Gait Analysis in Cerebral Palsy
Atypical gait is a common problem in ambulant children with Cerebral Palsy, making optimising or improving the efficacy of gait a key orthotic treatment goal. Gait analysis plays an important part in clinical decision-making when managing children with Cerebral Palsy. It is used to identify gait abnormalities, assist with the setting of treatment goals and also in the appraisal of ambulation following orthotic intervention. Hence the assessment and chronicling of a child’s gait is a critical element of the orthotic assessment process for ambulant children with Cerebral Palsy.
Visual Observational Gait Analysis (VOGA) provides the clinician with useful information concerning the presence of any musculoskeletal abnormalities and the alignment, coordination and proprioception of the lower limbs. VOGA relies on the clinician being able to assess body segment motion in two planes and at many levels at particular points of the gait cycle. For optimal orthotic management to occur, the treating clinician requires an awareness of what constitutes normal and pathological gait for a child at their particular stage of development. The clinician should therefore be able to identify the motor function deficits and differentiate primary impairment from substitutive actions.  
VOGA is relatively subjective and relies on the individual orthotist to identify and record gait abnormalities in real time. This can lead to low validity, reliability, sensitivity and specificity when compared to kinematic analysis in a gait laboratory.   To improve reliability, validity and sensitivity to change during VOGA the following gait scales have all been used in the evaluation of Paediatric Cerebral Palsy Gait:
- Physicians Rating Scale (PRS)
- Observational Gait Scale (OGS)
- Visual Gait Assessment Scale (VGAS)
- Edinburgh Visual Gait Scale (EVGS)
These scales provide the assessor with tick box forms to identify gait abnormalities, rate severity and provide an overall score for a child’s gait.
Physicians Rating Scale (PRS)
The PRS classifies six gait variables that are viewed in the sagittal plane on a 2 - 4 point scale. It has been shown to have good intra-observer reliability but poor inter-observer reliability when used in children with spastic hemiplegia and bilateral lower limb spasticity. Development of the PRS led to the introduction of the OGS and VGAS. However, the major limitation of all of these scales is that they only assess gait in the sagittal plane. It has also been found that visual assessment using the PRS and subsequent versions does not appear to accurately measure what it is most commonly used to assess; the ankle position in stance phase.
Edinburgh Visual Gait Scale (EVGS)
The EVGS was developed specifically for children with Cerebral Palsy and has stronger psychometric properties to enhance reliability.  The assessment is carried out in both the sagittal and coronal planes and evaluates the lower limb joint angles in both the stance and swing phases of gait. By incorporating the sagittal and coronal planes it allows for inferences to be made about the transverse plane and provides a more comprehensive representation of the child’s gait pattern than gait classification systems based solely on sagittal plane data. Similar to the other observational gait analysis scales, the EVGS has good intra-observer reliability, but poor inter-observer reliability.   The EVGS has also shown good sensitivity to change in children with Cerebral Palsy following orthopaedic surgery and therapeutic interventions.  To ensure consistently good levels of reliability and sensitivity are achieved, the assessor must be well trained and experienced in the evaluation and application of the EVGS.   It may be possible to use the EVGS to evaluate orthotic intervention, however further work is required to evaluate the sensitivity of the EVGS to gait changes following orthotic intervention.
Visual Gait Assessment Scale (VGAS)
In an attempt to overcome some of the problems associated with naked eye evaluation of gait, such as the speed of movements and only seeing the gait cycle once, Video Gait Analysis (VGA) has become a popular tool in the clinical setting. The video recording of a child’s gait should be conducted along a five-metre walkway at a self-selected walking speed in both the coronal and sagittal planes. The conditions to examine should comprise of barefoot, shoes only and if orthoses are being used, with shoes and orthoses. Reasons for considering the use of VGA in children with Cerebral Palsy are:
1. To establish a baseline of walking ability at the initial assessment;
2. Allow the documenting of any changes in gait pattern during growth;
3. Permit the evaluation of interventions such as surgery, botulinum toxin injections, serial caring, intensive therapy or orthotic intervention. 
The use of video analysis software that enables the user to take measurements of joint angles, distances and timing directly on digital video recordings, offers the potential to decrease the bias associated with subjective real time image assessments.  VGA incorporating the EVGS and specific video analysis computer software is an efficient approach to improve the reliability and repeatability of VGA with the added benefit of being easily incorporated into the orthotic clinical setting.   It provides an alternative to a full-instrumented gait analysis for those children that would otherwise not be considered suitable or when time or other resources are limited.
Three Dimensional Gait Analysis (3DGA)
The Three Dimensional Gait Analysis (3DGA) has proven to be a particularly powerful instrument to explicitly quantify joint kinematics and kinetics of the gait in children with Cerebral Palsy. 3DGA involves the use of video and infra-red cameras to record a person walking along a five metre walkway (FIGURE 1). Reflective dots are applied to the joints at predetermined intervals to capture information on body segment movement during gait and a force platform is positioned in the middle of the walkway to collect information on the Ground Reaction Force (GRF) during stance phase.
FIGURE 1: Gait laboratory set up for Three Dimensional Video Gait Analysis. Six infra red motions sensitive cameras are positioned around the five-metre walkway, with a force platform located in the middle of the walkway. 
3DGA is the gold standard for the comprehensive assessment of gait function in ambulant children with Cerebral Palsy.  It allows for the in-depth analysis of three dimensional kinematics, kinetics, temporo-spatial measurements, dynamic electromyography and physiological testing. 3DGA also provides clinicians with the ultimate in outcome measures for evaluating the effect an orthosis may have on a child’s gait. Employing 3DGA for orthosis evaluation at the level of gait kinematics and kinetics can be regarded as a technical quality check of the orthotic intervention in itself.  However, the everyday application in a clinical setting is limited due to the costs involved of setting up and running a gait laboratory and the time required for each gait assessment.
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