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With an estimated 3. Biomechanical analysis of head impacts may provide quantitative information that can inform both prevention and diagnostic strategies. To assess available head-impact devices and their clinical utility. We performed a systematic search of the electronic database PubMed for peer-reviewed publications, using the following phrases: accelerometer and concussion , head impact telemetry , head impacts and concussion and sensor , head impacts and sensor , impact sensor and concussion , linear acceleration and concussion , rotational acceleration and concussion , and xpatch concussion. In addition to the literature review, a Google search for head impact monitor and concussion monitor yielded 15 more devices.VIDEO ON THE TOPIC: The Controversy Of The Crooked Referees: Lakers Vs Kings
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With an estimated 3. Biomechanical analysis of head impacts may provide quantitative information that can inform both prevention and diagnostic strategies. To assess available head-impact devices and their clinical utility. We performed a systematic search of the electronic database PubMed for peer-reviewed publications, using the following phrases: accelerometer and concussion , head impact telemetry , head impacts and concussion and sensor , head impacts and sensor , impact sensor and concussion , linear acceleration and concussion , rotational acceleration and concussion , and xpatch concussion.
In addition to the literature review, a Google search for head impact monitor and concussion monitor yielded 15 more devices. Included studies were performed in vivo, used commercially available devices, and focused on sport-related concussion. One author reviewed the title and abstract of each study for inclusion and exclusion criteria and then reviewed each full-text article to confirm inclusion criteria. Controversial articles were reviewed by all authors to reach consensus.
In total, 61 peer-reviewed articles involving 4 head-impact devices were included. Fourteen additional commercially available devices were presented. Measurements collected by impact monitors provided real-time data to estimate player exposure but did not have the requisite sensitivity to concussion. Proper interpretation of previously reported head-impact kinematics across age, sport, and position may inform future research and enable staff clinicians working on the sidelines to monitor athletes.
However, head-impact—monitoring systems have limited clinical utility due to error rates, designs, and low specificity in predicting concussive injury. Head-impact sensors have limited applications to concussion diagnosis but may provide sideline staff with estimates of athlete exposure and real-time data to monitor players. Given that concussion risk is influenced by many factors in addition to impact biomechanics, viewing an athlete's head-impact data may provide context for the clinician working on the sidelines, but impact sensors should not replace clinical judgment.
In , among the Concussion is a brain injury resulting from a direct or indirect blow to the head, typically resulting in transient neurologic impairment and neuropathologic symptoms. Similar findings of vulnerability and impaired recovery have also been shown in male athletes.
Removing injured athletes from participation close to the time of injury reduces the risk of secondary injury when they are vulnerable to the cumulative effect of concussions.
Researchers have investigated more objective measures for concussion diagnosis, including balance testing, 20 neuropsychological testing, 21 and advanced imaging. Head-impact biomechanics have been investigated to determine the kinematic signature of a concussion.
Impacts to the head cause a combined linear and angular acceleration of the skull. It is impossible to directly measure the tissue-level response of the brain to impact in vivo. Instead, skull acceleration is measured as a correlate to the pressure and strain responses of brain tissues. Acceleration represents the rate of change in velocity, and in this review, we report resultant linear accelerations LAs and resultant angular accelerations AAs of the head.
Resultant LA is the vector sum magnitude of the 3-dimensional LAs of the skull resulting from an impact. It is measured in gravitational units g , which is equal to the acceleration due to gravity approximately 9. Similarly, resultant AA is the vector sum of the 3-dimensional AAs of the skull resulting from an impact and is measured in units of radians per second squared.
Resultant LA and AA are closely correlated with each other. Vectors farther away from the center of gravity create greater resultant AA relative to resultant LA. Alternatively, force vectors in line with the center of gravity create greater resultant LA.
Therefore, in some instances, lowering resultant LA magnitude lowers resultant AA. Determining the mechanics of brain injury is not a recent area of investigation. In , Holbourn 29 studied the mechanics of head injuries, focusing on rotational forces. In subsequent primate work, Ommaya 30 suggested that, whereas resultant AA may produce diffuse and focal injury, resultant LA produces only focal injury. Since then, resultant LA and AA have been posited to influence concussive injury 23 , 31 , 32 through pressure gradients and shearing stress, respectively.
In addition to simple magnitudes, impact-severity measures quantify injury tolerance, and the original work in car impacts yielded the Wayne State Tolerance Curve WSTC.
Whereas the GSI was a good tool for estimating short-duration impacts ie, focal brain injuries , it was not as good at estimating longer-duration injuries that are more indicative of diffuse brain injury. A millisecond HIC window HIC15 was selected on the basis of auto-industry work, with cadaver simulations of injury indicating that durations less than 15 milliseconds mimic the WSTC.
The HIC15 indicates that 15 milliseconds is the selected time range for integrating the linear time curve. It combines resultant LA, rotational acceleration, impact location, and impact duration using a weighted principal component analysis. Greater proportions for sensitivity and specificity indicate that the kinematic measure can discern between concussive and nonconcussive events. Angular acceleration identified the greatest proportion of nonconcussive events as concussive Most biomechanics research on brain injury has been limited to laboratory experiments focusing on moderate to severe injury.
Concussion has been particularly challenging to study because human-volunteer experiments must be noninjurious, and human surrogates eg, cadaver, dummy do not produce the physiological signs and symptoms required to identify concussion. Recent computer and technologic advances, however, have enabled in vivo concussion studies to be conducted using impact-monitoring devices. In addition, numerous devices have been marketed to athletes, parents, and clinicians with the suggestion that these devices offer clinical utility.
