Novel Insights from Clinical Practice Pediatr Neurosurg 2013;49:43–49 DOI: 10.1159/000355121
Received: May 22, 2013 Accepted after revision: August 18, 2013 Published online: October 29, 2013
Subdural Hemorrhage in Two High-School Football Players: Post-Injury Helmet Testing Jonathan A. Forbes a Scott L. Zuckerman a Lucy He a Elizabeth McCalley c Young M. Lee b Gary S. Solomon a P. David Halstead c Allen K. Sills a a c
Department of Neurological Surgery and b Vanderbilt University School of Medicine, Nashville, Tenn., and Southern Impact Research Center, Rockford, Tenn., USA
Key Words Concussion · Football · Subdural hemorrhage · Helmet safety
by contemporary helmet quality assurance criteria. To the authors’ knowledge, this is the first published report of helmet testing following sports-related helmeted collisions resulting in severe traumatic intracranial injuries. © 2013 S. Karger AG, Basel
Abstract The incidence of catastrophic head injury in American football is at a 30-year high; over 90% of these injuries are secondary to subdural hemorrhage (SDH). At the present time, it is unknown why the incidence of this devastating injury complex continues to rise. Because previous investigations have documented deficiencies in the process of equipment certification at youth and high-school levels, we sought to investigate the adequacy of headgear worn by two athletes who suffered contact-related SDH on the football field and presented to Vanderbilt Children’s Hospital between 2009 and 2011. Helmets worn by the struck players at the time of collision (Medium Schutt Air Advantage 7888 and Large Schutt Air XP 7890) were obtained for formal biomechanical testing at a National Operating Committee on the Safety of Athletic Equipment (NOCSAE)-certified facility. Both helmets were found to be compliant with a modified version of the NOCSAE standard ND002-11m12. Based on the aforementioned tests, it can be concluded that headgear worn by both players who suffered SDH was not substandard, as defined
© 2013 S. Karger AG, Basel 1016–2291/13/0491–0043$38.00/0 E-Mail [email protected] www.karger.com/pne
Introduction
In a recent report published by Mueller and colleagues [1, 2], investigators noted the number of catastrophic head injuries in organized football was the highest since the National Center for Catastrophic Sports Injury Research (NCCSIR) began collecting statistics in 1984 with over 90% of catastrophic head injuries are secondary to subdural hemorrhage (SDH). All of the athletes reported to have suffered SDH in the Mueller report were 18 years of age or younger. There are many potential hypotheses as to why the incidence of this devastating injury complex appears to be increasing: increases in the mass and velocity of modern football players might be resulting in more violent collisions with a greater amount of energy transfer; systems of data tracking might be becoming more efficient at identifying these ‘catastrophic injuries’; despite increased regulatory scrutiny and rule changes designed Jonathan A. Forbes, MD T-4224 Medical Center North Nashville, TN 37232 (USA) E-Mail jonathan.a.forbes @ gmail.com
to act as a deterrent, the incidence of helmet-to-helmet hits may actually be increasing, and finally, players who suffer these catastrophic injuries may be wearing helmets of substandard quality. This final hypothesis is supported by recent investigations which have documented deficiencies in the practice of equipment certification at youth and high-school levels [3]. While SDH secondary to collisions in American football has been reported many times in the literature [4– 8], to the authors’ knowledge, associated helmet testing has not been included to evaluate whether or not the quality of the helmet worn by the struck player was compliant with conventional headgear standards. The purpose of this study was to test whether helmets worn by two high-school American football players who suffered contact-related SDH met National Operating Committee on the Safety of Athletic Equipment (NOCSAE) helmet standards. Both football helmets were obtained and subsequently tested at an authorized, accredited, and NOCSAE-certified laboratory.
