SLIDE 1:
Inova Regional Trauma Center

Inova Fairfax Hospital
Falls Church, VA



SLIDE 2:
Honda Inova Fairfax Honda Inova Fairfax Hospital CIREN Team


SLIDE 3:
Non Ankle Lower extremity Fractures in Frontal Crashes: The 
importance of Occupant Height and Vehicle Type


SLIDE 4:
Team Members:
 * Samir M. Fakhry, MD, Principal Investigator
 * Dorraine D. Watts, PhD, RN, Principal Investigator
 * Refaat Hanna, M.D., M.A., Epidemiologist
 * James D. Bean, Crash Reconstructionist
 * Christine Burke, CIREN Study Coordinator
 * Christopher Sherwood, Auto Safety Lab, University of VA
 * Capt. Christine Woodard, Fairfax County Fire and Rescue
 * Detective J.J. Banachoski, Fairfax County Police CRU


SLIDE 5:
Non-Ankle Lower Extremity Fracture (NALEF) 
Lower Extremity Regions under study:
 1-Pelvis/Hip
 2-Femur
 3-Knee/Patella
 4-Tibia/Fibula


SLIDE 6:
Research Questions??

 * Does the drivers height play a role in NALEF injuries?

 * Does the vehicle type play a role in the type of NALEF injury?


SLIDE 7:
Selection Criteria
 Age: > 16 Years
 Vehicle Make Year: > 1996
 Role: Belted Drivers Only
 PDOF: 11  1 Oclock
 No Ejection
 No Rollover
 No Fire
 AIS > 2
 The Vehicle types included in the study are:
 a) Passenger Cars 
 b) SUV/Light Trucks


SLIDE 8:
SAMPLE SIZE

1- NASS Data
	613 cases met the selection criteria in NASS data
	473 cases in passenger cars
	 140 cases in SUV/Light Trucks

2- CIREN Data
	233 cases met the selection criteria in CIREN data
	175 cases in passenger cars
	58 in SUV/Light Trucks


SLIDE 9:
Binary Logistic Regression
 
Logistic regression is useful for situations in which we want to be able to predict the presence or absence of a characteristic or outcome based on values of a set of predictor variables. It is similar to a linear regression model but is suited to models where the dependent variable is dichotomous. Logistic regression coefficients can be used to estimate odds ratios (OR) for each of the independent variables in the model.


SLIDE 10:
Variables Tested
Vehicle Type
 (Passenger Cars Vs. SUV/Light Trucks)
Height
 (3 categories < 65 Inch, 65 to 69 Inch & > 69 Inch)

Reference Values
 Vehicle type: Passenger Cars
 Height: < 65 Inch




SLIDE 11:
Individual Analysis of Different Components of Non Ankle Lower Extremity Fractures


SLIDE 12:
 Pelvic/Hip Fracture
 CIREN Data Analysis

Passenger Cars
Drivers height played a significant role in Hip/Pelvic fractures
 
 OR =2.06 < 65 Inch : 65-69 Inch 
	P = 0.165
 OR = 1.88 < 65 Inch : > 69 Inch
 P = 0.154


SUV/Light Trucks: 

Drivers height did not play a significant role in Hip/Pelvic fractures

OR= 0.714 65-69 : > 69 Inch
 P = 0.683


Drivers > 69 inch are less likely to sustain Pelvic/Hip fractures in SUV/Light Trucks than in Passenger Cars

OR=0.385 SUV/Light Trucks : Passenger Cars P = 0.171

P value is considered statistically significant if < 0.05 


SLIDE 13:
	 Pelvic/Hip Fracture
	NASS Data Analysis

Passenger Cars

Drivers height played a significant role in Hip/Pelvic fractures
 
 OR=2.70 < 65 Inch : 65 to 69 Inch
 P = 0.027
 OR = 1.75 < 65 Inch : > 69 Inch 
 P = 0.126


SUV/Light Trucks

Drivers height did not play a significant role in Hip/Pelvic fractures

OR = 1.37 65 to 69 : > 69 Inch
 P = 0.599

Drivers > 69 inch are less likely to sustain Pelvic/Hip fractures in 
SUV/Light Trucks than in Passenger Cars