Therefore, the purpose of our systematic review was to supply clinicians with a comprehensive review of currently available devices and discuss their clinical utility and limitations. First, we summarize data collected in vivo across age levels and sports. Second, results from laboratory studies provide context on the utility and limitations of each device. A PubMed search was completed in March using the following phrases: accelerometer and concussion , head impact telemetry , head impacts and concussion and sensor , head impacts and sensor , impact sensor and concussion , linear acceleration and concussion , rotational acceleration and concussion , and xpatch concussion.
In addition to the literature review, a Google search for head impact monitor and concussion monitor yielded 15 more devices Table 1.
The reference list of each included article was reviewed for relevant additional articles. We included articles if they were written in English and if the investigators studied an athlete sample and used concussion-specific accelerometer s to measure head mechanics. We excluded articles if they were laboratory studies, review papers, or commentaries or if investigators included a nonathlete sample, used an accelerometer that was not targeted for concussion measurement, or included a device that was not commercially available.
Using these inclusion and exclusion criteria allowed us to generate the list of in vivo studies to evaluate and present compiled head-impact values. One author K. She further reviewed each full-text article to confirm inclusion criteria. Controversial articles were reviewed by all authors K. When available, total number of impacts; impacts per season; impacts per session; and means, standard deviations, medians, interquartile ranges, and 95th percentiles were extracted for resultant LA, resultant AA, and HITsp.
A total of records were initially identified via PubMed; of these, were unique. Each unique study was evaluated for inclusion and exclusion criteria, and 46 were screened out by review of the title and abstract. To the remaining , we added 5 articles from citation lists. Device information, metrics, validity, and limitations were reviewed for all devices.
Specifically tailored versions of the HITS device have been placed in boxing, 89 ice hockey, 16 , 42 , 44 , 45 , 77 , 78 , 80 soccer, 87 and snow sports 88 headgear. For the device to record an impact, 1 of the 6 accelerometers must exceed Resultant LA is recorded at 1 kHz, with 8 milliseconds of preimpact data and 32 milliseconds of postimpact data determined when the threshold is reached composing a millisecond acceleration-time trace.
When recorded, the data are filtered to eliminate any impact in which the peak resultant LA did not exceed 10 g , meaning that all impacts in the final database were greater than 10 g. Resultant AA values are regression-based estimates derived from the resultant LA. An algorithm computes resultant LA. Resultant LAs are recorded at 1 kHz and resultant AAs are recorded at approximately Hz, which is interpolated to match the resultant LA time sequence. Compared with the HITS device, the X2 system supplies a millisecond trace 10 milliseconds preimpact and 90 milliseconds postimpact for each linear and angular sensor channel when an impact exceeds the 10 g trigger.
Acceleration and loading of the head place strain on brain tissue that may cause concussive injury. Even in the ideal scenario with sensors affixed directly to the cranial bones, brain movement cannot be measured because the brain moves independently within the skull cavity. The helmeted design of HITS uses spring-loaded accelerometers to maintain contact with the skull as the helmet moves and deforms.
In more recent validity tests, Simbex, the manufacturer of the HITS, attempted to simulate National Football League impacts by using impact sites and velocities identified by the league. Using specific impact locations and velocities possibly reduced the error compared with other studies. Compared with the observations of Beckwith et al, Rowson et al 26 found that resultant AA was overestimated, leading to a correction factor that has been applied to all HITS datasets since Error associated with individual data points is greater than aggregate distributions of the data.
The pooled measurements are more representative of the distribution of resultant AA. They observed that 55 of 64 impacts were in the direction opposite the actual impact direction. Whereas video captured confirmed head impacts, the X-Patch recorded impacts.
The X-Patch recorded false-positive and true-positive impacts, yielding a positive predictive value of Error rates should be considered when evaluating impact magnitudes 94 and frequencies.
Recording thresholds for HITS literature varied from 9. The default trigger is Although many researchers have suggested a 10 g minimal value, it is most likely not the trigger value; rather, the HITS software filters all peak resultant LAs that are less than 10 g. Consequently, the 10 g reported values most likely refer to the filtering process and not the minimal trigger value of the single accelerometer.
One needs to know the minimal triggering value to compare impact magnitudes across studies. King et al evaluated how varying recording thresholds would change the head-impact data.
The descriptions of each device and their relative limitations should be considered when examining the data that we have summarized. Moreover, caution should be used when comparing results across studies in which different devices were examined. To facilitate the interpretation of data based on similar methods, data for helmeted devices are summarized in Table 2 , and data for nonhelmeted devices are summarized in Table 3.
In addition, head-impact data, regardless of the sport or collection device, are heavily right skewed, with most impacts tending to have lower magnitudes.
Therefore, means reported are greater than medians reported, indicating that the measure of central tendency should be considered when interpreting results. Whereas means and standard deviations are commonly provided, medians and interquartile ranges are better assessments of the typical impact magnitude.
Normative data for head-impact exposure and magnitudes by level, sport, and sex are summarized. Impacts per season, impacts per player per session, peak resultant LA, peak resultant AA, and HITsp were extracted from each article when available. Impact magnitudes are described by means, medians, and 95th percentiles.
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Head-Impact–Measurement Devices: A Systematic Review
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In association football , goal-line technology sometimes referred to as a Goal Decision System  is the use of electronic aid to determine if a goal has been scored or not. In detail, it is a method used to determine when the ball has completely crossed the goal line in between the goal-posts and underneath crossbar with the assistance of electronic devices and at the same time assisting the referee in awarding a goal or not. The objective of goal-line technology GLT is not to replace the role of the officials, but rather to support them in their decision-making. The GLT must provide a clear indication as to whether the ball has fully crossed the line, and this information will serve to assist the referee in making his final decision. Compared to similar technology in other sports, goal-line technology is a relatively recent addition to association football, its integration having been opposed by the sport's authorities.
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