Reducing Knee Hyperextension With an Exoskeleton in Children and Adolescents With Genu Recurvatum: A Feasibility Study.

Genu recurvatum, or knee hyperextension, is a complex gait pattern with a variety of etiologies, and is often connected with knee weakness, lack of motor control, and spasticity. Because of the atypical forces placed on the soft tissues, early treatment or prevention of knee hyperextension may help prevent further degradation of the knee joint. In this study, we assessed the feasibility of a knee exoskeleton to mitigate hyperextension and increase swing range of motion in five children/adolescents who presented with unilateral genu recurvatum. Over the course of three visits, each participant practiced walking with the exoskeleton, which provided torque assistance during both stance and swing based on an impedance control law. In final validation trials, the exoskeleton was effective in reducing knee hyperextension (0.2 ± 4.7° average peak knee extension without exo to 9.9 ± 10.3° with exo) and improving swing range of motion by 14.0 ± 4.5° increase on average. However, while the exoskeleton was effective in normalizing the kinematics, it did not lead to improved spatio-temporal asymmetry measures. This work showcases a promising potential application of a robotic knee exoskeleton for improving the kinematic characteristics of genu recurvatum gait.

Ankle dorsiflexor function after plantar flexor surgery in children with cerebral palsy.

BACKGROUND: Surgical lengthening is used to address both overactivity and shortening of the spastic agonist muscle in children with cerebral palsy. It has been presumed that the function of the antagonist muscle will improve when the spastic agonist muscle has been surgically lengthened. The purposes of the current study were to use quantitative gait analysis to determine the prevalence of the ankle dorsiflexor muscles (antagonist) dysfunction during the swing phase of the gait cycle and to analyze how this function is affected following surgical lengthening of the ankle plantar flexor muscles (agonist). METHODS: The study design was a retrospective, cohort series of fifty-three children with cerebral palsy who underwent gait analysis before and after surgical lengthening of the gastrocnemius-soleus muscle group. Data from the physical examination, gait study kinematics, and dynamic electromyography in swing phase were analyzed. RESULTS: The mean age at the time of the initial gait analysis was eight years and eleven months. Significant improvements were noted in ankle dorsiflexion passive range of motion (p < 0.001), ankle dorsiflexor selective control (p = 0.002), ankle dorsiflexor strength (p = 0.001), and peak and mean ankle dorsiflexion in swing phase (p < 0.001 for each) following ankle plantar flexor lengthening surgery. Active ankle dorsiflexor function in swing phase was present in 79% of the extremities prior to ankle plantar flexor surgery. Swing phase dorsiflexor function was present in 96% of the extremities following surgery, with ten extremities improving from absent to present. CONCLUSIONS: The kinematic data support the clinical impression that ankle dorsiflexion during swing phase is improved following ankle plantar flexor lengthening surgery in children with cerebral palsy. In the majority of patients, this was a consequence of the correction of a fixed equinus contracture of the ankle plantar flexors that was constraining preexisting ankle dorsiflexor function. Weakness of all of the muscles is common, and surgical lengthening should only be considered for the correction of recalcitrant muscle contractures. Improved function of the antagonist muscle should be anticipated and optimized by appropriately focused strength training and other modalities during rehabilitation.

The efficacy of the floor-reaction ankle-foot orthosis in children with cerebral palsy.

