Brock Schnebel

Biomechanical properties of concussions in high school football

INTRODUCTION Sport concussion represents the majority of brain injuries occurring in the United States with 1.6–3.8 million cases annually. Understanding the biomechanical properties of this injury will support the development of better diagnostics and preventative techniques. METHODS We monitored all football related head impacts in 78 high school athletes (mean age = 16.7 yr) from 2005 to 2008 to better understand the biomechanical characteristics of concussive impacts. RESULTS Using the Head Impact Telemetry System, a total of 54,247 impacts were recorded, and 13 concussive episodes were captured for analysis. A classification and regression tree analysis of impacts indicated that rotational acceleration (95582.3 rad·s−²), linear acceleration (996.1g), and impact location (front, top, and back) yielded the highest predictive value of concussion. CONCLUSIONS These threshold values are nearly identical with those reported at the collegiate and professional level. If the Head Impact Telemetry System were implemented for medical use, sideline personnel can expect to diagnose one of every five athletes with a concussion when the impact exceeds these tolerance levels. Why all athletes did not sustain a concussion when the impacts generated variables in excess of our threshold criteria is not entirely clear, although individual differences between participants may play a role. A similar threshold to concussion in adolescent athletes compared with their collegiate and professional counterparts suggests an equal concussion risk at all levels of play.

In vivo study of head impacts in football: a comparison of National Collegiate Athletic Association Division I versus high school impacts.

OBJECTIVETo compare the frequency and magnitude of head impacts between National Collegiate Athletic Association Division I and American high school football players. The long-term goal is to correlate impact forces with injury patterns, leading to improvements in protective headgear. METHODSThe helmets of football players at the University of Oklahoma (n = 40) and Casady High School (n = 16) were instrumented with the Head Impact Telemetry System (Simbex, Lebanon, NH). Data were collected for practices and games for the 2005 football season and were analyzed by player position and school. Player positions were separated into two groups (skill and line) for analysis. Two case studies of athletes who sustained a concussion are also presented. RESULTSA total of 54,154 impacts were recorded at the University of Oklahoma and 8326 at Casady High School. College players sustained high-level impacts greater than 98 g more frequently than high school players. The mean linear accelerations for the top 1, 2, and 5% of all impacts were also higher for college players (P < 0.02). Skill position players received 24.6% of all impacts and sustained an impact greater than 98 g once every 70 impacts. In contrast, linemen sustained the highest number of impacts, but most were relatively low-magnitude (20–30 g). Linemen sustained an impact greater than 98 g once every 125 impacts. CONCLUSIONDifferences in the frequency and magnitude of head acceleration after impact exist between a Division I college team and a high school team. Compared with linemen, skill position players typically sustain the highest-level impacts. Additional data collection and analysis are required to correlate concussion diagnosis with acceleration magnitude and impact location.

Head impact exposure sustained by football players on days of diagnosed concussion

PURPOSE This study compares the frequency and severity of head impacts sustained by football players on days with and without diagnosed concussion and to identify the sensitivity and specificity of single-impact severity measures to diagnosed injury. METHODS One thousand two hundred eight players from eight collegiate football teams and six high school football teams wore instrumented helmets to measure head impacts during all team sessions, of which 95 players were diagnosed with concussion. Eight players sustained two injuries and one sustained three, providing 105 injury cases. Measures of head kinematics (peak linear and rotational acceleration, Gadd severity index, head injury criteria (HIC15), and change in head velocity (Δv)) and the number of head impacts sustained by individual players were compared between days with and without diagnosed concussion. Receiver operating characteristic curves were generated to evaluate the sensitivity and specificity of each kinematic measure to diagnosed concussion using only those impacts that directly preceded diagnosis. RESULTS Players sustained a higher frequency of impacts and impacts with more severe kinematic properties on days of diagnosed concussion than on days without diagnosed concussion. Forty-five injury cases were immediately diagnosed after head impact. For these cases, peak linear acceleration and HIC15 were most sensitive to immediately diagnosed concussion (area under the curve = 0.983). Peak rotational acceleration was less sensitive to diagnosed injury than all other kinematic measures (P = 0.01), which are derived from linear acceleration (peak linear, HIC15, Gadd severity index, and Δv). CONCLUSIONS Players sustained more impacts and impacts of higher severity on days of diagnosed concussion than on days without diagnosed concussion. In addition, of historical measures of impact severity, those associated with peak linear acceleration are the best predictors of immediately diagnosed concussion.

Timing of concussion diagnosis is related to head impact exposure prior to injury

PURPOSE Concussions are commonly undiagnosed in an athletic environment because the postinjury signs and symptoms may be mild, masked by the subject, or unrecognized. This study compares measures of head impact frequency, location, and kinematic response before cases of immediate and delayed concussion diagnosis. METHODS Football players from eight collegiate and six high school teams wore instrumented helmets during play (n = 1208), of which 95 were diagnosed with concussion (105 total cases). Acceleration data recorded by the instrumented helmets were reduced to five kinematic metrics: peak linear and rotational acceleration, Gadd severity index, head injury criterion, and change in head velocity (Δv). In addition, each impact was assigned to one of four general location regions (front, back, side, and top), and the number of impacts sustained before injury was calculated over two periods (1 and 7 days). RESULTS All head kinematic measures associated with injury, except peak rotational acceleration (P = 0.284), were significantly higher for cases of immediate diagnosis than delayed diagnosis (P < 0.05). Players with delayed diagnosis sustained a significantly higher number of head impacts on the day of injury (32.9 ± 24.9, P < 0.001) and within 7 d of injury (69.7 ± 43.3, P = 0.006) than players with immediate diagnosis (16.5 ± 15.1 and 50.2 ± 43.6). Impacts associated with concussion occurred most frequently to the front of the head (46%) followed by the top (25%), side (16%), and back (13%) with the number of impacts by location independent of temporal diagnosis (χ(3) = 4.72, P = 0.19). CONCLUSIONS Concussions diagnosed immediately after an impact event are associated with the highest kinematic measures, whereas those characterized by delayed diagnosis are preceded by a higher number of impacts.

