Damages of individual flat bones

The most common mechanism of injury separate flat bones is their destruction from bending. Under the action of a hard blunt object mechanism of fracture flat bones from bending is to compress one compact discs and stretch the other (opposite), this destroys the plate facing efforts to break. The crack spread through the thickness of the bones to the opposite plate, destroying spongy substance (in the transverse direction). Along the surface of bone fracture (broken) applies accordingly bend. On the edge of a fracture (on the surface experiencing compression during flexion) found chipping compact matter, allowing you to determine the location and direction of external influence (Fig. 21).
the mechanism of fractures flat bones

Fig. 21. The mechanism of fractures flat bones. 1 - broken from bending when struck oblong object; 2 - the formation of a perforated fracture; 3 - terrace-like formation fracture; 4 - fracture due to rupture; 5 - broken from bending compression; 6 - formation valikoobraznye expansion; 7 - formation valikoobraznye collapse.

The destruction of the bones may occur from cracking (thrust) or even herniation before surgery the most damaging of the object. In this case, the collapse of one-stage two plates and cancellous and crack propagation direction coincides with the action of damaging the subject.

fracture of the vault of the skull
Figure 22. Perforated fracture of the vault of the skull.

When struck dumb by a hard object with a relatively small and clearly limited hitting surface (hammer, the butt of an axe and others) flat bone destroyed by type "shift" (chip). Plot outer plates flat bones out the edges of the contact square damaging of the object, and the internal record is destroyed on several larger area. There are so-called depressed or perforated fractures. When this occurs whether the size of the bone defect shape and size hitting the surface. This is important in forensic respect, because it creates the possibility of establishing damaging of the object by comparing it with the bone defect (Fig. 22).
Action hard blunt object on a flat bone can be expressed in the form of pressure in the direction parallel plates bones. This effect causes a kind of deformation, which is usually presented in two variants. Under the action of a compressing efforts parallel to the surface of the flat bones and eliminating the possibility of deformation it from bending bone experiencing stress only in the direction of the force. Arising kind of swelling possible with the most significant elasticity of bones (usually occurs in childhood and adolescence). Compression is exposed and the sponge-like material that enhances swelling (shift) compact flat plates of a bone.
If the flat bone has some convexity, such as the bones of the skull, then under the action of an external force parallel to its surface, it can bend and then there is the cross-reaching fracture with all the signs of strain curve.
Despite the General regularities of bone destruction under action of blunt objects, in each specific case there is a fracture that has its own characteristics, which greatly depends on the individual properties, form and structure of the complex bones (skull, thorax and the pelvis). When exposed to a hard blunt object (impact or compression) on bone formation (complexes) of the latter can be damaged as at the point of application of external force (contact fractures)and distance (structural fractures), based primarily on the form (structure) of this complex.