Table of Contents
List of Figures ........................................................................................................ iv
List of Tables .......................................................................................................... v
Summary ................................................................................................................ vi
1.0
Introduction .................................................................................................. 1
2.0
Background and Provided Information ........................................................ 2
2.1
Important Terms ....................................................................................... 2
2.2
Witness Accounts of the Incident ............................................................. 3
2.3
Medical Records ....................................................................................... 4
3.0
Bus Examination .......................................................................................... 6
3.1
Incident Bus .............................................................................................. 6
3.2
Tire Contact Geometry ............................................................................. 7
3.3
Tire Contact Force .................................................................................... 7
4.0
Injury Extent Analysis ................................................................................. 8
4.1
Sustained Injuries ..................................................................................... 8
4.2
Lost Nails ................................................................................................. 8
4.3
Phalangeal Fractures ................................................................................ 9
4.4
Abrasions and Lacerations ..................................................................... 10
5.0
Injury Causation Analysis .......................................................................... 11
5.1
Fall Analysis ........................................................................................... 11
5.2
Crush due to Bus Weight ....................................................................... 11
5.3
Entrapment/Hyperextension Injury ........................................................ 12
5.4
Other Possible Scenarios ........................................................................ 13
ii
5.5
Injury Mechanism Selection................................................................... 14
6.0
Conclusions ................................................................................................ 16
7.0
Recommendations ...................................................................................... 17
8.0
References .................................................................................................. 18
Appendix A: Bus Individual Tire Pressure Calculation ....................................... 19
iii
List of Figures
Figure 1: Exemplar Orion VII bus. ..........................................................................6
Figure 2: Tire Contact Geometry Measurement .....................................................7
Figure 1: Radiograph of the Victim's Hand with Fractures Indicated. ....................9
iv
List of Tables
Table 1: Table of Technical Terms and their Definitions ........................................2
Table 2: Determination of Fracture Cause .............................................................14
Table 3: Determination of Nail Injury Cause.........................................................15
Table 4: Determination of Laceration and Abrasion Cause ..................................15
v
Summary
This report investigates the circumstances of an alleged “bus run over”
incident which caused the victim several injuries. These injuries include a
laceration on base of their thumb, numerous small abrasions on the palmar surface
of their hand, lost index nail with contusion of the nail bed of their 3rd and 4th
digits, fracture of the middle phalanges of their 2nd-5th digits, and no fractures of
their distal phalanges. This analysis is to determine if the sustained injuries could
be caused by a bus running over the victim’s hand, as the victim alleges.
The contact geometry of the rear tires on six exemplar buses are measured to
be 9 to 11” by 10” and the weight on the rear axle of the bus is 9067.3 kg. From
this, a contact pressure between 0.313 and 0.383 MPa is determined. This range is
far lower than the minimum necessary pressure of 103 MPa needed to break
cortical bone, ruling out crushing as a cause of fracture injury. The fractures
sustained by the victim are still found to be possible in the case of a bus run over,
through a knee-jerk hand removal reflex causing hyperextension of the fingers
while the bus traps the victim’s fingers. The lacerations and abrasions are found
to be caused by any part of the bun run over, and nail loss is caused by crushing.
It is concluded that the victim’s injuries are possible in the event of a bus run
over. It is also concluded that the victim was unaware of their impending injury
and that industrial machines or entrapment in other car areas were both not
possible methods of injury. It is also recommended to continue looking for
possible other causes of the injuries and vet other injury mechanisms to prepare
should this case ever go to trial.
vi
1.0 Introduction
This report investigates and discusses the incident which befell the victim of a
severe hand injury, which caused permanently crippling damage to the fingers of
their right hand, accompanied by various other injuries. The objective of this
investigation is to conduct a biomechanical assessment of the circumstances
surrounding this incident. In particular, the investigation is to determine if the
injuries sustained by the victim could be caused by a bus running over their hand
as alleged. Though the bus’s capacity to inflict harm may seem obvious, videos
available on YouTube of individuals voluntarily having extremities run over by
buses and emerging unscathed display the need for this investigation[3] [10].
The victim alleges the injury took place when a public transit bus drove over
their hand. The victim was disembarking from the rear doors of the bus when they
lost their balance and fell onto the sidewalk. They put their right hand on the road
palm side down to lift themselves up, and at the same time, the bus drove forward
and the back wheel ran over the victim’s fingers. The victim arrived in the local
hospital’s Emergency Room later that night where they were observed to have
injuries to their right hand, which included fractured fingers intermediate
phalanges on all fingers, several removed nails, and lacerations to the palm and
back of the hand.
Names of all parties related or involved in any way in this incident were
removed for confidentiality reasons. Any locations mentioned in any reviewed
document have been omitted from this report for the same reason. Colour
photographs of the victim’s injury were also omitted.
1
2.0 Background and Provided Information
This section provides a synopsis of all the provided information surrounding
this incident. This will include all witness accounts and medical records relevant
for use in this case. Photos of the injury were also received from groups
mentioned in Section 2.2, but most were not included in this report.
2.1
Important Terms
Table 1: Table of Technical Terms and their Definitions
Abrasion
A region on the human body effected by the removal of
multiple layers of skin, often caused by impact.
Laceration
A linear cut or tear in skin.
Avulsion
Occurs when loading through the tendon is great enough to
cause part of the bone to break away, thus severing one of
the tendon’s boney attachments.
Phalanges
The bones of the fingers. (phalangeal meaning “of the
finger”)
Splintering fracture of a bone.
Comminution
The first joint in the 2nd through 5th digits, closest to the
Proximal
Interphalangeal hand.
Joint (PIP)
Fingers. The 1st digit refers to the thumb, 2nd to the index
Digits
finger, and fifth to the pinky finger.
Webspace
The fleshy region of the hand between the 1st and 2nd digits.
Volar Plate
A ligament the palm (or palmar) side of phalangeal joint.
(“Volar Surface” refers to the surface of the ligament)
Distal
States that a part of the body is “farther from the center”
than another. For example, the wrist is distal to the elbow,
and the elbow is distal to the shoulder.
Proximal
States that a part of the body is “closer to the center” than
another. For example, the wrist is proximal to the fingers
Shearing
A force between two bodies acting along their attached
surfaces, causing their attachment to deform and eventually
separate.
2
2.2
Witness Accounts of the Incident
In their statement to the public transit organization, the victim indicated that:

