RECOVERY OF LOCOMOTION AFTER SPINAL-CORD HEMISECTION - AN X-RAY STUDYOF THE CAT HINDLIMB

Hemisection of the spinal cord in adult cats is a suitable model to st udy the mechanisms underlying recovery of motor functions. The initial paresis of the hindlimb is followed by a considerable improvement of locomotor functions of the affected hindlimb. Kinematic analyses of tr eadmill locomotion were performed from 10 days to 8 months after compl ete hemisections (right side) of the spinal cord at the thoracolumbar level, using X-ray cinematography for precise measurements of the hind limb joint angles. The footfall pattern and the electromyogram were re corded. Motor control of both proximal and distal hindlimb joints impr oved substantially during the Ist postoperative month. However, persis tent locomotor deficits were still present several months after hemise ction. They could be divided into three groups of symptoms: (1) The ga it pattern was disturbed with regard to interlimb coordination. The st ance-phase duration of the right hindlimb was shortened. (2) The flexo r capacity of the affected hindlimb was reduced, resulting in a slow i nsufficient flexion of the hip, knee, and ankle during the swing phase . (3) The timing of the flexion-extension events was impaired. The ons et of the E1-extension was delayed and the amplitude was reduced. Elec tromyographic patterns of muscle activity during locomotion of the les ioned side hindlimb differed from the contralateral hindlimb, which se rved as a control. The results indicate that in spite of a good short- term functional improvement there are long-term locomotor deficits pre sent after spinal cord hemisection. (C) 1996 Academic Press, Inc.