title: Validation of a new biomechanical model to measure muscle tone in spastic muscles.
abstract: BACKGROUND
  There is no easy and reliable method to measure spasticity, although it is a common and important symptom after a brain injury.
  
  
  OBJECTIVE
  The aim of this study was to develop and validate a new method to measure spasticity that can be easily used in clinical practice.
  
  
  METHODS
  A biomechanical model was created to estimate the components of the force resisting passive hand extension, namely (a) inertia (IC), (b) elasticity (EC), (c) viscosity (VC), and (d) neural components (NC). The model was validated in chronic stroke patients with varying degree of hand spasticity. Electromyography (EMG) was recorded to measure the muscle activity induced by the passive stretch.
  
  
  RESULTS
  The model was validated in 3 ways: (a) NC was reduced after an ischemic nerve block, (b) NC correlated with the integrated EMG across subjects and in the same subject during the ischemic nerve block, and (c) NC was velocity dependent. In addition, the total resisting force and NC correlated with the modified Ashworth score. According to the model, the neural and nonneural components varied between patients. In most of the patients, but not in all, the NC dominated.
  
  
  CONCLUSIONS
  The results suggest that the model allows valid measurement of spasticity in the upper extremity of chronic stroke patients and that it can be used to separate the neural component induced by the stretch reflex from resistance caused by altered muscle properties.
authors.affiliation: Karolinska Institute, Stockholm, Sweden. pavel.lindberg@ki.se
authors.forename: Påvel G
authors.initials: PG
authors.lastname: Lindberg
authors.forename: Johan
authors.initials: J
authors.lastname: Gäverth
authors.forename: Mominul
authors.initials: M
authors.lastname: Islam
authors.forename: Anders
authors.initials: A
authors.lastname: Fagergren
authors.forename: Jörgen
authors.initials: J
authors.lastname: Borg
authors.forename: Hans
authors.initials: H
authors.lastname: Forssberg
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D001696:Biomechanical Phenomena; D002908:Chronic Disease; D004548:Elasticity; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D009119:Muscle Contraction / Q000502:physiology; D009128:Muscle Spasticity / Q000503:physiopathology*; D009129:Muscle Tonus / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology / Q000503:physiopathology*; D009407:Nerve Block; D010291:Paresis / Q000209:etiology / Q000503:physiopathology; D012026:Reflex, Stretch / Q000502:physiology; D015203:Reproducibility of Results; D020521:Stroke / Q000150:complications / Q000503:physiopathology; D034941:Upper Extremity / Q000502:physiology; D014783:Viscosity