Paediatrics (RCH) - Theses
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ItemProximal femoral osteotomy in children and adolescents with cerebral palsy( 2018)Background Cerebral Palsy (CP) is the most common cause of physical disability affecting children in developed countries. Approximately one third of children with CP may develop hip displacement. Non-ambulant children at Gross Motor Function Classification System (GMFCS) levels IV and V are at highest risk. Without early detection through surveillance programs, hip displacement can progress to hip dislocation, which is frequently painful and negatively impacts health-related quality of life (HRQoL). Injections of Botulinum Neurotoxin A (BoNT-A) have no role, and soft tissue surgery has a limited role in preventing hip displacement in non-ambulant children with CP. Bony hip reconstruction surgery such as a proximal femoral osteotomy (PFO) is effective in stabilising the hip and HRQoL. PFOs include Femoral Derotation Osteotomies (FDO) which aim to improve the gait of an ambulant child (GMFCS I-III), and Varus Derotation Osteotomies (VDRO) which aim to contain the hips in non-ambulant children (GMFCS IV-V). However, PFOs can carry high risks, especially in children with medical co-morbidities such as respiratory disease, nutritional deficiencies, hypertonia and osteopenia. Aim This thesis involved a series of three studies, which aimed to expand our knowledge of the trainee learning curve, outcomes and adverse events relating to PFO in children and adolescents with CP. Method and Results A new implant combining locking and cannulated technology (Locking Cannulated Blade Plate, LCBP) was recently developed for use in PFO. A pilot study was performed on the first 25 patients who had surgery with the LCBP, at the Royal Children’s Hospital (RCH), Melbourne. This study established safety for use in children as young as three, with weights as low as eleven kilograms. A further prospective, parallel cohort study of 90 consecutive children with CP was conducted to compare the LCBP against with existing non-cannulated, non-locking implant (Angled Blade Plate, ABP). Technical and radiological outcomes of surgery were similar between implants. However, the surgical technique was reported by trainees to be easier when using the LCBP, with less technical errors. Approximately 60 percent of the children experienced minor adverse events including: constipation, inadequate pain control, and respiratory compromise. However, a CP specific tool was not available to classify the severity of events. Study three was performed to clarify the Modified Clavien-Dindo (MCD) system for lower limb surgery in children with CP and test its’ reliability for classifying adverse events. Very good reliability was demonstrated amongst members within a multidisciplinary team. Conclusion Novel findings from these studies may help improve the safety and efficacy of the management of hip displacement in children with CP. Further research should address the long-term outcomes of PFO in children with CP, evaluate the validity of the MCD for children in CP and determine if the MCD can be embedded in the electronic medical records (EMR) as a routine tool for audit and clinical research.
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ItemDaytime predictors of sleep disordered breathing in Duchenne muscular dystrophy( 2017)Sleep disordered breathing (SDB) in Duchenne muscular dystrophy (DMD) progresses to respiratory failure. The gold standard for diagnosis is polysomnography (PSG) but the optimal timing is unknown. Twenty boys with DMD, aged 10 – 16 previously undiagnosed with nocturnal hypoventilation (NH), had repeat PSG. Concurrent clinical data was correlated to outcomes of PSG. 90% had OSA, O% NH (PtcCO2 > 50 mmHg > 25% TST) after 2 years. Boys younger than 10 years of age with DMD need PSG to elicit OSA.
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ItemNovel technology for the measurement of newborn and infant heart rate( 2017)Background: Monitoring heart rate in newborns and infants is crucially important in guiding resuscitation and medical care. Established methods for heart rate assessment of these children have inherent drawbacks. In recent years, novel methods for assessing neonatal and infant heart rate have been developed, with varying levels of evaluation conducted. Digital stethoscopes may provide a better means of heart rate assessment for newborns and infants. Aim: The aim of this thesis was to comprehensively review existing established and novel technologies used to monitor newborn and infant heart rate, and compare new digital stethoscope technology with the gold standard, electrocardiogram (ECG). Methods: This thesis (a) outlines the definition and importance of heart rate in medicine, presented in the context of a review of cardiac anatomy and physiology relevant to understanding this vital sign and aspects of its measurement in neonates and infants; (b) presents a narrative review of established methods for monitoring heart rate; (c) expands the scope of this review from established to emerging methods for monitoring heart rate with a systematic literature review of novel methods for newborn and infant heart rate assessment; (d) describes original research using a prototype digital stethoscope attached to a smart device containing software for detecting and displaying heart rate in real-time that was conducted on infants in the neonatal intensive and special care setting, as well in the delivery room setting using an improved version of the device and software. Results: A review of the literature analysing methods of assessing neonatal and infant heart rate found strengths as well as significant weaknesses in the various methods in clinical use or in development. In the neonatal unit, a prototype digital stethoscope and smartphone device for assessing heart rate had a mean difference (±2 standard deviations) of 7.4 (48.5) beats per minute (bpm) when compared to the gold standard of electrocardiography. The mean (interquartile range) time to first digital stethoscope heart rate display was 4.8 (1 to 7) seconds, and the device failed in 12.3% of use attempts. Repeating the comparison in the delivery room setting using an updated algorithm and new hardware, Bland-Altman analysis revealed a smaller mean difference (±2 standard deviations) between the digital stethoscope and electrocardiography of 0.2 (-18 to +18) bpm including crying periods (Figure 23), and 1.0 (-11 to +12) bpm excluding crying periods. The improved digital stethoscope took a median (interquartile range) of 7 (5 to 11.5) seconds after application to display a heart rate. It failed to detect heart rate in 37% of cases, all of which were in crying infants. Conclusion: A digital stethoscope and smart device with software can rapidly detect neonatal and infant heart rate. In the delivery room, device failure primarily occurred during infant crying, with improved accuracy during non-crying periods.