a
b
Case Reports Case Report 1 A 17-year-old male initially presented to the Vanderbilt Children’s Hospital emergency department (ED) approximately 60 h following a helmet-to-helmet collision at football practice. According to self-report, he was carrying the ball during a tackling drill when he was struck slightly to the left of the midline at midfacemask level by the crown of the opposing player’s helmet. Witnesses reported that his head underwent sudden extension during the impact. However, there was no loss of consciousness (LOC). The patient also reported another high-impact collision, this time as the striking player, in a similar tackling drill approximately 4 days prior to the second collision. This first collision occurred with neither LOC nor any significant associated symptoms. There was no other reported history of head trauma or concussions in the preceding weeks. During the initial 48 h following the second collision, the patient complained of a moderate to severe headache. When he awoke on the second day following the collision, the headache had increased in severity and was associated with significant nausea. The headache progressively worsened throughout the day and his father took him to the ED that evening. In the ED, a non-contrast computed tomography (CT) scan of the head revealed a subacute left frontoparietal subdural hematoma, slightly hyperdense to the cortex, measuring approximately 11 mm in widest thickness. A left-to-right midline shift of 6 mm was also visible on the scan (fig. 1a). No underlying fracture of the calvaria was present. Of note, the bony windows demonstrated a focal calvarial irregularity overlying the side of SDH (fig. 1b) suggestive of a potential underlying arachnoid cyst. Physical examination in the ED demonstrated a healthy, neurologically intact adolescent male in significant distress. The patient stood approximately 1.83 m tall and weighed
44
Pediatr Neurosurg 2013;49:43–49 DOI: 10.1159/000355121
c
Fig. 1. a Preoperative CT imaging with soft-tissue windowing demonstrates a left subacute frontoparietal subdural hematoma (arrowhead) slightly hyperdense to the cortex, measuring approximately 11 mm in widest thickness with 6 mm of left-to-right midline shift. b Preoperative CT imaging with bone windowing reveals a small focal calvarial irregularity overlying the SDH (arrowhead). c CT imaging of the head with soft-tissue windowing status after craniotomy for evacuation.
76 kg. Following evaluation in the ED, the patient was admitted to the Pediatric Intensive Care Unit. In the context of persistent and debilitating headaches, the decision was made to proceed with craniotomy for evacuation of clot, which was performed without complication. Notably, during hematoma evacuation, an area of venous bleeding involving a bridging vessel along the parasagittal, posterior frontal region was identified. This site was felt to represent the source of the subdural hematoma and was cauterized with bipolar electrocautery. Although inspection was limited by the presence of hematoma, no definitive intra-operative findings con-
Forbes/Zuckerman/He/McCalley/Lee/ Solomon/Halstead/Sills
ing this discharge in the outpatient neurosurgery clinic, where he continued to complain of persistent headaches, generalized lassitude, and difficulty with concentration. At a subsequent visit 6 weeks later, these symptoms had improved considerably and a repeat CT scan showed effective resolution of the SDH (fig. 2b).
Methods
a
b
Fig. 2. a CT imaging of the head obtained on admission: soft-tissue windowing demonstrates a left acute frontoparietal subdural hematoma, hyperdense to the cortex, measuring approximately 4 mm in widest thickness (arrowhead). b CT imaging of the head with soft-tissue windowing approximately 6 weeks following hospital admission demonstrates hematoma resorption following observation.
sistent with the presence of an arachnoid cyst were encountered. Following the operation, CT imaging (fig. 1c) demonstrated evacuation of the clot. The patient did well following the operation and was discharged home on postoperative day 2. During his next clinic visit 6 weeks following the operation, he was found to be neurologically intact and without complaint. The patient was counseled not to return to the football field at that time.
Helmet Examination Each helmet was visually inspected before testing (fig. 3). The Schutt Air Advantage was manufactured in July of 2003 and was last reconditioned in 2008. The Schutt Air XP was manufactured in July 2008 and was most recently reconditioned in 2011. Generally, the exteriors of both helmets appeared to be in acceptable condition. There were some scratches and small gouges on the shell, typical of a helmet used during football practices and games. Both of the facemasks also appeared to be in good, serviceable condition and did not have exposed metal. Each helmet’s respective internal pads and fit systems were present and fit the helmet appropriately. The internal padding of the Schutt Air Advantage showed signs of aging and was worn and dirty. The Schutt Air XP’s padding system showed signs of light use, but was clean and in good repair overall.
