USING EMG SIGNAL TO IMPROVE PROSTHESIS

CONTROLCarolyn Carr

INTRODUCTION

Kuiken, T. et al, (2004) The use of targeted muscle reinnervation for improved myoelectric prothesis control in a bilateral shoulder disarticulation Amputee

INTRODUCTION

Control of disarticulation shoulder

prostheses Elbow, wrist, and hand Externally controlled

One function at a time myoelectric signal or body powered Locks need to be done sequentially

INTRODUCTION

Brachial plexus Function

Upperlimb muscular innervation Cutaneious

Amputation of the arm the “control information” for the

arm is still in the Brachial Plexus Relocate the nerves

Use the nerve muscle units for control

INTRODUCTION

Difficulties: After transecting nerves do not reinnervate their

own muscles consistently Controlling the independent nerve-muscle units

Beneifts: Myoelectric control

Motorneutrons transfer onto small amounts of muscle Hyper-reinnervate

Hyper-reinnervate Improves muscle recovery Full muscle recovery possible

INTRODUCTION

Purpose of this study is to use nerve

transfers to improve control of the prosthesis

using myoelectric control sites.

METHODS

Subject 54 year old white male Bilateral shoulder disarticulation amputations

Right side Body powered prothesis Voluntary opening split hook Four function unit

3 mechanical chin switches Elbow, wrist, and shoulder

Left side to be replaced Externally powered prosthesis Use the muscles as a biological amplifier for

independent signals

METHODS

Reason for surgery Good shoulder motion Strong pectoralis muscle contraction No sign of brachial plexopathy

Benefits Significant improvement in the left prosthesis

If failed Still able to use what he was already using, touch

pad control

METHODS

Surgery Brachial Plexus identified Muscles in chest subdivided into individual units

based on muscle innervations and vascularity Brachial plexus nerves mobilized down to the

muscle segments

METHODS

Surgery details: Pectoralis major was divided into three parts

The clavicular head Lateral pactoral nerve, upper and lower segements. Sternal Head

upper segments lower segments

The pectoralis minor moved Moved laterally to the mid-axillary line

Prevent EMG-Cross talk To Improve EMG signal, subcutaneious fat was

surgically removed

METHODS

Recovery Physical therapy

The patient was told to open and close hand on daily basis

5 months active muscle contraction in different areas of the muscle

METHODS

How to operate EMG signal held for 1-2 seconds causes elbow

lock Higher EMG signal to release

Median area, controls open/close of hand Due to the two signals in Mid-pectoral, there were

more options for wrist rotation A touch pad A strong contraction of open/close would switch the

unit to pronation and supination a strong contraction to switch back, again,

METHODS

Testing Box and Blocks test (Mathiowetx et al, 1985)

1 inch square blocks moved to another box, with an obstacle of a short wall in between box

Modified, to test patient in a two minute time frame Clothes pins

On a horizontal bar, rotation pin and move to high vertical bar

Used three pins

METHODS

EMG Programming, Three strongest signals used for control Signal under clavicle (large signal)

musculocutaneious nerve

Flexing elbow Mid-pectoral region, two independent signals

Median Nerve Lateral, closing hand Medial opening hand

Method

Inferior pectoral region Radial Nerve

Extended elbowopen hand extend the wrist

Weak signal and difficult signal to isolate

RESULTS

3 out of 4 nerves were successful musculocutaneous nerve the median nerve the radial nerve

Ulnar nerve to pectoralis minor nerve anastomosis No visible or EMG signal detected on the later

pectoral region, where it was moved

RESULTS

Touch Pad Control Number

of Blocks

Myoelectric control Number

of blocks

Trial 1 5 10

Trial 2 5 14

Trial 3 7 18

Average 5.7 14

Box and Block Test Results

RESULTS

Touch pad control Time (sec)

Myoelectric control Time (sec)

Trial 1 153 83

Trial 2 137 122

Trial 3 121 99

Average 137 101

Clothes Pin Results

DISCUSSION

Three anatomical principles1. Brachial plexus differentiates into the median,

ulnar, musculocutaneous and radial nerves in mid-clavicle region

Important for individual control

2. The length of the distal brachial plexus and the terminal nerve were long enough to mobilize to the chest wall, without further grafting

3. Pectoralis muscles was sub-divided into three parts

If there where any overlap of the reinnervation, the EMG signals would have been comprimised.

DISCUSSION

Musculocutaneous nerve: Successful Largest EMG signal, may be due to the proximity

of the clavicle. Clavicle acted as an “electrical insulator”

Median Nerve: Successful 2 different signals: Hand closing, hand opening

Reinnervation of the abductor pollicis brevis Future studies should look into separating these out

DISCUSSION

Radial Nerve: Weak Visibly and tangibly successful Not independent of other signals, and weak Electrocardiogram was large enough to interfere

with the EMG signal Subcutaneous fat removed

Ulnar nerve: Failed Reinnervation at the pactoralis minor

When moving the pactoralis minor lateral, the blood supply was compromised

Unexpected results Skin sensory

Due to removal of subcutaneous fat

DISCUSSION

Three independent signals Two degrees of freedom Faster control

All test results showed compared to previous prosthetic the movement was more natural, and easier to control

For the future Could apply to the shoulder movement Other levels of amputees

CONCLUSION

Peripheral nerves were relocated to the pectoralis major muscle in a disarticulation patient

Obtain simultaneous control, using EMG signal, for two degrees of freedom

Sensory reinnervation was obtained in the upper portion of the chest

THANK YOU Questions?

REFERENCES Kuiken, T., Dumanian, G., Lipschutz, R., Miller, L., & Stubblefield, K.

(2004). The use of targeted muscle reinnervation for improved myoelectric prosthesis control in a bilateral shoulder disarticulation amputee. Prosthetics And Orthotics International, 28(3), 245-253. Retrieved from MEDLINE with Full Text database.

Huang, H., Zhol, P., Guanglin, L, & Kuiken, T. (2009) Spatial Filtering Improves EMG Classification Accuracy Following Targeted Muscle Reinnervation. Biomedical Engineering, 37, 1849-1857. doi: 10.1007/s10439-009-9737-7