The accuracy and repeatability of an automatic 2D-3D fluoroscopic image-model registration technique for determining shoulder joint kinematics

Severity of rotator cuff disorders and additional load affect fluoroscopy-based shoulder kinematics during arm abduction

BACKGROUND

Rotator cuff disorders, whether symptomatic or asymptomatic, may result in abnormal shoulder kinematics (scapular rotation and glenohumeral translation). This study aimed to investigate the effect of rotator cuff tears on in vivo shoulder kinematics during a 30° loaded abduction test using single-plane fluoroscopy.

MATERIALS AND METHODS

In total, 25 younger controls, 25 older controls and 25 patients with unilateral symptomatic rotator cuff tears participated in this study. Both shoulders of each participant were analysed and grouped on the basis of magnetic resonance imaging into healthy, rotator cuff tendinopathy, asymptomatic and symptomatic rotator cuff tears. All participants performed a bilateral 30° arm abduction and adduction movement in the scapular plane with handheld weights (0, 2 and 4 kg) during fluoroscopy acquisition. The range of upward-downward scapular rotation and superior-inferior glenohumeral translation were measured and analysed during abduction and adduction using a linear mixed model (loads, shoulder types) with random effects (shoulder ID).

RESULTS

Scapular rotation was greater in shoulders with rotator cuff tendinopathy and asymptomatic rotator cuff tears than in healthy shoulders. Additional load increased upward during abduction and downward during adduction scapular rotation (P < 0.001 in all groups but rotator cuff tendinopathy). In healthy shoulders, upward scapular rotation during 30° abduction increased from 2.3° with 0-kg load to 4.1° with 4-kg load and on shoulders with symptomatic rotator cuff tears from 3.6° with 0-kg load to 6.5° with 4-kg load. Glenohumeral translation was influenced by the handheld weights only in shoulders with rotator cuff tendinopathy (P ≤ 0.020). Overall, superior glenohumeral translation during 30° abduction was approximately 1.0 mm with all loads.

CONCLUSIONS

The results of glenohumeral translation comparable to control but greater scapular rotations during 30° abduction in the scapular plane in rotator cuff tears indicate that the scapula compensates for rotator cuff deficiency by rotating. Further analysis of load-dependent joint stability is needed to better understand glenohumeral and scapula motion.

LEVEL OF EVIDENCE

Level 2.

TRIAL REGISTRATION

Ethical approval was obtained from the regional ethics committee (Ethics Committee Northwest Switzerland EKNZ 2021-00182), and the study was registered at clinicaltrials.gov on 29 March 2021 (trial registration number NCT04819724, https://clinicaltrials.gov/ct2/show/NCT04819724 ).

Elbow Kinematics and Function Following Treatment with Open Arthrolysis and Hinged External Fixator

OBJECTIVE

Open arthrolysis (OA) combined with hinged external fixator (HEF) is a promising surgical option for patients with elbow stiffness. This study aimed to investigate elbow kinematics and function following a combined treatment with OA and HEF in elbow stiffness cases.

METHODS

Patients treated with OA with or without HEF due to elbow stiffness were recruited between August 2017 and July 2019. Elbow flexion-extension motion and function (Mayo elbow performance scores, MEPS) were recorded and compared between patients with and without HEF during a 1-year follow-up period. Additionally, those with HEF were assessed by dual fluoroscopy at week 6 postoperatively. Flexion-extension and varus-valgus motions, as well as ligament insertion distances of the anterior medial collateral ligament (AMCL) and lateral ulnar collateral ligament (LUCL), were compared between the surgical and intact sides.

RESULTS

This study included 42 patients, of which 12 with HEF demonstrated a similar flexion-extension angle and range of motion (ROM) and MEPS as the other patients. In patients with HEF, the surgical elbows showed limitations in flexion-extension (maximal flexion, 120.5° ± 5.3° vs 140.4° ± 6.8°; maximal extension, 13.1° ± 6.0° vs 6.4° ± 3.0°; ROM, 107.4° ± 9.9° vs 134.0° ± 6.8°; all Ps < 0.01) compared with the contralateral sides. During elbow flexion, a gradual valgus-to-varus transition of the ulna, increase in the AMCL insertion distance, and steady change in the LUCL insertion distance were observed, with no significant differences between the bilateral sides.

CONCLUSIONS

Patients treated with OA and HEF demonstrated similar elbow flexion-extension motion and function to those treated with OA alone. Although the use of HEF could not restore an intact flexion-extension ROM and might result in some minor but not significant changes in kinematics, it contributed to clinical outcomes comparable to that of the treatment with OA alone.

Comparison of instantaneous knee kinematics during walking and running

BACKGROUND

Accurate measurements of in-vivo knee joint kinematics are essential to elucidate healthy knee motion and the changes that accompany injury and repair. Although numerous experimental measurements have been reported, the accurate non-invasive analysis of in-vivo knee kinematics remains a challenge in biomechanics.

RESEARCH QUESTION

The study objective was to investigate in-vivo knee kinematics before, at, and after contact during walking and running using a combined high-speed dual fluoroscopic imaging system (DFIS) and magnetic resonance (MR) imaging technique.

METHODS

Three-dimensional (3D) knee models of ten participants were created using MR images. Knee kinematics during walking and running were determined using high-speed DFIS. The 3D knee models were then related to fluoroscopic images to obtain in-vivo six-degrees-of-freedom knee kinematics.

RESULTS

Before contact knee flexion, external femoral rotation, and proximal-distal distance were 11.9°, 3.4°, and 1.0 mm greater during running compared to walking, respectively. Similar differences were observed at initial contact (9.9°, 7.9°, and 0.9 mm, respectively) and after contact (6.4°, 2.2°, and 0.8 mm, respectively). Posterior femoral translation at initial contact was also increased during running compared to walking.

SIGNIFICANCE

This study demonstrated accurate instantaneous in-vivo knee kinematic characteristics that may further the understanding of the intrinsic biomechanics of the knee during gait.

Comparison of glenohumeral joint kinematics between manual wheelchair tasks and implications on the subacromial space: A biplane fluoroscopy study

Scapula and humerus motion associated with common manual wheelchair tasks is hypothesized to reduce the subacromial space. However, previous work relied on either marker-based motion capture for kinematic measures, which is prone to skin-motion artifact; or ultrasound imaging for arthrokinematic measures, which are 2D and acquired in statically-held positions. The aim of this study was to use a fluoroscopy-based approach to accurately quantify glenohumeral kinematics during manual wheelchair use, and compare tasks for a subset of parameters theorized to be associated with mechanical impingement. Biplane images of the dominant shoulder were acquired during scapular plane elevation, propulsion, sideways lean, and weight-relief raise in ten manual wheelchair users with spinal cord injury. A computed tomography scan of the shoulder was obtained, and model-based tracking was used to quantify six-degree-of-freedom glenohumeral kinematics. Axial rotation and superior/inferior and anterior/posterior humeral head positions were characterized for full activity cycles and compared between tasks. The change in the subacromial space was also determined for the period of each task defined by maximal change in the aforementioned parameters. Propulsion, sideways lean, and weight-relief raise, but not scapular plane elevation, were marked by mean internal rotation (8.1°, 10.8°, 14.7°, -49.2° respectively). On average, the humeral head was most superiorly positioned during the weight-relief raise (1.6 ± 0.9 mm), but not significantly different from the sideways lean (0.8 ± 1.1 mm) (p = 0.191), and much of the task was characterized by inferior translation. Scaption was the only task without a defined period of superior translation on average. Pairwise comparisons revealed no significant differences between tasks for anterior/posterior position (task means range: 0.1-1.7 mm), but each task exhibited defined periods of anterior translation. There was not a consistent trend across tasks between internal rotation, superior translation, and anterior translation with reductions in the subacromial space. Further research is warranted to determine the likelihood of mechanical impingement during these tasks based on the measured task kinematics and reductions in the subacromial space.

