Academic literature on the topic 'Knee Grand Challenge'

Ballet deep squat with legs rotated externally (grand plié) is a fundamental movement for dancers. However, performing this task is a challenge to ankle control, particularly for those with ankle injury. Thus, the purpose of this study was to investigate how ankle sprains affect the ability of postural and muscular control during grand plié in ballet dancers. Thirteen injured dancers and 20 uninjured dancers performed a 15 second grand plié consisting of lowering, squatting, and rising phases. The lower extremity motion patterns and muscle activities, pelvic orientation, and center of pressure (COP) excursion were measured. In addition, a principal component analysis was applied to analyze waveforms of muscle activity in bilateral medial gastrocnemius, peroneus longus, and tibialis anterior. Our findings showed that the injured dancers had smaller pelvic motions and COP excursions, greater maximum angles of knee flexion and ankle dorsiflexion as well as different temporal activation patterns of the medial gastrocnemius and tibialis anterior. These findings suggested that the injured dancers coped with postural challenges by changing lower extremity motions and temporal muscle activation patterns.

A musculoskeletal model of the right lower limb was developed to estimate 3D tibial contact forces in high knee flexion postures. This model determined the effect of intersegmental contact between thigh–calf and heel–gluteal structures on tibial contact forces. This model includes direct tracking and 3D orientation of intersegmental contact force, femoral translations from in vivo studies, wrapping of knee extensor musculature, and a novel optimization constraint for multielement muscle groups. Model verification consisted of calculating the error between estimated tibial compressive forces and direct measurements from the Grand Knee Challenge during movements to ∼120° of knee flexion as no high knee flexion data are available. Tibial compression estimates strongly fit implant data during walking (R2 = .83) and squatting (R2 = .93) with a root mean squared difference of .47 and .16 body weight, respectively. Incorporating intersegmental contact significantly reduced model estimates of peak tibial anterior–posterior shear and increased peak medial–lateral shear during the static phase of high knee flexion movements by an average of .33 and .07 body weight, respectively. This model supports prior work in that intersegmental contact is a critical parameter when estimating tibial contact forces in high knee flexion movements across a range of culturally and occupationally relevant postures.

The purpose of this study was to determine what differences exist when performing grand plié with and without the barre. Differences in center of pressure (COP) sway, trunk kinematics, and lower extremity kinematics were used in this analysis for both first (P1) and fifth positions (P5). It was hypothesized that use of the barre would result in decreased COP sway, but increased asymmetries in trunk and lower extremity kinematics would be seen compared with the same movements performed without the barre in both positions. Sixteen collegiate dancers (1 male, 15 female) performed three trials of grand plié in P1 and P5 (right leg crossed in front) with or without the barre, for a total of 12 trials. For the barre condition (BC), participants demonstrated less time to complete grand plié, slightly less depth in grand plié, and decreased anterior-posterior (AP) sway compared to the without barre condition (WBC). The BC condition showed increased peak left trunk rotation, right knee flexion, decreased right and left peak hip flexion, and increased right hip abduction in both P1 and P5. Comparing P1 to P5, there was decreased AP sway, decreased peak left trunk rotation, decreased peak right and left hip flexion, increased left hip abduction, and decreased right knee flexion in both BC and WBC conditions. For the BC, there was increased right hip abduction in P1 compared to P5. Our results indicate that while use of the barre provides proprioceptive information, which helps dancers to control balance and learn a motor control strategy, grand plié should also be taught without the barre to challenge the dancer's balance control with different movement patterns in space.

Background: Ligaments and cartilage contact contribute to the mechanical constraints in the knee joints. However, the precise influence of these structural components on joint movement, especially when the joint constraints are computed using inverse dynamics solutions, is not clear. Methods: We present a mechanical characterization of the connections between the infinitesimal twist of the tibia and the femur due to restraining forces in the specific tissue components that are engaged and responsible for such motion. These components include the anterior cruciate, posterior cruciate, medial collateral, and lateral collateral ligaments and cartilage contact surfaces in the medial and lateral compartments. Their influence on the bony rotation about the instantaneous screw axis is governed by restraining forces along the constraints explored using the principle of reciprocity. Results: Published kinetic and kinematic joint data (American Society of Mechanical Engineers Grand Challenge Competition to Predict In Vivo Knee Loads) are applied to define knee joint function for verification using an available instrumented knee data set. We found that the line of the ground reaction force (GRF) vector is very close to the axis of the knee joint. It aligns the knee joint with the GRF such that the reaction torques are eliminated. The reaction to the GRF will then be carried by the structural components of the knee instead. Conclusions: The use of this reciprocal system introduces a new dimension of foot loading to the knee axis alignment. This insight shows that locating knee functional axes is equivalent to the static alignment measurement. This method can be used for the optimal design of braces and orthoses for conservative treatment of knee osteoarthritis. (J Am Podiatr Med Assoc 103(2): 126–135, 2013)

