EOS(®) biplanar X-ray imaging: concept, developments, benefits, and limitations

Is the EOS imaging system as accurate as conventional radiography in grading osteoarthritis of the knee?

OBJECTIVES

The EOS imaging system allows for the acquirement of long-leg radiographic images in a standing position without stitching artifacts or projection bias and at a comparatively low-radiation-dose exposure. The aim of our study was to compare the accuracy of EOS images of the lower limb to conventional radiographs (CR) of the knee in a.p. view for the grading of osteoarthritis (OA).

METHODS

One hundred forty-two patients who had undergone EOS of the lower limb and radiography of the knee on the same day were included. For the grading of OA, the Kellgren and Lawrence score (KL) score and the Osteoarthritis Research Society International (OARSI) system were used. Additionally, the joint space was measured and compared between the two techniques. EOS images were compared to conventional anteroposterior radiographs of the knee which constitute the gold standard.

RESULTS

Measurements of the joint space showed very good intra-class correlation. The calculated weighted kappa for the KL score of EOS versus CR was excellent. The comparison of the different parameters of the OARSI score showed superb weighted kappa scores between 0.9 and 0.96 (α < 0.001) for the parameters osteophytes and joint space narrowing. The parameter deformity showed a good agreement between EOS and radiographs (sensitivity 93.6%; specificity 100%). For the sclerosis parameter, an overall sensitivity of 71.3% and a specificity of 99.3% were calculated.

CONCLUSIONS

The grading of OA using the KL score as well as the quantitative assessment of joint space width can be performed on EOS images in a.p. view as reliably as on CR. Subchondral sclerosis of the lateral and medial femur condyle or tibia is sometimes not as evident on EOS images.

KEY POINTS

• Grading of OA may be performed as reliably with EOS images in a.p. view as with conventional radiographs in a.p. view. • EOS can be safely used for primary assessment of osteoarthritis of the knee. • In the preoperative setting for knee replacement surgery, conventional radiographs in two or three planes of the knee should still be acquired in addition to long-leg EOS images.

EOS® imaging: Concept and current applications in spinal disorders

EOS® imaging is a proprietary imaging technology that was launched in 2007. Based on a gaseous particle detector with a multi-wire proportional chamber, it offers several advantages over other imaging modalities: low dose of radiation, ability to create 3D reconstructions, ability to conduct whole body imaging, high reproducibility in measuring various parameters of alignment and faster imaging time. EOS® imaging is slowly gaining widespread acceptance as its applications in various disorders continue to evolve. It has been found to be particularly useful and has opened up new avenues of research in the field of spinal deformities. This narrative review seeks to provide an overview of the proprietary technology behind EOS® imaging, compare it to existing imaging modalities, summarize its current applications in various spinal disorders and outline its limitations.

Reliability of EOS compared to conventional radiographs for evaluation of lower extremity deformity in adult patients

OBJECTIVE

The purpose of this study was to compare reliability of lower extremity imaging measurements using EOS and conventional X-ray (CR) of adult patients with mechanical axis malalignment.

MATERIALS AND METHODS

Ten patients (20 lower limbs) of mean age of 31.6 years (range 21-39) with post-traumatic deformities who presented for evaluation of osteotomies and/or ligament and cartilage reconstructions were prospectively enrolled. Two independent observers performed full-length anterior-posterior (AP) measurements 2 weeks apart on both CXR and two-dimensional (2D) EOS images. Measurements included weight-bearing axis (WBA), varus/valgus angle (V/V), femoral length (FL), tibial length (TL), femoral mechanical axis (FMA), tibial mechanical axis (TMA), and total limb length (TLL). Reliability was determined with random effects modeling of intraclass correlation coefficients (ICC) set to consistency. Three statistical operations were performed to compare interrater validity in CXR and EOS: students' two-sample t test, paired two-sample t test, and Pearson's correlative r-statistical agreement.

RESULTS

There was a statistically significant difference for V/V, FL, and TLL (all p < 0.01) between CXR and EOS. A relatively large proportion of the population consistently had larger V/V measures for EOS compared to CXR. In contrast, the FL and TLL measures were consistently larger for CXR compared to EOS. The differences between CXR and EOS measurements were statistically significant, though the small differences in values were not clinically meaningful. Agreement of all measures remained high (r = 0.84-0.99).

CONCLUSION

Using 2D EOS for lower extremity measurements is reproducible, reliable, and comparable to the gold standard, standing long leg radiographs.

Segmented lordotic angles to assess lumbosacral transitional vertebra on EOS

PURPOSE

To test the vertical posterior vertebral angles (VPVA) of the most caudal lumbar segments measured on EOS to identify and classify the lumbosacral transitional vertebra (LSTV).

METHODS

We reviewed the EOS examinations of 906 patients to measure the VPVA at the most caudal lumbar segment (cVPVA) and at the immediately proximal segment (pVPVA), with dVPVA being the result of their difference. Mann-Whitney, Chi-square, and ROC curve statistics were used.

RESULTS

172/906 patients (19%) had LSTV (112 females, mean age: 43 ± 21 years), and 89/172 had type I LSTV (52%), 42/172 type II (24%), 33/172 type III (19%), and 8/172 type IV (5%). The cVPVA and dVPVA in non-articulated patients were significantly higher than those of patients with LSTV, patients with only accessory articulations, and patients with only bony fusion (all p < .001). The cVPVA and dVPVA in L5 sacralization were significantly higher than in S1 lumbarization (p < .001). The following optimal cutoff was found: cVPVA of 28.2° (AUC = 0.797) and dVPVA of 11.1° (AUC = 0.782) to identify LSTV; cVPVA of 28.2° (AUC = 0.665) and dVPVA of 8° (AUC = 0.718) to identify type II LSTV; cVPVA of 25.5° (AUC = 0.797) and dVPVA of - 7.5° (AUC = 0.831) to identify type III-IV LSTV; cVPVA of 20.4° (AUC = 0.693) and dVPVA of - 1.8° (AUC = 0.665) to differentiate type II from III-IV LSTV; cVPVA of 17.9° (AUC = 0.741) and dVPVA of - 4.5° (AUC = 0.774) to differentiate L5 sacralization from S1 lumbarization.

CONCLUSION

The cVPVA and dVPVA measured on EOS showed good diagnostic performance to identify LSTV, to correctly classify it, and to differentiate L5 sacralization from S1 lumbarization.

HOW MANY DOSEMETERS ARE NEEDED FOR CORRECT MEAN ORGAN DOSE ASSESSMENT WHEN PERFOMING PHANTOM DOSIMETRY? A PHANTOM STUDY EVALUATING LIVER ORGAN DOSE AND INVESTIGATING TLD NUMBERS AND WAYS OF DOSEMETER PLACEMENT

This study evaluated repeated mean organ dose measurements of the liver by phantom dosimetry and statistical modelling in order to find a way to reduce the number of dosemeters needed for precise organ dose measurements. Thermoluminescent dosemeters were used in an adult female phantom exposed to a biplanar x-ray source at three different axial phantom rotations. Generalised mixed linear effect modelling was used for statistical analysis. A subgroup of five to six organ-specific locations out of 28 yielded mean liver organ doses within 95% confidence intervals of measurements based on all 28 liver-specific dosemeter locations. No statistical difference of mean liver dose was observed with rotation of the phantom either 10° clockwise or counter-clockwise as opposed to the coronal plane. Phantom dosimetry handling time during organ dose measurements can be markedly reduced, in this case the liver, by 79% (22/28), while still providing precise mean organ dose measurements.

The effect of knee joint rotation in the sagittal and axial plane on the measurement accuracy of coronal alignment of the lower limb

Background

Although the measurement of coronal alignment of the lower limb on conventional full-length weight-bearing anteroposterior (FLWAP) radiographs was reported to be influenced by the knee joint rotation, no comparative analysis was performed considering the effects of knee joint rotation on the sagittal and axial planes simultaneously using the three-dimensional images while taking into account the actual weight-bearing conditions. The aim of this study was to investigate the effect of knee joint rotation on the measurement accuracy of coronal alignment of the lower limb on the FLWAP radiograph.

Methods

Radiographic images of 90 consecutive patients (180 lower limbs) who took both the FLWAP radiograph and the EOS image were retrospectively reviewed. The relationship among delta values of mechanical tibiofemoral angle (mTFA) between the FLWAP radiographs and the EOS images (ΔmTFA), knee flexion/extension angle (sagittal plane rotation) on the EOS images, and patellar rotation (axial plane rotation) on the FLWAP radiographs were analyzed. Further, subgroup analysis according to each direction of knee joint rotation was performed.

