blog

D-flow: immersive virtual reality and real-time feedback for rehabilitation

Thu, 22 Dec 2011 12:55:03 +0100

T. Geijtenbeek, F. Steenbrink, E. Otten, O. Even-Zohar

VRCAI '11 Proceedings of the 10th International Conference on Virtual Reality Continuum and Its Applications in Industry

D-flow: immersive virtual reality and real-time feedback for rehabilitation

http://dl.acm.org/citation.cfm?id=2087785

Abstract:

D-Flow is a software system designed for the development of interactive and immersive virtual reality applications, for the purpose of clinical research and rehabilitation. Key concept of the D-Flow software system is that the subject is regarded as an integral part of a real-time feedback loop, in which multi-sensory input devices measure the behavior of the subject, while output devices return motor-sensory, visual and auditory feedback to the subject. The D-Flow software system allows an operator to define feedback strategies through a flexible and extensible application development framework, based on visual programming. We describe the requirements, architecture and design considerations of the D-Flow software system, as well as a number of applications that have been developed using D-Flow, both for clinical research and rehabilitation.

Application of a Mild Traumatic Brain Injury Rehabilitation Program in a Virtual Realty Environment

Mon, 24 Oct 2011 11:18:27 +0200

Christopher A. R´abago, PT, PhD, and Jason M. Wilken, PT, PhD

J Neurol Phys Ther. 2011 Oct 24

Application of a Mild Traumatic Brain Injury Rehabilitation Program in a Virtual Realty Environment

http://www.ncbi.nlm.nih.gov/pubmed/22027473

Abstract:

BACKGROUND AND PURPOSE: Mild traumatic brain injury (mTBI) can compromise reaction time, visual perception, memory, attention, balance, and gait. These deficits, especially if persistent, can restrict participation in daily activities and the resumption of personal and profession roles. The purpose of this case study is to describe an mTBI-specific clinical assessment and rehabilitation intervention administered in a virtual reality environment.

CASE DESCRIPTION: The case involved a 31-year-old male service member who had sustained an mTBI (concussion) during a recreational softball game 36 days prior to physical therapist evaluation. He had complaints of severe visual and physical motion intolerance. He demonstrated impaired static balance and was restricted from full military duty.

INTERVENTIONS: The assessment included measurements of postural and gait balance during cognitive, visual, and vestibular challenges within a Computer-Assisted Rehabilitation Environment. Phase 1 of the intervention consisted of clinical techniques (ie, optokinetic stimulation/habituation, visual/physical perturbations, and postural stability exercises) targeting specific impairments. Phase 2 training consisted of weapon handling and target recognition tasks to simulate the requirements of his military occupation.

OUTCOMES: At the conclusion of 6 treatments, the patient demonstrated significant increases in postural and gait balance with a near complete resolution of all postconcussion symptoms. He successfully returned to full duty and training for combat deployment.

DISCUSSION: Service members and civilians exhibit similar impairments, limitations, and restrictions following mTBI. A rehabilitation program delivered in a virtual-reality environment can be structured to manage complex mTBI symptoms through the integration of multiple treatment modalities specific to a patient's personal and professional roles.

Gait Training With Virtual Reality-Based Real-Time Feedback: : Improving Gait Performance Following Transfemoral Amputation.

Thu, 14 Jul 2011 11:23:47 +0200

Darter BJ, Wilken JM.

Phys Ther. 2011 Jul 14. [Epub ahead of print]

Gait Training With Virtual Reality-Based Real-Time Feedback: Improving Gait Performance Following Transfemoral Amputation.

http://www.ncbi.nlm.nih.gov/pubmed/21757579

Abstract:

BACKGROUND AND PURPOSE: Gait training is an important component of rehabilitation after lower-extremity amputation. Abnormal gait performance often persists even for individuals who reacquire a high level of function. This case report describes the use of a virtual reality (VR)-based gait training program that provides real-time feedback in order to improve biomechanical and physiological performance. The aim of this case report is to describe the effects of the training in a person with a transfemoral amputation.

CASE DESCRIPTION: A 24-year-old man with a transfemoral amputation completed a 3-week gait training program. The intervention consisted of 12 sessions of treadmill walking with real-time visual feedback on full-body gait kinematics. A treating therapist directed the patient's attention to specific gait deviations as a means to normalize gait biomechanics.

