Advancing quantitative techniques to improve understanding of the skeletal structure-function relationship.

Although all functional movement arises from the interplay between the neurological, skeletal, and muscular systems, it is the skeletal system that forms the basic framework for functional movement. Central to understanding human neuromuscular development, along with the genesis of musculoskeletal pathologies, is quantifying how the human skeletal system adapts and mal-adapts to its mechanical environment. Advancing this understanding is hampered by an inability to directly and non-invasively measure in vivo strains, stresses, and forces on bone. Thus, we traditionally have turned to animal models to garner such information. These models enable direct in vivo measures that are not available for human subjects, providing information in regards to both skeletal adaptation and the interplay between the skeletal and muscular systems. Recently, there has been an explosion of new imaging and modeling techniques providing non-invasive, in vivo measures and estimates of skeletal form and function that have long been missing. Combining multiple modalities and techniques has proven to be one of our most valuable resources in enhancing our understanding of the form-function relationship of the human skeletal, muscular, and neurological systems. Thus, to continue advancing our knowledge of the structural-functional relationship, validation of current tools is needed, while development is required to limit the deficiencies in these tools and develop new ones.

Biomechanical Analysis of a Dynamic Stability Test System to Evoke Sway and Step Recovery.

This paper reports on the dynamic analysis and experimental validation of a method to perturb the balance of subjects in quiet standing. Electronically released weights pull the subject's waist through a specified displacement sensed by a photoelectric sensor. A dynamic model is derived that computes the force applied to the subject as a function of waist acceleration. This model accurately predicts the acceleration of mock subjects (suspended masses) with high repeatability. The validity and simplicity of this model suggest that this method can provide a standard for provocation testing on stable surfaces. Proof-of-concept trials on human subjects demonstrate that the device can be used with a force platform and motion tracking and that the device can induce both sway and step recoveries in healthy male adults.

Tie-fibre structure and organization in the knee menisci.

The collagenous structure of the knee menisci is integral to the mechanical integrity of the tissue and the knee joint. The tie-fibre structure of the tissue has largely been neglected, despite previous studies demonstrating its correlation with radial stiffness. This study has evaluated the structure of the tie-fibres of bovine menisci using 2D and 3D microscopy techniques. Standard collagen and proteoglycan (PG) staining and 2D light microscopy techniques were conducted. For the first time, the collagenous structure of the menisci was evaluated using 3D, second harmonic generation (SHG) microscopy. This technique facilitated the imaging of collagen structure in thick sections (50-100 µm). Imaging identified that tie-fibres of the menisci arborize from the outer margin of the meniscus toward the inner tip. This arborization is associated with the structural arrangement of the circumferential fibres. SHG microscopy has definitively demonstrated the 3D organization of tie-fibres in both sheets and bundles. The hierarchy of the structure is related to the organization of circumferential fascicles. Large tie-fibre sheets bifurcate into smaller sheets to surround circumferential fascicles of decreasing size. The tie-fibres emanate from the lamellar layer that appears to surround the entire meniscus. At the tibial and femoral surfaces these tie-fibre sheets branch perpendicularly into the meniscal body. The relationship between tie-fibres and blood vessels in the menisci was also observed in this study. Tie-fibre sheets surround the blood vessels and an associated PG-rich region. This subunit of the menisci has not previously been described. The size of tie-fibre sheets surrounding the vessels appeared to be associated with the size of blood vessel. These structural findings have implications in understanding the mechanics of the menisci. Further, refinement of the complex structure of the tie-fibres is important in understanding the consequences of injury and disease in the menisci. The framework of meniscus architecture also defines benchmarks for the development of tissue-engineered replacements in the future.

Ankle kinematics and muscle activity in functional ankle instability.

