Publications by authors named "Joseph E Langenderfer"

20 Publications

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Reductions in Kinematics from Brassieres with Varying Breast Support.

Int J Exerc Sci 2019 1;12(1):402-411. Epub 2019 Mar 1.

School of Engineering and Technology, Central Michigan University, Mt. Pleasant, MI, USA.

Given the abundance of brassieres, manufacturers, and investigations of bras, it remains unclear whether the continued development of bras will provide many additional improvements in support. This study measured performance of sport bras including 4 popular bras and a new style bra at reducing breast motion during five common exercises. Bras demonstrated varying effectiveness and consistency across exercises at reducing undesirable breast motion, (hereafter referred to as kinematics). The new style bra significantly reduced vertical breast displacement and acceleration more consistently than other bras. When significant differences between bras were detected, the newer bra provided 31% greater reduction in vertical displacements and accelerations on average than other bras. Lateral reductions were smaller, less significant and no differences between bras were detected. When participants evaluated bras in terms of performance and ease of use, the newer bra was rated better than other bras by nearly a two to one ratio. There were no differences in how the bras felt, or in terms of pain and discomfort. Correlations between participant comfort and reductions in kinematics were weak and inconsistent. Results suggest continued bra development is possible in order to reduce undesirable motion especially in terms of reducing lateral motion. Additional investigation is required to examine the mechanistic reasons why bras improve comfort and potentially performance.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6413842PMC
March 2019

Sensitivity Analysis and Uncertainty Quantification in Pulmonary Drug Delivery of Orally Inhaled Pharmaceuticals.

J Pharm Sci 2017 11 20;106(11):3303-3315. Epub 2017 Jun 20.

School of Engineering and Technology, Central Michigan University, Mount Pleasant, Michigan 48859.

In spite of widespread use of modeling tools in inhalation dosimetry, it remains difficult to quantify the output uncertainties when subjected to various sources of input variability. This study aimed to develop a computational model that can quantify the input sensitivity and output uncertainty in pulmonary drug delivery by coupling probabilistic analysis package NESSUS with ANSYS Fluent. An image-based mouth-lung model was used to simulate the transport and deposition of drug particles and variability in particle size, density, and inhalation speed were considered. Results show that input variables have different importance levels on the delivered doses to lungs. For a given level of variability, the delivered dose is more sensitive to the variance of particle diameter than that of the inhalation speed and particle density. The range of input scatters has a profound impact on the outcome probability of delivered efficiencies, while the input distribution type (normal vs. log-normal) appears to have an insignificant effect. Despite normal distributions for all input variables, the output exhibits a non-normal distribution. The proposed model in this study allows easy specification of input distributions to conduct multivariable probabilistic analysis of inhalation drug deliveries, which can facilitate more reliable treatment planning and outcome assessment.
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http://dx.doi.org/10.1016/j.xphs.2017.06.011DOI Listing
November 2017

Effect of hammer mass on upper extremity joint moments.

Appl Ergon 2017 Apr 11;60:231-239. Epub 2016 Dec 11.

School of Engineering and Technology, Central Michigan University, Mount Pleasant, MI 48859, USA. Electronic address:

This study used an OpenSim inverse-dynamics musculoskeletal model scaled to subject-specific anthropometrics to calculate three-dimensional intersegmental moments at the shoulder, elbow and wrist while 10 subjects used 1 and 2 lb hammers to drive nails. Motion data were collected via an optoelectronic system and the interaction of the hammer with nails was recorded with a force plate. The larger hammer caused substantial increases (50-150%) in moments, although increases differed by joint, anatomical component, and significance of the effect. Moment increases were greater in cocking and strike/follow-through phases as opposed to swinging and may indicate greater potential for injury. Compared to shoulder, absolute increases in peak moments were smaller for elbow and wrist, but there was a trend toward larger relative increases for distal joints. Shoulder rotation, elbow varus-valgus and pronation-supination, and wrist radial-ulnar deviation and rotation demonstrated large relative moment increases. Trial and phase durations were greater for the larger hammer. Changes in moments and timing indicate greater loads on musculoskeletal tissues for an extended period with the larger hammer. Additionally, greater variability in timing with the larger hammer, particularly for cocking phase, suggests differences in control of the motion. Increased relative moments for distal joints may be particularly important for understanding disorders of the elbow and wrist associated with hammer use.
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http://dx.doi.org/10.1016/j.apergo.2016.12.001DOI Listing
April 2017

Enhanced arm swing alters interlimb coordination during overground walking in individuals with traumatic brain injury.