They exited the bus through the rear doors.

When exiting, they fell on their left side, striking their head in the process.

Their glasses and items in their shopping were thrown when they fell.

They were not sure if they slipped or missed the curb.

They had a prosthetic leg.

Their body was on the sidewalk, and their right hand was on the road.

The bus began to drive; as it pulled away it ran over their right hand with
the rear wheels.

They were unsure of the bus number, but the incident bus was an
eastbound bus.

They required stitches to close a cut on their hand and their right arm was
placed in a cast.

They lost three fingernails. They are unable to bend their fingers to make a
fist because the tendons were damaged.
On the Disability Certificate, the victim reported:

“When I stepped off the bus, I don’t know if I stepped off the curb or
missed the curb.”

“I brought my hand out. I put my hand out to pick myself off the road.
The bus driver closed the door and ran over my hand.”
3
At their In-Home Functional Assessment the victim indicated that:

They stepped out of the bus and possibly missed the curb with their
artificial leg.

They did not lose consciousness after falling.

They put their right hand out to get up.

The bus ran over their four fingers.
At a doctor’s examination, the victim reported:

They were on a TTC bus eastbound.

They were exiting the bus when they miss-stepped and fell onto the road.

The bus ran over their hand before they were able to get up.
At their examination by a second doctor, the victim reported:

They stepped off bus, probably lost their balance, and fell.

They placed their right hand on the ground to help themselves up and the
bus ran over their hand.

They were subsequently helped by a cab driver.
2.3
Medical Records
The Emergency Room records from the hospital the victim was admitted to
indicated that:

They slipped while getting off the bus.

The bus ran over their right hand.
4
Triage Documentation from the hospital which the victim was admitted to post
accident indicated that the victim:

Sustained large laceration on base of thumb and lost their index nail.