OBJECTIVE: Following an ankle injury, many patients have functional ankle instability (FAI) with an increased predisposition to reinjury. The purpose of this study was to assess the effects of FAI on ankle kinematics and muscle activity during a lateral hop movement. DESIGN: Cross-sectional and observational study; all data collection for each subject was performed on 1 day. SETTING: Clinical biomechanics laboratory. PATIENTS: Two groups were studied: (1) Control group-no ankle injury (n = 12), and (2) FAI group (n = 12). INTERVENTIONS: The lateral hop movement consisted of multiple lateral and medial 1-legged hops over an obstacle (width, 72.5 cm; depth, 25.5 cm; height, 14.3 cm) onto adjacent force platforms. Each subject was instructed to perform as many lateral hops as possible during the 6-second trial. Means, SDs, 95% confidence intervals of the differences, and P-values were calculated. MAIN OUTCOME MEASURES: Ankle kinematics and muscle activity throughout the lateral hop movement. RESULTS: Significant differences existed between groups for mean (SD) dorsiflexion ankle positions--FAI 82.4 degrees (6.4) versus normal 75.2 degrees (10.1) and tibialis anterior normalized muscle activity--FAI 0.27 (0.21) versus normal 0.16 (0.13) at ground contact. CONCLUSIONS: The FAI group revealed greater tibialis anterior muscle activity and dorsiflexion ankle position at contact moving in the lateral direction. These differences between groups may have been related to an inherent predisposition to ankle injuries, a preexisting difference in task performance, a consequence of injuries, or a compensatory adaptation to previous injuries.

A Rigorous 2D-3D Registration Method for a High-Speed Bi-Planar Videoradiography Imaging System.

High-speed biplanar videoradiography can derive the dynamic bony translations and rotations required for joint cartilage contact mechanics to provide insights into the mechanical processes and mechanisms of joint degeneration or pathology. A key challenge is the accurate registration of 3D bone models (from MRI or CT scans) with 2D X-ray image pairs. Marker-based or model-based 2D-3D registration can be performed. The former has higher registration accuracy owing to corresponding marker pairs. The latter avoids bead implantation and uses radiograph intensity or features. A rigorous new method based on projection strategy and least-squares estimation that can be used for both methods is proposed and validated by a 3D-printed bone with implanted beads. The results show that it can achieve greater marker-based registration accuracy than the state-of-the-art RSA method. Model-based registration achieved a 3D reconstruction accuracy of 0.79 mm. Systematic offsets between detected edges in the radiographs and their actual position were observed and modeled to improve the reconstruction accuracy to 0.56 mm (tibia) and 0.64 mm (femur). This method is demonstrated on in vivo data, achieving a registration precision of 0.68 mm (tibia) and 0.60 mm (femur). The proposed method allows the determination of accurate 3D kinematic parameters that can be used to calculate joint cartilage contact mechanics.

Patellofemoral joint geometry and osteoarthritis features 3-10 years after knee injury compared with uninjured knees.

In this cross-sectional study, we compared patellofemoral geometry in individuals with a youth-sport-related intra-articular knee injury to uninjured individuals, and the association between patellofemoral geometry and magnetic resonance imaging (MRI)-defined osteoarthritis (OA) features. In the Youth Prevention of Early OA (PrE-OA) cohort, we assessed 10 patellofemoral geometry measures in individuals 3-10 years following injury compared with uninjured individuals of similar age, sex, and sport, using mixed effects linear regression. We also dichotomized geometry to identify extreme (>1.96 standard deviations) features and assessed likelihood of having extreme values using Poisson regression. Finally, we evaluated the associations between patellofemoral geometry with MRI-defined OA features using restricted cubic spline regression. Mean patellofemoral geometry did not differ substantially between groups. However, compared with uninjured individuals, injured individuals were more likely to have extremely large sulcus angle (prevalence ratio [PR] 3.9 [95% confidence interval, CI: 2.3, 6.6]), and shallow lateral trochlear inclination (PR 4.3 (1.1, 17.9)) and trochlear depth (PR 5.3 (1.6, 17.4)). In both groups, high bisect offset (PR 1.7 [1.3, 2.1]) and sulcus angle (PR 4.0 [2.3, 7.0]) were associated with cartilage lesion, and most geometry measures were associated with at least one structural feature, especially cartilage lesions and osteophytes. We observed no interaction between geometry and injury. Certain patellofemoral geometry features are correlated with higher prevalence of structural lesions compared with injury alone, 3-10 years following knee injury. Hypotheses generated in this study, once further evaluated, could contribute to identifying higher-risk individuals who may benefit from targeted treatment aimed at preventing posttraumatic OA.