Hum Mov Sci 2017 Apr 20;52:45-54. Epub 2017 Jan 20.

Doctoral Program in Physical Therapy, Central Michigan University, Mt. Pleasant, MI, USA.

The current study investigated interlimb coordination in individuals with traumatic brain injury (TBI) during overground walking. The study involved 10 participants with coordination, balance, and gait abnormalities post-TBI, as well as 10 sex- and age-matched healthy control individuals. Participants walked 12m under two experimental conditions: 1) at self-selected comfortable walking speeds; and 2) with instructions to increase the amplitude and out-of-phase coordination of arm swinging. The gait was assessed with a set of spatiotemporal and kinematic parameters including the gait velocity, step length and width, double support time, lateral displacement of the center of mass, the amplitude of horizontal trunk rotation, and angular motions at shoulder and hip joints in sagittal plane. Interlimb coordination (coupling) was analyzed as the relative phase angles between the left and right shoulders, hips, and contralateral shoulders and hips, with an ideal out-of-phase coupling of 180° and ideal in-phase coupling of 0°. The TBI group showed much less interlimb coupling of the above pairs of joint motions than the control group. When participants were required to increase and synchronize arm swinging, coupling between shoulder and hip motions was significantly improved in both groups. Enhanced arm swinging was associated with greater hip and shoulder motion amplitudes, and greater step length. No other significant changes in spatiotemporal or kinematic gait characteristics were found in either group. The results suggest that arm swinging may be a gait parameter that, if controlled properly, can improve interlimb coordination during overground walking in patients with TBI.
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http://dx.doi.org/10.1016/j.humov.2017.01.001DOI Listing
April 2017

A probabilistic orthopaedic population model to predict fatigue-related subacromial geometric variability.

J Biomech 2016 Feb 19;49(4):543-9. Epub 2016 Jan 19.

Department of Kinesiology, University of Waterloo, Waterloo, Canada N2L 3G1. Electronic address:

Fatigue-related glenohumeral and scapulothoracic kinematic relationships, in addition to morphological characteristics of the scapula and humerus, affect the dimensions of the subacromial space. Each exhibits considerable interpersonal variability, which if only considering the mean, can lead to misleading population estimations of subacromial impingement risk, particularly for outliers. Additionally, the relative influence of each parameter on subacromial space variability is unclear. Applying empirically-derived morphological and kinematic distributions (n=31), this research used Advanced Mean Value and Monte Carlo probabilistic modeling approaches to predict the distribution of the minimum subacromial space width (SAS) and establish which parameters contributed more to modulating the SAS. The predicted SAS differed by 8mm between 1% and 99% confidence intervals. While the SAS was not influenced by muscle fatigue, the space reduced with arm elevation to magnitudes between 4.5 and 5mm. This reduction resulted in an estimated 65-75% of the population at risk for tissue compression at elevation angles≥90° when considering the interposed tissue thickness. Morphological parameters, notably glenoid inclination, showed higher relative importance for modulating the predicted SAS across conditions, while kinematic parameters (humeral head translation, scapular orientation), which differed by elevation angle and fatigue state, demonstrated less consistent importance levels across experimental conditions. Overall, the findings reinforce the shoulder health risks related to overhead activities, as they pose an increased likelihood of mechanical rotator cuff tendon compression. Further, probabilistic methods are highly innovative, in that they are capable of determining relative parameter importance and subsequently identifying key injury risk factors. As glenoid inclination is difficult to diagnose and treat, and is associated with superior humeral head translation, interventions to improve rotator cuff strength and glenohumeral stability are recommended, particularly in populations exposed to overhead postures.
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http://dx.doi.org/10.1016/j.jbiomech.2015.12.049DOI Listing
February 2016

The influence of cycle time on shoulder fatigue responses for a fixed total overhead workload.

J Biomech 2015 Aug 14;48(11):2911-8. Epub 2015 May 14.