BACKGROUND: The floor-reaction ankle-foot orthosis is commonly prescribed for children with cerebral palsy who walk with excessive ankle dorsiflexion and excessive knee flexion during the stance phase of gait. The purposes of this study were to evaluate the efficacy of this orthosis objectively and to identify clinical parameters that may compromise its function. METHODS: All children with cerebral palsy who had comprehensive gait analyses in both barefoot and braced walking conditions during a single visit to our Motion Analysis Laboratory between January 2001 and August 2007 were identified. Kinematic study parameters included mean sagittal dynamic range of motion of the ankle in stance, peak ankle dorsiflexion in stance, peak knee extension in midstance, and mean foot progression angle in stance. The minimum sagittal knee moment in midstance was also examined in this study for subjects who walked without assistive devices. Range-of-motion and skeletal alignment data obtained from the physical examination record of each subject included knee flexion contracture, popliteal angle, hip flexion contracture, and thigh-foot angle. RESULTS: Twenty-seven children had quantitative gait analyses (barefoot and with the orthoses in the same visit). The mean sagittal plane dynamic range of motion of the ankle in stance was reduced from 23 degrees +/- 9 degrees when walking barefoot to 10 degrees +/- 3 degrees when the orthosis was worn (p < 0.001), and the mean peak knee extension in midstance improved from 29 degrees +/- 14 degrees of flexion to 18 degrees +/- 14 degrees of flexion (p = 0.013). Strong negative linear correlations were found between the magnitude of knee and hip flexion contractures on physical examination and the amount of peak knee extension in midstance (r = -0.784 and r = -0.705, respectively). A strong positive correlation was found between the mean minimum sagittal knee moment in midstance and the amount of peak knee extension in midstance (r = 0.820). Our investigation did not provide evidence of a correlation between peak knee extension in midstance and any of the following parameters in the orthosis: clinical examination measurements of the thigh-foot angle (r = 0.120), the popliteal angle (r = -0.300), or the mean foot progression angle in the stance phase of gait (r = -0.188). CONCLUSIONS: The floor-reaction ankle-foot orthosis is effective in restricting sagittal plane ankle motion during the stance phase of gait in patients with cerebral palsy. As a result, improvements in knee extension and the sagittal plane knee extensor moment in stance phase are achieved. The best outcomes with this orthosis, as determined by peak knee extension in midstance, were seen in the subjects with knee and hip flexion contracture of < or =10 degrees . Knee and hip flexion contractures of > or =15 degrees were found to limit the efficacy of the orthosis in controlling knee extension in midstance. Such contractures should be considered as contraindications to the prescription of this orthosis or should be addressed (surgically or otherwise) prior to the application of a floor-reaction ankle-foot orthosis in these patients.

Prevalence of obesity in ambulatory children with cerebral palsy.

BACKGROUND: According to the most recent data, an estimated 17.1% of children in the United States are obese. We found no published studies documenting the prevalence of obesity in ambulatory children with cerebral palsy. The purpose of this study was to document the prevalence of obesity in ambulatory children with cerebral palsy and examine the trend in this measure over the last decade. METHODS: A retrospective review was performed to analyze the age, gender, height, weight, physical classification of the cerebral palsy, and functional level as determined with the Gross Motor Function Classification System (GMFCS) of all children with cerebral palsy who had a gait analysis performed in the Motion Analysis Laboratory of our institution between January 1994 and December 2004. This information was used to determine the prevalence of obesity (a body mass index in or above the 95th percentile of the sex-specific body mass index-for-age growth chart) in this population and its relationship to age, gender, the physical classification of the cerebral palsy, and the GMFCS level. RESULTS: When the data were grouped into three time periods (1994 to 1997, 1998 to 2002, and 2003 to 2004), a significant increase in obesity over time was noted (p = 0.017). The prevalences increased from 7.7% to 14% to 16.5% in the respective time periods. The prevalence increased over time in both males and females, those with hemiplegia and those with diplegia, and those with level-I function and those with level-II function according to the GMFCS. The association between obesity and time was significant in the female (p = 0.015), hemiplegic (p = 0.049), less than eight-year-old (p = 0.020), and GMFCS level-II (p = 0.003) groups. We found that the time period was independently associated with obesity when we controlled for age, type of cerebral palsy, and GMFCS level (p = 0.014). Children with a lesser degree of involvement (GMFCS level II) had twice the odds of becoming obese than did children with greater involvement (GMFCS level III). CONCLUSIONS: The prevalence of obesity in ambulatory children with cerebral palsy has risen over the last decade from 7.7% to 16.5%, an increase that is similar to that seen in the general pediatric population in the United States. This finding may have a major impact on the general health and functional abilities of these children as they reach adult life.