Had a medical history including stroke, hypertension, cholesterol,
alcoholism, and a prosthesis to lower left leg.
The Emergency Room record from the hospital which the victim was admitted to
post accident indicated that:

The victim fell on an outstretched hand ("FOOSH").

There was a 2 cm laceration to first webspace requiring sutures.

They had numerous abrasions on various digits.

The 2nd-5th digits were tender and swollen.

They were able to flex all of the digits at the IP joint.
An X-ray of the victim's right hand showed:

Mild persistent flexion of the hand limiting evaluation.

Comminuted intra-articular fractures of the second, third, fourth and fifth
middle phalanx into the PIP joint.

Mild fragment separation involving the third, fourth and fifth phalanges of
up to 2 mm.
5
3.0 Bus Examination
This section describes all the necessary specifications for the bus accused of
injury causation. Specifically, the bus shall be analysed regarding weight
distribution and rear tire road-contact geometry.
3.1
Incident Bus
The make and model of the bus in question is found by researching the make
and model of buses from the route which the victim disembarked. After reviewing
sources on the history of the bus models used on the public transit route in
question, the Orion VII is determined to be the model of the bus in question
(Figure 2). The Orion VII bus is outfitted with four tires on the rear axle (two
tires on each side), and a rear axle curb weight of 9067.3 kg [4].
The victim stated that they lost their balance and fell while exiting the rear
doors of the bus, and that their hand was run over while they attempted to get up.
The rear doors are located in front of the rear wheels, which does not conflict with
the currently accepted incident narrative.
Figure 2: Exemplar Orion VII bus. [2]
.
6
3.2
Tire Contact Geometry
To determine the pressure exerted by rear tires of the bus on the victim’s
hand, a measurement is taken of the rear tire’s contact geometry. These
measurements are taken from a single back tire on six separate Orion VII buses,
all of which are in active use on the public transit route in question. The
measurement of these six different Orion VII buses yields a contact length along
the deformed edge of the tire between 9 and 11 inches (Figure 3), depending on
differences in tire inflation and tread status. The tire width consistently measures
to be 10 inches.
Figure 3: Tire Contact Geometry Measurement
3.3 Tire Contact Force
Based on calculations done in Appendix A, the tire contact pressure on the
ground is approximately between 0.313 and 0.383 MPa, assuming pressure is
exerted evenly across the tire contact area.
7
4.0 Injury Extent Analysis
This section discusses the extent of the injuries reported by the Medical
Records, analyses the injury profile depicted in the provided images, and names
the possible causes of each injury.
4.1
Sustained Injuries
Review of the provided medical documents and photographs indicate that the
victim’s injuries included:
1. A laceration on base of thumb
2. Numerous small abrasions on the palmar surface of the hand
3. Lost index nail with contusion of the nail bed of the 3rd and 4th digits
4. Fracture of the middle phalanges of the 2nd-5th digits
5. No fractures of the distal phalanges
4.2
Lost Nails
The injuries to the victim's nails are characteristic of a compressive
mechanism. A crush injury occurs when a compressive force is applied to the
tissues, although the tissues may actually experience a variety of forces, including
shearing [6]. The provided photographs show that there was a collection of blood
below the nails of the 3rd and 4th digits and that the nail of the index finger was
missing. These injuries occur when the nail bed is squeezed between the hard nail
and distal phalanx [1]. According to the hospital records, the nail on the victim's
index finger was missing upon arrival. This may indicate that it was pulled off
during the incident due to a shearing force.
8
4.3
Phalangeal Fractures
The victim sustained intra-articular fractures at the base of the
intermediate phalanges of the 2nd-5th digits. The fractures occurred at the
location of the proximal-interphalangeal (PIP) joints. From a review of the
victim's radiographs, these fractures occurred on the volar surface of the hand
(Figure 4). Specifically, there appears to be disruption along the volar plate with
small bone fragments characteristic of an avulsion mechanism [8].
Figure 4: Radiograph of the Victim's Hand with Fractures Indicated.
The observed fracture pattern is caused by axial loading across the PIP
joint and is typically associated with hyperextension of the PIP joint [8]. In
contrast, a true compressive fracture would likely feature a longitudinal fracture
or uniform comminution along the length of the bone. The injuries to the 2nd-5th
digits are also found directly at the insertion point for the muscle flexor digitorum
superficialis, and have a similar triangular breakage geometry. This hints at the
possibility of an avulsion being the cause of injury.
9
4.4
Abrasions and Lacerations
The victim had a large laceration at the base of their thumb in the
webspace between the thumb and index fingers. The laceration was likely caused
by tearing of the skin, as opposed to rupture or cutting. The skin is highly mobile
at that location, increasing the chance of tearing in any situation where the skin is
