Redefining the abdominal seatbelt sign: Enhanced CT imaging metrics improve injury prediction.

INTRODUCTION

The abdominal seatbelt sign (ASBS) has an established association with abdominal injury, yet its definition remains ill-defined. We hypothesize specific imaging characteristics associated with the ASBS such as location above the pelvic brim and depth of abdominal wall contusion would better predict underlying injury and need for operative intervention.

METHODS

We performed a retrospective chart review of subjects suffering from restrained motor vehicle collisions (MVC) evaluated at a level one trauma facility from 2010 to 2015. CT imaging was reviewed for the presence of a transverse abdominal wall contusion consistent with lap belt use. Contusion location was determined in relation to the anterior superior iliac spine (ASIS). Abdominal wall thickness as well as contusion depth were measured at the contusion level and an abdominal seatbelt sign depth index (ASBSI) was calculated.

RESULTS

Sample size for the cohort was 551 subjects. Operative need was 19.73% in those with ASBS on CT (CT ASBS) above the ASIS and 4.05% (p-value < 0.01) in those with only clinical evidence of ASBS (CL ASBS). CT ASBS above the ASIS was associated with higher incidence of intra-abdominal injuries (31.97% vs 16.45%; p = 0.01) and a higher rate of abdominal operations (19.73% vs. 7.59%; p < 0.01) compared to below the ASIS. In contrast, CT ASBS below the ASIS was associated with a higher incidence of pelvic fractures (17.72% vs. 8.16%; p = 0.01) with fractures being an independent risk factor for abdominal injury requiring intervention. Logistic regression analyses and receiver-operator characteristic curves demonstrated ASBSI was significantly associated with abdominal injury requiring operative intervention.

CONCLUSION

Characteristics of abdominal wall injury on imaging such as location and contusion depth (ASBSI) are better predictors of abdominal operative need than standard clinical measures. This analysis substantiates a novel diagnostic tool which may have the potential to facilitate clinical diagnosis and management decisions in patients with abdominal seatbelt sign.