Validation and application of a novel in vivo cervical spine kinematics analysis technique

To validate the accuracy of Cone beam computed tomography (CBCT) cervical spine modeling with three dimensional (3D)-3D registration for in vivo measurements of cervical spine kinematics. CBCT model accuracy was validated by superimposition with computed tomography (CT) models in 10 healthy young adults, and then cervical vertebrae were registered in six end positions of functional movements, versus a neutral position, in 5 healthy young adults. Registration errors and six degrees of freedom (6-DOF) kinematics were calculated and reported. Relative to CT models, mean deviations of the CBCT models were < 0.6 mm. Mean registration errors between end positions and the reference neutral position were < 0.7 mm. During flexion–extension (F–E), the translation in the three directions was small, mostly < 1 mm, with coupled LB and AR both < 1°. During lateral bending (LB), the bending was distributed roughly evenly, with coupled axial rotation (AR) opposite to the LB at C1–C2, and minimal coupled F–E. During AR, most of the rotation occurred in the C1–C2 segment (29.93 ± 7.19° in left twist and 31.38 ± 8.49° in right twist) and coupled LB was observed in the direction opposite to that of the AR. Model matching demonstrated submillimeter accuracy in cervical spine kinematics data. The presently evaluated low-radiation-dose CBCT technique can be used to measure 3D spine kinematics in vivo across functional F–E, AR, and LB positions, which has been especially challenging for the upper cervical spine.

Advances in the Application of the Dual Fluoroscopic Imaging System in Sports Medicine: A Literature Review

The dual fluoroscopic imaging system (DFIS) is a new non-invasive motion analysis system that does not interfere with movement, has high precision and repeatability and is not affected by the errors caused by the relative movement of skin and soft tissues. DFIS has been recently used in the field of sports medicine. This narrative review focuses on relevant literature on the origin, development and mechanism of action of DFIS and summarises the application of DFIS in injury and rehabilitation treatment, such as the reliability of test results; the position relationships of bony structures in the shoulder, lumbar spine, knee joint and ankle joint during exercise and its six degree-of-freedom (6DOF) movement to calculate cartilage deformation, contact area/trajectory and ligament strain. This article puts forward the problems encountered in practice that need to be solved and looks forward to the future applications of DFIS in the field of sports, especially in injury prevention and treatment.

In Vivo Foot and Ankle Kinematics During Activities Measured by Using a Dual Fluoroscopic Imaging System: A Narrative Review

Foot and ankle joints are complicated anatomical structures that combine the tibiotalar and subtalar joints. They play an extremely important role in walking, running, jumping and other dynamic activities of the human body. The in vivo kinematic analysis of the foot and ankle helps deeply understand the movement characteristics of these structures, as well as identify abnormal joint movements and treat related diseases. However, the technical deficiencies of traditional medical imaging methods limit studies on in vivo foot and ankle biomechanics. During the last decade, the dual fluoroscopic imaging system (DFIS) has enabled the accurate and noninvasive measurements of the dynamic and static activities in the joints of the body. Thus, this method can be utilised to quantify the movement in the single bones of the foot and ankle and analyse different morphological joints and complex bone positions and movement patterns within these organs. Moreover, it has been widely used in the field of image diagnosis and clinical biomechanics evaluation. The integration of existing single DFIS studies has great methodological reference value for future research on the foot and ankle. Therefore, this review evaluated existing studies that applied DFIS to measure the in vivo kinematics of the foot and ankle during various activities in healthy and pathologic populations. The difference between DFIS and traditional biomechanical measurement methods was shown. The advantages and shortcomings of DFIS in practical application were further elucidated, and effective theoretical support and constructive research direction for future studies on the human foot and ankle were provided.

High-speed fluoroscopic imaging for investigation of three-dimensional knee kinematics before and after marathon running

BACKGROUND

Knee injuries often occur during or shortly after marathon running, and are linked to altered knee kinematics.

RESEARCH QUESTION

The kinematics of healthy knees during pre- and post-marathon running have not been examined with high-speed fluoroscopy. This study aimed to evaluate the effects of marathon running on knee kinematics during walking and running by using a combined high-speed fluoroscopy and MRI technique.

METHODS

Ten healthy runners underwent knee MRI within 24 h before marathon running to construct three-dimensional (3D) knee models. Knee kinematics during treadmill walking and running were evaluated using high-speed fluoroscopy (200hz) within 24 h before and as soon as possible (within 5 h) after marathon running. All pre- and post-marathon measurements were compared.

RESULTS

(1) For post-marathon walking, posterior femoral translation increased 1.4 mm at initial contact (p = 0.015); proximal-distal distance of tibia and femur decreased 0.7 mm and 0.8 mm at initial contact and after contact, respectively (p = 0.039, p = 0.046); and valgus femur rotation increased 1.2° after contact (p = 0.027). (2) For post-marathon running, proximal-distal distance decreased 0.7 mm and 1.0 mm at initial contact and after contact (p = 0.011, p = 0.003) respectively; knee flexion decreased 4.3° before contact (p = 0.007); knee flexion increased 1.8° and 2.6° at initial contact and after contact, respectively (p = 0.038, p = 0.011); external femoral rotation increased 1.2° and 1.8° at initial contact and after contact, respectively (p = 0.012, p = 0.037). Valgus femoral rotation after contact increased 2.3° (p = 0.001).

SIGNIFICANCE

Post-marathon changes in valgus and external femoral rotation, knee flexion, posterior femoral translation, and proximal-distal distance may increase the risk of knee injury. This study provides information to better understand the response of the knee to marathon running.

Soft tissue artifact causes underestimation of hip joint kinematics and kinetics in a rigid-body musculoskeletal model

Rigid body musculoskeletal models have been applied to study kinematics, moments, muscle forces, and joint reaction forces in the hip. Most often, models are driven with segment motions calculated through optical tracking of markers adhered to the skin. One limitation of optical tracking is soft tissue artifact (STA), which occurs due to motion of the skin surface relative to the underlying skeleton. The purpose of this study was to quantify differences in musculoskeletal model outputs when tracking body segment positions with skin markers as compared to bony landmarks measured by direct imaging of bone motion with dual fluoroscopy (DF). Eleven asymptomatic participants with normally developed hip anatomy were imaged with DF during level treadmill walking at a self-selected speed. Hip joint kinematics and kinetics were generated using inverse kinematics, inverse dynamics, static optimization and joint reaction force analysis. The effect of STA was assessed by comparing the difference in estimates from simulations based on skin marker positions (SM) versus virtual markers on bony landmarks from DF. While patterns were similar, STA caused underestimation of kinematics, range of motion (ROM), moments, and reaction forces at the hip, including flexion-extension ROM, maximum internal rotation joint moment and peak joint reaction force magnitude. Still, kinetic differences were relatively small, and thus they may not be relevant nor clinically meaningful.

In Vivo Evaluation of Subacromial and Internal Impingement Risk in Asymptomatic Individuals

OBJECTIVE

The study aim was to evaluate subacromial and internal impingement risk between shoulders (dominant/nondominant) during dynamic motion using subject-specific anatomy and precise in vivo kinematics.

