography. • Valgus/varus deviations also can be evaluated with microdose biplanar radiography. • Microdose biplanar radiography significantly reduces delivered and absorbed dose in children.

Kinematics and arthrokinematics in the chronic ACL-deficient knee are altered even in the absence of instability symptoms.

To analyze the in vivo kinematics and arthrokinematics of chronic ACL-deficient (ACL-D) and unaffected contralateral knees during level walking and downhill running using dynamic biplane radiography. It was hypothesized that ACL-D knees would demonstrate increased anterior translation and internal rotation, and that ACL-deficiency would alter the tibiofemoral contact paths in comparison to the unaffected contralateral side. Eight participants with unilateral chronic ACL-D without instability symptoms were recruited. The contralateral unaffected knee was considered as control. Kellgren-Lawrence (K-L) grades were determined from ACL-D and unaffected knees. Dynamic knee motion was determined from footstrike through the early-stance phase (20-25% of gait cycle) using a validated volumetric model-based tracking process that matched subject-specific CT bone models to dynamic biplane radiographs. Participants performed level walking at 1.2m/s and downhill running at 2.5m/s while biplane radiographs were collected at 100 and 150 images per second, respectively. Tibiofemoral kinematics and arthrokinematics (the path of the closest contact point between articulating subchondral bone surfaces) were determined and compared between ACL-D and unaffected knees. A two-way repeated measures analysis of variance was used to identify differences between ACL-D and unaffected knees at 5% increments of the gait cycle. Anterior-posterior translations were significantly larger in ACL-D than unaffected knees during level walking (all p < 0.001) and downhill running (all p ≤ 0.022). Internal rotation showed no significant difference between ACL-D and unaffected knees during level walking and downhill running. Closest contact points on the femur in ACL-D knees were consistently more anterior in the lateral compartment during downhill running (significant from 10 to 20% of the gait cycle, all p ≤ 0.044), but not during level walking. No differences in medial compartment contact paths were identified. Half of the participants had asymmetric K-L grades, with all having worse knee OA in the involved knee. Only 2 relatively young individuals had not progressed beyond stage 1 in either knee. The results suggest that anterior translation and knee joint contact paths are altered in ACL-D knees even in the absence of instability symptoms. The clinical relevance is that ACL-D patients who do not report symptoms of instability likely still demonstrate altered knee kinematics and arthrokinematics compared to their uninvolved limb. Case-control study, Level III.

Lower-limb lengths and angles in children older than six years: Reliability and reference values by EOS® stereoradiography.

Lower-limb alignment in children is classically assessed clinically or based on conventional radiography, which is associated with projection bias. Low-dose biplanar radiography was described recently as an alternative to conventional imaging. The primary objective of this study was to assess the reliability of length and angle values inferred from 3D reconstructions in children seen in everyday practice. The secondary objective was to obtain reference values for goniometry parameters in children. 3D reconstructions can be used to assess the lower limbs in children. The paediatric reliability study was done in 18 volunteers who were divided into three groups based on whether they were typically developing (TD) children, had skeletal development abnormalities, or had cerebral palsy. The reference data were obtained in 129 TD children. Each study participant underwent biplanar radiography with 3D reconstruction performed by experts and radiology technicians. Goniometry parameters were computed automatically. Reproducibility was assessed based on the intra-class coefficient (ICC) and the ISO 5725 standard (standard deviation of reproducibility, SDR). For length parameters, the ICCs ranged from 0.94 to 1.00 and the SDR from 2.1 to 3.5mm. For angle parameters, the ICC and SDR ranges were 0.60-0.95 and 0.9°-4.6°, respectively. No significant differences were found across experts or radiology technicians. Age-specific reference data are reported. These findings confirm the reliability of low-dose biplanar radiography for assessing lower-limb parameters in children seen in clinical practice. In addition, the study provides reference data for commonly measured parameters. IV.

