Exosomal LRG1 promotes non-small cell lung cancer proliferation and metastasis by binding FN1 protein.

Leucine-rich α2-glycoprotein-1 (LRG1) is overexpressed in various cancers, including non-small cell lung cancer (NSCLC), but its role in NSCLC cell metastasis is not well understood. In this study, NSCLC cell exosomes were analyzed using different techniques, and the impact of exosomal LRG1 on NSCLC cell behavior was investigated through various assays both in vitro and in vivo. The study revealed that LRG1, found abundantly in NSCLC cells and exosomes, enhanced cell proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT). Exosomal LRG1 was shown to promote NSCLC cell metastasis in animal models. Additionally, the interaction between LRG1 and fibronectin 1 (FN1) in the cytoplasm was identified. It was observed that FN1 could counteract the effects of LRG1 knockdown on cell regulation induced by exosomes derived from NSCLC cells. Overall, the findings suggest that targeting exosomal LRG1 or FN1 may hold therapeutic potential for treating NSCLC.

Tibiofemoral articulation and axial tibial rotation of the knee after a cruciate retaining total knee arthroplasty.

PURPOSE: Numerous research has reported that total knee arthroplasty (TKA) cannot reproduce axial tibial rotations of normal knees. The objective of this study was to measure the tibiofemoral articular contact motions and axial tibial rotations of TKA knees to investigate the mechanism causing the knee kinematics change of after TKAs. METHODS: Eleven patients with unilateral cruciate retaining (CR) TKA were tested for measurements of knee motion during a weight-bearing flexion from 0° to 105° using an imaging technique. The tibiofemoral contact kinematics were determined using the contact points on medial and lateral surfaces of the tibia and femoral condyles. Axial tibial rotations were calculated using the differences between the medial and lateral articulation distances on the femoral condyles and tibial surfaces at each flexion interval of 15°. RESULTS: On femoral condyles, articular contact distances are consistently longer on the medial than on the lateral sides (p < 0.05) up to 60° of flexion, corresponding to internal tibial rotations (e.g., 1.3° ± 1.0° at 15-30° interval). On tibial surfaces, the articular contact point on the medial side moved more posteriorly than on the lateral side at low flexion angles, corresponding to external tibial rotations (e.g., -1.4° ± 1.8° at 15-30° interval); and more anteriorly than on the lateral sides at mid-range flexion, corresponding to internal tibial rotations (e.g., 0.8° ± 1.7° at 45-60° interval). At higher flexion, articular motions on both femoral condyles and tibial surfaces caused minimal changes in tibial rotations. CONCLUSIONS: These results indicate that the axial tibial rotations of these TKA knees were mainly attributed to asymmetric articulations on the medial and lateral femoral condyles and tibial surfaces. The data can help understand the mechanisms causing axial tibial rotations of TKA knees and help improve implant designs for restoration of normal knee kinematics.

Rh(III)-Catalyzed C7-Alkylation of Isatogens with Malonic Acid Diazoesters.

Rh(III)-catalyzed C7-alkylation of isatogens (indolin-3-one N-oxides) with malonic acid diazoesters has been developed. This strategy utilizes oxygen anion on the N-oxide group of isatogens as a directing group and successfully achieves the synthesis of a series of C7-alkylated isatogens with moderate to good yields (48-86% yields). Moreover, the N-oxides of isatogens can not only serve as the simple directing group for C7-H bond cleavage but also be deoxidized for easy removal.

Background Subtraction Angiography with Deep Learning Using Multi-frame Spatiotemporal Angiographic Input.

