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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.

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.

Albert C.,Marquette University | Albert C.,Orthopaedic and Rehabilitation Engineering Center | Jameson J.,Marquette University | Jameson J.,Orthopaedic and Rehabilitation Engineering Center | And 7 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.

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 11 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.

Slavens B.A.,University of Wisconsin - Milwaukee | Bhagchandani N.,Marquette University | Wang M.,Marquette University | Wang M.,Medical College of Wisconsin | And 6 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.

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