stiffness of the ankle joints in spastic hemiplegia patients

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The mechanism of stiffness that occurs during passive movement of the ankle in patients with spastic hemiplegia was investigated. The subjects consisting of 15 healthy subjects (7 males and 8 females ; mean age 41.0 y/o) and 30 spastic hemiplegic patients (16males and 14 females ; mean age 55.7 y/o) were positioned in a resting supine position with the knees at either 0 or 80 degrees of flexion. Both ankles of each subject were passively moved 20 degrees, from 10 degrees of plantar flexion at an angular velocity of 10 degrees per second by an isokinetic maschine KINCOM-500H^<TM> and the paralyzed ankles were also dorsiflexed at 50 and 100 degrees per second. The torque during passive movement of the ankle was measured together with the angular position of the ankle and surface EMGs of the tibialis anterior and triceps surae muscles. The change in torque per degree was defined as the stiffness. The muscle tone of the ankle extensors and the grade of palsy were evaluated using the Ashworth scale and SIAS (stroke impairment assessment set) motor score respectively.There was no activity in the triceps surae muscles during passive movement at 10 degrees per second. The stiffness in paralyzed ankles significantly increased in the extended knee position, and in both knee positions, the stiffness in paralyzed ankles was significantly greater than in the non-paralyzed side. Those subjects with paralyzed ankles were divided into two groups according to the presence of the stretch reflex in the triceps surae muscles during passive movement at 50 and 100 degrees per second, results indicated that there was no significant difference in the stiffness between the two. The stiffness in paralyzed ankles significantly correlated with the Ashworth scale and SIAS motor score respectively.