No change in calf muscle passive stiffness after botulinum toxin injection in children with cerebral palsy.

AIM: Stiffness and shortening of the calf muscle due to neural or mechanical factors can profoundly affect motor function. The aim of this study was to investigate non-neurally mediated calf-muscle tightness in children with cerebral palsy (CP) before and after botulinum toxin type A (BoNT-A) injection. METHOD: Sixteen children with spastic CP (seven females, nine males; eight at Gross Motor Function Classification System level I, eight at level II; age range 4-10 y) and calf muscle spasticity were tested before and during the pharmaceutically active phase after injection of BoNT-A. Measures of passive muscle compliance and viscoelastic responses, hysteresis, and the gradient of the torque-angle curve were computed and compared before and after injection. RESULTS: Although there was a slight, but significant increase in ankle range of motion after BoNT-A injection and a small, significant decrease in the torque required to achieve plantigrade and 5° of dorsiflexion, no significant difference in myotendinous stiffness or hysteresis were detected after BoNT-A injection. INTERPRETATION: Despite any effect on neurally mediated responses, the compliance of the calf muscle was not changed and the muscle continued to offer significant resistance to passive motion of the ankle. These findings suggest that additional treatment approaches are required to supplement the effects of BoNT-A injections when managing children with calf muscle spasticity.

Mechanical properties of the plantarflexor musculotendinous unit during passive dorsiflexion in children with cerebral palsy compared with typically developing children.

AIM: To examine the passive length-tension relations in the myotendinous components of the plantarflexor muscles of children with and without cerebral palsy (CP) under conditions excluding reflex muscle contraction. METHOD: A cross-sectional, non-interventional study was conducted in a hospital outpatient clinic. Passive torque-angle characteristics of the ankle were quantified from full plantarflexion to full available dorsiflexion in 26 independently ambulant children with CP (11 females, 15 males; mean age: 6 y 11 mo, range 4 y 7 mo-9 y 7 mo) and 26 age-matched typically developing children (18 females, 8 males; mean age 7 y 2 mo, range 4 y 1 mo-10 y 4 mo). In the children with CP, the affected (hemiplegia; n=21) or more affected (diplegia; n=5) leg was tested; in typically developing children, the leg tested was randomly selected. Gross Motor Function Classification System levels were I (n=15) and II (n=11). Care was taken to eliminate active or reflex muscle contribution to the movement, confirmed by the absence of electromyographic activity. RESULTS: There were small but significant differences between the two groups for maximum ankle dorsiflexion (p=0.003), but large and significant differences in the torques required to produce the same displacement (p<0.001). Further, the hysteresis of the average loading cycle in the children with CP was over three times that of the typically developing children (p<0.001). INTERPRETATION: We believe that the plantarflexor muscles of children with CP are stiffer and intrinsically more resistant to stretch, even though they retain near normal excursion. This increased stiffness is a non-neurally-mediated feature demonstrated by these children. The extent to which it influences function and predisposes the children to development of soft tissue contracture is unknown.

Plantarflexor muscle and spatiotemporal gait characteristics of children with hemiplegic cerebral palsy: an observational study.

OBJECTIVE: The study investigated associations between the active and passive mechanical properties of the calf muscle in children with cerebral palsy and the spatiotemporal features of their gait on both level ground and over stairs. METHODS: 26 children with hemiplegic cerebral palsy (age 4 - 10 years) walked barefoot across a level ten metre pathway and a staircase. Walking speed, stride length and cadence were calculated and spasticity, maximum isometric strength, stiffness and hysteresis of the affected side calf muscle measured. Multiple linear regression was used to determine the associations among variables. RESULTS: Walking speed and stride length were significantly associated with dorsiflexor muscle strength and the stiffness of the calf muscle, while stair ascent and descent speeds were significantly and inversely related to the amount of hysteresis displayed by the calf muscle. CONCLUSION: Passive mechanical properties of the calf muscle are influential in gait performance in these children.

Evaluation of spasticity in children with cerebral palsy using Ashworth and Tardieu Scales compared with laboratory measures.

The content validity of the Tardieu Scale and the Ashworth Scale was assessed in 27 independently ambulant children with cerebral palsy (gender: 17 males, 10 females; age: 5-9 years; Gross Motor Function Classification: level I and II). Ashworth and Tardieu Scale scores and laboratory measures of spasticity and contracture were collected from the plantarflexor muscles by 2 examiners who were blinded to the results. The Tardieu Scale was more effective than the Ashworth Scale in identifying the presence of spasticity (88.9%, kappa = 0.73; P = .000), the presence of contracture (77.8%, kappa = 0.503; P = .008) and the severity of contracture (r = 0.49; P = .009). However, neither scale was able to identify the severity of spasticity. The Tardieu Scale can provide useful information in children with cerebral palsy because it differentiates spasticity from contracture. However, a more comprehensive clinical method of testing neural and non-neural contributions to impairments and function is needed.