355 - Height-related effects on skull fracture complexity in young infants

Publication Number: 355.5522

Tagrid Ruiz-Maldonado, University of Utah School of Medicine, Salt Lake City, UT, United States; Kenneth W. F, University of Washington School of Medicine, Seattle, WA, United States; James B. Metz, The University of Vermont Children's Hospital, Burlington, VT, United States; Yousef Alsanea, University of Utah, Salt Lake City, UT, United States; Rosemary Schaefer, University of Wisconsin-Madison, Madison, WI, United States; Jeffrey Otjen, Seattle Children's Hospital, SEATTLE, WA, United States; Brittany Coats, University of Utah, Salt Lake City, UT, United States

Background: There is a greater prevalence of fracture complexity features in 0–4-month-old infants following low-height falls. Characterization of height-related effects within this age group would bolster our understanding of the infant skull’s response to trauma, improving biofidelity of age-dependent biomechanical models.

Objective: We aimed to characterize nuances in skull fracture patterns in 0-4-months-old infants, hypothesizing that greater fall height, younger infant age, and surface of high coefficient of restitution (COR) is associated with fracture complexity.

Design/Methods: We conducted a retrospective multi-center cross-sectional study. We included infants 0-4-months-old with a low-height fall history, skull fracture on head CT and a low concern determination for physical abuse. Cases without head CT 3D reconstruction or without fall height estimation were excluded. Complexity features included crack branching, suture-to-suture spanning, cross-suture extension, and biparietal involvement. Greater numbers of fractures and crack fronts suggested greater complexity. We used logistic regression to study the associations of age, height, and surface with complexity features. Interactions were included with the main effects.

Results: For 129 cases, median (IQR) fall height was 0.889 (0.71-1.33) m; median (IQR) age was 1.9 (1-3) mo. Number of fractures and crack fronts averaged 1.2 and 1.7, respectively. 6 cases (4.6%) had cross-suture extension, 10 (7.8%) had branching, 43 (33.3%) had suture-to-suture spanning, and 14 (10.9%) had biparietal involvement. 59 (45.7%) had any of these indices of complexity. Greater fall height, greater fall height with younger infant age, and greater fall height with high surface COR was associated with more crack fronts (all p< 0.001). Greater fall height was also associated with suture-to-suture spanning (p=0.003). We did not identify associations between age, height, or surface COR and the number of fractures or cross-suture extension, branching, or biparietal involvement.

Conclusion(s): This study further supports the occurrence of complex skull fractures following low-height falls. In young infants, fall height, infant age, and surface COR significantly affects the number of fracture cracks fronts; fall height affects the presence of suture-to-suture spanning. Both findings are consistent with greater energy release upon head impact. The lack of associations with biparietal involvement may indicate malleability of the younger infant skull. In this age group, it is likely that impact location or angle of impact carries a greater role in determining biparietal involvement.