Assisting Clinical Decision-Making for Paediatric Movement Disorders - Towards assessing the effectiveness of therapy in cerebral palsy through mapping of gait maturation
Cerebral Palsy (CP), caused by a lesion to or abnormality of the developing brain, is the most common movement disability in childhood within western countries. The central lesion affects motor control and leads to abnormal development of muscles and bones. Treatment targets the musculoskeletal deformities and focuses on optimizing quality of life by bringing walking patterns of affected individuals closer to those of typically developing children (TDC). Clinical gait analysis (CGA) is used to objectively assess walking patterns and determine the causes of gait deviations. While CGA provides added value to clinical decision making and has shown to improve treatment outcomes, it did not lead to the expected improvement in patient satisfaction. One-third of patients remain unsatisfied with outcomes after intervention, but this could be due to unrealistic expectations. Additionally, some useful information could be hidden in the high dimensional CGA data, which are difficult to interpret. Until now, mainly kinematic features and overall summary scores for gait and motor function are extracted from CGA to assist clinical decision making. However, it is questionable whether this practice can capture the complexity of walking and motor development. Therefore, there is a need for more in-depth evaluation of the possible approaches to translate CGA outcomes into clinically relevant and easily interpretable outcomes. By providing relevant information from CGA to clinicians, unnecessary treatments can be prevented, patients can receive the optimal treatment for their condition in a timelier fashion, and more realistic expectations can be set. This can help reduce healthcare costs, optimize treatment outcomes, and improve patient satisfaction. Therefore, this doctoral thesis aimed to identify CGA parameters capable of capturing gait development with age and the effects of treatment. As fluctuations in walking behaviour have shown promise in capturing development and skill acquisition, this work focussed on the ability of gait variability and asymmetry to differentiate age and different levels of motor impairment. First, methods for estimating gait events, such as touch-down (initial contact) and lift-off (toe-off), were evaluated for their efficacy on paediatric pathological gait. The optimal methodology identified was afterwards applied in a retrospective cohort study to extract spatiotemporal parameters and quantify their variability in a (semi-)automatic manner from kinematic data. This data was then used to present the concept of motor-developmental trajectories in movement variability and assess the ability of gait asymmetry and variability to capture development and motor function in children and adolescents with CP and those with typical development. It was then investigated whether these motor-developmental trajectories could be interrupted by surgical interventions. From all the evaluated methods to estimate timing of gait events, the sagittal velocity approach applied to markers located on the mid-foot (where the peaks from the marker velocity in the sagittal plane are used to estimate timing of gait events), was found to preform best across various paediatric pathological gait patterns. With this sagittal velocity method, gait variability and asymmetry parameters were extracted from a retrospective clinical dataset. Through childhood, significant differences in movement variability were present between TDC and children with CP. Walking patterns tended to become less variable and more symmetrical with increasing age in both TDC and children with CP. However, the change with age was greater in individuals with CP who underwent the standard care in Switzerland, compared to TDC, leading to less profound differences at greater age. The difference in severity levels of CP remained stable during child development. Following a multilevel surgery (i.e., operations on both hips, knees, and feet in one surgical session), gait variability and asymmetry reduced with time in individuals with CP, indicating that invasive musculoskeletal intervention does not disrupt motor maturation. While routinely reported parameters, such as gait profile score, improved short-term after surgery and were afterwards maintained, gait variability and asymmetry parameters further improved into adulthood. The motor-developmental trajectories in movement variability, that were developed as part of this thesis, enable the prognosis of gait function in children and adolescents with typical development and CP. Like growth charts commonly used for height and weight, these trajectories capture age-related changes for multiple gait domains. Motor-developmental trajectories in movement variability can be used for identification and detection of motor characteristics of CP and allow for expectations of development and functional discrepancies to be managed effectively. Additionally, motor-developmental trajectories elucidate underlying deficits and could therefore be used as functional biomarkers to support clinical decisionmaking for targeted treatment programmes. In the rapidly changing field of CGA, the concept of motor-developmental trajectories in movement variability is one of many new tools being developed. Each of these new tools contribute in their own unique way. Musculoskeletal modelling, in combination with measures for motor control, can be an asset to test hypotheses regarding the causes of motor deficits at the population level; machine learning can be used to provide patient-specific predictions and thereby support patient-centred care. The strength of the presented motor-developmental trajectories lies within monitoring of gait function over time and can be used to visualize progress and support management of CP