School of Engineering and Technology, Central Michigan University, Mount Pleasant, MI, USA.

The relationship between overhead work and musculoskeletal health depends on multiple task and individual factors. Knowledge gaps persist, despite examination of many of these factors individually and in combination. This investigation targeted task variation, as parameterized by cycle time within a fixed overall workload. Participants performed an intermittent overhead pressing task with four different cycle time conditions while overall workload and duty cycle was held constant. Several manifestations of fatigue were monitored during task performance. Endurance time was influenced by cycle time with shorter cycle times having endurance times up to 25% higher than longer cycle times. Surface electromyography (sEMG) results were mixed, with two muscles demonstrating amplitude increases (middle deltoid and upper trapezius) that varied with cycle time. sEMG frequency was not influenced by cycle time for any muscle monitored, despite decreases for several cycle times. Trends existed for the influence of cycle time on time-varying reported discomfort (p=0.056) and static strength (p=0.055); large effect sizes were present (ηp(2)=0.31 and 0.27, respectively). The equivocal association of fatigue indicators and cycle time is analogous to the influence of other factors implicated in overhead work musculoskeletal risk, and probabilistic modeling offers a compelling avenue for integration of the known variation in the many factors that combine to inform this risk.
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http://dx.doi.org/10.1016/j.jbiomech.2015.04.043DOI Listing
August 2015

Probabilistic evaluation of predicted force sensitivity to muscle attachment and glenohumeral stability uncertainty.

Ann Biomed Eng 2014 Sep 28;42(9):1867-79. Epub 2014 May 28.

Department of Kinesiology, University of Waterloo, Waterloo, ON, N2L 3G1, Canada,

A major benefit of computational modeling in biomechanics research is its ability to estimate internal muscular demands given limited input information. However, several assumptions regarding model parameters and constraints may influence model outputs. This research evaluated the influence of model parameter variability, specifically muscle attachment locations and glenohumeral stability thresholds, on predicted rotator cuff muscle force during internal and external axial humeral rotation tasks. Additionally, relative sensitivity factors assessed which parameters were more contributory to output variability. Modest model parameter variation resulted in considerable variability in predicted force, with origin-insertion locations being particularly influential. Specifically, the scapula attachment site of the subscapularis muscle was important for modulating predicted force, with sensitivity factors ranging from α=0.2 to 0.7 in a neutral position. The largest variability in predicted forces was present for the subscapularis muscle, with average differences of 33.0±9.6% of normalized muscle force (1-99% CI), and a maximal difference of 51% in neutral exertions. Infraspinatus and supraspinatus muscles elicited maximal differences of 15.0 and 20.6%, respectively, between confidence limits. Overall, origin and insertion locations were most influential and thus incorporating geometric variation in the prediction of rotator cuff muscle forces may provide more representative population estimates.
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http://dx.doi.org/10.1007/s10439-014-1035-3DOI Listing
September 2014

Postural stabilization by gripping a stick with different force levels.

Gait Posture 2013 May 26;38(1):97-103. Epub 2012 Nov 26.

Department of Physical Therapy, Central Michigan University, Mt. Pleasant, MI 48858, USA.

Hand contact with a stationary surface reduces postural sway in healthy individuals even when the level of force applied is mechanically insufficient. To make this phenomenon more applicable to a real-life situation, where a stationary support is not available, a mobile stick was used to measure and control grip force. The effect of a supra-postural task of stick gripping on stability was tested in 18 healthy individuals during quiet standing, standing in semi-tandem, and with eyes closed. Subjects stood either holding no haptic stick, or gripping with one of six force levels ranging from 1 to 9N and a self-selected force in the same range. The path length and velocity of the center of pressure (COP) were measured and compared within and between experimental conditions. Gripping the stick reduced the COP path length and velocity by up to 23% and 25%, respectively, and postural stability was increased at all force levels, including self-selected. The results confirmed the stabilizing effects of gripping an external portable object regardless of the amount of force applied. This knowledge may be useful for counseling people on prevention of stability loss in real life situations where balance is challenged.
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http://dx.doi.org/10.1016/j.gaitpost.2012.10.020DOI Listing
May 2013

Development of subject-specific and statistical shape models of the knee using an efficient segmentation and mesh-morphing approach.

