Traffic Injury Prevention
ISSN: 1538-9588 (Print) 1538-957X (Online) Journal homepage: http://www.tandfonline.com/loi/gcpi20
Short Communications from AAAM's 58th Annual Scientific Conference To cite this article: (2014) Short Communications from AAAM's 58th Annual Scientific Conference, Traffic Injury Prevention, 15:sup1, S238-S269, DOI: 10.1080/15389588.2014.956646 To link to this article: http://dx.doi.org/10.1080/15389588.2014.956646
Published online: 11 Oct 2014.
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Date: 06 November 2015, At: 07:18
Traffic Injury Prevention (2014) 15, S238–S269 C Taylor & Francis Group, LLC Copyright ISSN: 1538-9588 print / 1538-957X online DOI: 10.1080/15389588.2014.956646
Short Communications from AAAM’s 58th Annual Scientific Conference
Research Into Seatbelt Wearing in the KSA∗
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1
BRIAN FILDES , MARK STEVENSON , SHAMSUL HOQUE2, ABD HAMMID2, MOHAMMED AMR2, OMAR JABARI2, AMEIN AL-ALI2, and MOHAMED ABDEL-ATY3 1
Monash University Accident Research Centre, Victoria, Australia 2 Chair of Traffic Safety, University of Dammam, KSA 3 University of Central Florida, Orlando, FL
Introduction This study was carried out in the city of Dammam, the capital of the Eastern Province, and with a population of more than 4million people (29% expats), is the fifth largest city in the Kingdom of Saudi Arabia (KSA). Cars are freely available to all. According to World Life Expectancy (2011), road crash rates in KSA currently exceed 23 deaths per 100,000 population, substantially greater than other highly motorised countries (Sweden is less than 4 per 100,000 currently). There are no reliable figures available on adult seatbelt use, nor the use of Child Restraint Systems (CRS) in passenger vehicles in the KSA. This study was based on the premise that an increase in seatbelt wearing will significantly reduce personal injury in traffic crashes and that local data will help identify intervention strategies necessary to improve seatbelt wearing in the region. This study set out to identify (i) what residents of Dammam, understand about the importance of wearing seat belts in cars; and (ii) what the level of seat belt wearing is on roads in the region.
Methodology The research involved two proven methodologies. In the first, face-to-face interviews of 1400 males and females were conducted in several regional shopping plazas, questioning their own, and their children’s seatbelt wearing behaviour while travelling in passenger vehicles and reporting the reasons for © 2014 Crown Copyright
these attitudes and beliefs (Fildes et al. 1994). The second study involved a structured on-road observation procedure where trained observers recorded adult and child seat belt wearing for approximately 5000 passenger vehicles stopped at randomised representative traffic signalised intersections (Smith and Drummond 1988; Stevenson et al. 2007). Questionnaires and observation forms were created for both these studies using appropriate response formats.
Interview Study Results Data from the survey were analysed addressing a number of research questions for both adults and children (significance using Chi-Square1 statistics) Of particular note for adults, the proportion of those who always wore their seatbelt was considerably lower among younger respondents (Figure 1) and increased with age∗∗∗ . In addition, males were more likely to always wear their seatbelt than females (Figure 2) - only males can legally drive in KSA. Those with a higher education were more likely to always wear their seatbelt, compared to those without, although those with “no education” also reported a slightly higher likelihood of always wearing a seatbelt∗∗∗ . Main reasons given for not wearing a seat belt included attitude not to wear, wear only at (police) checkpoints, during long distance travel only, culture not to wear seatbelts, and not fit for women. Older respondents∗∗∗ and nationals from the KSA were less aware that seatbelts definitely saved lives and serious injuries than those from other nationalities∗∗∗ . Similarly, those under 30 and national respondents were also less aware of the importance to wear seatbelts in the rear seat. More than 80% of the respondents of all ages and genders agreed that it is necessary for young children to be restrained in a suitable Child Restraint System in vehicles (Figure 3). Those who currently have children were significantly more likely to claim to carry their children in a suitable restraint than those who have had children previously (Figure 4). This may reflect more increased knowledge about CRS among current parents. There were no significant differences in the responses as to whether it is, or is not, an offense for children to be unrestrained in a vehicle depending on the education level of the respondent, male or female gender, the region they live in, or whether they currently have or had children or not.
∗
This short communication was reviewed and accepted for publication by The Association for the Advancement of Automotive Medicine (AAAM).
Chi-Square probabilities-∗ 60 years old compared with < 40 years old); being a woman (OR = 1.53); being addicted to alcohol (OR = 0.47); the presence of headache within five hours following injury (OR = 2.91); a history of epilepsy (OR = 4.76); the use of anxiolytics or antidepressants (OR = 1.74); and reporting an average (OR = 0.37) or mediocre to poor health (OR = 0.32) before the event. Other variables considered in the models were patient group (P = 0.1329), positive blood alcohol concentration (P = 0.2422), work status (P = 0.0586), the presence of dizziness within five hours after admission (P = 0.2105), the presence of anxiety within five hours after admission (P = 0.1437), and a history of cardiovascular disorder (P = 0.2091). In the final multivariate weighted model (Table 1), being involved in a road traffic collision was positively associated with PCS at one year, as well as having a MHI/NB, the presence of dizziness within five hours after admission, a history of epilepsy, use of anxiolytic or antidepressants, and reporting a normal health before the event. Being active, more than 60 years old and addicted to alcohol were negatively associated to PCS at one year.
Discussion In this nested case-control study, being injured in a road traffic collision was among the strongest factor associated with persisting PCS at one year. On the other hand, MHI with mild brain injury was not associated with the risk of PCS at one year. Strength of this study is that it was nested in a cohort study, included patients without head injuries, and considered the likelihood of being seen at one year in the weighted model.
Nevertheless, as in any cohort study, losses to follow up were a possible limitation. The proportion and characteristics of losses to follow-up, however, was not different from one group to the other, and similar, whether patients had a PCS at three months or not, except for smoking status (data not shown). The proportion of patients with PCS at one year is also similar to observations from the literature (Emmanuelson et al. 2003; Sterr et al. 2006), thus suggesting that our cases are representative of all PCS in the population. Another possible limitation was that many data were based on self-reports. It is for instance possible that symptoms occurring after the injury have modified the recollection of pre-injury symptoms. Hypotheses regarding a variation of this memorization from one group to another remain difficult to explore. Finally, although our study is one of the largest reported case-control studies on persisting symptoms following MHI, the relatively limited number of cases made it difficult to analyze or interpret the effect of rare characteristics such as epilepsy or dizziness; further, small subgroup sizes precluded us to explore interactions between possible determinants of PCS. Lack of statistical power might also explain the strongest association in patients reporting moderate than mediocre to bad health before the injury. Similarly, the unexpected negative association between reported addiction to alcohol and persisting PCS might be related to the perception of psychological symptoms or the impact of these symptoms on daily living activities in patients with addictions. The definitions of MHI and of PCS remain controversial (Hartvigsen et al. 2014; Iverson 2005), and the diagnosis of both entities is instable (Kristman et al. 2014). Notably, the American Psychological Association (2013) has changed the definition of PCS since the Pericles cohort was conducted. Consequently, some associations observed in our study are difficult to interpret. For instance, it is difficult to interpret
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Table 1. Multivariable analysis of determinants of patients with and without post-concussion syndrome at one year, Bordeaux, France
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PCS (n = 68)
No PCS (n = 302)
Characteristic
#
%
#
%
OR
95%CI
P
Circumstances Road traffic Fall Violence Other Injury group MHI/Ba MHI/NBb NCIc Dizziness within 5 h Yes No History of epilepsy Yes No Previous use of anxiolytics Yes No Reported health Mediocre to poor Moderate Good Being active Yes No Age (y) >60 40 to 59 60 g/day for men).3 Ethyl glucuronide (EtG) is a minor, non volatile, direct metabolite of ethanol that can be detected in body fluids for an extended time period after the complete elimination of alcohol from the body,4,5 and has been proposed as a marker in hair to detect alcohol consumption over long time periods.6,7 The two hypotheses tested in the presented case-control study were: 1. the specific marker HEtG performs better than CDT in identifying potential drivers with current severe alcohol use disorders, and 2. that neither CDT or HEtG can not currently be used “alone” for the diagnosis of alcohol correlated disorders in a forensic setting.
