Shoulder bony landmarks location using the EOS® low-dose stereoradiography system: a reproducibility study

Blending Conventional Learning Approach with Contemporary Visualization Technologies: Prerequisite Toward Evidence-Based Surface Anatomy

Proficiency in surface anatomy knowledge plays a pivotal role in fostering complication-free and efficacious clinical practice across a wide spectrum of healthcare specialties. This comprehensive understanding and adept utilization of surface anatomy principles serve as the linchpin for deciphering normal anatomical structures within medical imaging and the aptitude to articulate the topographical attributes, visual characteristics, and interrelations of palpable anatomical entities. Despite the advent of advanced direct visualization techniques, such as ultrasound guidance, which assist in interventional procedures, clinicians have not relinquished the indispensable requirement for pertinent surface anatomy knowledge to ensure the successful and secure execution of procedures. Regrettably, evidence-based surface anatomy remains an underemphasized facet in the pedagogy of anatomical sciences. The current narrative review underscores the various methodologies employed in imparting surface anatomy education to students. However, it is noteworthy that no singular, unequivocal best practice has emerged for the teaching and acquisition of surface anatomy knowledge. Therefore, as custodians of anatomical education, there is a pressing need to innovate and amalgamate contemporary pedagogical approaches with state-of-the-art technologies to furnish students with evidence-based surface anatomy insights, thereby enhancing comprehension, retention, and the lasting utility of this essential domain of medical knowledge.

Evaluation of a method to quantify posture and scapula position using biplanar radiography

BACKGROUND

Recent studies have stated the relevance of having new parameters to quantify the position and orientation of the scapula with patients standing upright. Although biplanar radiography can provide 3D reconstructions of the scapula and the spine, it is not yet possible to acquire these images with patients in the same position.

METHODS

Two pairs of images were acquired, one for the 3D reconstruction of the spine and ribcage and one for the 3D reconstruction of the scapula. Following 3D reconstructions, scapular alignment was performed in two stages, a coarse alignment based on manual annotations of landmarks on the clavicle and pelvis, and an adjusted alignment. Clinical parameters were computed: protraction, internal rotation, tilt and upward rotation. Reproducibility was assessed on an in vivo dataset of upright biplanar radiographs. Accuracy was assessed using supine cadaveric CT-scans and digitally reconstructed radiographs.

FINDINGS

The mean error was less than 2° for all clinical parameters, and the 95 % confidence interval for reproducibility ranged from 2.5° to 5.3°.

INTERPRETATION

The confidence intervals were lower than the variability measured between participants for the clinical parameters assessed, which indicates that this method has the potential to detect different patterns in pathological populations.

3D reconstruction of the scapula from biplanar X-rays for pose estimation and morphological analysis

BACKGROUND

Patient-specific scapular shape in functional posture can be highly relevant to clinical research. Biplanar radiography is a relevant modality for that purpose with already two existing assessment methods. However, they are either time-consuming or lack accuracy. The aim of this study was to propose a new, more user-friendly and accurate method to determine scapular shape.

METHODS

The proposed method relied on simplified manual inputs and an upgraded version of the first 3D estimate based on statistical inferences and Moving-Least Square (MLS) deformation of a template. Then, manual adjustments, with real-time MLS algorithm and contour matching adjustments with an adapted minimal path method, were added to improve the match between the projected 3D model and the radiographic contours. The accuracy and reproducibility of the method were assessed (with 6 and 12 subjects, respectively).

FINDINGS

The shape accuracy was in average under 2 mm (1.3 mm in the glenoid region). The reproducibility study on the clinical parameters found intra-observer 95% confidence intervals under 3 mm or 3° for all parameters, except for glenoid inclination and Critical Shoulder Angle, ranging between 3° and 6°.

INTERPRETATION

This method is a first step towards an accurate reconstruction of the scapula to assess clinical parameters in a functional posture. This can already be used in clinical research on non-pathologic bones to investigate the scapulothoracic joint in functional position.

Experiences with a new biplanar low-dose X-ray device for imaging the facial skeleton: A feasibility study

Background

This study aimed to evaluate the feasibility of a new biplanar low-dose X-ray device for facial skeletal imaging.