Causes of intoeing and outtoeing gait in asymptomatic subjects: 3D reconstruction of the acetabulum and lower limbs

Introduction Foot progression angle (FPA), measuring intoeing and outtoeing gait, has been shown to be related to torsions of the tibia and/or the femur [1,2]. However, it is still unknown how the entire morphology of the pelvis, acetabulum and lower limbs dictate the axial foot orientation during walking. The aim was to evaluate the lower limbs morphological profile in subjects with different foot progression angles. Materiel et methodes One hundred and forty-five asymptomatic subjects (70F, age = 29.2 ± 11.1 years) underwent 3D gait analysis from which FPA was extracted. Subjects then underwent low-dose full-body biplanar radiographs. Pelvis and lower limbs were reconstructed in 3D to calculate: pelvic incidence, sacral slope, pelvic tilt, pelvic axial rotation, neck-shaft angle, femoral torsion (FT), varus/valgus, knee flexion/extension, femoral mechanical angle, tibial mechanical angle, tibial torsion (TT), femorotibial rotation (FTR), vertical center-edge angle, anterior and posterior acetabular sector angles, acetabular coverage over the femoral head (AC), acetabular tilt, abduction and anteversion, and Idelberg and Frank angle (IFA). FPA data was classified using agglomerative hierarchical clustering (AHC) into 3 groups: internal, neutral, external FPA. Demographic data (age, height, weight, sex) was compared between AHC groups using Kruskal–Wallis and Fisher tests. The morphologic parameters were compared between the FPA classes using ANCOVA while controlling for demographic data. Stepwise multiple linear regression (SMLR) was then performed to identify which morphologic parameters determined FPA. Resultats FPA varied from −28.7 to 3.1°. AHC divided FPA data as: external (E) FPA [−17.4 ± 3.6°], neutral (N) FPA [−9.9 ± 1.8°], internal (I) FPA [−2.9 ± 2.5°]. Weight, height and, significantly differed between groups (P Discussion Subjects with a higher weight and of the male sex tended to walk with a more outtoeing gait. Subjects with an outtoeing gait had a high TT and FTR as well as a low FT, therefore presenting a more outwards rotational profile. However, subjects with a more in toeing gait had a low TT, FTR and a high FT, therefore presenting a more inwards rotational profile. This profile extends over the whole lower limb, and includes FT, FTR, and TT excluding the acetabular morphology.

Reliability of head and cervical spine parameters measured on lateral radiographs

Introduction The cervical spine is an essential element in the assessment of global posture and it has been demonstrated that compensatory mechanisms can occur to maintain horizontal gaze [1] . To our knowledge, errors of measurement on head and cervical spine parameters are not yet known. The aim was to quantify the reliability of head and cervical parameters measured on full body radiographs. Materiel et methodes Seventy subjects (30 with adult spinal deformity, 30 with adolescent idiopathic scoliosis and 20 asymptomatic subjects) underwent full body low dose biplanar radiographs in free-standing position and were included in this study. Four well-trained operators measured digitally, 16 cervical spine and head parameters on the lateral radiographs, 3 times each. The collected parameters were: radiographic chin brow vertical angle (CBVA), slope of line of sight (SLS: angle between the horizontal and Frankfort plane), angle between McGregor line and the lower endplate of C2 (OC2), C1–C2 angle, C2 slope, C2–C7 angle (cervical lordosis/kyphosis), T1 slope, cervical sagittal vertical axis (cSVA), cranial tilt, cervical tilt, cranial offset, neck tilt (NT), thoracic inlet angle (TIA), C2 pelvic angle (CPA), thoracic pelvic angle (TPA) and cervico-thoracic pelvic angle (CTPA). General reliability (including both inter and intra-operator) was assessed by calculating the intraclass correlation coefficient (ICC), the errors of measurement were evaluated as the confidence interval at 95% (CI95%) for each parameter (ISO 5725-2, IC95% calculated with a precision of 5%). Resultats ICC values were high (> 0.85) for all parameters. CSVA, CTPA, CPA, Cranial offset, TPA, CBVA, cranial tilt showed low CI95% values (0.30 mm, 0.32o, 0.36o, 0.42 mm, 0.44o, 1.44o, 1.64˚ respectively). More elevated CI95% were found for C2 slope, SLS, T1 slope, C1–C2, OC2, cervical tilt, C2–C7 (4.1o, 4.3o, 5.0o, 5.1o, 5.2o, 5.1o, 5.8o respectively). TIA and NT showed the highest CI95% values (8.22o and 6.16o respectively). Discussion All head and cervical parameters were deemed highly repeatable when measured on full body low dose radiographs. The TIA and NT had higher uncertainties due to the poor visibility of the sternum because of the superimposition of the bony structures on the lateral radiographs. This study established the thresholds on head and cervical spine parameters, below which any differences should be considered due to uncertainties and should not be interpreted as a consistent variation.