An evaluation of meniscal collagenous structure using optical projection tomography.

BACKGROUND: The collagenous structure of menisci is a complex network of circumferentially oriented fascicles and interwoven radially oriented tie-fibres. To date, examination of this micro- architecture has been limited to two-dimensional imaging techniques. The purpose of this study was to evaluate the ability of the three-dimensional imaging technique; optical projection tomography (OPT), to visualize the collagenous structure of the meniscus. If successful, this technique would be the first to visualize the macroscopic orientation of collagen fascicles in 3-D in the meniscus and could further refine load bearing mechanisms in the tissue. OPT is an imaging technique capable of imaging samples on the meso-scale (1-10 mm) at a micro-scale resolution. The technique, similar to computed tomography, takes two-dimensional images of objects from incremental angles around the object and reconstructs them using a back projection algorithm to determine three-dimensional structure. METHODS: Bovine meniscal samples were imaged from four locations (outer main body, femoral surface, tibial surface and inner main body) to determine the variation in collagen orientation throughout the tissue. Bovine stifles (n = 2) were obtained from a local abattoir and the menisci carefully dissected. Menisci were fixed in methanol and subsequently cut using a custom cutting jig (n = 4 samples per meniscus). Samples were then mounted in agarose, dehydrated in methanol and subsequently cleared using benzyl alcohol benzyl benzoate (BABB) and imaged using OPT. RESULTS: Results indicate circumferential, radial and oblique collagenous orientations at the contact surfaces and in the inner third of the main body of the meniscus. Imaging identified fascicles ranging from 80-420 µm in diameter. Transition zones where fascicles were found to have a woven or braided appearance were also identified. The outer-third of the main body was composed of fascicles oriented predominantly in the circumferential direction. Blood vessels were also visualized using this technique, as their elastin content fluoresces more brightly than collagen at the 425 nm wavelength used by the OPT scanner. CONCLUSIONS: OPT was capable of imaging the collagenous structure, as well as blood vessels in the bovine meniscus. Collagenous structure variability, including transition zones between structural regions not previously described in the meniscus, was identified using this novel technique.

Empirical joint contact mechanics: A comprehensive review.

Empirical joint contact mechanics measurement (EJCM; e.g. contact area or force, surface velocities) enables critical investigations of the relationship between changing joint mechanics and the impact on surface-to-surface interactions. In orthopedic biomechanics, understanding the changes to cartilage contact mechanics following joint pathology or aging is critical due to its suggested role in the increased risk of osteoarthritis (OA), which might be due to changed kinematics and kinetics that alter the contact patterns within a joint. This article reviews and discusses EJCM approaches that have been applied to articulating joints such that readers across different disciplines will be informed of the various measurement and analysis techniques used in this field. The approaches reviewed include classical measurement approaches (radiographic and sectioning, dye staining, casting, surface proximity, and pressure measurement), stereophotogrammetry/motion analysis, computed tomography (CT), magnetic resonance imaging (MRI), and high-speed videoradiography. Perspectives on approaches to advance this field of EJCM are provided, including the value of considering relative velocity in joints, tractional stress, quantification of joint contact area shape, consideration of normalization techniques, net response (superposition) of multiple input variables, and establishing linkages to regional cartilage health status. EJCM measures continue to provide insights to advance our understanding of cartilage health and degeneration and provide avenues to assess the efficacy and guide future directions of developing interventions (e.g. surgical, biological, rehabilitative) to optimize joint's health and function long term.

Comparison of Dynamic Knee Contact Mechanics with T2 Imaging in Different Ages of Healthy Participants.

