Shady Elmasry

Exponent · Biomechanics

Model reproducibility is a point of emphasis for the National Institutes of Health (NIH) and in science, broadly. As the use of computational modeling in biomechanics and orthopaedics grows, so does the need to assess the reproducibility of modeling workflows and simulation predictions. The long-term goal of the KneeHub project is to understand the...

Stakeholders in the modeling and simulation (M&S) community organized a workshop at the 2019 Annual Meeting of the Orthopaedic Research Society (ORS) entitled "Reproducibility in Modeling and Simulation of the Knee: Academic, Industry, and Regulatory Perspectives". The goal was to discuss efforts among these stakeholders to address irreproducibilit...

Reproducible research serves as a pillar of the scientific method and is a foundation for scientific advancement. However, estimates for irreproducibility of preclinical science range from 75% to 90%. The importance of reproducible science has not been assessed in the context of mechanics-based modeling of human joints such as the knee, despite thi...

Background: In TKA, soft tissue balancing is assessed through manual intraoperative trialing. This assessment is a physical examination via manually applied forces at the ankle, generating varus and valgus moments at the knee while the surgeon visualizes the lateral and medial gaps at the joint line. Based on this examination, important surgical d...

Background Surgeons may resect additional distal femur during primary posterior stabilized (PS) total knee arthroplasty (TKA) to correct a flexion contracture. However, the resultant joint line elevation (JLE) increases midflexion laxity. We determined whether a mid-level constraint (MLC) insert reduced mid-flexion laxity after JLE. Methods Six co...

Lower back pain is a medical condition of epidemic proportion, and the degeneration of the intervertebral disc has been identified as a major contributor. The etiology of intervertebral disc (IVD) degeneration is multifactorial, depending on age, cell-mediated molecular degradation processes and genetics, which is accelerated by traumatic or gradua...

Aims: Surgeons commonly resect additional distal femur during primary total knee arthroplasty (TKA) to correct a flexion contracture, which leads to femoral joint line elevation. There is a paucity of data describing the effect of joint line elevation on mid-flexion stability and knee kinematics. Thus, the goal of this study was to quantify the ef...

Accurately capturing the bone and cartilage morphology and generating a mesh remains a critical step in the workflow of computational knee joint modeling. Currently there is no standardized method to compare meshes of different element types and nodal densities, making comparisons across research teams a significant challenge. The aim of this paper...

Preoperative flexion contracture is a risk factor for patients’ dissatisfaction following primary total knee arthroplasty (TKA). Previous studies utilizing navigation technology and cadaveric models attempted to identify surgical techniques to correct knees with flexion contracture and minimize undesirable outcomes such as knee instability. However...

The use of computational modeling to investigate knee joint biomechanics has increased exponentially over the last few decades. Developing computational models is a creative process where decisions have to be made, subject to the modelers' knowledge and previous experiences, resulting in the "art" of modeling. The long-term goal of the KneeHub proj...

OBJECTIVES/GOALS: To quantify clinical exam in total knee arthroplasty by answering the following questions: (1) What are the magnitudes of forces applied by surgeons during the varus-valgus exam? (2) Is the choice of tibial insert thickness related to the magnitude of the applied forces? (3) How accurately does a surgeon estimate the gaps in the v...

Measured resection is a common technique for obtaining symmetric flexion and extension gaps in posterior‐stabilized total knee arthroplasty (TKA). A known limitation of measured resection, however, is its reliance on osseous landmarks to guide bone resection and component alignment while ignoring the geometry of the surrounding soft tissues such as...

Purpose The purpose of this study was to evaluate the thickness of medial and lateral posterior femoral condylar bone resected with five implant systems using posterior referencing jigs set at 3° of external rotation. The hypothesis was that posterior condylar resection thickness on the medial side would be equal to the thickness of the femoral imp...

Background: Whether anterior referencing (AR) or posterior referencing (PR) produces a more balanced flexion gap in total knee arthroplasty (TKA) using measured resection remains controversial. Our goal was to compare AR and PR in terms of (1) medial and lateral gaps at full extension and 90° of flexion, and (2) maximum medial and lateral collater...

