Karen L Troy

Karen L Troy
Worcester Polytechnic Institute | WPI · Department of Biomedical Engineering

36.16
 · 
PhD

About

87
Publications
8,013
Reads
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1,197
Citations
Introduction
My broad research focus is on understanding how we can use physical activity in a targeted and mechanistic manner to promote healthy aging. I specifically take a biomechanics perspective on how physical forces applied to the musculoskeletal system generated through exercise or other physical activity can be used to improve bone and joint health. My experimental approach utilizes medical image analysis and patient-specific computational models, combined with human subjects in a clinical setting.
Research Experience
August 2013 - present
Worcester Polytechnic Institute
Position
  • Professor (Associate)
September 2003 - July 2013
University of Illinois at Chicago
Position
August 1999 - July 2003
University of Iowa
Position
Education
August 2003 - December 2006
University of Illinois at Chicago
Field of study
  • Biomechanics
August 1999 - July 2003
University of Iowa
Field of study
  • Biomedical Engineering
August 1995 - May 1999
Washington University in St. Louis
Field of study
  • Biomedical Engineering

Publications

Publications (87)
Article
We investigated the effect of 12 months of functional electrical stimulation-assisted rowing with and without zoledronic acid (ZA) on computationally estimated bone strength and stiffness in individuals with spinal cord injury. We found that rowing with ZA, but not rowing alone, improved stiffness at the distal femur, but not the proximal tibia. I...
Article
Work in animal models suggest that bone structure adapts to local bone strain, but this relationship has not been comprehensively studied in humans. Here, we quantified the influence of strain magnitude and gradient on bone adaptation in the forearm of premenopausal women performing compressive forearm loading (n=11) and non-loading controls (n=10)...
Preprint
Full-text available
Work in animal models suggest that bone structure adapts to local bone strain, but this relationship has not been comprehensively studied in humans. Here, we quantified the influence of strain magnitude and gradient on bone adaptation in the forearm of premenopausal women performing compressive forearm loading (n=11) and non-loading controls (n=10)...
Article
Although strong evidence exists that certain activities can increase bone density and structure in people, it is unclear what specific mechanical factors govern the response. This is important because understanding the effect of mechanical signals on bone could contribute to more effective osteoporosis prevention methods and efficient clinical tria...
Article
Full-text available
Spinal cord injury (SCI) causes rapid osteoporosis that is most severe below the level of injury. More than half of those with motor complete SCI will experience an osteoporotic fracture at some point following their injury, with most fractures occurring at the distal femur and proximal tibia. These fractures have devastating consequences, includin...
Article
Quantifying joint deformity in people with rheumatoid (RA) and psoriatic arthritis (PsA) remains challenging. Here, we demonstrate a new method to measure bone erosions and abnormal periosteal growths, based on the difference between a predicted healthy and actual diseased joint surface. We optimized the method by creating and measuring artificial...
Chapter
Full-text available
This chapter provides a comprehensive overview of biomechanics experimental procedures, data analysis, modeling, and simulation. This chapter also overviews several examples of advanced biomechatronics systems for sports, exercise, and entertainment.
Article
Full-text available
The Surgeon General estimates that by 2020, half of all Americans could have weak bones due to bone loss. Osteoporosis causes more than 1.5 million fractures every year. Identifying effective interventions based on individual patient characteristics remains a major challenge. Proximal femur fractures are common and devastating events for individual...
Article
Full-text available
Spinal cord injury (SCI) results in rapid, severe osteoporosis and an increased risk of lower extremity fractures. Despite the medical complications associated with these fractures, there is no standard of care to prevent osteoporotic fractures following SCI. Functional electrical stimulation‐ (FES‐) assisted rowing is a promising intervention to i...
Article
Though smokers have poor clinical outcomes after treatment for fractures, the skeletal effects of smoking are still debated. Our results showed that female smokers had 33% higher cortical bone porosity. Smoking targets cortical compartment microstructure and mechanics, and micron-scale variables are essential to better understand the specific effec...
Preprint
Full-text available
Although there is strong evidence that certain activities can increase bone density and structure in some individuals, it is not clear what specific mechanical factors govern the response. Animal in vivo loading models have demonstrated that mechanical signals related to strain rate and strain magnitude regulate bone adaptation. However, the degree...
