Football Helmets Fail to Protect Against Side Impact

Megan Brooks

February 18, 2014

Football helmets provide little or no protection against hits to the side of the head, or rotational forces, that are an important source of brain injury and encephalopathy, a new study hints.

Study investigator Frank Conidi, MD, told Medscape Medical News he was "not at all" surprised by the findings.

"This study confirmed current consensus that football helmets do little to protect against concussion," said Dr. Conidi, director, Florida Center for Headache and Sports Neurology and assistant clinical professor of neurology, Florida State University College of Medicine, Port St. Lucie. He is also vice chair of the American Academy of Neurology's (AAN's) Sports Neurology Section.

The study results were released February 17 and will be presented at the upcoming 66th Annual Meeting of the AAN annual meeting in Philadelphia, Pennsylvania, in April.

Modified Drop Test

The effectiveness of helmets is measured through a linear drop test approved by the National Operating Committee on Standards for Athletic Equipment (NOCSAE), Dr. Conidi and coauthor John Lloyd, PhD, from the Center for Product Ergonomics in San Antonio, Florida, note in a meeting abstract.

The result is helmets that are optimized to protect against linear forces that cause skull fractures, visible bruising, and other focal effects. "However, biomechanics researchers have long understood that rotational forces, not linear forces, are responsible for serious brain damage including concussion, axonal injury and hemorrhages," the investigators note.

They devised a "reasonable" modification to the standard drop test system, incorporating a crash test dummy head and neck, to generate a more realistic impact. They installed miniature sensors at the center of the surrogate head to measure linear and rotational responses to repeated 12 mile per hour head impacts.

They performed 330 tests measuring how well 10 popular football helmet designs protect against traumatic brain injury, including the Adams A2000, Rawlings Quantum, Riddell 360, Riddell Revolution, Riddell Revolution Speed, Riddell VSR4, Schutt Air Advantage, Schutt DNA Pro+, Xenith X1, and Xenith X2.

As expected, the football helmets protected against linear impacts. Compared with tests using dummies with no helmets, the helmets reduced the risk for skull fracture by 60% to 70% and the risk for focal brain tissue bruising by 70% to 80%, the investigators say.

However, the helmets reduced the risk for traumatic brain injury by only 20%, on average, compared with not wearing a helmet.

 
Alarmingly, those that offered the least protection are among the most popular on the field. Dr. Frank Conidi
 

Of the 10 helmet brands tested, the investigators found that the Adams A2000 provided the best protection against concussion and the Schutt Air Advantage the worst. Overall, the Riddell 360 provided the most protection against closed-head injury and the Adams a2000 the least, despite rating the best against concussion.

  "Alarmingly, those that offered the least protection are among the most popular on the field," Dr. Conidi said in the conference statement.

"Concussion does not require a direct blow to the head and is often induced by transfer of force to the head by impact with the upper body. Helmets cannot dissipate these types of biomechanical forces," Dr. Conidi told Medscape Medical News.

Making a Better Football Helmet?

As previously reported, updated AAN guidelines published in March 2013 note that while helmets may prevent concussion (vs no helmet), there is no clear evidence that one type of football helmet can better protect against concussion over another kind of helmet.

Dr. Conidi noted that National Hockey League (NHL) goalie masks are angled in a manner similar to a stealth fighter. "These angles help dissipate some of the puck's energy. Unfortunately, forces sustained by football players are far too great to be dissipated by designing a football helmet with angles," he said.

"A number of manufacturers have stated publicly that they are developing helmets to protect against concussion. They may be able to lower the risk slightly by increasing padding, however, not to the extent that it is going to make any significant difference," Dr. Conidi added.

Asked for comment on the new study, Christopher C. Giza, MD, professor of pediatric neurology and neurosurgery, University of California Los Angeles (UCLA) Brain Injury Research Center and UCLA Brain SPORT: Sports Concussion–Mild TBI Program, cautioned that it's "not readily possible to predict the rates of clinical concussion from use of biomechanical sensors on crash test dummies. It is very possible to measure changes in force in the lab, but the relationship between force and concussion and subconcussive injuries is still not clearly delineated."

"Helmets were originally designed (and their primary goal still is) to prevent skull fracture, intracranial bleeding and neurological catastrophe. They actually do this pretty well," said Dr. Giza, who was the lead author on the updated AAN sports concussion guidelines.

"Concussion is a brain movement injury, and any currently designed helmet is going to have a limited ability to prevent brain/head movement. There are some theoretical new designs that may address the rotational vs linear issue, but the data from these is not readily available. Even when it is published, the helmet biomechanics investigators will still have the issue about clinical translation to address," Dr. Giza said.

The study was supported by BRAINS Inc, a research and development company based in San Antonio, Florida, focused on biomechanics of traumatic brain injury. Dr. Lloyd is research director at the company.

66th Annual Meeting of the American Academy of Neurology (AAN), April 26 to May 3, 2014. Abstract 2928.

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