Scott Tashman

Bio: Scott Tashman is an academic researcher from University of Texas Health Science Center at Houston. The author has contributed to research in topics: Anterior cruciate ligament & Anterior cruciate ligament reconstruction. The author has an hindex of 43, co-authored 136 publications receiving 7256 citations. Previous affiliations of Scott Tashman include Henry Ford Hospital & University of Texas at Austin.

Abnormal Rotational Knee Motion During Running After Anterior Cruciate Ligament Reconstruction

Abstract: Background: The effectiveness of anterior cruciate ligament reconstruction for restoring normal knee kinematics is largely unknown, particularly during sports movements generating large, rapidly applied forces.Hypothesis: Under dynamic in vivo loading, significant differences in 3-dimensional kinematics exist between anterior cruciate ligament-reconstructed knees and the contralateral, uninjured knees.Study Design: Prospective, in vivo laboratory study.Methods: Kinematics of anterior cruciate ligament-reconstructed and contralateral (uninjured) knees were evaluated for 6 subjects during downhill running 4 to 12 months after anterior cruciate ligament reconstruction, using a 250 frame/s stereoradiographic system. Anatomical reference axes were determined from computed tomography scans. Kinematic differences between the uninjured and reconstructed limbs were evaluated with a repeated-measures analysis of variance.Results: Anterior tibial translation was similar for the reconstructed and uninjured limbs. How...

Investigation of Head Injury Mechanisms Using Neutral Density Technology and High-Speed Biplanar X-ray.

Abstract: The principal focus of this study was the measurement of relative brain motion with respect to the skull using a high-speed, biplanar x-ray system and neutral density targets (NDTs). A suspension fixture was used for testing of inverted, perfused, human cadaver heads. Each specimen was subjected to multiple tests, either struck at rest using a 152-mm-diameter padded impactor face, or stopped against an angled surface from steady-state motion. The impacts were to the frontal and occipital regions. An array of multiple NDTs was implanted in a double-column scheme of 5 and 6 targets, with 10 mm between targets in each column and 80 mm between columns. These columns were implanted in the temporoparietal and occipitoparietal regions. The impacts produced peak resultant accelerations of 10 to 150 g, and peak angular accelerations between 1000 and 8000 rad/s(2). For all but one test, the peak angular speeds ranged from 17 to 22 rad/s. The relative 3D displacements between the skull and the NDTs were analyzed. The localized motions of the brain generally followed loop or figure eight patterns, with peak displacements on the order of +/- 5 mm. These results can be used to further finite-element modeling efforts.

A Study of the Response of the Human Cadaver Head to Impact

Abstract: High-speed biplane x-ray and neutral density targets were used to examine brain displacement and deformation during impact Relative motion, maximum principal strain, maximum shear strain, and intracranial pressure were measured in thirty-five impacts using eight human cadaver head and neck specimens The effect of a helmet was evaluated During impact, local brain tissue tends to keep its position and shape with respect to the inertial frame, resulting in relative motion between the brain and skull and deformation of the brain The local brain motions tend to follow looping patterns Similar patterns are observed for impact in different planes, with some degree of posterior-anterior and right-left symmetry Peak coup pressure and pressure rate increase with increasing linear acceleration, but coup pressure pulse duration decreases Peak average maximum principal strain and maximum shear are on the order of 009 for CFC 60 Hz data for these tests Peak average maximum principal strain and maximum shear increase with increasing linear acceleration, coup pressure, and coup pressure rate Linear and angular acceleration of the head are reduced with use of a helmet, but strain increases These results can be used for the validation of finite element models of the human head

Dynamic function of the ACL-reconstructed knee during running.

Abstract: Little is known about the three-dimensional behavior of the anterior cruciate ligament (ACL) reconstructed knee during dynamic, functional loading, or how dynamic knee function changes over time in the reconstructed knee. We hypothesized dynamic, in vivo function of the ACL-reconstructed knee is different from the contralateral, uninjured knee and changes over time. We measured knee kinematics for 16 subjects during downhill running 5 and 12 months after ACL reconstruction (bone-patellar tendon-bone or quadrupled hamstring tendon with interference screw fixation) using a 250 frame per second stereoradiographic system. We used repeated-measures ANOVA to ascertain whether there were differences between the uninjured and reconstructed limbs and over time. We found no differences in anterior tibial translation between limbs, but reconstructed knees were more externally rotated and in more adduction (varus) during the stance phase of running. Anterior tibial translation increased from 5 to 12 months after surgery in the reconstructed knees. Anterior cruciate ligament reconstruction failed to restore normal rotational knee kinematics during dynamic, functional loading and some degradation of graft function occurred over time. These abnormal motions may contribute to long-term joint degeneration associated with ACL injury and reconstruction.