OUTCOMES: The patient completed overground biomechanical gait analyses and multiple-speed treadmill tests 3 weeks apart prior to and following the training program. Biomechanical gait analyses indicated the training produced improved frontal-plane hip, pelvis, and trunk motion during overground walking. Improvement in trunk motion was observed at the posttraining test, and improvements in pelvis and hip motion were observed at the 3-week follow-up test. Decreases of up to 23% in oxygen consumption also were demonstrated.

DISCUSSION: Although the exact contribution of the visual feedback could not be isolated, the training was effective in improving the patient's walking performance. Biomechanical data suggest correcting trunk motion and increasing hip abductor strength (force-generating capacity) may be important in facilitating improvements at the pelvis and hip. Observed improvements in oxygen consumption were significantly larger than achieved through previously reported interventions.

Changes in margins of stability during human walking in destabilizing environments.

Tue, 05 Jul 2011 11:25:57 +0200

McAndrew Young PM, Dingwell JB, Wilken JM.

XXIII^rdConference of the International Society of Biomechanics, Brussels Belgium 2011.

Changes in margins of stability during human walking in destabilizing environments.

http://homepages.ulb.ac.be/~labo/ISB2011/ISB2011_ScientificProgram_files/604.pdf

SUMMARY

We studied the effects of anterior-posterior (AP) and mediolateral (ML) oscillations on control of stability during walking in humans. We found that independent of
perturbation applied, mean ML margins of stability remained approximately constant whereas AP margins of stability were influenced by ML perturbations more than AP perturbations.
Our results support the idea that maintaining lateral margin of stability magnitude could be a goal in controlling human walking.

Kinematic and temporospatial effects of medio-tareral mechanical and visual perturbation amplitudes during gait.

Tue, 05 Jul 2011 10:12:00 +0200

Terry K, Sinitski EH, Wilken JM, Dingwell JB.

XXIII^rdConference of the International Society of Biomechanics, Brussels Belgium 2011.

Kinematic and temporospatial effects of medio-tareral mechanical and visual perturbation amplitudes during gait.

http://homepages.ulb.ac.be/~labo/ISB2011/ISB2011_ScientificProgram_files/558.pdf

This study examined how kinematic and temporo-spatial gait parameters change in response to multiple amplitudes of sinusoidal pseudo-random medio-lateral (M-L) visual and support surface (mechanical) perturbations in an immersive virtual reality (VR) environment. Our goal was to determine how perturbation magnitude altered gait variability. The variability of center of mass (COM) position, COM velocity, and step width in the M-L direction systematically increased with perturbation amplitude for the mechanical perturbations. However, larger visual perturbation amplitudes did not produce corresponding increases in any of these gait parameters.

Speeding up or slowing down; how to deal with balance perturbations during gait?

Mon, 04 Jul 2011 10:05:52 +0200

Hak L, Houdijk H, Steenbrink F, Mert A, Beek PJ, van Dieën J.

XXIII^rdConference of the International Society of Biomechanics, Brussels Belgium 2011.

Speeding up or slowing down; how to deal with balance perturbations during gait?

http://homepages.ulb.ac.be/~labo/ISB2011/ISB2011_ScientificProgram_files/71.pdf

In this study, the effect of medio-lateral balance perturbations of walking speed was examined. In addition, the effect of the resulting speed adaptations on local dynamic stability was assessed. Remarkably, subjects did not lower their walking speed, but rather changed the underlying step parameters, step time and step length. Furthermore, local dynamic instability increased with perturbation amplitude.

Dynamic stability of human walking in visually and mechanically destabilizing environments.

Thu, 24 Feb 2011 13:17:31 +0100

McAndrew PM, Dingwell JB, Wilken JM.

Dynamic stability of human walking in visually and mechanically destabilizing environments.