Results

There was a significant correlation between ΔmTFA and sagittal plane rotation (r = 0.368, P <  0.001), whereas axial plane rotation was not correlated. In the analysis according to the direction, statistically significant correlation was observed only in the knee flexion group (r = 0.399, P <  0.001). The regression analysis showed a significant linear relationship between ΔmTFA and sagittal plane rotation (r² = 0.136, P <  0.001). Additional subgroup analysis in patients with the patellar rotation greater than 3% showed a similar result of a linear relationship between ΔmTFA and sagittal plane rotation (r² = 0.257, P <  0.001), whereas no statistically significant relationship was found in patients with the patellar rotation less than 3%.

Conclusion

The measurement accuracy of coronal alignment of the lower limb on the FLWAP radiographs would be influenced by knee flexion, specifically when there is any subtle rotation of the knee joint in the axial plane. A strict patellar forward position without axial plane rotation of the knee could provide accurate results of the measurement even if there is a fixed flexion contracture of the knee.

Introduction and evaluation of a novel multi-camera surface topography system

BACKGROUND

Surface topography can be used for the evaluation of spinal deformities without any radiation. However, so far this technique is limited to posterior trunk measurements due to the use of a single posterior camera.

RESEARCH QUESTION

Purpose of this study was to introduce a new multi camera surface topography system and to test its reliability and validity.

METHODS

The surface topograph uses a two-camera system for imaging and evaluating the subjects front and back simultaneously. Inter- and intra-rater reliability was tested on 40 human subjects by two observers. For validation human, subjects were scanned by MRI and surface-topography. For additional validation we used a phantom with an anthropomorphic body which was scanned by CT and surface topography.

RESULTS

Inter- (0.97-0.99) and intra-rater reliability (0.81-0.98) testing revealed good and excellent results in the detection of the body surface structures and measurement of areas and volumes. CT based validation revealed good correspondence between systems in the imaging and evaluation of the phantom model (0.61-10.52 %). Results on validation of human subjects revealed good to moderate results in the detection and measurements of almost all body surface structures (1.36-13.34 %). Only measurements using jugular notch as a reference showed moderate results in validity (0.62-27.5%) testing.

SIGNIFICANCE

We have introduced a novel and innovative surface topography system that allows for simultaneous anterior and posterior trunk measurements. The results of our reliability and validity tests are satisfactory. However, in particular around the jugular notch region further improvements in the surface topography reconstruction are needed.

Can EOS Imaging Substitute for Conventional Radiography in Measurement of Acetabular Morphology in the Young Dysplastic Hip?

BACKGROUND

EOS imaging offers a low-radiation alternative to conventional radiography (CR) and has little to no magnification effects. However, it is unclear how radiographic measures may be affected using EOS. The present study aims to determine the reproducibility of measures of acetabular morphology on EOS images as compared with CR, and to directly compare the 2 imaging modalities.

METHODS

A total of 21 consecutive patients (66.7% female; 14.4±4.7 y) indicated for an open hip preservation procedure with both an anterior-posterior pelvis radiograph and EOS image performed preoperatively were included. Three orthopaedic surgeons measured Tönnis angle, lateral center edge angle (LCEA), acetabular depth-width ratio (ADR), and extrusion index (EI). Measurements were performed twice, 2 weeks apart. Reliability between observers and time points was measured using intraclass correlation coefficients, and agreement between time points and modalities was measured using Bland-Altman analysis.

RESULTS

On EOS images, inter-rater reliability was 0.86 for Tönnis angle, 0.86 for LCEA, 0.74 for ADR, and 0.93 for EI. On CR, inter-rater reliability was 0.86 for Tönnis anlge, 0.90 for LCEA, 0.82 for ADR, and 0.84 for EI. In the agreement analysis, biases between imaging modalities were observed. On average, raters measured Tönnis angle and EI higher on EOS images than CR (2.22 degrees, 1.09%, respectively); and LCEA and ADR lower on EOS images than CR (1.54 degrees, 1.14% respectively). Limits of agreement (LOA) between modalities were similar to that of LOA observed in intra-rater analysis.

CONCLUSIONS

Measures of acetabular morphology performed on EOS images have similarly high intra-rater and inter-rater reliability compared with CR. Measures performed on EOS also have similar intra-rater agreement as compared with CR. Intermodality agreement had similar LOA as intra-rater agreement on either individual imaging modality. Small biases between imaging modalities were detected.

LEVELS OF EVIDENCE

Level I-diagnostic study: investigating a diagnostic test.

Two-dimensional/three-dimensional EOS™ imaging is reliable and comparable to traditional X-ray imaging assessment of knee osteoarthritis aiding surgical management

BACKGROUND

X-ray imaging is the gold standard for assessing lower limb conditions and preoperative planning. A novel low-radiation-dose EOS™ imaging system enables full-length weight-bearing imaging in one session and three-dimensional (3D) reconstruction. Thus, it can improve assessment of limb deformities, preoperative planning and follow-up with lower radiation exposure. The objective of this study was to measure lower limbs from EOS™ images to determine its accuracy and reproducibility in comparison with long-leg X-ray images.

METHODS

Over a one-year period, twenty patients (forty lower limbs) with knee osteoarthritis were recruited from clinic. Thirty-five (five excluded due to knee prosthesis) two-dimensional- (2D) EOS™, 3D EOS™ and X-ray images were measured independently by four observers, measuring lower limb angles and lengths. On average, twelve weeks later, observers repeated measurements on 2D EOS™ and X-ray images.

RESULTS

A t-test comparing 2D EOS™ with X-ray images showed no significant difference in all angle and length measurements (P > 0.05). When analysing observers separately, all measurements showed no significant difference, apart from the femoral anatomic-mechanical angle (fAMA) from observer 2 (2D EOS™ fAMA 6.21° vs. X-ray fAMA 7.10°, P = 0.02). Intra-observer intraclass correlation coefficient (ICC) for 2D EOS™ and X-ray was 1.00 and 1.00, respectively, and inter-observer ICC was 1.00 and 0.99, respectively. A t-test comparing 2D- with 3D EOS™ images showed no significant difference in all measurements. A t-test comparing 3D EOS™ with X-ray images showed no significant difference in all measurements.

CONCLUSION

This study showed the EOS™ imaging system to be a valid alternative method of imaging lower limbs for alignment, measurements and preoperative arthroplasty planning.

Evaluating the role of surface topography in the surveillance of scoliosis

STUDY DESIGN

Literature review.

OBJECTIVE

To review the history, modern uses, limitations, and future direction of surface topography (ST) in surveillance of scoliosis. Spinal deformities, including scoliosis, can be characterized using measurements such as the Cobb angle, lateral curvature, and vertebral rotation. The gold standard for diagnosis and surveillance of such deformities utilizes radiographic images. To minimize repeated radiation exposure, many systems have been developed utilizing ST. ST measures local deviations of a surface from a flat plane. Applying this concept to spinal deformities, ST can non-radiographically study the 3-dimensional shape of the back. One ST system, rasterstereography, projects parallel white light lines onto a patient's back and analyzes line distortion with a camera. While radiography has long been considered the primary diagnostic tool for scoliosis, rasterstereography may possess alternative or complementary benefits in monitoring scoliosis and other diseases.

METHODS

A comprehensive literature review was performed on the history, development, and validity of ST. The advantages and limitations of this technique were compared to those of radiography.

RESULTS

While the initial goal of ST, designing a system to accurately reproduce the Cobb angle, was not successful, research efforts over the last 40 years have attempted to improve this correlation. ST technologies, including rasterstereography and the Formetric ST System, currently play important roles in scoliosis surveillance, research, and minimizing radiation exposure in longitudinal care of patients. Such technologies are also useful as an adjunct to X-rays for monitoring disease progression, especially in Parkinson's disease.

CONCLUSION

Despite its limitations, ST has proven useful across multiple fields of medicine. It is a safe and cost-effective tool for long-term surveillance of scoliosis and early detection of progressive disease. With technological improvements, the Formetric System will become a critical alternative in dynamic spinal motion and gait analysis.

LEVEL OF EVIDENCE

N/A.

Skeletal growth velocity of adolescent idiopathic scoliosis: abnormal in spine but normal in lower limbs

Background

Abnormal spinal overgrowth has been identified in patients with adolescent idiopathic scoliosis (AIS), which may be attributed to a secondary change. However, growth velocity in adolescents with different maturity statuses, and the final length of the lower extremities were not investigated in patients with AIS. Here, we compared the peak height velocity (PHV) time point of the lower limbs between AIS and healthy adolescents and analyzed whether abnormal growth of the lower limbs exists in patients with AIS.