Case Report 2 A 15-year-old male presented to the Vanderbilt Children’s Hospital ED the morning after being struck on the head by an opposing player during a scrimmage. At the time of collision, he did not suffer LOC but felt ‘wobbly’ as he walked off the field. Upon reaching the sideline, the patient developed a headache which improved minimally with ibuprofen. When the player awoke the morning after this collision, the severity of his headache had increased significantly, prompting his family to bring him to the ED. Upon further questioning in the ED, the patient reported a previous collision approximately 7 days prior to presentation during a tackling drill. This collision had resulted in a mild headache which lasted for 3 days before resolving. On examination in the ED, the patient described a severe headache, but otherwise had no other complaints and was neurologically intact on examination. He was 1.70 m in height and had a weighed 60 kg. A CT scan revealed a 4-mm acute left frontal convexity SDH (fig. 2a). The patient was admitted to the Pediatric Intensive Care Unit for serial neurological examinations. A repeat scan obtained 6 h following the initial scan revealed no interval change. The patient’s headache improved gradually and he was eventually discharged home on post-injury day 3. The patient returned to the ED 1 week following discharge, complaining of persistent headaches and lethargy. A repeat scan at this time revealed expected evolution of a stable 3- to 4-mm left frontal SDH. Surgical options were discussed with the family, but ultimately, the decision was made to continue with conservative medical management. The patient was seen again 2 weeks follow-
Helmet Testing Each helmet was tested according to a modified version of NOCSAE DOC (ND) 002 ‘Standard Performance Specification for Newly Manufactured Football Helmets’, with facemasks attached to the helmets. Prior to testing, each helmet was fitted on an appropriately sized NOCSAE headform according to the manufacturer’s sizing chart. Both helmets were tested in the configuration in which they arrived at the Southern Impact Research Center. Thus, no air was added to or removed from the air bladder fit systems, the internal pads were not moved or changed, and the chin straps were not replaced with new ones. Prior to testing, a good fit was ensured between helmet and headform. The drop testing was conducted on a twin guidewire drop system onto a 1.3 cm firm rubber impact surface in compliance with the NOCSAE standard. Testing was completed at six standard locations – front boss, front, side, rear boss, rear, and top. Additionally, one random location chosen by the technician was tested (fig. 4). The upper side location was chosen for the Schutt Air XP, while the left front boss location was chosen for the Schutt Air Advantage. Both helmets were tested with the facemasks attached – the only notable deviation from the NOCSAE standard. The decision to keep the facemask attached during helmet testing was based on the need to test the helmets in the configuration in which the injuries occurred; a method in accordance with previous benchmark studies performed by the senior author (P.D.H.) assessing helmet performance [9]. While some of the impact locations included drops at 91 and 122 centimeters, the formal evaluation of each helmet was based on the average Severity Index (SI) of the two 122 cm drops at each of the standard locations and the random location. The linear acceleration pulse was collected by a tri-axial accelerometer located at the center of gravity of the headform. These data were analyzed by the KME 200 data analyzer to calculate the SI. Lab conditions at the time of testing were 22.2°C and 50% relative humidity. The hightemperature condition was not evaluated during this test protocol.
SDH in High-School Football Players: Post-Injury Helmet Testing
Pediatr Neurosurg 2013;49:43–49 DOI: 10.1159/000355121
45
Fig. 3. Photos of the two helmets worn by players who suffered SDHs.
Results
Both helmets passed the modified version of the NOCSAE standardized drop test and were deemed to be compliant. Results are summarized in table 1. The Medium Schutt Air Advantage 7888 achieved an average SI of 451.9, with a maximum SI of 699.0 on rear impact and a minimum SI of 203.0 on left frontal boss impact. The Large Schutt Air XP 7890 achieved an average SI of 446.5, with a maximum SI of 568.5 on rear impact and a minimum SI of 309.5 on front impact.
Discussion
Brief Description of NOCSAE NOCSAE was founded in 1969 after an alarming increase in the incidence of brain injury-related fatalities in American football during the period of time from 1965 to 1969 was noted [10]. NOCSAE helmet specifications were based on research performed at Wayne State University and were designed to assess the helmet’s ability to limit SI, a value calculated by integrating translational acceleration to the 2.5th power with respect to time, following a standardized drop test [11]. Under the guidance of NOCSAE, standards regarding the energy-attenuating properties of helmets were expanded to include college football in 1978 and high-school football in 1980. At the present time, all high-school and collegiate football players are required to wear helmets meeting NOCSAE standards. While compliance with NOCSAE standards is required for all levels of American football, the majority of clinicians who care for athletes involved in helmeted injuries are unfamiliar with the specific details of helmet regulation. The NOCSAE standard is a pass/fail assess46
