Morphometric comparison of Kenyan adult mandibles with reconstruction plate parameters

Abstract

Objective: To determine the archival morphometry of the mandible of Kenyan male and female adults and to relate them to available mandibular reconstruction plates. Study design: A descriptive cross-sectional study using quantitative techniques. Material and Methods: Intact adult mandibles were obtained from the National Museums of Kenya, Nairobi and from the Department of Human Anatomy, University of Nairobi. Standardized selective measurements including curvilinear measurement of the body and linear measurement of the height of the ramus of the mandible and thickness of the ramus and body at the lower border of the mandible, were taken on 82 mandibles (n=48 for males and n=34 for females) and recorded on a special data collection chart. The morphometry of the mandible was then analysed statistically for differences between the male and female, for the left and right sides of the mandible and; with the sizes of the available mandibular reconstruction plates of the 2.7 mm type manufactured by SYNTHESR with a level of significance of p<0.05 having been set. Pearson's correlation coefficients were computed for the variables to determine the nature and strength of the relationship between them. Results: The average length of the mandible in males for the right and left sides was 98.6 mm and 100.5 mm respectively while for the females this was 92.2 mm and 94.5 mm respe6iively. The average height of the ramus ofthe mandible in males for the right and left sides was 57.40 mm and 58.07 mm respectively while for females this was 51.81 and 52.20 respectively. Significant differences were noted among the curved lengths and heights of the mandible between males and females (p<0.05) with a strong positive correlation (r= 0.902 and 0.825). In addition significant differences between the right and left sides of the mandible were noted (p<0.05) with a strong positive correlation (r= 0.964). Significant differences were noted between the length of the mandible and the lengths o~ the reconstruction plates (p<0.05) with a weak positive correlation for the straight plate (r= 0.284), a weak negative correlation for the angled plate (r= -0.327) and a weak negative correlation for the plate with condylar head (r= -0.156). There were no significant differences in the thicknesses of the mandible between males and females and; between the left and right sides of the mandible with averages of 13.94mm at the symphysis, 11.00 mm at the canine, 10.33 at the mental foramen, 11.06 at the bifurcation of the 1st molar, 12.36 mm at the bifurcation of the 2nd molar, 8.62 mm at the level of the anterior ramus, 5.47 mm at gonion and 5.89 mm at the midpoint of the ramus, (p>0.05) with strong positive correlations. Significant differences were, however, noted between the thicknesses of the body and ramus of the mandible and the sizes of the screws (p<0.05) with weak negative correlations. Conclusions: There were significant differences between the sizes of Kenyan mandibles and the available reconstruction plates. There were significant differences between male and female mandibles in relation to curvilinear dimensions but not in the thickness with strong positive correlations. There was also a significant difference between the right and left sides of the mandible with strong positiv•e correlations. There were significant differences between the sizes of the mandibles and the plates with weak correlations. Recommendations: The average linear dimensions and thickness obtained from a sample of Kenyan mandibles can be used in the selection of appropriate plates or their modification during surgical reconstructive procedures. A further study to compare the direct measurements obtained in this study with measurements of mandibles obtained from standadized panoramic radiographs could be done to assess their accuracy and enable extrapolation of actual sizes of mandibles from the radiographs. Where available, 3-D CTscan should be used to take accurate measurements of the mandible before reconstruction