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Estimates of Gastrocnemius Muscle Length During Simulated Pathological Gait

Smita Rao, Fred Dietz, and H. John Yack

The purpose of this study was to compare estimates of gastrocnemius muscle length (GML) obtained using a segmented versus straight-line model in children. Kinematic data were acquired on eleven typically developing children as they walked under the following conditions: normal gait, crouch gait, equinus gait, and crouch with equinus gait. Maximum and minimum GML, and GML change were calculated using two models: straight-line and segmented. A two-way RMANOVA was used to compare GML characteristics. Results indicated that maximum GML and GML change during simulated pathological gait patterns were influenced by model used to calculate gastrocnemius muscle length (interaction: P = .004 and P = .026). Maximum GML was lower in the simulated gait patterns compared with normal gait (P < .001). Maximum GML was higher with the segmented model compared with the straight-line model (P = .030). Using either model, GML change in equinus gait and crouch with equinus gait was lower compared with normal gait (P < .001). Overall, minimum GML estimated with the segmented model was higher compared with the straight-line model (P < .01). The key findings of our study indicate that GML is significantly affected by both gait pattern and method of estimation. The GML estimates tended to be lower with the straight-line model versus the segmented model.

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Equinus Deformity as a Compensatory Mechanism for Ankle Plantarflexor Weakness in Cerebral Palsy

David A. Hampton, Kevin W. Hollander, and Jack R. Engsberg

A theory for equinus gait in cerebral palsy (CP) is that the strong plantarflexors prevent the weak dorsiflexors from achieving dorsiflexion, thereby causing the ankle to be in a plantarflexed position. Recent work has indicated that both the ankle dorsiflexors and plantarflexors are weak. The purpose of this research was to theoretically and experimentally demonstrate that equinus deformity gait could be a compensatory strategy for plantarflexor weakness. It was hypothesized that children with CP utilize an equinus position during gait as a consequence of their weakness. A two-dimensional, sagittal plane model estimating plantarflexor forces through the Achilles tendon was developed. Five able-bodied (AB) children were tested utilizing heel-toe and progressively increasing toe walking strategies. Four children with CP were tested as they walked using their equinus gait. Results demonstrated that AB children assuming the toe walking stance progressively reduced the plantarflexor force when compared to their heel-toe walking trials. However, their toe walking strategy could not reduce the plantarflexor force level to that of the children with CP during the gait cycle. It was concluded that the equinus deformity posture complemented the CP children's plantarflexor weakness. Therefore, by implementing a concomitant strategy to maintain a reduced force state, equinus deformity could be used as a compensatory mechanism for individuals with plantarflexor weakness.

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Muscle Contracture Emulating System for Studying Artificially Induced Pathological Gait in Intact Individuals

Andrej Olenšek, Zlatko Matjačić, and Tadej Bajd

When studying pathological gait it is important to correctly identify primary gait anomalies originating from damage to the central nervous and musculoskeletal system and separate them from compensatory changes of gait pattern, which is often challenging due to the lack of knowledge related to biomechanics of pathological gait. A mechanical system consisting of specially designed trousers, special shoe arrangement, and elastic ropes attached to selected locations on the trousers and shoes is proposed to allow emulation of muscle contractures of soleus (SOL) and gastrocnemius (GAS) muscles and both SOL-GAS. The main objective of this study was to evaluate and compare gait variability as recorded in normal gait and when being constrained with the proposed system. Six neurologically and orthopedically intact volunteers walked along a 7-m walkway while gait kinematics and kinetics were recorded using VICON motion analysis system and two AMTI forceplates. Statistical analysis of coefficient of variation of kinematics and kinetics as recorded in normal walking and during the most constrained SOL-GAS condition showed comparable gait variability. Inspection of resulting group averaged gait patterns revealed considerable resemblance to a selected clinical example of spastic diplegia, indicating that the proposed mechanical system potentially represents a novel method for studying emulated pathological gait arising from artificially induced muscle contractures in neurologically intact individuals.

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Computer Simulation of Surgical Treatment for Equinus Deformity in Cerebral Palsy

Kenton R. Kaufman and William J. Shaughnessy

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Detecting Postoperative Change in Children with Cerebral Palsy: Net Nondimensional versus Body Mass Oxygen Normalization

Martin Švehlík, Kryštof Slabý, Tomáš Trc̆, and Jir̆í Radvanský

The aim of the study is to investigate whether the net nondimensional oxygen utilization scheme is able to detect postoperative improvement in the energy cost of walking in children with cerebral palsy and to compare it with a body mass normalization scheme. We evaluated 10 children with spastic cerebral palsy before and 9 months after equinus deformity surgery. Participants walked at a given speed of 2 km/hr and 3 km/hr on a treadmill. Oxygen utilization was measured, and mass relative VO2 and net nondimensional VO2 were calculated. Coefficient of variation was used for the description of variability among subjects. Postoperatively, gait kinematics normalized and the mass relative VO2 and net nondimensional VO2 showed significant improvement. Net nondimensional VO2 is able to detect postoperative improvement with smaller variability among subjects than body mass related normalization in children with cerebral palsy.

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Effects of Gluteus Medius and Biceps Femoris Stimulation on Reduction of Knee Abduction Moment During a Landing Task

Dan Wang, Man Wang, Vikki Wing-Shan Chu, Patrick Shu-Hang Yung, and Daniel T.P. Fong

of the knee, lateral malleolus along an imaginary line that passes through the transmalleolar axis, the second metatarsal head on the midfoot side of the equinus break between forefoot and midfoot, and calcaneus at the same height above the plantar surfaces of the left and right feet; 4 reflective

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In Silico Biomarkers of Motor Function to Inform Musculoskeletal Rehabilitation and Orthopedic Treatment

Ilse Jonkers, Erica Beaucage-Gauvreau, Bryce Adrian Killen, Dhruv Gupta, Lennart Scheys, and Friedl De Groote

apparent equinus. 49 To summarize, MSK modeling can provide insight into how treatment affects MSK loading, an important driver of MSK impairments. An important benefit of MSK model-based simulations is that they allow study of the influence of isolated neuro-MSK features by adjusting the related model

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Skeletal Muscle Adaptations and Passive Muscle Stiffness in Cerebral Palsy: A Literature Review and Conceptual Model

Alif Laila Tisha, Ashley Allison Armstrong, Amy Wagoner Johnson, and Citlali López-Ortiz

. 2017 ; 11 : 30 . PubMed ID: 28487645 doi:10.3389/fncom.2017.00030 28487645 10.3389/fncom.2017.00030 18. Mathewson MA , Ward SR , Chambers HG , Lieber RL . High resolution muscle measurements provide insights into equinus contractures in patients with cerebral palsy . J Orthop Res . 2015