Biplanar Radiographs Research Articles

Effect of the type of brace on head to pelvis sagittal alignment of adolescents with Scheuermann’s kyphosis

ABSTRACT The aim of this study was to determine the effects of the Milwaukee brace and thoracolumbosacral orthosis (TLSO) on head to pelvis sagittal alignment in adolescents with Scheuermann’s kyphosis (SK). A total of 52 adolescents with SK who were under brace treatment were studied. They underwent biplanar radiography of the head to pelvis (EOS Imaging, Paris, France) before and 6 months after the beginning of bracing. We measured T1 slope, neck tilt (NT), cervical sagittal vertical axis (cSVA), thoracic inlet angle (TIA), C0-C2 lordosis, C2-C7 lordosis, thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), sagittal vertical axis (SVA) and T1 spinopelvic inclination (T1SPi). There were no significant differences in baseline values of TIA, PT, SS, PI, SVA, TK, cSVA, NT and T1 slope between the two groups (p > 0.05). There were significant differences between the baseline and final measurements of T1 slope, cSVA, TK, LL, T1SPi and TIA in both groups (p < 0.05). The results imply that brace treatment can significantly affect head to pelvis sagittal parameters of adolescents with SK. However, there are no significant differences in the values of head to pelvis sagittal parameters when comparing short-term effect of TLSO and the Milwaukee brace.

Use of a Novel Multimodal Imaging Technique to Model In Vivo Quadriceps Force and ACL Strain During Dynamic Activity

Background: Quadriceps loading of the anterior cruciate ligament (ACL) may play a role in the noncontact mechanism of ACL injury. Musculoskeletal modeling techniques are used to estimate the intrinsic force of the quadriceps acting at the knee joint. Purpose/Hypothesis: The purpose of this paper was to develop a novel musculoskeletal model of in vivo quadriceps force during dynamic activity. We used the model to estimate quadriceps force in relation to ACL strain during a single-leg jump. We hypothesized that quadriceps loading of the ACL would reach a local maximum before initial ground contact with the knee positioned in extension. Study Design: Descriptive laboratory study. Methods: Six male participants underwent magnetic resonance imaging in addition to high-speed biplanar radiography during a single-leg jump. Three-dimensional models of the knee joint, including the femur, tibia, patellofemoral cartilage surfaces, and attachment-site footprints of the patellar tendon, quadriceps tendon, and ACL, were created from the magnetic resonance imaging scans. The bone models were registered to the biplanar radiographs, thereby reproducing the positions of the knee joint at the time of radiographic imaging. The magnitude of quadriceps force was determined for each knee position based on a 3-dimensional balance of the forces and moments of the patellar tendon and the patellofemoral cartilage contact acting on the patella. Knee kinematics and ACL strain were determined for each knee position. Results: A local maximum in average quadriceps force of approximately 6500 N (8.4× body weight) occurred before initial ground contact. ACL strain increased concurrently with quadriceps force when the knee was positioned in extension. Conclusion: This novel participant-specific modeling technique provides estimates of in vivo quadriceps force during physiologic dynamic loading. A local maximum in quadriceps force before initial ground contact may tension the ACL when the knee is positioned in extension. Clinical Relevance: These data contribute to understanding noncontact ACL injury mechanisms and the potential role of quadriceps activation in these injuries.

Medial Unicompartmental Knee Arthroplasty Restores Native Knee Kinematics During Activities of Daily Living: A Pilot Study.

The ability of unicompartmental knee arthroplasty (UKA) to restore native knee kinematics during activities of daily living remains unclear. The objectives of this prospective study were to identify changes in knee kinematics after medial UKA (mUKA) and to determine if mUKA restores native knee kinematics during activities of daily living. We hypothesized that kinematics are different between the mUKA knee and contralateral knee before surgery, that mUKA restores native knee kinematics, and that mUKA does not affect lateral compartment dynamic joint space. Nine participants performed walking, chair rise, stair ascent and stair descent within a biplane radiography system before and after mUKA. Bilateral knee kinematics were determined for each activity using a validated tracking process that matched subject-specific bones and implants to the biplane radiographs. Compared to contralateral knee, the pre-UKA knee was more adducted (p ≤ 0.019), and more laterally translated (p ≤ 0.008) during all four activities. Additionally, compared to contralateral knee, pre-UKA knee was less internally rotated (p ≤ 0.044) during chair rise and stair ascent. Lateral compartment dynamic joint space did not change during any activity from pre to post mUKA. Our results indicate that mUKA generally restores native kinematics during activities of daily living without altering lateral compartment dynamic joint space.

