Transcript Free fall trauma

Free fall trauma
S Tan and K Porter
Trauma 2006; 8: 157–167
Intern 王俏慧
96-4-3
Introduction
Terminology
Free fall
 An unimpeded drop from a known point to a
known impaction point.
Vertical deceleration
 Decrease in the speed attained by a falling body,
usually at impact.
Autokabalesis
 the basic components of ‘throw-out-window-self’
(Sims and O’Brien, 1979)
 the phenomenon of intentional jumping from a
height.
Epidemiology
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Among the causes of trauma deaths in the U.K. and the
U.S., falls rank only second to motor vehicle accidents.
all deaths by suicide: in 1961 1.38% rising to 4.4% in 1986
Isbister and Roberts, 1992
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In the U.S., approximately 50% of free falls are accidental,
about 20% are suicide attempts, another 20% are crime
related, and the remainder are from undetermined causes
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Sex : Men predominate over women (5:1 to 32:1)
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intentional falls: the difference is less clear
males opted for higher heights in their suicide attempts
Age : the young adult age range (18–41)
Season : summer prevailing
Alcohol and drug intoxication is commonly implicated
Psychiatric illness : in intentional jumpers ;Schihizophrenia,
depression
Physical and biomechanical
principles
Impact velocity
V = √2 gh
Discounting the effect of air drag
 a two-story free fall, 30 feet → 30 mph
 a six-story fall →53 mph
 The terminal velocity in the earth’s
atmosphere, 120 mph, will be reached by
a fall from 32 stories
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Impact energy
KE = 1/2 mv^2
KE = ME + PE + heat.
KE (kinetic energy) related more to the
velocity than the mass of the falling body
 At impact the vast majority of this KE is
converted to mechanical energy (ME).
 Tissue injury occurs as a result of the
body absorbing the energy (ME)
accumulated during the period of free fall.
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Impact force
F = ma
d (deceleration)= gh/s
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Stopping distance is determined largely by the
properties of the impact surface, softer surfaces
allow penetration by the fallen body leading to
larger stopping distances.
a fall from one story onto concrete, with a
stopping distance of ¼ inch → a deceleration of
720 g.
a fall from three stories onto mud with a stopping
distance of 8 inches → a deceleration of only 67 g.
Duration of impact
t = 2 s/v
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Longer impact durations allow for greater
dissipation of mechanical energy over time
and theoretically decrease the severity of
tissue injury sustained
Distribution of forces
S (The amount of stress)=F/A
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A body landing feet first will have relatively high
stresses distributed over a small area.
The orientation of the body undergoes change
throughout impact and these changes will also
have an effect on how the deceleration forces are
distributed through the body.
Parachutists are trained to land with hips and
knees flexed, they then further cushion their falls
by rolling.
Biomechanical factors
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Human bodies are composites of many tissues
and organs with different elasticities, viscosities
and resistances to deceleration forces.
In addition, these tissues and organs do not
impact in their entirety all at once: each organ
and structure has a different deceleration
distance depending on its position and moment
relative to the body parts making initial and
subsequent contacts.
Furthermore the transmission of forces at contact
may be in the form of compression, distraction,
rotation, shearing or a combination thereof.
Miscellaneous factors
wind may alter the body position at impact.
 rain, snow or frost
 The physical condition of the victim
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Young : the flexible skeleton, relaxed muscle
tone, higher proportion of subcutaneous fat
and lower body mass
Victims with altered conscious level through
drug or alcohol intoxication may have
depressed protective mechanisms
Risk of dying
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The height of the fall is the most significant
determinant
the surface impacted, attitude of the body at
impact, location of fall
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Softer impact surfaces → greater impact durations →
dissipating the ME
in an urban setting fallers are more likely to strike
architectural abutments in flight. This potentially
enhances survival by modifying the mechanism of injury.
Scalea et al.,1986
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Immediate death from free fall is usually a result
of massive brain damage, thoracic trauma or
intra-abdominal bleeding alone or in combination
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The risk of dying increased ten fold after falling
four storeys as opposed to one storey and 28fold increases were seen following falls from five
storeys
Risser et al., 1996
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The risk of dying from a third storey fall was 50%
Lewis et al.,1965
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similarly reported 50% overall mortality in suicide
jumpers from three storeys. All jumpers falling
six storeys or greater onto a hard surface died in
this series. Severe head and facial injuries were
the most commonly seen principle causes of
death.
