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ABSTRACT: The Ponseti method is a widely accepted and highly successful conservative treatment of pediatric clubfoot involving weekly manipulations and cast applications. Qualitative assessments have indicated the potential success of the technique with cast materials other than standard plaster of Paris. However, guidelines for clubfoot correction based on the mechanical response of these materials have yet to be investigated. The current study sought to characterize and compare the ability of three standard cast materials to maintain the Ponseti-corrected foot position by evaluating cast creep response. A dynamic cast testing device, built to model clubfoot correction, was wrapped in plaster of Paris, semi-rigid fiberglass, and rigid fiberglass. Three-dimensional motion responses to two joint stiffnesses were recorded. Rotational creep displacement and linearity of the limb-cast composite were analyzed. Minimal change in position over time was found for all materials. Among cast materials, the rotational creep displacement was significantly different (p < 0.0001). The most creep displacement occurred in the plaster of Paris (2.0°), then the semi-rigid fiberglass (1.0°), and then the rigid fiberglass (0.4°). Torque magnitude did not affect creep displacement response. Analysis of normalized rotation showed quasi-linear viscoelastic behavior. This study provided a mechanical evaluation of cast material performance as used for clubfoot correction. Creep displacement dependence on cast material and insensitivity to torque were discovered. This information may provide a quantitative and mechanical basis for future innovations for clubfoot care.
Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine 04/2013; · 1.21 Impact Factor
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ABSTRACT: BACKGROUND: Fine wire electromyography (EMG) is commonly used for surgical decision making in equinovarus foot deformity. However, this invasive technique may have the unwanted effect of altering the gait of children with cerebral palsy (CP). The purpose of this study was to determine if fine wire insertion into the posterior tibialis muscle affects temporal-spatial parameters and hindfoot kinematics during gait in children with equinovarus secondary to hemiplegic CP. METHODS: 12 children with hemiplegic CP who presented with an equinovarus foot (mean age 12.5 yrs, four right-sided, eight left-sided) were recruited. Temporal-spatial parameters and 3-D segmental foot and ankle kinematic gait data were collected utilizing standard gait analysis and the Milwaukee Foot Model (MFM). Three representative trials with and without fine wire electrode insertion were compared to determine the effect of electrode placement in the posterior tibialis on temporal spatial-parameters and hindfoot sagittal, coronal and transverse plane kinematic peaks, timing of kinematic peaks, and excursions. RESULTS: No significant differences in any temporal-spatial or kinematic parameters were observed between "with wire" and "without wire" conditions. Strong correlations were observed among the gait parameters, with the exception of cadence, for the two conditions. DISCUSSION: Fine wire insertion into the posterior tibialis had no measurable effect on the gait of individuals with equinovarus secondary to hemiplegic CP. This suggests that the simultaneous collection of segmental foot and ankle kinematics and fine wire EMG data of the posterior tibialis is acceptable for surgical decision making in this patient population.
Gait & posture 08/2012; · 2.58 Impact Factor
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ABSTRACT: The Ponseti method is a widely accepted and highly successful conservative treatment of pediatric clubfoot that relies on weekly manipulations and cast applications. However, the material behavior of the cast in the Ponseti technique has not been investigated. The current study sought to characterize the ability of two standard casting materials to maintain the Ponseti corrected foot position by evaluating creep response. A dynamic cast testing device (DCTD) was built to simulate a typical pediatric clubfoot. Semi-rigid fiberglass and rigid fiberglass casting materials were applied to the device, and the rotational creep was measured at various constant torques. The movement was measured using a 3D motion capture system. A 2-way ANOVA was performed on the creep displacement data at a significance level of 0.05. Among cast materials, the rotational creep displacement was found to be significantly different (p-values ≪ 0.001). The most creep displacement occurs in the semi-rigid fiberglass (approximately 1.0 degrees), then the rigid fiberglass (approximately 0.4 degrees). There was no effect of torque magnitude on the creep displacement. All materials maintained the corrected position with minimal change in position over time.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2012; 2012:3352-5.
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ABSTRACT: Current methods for evaluating upper extremity (UE) dynamics during pediatric wheelchair use are limited. We propose a new model to characterize UE joint kinematics and kinetics during pediatric wheelchair mobility. The bilateral model is comprised of the thorax, clavicle, scapula, upper arm, forearm, and hand segments. The modeled joints include: sternoclavicular, acromioclavicular, glenohumeral, elbow and wrist. The model is complete and is currently undergoing pilot studies for clinical application. Results may provide considerable quantitative insight into pediatric UE joint dynamics to improve wheelchair prescription, training and long term care of children with orthopaedic disabilities.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2012; 2012:4788-91.