Materials and Methods The research was structured as a case-control study. The patient cohort included 156 Caucasian subjects (80% males and 20% females): 122 subjects had applied for driving licence re-granting after violation of the Italian highway code for drunk driving, 34 subjects were volunteers for the control group. They all signed an informed consent and were subdivided in four groups according to the manner of DUI offence. Group I: 25 were drunk drivers with blood alcohol concentrations (BAC) of 0.51–0.80 g/L; Group II: 89 were drunk drivers with BACs >1.50 g/L; Group III: consisted of 15 subjects that were repeatedly convicted of drunk driving, with a BAC > 0.80 g/L at the time of DUI offences; and Group IV (control): was composed of 34 licensed drivers who had not been convicted of alcohol-related traffic offences. The groups were mutually exclusive, and Group III included only subjects that were convicted more than once with an elevated BAC. The local protocol for re-granting of the driving privilege after licence DUI offences routinely includes: 1. obtaining a consent; 2. assessing drunk driving offence circumstances; 3. examining medical records; 4. collecting bio-clinical analysis results; 5. clinical-behavioural MCV, CDT. To that protocol, the determination of EtG in hair was added on a voluntary basis for the present study. Serum examination; 6. general and toxicological objective examination; and 7. clinical and toxicological analyses including GGT, CDT was determined by capillary zone electrophoresis, calculating the ratio disialotransferrin/tetrasialotransferrin at 2.1% (CDT index) as a cut–off for ascertaining chronic excessive ethanol consumption,8,9 while HEtG was determined using 3 cm proximal segments of head hair by liquid chromatography-tandem mass spectrometry (LC-MS/MS)10 with 30 pg/mg hair as a cut-off for identification of chronic excessive ethanol consumption (>60 g/day for men) as suggested by the Society of Hair Testing (SoHT).11 The program used to evaluate the significance of the data collected was SAS 9.2. The performances of HEtG and serum CDT were compared with the Wilcoxon rank sum, divided by the value above or below the established cut-offs.
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Results The selected population included 122 subjects that had applied for driving licence re-granting after violation of the Italian highway code for drunk driving and received the reinstatement decisions following the “normal” protocol, without considering HEtG results for re-granting licence. They were subdivided into three groups according to the severity of their offence as evidenced in Table 1. As to the Italian highway code, DUI offence has three “cut-off” values with increasing penalties and fines: BAC >0.50 g/L or >0.80 or >1.50 g/L. In the fourth group, 34 volunteers were recruited as controls As seen in Table 2, EtG values were significantly higher in hair in Group II and III than in Group I and IV. In Group I, 12% had HEtG values >30 pg/mg and in Group IV no subject was positive at the established cut-off (and most were lower than 7 pg/mg, a cut-off proposed by SoHT for individuals who abstain from alcohol consumption11), whereas in Group II and in Group III respectively 20% and 27% of subjects had values higher than 30 pg/mg. Group II and III were significantly different from Group I and IV when HEtG was used as a biomarkers for chronic, excessive alcohol consumption. In contrast when the biomarker CDT alone was considered (see Table 3), CDT values were higher in Group I (40% positive) than in Group II (4.5%) and Group III (20%) subjects. In total, by CDT alone 13% of subjects undergoing the assessment were declared unfit to drive, whereas by using HEtG the percentage rose to 20%. Only in 5 out of 122 samples (4%) were CDT and HEtG at the levels greater than cut-offs for both markers for were noted. Using HEtG independently is a more accurate marker than CDT for chronic alcohol correlated disorders, 25 out of 122 subjects would be diagnosed as unfit to drive.
Discussion For individuals that committed violations to the highway code for DUI of alcohol (and/or drug), the Italian law requires the offenders to undergo a mandatory examination that should produce a medico-legal diagnosis of fitness/unfitness to drive. The whole re-granting procedure is entrusted to local health authorities (Local Medical Commissions) that often apply different, non-standardized protocols to achieve the diagnosis of fitness/unfitness to drive. This case-control study included three groups of drivers involved in DUI and a group of controls, and disclosed concentrations of the biomarker HEtG higher than the proposed cut-off of 30 pg/mg in subjects presumed to be “abusers” (20% HEtG positive in drivers with a BAC >1.5 g/L) and in “repeated offenders ” (27% HEtG positive in subjects that drunk drove more than once with BAC > 0.80 g/L) compared to the presumed “social” drinkers that had a BAC between 0.5 and 0.8 g/L at the time of the offense (Group 1, 12% HEtG positive) and to the control population (Group 4, 0%). The higher prevalence of the subjects positive for the direct ethanol metabolite HEtG with respect to those positive for CDT (an indirect marker routinely used in forensic and
253 clinical protocols for alcohol abuse) shows the greatest diagnostic power of HEtG (20% versus 13%), confirming its higher sensitivity as reported in the dedicated literature.12,13 However, it should be noted that there is not a correlation between the two markers, being their distribution different in the three groups of DUI subjects, with only 5 subjects (4%) having both CDT and HEtG values than greater than the designated cut-offs. This apparent discrepancy may be due to the different metabolism/turnover of CDT in serum and EtG in hair. When an excessive chronic drinker stops his/her usual pattern of drinking, the CDT levels turn to normal levels in 2–3 weeks,14 while EtG accumulates in hair and remains almost fixed in a specific hair segment for months/years, unless washout effects occur. Considering that HEtG must be determined in 3 up to 6 cm of proximal hair, corresponding to a time span of 3–6 months,11 it may be possible to have CDT negative in serum and HEtG positive for a heavy drinker that was able to reduce the alcohol consumption in the last 2–3 weeks before undergoing the re-granting assessment. On the other end, the positive CDT values in subjects with negative HEtG could be ascribed to the various clinical or genetic factors that are recognized able to elevate CDT isoforms in non alcoholic individuals, such as glycosilation pattern disorders, genetic variants, ethnicity, alcoholic or non-alcoholic hepatopaties; however, the apparently high concentrations of CDT levels in Group I (potentially social drinkers) needs more investigation. When comparing our results with those of Liniger et al.12, that retrospectively investigated on HEtG and CDT of 154 subjects whose fitness to drive had to be assessed because of the suspicion of relevant alcohol problems, similar results were obtained. EtG findings in the hair samples were positive in 84 out of the 154 self-reported teetotalers; however, only 39 of these 84 subjects had a CDT value above the upper limit of normal using an immunochemical method and only 15 subjects had a CDT value above the cut-off measured by HPLC. Conversely, of 70 subjects that tested negative for HEtG, 15 or 3 had a CDT value above the upper limit using respectively the immunochemical or the HPLC method. However, differently from our study, the cut-off used by Liniger for HEtG was 7 pg/mg for detection of abstinence; two diverse methods were used for CDT; the selected subjects were all “self-reported” teetotallers and no detail on their BAC at the time of offences was given; no control group was used. In conclusion the determination of HEtG supports the clinical diagnosis of problems related to alcohol in drunk drivers and allows the identification of a larger number of potentially unfit subjects than CDT: if the decision on re-granting was based on CDT values only, 13% of subjects undergoing the assessment could be declared unfit to drive, whereas by using HEtG values only the percentage rose to 20% and the accuracy of the reinstatement examination is improved by extending the number of markers of an alcohol risky use. The first tested hypothesis holds true. However, the observed discrepancies between CDT and HEtG need more consideration, suggesting that neither CDT nor HEtG alone are ideal markers of excessive alcohol consumption and that the ascertainment of fitness to drive must take into account more than one biomarker including their critical evaluation of a more comprehensive legal-medical protocol.
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Table 1. Characteristic of the 156 enrolled subjects according to their gender and manner of DUI
Total Male Female
Group I BAC ≥0.5 g/L ≤0.8 g/L
Group II BAC ≥1.5 g/L
Group III More than one DUI offense
Group IV Control
25 20 5
89 77 12
15 14 1
34 12 22
Group I BAC ≥0.5 g/L ≤0.8 g/L
Group II BAC ≥1.5 g/L
Group III More than one DUI offense
Group IV Control
25 22 3
89 71 18
15 11 4
34 23 —
Group I BAC ≥0.5 g/L ≤0.8 g/L
Group II BAC ≥1.5 g/L
Group III More than one DUI offense
Group IV Control
25 15 10
89 85 4
15 11 3
34 34 —
Table 2. HEtG values compared to manner of DUI
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Total HEtG 3 ribs on one side and no more than 3 ribs on the side, with hemo/pneumothorax Thoracic cavity injury NFS, with pneumomediastinum Humerus fracture, open/displaced/ comminuted Ulnar fracture, open/displaced/ comminuted Radius fracture, open/displaced/ comminuted Subarchanoid hemorrhage Cerebral contussion
7
The AIS coder that performed the AIS scoring and ISS/MAIS calculations is AIS trained through the AAAM curriculum and is a Certified AIS Specialist (CAISS).