Comput Methods Programs Biomed 2010 Mar 19;97(3):232-40. Epub 2009 Aug 19.

Computational Biomechanics Laboratory, Department of Mechanical and Materials Engineering, University of Denver, 2390 S. York St., Denver, CO, USA.

Subject-specific finite element models developed from imaging data provide functional representation of anatomical structures and have been used to evaluate healthy and pathologic knee mechanics. The creation of subject-specific models is a time-consuming process when considering manual segmentation and hexahedral (hex) meshing of the articular surfaces to ensure accurate contact assessment. Previous studies have emphasized automated mesh mapping to bone geometry from computed tomography (CT) scans, but have not considered cartilage and soft tissue structures. Statistical shape modeling has been proposed as an alternative approach to develop a population of subject models, but still requires manual segmentation and registration of a training set. Accordingly, the aim of the current study was to develop an efficient, integrated mesh-morphing-based segmentation approach to create hex meshes of subject-specific geometries from scan data, to apply the approach to natural femoral, tibial, and patellar cartilage from magnetic resonance (MR) images, and to demonstrate the creation of a statistical shape model of the knee characterizing the modes of variation using principal component analysis. The platform was demonstrated on MR scans from 10 knees and enabled hex mesh generation of the knee articular structures in approximately 1.5h per subject. In a subset of geometries, average root mean square geometric differences were 0.54 mm for all structures and in quasi-static analyses over a range of flexion angles, differences in predicted peak contact pressures were less than 5.3% between the semi-automated and manually generated models. The integrated segmentation, mesh-morphing approach was employed in the efficient development of subject-specific models and a statistical shape model, where populations of subject-specific models have application to implant design evaluation or surgical planning.
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http://dx.doi.org/10.1016/j.cmpb.2009.07.005DOI Listing
March 2010

A multi-subject evaluation of uncertainty in anatomical landmark location on shoulder kinematic description.

Comput Methods Biomech Biomed Engin 2009 Apr;12(2):211-6

Department of Engineering and Technology, Central Michigan University, Mount Pleasant, MI, USA.

An accurate assessment of shoulder kinematics is useful for understanding healthy normal and pathological mechanics. Small variability in identifying and locating anatomical landmarks (ALs) has potential to affect reported shoulder kinematics. The objectives of this study were to quantify the effect of landmark location variability on scapular and humeral kinematic descriptions for multiple subjects using probabilistic analysis methods, and to evaluate the consistency in results across multiple subjects. Data from 11 healthy subjects performing humeral elevation in the scapular plane were used to calculate Euler angles describing humeral and scapular kinematics. Probabilistic analyses were performed for each subject to simulate uncertainty in the locations of 13 upper-extremity ALs. For standard deviations of 4 mm in landmark location, the analysis predicted Euler angle envelopes between the 1 and 99 percentile bounds of up to 16.6 degrees . While absolute kinematics varied with the subject, the average 1-99% kinematic ranges for the motion were consistent across subjects and sensitivity factors showed no statistically significant differences between subjects. The description of humeral kinematics was most sensitive to the location of landmarks on the thorax, while landmarks on the scapula had the greatest effect on the description of scapular elevation. The findings of this study can provide a better understanding of kinematic variability, which can aid in making accurate clinical diagnoses and refining kinematic measurement techniques.
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http://dx.doi.org/10.1080/10255840903093441DOI Listing
April 2009

An efficient probabilistic methodology for incorporating uncertainty in body segment parameters and anatomical landmarks in joint loadings estimated from inverse dynamics.

J Biomech Eng 2008 Feb;130(1):014502

Computational Biomechanics Laboratory, Department of Mechanical and Materials Engineering, University of Denver, Denver, CO 80208, USA.

