# **Brain injuries:** *Does Severity, Sources, and Type of Injury vary for Distributed, Off-set, and Corner Frontal Impacts?*

## **Presenters:**

## **Raul Coimbra, MD, PhD, FACS, Principal Investigator** 

## **Steve Erwin, Crash Investigator** 

## **San Diego CIREN Center**

## 

## **March 2007 CIREN Public Meeting, Washington, DC**

# **Objectives**

## Address the magnitude of the brain injury problem 

## 

## Define Distributed, Off-set, and Corner frontal crashes

## 

## Present examples of frontal crashes, resulting in brain injury, investigated by CIREN

## 

## Compare brain injuries associated with specific frontal crashes using CIREN data

## 

# **Traumatic Brain Injury**

## 

## About 1.4 million people sustain a traumatic brain injury (TBI) every year

## 

## Almost 50,000 die annually and people with severe TBI may have long-term disability

## 

## Motor vehicle crashes are one of the leading causes of TBI severe enough to require hospitalization

## 

## Brain injuries are a compelling public health and motor vehicle safety problem and a treatment challenge for trauma surgeons and other medical care providers

## 

## 

# **Why Study Brain Injuries Using CIREN Data?**

## Crash tests assess safety system effectiveness and crashworthiness

## 

### Current Head Injury Criterion (HIC) used in crash tests is based only on linear acceleration

## 

## NHTSA : tests distributed frontal impacts

### 

## IIHS: tests off-set frontals 

## 

## Real world experience provides information on safety system effectiveness and crashworthiness for all types of frontal impacts (including corner)

## 

## 

# **Head Injury Criterion (HIC)**

## One of the "Injury Criterion Performance Limits" for testing vehicle safety

## 

## Used to provide a quantitative measure of head injury risk during motor vehicle crash tests

## 

## Based on average value for linear acceleration of the head's center of gravity during a crash 

## 

### Previously, set at "1000" for an adult mid-size male anthropomorphic dummy

### In 2000, set at "700" for a 15 millisecond crash

### Currently, possible changes for children (FMVSS 213)

### Currently, possible changes using a different brain model

# **Biomechanics of Brain Injury**

## Different cephalic components (brain, skull, arteries, nerves) have different physical features and anatomical structure

## 

## Rotational forces in addition to linear acceleration may cause brain injury 

## 

## Different regional and organ mechanisms of injury are associated with different types of brain injuries 

### Tissue "strain": Compression, shearing, tension

## 

## Mechanism of injury may differ for different components of the brain

#  

# 

# **Frontal Impact Definitions developed for Study**

# We developed definitions for different types of frontal impacts for the purposes of this study\-\--part of on-going work through our participation in the CIREN Research Committee which is developing standardized approaches to analyzing CIREN data

# 

# These examples illustrate the differences between "frontal" impacts and why we chose to stratify our analyses on these different types to see if brain injuries differed depending on the type of impact

# 

**Distributed Frontal Impact**

We used the Collision Deformation Classification (CDC) to define and
categorize frontal impacts---this example of a distributed frontal
impact is similar to the NCAP full frontal crash test used by NHTSA

PDOF (Principal Direction of Force) equal to 1, 11, or 12

The 3rd column (area of vehicle plane damaged) is Frontal

The 4th column is D for distributed across the frontal plane

The 6th column is W (at least 66% of frontal plane was damaged)

# **"Head-on" Distributed Frontal** 

# Comparable to the NHTSA NCAP Tests

# **["Head-on"]{.underline}** Example of head-on distributed frontal crashes

# Pink example is when vehicles are traveling the same traffic way but in Opposite Directions

# This has the potential for the highest energy crash and is comparable with crash testing

#  Both vehicles in this example have relatively straight pre-impact trajectories 

# 

# The blue example is still a head on frontal impact but results from a vehicle 'crossing the centerline'.

# 

# 

# **Off-set Frontal Impact**

# Example of an offset frontal impact

# Here, the PDOF and vehicle plane damaged is the same as the full frontal but there is only 35-65% of the vehicle front damaged and the damage is on the right or left side of the frontal plane

# This type of frontal impact may result in different occupant kinematics than a distributed frontal

# 

# 

# **'Head-on' Front Left Off-set Impacts**

# Comparable to IIHS Crash Tests (Drivers "Left" side)

# 

#  These are examples of "head on" off-set impacts\-\--the trajectory and crash scenarios are the same as for the full frontal impacts, but less of the vehicle frontal plane is damaged

# 

# This means less of the vehicle structure (especially the front frame rails) are going to absorb the energy of the crash