3
4
4
3
3 3
Appendix Table A1. Corrections from original CIREN coding (all cases requiring correction with originally coded in AIS98). Note that in two instances, the spine fractures needed to be separated into distinct injuries Original Code [AIS98]
Original Description
Corrected Code(s) [AIS98]
850610.2
Hip dislocation NFS
850618.2
650212.3
Cervical Spine, dislocation facet bilateral; C1C2 Cervical Spine, fracture transverse process; C6C7
650206.3
650220.2
650220.2
650220.2
650220.2
Cervical Spine, fracture transverse process; C6C7
650220.2
650220.2
AIS Note
4 4
Corrected Description Hip dislocation, involving articular cartilage Cervical spine, dislocation, altanto-axial Cervical Spine, fracture transverse process, C6 Cervical Spine, fracture transverse process, C7 Cervical Spine, fracture transverse process, C6 Cervical Spine, fracture transverse process, C7
Table A2. Comparison of MAIS, Thoracic MAIS, ISS, and NISS for each case based on AIS98 and AIS05 coding
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265 AIS98
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Case 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
AIS05
MAIS
Thoracic MAIS
ISS
NISS
MAIS
Thoracic MAIS
ISS
NISS
3 4 4 5 2 4 3 3 4 4 3 3 4 4 4 4 4 4
3 4 4 5 2 4 3 2 4 3 3 3 4 4 4 4 4 4
14 26 21 42 9 21 10 22 29 34 27 17 29 29 41 41 29 34
14 41 34 57 12 29 17 27 29 34 27 27 34 34 41 41 29 34
2 3 2 5 2 4 2 3 4 4 3 3 3 3 4 4 3 3
2 3 2 5 2 4 2 3 4 3 2 3 3 3 4 3 3 3
9 14 9 30 6 21 5 22 24 29 17 17 22 22 41 29 17 17
9 22 12 38 12 24 12 27 24 34 22 17 27 22 41 29 17 22
References
Introduction
Gennarelli TA, Wodzin E. Abbreviated Injury Scale 2005: Update 2008. Association for the Advancement of Automotive Medicine; 2008. Yoganandan N, Pintar FA, Humm JR, et al. Comparison of AIS 1990 update 98 versus AIS 2005 for describing PMHS injuries in lateral and oblique sled tests. Ann Adv Automot Med. 2013;57:197–208.
The Nij neck injury criteria for compressive loading, which is described in three reports published by the National Highway Traffic Safety Administration (Kleinberger et al. 1998; Eppinger et al. 1999; Eppinger et al. 2000), is not derived from biomechanics tests that produced compressive injury in humans or cadavers. It is derived from the assumption that compressive and tensile tolerances should be the same and that the response of juvenile pigs and the Hybrid III 3 YO can be scaled to be representative of adult human responses. As a result, there is some impetus to consider updating such criteria for predicting compressive neck injuries in rollover crashes. Since occupant-to-roof impact velocity is a difficult quantity to measure in a rollover crash test, a velocity-based injury criterion would not be incredibly useful with a dummy. However, a velocity-based injury criterion is an attractive alternative in retrospective biomechanical analyses of rollover crashes since basic kinematics equations can be used with accident reconstruction results to evaluate injury risk for a particular vehicle-ground impact in a multi-impact rollover crash. While we have some anecdotal evidence that a velocity-based injury criterion is being used to assist in the forensic analyses of rollover crash occupant injury, no published technical studies, to our knowledge, clearly describe the validity of such a criterion. Viano and Parenteau (2008) compared tests and compiled data from whole body inverted drop tests presented by Nusholtz et al. (1983), Sances et al. (1986), and Yoganandan et al. (1986). They found that there are no data for human impact response and injury occurrence in tests between 2.0 and 4.0 m/s, but that all tests performed with velocities exceeding 4.0 m/s produced injury. The research by Nightingale et al. (1996) and Nightingale et al. (1997) suggests that impacts exceeding 3.1 m/s usually produce injury. However, since the studies by Nightingale use a fixed mass (16 kg) to estimate the portion of the torso mass that compresses the spine when an inverted human (possibly a forward-facing vehicle occupant in a driving posture) with a neutral (lordotic) cervical spine sustains a vertex impact, the
Axial Compression Injury Tolerance of the Cervical Spine: Initial Results∗ JASON R. KERRIGAN1, JONATHAN B. FOSTER2, MARK SOCHOR3, JASON L. FORMAN3, JACEK TOCZYSKI1, CAROLYN W. ROBERTS2, and JEFF R. CRANDALL University of Virginia Center for Applied Biomechanics
Four whole-body male PMHS were subjected to inverted headto-ground impacts that resulted in cervical compression in an attempt to compare the response of whole-body PMHS to component tests performed previously. Peak head forces in the current study (4495 N) were similar to those in previous studies, but differences in timing and magnitudes of second force peaks suggest that differences in constraints and/or boundary conditions affected the dynamics of the impact. While only moderate (AIS 2) injuries were produced in the current study, more serious and severe injuries have been produced previously, which suggests that constraint and/or boundary condition differences also affect injury type and tolerance.
∗
This short communication was reviewed and accepted for publication by The Association for the Advancement of Automotive Medicine (AAAM).
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3.1 m/s velocity threshold is directly dependent on the validity of the 16 kg assumption. To further simplify conditions, the first thoracic vertebra (T1) is potted and constrained to move only in vertical direction. However, the Nightingale study does utilize an isolated cadaveric component (head/neck), which is an attractive option that could reduce the costs of the potentially substantial number of tests that would be required to develop a velocity or other injury criterion. This study aims to evaluate head/neck response in inverted impacts that produce compressive loads on the cervical spine in an attempt to assess whether the simplified conditions used by Nightingale et al. (1997) are sufficient to determine injury thresholds for cervical spine compression injuries. The current study utilizes whole-body subjects in inverted impacts at velocities between 3.0 and 3.6 m/s to attempt to fill the void identified by Viano and Parenteau (2008).
Methods Four male fresh-frozen post mortem human subjects (PMHS) were selected for this study (Table 1). The PMHS were obtained and treated in accordance with the ethical guidelines established by the Human Usage Review Panel of the United States National Highway Traffic Safety Administration, and all testing and handling procedures were reviewed and approved by the Center for Applied Biomechanics Biological Protocol Committee and an independent Oversight Committee at the University of Virginia. Each subject was instrumented with kinematics instrumentation on the head and T1. An instrumentation cube consisting of three mutually perpendicular linear accelerometers (7264B2000, Endevco, San Juan Capistrano, CA, USA) and angular rate sensors (ARS-8K, DTS, Seal Beach, CA, USA) was fixed to an aluminum plate and fixed to the temperoparietal skull with screws. A second cube was fixed to a clamp that joined the posterior ends of a pair of pedicle screws installed in the first thoracic vertebra (T1). For subjects 631 and 553, no angular rate sensors were used on T1. A coordinate measurement machine (CMM) was used to identify the location and orientation of the head instrumentation cube relative to skeletal landmarks that were used to estimate the location of the head center of gravity (CG) and the orientation of a head coordinate system (Robbins 1983). After sensor mount installation, the subjects were CT scanned to facilitate identification of sensor mounting orientation relative to the head and T1 and to determine the angle of the T1 mount relative to the C7-T1 intervertebral disc. On the day of each test, the subject was wrapped in a thin layer of mechanically adhesive wrap (Coban, 3M, St. Paul, MN, USA) and outfitted with a tactical body harness (355 Extraction Harness, Yates Gear Inc, Redding, CA, USA). The lower extremities were bound together at the distal thigh and ankle. Adjustable nylon ropes were fixed to several locations on the harness and at the bindings and the subject was hoisted for positioning. Each subject was inverted and a standard seating position (Manary et al. 1998) with a 20-27 degrees (from vertical) torso angle was implemented. The lower extremities were oriented such that they were parallel to the ground. Head
Short Communications and neck positioning was performed to facilitate comparison with previous tests (Nightingale et al. 1996): C7/T1 disc rotated (sagittal plane) 25 degrees relative to ground, and the Frankfurt plane parallel to the ground. The combination of the C7/T1 disc and head orientation was used (in Nightingale et al. 1996) to preserve the resting lordosis present in drivers ((Matsushita et al. 1994). The ends of the supporting ropes were joined together in a ring that was connected to a solenoid release mechanism to permit electronic test initiation. The impact surface consisted of a five-axis load cell (Denton B-3868-D, Humanetics Innovative Solutions, Plymouth, MI, USA), sandwiched between two steel plates. On the top plate, a piece of 25.4 mm thick light-density closed-cell, polyvinyl chloride general purpose foam (V700 Series 1.00”, Gaska Tape Inc., Elkhart, IN, USA), was adhered to the steel plate. This foam was used previously (Frechede et al. 2009) to mimic the foam used by Nightingale et al. (1996). The load plate assembly was positioned under the subject’s skull (apex), and the subject was raised to the drop height (approximately 53 cm, Table 1). The orientation of the head, and head/T1 instrumentation cubes were then measured with the CMM. Then, the subject was released and allowed to sustain unimpeded impact with load plate and floor. After the test, skeletal injury pathology and extent of injury was determined via radiology and subsequent dissection. The subjects’ head weights were determined after decapitation during dissection. Head acceleration data were transformed to the head CG coordinate system and the measurement location was translated to the head CG using the rigid body assumption. Time histories of the head and T1 local-to-global coordinate system transformations were determined from the angular rate data (Beard and Schlick, 2003). Global head acceleration data were multiplied by the head mass, to determine the inertial contribution of the force applied to the neck. Then the neck force (at the atlanto-occipital (AO) junction) was calculated by component-wise subtraction of the load cell force from the inertial force (Flc -mahead = Fneck ) under the assumption that the head is a rigid body acted upon by only two forces.