Unicompartmental knee arthroplasty has been shown to provide superior functional outcomes compared to total knee arthroplasty and have motivated development of advanced implant designs including bicruciate retaining knee arthroplasty. However, few validated frameworks are available to directly compare the effect of implant design and surgical techniques on ligament function and joint kinematics. In the present study, the subject-specific lower extremity models were developed based on musculoskeletal modeling framework using force-dependent kinematics method, and validated against in vivo telemetric data. The experiment data of two subjects who underwent TKA were obtained from the SimTK “Grand Challenge Competition” repository, and integrated into the subject-specific lower extremity model. Five walking gait trials and three different knee implant models for each subject were used as partial inputs for the model to predict knee biomechanics for unicompartmental, bicruciate retaining, and total knee arthroplasty. The results showed no significant differences in the tibiofemoral contact forces or angular kinematic parameters between three groups. However, unicompartmental knee arthroplasty demonstrated significantly more posterior tibial location between 0% and 40% of the gait cycle ( p < 0.017). Significant differences in range of tibiofemoral anterior/posterior translation and medial/lateral translation were also observed between unicompartmental and bicruciate retaining arthroplasty ( p < 0.017). Peak values of anterior cruciate ligament forces differed between unicompartmental and bicruciate retaining arthroplasty from 10% to 30% of the gait cycle. Findings of this study indicate that unicompartmental and bicruciate retaining arthroplasty do not have identical biomechanics and point to the complementary role of anterior cruciate ligament and articular geometry in guiding knee function. Further, the patient-specific musculoskeletal model developed provides a reliable framework for assessing new implant designs, and effect of surgical techniques on knee biomechanics following arthroplasty.

Bi-cruciate retaining total knee arthroplasty has several potential advantages including improved anteroposterior knee stability compared to contemporary posterior cruciate-retaining total knee arthroplasty. However, few studies have explored whether there is significant differences of knee biomechanics following bi-cruciate retaining total knee arthroplasty compared to posterior cruciate-retaining total knee arthroplasty. In the present study, subject-specific lower extremity musculoskeletal multi-body dynamics models for bi-cruciate retaining, bi-cruciate retaining without anterior cruciate ligament, and posterior cruciate-retaining total knee arthroplasty were developed based on the musculoskeletal modeling framework using force-dependent kinematics method and validated against in vivo telemetric data. The experiment data of two subjects who underwent total knee arthroplasty were obtained for the SimTK “Grand Challenge Competition” repository, and integrated into the musculoskeletal model. Five walking gait trials for each subject were used as partial inputs for the model to predict the knee biomechanics for bi-cruciate retaining, bi-cruciate retaining without anterior cruciate ligament, and posterior cruciate-retaining total knee arthroplasty. The results revealed significantly greater range of anterior/posterior tibiofemoral translation, and significantly more posterior tibial location during the early phase of gait and more anterior tibial location during the late phase of gait were found in bi-cruciate retaining total knee arthroplasty without anterior cruciate ligament when compared to the bi-cruciate retaining total knee arthroplasty. No significant differences in tibiofemoral contact forces, rotations, translations, and ligament forces between bi-cruciate retaining and posterior cruciate-retaining total knee arthroplasty during normal walking gait, albeit slight differences in range of tibiofemoral internal/external rotation and anterior/posterior translation were observed. The present study revealed that anterior cruciate ligament retention has a positive effect on restoring normal knee kinematics in bi-cruciate retaining total knee arthroplasty. Preservation of anterior cruciate ligament in total knee arthroplasty and knee implant designs interplay each other and both contribute to restoring normal knee kinematics in different types of total knee arthroplasty. Further evaluation of more demanding activities and subject data from patients with bi-cruciate retaining and posterior cruciate-retaining total knee arthroplasty via musculoskeletal modeling may better highlight the role of the anterior cruciate ligament and its stabilizing influence.