OR= 0.904 SUV/Light Trucks : Passenger Cars P = 0.827

P value is considered statistically significant if < 0.05 


SLIDE 14:
 Femur Fracture
 CIREN Data Analysis

Passenger Cars

Drivers height played a significant role in Femur fractures
 
 OR = 2.28 < 65 Inch : 65 to 69 Inch
 P = 0.075
 OR = 2.31 < 65 Inch : > 69 Inch
 P = 0.037



SUV/Light Trucks
Drivers height did not play a significant role in Femur fractures


OR = 0.639 65 to 69 : > 69 Inch
 P = 0.507


Drivers > 69 inch are less likely to sustain Femur fractures in SUV/Light Trucks than in Passenger Cars
OR = 0.416 SUV/Light Trucks : Passenger Cars P = 0.131

P value is considered statistically significant if < 0.05 


SLIDE 15:
Femur Fracture 
NASS Data Analysis

Passenger Cars

Drivers height played a significant role in Femur fractures
 
 OR = 2.29 < 65 Inch : 65 to 69 Inch
 P = 0.075
 OR = 1.65 < 65 Inch : > 69 Inch
 P = 0.154



SUV/Light Trucks

Drivers height did not play a significant role in Femur fractures


OR = 0.436 < 65 to 65 to 69 Inch
 P = 0.386
OR = 0.382 <65 to > 69 Inch
 P = 0.191


Drivers > 69 inch are less likely to sustain Femur fractures in SUV/Light Trucks than in Passenger Cars
OR = 0.288 SUV/Light Trucks : Passenger Cars P = 0.054

P value is considered statistically significant if < 0.05 



SLIDE 16:
 
Passenger Cars

Taller drivers were less likely to sustain Knee/Patella fractures than shorter drivers
(The results are statistically insignificant)

 OR = 0.777 65 to 69 : < 65 Inch : Inch
 P = 0.674
 OR = 0.963 > 69 : < 65 Inch Inch
 P = 0.945



SUV/Light Trucks

Taller drivers were less likely to sustain Knee/Patella fractures than shorter drivers

OR = 0.818 65 to 69 : < 65 Inch
 P = 0.876
 OR = 0.221 > 69 : < 65 Inch 
 P = 0.081




SLIDE 17:
Knee/Patella
CIREN Data Analysis

Drivers < 65 inch are more likely to sustain Knee/Patella fractures in SUV/Light Trucks than in Passenger Cars
OR = 1.615 Passenger Cars : SUV/Light Trucks P = 0.672

 -------

Drivers 65 to 69 inch are less likely to sustain Knee/Patella fractures in SUV/Light Trucks than in Passenger Cars
OR = 0.352 SUV/Light Trucks : Passenger Cars P = 0.063

 -------

Drivers > 69 inch are more likely to sustain Knee/Patella fractures in SUV/Light Trucks than in Passenger Cars
OR = 1.535 Passenger Cars : SUV/Light Trucks P = 0.617






SLIDE 18:
Passenger Cars

 Taller drivers were less likely to
 sustain Knee/Patella fractures than
 shorter drivers
(The results are statistically insignificant)
OR = 0.993 > 69 : < 65 Inch 
 P = 0.983

 Drivers 65 to 69 inch were more likely to sustain Knee/Patella fractures than those < 65 inch
 OR:- 65 to 69 : < 65 Inch : Inch 1.59
 P : 0.236



SUV/Light Trucks
Taller drivers were more likely to sustain Knee/Patella fractures than shorter drivers


OR = 0.2.33 < 65 : 65 to 69 Inch
 P = 0.443

 OR = 2.05 > 69 : < 65 Inch 
 P = 0.316



SLIDE 19:
Knee/Patella
NASS Data Analysis


Drivers < 65 inch are less likely to sustain Knee/Patella fractures in 
SUV/Light Trucks than in Passenger Cars
OR = .529 Passenger Cars : SUV/Light Trucks P = 0.552

 -------

Drivers 65 to 69 inch are less likely to sustain Knee/Patella fractures in 
SUV/Light Trucks than in Passenger Cars
OR = 0.374 SUV/Light Trucks : Passenger Cars P = 0.119

 -------

 Drivers > 69 inch are less likely to sustain Knee/Patella fractures in 
SUV/Light Trucks than in Passenger Cars
OR = 775 Passenger Cars : SUV/Light Trucks . P = 0.597