Results The head force (applied to the head through the load plate) showed an initial short duration (8-10 ms) peak at approximately 10 ms after impact, followed by a lower magnitude longer duration (30–40 ms) peak centered around 38 ms after impact (Figure 1 and Figure 2). The axial compressive force applied to the neck at the AO junction showed a similar character with an initial short duration peak just after the peak in head force (12 ms), and a longer duration lower magnitude peak later 39 ms. Variation in average peak forces (Table 1) for the first and second peaks decreased by mass scaling the forces using the body weight: SD 731 N vs. 270 N, 792 N vs. 519 N, 300 N vs. 57 N, 592 N vs. 443 N for the first and second head, and first and second neck force peaks, respectively. T1 global accelerations were integrated to determine velocities and displacements and T1 local-to-global transformations were used to determine vertebral rotations. The T1 kinematics data showed that T1 (in 516) reached 800 deg/s in flexion
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Table 1. Subject information, test conditions, and results UVA Specimen Number
516
552
631
553
Sex Age Weight [kg] Stature [mm] DEXA Dual Femur Total [T-score] Head Mass [kg] Impact Velocity [m/s] First Peak Head Force [N] (time in ms) Second Peak Head Force [N] (time in ms) First Peak Neck Force [N] (time in ms) Second Peak Neck Force [N] (time in ms) FheadZ/AccZ at Time of First Peak in Head Force [kg]
M 89 54.4 155 -2.7
M 82 77.6 170 0.9
M 71 68.9 178 -0.5
M 60 57.2 170 -2.8∗
3.275 3.08 3819 (10.3)
3.775 3.01 5347 (10.0)
4.07 3.63 4858 (9.5)
3.54 3.54 3956 (9.9)
2353 (43.9)
4058 (26.2)
3053 (35.1)
2411 (46.7)
2730 (10.9)
4264 (42.5)
3299 (11.9)
2852 (12.4)
2076 (42.3)
∗∗
3239 (38.7)
2457 (37.3)
9.93
7.18
9.26
8.12
∗ Dual ∗∗ no
Femur Total score was not available and AP Spine, so AP Spine score is provided. second peak in neck force the test on subject 552.
rotation over the first 10 ms after impact, and over 1200 deg/s by 15 ms after impact, and sustained between 9 and 24 deg rotation within the first 40 ms. Furthermore, the acceleration data also suggest that the vertebra (in 516/552) translated linearly more than 80 mm in the first 40 ms. Three of the four cadavers sustained bony fracture while subject 516 sustained no injury: • 516-No injury • 552-C7 bilateral pedicle/lamina fractures (assumed to be iatrogenic) • 631-small (5 mm) anterior chip fracture of the superior endplate of C4 vertebral body • 553-Type III Odontoid fracture (post-test) Some intervertebral laxity was noted during some dissections, however, no facet joint dislocation nor ligament laxity/disruption was clearly identified. The C7 fracture was determined during dissection to be, at least minimally, related to the orientation of the pedicle screws in T1 used to mount the sensor block. High speed (1000 Hz) Xray was attempted with both subject 631 and 553 in an effort to clearly visualize injuries. While the vertebral body fracture in 631 was not clearly visualized, the odontoid fracture was clearly identified to occur 182 ms after initial head contact, during extreme flexion that occurred after the subject bounced off the plate.
Discussion While it is tempting to model the head-neck-torso as a massspring-mass system due to the bimodal shape of the head force time history seen in the subjects, the calculated upper neck loads show that the neck force has a bimodal shape and the first peak occurs just 1-2 ms after the first peak in head force. This suggests that at least some of the neck/torso mass is coupled well enough to the head that it begins decelerating immediately upon impact. The normal load cell (head Z)
force divided by the head global vertical acceleration in the Z direction estimates the effective mass of the part of the body that is decelerated during the initial force peak (Table 1). On average, subjects in the current study had effective masses that exceeded the head mass by approximately 5 kg, suggesting that the entire neck, and some of the torso, may be decelerated during that first impact. Subject 552 had the shortest time duration between the first and second peaks in head force (16.2 ms), and the lowest effective impact mass (7.18). This could be the result of abnormalities with that subject since substantial metastases were noted throughout the lumbar and thoracic spines. However, the shorter duration and lower effective mass suggest that the lax element, which represents the spring in the mass-spring-mass model, was higher up (possibly in the cervical spine) than in the other subjects. Such an analysis could benefit from knowing the mass of the cervical spine, however, it should be noted that the mass-spring-mass model is no longer valid when the cervical spine begins to undergo increased bending (superior extension and inferior flexion). While the high-speed Xray imagery used in the current study did not provide a significant contribution because of operational problems with the Xray system, it did indicate that this increased bending, or a change in the orientation of the vertebral bodies (called “buckling” by Nightingale et al. 1997 and other previous studies), occurred almost exactly at the time of the first peak in force. Thus, the “rigid body” assumption inherent in a mass-spring-mass model is no longer valid after this peak since the lower mass (head, neck, some of torso) begins deforming at the time of the first peak. While all of whole-body drop test subjects tested previously (Nusholtz et al. 1983; Yoganandan et al. 1986; Sances et al. 1986) were tested at either a substantially higher or lower velocity than the subjects tested in the current study, Nightingale et al. (1997) described three head/neck restrained subjects (N02, N03, D40) tested with the same conditions as in the current test: ∼3.1 m/s impact velocity, neutral neck flexion/extension angle, vertex impact, padded surface. While the
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Fig. 2. Load cell normal (Z) force (top) and Z-direction (axial) neck force (bottom) time histories from all four subjects.
Fig. 1. Lateral view images from the test on subject 516. Video times are taken from initial contact (top), time of first peak load cell force (next), time of load cell minimum between peaks (next), and time of the second (next), and peak load cell force (bottom).
current study utilized whole body PMHS, and the tests by Nightingale et al. (1997) utilized only PMHS components, it was hypothesized that the conditions were comparable. However, there were several differences in the forces response and injury values. While two of the three subjects in the Nightingale et al. (1997) study clearly showed the same bimodal shape of head force as three of the four subjects in the current study,
there were several differences in timing and magnitude. The first peak in the Nightingale tests occurred approximately 10 ms later (15.8-23.5 ms, avg. 20.1 ms) than in the current study. This suggests that there was a difference in the stiffness of the foam between the two studies. There were similar values for the averaged peak head force magnitude between the two studies (4495 N vs. 4433 N for the three subjects in Nightingale), which suggests that the portion of mass coupled well enough to the head to be decelerated during the time of the initial force peak was similar between the tests. However, the second peak force was substantially higher in the current study than in the previous study (2970 N vs. 1925 N), which suggests that the 16 kg used in the Nightingale study to represent the portion of the torso mass that serves to compress the spine in such an impact is an underestimate of the real mass. The time difference between the two peaks was longer in the current study (27.9 ms, or 32 ms if subject 552 is not counted) than in the Nightingale study (17.4 ms). The reason for this is not clear, but it may be related to the constraint on T1 in the Nightingale study, which may have caused different vertebral kinematics subsequent to the first impact than in the current study. Injuries in the current study were much less severe than in the Nightingale study. Subjects from tests N03, D40, and N02 sustained seven fractures, five intervertebral/facet joint
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Short Communications disruptions (including one case of bilateral facet dislocation), and four generally unstable injuries. In the current study, there was only one fracture that appeared to be related to the loading that occurred during the first 100 ms after impact (C4 chip fracture in 631). Even if the C7 fractures in 552 were not iatrogenic, there is a substantial difference in the injury severity between the current study and previous studies, especially given the relatively low bone quality of the subjects in the current study (as indicated by DEXA T-scores). Nightingale et al. (1997) and others have indicated that producing such severe bilateral fractures requires at least near-perfect alignment of the load vector and vertebral bodies. While it is possible that such severe fractures were not produced in the current study because of slight variations in the alignment, much more severe injuries, including some that were similar to those produced by Nightingale et al. (1997), were produced in the subjects tested by Nusholtz et al. (1983) in impacts between 4.4 and 5.9 m/s. In the current study, sensor data showed that T1 translates and rotates substantially during even the initial phase of loading (first 20-40 ms). It is thus hypothesized that constraining T1 motion to restrict transverse translations and rotations results in an artificial boundary condition that subjects the cervical spine to a lower fracture tolerance than would exist in the absence of such a constraint. Cervical spine boundary conditions have been shown to have a substantial effect on the injury type and tolerance in compressive loading (Myers et al. 1991). While T1 was more constrained in the Nightingale et al. (1997) tests than it is when a living human is in a rollover crash, it seems possible that the active musculature in a living human provides more constraint on T1’s motion than a PMHS model can accurately reproduce. Lastly, data from the current study suggest that Nij injury criteria for compressive loading should be reconsidered. While other tests have been performed to evaluate Hybrid III crash dummy response (Frechede et al. 2009 and others) in inverted impacts, two tests performed as part of the current study showed that the peak upper neck compressive load recorded by the Hybrid III in a 3.1 m/s impact was between 9200 N and 11800 N (depending on head/neck/chest orientation). Thus, in impacts that resulted in only minor or no injury in PMHS with low bone quality, the Hybrid III dummy predicts a force that is between 230% and 296% of the compressive limit, and 140% to 180% of the compression intercept for Nij. As discussed by other authors, this is because the dummy spine (cervical and thoracic) is far too stiff to accurately represent human response in an inverted impact, and thus will likely need to be modified to accurately predict neck injuries in rollover crash tests.