J Biomech. 2011 Feb 24;44(4):644-9. Epub 2010 Nov 20.

http://www.ncbi.nlm.nih.gov/pubmed/21094944

Abstract: Understanding how humans remain stable during challenging locomotor activities is critical to developing effective tests to diagnose patients with increased fall risk. This study determined if different continuous low-amplitude perturbations would induce specific measureable changes in measures of dynamic stability during walking. We applied continuous pseudo-random oscillations of either the visual scene or support surface in either the anterior-posterior or mediolateral directions to subjects walking in a virtual environment with speed-matched optic flow. Floquet multipliers and short-term local divergence exponents both increased (indicating greater instability) during perturbed walking. These responses were generally much stronger for body movements occurring in the same directions as the applied perturbations. Likewise, subjects were more sensitive to both visual and mechanical perturbations applied in the mediolateral direction than to those applied in the anterior-posterior direction, consistent with previous experiments and theoretical predictions. These responses were likewise consistent with subjects' anecdotal perceptions of which perturbation conditions were most challenging. Contrary to the Floquet multipliers and short-term local divergence exponents, which both increased, long-term local divergence exponents decreased during perturbed walking. However, this was consistent with specific changes in the mean log divergence curves, which indicated that subjects' movements reached their maximum local divergence limits more quickly during perturbed walking. Overall, the Floquet multipliers were less sensitive, but reflected greater specificity in their responses to the different perturbation conditions. Conversely, the short-term local divergence exponents exhibited less specificity in their responses, but were more sensitive measures of instability in general.

The CAREN system is useful in the rehabilitation process: user survey of 50 patients.

Wed, 10 Nov 2010 13:01:41 +0100

Mert A, Frunt T, van der Lint R, Uittewaal KJM, and Wurff vd P.

Dutch Society for Rehabilitation Physicians (VRA) annual congress 2010.

The CAREN system is useful in the rehabilitation process: user survey of 50 patients.

50 patients underwent training on the CAREN system for 10 sessions twice a week. The patients were asked to give their opinion on relationship with the therapist, goal oriented therapy, the approach of the therapist, the way the patient thinks about the general therapeutic contact, is the rehabilitation process accelerated by the CAREN system, is the CAREN straining challenging, is the CAREN training transferable to the real world, using a Visual Analog Scale. Zero implying “does not”, 10 implying “does” Patients scored above 8 on all investigated domains.

The association between VAS and TSK compared with a performance test on the CAREN system in Chronic Low Back Pain (CLBP) patients.

Wed, 10 Nov 2010 10:37:55 +0100

Mert A, Frunt T and Wurff vd P.

Dutch Society for Rehabilitation Physicians (VRA) annual congress 2010.

The association between VAS and TSK compared with a performance test on the CAREN system in Chronic Low Back Pain (CLBP) patients.

Introduction: Pain related fear and pain intensity have been identified as factors negatively influencing performance tasks in CLBP patients. Aim: To analyze the relationship between pain intensity (VAS scale) and pain related fear (TSK) compared to a performance test on the CAREN system. Methods: Fifty-five consecutive patients with chronic low back pain who visit our clinic from Jan 2009 to March 2009 were included in this study. In a cross sectional observation study pain related fear was defined as the score on the Tampa Scale of Kinesiophobia (TSK) and pain intensity on a Visual Analogue Scale (VAS). The performance task on the CAREN system was especially developed for this study and consisted of a boat scenery with various obstacles to evoke lumbar movements and measured by time registration. Pearson product moment correlations were calculated to express linear associations between VAS and TSK compared to the performance test on the CAREN system. When differences were significant a ROC curve was constructed. Results: For the VAS score just a score of r = -.13 (not significant) was achieved. For the TSK only with a cutoff point of 42 we noticed that Pearson’s r = .37 (significant) The area under the ROC curve revealed only a score of 0.593 indicating no benefit from the performance task above the TSK.

Conclusion: In this study we could not establish any relationship between the VAS score and the performance task on the CAREN system. For the TSK only above a cut-off point of 42 points a poor relationship was determined.

Case report: Succesvolle correctie van het gangpatroon na een kwantitatieve ganganalyse bij een patiënte met een correctieve osteotomie wegens heupdysplasie (Dutch)

Wed, 15 Sep 2010 09:39:35 +0200

Mert A, Glashouwer P, Wertheim WJ, Frunt T, van der Wurff P.

Nederlands Millitair Geneeskundig Tijdschrift 63, 2010.

Case report: Succesvolle correctie van het gangpatroon na een kwantitatieve ganganalyse bij een patiënte met een correctieve osteotomie wegens heupdysplasie.

