The objective of this case series study was reautomatization of gait after limb-saving surgery for tumors at a laboratory of gait analysis. Twelve patients (9 males and 3 females; mean age, 38 years) who underwent limb-saving surgery of the lower limb at least 1 year previously and ten normal subjects (3 males and 7 females; mean age, 37.5 years) were studied. The main outcome measures were walking speed and stride time duration under normal walking conditions as well as the use of different types of constraints. Patients walked with a lower preferred walking speed than the normal subjects. Patients showed a higher coefficient of variation of stride time in normal walking as well as complex walking compared with normal subjects. During walking with constraints, a significant decrease in stride time was found in patients but not in normal subjects. Although restoration of gait after limb-saving surgery is impressive, it is not complete (lower walking speed) and can break down under conditions of visual and cognitive load. Hence, the application of complex tasks reveals that gait reautomatization is not complete in these patients during a period of 2 to 5 years after surgery

de Visser, E

Duysens, JEJ

Mulder, T

Pauwels, J

Veth, RPH

The objective of this case series study was reautomatization of gait after limb-saving surgery for tumors at a laboratory of gait analysis. Twelve patients (9 males and 3 females; mean age, 38 years) who underwent limb-saving surgery of the lower limb at least 1 year previously and ten normal subjects (3 males and 7 females; mean age, 37.5 years) were studied. The main outcome measures were walking speed and stride time duration under normal walking conditions as well as the use of different types of constraints. Patients walked with a lower preferred walking speed than the normal subjects. Patients showed a higher coefficient of variation of stride time in normal walking as well as complex walking compared with normal subjects. During walking with constraints, a significant decrease in stride time was found in patients but not in normal subjects. Although restoration of gait after limb-saving surgery is impressive, it is not complete (lower walking speed) and can break down under conditions of visual and cognitive load. Hence, the application of complex tasks reveals that gait reautomatization is not complete in these patients during a period of 2 to 5 years after surgery.</p

Dissertations of the University of Groningen

Gait adaptations during walking under visual and cognitive constraints - A study of patients recovering from limb-saving surgery of the lower limb

University of Groningen Research Database

ARTS repository - University of Groningen

NARCIS 

Marmaras, Konstantinos

Stolpe, Mathias

Online Research Database In Technology

                       General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.  • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal   If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.     Downloaded from orbit.dtu.dk on: Dec 15, 2017Optimal Design of Composite Structures by Advanced Mixed Integer NonlinearOptimizationMarmaras, Konstantinos; Stolpe, MathiasPublication date:2013Link back to DTU OrbitCitation (APA):Marmaras, K., & Stolpe, M. (2013). Optimal Design of Composite Structures by Advanced Mixed IntegerNonlinear Optimization. Abstract from 10th World Congress on Structural and Multidisciplinary Optimization,Orlando, FL, United States.Optimal Design of Composite Structures by Advanced Mixed Integer Nonlinear Optimization Authors: Konstantinos Marmaras, Mathias Stolpe Keywords: Structural Optimization, Laminated Composites, Global Optimization, Discrete Material Optimization, Heuristics We consider optimal lay-up design of laminated composite structures. Our aim is to solve both minimum compliance mass constrained and minimum weight compliance constrained problems to global optimality by modern special purpose global optimization methods and heuristics. The design variables are, in our case, binary and represent locally presence or absence of a material in the structure from a list of pre defined isotropic and orthotropic candidate materials. In their primal formulation, these problems are stated as non-convex mixed integer problems. We use different reformulation techniques to state them as mixed integer convex problems with special properties. This way we can make use of general robust and efficient methods and heuristics developed for solving this type of problems. The continuous relaxation of the mixed integer problem is being solved by an implementation of a modern primal-dual interior point method for nonlinear programming. This method is chosen for its robustness and its ability to react swiftly to changes of scale in the problem. An efficient heuristic technique for obtaining a discrete feasible solution then applied. The heuristic consists of solving a sequence of 0-1 linear mixed integer programs, based on the solution to the continuous relaxation of the original mixed integer optimization problem. The numerical experiments indicate that for many problem instances, the heuristic provides us with close to optimal solutions.  Based on the principles of decomposition, outer approximation and relaxation, we have developed a framework that provides us with globally optimal solutions. We propose a combination of the convergent Outer Approximation and Local Branching algorithms to perform the global optimization. Outer approximation is a method that consists of solving a sequence of nonlinear programming sub problems and relaxed versions of a mixed-integer linear master program. The Local Branching algorithm alternates between a sequence of high-level strategic branching to define the solution neighborhoods, and low-level tactical branching to explore them. The numerical experience of our methods and heuristics are reported on a set of discrete material optimization problems. Minimum compliance and minimum weight designs for constant stiffness laminated composite plates are obtained for both in-plane and out of plane loadings. The ability of our framework to perform multi-material optimization is examined and we are considering both single and multiple load cases. The obtained results are in good agreement with previous studies performed on the same examples. Our implementation outperforms existing methods for optimal design of laminated composite structures. Several of the problem instances were solved to global optimality. The obtained results indicate the importance of including manufacturing and stress constraints in the design problem. For the purpose of this presentation we have not taken such constraints into consideration. The inclusion of such constraints poses several theoretical and computational challenges that have to be overcome before they can be included in practical lay-up design problems of laminated composite structures with many design variables. The presentation will include ideas on how manufacturing constraints can be included as linear constraints in the problem formulations and the methods. Some promising preliminary results will be demonstrated. 