Pediatr Neurosurg 2013;49:43–49 DOI: 10.1159/000355121
ment whose threshold has been set at a SI of 1,200 [12]. A helmet must test below a SI of 1,200 during standardized drop tests at all designated impact locations (a more specific description of the details of helmet testing can be found in the Methods section). The 122 cm drop test that is used is roughly equivalent to a player running at 5.46 meters per second (19.6 kmh) into a flat surface that stops his/her head in less than 1 inch – approximating a severe, helmeted collision. Notably, NOCSAE does not require recertification at any specified interval. Instead, it defers this decision to individual schools and national organizations. NOCSAE does, however, determine the specifications of the recertification process, which are extremely similar to those of the initial certification. While manufacturers test their own helmets following production, licensed re-conditioners oversee testing of used helmets. Licensed re-conditioning companies who are in appropriate compliance with NOCSAE certification visually inspect all helmets for cracks and other evidence of dysfunction. However, current NOCSAE requirements mandate that only 2% of helmets (or approximately 50,000 individual tests annually) be subjected to direct assessment with standard drop testing; the remaining approximately 98% of helmets receive visual inspection alone with replacement of broken parts, if necessary. NOCSAE does not possess the means and/or resources to enforce proper compliance with the standards it has set forth and instead relies on a voluntary ‘honor’ system. Questions Surrounding Helmet Recertification The ability of helmets to attenuate energy is central to the prevention of underlying injury to intracranial structures. Increased helmet wear can lead to a phenomenon of ‘pre-compression’ in the foam layer and a decrease in the properties of energy attenuation [13]. Forbes/Zuckerman/He/McCalley/Lee/ Solomon/Halstead/Sills
While a large amount of funding at the collegiate and professional levels allows for high standards in the quality of the equipment used, previous investigations have brought the practice of equipment certification at youth and high-school levels into the national spotlight, including one company responsible for helmet certification who faces legal ramifications for improperly returning approximately 4,000 helmets to be used in play during the 2005–2006 season [3]. As both of the athletes described in this case report were high-school players from poor, rural communities, one potential concern was that the quality of headgear worn by these players was substandard. As described above, formal testing of the equipment performed in this study demonstrated that both helmets were fully compliant with a modified version of the NOCSAE standards. One interpretation of this finding is that a NOCSAE-certified football helmet does not guarantee protection against SDH. Additional Considerations Scientific investigation performed in this study clearly demonstrates that the headgear worn by struck players adhered to the modified NOCSAE standards. However, important questions remain: why did these two players suffer SDH? Despite numerous technological advances and regulatory changes, why is the reported incidence of catastrophic head injury in American football at a 30-year high? One clue may have to do with the epidemiology of SDH in American football players. Curiously, despite lower mass, lower impact velocity, and lower impact translational acceleration, high-school football players have an incidence of SDH that is 3.3 times of college football players [10]. One potential explanation of this disparity in SDH incidence between high-school and collegiate athletes is a difference in the type of biomechanical forces commonly experienced between these groups. Interestingly, in a review of 5 studies measuring head acceleration in concussed athletes, high-school athletes experienced a smaller amount of translational acceleration with associated collisions, but a larger amount of rotational acceleration [14]. While SI (a rough marker of translational acceleration) has formed the basis of the helmet quality assurance standard since the Wayne State studies on cadaveric skull fractures of the 1960s, previous studies in the neurosurgical literature have suggested that high levels of rotational acceleration are instead responsible for SDH [15]. Highschool athletes might be predisposed to increased rotaSDH in High-School Football Players: Post-Injury Helmet Testing
Front impacts
Side impacts
Front boss impacts
Rear boss impacts
Rear impacts
Top impacts
Fig. 4. Diagram of NOCSAE standard impact testing. Per NOCSAE,
a 122 cm drop test is roughly equivalent to a player running at 5.46 meters per second (19.6 kmh) into a flat surface which stops his head in less than 1 inch (most players run faster than this, but rarely would the head be stopped in such a short distance on the football field; thus, this approximately is consistent with a severe helmeted collision).