Methods

Female AIS patients with a thoracic Cobb angle of 20° to 60° were enrolled in the current study. The major Cobb angle, length of the spine (LOS), length of the lower limbs (LLL), and height of the pelvis (HOP) were measured. In addition, RatioSL was defined as LOS/LLL; RatioSP was defined as LOS/HOP; and RatioPL was defined as HOP/LLL. All patients and healthy controls were classified into three groups according to skeleton maturity status: pre-PHV, defined as Risser 0, and open triradiate cartilage (TC); during-PHV (Risser 0, and closed TC); and post-PHV (Risser ranging from 1 to 5).

Results

RatioSL and RatioSP were significantly higher in scoliosis patients at Risser ≥4 compared to healthy controls (all, P<0.05). However, RatioPL was similar between patients with AIS and healthy controls in both the Risser 0 and Risser ≥4 groups. The change in ratio from pre-PHV to post-PHV showed similar trends between patients with AIS and healthy controls; both RatioSL and RatioPL were significantly lower in the during-PHV group (all, P<0.05).

Conclusions

The final length of the lower extremities was similar between groups, while the peak growth of the lower extremities was earlier than that of pelvis and spine in both patients with AIS and healthy adolescents, indicating that lower limb growth pattern was not altered in AIS patients.

BIPLANAR IMAGING WITH TRIDIMENSIONAL CAPABILITIES: APPLICABILITY OF THIS NEW EXAMINATION TO SPINAL DEFORMITIES

ABSTRACT This study presents details about the applicability of the new image acquisition system, called the biplanar imaging system, with three-dimensional capabilities (EOS®) to the treatment of spinal deformities. This system allows radiographic acquisition of the entire body, with a great reduction in the dose of radiation absorbed by the patient and three-dimensional (3D) stereoradiographic image reconstruction of bone structures, including the spine. In the case of adolescent idiopathic scoliosis, the analysis of the spinal deformity with 3D reconstruction allows better understanding of the deformity and surgical planning. In the case of adult spinal deformity, full-body analysis allows an evaluation of the spinopelvic deformity, including loss of sagittal alignment, in addition to an evaluation of compensatory mechanisms recruited by the individual in an attempt to maintain the sagittal balance. Level of evidence III; Descriptive Review.

Clinical practice recommendations for the diagnosis and management of X-linked hypophosphataemia

X-linked hypophosphataemia (XLH) is the most common cause of inherited phosphate wasting and is associated with severe complications such as rickets, lower limb deformities, pain, poor mineralization of the teeth and disproportionate short stature in children as well as hyperparathyroidism, osteomalacia, enthesopathies, osteoarthritis and pseudofractures in adults. The characteristics and severity of XLH vary between patients. Because of its rarity, the diagnosis and specific treatment of XLH are frequently delayed, which has a detrimental effect on patient outcomes. In this Evidence-Based Guideline, we recommend that the diagnosis of XLH is based on signs of rickets and/or osteomalacia in association with hypophosphataemia and renal phosphate wasting in the absence of vitamin D or calcium deficiency. Whenever possible, the diagnosis should be confirmed by molecular genetic analysis or measurement of levels of fibroblast growth factor 23 (FGF23) before treatment. Owing to the multisystemic nature of the disease, patients should be seen regularly by multidisciplinary teams organized by a metabolic bone disease expert. In this article, we summarize the current evidence and provide recommendations on features of the disease, including new treatment modalities, to improve knowledge and provide guidance for diagnosis and multidisciplinary care.

In this Evidence-Based Guideline on X-linked hypophosphataemia, the authors identify the criteria for diagnosis of this disease, provide guidance for medical and surgical treatment and explain the challenges of follow-up.

Revision strategies for failed adult spinal deformity surgery

PURPOSE

The aim of this study is to analyse the results of revision surgery for failed adult spinal deformity patients and to describe the surgical strategy selection process, based on the identification of the main clinical diagnosis responsible for failure.

METHODS

We retrospectively reviewed the clinical and radiological data of 77 consecutive patients treated in a 3-year time (2016-2019) for surgical revision of long fusion (more than five levels fused) for adult spinal deformity in a high-volume spine centre, divided into four groups based on the diagnosis: rod breakage (RB) group, proximal junctional failure (PJF) group, distal junctional failure (DJF) group and loss of correction (LOC) group with symptomatic sagittal or coronal malalignment (including iatrogenic flatback).

RESULTS

Seventy-seven patients met our inclusion criteria, with a female prevalence (66 F vs. 11 M). The mean age at revision surgery was 63. Fused levels before surgery were averagely 12, and revision added averagely two levels to the preexisting fusion area. Clinical status was apparently improved in ODI scores and VAS scores, while it was slightly worsened in SF36 scores. Different diagnosis groups have been addressed with different surgical strategies, according to the different surgical goals: interbody cages and multi-rod construct to improve stiffness and favour bony fusion, "kickstand" rod and "tie" rod to correct coronal and sagittal malalignment, specific rod contouring and proximal hooks in "claw" configuration to reduce mechanical stress at the proximal junctional area. Intraoperative complications occurred in 18% of patients and perioperative complications in 39%.

CONCLUSION

Revision surgery in long fusions for adult spinal deformity is a challenging field. Surgical strategy should always be planned carefully. A successful treatment is a direct consequence of a correct preoperative diagnosis, and surgery should address the primary cause of failure. All the above-mentioned surgical techniques and clinical skills should be part of surgeon's expertise when managing these patients. These slides can be retrieved under Electronic Supplementary Material.

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

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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 OF EVIDENCE

Level III.

Accuracy and kinematics consistency of marker-based scaling approaches on a lower limb model: a comparative study with imagery data

Medical images are not typically included in protocol of motion laboratories. Thus, accurate scaling of musculoskeletal models from optoelectronic data are important for any biomechanical analysis. The aim of the current study was to identify a scaling method based on optoelectronic data, inspired from literature, which could offer the best trade-off between accurate geometrical parameters (segment lengths, orientation of joint axes, marker coordinates) and consistent inverse kinematics outputs (kinematic error, joint angles). The methods were applied on 26 subjects and assessed with medical imagery building EOS-based models, considered as a reference. The main contribution of this paper is to show that the marker-based scaling followed by an optimisation of orientation joint axes and markers local coordinates, gives the most consistent scaling and joint angles with EOS-based models. Thus, when a non-invasive mean with an optoelectronic system is considered, a marker-based scaling is preliminary needed to get accurate segment lengths and to optimise joint axes and marker local coordinates to reduce kinematic errors.AbbrevationsAJCAnkle joint centreCKEcumulative kinematic errorDoFdegree of freedomEBEOS-basedHBheight-basedHJChip joint centreKJCknee joint centreMBmarker-basedMSMmusculoskeletal modelsSPMstatistical parametric mappingSTAsoft tissue artifactEB_a.m∗EOS-based with optimised joint axes, and all model markers coordinatesMB_a.m∗marker-based with optimised joint axes, and all model markers coordinatesMB_l.a.mmarker-based with optimised segment lengths, joint axes, and selected model markers coordinatesASISanterior superior illiac spinePSISposterior superior illiac spine.

COMPARISON OF RADIATION EXPOSURE TO THE PATIENT AND CONTRAST DETAIL RESOLUTIONS ACROSS LOW DOSE 2D/3D SLOT SCANNER AND TWO CONVENTIONAL DIGITAL RADIOGRAPHY X-RAY IMAGING SYSTEMS

PURPOSE

To assess and compare the radiation dose and image quality of the low dose 2D/3D EOS slot scanner (LDSS) to conventional digital radiography (DR) X-ray imaging systems for chest and knee examination protocols.

METHODS AND MATERIALS

The effective doses (ED) to the patient in the chest and knee clinical examination protocols for LDSS and DR X-ray imaging systems were determined using the dose area product and PCXMC Monte Carlo simulation software. The CDRAD phantom was imaged with 19 cm, and 13 cm thick Polymethyl Methacrylate (PMMA) blocks to simulate the chest and knees respectively of a patient of average adult size. The contrast detail resolution was calculated using image analysis software.

RESULTS

The EDs for the LDSS default setting were up to 69% and 51% lower than for the DR systems for the chest (speed 4) and knee (speed 6) protocols, respectively, while for the increased dose level setting then the EDs were up to 42% and 35% lower than for the DR systems for the chest (speed 6) and knee (speed 8) protocols respectively. At the default setting, the contrast detail was lowest for the default setting of the 2D/3D low dose slot scanner (LDSS) for both chest and knee examinations, but at the highest dose levels then the threshold were equal or higher than the contrast resolution of DR imaging systems.

CONCLUSION

The LDSS has the potential to be used for clinical diagnosis of chest and knee examinations using the higher dose level. For speed 6 in chest protocol and speed 8 in knee protocol, the measured contrast detail resolution was comparable with the DR systems but at a lower effective dose.

