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Sovo A.W.,Marquette University | Bustamante Valles K.D.,Orthopaedic and Rehabilitation Engineering Center | Bustamante Valles K.D.,Chihuahua Institute of Technology | Riedel S.A.,Medical College of Wisconsin | And 5 more authors.
2010 Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBC'10 | Year: 2010

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. © 2010 IEEE.

Albert C.,Marquette University | Albert C.,Orthopaedic and Rehabilitation Engineering Center | Jameson J.,Marquette University | Jameson J.,Orthopaedic and Rehabilitation Engineering Center | And 8 more authors.
Clinical Biomechanics | Year: 2013

Background: Osteogenesis imperfecta is a heterogeneous genetic disorder characterized by bone fragility. Previous research suggests that impaired collagen network and abnormal mineralization affect bone tissue properties, however, little data is yet available to describe bone material properties in individuals with this disorder. Bone material properties have not been characterized in individuals with the most common form of osteogenesis imperfecta, type I. Methods: Bone tissue elastic modulus and hardness were measured by nanoindentation in eleven osteotomy specimens that were harvested from children with osteogenesis imperfecta during routine surgeries. These properties were compared between osteogenesis imperfecta types I (mild, n = 6) and III (severe, n = 5), as well as between interstitial and osteonal microstructural regions using linear mixed model analysis. Findings: Disease severity type had a small but statistically significant effect on modulus (7%, P = 0.02) and hardness (8%, P < 0.01). Individuals with osteogenesis imperfecta type I had higher modulus and hardness than did those with type III. Overall, mean modulus and hardness values were 13% greater in interstitial lamellar bone regions than in osteonal regions (P < 0.001). Interpretation: The current study presents the first dataset describing bone material properties in individuals with the most common form of osteogenesis imperfecta, i.e., type I. Results indicate that intrinsic bone tissue properties are affected by phenotype. Knowledge of the material properties of bones in osteogenesis imperfecta will contribute to the ability to develop models to assist in predicting fracture risk. © 2012 Elsevier Ltd.

Long J.T.,Orthopaedic and Rehabilitation Engineering Center | Long J.T.,Medical College of Wisconsin | Groner J.B.,Medical College of Wisconsin | Eastwood D.C.,Medical College of Wisconsin | And 4 more authors.
Journal of Experimental and Clinical Medicine | Year: 2011

Background: Literature indicates the importance of the upper extremities in providing stability and propulsion for the body during ambulation. However, the kinetic implications of upper extremity restraint during gait are not as well documented. Aim: The objective of this study was to examine the effect of arm restraint (unilateral and bilateral) on lower extremity joint kinetics during walking. Methods: Twenty-three healthy young participants were instrumented for three dimensional motion analysis, and tested in four randomly ordered upper extremity restraint conditions (unrestrained, bilateral restraint, right side restraint, and left side restraint). Temporal spatial parameters and gait/phase-specific lower extremity kinetics and kinematics were measured. For each restraint condition, pointwise differences from the unrestrained condition were compared using a two-way ANOVA model of restraint condition (" Condition" ) and gait cycle phase (" Timing" ). Results: Decreases in walking speed and stride length were observed for all restraint conditions. Differences in kinetic demands were also noted, primarily at the hip and knee. Conclusion: Upper extremity restraint in healthy young adults leads to significant changes in temporal-spatial parameters and proximal joint kinetics, most prominently during periods of load accommodation and balance. © 2011.

Slavens B.A.,University of Wisconsin - Milwaukee | Slavens B.A.,Shriners Hospital for Children | Bhagchandani N.,Marquette University | Wang M.,Marquette University | And 7 more authors.
Journal of Biomechanics | Year: 2011

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. © 2011 Elsevier Ltd.

Kertis J.D.,Orthopaedic and Rehabilitation Engineering Center | Fritz J.M.,Orthopaedic and Rehabilitation Engineering Center | Long J.T.,Medical College of Wisconsin | Harris G.F.,Cincinnati Childrens Hospital Medical Center
Critical Reviews in Physical and Rehabilitation Medicine | Year: 2010

An eight-camera Optitrack motion capture system was evaluated by performing static, linear dynamic, and angular dynamic calibrations using marker distances associated with upper and lower extremity gait and wheelchair models. Data were analyzed to determine accuracy and resolution within a defined capture volume using a standard Cartesian reference system. Static accuracy ranged from 99.31 to 99.90%. Static resolution ranged from 0.04 ± 0.15 to 0.63 ± 0.15 mm at the 0.05 level of significance. The dynamic accuracy ranged from 94.82 to 99.77%, and dynamic resolution ranged from 0.09 ± 0.26 to 0.61 ± 0.31 mm at the 0.05 level of significance. These values are comparable to those reported for a standard Vicon 524 (Oxford Metrics, Oxford, England) motion analysis system. The results support application of the lower cost Optitrack system for 3D kinematic assessment of upper and lower extremity motion during gait, assisted ambulation, and wheelchair mobility. © 2010 Begell House, Inc.