Pediatr Neurosurg 2013;49:43–49 DOI: 10.1159/000355121
47
Table 1. Summary of standardized modified NOCSAE-certified helmet testing
Helmet
SI
Schutt 7888 Air Advantage Schutt 7890 Air XP
front boss
front
side
rear boss
rear
top
random
average
304.5 309.5
252.5 380.5
559.5 469.5
493.5 440.5
699.0 568.5
651.5 537.5
203.0 419.5
451.9 446.5
This table is a summary of the results of standardized modified NOCSAE-certified helmet testing. The two helmets are listed to the left. The location of each pair of impacts is indicated in the uppermost column. Each value listed represents the average of two standardized impacts obtained by dropping a helmet from rest 60 inches above ground at a given location. The magnitude of the re-
sultant imputes is measured by SI, which is equal to the integral of translational acceleration to a power of 2.5, with respect to time. Per NOCSAE criteria, a helmet ‘passes’ if the SI from all drop tests is
Received: May 22, 2013 Accepted after revision: August 18, 2013 Published online: October 29, 2013
Subdural Hemorrhage in Two High-School Football Players: Post-Injury Helmet Testing Jonathan A. Forbes a Scott L. Zuckerman a Lucy He a Elizabeth McCalley c Young M. Lee b Gary S. Solomon a P. David Halstead c Allen K. Sills a a c
Department of Neurological Surgery and b Vanderbilt University School of Medicine, Nashville, Tenn., and Southern Impact Research Center, Rockford, Tenn., USA
Key Words Concussion · Football · Subdural hemorrhage · Helmet safety
by contemporary helmet quality assurance criteria. To the authors’ knowledge, this is the first published report of helmet testing following sports-related helmeted collisions resulting in severe traumatic intracranial injuries. © 2013 S. Karger AG, Basel
Abstract The incidence of catastrophic head injury in American football is at a 30-year high; over 90% of these injuries are secondary to subdural hemorrhage (SDH). At the present time, it is unknown why the incidence of this devastating injury complex continues to rise. Because previous investigations have documented deficiencies in the process of equipment certification at youth and high-school levels, we sought to investigate the adequacy of headgear worn by two athletes who suffered contact-related SDH on the football field and presented to Vanderbilt Children’s Hospital between 2009 and 2011. Helmets worn by the struck players at the time of collision (Medium Schutt Air Advantage 7888 and Large Schutt Air XP 7890) were obtained for formal biomechanical testing at a National Operating Committee on the Safety of Athletic Equipment (NOCSAE)-certified facility. Both helmets were found to be compliant with a modified version of the NOCSAE standard ND002-11m12. Based on the aforementioned tests, it can be concluded that headgear worn by both players who suffered SDH was not substandard, as defined
© 2013 S. Karger AG, Basel 1016–2291/13/0491–0043$38.00/0 E-Mail [email protected] www.karger.com/pne
Introduction
In a recent report published by Mueller and colleagues [1, 2], investigators noted the number of catastrophic head injuries in organized football was the highest since the National Center for Catastrophic Sports Injury Research (NCCSIR) began collecting statistics in 1984 with over 90% of catastrophic head injuries are secondary to subdural hemorrhage (SDH). All of the athletes reported to have suffered SDH in the Mueller report were 18 years of age or younger. There are many potential hypotheses as to why the incidence of this devastating injury complex appears to be increasing: increases in the mass and velocity of modern football players might be resulting in more violent collisions with a greater amount of energy transfer; systems of data tracking might be becoming more efficient at identifying these ‘catastrophic injuries’; despite increased regulatory scrutiny and rule changes designed Jonathan A. Forbes, MD T-4224 Medical Center North Nashville, TN 37232 (USA) E-Mail jonathan.a.forbes @ gmail.com
to act as a deterrent, the incidence of helmet-to-helmet hits may actually be increasing, and finally, players who suffer these catastrophic injuries may be wearing helmets of substandard quality. This final hypothesis is supported by recent investigations which have documented deficiencies in the practice of equipment certification at youth and high-school levels [3]. While SDH secondary to collisions in American football has been reported many times in the literature [4– 8], to the authors’ knowledge, associated helmet testing has not been included to evaluate whether or not the quality of the helmet worn by the struck player was compliant with conventional headgear standards. The purpose of this study was to test whether helmets worn by two high-school American football players who suffered contact-related SDH met National Operating Committee on the Safety of Athletic Equipment (NOCSAE) helmet standards. Both football helmets were obtained and subsequently tested at an authorized, accredited, and NOCSAE-certified laboratory.