 
Passenger Cars

 Taller drivers were less likely to
 sustain Tibia/Fibula fractures than
 shorter drivers
 OR = 0.528 65 to 69 : < 65 Inch
 P = 0.148

 OR = 0.607 > 69 : < 65 Inch Inch
 P = 0.210


SUV/Light Trucks

Drivers 65 to 69 inch were less likely to sustain Tibia/Fibula fractures than shorter drivers

OR = 0.618 65 to 69 : < 65 Inch
 P = 0.540
 
There was no relationship between Tibia/Fibula fracture and height > 69 inch

OR = 1.000 , P = 1.00 






SLIDE 20:
Tibia/Fibula
CIREN Data Analysis

Drivers < 65 inch are more likely to sustain Tibia/Fibula fractures in 
Passenger Cars than SUV/Light Trucks 
OR = 0.947 SUV/Light Trucks : Passenger Cars P = 0.939

 -------

Drivers 65 to 69 inch are more likely to sustain Tibia/Fibula fractures in 
in Passenger Cars than SUV/Light Trucks
OR = 0.673 SUV/Light Trucks : Passenger Cars P = 0.433

 -------

 Drivers > 69 inch are more likely to sustain Tibia/Fibula fractures in 
SUV/Light Trucks than in Passenger Cars 
OR = 1.109 Passenger Cars : SUV/Light Trucks P = 0.852


SLIDE 21:
Tibia/Fibula
NASS Data Analysis

Passenger Cars

Taller drivers were less likely to sustain Tibia/Fibula fractures than shorter drivers
 OR = 0.569 65 to 69 : < 65 Inch 
 P = 0.099

 OR = 0.456 > 69 : < 65 Inch 
 P = 0.013


SUV/Light Trucks
Drivers 65 to 69 inch were less likely to sustain Tibia/Fibula fractures than shorter drivers

OR = 0.571 65 to 69 : < 65 Inch
 P = 0.539
 
Drivers > 69 inch were more likely to sustain Tibia/Fibula fracture than drivers < 65 inch

OR = 1.071 65 to 69 : < 65 Inch 
 P = 0.930



SLIDE 22:
Tibia/Fibula
NASS Data Analysis

Passenger Cars

 Taller drivers were less likely to
 sustain Tibia/Fibula fractures than
 shorter drivers
 OR = 0.569 65 to 69 : < 65 Inch 
 P = 0.099

 OR = 0.456 > 69 : < 65 Inch 
 P = 0.013



SUV/Light Trucks

Drivers 65 to 69 inch were less likely to sustain Tibia/Fibula fractures than shorter drivers

OR = 0.571 65 to 69 : < 65 Inch
 P = 0.539
 
Drivers > 69 inch were more likely to sustain Tibia/Fibula fracture than drivers < 65 inch

OR = 1.071 65 to 69 : < 65 Inch 
 P = 0.930




SLIDE 23:

Tibia/Fibula
NASS Data Analysis

Drivers < 65 inch are more likely to sustain Tibia/Fibula fractures in Passenger Cars than SUV/Light Trucks 

OR = 0.435 SUV/Light Trucks : Passenger Cars P = 0.286

 -------

Drivers 65 to 69 inch are more likely to sustain Tibia/Fibula fractures in 
in Passenger Cars than in SUV/Light Trucks
OR = 0.186 SUV/Light Trucks : Passenger Cars P = 0.007

 -------

Drivers > 69 inch are more likely to sustain Tibia/Fibula fractures in in Passenger Cars than in SUV/Light Trucks 
OR = 0.438 SUV/Light Trucks : Passenger Cars P = 0.157


SLIDE 24:
Attributable Source of NALEF Injuries
Belted Drivers - CIREN Data Analysis

Source of Injury / Percent

* knee bolster = 40%
* floor (incl. toe pan) = 24%
* left instrument panel and below = 13%
* left side interior surface. excl. hardware/armrest = 9%
* foot control incl. parking brake = 4%
* other = 9%
TOTAL	= 100%




SLIDES 25-26:
Attributable Source of NALEF Injuries

Belted Drivers In Passenger Cars 
Belted Drivers In SUV/Light Trucks 

CIREN Data Analysis

[charts - illegible]


