The relationship between lower limb muscle volume and body mass in ambulant individuals with bilateral cerebral palsy.

BACKGROUND: Individuals with cerebral palsy have smaller muscle volumes normalised to body mass than their typically developing peers. The aim of this study is to investigate the relationship between lower limb muscle volume and body mass in young people with bilateral cerebral palsy and their typically developing peers. METHODS: Twenty-five participants with bilateral cerebral palsy (aged 14.7±3.0 years, GMFCS level I-III) and 25 of their typically developing peers (aged 16.8±3.3 years) took part in this study. None of the participants had undergone orthopaedic surgery, botulinum toxin injections, or serial casting in the previous year. All participants underwent magnetic resonance imaging of both lower limbs. Nine major muscles of each lower limb were individually manually segmented and the muscle volumes calculated. RESULTS: Body mass and total lower limb muscle volume were significantly linearly related in both the cerebral palsy (R2 = 0.75, p<0.001) and typically developing (R2 = 0.77, p<0.001) groups. The slope of the relationship between muscle volume and body mass was significantly shallower in the cerebral palsy group compared to the typically developing group (p=0.007). CONCLUSIONS: This cross-sectional study suggests that the increase in size of lower limb muscles relative to body mass is reduced in adolescents and young adults with cerebral palsy. Longitudinal studies are required to further investigate altered muscle growth trajectories in this group and their impact on long-term mobility.

Selective motor control correlates with gait abnormality in children with cerebral palsy.

Children with bilateral cerebral palsy (CP) commonly have limited selective motor control (SMC). This affects their ability to complete functional tasks. The impact of impaired SMC on walking has yet to be fully understood. Measures of SMC have been shown to correlate with specific characteristics of gait, however the impact of SMC on overall gait pattern has not been reported. This study explored SMC data collected as part of routine gait analysis in children with bilateral CP. As part of their clinical assessment, SMC was measured with the Selective Control Assessment of the Lower Extremities (SCALE) in 194 patients with bilateral cerebral palsy attending for clinical gait analysis at a single centre. Their summed SCALE score was compared with overall gait impairment, as measured by Gait Profile Score (GPS). Score on SCALE showed a significant negative correlation with GPS (rs=-0.603, p<0.001). Cerebral injuries in CP result in damage to the motor tracts responsible for SMC. Our results indicate that this damage is also associated with changes in the development of walking pattern in children with CP.

Gastrocnemius muscle-tendon interaction during walking in typically-developing adults and children, and in children with spastic cerebral palsy.

BACKGROUND: Our understanding of the interaction of muscle bellies and their tendons in individuals with muscle pathology is limited. Knowledge of these interactions may inform us of the effects of musculoskeletal pathologies on muscle-tendon dynamics and the subsequent neurological control strategies used in gait. Here, we investigate gastrocnemius muscle-tendon interaction in typically-developing (TD) adults and children, and in children with spastic cerebral palsy (SCP). METHODS: We recruited six TD adults (4 female; mean age: 34 yrs. (24-54)), eight TD children (5 female; mean age: 10 yrs. (6-12)) and eight independently ambulant children with SCP (5 female; mean age 9 yrs. (6-12); 3 unilaterally-affected). A combination of 3D motion capture and 2D real-time ultrasound imaging were used to compute the gastrocnemius musculo-tendinous unit (MTU) length and estimate muscle belly and tendon lengths during walking. For the TD subjects, the measurements were made for heel-toe walking and voluntary toe-walking. RESULTS: The gastrocnemius muscle bellies of children with SCP lengthened during single support (p = 0.003). In contrast, the muscle bellies of TD subjects did not demonstrate an increase in length over the period of single support under heel-toe or toe-walking conditions. CONCLUSION: We observed lengthening of the gastrocnemius muscle bellies in children with SCP during single support, a phase of the gait cycle in which the muscle is reported consistently to be active. Repeated lengthening of muscle bellies while they are active may lead to muscle damage and have implications for the natural history of gait in this group.

Lower limb muscle volumes in bilateral spastic cerebral palsy.

AIM: Muscle weakness is a feature of individuals with spastic cerebral palsy (SCP) but there are few reports in the literature of muscle volume in this group. This study compares muscle volumes in adolescents and young adults with SCP with those of their typically developing (TD) peers. DESIGN: Measurements of the volumes of nine major lower limb muscles in 19 independently ambulant subjects with SCP (mean age 14.2 years (sd 2.7), 11 male, GMFCS I (n=5); GMFCS II (n=14)), 19 TD subjects (mean age 16.5 years (sd 3.0), 11 male) were made using magnetic resonance imaging. RESULTS: Lower limb muscles were smaller in the SCP group (p≤0.023 in all muscles) than the TD group with the exception of the vastii (lateralis+intermedius; p=0.868) and gluteus maximus (p=0.056). Average muscle volume deficit was 27.9%. Muscle volume deficits were significantly greater for distal muscles than proximal muscles (p<0.001). CONCLUSIONS: Reduced muscle size in adolescence and the natural history of sarcopenia in adulthood may contribute to the early loss of mobility of adults with SCP.

