A method for comparing manual muscle strength measurements with joint moments during walking.

This paper describes a protocol for dynamometer assisted manual muscle testing of the major muscle groups of the lower extremity and its application to 11 able-bodied children who also had conventional gait analysis to obtain joint kinetics. Data from the manual muscle testing was processed in such a way that the results for maximum muscle strength (grade 5) and resistance against gravity alone (grade 3) were presented in Nm/kg allowing direct comparison with conventional joint kinetics. The strength measurements of the hip muscles and the knee extensors were between two and three times the moments exerted during normal walking. Those of the knee flexors and dorsiflexors were about five times the joint moments. Measured plantarflexor strength was only just greater than the moment exerted during walking. These results, particularly those for the plantarflexors, question how valid it is to use measures of isometric muscle strength as indicators of muscle function during activity. The study also compares grade 3 muscle strength with both grade 5 strength and the maximum joint moments. For all muscle groups tested grade 3 muscle strength was less than the maximum moment exerted during normal walking. For the plantarflexors it was less than 1% of that moment. The study demonstrates that reliable isometric muscle testing is possible in able-bodied children but requires considerable care and is time consuming. More work is required to understand how measurements made in this way relate to how muscles function during activity.

Measures of muscle and joint performance in the lower limb of children with cerebral palsy.

The aim of this study was to determine the reliability and magnitude of error of three lower-limb clinical measures for children with cerebral palsy (CP): the Modified Ashworth Scale of Spasticity (MAS), passive range of movement (PROM) and the modified Tardieu scale (MTS). Six physiotherapists measured 11 females and seven males (mean age 6 years 4 months, SD 2 years 4 months; age range 2 years 4 months to 10 years) on two occasions using a repeated measures design, collecting all data over 6 days. The severity of CP spanned all five levels of the Gross Motor Function Classification System and all children demonstrated varying degrees of spasticity. Exclusion criteria included botulinum toxin injections, inhibitory plasters, and orthopaedic surgery within the 6 months before study entry. For PROM and the MTS interrater reliability was acceptable with an intraclass correlation coefficient of 0.7, but results for MAS were lower. Standard error of measurement for repeated measures of PROM and MTS was about five degrees, but 95% confidence interval ranges were considerably higher. Test-retest results varied widely, particularly for the MAS. These measurement tools should be used with caution when evaluating changes in young children with CP.

Functional outcome of botulinum toxin A injections to the lower limbs in cerebral palsy.

We evaluated gross motor function following botulinum toxin A (BTX-A) injections in the lower limbs of children with spastic cerebral palsy in a randomized clinical trial, using a cross-over design. Forty-nine children (24 males, 25 females, age range 22 to 80 months) were randomly allocated to two groups: group 1 received BTX-A and physiotherapy, and group 2 received physiotherapy alone for 6 months. At the end of this period, group 2 received BTX-A and physiotherapy and group 1 continued with physiotherapy alone. Assessment measures were the Gross Motor Function Measure (GMFM), the Vulpe Assessment Battery (VAB), joint range of movement, the Modified Ashworth Scale, and a parental questionnaire. Sustained gains in gross motor function were found in both groups of children but the only additional benefit found in group 1 was a significant increase in fine motor rating on the VAB. By contrast, parents rated the benefit of treatment highly. It is likely that assessment at 3 and 6 months post injection was too late to demonstrate peak gross motor function response and that changes in GMFM are not sustained over 6 months with a single dose. Further studies should investigate changes over shorter time periods and consider covariables such as BTX-A dosage, number of injection sites, and the role of repeated injections combined with other interventions such as casting.