Methods

We evaluated 48 biplanar radiographs from 12 patients (posteroanterior/lateral), originally taken for a scoliosis examination with a biplanar low-dose X-ray device. For this study, the images were further evaluated for the perceptibility of 38 facial skeleton landmarks. To determine the reliability and reproducibility of perceptibility, two independent observers determined the landmarks twice, during a time interval of at least two weeks.

Results

Both interoperator and intraoperator reliability were excellent for all landmarks [intraclass correlation coefficient (ICC) > 0.92].

Conclusions

The biplanar low-dose X-ray device demonstrated good feasibility for precisely assessing the anatomical landmarks of the facial skeleton. Given its excellent precision, the biplanar low-dose X-ray device data sets should be forwarded from the treating orthopedic surgeon or neurosurgeon to the orthodontist or dentist for further assessment in their field.

Can three-dimensional pelvimetry using low-dose stereoradiography replace low-dose CT pelvimetry?

PURPOSE

To evaluate the reliability of pelvimetric measurements performed using stereoradiographic imaging (SRI), and to assess maternal and fetal radiation doses compared to low-dose computer tomography (CT) pelvimetry.

MATERIALS AND METHODS

Thirty-five pregnant women (mean age, 29.6±5.5 [SD] years; range: 20-41 years) were prospectively included. All women underwent simultaneous frontal and lateral low-dose SRI and low-dose CT examination of the pelvis. Pelvimetry measurements were obtained from both examinations and radiation doses obtained with the two techniques were compared.

RESULTS

SRI-CT correlation (Pearson coefficient correlation [r]; mean bias [mb]) was strong for transverse inlet diameter (r=0.92; mb=-0.09cm), anteroposterior diameter of the pelvic inlet (r=0.92; mb = 0.47cm), maximal transverse diameter (r=0.9; mb=0.21cm), sacrum length (r=0.9; mb=0.09cm). Correlation was good. Correlation was good for the sacrum depth (r=0.75; mb=0.06cm) and Magnin's index (r=0.7; mb=0.5cm). Correlation was moderate for anteroposterior diameter of pelvic outlet (r=0.6; mb=0.52cm). The fetal dose was 13.1 times lower using SRI (87±26μGy) than CT (1140±220μGy, P<0.0001). The effective maternal dose was 3.1 times lower using SRI (97±21μSv) than CT (310±60μSv; P<0.0001).

CONCLUSION

Pelvic inlet measurements using SRI are reliable. Compared to CT pelvimetry, SRI leads to a significant decrease in fetal and maternal radiation doses. These findings should prompt physicians to use SRI as the first-line approach for pelvimetry.

Interactive patient-specific 3D approximation of scapula bone shape from 2D X-ray images using landmark-constrained statistical shape model fitting

We report on an interactive tool for patientspecific 3D approximation of scapula bone shape from 2D X-ray images using landmark-constrained statistical shape model (SSM) fitting. The 3D localization of points on the 2D X-ray images was done through X-ray stereophotogrammetry. The inferior angle, acromion and the coracoid process were identified as reliable landmarks from the anteroposterior (AP) and oblique lateral views in a landmark selection study. The 3D scapula surface was approximated through fitting the scapula SSM to the 3D reconstructed coordinates of the selected landmarks. 3D point localization yielded average (X, Y, Z) coordinate reconstruction errors of (X=0.14, Y=0.07, Z=0.04) mm. The landmark-constrained fitting algorithm yielded an average error between the mean posterior model landmarks and the corresponding target landmarks of 0.49 mm using the three landmarks, and later 0.19 mm with sixteen landmarks. Average surface to surface error between the CT ground truth model and approximated model from within the dataset improved from 3.20 mm to 2.46 mm using three landmarks and using sixteen landmarks, respectively. Average surface to surface error between the CT ground truth model and the approximated model from outside the dataset improved from 4.28 mm to 3.20 mm using three landmarks and using sixteen landmarks, respectively.

Femoral and tibial torsion measurements in children and adolescents: comparison of MRI and 3D models based on low-dose biplanar radiographs

OBJECTIVE

The aim of our study was to evaluate the reliability and interchangeability of femoral (FT) and tibial torsion (TT) measurements in children using magnetic resonance (MR) imaging compared to measurements on 3D models based on biplanar radiographs (BPR).

