Determining normal and abnormal lip shapes during movement for use as a surgical outcome measure

Popat, Hashmat 2012. Determining normal and abnormal lip shapes during movement for use as a surgical outcome measure. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

Craniofacial assessment for diagnosis, treatment planning and outcome has traditionally relied on imaging techniques that provide a static image of the facial structure. Objective measures of facial movement are however becoming increasingly important for clinical interventions where surgical repositioning of facial structures can influence soft tissue mobility. These applications include the management of patients with cleft lip, facial nerve palsy and orthognathic surgery. Although technological advances in medical imaging have now enabled three-dimensional (3D) motion scanners to become commercially available their clinical application to date has been limited. Therefore, the aim of this study is to determine normal and abnormal lip shapes during movement for use as a clinical outcome measure using such a scanner. Lip movements were captured from an average population using a 3D motion scanner. Consideration was given to the type of facial movement captured (i.e. verbal or non-verbal) and also the method of feature extraction (i.e. manual or semi-automatic landmarking). Statistical models of appearance (Active Shape Models) were used to convert the video motion sequences into linear data and identify reproducible facial movements via pattern recognition. Average templates of lip movement were created based on the most reproducible lip movements using Geometric Morphometrics (GMM) incorporating Generalised Procrustes Analysis (GPA) and Principal Component Analysis (PCA). Finally lip movement data from a patient group undergoing orthognathic surgery was incorporated into the model and Discriminant Analysis (DA) employed in an attempt to statistically distinguish abnormal lip movement. The results showed that manual landmarking was the preferred method of feature extraction. Verbal facial gestures (i.e. words) were significantly more reproducible/repeatable over time when compared to non-verbal gestures (i.e. facial expressions). It was possible to create average templates of lip movement from the control group, which acted as an outcome measure, and from which abnormalities in movement could be discriminated pre-surgery. These abnormalities were found to normalise post-surgery. The concepts of this study form the basis of analysing facial movement in the clinical context. The methods are transferrable to other patient groups. Specifically, patients undergoing orthognathic surgery have differences in lip shape/movement when compared to an average population. Correcting the position of the basal bones in this group of patients appears to normalise lip mobility.

Item Type:	Thesis (PhD)
Status:	Unpublished
Schools:	Dentistry
Subjects:	R Medicine > RK Dentistry
Uncontrolled Keywords:	Anatomic Landmarks; Orthognathic Surgical Procedures/Methods; Malocclusion, Angle Class III/Surgery; Imaging; Three-Dimensional/Methods; Lip/Movement; Speech Articulation Tests
Date of First Compliant Deposit:	30 March 2016
Last Modified:	08 May 2019 02:50
URI:	https://orca.cardiff.ac.uk/id/eprint/41194

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