Background:Osteoarthritis (OA) is a degenerative joint disease involving structural pathology of all joint tissues, and most commonly affecting the knee, hip and hand. Degradation of the cartilage extracellular matrix represents a central feature of OA and is widely thought to be mediated by proteinases that degrade primarily aggrecan and collagen. ADAMTS-5, a Disintegrin And Metalloproteinase with ThromboSpondin-motif-5, is a key aggrecan-cleaving enzyme involved in cartilage degradation. S201086/GLPG1972, a potent and highly selective inhibitor of ADAMTS-5, is an oral Disease-Modifying OsteoArthritis Drug (DMOAD) candidate.Objectives:The primary objective of the ROCCELLA phase 2 clinical trial (NCT03595618) is to evaluate the effect of S201086/GLPG1972 over 52 weeks of treatment (3 dose groups compared to placebo) in reducing cartilage loss. Cartilage thickness of the knee is being measured quantitatively by Magnetic Resonance Imaging. Here, we describe the baseline characteristics of patients included in the ROCCELLA clinical trial.Methods:The main inclusion criteria were: male or female, aged 40 to 75, with a diagnosis of knee OA according to the clinical and radiological criteria of the American College of Rheumatology. The target knee had to meet a pain score between 40 and 90 mm on a 100 mm Visual Analog Scale (VAS), and the following radiographic feature upon central radiographic readings: Kellgren/Lawrence (KL) 2 or 3 and OARSI medial joint space narrowing (JSN) 1 or 2 (for more details see Deckxet al. OARSI 2020). The rationale for these specific radiographic inclusion criteria was to ensure sufficient cartilage loss over 12 months to assess the efficacy of S201086/GLPG1972.Results:Across 12 countries, 3319 patients were screened and 932 were finally included in the study. The screen failure of 72% is mainly due to the radiological criteria. The age of the patients was 62.9 ± 7.3 years (mean ± SD) with a majority of women (69.3%). The BMI was 30.5 ± 4.7 kg/m2. The duration of knee OA was 7.2 ± 6.9 years. Five hundred and one (53.8%) patients reported a medical history of musculoskeletal and connective tissue disorders, mainly osteoarthritis in other sites (20.2%), back pain (13.6%), and arthralgia (9.8%). At inclusion, 97.2% of the patients were taking different types of drug treatments, mainly anti-inflammatory and anti-rheumatic products (69.4%) and analgesics (42%). At baseline, 11% of the target knees were KL2 and 89% were KL3; 32% were OARSI medial JSN grade 1 and 68% grade 2. Target knees at inclusion had a pain score on the VAS of 63.5 ± 11.4 mm (range 0-100, with 0 for no and 100 for extreme pain) and a total WOMAC (Likert 3.1) score of 48.0 ± 15.0 (range 0-96). The WOMAC subscores for pain, stiffness and physical function were 10.0 ± 3.2 (range 0-20), 4.2 ± 1.6 (range 0-8) and 33.8 ± 11.2 (range 0-68, indicating functional limitation), respectively.Conclusion:For this clinical trial, patients were selected to present radiological criteria (i.e.OARSI JSN 1 and 2) to ensure sufficient structural progression (cartilage loss) over 12 months, as well as clinical symptoms. These stringent selection criteria were the main cause for the high screen failure rate. These baseline characteristics should warrant the ability to evaluate the efficacy of S201086/GLPG1972 as a DMOAD candidate. The search for an effective pharmacological treatment that can prevent or cure OA remains a major challenge and unmet medical need.Disclosure of Interests:Katy Bernard Employee of: Institut de Recherches Internationales Servier, Sergey GRANKOV Employee of: Institut de Recherches Internationales Servier, Marjolijne van der Stoep Employee of: Galapagos, Agnès Lalande Employee of: Institut de Recherches Internationales Servier, Olivier Imbert Employee of: Institut de Recherches Internationales Servier, De Phung Employee of: Galapagos, Damien Chimits Employee of: Institut de Recherches Internationales Servier, Karine Muller Employee of: Galapagos, Ellen van der Aar Employee of: Galapagos, Henri Deckx Employee of: Galapagos, Maria Pueyo Employee of: Institut de Recherches Internationales Servier, Felix Eckstein Grant/research support from: Merck, Orthotrphix, Servier, Galapagos, Kolon Tissuegene, Samumed, Novartis, Consultant of: Merck, Bioclinica, Servier, Samumed, Roche, Kolon Tissuegene, Galapagos and Novartis, Employee of: co-owner and employment with Chondrometrics