forcibly stretched. Tearing of the skin is commonly observed in crush injuries.
The victim also had numerous small cuts and abrasions on the palmar
surface of the fingers and hand. These could be the result of small stones and
debris on the road surface that were compressed into the skin. They may also have
been caused when the victim fell from the bus onto the sidewalk.
10
5.0 Injury Causation Analysis
This section discusses the most likely injuries that would be attained from the
three possible injury modalities thus far agreed upon. This will include an analysis
of falling, crushing, and hyperextension injury mechanisms. All information will
be attained through literature review or from testing done previously to this point.
5.1
Fall Analysis
The victim indicated that, upon exiting the bus onto the sidewalk, they
were caused to fall. The hospital records report that their injuries were related to a
fall on an outstretched hand ("FOOSH"). Extending the arms to brace for impact
is a well-known response in fall scenarios. In high-energy falls, this could result in
fractures of the wrist (specifically the scaphoid and distal radius) and injuries of
the elbow or shoulder. Hyperextension injury of the fingers would be unusual, and
unlikely in the absence of other fall trauma. Moreover, the victim's nail bed injury
would not be caused in this manner, assuming the victim fell with an open palm.
It is still likely that palmer abrasions were caused the hand’s impact with the
ground.
5.2
Crush due to Bus Weight
The second injury mechanism to be explored is crush or shearing damage
done by the weight of the bus. To achieve this “bone crushing fracture” effect, a
minimum compressive fracture stress of 103 MPa is necessary based on the
compressive strength of cortical bone [6] [9] [11]. From the results of calculations
done in Appendix A, the pressure on the victim's fingers would have been about
0.313 to 0.383 MPa. As such, the weight of the bus alone is be sufficient to cause
11
compressive fracture in this manner. Even taking into account the possibility of
over inflated tires and an uneven distribution of pressure exerted in the tire contact
area (all of which would increase the maximum pressure exerted by the tire on the
road), the pressure exerted the bus is far too low. For the same reason, it is also
impossible for a car running over a hand to cause a purely compressive fracture.
Finger nail loss is common in cases of excessive force exertion injuries, as
mentioned in Section 4.2. The combination of the moving tire and weight of the
rear end of the bus create a scenario with the capacity to create the shearing forces
needed to separate the nail from the nail bed. The compressive forces required to
crush or damage the nail bed are also present.
5.3
Entrapment/Hyperextension Injury
In events directly preceding the time of injury, the victim described lying on
the sidewalk with their hand on the ground while attempting to push themselves
up. In this position the PIP, metacarpophalangeal (MCP), and carpal (wrist) joints
of the victim’s right hand would all have been extended. Under these conditions a
retractile reflex would cause extreme hyperextension of the PIP joints. The
pressure created by the weight of the bus (combined with the friction between
skin, road asphalt, and tire rubber) would trap the victim’s fingers in place. With
the tire of the bus positioned over the distal and middle phalanges, a retractile
force would cause violent hyperextension of the PIP joints and the flexor
digitorum superficialis tendon as a result. This would result in the comminuted
intra-articular fractures at the base of the middle phalanges through axial loading
across the joint and avulsion of the flexor tendons.
12
The withdrawal reflex is not controlled consciously, and is intended to
protect the body from damaging stimuli. Arousal at the sight of danger, such as
the sight of your fingers under a bus tire, invokes an instinctive response to pull
the hand away. This response would be able to cause hyperextension at the PIP
joint if the fingers were trapped. This possible chain of events corroborate the
previous section, where it was noted that provided images of the fractures
sustained by the victim indicate the injuries caused through an avulsion fracture
mechanism.
This injury would not likely have occurred if the victim was not surprised
by the vehicle's presence on their hand. The fractures were likely the result of the
victim instinctively pulling their hand away. As we observed in the videos of
individuals willingly having their hands run over, they remained very still in order
to avoid injury [3] [10]. As such, the victim likely did not intend to have their hand
run over.
5.4
Other Possible Scenarios
Other typical scenarios could include crush injuries due to industrial
machinery or entrapment injury due to motor vehicle windows and doors.
Industrial equipment, such as rollers and presses, typically exhibit high
compressive forces. As such, the victim would likely have sustained true
compressive fractures to their fingers including involvement of the distal
phalanges, which was not observed. The high compressive forces associated with
industrial equipment would likely cause extensive injury to the blood vessels,
fascia and musculature which also did not occur. The victim was also not working