MATERIALS AND METHODS

FT and TT were measured in 60 children (mean age 10.1 years; range 6.2-16.2 years; 28 female) using axial MR images by two readers. MR measurements were compared to measurements based on BPR-3D models by two separate independent readers. Interreader and intermethod agreements were calculated using descriptive statistics, the intraclass correlation coefficient (ICC), and Bland-Altman analysis.

RESULTS

FT/TT was -8.4°-54.1°/0°-45.9° on MR images and -13°-63°/4°-52° for measurements on BPR-3D models. The median of difference between the two methods was -0.18° (range -13.6°-19.1°) for FT and -0.20° (range -18.4°-9.5°) for TT, respectively. Interreader agreement (ICC) of FT/TT measurements was 0.98/0.96 on MR images and 0.98/0.94 on BPR 3D models. Intermethod agreement (ICC) for MR measurements was 0.95 [95% confidence interval (CI), 0.93-0.96] for FT and of 0.86 (CI, 0.24-0.95) for TT. Mean interreader differences at MR were 3.1° (0.0°-8.0°) for FT and 3.2° (0.1°-9.5°) for TT. On Bland-Altman plots all measurements were within the 95% limit of agreement (-10.8°; 11.5° for FT; -14.6°; 4.2°) for TT-except for five measurements of FT and six measurements of TT.

CONCLUSION

FT measurements on MR images are comparable to measurements using BPR-3D models. TT measurements differ between the two modalities, but the discrepancy is comparable to measurement variations between CT and BPR.

Assessment of two-dimensional (2D) and three-dimensional (3D) lower limb measurements in adults: Comparison of micro-dose and low-dose biplanar radiographs

OBJECTIVE

To evaluate reliability of 2D and 3D lower limb measurements in adults using micro-dose compared to low-dose biplanar radiographs(BPR).

MATERIALS AND METHODS

One hundred patients (mean 54.9 years) were examined twice using micro-dose and low-dose BPR. Length and mechanical axis of lower limbs were measured on the antero-posterior(ap) micro-dose and low-dose images by two independent readers. Femoral and tibial torsions of 50 patients were measured by two independent readers using reconstructed 3D-models based on the micro-dose and low-dose BPR. Intermethod and interreader agreements were calculated using descriptive statistics, intraclass-correlation-coefficient(ICC), and Bland-Altman analysis.

RESULTS

Mean interreader-differences on micro-dose were 0.3 cm(range 0-1.0)/ 0.7°(0-2.9) for limb length/axis and 0.4 cm (0-1.0)/0.8°(0-3.3) on low-dose BPR. Mean intermethod-difference was 0.04 cm ± 0.2/0.04° ± 0.6 for limb length/axis. Interreader-ICC for limb length/axis was 0.999/0.991 on micro-dose and 0.999/0.987 on low-dose BPR. Interreader-ICC for micro-dose was 0.879/0.826 for femoral/ tibial torsion, for low-dose BPR was 0.924/0.909. Mean interreader-differences on micro-dose/low-dose BPR were 3°(0-13°)/2°(0°-12°) for femoral and 4°(0-18°)/3°(0°-10°) for tibial torsion. Mean intermethod-difference was -0.1° ± 5.0/-0.4° ± 2.9 for femoral/tibial torsion. Mean dose-area-product was significantly lower (9.9 times;p < 0.001) for micro-dose BPR.

CONCLUSION

2D-and 3D-measurements of lower limbs based on micro-dose BPR are reliable and provide a 10-times lower radiation dose.

KEY POINTS

• Lower limb length and mechanical axis can be reliably measured with micro-dose. • Femoral and tibial torsion can be reliably assessed with micro-dose. • Micro-dose allows a huge reduction of radiation exposure.

3D scapular orientation on healthy and pathologic subjects using stereoradiographs during arm elevation

BACKGROUND

Alterations of the scapular kinematics in different pathologic conditions have been widely studied. However, results have shown considerable discrepancies concerning the direction and the amplitude of scapular movement. The lack of consistency in the literature probably has several explanations. The purpose of this study was to analyze scapular orientation with the arm at rest and with 90° lateral elevation in healthy and pathologic subjects by use of stereoradiographs.