Background:The role of nurses in managing painful knee OA has been advocated but whether nurses can deliver such interventions as a package of care is unknown.The overall aim of this research is to develop and test a nurse-led complex intervention for knee pain comprising non-pharmacological and pharmacological components. In the first study phase, we report on fidelity and acceptability of a non-pharmacological intervention, to resolve possible challenges to delivery.Objectives:To evaluate fidelity of delivery and acceptability of non-pharmacological components of a complex intervention.Methods:This was a mixed-methods study. Participants with chronic knee pain were recruited from the community to receive the intervention, delivered in 4-sessions over a 5-week period by a trained research nurse. The intervention consisted of holistic assessment, patient education and advice, aerobic and strengthening exercise and weight-loss advice if required. All sessions were video-recorded. Fidelity checklists were completed by the nurse (nurse-rated) and two researchers from the video-recordings (video-rated). Median fidelity scores (%) and interquartile ranges (IQR) were calculated for each component and each session. Semi-structured interviews were conducted with participants. These were audio recorded, transcribed and analysed following the framework approach.Results:18 participants (34% women), with a mean (SD) age and BMI of 68.7 (9.0) years and 31.2 (8.4) kg/m2, took part in the study. Of these, 14 completed all visits. In total, 62 intervention sessions were assessed for fidelity. Overall fidelity was rated high by both nurse-rated scores (97.7%) and video-rated scores (84.2%). The level of agreement between nurse-rated and video-recorded methods was 73.3% (CI 71.3, 75.3) and the inter-rater agreement was 65.5% (CI 60.3, 70.5). Fidelity of delivery was lower for advice on footwear modification and walking aids in all sessions and moderate for education in session 1 and for exercise in session 4 (Table 1).Table 1.Fidelity scores of the components of the intervention for each session,Intervention componentsSession 1*Session 2*Session 3*Session 4*Education78.1 (74.1, 93.7)87.5 (50, 100)87.5 (50, 100)100 (93.7, 100)Exercise94.4 (88.9, 100)88.9 (75, 94)86.1 (72, 100)75 (67.6, 82.8)Adjunctive treatments50 (45.83, 100)0 (0, 50)50 (0, 100)-*median (IQR)17 participants were interviewed. Most found advice supplied straightforward. They were satisfied with the package, which changed their perception of managing knee pain, understanding it can be improved though self-management. However, too much information was provided in a short time-span and it was difficult to fit exercises into their daily routine.Conclusion:Delivery of a non-pharmacological intevention by a nurse is feasible within a research setting. Most components of the intervention were delivered as intended, except for advice about the use of adjunctive treatment.Acknowledgments:This research was funded by the NIHR Nottingham BRC and Pain Centre Versus ArthritisDisclosure of Interests:Polykarpos Angelos Nomikos: None declared, Amy Fuller: None declared, Michelle Hall: None declared, Bonnie Millar: None declared, Reuben Ogollah: None declared, Michael Doherty: None declared, Roshan Nair Speakers bureau: Financial support from pharmaceutical companies (Biogen and Novartis) to present lectures at events related to psychological support for people with multiple sclerosis (Speaker’s bureau)., David Walsh Grant/research support from: 2016: Investigator-led grant from Pfizer Ltd (ICRP) on Pain Phenotypes in RA; non-personal financial disclosure (payment to University)., Consultant of: DAW has undertaken paid consultancy to Pfizer Ltd, Eli Lilly and Company and GSK Consumer Healthcare., Paid instructor for: 2019: Consultancy to Love Productions; consultancy on programme design, contribution to programme content on self-management of chronic pain (payments to University)2019: Consultancy to AbbVie Ltd; 13.06.19; presentation on RA pain at EULAR, Madrid, and webinar (payments to University).2019: Consultancy to Eli Lilly and Company Ltd. 06.06.19 Centre for Collaborative Neuroscience, Windlesham, Surrey, UK (payment to University).2019: Consultancy to Pfizer (payment to University).2018: Consultancy to Pfizer. 07.12.18. USA. 1 day. Tanezumab (payment to University).2018: Consultancy to Pfizer. 23.11.18. Manchester UK. 1 day. Tanezumab (payment to University).2018: Consultancy to Pfizer. 1.11.18. Skype. 4h. Tanezumab (payment to University).2018: Consultancy to GlaxoSmithKline Plc. 1 day. Pain in RA and anti-GM-CSF (payment to University).2018: Consultancy to Pfizer Ltd; Presentation at OARSI; non-personal financial disclosure (payment to University)2018: Consultancy to Pfizer Ltd; Patient preference study; non-personal financial disclosure (payment to University)2017: Consultancy to Pfizer Ltd; personal financial disclosure2017: Consultancy to Pfizer Ltd through Nottingham University; non-personal financial disclosure (payment to University).2015: Consultancy to GSK Consumer Healthcare; personal financial disclosure., Speakers bureau: 2019: Irish Society of Rheumatology: speaker fees (personal pecuniary), Ana Valdes Grant/research support from: Awarded a grant from Pfizer, Abhishek Abhishek: None declared