Article
Mechanical loading through youth exercise is highly modifiable and represents a strategy to maximize peak adult bone mass, with the potential for broad implementation across the population to lower fracture risk. For girls, circum-menarcheal growth is critical, with around 50% of adult bone acquired over a 4-year period. Here, we prospectively foll...
Article
Equipping engineering students for career success requires more than technical proficiency; mindset and contextual interpretation also matter. Entrepreneurial mindset learning (EML) is one framework that faculty can use to systematically enrich course projects to encourage development of these important career skills. We present the thought process...
Article
Spinal cord injury (SCI) is associated with marked bone loss and an increased risk of fracture. We randomized 61 individuals with chronic SCI and low bone mass to receive either: teriparatide 20 µg/day plus sham vibration 10 min/day (n = 20), placebo plus vibration 10 min/day (n = 20), or teriparatide 20 µg/day plus vibration 10 min/day (n = 21). P...
Article
Full-text available
In 2011 over 1.7 million people were hospitalized because of a fragility fracture, and direct costs associated with osteoporosis treatment exceeded 70 billion dollars in the United States. Failure to reach and maintain optimal peak bone mass during adulthood is a critical factor in determining fragility fracture risk later in life. Physical activit...
Article
Full-text available
While weight-bearing and resistive exercise modestly increases aBMD, the precise relationship between physical activity and bone microstructure, and strain in humans is not known. Previously, we established a voluntary upper-extremity loading model that assigns a person's target force based on their subject-specific, continuum FE-estimated radius b...
Article
Full-text available
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...
Article
Quantitative CT (QCT) analysis involves the calculation of specific parameters such as bone volume and density from CT image data, and can be a powerful tool for understanding bone quality and quantity. However, without careful attention to detail during all steps of the acquisition and analysis process, data can be of poor- to unusable-quality. Go...
Article
Full-text available
[This corrects the article DOI: 10.1371/journal.pone.0188200.].
Article
Full-text available
Trabecular bone of the human calcaneus is subjected to extreme repetitive forces during endurance running and should adapt in response to this strain. To assess possible bone functional adaptation in the posterior region of the calcaneus, we recruited forefoot-striking runners (n = 6), rearfoot-striking runners (n = 6), and non-runners (n = 6), all...
Conference Paper
Full-text available
A high fidelity biomimetic hand actuated by 9 stepper motors packaged within forearm casing was manufactured for less than 350 USD; it has 18 mechanical degrees of freedom, is 38 cm long, weighs 2.2 kg. The hand model has 3D printed replicas of human bones and laser cut tendons and ligaments. The user intent is deduced from EEG and EMG signals, obt...
Data
The paramount challenge for hand prosthesis and braces is the achievement of human-like dexterity through the development of a highly biomimetic device that can be easily controlled and that is cost-effective and readily accessible to the general user. The prototype was manufactured for less than 350 USD and has 18 mechanical degrees of freedom,...
Article
High-resolution peripheral quantitative computed tomography (HR-pQCT) derived micro-finite element (FE) modeling is used to evaluate mechanical behavior at the distal radius microstructure. However, these analyses typically simulate non-physiologic simplified platen-compression boundary conditions on a small section of the distal radius. Cortical a...
Data
The purpose of this project, Accurate Prosthetic Hand, is to explore a method by which to improve the dexterity of artificial hands by closely mimicking the biomechanics of a human hand. The biomechanics of each human finger was analyzed to determine the kinematics and finger trajectories that the experimental hand should be able to mimic. In addit...
Article
High-resolution peripheral computed tomography is commonly used to evaluate mechanical behavior of the distal radius microstructure using micro-finite element (FE) modeling. However, only a 9mm section is considered and boundary conditions (BCs) are usually simplified (platen-compression), and may not represent physiologic loading. Regardless, thes...
Article
People with spinal cord injury (SCI) experience bone and muscle loss in their paralyzed limbs that is most rapid and severe in the first 3 years after injury. Restoration of mechanical loading through therapeutic physical activity may potentially slow or reverse post-SCI bone loss, however, therapeutic targets cannot be developed without accurate b...
Article
Background: Spinal cord injury (SCI) is associated with a rapid loss of bone mass, resulting in severe osteoporosis and a 5- to 23-fold increase in fracture risk. Despite the seriousness of fractures in SCI, there are multiple barriers to osteoporosis diagnosis and wide variations in treatment practices for SCI-induced osteoporosis. Methods: We...
