Article

Spastic cerebral palsy (CP) is characterized by increased joint resistance,
caused by a mix of increased tissue stiffness, as well as involuntary reflex and
background muscle activity. These properties can be quantified using a
neuromechanical model of the musculoskeletal complex and instrumented assessment.
The construct validity of the neuromechanical parameters was examined (i.e. the
internal model validity, effect of knee angle, speed and age, sensitivity to
patients versus controls, spasticity severity and treatment), together with the
repeatability. We included 38 children with CP and 35 controls. A motor driven
footplate applied two slow (15 degrees /s) and two fast (100 degrees /s)
rotations around the ankle joint, at two different knee angles. Ankle angle,
torque and EMG of the gastrocnemius (GA), soleus (SO) and tibialis anterior (TA)
muscle were used to optimize a nonlinear neuromuscular model. Outcome measures
were tissue stiffness, reflex and background activity for GA, SO and TA. The
internal model validity showed medium to high parameter confidence and good model
fits. All parameter could discriminate between patients with CP and controls
according to CP pathology. Other measures of external model validity (effect of
test position, speed and age) showed behaviour along the lines of current
knowledge of physiology. GA/SO background activity was sensitive to spasticity
severity, but reflex activity was not. Preliminary data indicated that reflex
activity was reduced after spasticity treatment.
The between-trial and -day
repeatability was moderate to good. The large variance between patients in the
ratio of stiffness and neural resistance indicates that the method could
potentially contribute to patient-specific treatment selection.
CI - Copyright (c) 2015 Elsevier B.V. All rights reserved.

Langue : ANGLAIS