A survey of gardeners in Minnesota found they get their information from friends and garden centers. Older gardeners were less likely to use the Internet. The highest interest was indicated for annuals, perennials, and containers, followed by trees and shrubs. Most participants had not attended a gardening class in the past year and indicated they learn best from talking with friends. Publications are of interest to gardeners, and they highly value color photos and illustrations. The University of Minnesota and Minnesota Landscape Arboretum were perceived as significantly more credible and trustworthy than garden centers, and participants felt these institutions should provide educational programs, even if survey respondents were not participating in these programs. About half the participants were not able to comment on the level of bias of the university and arboretum, and other traits (credible, trustworthy, expert, and knowledgeable) were unknown to one-third to one-half of the participants. Participants knew more about these traits for garden centers and home stores. Participants in this survey indicated they look for convenient sources of gardening information and, although many felt the land-grant university and arboretum were highly credible and knowledgeable, they were still more likely to use other sources for their gardening information. This poses a challenge to universities and arboreta to use new ways to reach gardeners.

La modellazione muscoloscheletrica consente di visualizzare pattern motori complessi e di indagare variabili difficilmente misurabili altrimenti. Esistono modelli muscoloscheletrici “generici”, completi e rappresentativi di soggetti sani adulti, e sono in grande sviluppo modelli “soggetto-specifici”, caratterizzati da parametri personalizzati per essere resi più anatomicamente accurati. Tuttavia, la personalizzazione è costosa perché richiede tempo, esami clinici, denaro. L’obiettivo di questo documento è indagare come personalizzazioni progressive del modello, svolte esclusivamente utilizzando informazioni mediche del soggetto, influenzino i risultati delle simulazioni validando i risultati predetti dai modelli tramite confronto con il dato sperimentale effettuando una analisi SPM. Il soggetto è un uomo (86 anni, altezza 180cm, peso 75Kg) dotato di una protesi strumentata al ginocchio sinistro. Utilizzando il dataset della Grand Challenge 5, sono stati sviluppati quattro modelli muscoloscheletrici caratterizzati da un livello di personalizzazione crescente. Inizialmente, sono stati confrontati su OpenSim due modelli generici opportunamente scalati sulle dimensioni del soggetto. Poi, è stato selezionato un modello tra i precedenti e ne è stata personalizzata la forza massimale isometrica di un gruppo di muscoli. In seguito, sono state personalizzate le geometrie ossee creando un modello soggetto-specifico utilizzando il software NMSBuilder e le forze personalizzate nella fase precedente. Lo studio, in accordo con la letteratura, conferma che la personalizzazione dei modelli MS influisce notevolmente sull’accuratezza delle predizioni migliorandola sensibilmente. I modelli generici di partenza mostrano profili di forza di contatto al ginocchio lontani dal valore sperimentale misurato sul soggetto (r2≈0.6, RMSE≈0.6 BW). I modelli personalizzati mostrano migliore accuratezza sia nell’analisi SPM sia nella valutazione mediante indici statistici.