Catheter Digital Subtraction Angiography (DSA) is markedly degraded by all voluntary, respiratory, or cardiac motion artifact that occurs during the exam acquisition. Prior efforts directed toward improving DSA images with machine learning have focused on extracting vessels from individual, isolated 2D angiographic frames. In this work, we introduce improved 2D + t deep learning models that leverage the rich temporal information in angiographic timeseries. A total of 516 cerebral angiograms were collected with 8784 individual series. We utilized feature-based computer vision algorithms to separate the database into "motionless" and "motion-degraded" subsets. Motion measured from the "motion degraded" category was then used to create a realistic, but synthetic, motion-augmented dataset suitable for training 2D U-Net, 3D U-Net, SegResNet, and UNETR models. Quantitative results on a hold-out test set demonstrate that the 3D U-Net outperforms competing 2D U-Net architectures, with substantially reduced motion artifacts when compared to DSA. In comparison to single-frame 2D U-Net, the 3D U-Net utilizing 16 input frames achieves a reduced RMSE (35.77 ± 15.02 vs 23.14 ± 9.56, p < 0.0001; mean ± std dev) and an improved Multi-Scale SSIM (0.86 ± 0.08 vs 0.93 ± 0.05, p < 0.0001). The 3D U-Net also performs favorably in comparison to alternative convolutional and transformer-based architectures (U-Net RMSE 23.20 ± 7.55 vs SegResNet 23.99 ± 7.81, p < 0.0001, and UNETR 25.42 ± 7.79, p < 0.0001, mean ± std dev). These results demonstrate that multi-frame temporal information can boost performance of motion-resistant Background Subtraction Deep Learning algorithms, and we have presented a neuroangiography domain-specific synthetic affine motion augmentation pipeline that can be utilized to generate suitable datasets for supervised training of 3D (2d + t) architectures.

Evaluating outcome associations with race after mechanical thrombectomy: an analysis of the NVQI-QOD acute ischemic stroke registry.

BACKGROUND: Mechanical thrombectomy has become the standard of care for acute ischemic stroke due to large vessel occlusions. Racial differences in outcomes after mechanical thrombectomy for acute ischemic stroke have not been extensively studied. We evaluate the real-world evidence for differences between races in the outcomes of thrombectomy for large vessel occlusions using the NeuroVascular Quality Initiative-Quality Outcomes Database (NVQI-QOD). METHODS: Data from the NVQI-QOD acute ischemic stroke registry were analyzed and compared for racial differences in outcomes after mechanical thrombectomy in 4507 patients from 28 US centers (17 states) between January 2014 and April 2021. Race was dichotomized into non-Hispanic White (NHW, n=3649) and non-Hispanic Black (NHB, n=858). We performed 1:1 propensity score matching resulting in a subsample of matched groups (n=761 each for NHB and NHW) to compare study endpoints using Welch's two-sided t-tests and Χ2 test for continuous and categorical outcomes, respectively. RESULTS: Prior to matching, NHW and NHB patients significantly differed in age, comorbidities, medication use, smoking status, and presenting stroke severity. No significant difference in functional outcomes or mortality, at discharge or follow-up, were revealed. NHB patients had higher average postprocedure length of stay than NHW patients, which persisted following matching (11.2 vs 9.1 days, P=0.004). CONCLUSION: Evidence from the NVQI-QOD acute ischemic stroke registry showed that outcome metrics, such as modified Rankin Scale score and mortality, did not differ significantly between racial groups; however, disparity between NHW and NHB patients in postprocedure length of stay following mechanical thrombectomy was revealed.

Evaluation of bone mineral density in adolescent idiopathic scoliosis using a three-dimensional finite element model: a retrospective study.

BACKGROUND: Adolescent idiopathic scoliosis (AIS) is often accompanied by osteopenia and osteoporosis, which can cause serious complications. The aim of this study was to determine the specific bone mineral density (BMD) of each vertebral body in patients with AIS using biomechanical finite element modeling based on three-dimensional (3D) reconstruction. METHODS: This retrospective study involved 56 patients with AIS. Computed tomography (CT) and radiography were performed. Spinal vertebrae were segmented from the spinal CT images of patients with AIS to reconstruct 3D vertebral models. The vertebral models were meshed into tetrahedral finite elements to assess the BMD. RESULTS: The mean main curve Cobb angle was 88.6 ± 36.7°, and the mean kyphosis angle was 36.8 ± 31.5°. The mean BMD of the global spine was 0.83 ± 0.15 g/cm2. The highest BMD was measured on the concave side of the apex (0.98 ± 0.16 g/cm2). Apical vertebral BMD was negatively correlated with age and height (r = - 0.490, p = 0.009 and r = - 0.478, p = 0.043, respectively). There were no significant differences in BMD values between the concave and convex sides (p > 0.05). CONCLUSIONS: The 3D finite element modeling of BMD in patients with AIS is a reliable and accurate BMD measurement method. Using this method, the overall BMD of patients with AIS was shown to gradually decrease from the top to the bottom of the spine. Our findings provide valuable insights for surgical planning, choice of screw trajectories, and additional biomechanical analyzes using finite element models in the context of scoliosis.