Canseco K.,Orthopaedic and Rehabilitation Engineering Center | Canseco K.,Marquette University | Albert C.,Orthopaedic and Rehabilitation Engineering Center | Albert C.,Marquette University | And 8 more authors.
Journal of Experimental and Clinical Medicine | Year: 2011

Introduction: Rheumatoid arthritis (RA) is a systemic autoimmune disease that can cause weakening and destruction of various joints of the foot and may result in pain and deformity. This clinical presentation can cause eventual loss of function, shoe-wear difficulties, and altered gait patterns. Purpose: The goal of this prospective study was to quantify changes in temporal-spatial parameters and multisegmental foot and ankle kinematics in a group of patients with RA of the forefoot following surgery. Methods: Three-dimensional (3-D) motion analysis was conducted preoperatively and postoperatively using a 15-camera Vicon Motion Analysis System (Vicon Motion Systems, Inc.; Lake Forest, CA) on 14 feet in 13 patients with forefoot RA. The Milwaukee foot model was used to characterize segmental kinematics and temporal-spatial parameters. Preoperative and postoperative data were compared using paired nonparametric methods; comparisons with normative data were performed using unpaired nonparametric methods. Results: Preoperatively, the hallux was in a valgus position, the forefoot was abducted and in valgus, and range of motion was limited in various phases in all segments. Walking speed and stride length were decreased and stance prolonged when compared with normal controls. Postoperatively, the hallux alignment was restored to normal but a limited range of motion remained. Kinematics also demonstrated forefoot valgus and tibial internal rotation compared with the control population. Comparisons to healthy ambulators also showed decreased stride lengths and prolonged stance phase durations. Conclusion: Surgery effectively restored alignment and weight-bearing capacity of the rheumatoid feet. Temporal-spatial parameters and kinematics, however, were not restored to control values, but rather were consistent with first metatarsophalangeal joint fusion effects. The altered mechanics after surgery demonstrate the importance of quantitative assessment in understanding the geometric and kinematic effects of surgical realignment with implications for postoperative rehabilitation and gait training. © 2011.

Bustamante Valles K.D.,Orthopaedic and Rehabilitation Engineering Center | Bustamante Valles K.D.,Chihuahua Institute of Technology | Long J.T.,Orthopaedic and Rehabilitation Engineering Center | Long J.T.,Marquette University | And 12 more authors.
Studies in Health Technology and Informatics | Year: 2010

This study uses experimental data acquired from adolescents with idiopathic scoliosis to assess their postural control during quiet standing before and after posterior spinal fusion. Statistically significant differences were seen when comparing the pre- and post-surgical measures of balance calculated from data for three different test conditions. © 2010 The authors and IOS Press. All rights reserved.

Jameson J.,Marquette University | Jameson J.,Orthopaedic and Rehabilitation Engineering Center | Albert C.,Marquette University | Albert C.,Orthopaedic and Rehabilitation Engineering Center | And 9 more authors.
Progress in Biomedical Optics and Imaging - Proceedings of SPIE | Year: 2011

Osteogenesis imperfecta (OI) is a genetic syndrome affecting collagen synthesis and assembly. Its symptoms vary widely but commonly include bone fragility, reduced stature, and bone deformity. Because of the small size and paucity of human specimens, there is a lack of biomechanical data for OI bone. Most literature has focused on histomorphometric analyses, which rely on assumptions to extrapolate 3-D properties. In this study, a micro-computed tomography (μCT) system was used to directly measure structural and mineral properties in pediatric OI bone collected during routine surgical procedures. Surface renderings suggested a poorly organized, plate-like orientation. Patients with a history of bone-augmenting drugs exhibited increased bone volume fraction (BV/TV), trabecular number (Tb.N), and connectivity density (Eu.Conn.D). The latter two parameters appeared to be related to OI severity. Structural results were consistently higher than those reported in a previous histomorphometric study, but these differences can be attributed to factors such as specimen collection site, drug therapy, and assumptions associated with histomorphometry. Mineral testing revealed strong correlations with several structural parameters, highlighting the importance of a dual approach in trabecular bone testing. This study reports some of the first quantitative μCT data of human OI bone, and it suggests compelling possibilities for the future of OI bone assessment.© 2011 SPIE.

Krzak J.J.,Shriners Hospitals for Children | Graf A.,Shriners Hospitals for Children | Flanagan A.,Shriners Hospitals for Children | Caudill A.,Shriners Hospitals for Children | And 3 more authors.
Journal of Experimental and Clinical Medicine | Year: 2011

Background/Purpose: Children with type 1 osteogenesis imperfecta (OI) present with abnormal gait characteristics, including reduced power generation during pushoff. However, the exact biomechanical factors associated with reduced power generation are not clearly understood. The purpose of this study was to investigate the biomechanical factors associated with a reduction in ankle power generation in children with type 1 OI. Methods: Twenty-four participants with type 1 OI (12.5 ± 3.6 years of age) and 24 typically developing children (12.4 ± 3.7 years of age) were evaluated. Three-dimensional gait analysis, isometric plantar flexion strength using dynamometry, and pedobarography were collected on each participant. Results were statistically compared between the groups and a correlation matrix analyzed the associations among the measures. Results: Children with OI presented with weaker plantar flexors, reduced ankle power generation, and decreased sagittal plane ankle angular velocity during pushoff. However, they presented with similar moment arm distances and ground reaction force magnitudes as typically seen in developing children. There was a higher incidence of pes valgus, increased subarch angles, increased time spent loading the midfoot, and deceased time spent loading the forefoot in children with OI. Plantar flexion strength and the time spent at the midfoot and forefoot were most associated with ankle power generation. Conclusion: The presence of pes valgus alone does not indicate a reduction of push-off power in children with type 1 OI, but those individuals who have both a flat foot and reduced time spent loading the forefoot during pushoff are the most likely to have reduced push-off power. © 2011.

Slavens B.A.,Marquette University | Slavens B.A.,Orthopaedic and Rehabilitation Engineering Center | Slavens B.A.,Shriners Hospital for Children | Sturm P.F.,Shriners Hospital for Children | And 3 more authors.
Journal of Biomechanics | Year: 2010

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. © 2010 Elsevier Ltd.

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