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TitleMechanisms of injury
AuthorsSimpson DA, McLean AJ, Leitch IOW
TypeBook Chapter
AbstractMechanical injury results when a part of the body suffers deformation beyond its limits of tolerance. The severity of the injury will depend on the magnitude of the causative force, but also on other factors, notably the time-base of its action. When the force is due to an impact, it is usually necessary to know the impact duration, the acceleration imparted by it to the part of the body struck, and the rate of acceleration change. The surface area on which the impact strikes is also very relevant. There is much practical importance in studying and if possible quantifying the forces that cause craniomaxillofacial (CMF) injury. Engineers must do so, to calculate the limits of tolerance of the head in various types of accident; on such calculations are based design standards relating to car and aircraft safety, helmets and other aspects of injury prevention. Surgeons who see injuries in clinical settings will better understand the pathology of these injuries if they can visualize the impact forces that caused the injury: failure to do so when confronted by some unfamiliar cause of a wound, such as a high velocity missile, has often led to errors in management (Owen- Smith 198 1). However, the anatomy of the head is very complex: skin, bone and brain have very different physical properties, and the calculation of the effects of real-life impacts is a difficult and controversial undertaking (Ryan et a1 1989, Simpson et a1 199 1). Information derived from animal experiments and from simulated accidents using anthropometric dummies can be extrapolated to give rough estimates of the tolerance of the human head, but such estimates can be misleading. Cadaver experiments are more reliable, especially with respect to skeletal structures, but cannot reproduce the effects of injury on the function of the brain. Efforts are being made to correlate the data from all the available experimental sources and to match these with data from clinicopathological studies. Surgeons and pathologists working in accident services can advance this process of synthesis very greatly by collecting accurate data on impact sites, clinical effects and autopsy findings. Radiological evidence is also invaluable. This chapter reviews some of the data on the mechanisms of CMF injury due to impacts from various causes; in Chapter 5, these mechanisms are related to the injuries produced. The Standard International (SI) units commonly used to quantify impacts are given in Appendix I; in the context of CMF trauma, impact force and acceleration are of chief importance, and to facilitate comparisons these have been expressed wherever possible as kilonewtons (kN) and meterslsecond per second (rn/s2) respectively.
Book DetailsCraniomaxillofacial trauma, David DJ, Simpson DA (Eds)
Page Range101-117
Page Count16
NotesAvailable from CASR library on request

Simpson DA, McLean AJ, Leitch IOW (1995). Mechanisms of injury. In Craniomaxillofacial trauma, David DJ, Simpson DA (Eds) (pp. 101-117).