Session IV - Spine
Fri., 10/8/04 Spine & Pelvis, Paper #24, 4:14 pm
The Effect of an Airbag on Prevention of Injury to the Cervical Spine and Spinal Cord in Motor Vehicle Accidents
Purpose: The requirement for automobile airbags was initiated in 1987 under Federal Motor Vehicle Safety standard 208, and by 1994, 91% of new cars were equipped with driver's-side airbags. The purpose of this study was to determine the role of automobile air bags in preventing cervical spine injury and to describe the distribution of spinal injuries sustained in motor vehicle accidents in patients in four groups: airbag plus seatbelt, airbag only, seatbelt only, and no restraint.
Methods: Information on patients who sustained a spinal injury in a motor vehicle accident between 1990 and 2002 was obtained from the Pennsylvania Trauma Systems Foundation in Mechanicsburg, Pennsylvania. The patient data evaluated for this report consisted of patient age, sex, race, position in car, mechanism of collision, number of hospital days, and number of intensive care unit days, Glasgow coma scale (GCS), injury severity scores (ISS), and the ICD-9 codes defining the patients' injuries. On the basis of the ICD-9 codes, spinal injuries were defined as fractures only, spinal cord injury only, fracture with spinal cord injury, or spinal root injury. The means of continuous variables were compared by general linear modeling techniques, and logistic regression techniques were used to calculate the odds ratio of spinal injuries in all groups relative to the air bag with seat belt group.
Results: During the study period, 86,959 patients were entered into the trauma database as a result of automobile accidents. Out of this pool of patients, 12,678 patients had a spinal injury. Of these, 5,506 sustained an injury of the cervical spine involving fracture, spinal cord injury, or both; 203 of these patients were using an airbag and seat belt at the time of the accident, 187 were using an airbag only, 1658 were restrained only by seatbelts, and 3458 had no protective device. Drivers accounted for 175 of the patients who used an airbag and a seatbelt, 166 who used an airbag only, 1153 who used a seatbelt only, and 2370 of those unrestrained. Of all patients (drivers) with a spinal injury, 42.1% who used an airbag and seatbelt had a cervical spine fracture, 4.8% had a cervical spine fracture and spinal cord injury, and 6.2% had a spinal cord injury alone. Drivers who used an airbag alone had fractures of the cervical spine in 54.1%, a fracture and spinal cord injury in 5.2%, and a spinal cord injury alone in 13.7%. The differences between airbag alone and airbag plus seatbelt for cervical fractures and spinal cord injury alone were significant (P <0.05). Drivers protected by a seatbelt alone had cervical fractures in 42.6%, a cervical fracture and spinal cord injury in 5.3%, and a spinal cord injury alone in 7.2%. Unrestrained drivers had cervical fractures in 47.0%, a cervical fracture and spinal cord injury in 9.6% and a spinal cord injury alone in 7.0%. Significant differences (P <0.05) were seen between the airbag only group, the seatbelt only group, and the unrestrained group for spinal cord injury only. The unrestrained group was significantly different (P <0.05) from the other three groups for fracture with spinal cord injury and for cervical fracture alone. Multivariate logistic regression showed drivers using an airbag alone were 1.7 times more likely (1.2, 2.3, 95% CI) to suffer a cervical spine fracture than drivers restrained with an airbag and a seatbelt. Drivers using an airbag alone were 2.4 times (1.43, 4.02, 95% CI) more likely to sustain a spinal cord injury than those using an airbag and seatbelt. Unrestrained drivers were 1.32 times more likely (1.1, 1.6, 95% CI) to suffer a cervical spine fracture and 1.8 times (1.14, 2.87, 95% CI) more likely to have a cervical spine fracture with spinal cord injury than those protected with an airbag and a seatbelt.
Passengers (front seat) showed similar trends in significant associations across the four protective categories, and significant differences were also seen in age and sex categories for both drivers and passengers. Additionally, ISS and GCS scores as well as intensive care unit and total hospital days were significantly different for drivers and passengers across the four protective categories.
Conclusions/Significance: In this study, the effectiveness of automobile restraints was studied by comparing four different categories of protection and the spinal injuries sustained by patients admitted to 26 accredited trauma centers in Pennsylvania. The most striking differences were found in the group of patients who were restrained with only an airbag. These patients had 140% more spinal cord injuries than the group protected with both an airbag and a seatbelt. They also had 69% more cervical fractures and had more ICU and total hospital days than those protected with an airbag and a seatbelt. From this data, it appears that the combination of an airbag with a seatbelt is effective in reducing the chance of cervical spine fracture and spinal cord injury for patients involved in motor vehicle accidents.