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Discrimination between the neural and non-neural origin of increased joint stiffness of the ankle in Cerebral Palsy
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Abstracts / Gait & Posture 36 (2012) S1–S101
was characterized by lower spastic threshold velocity (=velocity at EMG-onset) than GAS. Change parameters for GAS and MEH comparing CP with TD Change parameters (V2–V0)
GAS
Change between tow and high
CP
MEH
Average normalized EMG SD p-Value Torque at ankle/knee angle (Nm) SD p-Value
7.53 0.04 10.62 0.28 <0.0001 4.20 3.45 2.51 1.67 0.45
TD
CP
TD
9.49 8.86
0.54 0.65 <0.0001 5.96 1.73 3.65 1.07 0.0007
Discussion and conclusion: The results clearly indicated that electrophysiological and biomechanical parameters were able to quantify spasticity. Characteristics of sEMG also allowed to classify patients, by decomposing neurogenic and non-neurogenic spasticity components. It can be concluded that different integrated spasticity parameters, studied for an individual patient or a group of patients, provide quantitative levels of spasticity, which seems to be more sensitive than current subjective clinical spasticity scales. Disclosure: No significant relationships. doi:10.1016/j.gaitpost.2011.10.225 O46 Discrimination between the neural and non-neural origin of increased joint stiffness of the ankle in Cerebral Palsy K.L. de Gooijer-van de Groep 1,∗ , E. de Vlugt 2 , J.H. de Groot 1 , H.C.M. van der Heijden-Maessen 3 , D.H.M. Wielheesen 1 , J. Harlaar 4 , M.S. van Wijlen-Hempel 1 , J.H. Arendzen 1 , C.G.M. Meskers 1
subsequently fitted onto the total measured ankle torque. Model inputs were recorded ankle angle and EMG signals. Output parameters were elastic tissue stiffness (connective tissue and muscle), viscosity, TA and TS reflex torques. Tissue stiffness and viscosity were determined at the smallest maximal dorsiflexion angle among subjects. Results: In CP, RoM was smaller and tissue stiffness and viscosity were larger compared to controls, although the difference in tissue viscosity was small. Reflexive torque of TS was substantially increased in CP patients. In contrast to stroke patients, joint stiffness in CP was generally dictated by reflexive torque more than tissue stiffness. Discussion and conclusion: Ankle joint stiffness in CP was successfully disentangled in its neural and non-neural components using a nonlinear neuromuscular model. CP patients were distinguished from healthy controls by RoM, TS reflex torque and tissue stiffness. Within the RoM, tissue stiffness was smaller and reflexive torque larger compared to stroke patients. Reduced RoM in CP patients can be explained by the relative short structural length of the muscle tendon complex of triceps surae. The used approach may be successfully applied to select patient and component specific therapy to tune improper joint stiffness in CP. Next steps are to relate outcome parameters to clinical phenotype in a larger cohort of patients, to assess the influence of interventions like casting and botulinum toxin treatment and to relate the currently applied single joint approach to walking ability. Disclosure: No significant relationships. References [1] Dietz, Sinkjaer. Lancet Neurol 2007;6:725. [2] de Vlugt, et al. J Neuroeng Rehabil 2010;7:35.