Conclusions The current study was an initial step in determining injury criteria for the cervical spine to predict severe injuries like those that occur in rollover crashes. The current study showed:
269 • inverted head/ground impacts at 3.1 m/s are not sufficient to cause severe cervical spine injury; • the combination of constraining T1 and using 16 kg to estimate the portion of the torso that serves to compress the spine in an inverted head/ground impact results in a response that has different dynamics than when an unconstrained whole body cadaver is subjected to a similar impact; and • the T1 vertebra undergoes substantial translation and rotation during the axial compressive loading that occurs subsequent to an inverted head/ground impact.
References Beard DA, and Schlick T. Unbiased rotational moves for rigid-body dynamics. Biophysical Journal. 2003;85:2973–2976. Eppinger R, Sun E, Nadak F, et al. Development of Improved Injury Criteria for the Assessment of Advanced Automotive Restraint Systems – II. NHTSA Technical Report; 1999. Eppinger R, Sun E, Kuppa S, Saul R. Supplement: development of improved injury criteria for the assessment of advanced automotive restraint systems – II. NHTSA Technical Report. March 2000. Frechede B, McIntosh A, Grzebieta R, Bambach M. Hybrid III ATD in inverted impacts: influence of impact angle on neck injury risk assessment. Annals of Biomedical Engineering. 2009;37(7):1403–1414. Kleinberger M, Sun E, Eppinger R, Kuppa S, Saul R. Development of Improved Injury Criteria for the Assessment of Advanced Automotive Restraint Systems. NHTSA Technical Report. September 1998. Manary MA, Reed MP, Flannagan CA, Schneider LW. ATD positioning based on driver posture and position. In: Proceedings of the 42nd Stapp Car Crash Conference. 1998:1–13. Matsushita T, Sato TB, Hirabayashi K, et al. X-ray study of the human neck motion due to head inertia loading. In: Proceedings of the 38th Stapp Car Crash Conference. 1994: 55–64. Myers BS, Nightingale RW, McElhaney JH, Doherty DJ, Richardson WJ. The Influence of End Condition on Human Cervical Spine Injury Mechanisms. Warrendale, PA: Society of Automotive Engineers; 1991:391–99. Nightingale RW, McElhaney JH, Richardson WJ, Myers BS. Dynamic responses of the head and cervical spine to axial impact loading. J Biomechanics. 1996;29:307–18. Nightingale RW, McElhaney JH, Camacho DL, et al. The dynamic responses of the cervical spine: buckling, end conditions, and tolerance in compressive impacts. In: Proceedings of the 41st Stapp Car Crash Conference. 1997:451–71. Paper number 973344. Nusholtz GS, Huelke DE, Lux P, Alem NM, Motalvo F. Cervical spine injury mechanisms. In: Proceedings of 27th Stapp Car Crash Conference. Warrendale, PA: Society of Automotive Engineers; 1983. SAE 831616. Sances A, Yoganandan N, Maiman D, et al. Spinal injuries with vertical impact. In: Mechanisms of Head and Spine Trauma. Goshen, NY: Aloray Publishers; 1986:717–736. Robbins DH. Anthropometric Specifications for Mid-Sized Male Dummy (Volume 2). Ann Arbor, MI: University of Michigan Transportation Research Institute; 1983. Report number UMTRI-83-53-2. Viano DC, Parenteau CS, Analysis of head impacts causing neck compression injury. Traffic Injury Prevention. 2008;9(2):144–52. Yoganandan N, Sances A, Maiman, D, et al. Experimental spinal injuries with vertical impact. Spine. 1986;11(9):855–60.
ISSN: 1538-9588 (Print) 1538-957X (Online) Journal homepage: http://www.tandfonline.com/loi/gcpi20
Short Communications from AAAM's 58th Annual Scientific Conference To cite this article: (2014) Short Communications from AAAM's 58th Annual Scientific Conference, Traffic Injury Prevention, 15:sup1, S238-S269, DOI: 10.1080/15389588.2014.956646 To link to this article: http://dx.doi.org/10.1080/15389588.2014.956646
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Date: 06 November 2015, At: 07:18
Traffic Injury Prevention (2014) 15, S238–S269 C Taylor & Francis Group, LLC Copyright ISSN: 1538-9588 print / 1538-957X online DOI: 10.1080/15389588.2014.956646
Short Communications from AAAM’s 58th Annual Scientific Conference
Research Into Seatbelt Wearing in the KSA∗
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BRIAN FILDES , MARK STEVENSON , SHAMSUL HOQUE2, ABD HAMMID2, MOHAMMED AMR2, OMAR JABARI2, AMEIN AL-ALI2, and MOHAMED ABDEL-ATY3 1
Monash University Accident Research Centre, Victoria, Australia 2 Chair of Traffic Safety, University of Dammam, KSA 3 University of Central Florida, Orlando, FL
Introduction This study was carried out in the city of Dammam, the capital of the Eastern Province, and with a population of more than 4million people (29% expats), is the fifth largest city in the Kingdom of Saudi Arabia (KSA). Cars are freely available to all. According to World Life Expectancy (2011), road crash rates in KSA currently exceed 23 deaths per 100,000 population, substantially greater than other highly motorised countries (Sweden is less than 4 per 100,000 currently). There are no reliable figures available on adult seatbelt use, nor the use of Child Restraint Systems (CRS) in passenger vehicles in the KSA. This study was based on the premise that an increase in seatbelt wearing will significantly reduce personal injury in traffic crashes and that local data will help identify intervention strategies necessary to improve seatbelt wearing in the region. This study set out to identify (i) what residents of Dammam, understand about the importance of wearing seat belts in cars; and (ii) what the level of seat belt wearing is on roads in the region.
Methodology The research involved two proven methodologies. In the first, face-to-face interviews of 1400 males and females were conducted in several regional shopping plazas, questioning their own, and their children’s seatbelt wearing behaviour while travelling in passenger vehicles and reporting the reasons for © 2014 Crown Copyright
these attitudes and beliefs (Fildes et al. 1994). The second study involved a structured on-road observation procedure where trained observers recorded adult and child seat belt wearing for approximately 5000 passenger vehicles stopped at randomised representative traffic signalised intersections (Smith and Drummond 1988; Stevenson et al. 2007). Questionnaires and observation forms were created for both these studies using appropriate response formats.
Interview Study Results Data from the survey were analysed addressing a number of research questions for both adults and children (significance using Chi-Square1 statistics) Of particular note for adults, the proportion of those who always wore their seatbelt was considerably lower among younger respondents (Figure 1) and increased with age∗∗∗ . In addition, males were more likely to always wear their seatbelt than females (Figure 2) - only males can legally drive in KSA. Those with a higher education were more likely to always wear their seatbelt, compared to those without, although those with “no education” also reported a slightly higher likelihood of always wearing a seatbelt∗∗∗ . Main reasons given for not wearing a seat belt included attitude not to wear, wear only at (police) checkpoints, during long distance travel only, culture not to wear seatbelts, and not fit for women. Older respondents∗∗∗ and nationals from the KSA were less aware that seatbelts definitely saved lives and serious injuries than those from other nationalities∗∗∗ . Similarly, those under 30 and national respondents were also less aware of the importance to wear seatbelts in the rear seat. More than 80% of the respondents of all ages and genders agreed that it is necessary for young children to be restrained in a suitable Child Restraint System in vehicles (Figure 3). Those who currently have children were significantly more likely to claim to carry their children in a suitable restraint than those who have had children previously (Figure 4). This may reflect more increased knowledge about CRS among current parents. There were no significant differences in the responses as to whether it is, or is not, an offense for children to be unrestrained in a vehicle depending on the education level of the respondent, male or female gender, the region they live in, or whether they currently have or had children or not.
∗
This short communication was reviewed and accepted for publication by The Association for the Advancement of Automotive Medicine (AAAM).
Chi-Square probabilities-∗ 60 years old compared with < 40 years old); being a woman (OR = 1.53); being addicted to alcohol (OR = 0.47); the presence of headache within five hours following injury (OR = 2.91); a history of epilepsy (OR = 4.76); the use of anxiolytics or antidepressants (OR = 1.74); and reporting an average (OR = 0.37) or mediocre to poor health (OR = 0.32) before the event. Other variables considered in the models were patient group (P = 0.1329), positive blood alcohol concentration (P = 0.2422), work status (P = 0.0586), the presence of dizziness within five hours after admission (P = 0.2105), the presence of anxiety within five hours after admission (P = 0.1437), and a history of cardiovascular disorder (P = 0.2091). In the final multivariate weighted model (Table 1), being involved in a road traffic collision was positively associated with PCS at one year, as well as having a MHI/NB, the presence of dizziness within five hours after admission, a history of epilepsy, use of anxiolytic or antidepressants, and reporting a normal health before the event. Being active, more than 60 years old and addicted to alcohol were negatively associated to PCS at one year.
