Under The Microscope: The Chest Wall Injuries

 

The major categories of wound previously described can be inflicted on any part of the body. In forensic practice certain areas are particularly vulnerable or have special medico-legal significance. Head injuries are so important that will be presented in sets of articles, but here consideration will be given to other regions, especially the chest and abdomen. The most important aspect is the relationship of the visceral contents to external landmarks. This is best described by reference to diagrams, where the relationship of pleural cavities, lungs, heart, mediastinum and diaphragm is depicted. It should be appreciated that, from the forensic aspect, the spleen and most of the liver and stomach are thoracic organs in that they lie largely beneath the costal margin, and are vulnerable to both stabbing and blunt injury to the chest. Penetrating injuries, especially by knife to the lower lateral wall of the thorax, may enter the peritoneal cavity as well as the pleural spaces, perforating the diaphragm en route. The stomach, being largely within the rib cage, may often be penetrated. The common stab wounds of the heart may also include diaphragmatic and upper abdominal injuries. A knife can enter the front of the lower thorax, pass through either or both ventricles, and exit through the pericardial surface of the diaphragm to enter the upper surface of the liver. The orientation of the heart is often not appreciated after it is removed as an isolated organ, as the tendency is to visualize it as hang- ing with the apex downwards. In fact, it sits flat on the diaphragm on the lateral edge of the right ventricle, with the inferior vena cava passing immediately downwards into the abdomen.

Respiration is dependent on the integrity of the rigid ‘chest wall and, if the expansion is prevented or severely limited, then air entry will be correspondingly diminished. The integrity can be compromised either by severe mechanical failure of the rib cage or by penetration of the pleural cavities. Fractures of ribs are common, but do not greatly embarrass respiration unless:

-          they are so numerous that they prevent expansion of the thorax;

-          broken ends penetrate the pleura and lungs;

-          pleural and muscular pain limit respiratory effort.

Where many bilateral fractures are present, especially on the anterolateral sides of the thorax, the condition of 'flail chest' may be present, usually with multiple fractures of some ribs and sometimes with added fracture(s) of the sternum. As a result of loss of rigidity of the chest cage, attempts at expanding the thoracic volume during inspiration are impaired. The loose section is sucked inwards during inspiration, this clinical sign being known as 'paradoxical respiration'. Dyspnoea and cyanosis may develop and extreme degrees of flail chest are rapidly incompatible with life because of progressive hypoxia.

The flail chest is caused by frontal violence, most often sustained in motor vehicle accidents - where the victim is thrown against the steering wheel or fascia - or in stamping assaults, where the shod foot is violently applied to the supine body. In any substantial chest injury, broken rib ends may be displaced inwards, the jagged tips ripping the parietal and visceral pleura. This may cause a pneumothorax or a haemothorax, or both, from penetration of the lungs, with the formation of a bronchopleural fistula. In gross chest injuries there may be corn- pound fractures of ribs that allow a pneumothorax to form from external communication with the atmosphere, but this is rare in civil practice, though common in battle casualties.

Rib fractures are most often seen in the anterior or posterior axillary lines caused by falls onto the side. The upper ribs are less often fractured, except by direct violence from kicking, heavy punching or traffic accidents. The fracture sites almost always show bleeding beneath the periosteum or the parietal pleura if the fractures occurred during life - though it must be admitted that (rarely) undoubted ante-mortem fractures may be totally bloodless, whereas some post-mortem cracks may exhibit slight oozing from the marrow cavity into the adjacent tissues. Attempts at resuscitation, especially external cardiac massage, now provide a common cause for extensive rib fractures (up to 40 per cent) and make the task of the pathologist much more difficult when trying to differentiate original trauma from the effects of enthusiastic first aid.

Bleeding may or may not be seen in these resuscitation fractures and, as the attempts at revival are, by definition, peri mortal in timing, it is often impossible to say if they were immediately ante-mortem or post-mortem. As the bracing action of adjacent intercostal muscles may conceal any mobility of the ribs when being examined at autopsy, it is a useful procedure to slit all the intercostal muscles with a knife when chest injury is suspected to allow any mobility to be detected more easily. In the osteoporosis of senility and some diseases, the ribs may be so fragile as to be breakable by finger pressure. Allowance must be made for this fragility in interpreting the cause of the fractures.

In infants, especially victims of child abuse, rib fractures are common and may be an important diagnostic sign of abuse in doubtful cases. Where a small infant is squeezed from side to side, as when adult hands are clamped in each axilla or lower on the lateral sides of the chest, the hyperflexion can easily break ribs in their posterior segments, usually near their necks. The ribs are levered against the transverse processes of the vertebrae by excessive anterior flexion, which explains the tendency to fracture in the paravertebral gutter. Fresh fractures will be obvious, both on radiography and at autopsy. Within about 2 weeks (though this is very variable), callus will form and be visible both on X-ray and by direct post-mortem inspection. It is extremely difficult to date such callus.

It is said by paediatricians and radiologists that anterior rib fractures are rare in infancy other than from child abuse; though this is probably generally correct, care must be taken to exclude bony injury from the now almost universal attempts at resuscitation (even though infant ribs are very pliable). In very young infants, the possibility of older fractures dating back to birth injury cannot be dismissed, though again these are rare. The sternum may be fractured by stamping or other frontal impacts, but far more force is necessary than with ribs. If posterior displacement of a fragment occurs, the underlying heart or great vessels may be severely damaged.

Acknowledgements:

www.aived.nl    AIVD – @Erik Akerboom ©

www.politie.nl  Politiekorpschef  @Janny Knol©

www.politie.nl WEB Politie - @Henk van Essen©

 

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