Biomechanical examination of a commonly used measure of spasticity A.D. Pandyan a, * , C.I.M. Price b , H. Rodgers c , M.P. Barnes a , G.R. Johnson a a Centre for Rehabilitation and Engineering Studies CREST), University of Newcastle, Stephenson Building, Newcastle upon Tyne NE1 7RU, UK b Freeman Hospital, Newcastle upon Tyne, UK c Department of Medicine Geriatrics) and Department of Epidemiology and Public Health, University of Newcastle, Newcastle upon Tyne, UK Received 3 May 2001; accepted 29 August 2001 Abstract Background. An increase in the prevalence of neurological disability puts pressure on service providers to restrict costs associated with rehabilitation. Spasticity is an important neurological impairment for which many novel and expensive treatment options now exist. The antispastic eects of these techniques remain unexplored due to a paucity of valid outcome measures. Aim. To develop a biomechanical measure of resistance to passive movement, which could be used in routine clinical practice, and to examine the validity of the modi®ed Ashworth scale. Study design. Repeated measure cross-section study on 16 subjects who had a unilateral stroke one-week previously and had no elbow contractures. Outcome measures. Simultaneous measurement of resistance to passive movement using a custom built measuring device and the modi®ed Ashworth scale. Passive range of movement and velocity were also measured. The ``catch'', a phenomenon associated with the modi®ed Ashworth scale, was identi®ed by the assessor using a horizontal visual analogue scale and biomechanically quanti®ed using the residual calculated from a linear regression technique. Results. Half the study population had a modi®ed Ashworth score greater than zero. The association between the two measures was poor j  0:366). The speed and range of passive movement were greater in subjects with modi®ed Ashworth score ``0'' P < 0:05). Resistance to passive movement was higher in the impaired arm P < 0:05) and tended to decrease with repeated measures and increasing speeds. Conclusions. A device to measure resistance to passive movement at the elbow was developed. The modi®ed Ashworth scale may not provide a valid measure of spasticity but a measure of resistance to passive movement in an acute stroke population. Relevance Spasticity is an important neurological impairment for which many novel and expensive treatment options are being made available. There is a paucity of clinically usable outcomes to measure spasticity. A device to measure resistance to passive movement at the elbow, which was more reliable than the modi®ed Ashworth scale was developed. This device may provide a much needed objective clinical measure to evaluate the ecacy of antispasticity treatment. Ó 2001 Elsevier Science Ltd. All rights reserved. 1. Introduction Demographic changes in the Western world are placing an increasing burden on social and health service providers, as the number of people over 70 years of age grows rapidly [1]. The consequent increase in the inci- dence of stroke and other neurological disorders, com- bined with the increase in survival brought about by improvements in acute medical care, is leading to a dramatic increase in the prevalence of people with neurological impairment and associated disabilities. These factors, combined with the pressure to restrict the costs of healthcare, will demand more ecient rehabil- itation techniques. Spasticity is one of many impairments that can de- velop following an injury to the central nervous system [2]. It is de®ned as ``... a velocity dependent increase in the tonic stretch re¯ex muscle tone) with exaggerated Clinical Biomechanics 16 2001) 859±865 www.elsevier.com/locate/clinbiomech * Corresponding author. E-mail address: a.d.pandyan@ncl.ac.uk A.D. Pandyan). 0268-0033/01/$ - see front matter Ó 2001 Elsevier Science Ltd. All rights reserved. PII:S0268-003301)00084-5