DESIGN

In a prospective cross-sectional study, nine subjects underwent bilateral magnetic resonance (N = 18 shoulders) and fluoroscopic imaging during elevation and external rotation at 90 degrees of abduction. Subject-specific bone models were created and distances from footprint to (a) acromion and (b) glenoid were measured to evaluate risk.

RESULTS

Throughout elevation, subacromial impingement risk was greater in the dominant shoulder (P = 0.0178). Regardless of side, high subacromial impingement risk occurred at 30% (78 degrees), 50% (101 degrees), and 70% (57 degrees) of the elevation cycle (P < 0.0001). High subacromial impingement risk also occurred at 30% (94 degrees), 50% (120 degrees), and 70% (63 degrees) of the external rotation motion cycle (P < 0.0001). Throughout both motions, internal impingement risk was not observed; however, the footprint and glenoid were closest at 50% of the elevation (101 degrees) and external rotation (120 degrees) cycles (P < 0.0001).

CONCLUSIONS

During elevation, subacromial impingement risk is greatest at lower arm positions (30% cycle, 78 degrees) and is greater in the dominant shoulder. High subacromial impingement risk also occurs with external rotation (63-120 degrees). Internal impingement risk does not occur with maximal elevation (101 degrees) or external rotation at 90-degree abduction but is more closely approached with elevation.

A novel auto-positioning method in Iodine-125 seed brachytherapy driven by preoperative planning

Iodine‐125 seed brachytherapy has great potential in the treatment of malignant tumors. However, the success of this treatment is highly dependent on the ability to accurately position the coplanar template. The aim of this study was to develop an auto‐positioning system for the template with a design focus on efficiency and accuracy. In this study, an auto‐positioning system was presented, which was composed of a treatment planning system (TPS) and a robot‐assisted system. The TPS was developed as a control system for the robot‐assisted system. Then, the robot‐assisted system was driven by the output of the TPS to position the template. Contrast experiments for error validation were carried out in a computed tomography environment to compare with the traditional positioning method (TPM). Animal experiments on Sprague–Dawley rats were also carried out to evaluate the auto‐positioning system. The error validation experiments and animal experiments with this auto‐positioning system were successfully carried out with improved efficiency and accuracy. The error validation experiments achieved a positioning error of 1.04 ± 0.19 mm and a positioning time of 23.15 ± 2.52 min, demonstrating a great improvement compared with the TPM (2.55 ± 0.21 mm and 40.35 ± 2.99 min, respectively). The animal experiments demonstrated that the mean deviation of the seed position was 0.75 mm. The dose‐volume histogram of the preoperative planning showed the same as the postoperative dosimetry validation. A novel auto‐positioning system driven by preoperative planning was established, which exhibited higher efficiency and accuracy compared with the TPM.

Analysis of forearm rotational motion using biplane fluoroscopic intensity-based 2D-3D matching

Measuring three-dimensional (3D) forearm rotational motion is difficult. We aimed to develop and validate a new method for analyzing 3D forearm rotational motion. We proposed biplane fluoroscopic intensity-based 2D-3D matching, which employs automatic registration processing using the evolutionary optimization strategy. Biplane fluoroscopy was conducted for forearm rotation at 12.5 frames per second along with computed tomography (CT) at one static position. An arm phantom was embedded with eight stainless steel spheres (diameter, 1.5 mm), and forearm rotational motion measurements using the proposed method were compared with those using radiostereometric analysis, which is considered the ground truth. As for the time resolution analysis, we measured radiohumeral joint motion in a patient with posterolateral rotatory instability and compared the 2D-3D matching method with the simulated multiple CT method, which uses CTs at multiple positions and interpolates between the positions. Rotation errors of the radius and ulna between these two methods were 0.31 ± 0.35° and 0.32 ± 0.33°, respectively, translation errors were 0.43 ± 0.35 mm and 0.29 ± 0.25 mm, respectively. Although the 2D-3D method could detect joint dislocation, the multiple CT method could not detect quick motion during joint dislocation. The proposed method enabled high temporal- and spatial-resolution motion analyses with low radiation exposure. Moreover, it enabled the detection of a sudden motion, such as joint dislocation, and may contribute to 3D motion analysis, including joint dislocation, which currently cannot be analyzed using conventional methods.

Kinematic Accuracy in Tracking Total Wrist Arthroplasty with Biplane Videoradiography using a CT-generated Model

Total Wrist Arthroplasty (TWA) for improving the functionality of severe wrist joint pathology has not had the same success, in parameters such as motion restoration and implant survival, as hip, knee, and shoulder arthroplasty. These other arthroplasties have been studied extensively, including the use of biplane videoradiography (BVR) that has allowed investigators to study the in-vivo motion of the total joint replacement during dynamic activities. The wrist has not been a previous focus, and utilization of BVR for wrist arthroplasty presents unique challenges due to the design characteristics of TWAs. Accordingly, the aims of this study were 1) to develop a methodology for generating TWA component models for use in BVR, and 2) to evaluate the accuracy of model-image registration in a single cadaveric model. A model of the carpal component was constructed from a CT scan, and a model of the radial component was generated from a surface scanner. BVR was acquired for three anatomical tasks from a cadaver specimen. Optical motion capture was used as the gold standard. BVR's bias in flexion/extension, radial/ulnar deviation, and pronosupination was less than 0.3°, 0.5°, and 0.6°. Translation bias was less than 0.2 mm with a standard deviation of less than 0.4 mm. This BVR technique achieved a kinematic accuracy comparable to previous studies on other total joint replacements. BVR's application to the study of TWA function in patients could advance the understanding of TWA and thus the implant's success.

Pathological kinematic patterns of the tarsal complex in stage II adult-acquired flatfoot deformity

The in vivo kinematic characteristics of the tarsal joints during gait stance phase were still unclear in adult-acquired foot deformity (AAFD). This study included seven healthy subjects (14 feet) and 12 stage II AAFD patients (14 feet). The 3D models of tarsal bones were reconstructed based on CT scan. Each subject took standard gait on the single fluoroscopy system. Continuous lateral fluoroscopic images were collected. The key postures during the stance phase were selected. The 2D-3D registration technique was applied to explore the spatial motions of the tarsal joints in 6 degrees of freedom (DOF). During the whole stance phase, the AAFD talo-navicular joint (TNJ) exhibited ROM of 13 ± 6° in the sagittal plane while the normal subjects showed ROM of 7 ± 3° (p = 0.004). In AAFD, the subtalar joint (STJ) demonstrated 19 ± 8° and 7 ± 3° of motion in coronal and horizontal plane, respectively, while the normal subjects showed 14 ± 4°(p = 0.031) and 11 ± 3° (p = 0.014) of motion, respectively. Additionally STJ of AAFD patients showed significantly less dorsiflexion during the weight acceptance and showed significantly less external rotation both during the weight acceptance and single limb support of stance phase. In conclusion, for stage II AAFD patients, the talonavicular joint and the subtalar joint showed hypermobility in dorsi/planterflexion and inversion/eversion, respectively, during the gait stance phase while the internal/external rotation of the subtalar joint was reduced. The current study improves our understanding of the pathological kinematics of the tarsal complex in AAFD patients. Notice should be taken about these tarsal joints mobility in AAFD during clinical practice. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:477-482, 2019.

Assessment of In Vivo Lumbar Inter-Vertebral Motion: Reliability of a Novel Dynamic Weight-Bearing Magnetic Resonance Imaging Technique Using a Side-Bending Task

Study Design

Between-session reliability of a magnetic resonance imaging (MRI) based experimental technique to quantify lumbar inter-vertebral motion in humans.

