An Introduction to Factored Regression Models with Blimp

In this paper, we provide an introduction to the factored regression framework. This modeling framework applies the rules of probability to break up or “factor” a complex joint distribution into a product of conditional regression models. Using this framework, we can easily specify the complex multivariate models that missing data modeling requires. The article provides a brief conceptual overview of factored regression and describes the functional notation used to conceptualize the models. Furthermore, we present a conceptual overview of how the models are estimated and imputations are obtained. Finally, we discuss how users can use the free software package, Blimp, to estimate the models in the context of a mediation example.

Overuse-related instability of the elbow: the role of CT-arthrography

The elbow is a complex joint whose biomechanical function is granted by the interplay and synergy of various anatomical structures. Articular stability is achieved by both static and dynamic constraints, which consist of osseous as well as soft-tissue components. Injuries determining instability frequently involve several of these structures. Therefore, accurate knowledge of regional anatomy and imaging findings is fundamental for a precise diagnosis and an appropriate clinical management of elbow instability. This review focuses particularly on the varied appearance of overuse-related elbow injuries at CT-arthrography.

Biomechanics of the Canine Elbow Joint

The canine elbow joint is a complex joint, whose musculoskeletal anatomy is well investigated. During the last 30 years kinematic analysis has gained importance in veterinary research and kinematics of the healthy and medial coronoid disease affected canine elbow joint are progressively investigated. Video-kinematographic analysis represents the most commonly used technique and multiple studies have investigated the range of motion, angular velocity, duration of swing and stance phase, stride length and other kinematic parameters, mostly in the sagittal plane only. However, this technique is more error-prone and data gained by video-kinematography represent the kinematics of the whole limb including the soft tissue envelope. A more precise evaluation of the in vivo bone and joint movement can only been achieved using fluoroscopic kinematography. Based on recent studies significant differences in the motion pattern between healthy joints and elbows with medial coronoid disease could be detected. Thereby not only adaptive changes, caused by pain and lameness, could be described, but primary changes in the micromotion of the joint forming bones could be found, which potentially represent new factors in the pathogenesis of medial coronoid disease. This chapter gives a review of current literature on elbow joint kinematics, with particular focus onto pathologic biomechanics in dysplastic canine elbows.

Determination of Blood Vessel Parameters by Pulse Wave

A pulse wave is a complex joint motion of blood and vessel walls described by a nonlinear system of differential equations of hydrodynamics and elasticity theory with a mobile boundary. Even an approximate solution to such a problem is currently not possible without significant simplifications, reducing the problem to almost uninteresting cases. Therefore, to mathematically describe the practically important changes in the pulse wave between the norm and pathology and to identify the main physical parameters that characterize the pathology, it is necessary to build a phenomenological model, the parameters of which are determined from comparison with the experiment.The results obtained indicate that the pulse wave transformation in the cuff area is significantly nonlinear in pressure. Attention is also drawn to the effect of a decrease in the elastic modulus with an increase in the diameter of the vessel.

Dysplastic Patellofemoral Joints Lead to a Shift in Contact Forces: A 3D-Printed Cadaveric Model

Background: The distribution of contact forces across the dysplastic patellofemoral joint has not been adequately quantified because models cannot easily mimic the dysplasia of both the trochlea and the patella. Thus, the mechanical consequences of surgical treatments to correct dysplasia cannot be established. Purpose/Hypothesis: The objective of this study was to quantify the contact mechanics and kinematics of normal, mild, and severely dysplastic patellofemoral joints using synthetic mimics of the articulating surfaces on cadavers. We tested the hypothesis that severely dysplastic joints would result in significantly increased patellofemoral contact forces and abnormal kinematics. Study Design: Controlled laboratory study. Method: Patellofemoral dysplasia was simulated in 9 cadaveric knees by replacing the native patellar and trochlear surfaces with synthetic patellar and trochlear implants. For each knee, 3 synthetic surface geometries (normal, showing no signs of dysplasia; mild, exemplifying Dejour type A; and severe, exemplifying Dejour type B) were randomized for implantation and testing. Patellar kinematics and the sum of forces acting on the medial and lateral patellar facets were computed for each knee and for each condition at 10° increments from 0° to 70° of flexion. Results: A pronounced lateral shift in the weighted center of contact of the lateral facet occurred for severely dysplastic knees from 20° to 70° of flexion. Compared with normal geometries, lateral patellar facet forces exhibited a significant increase only with mild dysplasia from 50° to 70° of flexion and with severe dysplasia at 70° of flexion. No measurable differences in medial patellar facet mechanics or joint kinematics occurred. Conclusion: Our hypothesis was rejected: Severely dysplastic joints did not result in significantly increased patellofemoral contact forces and abnormal kinematics in our cadaveric simulation. Rather, severe dysplasia resulted in a pronounced lateral shift in contact forces across the lateral patellar facet, while changes in kinematics and the magnitude of contact forces were not significant. Clinical Relevance: Including dysplasia of both the patella and trochlea is required to fully capture the mechanics of this complex joint. The pronounced lateralization of contact force in severely dysplastic patellofemoral joints should be considered to avoid cartilage overload with surgical manipulation.

