Development of the STAR Evaluation System for Football Helmets: Integrating Player Head Impact Exposure and Risk of Concussion STEVEN ROWSON and STEFAN M. DUMA Virginia Tech – Wake Forest University, School of Biomedical Engineering and Sciences, 440 ICTAS Building, Stanger St., Blacksburg, VA 24061, USA (Received 28 February 2011; accepted 2 May 2011; published online 7 May 2011) Associate Editor Thurmon E. Lockhart oversaw the review of this article. Abstract—In contrast to the publicly available data on the safety of automobiles, consumers have no analytical mech- anism to evaluate the protective performance of football helmets. The objective of this article is to fill this void by introducing a new equation that can be used to evaluate helmet performance by integrating player head impact exposure and risk of concussion. The Summation of Tests for the Analysis of Risk (STAR) equation relates on-field impact exposure to a series of 24 drop tests performed at four impact locations and six impact energy levels. Using 62,974 head acceleration data points collected from football players, the number of impacts experienced for one full season was translated to 24 drop test configurations. A new injury risk function was developed from 32 measured concussions and associated exposure data to assess risk of concussion for each impact. Finally, the data from all 24 drop tests is combined into one number using the STAR formula that incorporates the predicted exposure and injury risk for one player for one full season of practices and games. The new STAR evalua- tion equation will provide consumers with a meaningful metric to assess the relative performance of football helmets. Keywords—Concussion, Mild traumatic brain injury, Accel- eration, Risk, Exposure, HITS, Impact. INTRODUCTION Recent research has suggested that there are as many as 3.8 million sports-related concussions each year in the United States, with participation in football result- ing in the highest incidence of injury. 8,29 Studies showing the potential long-term effects of these injuries have put sports-related concussions under the national spotlight as a primary health concern. 16,35,36 Furthermore, there is concern that repetitive sub-concussive head impacts in sports may lead to neurocognitive deficits. 18,19,25 While limiting the number of head impacts in sports is an important component of reducing injury incidence, improving head protection is another essential element of injury mitigation. 7 This article focuses on a new mechanism to evaluate the protective capabilities of football helmets. Substantial effort has been invested in researching head acceleration in relation to brain injury. 27 Head acceleration is thought to be indicative of the inertial response of the brain, and therefore is used to predict brain injury. 27 All head injury safety standards for automobiles and helmets (motorcycle, sports, or bicy- cle) use measured humanoid head acceleration (or a function of head acceleration) during specified testing conditions to determine whether a product is safe to sell to consumers. While the Federal Motor Vehicle Safety Standards (FMVSS) 201 and 208 govern whe- ther an automobile is safe to sell using pass/fail injury criteria, the New Car Assessment Program (NCAP) provides consumers with a quantitative metric of the relative safety between automobile models. 23,28 NCAP is a valuable tool for consumers who are concerned with safety. In contrast to the publicly available NCAP safety data on automobiles, consumers have no information on the relative impact performance between different helmets; moreover, there is no quantified metric that provides meaningful interpretation of the test results. The National Operating Committee on Standards for Athletic Equipment (NOCSAE) provides a set of vol- untary standards that are designed to assess a helmet’s ability to prevent skull fracture. NOCSAE certification involves testing helmets through a series of drop tests, in which every drop test must result in a head form impact response below a specified threshold. The NOCSAE standards have done an excellent job of Address correspondence to Steven Rowson, Virginia Tech – Wake Forest University, School of Biomedical Engineering and Sciences, 440 ICTAS Building, Stanger St., Blacksburg, VA 24061, USA. Electronic mail: srowson@vt.edu Annals of Biomedical Engineering, Vol. 39, No. 8, August 2011 (Ó 2011) pp. 2130–2140 DOI: 10.1007/s10439-011-0322-5 0090-6964/11/0800-2130/0 Ó 2011 Biomedical Engineering Society 2130