Decreased Vertical Trunk Inclination Angle and Pelvic Inclination as the Result of Mid-High-Heeled Footwear on Static Posture Parameters in Asymptomatic Young Adult Women

The influence of high-heel footwear on the lumbar lordosis angle, anterior pelvic tilt, and sacral tilt are inconsistently described in the literature. This study aimed to investigate the impact of medium-height heeled footwear on the static posture parameters of homogeneous young adult standing women. Heel geometry, data acquisition process, as well as data analysis and parameter extraction stage, were controlled. Seventy-six healthy young adult women with experience in wearing high-heeled shoes were enrolled. Data of fifty-three subjects were used for analysis due to exclusion criteria (scoliotic posture or missing measurement data). A custom structured light surface topography measurement system was used for posture parameters assessment. Three barefoot measurements were taken as a reference and tested for the reliability of the posture parameters. Two 30-degree wedges were used to imitate high-heel shoes to achieve a repeatable foot position. Our study confirmed the significant (p < 0.001) reduced vertical balance angle and pelvis inclination angle with large and medium-to-large effects, respectively, due to high-heel shoes. No significant differences were found in the kyphosis or lordosis angles. High-heeled shoes of medium height in young asymptomatic women can lead to a straightening effect associated with a reduced vertical balance angle and decreased pelvic inclination.

Physiological variations in the sagittal spine alignment in an asymptomatic elderly population

BACKGROUND CONTEXT

Sagittal plane alignment is of crucial importance for the treatment of spinal deformities. When planning corrective strategies, spine surgeons need to refer to normative parameters' ranges which characterize the alignment in the asymptomatic population. Changes are known to occur with age. For the Caucasian population, the reference ranges are extensively documented for the young and middle-aged adults. In contrast, only a few studies have evaluated individuals in advanced age (>60 years) and in groups of limited numbers of subjects (less than 50).

PURPOSE

To describe the normative parameter ranges of sagittal spine alignment in a large population of asymptomatic elderly subjects.

STUDY DESIGN/SETTING

Monocentric, prospective, cross-sectional study.

PATIENT SAMPLE

One hundred sixty asymptomatic elderly volunteers (age>60 years, Caucasian heritage), consecutively enrolled.

OUTCOME MEASURES

Sagittal parameters of spine and pelvis: thoracic kyphosis (TK); lumbar lordosis (LL); sacral slope (SS); pelvic incidence (PI); pelvic tilt (PT); sagittal vertical axis (SVA); T1 pelvic angle (TPA); mismatch between PI and LL (PI-LL); Roussouly classification of the lumbopelvic profile.

METHODS

Each subject underwent one radiographic scan, performed in standing position with EOS low-dose system (EOS Imaging, Paris, France). The radiographic images were processed with sterEOS software allowing identification of the anatomical parameters and the presence of scoliosis. SVA, TPA, and the lumbopelvic profile were manually measured in the lateral images. The results were compared to previous studies describing younger adult populations. The study was supported by the Italian Ministry of Health in the amount of $15,000. The authors declare that there are no conflicts of interests.

RESULTS

Overall, the average values of the spinopelvic parameters were the followings: TK, 55±14°; LL, 57±12°; PI, 55±11°; SS, 38±10°; PT, 16±7°. The average PI-LL, SVA, and TPA was -3±11°, 25±32 mm, and 14.6±7.4°, respectively. TK, TPA, and SVA were found increasing with age. As for classification of the lumbopelvic profile, 16% of subjects were excluded because they were considered not to belong to any of the Roussouly types. In the classified subjects, the distribution was similar to that of younger adults. Asymptomatic scoliosis (average Cobb angle, 22±7°) was identified in 27% of individuals.

CONCLUSIONS

The ranges of values pointed out differences compared to younger adults and represent an important resource for spine surgeons in planning the surgical correction of spinal deformities. The characteristic changes occurring with age, as well as the observed presence of mild or moderate asymptomatic scoliosis, should be carefully taken into account. The classification of the lumbopelvic profile based on the Roussouly scheme revealed some limitations, although similar frequencies were identified compared to younger adults.

Is Radiation-Free Ultrasound Accurate for Quantitative Assessment of Spinal Deformity in Idiopathic Scoliosis (IS): A Detailed Analysis With EOS Radiography on 952 Patients

Radiation exposure with repeated radiography required at follow-up poses serious health concerns for scoliosis patients. Although spinous process angle (SPA) measurement of spinal curvatures with ultrasound has been reported with promising results, an evidence-based account on its accuracy for translational application remains undefined. This prospective study involved 952 idiopathic scoliosis patients (75.7% female, mean age 16.7 ± 3.0 y, Cobb 28.7 ± 11.6°). Among 1432 curves (88.1%) detected by ultrasound, there was good correlation between radiologic Cobb angles measured manually on EOS (E_Cobb) whole-spine radiographs and automatic ultrasound SPA measurement for upper spinal curves (USCs) (r = 0.873, apices T7-T12/L1 intervertebral disc) and lower spinal curves (LSCs) (r = 0.740, apices L1 or below) (p < 0.001). Taller stature was associated with stronger correlation. For E_Cobb <30°, 66.6% USCs and 62.4% LSCs had absolute differences between E_Cobb and predicted Cobb angle calculated from SPA ≤5°. Ultrasound could be a viable option in lieu of radiography for measuring coronal curves with apices at T7 or lower and Cobb angle <30°.

Imaging in Spine Surgery: Current Concepts and Future Directions

OBJECTIVE

To review and highlight the historical and recent advances of imaging in spine surgery and to discuss current applications and future directions.

METHODS

A PubMed review of the current literature was performed on all relevant articles that examined historical and recent imaging techniques used in spine surgery. Studies were examined for their thoroughness in description of various modalities and applications in current and future management.

RESULTS

We reviewed 97 articles that discussed past, present, and future applications for imaging in spine surgery. Although most historical approaches relied heavily upon basic radiography, more recent advances have begun to expand upon advanced modalities, including the integration of more sophisticated equipment and artificial intelligence.

CONCLUSIONS

Since the days of conventional radiography, various modalities have emerged and become integral components of the spinal surgeon's diagnostic armamentarium. As such, it behooves the practitioner to remain informed on the current trends and potential developments in spinal imaging, as rapid adoption and interpretation of new techniques may make significant differences in patient management and outcomes. Future directions will likely become increasingly sophisticated as the implementation of machine learning, and artificial intelligence has become more commonplace in clinical practice.

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

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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 OF EVIDENCE

Level IV.

McGregor's slope and slope of line of sight: two surrogate markers for Chin-Brow vertical angle in the setting of cervical spine pathology

BACKGROUND CONTEXT

Chin-Brow Vertical Angle (CBVA) is not routinely measured on radiographs even though it is a strong assessor of horizontal gaze.

STUDY DESIGN

Retrospective cohort study of patients with full-body stereoradiographs and a primary cervical diagnosis at the time of presentation.

PURPOSE

Assess the utility of McGregor's Slope (McGS) and Slope of Line of Sight (SLS) as surrogate markers for the CBVA in cervical spine pathology.

METHODS

A retrospective review of patients with full-body stereoradiographs was performed. Patients were ≥18 years of age with a primary cervical diagnosis. Analysis of CBVA, McGS, and SLS was conducted as markers of horizontal gaze. Sagittal alignment was characterized by: pelvic tilt (PT), pelvic incidence minus lumbar lordosis (PI-LL), T1-pelvic angle (TPA), sagittal vertical axis (SVA), T2-T12 thoracic kyphosis, C2-C7 SVA (cSVA), C2-C7 Cervical lordosis, T1-Slope minus Cervical Lordosis (TS-CL), and C2-Slope (C2S). A subgroup analysis was performed in patients with cervical deformity. Independent sample t tests and paired t tests compared radiographic alignment. Pearson correlations characterized linear relationships. Linear regression analysis identified relationships between the parameters.

RESULTS

In all, 329 patients were identified with primary cervical spine diagnoses. Chin-Brow Vertical Angle was visible in 171 patients (52.0%), McGS in 281 (85.4%), and SLS in 259 (78.7%). Of the 171 patients with visible CBVA, the mean CBVA was 2.30±7.7, mean McGS was 5.02±8.1, and mean SLS was -1.588±2.03. Chin-Brow Vertical Angle strongly correlated with McGS (r=0.83) and SLS (r=0.89) with p<.001. McGregor's Slope positively correlated with SLS (r=0.89, p=.001).

CONCLUSIONS

This study demonstrates that McGS and SLS serve as strong, positive correlates for CBVA. The reported mean differences between these measurements provide a useful conversion, broadening CBVA's use as a radiographic assessment of horizontal gaze.

Is the apical vertebra the most rotated vertebra in the scoliotic curve?

OBJECTIVE

The aim of this study was to determine if the apical vertebra (AV) in patients with adolescent idiopathic scoliosis (AIS) is the most rotated vertebra in the scoliotic segment.

