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Browsing Medical Physics by Subject "Anatomy -- Variation -- South Africa"

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    Mandibular morphological variation : implications for fracture repair
    (Stellenbosch : Stellenbosch University, 2019-12) McKay, Cyrilleen; Baatjes, Karin J.; Kotze, Sanet; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Medical Imaging and Clinical Oncology. Medical Physics.
    ENGLISH SUMMARY : Achieving a predictable clinical outcome during mandibular fracture repair necessitates thorough knowledge of variations of the neurovascular bundle, the location of tooth roots and bone quantity in the region of interest. In South Africa, the prevalence of mandibular body fractures due to alcohol-related interpersonal violence is increasing and is largely stratified socio-economically. Approximately 80% of people presenting with mandibular fractures rely on the resource-limited public health care system. In addition, South African population groups have a high prevalence of structures resembling accessory mental foramina (AMF) which may impede fracture fixation and outcomes. These considerations form the basis of this study which aimed to define population specific information on interforaminal variations and assess their applicability in clinical decision-making prior to fracture repair, using dry mandibles. Hemi-mandibles (N = 213) with known age and varying tooth loss patterns were obtained from four ancestry and sex subgroups, namely South African Coloured (SAC) females, SAC males, Black (SAB) males and White (SAW) males. The location of the mental foramen (MF) and AMF was determined in relation to mandibular topographical landmarks. Buccal cortical plate (BCP) and buccal bone thickness was assessed at 12 points – four points on transverse planes through, superior, and inferior to the MF midpoint. Transverse planes correspond with possible locations for mini-plate fracture fixation and the four points on each plane corresponds with locations for mono-cortical screw insertion. The MF was most commonly located between the first and second premolar teeth and the distance from the symphysis menti to the anterior border of the MF was smaller in SAC males when compared to SAC females. However, this parameter had a greater reading on right hemi-mandibles of SAB males when compared to SAC males. Tooth loss was associated with a decreased height of the mandible superior to the MF and age was associated with an increased MF diameter. Accessory mental foramina were observed in 6.54% of hemi-mandibles and was most commonly located mesial and superior to the MF. The BCP differed between subgroups and showed negative associations with tooth loss and age at selected assessment points. The buccal bone was thickest at the foraminal transverse plane when compared to superior and inferior transverse planes. It was thicker in SAC females when compared to SAC males on the inferior transverse plane of left hemi-mandibles. Overall, the influence of tooth loss and age on mandibular morphology did not vary between sex and ancestral subgroups. Results show that in comparison to superior and inferior transverse planes, the foraminal transverse plane had the lowest risks for inadvertent injuries to vital structures. Risks on this plane increased from 1.9 to below 8% for screw lengths 4 – 8 mm bilaterally. These findings expand population-specific knowledge of anatomical variations which could aid clinical and preoperative decision-making in the repair of mandibular fractures in South Africa.