Combined Thoracic Injury (CTI)

Overview

Combined Thoracic Injury is an injury assessment metric that integrates chest deflection and chest acceleration to evaluate thoracic injury risk [1]. First proposed by Eppinger et al., this approach recognizes that neither deflection nor acceleration alone sufficiently predicts injury, but their combination improves correlation with rib fractures and soft tissue trauma [1]. It is often used in regulatory and research settings to assess restraint system performance and occupant safety in frontal crashes [2].

Inputs

Signals:

• Chest Deflection (X)
• Chest Acceleration (X, Y, and Z)

Calculation

Calculation from Eppinger et al. [1],

1. Filter the chest displacement (CFC = 600) and all chest accelerations (CFC = 180)
2. Calculate chest resultant with the filtered signals
3. Calculate maximum chest displacement
4. Calculate the 3ms Clip of the resultant chest acceleration
5. Calculate Criteria

$$\tag{Equation 1}CTI = \frac{A_{max}}{A_{int}} + \frac{D_{max}}{D_{int}}$$

$CTI = Combined\,Thoracic\,Injury$

$A_{max} = Maximum\,3\,ms\,clip\,of\,Resultant\,Chest\,Acceleration$

$A_{int} = CTI\,Acceleration\,Intercept$

$D_{max} = Maximum\,Chest\,Displacement$

$D_{int} = CTI\,Displacement\,Intercept$

Intercepts for CTI Calculation,

ATD	Chest Acceleration Intercept (g)	Chest Deflection Intercept (mm)
HIII - M95	83	114
HIII - M50	90	103
HIII - F05	90	84
HIII - 6yo	90	64
HIII - 3yo	74	57
CRABI - 12mo	57	50

Chest Deflection Measurement Sites [3]

Injury Criteria

ATD	Chest Acceleration Limit (g)	Chest Deflection Limit (mm)
HIII - M95	55	70
HIII - M50	60	63
HIII - F05	60	52
HIII - 6yo	60	40
HIII - 3yo	55	34
CRABI - 12mo	50	30

Limits for Chest Acceleration and Chest Deflection [3]

References

[1] Eppinger, Rolf, et al. "Development of improved injury criteria for the assessment of advanced automotive restraint systems." (1998).

[2] Eppinger, Rolf, et al. "Supplement: development of improved injury criteria for the assessment of advanced automotive restraint systems: Ii." (2000).

[3] Bandak, Faris, et al. "Development of improved injury criteria for the assessment of advanced automotive restraint systems: II." (1999).