a
b
Case Reports Case Report 1 A 17-year-old male initially presented to the Vanderbilt Children’s Hospital emergency department (ED) approximately 60 h following a helmet-to-helmet collision at football practice. According to self-report, he was carrying the ball during a tackling drill when he was struck slightly to the left of the midline at midfacemask level by the crown of the opposing player’s helmet. Witnesses reported that his head underwent sudden extension during the impact. However, there was no loss of consciousness (LOC). The patient also reported another high-impact collision, this time as the striking player, in a similar tackling drill approximately 4 days prior to the second collision. This first collision occurred with neither LOC nor any significant associated symptoms. There was no other reported history of head trauma or concussions in the preceding weeks. During the initial 48 h following the second collision, the patient complained of a moderate to severe headache. When he awoke on the second day following the collision, the headache had increased in severity and was associated with significant nausea. The headache progressively worsened throughout the day and his father took him to the ED that evening. In the ED, a non-contrast computed tomography (CT) scan of the head revealed a subacute left frontoparietal subdural hematoma, slightly hyperdense to the cortex, measuring approximately 11 mm in widest thickness. A left-to-right midline shift of 6 mm was also visible on the scan (fig. 1a). No underlying fracture of the calvaria was present. Of note, the bony windows demonstrated a focal calvarial irregularity overlying the side of SDH (fig. 1b) suggestive of a potential underlying arachnoid cyst. Physical examination in the ED demonstrated a healthy, neurologically intact adolescent male in significant distress. The patient stood approximately 1.83 m tall and weighed
44
Pediatr Neurosurg 2013;49:43–49 DOI: 10.1159/000355121
c
Fig. 1. a Preoperative CT imaging with soft-tissue windowing demonstrates a left subacute frontoparietal subdural hematoma (arrowhead) slightly hyperdense to the cortex, measuring approximately 11 mm in widest thickness with 6 mm of left-to-right midline shift. b Preoperative CT imaging with bone windowing reveals a small focal calvarial irregularity overlying the SDH (arrowhead). c CT imaging of the head with soft-tissue windowing status after craniotomy for evacuation.
76 kg. Following evaluation in the ED, the patient was admitted to the Pediatric Intensive Care Unit. In the context of persistent and debilitating headaches, the decision was made to proceed with craniotomy for evacuation of clot, which was performed without complication. Notably, during hematoma evacuation, an area of venous bleeding involving a bridging vessel along the parasagittal, posterior frontal region was identified. This site was felt to represent the source of the subdural hematoma and was cauterized with bipolar electrocautery. Although inspection was limited by the presence of hematoma, no definitive intra-operative findings con-
Forbes/Zuckerman/He/McCalley/Lee/ Solomon/Halstead/Sills
ing this discharge in the outpatient neurosurgery clinic, where he continued to complain of persistent headaches, generalized lassitude, and difficulty with concentration. At a subsequent visit 6 weeks later, these symptoms had improved considerably and a repeat CT scan showed effective resolution of the SDH (fig. 2b).
Methods
a
b
Fig. 2. a CT imaging of the head obtained on admission: soft-tissue windowing demonstrates a left acute frontoparietal subdural hematoma, hyperdense to the cortex, measuring approximately 4 mm in widest thickness (arrowhead). b CT imaging of the head with soft-tissue windowing approximately 6 weeks following hospital admission demonstrates hematoma resorption following observation.
sistent with the presence of an arachnoid cyst were encountered. Following the operation, CT imaging (fig. 1c) demonstrated evacuation of the clot. The patient did well following the operation and was discharged home on postoperative day 2. During his next clinic visit 6 weeks following the operation, he was found to be neurologically intact and without complaint. The patient was counseled not to return to the football field at that time.
Helmet Examination Each helmet was visually inspected before testing (fig. 3). The Schutt Air Advantage was manufactured in July of 2003 and was last reconditioned in 2008. The Schutt Air XP was manufactured in July 2008 and was most recently reconditioned in 2011. Generally, the exteriors of both helmets appeared to be in acceptable condition. There were some scratches and small gouges on the shell, typical of a helmet used during football practices and games. Both of the facemasks also appeared to be in good, serviceable condition and did not have exposed metal. Each helmet’s respective internal pads and fit systems were present and fit the helmet appropriately. The internal padding of the Schutt Air Advantage showed signs of aging and was worn and dirty. The Schutt Air XP’s padding system showed signs of light use, but was clean and in good repair overall.
