Thorax Injury Mechanisms And Injury Criteria

Sections Thorax Injury Types and Locations Thorax Injury Mechanisms Thorax Injury Criteria Thorax Injury tolerance Levels

Figure 16

Definition And Anatomy

The human torso is normally divided into 2 main areas divided by the diaphragm.

• Thoracic cavity which contains the heart and lungs and is located wholly with in the rib cage with its lower boundary defined by the diaphragm

• Abdominal cavity which contains the liver, spleen, kidneys, stomach, female reproductive organs, bladder and intestines with the diaphragm as the upper boundary and pelvis the lower

In biomechanical terms these divisions are not so definitive as the organs in the upper part of the abdominal cavity are partially protected by the lower part of the rib cage.  Also the organs can be divided into two major categories.  The ‘solid’ organs, liver, spleen and kidneys, which are filled with fluid and the ‘hollow’ organs, stomach, uterus and intestines, which contain a large proportion of air.  The effect of the rib cage and the category of organ involved, affect the biomechanical response to impact and the injury types and mechanisms.  As the ‘solid’ organs are located in the upper part of the abdominal cavity it would make sense to divide the torso in to three main areas with different biomechanical responses and injury criteria.  For example:

• Thorax containing the heart and lungs with the biomechanical response controlled by the upper rib cage where it totally encompasses the cavity joining at the front with the sternum

• Upper abdominal cavity containing the ‘solid’ organs of the liver, spleen and kidneys, which are partially protected at the front and totally at the sides by the lower rib cage which would control the biomechanical response

• Lower abdominal cavity containing the ‘hollow’ organs of the intestine, uterus and bladder in which the abdominal muscles would control the biomechanical response along with the organs themselves

Unfortunately the majority of biomechanical research has either concentrated on the thorax (or chest, or the abdomen as a whole) injuries to which constituted the second highest cause of fatalities in rail vehicle accidents.  Discrete biomechanical responses or injury criteria have not been defined specifically to the upper abdominal cavity.

Therefore in assessing injury mechanisms and corresponding injury criteria in this OPERAS project the torso will be divided into two areas, which where appropriate, may have different injury criteria and levels in the frontal and lateral impact directions.  These 2 areas are:

• Thorax or Chest containing the heart, lungs, liver, spleen, stomach and kidneys which is protected or partially protected by the rib cage

• Abdomen containing the intestines, uterus and bladder which is not protected by the rib cage