3D Modeling of Lower Extremities With Biplanar Radiographs: Reliability of Measures on Subsequent Examinations.

Biplanar radiography with 3-dimensional (3D) modeling (EOS) provides a comprehensive assessment of lower limb alignment in an upright weight-bearing position with less radiation than conventional radiography. A study was performed to assess the consistency and reliability of 2 lower extremity 3D biplanar radiograph models created at least 1 year apart in a pediatric population. All patients who had 2 lower extremity radiographic evaluations with EOS performed at visits a minimum of 1 year apart were reviewed. Digital radiographs, of lower extremities in both frontal and sagittal planes, were acquired simultaneously, using the EOS system. The 3D reconstruction of the images was achieved utilizing the SterEOS software. Pelvic position, femoral and tibial anatomy, and the torsional profile were evaluated and compared using t tests. In total, 53 patients with a mean age of 11.7 years (range, 6.1 to 18.9 y) met inclusion criteria. When comparing 3D models between visits, minimal differences were noted in proximal femoral anatomy and pelvic alignment (pelvic incidence, sacral slope, sagittal tilt, neck shaft angle). Expected differences in femoral and tibial length corresponded with normal longitudinal growth between visits. Sagittal plane knee position varied widely between examinations. Femoral and/or tibial rotational osteotomies were performed in 37% of extremities between examinations. After femoral derotational osteotomy, a significant difference in femoral anteversion was appreciated when comparing preoperative and postoperative 3D models. However, this difference was less than the expected difference based on the anatomic correction achieved intraoperatively. No differences were noted in tibial torsion measures after tibial derotational osteotomy. The 3D modeling based on biplanar radiographs provides consistent and reliable measures of pelvic and hip joint anatomy of the lower extremity. Patient positioning may influence the reproducibility of knee alignment. The torsional profile assessment did not accurately reflect changes obtained by derotational osteotomy. Level III.

Are There 3D Changes in Spine and Rod Shape in the 2 Years After Adolescent Idiopathic Scoliosis Instrumentation?

Retrospective analysis of spine and rods 3D shape in the 2 years after adolescent idiopathic scoliosis (AIS) posterior surgical instrumentation. To evaluate spine and rod shape 3D changes in the 2 years after AIS instrumentation with different rod materials. Postoperative loss of correction has been reported with modern segmental instrumentation. The postoperative 3D rod shape changes of different rod materials and their implication in postoperative loss of correction have never been studied. A total of 42 Lenke 1 AIS cases who underwent surgery all with pedicle screws and 5.5 mm rods of three different materials were retrospectively reviewed (14 cases for each of the three rod material subgroups: titanium, cobalt-chromium, stainless steel). 3D reconstructions of the spine were performed using biplanar radiographs preoperatively, 1-week postoperatively (1WPO), and 2 years follow-up (2YFU). Rods 3D shape also was reconstructed at 1WPO and 2YFU. The spine and rods shapes were analyzed and compared between time points. An average of 1.93 implant per vertebra was used. The main thoracic curve (61° ± 9°) was corrected on average by 75% (15° ± 6°, P < 0.01) with no change at 2YFU (17° ± 7°, P = 0.14). The apical vertebral rotation (23° ± 7°) was corrected by 44% (13° ± 9°, P < 0.01) with no change at 2YFU (14° ± 9°, P = 0.64). The thoracic kyphosis (24° ± 12°) remained unchanged (P = 0.78). The orientation of the planes of maximal curvature with respect to the sagittal plane of the main thoracic curve (39° ± 15°) and of the rods (concave: 28° ± 23°, convex: 12° ± 10°) at 1WPO was unchanged at 2YFU (all P > 0.05). Rod curvature and deflection also remained unchanged (all P > 0.05). 3D curve correction was maintained in the 2YFU for all rod materials subgroups (all P > 0.05). The lumbar lordosis changed from 1WPO (47° ± 8°) to 2YFU (56° ± 9°, P < 0.01). At preoperatively, 57% of the cases had a balanced posture (sacral vertical axis/sacral femoral distance ≤0.5 and sacral vertical axis ≤0), 33% at 1WPO and 79% at 2YFU. There was no significant 3D shape change of the instrumented thoracic spine or of the rods postoperatively for any of the segmental pedicle screw constructs with titanium, stainless steel, and cobalt-chromium rods. Patients overall unbalanced sagittal posture documented immediately after surgery came back to balanced 2 years after surgery. 3.