Case Report 2 A 15-year-old male presented to the Vanderbilt Children’s Hospital ED the morning after being struck on the head by an opposing player during a scrimmage. At the time of collision, he did not suffer LOC but felt ‘wobbly’ as he walked off the field. Upon reaching the sideline, the patient developed a headache which improved minimally with ibuprofen. When the player awoke the morning after this collision, the severity of his headache had increased significantly, prompting his family to bring him to the ED. Upon further questioning in the ED, the patient reported a previous collision approximately 7 days prior to presentation during a tackling drill. This collision had resulted in a mild headache which lasted for 3 days before resolving. On examination in the ED, the patient described a severe headache, but otherwise had no other complaints and was neurologically intact on examination. He was 1.70 m in height and had a weighed 60 kg. A CT scan revealed a 4-mm acute left frontal convexity SDH (fig. 2a). The patient was admitted to the Pediatric Intensive Care Unit for serial neurological examinations. A repeat scan obtained 6 h following the initial scan revealed no interval change. The patient’s headache improved gradually and he was eventually discharged home on post-injury day 3. The patient returned to the ED 1 week following discharge, complaining of persistent headaches and lethargy. A repeat scan at this time revealed expected evolution of a stable 3- to 4-mm left frontal SDH. Surgical options were discussed with the family, but ultimately, the decision was made to continue with conservative medical management. The patient was seen again 2 weeks follow-
Helmet Testing Each helmet was tested according to a modified version of NOCSAE DOC (ND) 002 ‘Standard Performance Specification for Newly Manufactured Football Helmets’, with facemasks attached to the helmets. Prior to testing, each helmet was fitted on an appropriately sized NOCSAE headform according to the manufacturer’s sizing chart. Both helmets were tested in the configuration in which they arrived at the Southern Impact Research Center. Thus, no air was added to or removed from the air bladder fit systems, the internal pads were not moved or changed, and the chin straps were not replaced with new ones. Prior to testing, a good fit was ensured between helmet and headform. The drop testing was conducted on a twin guidewire drop system onto a 1.3 cm firm rubber impact surface in compliance with the NOCSAE standard. Testing was completed at six standard locations – front boss, front, side, rear boss, rear, and top. Additionally, one random location chosen by the technician was tested (fig. 4). The upper side location was chosen for the Schutt Air XP, while the left front boss location was chosen for the Schutt Air Advantage. Both helmets were tested with the facemasks attached – the only notable deviation from the NOCSAE standard. The decision to keep the facemask attached during helmet testing was based on the need to test the helmets in the configuration in which the injuries occurred; a method in accordance with previous benchmark studies performed by the senior author (P.D.H.) assessing helmet performance [9]. While some of the impact locations included drops at 91 and 122 centimeters, the formal evaluation of each helmet was based on the average Severity Index (SI) of the two 122 cm drops at each of the standard locations and the random location. The linear acceleration pulse was collected by a tri-axial accelerometer located at the center of gravity of the headform. These data were analyzed by the KME 200 data analyzer to calculate the SI. Lab conditions at the time of testing were 22.2°C and 50% relative humidity. The hightemperature condition was not evaluated during this test protocol.
SDH in High-School Football Players: Post-Injury Helmet Testing
Pediatr Neurosurg 2013;49:43–49 DOI: 10.1159/000355121
45
Fig. 3. Photos of the two helmets worn by players who suffered SDHs.
Results
Both helmets passed the modified version of the NOCSAE standardized drop test and were deemed to be compliant. Results are summarized in table 1. The Medium Schutt Air Advantage 7888 achieved an average SI of 451.9, with a maximum SI of 699.0 on rear impact and a minimum SI of 203.0 on left frontal boss impact. The Large Schutt Air XP 7890 achieved an average SI of 446.5, with a maximum SI of 568.5 on rear impact and a minimum SI of 309.5 on front impact.
Discussion
Brief Description of NOCSAE NOCSAE was founded in 1969 after an alarming increase in the incidence of brain injury-related fatalities in American football during the period of time from 1965 to 1969 was noted [10]. NOCSAE helmet specifications were based on research performed at Wayne State University and were designed to assess the helmet’s ability to limit SI, a value calculated by integrating translational acceleration to the 2.5th power with respect to time, following a standardized drop test [11]. Under the guidance of NOCSAE, standards regarding the energy-attenuating properties of helmets were expanded to include college football in 1978 and high-school football in 1980. At the present time, all high-school and collegiate football players are required to wear helmets meeting NOCSAE standards. While compliance with NOCSAE standards is required for all levels of American football, the majority of clinicians who care for athletes involved in helmeted injuries are unfamiliar with the specific details of helmet regulation. The NOCSAE standard is a pass/fail assess46
Pediatr Neurosurg 2013;49:43–49 DOI: 10.1159/000355121