Investigation of Characteristic Motion Patterns of the Knee Joint During a Weightbearing Flexion.

This study aimed to develop and validate a novel flexion axis concept by calculating the points on femoral condyles that could maintain constant heights during knee flexion. Twenty-two knees of 22 healthy subjects were investigated when performing a weightbearing single leg lunge. The knee positions were captured using a validated dual fluoroscopic image system. The points on sagittal planes of the femoral condyles that had minimal changes in heights from the tibial plane along the flexion path were calculated. It was found that the points do formulate a medial-lateral flexion axis that was defined as the iso-height axis (IHA). The six degrees of freedom (6DOF) kinematics data calculated using the IHA were compared with those calculated using the conventional transepicondylar axis and geometrical center axis. The IHA measured minimal changes in proximal-distal translations and varus-valgus rotations along the flexion path, indicating that the IHA may have interesting clinical implications. Therefore, identifying the IHA could provide an alternative physiological reference for improvement of contemporary knee surgeries, such as ligament reconstruction and knee replacement surgeries that are aimed to reproduce normal knee kinematics and medial/lateral soft tissue tensions during knee flexion.

mfeeU-Net: A multi-scale feature extraction and enhancement U-Net for automatic liver segmentation from CT Images.

Medical image segmentation of the liver is an important prerequisite for clinical diagnosis and evaluation of liver cancer. For automatic liver segmentation from Computed Tomography (CT) images, we proposed a Multi-scale Feature Extraction and Enhancement U-Net (mfeeU-Net), incorporating Res2Net blocks, Squeeze-and-Excitation (SE) blocks, and Edge Attention (EA) blocks. The Res2Net blocks which are conducive to extracting multi-scale features of the liver were used as the backbone of the encoder, while the SE blocks were also added to the encoder to enhance channel information. The EA blocks were introduced to skip connections between the encoder and the decoder, to facilitate the detection of blurred liver edges where the intensities of nearby organs are close to the liver. The proposed mfeeU-Net was trained and evaluated using a publicly available CT dataset of LiTS2017. The average dice similarity coefficient, intersection-over-union ratio, and sensitivity of the mfeeU-Net for liver segmentation were 95.32%, 91.67%, and 95.53%, respectively, and all these metrics were better than those of U-Net, Res-U-Net, and Attention U-Net. The experimental results demonstrate that the mfeeU-Net can compete with and even outperform recently proposed convolutional neural networks and effectively overcome challenges, such as discontinuous liver regions and fuzzy liver boundaries.

Physiological Axial Tibial Rotation of the Knee During a Weightbearing Flexion.

Axial tibial rotation is a characteristic motion of the knee, but how it occurs with knee flexion is controversial. We investigated the mechanisms of tibial rotations by analyzing in vivo tibiofemoral articulations. Twenty knees of 20 living human subjects were investigated during a weightbearing flexion from full extension to maximal flexion using a dual fluoroscopic imaging system. Tibiofemoral articular contact motions on medial and lateral femoral condyles and tibial surfaces were measured at flexion intervals of 15 deg from 0 deg to 120 deg. Axial tibial rotations due to the femoral and tibial articular motions were compared. Articular contact distances were longer on femoral condyles than on tibial surfaces at all flexion intervals (p < 0.05). The articular distance on medial femoral condyle is longer than on lateral side during flexion up to 60 deg. The internal tibial rotation was 6.8 ± 4.5 deg (Mean ± SD) at the flexion interval of 0-15 deg, where 6.1 ± 2.6 deg was due to articulations on femoral condyles and 0.7 ± 5.1 deg due to articulations on tibial surfaces (p < 0.05). The axial tibial rotations due to articulations on femoral condyles are significantly larger than those on tibial surfaces until 60 deg of flexion (p < 0.05). Minimal additional axial tibial rotations were observed beyond 60 deg of flexion. The axial tibial rotations were mainly attributed to uneven articulations on medial and lateral femoral condyles. These data can provide new insights into the understanding of mechanisms of axial tibial rotations and serve as baseline knowledge for improvement of knee surgeries.

