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Viano D.C.,ProBiomechanics LLC | Halstead D.,University of Tennessee at Knoxville | Halstead D.,Southern Impact Research Center
Annals of Biomedical Engineering | Year: 2012

Linear impactor tests were conducted on football helmets from the 1970s-1980s to complement recently reported tests on 1990s and 2010s helmets. Helmets were placed on the Hybrid III head with an array of accelerometers to determine translational and rotational acceleration. Impacts were at four sites on the helmet shell at 3.6-11.2 m/s. The four generations of helmets show a continuous improvement in response from bare head impacts in terms of Head Injury Criterion (HIC), peak head acceleration and peak rotational acceleration. Helmets of 2010s weigh 1.95 ± 0.2 kg and are 2.7 times heavier than 1970s designs. They are also 4.3 cm longer, 7.6 cm higher, and 4.9 cm wider. The extra size and weight allow the use of energy absorbing padding that lowers forces in helmet impacts. For frontal impacts at 7.4 m/s, the four best performing 2010s helmets have HIC of 148 ± 23 compared to 179 ± 42 for the 1990s baseline, 231 ± 27 for the 1980s, 253 ± 22 for the 1970s helmets, and 354 ± 3 for the bare head. The additional size and padding of the best 2010s helmets provide superior attenuation of impact forces in normal play and in conditions associated with concussion than helmets of the 1970s-1990s. © 2011 Biomedical Engineering Society.


Viano D.C.,ProBiomechanics LLC | Withnall C.,Biokinetics and Associates Ltd. | Wonnacott M.,Biokinetics and Associates Ltd.
Annals of Biomedical Engineering | Year: 2012

The potential for mouthguards to change the risk of concussion was studied in football helmet impacts. The Hybrid III head was modified with an articulating mandible, dentition, and compliant temporomandibular joints (TMJ). It was instrumented for triaxial head acceleration and triaxial force at the TMJs and upper dentition. Mandible force and displacement were validated against cadaver impacts to the chin. In phase 1, one of five mouthguards significantly lowered HIC in 6.7 m/s impacts (p = 0.025) from the no mouthguard condition but not in 9.5 m/s tests. In phase 2, eight mouthguards increased HIC from +1 to +17% in facemask impacts that loaded the chinstraps and mandible; one was statistically higher (p = 0.018). Peak head acceleration was +1 to +15% higher with six mouthguards and 2-3% lower with two others. The differences were not statistically significant. Five of eight mouthguards significantly reduced forces on the upper dentition by 40.8-63.9%. Mouthguards tested in this study with the Hybrid III articulating mandible lowered forces on the dentition and TMJ, but generally did not influence HIC or concussion risks. © 2011 Biomedical Engineering Society.


Viano D.C.,ProBiomechanics LLC | Parenteau C.S.,ProBiomechanics LLC
Traffic Injury Prevention | Year: 2015

Purpose: Starting in 1997, General Motors (GM) introduced high retention seats in new model vehicles to improve rear impact safety. The seat allowed the occupant to pocket into the seatback and had increased strength and improved head restraint coverage. The initial 4-year safety trends were evaluated using the 1991–2000 Fatality Analysis Reporting System (FARS). The reduction in odds of fatal injury was 30.4% (95% confidence interval [CI], 0.9–51.1, P <.05). This study updates the earlier one by adding 8 years of FARS data.Methods: The 2001–2008 FARS was analyzed for rear impacts of 1992 to 2008 model year GM vehicles that transitioned to high retention seats. The number of fatal and nonfatal injuries to drivers and right-front passengers was determined in vehicles with baseline (earlier designs) and high retention seats. The odds ratio for fatal injury and the change in fatality risk were determined with ±95% confidence intervals, z-statistic, and significance level. The data were further subdivided by passenger car, light truck (truck, SUV, and van) and driver-only crashes.Results: Based on 9,570 drivers and right-front passengers in fatal rear impacts in 1991–2008 FARS data, the fatality risk was 16.6% (95% CI, 15.1–18.3) in vehicles with high retention seats and 27.1% (95% CI, 26.1–28.1) in vehicles with baseline seats. The reduction in odds for fatal injury was 46.3% (95% CI, 39.3–52.4) with high retention seats and it was statistically significant with z = 9.982, P <.0001. The reduction in odds for fatal injury was similar for occupants in passenger cars at 45.4% (95% CI, 35.4–53.8) and light trucks, SUVs, and vans at 45.0% (95% CI, 28.8–57.5) using 2001–2008 FARS; however, the fatality risk was higher in passenger cars, at 23.1% (95% CI, 20.6–25.7), than in light trucks, SUVs, and vans, at 8.7% (95% CI, 7.0–10.7).Conclusions: Vehicles with high retention seats significantly reduced the odds for fatal injury by 46.3% (95% CI, 39.3–52.4, P <.0001) in rear impacts compared to vehicles with earlier seat designs. The new generation of yielding seats has significantly improved occupant safety in rear impacts. © 2015, Copyright © Taylor & Francis Group, LLC.


