Timing Mandibular Trauma
This section aims to give an insight into some key features which aid the classification of trauma depending on its timing.
Timing mandibular trauma remains a challenging aspect of skeletal remain assessment. Such analysis allows the distinguishment between ante-mortem, peri-mortem and post-mortem mandibular trauma, allowing the determination of whether skeletal injuries are connected to the events surrounding the deceased’s death.
Properties and features of mandibular fractures are largely dependent on the hydration and organic component of bone which differs significantly between ante-mortem, peri-mortem and post-mortem bone.
Properties and features of mandibular fractures are largely dependent on the hydration and organic component of bone which differs significantly between ante-mortem, peri-mortem and post-mortem bone.
Ante Mortem
Ante-mortem trauma encompasses injuries which occurred before the deceased's death. There are various features indicative of ante-mortem trauma:
During this time bone is hydrated, elastic and capable of repair.
As ante-mortem trauma occurs before death, such trauma is predominantly recognised by the presence of the healing (either partial or complete) While the healing process commences straight after an injury occurs, no signs of the process are evident for around 1-3 weeks.
Around 1 week after the trauma has occurred, fracture edges which were previously sharp, transform to exhibit a rounded shape (2), which indicates the presence of the healing and remodelling process. Indeed this feature is thought to indicate that the trauma occurred at least a week prior to the deceased's death.
An imprinted line in the bone may run parallel to the fracture, indicating the process of periosteal elevation. Broken pieces of bone may have re-joined with the surrounding bone and the fracture edges are smooth in texture. Bone porosity (1) is maintained in the areas surrounding the fracture margins, indicating bone resorption and activity, as well as fracture healing.
The long process of continuous bone remodelling leads to the fracture line being replaced with a 'v-shaped' (3) groove.
When it reaches the 6th week of fracture healing, a callus (4) forms over the fracture and surrounding bone. This callus has a bumpy, irregular shape and so is easily distinguished from the surrounding bone. The colour of bone at the fracture site matches that of the surrounding bone as both areas have been exposed to the same conditions.
During this time bone is hydrated, elastic and capable of repair.
As ante-mortem trauma occurs before death, such trauma is predominantly recognised by the presence of the healing (either partial or complete) While the healing process commences straight after an injury occurs, no signs of the process are evident for around 1-3 weeks.
Around 1 week after the trauma has occurred, fracture edges which were previously sharp, transform to exhibit a rounded shape (2), which indicates the presence of the healing and remodelling process. Indeed this feature is thought to indicate that the trauma occurred at least a week prior to the deceased's death.
An imprinted line in the bone may run parallel to the fracture, indicating the process of periosteal elevation. Broken pieces of bone may have re-joined with the surrounding bone and the fracture edges are smooth in texture. Bone porosity (1) is maintained in the areas surrounding the fracture margins, indicating bone resorption and activity, as well as fracture healing.
The long process of continuous bone remodelling leads to the fracture line being replaced with a 'v-shaped' (3) groove.
When it reaches the 6th week of fracture healing, a callus (4) forms over the fracture and surrounding bone. This callus has a bumpy, irregular shape and so is easily distinguished from the surrounding bone. The colour of bone at the fracture site matches that of the surrounding bone as both areas have been exposed to the same conditions.
Peri Mortem
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Peri-mortem trauma encompasses injuries which occurred around the time of the deceased's death. There are various fracture features indicative of peri-mortem trauma:
During this time, bone maintains a degree of hydration and collagen component preserving some of its flexible and elastic attributes. Unlike 'dry' post-mortem bone, 'wet' peri-mortem bone undergoes plastic deformation prior to fracturing. Peri-mortem fractures typically exhibit straight edges similar to a 'crack', the opposite of the irregular fractures found in post-mortem bone which lacks the collagen component. The surface of the fracture is smooth and often depicts a ‘v shaped’ contour. As the fracture occurs around the time of death, there is no evidence of any healing process. The fracture demonstrates an obtuse angulation (5). While the fracture patterns sometimes appear sharp and jagged, the margins are typically smooth and bevelled to the underlying peri-mortem bone. The bone exhibits undulated and crushed margins. ‘Bone splinters’ resembling small flecks of bone, surround the inner parts of the fracture and fragments remain adhered to the bone – this emphasises that the underlying tissues were still located at the time of trauma, emphasising the peri-mortem nature of the fracture. Radiating and concentric fractures (3) are other typical features of peri-mortem trauma, with the fragments still tethered to the underlying bone. The colour of bone at the fracture site matches that of the surrounding bone (1). However, the cortical margin of the bone sometimes exhibits staining (4). This may be due to haemorrhage/ haematoma formation during the trauma. |
Post Mortem
Post-mortem trauma encompasses injuries which occurred after the time of the deceased's death. There are various fracture features indicating post-mortem trauma:
Like peri-mortem trauma, the post-mortem trauma does not exhibit any evidence of healing as they occurred after the individuals death.
During this time, bone is dehydrated and its collagen component is lost. Post-mortem fractures, unlike peri-mortem fractures, do not exhibit radiating/ concentric fracture lines, or 'bone splinters'. This is due to the reduced elasticity of post-mortem bone, meaning it fractures and separates more easily, rather leading to bone shattering into large fragments (2), with the absence of the plastic deformation stage. This leads to the formation of fractures which demonstrate square, jagged edges (4) which feel sharp to touch (5), and they are typically at right angles (3) to the surrounding bone surface. Compressive forces exhibited during mandibular trauma cause post-mortem fracture surfaces to crumble.
The fracture lines typically exhibit a lighter colouring than the surrounding bone (1), most likely due to the fractured site being exposed at a later time, and to different conditions. Colour of the bone and fracture line may also be altered by handling processes during the post-mortem phase as well as animal scavenging (6).
Like peri-mortem trauma, the post-mortem trauma does not exhibit any evidence of healing as they occurred after the individuals death.
During this time, bone is dehydrated and its collagen component is lost. Post-mortem fractures, unlike peri-mortem fractures, do not exhibit radiating/ concentric fracture lines, or 'bone splinters'. This is due to the reduced elasticity of post-mortem bone, meaning it fractures and separates more easily, rather leading to bone shattering into large fragments (2), with the absence of the plastic deformation stage. This leads to the formation of fractures which demonstrate square, jagged edges (4) which feel sharp to touch (5), and they are typically at right angles (3) to the surrounding bone surface. Compressive forces exhibited during mandibular trauma cause post-mortem fracture surfaces to crumble.
The fracture lines typically exhibit a lighter colouring than the surrounding bone (1), most likely due to the fractured site being exposed at a later time, and to different conditions. Colour of the bone and fracture line may also be altered by handling processes during the post-mortem phase as well as animal scavenging (6).