# 

# **Off-set Frontal Impact**

# Example of an offset frontal impact

# 

# Here, the PDOF and vehicle plane damaged is the same as the full frontal but there is only 35-65% of the vehicle front damaged and the damage is on the right or left side of the frontal plane

# 

# This type of frontal impact may result in different occupant kinematics than a distributed frontal

# 

**'Head-on' Front Left Off-set Impacts**

Comparable to IIHS Crash Tests (Drivers "Left" side)

These are examples of "head on" off-set impacts\-\--the trajectory and
crash scenarios are the same as for the full frontal impacts, but less
of the vehicle frontal plane is damaged

This means less of the vehicle structure (especially the front frame
rails) are going to absorb the energy of the crash

**'Head-on' Front Right Off-set (Passenger Side) Impacts**

These are two more examples showing off-set frontal impacts with the
passenger (right) side of the vehicle damaged

**Corner (Extreme Off-set) Frontal Impact**

The third type of frontal impact is the corner which can be thought of
as an extreme off-set impact

Again, the first 3 columns of the CDC are the same as for frontal and
off-set, but a narrower area of the frontal plane is damaged

There is greater potential for vehicle rotation after impact with this
type of crash and there may be different occupant kinematics

**Extreme Off-set (Left or Right) Impacts:**

Comparable with Narrow Rigid Object corner impacts

Again, here are the same some scenarios...showing head on frontal
impacts but only involving the corner of the vehicle. This type of
impact also can occur with a fixed object such as a pole or tree.

# **CIREN Investigations**

**Distributed Frontal Impact**

2000 Dodge Stratus, 4 door sedan, crossed center line and went off road
and struck large diameter tree

**Distributed Frontal Impact**

Brain injuries are sourced to steering wheel (through the airbag)\
20 year old female driver

Using safety belt and steering wheel air bag deployed

Right frontal and temporal lobe intraparenchymal hemorrhage

Right subarachnoid hemorrhage

Left mandibular fx

Right pulmonary contusion

Right subtalar dislocation

Right talar head and neck fx

Right cuneiform fx and metatarsal fx

**Off-set Frontal Impact**

This is an example of an off-set frontal crash in which our case vehicle
(large SUV) was struck by another vehicle which crossed the center line.
However, only part of the frontal plane of the case vehicle was damaged
in the impact.

2001-14

**Off-set Frontal Impact**

Front right seat passenger

34 year old female

Wearing safety belt

Front IP Air bag deployment

Right comminuted distal femur fx

Left acetabular fx

**Concussion and scalp lac**

She was sleeping. Not drinking. Brain injury sourced to right A pillar.
Also, had scalp lac.

**Corner Frontal Impact**

Finally, here is an example of a corner frontal impact...again our case
vehicle was struck head on by a vehicle which crossed the center line.
However, only the left (driver) side of our case vehicle was damaged.

Driver

35 year old male

Wearing safety belt

Steering wheel Air bag deployment

[Injuries]{.underline}:

**Left SAH**

**Left SDH**

Left tibial plateau fx

Shows more rotation after the impact occurs with a corner impact. Also,
may result in some lateral damage---more like a side impact for some
impacts (FLEE)

Brain Injuries sourced to non-contact.