METHODS

A total of 158 patients with AIS (Cobb angle range 20°-101°) underwent biplanar radiography with 3D reconstructions of the spine and calculation of vertebral axial rotations. The type of major curvature was recorded (thoracic, thoracolumbar, or lumbar), and both major and minor curvatures were included. The difference of levels (DL) between the level of maximal vertebral rotation (LMVR) and the AV was calculated as follows: DL = 0 if LMVR and AV were the same, DL = 1 if LMVR was directly above or below the AV, and DL = 2 if LMVR was separated by 1 vertebra or more from the AV. To investigate which factors explained the divergence of the LMVR from the AV, multinomial models were computed.

RESULTS

The distribution of the DL was as follows: for major curvatures, 143 were DL = 0, 11 were DL = 1, and 4 were DL = 2; and for minor curvatures, 53 were DL = 0, 9 were DL = 1, and 31 were DL = 2. The determinants of a DL = 2 (compared with DL = 0) were lumbar curvature (compared with thoracic; adjusted OR 0.094, p = 0.001), major curvature (compared with minor; adjusted OR 0.116, p = 0.001), and curvatures with increasing apical vertebral rotation (adjusted OR 0.788, p < 0.001).

CONCLUSIONS

This study showed that the AV is the most rotated vertebra in the majority of major curvatures, while in minor curvatures, the most rotated vertebra appears to be the junctional vertebra between major and minor curvatures in a significant proportion of cases.

The migration percentage measured on EOS® standing full-leg radiographs: equivalent and advantageous in ambulant children with cerebral palsy

BACKGROUND

During ambulatory follow-up of patients with cerebral palsy (CP) systematic radiographic screening is required firstly to evaluate hip migration and development in the prevention of hip dislocation and secondly to analyse lower limb alignment and leg length. The Migration Percentage (MP) is a radiographic measurement used to describe the extent of femoral head lateralisation on conventional supine pelvic radiographs. Our goal was to assess the comparability of the MP measured on low radiation dose EOS® standing full-leg radiographs with that of conventional supine pelvic radiographs.

METHODS

Patients presenting with CP were prospectively selected from our outpatient follow-up consultation at our institutions CP reference centre and underwent conventional supine pelvic and EOS® standing full-leg radiographs the same day for diagnostic and screening reasons.

RESULTS

Out of 28 prospectively selected patients we included 21 (42 hips), of which 10 were female, with a mean age of 9.25 years and GMFCS levels of I, II and III. Seven out of 28 patients were excluded due to insufficient quality of radiographic images. The absolute differences in MP measured on both conventional supine pelvic and EOS® standing full-leg radiographs ranged between - 8 and 6% with an absolute mean difference of 0% (SD ±3.5) and were not statistically significant (p = 0.99). A Bland-Altman plot showed acceptable agreement between both measurements without proportional bias.

CONCLUSION

There is no statistical significant difference between the Migration Percentage measured on conventional supine pelvic radiographs and EOS® standing full-leg radiographs in ambulant patients. These images use lower radiation doses and contain more radiographic information.

TRIAL REGISTRATION

Approved by the Medical Research Ethics committee of the University Hospitals Leuven ( MP001492 ).

A Nano-Dose Protocol For Cobb Angle Assessment in Children With Scoliosis: Results of a Phantom-based and Clinically Validated Study

STUDY DESIGN

This was a prospective validation study with technical notes.

OBJECTIVE

This study aimed to validate a new ultra-low-dose full-spine protocol for reproducible Cobb angle measurements-the "nano-dose" protocol.

SUMMARY OF BACKGROUND DATA

Scoliosis is a 3-dimensional (3D) deformity of the spine characterized by 3D clinical parameters. Nevertheless, 2D Cobb angle remains an essential and widely used radiologic measure in clinical practice. Repeated imaging is required for the assessment and follow-up of scoliosis patients. The resultant high dose of absorbed radiation increases the potential risk of developing radiation-induced cancer in such patients. Micro-dose radiographic imaging is already available in clinical practice, but the radiation dose delivered to the patient could be further reduced.

METHODS

An anthropomorphic child phantom was used to establish an ultra-low-dose protocol in the EOS Imaging System still allowing Cobb angle measurements, defined as nano-dose. A group of 23 consecutive children presenting for scoliosis assessment, 12 years of age or younger, were assessed with standard-dose or micro-dose and additional nano-dose full-spine imaging modalities. Intraobserver and interobserver reliability of determining the reliability of 2D Cobb angle measurements was performed. The dosimetry was performed in the anthropomorphic phantom to confirm theoretical radiation dose reduction.

RESULTS

A nano-dose protocol was established for reliable Cobb angle measurements. Dose area product with this new nano-dose protocol was reduced to 5 mGy×cm, corresponding to one sixth of the micro-dose protocol (30 mGy×cm) and <1/40th of the standard-dose protocol (222 mGy×cm). Theoretical dose reduction, for posteroanterolateral positioning was confirmed using phantom dosimetry. Our study showed good reliability and repeatability between the 2 groups. Cobb variability was <5 degrees from the mean using 95% confidence intervals.

CONCLUSIONS

We propose a new clinically validated nano-dose protocol for routine follow-up of scoliosis patients before surgery, keeping the radiation dose at a bare minimum, while allowing for reproducible Cobb angle measurements.

Sequential spine-hand radiography for assessing skeletal maturity with low radiation EOS imaging system for bracing treatment recommendation in adolescent idiopathic scoliosis: a feasibility and validity study

PURPOSE

The EOS-imaging system is increasingly adopted for clinical follow-up in scoliosis with the advantages of simultaneous biplanar imaging of the spine in an erect position. Skeletal maturity assessment using a hand radiograph is an essential adjunct to spinal radiography in scoliosis follow-up. This study aims at testing the feasibility and validity of a newly proposed EOS workflow with sequential spine-hand radiography for skeletal maturity assessment and bracing recommendation.

METHODS

EOS spine-hand radiographs from patients with diagnosis of idiopathic scoliosis, including both sexes and an age range of ten to 14 years, were scored using the Thumb Ossification Composite Index (TOCI), Sanders and Risser methods. Intraclass correlation coefficients (ICCs) were calculated for inter/intraobserver agreement and were tested with Cronbach's alpha values.

RESULTS

In all, 60 EOS-spine hand radiographs selected from subjects with diagnosis of adolescent idiopathic scoliosis (AIS), including 32 male patients (mean age 11.53 years; 10 to 14) and 28 female patients (mean age 11.50 years; 10 to 13) who underwent sequential spine-hand low dose EOS imaging were generated for analysis. The overall interobserver (ICC = 0.997) and intraobserver agreement (α > 0.9) demonstrated excellent agreement for TOCI staging; ICC > 0.994 for both TOCI and Sanders staging comparing traditional digital versus EOS hand radiography; ICC ≥ 0.841 for agreement on bracing recommendation among TOCI versus the Risser and Sanders system.

CONCLUSION

With the proposed new EOS workflow it was feasible to produce high image quality for skeletal maturity assessment with excellent reliability and validity to inform consistent bracing recommendation in AIS. The workflow is applicable for busy daily clinic settings in tertiary scoliosis centres with reduced time cost, improved efficiency and throughput of the radiology department.

LEVEL OF EVIDENCE

III.

Adult spinal deformity

Adult spinal deformity affects the thoracic or thoracolumbar spine throughout the ageing process. Although adolescent spinal deformities taken into adulthood are not uncommon, the most usual causes of spinal deformity in adults are iatrogenic flatback and degenerative scoliosis. Given its prevalence in the expanding portion of the global population aged older than 65 years, the disorder is of growing interest in health care. Physical examination, with a focus on gait and posture, along with radiographical assessment are primarily used and integrated with risk stratification indices to establish optimal treatment planning. Although non-operative treatment is regarded as the first-line response, surgical outcomes are considerably favourable. Global disparities exist in both the assessment and treatment of adults with spinal deformity across countries of varying incomes, which represents an area requiring further investigation. This Seminar presents evidence and knowledge that represent the evolution of data related to spinal deformity in adults over the past several decades.

Madelung's Deformity of the Wrist-Current Concepts and Future Directions

Madelung's deformity of the wrist arises from premature closure of the medial and volar aspect of the distal radial physis. True Madelung deformities reveal the presence of a "Vickers" ligament which is a short, volar, radioulnar ligament. Clinically, patients report increasing deformity, pain, and poor range of motion. Radiological features include increased radial inclination, volar tilt of the distal radius, and a positive ulnar variance. Surgical intervention usually comprises either a "Vickers" ligament release and distal radius physiolysis or a radial dome osteotomy. In future, EOS Imaging could aid diagnosis by providing more detailed images of the deformity while minimizing radiation exposure. Furthermore, three-dimensional printing and computer-navigated deformity correction could revolutionize management by facilitating simulation training, expediting surgery, and reducing intraoperative error.

