Rib Season: Temporal Variation in Chest Wall Injuries.

Introduction: Trauma to the chest wall is one of the most common injuries suffered. Knowing whether there are regular and reproducible changes in frequency or severity of certain injury types may help resource allocation and improve prevention efforts or outcomes; however, no prior studies have evaluated seasonal variation in chest wall injuries (CWIs). We aimed to determine if CWIs vary annually in a consistent distinct temporal variation.

Methods: Using an established traumatic blunt CWI database at a single urban level 1 trauma center, patients with a moderate-to-severe (chest wall Abbreviated Injury Score (AIS) ≥2) CWI were reviewed. A subpopulation of predominant chest wall injury (pCWI) was defined as those with a chest wall AIS ≥3 and no other anatomic region having a higher AIS. Demographics, injury patterns, mechanisms of injury, and AIS were collected in addition to date of injury over a 4-y period. Data were analyzed using descriptive statistics as well as Poisson time-series regression for periodicity. Seasonal comparison of populations was performed using Student's t-tests and Analysis of Variance (ANOVA) with significance assessed at a level of P < 0.05.

Results: Over a 4-y period nearly 16,000 patients presented with injury, of which 3042 patients were found to have a blunt CWI. Total CWI patients per year from 2014 to 2017 ranged from 571 to 947. Over this period, August had the highest incidence for patients with any CWI, moderate-to-severe injuries, and pCWI. February had the lowest overall injury incidence as well as lowest moderate-to-severe injury incidence. January had the lowest pCWI incidence. Yearly changes followed a quadratic sinusoid model that predicted a peak between incidence, between June and October, and the low season. A low season was found to be December-April. Comparing low to high seasons of injured patient monthly means revealed significant differences: total injuries (69.94 versus 85.56, P = 0.04), moderate to severe (62.25 versus 78.19, P = 0.06), and pCWI (25.25 versus 34.44, P = 0.01). Analysis of injuries by mechanism revealed a concomitant increase in motorcycle collisions during this period.

Conclusions: There appears to be a significant seasonal variation in the overall incidence of CWI as well as severe pCWI, with a high-volume injury season in summer months (June-October) and low-volume season in winter (December-April). Motorcycle accidents were the major blunt injury mechanism that changed with this seasonality. These findings may help guide resource utilization and injury prevention.