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A clear definition is needed
Paramount to the study of any disease is the clear definition of the subject of interest. The definition of injury is fraught with challenges and complexities. Importantly, injuries unlike most diseases must
Statistics from Altmetric.com
A clear definition is needed
Paramount to the study of any disease is the clear definition of the subject of interest. The definition of injury is fraught with challenges and complexities. Importantly, injuries unlike most diseases must be defined simultaneously by the causative event and by the resulting pathology. For example, bruising can occur in the absence of a mechanical insult to the body (for example, in the case of sepsis or a bleeding disorder) and thus, taken alone, cannot be considered an injury. Similarly there are many events, such as car crashes, that result in no pathology, even if “victims” are bought to an emergency department for observation. Thus, the theoretical definition of injury must incorporate both cause and outcome. Equally challenging is the operational definition of injury, for example, which diagnoses, codes, or combination of codes from the International Classification of Diseases (ICD)1 define injury? In this paper we discuss shortcomings in existing theoretical and operational definitions of injury with a view to advancing injury prevention research and practice.
The theoretical definition of injury is problematic since there is no basic scientific distinction between disease and injury. In some cases the etiologic agents are identical, for example the result of the brief exposure to toxic gas is often called injury whereas eventual pulmonary effect of chronic exposures to low concentrations of the same gas may be called disease.2 Many of the public health orientated injury texts consider that the “energy definition” best describes the causes and pathologies of interest, namely “injury” refers to damage to the body produced by energy exchanges that have relatively sudden discernible effects.3 In contrast, “disease” tends to be used for pathologies such as cancer which manifest themselves over longer periods after first exposure to their causes. While this seems to be a reasonable starting point, a number of issues remain. These issues are perhaps best explored through specific examples. First, what is meant by “damage to the body”. If damage to the body refers to tissue damage, strict adherence to the theoretical definition would lead to the exclusion of many events that are routinely classified as injuries. For example, ingestion of a foreign body, such as a coin, often results in no tissue damage and foreign bodies can be removed from other orifices such as the nose or ear, without damage to the surrounding tissues. Similarly, a sexual assault which results in no tissue damage but from which the victim experiences severe depression, will only be covered by the theoretical definition if the scope of bodily damage is broadened to include psychological damage. There would seem to be a case for such harm to be included in a theoretical definition given that significant numbers of those in injury research and practice consider this a legitimate area of concern for the field. Moreover, in New Zealand (population 4 million) at least, the agency, Accident Compensation Corporation, which has the primary mandate for injury prevention, rehabilitation, and compensation, compensates victims who suffer such harm. In the 2000/2001 financial year 267 people were compensated for psychological injury at a total cost $NZ2 659 000.
Second, consider also the meaning of “energy exchange”. Clearly a surgical incision is the result of intentional transfer of mechanical energy and this transfer results in tissue damage, yet, traditionally surgical incisions are not included in counts of intentional injuries. Perhaps, when the benefits of the purposely intended injury are thought to outweigh the costs, the theoretical definition is not applicable. But that approach is inconsistent with our approach for counting injury due to the lawful use of force (for example, police), where presumably the benefits are also thought to outweigh the costs of using such force. In this case, however, provision is made in ICD to code injuries due to this cause (E970–978: legal intervention).
Most injury prevention experts expand the theoretical definition of injury to include not only bodily damage caused by transfers of energy but also damage caused by the absence of energy.3 While this serves us well by bringing injuries due to a number of causes (for example, drowning, hypothermia, and asphyxia) under the broad umbrella of the theoretical definition, it also obscures the boundaries as it could be argued that the final pathway for death of any etiology is ultimately an absence of energy.
Finally, the notion that an injury must have “sudden discernable effects” leads to the exclusion of tissue damage due to chronic low energy exposures (for example, carpal tunnel syndrome) but as Robertson has pointed out some have modified the energy definition to include such cases.3
The development of the theoretical “energy” definition of injury by Haddon represented a significant advance in our thinking and provided a useful basis on which to consider injury control measures.4 One of its major strength