Does contemporary bicruciate retaining total knee arthroplasty restore the native knee kinematics? A descriptive literature review.

BACKGROUND: There has been no consensus on the benefit of retaining the anterior cruciate ligament (ACL) in TKAs. This study aims to review recent evidences around the kinematics of bicruciate retaining (BCR) total knee arthroplasty (TKA). MATERIALS AND METHODS: A search of the literature was conducted on PubMed and Web of Science. Reports that assessed the BCR TKA kinematics, including both in vitro cadaveric studies and in vivo clinical studies, were reviewed. RESULTS: A total number of 169 entries were obtained. By exclusion criteria, five in vitro studies using cadaveric knee specimens and six in vivo studies using patient cohorts were retained. In vitro studies showed a low internal rotation (< 10°) throughout the flexion path in all BCR TKAs. Compared to native knees, the difference in the internal rotation was maximal during early and late flexion; the femur in the BCR TKA was significantly more anteriorly positioned (1.7-3.6 mm from 0° to 110°) and more externally rotated (3.6°-4.2° at 110° and 120°). In vivo studies revealed that the native knee kinematics, in general, were not fully restored after BCR TKA during various knee activates (squatting, level-walking, and downhill-walking). There are asymmetric kinematics during the stance phase of gait cycle and a smaller range of axial rotation (23% patients exhibiting external tibial rotation) throughout the gait cycle in BCR TKAs. CONCLUSIONS: Critical insights in the complex BCR TKA biomechanics have been reported from recent laboratory kinematics studies. However, whether contemporary BCR TKAs can fully restore native knee kinematics remains debatable, warranting further investigations.

Investigation of femoral condyle height changes during flexion of the knee: implication to gap balance in TKA surgery.

BACKGROUND: Gap balance of the knee at 0° and 90° of flexion has been pursued in total knee arthroplasty (TKA) with the trans-epicondyle axis (TEA) as a reference. This study investigated the height changes of the tibiofemoral articulation and compared the data with the femoral condyle height changes measured using different flexion axes. MATERIALS AND METHODS: Twenty healthy knees were investigated during an in vivo weightbearing flexion using a technique combining MRI and a dual fluoroscopic imaging system (DFIS). The tibiofemoral contact points and the femoral condyle heights [measured using: TEA, geometric center axis (GCA), and iso-height axis (IHA)] were determined at each flexion angle. The height changes of the articular contact points and the femoral condyles were compared along the flexion path. RESULTS: The changes of the medial and lateral contact point heights were within 2.5 mm along the flexion path. The changes of the medial and lateral condyle heights were within 8.9 mm for TEA, within 4.2 mm for GCA and within 3.0 mm for IHA. The height changes measured by the contact points and IHA are similar (p > 0.05), and both are significantly smaller than those measured using the TEA and GCA (p < 0.05). CONCLUSIONS: The TEA and GCA measured varying femoral condyle heights, but the IHA resulted in minimal condyle height changes and could better represent the articulation characteristics of the knee. The data suggested that the IHA could be used as an alternative reference to guide surgical preparation of gap balance along the knee flexion path during TKA surgeries.

Articulation of the femoral condyle during knee flexion.

Femoral condyle motion of the knee is generally reported using a morphological trans-epicondyle axis (TEA) or geometric center axis (GCA) in the investigation of the knee kinematics. Axial rotation of the femur is recognized as a characteristic motion of the knee during flexion, but is controversial in the literature. This study investigated the biomechanical factors that could be associated to the axial rotations of the femur using both physiological and morphological measurement methods. Twenty healthy knees were investigated during a weightbearing flexion from 0° to 120° at a 15° increment using an imaging technique. A 3D model was constructed for each knee using MR images. Tibiofemoral cartilage contact points were determined at each flexion position to represent physiological knee motion. The contact distance on each condyle was measured between consecutive contact points. The TEA and GCA were used to measure morphological anteroposterior translations of the femoral condyles. The differences between the medial and lateral condyle motions were used to calculate the physiological and morphological axial rotations of the femur. Both the physiological and morphological methods measured external rotations of the femur at low flexion range (0°-45°) and minimal rotations at higher flexion angles. However, the morphological method measured larger posterior translations of the lateral femoral condyle than the medial condyle (p < 0.05), implying a medial pivoting rotation; in contrast, the physiological method measured larger contact distances on the medial condyle than on the lateral condyle (p < 0.05), implying a lateral pivoting rotation. These data could provide useful references for future investigation of kinematics of the knee before and after surgical repair, such as using total knee arthroplasty.