Aging is a known risk factor for Osteoarthritis (OA), however, relations between cartilage composition and aging remain largely unknown in understanding human OA. T2 imaging provides an approach to assess cartilage composition. Whether these T2 relaxation times in the joint contact region change with time during gait remain unexplored. The study purpose was to demonstrate a methodology for linking dynamic joint contact mechanics to cartilage composition as measured by T2 relaxometry. T2 relaxation times for unloaded cartilage were measured in a 3T General Electric magnetic resonance (MR) scanner in this preliminary study. High-speed biplanar video-radiography (HSBV) was captured for five 20-30-year-old and five 50-60-year-old participants with asymptomatic knees. By mapping the T2 cartilages to the dynamic contact regions, T2 values were averaged over the contact area at each measurement within the gait cycle. T2 values demonstrated a functional relationship across the gait cycle. There were no statistically significant differences between 20- and 30-year-old and 50-60-year-old participant T2 values at first force peak of the gait cycle in the medial femur (p = 1.00, U = 12) or in the medial tibia (p = 0.31, U = 7). In the medial and lateral femur in swing phase, the joint moved from a region of high T2 values at 75% of gait to a minimum at 85-95% of swing. The lateral femur and tibia demonstrated similar patterns to the medial compartments but were less pronounced. This research advances understanding of the linkage between cartilage contact and cartilage composition. The change from a high T2 value at ~ 75% of gait to a lower value near the initiation of terminal swing (90% gait) indicates that there are changes to T2 averages corresponding to changes in the contact region across the gait cycle. No differences were found between age groups for healthy participants. These preliminary findings provide interesting insights into the cartilage composition corresponding to dynamic cyclic motion and inform mechanisms of osteoarthritis.

Tricompartment offloader knee brace reduces sagittal plane knee moments, quadriceps muscle activity, and pain during chair rise and lower in individuals with knee osteoarthritis.

The Levitation tricompartment offloader (TCO) knee brace provides an assistive knee extension moment with the goal of unloading all three compartments of the knee and reducing pain for individuals with multicompartment knee osteoarthritis (OA). This study aimed to determine the effect of the TCO brace on sagittal plane knee moments, quadriceps muscle activity, and pain in individuals with multicompartment knee OA. Lower limb kinematics, kinetics, and electromyography data were collected during a chair rise and lower to determine differences between bracing conditions. TCO brace use significantly decreased the peak net knee external flexion moment in high power mode, providing extension assistance during chair rise [p<0.001; mean difference (MD) (98.75% CI) -0.8 (-1.0, -0.6)%BWxH] and bodyweight support during chair lower [p<0.001; -1.1 (-1.6, -0.7)%BWxH]. Quadriceps activation intensity was significantly reduced with brace use by up to 67% for the vastus medialis [Z = -2.55, p = 0.008] and up to 39% for the vastus lateralis [Z = -2.67, p = 0.004]. Participants reported significantly reduced knee pain with the TCO brace worn in high power mode compared to the no brace condition [p = 0.014; MD (97.5% CI) -18.8 (-32.22, -2.34) mm]. These results support the intended mechanism of joint unloading via extension assistance with the TCO brace. The observed biomechanical changes were accompanied by immediate reductions in user reported pain levels, and support the use of the TCO for conservative management to reduce knee pain in patients with multicompartment knee OA.

Self-supervised-RCNN for medical image segmentation with limited data annotation.

Many successful methods developed for medical image analysis based on machine learning use supervised learning approaches, which often require large datasets annotated by experts to achieve high accuracy. However, medical data annotation is time-consuming and expensive, especially for segmentation tasks. To overcome the problem of learning with limited labeled medical image data, an alternative deep learning training strategy based on self-supervised pretraining on unlabeled imaging data is proposed in this work. For the pretraining, different distortions are arbitrarily applied to random areas of unlabeled images. Next, a Mask-RCNN architecture is trained to localize the distortion location and recover the original image pixels. This pretrained model is assumed to gain knowledge of the relevant texture in the images from the self-supervised pretraining on unlabeled imaging data. This provides a good basis for fine-tuning the model to segment the structure of interest using a limited amount of labeled training data. The effectiveness of the proposed method in different pretraining and fine-tuning scenarios was evaluated based on the Osteoarthritis Initiative dataset with the aim of segmenting effusions in MRI datasets of the knee. Applying the proposed self-supervised pretraining method improved the Dice score by up to 18% compared to training the models using only the limited annotated data. The proposed self-supervised learning approach can be applied to many other medical image analysis tasks including anomaly detection, segmentation, and classification.