Differences between men and women in coupled subtalar and tibiofemoral joint kinematics during gait revealed through dynamic biplane radiography

It has been suggested that subtalar and tibiofemoral kinematics are coupled, such that abnormal subtalar inversion during the impact and push-off portions of stance may affect tibial rotation, leading to abnormal compensatory knee motion. This study aimed to characterize tibiofemoral and subtalar coupled motion and to determine if sex-dependent differences exist in lower extremity coupled motion. Twenty young adults were imaged at 100 frames/s using dynamic biplane radiography while walking. Lower extremity CT scans were obtained and segmented into subject-specific 3D bone models. Digitally reconstructed radiographs generated from the models were matched to the biplane radiographs via a validated tracking process to obtain tibiofemoral and subtalar joint kinematics. Subtalar inversion/eversion was strongly associated with tibiofemoral internal/external rotation and tibiofemoral ab/adduction during impact and push-off (P < 0.001). Men reached neutral subtalar and tibiofemoral orientation at midstance, while women remained more inverted at the subtalar joint and more externally rotated at the tibiofemoral joint. The rate of tibiofemoral ab/adduction to subtalar eversion differed between sexes during push-off (P = 0.005). Women underwent subtalar inversion, as well as tibiofemoral internal rotation and adduction during push-off, while men underwent only subtalar inversion and tibiofemoral internal rotation, with effectively no tibiofemoral adduction. These results provide the first quantitative evidence characterizing subtalar and tibiofemoral coupled motion. Differences in coupled motion trajectories between men and women may be associated with the higher incidence of knee-related pathology in women. These novel findings may serve as a standard for comparison when evaluating patients with patellofemoral pain.

A fresh look at spinal alignment and deformities: Automated analysis of a large database of 9832 biplanar radiographs.

We developed and used a deep learning tool to process biplanar radiographs of 9,832 non-surgical patients suffering from spinal deformities, with the aim of reporting the statistical distribution of radiological parameters describing the spinal shape and the correlations and interdependencies between them. An existing tool able to automatically perform a three-dimensional reconstruction of the thoracolumbar spine has been improved and used to analyze a large set of biplanar radiographs of the trunk. For all patients, the following parameters were calculated: spinopelvic parameters; lumbar lordosis; mismatch between pelvic incidence and lumbar lordosis; thoracic kyphosis; maximal coronal Cobb angle; sagittal vertical axis; T1-pelvic angle; maximal vertebral rotation in the transverse plane. The radiological parameters describing the sagittal alignment were found to be highly interrelated with each other, as well as dependent on age, while sex had relatively minor but statistically significant importance. Lumbar lordosis was associated with thoracic kyphosis, pelvic incidence and sagittal vertical axis. The pelvic incidence-lumbar lordosis mismatch was found to be dependent on the pelvic incidence and on age. Scoliosis had a distinct association with the sagittal alignment in adolescent and adult subjects. The deep learning-based tool allowed for the analysis of a large imaging database which would not be reasonably feasible if performed by human operators. The large set of results will be valuable to trigger new research questions in the field of spinal deformities, as well as to challenge the current knowledge.

Ultrasound in the Diagnosis of Pediatric Distal Radius Fractures: Does it Really Change the Treatment Policy? An Orthopedic View.