In-Vivo Measurement of Dynamic Joint Motion Using High Speed Biplane Radiography and CT: Application to Canine ACL Deficiency

Abstract: Dynamic assessment of three-dimensional (3D) skeletal kinematics is essential for understanding normal joint function as well as the effects of injury or disease. This paper presents a novel technique for measuring in-vivo skeletal kinematics that combines data collected from high-speed biplane radiography and static computed tomography (CT). The goals of the present study were to demonstrate that highly precise measurements can be obtained during dynamic movement studies employing high frame-rate biplane video-radiography, to develop a method for expressing joint kinematics in an anatomically relevant coordinate system and to demonstrate the application of this technique by calculating canine tibio-femoral kinematics during dynamic motion. The method consists of four components: the generation and acquisition of high frame rate biplane radiographs, identification and 3D tracking of implanted bone markers, CT-based coordinate system determination, and kinematic analysis routines for determining joint motion in anatomically based coordinates. Results from dynamic tracking of markers inserted in a phantom object showed the system bias was insignificant (-0.02 mm). The average precision in tracking implanted markers in-vivo was 0.064 mm for the distance between markers and 0.31 degree for the angles between markers. Across-trial standard deviations for tibio-femoral translations were similar for all three motion directions, averaging 0.14 mm (range 0.08 to 0.20 mm). Variability in tibio-femoral rotations was more dependent on rotation axis, with across-trial standard deviations averaging 1.71 degrees for flexion/extension, 0.90 degree for internal/external rotation, and 0.40 degree for varus/valgus rotation. Advantages of this technique over traditional motion analysis methods include the elimination of skin motion artifacts, improved tracking precision and the ability to present results in a consistent anatomical reference frame.

A framework for the in vivo pathomechanics of osteoarthritis at the knee

Abstract: The in vivo pathomechanics of osteoarthritis (OA) at the knee is described in a framework that is based on an analysis of studies describing assays of biomarkers, cartilage morphology, and human function (gait analysis). The framework is divided into an Initiation Phase and a Progression Phase. The Initiation Phase is associated with kinematic changes that shift load bearing to infrequently loaded regions of the cartilage that cannot accommodate the loads. The Progression Phase is defined following cartilage breakdown. During the Progression Phase, the disease progresses more rapidly with increased load. While this framework was developed from an analysis of in vivo pathomechanics, it also explains how the convergence of biological, morphological, and neuromuscular changes to the musculoskeletal system during aging or during menopause lead to the increased rate of idiopathic OA with aging. Understanding the in vivo response of articular cartilage to its physical environment requires an integrated view of the problem that considers functional, anatomical, and biological interactions. The integrated in vivo framework presented here will be helpful for the interpretation of laboratory experiments as well as for the development of new methods for the evaluation of OA at the knee.

A Proposed Injury Threshold for Mild Traumatic Brain Injury

Abstract: Traumatic brain injuries constitute a significant portion of injury resulting from automotive collisions, motorcycle crashes, and sports collisions. Brain injuries not only represent a serious trauma for those involved but also place an enormous burden on society, often exacting a heavy economical, social, and emotional price. Development of intervention strategies to prevent or minimize these injuries requires a complete understanding of injury mechanisms, response and tolerance level. In this study, an attempt is made to delineate actual injury causation and establish a meaningful injury criterion through the use of the actual field accident data. Twenty-four head-to-head field collisions that occurred in professional football games were duplicated using a validated finite element human head model. The injury predictors and injury levels were analyzed based on resulting brain tissue responses and were correlated with the site and occurrence of mild traumatic brain injury (MTBI). Predictions indicated that the shear stress around the brainstem region could be an injury predictor for concussion. Statistical analyses were performed to establish the new brain injury tolerance level.

Control strategies for active lower extremity prosthetics and orthotics: a review

Abstract: Technological advancements have led to the development of numerous wearable robotic devices for the physical assistance and restoration of human locomotion. While many challenges remain with respect to the mechanical design of such devices, it is at least equally challenging and important to develop strategies to control them in concert with the intentions of the user. This work reviews the state-of-the-art techniques for controlling portable active lower limb prosthetic and orthotic (P/O) devices in the context of locomotive activities of daily living (ADL), and considers how these can be interfaced with the user’s sensory-motor control system. This review underscores the practical challenges and opportunities associated with P/O control, which can be used to accelerate future developments in this field. Furthermore, this work provides a classification scheme for the comparison of the various control strategies. As a novel contribution, a general framework for the control of portable gait-assistance devices is proposed. This framework accounts for the physical and informatic interactions between the controller, the user, the environment, and the mechanical device itself. Such a treatment of P/Os – not as independent devices, but as actors within an ecosystem – is suggested to be necessary to structure the next generation of intelligent and multifunctional controllers. Each element of the proposed framework is discussed with respect to the role that it plays in the assistance of locomotion, along with how its states can be sensed as inputs to the controller. The reviewed controllers are shown to fit within different levels of a hierarchical scheme, which loosely resembles the structure and functionality of the nominal human central nervous system (CNS). Active and passive safety mechanisms are considered to be central aspects underlying all of P/O design and control, and are shown to be critical for regulatory approval of such devices for real-world use. The works discussed herein provide evidence that, while we are getting ever closer, significant challenges still exist for the development of controllers for portable powered P/O devices that can seamlessly integrate with the user’s neuromusculoskeletal system and are practical for use in locomotive ADL.