3D correction of AIS in braces designed using CAD/CAM and FEM: a randomized controlled trial

BackgroundRecent studies showed that finite element model (FEM) combined to CAD/CAM improves the design of braces for the conservative treatment of adolescent idiopathic scoliosis (AIS), using 2D measurements from in-brace radiographs. We aim to assess the immediate effectiveness on curve correction in all three planes of braces designed using CAD/CAM and numerical simulation compared to braces designed with CAD/CAM only.MethodsSRS standardized criteria for bracing were followed to recruit 48 AIS patients who were randomized into two groups. For both groups, 3D reconstructions of the spine and patient’s torso, respectively built from bi-planar radiographs and surface topography, were obtained and braces were designed using the CAD/CAM approach. For the test group, 3D reconstructions of the spine and patient’s torso were additionally used to generate a personalized FEM to simulate and iteratively improve the brace design with the objective of curve correction maximization in three planes and brace material minimization.ResultsFor the control group (CtrlBraces), average Cobb angle prior to bracing was 29° (thoracic, T) and 25° (lumbar, L) with the planes of maximal curvature (PMC) respectively oriented at 63° and 57° on average with respect to the sagittal plane. Average apical axial rotation prior to bracing was 7° (T) and 9° (L). For the test group (FEMBraces), initial Cobb angles were 33° (T) and 28° (L) with the PMC at 68° (T) and 56° (L) and average apical axial rotation prior to bracing at 9° (T and L). On average, FEMBraces were 50% thinner and had 20% less covering surface than CtrlBraces while reducing T and L curves by 47 and 48%, respectively, compared to 25 and 26% for CtrlBraces. FEMBraces corrected apical axial rotation by 46% compared to 30% for CtrlBraces.ConclusionThe combination of numerical simulation and CAD/CAM approach allowed designing more efficient braces in all three planes, with the advantages of being lighter than standard CAD/CAM braces. Bracing in AIS may be improved in 3D by the use of this simulation platform. This study is ongoing to recruit more cases and to analyze the long-term effect of bracing.Trial registrationClinicalTrials.gov, NCT02285621

Knee Kinematics Following Anatomic Single vs. Double Bundle ACL Reconstruction: A Randomized Clinical Trial