Purpose

We have developed a novel, dynamic, MRI-based approach for quantifying in vivo lumbar inter-vertebral motion. In this study, we present the protocol’s reliability results to quantify inter-vertebral spine motion.

Overview of Literature

Morphometric studies on intervertebral displacements using static, supine MRI and quantification of dynamic spine motion using different X-ray based radiography techniques are commonly found in the literature. However, reliability testing of techniques assessing real-time lumbar intervertebral motion using weight-bearing MRI has rarely been reported.

Methods

Ten adults without a history of back pain performed a side-bending task on two separate occasions, inside an open-MRI, in a weight-bearing, upright position. The images were acquired during the task using a dynamic magnetic resonance (MR) sequence. The MRI imaging space was externally calibrated before the study to recreate the imaging volume for subsequent use in an animation software. The dynamic MR images were processed to create side-bending movement animations in the virtual environment. Participant-specific three-dimensional models were manually superimposed over vertebral image silhouettes in a sequence of image frames, representing the motion trials. Inter-vertebral axes and translation and rotational displacements of vertebrae were quantified using the animation software.

Results

Quantification of inter-vertebral rotations and translations shows high reliability. Between-session reliability results yielded high values for the intra-class correlation coefficient (0.86–0.93), coefficient of variation (13.3%–16.04%), and Pearson’s correlation coefficients (0.89–0.98).

Conclusions

This technique may be developed further to improve its speed and accuracy for diagnostic applications, to study in vivo spine stability, and to assess outcomes of surgical and non-surgical interventions applied to manage pathological spine motion.

A survey of human shoulder functional kinematic representations

In this survey, we review the field of human shoulder functional kinematic representations. The central question of this review is to evaluate whether the current approaches in shoulder kinematics can meet the high-reliability computational challenge. This challenge is posed by applications such as robot-assisted rehabilitation. Currently, the role of kinematic representations in such applications has been mostly overlooked. Therefore, we have systematically searched and summarised the existing literature on shoulder kinematics. The shoulder is an important functional joint, and its large range of motion (ROM) poses several mathematical and practical challenges. Frequently, in kinematic analysis, the role of the shoulder articulation is approximated to a ball-and-socket joint. Following the high-reliability computational challenge, our review challenges this inappropriate use of reductionism. Therefore, we propose that this challenge could be met by kinematic representations, that are redundant, that use an active interpretation and that emphasise on functional understanding.

MRI vs CT-based 2D-3D auto-registration accuracy for quantifying shoulder motion using biplane video-radiography

Biplane 2D-3D registration approaches have been used for measuring 3D, in vivo glenohumeral (GH) joint kinematics. Computed tomography (CT) has become the gold standard for reconstructing 3D bone models, as it provides high geometric accuracy and similar tissue contrast to video-radiography. Alternatively, magnetic resonance imaging (MRI) would not expose subjects to radiation and provides the ability to add cartilage and other soft tissues to the models. However, the accuracy of MRI-based 2D-3D registration for quantifying glenohumeral kinematics is unknown. We developed an automatic 2D-3D registration program that works with both CT- and MRI-based image volumes for quantifying joint motions. The purpose of this study was to use the proposed 2D-3D auto-registration algorithm to describe the humerus and scapula tracking accuracy of CT- and MRI-based registration relative to radiostereometric analysis (RSA) during dynamic biplanar video-radiography. The GH kinematic accuracy (RMS error) was 0.6-1.0 mm and 0.6-2.2° for the CT-based registration and 1.4-2.2 mm and 1.2-2.6° for MRI-based registration. Higher kinematic accuracy of CT-based registration was expected as MRI provides lower spatial resolution and bone contrast as compared to CT and suffers from spatial distortions. However, the MRI-based registration is within an acceptable accuracy for many clinical research questions.

An interpolation technique to enable accurate three-dimensional joint kinematic analyses using asynchronous biplane fluoroscopy

Biplane 2D-3D model-based registration and radiostereometric analysis (RSA) approaches have been commonly used for measuring three-dimensional, in vivo joint kinematics. However, in clinical biplane systems, the x-ray images are acquired asynchronously, which introduces registration errors. The present study introduces an interpolation technique to reduce image registration error by generating synchronous fluoroscopy image estimates. A phantom study and cadaveric shoulder study were used to evaluate the level of improvement in image registration that could be obtained as a result of using our interpolation technique. Our phantom study results show that the interpolated bead tracking technique was in better agreement with the true bead positions than when asynchronous images were used alone. The overall RMS error of glenohumeral kinematics for interpolated biplane registration was reduced by 1.27 mm, 0.40 mm, and 0.47 mm in anterior-posterior, superior-inferior, and medial-lateral translation, respectively; and 0.47°, 0.67°, and 0.19° in ab-adduction, internal-external rotation and flexion-extension, respectively, compared to asynchronous registration. The interpolated biplane registration results were consistent with previously reported studies using custom synchronous biplane fluoroscopy technology. This approach will be particularly useful for improving the kinematic accuracy of high velocity activities when using clinical biplane fluoroscopes or two independent c-arms, which are available at a number of institutions.

Additively manufactured implant components for imaging validation studies

Radiographic imaging is the current standard for evaluating postoperative joint replacements. Prior to application, such imaging methods need to be validated to determine the lower limits of performance under ideal conditions, using either a phantom or cadaver setup. Conventionally manufactured orthopedic implants for use in such studies are not always accessible and may be cost-prohibitive to purchase. We propose the use of additively manufactured implants as a cheaper, more accessible alternative for use in radiographic imaging validation studies. Bias and repeatability were compared between conventionally manufactured and additively manufactured reverse total shoulder implant sets under a standard model-based radiostereometric analysis phantom study environment. Measurements were compared using the humeral stem or glenosphere model relative to reference bone beads, and the humeral stem relative to the glenosphere model to measure implant relative displacement. Compared to the conventionally manufactured implants, the additively manufactured implants had less bias along the internal-external rotation axis (p < 0.001), but greater bias along the abduction-adduction and flexion-extension rotation axes (p = 0.005, 0.011). Additively manufactured implants had greater repeatability along the internal-external rotation axis (p < 0.001), but worse repeatability along the medial-lateral translation axis (p = 0.001) and the abduction-adduction rotation axis (p < 0.001). Differences were on the orders of 0.01 mm and 0.5°. For the purpose of validating two-dimensional-three-dimensional radiographic imaging techniques of orthopedic implants, additively manufactured implants can be used in place of conventionally manufactured implants, assuming they are fabricated to the manufacturer's specifications. Observed differences were within the errors of the measurement technique and not clinically meaningful.

Validation of imaging-based quantification of glenohumeral joint kinematics using an unmodified clinical biplane fluoroscopy system

Model-based tracking, using CT and biplane fluoroscopy, allows highly accurate quantification of glenohumeral motion and changes in the subacromial space. Previous investigators have used custom-built biplane fluoroscopes designed specifically for kinematic applications, which are available at few institutions and require FDA approval prior to clinical use. The aim of this study was to demonstrate the utility of an off-the-shelf clinical biplane fluoroscope for kinematic applications by validating model-based tracking for measurement of glenohumeral motion using an unmodified clinical system. Biplane images of each shoulder of a cadaver torso were acquired at various joint positions and during simulated movements along anatomical planes of motion. The pose of each humerus and scapula was determined using model-based tracking and compared to a bead-based gold standard. Error due to a temporal-offset between corresponding biplane images, characteristic of clinical biplane systems, was determined by comparison of measured and known relative position of 2 bead clusters of a phantom that was imaged while moved throughout the fluoroscopy image volume. Model-based tracking had global kinematic mean absolute errors of 0.27 mm and 0.29° (static), and 0.22-0.32 mm and 0.12-0.45° (dynamic). Glenohumeral mean absolute errors were 0.39 mm and 0.45° (static), and 0.36-0.42 mm and 0.41-0.48° (dynamic). The temporal-offset was predicted to add errors of 0.06-0.85 mm and 0.05-0.28° for cadaveric trials for the speeds examined. For defined speeds, sub-millimeter and sub-degree kinematic accuracy and precision were achieved using an unmodified clinical biplane fluoroscope for quantification of glenohumeral motion.