3D Geometric Shape Reconstruction for Revision TKA and UKA Knees Using Gaussian Process Regression.

Revision knee surgery is complicated by distortion of previous components and removal of additional bone, potentially causing misalignment and inappropriate selection of implants. In this study, we reconstructed the native femoral and tibial surface shapes in simulated total/unicompartmental knee arthroplasty (TKA/UKA) for 20 femurs and 20 tibias using a statistical inference method based on Gaussian Process regression. Compared to the true geometry, the average absolute errors (mean absolute distances) in the prediction of resected femur bones in TKA, medial UKA, and lateral UKA were 1.0 ± 0.3 mm, 1.0 ± 0.3 mm, and 0.8 ± 0.2 mm, respectively, while those in the prediction of tibia resections in the corresponding surgeries were 1.0 ± 0.4 mm, 0.8 ± 0.2 mm, and 0.7 ± 0.2 mm, respectively. Furthermore, it was found that the prediction accuracy depends on the size and gender of the resected bone. For example, the prediction accuracy for UKA cuts was significantly better than that for TKA cuts (p < 0.05). The female and male cuts were often overfit and underfit, respectively. The data indicated that this reconstruction approach can be a viable option for planning of revision surgeries, especially when contralateral anatomy is pathological or cannot be available.

Transfer learning from an artificial radiograph-landmark dataset for registration of the anatomic skull model to dual fluoroscopic X-ray images.

Registration of 3D anatomic structures to their 2D dual fluoroscopic X-ray images is a widely used motion tracking technique. However, deep learning implementation is often impeded by a paucity of medical images and ground truths. In this study, we proposed a transfer learning strategy for 3D-to-2D registration using deep neural networks trained from an artificial dataset. Digitally reconstructed radiographs (DRRs) and radiographic skull landmarks were automatically created from craniocervical CT data of a female subject. They were used to train a residual network (ResNet) for landmark detection and a cycle generative adversarial network (GAN) to eliminate the style difference between DRRs and actual X-rays. Landmarks on the X-rays experiencing GAN style translation were detected by the ResNet, and were used in triangulation optimization for 3D-to-2D registration of the skull in actual dual-fluoroscope images (with a non-orthogonal setup, point X-ray sources, image distortions, and partially captured skull regions). The registration accuracy was evaluated in multiple scenarios of craniocervical motions. In walking, learning-based registration for the skull had angular/position errors of 3.9 ± 2.1°/4.6 ± 2.2 mm. However, the accuracy was lower during functional neck activity, due to overly small skull regions imaged on the dual fluoroscopic images at end-range positions. The methodology to strategically augment artificial training data can tackle the complicated skull registration scenario, and has potentials to extend to widespread registration scenarios.

Investigation of in vivo three-dimensional changes of the spinal canal after corrective surgeries of the idiopathic scoliosis.

OBJECTIVE: To determine the three-dimensional (3D) changes of the spinal canal length (SCL) after corrective surgeries and their association with the radiographic and clinical outcomes of idiopathic scoliosis patients. The length of the spinal cord has been demonstrated to be strongly correlated with the SCL. Understanding the changes in SCL could help determine the morphologic changes in the spinal cord to prevent spinal cord injury. METHODS: Twenty-seven scoliotic patients' 3D spinal canal were investigated using computed tomography images. The SCL between the upper and lower end vertebrae (U/L-EV) was measured at five locations. The radiographic parameters of each patient and the patient-reported outcomes (PROs) scores were also collected. The correlations of the changes of the SCLs with the other factors were analyzed. RESULTS: The SCL between the U/L-EV changed non-uniformly at different locations. The post-operative SCLs were significantly elongated by 7.5 ± 3.5 mm (6.0 ± 2.5%, P < .001) at the concave side and compressed by -2.6 ± 2.6 mm (-1.9 ± 1.9%, P < .001) at the convex side. The elongations of the SCL at the concave and posterior locations were correlated with the radiographic parameters including the pre-operative main Cobb angles (r = .511, P = .006; r = .613, P = .001) and apical vertebral translation (AVT) (r = .481, P = .011; r = .684, P = .000). No PRO scores were found to correlate with the SCL changes. CONCLUSION: The corrective surgeries elongated the spinal canal mainly at the concave side and compressed at the convex side. The main thoracic Cobb angle, the changes of AVT, and Cobb angles were moderately associated with the changes of the SCLs, but no PRO score was found to associate with the changes of the SCLs. The data could be instrumental for the improvement of corrective surgeries that are aimed to maximize the correction of scoliosis and minimize the negative effect on the spinal cord to prevent neurological complications.