Changes in the volume and length of the medial gastrocnemius after surgical recession in children with spastic diplegic cerebral palsy.

BACKGROUND: Morphology is an important determinant of muscle force and power generation. Children with spastic diplegic cerebral palsy (SDCP) have reduced muscular strength, which in part is caused by inadequate muscle growth. There is a widespread concern that surgery to correct soft tissue deformities may exacerbate the underlying muscle weakness and further retard muscle growth. In this study, we compared measurements of medial gastrocnemius (MG) muscle morphology in typically developing (TD) children to those in children with SDCP with calf muscle deformities before and after corrective surgery. METHODS: We measured the length and volume of the MG muscle belly using 3-dimensional ultrasound immediately before and at 7 weeks and 1 year after vulpius procedure (VP) surgery in children with SDCP. We made similar measurements in a group of TD children. The SDCP group consisted of 7 children (6 boys, 1 girls; total of 8 limbs; age range, 6-10 years; mean 8 years 1 month, SD +/- 1 year 11 months) and the TD group consisted of 10 children (4 boys, 6 girls; age range, 6-12 years; mean, 9 years 5 months; SD +/- 2 years 6 months). RESULTS: The children with SDCP presented with MG muscle bellies both smaller and shorter than the TD children even when normalized to body mass and limb length, respectively. Muscle belly length was reduced by surgery and remained unaltered 1 year later, despite skeletal growth. Muscle volume was not significantly changed 7 weeks after surgery, but increased significantly between 7 weeks and 1 year after surgery. CONCLUSIONS: Children with SDCP presented with short and small MG when compared with TD children. Our results indicate that gastrocnemius muscle volume recovers within a year of VP surgery. CLINICAL RELEVANCE: This study is the first to investigate the effects of surgery on muscle belly volume and length in the human subject. The study indicates that VP surgery is not an agent of long-term muscle atrophy in individuals with SDCP with plantarflexion deformities.

The morphology of the medial gastrocnemius in typically developing children and children with spastic hemiplegic cerebral palsy.

We collected 3D ultrasound images of the medial gastrocnemius muscle belly (MG) in 16 children with spastic hemiplegic cerebral palsy (SHCP) (mean age: 7.8 years; range: 4-12) and 15 typically-developing (TD) children (mean age: 9.5 years; range: 4-13). All children with SHCP had limited passive dorsiflexion range on the affected side with the knee extended (mean+/-1SD: -9.3 degrees +/-11.8). Scans were taken of both legs with the ankle joint at its resting angle (RA) and at maximum passive dorsiflexion (MD), with the knee extended. RA and MD were more plantar flexed (p<0.05) in children with SHCP than in TD children. We measured the volumes and lengths of the MG bellies. We also measured the length of muscle fascicles in the mid-portion of the muscle belly and the angle that the fascicles made with the deep aponeurosis of the muscle. Volumes were normalised to the subject's body mass; muscle lengths and fascicle lengths were normalised to the length of the fibula. Normalised MG belly lengths in the paretic limb were shorter than the non-paretic side at MD (p=0.0001) and RA (p=0.0236). Normalised muscle lengths of the paretic limb were shorter than those in TD children at both angles (p=0.0004; p=0.0003). However, normalised fascicle lengths in the non-paretic and paretic limbs were similar to those measured in TD children (p>0.05). When compared to the non-paretic limb, muscle volume was reduced in the paretic limb (p<0.0001), by an average of 28%, and normalised muscle volume in the paretic limb was smaller than in the TD group (p<0.0001). The MG is short and small in the paretic limb of children with SHCP. The altered morphology is not due to a decrease in fascicle length. We suggest that MG deformity in SHCP is caused by lack of cross-sectional growth.

Changes to medial gastrocnemius architecture after surgical intervention in spastic diplegia.

We assessed the architecture of the medial gastrocnemius in nine children (five males, four females; age range 6 to 15 years; mean 10 years 10 months, SD 3 years 6 months) with spastic diplegia by ultrasound imaging before and after a gastrocnemius recession. The children were ambulant (seven independent, one with a posterior walker, one using crutches) before and after surgical intervention. We compared values for fascicle lengths and deep fascicular-aponeurosis angles with those from a group of normally developing children (five males, five females; age range 6 to 11 years; mean 8 years 4 months, SD 1 year 4 months). Despite a variable interval between assessments (from 56 to 610 days), fascicles were shorter (p=0.00226) and the deep fascicular-aponeurosis angle increased (p=0.0152) after intervention. Fascicle lengths of patients were similar to those in the group of normally developing children before surgery. After surgery, fascicles in the group of children with spastic diplegia were shorter than in their normally developing peers (p=0.00109). The gastrocnemius recession procedure alters muscle architecture, though the degree of fascicular shortening varied, with four of the participants in our study losing less than 10% of their original fascicular length at maximum dorsiflexion. Increases in ankle-joint power in walking, observed after surgical intervention in children with spastic diplegia, may be due to a more normal ankle position rather than to improvements in the active mechanical performance of the gastrocnemius.