What types of falls in older adults lead to head impact? An analysis of biomechanical factors based on video evidence from real-life falls

BACKGROUND: Approximately 80% of traumatic brain injuries in older adults are caused by head impact during a fall. Risk for head impact and injury is especially high in long-term care, due in part to a loss of effectiveness in upper limb protective responses. This study seeks to inform prevention strategies by identifying factors that separate falls where upper limb bracing was successful versus unsuccessful in preventing head impact. METHODS: We analyzed videos of real-life forward falls with bracing experienced by older adults in long-term care (aged 83 years; SD 7.6), comparing falls with head impact (n = 9) to falls without head impact (n = 9). The time-varying vertical and horizontal positions of eight anatomical landmarks were digitized using Kinovea software. Linear mixed models with repeated measures were used to compare the kinematics of falls with versus without head impact, at time instants before, during and after hand impact. FINDINGS: Compared to falls without head impact, falls with head impact involved larger horizontal velocities (p ≤ 0.041), but no differences in vertical velocities (p ≥ 0.307) or arm angles (p = 0.067). There were significant interactions between head impact and timing during the fall for arm angle (p = 0.035), reflecting toppling of the body over the hands in falls with head impact. INTERPRETATION: Our results suggest that head impact during forward falls in older adults is driven primarily by excessive horizontal momentum and inadequate compensation through changes in hand position, resulting in pitching of the body over the hands and head strike.