Discussion In this nested case-control study, being injured in a road traffic collision was among the strongest factor associated with persisting PCS at one year. On the other hand, MHI with mild brain injury was not associated with the risk of PCS at one year. Strength of this study is that it was nested in a cohort study, included patients without head injuries, and considered the likelihood of being seen at one year in the weighted model.
Nevertheless, as in any cohort study, losses to follow up were a possible limitation. The proportion and characteristics of losses to follow-up, however, was not different from one group to the other, and similar, whether patients had a PCS at three months or not, except for smoking status (data not shown). The proportion of patients with PCS at one year is also similar to observations from the literature (Emmanuelson et al. 2003; Sterr et al. 2006), thus suggesting that our cases are representative of all PCS in the population. Another possible limitation was that many data were based on self-reports. It is for instance possible that symptoms occurring after the injury have modified the recollection of pre-injury symptoms. Hypotheses regarding a variation of this memorization from one group to another remain difficult to explore. Finally, although our study is one of the largest reported case-control studies on persisting symptoms following MHI, the relatively limited number of cases made it difficult to analyze or interpret the effect of rare characteristics such as epilepsy or dizziness; further, small subgroup sizes precluded us to explore interactions between possible determinants of PCS. Lack of statistical power might also explain the strongest association in patients reporting moderate than mediocre to bad health before the injury. Similarly, the unexpected negative association between reported addiction to alcohol and persisting PCS might be related to the perception of psychological symptoms or the impact of these symptoms on daily living activities in patients with addictions. The definitions of MHI and of PCS remain controversial (Hartvigsen et al. 2014; Iverson 2005), and the diagnosis of both entities is instable (Kristman et al. 2014). Notably, the American Psychological Association (2013) has changed the definition of PCS since the Pericles cohort was conducted. Consequently, some associations observed in our study are difficult to interpret. For instance, it is difficult to interpret
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Table 1. Multivariable analysis of determinants of patients with and without post-concussion syndrome at one year, Bordeaux, France
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PCS (n = 68)
No PCS (n = 302)
Characteristic
#
%
#
%
OR
95%CI
P
Circumstances Road traffic Fall Violence Other Injury group MHI/Ba MHI/NBb NCIc Dizziness within 5 h Yes No History of epilepsy Yes No Previous use of anxiolytics Yes No Reported health Mediocre to poor Moderate Good Being active Yes No Age (y) >60 40 to 59 60 g/day for men).3 Ethyl glucuronide (EtG) is a minor, non volatile, direct metabolite of ethanol that can be detected in body fluids for an extended time period after the complete elimination of alcohol from the body,4,5 and has been proposed as a marker in hair to detect alcohol consumption over long time periods.6,7 The two hypotheses tested in the presented case-control study were: 1. the specific marker HEtG performs better than CDT in identifying potential drivers with current severe alcohol use disorders, and 2. that neither CDT or HEtG can not currently be used “alone” for the diagnosis of alcohol correlated disorders in a forensic setting.
Materials and Methods The research was structured as a case-control study. The patient cohort included 156 Caucasian subjects (80% males and 20% females): 122 subjects had applied for driving licence re-granting after violation of the Italian highway code for drunk driving, 34 subjects were volunteers for the control group. They all signed an informed consent and were subdivided in four groups according to the manner of DUI offence. Group I: 25 were drunk drivers with blood alcohol concentrations (BAC) of 0.51–0.80 g/L; Group II: 89 were drunk drivers with BACs >1.50 g/L; Group III: consisted of 15 subjects that were repeatedly convicted of drunk driving, with a BAC > 0.80 g/L at the time of DUI offences; and Group IV (control): was composed of 34 licensed drivers who had not been convicted of alcohol-related traffic offences. The groups were mutually exclusive, and Group III included only subjects that were convicted more than once with an elevated BAC. The local protocol for re-granting of the driving privilege after licence DUI offences routinely includes: 1. obtaining a consent; 2. assessing drunk driving offence circumstances; 3. examining medical records; 4. collecting bio-clinical analysis results; 5. clinical-behavioural MCV, CDT. To that protocol, the determination of EtG in hair was added on a voluntary basis for the present study. Serum examination; 6. general and toxicological objective examination; and 7. clinical and toxicological analyses including GGT, CDT was determined by capillary zone electrophoresis, calculating the ratio disialotransferrin/tetrasialotransferrin at 2.1% (CDT index) as a cut–off for ascertaining chronic excessive ethanol consumption,8,9 while HEtG was determined using 3 cm proximal segments of head hair by liquid chromatography-tandem mass spectrometry (LC-MS/MS)10 with 30 pg/mg hair as a cut-off for identification of chronic excessive ethanol consumption (>60 g/day for men) as suggested by the Society of Hair Testing (SoHT).11 The program used to evaluate the significance of the data collected was SAS 9.2. The performances of HEtG and serum CDT were compared with the Wilcoxon rank sum, divided by the value above or below the established cut-offs.
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Results The selected population included 122 subjects that had applied for driving licence re-granting after violation of the Italian highway code for drunk driving and received the reinstatement decisions following the “normal” protocol, without considering HEtG results for re-granting licence. They were subdivided into three groups according to the severity of their offence as evidenced in Table 1. As to the Italian highway code, DUI offence has three “cut-off” values with increasing penalties and fines: BAC >0.50 g/L or >0.80 or >1.50 g/L. In the fourth group, 34 volunteers were recruited as controls As seen in Table 2, EtG values were significantly higher in hair in Group II and III than in Group I and IV. In Group I, 12% had HEtG values >30 pg/mg and in Group IV no subject was positive at the established cut-off (and most were lower than 7 pg/mg, a cut-off proposed by SoHT for individuals who abstain from alcohol consumption11), whereas in Group II and in Group III respectively 20% and 27% of subjects had values higher than 30 pg/mg. Group II and III were significantly different from Group I and IV when HEtG was used as a biomarkers for chronic, excessive alcohol consumption. In contrast when the biomarker CDT alone was considered (see Table 3), CDT values were higher in Group I (40% positive) than in Group II (4.5%) and Group III (20%) subjects. In total, by CDT alone 13% of subjects undergoing the assessment were declared unfit to drive, whereas by using HEtG the percentage rose to 20%. Only in 5 out of 122 samples (4%) were CDT and HEtG at the levels greater than cut-offs for both markers for were noted. Using HEtG independently is a more accurate marker than CDT for chronic alcohol correlated disorders, 25 out of 122 subjects would be diagnosed as unfit to drive.
Discussion For individuals that committed violations to the highway code for DUI of alcohol (and/or drug), the Italian law requires the offenders to undergo a mandatory examination that should produce a medico-legal diagnosis of fitness/unfitness to drive. The whole re-granting procedure is entrusted to local health authorities (Local Medical Commissions) that often apply different, non-standardized protocols to achieve the diagnosis of fitness/unfitness to drive. This case-control study included three groups of drivers involved in DUI and a group of controls, and disclosed concentrations of the biomarker HEtG higher than the proposed cut-off of 30 pg/mg in subjects presumed to be “abusers” (20% HEtG positive in drivers with a BAC >1.5 g/L) and in “repeated offenders ” (27% HEtG positive in subjects that drunk drove more than once with BAC > 0.80 g/L) compared to the presumed “social” drinkers that had a BAC between 0.5 and 0.8 g/L at the time of the offense (Group 1, 12% HEtG positive) and to the control population (Group 4, 0%). The higher prevalence of the subjects positive for the direct ethanol metabolite HEtG with respect to those positive for CDT (an indirect marker routinely used in forensic and
253 clinical protocols for alcohol abuse) shows the greatest diagnostic power of HEtG (20% versus 13%), confirming its higher sensitivity as reported in the dedicated literature.12,13 However, it should be noted that there is not a correlation between the two markers, being their distribution different in the three groups of DUI subjects, with only 5 subjects (4%) having both CDT and HEtG values than greater than the designated cut-offs. This apparent discrepancy may be due to the different metabolism/turnover of CDT in serum and EtG in hair. When an excessive chronic drinker stops his/her usual pattern of drinking, the CDT levels turn to normal levels in 2–3 weeks,14 while EtG accumulates in hair and remains almost fixed in a specific hair segment for months/years, unless washout effects occur. Considering that HEtG must be determined in 3 up to 6 cm of proximal hair, corresponding to a time span of 3–6 months,11 it may be possible to have CDT negative in serum and HEtG positive for a heavy drinker that was able to reduce the alcohol consumption in the last 2–3 weeks before undergoing the re-granting assessment. On the other end, the positive CDT values in subjects with negative HEtG could be ascribed to the various clinical or genetic factors that are recognized able to elevate CDT isoforms in non alcoholic individuals, such as glycosilation pattern disorders, genetic variants, ethnicity, alcoholic or non-alcoholic hepatopaties; however, the apparently high concentrations of CDT levels in Group I (potentially social drinkers) needs more investigation. When comparing our results with those of Liniger et al.12, that retrospectively investigated on HEtG and CDT of 154 subjects whose fitness to drive had to be assessed because of the suspicion of relevant alcohol problems, similar results were obtained. EtG findings in the hair samples were positive in 84 out of the 154 self-reported teetotalers; however, only 39 of these 84 subjects had a CDT value above the upper limit of normal using an immunochemical method and only 15 subjects had a CDT value above the cut-off measured by HPLC. Conversely, of 70 subjects that tested negative for HEtG, 15 or 3 had a CDT value above the upper limit using respectively the immunochemical or the HPLC method. However, differently from our study, the cut-off used by Liniger for HEtG was 7 pg/mg for detection of abstinence; two diverse methods were used for CDT; the selected subjects were all “self-reported” teetotallers and no detail on their BAC at the time of offences was given; no control group was used. In conclusion the determination of HEtG supports the clinical diagnosis of problems related to alcohol in drunk drivers and allows the identification of a larger number of potentially unfit subjects than CDT: if the decision on re-granting was based on CDT values only, 13% of subjects undergoing the assessment could be declared unfit to drive, whereas by using HEtG values only the percentage rose to 20% and the accuracy of the reinstatement examination is improved by extending the number of markers of an alcohol risky use. The first tested hypothesis holds true. However, the observed discrepancies between CDT and HEtG need more consideration, suggesting that neither CDT nor HEtG alone are ideal markers of excessive alcohol consumption and that the ascertainment of fitness to drive must take into account more than one biomarker including their critical evaluation of a more comprehensive legal-medical protocol.