Isbister and Roberts, 1992
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Victims have survived the initial fall and die after
reaching a hospital → this is secondary to
uncontrollable haemorrhage and massive CNS
injury in the early stages but intermediate and
late complications of pulmonary embolus, ARDS,
multiple organ failure and sepsis are other causes
of mortality.
In terms of the ISS( Injury Severity Score)
a clear-cut off between survivors and nonsurvivors was seen, with all but one patient with
a ISS>29 dying and all but one with a ISS<29
surviving
Isbister Roberts, 1992.
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the high incidence of intoxication with alcohol or
illicit drugs
Velmahos, 1997
Pattern of injury
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Our understanding of injury pattern and injury
severity is based on autopsy studies as well as
studies on survivors of free fall.
massive head injury, intra-abdominal injury to
solid organs and, to a lesser extent, intrathoracic
injury as being the predominant pattern of lethal
injury.
The height fallen, the surface impacted and the
body position at impact appear to be the
predominant determining factors, but the age of
the patient, locality of fall and intentionality of
the fall also modify the pattern of injury, severity
of injury and outcome.
Regional injury
Head injuries
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Massive head injury is a major cause of immediate death
following free fall.
The body’s position at impact obviously significantly alters
risk of head injury.
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Height of fall
The presence of skull fracture
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Incidence of head injury in feet first landings: 8.3% to 60%
A head first position at impact
Skull fractures occur in 60% and nearly all sustain some form
of cerebral damage, which is the most common mode of death
Fractures occur to the vault, producing linear and comminuted
fractures rather than localized, depressed ones.
Basal fractures usually occur as a result of transmitted force
from the spinal column such as in a feet first landing
Contusion and edema the most common finding in fallers
with head injury,
Spinal injury
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‘jumper’s fracture’
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transverse fractures of the upper sacrum resulting from
falls from a height and usually associated with suicidal
attempts by jumping
The incidence of this fracture in falls patients is most
probably low.
awareness of the possibility of such an injury, especially
in the presence of perineal neurological deficit
The most common site of spinal injury following a
fall : thoraco-lumbar junction
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By direct impact or by axial loading
The latter transmits flexion forces to the spine, which
usually affects the junction between the relatively fixed
thoracic spine and the adjacent more mobile lumbar
region.
Pure flexion ordinarily results in a simple anterior wedge
deformity
Spinal injury
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Rates of cervical spine involvement in vertical
deceleration type injuries appear to be somewhat
lower, but far from rare.
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In head-first impacts, these may be burst fractures or
flexion and extension injuries.
Hyperflexion is more common in feet-first landings
causing ‘teardrop’ fractures and rupture of the posterior
ligaments with or without subluxation.
Notably 85% of these involved the 12th thoracic
vertebra.
On classifying type of fracture, compression and
burst type fractures predominate
Pelvic injury
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The pelvis may be directly impacted through horizontal
landings and also when landing on the buttocks.
the most frequent impact pattern is the feet first landing.
Axial loading is transmitted from the lower limbs, across
the hip joint to the pelvis.
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Acetabular fractures
pelvic ring disruption, associated with life-threatening
hemorrhage.
Incidence of pelvic injury was second only to head injury in
Lewis’ report of high falls.
1/2 were deemed stable (Type A), about 1/3 were stable in
the vertical plane (Type B), and 1/3 there was also
instability in the vertical plane (Type C).
Associated bladder injuries and sciatic nerve injuries were
also recorded.
Thoracic injury
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Ruptures of the thoracic aorta, pericardium and
heart although common in autopsy series, are
uncommon in patients who survive to reach
hospital.
Azygous vein laceration as a result of free fall has
been reported but again is rare.
landing on the buttocks from a fall gives rise to a
higher incidence of intra-thoracic and intraabdominal injury
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impact forces cannot be dispersed by the knees and hips
flexing, and consequently more force is transmitted to
the trunk.
Pulmonary injury of differing severity is common
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Multiple rib fractures with lung contusion, haemothorax
and pneumothorax
Abdominal injuries
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The liver has been reported as being the most
commonly injured organ and also the most fatal
abdominal injury
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Splenic injuries are caused by a severe degree of
violence.