Atricle (page 17)

In dit case report wordt de ziektegeschiedenis beschreven van een 28-jarige waterpolospeelster die in 2 tempi een dubbelzijdige osteotomie wegens heupdysplasie onderging. In het postoperatieve traject bleek het herstel van de rechterheup probleemloos te verlopen. De linkerheup daarentegen herstelde in functioneel opzicht niet naar verwachting waardoor het fysiek hoge sportniveau niet binnen de gestelde tijd werd bereikt. Zij gaf pijn ter plaatse van de mediale zijde van het linkerbeen aan en kon bepaalde fysieke acties onvoldoende uitvoeren. Omdat analyse van dit probleem met de bestaande middelen niet lukte, is met behulp van het CAREN-systeem (Computer Assisted Rehabilitation Environment) wel een geslaagde poging gedaan. Het bleek dat de abductie van het heupgewricht een te grote uitslag liet zien hetgeen duidt op een tekort aan adductiekracht. Vervolgens werd met de uitkomsten een trainingsprogramma opgesteld hetgeen voor een belangrijk deel tot een succesvolle functieverbetering heeft geleid.

Walking variability during continuous pseudo-random oscillations of the support surface and visual field

Fri, 28 May 2010 13:14:03 +0200

McAndrew PM, Dingwell JB, Wilken JM.

Walking variability during continuous pseudo-random oscillations of the support surface and visual field

J Biomech. 2010 May 28;43(8):1470-5. Epub 2010 Mar 26. http://www.ncbi.nlm.nih.gov/pubmed/20346453

Department of Biomedical Engineering, University of Texas, Austin, TX 78712, USA.

Abstract: Walking on uneven surfaces or while undergoing perturbations has been associated with increased gait variability in both modeling and human studies. Previous gait research involving continuous perturbations has focused on sinusoidal oscillations, which can result in individuals predicting the perturbation and/or entraining to it. Therefore, we examined the effects of continuous, pseudo-random support surface and visual field oscillations on 12 healthy, young participants. Participants walked in a virtual reality environment under no perturbation (NOP), anterior-posterior (AP) walking surface and visual oscillation and mediolateral (ML) walking surface and visual oscillation conditions. Participants exhibited shorter (p< or =0.005), wider (p<0.001) and faster (p<0.001) steps relative to NOP during ML perturbations and shorter (p< or =0.005) and wider (p<0.001) steps during AP perturbations. Step length variability and step width variability both increased relative to NOP during all perturbation conditions (p<0.001) but exhibited greater increases for the ML perturbations (p<0.001). Participants exhibited greater trunk position variability and trunk velocity variability in the ML direction than in the AP direction during ML perturbations relative to NOP (p<0.001). Significantly greater variability in the ML direction indicates that to maintain stability, participants needed to exert greater control in the ML direction. This observation is consistent with prior modeling predictions. The large and consistent responses observed during ML visual and walking surface perturbations suggest potential for application during gait training and patient assessment.

Cognitive Load and Dual-Task Performance During Locomotion Poststroke: A Feasibility Study Using a Functional Virtual Environment

Wed, 10 Feb 2010 13:11:24 +0100

Kizony R, Levin MF, Hughey L, Perez C, Fung J

Cognitive Load and Dual-Task Performance During Locomotion Poststroke: A Feasibility Study Using a Functional Virtual Environment

Phys. Ther. 2010 Feb;90(2):252-60. Epub 2009 Dec 18. http://www.ncbi.nlm.nih.gov/pubmed/20023003

Department of Occupational Therapy, Faculty of Social Welfare and Health Sciences, University of Haifa, Mount Carmel, Haifa 31905

Background: Gait and cognitive functions can deteriorate during dual tasking, especially in people with neurological deficits. Most studies examining the simultaneous effects of dual tasking on motor and cognitive aspects were not performed in ecological environments. Using virtual reality technology, functional environments can be simulated to study dual tasking.

Objectives: The aims of this study were to test the feasibility of using a virtual functional environment for the examination of dual tasking and to determine the effects of dual tasking on gait parameters in people with stroke and age-matched controls who were healthy.

Design: This was a cross-sectional observational study.

Methods: Twelve community-dwelling older adults with stroke and 10 age-matched older adults who were healthy participated in the study. Participants walked on a self-paced treadmill while viewing a virtual grocery aisle projected onto a screen placed in front of them. They were asked to walk through the aisle (single task) or to walk and select ("shop for") items according to instructions delivered before or during walking (dual tasking).