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ABSTRACT: Gait changes in patients with hallux valgus, including altered kinematic and temporal-spatial parameters, have been documented in the literature. Although operative treatment can yield favorable clinical and radiographic results, restoration of normal gait in this population remains unclear. Segmental kinematic changes within the foot and ankle during ambulation after operative correction of hallux valgus have not been reported. The aim of this study was to analyze changes in multisegmental foot and ankle kinematics in patients who underwent operative correction of hallux valgus.
A 15-camera Vicon Motion Analysis System was used to evaluate 24 feet in 19 patients with hallux valgus preoperatively and postoperatively. The Milwaukee Foot Model was used to characterize segmental kinematics and temporal-spatial parameters (TSPs). Preoperative and postoperative kinematics and TSPs were compared using paired nonparametric methods; comparisons with normative data were performed using unpaired nonparametric methods. Outcomes were evaluated using the SF-36 assessment tool.
Preoperatively, patients with hallux valgus showed significantly altered temporal-spatial and kinematic parameters. Postoperatively, kinematic analysis demonstrated restoration of hallux position to normal. Hallux valgus angles and intermetatarsal angles were significantly improved, and outcomes showed a significant increase in performance of physical activities. Temporal-spatial parameters and kinematics in the more proximal segments were not significantly changed postoperatively.
Postoperative results demonstrated significant improvement in foot geometry and hallux kinematics in the coronal and transverse planes. However, the analysis did not identify restoration of proximal kinematics.
Further investigation is necessary to explore possible causes/clinical relevance and appropriate treatment interventions for the persistently altered kinematics.
The Foot and Ankle Online Journal 02/2012; 33(2):141-7. · 1.22 Impact Factor
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ABSTRACT: Current methods for the evaluation of upper extremity dynamics during wheelchair mobility in children are limited. The goal of this study was to characterize upper extremity joint kinematics during wheelchair mobility. A 3-D biomechanical model of the upper extremities is presented for kinematic assessment of manual wheelchair propulsion in children with Spinal Cord Injury (SCI). The bilateral upper extremity model consists of the thorax, upper arms, forearms, and hands. The model was applied to thirteen (13) children with SCI. Joint angles and joint ranges of motion of the shoulders, elbows, and wrists were quantified. Peak joint motions during the stroke cycle were compared between right and left sides for further insight to mobility patterns. This work will provide insight to be used in future kinetic studies of wheelchair mobility.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 08/2011; 2011:8158-61.
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ABSTRACT: The objective of this study was to develop an instrumented Lofstrand crutch system, which quantifies three-dimensional (3-D) upper extremity (UE) kinematics and kinetics using an inverse dynamics model. The model describes the dynamics of the shoulders, elbows, wrists, and crutches and is compliant with the International Society of Biomechanics (ISB) recommended standards. A custom designed Lofstrand crutch system with four, six-degree-of-freedom force transducers was implemented with the inverse dynamics model to obtain triaxial UE joint reaction forces and moments. The crutch system was validated statically and dynamically for accuracy of computing joint reaction forces and moments during gait. The root mean square (RMS) error of the system ranged from 0.84 to 5.20%. The system was demonstrated in children with diplegic cerebral palsy (CP), incomplete spinal cord injury (SCI), and type I osteogenesis imperfecta (OI). The greatest joint reaction forces were observed in the posterior direction of the wrist, while shoulder flexion moments were the greatest joint reaction moments. The subject with CP showed the highest forces and the subject with SCI demonstrated the highest moments. Dynamic quantification may help to elucidate UE joint demands in regard to pain and pathology in long-term assistive device users.
Journal of biomechanics 06/2011; 44(11):2162-7. · 2.66 Impact Factor
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ABSTRACT: Current inverse dynamics models of the upper extremity (UE) are limited for the measurement of Lofstrand crutch-assisted gait. The objective of this study is to develop, validate, and demonstrate a three-dimensional (3-D) UE motion assessment system to quantify crutch-assisted gait in children. We propose a novel 3-D dynamic model of the UEs and crutches for quantification of joint motions, forces, and moments during Lofstrand crutch-assisted gait. The model is composed of the upper body (i.e., thorax, upper arms, forearms, and hands) and Lofstrand crutches to determine joint dynamics of the thorax, shoulders, elbows, wrists, and crutches. The model was evaluated and applied to a pediatric subject with myelomeningocele (MM) to demonstrate its effectiveness in the characterization of crutch gait during multiple walking patterns. The model quantified UE dynamics during reciprocal and swing-through crutch-assisted gait patterns. Joint motions and forces were greater during swing-through gait than reciprocal gait. The model is suitable for further application to pediatric crutch-user populations. This study has potential for improving the understanding of the biomechanics of crutch-assisted gait and may impact clinical intervention strategies and therapeutic planning of ambulation.