Distal radius fractures are the most common pediatric fractures, increasing in number in recent decades. Although simple bi-planar radiographs are sufficient for diagnosis, wrist ultrasonography has been popularized in recent years for fracture detection, mostly because of the concern about children's radiation exposure. Despite its availability and diagnostic accuracy, ultrasound has not gained widespread acceptance and popularity among orthopedic surgeons. We asked about the reasons for its lack of acceptance as a diagnostic tool by orthopedic surgeons, and its failure to be incorporated into diagnostic algorithms. We reviewed the latest articles concerning the use of ultrasound in the diagnosis of pediatric distal radius fracture. Data extraction was performed from each study with a focus on the following items: the specialty field of the authors, number of patients, number of fractures, mean age of the patients, and the gold standard method of diagnosis. Nine studies concerning the diagnostic accuracy of ultrasound in detecting distal radius fractures in children were included in the review. The most common field of practice of the authors was emergency medicine. Only two studies had an orthopedic surgeon among their authors. All studies employed X-ray imaging as the gold standard method. All studies were designed as prospective trials without randomization of patients. Generally, there was no independent blinded reviewer for the interpretation of ultrasound and X-ray images. Most studies were completed by emergency medicine physicians, without involving an orthopedic surgeon. Ultrasound evaluation was undertaken primarily by emergency medicine physicians with little experience. These studies were not randomized controlled trials, and knowledge of the history and clinical presentation of the subjects could have led to information bias. The relatively low number of included patients and lack of follow-up examinations were other limitations. As a result, we believe that ultrasound has not proven to be a suitable substitute for conventional X-ray imaging in the detection of pediatric distal radius fractures. We propose X-ray evaluation as the clinical gold standard method for pediatric wrist fractures.

In Vivo Evidence of Early Instability and Late Stabilization in Motion Segments Immediately Superior to Anterior Cervical Arthrodesis.

Prospective cohort study. The aim was to identify patient factors that affect adjacent segment kinematics after anterior cervical discectomy and fusion (ACDF) as measured by biplane radiography. The etiology of adjacent segment disease (ASD) may be multifactorial. Previous studies have investigated associations between patient factors and ASD, although few attempted to link patient factors with mechanical changes in the spine that may explain ASD development. Previous studies manually measured intervertebral motion from static flexion/extension radiographs, however, manual measurements are unreliable, and those studies failed to measure intervertebral motion during rotation. Patients had continuous cervical spine flexion/extension and axial rotation movements captured at 30 images per second in a dynamic biplane radiography system preoperatively and 1 year after ACDF. Digitally reconstructed radiographs generated from subject-specific computed tomography scans were matched to the biplane radiographs using a validated tracking process. Dynamic kinematics and preoperative disc height were calculated from this tracking process. Preoperative magnetic resonance imagings were evaluated for disc bulge. Patient age, sex, body mass index, smoking status, diabetes, psychiatric history, presence of an inciting event, and length of symptoms were collected. Multivariate linear regression was performed to identify patient factors associated with 1-year postoperative changes in adjacent segment kinematics. Sixty-three patients completed preoperative and postoperative testing. Superior adjacent segment disc height and disc bulge predicted the change in superior adjacent segment range of motion after surgery. Inferior adjacent segment disc bulge, smoking history, and the use of psychiatric medications predicted the change in inferior adjacent segment flexion/extension range of motion after surgery. Preexisting adjacent segment disc degeneration, as indicated by disc height and disc bulge, was associated with reduced adjacent segment motion after ACDF, while lack of preexisting adjacent disc degeneration was associated with increased adjacent segment motion after ACDF. These findings provide in vivo evidence supporting early instability and late stabilization in the pathophysiology of disc degeneration.

Verifying a C-arm-based roentgen stereophotogrammetric analysis protocol for assessing tibial implant movement in total knee arthroplasty.