Ligament deformation patterns of the craniocervical junction during head axial rotation tracked by biplane fluoroscopes.

BACKGROUND: Frequently, treatment decisions for craniocervical injuries and instability are based on imaging findings, but in vivo ligament kinematics were poorly understood. This study was to determine in vivo deformation patterns of primary ligaments in the craniocervical junction (i.e., C0-2), including the cruciform ligament, alar ligaments, and accessory ligaments, during dynamic head axial rotation. METHODS: The skulls and cervical spines of eight asymptomatic female subjects were dynamically imaged using a biplane fluoroscopic imaging system, when they performed left and right head axial rotations. Using a 3D-to-2D registration technique, the in vivo positions and orientations of cervical segments were determined. An optimization algorithm was implemented to determine ligament wrapping paths, and the resulting ligament deformations were represented by percent elongations. Using paired t-tests, ligament deformations in the end-range position were compared to those in the neutral position. FINDINGS: No significant differences were observed in segmental motions during left and right head rotations (p > 0.05). In general, slight deformations occurred in each component of the cruciform ligament. For the alar ligaments, the ipsilateral ligament was lengthened from -0.7 ± 13.8% to 16.6 ± 15.7% (p < 0.001*). For the accessory ligaments, the contralateral ligament was lengthened from -2.9 ± 7.5% to 10.1 ± 6.2% (p < 0.001*). INTERPRETATION: This study reveals that there are distinct deformation patterns in craniocervical junction ligaments during dynamic axial head rotation. These ligament deformation data can enhance our understanding of the synergic function of craniocervical junction ligaments, and guide the treatment of craniocervical instability.

Influence of structural and material property uncertainties on biomechanics of intervertebral discs - Implications for disc tissue engineering.

This study investigated how variations of structural and material properties of human intervertebral discs (IVDs) affect the biomechanical responses of the IVDs under simulated physiological loading conditions using a stochastic finite element (SFE) model. An SFE method, which combined an anatomic FE model of human lumbar L3-4 segment and probabilistic analysis of its structural and material properties, was used to generate a dataset of 500 random disc samples with varying structural and material properties. The sensitivity of the biomechanical responses, including intervertebral displacements/rotations, intradiscal pressures (IDP), fiber stresses and matrix strains of annulus fibrosus (AF), were systematically quantified under various physiological loading conditions, including a 500N compression and 7.5Nm moments in the 3 primary rotations. Significant variations of the IDPs, IVD displacements/rotations, and stress/strain distributions were found using the dataset of 500 ramdom disc samples. Under all the loading conditions, the IDPs were positively correlated with the Poisson's ratio of the NP (r = 0.46 to 0.75, p = 0.004-0.001) and negatively with the Young's modulus of the annulus matrix (r = -0.48 to -0.65, p = 0.003-0.001). The primary intervertebral rotations were significantly affected by the Young's modulus of the annulus matrix (r = -0.44 to -0.71, p = 0.001-0.032) and the orientations of the annular fibers (r = -0.45 to -0.69, p = 0.001-0.029). The heterogeneity of structures and material properties of the IVD had distinct effects on the biomechanical performances of the IVD. These data could help improve our understanding of the intrinsic biomechanics of the IVD and provide references for optimal design of tissue engineered discs by controlling structural and material properties of the disc components.

Prediction of biomechanical responses of human lumbar discs - a stochastic finite element model analysis.