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Table 1. Characteristic of the 156 enrolled subjects according to their gender and manner of DUI
Total Male Female
Group I BAC ≥0.5 g/L ≤0.8 g/L
Group II BAC ≥1.5 g/L
Group III More than one DUI offense
Group IV Control
25 20 5
89 77 12
15 14 1
34 12 22
Group I BAC ≥0.5 g/L ≤0.8 g/L
Group II BAC ≥1.5 g/L
Group III More than one DUI offense
Group IV Control
25 22 3
89 71 18
15 11 4
34 23 —
Group I BAC ≥0.5 g/L ≤0.8 g/L
Group II BAC ≥1.5 g/L
Group III More than one DUI offense
Group IV Control
25 15 10
89 85 4
15 11 3
34 34 —
Table 2. HEtG values compared to manner of DUI
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Total HEtG 3 ribs on one side and no more than 3 ribs on the side, with hemo/pneumothorax Thoracic cavity injury NFS, with pneumomediastinum Humerus fracture, open/displaced/ comminuted Ulnar fracture, open/displaced/ comminuted Radius fracture, open/displaced/ comminuted Subarchanoid hemorrhage Cerebral contussion
7
The AIS coder that performed the AIS scoring and ISS/MAIS calculations is AIS trained through the AAAM curriculum and is a Certified AIS Specialist (CAISS).
3
4
4
3
3 3
Appendix Table A1. Corrections from original CIREN coding (all cases requiring correction with originally coded in AIS98). Note that in two instances, the spine fractures needed to be separated into distinct injuries Original Code [AIS98]
Original Description
Corrected Code(s) [AIS98]
850610.2
Hip dislocation NFS
850618.2
650212.3
Cervical Spine, dislocation facet bilateral; C1C2 Cervical Spine, fracture transverse process; C6C7
650206.3
650220.2
650220.2
650220.2
650220.2
Cervical Spine, fracture transverse process; C6C7
650220.2
650220.2
AIS Note
4 4
Corrected Description Hip dislocation, involving articular cartilage Cervical spine, dislocation, altanto-axial Cervical Spine, fracture transverse process, C6 Cervical Spine, fracture transverse process, C7 Cervical Spine, fracture transverse process, C6 Cervical Spine, fracture transverse process, C7
Table A2. Comparison of MAIS, Thoracic MAIS, ISS, and NISS for each case based on AIS98 and AIS05 coding
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265 AIS98
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Case 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
AIS05
MAIS
Thoracic MAIS
ISS
NISS
MAIS
Thoracic MAIS
ISS
NISS
3 4 4 5 2 4 3 3 4 4 3 3 4 4 4 4 4 4
3 4 4 5 2 4 3 2 4 3 3 3 4 4 4 4 4 4
14 26 21 42 9 21 10 22 29 34 27 17 29 29 41 41 29 34
14 41 34 57 12 29 17 27 29 34 27 27 34 34 41 41 29 34
2 3 2 5 2 4 2 3 4 4 3 3 3 3 4 4 3 3
2 3 2 5 2 4 2 3 4 3 2 3 3 3 4 3 3 3
9 14 9 30 6 21 5 22 24 29 17 17 22 22 41 29 17 17
9 22 12 38 12 24 12 27 24 34 22 17 27 22 41 29 17 22
References
Introduction
Gennarelli TA, Wodzin E. Abbreviated Injury Scale 2005: Update 2008. Association for the Advancement of Automotive Medicine; 2008. Yoganandan N, Pintar FA, Humm JR, et al. Comparison of AIS 1990 update 98 versus AIS 2005 for describing PMHS injuries in lateral and oblique sled tests. Ann Adv Automot Med. 2013;57:197–208.
The Nij neck injury criteria for compressive loading, which is described in three reports published by the National Highway Traffic Safety Administration (Kleinberger et al. 1998; Eppinger et al. 1999; Eppinger et al. 2000), is not derived from biomechanics tests that produced compressive injury in humans or cadavers. It is derived from the assumption that compressive and tensile tolerances should be the same and that the response of juvenile pigs and the Hybrid III 3 YO can be scaled to be representative of adult human responses. As a result, there is some impetus to consider updating such criteria for predicting compressive neck injuries in rollover crashes. Since occupant-to-roof impact velocity is a difficult quantity to measure in a rollover crash test, a velocity-based injury criterion would not be incredibly useful with a dummy. However, a velocity-based injury criterion is an attractive alternative in retrospective biomechanical analyses of rollover crashes since basic kinematics equations can be used with accident reconstruction results to evaluate injury risk for a particular vehicle-ground impact in a multi-impact rollover crash. While we have some anecdotal evidence that a velocity-based injury criterion is being used to assist in the forensic analyses of rollover crash occupant injury, no published technical studies, to our knowledge, clearly describe the validity of such a criterion. Viano and Parenteau (2008) compared tests and compiled data from whole body inverted drop tests presented by Nusholtz et al. (1983), Sances et al. (1986), and Yoganandan et al. (1986). They found that there are no data for human impact response and injury occurrence in tests between 2.0 and 4.0 m/s, but that all tests performed with velocities exceeding 4.0 m/s produced injury. The research by Nightingale et al. (1996) and Nightingale et al. (1997) suggests that impacts exceeding 3.1 m/s usually produce injury. However, since the studies by Nightingale use a fixed mass (16 kg) to estimate the portion of the torso mass that compresses the spine when an inverted human (possibly a forward-facing vehicle occupant in a driving posture) with a neutral (lordotic) cervical spine sustains a vertex impact, the
Axial Compression Injury Tolerance of the Cervical Spine: Initial Results∗ JASON R. KERRIGAN1, JONATHAN B. FOSTER2, MARK SOCHOR3, JASON L. FORMAN3, JACEK TOCZYSKI1, CAROLYN W. ROBERTS2, and JEFF R. CRANDALL University of Virginia Center for Applied Biomechanics
Four whole-body male PMHS were subjected to inverted headto-ground impacts that resulted in cervical compression in an attempt to compare the response of whole-body PMHS to component tests performed previously. Peak head forces in the current study (4495 N) were similar to those in previous studies, but differences in timing and magnitudes of second force peaks suggest that differences in constraints and/or boundary conditions affected the dynamics of the impact. While only moderate (AIS 2) injuries were produced in the current study, more serious and severe injuries have been produced previously, which suggests that constraint and/or boundary condition differences also affect injury type and tolerance.
∗
This short communication was reviewed and accepted for publication by The Association for the Advancement of Automotive Medicine (AAAM).
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3.1 m/s velocity threshold is directly dependent on the validity of the 16 kg assumption. To further simplify conditions, the first thoracic vertebra (T1) is potted and constrained to move only in vertical direction. However, the Nightingale study does utilize an isolated cadaveric component (head/neck), which is an attractive option that could reduce the costs of the potentially substantial number of tests that would be required to develop a velocity or other injury criterion. This study aims to evaluate head/neck response in inverted impacts that produce compressive loads on the cervical spine in an attempt to assess whether the simplified conditions used by Nightingale et al. (1997) are sufficient to determine injury thresholds for cervical spine compression injuries. The current study utilizes whole-body subjects in inverted impacts at velocities between 3.0 and 3.6 m/s to attempt to fill the void identified by Viano and Parenteau (2008).