Pediatric Imaging of the Elbow: A Pictorial Review

The elbow is a complex joint, subject to a wide range of traumatic, inflammatory, metabolic and neoplastic insults. The pediatric elbow has several diagnostic pitfalls due to the normal developmental changes in children. Knowledge of these normal variants is essential for both diagnosis and management of their elbow injuries. Radiography remains the first imaging modality of choice. Magnetic resonance imaging is excellent in evaluating lesions within the bone and soft tissues. In this pictorial essay, we provide insights into pediatric elbow imaging, show a range of entities specific to the pediatric elbow, and discuss diagnostic pitfalls that result from normal elbow growth in children.

THE ARCHAEOLOGICAL SITE OF PALMYRA BEFORE AND AFTER THE WAR IN SYRIA

In the article there is example of the ancient Syrian city of Palmyra, the article examines the problems of loss and preservation of the world historical, cultural, archaeological and architectural heritage in the context of modern local military confl icts. During the periods of Antiquity and the middle Ages, a complex of monuments, unique in composition and size, was formed here, combining ancient Eastern, Roman, Byzantine and Arab elements. During the ongoing acute armed confl ict in Syria, because of the purposeful actions of religious terrorist-extremist organizations, defi ned by the author as an "international historian of cultural terrorism", hesuffered catastrophic damage. An analysis of the scale of this damage, as well as the effectiveness of the efforts of the Syrian authorities, international organizations and the world community, shows that the preservation and restoration of Palmyra's heritage is possible because of painstaking, complex, joint work of all interested parties. Thus, the example of Palmyra showed the military confl icts in the Middle East, along with the actual destruction of entire states, the death of a huge number of people, the economic crisis, millions of refugees, was an attack on the heritage of ancient civilizations, which caused unprecedented loss of world cultural heritage in modern history. Now the world community faces a long and comprehensive joint effort to determine the damage, restore, and prevent further destruction and looting of the cultural heritage of Palmyra and Syria.

Generalized Givens Rotations Applied to Complex Joint Eigenvalue Decomposition

This paper shows the different ways of using generalized Givens rotations in complex joint eigenvaluedecomposition (JEVD) problem. It presents the different schemes of generalized Givens rotation, justifies the introducedapproximations and focuses on the process of extending an algorithm developed for real JEVD to the complex JEVD.Several Joint Diagonalization problem use generalized Givens rotations to achieve the solution, many algorithmsdeveloped in the real case exist in the literature and are not generalized to the complex case. Hence, we show herein asimple and not trivial way to get the complex case from the real one. Simulation results are provided to highlight theeffectiveness and behaviour of the proposed techniques for different scenarios.

Shoulder examination: a systematic approach

The shoulder is a complex joint with static and dynamic stabilising structures working synchronously. These allow a full range of movement while preserving stability of the joint. Patients may present with pain, stiffness, weakness, deformity or instability. The authors suggest a systematic examination sequence to ensure that important pathology is not overlooked. Adopting this approach allows common pathologies, including tears of the rotator cuff, impingement and tendinopathy, to be easily identified. This shoulder examination sequence may be used by all healthcare professionals and can also act as a revision aid for those undergoing exams in this field, at different levels of training.