Inverse dynamics is a standard approach for estimating joint loadings in the lower extremity from kinematic and ground reaction data for use in clinical and research gait studies. Variability in estimating body segment parameters and uncertainty in defining anatomical landmarks have the potential to impact predicted joint loading. This study demonstrates the application of efficient probabilistic methods to quantify the effect of uncertainty in these parameters and landmarks on joint loading in an inverse-dynamics model, and identifies the relative importance of the parameters and landmarks to the predicted joint loading. The inverse-dynamics analysis used a benchmark data set of lower-extremity kinematics and ground reaction data during the stance phase of gait to predict the three-dimensional intersegmental forces and moments. The probabilistic analysis predicted the 1-99 percentile ranges of intersegmental forces and moments at the hip, knee, and ankle. Variabilities, in forces and moments of up to 56% and 156% of the mean values were predicted based on coefficients of variation less than 0.20 for the body segment parameters and standard deviations of 2 mm for the anatomical landmarks. Sensitivity factors identified the important parameters for the specific joint and component directions. Anatomical landmarks affected moments to a larger extent than body segment parameters. Additionally, for forces, anatomical landmarks had a larger effect than body segment parameters, with the exception of segment masses, which were important to the proximal-distal joint forces. The probabilistic modeling approach predicted the range of possible joint loading, which has implications in gait studies, clinical assessments, and implant design evaluations.
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http://dx.doi.org/10.1115/1.2838037DOI Listing
February 2008

A stochastic analysis of glenoid inclination angle and superior migration of the humeral head.

Clin Biomech (Bristol, Avon) 2008 Jun 14;23(5):554-61. Epub 2008 Feb 14.

Laboratory for Optimization and Computation in Orthopaedic Surgery, Department of Orthopaedic Surgery, University of Michigan, 2019 BSRB, 109 Zina Pitcher Pl., Ann Arbor, MI 48109-2200, USA.

Background: Superior glenoid inclination, which is a relatively upward facing of the glenoid in the plane of the scapula, has been associated with rotator cuff pathology. Increased glenoid inclination may cause superior humeral head migration, which can cause impingement of the supraspinatus tendon. The purpose of this study was to test the hypothesis that inclination angle affects the probability of superior humeral head migration.

Methods: A three-dimensional model of the glenohumeral joint was developed in which muscle forces were modeled as random variables. Monte Carlo simulation was used to compute the probability that the glenohumeral reaction force was directed such that superior humeral head migration should occur. An electromyogram-driven model was used to estimate shoulder muscle forces in healthy volunteers performing arm elevation.

Findings: The model predicted that the probability of superior humeral head migration increased as glenoid inclination angle was increased. This finding was independent of the assumed shape of the muscle force probability distributions.

Interpretation: The results support the theory that glenoid inclination may be a risk factor for rotator cuff pathology.
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http://dx.doi.org/10.1016/j.clinbiomech.2008.01.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2515172PMC
June 2008

Evaluation of three methods for determining EMG-muscle force parameter estimates for the shoulder muscles.

Clin Biomech (Bristol, Avon) 2008 Feb 22;23(2):166-74. Epub 2007 Oct 22.

Laboratory for Optimization and Computation in Orthopaedic Surgery, University of Michigan, 2019 Biomedical Science Research Building, 109 Zina Pitcher Place, Ann Arbor, MI 48109-2200, USA.

Background: Accurate prediction of in vivo muscle forces is essential for relevant analyses of musculoskeletal biomechanics. The purpose of this study was to evaluate three methods for predicting muscle forces of the shoulder by comparing calculated muscle parameters, which relate electromyographic activity to muscle forces.

Methods: Thirteen subjects performed sub-maximal, isometric contractions consisting of six actions about the shoulder and two actions about the elbow. Electromyography from 12 shoulder muscles and internal shoulder moments were used to determine muscle parameters using traditional multiple linear regression, principal-components regression, and a sequential muscle parameter determination process using principal-components regression. Muscle parameters were evaluated based on their sign (positive or negative), standard deviations, and error between the measured and predicted internal shoulder moments.

Findings: It was found that no method was superior with respect to all evaluation criteria. The sequential principal-components regression method most frequently produced muscle parameters that could be used to estimate muscle forces, multiple regression best predicted the measured internal shoulder moments, and the results of principal-components regression fell between those of sequential principal-components regression and multiple regression.

Interpretation: The selection of a muscle parameter estimation method should be based on the importance of the evaluation criteria. Sequential principal-components regression should be used if a greater number of physiologically accurate muscle forces are desired, while multiple regression should be used for a more accurate prediction of measured internal shoulder moments. However, all methods produced muscle parameters which can be used to predict in vivo muscle forces of the shoulder.
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http://dx.doi.org/10.1016/j.clinbiomech.2007.08.026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2258142PMC
February 2008

Effects of rotator cuff tears on muscle moment arms: a computational study.