MATERIALS AND METHODS

All participants (n = 65) underwent a clinical examination and magnetic resonance imaging of the shoulder to assess rotator cuff status. Participants were separated into 3 groups: healthy, rotator cuff tear (RCT), and RCT and subacromial impingement syndrome (RCT+ SIS). A 3-dimensional model of the scapula was fitted to each low-dose stereoradiograph acquired with the arm at rest and 90° arm elevation.

RESULTS

Orientation of the scapula with the arm at rest was not significantly different between groups. During lateral elevation, scapular orientation was not significantly different between the healthy group and the RCT group. However, upward rotation was significantly reduced in the RCT + SIS group.

CONCLUSION

Alterations of scapular kinematics in symptomatic subjects are multifactorial. We observed a link between clinically assessed subacromial impingement and scapular orientation during lateral elevation of the arm.

Radiographic landmark for humeral head rotation: a new radiographic landmark for humeral fracture fixation

BACKGROUND

There is no definite radiographic landmark in plain radiographs for proximal humeral rotation, which is an important parameter for avoiding rotational malalignment during fracture fixation. Here, we used radiographic images of cadaveric humeri to determine whether the landmark of the crest of lesser tuberosity (CoLT) in plain radiographs could be used to determine humeral rotation.

METHODS

Twenty adult cadaveric humeri were collected and seven consecutive radiographic anteroposterior views (45°, 30°, 15° internal rotation; neutral rotation; and 15°, 30°, 45° external rotation) were obtained for each specimen.

RESULTS

The proportional distance (PD) of the CoLT landmark relative to the humeral head was measured and analysed. The mean PDs of the CoLT landmark were 10.2%, 17.9%, 25.6%, 35.9%, 53.4%, and 62.9% of the diameter of the humeral head, corresponding to 45°, 30°, and 15° external rotation, neutral rotation, and 15° and 30° internal rotation, respectively. We found significant differences in the mean PDs with humeral rotation.

CONCLUSION

The projection of the CoLT in plain radiographs can be used as an important landmark to assess humeral head rotation and will be a useful landmark for rotational control of fracture fixation.

Three-dimensional quantitative analysis of the proximal femur and the pelvis in children and adolescents using an upright biplanar slot-scanning X-ray system

BACKGROUND

The anatomy and biomechanics of the pelvis and lower limbs play a key role in the development of orthopaedic disorders.

OBJECTIVE

This study aimed to establish normal reference standards for the measurement of gender-specific pelvic and femoral parameters in children and adolescents with the EOS 2-D/3-D system.

MATERIALS AND METHODS

EOS 2-D images of 508 individuals (ages 4-16 years) were obtained as part of routine diagnostics. Patients with lower limb abnormalities were excluded. Pelvic and femoral surface 3-D models were generated and clinical parameters calculated by sterEOS 3-D reconstruction software. Data were evaluated using Spearman correlation, paired-samples and independent-samples t-test and linear regression analysis.

RESULTS

Changes in anatomical parameters were found to correlate with age and gender in 1) femoral mechanical axis length: 27.3-43.7 cm (males), 25.5-41.2 cm (females), 2) femoral head diameter: 29.4-46.1 mm (males), 27.7-41.3 mm (females), 3) femoral offset: 26.8-42.4 mm (males), 25.5-37.9 mm (females) and 4) femoral neck length: 35.1-52.9 mm (males), 32.8-48.1 mm (females). There was no gender-specific correlation for the neck shaft angle with values from 130.4° to 129.3°, for femoral torsion (22.5°-19.4°), for sacral slope (39.0°-44.4°) and for lateral pelvic tilt (5.1 mm-6.2 mm). Sagittal pelvic tilt exhibited no significant correlation with age showing average values of 6.5°.

CONCLUSIONS

The EOS 2-D/3-D system proved to be a valuable method in the evaluation of female and male developmental changes in pelvic and lower limb anatomical parameters, in normal individuals younger than 16 years of age.

[Evaluation of the usefulness of the EOS 2D/3D system for the measurement of lower limbs anatomical and biomechanical parameters in children]

INTRODUCTION

Lower limbs anatomical and biomechanical parameters are essential in several paediatric orthopaedic disease, which makes their exact measurement necessary.

AIM

The aim of the author was to evaluate the reliability of the EOS 2D/3D System, a 3D reconstruction capable imaging device in children.

METHOD

3D reconstructions were performed in 523 cases aged between 2 and 16 years in whom no abnormality influencing lower limbs biomechanics was observed. For statistical analysis intraclass correlation, paired-samples t-test, Spearman-correlation and Welch-test were used.