Validation of single-plane fluoroscopy and 2D/3D shape-matching for quantifying shoulder complex kinematics

Fluoroscopy and 2D/3D shape-matching has emerged as the standard for non-invasively quantifying kinematics. However, its accuracy has not been well established for the shoulder complex when using single-plane fluoroscopy. The purpose of this study was to determine the accuracy of single-plane fluoroscopy and 2D/3D shape-matching for quantifying full shoulder complex kinematics. Tantalum markers were implanted into the clavicle, humerus, and scapula of four cadaveric shoulders. Biplane radiographs were obtained with the shoulder in five humerothoracic elevation positions (arm at the side, 30°, 60°, 90°, maximum). Images from both systems were used to perform marker tracking, while only those images acquired with the primary fluoroscopy system were used to perform 2D/3D shape-matching. Kinematics errors due to shape-matching were calculated as the difference between marker tracking and 2D/3D shape-matching and expressed as root mean square (RMS) error, bias, and precision. Overall RMS errors for the glenohumeral joint ranged from 0.7 to 3.3° and 1.2 to 4.2 mm, while errors for the acromioclavicular joint ranged from 1.7 to 3.4°. Errors associated with shape-matching individual bones ranged from 1.2 to 3.2° for the humerus, 0.5 to 1.6° for the scapula, and 0.4 to 3.7° for the clavicle. The results of the study demonstrate that single-plane fluoroscopy and 2D/3D shape-matching can accurately quantify full shoulder complex kinematics in static positions.

Quantification of intervertebral displacement with a novel MRI-based modeling technique: Assessing measurement bias and reliability with a porcine spine model

The purpose of this study was to develop a novel magnetic resonance imaging (MRI)-based modeling technique for measuring intervertebral displacements. Here, we present the measurement bias and reliability of the developmental work using a porcine spine model. Porcine lumbar vertebral segments were fitted in a custom-built apparatus placed within an externally calibrated imaging volume of an open-MRI scanner. The apparatus allowed movement of the vertebrae through pre-assigned magnitudes of sagittal and coronal translation and rotation. The induced displacements were imaged with static (T₁) and fast dynamic (2D HYCE S) pulse sequences. These images were imported into animation software, in which these images formed a background 'scene'. Three-dimensional models of vertebrae were created using static axial scans from the specimen and then transferred into the animation environment. In the animation environment, the user manually moved the models (rotoscoping) to perform model-to-'scene' matching to fit the models to their image silhouettes and assigned anatomical joint axes to the motion-segments. The animation protocol quantified the experimental translation and rotation displacements between the vertebral models. Accuracy of the technique was calculated as 'bias' using a linear mixed effects model, average percentage error and root mean square errors. Between-session reliability was examined by computing intra-class correlation coefficients (ICC) and the coefficient of variations (CV). For translation trials, a constant bias (β₀) of 0.35 (±0.11) mm was detected for the 2D HYCE S sequence (p=0.01). The model did not demonstrate significant additional bias with each mm increase in experimental translation (β₁Displacement=0.01mm; p=0.69). Using the T₁ sequence for the same assessments did not significantly change the bias (p>0.05). ICC values for the T₁ and 2D HYCE S pulse sequences were 0.98 and 0.97, respectively. For rotation trials, a constant bias (β₀) of 0.62 (±0.12)° was detected for the 2D HYCE S sequence (p<0.01). The model also demonstrated an additional bias (β₁Displacement) of 0.05° with each degree increase in the experimental rotation (p<0.01). Using T₁ sequence for the same assessments did not significantly change the bias (p>0.05). ICC values for the T₁ and 2D HYCE S pulse sequences were recorded 0.97 and 0.91, respectively. This novel quasi-static approach to quantifying intervertebral relationship demonstrates a reasonable degree of accuracy and reliability using the model-to-image matching technique with both static and dynamic sequences in a porcine model. Future work is required to explore multi-planar assessment of real-time spine motion and to examine the reliability of our approach in humans.

Marker-free motion correction in weight-bearing cone-beam CT of the knee joint

PURPOSE

To allow for a purely image-based motion estimation and compensation in weight-bearing cone-beam computed tomography of the knee joint.

METHODS

Weight-bearing imaging of the knee joint in a standing position poses additional requirements for the image reconstruction algorithm. In contrast to supine scans, patient motion needs to be estimated and compensated. The authors propose a method that is based on 2D/3D registration of left and right femur and tibia segmented from a prior, motion-free reconstruction acquired in supine position. Each segmented bone is first roughly aligned to the motion-corrupted reconstruction of a scan in standing or squatting position. Subsequently, a rigid 2D/3D registration is performed for each bone to each of K projection images, estimating 6 × 4 × K motion parameters. The motion of individual bones is combined into global motion fields using thin-plate-spline extrapolation. These can be incorporated into a motion-compensated reconstruction in the backprojection step. The authors performed visual and quantitative comparisons between a state-of-the-art marker-based (MB) method and two variants of the proposed method using gradient correlation (GC) and normalized gradient information (NGI) as similarity measure for the 2D/3D registration.

RESULTS

The authors evaluated their method on four acquisitions under different squatting positions of the same patient. All methods showed substantial improvement in image quality compared to the uncorrected reconstructions. Compared to NGI and MB, the GC method showed increased streaking artifacts due to misregistrations in lateral projection images. NGI and MB showed comparable image quality at the bone regions. Because the markers are attached to the skin, the MB method performed better at the surface of the legs where the authors observed slight streaking of the NGI and GC methods. For a quantitative evaluation, the authors computed the universal quality index (UQI) for all bone regions with respect to the motion-free reconstruction. The authors quantitative evaluation over regions around the bones yielded a mean UQI of 18.4 for no correction, 53.3 and 56.1 for the proposed method using GC and NGI, respectively, and 53.7 for the MB reference approach. In contrast to the authors registration-based corrections, the MB reference method caused slight nonrigid deformations at bone outlines when compared to a motion-free reference scan.

CONCLUSIONS

The authors showed that their method based on the NGI similarity measure yields reconstruction quality close to the MB reference method. In contrast to the MB method, the proposed method does not require any preparation prior to the examination which will improve the clinical workflow and patient comfort. Further, the authors found that the MB method causes small, nonrigid deformations at the bone outline which indicates that markers may not accurately reflect the internal motion close to the knee joint. Therefore, the authors believe that the proposed method is a promising alternative to MB motion management.