Tricompartment offloader knee brace reduces contact forces in adults with multicompartment knee osteoarthritis.

The levitation tricompartment offloader (TCO) brace is designed to unload all three knee compartments by reducing compressive forces caused by muscle contraction. This study aimed to determine the effect of the TCO on knee contact forces and quadriceps muscle activity in individuals with knee osteoarthritis. Lower limb kinematics, kinetics, and electromyography data were collected during a chair rise-and-lower task. A three-dimensional inverse dynamics model of the lower leg and foot was used with a sagittal plane knee model to compute knee joint forces. TCO brace use significantly decreased forces in the tibiofemoral [p = 0.001; mean difference, MD (97.5% confidence interval, CI) -0.62 (-0.91, -0.33) body weight (BW)] and patellofemoral [p = 0.001; MD (97.5% CI) -0.88 (-1.36, -0.39) BW] compartments in high-power mode. Significant reductions in quadriceps tendon force [p = 0.002; MD (97.5% CI) -0.53 (-0.83, -0.23) BW] and electromyography intensity of the vastus medialis [p = 0.018, MD (97.5% CI) -30.7 (-59.1, -2.3)] and vastus lateralis [p = 0.012, MD (97.5% CI) -26.2 (-48.5, -3.9)] were also observed. The TCO significantly reduced tibiofemoral and patellofemoral contact forces throughout chair lower, and when knee flexion was greater than 50° during chair rise in high power. These results demonstrate that the TCO reduces contact forces in the tibiofemoral and patellofemoral joint compartments and confirms that the TCO unloads the joint by reducing compressive forces caused by the quadriceps. Clinical significance: The magnitude of knee joint unloading provided by the TCO is similar to that achieved by clinically recommended levels of bodyweight loss and is therefore expected to result in clinical benefits for knee osteoarthritis patients.

Lateral hop movement assesses ankle dynamics and muscle activity.

Ankle function is frequently measured using static or dynamic tasks in normal and injured patients. The purpose of this study was to develop a novel task to quantify ankle dynamics and muscle activity in normal subjects. Twelve subjects with no prior ankle injuries participated. Video motion analysis cameras, force platforms, and an EMG system were used to collect data during a lateral hop movement task that consisted of multiple lateral-medial hops over an obstacle. Mean (SD) inversion ankle position at contact was 4.4° (4.0) in the medial direction and -3.5° (4.4) in the lateral direction; mean (SD) tibialis anterior normalized muscle activity was 0.11 (0.08) in the medial direction and 0.16 (0.13) in the lateral direction. The lateral hop movement was shown to be an effective task for quantifying ankle kinematics, forces, moments, and muscle activities in normal subjects. Future applications will use the lateral hop movement to assess subjects with previous ankle injuries in laboratory and clinical settings.

Improved-Mask R-CNN: Towards an accurate generic MSK MRI instance segmentation platform (data from the Osteoarthritis Initiative).