J Biomech 2007 26;40(15):3373-80. Epub 2007 Jun 26.

Computational Biomechanics Laboratory, Department of Mechanical and Materials Engineering, University of Denver, Denver, CO, USA.

Rotator cuff tears cause morphologic changes to cuff tendons and muscles, which can alter muscle architecture and moment arm. The effects of these alterations on shoulder mechanical performance in terms of muscle force and joint strength are not well understood. The purpose of this study was to develop a three-dimensional explicit finite element model for investigating morphological changes to rotator cuff tendons following cuff tear. The subsequent objectives were to validate the model by comparing model-predicted moment arms to empirical data, and to use the model to investigate the hypothesis that rotator cuff muscle moment arms are reduced when tendons are divided along the force-bearing direction of the tendon. The model was constructed by extracting tendon, cartilage, and bone geometry from the male Visible Human data set. Infraspinatus and teres minor muscle and tendon paths were identified relative to the humerus and scapula. Kinetic and kinematic boundary conditions in the model replicated experimental protocols, which rotated the humerus from 45 degrees internal to 45 degrees external rotation with constant loads on the tendons. External rotation moment arms were calculated for two conditions of the cuff tendons: intact normal and divided tendon. Predicted moment arms were within the 1-99% confidence intervals of experimental data for nearly all joint angles and tendon sub-regions. In agreement with the experimental findings, when compared to the intact condition, predicted moment arms were reduced for the divided tendon condition. The results of this study provide evidence that one potential mechanism for the reduction in strength observed with cuff tear is reduction of muscle moment arms. The model provides a platform for future studies addressing mechanisms responsible for reduced muscle force and joint strength including changes to muscle length-tension operating range due to altered muscle and tendon excursions, and the effects of cuff tear size and location on moment arms and muscle forces.
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http://dx.doi.org/10.1016/j.jbiomech.2007.05.017DOI Listing
January 2008

Probabilistic modeling of knee muscle moment arms: effects of methods, origin-insertion, and kinematic variability.

Ann Biomed Eng 2007 Sep 2;35(9):1632-42. Epub 2007 Jun 2.

Computational Biomechanics Lab, Department of Mechanical & Materials Engineering, University of Denver, 2390 S. York, Denver, CO 80208, USA.

In musculoskeletal modeling, reliable estimates of muscle moment arms are an important step in accurately predicting muscle forces and joint moments. The degree of agreement between the two common methods of calculating moment arms-tendon excursion (TE) and geometric origin-insertion, is currently unknown for the muscles crossing the knee joint. Further, measured moment arm data are subject to variability in estimation of attachment sites as points from irregular surfaces on the bones, and due to differences in joint kinematics observed in vivo. Thus, the objectives of the present study were to compare moment arms of major muscles crossing the knee joint obtained from TE and geometric methods using a finite element-based lower extremity model, and to quantify the effects of potential muscle origin-insertion and tibiofemoral kinematic variability on the predicted moment arms using probabilistic methods. A semiconstrained, fixed bearing, posterior cruciate-retaining total knee arthroplasty was included due to available in vivo kinematic data. In this study, muscle origin and insertion locations and kinematic variables were represented as normal distributions with standard deviations of 5 mm for origin-insertion locations and up to 1.6 mm and 3.0 degrees for the kinematic parameters. Agreement between the deterministic moment arm calculations from the two methods was excellent for the flexors, while differences in trends and magnitudes were observed for the extensor muscles. Model-predicted deterministic moment arms from both methods agreed reasonably with the experimental values from available literature. The uncertainty in input parameters resulted in substantial variability in predicted moment arms, with the size of 1-99% confidence interval being up to 41.3 and 35.8 mm for the TE and geometric methods, respectively. The sizeable range of moment arm predictions and associated excursions has the potential to affect a muscle's operating range on the force-length curve, thus affecting joint moments. In this study, moment arm predictions were more dependent on muscle origin-insertion locations than the kinematic variables. The important parameters from the TE method were the origin and insertion locations in the sagittal plane, while the insertion location in the sagittal plane was the dominant parameter using the geometric method.
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http://dx.doi.org/10.1007/s10439-007-9334-6DOI Listing
September 2007

Variation in external rotation moment arms among subregions of supraspinatus, infraspinatus, and teres minor muscles.