Percutaneous pedicle screw fixation (PPSF) is a minimally invasive surgery (MIS) employed in the treatment of thoracolumbar burst fractures (TBF). However, hardware failure and loss of angular correction are common limitations caused by the poor support of the anterior column of the spine. Balloon Kyphoplasty (KP) is another MIS successfully used i...

When treating thoracolumbar burst fractures (BF), short-segment posterior fixation (SSPF) represents a less invasive alternative to the traditional long-segment posterior fixation (LSPF) approach. However, hardware failure and loss of sagittal alignment have been reported in patients treated with SSPF. Including pedicle screws at the fracture level...

Approximately 90% of spinal fractures occur at the thoracolumbar junction. Among these fractures, 10% to 20% are considered burst fracture (BF) [1]. In such cases, posterior fixation is commonly performed as a surgical treatment, especially when the fracture is moderate and associated with partial neurologic dysfunction [2]. Different posterior fix...

INTRODUCTION • Unstable thoracolumbar fracture (UTF) is characterized by loosing > 50% of the vertebral body height and causing kyphotic deformity >20° [1]. • UTF is surgically treated using long-segment posterior constructs (LS) [2], which are rather invasive and disrupt the natural mobility of the spine. • Short-segment constructs (SS) are a less...

Insulin-like growth factor-1 (IGF-1) is well-known for upregulating cell proliferation and biosynthesis of the extracellular matrix in the intervertebral disc (IVD). Pathological conditions, such as obesity or chronic kidney disease cause IGF-1 deficiency in plasma. How this deficiency impacts disc homeostasis remains unknown. Pro-anabolic approach...

Thoracolumbar fractures represent approximately 90% of fractures found at spine, and nearly 20% of such injuries are burst fractures [1]. Surgical correction with corpectomy and subsequent fusion of neighbouring levels is a well-known treatment, which can be performed with different fixation techniques. The objective of fixation is to correct angul...

Surgeries for Lumbar Spinal Stenosis (LSS) aim at decompressing spinal nerves and relieving symptoms of radiculopathy or myelopathy. Frequently after surgery, stenosis may progress in adjacent spinal segments, but the etiology of adjacent segment degeneration is still unclear. It is hypothesized that surgical approaches for LSS may alter the normal...

Tobacco smoking is associated with numerous pathological conditions. Compelling experimental evidence associates smoking to the degeneration of the intervertebral disc (IVD). In particular, it has been shown that nicotine down-regulates both the proliferation rate and glycosaminoglycan (GAG) biosynthesis of disc cells. Moreover, tobacco smoking cau...

Lumbar spinal stenosis (LSS): a disease of epidemic proportions in the Nation is often treated by surgeries to decompress the spinal nerve. However, often after surgery, stenosis can propagate to adjacent spinal segments. We hypothesize that surgeries for LSS may change the biomechanical environment of the adjacent segments, eventually leading to a...

The natural process of aging is considered to be one of the primary causes for intervertebral disc degeneration. Insulin-like growth factor-1 (IGF-1) upregulates anabolism in IVD via binding to IGF-1 cell receptors (IGF-1R). At the same time, IGF-1 can reversibly bind to IGF binding proteins (IGFBP). It has been shown that, in IVD, IGF-1R expressio...

Background/aims: Loading during concurrent bending and compression associated with deadlift, hang clean and hang snatch lifts carries the potential for injury to the intervertebral discs, muscles and ligaments. This study examined the capacity of a newly developed spinal model to compute shear and compressive forces, and bending moments in lumbar...

This study presents a system dynamics approach to model and analyse a single stage reconfigurable manufacturing system (RMS). The system is exposed to a random demand that follow a normal distribution. New modifications to the existing state of the art capacity scaling model are applied to bring it closer to reality. A module to account capacity sc...

This research presents a System Dynamics approach to model and analyze a single stage Reconfigurable manufacturing system (RMS). The model is a continuous time model. The system is exposed to a random demand that is assumed to follow a normal distribution pattern. Scaling capacity up or down is assumed unrestricted, and no outsourcing is allowed. N...