1
Rehabilitation Medicine, Leiden University Medical Center, Leiden, Netherlands 2 Biomechanical Engineering, Delft University of Technology, Delft, Netherlands 3 Rijnlands Rehabilitation Center, Leiden, Netherlands 4 V.U. Medical Center, Amsterdam, Netherlands Introduction: Cerebral Palsy (CP) is characterized by increased joint stiffness, i.e. resistance to movement which can be of neural or non-neural origin [1] by respectively improper muscle activation and changes in viscoelastic properties of connective tissues. Current manual tests cannot discriminate between underlying contributors to joint stiffness, i.e. elastic ‘muscle stiffness’, ‘viscosity’ and ‘reflex activity’. Specific therapy aimed at stiffness reduction can therefore not be selected beforehand. de Vlugt et al. [2] developed an assessment method to quantify neural and non-neural contributions to ankle joint stiffness in stroke patients. Stroke patients were distinguished from controls by increased tissue stiffness, viscosity and reflexive torque. We applied aforementioned approach to CP patients. Patients/materials and methods: Twenty CP patients (GMFCS level I–III) and fifteen healthy subjects matched for age and sex were seated with their foot fixated onto an electrically powered single axis footplate (MOOG FCS Inc., Nieuw Vennep, The Netherlands). During passive ankle rotations, foot reaction torque and angular displacement were measured. Muscle activation of the tibialis anterior (TA) and triceps surae muscles (TS) was recorded by surface EMG. The motor was driven in either torque mode to assess ankle Range of Motion (RoM) and position mode to impose Ramp and Hold (RaH) perturbations at four different angular velocities (15, 30, 60, 120◦ /s) over the full, individually assessed RoM, starting in maximal plantar flexion and ending at the maximal dorsal flexion angle. Subjects were asked to remain maximally relaxed during the entire experiment. A nonlinear neuromuscular model [2] was
doi:10.1016/j.gaitpost.2011.10.226 O47 Changes in inter-segmental coordination and gait performance after the rectus femoris transfer procedure in children with cerebral palsy J. Carollo ∗ , K. Worster, Z. Pan, F. Chang, J. Valvano Center for Gait and Movement Analysis (cgma), Children’s Hospital Colorado, Aurora, CO, United States Introduction: While the rectus femoris transfer procedure (RFT) has often been shown to improve overall gait performance in children with cerebral palsy (CP) exhibiting stiff knee gait (SKG), few previous studies have investigated inter-segmental coordination (ISC) after surgery using the tools common to dynamic systems theory [1]. ISC is quantified by analytical procedures including phase plane portraits and continuous relative phase (CRP) plots, which describe the elegant interaction between lower body segments as they oscillate in a manner similar to compound pendulums in normal gait [2]. The CRP plot quantifies the uncoupling of lower extremity segment oscillations, a requirement for rapid thigh acceleration in pre-swing, and a precursor to swing period knee flexion. CRP measures of ISC are particularly useful in addressing the impaired knee flexion dynamics characteristic of SKG because kinematic achievements in knee flexion require complex coordination of the thigh and shank segments. A previous analysis demonstrated that changes in thigh/shank (T/S) ISC explained much of the variance in gait performance change after RFT [3]. This retrospective study expands prior knowledge by describing how pelvis–thigh (P/T) and shank–foot (S/F) ISC changes complement T/S change in these patients, leading to a more complete understanding of how lower limb coordination is modified after a successful RFT.
Abstracts / Gait & Posture 36 (2012) S1–S101
was characterized by lower spastic threshold velocity (=velocity at EMG-onset) than GAS. Change parameters for GAS and MEH comparing CP with TD Change parameters (V2–V0)
GAS
Change between tow and high
CP
MEH
Average normalized EMG SD p-Value Torque at ankle/knee angle (Nm) SD p-Value
7.53 0.04 10.62 0.28 <0.0001 4.20 3.45 2.51 1.67 0.45
TD
CP
TD
9.49 8.86
0.54 0.65 <0.0001 5.96 1.73 3.65 1.07 0.0007
Discussion and conclusion: The results clearly indicated that electrophysiological and biomechanical parameters were able to quantify spasticity. Characteristics of sEMG also allowed to classify patients, by decomposing neurogenic and non-neurogenic spasticity components. It can be concluded that different integrated spasticity parameters, studied for an individual patient or a group of patients, provide quantitative levels of spasticity, which seems to be more sensitive than current subjective clinical spasticity scales. Disclosure: No significant relationships. doi:10.1016/j.gaitpost.2011.10.225 O46 Discrimination between the neural and non-neural origin of increased joint stiffness of the ankle in Cerebral Palsy K.L. de Gooijer-van de Groep 1,∗ , E. de Vlugt 2 , J.H. de Groot 1 , H.C.M. van der Heijden-Maessen 3 , D.H.M. Wielheesen 1 , J. Harlaar 4 , M.S. van Wijlen-Hempel 1 , J.H. Arendzen 1 , C.G.M. Meskers 1
subsequently fitted onto the total measured ankle torque. Model inputs were recorded ankle angle and EMG signals. Output parameters were elastic tissue stiffness (connective tissue and muscle), viscosity, TA and TS reflex torques. Tissue stiffness and viscosity were determined at the smallest maximal dorsiflexion angle among subjects. Results: In CP, RoM was smaller and tissue stiffness and viscosity were larger compared to controls, although the difference in tissue viscosity was small. Reflexive torque of TS was substantially increased in CP patients. In contrast to stroke patients, joint stiffness in CP was generally dictated by reflexive torque more than tissue stiffness. Discussion and conclusion: Ankle joint stiffness in CP was successfully disentangled in its neural and non-neural components using a nonlinear neuromuscular model. CP patients were distinguished from healthy controls by RoM, TS reflex torque and tissue stiffness. Within the RoM, tissue stiffness was smaller and reflexive torque larger compared to stroke patients. Reduced RoM in CP patients can be explained by the relative short structural length of the muscle tendon complex of triceps surae. The used approach may be successfully applied to select patient and component specific therapy to tune improper joint stiffness in CP. Next steps are to relate outcome parameters to clinical phenotype in a larger cohort of patients, to assess the influence of interventions like casting and botulinum toxin treatment and to relate the currently applied single joint approach to walking ability. Disclosure: No significant relationships. References [1] Dietz, Sinkjaer. Lancet Neurol 2007;6:725. [2] de Vlugt, et al. J Neuroeng Rehabil 2010;7:35.