ment whose threshold has been set at a SI of 1,200 [12]. A helmet must test below a SI of 1,200 during standardized drop tests at all designated impact locations (a more specific description of the details of helmet testing can be found in the Methods section). The 122 cm drop test that is used is roughly equivalent to a player running at 5.46 meters per second (19.6 kmh) into a flat surface that stops his/her head in less than 1 inch – approximating a severe, helmeted collision. Notably, NOCSAE does not require recertification at any specified interval. Instead, it defers this decision to individual schools and national organizations. NOCSAE does, however, determine the specifications of the recertification process, which are extremely similar to those of the initial certification. While manufacturers test their own helmets following production, licensed re-conditioners oversee testing of used helmets. Licensed re-conditioning companies who are in appropriate compliance with NOCSAE certification visually inspect all helmets for cracks and other evidence of dysfunction. However, current NOCSAE requirements mandate that only 2% of helmets (or approximately 50,000 individual tests annually) be subjected to direct assessment with standard drop testing; the remaining approximately 98% of helmets receive visual inspection alone with replacement of broken parts, if necessary. NOCSAE does not possess the means and/or resources to enforce proper compliance with the standards it has set forth and instead relies on a voluntary ‘honor’ system. Questions Surrounding Helmet Recertification The ability of helmets to attenuate energy is central to the prevention of underlying injury to intracranial structures. Increased helmet wear can lead to a phenomenon of ‘pre-compression’ in the foam layer and a decrease in the properties of energy attenuation [13]. Forbes/Zuckerman/He/McCalley/Lee/ Solomon/Halstead/Sills
While a large amount of funding at the collegiate and professional levels allows for high standards in the quality of the equipment used, previous investigations have brought the practice of equipment certification at youth and high-school levels into the national spotlight, including one company responsible for helmet certification who faces legal ramifications for improperly returning approximately 4,000 helmets to be used in play during the 2005–2006 season [3]. As both of the athletes described in this case report were high-school players from poor, rural communities, one potential concern was that the quality of headgear worn by these players was substandard. As described above, formal testing of the equipment performed in this study demonstrated that both helmets were fully compliant with a modified version of the NOCSAE standards. One interpretation of this finding is that a NOCSAE-certified football helmet does not guarantee protection against SDH. Additional Considerations Scientific investigation performed in this study clearly demonstrates that the headgear worn by struck players adhered to the modified NOCSAE standards. However, important questions remain: why did these two players suffer SDH? Despite numerous technological advances and regulatory changes, why is the reported incidence of catastrophic head injury in American football at a 30-year high? One clue may have to do with the epidemiology of SDH in American football players. Curiously, despite lower mass, lower impact velocity, and lower impact translational acceleration, high-school football players have an incidence of SDH that is 3.3 times of college football players [10]. One potential explanation of this disparity in SDH incidence between high-school and collegiate athletes is a difference in the type of biomechanical forces commonly experienced between these groups. Interestingly, in a review of 5 studies measuring head acceleration in concussed athletes, high-school athletes experienced a smaller amount of translational acceleration with associated collisions, but a larger amount of rotational acceleration [14]. While SI (a rough marker of translational acceleration) has formed the basis of the helmet quality assurance standard since the Wayne State studies on cadaveric skull fractures of the 1960s, previous studies in the neurosurgical literature have suggested that high levels of rotational acceleration are instead responsible for SDH [15]. Highschool athletes might be predisposed to increased rotaSDH in High-School Football Players: Post-Injury Helmet Testing
Front impacts
Side impacts
Front boss impacts
Rear boss impacts
Rear impacts
Top impacts
Fig. 4. Diagram of NOCSAE standard impact testing. Per NOCSAE,
a 122 cm drop test is roughly equivalent to a player running at 5.46 meters per second (19.6 kmh) into a flat surface which stops his head in less than 1 inch (most players run faster than this, but rarely would the head be stopped in such a short distance on the football field; thus, this approximately is consistent with a severe helmeted collision).
Pediatr Neurosurg 2013;49:43–49 DOI: 10.1159/000355121
47
Table 1. Summary of standardized modified NOCSAE-certified helmet testing
Helmet
SI
Schutt 7888 Air Advantage Schutt 7890 Air XP
front boss
front
side
rear boss
rear
top
random
average
304.5 309.5
252.5 380.5
559.5 469.5
493.5 440.5
699.0 568.5
651.5 537.5
203.0 419.5
451.9 446.5
This table is a summary of the results of standardized modified NOCSAE-certified helmet testing. The two helmets are listed to the left. The location of each pair of impacts is indicated in the uppermost column. Each value listed represents the average of two standardized impacts obtained by dropping a helmet from rest 60 inches above ground at a given location. The magnitude of the re-
sultant imputes is measured by SI, which is equal to the integral of translational acceleration to a power of 2.5, with respect to time. Per NOCSAE criteria, a helmet ‘passes’ if the SI from all drop tests is