Roentgen stereophotogrammetric analysis (RSA) is the "gold standard" technique for measuring sub-millimetric relative motion between implant and bone to quantify post-operative implant migration over time. The vast majority of RSA studies addressing implant motion in knee replacements, however, have been conducted using expensive biplanar radiography systems and commercial software that are not readily available at many institutions. In this study, we evaluated the feasibility of performing RSA using ordinary, readily available C-arm fluoroscopes and open-source software to assess tibial component migration.We developed an assessment protocol using a Siemens Arcadis Orbic C-arm and the open-source XROMM software and evaluated its accuracy and precision through a series of phantom-based verification tests. The results were highly promising: accuracies were in the range of - 39 to 11μm for translations and - 0.025 to 0.029° for rotations, while system precisions ranged between 16 to 27μm for translations and 0.041 to 0.059° for rotations. This performance is comparable to specialized RSA systems reported in the literature. The proposed RSA protocol is therefore capable of accurately measuring the relative motion of knee replacement implants in phantom scenarios, which justifies further the development of the protocol towards use in prospective clinical assessments of new implant designs and surgical techniques.

Associations between range of motion, strength, tear size, patient-reported outcomes, and glenohumeral kinematics in individuals with symptomatic isolated supraspinatus tears.

Clinical failure associated with nonoperative treatment of rotator cuff tears may be due to inadequate characterization of the individual's functional impairments. Clinically, restricted passive range of motion (ROM) (restrictions imply capsular tightness), limitations in muscle strength, and larger rotator cuff tears are hypothesized to be related to altered glenohumeral kinematics. Understanding these relationships, as well as the relationship between glenohumeral kinematics and patient-reported outcomes (PROs) prior to exercise therapy, may help characterize functional impairments in individuals with rotator cuff tears. The objectives of the study were to describe the baseline presentation of individuals with an isolated supraspinatus tear, including passive ROM, rotator cuff muscle strength, tear size, PROs, and glenohumeral kinematics, and to determine associations among these variables. One hundred one individuals with symptomatic isolated supraspinatus tears were recruited for the study and underwent assessments of passive glenohumeral ROM, isometric muscle strength, and ultrasonography to assess anterior-posterior tear size. Glenohumeral kinematics during scapular-plane abduction were measured using biplane radiography. Furthermore, PROs including the American Shoulder and Elbow Surgeons (ASES) score and the Western Ontario Rotator Cuff Index (WORC) score were collected. Individuals presented with decreased ROM, external rotation weakness compared with the uninvolved side, and pain and disability as measured by the ASES and WORC scores. These findings were not associated with glenohumeral kinematics, with the exception of a weak positive association between glenohumeral contact path lengths and WORC scores (ρ=0.25, P=.03). Tear size was 11.7±5.7 mm, and maximum anterior translation, superior translation, and contact path length were 3.0%±3.8% of glenoid width, 3.5%±3.8% of glenoid height, and 38.2%±20.7% of glenoid size, respectively. Individuals with a symptomatic isolated supraspinatus tear presented with decreased ROM, external rotation weakness, and pain and disability as measured by the ASES and WORC scores. However, no abnormal kinematics associated with these limitations were observed. Thus, given that the tear is isolated to the supraspinatus tendon and no capsular restrictions are present, normal function of the glenohumeral joint may be possible during scapular-plane abduction.

The Influence of Knee Osteoarthritis on Spinopelvic Alignment and Global Sagittal Balance.

Osteoarthritis (OA) of the knee is thought to lead to a loss of lumbar lordosis (LL) as a compensation for knee flexion contracture. Changes in sagittal alignment are not limited to the lumbar spine and involve a complex interplay of alignment of the hip, pelvis, and spine. While spine-hip interactions have been previously explored, the influence of knee OA sagittal alignment parameters on spinopelvic alignment and global sagittal balance remains unexplored. Standing radiological examination using EOS biplanar radiography was examined in 108 patients with knee OA. Whole-body sagittal alignment parameters (thoracic kyphosis, LL, pelvic incidence, pelvic tilt [PT], femoropelvic angle [FPA], femoral tilt angle [FTA], tibial tilt angle, and knee flexion angle [KFA]) and global balance parameters (sagittal vertical axis [SVA] and odontoid hip axis [OD-HA] angle) were measured three dimensionally (3D). The correlation coefficients among all parameters were assessed. A multiple stepwise linear regression model was built to investigate the direct association between SVA or OD-HA angle (dependent variables) and sagittal alignment parameters and demographic data (independent variables). Significant correlations between KFA, FPA, FTA, SVA, and OD-HA angle were found. FTA was correlated with LL and FPA. The FTA was the most influential predictor of both global sagittal balance parameters (p < 0.001). Knee OA leads to changes in global sagittal balance with effects at the hip, knee, pelvis, and spine. FTA (forward flexion of the femur vs. the vertical plane) is the largest driver of global sagittal plane balance in patients with knee OA.