1
Rehabilitation Medicine, Leiden University Medical Center, Leiden, Netherlands 2 Biomechanical Engineering, Delft University of Technology, Delft, Netherlands 3 Rijnlands Rehabilitation Center, Leiden, Netherlands 4 V.U. Medical Center, Amsterdam, Netherlands Introduction: Cerebral Palsy (CP) is characterized by increased joint stiffness, i.e. resistance to movement which can be of neural or non-neural origin [1] by respectively improper muscle activation and changes in viscoelastic properties of connective tissues. Current manual tests cannot discriminate between underlying contributors to joint stiffness, i.e. elastic ‘muscle stiffness’, ‘viscosity’ and ‘reflex activity’. Specific therapy aimed at stiffness reduction can therefore not be selected beforehand. de Vlugt et al. [2] developed an assessment method to quantify neural and non-neural contributions to ankle joint stiffness in stroke patients. Stroke patients were distinguished from controls by increased tissue stiffness, viscosity and reflexive torque. We applied aforementioned approach to CP patients. Patients/materials and methods: Twenty CP patients (GMFCS level I–III) and fifteen healthy subjects matched for age and sex were seated with their foot fixated onto an electrically powered single axis footplate (MOOG FCS Inc., Nieuw Vennep, The Netherlands). During passive ankle rotations, foot reaction torque and angular displacement were measured. Muscle activation of the tibialis anterior (TA) and triceps surae muscles (TS) was recorded by surface EMG. The motor was driven in either torque mode to assess ankle Range of Motion (RoM) and position mode to impose Ramp and Hold (RaH) perturbations at four different angular velocities (15, 30, 60, 120◦ /s) over the full, individually assessed RoM, starting in maximal plantar flexion and ending at the maximal dorsal flexion angle. Subjects were asked to remain maximally relaxed during the entire experiment. A nonlinear neuromuscular model [2] was
doi:10.1016/j.gaitpost.2011.10.226 O47 Changes in inter-segmental coordination and gait performance after the rectus femoris transfer procedure in children with cerebral palsy J. Carollo ∗ , K. Worster, Z. Pan, F. Chang, J. Valvano Center for Gait and Movement Analysis (cgma), Children’s Hospital Colorado, Aurora, CO, United States Introduction: While the rectus femoris transfer procedure (RFT) has often been shown to improve overall gait performance in children with cerebral palsy (CP) exhibiting stiff knee gait (SKG), few previous studies have investigated inter-segmental coordination (ISC) after surgery using the tools common to dynamic systems theory [1]. ISC is quantified by analytical procedures including phase plane portraits and continuous relative phase (CRP) plots, which describe the elegant interaction between lower body segments as they oscillate in a manner similar to compound pendulums in normal gait [2]. The CRP plot quantifies the uncoupling of lower extremity segment oscillations, a requirement for rapid thigh acceleration in pre-swing, and a precursor to swing period knee flexion. CRP measures of ISC are particularly useful in addressing the impaired knee flexion dynamics characteristic of SKG because kinematic achievements in knee flexion require complex coordination of the thigh and shank segments. A previous analysis demonstrated that changes in thigh/shank (T/S) ISC explained much of the variance in gait performance change after RFT [3]. This retrospective study expands prior knowledge by describing how pelvis–thigh (P/T) and shank–foot (S/F) ISC changes complement T/S change in these patients, leading to a more complete understanding of how lower limb coordination is modified after a successful RFT.