In vivo kinematic study of the tarsal joints complex based on fluoroscopic 3D-2D registration technique

The tarsal bones articulate with each other and demonstrate complicated kinematic characteristics. The in vivo motions of these tarsal joints during normal gait are still unclear. Seven healthy subjects were recruited and fourteen feet in total were tested in the current study. Three dimensional models of the tarsal bones were first created using CT scanning. Corresponding local 3D coordinate systems of each tarsal bone was subsequently established for 6DOF motion decompositions. The fluoroscopy system captured the lateral fluoroscopic images of the targeted tarsal region whilst the subject was walking. Seven key pose images during the stance phase were selected and 3D to 2D bone model registrations were performed on each image to determine joint positions. The 6DOF motions of each tarsal joint during gait were then obtained by connecting these positions together. The TNJ (talo-navicular joint) exhibited the largest ROMs (range of motion) on all rotational directions with 7.39±2.75°of dorsi/plantarflexion, 21.12±4.68°of inversion/eversion, and 16.11±4.44°of internal/external rotation. From heel strike to midstance, the TNJ, STJ (subtalar joint), and CCJ (calcaneao-cuboid joint) were associated with 5.97°, 5.04°, and 3.93°of dorsiflexion; 15.46°, 8.21°, and 5.82°of eversion; and 9.75°, 7.6°, and 4.99°of external rotation, respectively. Likewise, from midstance to heel off, the TNJ, STJ, and CCJ were associated with 6.39, 6.19°, and 4.47°of plantarflexion; 18.57°, 11.86°, and 6.32°of inversion and 13.95°, 9.66°, and 7.58°of internal rotation, respectively. In conclusion, among the tarsal joints, the TNJ exhibited the greatest rotational mobility. Synchronous and homodromous rotational motions were detected for TNJ, STJ, and CCJ during the stance phase.

Measuring Three-Dimensional Thorax Motion Via Biplane Radiographic Imaging: Technique and Preliminary Results

Measures of scapulothoracic motion are dependent on accurate imaging of the scapula and thorax. Advanced radiographic techniques can provide accurate measures of scapular motion, but the limited 3D imaging volume of these techniques often precludes measurement of thorax motion. To overcome this, a thorax coordinate system was defined based on the position of rib pairs and then compared to a conventional sternum/spine-based thorax coordinate system. Alignment of the rib-based coordinate system was dependent on the rib pairs used, with the rib3:rib4 pairing aligned to within 4.4 ± 2.1 deg of the conventional thorax coordinate system.

Dynamic Three-Dimensional Shoulder Mri during Active Motion for Investigation of Rotator Cuff Diseases

Background

MRI is the standard methodology in diagnosis of rotator cuff diseases. However, many patients continue to have pain despite treatment, and MRI of a static unloaded shoulder seems insufficient for best diagnosis and treatment. This study evaluated if Dynamic MRI provides novel kinematic data that can be used to improve the understanding, diagnosis and best treatment of rotator cuff diseases.

Methods

Dynamic MRI provided real-time 3D image series and was used to measure changes in the width of subacromial space, superior-inferior translation and anterior-posterior translation of the humeral head relative to the glenoid during active abduction. These measures were investigated for consistency with the rotator cuff diseases classifications from standard MRI.

Results

The study included: 4 shoulders with massive rotator cuff tears, 5 shoulders with an isolated full-thickness supraspinatus tear, 5 shoulders with tendinopathy and 6 normal shoulders. A change in the width of subacromial space greater than 4mm differentiated between rotator cuff diseases with tendon tears (massive cuff tears and supraspinatus tear) and without tears (tendinopathy) (p = 0.012). The range of the superior-inferior translation was higher in the massive cuff tears group (6.4mm) than in normals (3.4mm) (p = 0.02). The range of the anterior-posterior translation was higher in the massive cuff tears (9.2 mm) and supraspinatus tear (9.3 mm) shoulders compared to normals (3.5mm) and tendinopathy (4.8mm) shoulders (p = 0.05).

Conclusion

The Dynamic MRI enabled a novel measure; ‘Looseness’, i.e. the translation of the humeral head on the glenoid during an abduction cycle. Looseness was better able at differentiating different forms of rotator cuff disease than a simple static measure of relative glenohumeral position.

Development of a morphology-based modeling technique for tracking solid-body displacements: examining the reliability of a potential MRI-only approach for joint kinematics assessment

Background

Single or biplanar video radiography and Roentgen stereophotogrammetry (RSA) techniques used for the assessment of in-vivo joint kinematics involves application of ionizing radiation, which is a limitation for clinical research involving human subjects. To overcome this limitation, our long-term goal is to develop a magnetic resonance imaging (MRI)-only, three dimensional (3-D) modeling technique that permits dynamic imaging of joint motion in humans. Here, we present our initial findings, as well as reliability data, for an MRI-only protocol and modeling technique.

Methods

We developed a morphology-based motion-analysis technique that uses MRI of custom-built solid-body objects to animate and quantify experimental displacements between them. The technique involved four major steps. First, the imaging volume was calibrated using a custom-built grid. Second, 3-D models were segmented from axial scans of two custom-built solid-body cubes. Third, these cubes were positioned at pre-determined relative displacements (translation and rotation) in the magnetic resonance coil and scanned with a T₁ and a fast contrast-enhanced pulse sequences. The digital imaging and communications in medicine (DICOM) images were then processed for animation. The fourth step involved importing these processed images into an animation software, where they were displayed as background scenes. In the same step, 3-D models of the cubes were imported into the animation software, where the user manipulated the models to match their outlines in the scene (rotoscoping) and registered the models into an anatomical joint system. Measurements of displacements obtained from two different rotoscoping sessions were tested for reliability using coefficient of variations (CV), intraclass correlation coefficients (ICC), Bland-Altman plots, and Limits of Agreement analyses.

Results

Between-session reliability was high for both the T₁ and the contrast-enhanced sequences. Specifically, the average CVs for translation were 4.31 % and 5.26 % for the two pulse sequences, respectively, while the ICCs were 0.99 for both. For rotation measures, the CVs were 3.19 % and 2.44 % for the two pulse sequences with the ICCs being 0.98 and 0.97, respectively. A novel biplanar imaging approach also yielded high reliability with mean CVs of 2.66 % and 3.39 % for translation in the x- and z-planes, respectively, and ICCs of 0.97 in both planes.

Conclusions

This work provides basic proof-of-concept for a reliable marker-less non-ionizing-radiation-based quasi-dynamic motion quantification technique that can potentially be developed into a tool for real-time joint kinematics analysis.

Mobile Biplane X-Ray Imaging System for Measuring 3D Dynamic Joint Motion During Overground Gait

Most X-ray fluoroscopy systems are stationary and impose restrictions on the measurement of dynamic joint motion; for example, knee-joint kinematics during gait is usually measured with the subject ambulating on a treadmill. We developed a computer-controlled, mobile, biplane, X-ray fluoroscopy system to track human body movement for high-speed imaging of 3D joint motion during overground gait. A robotic gantry mechanism translates the two X-ray units alongside the subject, tracking and imaging the joint of interest as the subject moves. The main aim of the present study was to determine the accuracy with which the mobile imaging system measures 3D knee-joint kinematics during walking. In vitro experiments were performed to measure the relative positions of the tibia and femur in an intact human cadaver knee and of the tibial and femoral components of a total knee arthroplasty (TKA) implant during simulated overground gait. Accuracy was determined by calculating mean, standard deviation and root-mean-squared errors from differences between kinematic measurements obtained using volumetric models of the bones and TKA components and reference measurements obtained from metal beads embedded in the bones. Measurement accuracy was enhanced by the ability to track and image the joint concurrently. Maximum root-mean-squared errors were 0.33 mm and 0.65° for translations and rotations of the TKA knee and 0.78 mm and 0.77° for translations and rotations of the intact knee, which are comparable to results reported for treadmill walking using stationary biplane systems. System capability for in vivo joint motion measurement was also demonstrated for overground gait.

