Experimental modelling of internal surface laryngeal fracturing observed in fatal applied neck pressure

Pathological findings can be subtle or limited, in some cases of fatal neck compression. Decalcification and en-bloc transverse histological processing using mega block cassettes, revealed a number of internal unicortical fractures to the thyroid lamina (anteriorly at the midline and posteriorly) and bilaterally in the cricoid cartilage, not visible on external inspection, which proved to be medico-legally important, in a case with very few other pathological findings, and where the application of a neck/head lock was suspected. In order to explore the nature and mechanism of these poorly recognised "buckling" type fractures, simple experiments were undertaken using 3D data printed pliable models of the thyroid and cricoid cartilages, exposed to various types of compression. The models were coated internally with hardened/cooled isomalt (a sugar baking product), to allow the pattern of surface material stress cracking to be documented as compression was applied. Compression (including isolated anterior pressure and bilateral "squeezing") was confirmed to cause internal surface material cracking to both the thyroid and cricoid cartilage models, including in the locations found in the post mortem histology casework described above. Some surface material patterns of cracking were more commonly/typically associated with particular forms of compression. Over 90% of all the surface material cracking was obliquely or vertically orientated on the models, supporting transverse (rather than longitudinal) sectioning of the decalcified larynx as the best means for capturing these fractures within the plane of histological section, in appropriate casework.