Journal of biomechanics 07/2010; 43(10):2026-31. · 2.66 Impact Factor
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ABSTRACT: Hallux valgus is a common condition characterized by lateral deviation of the large toe and medial deviation of the first metatarsal. While some gait analyses of patients with hallux valgus have been performed using plantar pressures, very little is known about the kinematics of gait in this population. The purpose of this study was to evaluate triplanar kinematics in patients with hallux valgus using a multisegmental foot model.
A 15-camera Vicon Motion Analysis System was used to evaluate the gait of 38 feet in 33 patients with mild to severe hallux valgus. The Milwaukee foot model was used to characterize dynamic foot and ankle kinematics and temporal-spatial parameters. Values were compared with normal subjects. Outcomes were evaluated using the SF-36 assessment tool.
Patients with hallux valgus showed significantly decreased velocity and stride length and prolonged stance. Significant alterations in gait kinematics were observed in various planes in all segments (hallux, forefoot, hindfoot, and tibia) of the foot and ankle, particularly in the ranges of motion of the hallux and the forefoot.
The results demonstrate significantly altered kinematic and temporal-spatial parameters reflective of reduced ambulatory function in patients with hallux valgus. As reports describing multisegmental foot and ankle kinematics in this population are limited, this study is valuable in characterizing gait in patients with hallux valgus.
A better understanding of altered gait dynamics of the multisegmental foot in patients with hallux valgus provides valuable insight on how distal pathology affects proximal segments.
The Foot and Ankle Online Journal 02/2010; 31(2):146-52. · 1.22 Impact Factor
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ABSTRACT: Postural control can be a challenging task for many people, including those with cerebral palsy or idiopathic scoliosis. Assessment of postural stability can be used as one element of a comprehensive strategy to identify more efficient treatments and can provide a better understanding of postural control deficits. Several models and techniques have been developed to assess and understand postural imbalance. This study presents an improvement for an existing model that incorporates two algorithms designed to minimize a cost function.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2010; 2010:3962-5.
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ABSTRACT: Multi-site application of biomechanical models can be a powerful tool as quantitative methods are employed to improve clinical care and to assess larger populations for research purposes. However, the use of such models depends on adequate validation to assure reliability in inter-site measures. We assessed repeatability and sources of variability associated with the assessment of segmental foot kinematics using the Milwaukee Foot Model during multiple testing sessions at two sites. Six healthy ambulators were instrumented and tested during comfortable ambulation; data were analyzed with variance components analysis using a mixed effects linear model. Results indicated that the largest source of variability was inter-subject; measurement error associated with Site and Session fell below 3.5 degrees in over 80% of position measurements and below 2.5 degrees in over 80% of ROM measurements. These findings support the continued use of the segmental foot model at multiple sites for clinical and research purposes.
Gait & posture 09/2009; 31(1):32-6. · 2.58 Impact Factor
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ABSTRACT: The use of quantitative models for evaluating upper extremity (UE) dynamics in children with myelomeningocele (MM) is limited. A biomechanical model for assessment of UE dynamics during Lofstrand crutch-assisted gait in children with MM is presented. This pediatric model may be a valuable tool for clinicians to characterize crutch-assisted gait, which may advance treatment monitoring, crutch prescription, and rehabilitation planning for children with MM. Nine subjects with L3 or L4 level myelodysplasia (mean+/-S.D. age: 11.1+/-3.8 years) were analyzed during forearm crutch-assisted gait: (1) reciprocal gait and (2) swing-through gait. Three-dimensional (3D) dynamics of the UE were acquired and the Pediatric Outcomes Data Collection Instrument (PODCI) was administered. The goal of this study was to determine if meaningful differences occur between gait patterns in UE kinematics and kinetics, and if correlations exist between dynamics and functional outcomes. Temporal-distance parameters showed significant differences between reciprocal and swing-through gait in stride length, and stance duration. All joint ranges of motion were greater during swing-through gait. Thorax, elbow and crutch ranges of motion were found to be significantly different between gait patterns. Kinetic results demonstrated significant differences between reciprocal and swing-through gait, bilaterally, at all joints for the force variables of mean superior/inferior force, range of force, and maximum inferior force. Functional outcomes were strongly correlated with joint dynamics. Accurate quantitative assessment is essential for preventing injury in long-term crutch users. This study has potential for improving clinical intervention strategies and therapeutic planning of ambulation for children with MM.