Can helmet design reduce the risk of concussion in football

Of all sports, football accounts for the highest incidence of concussion in the US due to the large number of athletes participating and the nature of the sport. While there is general agreement that concussion incidence can be reduced through rule changes and teaching proper tackling technique, there remains debate as to whether helmet design may also reduce the incidence of concussion. A retrospective analysis was performed of head impact data collected from 1833 collegiate football players who were instrumented with helmet-mounted accelerometer arrays for games and practices. Data were collected between 2005 and 2010 from 8 collegiate football teams: Virginia Tech, University of North Carolina, University of Oklahoma, Dartmouth College, Brown University, University of Minnesota, Indiana University, and University of Illinois. Concussion rates were compared between players wearing Riddell VSR4 and Riddell Revolution helmets while controlling for the head impact exposure of each player. A total of 1,281,444 head impacts were recorded, from which 64 concussions were diagnosed. The relative risk of sustaining a concussion in a Revolution helmet compared with a VSR4 helmet was 46.1% (95% CI 28.1%-75.8%). When controlling for each players exposure to head impact, a significant difference was found between concussion rates for players in VSR4 and Revolution helmets (χ(2) = 4.68, p = 0.0305). This study illustrates that differences in the ability to reduce concussion risk exist between helmet models in football. Although helmet design may never prevent all concussions from occurring in football, evidence illustrates that it can reduce the incidence of this injury.

Isolated traumatic avulsion of the flexor digitorum sublimis A case report

Like the FDP, the FDS may be avulsed at its insertion. The diagnosis can be made based on a history of resisted extension, palmar pain and tenderness, lack of FDS function, and inability to completely extend the DIP joint secondary to the looping affect of the FDS. In the seven reported cases of FDS rupture no surgical intervention was required. This case represents a case in which surgical intervention was required secondary to an isolated avulsion of the FDS in a football player.

Sideline Neurological Evaluation: a Detailed Approach to the Sideline, In-Game Neurological Assessment of Contact Sport Athletes.

Contact sport holds inherent risk of traumatic injury to participant athletes. Neurologic injury, from trauma, portends significant potential for morbidity and mortality. The in-game sideline presents a challenging setting for injury evaluation. Athletic trainers and team physicians should understand general principles of the neurologic evaluation and apply a systematic approach that allows an organized evaluation of and differential diagnosis of neurologic injury. Athlete welfare demands an immediate, accurate diagnosis followed by targeted management. Management provides appropriate referral, timely treatment, and appropriate return-to-play decision. Management begins with recognition.

Estimated Brain Tissue Response Following Impacts Associated With and Without Diagnosed Concussion

Kinematic measurements of head impacts are sensitive to sports concussion, but not highly specific. One potential reason is these measures reflect input conditions only and may have varying degrees of correlation to regional brain tissue deformation. In this study, previously reported head impact data recorded in the field from high school and collegiate football players were analyzed using two finite element head models (FEHM). Forty-five impacts associated with immediately diagnosed concussion were simulated along with 532 control impacts without identified concussion obtained from the same players. For each simulation, intracranial response measures (max principal strain, strain rate, von Mises stress, and pressure) were obtained for the whole brain and within four regions of interest (ROI; cerebrum, cerebellum, brain stem, corpus callosum). All response measures were sensitive to diagnosed concussion; however, large inter-athlete variability was observed and sensitivity strength depended on measure, ROI, and FEHM. Interestingly, peak linear acceleration was more sensitive to diagnosed concussion than all intracranial response measures except pressure. These findings suggest FEHM may provide unique and potentially important information on brain injury mechanisms, but estimations of concussion risk based on individual intracranial response measures evaluated in this study did not improve upon those derived from input kinematics alone.

Acute Lumbar Paraspinal Myonecrosis in Football Players With Sickle Cell Trait: A Case Series.

ABSTRACT We report six cases of a novel syndrome of acute, exertional low back pain in football players, five in college and one in the National Football League. All six are African Americans with sickle cell trait (SCT). The acute low back pain is severe and can be disabling, and the condition can be confused with muscle strain, discogenic pain, stress fracture, or other problems in athletes. Our evidence shows that this syndrome is caused by lumbar paraspinal myonecrosis (LPSMN), which likely often contributes to the lumbar paraspinal compartment syndrome. We explain why we believe SCT is a risk factor for LPSMN in football conditioning/training, although SCT is not requisite for this syndrome, which has been reported rarely in other sports (e.g., snow or water skiing) and especially in weight lifting that targets lumbar muscles. The clinical course of LPSMN in football can be mild and allow return to play in a week or two, or it can be severe and lead to long-term sequelae. Knowledge of this syndrome will enable athletic trainers and team physicians to diagnose it early, treat it properly, and lessen its effect. Further research will help us learn how better to prevent it.