Power AFOs promote muscle activity, reduce therapist load

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Biomechanics Magazine June 2006 http://biomech.com

Power AFOs promote muscle activity, reduce therapist load

By: R.

While powered lower limb orthoses have many advantages for patients

with neurological injuries during the course of rehabilitation-and

certainly for the physical therapists who would otherwise be manually

assisting every step-the question remains: do the patients let the

device do the difficult work, inadvertently reducing their levels of

muscle activation just when they most need to be building strength?

Recent research from the University of Michigan suggests the answer

is no. Five patients with chronic incomplete spinal cord injury were

bilaterally fitted with ankle foot orthoses with pneumatic " muscles "

to assist ankle plantar flexion. Each patient walked on a bodyweight-

supported treadmill at four speeds under three orthotic conditions

(without orthoses, with passive orthoses, and with the powered

orthoses controlled by a therapist). Two of the five completed a

fourth condition in which they managed the orthoses themselves. The

other three were unable to control the devices well enough to develop

a steady gait pattern.

The investigators found that at slower speeds, ankle toe-off

kinematics for SCI patients under the therapist-controlled condition

were pretty close to those of healthy subjects. Slightly reduced

muscle activation occurred under the same condition at the soleus but

not the medial or lateral gastrocnemius at all speeds studied. The

decrease in soleus activity may be due to the bodyweight support. The

powered orthoses also provided enough propulsion to increase ankle

angle at toe-off at the slower speeds.

The results of this study indicate that powered AFOs can reduce the

physical strain on physical therapists of rehabilitative gait

training for neurologically impaired patients without substantially

affecting patient muscle activation.

The study was published in the February issue of the Journal of

NeuroEngineering and Rehabilitation.