Gait & posture 09/2009; 30(4):511-7. · 2.58 Impact Factor
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ABSTRACT: Osteogenesis imperfecta (OI) is a heritable bone fragility disorder characterized by skeletal deformities and increased bone fragility. There is currently no established clinical method for quantifying fracture risk in OI patients. This study begins the development of a patient-specific model for femur fracture risk assessment and prediction based on individuals' gait analysis data, bone geometry from imaging and material properties from nanoindentation (Young's modulus=19 GPa, Poisson's ratio=0.3). Finite element models of the femur were developed to assess fracture risk of the femur in a pediatric patient with OI type I. Kinetic data from clinical gait analysis was used to prescribe loading conditions on the femoral head and condyles along with muscle forces on the bone's surface. von Mises stresses were analyzed against a fracture strength of 115 MPa. The patient with OI whose femur was modeled showed no risk of femoral fracture during normal gait. The highest stress levels occurred during the mid-stance and loading responses phases of gait. The location of high stress migrated throughout the femoral diaphysis across the gait cycle. Maximum femoral stress levels occurred during the gait cycle phases associated with the highest loading. The fracture risk (fracture strength/von Mises stress), however, was low. This study provides a relevant method for combining functional activity, material property and analytical methods to improve patient monitoring.
Medical Engineering & Physics 09/2009; 31(9):1043-8. · 1.62 Impact Factor
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ABSTRACT: Upper extremity (UE) joint kinetics during aided ambulation is an area of research that is not well characterized in the current literature. Biped UE joints are not anatomically designed to be weight bearing, therefore it is important to quantify UE kinetics during assisted gait. This will help to better understand the biomechanical implications of UE weight bearing, and enable physicians to prescribe more effective methods for treatment and therapy, perhaps minimizing excessive loads and torques. To address this challenge, an UE model that incorporates both kinematics and kinetics has been developed for use with walkers instrumented with load cells. In this study, the UE joint kinetics are calculated for 10 children with cerebral palsy using both anterior and posterior walkers. Three-dimensional joint reaction forces and moments are fully characterized for the wrist, elbow, and shoulder (glenohumeral) joints for both walker types. Statistical analysis methods are used to quantify the differences in forces or moments between the two walker types. Comparisons showed no significant differences in kinetic joint parameters between walker types. Results from a power analysis of the current data are provided which may be useful for planning longer term clinical studies. If risk factors for UE joint pathology can be identified early, perhaps a change in gait training routine, walker prescription, or walker design could prevent further harm.
Gait & posture 08/2009; 30(3):364-9. · 2.58 Impact Factor
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ABSTRACT: Brace prescription for children with diplegic cerebral palsy challenges the clinician with a variety of options and little evidence for rational decisions. Previous studies have indicated that ankle-foot orthoses improve toe-walking, but it is unclear if any brace is better than another. The goal of the present study was to compare the effectiveness of hinged and dynamic ankle-foot orthoses in terms of improving gait and motor function in a homogeneous group of children with diplegic cerebral palsy exhibiting a jump gait pattern.
Fifteen children (mean age, 7.5 years) with spastic diplegic cerebral palsy who were able to walk independently with a jump gait pattern and twenty children (mean age, 10.6 years) with normal gait participated in the study. Standardized Gross Motor Function Classification System scores, Pediatric Outcomes Data Collection Instrument scores, and gait data were collected, analyzed, and compared. The subjects were tested while barefoot and while wearing hinged and dynamic ankle-foot orthoses. Data were analyzed to detect differences among these conditions.
Significant improvements in gait metrics were seen during brace wear. No significant differences were seen between the two different braces used. The barefoot and braced conditions differed most significantly in terms of ankle kinematics and kinetics. Among the patients with cerebral palsy, no significant differences in the standardized outcome measurements were found between the braced and unbraced conditions or between the two braced conditions.
Our data suggest that gait improves with brace wear in children with cerebral palsy with a level-I Gross Motor Function Classification System score. The Pediatric Outcomes Data Collection Instrument and the Gross Motor Function Measure were not sensitive to brace treatment in the population studied. The hinged and dynamic braces were equally effective for improving ankle kinematics and kinetics in these relatively highly functioning children with cerebral palsy.