Measurement Techniques for Leg Length Discrepancy in Total Hip Arthroplasty: A Systematic Review of Reliability and Validity

BackgroundTotal hip arthroplasty (THA) carries a substantial litigative burden. THA may introduce leg length discrepancy (LLD), necessitating a valid and reliable technique for LLD measurement. This study investigates the reliability and validity of techniques quantitively measuring LLD in both pre- and post-THA. MethodsEmbase and MEDLINE databases were searched following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines for articles assessing either the validity or reliability of LLD measurement techniques. Data was pooled using random effects meta-analysis to derive reliability estimates. Study quality was assessed using the Brink and Louw checklist. ResultsForty-two articles with 2059 participants were included. Thirty-three investigated reliability and 25 validity. Reliability displayed high heterogeneity. Poor to excellent intra-rater reliability was reported for antero-posterior pelvis radiographs, moderate to excellent for computed tomography scanograms, and good to excellent for clinical methods and teleradiography, and excellent for bi-planar radiography (BPR). Poor to excellent inter-rater reliability was reported for antero-posterior pelvis radiographs and clinical methods, moderate to excellent for teleradiography, good to excellent for computed tomography scanogram and excellent for BPR. The tape measure method is a valid clinical measure of LLD whilst markerless motion analysis and the block method are not. Imaging techniques are appropriately cross-validated with the exception of BPR. ConclusionThe reported intra- and inter-rater reliability for most measurement techniques vary widely. The tape measure method is a valid clinical measurement of LLD. Imaging techniques have been appropriately cross-validated, with the exception of BPR, although they lack validation against a common reference technique.

The rib cage: a new element in the spinopelvic chain.

This study analyzes anatomical variations of the thoracic cage (TC) according to spinopelvic alignment, age and gender using stereoradiography in erect position. This retrospective multicentric study analyzed computed parameters collected from free-standing position bi-planar radiographs, among healthy subjects. Collected data were: age, gender, pelvic parameters (Pelvic Incidence, Pelvic Tilt (PT) and Sacral Slope), T1-T12 Kyphosis (TK), L1-S1 Lordosis (LL), curvilinear spinal length, global TC parameters (maximum thickness and width,rib cage volume, mean Spinal Penetration Index (SPI)), 1st-10th rib parameters (absolute and relative (to the corresponding vertebra) sagittal angles). Totally, 256 subjects were included (140 females). Mean age was 34(range: 8-83). Significant correlations were found between TK and TC thickness (0.3,p < 0.001) and with TC Volume (0.3,p = 0.04), as well as rib absolute sagittal angle for upper and middle ribs (0.2,p = 0.02). Conversely, a -0.3 correlation has been exhibited between SPI and TK. Similar correlations were found with LL. PT significantly correlated with TC thickness (0.4,p = 0.003), SPI (-0.3,p = 0.03), and all rib relative sagittal angles. Among global TC parameters, only thickness and SPI significantly changed after 20years(respectively, 0.39 and -0.52,p < 0.001). Ribs relative sagittal angle showed negative correlation with age in skeletally mature subjects (p < 0.001). This study demonstrates the correlation between TC anatomy and spinopelvic parameters, confirming its part of the spinopelvic chain of balance. Indeed, higher spinal curvatures were associated with lower SPI and higher TC thickness, TC volume and rib absolute sagittal angles.

