Juan V. Durá Gil⁽¹⁾, Ignacio Bermejo Bosch⁽¹⁾⁽²⁾, Enrique Viosca Herrero⁽³⁾, Miguel Matas ⁽³⁾,  Jaime M.Prat Pastor⁽¹⁾⁽²⁾,  Laura Martínez Gómez⁽¹⁾,

(1) Instituto de Biomecánica (IBV). Universitat Politècnica de València. Edificio 9C .Camino de Vera s/n.(46022) Valencia, Spain
(2)  IBV’s Healhcare Technology Group, CIBER in Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN)
(3) La Fe Hospital

Cerebrovascular accidents are the most common cause of adult disability in Europe. Survival figures are 75%, although approximately half of the people affected lose the ability to live independently in their own home. Their rehabilitation and hospitalization mean a significant economic burden for the EU. In order to improve their rehabilitation and to increase the independence of the patients who experience these problems, the WalkX project developed a prototype that helps them to incorporate and rehabilitate gait by correcting their movement pattern. The prototype also helps to keep the trunk erect and to restore balance. It was designed to be used in rehabilitation centers, which will reduce the physical effort of physiotherapists and increase the duration and the intensity of therapy sessions.

INTRODUCTION

The WalkX Project is a European project funded by the Framework Programme 7, in the context of the granting of R&D funding for SMEs. Two Norwegian companies (Made for Movement Group AS, Xepto A), two companies from the UK (Newtrim Limited, MCT Engineering Limited), one company from France (VDI GROUP SA), one company from Italy (MOTUS SRL) and one company from Sweden (MOBILE ROBOTICS SWEDEN AB) took part in the project; as research and development centers, EESTI INNOVATSIOONI INSTITUUT (Estonia), INNORA (Greece) and the Instituto de Biomecánica, IBV (Spain) participated.

The objective of the project was to develop a device to facilitate the gait rehabilitation process in patients with stroke.

In the WalkX Project, the IBV defined the design requirements, developed the algorithms to simulate the gait pattern and validated the prototype in the tests with patients. These tests were performed with the collaboration of La Fe Hospital from Valencia.

DEVELOPMENT

The initial phase of the project consisted of a review of the state of the art and the establishment of discussion groups that included physiotherapists and rehabilitation doctors. On the basis of this information, the design of the requirements and the tasks that it should be possible to perform with the help of the device were defined.

These requirements determined the dimensions of the structure and the motors of the device (kinematic parameters - trajectories, speeds and accelerations of the moving parts - and dynamic parameters - forces and moments that the different components had to support). Thus, by using the gait patterns developed by the IBV and various functional assessment tools, it was possible to develop an algorithm that calculates the trajectories of the moving parts according to the stride length and the anthropometry of the patient.

In the last phase of the project, the IBV and La Fe Hospital collaborated to carry out the tests of the prototype developed, both with healthy subjects and patients.

The objective of the tests with healthy subjects was to determine whether their gait pattern was reproduced when using the prototype. Five men and five women took part in the tests with healthy subjects; they were individuals between 23 and 28 years whose kinematic gait pattern was characterized using electrogoniometers. These devices make it possible to continuously measure the joint angle, for example, the flexion and extension of the knee and the ankle.

Figure 1: Healthy subject with electrogoniometers

After measuring the subject while walking through a corridor, the same measurement was repeated with the subject using the prototype.

Figure 2: Healthy subject with electrogoniometers and using the prototype

Then, both records were compared to see the degree of coincidence between the two situations being analyzed.

Initially, 15 individuals were selected among the group of patients, four of whom could not complete the tests; therefore, a sample of only 11 patients was analyzed.

Table 1: Patients

The objective of the tests with patients was to detect problems related to usability, ergonomic adaptation, as well as opinions and improvement suggestions made by the physiotherapists who treat them.

RESULTS

Regarding the design requirements, and as a result of the discussion groups held with physiotherapists and rehabilitators, the tasks that it should be possible to perform with the prototype were defined as follows:

1. To move the patient’s ankle when sitting.
2. To stand up and sit down.
3. To stand with or without help, in such a way that the force that helps the subject support his or her own weight can be adjusted.
4. To walk with the ability to adjust different stride lengths and speeds. The pattern of movement for the various stride lengths should be natural.

Figure 3: Patient doing standing up and sitting down exercises

Additionally, professionals recommended the following:

1. The positioning of the patient and the adjustment of the prototype should be carried out in less than 10 minutes.
2. Due to the fact that some patients have cognitive problems, the patient and the system must be securely fixed; the patient should not be able to access the prototype control.
3. The rigidity of the harness or the trunk attachment system must be adjustable in order to correct posture.
4. The prototype should allow the physiotherapist to have simple access when handling the patient. For example, to move the patient’s legs or arms.

As a consequence of the above, in addition to the mechanisms to adjust gait pattern (stride length and speed), a vertical force adjustment system was designed to help support a percentage of the patient's weight. The therapist can adjust this percentage, or remove it when the patient can support his or her own weight.

With respect to the results of the tests with healthy subjects, the following figure shows the results of the comparative study. The blue line of the figure shows the knee flexion angle of a subject who was measured in the gait corridor without the prototype (left) and on the prototype (right), the red lines indicating the variability of the sample. A difference in the shape of the graphic can be seen for both situations. The result with the 10 healthy subjects showed that the prototype was able to correctly reproduce the kinematic gait pattern during 90% of the cycle.

Figure 4: Comparison of the knee flexion angle

During the tests with patients, the therapists positively assessed the prototype because it allows gait rehabilitation to start at an early stage, even if the patient is unable to stand. In addition, they stressed that patients were willing to use the prototype again, which could improve their adherence to the therapy. They also pointed out the need to include improvements in the access system, since it took too long to position the patient and adjust the prototype. These design enhancements should be implemented before beginning the marketing phase of the device.

CONCLUSIONS

The prototype proved that the design concepts applied are adequate. The prototype makes it possible to start gait rehabilitation at an early stage and could enhance patient adherence to the therapy.

Before starting the marketing phase, it would be necessary to improve the patient access system from a wheelchair in order to make the work of physiotherapists easier.

ACKNOWLEDGEMENTS

The research that led to these results received funding from the Framework Programme 7 of the European Community FP7/2007-2013 under grant agreement number 262569.