Robot-aided system identification (ROBIN) of neural and non-neural contributors to ankle joint impedance in children with CP

Interventions for spastic Cerebral Palsy (CP) patients are focused on neural
and non-neural causes of raised joint impedance. However, current clinical
assessment of joint impedance is based on manual, subjective tests of low
resolution. In addition, these tests are limited in in discriminating these
neural and non-neural components. Therefore, the clinical community is in great
need of quantitative and valid assessment of neuromuscular parameters to guide
therapy selection. In addition, assessments should be valid with regard to
activities, such as walking. Current clinical tests are based on a passive task
that is poorly related to activities in daily life.
Linear system identification and parameter estimation (SIPE) techniques are
used to date to identify the neuromuscular system. However, nonlinear SIPE
techniques are necessary to capture the neuromuscular system during movements
such as walking, i.e. within the whole range of motion and joint torques.
Therefore, it is required to test new nonlinear SIPE based idenfitication
methods to objectively estimate the neuromuscular components of the ankle joint
during active movement.

Primary objective of this study is to assess the reliability and validity of
the neuromuscular parameters of ankle joint impedance estimated by nonlinear
SIPE technology in children with CP compared to current clinical manual tests
and gait analysis. In addition, the effect of joint impedance related to
interventions on the neuromuscular parameters is examined. Secondary objectives
are the examination of the dose-effect in IntraThecal Baclofen (ITB) treatment
and the understanding of altered joint impedance in relation to mobility in
children with CP.

This study is an observational cohort study.
First, the inter- en intra-reliability of the SIPE approach will be assessed in
15 CP children and 10 TDC. Next, a baseline measurement is done for all
patients and controls. The correctness of the SIPE technology will be assessed
by comparing the neuromuscular parameters to clinical measures, i.e. the
spasticity test with (SAIS) and without (SPAT) inertial sensors, and based on
the ability to discriminate CP from TDC children. In addition, the
neuromuscular parameters will be compared to a standard performed clinical gait
analysis in a subgroup of 40 CP children. The CP patients are measured again
after the intervention. The effect of intervention will be based on the
difference between the before and after intervention measurement. In addition,
a dose-effect study is performed in the children receiving ITB-treatment.
Finally, the ability of the SIPE approach to forecast therapy success will be
determined and compared to the accuracy of clinical measures.

To further test the construct validity, the effect of the imposed movement
profile will be examined in a small sample of the participants, by imposing
more gradual velocity increases of different speeds, which better resamblences
the clinically applied manual movement profiles (n=20). In addition, in a
subset of the participants, it is examined whether the relation between the
rotations and musle-tendon lengthening is quasi-lineair, by using standard
ultrasound measurements (n=20).

Rotations of the foot performed by the Achilles.

The protocol runs in parallel to existing clinical practice and will not affect
clinical decision making. Therefore, no extra visits are required, except for
the control subjects and the participants of the reliability study. The burden
and risk are minimal because the measurements are non-invasive, painless and
easy to perform. During a short time, active participation of patient and
subjects is required. Extra measurement time does not exceed 60 minutes for
robotic measurements. Safety precautions are taken comprising the restriction
within the subject*s range of motion together with normal accelerations and
also prevention of falling. The result will not benefit the participant, but
they will contribute to the treatment of CP patients in the future. The study
is focused on children with CP, since they undergo many interventions during
childhood en will thus benefit from improved treatment selection.