13
at the time, making their access to these types of equipment limited, and this
mode of injury unlikely.
Motor vehicles are also a common source of hand injury. Hyperextension
injury has been documented in power window entrapment [5]. If the victim caught
their hand in a window, the trapping force would be isolated to the middle
phalanges, and would not likely result in nail bed injury and abrasions over the
palm of the hand that was apparent. Similarly, entrapment in a car door could also
cause hyperextension fracture, but the high-energy associated with this event
would likely result in injuries of increased severity than was observed, and would
not likely result in abrasions to the underside of the hand.
5.5
Injury Mechanism Selection
The following decision matrix is unweighted, provides a +1 for every
satisfied criteria, and 0 for every unsatisfied criteria. This is because unfulfilled
criteria do not reduce an injury mechanisms feasibility, but does not reinforce it.
Table 2: Determination of Fracture Cause
Criteria
Not Proven
Impossible
Supported by
Literature
Supported by
Calculations
Total
Fall Injury
Crush Injury
Entrapment
Injury
1
1
1
0
0
1
0
0
1
+1
+1
+3
14
Table 3: Determination of Nail Injury Cause
Criteria
Not Proven
Impossible
Supported by
Literature
Supported by
Calculations
Total
Fall Injury
Crush Injury
Entrapment
Injury
1
1
1
0
1
0
0
0
0
+1
+2
+1
Table 4: Determination of Laceration and Abrasion Cause
Criteria
Not Proven
Impossible
Supported by
Literature
Supported by
Calculations
Total
Fall Injury
Crush Injury
Entrapment
Injury
1
1
1
0
0
0
0
0
1
+1
+1
+1
Based on information gathers from the following decision matrices, the
fracture injuries were most likely caused by an entrapment or hyperextension
injury, the nail loss was likely a result of compressive forces, and the lacerations
and abrasions could have happened at any point during this injury
15
6.0 Conclusions
Based on the information provided, literature resourced, and analysis
conducted in this report, the following conclusions have been drawn:
1. The injuries sustained by the victim are all possible in a “bus run-over”
scenario:
i.
The victim’s intra-articular fractures are consistent with a
hyperextension.
ii.
The victim’s lacerations and abrasions could be due to the fall,
force from the weight of the bus, or shearing from the movement
of the tire.
iii.
The victim’s lost fingernails are consistent with damage caused by
excessive applied downward force or shearing from the movement
of the tire.
2. The victim was likely surprised by the presence of the vehicle on their
hand, indicating they had no prior knowledge of their impending injury.
3.
Industrial machines or entrapment in other car areas are both not possible
methods of injury.
16
7.0 Recommendations
According to the conclusions made earlier, the following future
recommendations have been made. These recommendations will be made with
regards to the possibility of court preparation and accountability assignment:
1. Maintain that from the conclusions of this report, the public transit
organization in question cannot deny liability on the grounds that these
injuries could not have been caused by a bus.
2. Maintain that based on the conclusions of this report, the person could not
have been aware of the impending incident for the finger fractures to have
occurred.
3. Continue to search for further proof that these injuries could only have
been caused by a “bus run-over”
4. Investigate other common self-inflicted harm hand injury profiles to be
contrasted against those the victim sustained
17
8.0 References
[1]
Bharathi and Bajantri. “Nail bed injuries and deformities of nail.”, Indian J
Plast Surg., Vol 44(2), pp. 197–202, 2011 May-Aug
[2]
Bow, J., Lubinski, R., “The Orion VII”, Transit Toronto, July 21, 2014,
Available: http://transit.toronto.on.ca/bus/8522.shtml
[3]
Crushing Dreams CD, “My Favourite Busdriver Lady Driving Again Over My
Hand”, Youtube, August 7 2015, Available: https://www.youtube.com/
watch?v=IpCa_GPufpk
[4]
Freund D., Skorupski D., “Commercial Vehicle Safety Technologies:
Applications for Brake Performance Monitoring,” FMCSA Paper 090097.
[5]
Hohendorff et al., “Finger injuries caused by power-operated windows of motor
vehicles: An experimental cadaver study.”, Injury, Int. J. Care Injured 43,
pp. 903–907, 2012
[6]
Keller, T. S., et al., “Young’s Modulus, Bending Strength, and Tissue Physical
Properties of Human Compact Bone”, Journal of Orthopaedic Research,
Issue 8, pp.592-603, 1990.
[7]
Semer, N., “Practical Plastic Surgery for Nonsurgeons. Chapter 35: Hand
crush injury and compartment syndrome”, Henley & Belfaus,
Philadelphia, 2001
[8]
Seno, N. et al., “Fractures of the base of the middle phalanx of the finger.”, J
Bone Joint Surg [Br], Vol 79-B, pp. 758-763, 1997
[9]
Simkin, A., Robin, G., “The Mechanical Testing of Bone in Bending”, Journal
of Biomechanics, Vol 6 pp. 31-39, 1973.
[10]
Silly Strats2, “Bus Runs Over Mans Hands”, Youtube, September 15 2012,
Available: www.youtube.com/watch?v=woYuCIMtYSI
[11]
Turner, C. Wang, T., Burr, D., “Shear Strength and Fatigue Properties of
Human Cortical Bone Determined from Pure Shear Tests”, Calcified
Tissue International, Issue 69, pp. 373-378, 2001.
18
Appendix A: Bus Individual Tire Pressure Calculation
General Information:
Maximum Contact Area (AMAX)