Objectives:A randomized clinical trial was conducted to compare knee kinematics during gait and running 24 months after ACL reconstruction, using either single-bundle (SB) or double-bundle (DB) quadriceps tendon grafts. We hypothesized that DB reconstruction would better restore kinematics than SB reconstruction, in comparison to the uninjured, contralateral knee.Methods:Subjects were between 14 and 50 years of age, participated in at least 100 hours of Level 1 or 2 sports activities and presented within 12 months of injury to both bundles of the ACL (with or without meniscal injury). Exclusion criteria included prior injury or surgery of the ipsilateral or contralateral knee or greater than a grade 1 concomitant knee ligament injury. Subjects were randomized to undergo SB or DB ACL reconstruction with a 10 mm quadriceps tendon autograft harvested with a patellar bone block. A single, anatomically placed femoral tunnel was used for all cases. For DB ACL reconstruction, the soft tissue portion of the graft was split and passed through two anatomically placed tibial tunnels. Biplane radiographic images were acquired 24 months after surgery while subjects performed downhill running on a treadmill (3.0 m/s, 10 degree slope, 150 images/s) and level gait (1.3 m/s, 100 images/s). Subject specific bone models were generated from computed tomography images and matched to the biplane radiographs using a previously validated model-based tracking process to determine tibiofemoral kinematics. Rotations of the tibia relative to the femur were calculated using the rotational component of the Joint Coordinate System originally described by Grood and Suntay. Displacements of the tibia relative to the femur were expressed in an orthogonal anatomical coordinate system fixed to the tibia. Primary outcome variables were based on previous findings of abnormalities in knee kinematics after ACL injury/reconstruction, and included peak knee external rotation, adduction and anterior translation during heelstrike to mid-stance. Three trials were collected for each limb and each task, and averaged for statistical analysis. Differences between SB and DB kinematics were determined using Wilcoxon Signed Rank tests, with significance level p < 0.05.Results:No significant differences were found in any of the primary kinematic variables between single and double bundle anatomic ACL reconstruction (Table). Differences between reconstructed and contralateral (uninjured) limbs were small, averaging less than 2 degrees in rotation and 2 mm in translation. Rotational differences were smaller during gait than during downhill running.Conclusion:Conclusions: Contrary to the study hypothesis, DB reconstruction was not found to be superior to SB reconstruction. While some abnormalities remained (particularly during the more stressful downhill running evaluation), both anatomical reconstructions were equally effective at restoring normal knee kinematics.kinematic differences between limbs (affected-contralateral) during gait and downhill runningSingle BundleSingle BundleSingle BundleDouble BundleDouble BundleDouble BundleNMeanStd DevNMeanStd DevWilcoxon pRunningPeak Knee Adduction25-0.231.1221-0.211.160.71RunningPeak External Rotation25-1.564.0421-0.173.120.20RunningPeak Anterior Translation250.572.62212.022.750.13GaitPeak Knee Adduction26-0.061.1921-0.051.110.83GaitPeak External Rotation26-0.444.3421-0.113.550.77GaitPeak Anterior Translation260.832.97212.002.560.20

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.

Geometric Torsion in Adolescent Idiopathic Scoliosis: A New Method to Differentiate Between Lenke 1 Subtypes.

Consecutive case series. To study geometric torsion in thoracic adolescent idiopathic scoliosis (AIS) to propose it as a numerical three-dimensional (3D) parameter that quantifies the scoliosis deformity. AIS is a 3D deformity of the spine. The most widely accepted and used classification systems, however, still rely on two-dimensional aspects of x-rays. Yet, a 3D classification of AIS remains elusive because there is no widely accepted 3D parameter in the clinical practice. Analysis of 141 patients with Lenke type-1 deformity recruited in our institution. The Lenke classification was identified by two observers and 3D reconstructions were obtained using biplanar radiographs. Geometric torsion measuring the twisting effect of the spine was computed using a novel technique by approximating local arc lengths at the neutral vertebra in the thoracolumbar segment. An inter- and intragroup statistical analysis was performed to evaluate the torsion index, and how it relates to other 3D indices. A statistically significant increase in torsion was observed between Lenke 1A (1.15 mm) and Lenke 1C (2.10 mm) subgroups. No differences were found between the Lenke 1B (1.75 mm) subgroup with either of the other two subgroups. An automatic classification based on torsion indices identified two groups: one with high torsion values (3.02 mm) and one with low torsion values (0.82 mm). Statistically significant differences were found between the main thoracic planes of maximum curvature (PMC) orientation of the high-torsion group (73.72°) and the low-torsion group (79.85°). Statistically significant differences were also found for the thoracolumbar/lumbar PMC orientation between the high-torsion group (56.41°) and the low-torsion group (49.25°). These results suggest that a numerical method of describing scoliosis in 3D is within reach. They also suggest the existence of two subgroups of 3D deformations based on torsion values (high and low) with links to PMC orientation. 4.