2001-08

Co-morbidity: previously had surgery for brain tumor

Injuries: small subdural hematoma and subarachnoid hemorrhage

**CIREN Database**

##  Used to compare brain injury patterns for Distributed, Off-set, Corner frontal impacts

## 

## Severity

## Sources

## Types of brain injuries 

**Study Inclusion Criteria**

## AIS [\>]{.underline} 2 brain injury severity

### Scalp lacerations excluded

### Cranial nerve injuries excluded

### Secondary injury (e.g., compression) excluded

## First row drivers and outboard passengers

### Adults (\>13 years old)

## Frontal in-line impacts ranked #1

### Only Distributed, Off-set, Corner impacts

## 

### 

**Brain Injuries Studied**

## **Skull fractures**

### Vault, Base

### 

## **Focal Injury**

### **Hemorrhage**

#### Subdural

#### Epidural

#### Subarachnoid

#### Intracranial

### **Contusions/Lacerations**

#### Cerebrum (Frontal, temporal/parietal, occipital), cerebellum

### 

## **Diffuse Injury**

### Diffuse Axonal Injury (DAI)

### Concussion/Loss of Consciousness (LOC)

**Occupants with Brain Injury**

**418 Occupants**

**171 Distributed** - 95 (56%) Belted; 72 (43%) Not Belted

**177 Off-set** - 98 (55%) Belted; 79 (45%) Not Belted

**70 Corner** - 45 (65%) Belted; 24 (35%) Not Belted

Characteristics of Occupants with Brain Injury

+---------------------+-------------------+-------------+-------------+
| #                   | #                 | # *         | #           |
|                     |  **Distributed**  | *Off-set**  | **Corner**  |
+---------------------+-------------------+-------------+-------------+
| # *Age (years)*     | # * *             | # * *       | # * *       |
+---------------------+-------------------+-------------+-------------+
| #  Mean             | # 40              | # 40        | # 41        |
+---------------------+-------------------+-------------+-------------+
| #  Median           | # 37              | # 36        | # 35        |
+---------------------+-------------------+-------------+-------------+
| #  Range            | # 13 - 86         | # 13 - 85   | # 16 - 94   |
+---------------------+-------------------+-------------+-------------+
| # *delta V (kmph)*  | # * *             | # * *       | # * *       |
+---------------------+-------------------+-------------+-------------+
| #  Mean             | # 51              | # 49        | # 30        |
+---------------------+-------------------+-------------+-------------+
| #  Median           | # 47              | # 46        | # 25        |
+---------------------+-------------------+-------------+-------------+
| #  Range            | # 15 - 137        | # 12 - 126  | # 12 - 94   |
+---------------------+-------------------+-------------+-------------+
| #                   | # 56.2%           | # 55.4%     | # 65.2%     |
|  *Safety belt used* |                   |             |             |
+---------------------+-------------------+-------------+-------------+
| # *                 | #  94%            | #  96%      | #  96%      |
| Front bag deployed* |                   |             |             |
+---------------------+-------------------+-------------+-------------+
| # *Male*            | # 49.4%           | # 57.5%     | # 64.7%     |
+---------------------+-------------------+-------------+-------------+
| # *Driver*          | # 81.9%           | # 85.3%     | # 87.1%     |
+---------------------+-------------------+-------------+-------------+

# 

# 

# **Graph Summary**

The next slide shows the type of brain injury (Concussion/LOC, artery,
hemorrhage, DAI, Contusions, Lacerations, Fractures) stratified by
whether the occupant is wearing a safety belt for each impact type
studied (Distributed, Off-set, Corner). There are no statistically
significant differences. There are some differences by safety belt
status within each of the impact types. There were fewer differences by
restraint status within the corner impacts.

The percent of fractures ranges from about 10-15% of injuries within
each impact category, regardless of safety belt status. Lacerations
account for less than 5% within each impact category, regardless of
safety belt status. Contusions vary slightly with more contusions (about
16% in the corner impact for both unrestrained and restrained
occupants), compared to about 12% in the off-set impacts (for both
unrestrained and restrained). For distributed frontal impacts, there
were 10 (restrained) to 12% (unrestrained). Only about 2-4% of brain
injuries for all impact categories, regardless of safety belt status,
were DAI. Hemorrhages accounted for 20-30% for each impact category,
regardless of safety belt status. For belted occupants in corner
impacts, there was more hemorrhage. There were very few arterial
injuries in each of the categories. Concussions and Loss of
Consciousness (LOC) accounted for most of the brain injuries for each
impact type; there were more concussions/LOC in restrained occupants for
distributed and off-set impacts. For corner impacts, when occupants were
not wearing a restraint there was less severe injury (i.e., concussions)
and more contusions for those in Distributed and off-set frontal
impacts.

# 

# **Graph Summary**

This slide shows the severity of brain injury (based on the Glasgow Coma
Scale (GCS)) for each impact type (Distributed, Off-set, Corner). There
were no significant differences, but for off-set and corner impacts,
occupants wearing safety belts had a smaller proportion of severe injury
(GCS 3-8). Most occupants in each of the impact categories, regardless
of restraint use had mild brain injury (GCS 13-15). For restrained
occupants in distributed impacts, about 70% were mild, only about 4%
were moderate, and about 25% had severe brain injury. The pattern was
similar for those in distributed impacts who were not wearing safety
belts but there were more occupants with moderate (GCS 9-12) brain
injury and fewer with mild or severe brain injury. Almost 80% of
restrained occupants in off-set impacts had mild brain injury compared
to 60% if not restrained. Again, restrained occupants in corner impacts
had more mild brain injury (about 70%) compared to about 55% for
unrestrained occupants.