A New Method for Quantifying 3D Skeletal Morphology in Living Subjects Using Low‐Dose Stereo Radiographs

Accurate and repeatable assessments of three‐dimensional (3D) skeletal morphology are critical to interpretations of vertebrate functional anatomy. In skeletal specimens, these goals can be accomplished using in‐silico models derived from 3D laser scan, photogrammetry, or computed tomography (CT) data. Assessments of skeletal morphology in living subjects, especially humans, are more challenging and are often either cost‐prohibitive (e.g., magnetic resonance) or expose subjects to high doses of ionizing radiation (e.g., CT). Here, we present a new, open‐source method for assessing 3D skeletal morphology using ultra‐low dose biplanar radiographs. Biplanar radiographs were obtained using an EOS Imaging System (EOS Imaging, Inc., Paris, France). A custom‐built calibration frame with radiopaque markers was scanned using this system on multiple days in multiple positions inside the scanning space. We quantified the 3D coordinates of markers by placing landmarks at the center of each marker in both anterior‐posterior and lateral radiographs. Landmark data for each scan were collected independently by two observers to determine inter‐observer error. 3D coordinates of landmarks in each scan differed by &lt;1 mm between observers, suggesting strong repeatability in assessing morphology of living subjects. To assess distortion in EOS images, we constructed a second calibration device, a flat plate with radiopaque markers at the corners of three squares with 10 cm, 20 cm, and 30 cm sides, respectively, surrounding an origin point. The calibration plate was scanned with the origin point at the center of the scan area and the sides of the squares parallel to the detectors. We identified distortion at the edges of EOS images which could significantly impact measurements on skeletal features near the margins of the scan area (i.e., hips, pelvis, lower limbs) and developed a method to mathematically correct for resulting distortion in landmark data. Finally, we demonstrate this method using measurements of iliac blade and spinous process orientation in a sample of living human participants. This method will be applicable to studies of multiple human cohorts, including symptomatic and asymptomatic groups, as well as to other biplanar radiograph platforms and study organisms.

Within-subject effects of standardized prosthetic socket modifications on physical function and patient-reported outcomes

BackgroundAmong the challenges of living with lower limb loss is the increased risk of long-term health problems that can be either attributed directly to the amputation surgery and/or prosthetic rehabilitation or indirectly to a disability-induced sedentary lifestyle. These problems are exacerbated by poorly fit prosthetic sockets. There is a knowledge gap regarding how the socket design affects in-socket mechanics and how in-socket mechanics affect patient-reported comfort and function. The objectives of this study are (1) to gain a better understanding of how in-socket mechanics of the residual limb in transfemoral amputees are related to patient-reported comfort and function, (2) to identify clinical tests that can streamline the socket design process, and (3) to evaluate the efficacy and cost of a novel, quantitatively informed socket optimization process.MethodsUsers of transfemoral prostheses will be asked to walk on a treadmill wearing their current socket plus 8 different check sockets with designed changes in different structural measurements that are likely to induce changes in residual limb motion, skin strain, and pressure distribution within the socket. Dynamic biplane radiography and pressure sensors will be used to measure in-socket residual limb mechanics. Patient-reported outcomes will also be collected after wearing each socket. The effects of in-socket mechanics on both physical function and patient-reported outcomes (aim 1) will be assessed using a generalized linear model. Partial correlation analysis will be used to examine the association between research-grade measurements and readily available clinical measurements (aim 2). In order to compare the new quantitative design method to the standard of care, patient-reported outcomes and cost will be compared between the two methods, utilizing the Wilcoxon-Mann-Whitney non-parametric test (aim 3).DiscussionKnowledge on how prosthetic socket modifications affect residual bone and skin biomechanics itself can be applied to devise future socket designs, and the methodology can be used to investigate and improve such designs, past and present. Apart from saving time and costs, this may result in better prosthetic socket fit for a large patient population, thus increasing their mobility, participation, and overall health-related quality of life.Trial registrationClinicalTrials.gov NCT05041998. Date of registration: Sept 13, 2021.

In Vivo Changes in Dynamic Adjacent Segment Motion 1 Year After One and Two-Level Cervical Arthrodesis.

