Mechanical work, energetic cost, and gait efficiency in children with cerebral palsy

Many authors have reported increased energy expenditure during walking in children with hemiplegia. The origin of this increase is not well documented. The aim of our study was to understand better the origin of this increased energy expenditure of walking in children with cerebral palsy (CP) by simultaneously assessing the total mechanical work performed by the muscles and the efficiency of the work production.Twenty independently walking children with spastic, hemiplegic CP and a dynamic foot equinus deformity participated in the study. Instrumented gait analysis, including the analysis of kinematic, mechanical, and energetic variables, was performed. Despite excellent Gross Motor Function Measurement scores (range, 97-99), the energy cost was 1.3 times greater in children with CP than in healthy children. This increase in energy cost was related to an increase in the total positive mechanical work performed by the muscles and not related to a decrease in the efficiency of this work production. This study shows how segmental impairments (foot spastic equinus) increase the total mechanical work performed by the muscles and the energetic cost and how these segmental impairments contribute to the patient's disability. It is useful to associate the clinical examination, classic gait analysis, mechanical work, and energetic assessment to complete the evaluation of the condition of children with CP.

Influence of equinus treatments on the vertical displacement of the body's centre of mass in children with cerebral palsy

We assessed the influence of equinus gait treatments on the vertical displacement of the body's centre of mass (COM) in 21 patients with cerebral palsy (14 males, 7 females; mean age 8 y 9 mo [SD 2 y]; range 3 y 7 mo-17 y) presenting different topographical types (quadriplegia, n = 1; diplegia, n = 6; right hemiplegia, n = 6; and left hemiplegia, n = 8). Vertical COM displacement was computed from ground reaction forces, and lower limb kinematics was recorded simultaneously. Equinus gait was treated with non-operative treatments (i.e. botulinum toxin injections and stretching casts) in 14 patients, and with operative treatments in seven patients. After non-operative treatments, the entire ankle displacement shifted towards dorsiflexion throughout the gait cycle, but the amplitude of the third foot rocker (TR) and vertical COM displacement remained unchanged. However, after operative treatments, the amplitude of TR increased and vertical COM displacement decreased. A negative linear correlation was found between the former variables in all the patients where 53% of the changes in their vertical COM displacement, after equinus gait treatments, were explained by the changes in TR amplitude. In fact, TR remains a main gait determinant, reducing the vertical COM displacement after equinus gait treatment and influencing the general gait pattern.

Influence of gait pattern on the body's centre of mass displacement in children with cerebral palsy

We assessed the influence of digitigrade gait pattern, topographical types, severity of motor involvement, and locomotor experience on the body's centre of mass (COM) displacement during gait in children with spastic cerebral palsy (CP). Three-dimensional COM displacements were computed from ground reaction forces in 51 independent digitigrade walkers (29 males, 22 females; mean age 10 years 6 months, SD 2 years 7 months, range 7 to 15 years). Results obtained from 10 participants without disabilities (five males, five females), in the same age range as the patients with CP, were used as a reference plantigrade group. Vertical and forward COM displacements were significantly different between the digitigrade and the plantigrade walkers. Neither the topographical type (quadriplegia, n=5; diplegia, n=20; right hemiplegia, n=13; left hemiplegia, n=13), nor the severity of motor involvement, nor the locomotor experience influenced COM displacements. We conclude that the COM displacement during gait in patients with CP was mainly influenced by the digitigrade gait pattern encountered in this neurological disorder rather than the different topographical types and motor involvements.

Development of displacement of centre of mass during independent walking in children

The aims of this study were to assess the characteristics of three-dimensional displacement of the centre of mass of the body (CMb) during walking in healthy children and to compare it with those of young adults. Twenty-one children (11 males, 10 females; age range 1 to 9 years) were recruited from the nursery and school attached to the Université catholique de Louvain, Brussels, Belgium; and three young adults (one male two females; mean age 26 years 4 months) were recruited from the Rehabilitation and Physical Medicine Unit of the same university. Displacement of CMb was assessed at different walking velocities in the children and adults by two successive mathematical integrations of ground reaction forces, measured by a large strain-gauge force platform. Displacement of CMb was controlled for leg length of the participant to eliminate the scaling effect that is dependent on growth. Results showed that vertical and lateral amplitudes of the CMb when controlled for leg length were greater for children before 4 years of age and that the forward amplitude when controlled for leg length was greater for children before 7 years of age. We conclude that the development of mature human CMb displacement during independent walking is a gradual neural process, evolving until the age of 7 years.