Long tubular bones

Under the action blunt solid objects in the transverse direction, these bones are destroyed with the formation of fragments, but can occur and mesoscopical fractures (Fig. 19).

fractures of long tubular bones Fig. 19. Mechanisms of fractures of long tubular bones.

a - power distribution of stresses in the moment of formation of fracture;
b - education bezobolochnoe fracture;
in - education comminuted fracture.

The resilience of the long bones in relation to external influence varies and depends on many factors, such as bones, the direction of impact, gender, age and so on). So, for example, for femoral diaphysis destructive energy upon impact is 140-170 j, torsion-150 - 180 j, breaking load bending - 3000-4000 N.
Bone stronger compression than the tensile, so when bending bone will break down at the point of maximum tension, i.e., on the convex side. The crack extends to the concave side, which in most cases is the place of external influence. Thus, the fracture is formed and distributed in the direction opposite to the direction of external influence. In the zone of compression bones crack often splits in two, forming a kind of triangle (in the profile) the splinter. At the front line of the fracture in relation to the diaphysis is located in the transverse direction. On the side from the impact point sides from the edge of the fracture depart cortical cracks. In the zone of compression bone surface of fracture always krupeshina, in the zone of tension is fine.
Similar in appearance fractures, but different localization arise when different mechanisms of injury (for Example, bending the diaphysis of long tubular bones in transversal pressure, bending under one caught the end, bending under longitudinal impact). This requires various external force (the smallest bending bones with rigid epiphysis, the largest, with longitudinal impact).
Frequent form of fractures of long tubular bones is their deformation due to the rotation of the body around a fixed limb or limbs for a fixed body. Torsional formed spiral fractures.
If (mentally) to restore the normal spiral line segment fracture, you can determine which direction was the rotation (Fig. 20).
diaphyseal fractures of long tubular bones

Fig. 20. Conditions for the occurrence of diaphyseal fractures of long tubular bones. a - transverse bending (blunt in the transverse direction); b - bend from longitudinal impact; in a shot at a sharp angle; Mr. bending one fixed pineal gland; d - rotation.

Fractures of the long bones in the same place can be formed under different conditions of external influence (e.g. fractures in the field of surgical neck shoulder). The analysis of features of a surface of a break helps to Orient in the mechanisms of injury (table. 6).

Table 6. Morphological features of diaphyseal fractures of long tubular bones when bending deformation
Sign The characteristic of
on the compression side side stretching on the side
Outline the edges of the broken As abruptly broken line, oriented oblique transverse to the longitudinal axis of the bone In the form of finely dentate or smooth lines, located in the transverse direction to the longitudinal axis of the bone In a broken line, diagonally to the longitudinal axis of the bone. Forks in cases comminuted fractures
Cracks Rarely longitudinal cortical No Curved away from the edge of the fracture. Can move in a longitudinal cracks cortical layer
Fragments Often diamond (in the triangular profile) No Sometimes small, Crescent-shaped
The surface of fracture Krupeshina Fine Gear
The plane of fracture Slanting towards the surface of the bone Perpendicular to the surface of the bone Perpendicular to the surface of the bone
The degree of matching fragments Mapping incomplete. Defect edge of a break (from chipping before the formation of fragments) The mapping is complete, without defect of bone mass The mapping is complete. You can chipping in the form of small triangular or semilunar defects

The impact of substantial forces along the bones can cause impacted fractures (for example, at falling from height in feet). When a large elasticity of bones (children) in these conditions metaepitome departments arise cortical valikoobraznye expansion bone substance without disturbing the integrity of the bone.