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ItemA tool for risk profiling and accurate prognostication in paediatric glioma integrating clinical features with epigenetics: it is time to move on from the binary classification( 2016)Paediatric glioma, the most common group of brain tumours in children, encompasses a wide range of entities with highly variable prognoses. Gliomas are grouped by histopathological features into high and low grade glioma but this classification does not take into account many established and emerging risk factors in this disease. Research into the molecular features of these lesions has shown that histology does not always correlate with biology and, where they differ, molecular features are usually superior at predicting outcome. Risk classifications have been developed for other paediatric malignancies which combine clinical, radiological, pathological and molecular factors to predict disease risk and prognosis. A comprehensive risk classification has not been published for paediatric glioma despite many risk factors being established in this disease. Using a clinical cohort of all paediatric glioma treated at a single institution (Royal Children’s Hospital, Melbourne, Australia) over an 18 year period a database was developed incorporating clinical, radiological, pathological and treatment factors. Where sufficient tumour tissue was available genome-wide methylation analysis was performed. The results of this were processed and evaluated by an established cluster analysis algorithm. Breaking the cohort into clinically appropriate subgroups, risk factors for disease progression and death were determined and prognosis estimated for distinct groups. A tool for robust risk profiling and prognostication was established with 5 main risk groups and 10 subgroups. Patients in the very low risk group have a predicted 100% overall survival and the majority require no treatment. In contrast there was a group of patients with 100% mortality within a short space of time where attempts at curative therapy are futile and may be deleterious to quality of life. The intermediate risk group contained a number of entities with a prognosis genuinely falling between that of low grade glioma and that of high grade glioma. Histopathological diagnosis retained prognostic importance for some, but not all, groups and methylation analysis was shown to have a significant role to play, particularly in high grade lesions or where diagnosis was unclear. This is likely to become part of routine care in the future and its place is strongly supported by the analysis presented here. Risk profiling is possible in paediatric glioma with far more accuracy than the current binary classification provides. A combination of established clinical factors and emerging molecular features provides an accurate and nuanced assessment of risk and prognosis.
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ItemAn exploration of multiple imputation strategies for handling missing data in composite scores with incomplete items( 2016)Missing data are common in medical research. One area where missing data can arise is in composite scores (or scale scores) when one or more of the items that form the scale is incomplete. A method that is becoming increasingly popular for handling missing data is multiple imputation (MI). In the context of missing data in scale scores, MI can be applied at either the item level or the scale level. Various strategies have been proposed in the literature for imputing missing data at the scale level and the item level. Yet there is little comparison of these strategies in longitudinal settings and not much guidance is available about how to best implement these strategies. The challenge with using the available strategies in longitudinal studies is that one may want to impute missing data in several scales, each of which comprises a large number of items that have been measured at several waves, leading to large imputation models which may result in convergence problems. It is therefore important to evaluate the performance of these strategies in longitudinal settings to provide proper guidance for users of MI. In this thesis, I used a simulation study and a real example from the Longitudinal Study of Australian Children (LSAC) to compare the performance of the four MI strategies that are available for handling missing data in composite scores within a longitudinal setting. These strategies are: scale-level imputation using scale scores as auxiliary variables; the “standard” item-level imputation, which uses other items as auxiliary variables; item-level imputation using scale scores as auxiliary variables; and item-level imputation using principal components, derived from other items, as auxiliary variables. I also compared the effect of implementing these strategies using two MI approaches, multivariate normal imputation (MVNI) and fully conditional specification (FCS). While the literature recommends item-level imputation over scale level imputation, the research in this thesis demonstrates that when implemented using FCS, item-level imputation, with items from other scales as auxiliary variables, could produce biased parameter estimates. This research also provides support for using scales scores or principal components as auxiliary variables in item-level imputation models when the “standard” item-level imputation strategy cannot be used due to convergence problems.