BACKGROUND: Accurate biomechanical investigation of human intervertebral discs (IVDs) is difficult because of their complicated structural and material features. AIM: To investigate probabilistic distributions of the biomechanical responses of the IVD by considering varying nonlinear structural and material properties using a stochastic finite element (FE) model. METHODS: A FE model of a L3-4 disc was reconstructed, including the nucleus pulposus (NP), annular matrix and fibers. A Monte Carlo method was used to randomly generate 500 sets of the nonlinear material properties and fiber orientations of the disc that were implemented into the FE model. The FE model was analyzed under seven loading conditions: a 500 N compressive force, a 7.5Nm moment simulating flexion, extension, left-right lateral bending, and left-right axial rotation, respectively. The distributions of the ranges of motion (ROMs), intradiscal pressures (IDP), fiber stresses and matrix strains of the disc were analyzed. RESULTS: Under the compressive load, the displacement varied between 0.29 mm and 0.76 mm. Under the 7.5Nm moment, the ROMs varied between 3.0° and 6.0° in primary rotations. The IDPs varied within 0.3 MPa under all the loading conditions. The maximal fiber stress (3.22 ± 0.64 MPa) and matrix strain (0.27 ± 0.12%) were observed under the flexion and extension moments, respectively. CONCLUSION: The IVD biomechanics could be dramatically affected by the structural and material parameters used to construct the FE model. The stochastic FE model that includes the probabilistic distributions of the structural and material parameters provides a useful approach to analyze the statistical ranges of the biomechanical responses of the IVDs.

In vivo primary and coupled segmental motions of the healthy female head-neck complex during dynamic head axial rotation.

While previous studies have greatly improved our knowledge on the motion capability of the cervical spine, few reported on the kinematics of the entire head-neck complex (C0-T1) during dynamic activities of the head in the upright posture. This study investigated in vivo kinematics of the entire head-neck complex (C0-T1) of eight female asymptomatic subjects during dynamic left-right head axial rotation using a dual fluoroscopic imaging system and 3D-to-2D registration techniques. During one-sided head rotation (i.e., left or right head rotation), the primary rotation of the overall head-neck complex (C0-T1) reached 55.5 ± 10.8°, the upper cervical spine region (C0-2) had a primary axial rotation of 39.7 ± 9.6° (71.3 ± 8.5% of the overall C0-T1 axial rotation), and the lower cervical spine region (C2-T1) had a primary rotation of 10.0 ± 3.7° (18.6 ± 7.2% of the overall C0-T1 axial rotation). Coupled bending rotations occurred in the upper and lower cervical spine regions in similar magnitude but opposite directions (upper: contralateral bending of 18.2 ± 5.9° versus lower: ipsilateral bending of 21.4 ± 5.1°), resulting in a compensatory cervical lateral curvature that balances the head to rotate horizontally. Furthermore, upper cervical segments (C0-1 or C1-2) provided main mobility in different rotational degrees of freedom needed for head axial rotations. Additionally, we quantitatively described both coupled segmental motions (flexion-extension and lateral bending) by correlation with the overall primary axial rotation of the head-neck complex. This investigation offers comprehensive baseline data regarding primary and coupled motions of craniocervical segments during head axial rotation.

Physiological articular contact kinematics and morphological femoral condyle translations of the tibiofemoral joint.

The changes of tibiofemoral articular cartilage contact locations during knee activities represent a physiological functional characteristic of the knee. However, most studies reported relative motions of the tibia and femur using morphological flexion axes. Few data have been reported on comparisons of morphological femoral condyle motions and physiological tibiofemoral cartilage contact location changes. This study compared the morphological and physiological kinematic measures of 20 knees during an in vivo weightbearing single leg lunge from full extension to 120° of flexion using a combined MRI and dual fluoroscopic imaging system (DFIS) technique. The morphological femoral condyle motion was measured using three flexion axes: trans-epicondylar axis (TEA), geometric center axis (GCA) and iso-height axis (IHA). At low flexion angles, the medial femoral condyle moved anteriorly, opposite to that of the contact points, and was accompanied with a sharp increase in external femoral condyle rotation. At 120° of flexion, the morphological measures of the lateral femoral condyle were more posteriorly positioned than those of the contact locations. The data showed that the morphological measures of femoral condyle translations and axial rotations varied with different flexion axes and did not represent the physiological articular contact kinematics. Biomechanical evaluations of the knee joint motion should include both morphological and physiological kinematics data to accurately demonstrate the functionality of the knee.