Premortem trauma/fracture and Perimortem trauma

Skeletal non metric traits (Premortem)

* Discrete traits, skeletal anomalies
* Non-fusion anomalies
* Retention of metopic suture
* Spondylolysis: separation of vertebral vertebrae
* Spina bifida occulta: incomplete dorsal wall
* Sternal foramen: elements of the sternum don’t fuse
* Septal aperture
* Accessory foramen: septa aperture

Pathologies (premortem)

* **Congenital** → birth defects (e.g., cleft palate, craniosynostosis \[sagittal suture fuses prematurely, increasing cranial pressure as the brain grows\]
* **Metabolic** → dietary deficiencies (e.g., scurvy, rickets \[bone fails to mineralise and can’t support body weight and start to bow\], fluorosis \[excess fluoride causes bones to hypermineralise\])
* **Trauma (injuries)**
* Pseudarthrosis → bone hasn’t set properly causing a false joint

Evidence of healing (premortem)

* Clot formation
* Hours after break
* Vascular bridge
* 4 days-8 weeks
* Bony bridges trying to unite the ends of the bones (woven bone)
* Clinical union
* The ends of the bone have come together
* Mass of woven bone trying to knit the ends together
* Eventually lamellar bone replaces woven bone causing a bony callus
* Remodelling
* Years
* Bone callus of lamellar bone remodels to look good as new

Perimortem trauma

* **Force (load)** → any mechanical disturbance that causes an object to either deform, or change its state of motion, or both
* **Magnitude** →the area of the force being applied
* **Direction** → the line in which the magnitude of the load travels
* **Stress** → force per area
* **Strain** → the relative deformation of material

Strangulation effect

* Hanging: body weight suspended, the force is the weight of the body against the rope
* Break pedicle C2 and hyoid bone
* Ligature: strangle → aim to block the arteries to reduce blood flow
* Manual: strangulation with the hands → aim to block the arteries to reduce blood flow → Might not leave any fractures to the hyoid bone

Deformation of perimortem trauma

* **Elastic deformation** → temporary modification of the object → the object returns to its original form
* **Plastic deformation** → when forces are applied to the object→ it deforms and stays in that shape (it never returns to the original)
* **Yield point** → the point where elastic deformation turns into the plastic deformation
* **Fracture point** → the point after plastic deformation when the bone fails and fractures

7 complete fracture types in Perimortem

* Tension = **transverse**
* Compression = **oblique**
* Bending = **butterfly**
* Tension = **spiral**
* **Comminuted → oblique fractures going in different directions creating small/isolated pieces of bone (multiple breaks at a site)**
* **Segmental** → a segment of bone is separated from the entire bone
* **Avulsed** → when the end of a bone where ligaments attach fails instead of the ligament

4 incomplete fracture types in Perimortem

* **Stress** → stress from the ligament causes tiny breaks
* **Impacted** → area of bone compressed into the shaft
* **Torus** → compression forces don’t fracture the bone completely → shrinkage of the limb
* **Greenstick** → bone resists forces → doesn’t break the bone completely (common in young individuals)

Intrinsic factors in perimortem fracture

* Properties of bone
* Wet (still has fats), or dry (no fats)
* Fractures on dry bone are irregular (square-shaped, boxy)
* Postmortem
* Fractures on wet bone are spiral
* Perimortem
* Geometry
* Strong bone (lots of cortical bone density)
* Force applied to the forearm that causes failure won’t cause failure in the tibia, because the tibia has a denser cortical bone
* Weak bone (less mineral density)
* Related to age
* Increases risk of fracture
* Thickness of cortical bone varies person-to-person

Intrinsic factors for Perimortem (age related)

* Age of individual (young people have more collagen that resists forces)
* Old adults (>50 years)
* Osteopenia → bone density below the normal range
* Osteoporosis → low bone density at risk for fracture
* Loss of trabecular bone leaving holes/gaps
* The more holes in the trabecular bone, the less resistant the bone is to failure
* Common in femurs and vertebrae

Pathologies/nutritions in perimortem

* **Osteogenesis imperfecta** (brittle bone disease) → loss of bone deformation ability
* **Scurvy** → destabilises collagen
* Vitamin C deficiencies
* **Rickets** → defective mineralisation
* Vitamin D deficiencies
* **Osteomalacia** → defective mineralisation
* Adult version of rickets

Human activity

Dismemberment

* Localised dismemberment
* Dismembering body parts in a strategic way, mainly to make the victim fit in a smaller container
* Generalised dismemberment
* Not specific or strategic
* Trying to break apart as much of the body as possible
* Used for disposal
* If the victim can’t be identified, it’s hard to link them to a suspect

Dismemberment tools

* Hand saw types
* Back saws
* Coping/fret saws
* Hacksaw
* Handsaw
* Keyhole/compass saw
* Frame saw
* Japanese saw
* Timber/log saw
* Power saw
* Straight or circular blade
* Chainsaw
* Two types of saw
* Crosscut (handsaw) and rip (chainsaw)
* (Based on blade type)

3 types of marks caused by saws on bone

* Superficial false start scratches
* Saw skips
* False start kerf
* Small cuts made using a hand or table saw before the right place to cut is found
* Sectioned bone cut
* When the sectioned part is cut

Effects of saw on bones

* Power saws
* Uniform, fine/linear striations
* Hand saws
* Irregular, more prominent striations
* Floor of the kerf
* Left if the bone isn’t fully cut through, only some of it is cut and the rest of it is snapped
* Rough = coarse saw
* Smooth = fine saw
* Breakaway spur
* The bone splinters as it’s being sawed, leaving a spur that prevents the blade from going all the way through

Analysis of saw marks

* Basic description
* Number of cuts, false starts
* Superficial false start scratches
* Cut widths
* Direction of saw cut
* Direction of saw progress
* Direction of saw stroke
* General tooth size
* Blade width
* = width of kerf/1.5
* Blade shape
* Fixed-radius striae
* Circular blades
* Nonfixed-radius striae
* Straight blades
* Source of energy
* Hand
* Power