A Reconfigurable High-Speed Stereo-Radiography System for Sub-Millimeter Measurement of In Vivo Joint Kinematics

Relative motions within normal and pathological joints of the human body can occur on the sub-millimeter and sub-degree scale. Dynamic radiography can be used to create a rapid sequence of images from which measurements of bone motion can be extracted, but available systems have limited speed and accuracy, limit normal subject movement, and do not easily integrate into existing traditional motion capture laboratories. A high-speed stereo radiography (HSSR) system is described that addresses these limitations. The custom radiography system was placed on a standalone reconfigurable gantry structure designed to allow freedom of subject movement while integrating into an existing motion capture laboratory. Validation of the system and measurement of knee kinematics of subjects during gait confirmed the ability to record joint motion with high accuracy and high-speed.

Direct assessment of 3D foot bone kinematics using biplanar X-ray fluoroscopy and an automatic model registration method

BACKGROUND

Quantifying detailed 3-dimensional (3D) kinematics of the foot in contact with the ground during locomotion is crucial for understanding the biomechanical functions of the complex musculoskeletal structure of the foot. Biplanar X-ray fluoroscopic systems and model-based registration techniques have recently been employed to capture and visualise 3D foot bone movements in vivo, but such techniques have generally been performed manually. In the present study, we developed an automatic model-registration method with biplanar fluoroscopy for accurate measurement of 3D movements of the skeletal foot.

METHODS

Three-dimensional surface models of foot bones were generated prior to motion measurement based on computed tomography. The bone models generated were then registered to biplanar fluoroscopic images in a frame-by-frame manner using an optimisation technique, to maximise similarity measures between occluding contours of the bone surface models with edge-enhanced fluoroscopic images, while avoiding mutual penetration of bones. A template-matching method was also introduced to estimate the amount of bone translation and rotation prior to automatic registration.

RESULTS

We analysed 3D skeletal movements of a cadaver foot mobilized by a robotic gait simulator. The 3D kinematics of the calcaneus, talus, navicular and cuboid in the stance phase of the gait were successfully reconstructed and quantified using the proposed model-registration method. The accuracy of bone registration was evaluated as 0.27 ± 0.19 mm and 0.24 ± 0.19° (mean ± standard deviation) in translation and rotation, respectively, under static conditions, and 0.36 ± 0.19 mm and 0.42 ± 0.30° in translation and rotation, respectively, under dynamic conditions.

CONCLUSIONS

The measurement was confirmed to be sufficiently accurate for actual analysis of foot kinematics. The proposed method may serve as an effective tool for understanding the biomechanical function of the human foot during locomotion.

Automatic bone segmentation and bone-cartilage interface extraction for the shoulder joint from magnetic resonance images

We present a statistical shape model approach for automated segmentation of the proximal humerus and scapula with subsequent bone-cartilage interface (BCI) extraction from 3D magnetic resonance (MR) images of the shoulder region. Manual and automated bone segmentations from shoulder MR examinations from 25 healthy subjects acquired using steady-state free precession sequences were compared with the Dice similarity coefficient (DSC). The mean DSC scores between the manual and automated segmentations of the humerus and scapula bone volumes surrounding the BCI region were 0.926  ±  0.050 and 0.837  ±  0.059, respectively. The mean DSC values obtained for BCI extraction were 0.806  ±  0.133 for the humerus and 0.795  ±  0.117 for the scapula. The current model-based approach successfully provided automated bone segmentation and BCI extraction from MR images of the shoulder. In future work, this framework appears to provide a promising avenue for automated segmentation and quantitative analysis of cartilage in the glenohumeral joint.

Results of automatic image registration are dependent on initial manual registration

Measurement of static alignment of articulating joints is of clinical benefit and can be determined using image-based registration. We propose a method that could potentially improve the outcome of image-based registration by using initial manual registration. Magnetic resonance images of two wrist specimens were acquired in the relaxed position and during simulated grasp. Transformations were determined from voxel-based image registration between the two volumes. The volumes were manually aligned to match as closely as possible before auto-registration, from which standard transformations were obtained. Then, translation/rotation perturbations were applied to the manual registration to obtain altered initial positions, from which altered auto-registration transformations were obtained. Models of the radiolunate joint were also constructed from the images to simulate joint contact mechanics. We compared the sensitivity of transformations (translations and rotations) and contact mechanics to altering the initial registration condition from the defined standard. We observed that with increasing perturbation, transformation errors appeared to increase and values for contact force and contact area appeared to decrease. Based on these preliminary findings, it appears that the final registration outcome is sensitive to the initial registration.

Kinematics of the shoulder joint in tennis players

OBJECTIVES

Shoulder pain and injury are common in tennis players. The precise causes for such pain remain unclear. Impingement at critical tennis positions and glenohumeral instability have never been dynamically evaluated in vivo. The purpose of this study was to evaluate the different types of impingement and stability during tennis movements.

DESIGN

Laboratory study.

METHODS

Type and frequency of impingement as well as percentage of subluxation were evaluated in 10 tennis players through a novel dedicated patient-specific measurement technique based on optical motion capture and Magnetic Resonance Imaging (MRI).

RESULTS

All volunteers, nine male and one female, had a clinically functional rotator cuff. MRI revealed 11 rotator cuff lesions in six subjects and six labral lesions in five subjects. Lateral subacromial, anterior subacromial, internal anterosuperior, and internal posterosuperior impingements were observed in four, three, two and seven subjects, respectively. No instability could be demonstrated in this population.

CONCLUSIONS

Tennis players presented frequent radiographic signs of structural lesions that could mainly be related to posterosuperior impingements due to repetitive abnormal motion contacts. This is the first study demonstrating that a dynamic and precise motion analysis of the entire kinematic chain of the shoulder is possible through a non-invasive method of investigation. This premier kinematic observation offers novel insights into the analysis of shoulder impingement and instability that could, with future studies, be generalized to other shoulder pathologies and sports. This original method may open new horizons leading to improvement in impingement comprehension.

A patient-specific measurement technique to model shoulder joint kinematics

BACKGROUND

Measuring dynamic in vivo shoulder kinematics is crucial to better understanding numerous pathologies. Motion capture systems using skin-mounted markers offer good solutions for non-invasive assessment of shoulder kinematics during dynamic movement. However, none of the current motion capture techniques have been used to study translation values at the joint, which is crucial to assess shoulder instability. The aim of the present study was to develop a dedicated patient-specific measurement technique based on motion capture and magnetic resonance imaging (MRI) to determine shoulder kinematics accurately.

HYPOTHESIS

Estimation of both rotations and translations at the shoulder joint using motion capture is feasible thanks to a patient-specific kinematic chain of the shoulder complex reconstructed from MRI data.

MATERIALS AND METHODS

We implemented a patient-specific kinematic chain model of the shoulder complex with loose constraints on joint translation. To assess the effectiveness of the technique, six subjects underwent data acquisition simultaneously with fluoroscopy and motion capture during flexion and empty-can abduction. The reference 3D shoulder kinematics was reconstructed from fluoroscopy and compared to that obtained from the new technique using skin markers.

RESULTS

Root mean square errors (RMSE) for shoulder orientation were within 4° (mean range: 2.0°-3.4°) for each anatomical axis and each motion. For glenohumeral translations, maximum RMSE for flexion was 3.7mm and 3.5mm for empty-can abduction (mean range: 1.9-3.3mm). Although the translation errors were significant, the computed patterns of humeral translation showed good agreement with published data.

