In vivo facial soft tissue thicknesses of adult Australians.

Facial soft tissue thicknesses (FSTT) set important quantitative guides in craniofacial identification, but so far Australian FSTTs have only been published for supine cadavers. This study aimed to use B-mode ultrasound to measure FSTTs in living Australians (N=63 participants; n=52 [x¯=21 years, s=2 years]; and n=11 [x¯=54years, s=13years]) using 14 craniometric landmarks with participants in both upright and supine positions. The multiple pre-existing Australian cadaver investigations (n=7 reporting FSTT means and 6 of these reporting raw datasets) enabled living and cadaveric samples drawn from the same parent population to be compared. By using a non-invasive and safe imaging method (no ionising radiation) repeated measurements could be taken in the in vivo participants to gauge measurement reliability (and compare to pre-existing reliability for cadaver measurements): mean r-TEM=12%; max r-TEM=25%. In terms of changes between upright and supine positions (as measured by B-mode ultrasound) only 2 of 14 measured landmarks had FSTT changes in excess of 1mm. Comparisons of the in vivo ultrasound data to pre-existing needle puncture studies demonstrated that mean B-mode ultrasound measurements were very similar to cadaver values. Contrary to popular thought, but in keeping with the findings of prior meta-analyses, cadaver FSTT data are good proxies to living subjects, at least as measured by ultrasound. To increase sample sizes and triangulate upon ground truth FSTT values, weighted grand means combining all Australian samples were calculated (n range=280-385) and compared to the multi-group 2018 adult T-Tables (max. n=10,333).