Three dimensional study to quantify the relationship between facial hard and soft tissue movement as a result of orthognathic surgery

Introduction Prediction of soft tissue changes following orthognathic surgery has been frequently attempted in the past decades. It has gradually progressed from the classic “cut and paste” of photographs to the computer assisted 2D surgical prediction planning; and finally, comprehensive 3D surgical planning was introduced to help surgeons and patients to decide on the magnitude and direction of surgical movements as well as the type of surgery to be considered for the correction of facial dysmorphology. A wealth of experience was gained and numerous published literature is available which has augmented the knowledge of facial soft tissue behaviour and helped to improve the ability to closely simulate facial changes following orthognathic surgery. This was particularly noticed following the introduction of the three dimensional imaging into the medical research and clinical applications. Several approaches have been considered to mathematically predict soft tissue changes in three dimensions, following orthognathic surgery. The most common are the Finite element model and Mass tensor Model. These were developed into software packages which are currently used in clinical practice. In general, these methods produce an acceptable level of prediction accuracy of soft tissue changes following orthognathic surgery. Studies, however, have shown a limited prediction accuracy at specific regions of the face, in particular the areas around the lips. Aims The aim of this project is to conduct a comprehensive assessment of hard and soft tissue changes following orthognathic surgery and introduce a new method for prediction of facial soft tissue changes.   Methodology The study was carried out on the pre- and post-operative CBCT images of 100 patients who received their orthognathic surgery treatment at Glasgow dental hospital and school, Glasgow, UK. Three groups of patients were included in the analysis; patients who underwent Le Fort I maxillary advancement surgery; bilateral sagittal split mandibular advancement surgery or bimaxillary advancement surgery. A generic facial mesh was used to standardise the information obtained from individual patient’s facial image and Principal component analysis (PCA) was applied to interpolate the correlations between the skeletal surgical displacement and the resultant soft tissue changes. The identified relationship between hard tissue and soft tissue was then applied on a new set of preoperative 3D facial images and the predicted results were compared to the actual surgical changes measured from their post-operative 3D facial images. A set of validation studies was conducted. To include: • Comparison between voxel based registration and surface registration to analyse changes following orthognathic surgery. The results showed there was no statistically significant difference between the two methods. Voxel based registration, however, showed more reliability as it preserved the link between the soft tissue and skeletal structures of the face during the image registration process. Accordingly, voxel based registration was the method of choice for superimposition of the pre- and post-operative images. The result of this study was published in a refereed journal. • Direct DICOM slice landmarking; a novel technique to quantify the direction and magnitude of skeletal surgical movements. This method represents a new approach to quantify maxillary and mandibular surgical displacement in three dimensions. The technique includes measuring the distance of corresponding landmarks digitized directly on DICOM image slices in relation to three dimensional reference planes. The accuracy of the measurements was assessed against a set of “gold standard” measurements extracted from simulated model surgery. The results confirmed the accuracy of the method within 0.34mm. Therefore, the method was applied in this study. The results of this validation were published in a peer refereed journal. • The use of a generic mesh to assess soft tissue changes using stereophotogrammetry. The generic facial mesh played a major role in the soft tissue dense correspondence analysis. The conformed generic mesh represented the geometrical information of the individual’s facial mesh on which it was conformed (elastically deformed). Therefore, the accuracy of generic mesh conformation is essential to guarantee an accurate replica of the individual facial characteristics. The results showed an acceptable overall mean error of the conformation of generic mesh 1 mm. The results of this study were accepted for publication in peer refereed scientific journal. Skeletal tissue analysis was performed using the validated “Direct DICOM slices landmarking method” while soft tissue analysis was performed using Dense correspondence analysis. The analysis of soft tissue was novel and produced a comprehensive description of facial changes in response to orthognathic surgery. The results were accepted for publication in a refereed scientific Journal. The main soft tissue changes associated with Le Fort I were advancement at the midface region combined with widening of the paranasal, upper lip and nostrils. Minor changes were noticed at the tip of the nose and oral commissures. The main soft tissue changes associated with mandibular advancement surgery were advancement and downward displacement of the chin and lower lip regions, limited widening of the lower lip and slight reversion of the lower lip vermilion combined with minimal backward displacement of the upper lip were recorded. Minimal changes were observed on the oral commissures. The main soft tissue changes associated with bimaxillary advancement surgery were generalized advancement of the middle and lower thirds of the face combined with widening of the paranasal, upper lip and nostrils regions. In Le Fort I cases, the correlation between the changes of the facial soft tissue and the skeletal surgical movements was assessed using PCA. A statistical method known as ’Leave one out cross validation’ was applied on the 30 cases which had Le Fort I osteotomy surgical procedure to effectively utilize the data for the prediction algorithm. The prediction accuracy of soft tissue changes showed a mean error ranging between (0.0006mm±0.582) at the nose region to (-0.0316mm±2.1996) at the various facial regions.