Biomechanical cadaver testing indicates adjacent segment motion increases after one-level anterior cervical spine arthrodesis, and two-level arthrodesis exacerbates these effects. There is little in vivo evidence to support those biomechanical studies. The purpose of this study was to assess the effects of one- and two-level cervical arthrodesis on adjacent segment motion. Fifty patients received either one-level C56 arthrodesis or two-level C456 or C567 arthrodesis and were tested preoperatively (PRE) and 1 year postoperatively (1YR-POST) along with 23 asymptomatic controls. A validated CT model-based tracking technique was used to measure 3D vertebral motion from biplane radiographs collected during dynamic flexion-extension and axial rotation of the cervical spine. Head and adjacent segment intervertebral end-range range of motion (ROM) and mid-range ROM were compared between one-level and two-level arthrodesis patients and controls. Small (2.3° or less) but non-significant increases in adjacent segment end-range ROM were observed from PRE to 1YR-POST. Mid-range flexion-extension ROM in the C67 motion segment inferior to the arthrodesis and mid-range axial rotation ROM in the C45 motion segment superior to the arthrodesis increased from PRE to 1YR-POST (all p < 0.022). This study provides in vivo evidence that contradicts long-held beliefs that adjacent segment end-range ROM increases appreciably after anterior cervical arthrodesis and that two-level arthrodesis exacerbates these effects. Mid-range ROM appears to be more useful than end-range ROM for detecting early changes in adjacent segment motion after cervical spine arthrodesis.

FM-Net: Deep Learning Network for the Fundamental Matrix Estimation from Biplanar Radiographs

Background and ObjectiveThe fundamental matrix estimation is a classic problem in computer vision. The traditional algorithms require high-precision correspondences. However, correspondences in biplanar radiographs are difficult to match accurately. MethodsWe propose an end-to-end network to estimate the F-Matrix directly from BR, which includes feature extraction and regression prediction. There is no publicly available dataset of biplanar radiographs. We produce the dataset in this paper to train and test the proposed network. Four metrics, Mean Square Error, Calculating R-squared, Square Value of Extreme Constraint, and Absolute Value of Extreme Constraint are used to measure the performance of the approaches. ResultsThe best Square Value of Extreme Constraint and Absolute Value of Extreme Constraint values we obtained on the datasets were 0.20 and 0.43, respectively. Compared with other methods, the estimation accuracy of FM-Net is improved by more than 53.53%. ConclusionsThe results of experiments demonstrate that the proposed network can estimate the fundamental matrix successfully. It outperforms the classical algorithms and other deep learning-based methods.

Three-dimensional reconstruction of In Vivo human lumbar spine from biplanar radiographs.

We present a method for three dimensional (3D) reconstruction of in vivo human lumbar spine from biplanar radiographs with comparable results to Computerised Tomography (CT) scans or Magnetic Resonance Imaging (MRI) models. In this work, we used uncalibrated radiographs to reconstruct the 3D vertebrae and a priori information stored in an Active Shape Model (ASM) that is constructed using the Spherical Demons Algorithm. The method is semi-automatic as bounding boxes are required to delimit the positions of the vertebrae on biplanar radiographs of a patient. Optimisation is based on comparisons between simulated and actual radiographs. Finally, we compare the results to the models generated from MRI and CT scans. The results show the feasibility of generating personalised models of patients from biplanar radiographs.

Spinopelvic Alignment as a Risk Factor for Poor Balance Function in Low Back Pain Patients.

Retrospective, observational study. This study aimed to examine the association between spinopelvic parameters and balance function in low back pain (LBP). Among patients in the rehabilitation medicine department, the data of 182 patients (mean age, 47.8years; M/F = 64/118) was obtained retrospectively. Spinopelvic parameters were measured through a whole-body low-dose biplanar radiography using the EOS imaging system, and balance function was evaluated by the center of pressure (COP) movement using the Zebris treadmill system. Pearson correlations were used to determine the relationship between radiographic and balance function. Stepwise multiple linear regression analyses were conducted with the balance function as a dependent variable and age and spinopelvic parameters as independent variables. Increased age, knee flexion (KF), pelvic tilt (PT), C7-central sacral line (C7-CSL) and C7 sagittal vertical axis (SVA), and decreased spino-sacral angle (SSA) were associated with both poor static and dynamic balance. Moreover, increased Cobb's angle and decreased thoracic kyphosis (TK) and lumbar lordosis (LL) was associated with poor static balance. Increased pelvic incidence (PI) was related to poor dynamic balance. Increased age, Cobb's angle, SVA, and decreased TK were risk factors for poor static balance. For dynamic balance, increased age, C7-CSL, and PT were risk factors for poor sagittal balance, whereas increased CAM-plumb line and PT were risk factors for poor coronal balance. Balance function was associated with spinopelvic parameters in patients with LBP. Increased SVA, followed by increased PT, was the strongest independent factor associated with poor static and dynamic balance.