DISCUSSION

To our knowledge, this study is the first attempt to calculate both rotations and translations at the shoulder joint based on skin-mounted markers. Results were encouraging and can serve as reference for future developments. The proposed technique could provide valuable kinematic data for the study of shoulder pathologies.

LEVEL OF EVIDENCE

Basic Science Study.

Dynamic comparison of segmentary scapulohumeral rhythm between athletes with and without impingement syndrome

Background:

Patients who have shoulder pain usually have compensatory or contributory deviation of shoulder motion during arm elevation. In the traditional scapulohumeral rhythm, the share of the acromioclavicular (AC) and the sternoclavicular (SC) joint movements and also the role of AC internal rotation angle are unknown.

Objectives:

The main purpose of this study was to measure and compare the segmentary scapulohumeral rhythm (SSHR) during scapular arm elevation at a steady rotational speed in athletes with and without impingement syndrome.

Patients and Methods:

Using a speedometer, the maximum speed of arm elevation was measured in 21 men in each of the involved and uninvolved groups. Using fluoroscopy on the dominant side, SSHR during scapular arm elevation at a rotational speed equal to 1/30 of maximum speed was compared between the two groups. The ratio of glenohumeral (GH) elevation angle to AC rotation angle in the scapular plane was considered as SSHR.

Results:

The maximum speed of arm elevation between the two groups was significantly different (P < 0.001). The rhythm of the involved group significantly exceeded the rhythm of the uninvolved group in a part of the first quarter range of the arm elevation. SSHR during arm elevation in the uninvolved group did not change significantly (P = 0.845); however, it decreased significantly in the involved group (P = 0.024).

Conclusions:

Speed differences between the two groups were probably due to the pain in some ranges of arm elevation. SSHR in the involved group probably changed in order to compensate downward rotation of the scapula in the resting position. Study of the AC upward rotation range can be misleading; therefore, the study of scapulohumeral rhythm is recommended.

Glenohumeral joint cartilage contact in the healthy adult during scapular plane elevation depression with external humeral rotation

The shoulder (glenohumeral) joint has the greatest range of motion of all human joints; as a result, it is particularly vulnerable to dislocation and injury. The ability to non-invasively quantify in-vivo articular cartilage contact patterns of joints has been and remains a difficult biomechanics problem. As a result, little is known about normal in-vivo glenohumeral joint contact patterns or the consequences that surgery has on altering them. In addition, the effect of quantifying glenohumeral joint contact patterns by means of proximity mapping, both with and without cartilage data, is unknown. Therefore, the objectives of this study are to (1) describe a technique for quantifying in-vivo glenohumeral joint contact patterns during dynamic shoulder motion, (2) quantify normal glenohumeral joint contact patterns in the young healthy adult during scapular plane elevation depression with external humeral rotation, and (3) compare glenohumeral joint contact patterns determined both with and without articular cartilage data. Our results show that the inclusion of articular cartilage data when quantifying in-vivo glenohumeral joint contact patterns has significant effects on the anterior-posterior contact centroid location, the superior-inferior contact centroid range of travel, and the total contact path length. As a result, our technique offers an advantage over glenohumeral joint contact pattern measurement techniques that neglect articular cartilage data. Likewise, this technique may be more sensitive than traditional 6-Degree-of-Freedom (6-DOF) joint kinematics for the assessment of overall glenohumeral joint health. Lastly, for the shoulder motion tested, we found that glenohumeral joint contact was located on the anterior-inferior glenoid surface.

3D CT to 2D low dose single-plane fluoroscopy registration algorithm for in-vivo knee motion analysis

A limitation to accurate automatic tracking of knee motion is the noise and blurring present in low dose X-ray fluoroscopy images. For more accurate tracking, this noise should be reduced while preserving anatomical structures such as bone. Noise in low dose X-ray images is generated from different sources, however quantum noise is by far the most dominant. In this paper we present an accurate multi-modal image registration algorithm which successfully registers 3D CT to 2D single plane low dose noisy and blurred fluoroscopy images that are captured for healthy knees. The proposed algorithm uses a new registration framework including a filtering method to reduce the noise and blurring effect in fluoroscopy images. Our experimental results show that the extra pre-filtering step included in the proposed approach maintains higher accuracy and repeatability for in vivo knee joint motion analysis.

Robust 3D-2D image registration: application to spine interventions and vertebral labeling in the presence of anatomical deformation

We present a framework for robustly estimating registration between a 3D volume image and a 2D projection image and evaluate its precision and robustness in spine interventions for vertebral localization in the presence of anatomical deformation. The framework employs a normalized gradient information similarity metric and multi-start covariance matrix adaptation evolution strategy optimization with local-restarts, which provided improved robustness against deformation and content mismatch. The parallelized implementation allowed orders-of-magnitude acceleration in computation time and improved the robustness of registration via multi-start global optimization. Experiments involved a cadaver specimen and two CT datasets (supine and prone) and 36 C-arm fluoroscopy images acquired with the specimen in four positions (supine, prone, supine with lordosis, prone with kyphosis), three regions (thoracic, abdominal, and lumbar), and three levels of geometric magnification (1.7, 2.0, 2.4). Registration accuracy was evaluated in terms of projection distance error (PDE) between the estimated and true target points in the projection image, including 14 400 random trials (200 trials on the 72 registration scenarios) with initialization error up to ±200 mm and ±10°. The resulting median PDE was better than 0.1 mm in all cases, depending somewhat on the resolution of input CT and fluoroscopy images. The cadaver experiments illustrated the tradeoff between robustness and computation time, yielding a success rate of 99.993% in vertebral labeling (with 'success' defined as PDE <5 mm) using 1,718 664 ± 96 582 function evaluations computed in 54.0 ± 3.5 s on a mid-range GPU (nVidia, GeForce GTX690). Parameters yielding a faster search (e.g., fewer multi-starts) reduced robustness under conditions of large deformation and poor initialization (99.535% success for the same data registered in 13.1 s), but given good initialization (e.g., ±5 mm, assuming a robust initial run) the same registration could be solved with 99.993% success in 6.3 s. The ability to register CT to fluoroscopy in a manner robust to patient deformation could be valuable in applications such as radiation therapy, interventional radiology, and an assistant to target localization (e.g., vertebral labeling) in image-guided spine surgery.

New dynamic three-dimensional MRI technique for shoulder kinematic analysis

PURPOSE

To establish a new imaging technique using dynamic MRI three-dimensional (3D) volumetric acquisition in real-time, on six normal shoulders for the analysis of the 3D shoulder kinematics during continuous motion.

MATERIALS AND METHODS

At first, a standard static acquisition was performed. Then, fast images were obtained with a multi-slice 3D balanced gradient echo sequence to get a real time series during the initial phase of shoulder abduction. Subsequently, the images were reconstructed; registered and the translational patterns of the humeral head relative to the glenoid and the size of the subacromial space were calculated. Additionally, the intraobserver reproducibility was tested.

RESULTS

The maximal abduction was on average 43° (30° to 60°) and the mean width of the subacromial space was 7.7 mm (SD: ±1.2 mm). Difference between extreme values and average values was low, respectively 2.5 mm on X-axis, 2 mm on Y-axis, 1.4 mm for the width of the subacromial space and 1.2° for the measure of the glenohumeral abduction.

CONCLUSION

This study reported a dynamic MRI protocol for the monitoring of shoulder 3D kinematics during continuous movement. The results suggest that there is no superior shift of the humeral head during the first phase of abduction.