Overstretching of sarcomeres may not cause cerebral palsy muscle contracture.
To answer the question whether the muscle contracture in patients with cerebral palsy is caused by overstretching of in-series sarcomeres we studied the active and passive force-length relationship of the flexor carpi ulnaris muscle (FCU) in relation to its operating length range in 14 such patients with a flexion deformity of the wrist. Force-length relationship was measured intra-operatively using electrical stimulation, a force transducer, and a data-acquisition system. Muscle length was measured in maximally flexed and maximally extended position of the wrist. The spastic FCU was found to exert over 80% of its maximum active force at maximal extension of the wrist and this indicates abundant overlap of the sarcomeres. At maximal wrist extension, FCU passive force corresponded with only 0.7-18% of maximum active force. Both findings imply that the FCU sarcomeres are not overstretched when the wrist is extended. We conclude that the overstretching of in-series sarcomeres appears not to be the cause of contracture of the spastic FCU.
Smeulders
Mark J C
MJ
Department of Plastic, Reconstructive and Hand Surgery, Academic Medical Center, Suite G4-226, PO Box 22700, Amsterdam 1100 DE, The Netherlands.
Kreulen
Michiel
M
Hage
J Joris
JJ
Huijing
Peter A
PA
van der Horst
Chantal M A M
CM
D000293:Adolescent; D000328:Adult; D002547:Cerebral Palsy / Q000150:complications / Q000503:physiopathology*; D002648:Child; D003286:Contracture / Q000209:etiology / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D009119:Muscle Contraction; D009128:Muscle Spasticity / Q000209:etiology / Q000503:physiopathology; D012518:Sarcomeres / Q000502:physiology*; D014955:Wrist Joint