Results: Overall, the stroke group walked slower than the control group in both conditions, whereas both groups walked faster overground than on the treadmill. The stroke group also showed larger variability in gait speed and shorter stride length than the control group. There was a general tendency to increase gait speed and stride length during dual-task conditions; however, a significant effect of dual tasking was found only in one dual-task condition for gait speed and stride duration variability. All participants were able to complete the task with minimal mistakes.

Limitations: The small size and heterogeneity of the sample were limitations of the study.

Conclusions: It is feasible to use a functional virtual environment for investigation of dual tasking. Different gait strategies, including an increase or decrease in gait speed, can be used to cope with the increase in cognitive demands required for dual tasking.

Dynamic control of a moving platform using the CAREN system to optimize walking in virtual reality environments.

Wed, 15 Jul 2009 13:04:39 +0200

Makssoud HE, Richards CL, Comeau F.

Dynamic control of a moving platform using the CAREN system to optimize walking in virtual reality environments.

Conf Proc IEEE Eng Med Biol Soc. 2009;2009:2384-7. http://www.ncbi.nlm.nih.gov/pubmed/19965194

CIHR Multidisciplinary Team in Locomotor Rehabilitation, Laval University, Canada.

Virtual reality (VR) technology offers the opportunity to expose patients to complex physical environments without physical danger and thus provides a wide range of opportunities for locomotor training or the study of human postural and walking behavior. A VR-based locomotor training system has been developed for gait rehabilitation post-stroke. A clinical study has shown that persons after stroke are able to adapt and benefit from this novel system wherein they walk into virtual environments (VEs) on a self-paced treadmill mounted on a platform with 6 degrees of freedom. This platform is programmed to mimic changes in the terrain encountered in the VEs. While engaging in these VEs, excessive trunk movements and speed alterations have been observed, especially during the pitch perturbations accompanying uphill or downhill terrain changes. An in-depth study of the subject's behavior in relation to the platform movements revealed that the platform rotational axes need to be modified, as previously shown by Barton et al [2], and in addition did not consider the subject's position on the treadmill. The aim of this study was to determine an optimal solution to simulate walking in real life when engaging in VEs.

Vestibulo-visual integration for postural stability during standing.

Fri, 10 Jul 2009 13:06:53 +0200

David Jessop, Laurent Bouyer, McFadyen BJ

Vestibulo-visual integration for postural stability during standing

Presented at International Symposium on Posture and Gait, Bologna, Italy, July 2009; Submitted to J. Neurophysiology

Abstract: The aim of the present study was to identify the contributions of integrated visual and vestibular information on postural control during standing using binaural-bipolar galvanic vestibular stimulation (GVS) and optokinetic stimulation (OS) in the form of a rightward rotating cluster field. Two visual conditions (unperturbed vision, nO; optokinetic stimulation, OS) were combined with 3 vestibular conditions (no stimulation, nG, GVS right, GR; GVS left, GL). The six conditions, therefore, were: no sensory stimulation (nG_nO), independent sensory stimulations (nG_OS, GR_nO and GL_nO) and combined sensory stimulations (GR_OS and GL_OS). Head and trunk lateral angular movement (roll) and lateral displacement of center of pressure were evaluated. Our data show a postural deviation toward the anode side for the head, trunk and CoP for the independent GVS stimulations. The OS also caused comparable lateral displacements of the head and trunk towards the right, but the displacement of the CoP was not different from quiet standing. A mathematical summation of individual mean displacements for NS_OS and GR_UV was comparable to results of the combined stimulations for the same directions. Furthermore, a mathematical summation of NS_OS and GL_UV results was similar to the opposing GL_OS combined stimulations as well as to NS_UV. These results demonstrate that visual and vestibular stimulations appear to differ with respect to lower body responses and that individual vestibular and visual information initially sum in a linear fashion before some information processing mechanisms may take over.

Balance Control on a moving platform in unilateral lower limb amputees.

Thu, 28 Aug 2008 12:59:04 +0200

Vrieling AH, van Keeken HG, Schoppen T, Otten E, Halbertsma JP, Hof AL, Postema K

Balance Control on a moving platform in unilateral lower limb amputees.

Gait Posture. 2008 Aug;28(2):222-8. Epub 2008 Jan 22. http://www.ncbi.nlm.nih.gov/pubmed/18207407

Center for Rehabilitation, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.

Objective: To study balance control on a moving platform in lower limb amputees.

Design: Observational cohort study.