RESULTS

Excellent results were found for all parameters in reliability test used by the operator. The step-forward position used during the examination influenced the sagittal tibiofemoral angle only. All examined parameters showed significant correlation with age and gender. Height correlated with neck-shaft angle, hip-knee shift, femoral and tibial torsion only.

CONCLUSIONS

The EOS technology proved to be an appropriate method to measure lower limbs anatomical parameters in children. Changes in these parameters during development correlated with age and gender.

Assessment of prosthesis alignment after revision total knee arthroplasty using EOS 2D and 3D imaging: a reliability study

Introduction

A new low-dose X-ray device, called EOS, has been introduced for determining lower-limb alignment in 2D and 3D. Reliability has not yet been assessed when using EOS on lower limbs containing a knee prosthesis. Therefore purpose of this study was to determine intraobserver and interobserver reliability of EOS 2D and 3D knee prosthesis alignment measurements after revision total knee arthroplasty (rTKA).

Methods

Forty anteroposterior and lateral images of 37 rTKA patients were included. Two observers independently performed measurements on these images twice. Varus/valgus angles were measured in 2D (VV2D) and 3D (VV3D). Intraclass correlation coefficients and the Bland and Altman method were used to determine reliability. T-tests were used to test potential differences.

Results

Intraobserver and interobserver reliability were excellent for VV2D and VV3D. No significant difference or bias between the first and second measurements or the two observers was found. A significant mean and absolute difference of respectively 1.00° and 1.61° existed between 2D and 3D measurements.

Conclusions

EOS provides reliable varus/valgus measurements in 2D and 3D for the alignment of the knee joint with a knee prosthesis. However, significant differences exist between varus/valgus measurements in 2D and 3D.

Robustness and reproducibility of a glenoid-centered scapular coordinate system derived from low-dose stereoradiography analysis

A robust and reproducible scapular coordinate system is necessary to study scapulothoracic kinematics. The coordinate system recommended by the ISB (International Society of Biomechanics) is difficult to apply in studies using medical imaging, which mostly use a glenoid-centered coordinate system. The aim of this study was to assess the robustness of a glenoid-centered coordinate system compared with the ISB coordinate system, and to study the reproducibility of this coordinate system measure during abduction. A Monte-Carlo analysis was performed to test the robustness of the two coordinate systems. This method enabled the variability of the orientation of the coordinate system to be assessed in a laboratory setting. A reproducibility study of the glenoid-centered coordinate system in the thorax reference frame was performed during abduction in the scapular plane using a low-dose stereoradiography system. We showed that the glenoid-centered coordinate system was slightly more robust than the ISB-recommended coordinate system. Most reproducible rotation was upward/downward rotation (x axis) and most reproducible translation was along the Y axis (superior-inferior translation). In conclusion, the glenoid-centered coordinate system can be used with confidence for scapular kinematics analysis. The uncertainty of the measures derived from our technique is acceptable compared with that reported in the literature. Functional quantitative analysis of the scapulothoracic joint is possible with this method.

An evaluation of the EOS X-ray imaging system in pelvimetry

OBJECTIVES

To demonstrate the reliability of the EOS imaging system in measuring the internal diameters of the bony pelvis.

MATERIALS AND METHODS

A prospective study comparing the results of the pelvimetry of 18 dry pelvises carried out on the EOS imaging system to measurements taken manually and using the two current gold standard CT methods. Pelvimetric measurements of each pelvic bone were obtained using four methods and compared: direct manual measurements, spiral and sequential CT pelvimetry, and 2D-3D low-dose biplanar X-rays. The various obstetric diameters were measured to the millimetre and compared.

RESULTS

There was no significant difference in the different diameters assessed, with the exception of the interspinous diameter. There was a highly significant correlation (P < 0.001) between the values measured manually and by EOS for the Magnin index (Pearson = 0.98), the obstetric conjugate diameter (Pearson = 0.99), and the median transverse diameter (Pearson = 0.87).

CONCLUSION

The EOS imaging system allows for an ex vivo determination of the obstetrical diameters that is reliable enough to estimate obstetric prognosis, producing comparable measurements to CT. In view of concerns about protection from radiation, this low-dose imaging technique could become, after in vivo prospective validation, the new gold standard for pelvimetry and therefore a good alternative to CT.