INTRODUCTION: Objective assessment of osteoarthritis (OA) Magnetic Resonance Imaging (MRI) scans can address the limitations of the current OA assessment approaches. Detecting and extracting bone, cartilage, and joint fluid is a necessary component for the objective assessment of OA, which helps to quantify tissue characteristics such as volume and thickness. Many algorithms, based on Artificial Intelligence (AI), have been proposed over recent years for segmenting bone and soft tissues. Most of these segmentation methods suffer from the class imbalance problem, can't differentiate between the same anatomic structure, or do not support segmenting different rang of tissue sizes. Mask R-CNN is an instance segmentation framework, meaning it segments and distinct each object of interest like different anatomical structures (e.g. bone and cartilage) using a single model. In this study, the Mask R-CNN architecture was deployed to address the need for a segmentation method that is applicable to use for different tissue scales, pathologies, and MRI sequences associated with OA, without having a problem with imbalanced classes. In addition, we modified the Mask R-CNN to improve segmentation accuracy around instance edges. METHODS: A total of 500 adult knee MRI scans from the publicly available Osteoarthritis Initiative (OAI), and 97 hip MRI scans from adults with symptomatic hip OA, evaluated by two readers, were used for training and validating the network. Three specific modifications to Mask R-CNN yielded the improved-Mask R-CNN (iMaskRCNN): an additional ROIAligned block, an extra decoder block in the segmentation header, and connecting them using a skip connection. The results were evaluated using Hausdorff distance, dice score for bone and cartilage segmentation, and differences in detected volume, dice score, and coefficients of variation (CoV) for effusion segmentation. RESULTS: The iMaskRCNN led to improved bone and cartilage segmentation compared to Mask RCNN as indicated with the increase in dice score from 95% to 98% for the femur, 95-97% for the tibia, 71-80% for the femoral cartilage, and 81-82% for the tibial cartilage. For the effusion detection, the dice score improved with iMaskRCNN 72% versus Mask R-CNN 71%. The CoV values for effusion detection between Reader1 and Mask R-CNN (0.33), Reader1 and iMaskRCNN (0.34), Reader2 and Mask R-CNN (0.22), Reader2 and iMaskRCNN (0.29) are close to CoV between two readers (0.21), indicating a high agreement between the human readers and both Mask R-CNN and iMaskRCNN. CONCLUSION: Mask R-CNN and iMaskRCNN can reliably and simultaneously extract different scale articular tissues involved in OA, forming the foundation for automated assessment of OA. The iMaskRCNN results show that the modification improved the network performance around the edges.

Validation of a magnetic resonance imaging based method to study passive knee laxity: An in-situ study.

Knee laxity can be described as an increased anterior tibial translation (ATT) or decreased stiffness of the tibiofemoral joint under an applied force. Küpper et al. (2013, 2016) and Westover et al. (2016) previously developed and reported on a magnetic resonance (MR)-based in vivo measure of knee laxity. In this study, the application of an in situ knee loading apparatus (ISKLA) is presented as a step toward validating the MR-based methodology for measuring ATT and stiffness. The ISKLA is designed to measure these outcome variables using MR imaging and is validated against a gold-standard ElectroForce mechanical test instrument (TA Instruments 3550). Accuracy was assessed through an in situ experimental setup by testing four cadaveric specimens with both the MR-based methodology and in the ElectroForce system. The outcome of the current study showed that the MR-based ATTs and stiffness measurements using the ISKLA were within 1.44-2.10 mm and 0.16-6.14 N/mm, respectively, of the corresponding values measured by the gold standard system. An excellent ICC was observed for ATT (0.97) and good ICC for stiffness (0.87) between the MR and ElectroForce-based systems across all target force levels. These findings suggest that the MR-based approach can be used with satisfactory accuracy and correlation to the gold standard measure.

Concurrent validity and reliability of a semi-automated approach to measuring the magnetic resonance imaging morphology of the knee joint in active youth.

Post-traumatic knee osteoarthritis is attributed to alterations in joint morphology, alignment, and biomechanics triggered by injury. While magnetic resonance (MR) imaging-based measures of joint morphology and alignment are relevant to understanding osteoarthritis risk, time consuming manual data extraction and measurement limit the number of outcomes that can be considered and deter widespread use. This paper describes the development and evaluation of a semi-automated software for measuring tibiofemoral and patellofemoral joint architecture using MR images from youth with and without a previous sport-related knee injury. After prompting users to identify and select key anatomical landmarks, the software can calculate 37 (14 tibiofemoral, 23 patellofemoral) relevant geometric features (morphology and alignment) based on established methods. To assess validity and reliability, 11 common geometric features were calculated from the knee MR images (proton density and proton density fat saturation sequences; 1.5 T) of 76 individuals with a 3-10-year history of youth sport-related knee injury and 76 uninjured controls. Spearman's or Pearson's correlation coefficients (95% CI) and Bland-Altman plots were used to assess the concurrent validity of the semi-automated software (novice rater) versus expert manual measurements, while intra-class correlation coefficients (ICC2,1; 95%CI), standard error of measurement (95%CI), 95% minimal detectable change, and Bland-Altman plots were used to assess the inter-rater reliability of the semi-automated software (novice vs resident radiologist rater). Correlation coefficients ranged between 0.89 (0.84, 0.92; Lateral Trochlear Inclination) and 0.97 (0.96, 0.98; Patellar Tilt Angle). ICC estimates ranged between 0.79 (0.63, 0.88; Lateral Patellar Tilt Angle) and 0.98 (0.95, 0.99; Bisect Offset). Bland-Altman plots did not reveal systematic bias. These measurement properties estimates are equal, if not better than previously reported methods suggesting that this novel semi-automated software is an accurate, reliable, and efficient alternative method for measuring large numbers of geometric features of the tibiofemoral and patellofemoral joints from MR studies.

