*Edit 10/21/16: Fixed broken link to pdf, sorry. :C
- Material Properties of Bone
- Classifying bone trauma by time of occurrence
- Types of bone trauma
- Blunt force
- Sharp
*Edit 10/21/16: Fixed broken link to pdf, sorry. :C
- Material Properties of Bone
- Classifying bone trauma by time of occurrence
- Types of bone trauma
- Blunt force
- Sharp force
I’m not gonna include a lot of pictures because this is a topic that not everyone will want to see images of. You can google stuff if you want to see examples, or read my final paper where everything is cited.
Material Properties of Bone
Bone is divided into two kinds of osseous material. Cortical bone is about 80% of the mass of the exoskeleton, and forms a hollow cylinder in which the cancellous bone resides. The main purpose of cortical is for structure, while cancellous bone is spongy interior that is responsible for nutrient storage and transport.
Injuries to bone are classified based on when the injury occurs.
Ante-mortem trauma: Refers to trauma on the skeleton that occurs prior to the death of the individual. In-vivo bone exhibits healing, and edges of a fracture will be fairly smooth. As healing rates differ depending on the characteristics of the individual, the same injury may look different from case to case.
Peri-mortem trauma: Refers to trauma occurring around death. Fracture patterns observed in peri-mortem trauma can be similar to those seen in ante-mortem trauma, but have sharper edges since no healing will have occurred (in most cases). Patterns will show evidence of some terminal event, i.e fast collision with an object, but fracture edges will show characteristics of plastic deformation as the external fibers of the bone tissue begin to show micro-tears.
Post-mortem damage: Refers to damage occurring after death. Bone becomes brittle once it has dried out, and exhibits ceramic-like material properties. Fractures will be jagged and exhibit no healing, and may also be irregular. I.E: Fractures lack a common correlation to an event that caused the damage, such as those resulting from post-mortem bone shrinkage.
Types of Bone Trauma
Ballistic trauma on bone is usually the result of a bullet or an explosive, though this categorization may be applied to any fast traveling object that has collided with bone. Features that indicate possible ballistic trauma include the presence of a projectile that can be associated with bone, fracture patterns corresponding to a high velocity impact, or fragmentary foreign material found within the bone or the environment.
Because of physics, entry wounds tend to be smaller than exit wounds, due to the bullet losing energy as it travels within the body. Because of the varying environment inside the body, it’s difficult to predict how a bullet may travel since it may bounce off of bones or move differently due to varying densities of tissue inside the body. Thus, while there will always be an entrance wound in cases of ballistic trauma, the presence or number of exit wounds will heavily depend on the situation.
Currently, CT scanning is heavily used in this realm, since it works well on both hard and soft tissue and can thus preserve the body in a virtual state.
While ballistic trauma can be kind of classified as blunt force trauma, here, blunt force trauma will refer to trauma resulting from a low velocity impact from a blunt object or blunt surface. Features suggesting blunt force trauma include plastic deformation, delamination, tool marks/impressions at trauma site, or fracture patterns on the bone suggesting low velocity impact. This is because during low velocity impact, the bone will have more time to bend and deform in response to the stress before it fails.
Different kinds of applied force will exhibit itself characteristic fracture patterns as well. Knowledge of these patterns can provide additional information about the events leading up to the fracture. That’s why it’s valuable to have a fully modeled human skeleton so that anthropologists will have immediate predictions as to forces necessary to produce fracture patterns.
Currently, computational human skeleton models are not robust enough to act as a substitute to real bone, though the area is very much in active research. Researchers have also experimented with nonhuman animal models, mostly focusing on porcine and deer due to similarities with the human skeleton.
Sharp force trauma is characterized by trauma resulting from a tool that is edged, pointed, or beveled. Features indicating this kind of trauma include straight-lined incisions, punctures or gouges, clefs or kerfs. Considerations must be taken when examining the wound, since alterations to the bone like scrapes or score marks are not classified as sharp force trauma.
Evidence of sharp force trauma is distinctive because the tool will leave a mark that can be readily differentiated from stress based fractures. It is possible to estimate the motion of the tool based on whether it is a slash (the incision is wider 