3D hindfoot alignment measurements based on low-dose biplanar radiographs: a clinical feasibility study

OBJECTIVE

To test a 3D-hindfoot alignment (HA) measurement technique based on low-dose biplanar radiographs (BPRs) in a clinical setting and compare the results with 2D-HA measurements on long axial view radiographs (LARs).

MATERIALS AND METHODS

This prospective study was approved by the local institutional review board. HA measurements on 3D-BPR and 2D-LAR of 50 patients (29 female; mean age 47 ± 16.6 years) were compared (positive values = valgus; negative values = varus). Two independent musculoskeletal radiologists (readers 1 and 2) performed 3D-HA measurements on BPR using a custom-made MATLAB code and measured HA on LAR during two separate readout sessions. Descriptive statistics and intraclass correlation coefficients (ICC) were calculated, and Bland-Altman plots were used for intermethod comparison.

RESULTS

Using BPRs, HA was 0.8° ± 9.°1 (range, -20.2 to 20.0) for reader 1, and 0.7° ± 9.5° (range, -21.2 to 18.3) for reader 2. HA on LARs was -2.0 ° ± 7.0° (range, -27.0° to 11.1°) for reader 1 and - 1.7° ± 7.0° (range, -24.1° to 14.3°) for reader 2. Interreader agreement for measurements was excellent, both for BPRs (ICC = 0.992; 95% CI:0.986-0.995) and LAR measurements (ICC = 0.962; 95% CI:0.932-0.978). Mean difference between the two methods was -2.43° (range, -29.4° to 25.6°) for reader 1 and -2.6° (range,-28.7° to 30.2°) for reader 2. On Bland-Altman plots, three measurements of reader 1 and six measurements of reader 2 were outside of the ±1.96 SD interval.

CONCLUSION

Hindfoot alignment measurements on 3D-BPR have an excellent interreader agreement in a clinical setting. Large measurement errors can occur in individual patients using 2D-LAR alone. Therefore, we suggest using 3D-BPR measurements in daily routine for the assessment of HA, which are independent of rotational foot malpositioning.

Measurement of Trabecular Bone Score of the Spine by Low-Dose Imaging System (EOS®): A Feasibility Study

Purpose/Introduction: Measurement of trabecular bone score (TBS^®) of the lumbar spine on dual energy X-ray absorptiometry (DXA) devices improves fracture risk prediction. We conducted a proof of concept study to assess the feasibility of TBS^® measured on the low-dose imaging system EOS^®.

METHODS

TBS was assessed on both DXA and EOS^® in 122 patients aged ≥ 50 yr, receiving no anti-osteoporotic treatment. The TBS^® was computed on full-body EOS^® images, focusing on the lumbar spine region. The patients were also scanned with a DXA bone densitometer (Hologic) and the spine and hip bone mineral density (g/cm²) were computed.

RESULTS

TBS^® measurement on EOS^® was not possible in 34 patients due to technical problems. It could be measured on both DXA and EOS^® in 88 patients (28 with severe low-trauma fracture and 60 without fracture). TBS-EOS values were significantly lower in fractured patients compared to nonfractured patients. TBS-EOS was associated with the presence of fractures as reported by an AUC of 0.70. Odds ratio of TBS-EOS for the presence of severe low-trauma fracture was 2.00 [1.24-3.25], p = 0.005.

CONCLUSIONS

This proof of concept study, based on a prototype version of the TBS-EOS, demonstrated the feasibility of the measurement of TBS^® on low-dose EOS^® imaging devices. Results show that the TBS-EOS was lower in patients with severe low-trauma fractures compared to nonfractured patients independently from bone mineral density. Some technical issues need to be solved before its eventual use in routine clinical settings. Additional prospective studies are still needed to define the actual contribution of this new technique.

A comparative evaluation of tibial metaphyseal-diaphyseal angle changes between physiologic bowing and Blount disease

The purpose of this study was to estimate the rate of spontaneous improvement in tibial metaphyseal-diaphyseal angle (TMDA) in physiologic bowing in comparison to that in Blount disease and to provide reference values of TMDA for monitoring patients with highly suspected to have Blount disease.We retrospectively reviewed patients with physiologic bowing meeting the following criteria:(1) TMDA greater than 9° before 36 months of age at initial evaluation;(2) two or more standing long bone radiographs available; and(3) follow-up conducted up to resolution of deformity.Patients with Blount disease had(1) more than 2 standing long bone radiographs obtained before 36 months of age and(2) underwent no treatment during the period in which these images were obtained.TMDA measurements were obtained from 174 patients with physiologic bowing and 32 patients with Blount disease. Rates of TMDA improvement were adjusted by multiple factors using a linear mixed model, with sex and laterality as fixed effects and age and individual patients as the random effects.In the physiologic bowing group, TMDA improved significantly, by 3° per 6 months and by 6° per year. Changes in TMDA were not significant in the Blount disease group.Knowing the rate of TMDA change can be helpful for physicians seeking to monitor infants with suspected as having Blount disease with a high TMDA and to avoid unnecessary repeat radiographic evaluations.

Value of 3D Preoperative Planning for Primary Total Hip Arthroplasty Based on Biplanar Weightbearing Radiographs

Two-dimensional (2D) planning on standard radiographs for total hip arthroplasty may not be sufficiently accurate to predict implant sizing or restore leg length and femoral offset, whereas 3D planning avoids magnification and projection errors. Furthermore, weightbearing measures are not available with computed tomography (CT) and leg length and offset are rarely checked postoperatively using any imaging modality. Navigation can usually achieve a surgical plan precisely, but the choice of that plan remains key, which is best guided by preoperative planning. The study objectives were therefore to (1) evaluate the accuracy of stem/cup size prediction using dedicated 3D planning software based on biplanar radiographic imaging under weightbearing and (2) compare the preplanned leg length and femoral offset with the postoperative result. This single-centre, single-surgeon prospective study consisted of a cohort of 33 patients operated on over 24 months. The routine clinical workflow consisted of preoperative biplanar weightbearing imaging, 3D surgical planning, navigated surgery to execute the plan, and postoperative biplanar imaging to verify the radiological outcomes in 3D weightbearing. 3D planning was performed with the dedicated hipEOS® planning software to determine stem and cup size and position, plus 3D anatomical and functional parameters, in particular variations in leg length and femoral offset. Component size planning accuracy was 94% (31/33) within one size for the femoral stem and 100% (33/33) within one size for the acetabular cup. There were no significant differences between planned versus implanted femoral stem size or planned versus measured changes in leg length or offset. Cup size did differ significantly, tending towards implanting one size larger when there was a difference. Biplanar radiographs plus hipEOS planning software showed good reliability for predicting implant size, leg length, and femoral offset and postoperatively provided a check on the navigated surgery. Compared to previous studies, the predictive results were better than 2D planning on conventional radiography and equal to 3D planning on CT images, with lower radiation dose, and in the weightbearing position.

New sagittal classification of AIS: validation by 3D characterization

INTRODUCTION AND AIM

In order to improve surgical planning of sagittal correction in AIS, we proposed a new sagittal classification-Abelin-Genevois et al. Eur Spine J (27(9):2192-2202, 2018. https://doi.org/10.1007/s00586-018-5613-1 ). The main criticism is related to the fact that 2D lateral view results from the projection of the 3D deformity. The aim of this study is to show that the new sagittal classification system is a reliable system to describe the different sagittal scenarios that AIS could create both in 2D and 3D.

METHODS

We performed retrospective radiograph analysis of prospectively collected data from 93 consecutive AIS patients who underwent an examination of the whole spine using the EOS^® imaging system. 2D (Keops^®) and 3D analyses (sterEOS^®) provided frontal and sagittal spinal and spinopelvic parameters. In addition, 3D analysis provided apical vertebra rotation (AVR).

RESULTS

Comparing 2D and 3D measurements for the general cohort, excellent correlation can be found for all parameters, but only fairly good for T10L2 and L1S1 angles. The highest variability was observed for T10L2, differences between 2D and 3D measurements being greater when the Cobb angle increased. AVR did not influence concordance between 2D and 3D measurements. Eighty-two percent were similarly classified in 2D and 3D according to the new classification. Misclassified patients were all AIS sagittal type 3 in 3D analysis, thoracolumbar junction (TLJ) lordosis being underestimated on 2D view.

DISCUSSION

In conclusion, for the majority of cases (82%), 2D analysis may provide enough information for decision making when using a semi-automated 2D measurement system. However, in severe cases, especially when Cobb angle exceeds 55°, 3D analysis should be used to get a more accurate view on the thoracolumbar junction behavior. These slides can be retrieved under Electronic Supplementary Material.