The Journal of Bone and Joint Surgery 03/2009; 91(2):356-65. · 3.27 Impact Factor
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ABSTRACT: Walkers are prescribed with the notion that one type of walker will be better for a child than another. One underlying justification for this practice is the theory that one walker may produce less stress on the upper extremities as the patient uses the walker. Nevertheless, upper extremity joint loading is not typically analyzed during walker assisted gait in children with spastic diplegic cerebral palsy. It has been difficult to evaluate the theory of walker prescription based on upper extremity stresses because loading on the upper extremities however has not been quantified until recently. In this study, weight bearing on the glenohumeral joints was analyzed in five children with spastic diplegic cerebral palsy using both anterior and posterior walkers fitted with 6-axis handle transducers. Though walkers' effects on the upper extremities proved to be similar between walker types, the differences between the walkers may have some clinical significance in the long run. In general, posterior walker use created larger glenohumeral joint forces. Though these differences are not statistically significant, over time and with repetitive loading they may be clinically significant.
Biomedical sciences instrumentation 02/2009; 45:304-9.
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ABSTRACT: A finite element analysis of a commercial forearm crutch for children during gait is presented. The geometric features of the crutch structure were acquired and modeled. The finite element model was created using shell elements based on the frame surfaces. Linear elastic material properties for aluminum alloy were utilized. Upper extremity kinetic data from reciprocal and swing-through gait patterns were applied to the model as boundary conditions and loads. Stress distributions during two gait patterns were determined. Stress distributions during swing-through gait were found to be statistically greater than those during reciprocal gait (p = 0.01). This work provides novel quantitative data to improve crutch design and stimulate further analyses of upper extremity (UE) joint loads during forearm crutch-assisted gait in children with spina bifida (myelomeningocele).
Biomedical sciences instrumentation 02/2009; 45:310-5.
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ABSTRACT: A finite element analysis of a commercial forearm crutch for children during gait is presented. The geometric features of the crutch structure were acquired and modeled. The finite element model was created using shell elements based on the frame surfaces. Linear elastic material properties for aluminum alloy were utilized. Upper extremity kinetic data from reciprocal and swing-through gait patterns were applied to the model as boundary conditions and loads. Stress distributions during two gait patterns were determined. Stress distributions during swing-through gait were found to be statistically greater than those during reciprocal gait (p = 0.01). This work provides novel quantitative data to improve crutch design and stimulate further analyses of upper extremity joint loads during forearm crutch-assisted gait in children with myelomeningocele (spina bifida).
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2009; 2009:5271-73.
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ABSTRACT: This paper implements a biomechanical model and actual tipover trajectory data to assess the risk of head and neck injuries in standup forklift accidents. Seven accident scenarios were analyzed for right tipover, left tipover and off-dock accidents both with and without a door on the operator compartment. Each model had specific data including human anthropometry and trajectory input into the modeling and analysis software packages, Visual-Safe MAD and MADYMO. For all three accident scenarios, each of the seven biomechanical models was analyzed for Injury Assessment Reference Values (IARVs) including angular velocity (omega, omega), angular acceleration (alpha, alpha), Head Injury Criterion (HIC), Neck Injury Criterion--shear, tension and bending (NIC) and the biomechanical Neck Injury Predictor (N(ij)). The study concluded that, in general, the addition of a door to the standup forklift operator compartment leads to a reduction in injury during tipover and off-dock accidents. The ability to brace for impact is not included in these MADYMO models. Bracing is far more effective with an enclosed compartment provided by a latching rear door.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2009; 2009:5267-70.
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ABSTRACT: We present a new kinematic model measuring the three-dimensional orientation of multiple segments of the foot and ankle. The model defines neutral alignments based on the alignments of the underlying bony segments, and indexes the orientation of skin-mounted markers to the bony anatomy using measures from weightbearing x-rays. The sensitivity of the model to these radiographic input parameters was analyzed using data from walking trials. Kinematic output in each plane was found to be most sensitive to perturbations of radiographic measurements in that same plane; however, perturbations in the coronal and transverse planes demonstrated significant carry-over into other planes. The analysis highlights the importance of accurately accounting for the underlying anatomy in measuring intersegmental kinematics.
Engineering in Medicine and Biology Society, 2008. EMBS 2008. 30th Annual International Conference of the IEEE; 09/2008