# **Graph Summary**

# 

This slide shows severity of brain injury based on the AIS for each
impact type (distributed, off-set, corner). It is the maximum severity
brain injury sustained. AIS 3 and 4 injuries are the most clinically
relevant. The mean AIS for the brain injury by type of impact are
similar regardless of restraint use. About 50-60% of all brain injuries
were moderate (AIS 2), about 20-30% were serious (AIS 3), 5-15% were
severe (AIS 4), about 10% were critical (AIS 5) for each impact
category, regardless of restraint status. There were a few AIS 6
(maximum) brain injuries in each of the categories except unrestrained
occupants in corner impacts. There were no statistically significant
differences.

# **Graph Summary**

This slide compares the proportion of occupants with only skull
fractures compared to those with intracranial brain injury without skull
fracture and those with both for each impact category (distributed,
off-set, corner). Regardless of impact type and restraint status, only
about 1-10% in each category had a fracture. The majority (70-90%) of
occupants only had intracranial injuries. There were no statistically
significant differences.

# **Graph Summary**

This slide shows the proportion of focal brain injury compared to
diffuse brain injury for each type of impact (distributed, off-set,
corner), stratified by restraint use. There is a similar pattern for
each type of impact although there are proportionally more diffuse brain
injuries if the occupant is wearing a safety belt except in corner
impacts. For corner impacts, there is more diffuse brain injury in
unrestrained occupants. About 30-50% of occupants in each category had
focal injuries. About 40-55% of occupants in each category had diffuse
brain injury. Fractures were included as a separate category and about
10-15% in each category had a skull fracture. There were no
statistically significant differences.

# **Graph Summary**

This slide shows the proportional distribution of different types of
hemorrhage (intracranial, epidural, subdural, subarachnoid) by impact
category (distributed, off-set, corner), stratified by restraint use.
Although the type of hemorrhage varies proportionally, there is no
significant difference. The most severe hemorrhage (intracranial) occurs
proportionally more often in the corner impacts. The majority of
hemorrhage for all impact types, regardless of restraint status is
subarachnoid, accounting for about 65-50% of hemorrhages. The only
category with epidural hemorrhage was the off-set impacts for
unrestrained occupants. Subdural hematomas accounted for 30-40% of
hemorrhages, regardless of impact type and restraint use status.

# **Graph Summary**

This slide shows that for each type of impact (distributed, off-set,
corner), if you are wearing a safety belt, you are less likely to have
"hard" contact with the windshield, instrument panel, roof, or roof
rails resulting in injury. Wearing safety belts prevent injury by
preventing the occupant from contacting the vehicle interior. The
pattern for "soft" contacts with the air bag is less clear. About 10-30%
of occupants in each impact category had air bag related injury.
Statistically, occupants are more likely to have air bag related brain
injury from distributed and off-set impacts compared to corner impacts.
Pillars were a source of injury in about 5-12% of all impacts,
regardless of safety belt status. However, although not significantly
different, there was less impact with pillars for restrained occupants
in each impact group compared to unrestrained occupants. This pattern
also occurred for roof and roof rail contact, although the proportion
was higher (ranging from about 5-20%). Contact with windows (including
glass, sill, and frame) accounted for about 4-15%) of injuries for each
type of impact. The steering wheel resulted in proportionally more brain
injuries in distributed and off-set impacts compared to corner impacts.
Restrained occupants within each impact category had proportionally more
steering wheel related injury compared to unrestrained occupants.
Unrestrained occupants in each category had more contact with the
windshield or instrument panel, resulting in injury.

# 

# 

# 

**Conclusions**

## Restraint use (wearing safety belt) may influence sources of brain injuries for all types of frontal impacts studied

## 

### Restrained: More non-contact brain injuries

### Unrestrained: More hard-contact brain injuries caused by roof, roof rails, windshield, instrument panel

### 

## Corner impacts may have different sources of injury (more hard contact with the windshield and instrument panel) compared to distributed and off-set frontal impacts (more soft contact air bag related brain injuries)

## 

## Brain injuries from corner impacts were more severe (based on GCS and more intracranial hemorrhage)

## 

## Suggests head model incorporating angular acceleration may be important for crash testing

### 

## Supports use of CIREN data and "real world" crash investigations to study brain injuries 

# **San Diego CIREN Team**

## **[Principal Investigators]{.underline}**

## 

## Raul Coimbra, MD, PhD, FACS (University of California at San Diego)

## Gail T. Tominaga, MD, FACS (Scripps Memorial Hospital, La Jolla)

## 

## **[Team]{.underline}**

## 

## Sharon Pacyna, RN, BSN, MPH 

## Steve Erwin

## Carol Conroy, MPH, PhD

## MarSue May, RN, BSN

## Barbara Frasier 

# 

# 

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