Participants: Unilateral transfemoral and transtibial amputees and able-bodied control subjects.

Interventions: Balance control on a platform that moved in the anteroposterior direction was tested with eyes open, blindfolded and while performing a dual task.

Main outcome measures: Weight bearing symmetry, anteroposterior ground reaction force and centre of pressure shift.

Results: Compared to able-bodied subjects, in amputees the anteroposterior ground reaction force was larger in the prosthetic and non-affected limb, and the centre of pressure displacement was increased in the non-affected limb and decreased in the prosthetic limb. In amputees body weight was loaded more on the non-affected limb. Blindfolding or adding a dual task did not influence the outcome measures importantly.

Conclusion: The results of this study indicate that experienced unilateral amputees with a high activity level compensate for the loss of ankle strategy by increasing movements and loading in the non-affected limb. The ability to cope with balance perturbations is limited in the prosthetic limb. To enable amputees to manage all possible balance disturbances in real life in a safe manner, we recommend to improve muscle strength and control in the non-affected limb and to train complex balance tasks in challenging environments during rehabilitation.

Effect of game speed and surface perturbations on postural control in a virtual environment

Fri, 06 Jun 2008 20:29:18 +0200

Hawkins PJR, Hawken MB, Barton GJ.

Proceedings of the 7th ICDVRAT with ArtAbilitation, Maia, Portugal.

Effect of game speed and surface perturbations on postural control in a virtual environment.

http://www.icdvrat.reading.ac.uk/2008/papers/ICDVRAT2008_S08_N02_Hawkins_Hawken_Barton.pdf

The aim of this study was to describe the relationship between performance and difficulty set by altering game velocity and surface perturbations in a virtual game environment. Performance deteriorates as game difficulty increases when changing game velocity and surface perturbations. Adjustment of both game velocity and the introduction of surface perturbations independently appear to be simple and effective methods of customising task difficulty as a function of patients’ motor ability during rehabilitation

Characteristics of personal space during obstacle circumvention in physical and virtual environments.

Wed, 27 Feb 2008 13:17:03 +0100

Gérin-Lajoie M, Richards CL, Fung J, McFadyen BJ.

Characteristics of personal space during obstacle circumvention in physical and virtual environments.

Gait Posture. 2008 Feb;27(2):239-47. Epub 2007 May 23. http://www.ncbi.nlm.nih.gov/pubmed/17512201

Center for Interdisciplinary Research in Rehabilitation and Social Integration, Department of Rehabilitation, Faculty of Medicine, Laval University, Quebec, Canada.

It is not known how the flexible protective zone maintained around oneself during locomotion (personal space or PS; see [Gérin-Lajoie M, Richards CL, McFadyen BJ. The negotiation of stationary and moving obstructions during walking: anticipatory locomotor adaptations and preservation of personal space. Motor Control 2005;9:242-69]) is modulated with walking speed, whether both sides of the PS are symmetrical, and whether the circumvention of physical and virtual obstructions elicit the same use of such PS. Personal space was measured in ten adults as they circumvented a cylindrical obstacle that was stationary within their path. Both left and right passes were performed at natural self-selected, slow and fast walking speeds. The same circumvention task was also performed at natural speeds in an immersive virtual environment (VE) replicating the same obstruction scenario. The shape and size of PS were maintained across walking speeds, and a smaller PS was generally observed on the dominant side. The general shape and lateral bias of the PS were preserved in the VE while its size was slightly increased. The systematic behavior across walking speeds and types of environment and the lateral bias suggest that PS is used to control navigation. This study deepens our understanding of normal adaptive walking behavior and has implications for the development of better tools for the assessment and retraining of locomotor capacity in different populations, from people with walking deficits to elite athletes. Since the PS behavior was shown to be robust in the VE used for this study, the virtual reality technology is proposed as a promising platform for the development of such assessment and retraining applications.

Gait termination in lower limb amputees.

Sun, 27 Jan 2008 12:54:08 +0100

Vrieling AH, van Keeken HG, Schoppen T, Otten E, Halbertsma JP, Hof AL, Postema K.

Gait termination in lower limb amputees.

Gait Posture. 2008 Jan;27(1):82-90. Epub 2007 Mar 21. http://www.ncbi.nlm.nih.gov/pubmed/17376689

Center for Rehabilitation, University Medical Center Groningen, University of Groningen, The Netherlands.