Viano D.C.,ProBiomechanics LLC | Parenteau C.S.,ProBiomechanics LLC
Traffic Injury Prevention | Year: 2010

Purpose: This study investigated the risk of severe-to-fatal injury (MAIS 4+F) to near- and far-seated front occupants in side impacts by belt use and crash severity (delta V). Methods: 1993-2007 NASS-CDS was analyzed for front-seat occupants in side impacts while they were either the nearside or far-side occupant by belt use. Light vehicles were included with model year 1994+. Injury severity was subdivided into MAIS 0-2, 3, and 4+F. The risk for MAIS 4+F injury was determined by dividing the number of MAIS 4+F by the number of exposed occupants with known injuries. Individual NASS-CDS cases were downloaded from the 1997-2007 electronic data to evaluate injury patterns causing high relative risks. Results: In 35+ mph side-impact delta Vs, the risk for MAIS 4+F injury was 75.4 ± 41.0% for unbelted near-side and 48.1 ± 14.6% for unbelted far-side occupants. The risk was 51.8 ± 14.8% for belted near-side and 30.9 ± 8.2% for far-side occupants. Seat belt use was 81.4% effective in preventing MAIS 4+F injury for near-side occupants and 93.5% for far-side occupants. The relative risk (RR) for unbelted compared to belted occupants was 35.9 for far-side occupants in 10-15 mph delta V crashes. The relative risk was 35.1 for near-side occupants in <10 mph delta V side impacts. The high relative risks were associated with complex, high-speed multi-collision crashes often with occupant impacts on the windshield, st eeringwheel, or other frontal components and ejection. Conclusions: Seat belt use was more effective in preventing severe injury (MAIS 4+F) to far-side occupants than near-side occupants in <25 mph delta V impacts. High relative risk for unbelted occupants in low-speed side impacts was explained by the fact that the accidents were high-speed, multi-impact collisions. Severe injury was caused by ejection, impact with the side interior, or impact with the frontal components where airbags sometimes deployed. © 2010 Taylor & Francis Group, LLC.


Viano D.C.,ProBiomechanics LLC | Parenteau C.S.,ProBiomechanics LLC
Traffic Injury Prevention | Year: 2010

