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W. Reichenfelser, J Karner, M. Gföhler:
"Modular arm orthosis with weight support: mechanical concept";
Poster: International Neurorehabilitation Symposium - INRS 2011, Zürich; 2011-06-27 - 2011-06-28; in: "Rehab Week Zürich 2011", (2011), 51.

Modular Arm Orthosis with Weight Support: Mechanical Concept

Reichenfelser W, Karner J, Gföhler M

Vienna University of Technology, Vienna, Austria

Introduction

Passive arm orthoses like the JAECO WREX [1] or the ARMON device [2] support patients with motor impairments in the upper limb when performing activities of daily living.
The presented modular arm orthosis is part of the European MUNDUS (MUltimodal Neuroprosthesis for Daily Upper limb Support) project that aims to assist patients with degenerative neuronal diseases or high level Spinal Cord Injuries (SCI). When clinically applied, it will be combined with Neuromuscular Electrical Stimulation (NMES) to enable the desired arm movements.

Materials and Methods

Representative motions associated with daily living were analyzed and the required ranges of motion estimated. Inverse dynamic simulations were performed in OpenSim [3] to determine the external joint torques. The characteristic of the weight support was calculated with Matlab and the resulting mechanical 3D design was done in Catia V5R19, focusing on modularity, simplicity and low weight.

Results

The outcome of the preliminary investigations is an orthosis design with two degrees of freedom (DoF) at the shoulder, one at the elbow joint and one for pro- and supination. These DoF can be locked with electromagnetic brakes to support the control of the NMES induced arm movement. The weight supporting spring is integrated in a tube that is attached to a harness for mobile use or mountable to a wheelchair. The compensating force of the spring is transferred via a rope to the upper arm shell. The orthosis is also prepared to carry a hand module that can activate the fingers. Depending on the severity or progression of the disease motors can be added to the DoF that can not be actuated by NMES sufficiently.

Discussion and Conclusion

The mechanical concept offers a both-sided, modular system which is assembled with regard to the severity of the motor impairment. It can be worn by the patient or attached to a wheelchair. Additionally to the provided weight support each DoF can be locked at defined positions what should ease the control of the arm motion when actuated by NMES. In a subsequent study the functionality of the prototype will be evaluated with patients at the rehabilitation centre.

Acknowledgment

This work is part of the European Project MUNDUS, funded by the call EC FP7 ICT 2009-4.

References

[1] http://jaecoorthopedic.com; cited April 28, 2011
[2] Herder J, et al., JRRD 43, 5, 591-604, 2006.
[3] Delp SL et al., IEEE Trans Biomed Eng, 54, 11, 1940-50, 2007.

arthosis, arm, weight support

http://publik.tuwien.ac.at/files/PubDat_202732.pdf