Article
Osteoporosis increases the risk of fracture and is often considered a late effect of breast cancer treatment. We examined the prevalence of compromised bone health in a sample of exclusively African-American (AA) breast cancer survivors since bone mineral density (BMD) varies by race/ethnicity in healthy populations. Using a case-control design, AA...
Article
Spinal cord injury (SCI) is characterized by marked bone loss and a high rate of low-energy fracture around regions of the knee. Changes in the mechanical integrity of bone after SCI are poorly defined, and a better understanding may inform approaches to prevent fractures. The purpose of this study was to quantify reductions in torsional stiffness...
Article
Bone adaptation is understood to be driven by mechanical strains acting on the bone as a result of some mechanical stimuli. Although the strain/adaptation relation has been extensively researched using in-vivo animal loading models, it has not been studied in humans, likely due to difficulties in quantifying bone strains and adaptation in living hu...
Article
Bone loss following spinal cord injury (SCI) is associated with an increased risk of fracture due to minor trauma. Proximal femoral fractures account for approximately 10–20% of the fractures in this population and are among the most serious of injuries. Our purpose was to quantify changes to proximal femoral strength in patients with acute SCI. Th...
Article
Trip-specific perturbation training reduces trip-related falls after laboratory-induced trips and, prospectively, in the community. Based on an emerging body of evidence we hypothesize that using task-specific perturbation training as a stand-alone approach or in conjunction with conventional exercise-based approaches will improve the effectiveness...
Article
Study design: Comparison of diagnostic tests; methodological validation. Objectives: Primary: to investigate the precision and reliability of a knee bone mineral density (BMD) assessment protocol that uses an existing dual energy X-ray absorptiometry (DXA) forearm acquisition algorithm in individuals with spinal cord injury (SCI). Secondary: to...
Article
Purpose: Because wheelchair users are unable to use standard fitness equipment such as treadmills and bikes, we developed an upper body rowing ergometer (UBRE) that can be retrofitted onto a standard stationary cycle and used to perform a rowing exercise. We validated a graded exercise testing protocol utilizing the UBRE and completed a 12-week pi...
Article
Computed tomography and finite element modeling were used to assess bone mineral and stiffness loss at the knee following acute spinal cord injury (SCI). Marked bone mineral loss was observed from a combination of trabecular and endocortical resorption. Reductions in stiffness were 2-fold greater than reductions in integral bone mineral. Introduct...
Article
A recently developed murine model of tendinopathy, induced by TGF-β1 injection, has been used to examine the reparative capacity of tendinopathic Achilles in Adamts5(-/-) mice. After TGF-β1 injection and 2 weeks of treadmill exercise, the Achilles from Adamts5(-/-) mice exhibited a reduction in maximum tensile stress of approximately 60%. However,...
Article
Bone is typically well suited for its habitual loading environment because of its ability to adapt. Although characteristics of the mechanical loading environment predict the bone adaptive response in animals, this has not been prospectively validated in humans. Here, we describe an in vivo loading model in which women apply forces to the radius by...
Article
Background: Declines in nutrition status and adverse body composition changes frequently occur in the critically ill. The objective of this cross-sectional study was to examine the prevalence of sarcopenia and its occurrence in patients classified as normal nourished using subjective global assessment (SGA). Methods: Exploiting diagnostic CT ima...
Article
Background: Assessment of nutritional status in intensive care unit (ICU) patients is limited. Computed tomography (CT) scans that include the first to fifth lumbar region completed for diagnostic purposes measures fat and lean body mass (LBM) depots and are frequently done in ICU populations and can be used to quantify fat and LBM depots. The pur...
Article
Individuals with spinal cord injury experience a rapid loss of bone mineral below the neurological lesion. The clinical consequence of this bone loss is a high rate of fracture around regions of the knee. The ability to predict the mechanical competence of bones at this location may serve as an important clinical tool to assess fracture risk in the...
Article
Unlabelled: This study used quantitative computed tomography to assess changes in bone mineral at the proximal femur after acute spinal cord injury (SCI). Individuals with acute SCI experienced a marked loss of bone mineral from a combination of trabecular and endocortical resorption. Targeted therapeutic interventions are thus warranted in this p...
Article