Purpose: This study investigates the risk of severe-to-fatal injury (Maximum Abbreviated Injury Score, MAIS 4+F) in crashes with two front-seat occupants. It determines the relative risk of injury in the same crash by belt use and seating position. Methods: 1993-2008 NASS-CDS was analyzed for crashes with occupants in both front-outboard seats. The effect of belt use was investigated for the driver and passenger. Light vehicles were included with model year 1990+. Injury severity was subdivided into MAIS 0-2 and 4+F in NASS-CDS to compare no-to-moderate injury with severe-to-fatal injury. Standard errors were calculated in SAS and the z-test was used to determine the significance of differences in risk. Relative risks were determined by seat belt use and seating position; odds ratios were determined for one or both occupants being severely injured. Results: In 76.7 percent of the MAIS 4+F crashes, either the driver (32.4%) or passenger (44.3%) was severely injured, rather than both occupants (23.3%). When both were belted, one occupant was severely injured in 86.5 percent of crashes. When both were unbelted, both occupants were severely injured in 68.9 percent of the crashes. Both occupants were belted in 74.7 percent of the cases and unbelted in 18.6 percent. In 6.7 percent of crashes, either the driver (4.4%) or passenger (2.3%) was unbelted when the other was belted. The highest risk occurred with an unbelted driver and belted passenger (4.98 ± 0.73% vs. 1.97 ± 0.38%, z = 3.65, p <.05). When both occupants were belted, the driver and passenger injury risk was similar (0.459 ± 0.098% vs. 0.449 ± 0.047%, z = 0.10, ns). Conclusions: In crashes with two front occupants, typically one occupant was severely injured, not both. Overall, the odds ratio was 3.28 for one compared to two occupants being severely injured; and, risks vary by seat belt use and seating position. The highest relative risk for unbelted versus belted occupants was 9.22 when both occupants were severely injured in the same crash. © 2010 Taylor & Francis Group, LLC.


Viano D.C.,ProBiomechanics LLC | Parenteau C.S.,ProBiomechanics LLC
Traffic Injury Prevention | Year: 2010

Purpose: This study investigated injury risks in frontal crashes by belt use and crash severity (delta V) with a focus on studying whether there is a pattern to the crashes causing serious head injuries in low-speed frontal collisions. Methods: 1996-2007 National Automotive Sample System-Crashworthiness Data System (NASS-CDS) was analyzed for frontal crashes involving front-outboard occupants. Light vehicles were included with model year 1997+. Injuries of maximum severity MAIS 0-6 and fatalities were determined by crash severity and belt. Body region injury (AIS 0-6) was also determined. NASS-CDS electronic cases involving lt;15 mph crashes were evaluated to determine the crash circumstances causing serious head injury (AIS 3+) in occupants with overall severe injuries (MAIS 4+F). Results: More than half (51.3%) of belted occupants in 10-15 mph delta V crashes were uninjured compared with 30.2 percent for unbelted occupants. The ratio of the fraction (relative risk) of belted occupants who were uninjured to the fraction of unbelted, uninjured occupants was highest at 3.74 in the 30-35 mph delta V. For 10-15 mph crashes, 0.40 ± 0.15 percent of unbelted occupants were severely injured (MAIS 4+F) compared to 0.033 ± 0.009 percent for belted occupants. For 30-35 mph crashes, 8.51 ± 2.20 percent of unbelted and 5.83 ± 1.93 percent of belted occupants were severely injured. Overall, seat belt use was 87.4 percent effective in preventing severe injury (MAIS 4+F). The effectiveness decreased with increasing crash severity. The highest relative risk for severe injury of unbelted compared to belted occupants was 12.3 in crashes of 10-15 mph delta V. The relative risk was 8.8 in lt;10 mph crashes. Overall, the relative risk was 8.0 for severe injury (MAIS 4+F) in frontal crashes. 16.5 ± 0.98 percent of unbelted occupants experienced serious (AIS 3-6) injury. This risk was 6.49 times greater than the 2.53 ± 0.10 percent risk with belted occupants. The largest relative risk for serious injury (AIS 3-6) was to the neck (367 times), face (15.5 times) and head (10.2 times). Conclusions: The highest relative risk for severe injury of unbelted occupants was in frontal crashes <15 mph. Most of the crashes involved multiple impacts and air bag deployment in the accident sequence. The use of long fill-time side curtains, additional curtain deployment logic, limited deflation front air bags and broader curtain coverage of the front interior may address these injuries. © 2010 Taylor & Francis Group, LLC.