Treatment of acetabular fractures in older patients-introduction of a new implant for primary total hip arthroplasty

BackgroundFractures of the acetabulum in younger patients are commonly treated by open reduction and internal fixation. For elderly patients, stable primary total hip arthroplasty with the advantage of immediate postoperative mobilization might be the adequate treatment. For this purpose, a sufficiently stable fixation of the acetabular component is required.Materials and MethodsBetween August 2009 and 2014, 30 cases were reported in which all patients underwent total hip arthroplasty additionally to a customized implant designed as an antiprotrusion cage. Inclusion criteria were an acetabular fracture with or without a previous hemiarthroplasty, age above 65 years, and pre-injury mobility dependent on a walking frame at the most. The median age was 79.9 years (65–92), and of 30 fractures, 25 were primary acetabular fractures (83%), four periprosthetic acetabular fractures (14%), and one non-union after a failed ORIF (3%).ResultsThe average time from injury to surgery was 9.4 days (3–23) and 295 days for the non-union case. Mean time of surgery was 154.4 min (range 100 to 303). In 21 cases (70%), mobilization with full weight bearing was possible within the first 10 days. Six patients died before the follow-up examination 3 and 6 months after surgery, while 24 patients underwent radiologic examination showing consolidated fractures in bi-plane radiographs. In 9 patients, additional CT scan was performed which confirmed the radiographical results. 13 had regained their pre-injury level of mobility including the non-union case. Only one patient did not regain independent mobility. Four complications were recognized with necessary surgical revision (one prosthetic head dislocation, one pelvic cement leakage, one femoral shaft fracture, and one infected hematoma).ConclusionThe presented cage provides the possibility of early mobilization with full weight bearing which represents a valuable addition to the treatment spectrum in this challenging patient group.

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.

3D-modeling of the spine using EOS imaging system: Inter-reader reproducibility and reliability.

ObjectivesTo retrospectively assess the interreader reproducibility and reliability of EOS 3D full spine reconstructions in patients with adolescent idiopathic scoliosis (AIS).Methods73 patients with mean age of 17 years and a moderate AIS (median Cobb Angle 18.2°) obtained low-dose standing biplanar radiographs with EOS. Two independent readers performed “full spine” 3D reconstructions of the spine with the “full-spine” method adjusting the bone contour of every thoracic and lumbar vertebra (Th1-L5). Interreader reproducibility was assessed regarding rotation of every single vertebra in the coronal (i.e. frontal), sagittal (i.e. lateral), and axial plane, T1/T12 kyphosis, T4/T12 kyphosis, L1/L5 lordosis, L1/S1 lordosis and pelvic parameters. Radiation exposure, scan-time and 3D reconstruction time were recorded.ResultsInterclass correlation (ICC) ranged between 0.83 and 0.98 for frontal vertebral rotation, between 0.94 and 0.99 for lateral vertebral rotation and between 0.51 and 0.88 for axial vertebral rotation. ICC was 0.92 for T1/T12 kyphosis, 0.95 for T4/T12 kyphosis, 0.90 for L1/L5 lordosis, 0.85 for L1/S1 lordosis, 0.97 for pelvic incidence, 0.96 for sacral slope, 0.98 for sagittal pelvic tilt and 0.94 for lateral pelvic tilt. The mean time for reconstruction was 14.9 minutes (reader 1: 14.6 minutes, reader 2: 15.2 minutes, p<0.0001). The mean total absorbed dose was 593.4μGy ±212.3 per patient.ConclusionEOS “full spine” 3D angle measurement of vertebral rotation proved to be reliable and was performed in an acceptable reconstruction time. Interreader reproducibility of axial rotation was limited to some degree in the upper and middle thoracic spine due the obtuse angulation of the pedicles and the processi spinosi in the frontal view somewhat complicating their delineation.

Three-dimensional intervertebral range of motion in the cervical spine: Does the method of calculation matter?