SLIDE 27:
Biomechanics

Role of Knee Bolster
In Non-Ankle Lower Extremity Injuries


SLIDE 28:
KNEE BOLSTER
* Control Occupant Kinematics in Frontal Crash
* Distribute Lower Extremity Contact Loads
* Absorb Occupant Energy through a Body Region Capable of Accepting Restraining Forces

Knee trajectories assuming a hypothetical heel point displacement, toepan rotation, and depression of the H-point. Aorrows indicated 90 deg. Leg angle open circles indicate intersection of hypothetical bolster profile with knee contact trajectory


SLIDE 29:
Lower Extremity Injury Research
	Bolster stiffness
	Knee flexion angle
	Gender
	Belt use
	Pre-impact bracing
	Intrusion


SLIDE 30:
Risk of Lower Limb Injury

Geometry
	Occupant (Lower Extremity)
	Vehicle (Knee Bolster, Seat)



SLIDE 31:
THIGH-KNEE LOADING
#1 Loading axial to the thigh: potential injury to the knee-thigh-hip complex

Inertial motion causes contact with instrument panel/knee bolster


#2 Loading axial to the leg: potential injury to the knee-leg-ankle complex

Entrapment between IP and floor pan


#3 Loading axial to the entire lower extremity: potential injury to all structures

Floor pan intrusion



SLIDE 32:
Seating Position

University of Michigan Transportation Research Institute (UMTRI) (1996-2001)
 - Anthropometric measurements of drivers
 - Dummy Positioning Model (vehicle parameters)
 - 5th Female  4 11 (59, 151 cm)
 - 50th Male  5 9 (69, 175 cm)
 - 95th Male  6 2 (74, 187 cm)

Insurance Institute for Highway Safety (IIHS) Tests
 - Nissan Titan
 - Nissan Maxima



SLIDE 33:
Lower Extremity Position  Nissan Maxima


SLIDE 34: 
Lower Extremity Position  Nissan Titan



SLIDE 35:
Estimating kinematics

Estimate lower extremity positions at time of contact with bolster (Culver & Viano, 1979)
 - Stationary ankle position
 - H-Point moved horizontally until contact with bolster



SLIDE 36:
Titan bolster/Titan seating position 
 vs. 
Maxima bolster/Maxima seating position

SLIDE 37:
50th Male [line drawing] Knee Contact
Knee more flexed in Pass. Car

Titan bolster/Titan seating position 
 vs. 
Maxima bolster/Maxima seating position



SLIDE 38:
95th Male [line drawing] Tibia contact

Femur more horizontal in SUV

Titan bolster/Titan seating position 
 vs. 
Maxima bolster/Maxima seating position



SLIDE 39:
[bar charts]
Tibia/Fibula fractures more likely in passenger cars


SLIDE 40:
Possible reasons for increased Tib/Fib injury risk in Passenger Cars

Knee flexion angle, bolster resistive force

Increased distance from bolster (also increased knee/patella risk)


SLIDE 41:
Femur and Pelvis/Hip risk increases for taller occupants
(Pass Cars) [bar chart - illegible]

Tibia/Fib risk decreases for taller occupants
(Pass Cars) [bar chart - illegible]


SLIDE 42:
Possible reason for decreased Tib/Fib injury risk for taller occupants

Bolster contact below knee

Tibia fractures due to compression more than bending


SLIDE 43:
Summary

Preliminary analysis of lower extremity kinematics
 - Occupant Height
	Initial distance to bolster
	Anatomic location of bolster contact

 - Vehicle Type
	Initial distance to bolster
	Femur angle
	Knee flexion angle

May explain some differences in injury patterns



SLIDE 44:
CONCLUSIONS
* The interactions between Driver Height and Vehicle Type play a significant role in the incidence of NALEF injuries

* Eighty-two percent of NALEF injuries are attributable to the Knee Bolster and adjacent areas (Left Instrument Panel, Toe Pan, Foot Control Including Parking Brake)

* Data from CIREN are consistent with data from NASS in most of the analyses presented


SLIDE 45:
RECOMMENDATIONS
Analyses of the bio-mechanics of car crashes may be of great value in pre-hospital screening for NALEF injuries
These observations should be considered by health care providers at the crash scene to better manage injured drivers during extrication
Educational efforts based on these findings may be an effective tool for injury prevention
The relationship of NALEF injuries and vehicle design require further investigation