Comparison of radiation dose, workflow, patient comfort and financial break-even of standard digital radiography and a novel biplanar low-dose X-ray system for upright full-length lower limb and whole spine radiography

OBJECTIVE

To compare the radiation dose, workflow, patient comfort, and financial break-even of a standard digital radiography and a biplanar low-dose X-ray system.

MATERIALS AND METHODS

A standard digital radiography system (Ysio, Siemens Healthcare, Erlangen, Germany) was compared with a biplanar X-ray unit (EOS, EOS imaging, Paris, France) consisting of two X-ray tubes and slot-scanning detectors, arranged at an angle of 90° allowing simultaneous vertical biplanar linear scanning in the upright patient position. We compared data of standing full-length lower limb radiographs and whole spine radiographs of both X-ray systems.

RESULTS

Dose-area product was significantly lower for radiographs of the biplanar X-ray system than for the standard digital radiography system (e.g. whole spine radiographs; standard digital radiography system: 392.2 ± 231.7 cGy*cm(2) versus biplanar X-ray system: 158.4 ± 103.8 cGy*cm(2)). The mean examination time was significantly shorter for biplanar radiographs compared with standard digital radiographs (e.g. whole spine radiographs: 449 s vs 248 s). Patients' comfort regarding noise was significantly higher for the standard digital radiography system. The financial break-even point was 2,602 radiographs/year for the standard digital radiography system compared with 4,077 radiographs/year for the biplanar X-ray unit.

CONCLUSION

The biplanar X-ray unit reduces radiation exposure and increases subjective noise exposure to patients. The biplanar X-ray unit demands a higher number of examinations per year for the financial break-even point, despite the lower labour cost per examination due to the shorter examination time.

Robust femur condyle disambiguation on biplanar X-rays

Three-dimensional (3D) reconstruction of the skeleton from biplanar X-rays relies on scarce information digitalised by an operator on both frontal and lateral radiographs. In clinical routine, difficulties occur for non-skilled operators to discriminate the medial from the lateral femur condyle on the lateral view. Our study proposes an algorithm able to detect automatically a possible inversion of the two condyles by the operator at an early stage of the reconstruction process. It relies on the computation of two 3D femur surfaces, one directly from the operator digitalisation and the other from the same digitalisation with medial and lateral condyles automatically swapped. Pairs of virtual biplanar X-rays are computed for both reconstructions and the closest pair to the original X-rays is selected on the basis of similarity measures, pointing the correct 3D surface. The algorithm shows a success rate higher than 85% for both asymptomatic and pathological femurs whatever the initial condyle digitalisation of the operator, bringing automatically non-skilled operators acting in clinical routine to the level of skilled operators. This study validates moreover the proof-of-concept of automatic shape adjustments of a 3D surface on the basis of similarity measures in the process of 3D reconstruction from biplanar X-rays.

3D morphometric analysis of 43 scapulae

BACKGROUND

Accurate knowledge of the scapular anatomy is fundamental for the preoperative evaluation but some bony landmarks are difficult to identify. Statistical approaches based on subject-specific parametric models could be used to overcome this difficulty. The aim of this study was to propose a quantitative parametric model of the scapula and to analyze correlations between descriptive morphologic parameters.

MATERIALS AND METHODS

Forty-three scapulae were scanned and reconstructed. Each 3D scapula was regionalized and a simple geometric element was best fitted on each region using least square method. Descriptive parameters of each region were obtained. Correlation and linear regression analyses were performed between all measurements in order to assess parameters that can be used as predictors of the other descriptive parameters.

RESULTS

Morphometric scapular measurements from 3D reconstructions were obtained. Correlation and linear regression analyses assessed correlations between the glenoid width and both the glenoid height and the acromial width. Also, we obtained correlation between the orientation of the inferior part of the acromion on the A-P view and on the axillary view.

DISCUSSION

Parametric models are widely used in biomechanics for identifying anatomical landmarks or rotations centers of these structures. For the scapula, no such model is available. We elaborated a first parametric model of scapula based on a large database of 43 scapulae. Our morphometric measurements are very close to others founded in literature. Correlations obtained should help to progress toward relevant subject-specific models of the scapula based on reduced information.