Il sistema muscolo-scheletrico è un importante apparato del corpo umano, sorregge il peso corporeo e ne favorisce il movimento. Risulta quindi importante definire il suo comportamento; per farlo bisogna stimare grandezze difficilmente misurabili in vivo (i.e. le forze muscolari) e stabilire relazioni causa-effetto a partire dai dati sperimentali. Per far ciò, si fa uso di modelli muscolo-scheletrici, che sono una rappresentazione matematica del corpo umano e delle sue strutture; mediante simulazioni al computer, tali modelli, permettono di analizzare il movimento umano. Solitamente si fa uso di modelli generici, che derivano dalla dissezione di cadavere, ma questi ultimi hanno il limite di considerare per ogni soggetto in analisi la stessa anatomia. Con lo sviluppo delle conoscenze in ambito biomeccanico e con un più facile accesso alle immagini mediche, è stato possibile generare modelli di dinamica muscolo-scheletrica specifici per il soggetto. Nel caso dello studio di alcune malattie neuromuscolari, oppure nel caso in cui l’analisi è rivolta ad una popolazione pediatrica, si fa uso di modelli personalizzati in quanto la modellazione generica non è sufficiente. Questo progetto di tesi mostra quelli che sono i passaggi principali per lo sviluppo e la validazione di un modello di dinamica muscolo-scheletrico soggetto specifico per l’analisi del cammino. Tale modello è stato creato partendo dai dati forniti dalla Knee Grand Challenge 4th che mette a disposizione immagini di tomografica computazionale della gamba destra. Vengono mostrati in questo elaborato risultati di cinematica inversa, dinamica inversa, ottimizzazione statica e forza di reazione ai giunti.

Life now seems so robust that it becomes difficult to imagine how it could ever end. Are we now masters of our own destiny? With the robustness of biological information, combined with deliberate genetic engineering, are we capable of adapting to any environment Nature throws at us? Aside from some exceptional force majeure (in which case no payout is guaranteed) is there any condition under which life may end? One of the most topical and interesting discussions is whether life could run out of energy to function. But how could life ever run out of energy; and what does this actually mean? Are we just talking about the Sun dying or natural resources being depleted? The argument is that however life evolves in the future, it is difficult to imagine how it could run without the basic fuel. So if the Sun does die, we may find ourselves in a bit of pickle. However, in my view this hypothesis is entirely incorrect. At the end of the day, regardless of what happens in the Universe, the total energy is always conserved and it is merely our ability to process this energy that remains in question. Regardless of the Sun dying or natural resources being depleted, the same energy still exists within the Universe, and the challenge would then be to find different ways of harnessing it. My argument in this chapter is that life paradoxically ends not when it underdoses on fuel, but, more fundamentally, when it overdoses on ‘information’ (i.e. when it reaches a saturation point and can no longer process any further information). We have all experienced instances where we feel we cannot absorb any more information. The question is: is this fatal? What would you like the epitaph on your tombstone to read when you die? Usually people do not have a strong desire to inscribe anything grand or meaningful themselves, but their close ones, the family, friends, and relatives, choose to write something down to commemorate their loss.

By the fall of 1969 we knew we had to challenge pesticide regulation by the federal government if we were to ultimately prevail against DDT, but we did not know how to do it. We had the science well in hand and knew how to present it, with literally hundreds of scientists prepared to testify within their areas of expertise. We did not have the organizational structure to launch such an effort at the federal level, however, and we were certainly short of money. At about that time Joseph L. Sax, then the leading proponent of the development of environmental law at the University of Michigan Law School, suggested that we contact the newly founded Center for Law and Social Policy (CLASP), a public-interest law firm in Washington, DC. Joe was a member of the CLASP board. He insisted that DDT was in violation of the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) and that the U.S. Department of Agriculture (USDA) was not enforcing FIFRA. I therefore called and talked at length with James W. Moorman (Fig. 7.1), attorney for CLASP, describing the DDT problem and proposed action against USDA. “If we are going to do this, then you are going to come down here and help me put the case together,” said Jim firmly. That was not music to my ears: I had other things I needed to do, but shortly I was on my way to Washington. CLASP was in a rundown part of Washington, and my “housing” consisted of sleeping on an old mattress in their dusty attic. But we got to work and wrote a petition to USDA in about a week. The petition was a formal legal request that the FIFRA registrations for DDT be canceled. The petition also requested that USDA suspend the registrations while it was considering their cancellation. We had no illusions that USDA would grant our request, but it was Jim’s advice that we go to USDA for administrative relief before seeking cancellation and suspension from the courts.