Kinematics of the head and associated vertebral artery length changes during high-velocity, low-amplitude cervical spine manipulation.

BACKGROUND: Cervical spine manipulation (CSM) is a frequently used treatment for neck pain. Despite its demonstrated efficacy, concerns regarding the potential of stretch damage to vertebral arteries (VA) during CSM remain. The purpose of this study was to quantify the angular displacements of the head relative to the sternum and the associated VA length changes during the thrust phase of CSM. METHODS: Rotation and lateral flexion CSM procedures were delivered bilaterally from C1 to C7 to three male cadaveric donors (Jan 2016-Dec 2019). For each CSM the force-time profile was recorded using a thin, flexible pressure pad (100-200 Hz), to determine the timing of the thrust. Three dimensional displacements of the head relative to the sternum were recorded using an eight-camera motion analysis system (120-240 Hz) and angular displacements of the head relative to the sternum were computed in Matlab. Positive kinematic values indicate flexion, left lateral flexion, and left rotation. Ipsilateral refers to the same side as the clinician's contact and contralateral, the opposite. Length changes of the VA were recorded using eight piezoelectric ultrasound crystals (260-557 Hz), inserted along the entire vessel. VA length changes were calculated as D = (L1 - L0)/L0, where L0 = length of the whole VA (sum of segmental lengths) or the V3 segment at CSM thrust onset; L1 = whole VA or V3 length at peak force during the CSM thrust. RESULTS: Irrespective of the type of CSM, the side or level of CSM application, angular displacements of the head and associated VA length changes during the thrust phase of CSM were small. VA length changes during the thrust phase were largest with ipsilateral rotation CSM (producing contralateral head rotation): [mean ± SD (range)] whole artery [1.3 ± 1.0 (- 0.4 to 3.3%)]; and V3 segment [2.6 ± 3.6 (- 0.4 to 11.6%)]. CONCLUSIONS: Mean head angular displacements and VA length changes were small during CSM thrusts. Of the four different CSM measured, mean VA length changes were largest during rotation procedures. This suggests that if clinicians wish to limit VA length changes during the thrust phase of CSM, consideration should be given to the type of CSM used.

Time series spinal radiographs as prognostic factors for scoliosis and progression of spinal deformities.

The effectiveness of clinical measures to predict scoliotic progression is unclear. The objective of this study was to identify potential prognostic factors affecting scoliosis progression. Consecutive measurements (181) from 35 non-instrumented adolescent idiopathic scoliosis patients with at least two follow-up assessments were studied. Potential prognostic factors of gender, curve pattern, age, curve magnitude, apex location and lateral deviation and spinal growth were analyzed. Stable and progressed groups were compared (threshold: Cobb angle ≥5° or 10°) with sequential clinical data collected in 6-month intervals. Double curves progressed simultaneously or alternatively on curve regions. Age was not significantly different prior to and at maximal Cobb angle. Maximal Cobb angles were significantly correlated to initial Cobb angles (r = 0.81-0.98). Progressed males had larger initial Cobb angles than progressed females. Apex locations were higher in progressed than stable groups, and at least a half vertebra level higher in females than males. Maximal apex lateral deviations correlated significantly with the initial ones (r = 0.73-0.97) and moderately with maximal Cobb angles (r = 0.33-0.85). In the progressed groups, males had larger apex lateral deviations than females. Spinal growth did not relate to curve progression (r = -0.64 to +0.59) and was not significantly different between groups and genders. Scoliosis may dynamically progress between major and minor curves. Gender, curve magnitude, apex location and lateral deviation have stronger effects on scoliosis progression than age or spinal growth. Females with high apex locations may be expected to progress.

