The Effects of Cranial Orientation on Forensic Frontal Sinus Identification as Assessed by Outline Analyses

Abstract

The utility of frontal sinuses for personal identification is widely recognized, but potential factors affecting its reliability remain uncertain. Deviations in cranial position between antemortem and postmortem radiographs may affect sinus appearance. This study investigates how slight deviations in orientations affect sinus size and outline shape and potentially impact identification. Frontal sinus models were created from CT scans of 21 individuals and digitally oriented to represent three clinically relevant radiographic views. From each standard view, model orientations were deviated at 5° intervals in horizontal, vertical, and diagonal (e.g., left-up) directions (27 orientations per individual). For each orientation, sinus dimensions were obtained, and outline shape was assessed by elliptical Fourier analyses and principal component (PC) analyses. Wilcoxon sign rank tests indicated that sinus breadth remained relatively stable (p > 0.05), while sinus height was significantly affected with vertical deviations (p < 0.006). Mann–Whitney U tests on Euclidean distances from the PC scores indicated consistently lower intra- versus inter-individual distances (p < 0.05). Two of the three orientations maintained perfect (100%) outline identification matches, while the third had a 98% match rate. Smaller and/or discontinuous sinuses were most problematic, and although match rates are high, practitioners should be aware of possible alterations in sinus variables when conducting frontal sinus identifications.

Frontal Sinus Morphological and Dimensional Variation as Seen on Computed Tomography Scans

“…However, clearly rotated skulls that would produce distorted outlines and measurements were removed prior to analysis. While Butaric et al [ 47 ] found that 5% deviations in CT skull orientation did not dramatically impact subsequent sinus outlines, measurements, or positive matches, minor inter-individual deviations in head position may have minimally impacted the results presented here. Additionally, a very slight error may have been introduced during the manually digitized tracing of the CT image slices.…”

“…This study used clinically derived cranial CT scans that were not necessarily oriented on the anthropologically preferred Frankfurt Horizonal Plane [ 22 , 47 ]. However, clearly rotated skulls that would produce distorted outlines and measurements were removed prior to analysis.…”

“…With more detail, it is presumed that more reliable positive identifications can be made as the number of concordances exponentially increases. Additionally, 3D-CT techniques eliminate the issue of discrepancies in angularity [ 47 ]. With the whole element or region captured in overlapping slices, practitioners are able to move the CT images to align more easily than when they had to mimic compressed 2D renderings.…”

Technical Modifications for the Application of the Total Difference Method for Frontal Sinus Comparison

“…Although ancestry is not listed, the samples are likely largely composed of European-American individuals. Radiographs and frontal sinus outlines (see details below) were previously collected for larger, ongoing studies of frontal sinus morphology and identification methods, e.g., [ 25 , 26 ]. The sample included ten outlines which were randomly selected in R from 244 possible sinus outlines on 128 adult individuals used in a previous study (note: some individuals had several radiographs at different age points, explaining the higher number of outlines versus individuals) [ 27 ].…”

Recent Advances in Forensic Anthropological Methods and Research

“…Within the realm of individualizing factors, Butaric, Richman, and Garvin [ 5 ] discuss the potential factors that might affect the reliability of using frontal sinuses for personal identification. Their study investigates how slight deviations in orientations affect sinus size and outline shape, which could potentially impact identification.…”