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Biomechanical Evaluation of Shaken Impact Syndrome

John D. Lloyd, Ph.D., M.Erg.S., CPE, CBIS
Board Certified Ergonomist | Certified Brain Injury Specialist
32824 Michigan Avenue, San Antonio, FL 33576
Tel: (813) 624-8986
Email: John@DrBiomechanics.com

A biomechanical evaluation was performed to evaluate the risk of injury to an infant associated with shaken impact syndrome. Injury risk was measured as a function of linear and angular head kinematics of a biofidelic infant surrogate during a biomechanical recreation.

Two adult males performed the shaken impact and impact activities.  A CRABI12 biofidelic mannequin, of height 0.75m and mass 10kg, was utilized as the infant surrogate. A piezo-electric tri-axial accelerometer was installed at the Center of Mass of the CRABI headform, in accordance with SAE J211 along with a tri-axial digital gyroscope.

A number of conditions were investigated using a height adjustable test apparatus. These included: non-contact shaking, shaken impact (which implies a brief shaking episode, followed immediately by impact) and impact only. For the shaken impact and impact only scenarios, the participants were instructed to impart gentle, moderate and vigorous impacts on the infant surrogate. Surfaces impacted included a standard infant crib mattress, a standard changing table pad, with cover, and a hard wooden table top. Participants performed five repeated trials for each condition, for a total of 230 trials.

Findings indicate that rotational accelerations associated with intentional impact and shaken impacts are typically below infant brain injury thresholds of 8,000-10,000 rad/s2. The exception was vigorous impact against the changing pad or wood tabletop.

Since all of the brain motion associated with this shaken impact / impact only mechanism was constrained to the sagittal plane, lateral and axial brain was minimal.

All events where sufficient rotational brain motion was recorded to produce significant brain injury, sufficient linear acceleration to cause skull fracture in an infant was also documented. Thus, considering the shaking impact or impact only mechanisms, findings suggest that for there to be an underlying brain injury a skull fracture is also likely.