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Lacerations
the right lobe
Capsular tears and divisions of the lower part of the
spleen
renal injury to be relatively rare in free fall
patients.
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the kidneys position and surrounding fat conferred
protection.
under-diagnosed and under-reported.
Abdominal injuries
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Hollow viscus injuries appear to be present in
similar proportions as solid organ injuries
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a shearing of the viscus at the junction between its fixed
and mobile portions.
lacerations may occur at the junction between the
terminal ileum and the caecum, in the sigmoid colon,
and at the duodenojejunal flexure
Retroperitoneal hemorrhage was identified by
Scalea and associates as the most likely source of
ongoing blood loss in patients surviving long
enough to present to hospital.
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The vascular injuries were attributed to pelvic and
vertebral fracture.
Extremity injury
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Lower limb injuries are consistently reported as
the commonest injuries found in all patients who
fall from a height.
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the feet first landing
the path of force transmission from impact, axially
through the bony skeleton.
metaphyseal and epiphyseal injuries of the distal joints
(foot, subtalar and ankle joints)
The os calcis consistently is reported as the single bone
most commonly fractured (18–64%)
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more common following lower (one to two storey) than
higher (3 storey) falls.
a significant association between os calcis and
thoracolumbar fractures
Extremity injury
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Upper limb injuries are commonly described
following free fall impact (24.8–38%)
 metaphyseal and epiphyseal regions of the
distal joints (wrist and elbow) are
predominantly involved.
 Fractures of the diaphyseal areas and the
proximal joints (shoulder and humerus) are
relatively rarer.
Jumpers and fallers
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There does not appear to be any specific injury
that is pathoneumonic of either intentional or
accidental fall.
Jumper
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‘suicidal jumper’s fracture’ to describe transverse
fractures of the sacrum
Roy-Camille et al. (1985)
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A high ratio of lower limb fractures and a small number
of head injuries are typical for patients landing on their
feet
tend to try and break their falls using their dominant
(usually right) side. ( based on injuries )
Jumpers and fallers
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Fallers
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The height of fall, striking architectural
abutments, wind conditions and alcohol or drug
intoxication may all modify the final impact.
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a lower incidence of feet first landings in fallers
the body tends to land as predicted by its center of
gravity in the upper torso
the difference in orientation seen with low and high falls,
suggesting a greater variation in impact position with
higher falls.
It was Teh et al.’s (2003) experience that
jumpers tended to suffer falls from greater
heights than did fallers. Thus, a higher incidence
of head injuries could be the product of the
height of fall.
Predicting the severity of injury
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The height of a fall has been shown to be a
strong predictor of mortality.
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a threshold height of 20 feet as the cut-off above
which major trauma is considered a clinically
important risk. However, the height of fall is a
poor predictor of injury severity
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Factors such as age and mechanism of fall
obviously have significant bearing on outcome
Summary
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Free fall trauma represents a distinct form of
blunt trauma.
The distance of fall, impact surface, body
orientation at impact, victim’s age and depressed
protective mechanisms are important factors to
be considered in our analysis.
The distance of a fall is perhaps the strongest
single predictor of mortality with falls from three
storeys carrying a 50% risk of death and those
from five storeys or more rarely being compatible
with survival.
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Massive head injury, intra-abdominal solid viscus
injury and, to a lesser extent, intra-thoracic
injury are the predominant lethal injuries.
A threshold of 20 feet is commonly cited in triage
as the level at which major trauma needs to be
considered.
Musculoskeletal injuries, lower extremities injury
in feet first landings.
os calcis fracture and Spinal injury, thoracolumbar junction
spinal injuries are commonly unstable, burst or
compression type configurations and carry a high
incidence of neurological injury
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Ruptures of the aorta, pericardium and heart as
well as major hepatic and splenic injuries are
common sequelae following massive
decelerations. However, such injuries are usually
not survivable.
haemodynamic instability in a free fall survivor
the possibility of retroperitoneal haemorrhage
especially from vertebral or pelvic fracture should
always be borne in mind.
The distinction between so called ‘jumpers and
fallers’
Thanks to your attention!