I once took a graduate course, from a well-published and finely educated writer, on the topic of voice. In the first moments of the class, several of us audaciously asked the instructor to define the term. A few minutes into her answer, I sensed confusion in the classroom. After 10 more minutes of wandering discussion, it became clear that our teacher couldn't handle this most basic query. She knew it when she read it, she said to our amazement, but who could hope to define voice or its literary twin, style? Today, after years of teaching voice myself—and of continuing my own writing—I finally understand my instructor's confusion. While all writers crave an individual style, and while we yearn for a distinctive voice for ourselves or the subjects we profile, those goals remain among our greatest challenges, and even experienced practitioners can retreat into debates over their mystery. Many science writers also must contend with journalistic precepts that subjugate or even eliminate individual style. In this chapter I review the complications and examine the tools of voice and style, concluding with exercises that should help writers identify and hone their own. When writers for the New York Times or the Modern Language Association or the New England Journal of Medicine talk of style, they often mean the strict rules of spelling, punctuation, abbreviation, and other usage as set forth in hallowed style manuals. Style is also used, more colloquially, to describe writing according to purpose or profession: academic, scientific, journalistic, digital, bureaucratic, literary, postmodern, and so forth. For academics, style has classical roots in Aristotle, Cicero, and that granddaddy of Rhetoric, Hermogenes, who rated style as grand, middle, or plain. Writer Ben Yagoda, in his The Sound on the Page: Style and Voice in Writing (2004), defines style as how a writer “uses language to forge or reflect an attitude toward the world.” For the purpose of this chapter, let's define voice as a writer's personality on the page. Style is the personality imposed on our writing by outside rules and/or our own techniques and mindset. Voice is an individual writing personality, whether distinctively our own, one we recount or create, or, sometimes inescapably, both.

Knowledge of knee loading would benefit prosthetic design, development of tissue engineered materials, orthopedic repair, and management of degenerative joint diseases such as osteoarthritis. Musculoskeletal modeling provides a method for estimating in vivo joint loading, but validation of model predictions is challenging. Data provided by the “Grand Challenge Competition to Predict In-Vivo Knee Loads” for the 2012 American Society of Mechanical Engineers Summer Bioengineering Conference [1] provides data from an instrumented prosthetic knee that can be used to validate load predictions. The Grand Challenge data set includes implant and bone geometries, motion, ground reaction forces, electromyography (EMG) as well as measured knee loading. Presented here are muscle driven forward dynamics simulations with a prosthetic knee for two of the calibration gait trials (SC_2legsquat and SC_calfrise) provided with the Grand Challenge data set. The calibration trials include the instrumented knee measurements and are provided to help “calibrate” models used in the Grand Challenge competition. Inputs to model simulations were experimental marker motion and outputs included muscle force, ground reaction forces, ligament forces, contact forces, and knee loading. Experimental measurements of knee loading, ground reaction force, and muscle activations were compared to model predictions.

A simplified computational model is presented with which axial knee implant forces can be estimated. The dataset provided in the IV Grand Challenge to Predict in-vivo Knee Loads [1] is used to assemble a musculoskeletal model, and perform an inverse dynamics analysis. The joint and muscle dynamics recorded during the inverse analysis is then used as target values during a forward dynamics analysis to compute the axial tibiofemoral load.

Numerical models are necessary to estimate forces through the knee joint during activities of daily living. However, the numerous muscles and soft tissues crossing the knee joint result in a computationally indeterminate problem. The recent availability of measured contact force data from telemeterized total knee replacements (TKRs) has given researchers the chance to validate models, but telemeterized TKRs represent only a few patients with a specific implant type. Computational models remain necessary to bridge the gap between the small instrumented patient population with a particular implant and larger patient populations executing various activities. Abstracted gait data from another lab tests the versatility of any model to accurately predict forces of TKR patients performing a variety of gaits with disparate implant types. In this study, we calculate and examine the differences between medial and lateral contact forces in level walking and medial thrust gait trials from a freely provided dataset1.

Accurate prediction of knee joint contact loading during gait is important for understanding knee pathology and development of suitable clinical interventions. While many researchers have modeled the knee contact loads during level walking, these predictions have ranged from 3.4 [1] to 7 [2] times body weight. Validation of contact loads is difficult; the joint contact load depends not only on readily obtainable external kinematics and reaction forces, but also on the forces generated by muscle and other soft tissues. Recently, an instrumented tibial implant, capable of telemetrically reporting the six degree-of-freedom loading environment of the tibial plateau, was used to tune and validate an EMG-driven model of the lower extremity [3]. Recognizing the value of these in vivo data, and the limitations of existing knee models, these researchers devised the Grand Challenge Competitions to Predict In Vivo Knee Loads.