Intervertebral range of motion (ROM) is commonly calculated using ordered rotations or projection angles. Ordered rotations are sequence-dependent, and projection angles are dependent upon on which orientation vectors are projected. This study assessed the effect of calculation method on intervertebral ROM in the subaxial cervical spine (C3–C7) during in vivo dynamic, three-dimensional, functional movement. Biplane radiographs were collected at 30 images per second while 29 participants performed full ROM flexion/extension, axial rotation and lateral bending movements of their cervical spine. In vivo bone motion was tracked with sub-millimeter accuracy using a validated volumetric model-based tracking technique. Intervertebral rotations were calculated using six Cardan angle sequences and two projection angle combinations. Within-subject comparisons revealed significant differences in intervertebral ROM among calculation methods (all p<0.002). Group mean ROM differences were small, but significantly different among calculation methods (p<0.001). A resampling technique demonstrated that as group size increases, the differences between calculation methods decreases substantially. It is concluded that the method used to calculate intervertebral rotations of the sub-axial cervical spine can significantly affect within-subject and between group comparisons of intervertebral ROM.

Semiautomated 3D Spine Reconstruction from Biplanar Radiographic Images: Prediction of Intervertebral Loading in Scoliotic Subjects.

The present study proposes a semiautomatic software approach to reconstruct 3D subject-specific musculoskeletal model of thoracolumbar spine from radiographic digitized images acquired with EOS system. The approach is applied to evaluate the intervertebral loads in 38 standing adolescents with mild idiopathic scoliosis. For each vertebra, a set of landmarks was manually identified on radiographic images. The landmark coordinates were processed to calculate the following vertebral geometrical properties in the 3D space (i) location (ii) dimensions; and (iii) rotations. Spherical joints simulated disks, ligaments, and facet joints. Body weight distribution, muscles forces, and insertion points were placed according to physiological–anatomical values. Inverse static analysis, calculating joints’ reactions in maintaining assigned spine configuration, was performed with AnyBody software. Reaction forces were computed to quantify intervertebral loads, and correlation with the patient anatomical parameters was then checked. Preliminary validation was performed comparing the model outcomes with that obtained from other authors in previous modeling works and from in vivo measurements. The comparison with previous modeling works and in vivo studies partially fulfilled the preliminary validation purpose. However, minor incongruities were pointed out that need further investigations. The subjects’ intervertebral loads were found significantly correlated with the anatomical parameters in the sagittal and axial planes. Despite preliminary encouraging results that support model suitability, future investigations to consolidate the proposed approach are necessary. Nonetheless, the present method appears to be a promising tool that once fully validated could allow the subject-specific non-invasive evaluation of a deformed spine, providing supplementary information to the routine clinical examination and surgical intervention planning.

２方向立位スロットラジオグラフィによる人工股関節設置位置評価法

２方向立位スロットラジオグラフィによる人工股関節設置位置評価法

Geometric Torsion in Adolescent Idiopathic Scoliosis: A Surgical Outcomes Study of Lenke Type 1 Patients.

Consecutive case series analysis. To evaluate the surgical outcomes of patients with thoracic adolescent idiopathic scoliosis (AIS) in relation to different degrees of geometric torsion. AIS is a three-dimensional (3D) deformity of the spine. A 3D classification of AIS, however, remains elusive because there is no widely accepted 3D parameter in the clinical practice. Recently, a new method of estimating geometric torsion has been proposed and detected two potential new 3D subgroups based on geometric torsion values. This is an analysis of 93 patients with Lenke type-1 deformity from our institution. 3D reconstructions were obtained using biplanar radiographs both pre- and postoperatively. Geometric torsion was computed using a novel technique by approximating local arc lengths at the neutral vertebra in the thoracolumbar segment. An inter- and intragroup statistical analysis was performed to compare clinical indices of patients with different torsion values. A qualitative assessment was also performed on each patient by two senior staff surgeons. Statistically significant differences were observed in clinical indices between high (2.85 mm) and low torsion (0.83 mm) Lenke type 1 subgroups. Preoperatively, the high torsion group showed higher Cobb angle values in the thoracic segment (71.18° vs. 63.74°), as well as higher angulation in the thoracolumbar plane of maximum deformity (67.79° vs. 53.30°). Postoperatively, a statistically significant difference was found in the orientation of the plane of maximum deformity in the thoracolumbar segment between the high and low torsion groups (47.95° vs. 30.03°). Results from the qualitative evaluation of surgical results showed different results between the two staff surgeons. These results suggest a link between preoperative torsion values and surgical outcomes within Lenke type 1 deformities. These results will need to be validated by an independent group, as it is a single-center study. 4.