Vertical Drop Jump Biomechanics of Patients With a 3- to 10-Year History of Youth Sport-Related Anterior Cruciate Ligament Reconstruction.

BACKGROUND: A better understanding of movement biomechanics after anterior cruciate ligament reconstruction (ACLR) could inform injury prevention, knee injury rehabilitation, and osteoarthritis prevention strategies. PURPOSE: To investigate differences in vertical drop jump (VDJ) biomechanics between patients with a 3- to 10-year history of youth sport-related ACLR and uninjured peers of a similar age, sex, and sport. STUDY DESIGN: Cross-sectional study. Level of evidence III. METHODS: Lower limb kinematics and bilateral ground-reaction forces (GRFs) were recorded for participants performing 10 VDJs. Joint angles and GRF data were analyzed, and statistical analysis was performed using 2 multivariate models. Dependent variables included sagittal (ankle, knee, and hip) and coronal (knee and hip) angles at initial contact and maximum knee flexion, the rate of change of coronal knee angles (35%-90% of the support phase; ie, slopes of linear regression lines), and vertical and mediolateral GRFs (normalized to body weight [BW]). Fixed effects included group, sex, and time since injury. Participant clusters, defined by sex and sport, were considered as random effects. RESULTS: Participants included 48 patients with a history of ACLR and 48 uninjured age-, sex-, and sport-matched controls (median age, 22 years [range, 18-26 years]; 67% female). Patients with ACLR demonstrated steeper negative coronal knee angle slopes (ß = -0.04 deg/% [95% CI, -0.07 to -0.00 deg/%]; P = .025). A longer time since injury was associated with reduced knee flexion (ß = -0.2° [95% CI, -0.3° to -0.0°]; P = .014) and hip flexion (ß = -0.1° [95% CI, -0.2° to -0.0°]; P = .018). Regardless of ACLR history, women displayed greater knee valgus at initial contact (ß = 2.1° [95% CI, 0.4° to 3.8°]; P = .017), greater coronal knee angle slopes (ß = 0.05 deg/% [95% CI, 0.02 to 0.09 deg/%]; P = .004), and larger vertical GRFs (landing: ß = -0.34 BW [95% CI, -0.61 to -0.07 BW]; P = .014) (pushoff: ß = -0.20 BW [95% CI, -0.32 to -0.08 BW]; P = .001). CONCLUSION: Women and patients with a 3- to 10-year history of ACLR demonstrated VDJ biomechanics that may be associated with knee motion control challenges. CLINICAL RELEVANCE: It is important to consider knee motion control during activities such as VDJs when developing injury prevention and rehabilitation interventions aimed at improving joint health after youth sport-related ACLR.

Volumetric quantitative measurement of hip effusions by manual versus automated artificial intelligence techniques: An OMERACT preliminary validation study.

OBJECTIVE: Preliminary assessment, via OMERACT filter, of manual and automated MRI hip effusion Volumetric Quantitative Measurement (VQM). METHODS: For 358 hips (93 osteoarthritis subjects, bilateral, 2 time points), 2 radiologists performed manual VQM using custom Matlab software. A Mask R-CNN artificial-intelligence (AI) tool was trained to automatically compute joint fluid volumes. RESULTS: Manual VQM had excellent inter-observer reliability (ICC 0.96). AI predicted hip fluid volumes with ICC 0.86 (status), 0.58 (change) vs. 2 human readers. CONCLUSION: Hip joint fluid volumes are reliably assessed by VQM. It is feasible to automate this approach using AI, with promising initial reliability.