J Orthop Res 2006 Aug;24(8):1737-44

Department of Biomedical Engineering, University of Michigan, 24 Frank Lloyd Wright Dr., P.O. Box 391, Ann Arbor, Michigan 48106-0391, USA.

A rotator cuff tear causes morphologic changes in rotator cuff muscles and tendons and reduced shoulder strength. The mechanisms by which these changes affect joint strength are not understood. This study's purpose was to empirically determine rotation moment arms for subregions of supraspinatus, infraspinatus, and for teres minor, and to test the hypothesis that subregions of the cuff tendons increase their effective moment arms through connections to other subregions. Tendon excursions were measured for full ranges of rotation on 10 independent glenohumeral specimens with the humerus abducted in the scapular plane at 10 and 60 degrees . Supraspinatus and infraspinatus tendons were divided into equal width subregions. Two conditions were tested: tendon divided to the musculotendinous junction, and tendon divided to the insertion on the humerus. Moment arms were determined from tendon excursion via the principle of virtual work. Moment arms for the infraspinatus (p < 0.001) and supraspinatus (p < 0.001) were significantly greater when the tendon was only divided to the musculotendinous junction versus division to the humeral head. Moment arms across subregions of infraspinatus (p < 0.001) and supraspinatus (p < 0.001) were significantly different. A difference in teres minor moment arm was not found for the two cuff tendon conditions. Moment arm differences between muscle subregions and for tendon division conditions have clinical implications. Interaction between cuff regions could explain why some subjects retain strength after a small cuff tear. This finding helps explain why a partial cuff repair may be beneficial when a complete repair is not possible. Data presented here can help differentiate between cuff tear cases that would benefit from cuff repair and cases for which cuff repair might not be as favorable.
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http://dx.doi.org/10.1002/jor.20188DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1551907PMC
August 2006

Variability in isometric force and moment generating capacity of glenohumeral external rotator muscles.

Clin Biomech (Bristol, Avon) 2006 Aug 18;21(7):701-9. Epub 2006 Apr 18.

Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI 48106-0391, USA.

Background: Muscles which cause glenohumeral external rotation possess varying ability for generating force and moment due to differences in muscle architecture, moment arm, and the interaction of these two factors. This study's purpose was to determine a complete dataset of muscle-tendon parameters for predicting the moment generating capacity and force-length dependence for external rotation of infraspinatus, supraspinatus and teres minor muscles.

Methods: Muscle fascicle length, sarcomere length, pennation angle, and muscle volume were measured for sub-regions of infraspinatus and supraspinatus, and teres minor from 10 glenohumeral specimens. Tendon excursion was measured for glenohumeral rotation. From these parameter measurements, optimal fascicle length, physiological cross-sectional area, muscle force-length dependence, and maximum isometric moment generating capacity were calculated.

Findings: Substantial differences were found for optimal muscle length, physiologic cross-sectional area, and tendon length for the 10 specimens of this study. Muscle sub-region had a significant effect on the force-length relationship for infraspinatus (P<0.001), but was not significant for supraspinatus (P=0.49). For infraspinatus and supraspinatus, maximum isometric rotation moment capacity was greater at 10 degrees versus 60 degrees abduction (P<0.001). Maximum isometric rotation moment capacity for the teres minor was greater at 10 degrees versus 60 degrees abduction (P<0.01). Sub-regions demonstrated significant differences in isometric moment capacity (P<0.001).

Interpretation: Functional capabilities of these muscles depend on muscle architecture and moment arm as well as their combined effects. The results allow for development of stochastic and deterministic models of glenohumeral external rotation strength which can be used for prediction of muscle forces and joint moments.
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http://dx.doi.org/10.1016/j.clinbiomech.2006.02.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1540460PMC
August 2006

A probabilistic model of glenohumeral external rotation strength for healthy normals and rotator cuff tear cases.

Ann Biomed Eng 2006 Mar 11;34(3):465-76. Epub 2006 Feb 11.

MedSport and Orthopaedic Research Laboratories, University of Michigan, Ann Arbor, MI 48106, USA.