Does Femoral Head Translation Vary by Sex and Side in Asymptomatic Hips During a Weightbearing Apprehension Test?

Hip microinstability is an increasingly recognized source of pain and dysfunction but has no agreed upon diagnostic criteria and the pathophysiology remains unclear. It has been suggested that pain associated with microinstability is caused by excess translation of the femoral head. Recent research indicates that single-plane femoral head translation can be reliably measured using dynamic ultrasonography during a supine clinical examination; however, the overall accuracy of that technique has not been established, and the range of femoral head translation values that are found in individuals with no history of surgery or symptomatic pathology is unknown. (1) How much femoral head translation is present in native, uninjured hips during a weightbearing apprehension position for females and males? (2) How large is the side-to-side difference in hip translation and rotation within the same individual in females and males with no history of surgery or pain during the weightbearing apprehension position? (3) What differences exist in femoral head translation and rotation when comparing females to males? Twenty-two young adults (11 males, 11 females; mean age 22 ± 2 years; BMI 22 ± 5 kg/m2) with no history of hip pain, no known hip injury, and who never had hip surgery participated in this study. High-resolution CT images of the femur and pelvis were acquired for each participant, and the bone tissue was segmented from the CT volume. Synchronized biplane radiographs were collected during a neutral standing trial and during a static weightbearing apprehension position in which the participant extended, externally rotated, and abducted at their back hip while standing with their feet split in the AP direction. A validated volumetric model-based tracking technique was used to match the patient-specific bone models to the biplane radiographs with an accuracy of 0.3 mm for translation and 0.8° for rotation. Translation of the center of the femoral head relative to the center of the acetabulum and rotation of the femur relative to the pelvis from neutral to the weightbearing apprehension position were calculated. Sex-based differences in hip kinematics were assessed by bivariate linear regression. The median (range) translation during the weightbearing apprehension position in females was 0.9 mm (0.2 to 2.7 mm), which was less than in the 1.3 mm (0.2 to 2.6 mm) translation found in males (median difference of 0.5 mm; p = 0.04). The median absolute side-to-side difference in translation during the pivot was 1.4 mm (0.1 to 3.8 mm) in females and 1.3 mm (0.1 to 4.4 mm) in males. These findings demonstrate that the femoral head translates the same under bodyweight loading as previously observed during supine exam, showing the inherent stability of the hip with no history of surgery or symptomatic pathology. This study also provides normal values for comparison with individuals who have suspected microinstability. Future directions for research include directly comparing biplane radiography to alternative imaging techniques, such as dynamic ultrasound, for identifying hip microinstability and identifying threshold values for symptomatic hip microinstability. Level III, prognostic study.

Fast quasi-automated 3D reconstruction of lower limbs from low dose biplanar radiographs using statistical shape models and contour matching

Three-dimensional bone reconstructions from medical imaging are essential for biomechanical modelling and are growing tools in clinics. Several methods of lower limbs reconstruction from biplanar radiographs have been proposed in the literature but with significant operator dependence. A novel reconstruction method based on reduced manual annotation, statistical shape models and fully automatic adjustments was proposed in this study. While significantly reducing operator intervention, the proposed method demonstrated similar or better precision than previous approaches on clinical parameters. Meanwhile, shape accuracy was improved to around 1mm. By quasi-automating the 3D reconstruction without loss of accuracy and precision, the proposed approach is a considerable step towards extensive use of 3D personalized models in clinical routine and large cohort biomechanical studies.