OBJECTIVE: To study the limitations in function and adjustment strategies of lower limb amputees in gait termination. DESIGN: Observational cohort study. SETTING: University Medical Centre. PARTICIPANTS: Unilateral transfemoral and transtibial amputees, and able-bodied control subjects. MAIN OUTCOME MEASURES: Leading limb preference, temporal variables, lower limb joint angles, ground reaction forces, and centre of pressure shift. RESULTS: Compared to able-bodied subjects, amputees showed a decreased peak braking ground reaction force in the prosthetic limb, no anterior centre of pressure shift during leading with the prosthetic limb and an increased mediolateral centre of pressure shift. Amputees used several adjustment strategies to compensate for the limitations in function; leading limb preference for the non-affected limb, longer production of braking force in the non-affected limb, decreased gait termination velocity and more weight-bearing on the non-affected limb. CONCLUSION: Limitations in function and adjustment strategies were mainly similar in transfemoral and transtibial amputees. Due to the lack of active ankle function, amputees were not able to increase the braking force and to shift the centre of pressure anteriorly. Leading with the non-affected limb is favourable for adequate deceleration and balance control, but in daily life not always applicable. It is important that amputees are trained in gait termination during rehabilitation and prosthetic design should focus on a more active role of the prosthetic foot and knee.

Detecting asymmetries in balance control with system identification: first experimental results from Parkinson patients.

Thu, 16 Aug 2007 12:56:52 +0200

van der Kooij H, van Asseldonk EH, Geelen J, van Vugt JP, Bloem BR.

Detecting asymmetries in balance control with system identification: first experimental results from Parkinson patients

J Neural Transm. 2007;114(10):1333-7. Epub 2007 Aug 16. http://www.ncbi.nlm.nih.gov/pubmed/17703275

Department of Biomechanical Engineering, University of Twente, Enschede, The Netherlands.

Cognitive processes can influence balance in various ways, but not all changes in postural performance can easily be identified with the naked clinical eye. Various studies have shown that dynamic posturography is able to detect more subtle changes in balance control. For patients with Parkinson's disease (which is typically an asymmetric disease), changes in the symmetry of balance control might provide a sensitive measure of cognitive influences on balance. Here, we describe a new posturography technique that combines dynamic platform perturbations with system identification techniques to detect such asymmetries in balance control of two patients with Parkinson's disease. Results were compared to those of six healthy controls. Our pilot data show clear asymmetries in dynamic balance control, even though patients themselves were not aware of this and had no subjective problems with stability or standing. We also found asymmetries in weight bearing, but the asymmetries in dynamic balance contribution were larger. Finally, asymmetries in weight bearing and dynamic balance in patients were not tightly coupled as in healthy controls. Future studies could incorporate this approach when examining the influence of mental decline on postural regulation.

Kinematic response characteristics of the CAREN moving platform system for use in posture and balance research.

Sun, 29 Jul 2007 12:56:21 +0200

Lees A, Vanrenterghem J, Barton G, Lake M.

Kinematic response characteristics of the CAREN moving platform system for use in posture and balance research.

Med Eng Phys. 2007 Jun;29(5):629-35. Epub 2006 Sep 6. http://www.ncbi.nlm.nih.gov/pubmed/16952478

Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Henry Cotton Campus, Webster Street, Liverpool L3 2ET, UK.

The CAREN system is a new and unique device for use in postural and balance research in clinical settings due to its ability to independently perturb the support surface in each of six degrees of freedom. Users of this system need knowledge of its technical performance which is not available. The aim of this study was to determine the technical performance of the CAREN system by defining its kinematic response characteristics to two commonly used input functions (sine and ramp) for each of its six translational and rotational axes. The translational and rotational displacement, velocity and acceleration limits of the CAREN system suggest that it is a mid-range system with regard to single degree of freedom moving platform devices reported in the literature. The maximum average displacement cross-talk was 1.5% of the viable working range in any specified direction. The maximum average velocity cross-talk was 3.3% of its maximum velocity in any specified direction. The CAREN system was able to respond to ramp input functions within its displacement and velocity limits although, for short duration ramps, there was evidence that target velocity was not reached. It is concluded that the CAREN system is an appropriate device for postural and balance research with some unique features. This specification of its technical performance should help researchers to identify the tasks for which it is most suitable.