The reigning paradigm of musculoskeletal modeling is to construct deterministic models from parameters of an "average" subject and make predictions for muscle forces and joint torques with this model. This approach is limited because it does not perform well for outliers, and it does not model the effects of population parameter variability. The purpose of this study was to simulate variability in musculoskeletal parameters on glenohumeral external rotation strength in healthy normals, and in rotator cuff tear case using a Monte Carlo model. The goal was to determine if variability in musculoskeletal parameters could quantifiably explain variability in glenohumeral external rotation strength. Multivariate Gamma distributions for musculoskeletal architecture and moment arm were constructed from empirical data. Gamma distributions of measured joint strength were constructed. Parameters were sampled from the distributions and input to the model to predict muscle forces and joint torques. The model predicted measured joint torques for healthy normals, subjects with supraspinatus tears, and subjects with infraspinatus-supraspinatus tears with small error. Muscle forces for the three conditions were predicted and compared. Variability in measured torques can be explained by differences in parameter variability.
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http://dx.doi.org/10.1007/s10439-005-9045-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1513644PMC
March 2006

A stochastic model of elbow flexion strength for subjects with and without long head biceps tear.

Comput Methods Biomech Biomed Engin 2005 Oct;8(5):315-22

University of Michigan, MedSport and Orthopaedic Research Laboratories, Ann Arbor, MI, USA.

The classical approach of musculoskeletal modeling is to predict muscle forces and joint torques with a deterministic model constructed from parameters of an average subject. However, this type of model does not perform well for outliers, and does not model the effects of parameter variability. In this study, a Monte-Carlo model was used to stochastically simulate the effects of variability in musculoskeletal parameters on elbow flexion strength in healthy normals, and in subjects with long head biceps (LHB) rupture. The goal was to determine if variability in elbow flexion strength could be quantifiably explained with variability in musculoskeletal parameters. Parameter distributions were constructed from data in the literature. Parameters were sampled from these distributions and used to predict muscle forces and joint torques. The median and distribution of measured joint torque was predicted with small errors (< 5%). Muscle forces for both cases were predicted and compared. In order to predict measured torques for the case of LHB rupture, the median force and mean cross-sectional area in the remaining elbow flexor muscles is greater than in healthy normals. The probabilities that muscle forces for the Tear case exceed median muscle forces for the No-Tear case are 0.98, 0.99 and 0.79 for SH Biceps, brachialis and brachioradialis, respectively. Differences in variability of measured torques for the two cases are explained by differences in parameter variability.
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http://dx.doi.org/10.1080/10255840500294988DOI Listing
October 2005

Changes in the long head of the biceps tendon in rotator cuff tear shoulders.

Clin Biomech (Bristol, Avon) 2005 Feb;20(2):162-5

MedSport and Orthopaedic Research Laboratories, Department of Orthopaedic Surgery, The University of Michigan, 400 N. Ingalls Building Ann Arbor, MI 48109-0486, USA.

Background: Morphologic changes in the long head of the biceps tendon have been described in association with rotator cuff disease, yet mechanical significance of these changes remains unclear.

Methods: An experiment was designed to test the hypotheses that the cross-sectional area and material properties of the long head of the biceps tendon are different in shoulders with full thickness rotator cuff tears and shoulders with intact rotator cuff tendons. Seven pairs of cadaver shoulders were tested. In each pair one shoulder had a full thickness rotator cuff tear and the other did not. Thus, a matched design was used. Cross sectional areas were measured. Tendon material properties were measured using an optical strain system.

Findings: We were unable to detect a statistically significant difference in the long head of the biceps area or material properties between tendons in shoulders with and without rotator cuff tears. An a priori power analysis was conducted indicating the sample size was sufficient to detect a difference of 70 MPa in the elastic modulus measurement.

Interpretation: Our data indicate there is no difference in the long head of the biceps cross sectional area or material properties. Therefore, the long head of the biceps tendon appears to retain its material properties in the presence of a rotator cuff tear. The clinical significance of this finding is that the long head of the biceps can be retained in the presence of a rotator cuff tear without concern that mechanical properties have substantially deteriorated.
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http://dx.doi.org/10.1016/j.clinbiomech.2004.09.009DOI Listing
February 2005
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