A radiographic and physical analysis of factors affecting seat belt position in sitting car seat

Abstract

The characteristic subcutaneous hemorrhage along the seat belt in motor vehicle accidents is called the seat belt sign (SBS). The risk of organ injuries is especially high when abdominal SBS is located above the anterior superior iliac spine (ASIS). The purpose of this study analyzed the physical and radiographic factors of healthy volunteers sit on car seat that affect initial position of abdominal seat belt, namely “lap belt”, related to the seat belt injury. This study was examined prospectively relation between physical characteristics of one hundred healthy volunteers and lap belt position sitting the car seat. Physical findings were clarified age, sex, height, body mass index (BMI), and waist circumference. Radiographical findings were measured lumber lordosis (LL), sacral slope (SS), and initial lap belt position by marking with lead tape for the center and ASIS of the lap belt installed on the driver’s car seat. In the lateral X-ray image, we measured the horizontal distance (X-value) and vertical distance (Z-value) from the ASIS to the central marker. The lap belt angle was determined to measure the angle between the horizontal line and the straight line connecting the upper edges of the markers. Statistical analysis of the relationships between physical characteristics and radiological findings was performed. X-value and Z-value were positively correlated with body weight, BMI, and waist circumference, while the lap belt angle was negatively correlated with body weight, BMI, and waist circumference. The relationship between physical characteristics and the initial position of seat belt was analyzed. Since the lap belt is positioned higher than the ASIS in occupants with a high BMI, it is likely to cause seat belt injury. This analysis can help to develop safer seat belts and to enlighten car occupants.

Variability in Body Shape, Superficial Soft Tissue Geometry, and Seatbelt Fit Relative to the Pelvis in Automotive Postures—Methods for Volunteer Data Collection With Open Magnetic Resonance Imaging

“…This protocol provides detailed 3D visualization of the external body shape, skeletal position, adipose tissue geometry (both superficial and visceral), organ geometry (including the major vasculature such as the aorta), and belt fit relative to the skeleton-effectively providing an anatomic atlas for each volunteer from the pelvis to the upper torso. While such detailed anatomical information is readily available for supine postures, there are few (if any) studies that have attempted to gather this depth of information in realistic automotive postures [17][18][19]. Recent approaches with upright CT scans, while valuable in their own right, were limited in the postures that they could attain by the geometric constraints of the CT scanner (effectively requiring the volunteers to sit with an erect posture [19]).…”

“…Recent approaches with upright CT scans, while valuable in their own right, were limited in the postures that they could attain by the geometric constraints of the CT scanner (effectively requiring the volunteers to sit with an erect posture [19]). Similarly, though X-Ray-based approaches provide great flexibility in posture, they are limited to capturing a two-dimensional planar image, often with limited fidelity to discern distinct tissues [17,18]. The Open MRI approach provides an ability to capture high fidelity, 3D information, including fine detail on distinct tissues.…”

“…Others have complemented this work using various radiology tools to directly observe skeletal posture and belt fit. This has included volunteer studies using planar X-ray [17,18] and computed tomography (CT) [19]. While each method provides valuable increments of information, each also carries its own limitations.…”

“…While each method provides valuable increments of information, each also carries its own limitations. The studies using planar X-ray are limited to twodimensional views of belt fit relative to the skeleton [17,18]. The recent study with upright CT was limited in the postures that they could study, where the "seated" posture was more upright than a typical automotive posture due to the geometric constraints of the upright CT [19].…”