To better understand the mechanisms underlying spiral fracture we would like to carry out biomechanical tests of long bones loaded in torsion to failure. A device was fabricated to perform torsional tests of long bones using a single-axis linear actuator. The principal operation of the device was to transform the vertical displacement of a material...
Article
Purpose: The potential of task-specific training as a fall-prevention intervention was studied. The primary purpose of the study was to determine the extent to which a task-specific training protocol decreased the number of falls by middle-age and older women after a laboratory-induced trip. Secondary purposes were to explore the ability of trunk...
Article
A small scale mechanical loading and testing device was designed and fabricated to apply in vivo loads to mouse tibiae and to mechanically test the bones in three-point bending. A linear actuator and load cell were used to apply accurately controlled forces to the samples. The device was tested and validated using standard materials of known proper...
Article
To provide preliminary information about the relationships between self-reported fear of falling (FOF) in healthy community-dwelling women, number of falls, and recovery kinematics in response to a laboratory-induced trip. Cohort study. Clinical research laboratory. A subset of community-dwelling older women (N=33) recruited from studies of laborat...
Article
Distal radius fracture strength has been quantified using in vitro biomechanical testing. These tests are frequently performed using one of two methods: (1) load is applied directly to the embedded isolated radius or (2) load is applied through the hand with the wrist joint intact. Fracture loads established using the isolated radius method are con...
Article
To better understand the mechanisms underlying distal radius fracture we have developed finite element models to predict radius bone strain and fracture strength under loading conditions simulating a fall. This study compares experimental surface strains and fracture loads of the distal radius with specimen-specific finite element models to validat...
Article
To develop guidelines for proper exercise execution on a novel device and to recommend design changes to the device based on biomechanical data and user feedback. Seven manual wheelchair users were instructed on proper exercise technique with a novel device, which allows a person to complete a seated row. Kinematics and kinetics of the dominant upp...
Article
Osteonecrosis of the femoral head remains a challenging orthopaedic problem. The disease frequently progresses to femoral head collapse, leading to debilitating osteoarthritis in the affected hip(s). Since a major goal of pre-collapse interventions is to forestall the need for hip arthroplasty, it is important that any animal models used to develop...
Article
Slips are frequently the cause of fall-related injuries. Identifying modifiable biomechanical requirements for successful recovery is a key prerequisite to developing task-specific fall preventive training programs. The purpose of this study was to quantify the biomechanical role of the upper extremities during the initial phase of a slip resulting...
Article
Full-text available
Osteoporosis and osteopenia are major contributors to the high incidence of fractures in older women. Habitual loading plays a crucial role in the acquisition and maintenance of bone. It may be possible to develop clinical interventions based on targeted modes of physical loading that can improve bone health and reduce fractures in women. If so, an...
Article
Falls are a major source of injury in older adults. Many falls occur after slipping. This study determined performance-related factors that both contribute to slip-related falls and that may be effectively and efficiently modified through targeted intervention. Thirty-five young adults and 21 healthy older adults (age: 70.9+/-5.1 years) were slippe...
Article
This paper reviews some of our experiences over nearly 15 years of trying to determine modifiable factors that contribute to the high incidence of fall by older adults. As part of our approach, we have subjected healthy young and older adults to very large postural disturbances during locomotion, in the form of trips and slips, to which rapid compe...
Article
Full-text available
People exhibit increased difficulty balancing when they perform secondary attention-distracting tasks while walking. However, a previous study by Grabiner and Troy (J. Neuroengineering Rehabil., 2005) found that young healthy subjects performing a concurrent Stroop task while walking on a motorized treadmill exhibited decreased step width variabili...
Article
Distal radius fractures are among the most common fall-related fractures. The manner in which the upper extremities are used for protection during a fall may exert a considerable influence on the incidence of injury. Here, we sought to determine the degree to which the assumption of sagittal plane symmetry was valid in unexpected falls after a trip...
Conference Paper
Full Paper Later Published as: Dingwell, J.B., Robb, R.T., Troy, K.L., and Grabiner, M.D. (2008) “Effects of an Attention Demanding Task on Dynamic Stability During Treadmill Walking” Journal of Neuroengineering & Rehabilitation, 5(1): 12. http://www.jneuroengrehab.com/content/5/1/12