Viano D.C.,ProBiomechanics LLC
SAE Technical Papers | Year: 2011

Purpose: This study presents cases of fracture-dislocation of the thoracic spine in extension during severe rear impacts. The mechanism of injury was investigated. Methods: Four crashes were investigated where a lap-shoulder belted, front-seat occupant experienced fracture-dislocation of the thoracic spine and paraplegia in a severe rear impact. Police, investigator and medical records were reviewed, the vehicle was inspected and the seat detrimmed. Vehicle dynamics, occupant kinematics and injury mechanisms were determined in this case study. Results: Each case involved a lap-shoulder belted occupant in a high retention seat with >1,700 Nm moment or >5.5 kN strength for rearward loading. The crashes were offset rear impacts with 40-56 km/h delta V involving under-ride or over-ride by the impacting vehicle and yaw of the struck vehicle. In each case, the occupant's pelvis was restrained on the seat by the open perimeter frame of the seatback and lap belt. The rear loading caused the head, neck and upper body to displace off the side or top of the seatback. The seatback frame acted like a fulcrum as the unsupported head and upper body was accelerated forward causing extension of the spine around the seatback frame as the head and shoulders moved rearward of the frame. In each case, there was fracture-dislocation of the thoracic spine in extension with spinal cord injury resulting in paraplegia. Two occupants were overweight and two were obese, which increased inertial loads on the spine. Conclusions: High retention seats have improved safety of occupants in rear crashes, but there are situations where the upper body becomes unsupported in a severe rear crash. This can lead to extension loads on the spine causing fracture-dislocation, spinal cord injury and paraplegia. Injury is a result of the strong seat frame remaining upright, the lap belt holding the pelvis on the seat and the upper body moving off the seatback concentrating load on the thoracic spine. The seatback frame acts like a fulcrum resulting in fracture-dislocation of the spine in extension. Copyright © 2011 SAE International.


Viano D.C.,ProBiomechanics LLC | Parenteau C.S.,ProBiomechanics LLC
Traffic Injury Prevention | Year: 2010

Purpose: This study investigated the risk of severe-to-fatal injury (MAIS 4+F) with complete and partial ejection by crash type and belt use with a focus on ejection in rear impacts. Methods: 1993-2007 NASS-CDS was analyzed for crashes with complete and partial ejection. The effect of belt use was investigated and crashes were grouped by front, side, rear, and rollovers. Light vehicles were included with model year 1994+. Injuries of severity MAIS 4+F and AIS 3-6 by body region were determined by crash type, belt use, and ejection status. NASS-CDS electronic cases of complete ejection and serious injury were evaluated to determine the circumstances in rear impacts. Results: For unbelted occupants, the highest risk for complete ejection is in rollovers (16.4 ± 1.1%) and the risk for severe injury is 37.6 ± 2.7%. The lowest risk for complete ejection is in frontal crashes (0.97 ± 0.22%), but the risk for serious injury is 31.3 ± 6.2% when ejection occurs. The risk for ejection is 2.7 ± 1.5% in rear impacts with a 7.4 ± 3.4% risk for severe injury. For belted occupants, the highest risk for complete ejection is in rollovers (0.068 ± 0.022%) and the risk for severe injury is 25.9 ± 13.3% when ejection occurs. The relative risk for ejection is 193 times greater for unbelted compared to belted occupants in all crashes with a range of 100 times in frontal crashes up to 847 times in rear impacts. Unbelted occupants have 20 times greater risk for severe injury when completely ejected and 18 times greater risk with partial ejection compared to nonejected occupants. Belted occupants have a 77 times greater risk of severe injury when completely ejected and 37 times greater risk when partially ejected. Conclusions: Ejection involves significantly higher risks for severe injury in all crash types. The relative risk for MAIS 4+F injury is 20 times greater for unbelted and 77 times greater for belted occupants who are completely ejected compared to nonejected occupants. Ejection of occupants in rear crashes often occurs during vehicle yaw motion after the primary impact. © 2010 Taylor & Francis Group, LLC.