Longitudinal Study of the Six Degrees of Freedom Cervical Spine Range of Motion During Dynamic Flexion, Extension, and Rotation After Single-level Anterior Arthrodesis.

A longitudinal study using biplane radiography to measure in vivo intervertebral range of motion (ROM) during dynamic flexion/extension, and rotation. To longitudinally compare intervertebral maximal ROM and midrange motion in asymptomatic control subjects and single-level arthrodesis patients. In vitro studies consistently report that adjacent segment maximal ROM increases superior and inferior to cervical arthrodesis. Previous in vivo results have been conflicting, indicating that maximal ROM may or may not increase superior and/or inferior to the arthrodesis. There are no previous reports of midrange motion in arthrodesis patients and similar-aged controls. Eight single-level (C5/C6) anterior arthrodesis patients (tested 7 ± 1 months and 28 ± 6 months postsurgery) and six asymptomatic control subjects (tested twice, 58 ± 6 months apart) performed dynamic full ROM flexion/extension and axial rotation whereas biplane radiographs were collected at 30 images per second. A previously validated tracking process determined three-dimensional vertebral position from each pair of radiographs with submillimeter accuracy. The intervertebral maximal ROM and midrange motion in flexion/extension, rotation, lateral bending, and anterior-posterior translation were compared between test dates and between groups. Adjacent segment maximal ROM did not increase over time during flexion/extension, or rotation movements. Adjacent segment maximal rotational ROM was not significantly greater in arthrodesis patients than in corresponding motion segments of similar-aged controls. C4/C5 adjacent segment rotation during the midrange of head motion and maximal anterior-posterior translation were significantly greater in arthrodesis patients than in the corresponding motion segment in controls on the second test date. C5/C6 arthrodesis appears to significantly affect midrange, but not end-range, adjacent segment motions. The effects of arthrodesis on adjacent segment motion may be best evaluated by longitudinal studies that compare maximal and midrange adjacent segment motion to corresponding motion segments of similar-aged controls to determine if the adjacent segment motion is truly excessive. 3.

Three-dimensional reconstruction using stereoradiography for evaluating adult spinal deformity: a reproducibility study.

In addition to the sagittal alignment, impact of transverse plane parameters (TPP) and rotatory subluxation on patients reported outcomes were highlighted. One of the hypotheses for genesis of degenerative scoliosis is disc degeneration with increased axial vertebral (AVR) and intervertebral rotation (AIR). Therefore, TPP analysis at early stage of the scoliosis seems of particular interest. This study aims at assessing reliability of tridimensional (3D) reconstructions of adult spinal deformity (ASD) patients. Thirty ASD patients underwent biplanar radiographs and were divided into two groups (Cobb angle >30° or <30°). Spinal parameters and TPP (apical AVR, AIR of upper and lower level of main curve) were measured. Four operators performed 3D reconstructions twice. Intra and inter-observer reliabilities were analyzed using ISO standard 5725-2, to quantify the global standard deviation of reproducibility (S R). Mean Cobb angle was 31°, mean age 55years (70% of female). Mean values of apical AVR, upper and lower level AIR were, respectively, 16°±15°, 6°±6° and 5°±5°. Spinopelvic parameters S R were below 4.5°. For Cobb angle <30°, S R was 7.8°, 9.6°, 4.5° and 4.9°, respectively, for AVR apex, torsion index, upper and lower AIR. Reliability was worse in the group of patients with Cobb angle above 30°. 3D analysis was reliable for Cobb and sagittal parameters. 3D analysis for TPP was reproducible when Cobb is below 30°. However, uncertainty is larger for Cobb above 30°. Nevertheless, 3D reconstructions could help surgeons to anticipate onset of rotatory subluxation while assessing axial rotation evolution for small deformity and choose best delay for surgical treatment.