A𝑀𝐴𝑋 = 11" × 10"
4 tires support each rear axle
Each tire has the road contact
profile shown above
A𝑀𝐴𝑋 = 110 𝑠𝑞𝑢𝑎𝑟𝑒 𝑖𝑛𝑐ℎ𝑒𝑠
A𝑀𝐴𝑋 = 0.070968 𝑚2
Single Tire Applied Force on Ground
Rear Axle Weight = 9067.3 kg
Maximum Pressure (PMAX)
𝐹𝑅𝑒𝑎𝑟 =
𝑔 × (𝑅𝑒𝑎𝑟 𝐴𝑥𝑙𝑒 𝑊𝑒𝑖𝑔ℎ𝑡)
4
P𝑀𝐴𝑋 =
𝐹𝑅𝑒𝑎𝑟
A𝑀𝐼𝑁
𝐹𝑅𝑒𝑎𝑟 =
9.81 × 9067.3
4
𝑃𝑀𝐴𝑋 =
22237.55
0.058064 𝑚2
𝐹𝑅𝑒𝑎𝑟 =
9.81 × 9067.3
4
𝑃𝑀𝐴𝑋 = 382983.49 𝑃𝑎 = 0.383 𝑀𝑃𝑎
𝐹𝑅𝑒𝑎𝑟 = 22237.55 𝑁/𝑇𝑖𝑟𝑒
Minimum Contact Area (AMIN)
A𝑀𝐼𝑁 = 9" × 10"
A𝑀𝐼𝑁 = 90 𝑠𝑞𝑢𝑎𝑟𝑒 𝑖𝑛𝑐ℎ𝑒𝑠
A𝑀𝐼𝑁 = 0.058064 𝑚2
Maximum Pressure (PMAX)
P𝑀𝐴𝑋 =
𝐹𝑅𝑒𝑎𝑟
A𝑀𝐴𝑋
𝑃𝑀𝐴𝑋 =
22237.55
0.070968 𝑚2
𝑃𝑀𝐴𝑋 = 313346.20 𝑃𝑎 = 0.313 𝑀𝑃𝑎
19