Parenteau C.S.,ProBiomechanics LLC | Viano D.C.,ProBiomechanics LLC
Traffic Injury Prevention | Year: 2014

Purpose: This study estimated the annual count of spinal cord injuries (SCIs) in motor vehicles crashes by type and seat belt use using 18 years of NASS-CDS data. It determined the rate for SCI and fracture-dislocation of the spine.Methods: 1994-2011 NASS-CDS was used to estimate the annual occurrence of spinal injuries in front seat occupants involved in motor vehicle crashes. Crashes were grouped by front, side, rear, and rollovers, and the effects of belt use were investigated. Light vehicles were included with model year 1994+. Spinal injuries were classified as minor (Abbreviated Injury Scale [AIS] 1), moderate (AIS 2), serious (AIS 3), fracture-dislocations, and SCI (AIS 4+). The annual count and rate for different types of spinal injury were estimated along with standard errors. The results were compared to estimates of head injuries. NASS-CDS electronic cases of SCIs in rear impacts were investigated.Results: There were 5,592 ± 1,170 fracture-dislocations of the spine and 1,046 ± 193 AIS 4+ SCI per year in motor vehicle crashes. Most of the injuries occurred in rollovers and frontal crashes and the least occurred in rear impacts. The rate of SCI was 0.054 ± 0.010%. The highest rate was 0.220 ± 0.056% in rollover crashes and the lowest rate was 0.032 ± 0.009% in frontal crashes. The highest rate for spinal fracture-dislocation was 1.552 ± 0.455% in rollovers and the lowest was 0.065 ± 0.021% in rear impacts. The rate for SCI was 0.027 ± 0.005% in belted and 0.145 ± 0.028% in unbelted occupants giving 81% effectiveness of belt use in reducing SCI. The cervical spine was associated with 66.3 ± 11.3% of the AIS 4+ SCI with 30.5 ± 7.4% in the thoracic spine and 3.2 ± 1.3% in the lumbar spine. Severe head injuries occurred 13.3 times more often than SCIs.Conclusions: Spinal cord injury occurred in one out of 1,860 front seat occupants in tow-away crashes. The rate was highest in rollover crashes and was reduced by seat belt use. Fracture-dislocation of the spine occurred about 5.3 times more often than SCIs and was also prevented by seat belt use. © 2014 Copyright Taylor & Francis Group, LLC.


Viano D.C.,ProBiomechanics LLC | Parenteau C.S.,ProBiomechanics LLC
Traffic Injury Prevention | Year: 2015

Purpose: A recent study used the Fatality Analysis Reporting System (FARS) to determine the safety performance of high retention seats in fatal rear impacts. The odds of fatal injury were reduced 46.3% (95% confidence interval [CI], 39.3–52.4, z = 9.982, P <.0001) with high retention seats. This study extends the earlier one by establishing an exposure group of nonfatal occupants in towaway crashes using NASS-CDS. Methods: The 2001–2008 NASS-CDS was analyzed for rear impacts of 1992 to 2008 model year GM vehicles with high retention or baseline seats using the same search strategy as in FARS. Injuries were analyzed by severity (Maximum Abbreviated Injury Scale [MAIS]). The number of fatalities from FARS and number of nonfatal occupants from NASS-CDS were used to determine the risk for fatal injury in towaway crashes with 5–7 o’clock principal direction of force (PDOF). The odds ratio for fatal injury and the change in fatality risk were determined with ±95% confidence intervals, z-statistics, and significance levels. Injury risks were also determined using NASS-CDS. Results: Based on 2001–2008 FARS and NASS-CDS, the fatality risk was 0.21% in high retention seats and 0.39% in baseline seats in 5–7 o’clock towaway crashes. The odds for fatality were 46.8% (95% CI, 39.8–53.0, z = 10.001, P <.0001) lower with high retention seats. There was a higher trend for lower serious-to-critical injury in high retention seats than baseline seats in NASS-CDS. Six electronic cases were available in NASS-CDS with fatal injury in high retention seats. Only one involved the seat performance as a factor in the fatality, a 72-year-old belted female in a 14 mph rear delta V impact who experienced fractures of the thoracic spine. Her upper body likely wrapped around the upright seatback. Conclusions: High retention seats significantly reduced the odds for fatal injury in towaway crashes with 5–7 o’clock PDOF. There was a trend for lower serious-to-critical injury risks, but more data are needed to determine significant differences. © 2015, Copyright © Taylor & Francis Group, LLC.

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