Original sin: divine and symbolic violence in the turn to the Apostle Paul

When we take a step back from the imposing figure of physical violence, it becomes possible to examine other structurally violent forces that constantly shape our cultural and political landscapes. One of the driving interests in the “turn to Paul” in recent continental philosophy stems from wrestling with questions about the real nature of contemporary violence. Paul is positioned as a thinker whose messianic experience began to cut through the violent masquerade of the existing order. The crucifixion and resurrection of the Messiah (a slave and a God co-existing in one body) exposed the empty grounding upon which power resided. The Christ-event signifies a moment of violent interruption in the existing order which Paul enjoins the Gentiles to participate in through a dedication of love for the neighbour. This divine violence aims to reveal and subvert the “powers,” epitomised in the Roman Empire, in order to fulfil the labour of the Messianic now-time which had arrived. The impetus behind this research comes from a typically enigmatic and provocative section of text by the Slovene philosopher, cultural critic, and Christian atheist Slavoj Žižek. He claims that 'the notion of love should be given here all its Paulinian weight: the domain of pure violence… is the domain of love' (2008a, 173). In this move he links Paul’s idea of love to that of Walter Benjamin’s divine violence; the sublime and the cataclysmic come together in this seemingly perverse notion. At stake here is the way in which uncovering violent forces in the “zero-level” of our narrative worldviews aids the diagnosis of contemporary political and ethical issues. It is not enough to imagine Paul’s encounter with the Christ-event as non-violent. This Jewish apocalyptic movement was engaged in a violent struggle within an existing order that God’s wrath will soon dismantle. Paul’s weak violence, inspired by his fidelity to the Christ-event, places all responsibility over creation in the role of the individual within the collective body. The centre piece of this re-imagined construction of the Pauline narrative comes in Romans 13: the violent dedication to love understood in the radical nature of the now-time. 3 This research examines the role that narratives play in the creation and diagnosis of these violent forces. In order to construct a new genealogy of violence in Christianity it is crucial to understand the role of the slave of Christ (the revolutionary messianic subject). This turn in the Symbolic is examined through creating a literary structure in which we can approach a radical Nietzschean shift in Pauline thought. The claim here, a claim which is also central to Paul’s letters, is that when the symbolic violence which manipulates our worldviews is undone by a divine violence, if even for a moment, new possibilities are created in the opening for a transvaluation of values. Through this we uncover the nature of original sin: the consequences of the interconnected reality of our actions. The role of literature is vital in the construction of this narrative; starting with Cormac McCarthy’s No Country for Old Men, and continuing through works such as Melville’s Bartleby the Scrivener, this thesis draws upon the power of literature in the shaping of our narrative worlds. Typical of the continental philosophy at the heart of this work, a diverse range of illustrations and inspirations from fiction is pulled into its narrative to reflect the symbolic universe that this work was forged through. What this work attempts to do is give this theory a greater grounding in Paul’s letters by demonstrating this radical kenotic power at the heart of the Christ-event. Romans 13 reveals, in a way that has not yet been picked up by Critchley, Žižek, and others, that Paul opposed the biopolitical power of the Roman Empire through the weak violence of love that is the labour of the slaves of Christ on the “now-time” that had arrived.

Men's experiences of receiving objective feedback on physical activity and other indicators of health risk, within the context of a gender-sensitised weight loss intervention

Receiving personalised feedback on body mass index and other health risk indicators may prompt behaviour change. Few studies have investigated men’s reactions to receiving objective feedback on such measures and detailed information on physical activity and sedentary time. The aim of my research was to understand the meanings different forms of objective feedback have for overweight/obese men, and to explore whether these varied between groups. Participants took part in Football Fans in Training, a gender-sensitised, weight loss programme delivered via Scottish Professional Football Clubs. Semi-structured interviews were conducted with 28 men, purposively sampled from four clubs to investigate the experiences of men who achieved and did not achieve their 5% weight loss target. Data were analysed using the principles of thematic analysis and interpreted through Self-Determination Theory and sociological understandings of masculinity. Several factors were vital in supporting a ‘motivational climate’ in which men could feel ‘at ease’ and adopt self-regulation strategies: the ‘place’ was described as motivating, whereas the ‘people’ (other men ‘like them’; fieldwork staff; community coaches) provided supportive and facilitative roles. Men who achieved greater weight loss were more likely to describe being motivated as a consequence of receiving information on their objective health risk indicators. They continued using self-monitoring technologies after the programme as it was enjoyable; or they had redefined themselves by integrating new-found activities into their lives and no longer relied on external technologies/feedback. They were more likely to see post-programme feedback as confirmation of success, so long as they could fully interpret the information. Men who did not achieve their 5% weight loss reported no longer being motivated to continue their activity levels or self-monitor them with a pedometer. Social support within the programme appeared more important. These men were also less positive about objective post-programme feedback which confirmed their lack of success and had less utility as a motivational tool. Providing different forms of objective feedback to men within an environment that has intrinsic value (e.g. football club setting) and congruent with common cultural constructions of masculinity, appears more conducive to health behaviour change.