Toward a Test-Based Methodology to Evaluate Unrestrained Torso Neck Braces Using the Hybrid III ATD and MATD Neck

The introduction of unrestrained torso neck braces as a safety intervention for helmeted motorcycle riders has introduced a set of unsolved challenges. Understanding the injury prevention afforded by these devices depends on a reliable test methodology by which to critically evaluate their efficacy against the most common mechanisms of neck injury. An inverted pendulum test is proposed to evaluate compression flexion (CF), tension flexion (TF), and tension extension (TE) of the neck using a Hybrid III anthropomorphic test device (HIII ATD) neck and a motorcycle-specific ATD (MATD) neck. In addition to investigating methods to quantify the beneficial effects of a neck brace, potential adverse effects of such a device are evaluated by measuring and evaluating relevant neck response measures. To that end, measured data using a current neck brace were analyzed and applied to various injury criteria related to the ATD neck used to compare the injury risk predicted by each parameter. The HIII ATD neck allows for a more conservative evaluation due to its exaggerated response in compression and may be more suitable in evaluating the neck injury criterion and injury risk in CF loading for low energy impacts. The MATD neck is limited to certain impact modalities, particularly the uncoupled behavior between head and neck during hyperextension, and individual neck measures at lower impact energy due to its limited structural integrity in direct head impacts. In the proposed tests, injury mechanisms were initially associated with a pre-impact head orientation and expected head and neck motion. However, these associations are not definitive. Although the most relevant neck injury mechanisms related to the unrestrained torso were addressed, the authors suggest that the presented tests are supplemented by a method to evaluate higher energy vertex impacts as a means to determine a neck brace’s efficacy during this loading modality.