Abstract
The shape of the craniofacial complex of patients with beta thalassaemia was evaluated using geometric morphometrics on lateral cephalometric radiographs and was compared with matched controls. The beta thalassaemia group consisted of 40 patients (16 females, 24 males, mean age 33.4). Each patient was matched by age and gender to two controls (32 females, 48 males, mean age 33.1). The 120 lateral cephalometric radiographs were digitized and traced with 15 curves, 10 landmarks and 117 sliding semi-landmarks. These landmarks were subjected to Procrustes superimposition and principal component analysis in order to describe shape variability of the cranial base, maxilla and mandible, as well as of the entire craniofacial complex for each sex. The first 4 principal components accounted for 50% of the total sample’s variability. The beta thalassaemia group was significantly different in overall shape to the control group for both sexes. Similar findings were noted for the maxilla, the mandible and the cranial base. The main differences were related to smaller mandibular body for the thalassaemia group, midface protrusion and decrease in posterior face height. The shape of the craniofacial complex in these patients is prone to be more convex and hyperdivergent.
Highlights
The shape of the craniofacial complex of patients with beta thalassaemia was evaluated using geometric morphometrics on lateral cephalometric radiographs and was compared with matched controls
The present study considered three main advantages of Geometric morphometrics (GM), compared to traditional cephalometrics, for the evaluation of patients with thalassaemia; (a) there is no strong reliance on a reference structure, such as the anterior cranial base, which may be affected by the condition, (b) sliding semilandmarks are available for a much denser description of the anatomy, including the curves between customary landmarks, and, (c) sub-regions of the craniofacial complex can be independently studied, even when the number of conventional landmarks on them is small
The present study evaluated a sample of cephalometric radiographs of patients with beta thalassaemia and matched healthy controls (Ctrl) (Fig. 1)
Summary
The shape of the craniofacial complex of patients with beta thalassaemia was evaluated using geometric morphometrics on lateral cephalometric radiographs and was compared with matched controls. The 120 lateral cephalometric radiographs were digitized and traced with 15 curves, 10 landmarks and 117 sliding semi-landmarks These landmarks were subjected to Procrustes superimposition and principal component analysis in order to describe shape variability of the cranial base, maxilla and mandible, as well as of the entire craniofacial complex for each sex. Previous studies on the structure of the craniofacial complex of beta thalassaemia patients relied on clinical examination or conventional cephalometric a nalysis[10,11,13,15,16,17,18]. GM methods have been used to study shape differences between healthy controls and patients affected by major syndromes, such as Down’s s yndrome[23], fetal alcohol s yndrome[24], Glut-1Ds25, 22q11.2
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