Article
Orthopaedic management of femoral head osteonecrosis remains problematic, partly because of inability to systematically compare treatments in an animal model whose natural history parallels the human in terms of progression to femoral head collapse. Recently, it was determined that collapse could be consistently achieved for cryogenically induced o...
Article
Distal radius (Colles') fractures are a common fall-related injury in older adults and frequently result in long-term pain and reduced ability to perform activities of daily living. Because the occurrence of a fracture during a fall depends on both the strength of the bone and upon the kinematics and kinetics of the impact itself, we sought to unde...
Article
Slipping and slip-related falls are a common and potentially dangerous problem, especially for older adults. We believe that it is possible to train compensatory stepping responses of older adults to reduce the incidence of slip-related falls. However, such an approach requires further understanding of the causal biomechanical distinctions between...
Article
We characterized the extent to which body mass influences the relationship between hip joint moments during locomotion and bone mineral density (BMD) of the proximal femur in healthy young women (n = 24). There is some evidence of a direct relationship between hip joint moments during locomotion and BMD of the proximal femur in patients with osteoa...
Article
Full-text available
The variability of step time and step width is associated with falls by older adults. Further, step time is significantly influenced when performing attention demanding tasks while walking. Without exception, step time variability has been reported to increase in normal and pathologically aging older adults. Because of the role of step width in man...
Chapter
Full-text available
The study of postural control spans diverse disciplines that include computer science, engineering, mathematics, medicine, pharmacology, physiology, and robotics. The influence of the aging neuromuscular system on postural control and mobility lies at an intersection of these and other disciplines. The typical trajectories of the age-related anatom...
Article
Falling is a frequent cause of serious injury in older adults and trips are a dominant cause of falls in this rapidly growing population. Although there are few laboratory protocols that induce actual trips, there are many protocols that utilize surrogate tasks. These surrogate tasks, which are time-critical but do not involve an obstacle, appear t...
Article
Femoral head osteonecrosis is often characterized histologically by the presence of empty lacunae in the affected bony regions. The shape, size and location of a necrotic lesion influences prognosis, and can, in principle, be quantified by mapping the distribution of empty lacunae within a femoral head. An algorithm is here described that automatic...
Article
Orthopaedic management of femoral head osteonecrosis is a common clinical problem for which there presently is no good solution. Current animal models are inappropriate to study potential new solutions, since it has been difficult to replicate the natural history of structural collapse seen in the human disorder. Recently, progression to collapse w...
Article
The emu (Dromaius novaehollandiae) shows potential as a unique animal model for replicating the femoral head collapse process seen in end-stage human osteonecrosis. Since the collapse phenomenon (and interventions to prevent it) involve mechanical processes, it is important to elucidate the similarities and differences of emus versus humans in term...
Article
Clinical and experimental evidence suggest that periprosthetic bone loss following total hip arthroplasty is caused in part by stress-shielding. Changes in bone stress in the proximal femur following implantation can be estimated with use of composite beam theory. We hypothesized that the degree of stress-shielding predicted by beam theory correlat...
Article
INTRODUCTION Forward falls are the dominant cause of upper extremity injuries (Oskam, et al 1998). Since a large percentage of these falls are unavoidable, focusing on strategies to reduce the incidence of injury resulting from such falls is important.
Article
INTRODUCTION In an effort to improve bone strength and prevent fracture at the distal radius, we have developed a mechanical loading intervention in which females cyclically load their forearm. To relate the applied stimulus with the bone adaptation response, an accurate characterization of the mechanical environment within the bone must be known....
Article
INTRODUCTION Older adults have a high incidence of trip-related falls that contribute to significant morbidity and mortality. A surrogate treadmill task has been proposed as a potential fall-preventive training tool for older adults. Successful motor response training must elicit stepping strategies as similar as possible to those evoked during act...

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Question & Answers (9)

Projects

Projects (7)
Project
To develop, validate, and implement new computational methods for quantitative image analysis and image-based model generation.