EOS Micro-dose Protocol: First Full-spine Radiation Dose Measurements in Anthropomorphic Phantoms and Comparisons with EOS Standard-dose and Conventional Digital Radiology

STUDY DESIGN

A comparative study of radiation dose measured in anthropomorphic phantoms.

OBJECTIVES

The aim of this study was to first report the first organ dose and effective dose measurements in anthropomorphic phantoms using the new EOS imaging micro-dose protocol in full-spine examinations, and to compare these measurements of radiation dose to measurements in the EOS standard-dose protocol and conventional digital radiology (CR).

SUMMARY OF BACKGROUND DATA

Few studies evaluating organ dose and effective dose for the EOS low-dose scanner exist, and mainly for the standard-dose protocol. To the best of our knowledge, no studies of effective dose based on anthropomorphic phantom measurements exist for the new micro-dose protocol.

METHODS

Two anthropomorphic phantoms, representing a 5-year-old (pediatric) and a 15-year-old (adolescent). The phantoms were exposed to EOS micro-dose and standard-dose protocols during full-spine imaging. Additionally, CR in scoliosis settings was performed. For all modalities, organ doses were measured and effective doses were calculated using thermoluminescent dosimeters.

RESULTS

We found a 17-fold reduction (94%) of effective dose in micro-dose protocol compared with our CR system in the adolescent phantom. Micro-dose versus standard-dose protocol, showed a 6-fold reduction (83%), and for standard-dose versus our CR system a 2.8-fold reduction (64%) reduction of effective dose was observed.For the pediatric phantom, a 5-fold reduction (81%) of effective dose in micro-dose protocol compared to our CR system was observed. Micro-dose versus standard-dose protocol, showed a seven-fold (86%) reduction. However, we observed an increase in absorbed dose of 38% when comparing the EOS standard-dose protocol with our CR system.

CONCLUSION

The EOS imaging micro-dose option exposes patients to lower radiation doses than any currently available modality for full-spine examination. Expected reduction of dose was established for the adolescent phantom when comparing CR and standard-dose protocol. However, no reduction of effective dose with EOS standard-dose protocol compared to our reference CR system was observed in the pediatric phantom.

LEVEL OF EVIDENCE

N/A.

The Effectiveness of Full-body EOS Compared With Conventional Chest X-ray in Preoperative Evaluation of the Chest for Patients Undergoing Spine Operations: A Preliminary Study

STUDY DESIGN

A prospective radiographic comparative study.

OBJECTIVE

The aim of this study was to compare full-body EOS with conventional chest X-ray (CXR) for use in the preoperative evaluation of the chest in patients undergoing spine operations.

SUMMARY OF BACKGROUND DATA

The full-body EOS reproduces an image of the chest similar to a routine CXR. The potential for the former replacing the latter is plausible. This is especially applicable in spine patients who would routinely have a preoperative full-body EOS performed.

METHODS

A radiographic comparative study of 266 patients was conducted at a single tertiary center from January 2013 to July 2016. Each patient had EOS and CXR done in random order <2 weeks apart. Two radiologists reported the image findings using a checklist. A third radiologist was consulted in cases of discrepancy. Interobserver agreement was calculated using Gwet AC1 and a comparison between EOS and CXR findings was analyzed using paired Chi-squared test. Multivariate analysis was performed to identify predictors for abnormal radiological findings. The institutional ethics committee approved this prospective study and waiver of informed consent was obtained.

RESULTS

There were 84 males (31.6%) and 182 females (68.4%). The mean age was 38.9 years (SD = 25.0 years). High interobserver agreement was found for EOS and CXR (Gwet AC1 0.993 and 0.988, respectively). There were no significant differences between both imaging modalities. Rare diagnoses precluded comparison of certain conditions. Age >18 years [odds ratio (OR) 7.69; P = 0.009] and American Society of Anesthesiologists physical status 3 (OR 6.64; P = 0.018) were independent predictors of abnormal radiological findings.

CONCLUSION

EOS is not inferior to, and may be used to replace CXR in preoperative radiological screening of thoracic conditions especially in low-risk patients ≤18 years old and patients with ASA <3. Preoperative assessment should never rely on a single modality. High-risk patients should be sent for a thorough work-up before spine surgery.

LEVEL OF EVIDENCE

4.

Combining acetabular and femoral morphology improves our understanding of the down syndrome hip

BACKGROUND

Hip instability is frequent in patients with Down syndrome. Recent studies have suggested that skeletal hip alterations are responsible for this instability; however, there are currently no studies simultaneously assessing femoral and acetabular anatomy in subjects with Down syndrome in the standing position. The aim was to analyze the three-dimensional anatomy of the Down syndrome hip in standing position.

METHODS

Down syndrome subjects were age and sex-matched to asymptomatic controls. All subjects underwent full body biplanar X-rays with three-dimensional reconstructions of their pelvises and lower limbs. Parameter means and distributions were compared between the two groups.

FINDINGS

Forty-one Down syndrome and 41 control subjects were recruited. Acetabular abduction (mean = 52° [SD = 9°] vs. mean = 56° [SD = 8°]) and anteversion (mean = 14° [SD = 8°] vs. mean = 17.5° [SD = 5°]) as well as posterior acetabular sector angle (mean = 91° [SD = 7°] vs. mean = 94° [SD = 7°]) were significantly lower in Down syndrome subjects compared to controls (P < 0.01). Anterior acetabular sector angle (mean = 62° [SD = 10°] vs. mean = 59° [SD = 7°]; P < 0.01) was significantly higher in Down syndrome compared to controls. The distributions of acetabular anteversion (P = 0.002;V = 0.325), femoral anteversion (P = 0.004;V = 0.309) and the instability index (P < 0.001;V = 0.383) were significantly different between the two groups, with subjects with Down syndrome having both increased anteversion and retroversion for each of these parameters.

INTERPRETATION

Subjects with Down syndrome were found to have a significantly altered and more heterogeneous anatomy of their proximal hips compared to controls. This heterogeneity suggests that treatment strategies of hip instability in Down syndrome should be subject-specific and should rely on the understanding of the underlying three-dimensional anatomy of each patient.

Normative 3D opto-electronic stereo-photogrammetric sagittal alignment parameters in a young healthy adult population

This paper describes and presents a stable and reliable set of stereo-photogrammetric normative data for global and spino-pelvic sagittal alignment, as a proven reference system for evaluating/measuring a fully unconstrained natural upright neutral standing attitude in a young healthy adult population. The methodological features described in this article will enable future studies to replicate and/or directly compare a wide range of different postural tests and/or sagittal alignment assessment procedures including the study of sagittal spine shape variations occurring during gait performance. To date, the quantitative evaluation of adult spinal deformity (ASD) has been mainly confined to the X-ray imaging approach and, more recently, to 3D X-ray reconstruction. Within the existing evaluation framework an opportunity exists for an additional approach: a quantitative evaluation procedure which is easy, accurate, relatively speedy and non-ionising, in order to monitor and track the progress of patients in the areas of both surgical and non-surgical treatment. The resources and methodology described in this paper have been proven to meet all these criteria. They have enabled full 3D posture (including 3D spine shape and sagittal alignment of the skeleton) to be consistently and successfully measured in adult volunteers. All the measurement/evaluation procedures and outcomes carried out were based entirely on the new non-ionising 3D opto-electronic stereo-photogrammetric approach described in this article. The protocol for this methodology was based on a standard set of 27 pre-selected anatomical “landmarks” on the human body, providing standard reference points for observation and measurement. A total of 124 healthy subjects were successfully assessed and, for each subject, 27 individual markers were applied to the corresponding locations on his/her body. Statistical tests to investigate gender differences were also carried out. Descriptive statistics are provided for all 15 of the spino-pelvic parameters under consideration. Results indicated significant differences between genders in five sets of parameters: Kyphosis tilt, Head tilt, Pelvic tilt, Spino-pelvic angle and T1-pelvic angle. The data also demonstrate a high degree of congruity with results obtained using the X-ray method, as evidenced by the existing literature in the field. In summary, the current study presents a new stereo-photogrammetric opto-electronic technology which can be used successfully for ASD evaluation and introduces a comprehensive set of normative data analogous to those proposed in X-ray analysis for sagittal spino-pelvic and total body alignment.

Computed Tomography Techniques Help Understand Wear Patterns in Retrieved Total Knee Arthroplasty

BACKGROUND

Suboptimal total knee arthroplasty (TKA) position of both femoral and tibial components is thought to be linked with poor clinical outcomes, polyethylene wear and the "unexplained" painful knee arthroplasty. The aim of this study was to better understand the effect of implant orientation on knee implant performance.