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ItemCardiovascular associations of HIV infection in children( 2015)Vertically-acquired HIV infection is a devastating disease in childhood that may affect any organ, including the cardiovascular system. With increased survival of HIV infected children due to antiretroviral (ART) treatment availability, chronic cardiovascular problems become a confronting challenge, not only because HIV infection may cause cardiac problems readily manifesting in childhood but also because it potentially increases future cardiovascular disease risk in adulthood. This thesis explores various possible cardiovascular effects of HIV infection in children, particularly the differential effects of ART-naïve compared to ART-exposed HIV infection on left ventricular (LV) remodelling, pulmonary hypertension, and arterial elasticity. We conducted a cross-sectional study enrolling 56 ART-naïve, 59 ART-exposed HIV infected, and 51 healthy children in Jakarta, Indonesia and performed cardiac/vascular ultrasound, and blood tests for biomarkers. There were marked differences in the cardiovascular parameters between the two groups. We found that ART-naïve HIV infection was associated with LV dilation while the ART-exposed seemed to cause concentric hypertrophic remodelling. ART-exposed HIV infected children who showed evidence of higher pulmonary artery pressure than healthy children, whereas the ART-naïve children had reduced right ventricular function. For arterial elasticity, the ART-naïve had higher strain and lower elastic modulus, but thicker intima-media thickness, whereas the ART-exposed had similar vascular properties as healthy children. In conclusion, HIV infection in children have significant impacts on childhood cardiovascular system with particular differential effects between ART-naïve and ART exposed HIV infection. Routine cardiovascular surveillance is needed for children with HIV infection.
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ItemScoliosis in children with cerebral palsy: a population based study( 2015)Introduction Scoliosis is the most common spinal deformity in children with cerebral palsy. Previous published studies have been based on institutionalised patients and not on a total population of individuals with cerebral palsy. Methods This study was based on both prospective and retrospective cross-section analysis of 292 children identified from the Victorian Cerebral Palsy Register. These children were spread across GMFCS levels I–V. The children were assessed during their transition clinic appointment prior to exit from the Royal Children’s Hospital. The research looked at three main sections: clinical review for scoliosis, radiographic assessment of scoliosis, and CHQ and CPCHILD questionnaires survey. Cobb angles were measured by two experienced observers. Results If a Cobb angle of more than 10° was used, then 40% of patients were classified with scoliosis. By changing the definition of scoliosis in cerebral palsy to a Cobb angle greater than 40°, the prevalence of “clinically important scoliosis” was 12.7%. The majority of the severe curves occurred in children at GMFCS levels IV and V. As the GMFCS level increased, the mean Cobb angle increased. The mean score for the questionnaires decreased as the GMFCS level increased. Conclusion The CP scoliosis and the scores for the questionnaire were closely related to the GMFCS levels. The prevalence of CP scoliosis is overestimated in other studies. Our study shows the prevalence of CP scoliosis is 12.7% using a Cobb angle of more than 40°. Non-ambulant children are at high risk of developing scoliosis and formal spine surveillance should be considered.
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ItemDefining the phenotype of a cohort of children with non-syndromic Pierre Robin Sequence( 2015)Background Pierre Robin Sequence (PRS) is a common craniofacial anomaly comprising of micrognathia, cleft palate, glossoptosis and upper airway obstruction. It is a condition which affects 1 in 6000 neonates, often resulting in airway and feeding difficulties. Although it is a well-known condition, many aspects about the diagnosis, aetiology and management of Pierre Robin Sequence are contentious or unknown. Specifically, the exact phenotypic spectrum of this condition has been poorly studied. The major aim of this Master of Surgery is to provide an accurate phenotypic characterisation of a large cohort of non-syndromic Pierre Robin Sequence patients. A retrospective review of diagnosis and management of this cohort was also performed, along with a preliminary investigation into the possible genetic aetiology of a subset of patients. Methods A cohort of 141 non-syndromic PRS patients managed at the Royal Children’s Hospital in Melbourne from 1985 to 2012 was identified by cross-referencing two clinical databases. A detailed review of each patient’s medical file was performed and patients were categorised into either “Isolated PRS” or “PRS-Plus” groups. A subset of patients with a family history of cleft and/or a musculoskeletal anomaly were selected for targeted DNA sequencing of the non-coding elements of SOX9 (chromosome 17), a potential candidate gene for non-syndromic PRS. Results Our cohort comprised 83 Isolated PRS patients and 58 PRS-Plus patients. In the PRS-Plus group, the most common malformations beyond the craniofacial region involved were the musculoskeletal and ocular systems, with choanal stenosis/atresia being the single most common coexisting condition. PRS-Plus patients were found to have worse outcomes at birth as well as during the neonatal period, with a higher proportion being born small-for-gestational-age, have failure to thrive and require surgical intervention for airway and feeding. No significant genetic mutations were identified in the non-coding elements of SOX9 in the subset of patients who had DNA sequencing. A single nucleotide substitution was identified in the GATA1 transcription factor binding site, however the functional significance of this variant is yet to be determined. Summary Pierre Robin Sequence is a phenotypically diverse condition which contains a wide spectrum of features far beyond what was initially described. The results of this study supports the existence of a “PRS Spectrum” ranging from the mildest isolated PRS patients to the more complex syndromic PRS patients. Patients with additional anomalies outside of the craniofacial system had poorer outcomes at birth and during the neonatal period. Further studies are required to determine whether these differences can be explained by underlying biological causes such as genetic mutations, or whether this is a result of inadequate initial management.