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I would like to thank the authors for submitting the above paper to the Journal of the Royal Army Medical Corps. The paper describes how they have developed a voxel model to compare the potential effectiveness of different bullet types.1 Of greater importance to readers of a military medical journal is the potential for such models to optimise the development of personal armour to protect against such weapons.2 Such approaches to modelling are to our knowledge now being developed in the USA, Germany, China and the UK. The UK is increasingly using finite element models, which in turn require material models of the anatomical structures they incorporate. This enables the model to potentially reflect the passage of a projectile through different tissue types.
The authors of the above paper have based their model on ballistic gelatin in a similar manner to the approach used by the UK.2 In turn, ballistic gelatin is a good simulacrum for the passage of both bullets and energised fragments through animal muscle.3 4 Therefore, within both the UK and Chinese models, projectiles pass through a 3D anatomically correct model based on measurements gained from a CT scan. Structures are represented as homogenous muscle, and the result of the interaction between the permanent cavity and an anatomical structure is predicted using Abbreviated Injury Score system. However, such a clinical injury scoring system was neither designed nor validated for such an approach and great caution must be taken when interpreting results based on this; we therefore applaud the authors of this paper in therefore using this paper to compare the effects of different bullets and not predict the clinical outcomes.
The great challenge in finite element modelling of ballistic projectile penetration is to include accurate material models representative of tissues other than muscle. Skin in particular is known to retard smaller energised fragments, particularly at lower velocities.5 In addition, the effect of ligaments interconnecting viscera and organs is complex, as well as the interaction of tissues with the temporary cavity, particularly bones. Generating algorithms for these material models will inevitably require experimental testing of animal tissues and the validation will be both expensive and time consuming.6 These understandably provide significant challenges in the current fiscal economies of most nations, but we would encourage those developing such finite element models to work collaboratively if at all possible.
Footnotes
Competing interests None declared.
Provenance and peer review Not commissioned; internally peer reviewed.