METHODS

We analyzed 30 retrieved contemporary TKA implants. Implant positioning measurements in the coronal plane were made prior to revision using a diagnostic algorithm, based on 3D computed tomography (CT) images. Each retrieved polyethylene component was imaged using a micro-CT scanner and a high resolution computational 3D model of each component was digitally reconstructed. The difference in thickness between medial and lateral components was calculated. Statistical analysis was performed to investigate the association between component positioning and damage patterns.

RESULTS

We found a significant correlation between both the tibiofemoral and femoral angles and difference in thickness between polyethylene compartments: varus angulations were strongly associated with thinner medial compartments, whilst valgus angulations were associated with thinner lateral compartments. Moreover, suboptimal tibiofemoral orientations and tibial component angulations were associated to greater differences in thickness between polyethylene compartments.

CONCLUSION

Our study is the first to compare accurate 3D CT measurements of prerevision TKA positioning in the coronal plane with postrevision retrieval analysis from innovative, accurate and highly reliable micro-CT-based method. Our results demonstrate the impact of component positioning on polyethylene damage and helps understanding of the in vivo performance of these implants.

LEVEL OF EVIDENCE

III.

The effect of coronal decompensation on the biomechanical parameters in lower limbs in adolescent idiopathic scoliosis

STUDY HYPOTHESIS

We hypothesized that altered coronal balance in adolescent scoliosis leads to asymmetric stress on the lower limbs, with subsequent effects on bone maturation and later morphology. We aimed to assess the correlation between the biomechanical parameters of the lower limbs and coronal balance in idiopathic scoliosis.

MATERIALS AND METHODS

In this study, EOS images of 280 patients and 56 controls were randomly selected from our clinics' database. The average age of AIS patients was 14.5years and average Cobb angle 33.48°. Three D reconstructions of the pelvis and lower limbs were performed and coronal balance assessed. Reliability of measurements was ensured by intra- and inter-observer agreement. During statistical analysis the Kolmogorov-Smirnov test, t-test and linear regression analysis were performed. A p value <0.05 was considered significant.

RESULTS

Of the 15 examined lower limb parameters, a significant difference between sides was found in those with AIS for femur length, total length, collodiaphyseal angle, angle between the femoral mechanical and anatomical axis and tibial torsion. In addition, the tibial length and the mechanical tibiofemoral angle were significantly higher than those of the controls. The coronal balance was found to be the strongest predictive factor showing a significant correlation with all of the previous parameters, except tibial torsion. With patients grouped based on coronal balance (compensated, right and left decompensated) the paired t-test also supported these findings.

CONCLUSION

The biomechanical parameters of the lower limbs are affected in cases of scoliosis with an altered coronal balance. It was thought that a shift in balance in the coronal plane accounted for the small but significant changes seen in our study, with the lower limb on the side of decompensation becoming shorter in comparison to its' counterpart, with a lower collodiaphyseal angle and increased varus at the knee joint.

LEVEL OF EVIDENCE

III, case-control study.

Spinal Deformity Surgery: A Critical Review of Alignment and Balance

Correction of the overall coronal and/or sagittal plane deformities is one of the main predictors of successful spinal surgery. In routine clinical practice, spinal alignment is assessed using several spinal and pelvic parameters, such as pelvic incidence and tilt, sacral slope, lumbar lordosis, thoracic kyphosis, and sagittal vertical axis. Standard values have been defined for all these parameters, and the formulas of correction have been set for determining the surgical strategy. However, several factors can potentially bias these formulas. First, all standard values are measured using conventional plain radiographs and are, therefore, prone to bias. The radiologist, measuring surgeon, and patient are possible confounding influencing factors. Second, spino-pelvic compensatory effects and biomechanically relevant structures for the patient’s posture, including ligaments, tendons, and muscles, have received minimal consideration in the literature. Therefore, even in cases of appropriately planned deformity correction surgeries, complications, revision rates, and surgical outcomes significantly vary. This study aimed to illustrate the current clinical weaknesses of the assessment of spinal alignment and the importance of holistically approaching the musculoskeletal system for any spinal deformity surgery. We believe that our detailed insights regarding spinal, sagittal, and coronal alignments as well as the considerations of an individual’s spinal balance will contribute toward improvement in routine patient care.

Radiologically defining horizontal gaze using EOS imaging-a prospective study of healthy subjects and a retrospective audit

BACKGROUND CONTEXT

As sagittal alignment of the cervical spine is important for maintaining horizontal gaze, it is important to determine the former for surgical correction. However, horizontal gaze remains poorly-defined from a radiological point of view.

PURPOSE

The objective of this study was to establish radiological criteria to define horizontal gaze.

STUDY DESIGN/SETTING

This study was conducted at a tertiary health-care institution over a 1-month period.

PATIENT SAMPLE

A prospective cohort of healthy patients was used to determine the best radiological criteria for defining horizontal gaze. A retrospective cohort of patients without rigid spinal deformities was used to audit the incidence of horizontal gaze.

OUTCOME MEASURES

Two categories of radiological parameters for determining horizontal gaze were tested: (1) the vertical offset distances of key identifiable structures from the horizontal gaze axis and (2) imaginary lines convergent with the horizontal gaze axis.

MATERIALS AND METHODS

Sixty-seven healthy subjects underwent whole-body EOS radiographs taken in a directed standing posture. Horizontal gaze was radiologically defined using each parameter, as represented by their means, 95% confidence intervals (CIs), and associated 2 standard deviations (SDs). Subsequently, applying the radiological criteria, we conducted a retrospective audit of such radiographs (before the implementation of a strict radioimaging standardization).

RESULTS

The mean age of our prospective cohort was 46.8 years, whereas that of our retrospective cohort was 37.2 years. Gender was evenly distributed across both cohorts. The four parameters with the lowest 95% CI and 2 SD were the distance offsets of the midpoint of the hard palate (A) and the base of the sella turcica (B), the horizontal convergents formed by the tangential line to the hard palate (C), and the line joining the center of the orbital orifice with the internal occipital protuberance (D). In the prospective cohort, good sensitivity (>98%) was attained when two or more parameters were used. Audit using Criterion B+D yielded compliance rates of 76.7%, a figure much closer to that of A+B+C+D (74.8%). From a practical viewpoint, Criterion B+D were most suitable for clinical use and could be simplified to the "3-6-12 rule" as a form of cursory assessment. Verbal instructions in the absence of stringent postural checks only ensured that ~75% of subjects achieved horizontal gaze.

CONCLUSIONS

Fulfillment of Criterion B+D is sufficient to evaluate for horizontal gaze. Further criteria can be added to increase sensitivity. Verbal instructions alone yield high rates of inaccuracy when attempting to image patients in horizontal gaze. Apart from improving methods for obtaining radiographs, a radiological definition of horizontal gaze should be routinely applied for better evaluation of sagittal spinal alignment.

Cumulative effective dose and cancer risk for pediatric population in repetitive full spine follow-up imaging: How micro dose is the EOS microdose protocol?

OBJECTIVE

To evaluate and to obtain analytic formulation for the calculation of the effective dose and associated cancer risk using the EOS microdose protocol for scoliotic pediatric patients undergoing full spine imaging at different age of exposure; to demonstrate the microdose protocol capable of delivering lesser radiation dose and hence of further reducing cancer risk induction when compared with the EOS low dose protocol; to obtain cumulative effective dose and cancer risk for both genders scoliotic pediatrics of US and Hong Kong population using the microdose protocol.

METHODS

Organ absorbed doses of full spine exposed scoliotic pediatric patients have been simulated with the use of EOS microdose protocol imaging parameters input to the Monte Carlo software PCXMC. Gender and age specific effective dose has been calculated with the simulated organ absorbed dose using the ICRP-103 approach. The associated radiation induced cancer risk, expressed as lifetime attributable risk (LAR), has been estimated according to the method introduced in the Biological Effects of Ionizing Radiation VII report. Values of LAR have been estimated for scoliotic patients exposed repetitively during their follow up period at different age for US and Hong Kong population.

RESULTS

The effective doses of full spine imaging with simultaneous posteroanterior and lateral projection for patients exposed at the age between 5 and 18 years using the EOS microdose protocol have been calculated within the range of 2.54-14.75 μSv. The corresponding LAR for US and Hong Kong population was ranged between 0.04 × 10^-6 and 0.84 × 10^-6. Cumulative effective dose and cancer risk during follow-up period can be estimated using the results and are of information to patients and their parents.

CONCLUSION

With the use of computer simulation and analytic formulation, we obtained the cumulative effective dose and cancer risk at any age of exposure for pediatric patients of US and Hong Kong population undergoing repetitive microdose protocol full spine imaging. Girls would be at a statistically significant higher cumulative cancer risk than boys undergoing the same microdose full spine imaging protocol and the same follow-up schedule.