Methods Four male fresh-frozen post mortem human subjects (PMHS) were selected for this study (Table 1). The PMHS were obtained and treated in accordance with the ethical guidelines established by the Human Usage Review Panel of the United States National Highway Traffic Safety Administration, and all testing and handling procedures were reviewed and approved by the Center for Applied Biomechanics Biological Protocol Committee and an independent Oversight Committee at the University of Virginia. Each subject was instrumented with kinematics instrumentation on the head and T1. An instrumentation cube consisting of three mutually perpendicular linear accelerometers (7264B2000, Endevco, San Juan Capistrano, CA, USA) and angular rate sensors (ARS-8K, DTS, Seal Beach, CA, USA) was fixed to an aluminum plate and fixed to the temperoparietal skull with screws. A second cube was fixed to a clamp that joined the posterior ends of a pair of pedicle screws installed in the first thoracic vertebra (T1). For subjects 631 and 553, no angular rate sensors were used on T1. A coordinate measurement machine (CMM) was used to identify the location and orientation of the head instrumentation cube relative to skeletal landmarks that were used to estimate the location of the head center of gravity (CG) and the orientation of a head coordinate system (Robbins 1983). After sensor mount installation, the subjects were CT scanned to facilitate identification of sensor mounting orientation relative to the head and T1 and to determine the angle of the T1 mount relative to the C7-T1 intervertebral disc. On the day of each test, the subject was wrapped in a thin layer of mechanically adhesive wrap (Coban, 3M, St. Paul, MN, USA) and outfitted with a tactical body harness (355 Extraction Harness, Yates Gear Inc, Redding, CA, USA). The lower extremities were bound together at the distal thigh and ankle. Adjustable nylon ropes were fixed to several locations on the harness and at the bindings and the subject was hoisted for positioning. Each subject was inverted and a standard seating position (Manary et al. 1998) with a 20-27 degrees (from vertical) torso angle was implemented. The lower extremities were oriented such that they were parallel to the ground. Head
Short Communications and neck positioning was performed to facilitate comparison with previous tests (Nightingale et al. 1996): C7/T1 disc rotated (sagittal plane) 25 degrees relative to ground, and the Frankfurt plane parallel to the ground. The combination of the C7/T1 disc and head orientation was used (in Nightingale et al. 1996) to preserve the resting lordosis present in drivers ((Matsushita et al. 1994). The ends of the supporting ropes were joined together in a ring that was connected to a solenoid release mechanism to permit electronic test initiation. The impact surface consisted of a five-axis load cell (Denton B-3868-D, Humanetics Innovative Solutions, Plymouth, MI, USA), sandwiched between two steel plates. On the top plate, a piece of 25.4 mm thick light-density closed-cell, polyvinyl chloride general purpose foam (V700 Series 1.00”, Gaska Tape Inc., Elkhart, IN, USA), was adhered to the steel plate. This foam was used previously (Frechede et al. 2009) to mimic the foam used by Nightingale et al. (1996). The load plate assembly was positioned under the subject’s skull (apex), and the subject was raised to the drop height (approximately 53 cm, Table 1). The orientation of the head, and head/T1 instrumentation cubes were then measured with the CMM. Then, the subject was released and allowed to sustain unimpeded impact with load plate and floor. After the test, skeletal injury pathology and extent of injury was determined via radiology and subsequent dissection. The subjects’ head weights were determined after decapitation during dissection. Head acceleration data were transformed to the head CG coordinate system and the measurement location was translated to the head CG using the rigid body assumption. Time histories of the head and T1 local-to-global coordinate system transformations were determined from the angular rate data (Beard and Schlick, 2003). Global head acceleration data were multiplied by the head mass, to determine the inertial contribution of the force applied to the neck. Then the neck force (at the atlanto-occipital (AO) junction) was calculated by component-wise subtraction of the load cell force from the inertial force (Flc -mahead = Fneck ) under the assumption that the head is a rigid body acted upon by only two forces.
Results The head force (applied to the head through the load plate) showed an initial short duration (8-10 ms) peak at approximately 10 ms after impact, followed by a lower magnitude longer duration (30–40 ms) peak centered around 38 ms after impact (Figure 1 and Figure 2). The axial compressive force applied to the neck at the AO junction showed a similar character with an initial short duration peak just after the peak in head force (12 ms), and a longer duration lower magnitude peak later 39 ms. Variation in average peak forces (Table 1) for the first and second peaks decreased by mass scaling the forces using the body weight: SD 731 N vs. 270 N, 792 N vs. 519 N, 300 N vs. 57 N, 592 N vs. 443 N for the first and second head, and first and second neck force peaks, respectively. T1 global accelerations were integrated to determine velocities and displacements and T1 local-to-global transformations were used to determine vertebral rotations. The T1 kinematics data showed that T1 (in 516) reached 800 deg/s in flexion
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Table 1. Subject information, test conditions, and results UVA Specimen Number
516
552
631
553
Sex Age Weight [kg] Stature [mm] DEXA Dual Femur Total [T-score] Head Mass [kg] Impact Velocity [m/s] First Peak Head Force [N] (time in ms) Second Peak Head Force [N] (time in ms) First Peak Neck Force [N] (time in ms) Second Peak Neck Force [N] (time in ms) FheadZ/AccZ at Time of First Peak in Head Force [kg]
M 89 54.4 155 -2.7
M 82 77.6 170 0.9
M 71 68.9 178 -0.5
M 60 57.2 170 -2.8∗
3.275 3.08 3819 (10.3)
3.775 3.01 5347 (10.0)
4.07 3.63 4858 (9.5)
3.54 3.54 3956 (9.9)
2353 (43.9)
4058 (26.2)
3053 (35.1)
2411 (46.7)
2730 (10.9)
4264 (42.5)
3299 (11.9)
2852 (12.4)
2076 (42.3)
∗∗
3239 (38.7)
2457 (37.3)
9.93
7.18
9.26
8.12
∗ Dual ∗∗ no
Femur Total score was not available and AP Spine, so AP Spine score is provided. second peak in neck force the test on subject 552.
rotation over the first 10 ms after impact, and over 1200 deg/s by 15 ms after impact, and sustained between 9 and 24 deg rotation within the first 40 ms. Furthermore, the acceleration data also suggest that the vertebra (in 516/552) translated linearly more than 80 mm in the first 40 ms. Three of the four cadavers sustained bony fracture while subject 516 sustained no injury: • 516-No injury • 552-C7 bilateral pedicle/lamina fractures (assumed to be iatrogenic) • 631-small (5 mm) anterior chip fracture of the superior endplate of C4 vertebral body • 553-Type III Odontoid fracture (post-test) Some intervertebral laxity was noted during some dissections, however, no facet joint dislocation nor ligament laxity/disruption was clearly identified. The C7 fracture was determined during dissection to be, at least minimally, related to the orientation of the pedicle screws in T1 used to mount the sensor block. High speed (1000 Hz) Xray was attempted with both subject 631 and 553 in an effort to clearly visualize injuries. While the vertebral body fracture in 631 was not clearly visualized, the odontoid fracture was clearly identified to occur 182 ms after initial head contact, during extreme flexion that occurred after the subject bounced off the plate.
Discussion While it is tempting to model the head-neck-torso as a massspring-mass system due to the bimodal shape of the head force time history seen in the subjects, the calculated upper neck loads show that the neck force has a bimodal shape and the first peak occurs just 1-2 ms after the first peak in head force. This suggests that at least some of the neck/torso mass is coupled well enough to the head that it begins decelerating immediately upon impact. The normal load cell (head Z)
force divided by the head global vertical acceleration in the Z direction estimates the effective mass of the part of the body that is decelerated during the initial force peak (Table 1). On average, subjects in the current study had effective masses that exceeded the head mass by approximately 5 kg, suggesting that the entire neck, and some of the torso, may be decelerated during that first impact. Subject 552 had the shortest time duration between the first and second peaks in head force (16.2 ms), and the lowest effective impact mass (7.18). This could be the result of abnormalities with that subject since substantial metastases were noted throughout the lumbar and thoracic spines. However, the shorter duration and lower effective mass suggest that the lax element, which represents the spring in the mass-spring-mass model, was higher up (possibly in the cervical spine) than in the other subjects. Such an analysis could benefit from knowing the mass of the cervical spine, however, it should be noted that the mass-spring-mass model is no longer valid when the cervical spine begins to undergo increased bending (superior extension and inferior flexion). While the high-speed Xray imagery used in the current study did not provide a significant contribution because of operational problems with the Xray system, it did indicate that this increased bending, or a change in the orientation of the vertebral bodies (called “buckling” by Nightingale et al. 1997 and other previous studies), occurred almost exactly at the time of the first peak in force. Thus, the “rigid body” assumption inherent in a mass-spring-mass model is no longer valid after this peak since the lower mass (head, neck, some of torso) begins deforming at the time of the first peak. While all of whole-body drop test subjects tested previously (Nusholtz et al. 1983; Yoganandan et al. 1986; Sances et al. 1986) were tested at either a substantially higher or lower velocity than the subjects tested in the current study, Nightingale et al. (1997) described three head/neck restrained subjects (N02, N03, D40) tested with the same conditions as in the current test: ∼3.1 m/s impact velocity, neutral neck flexion/extension angle, vertex impact, padded surface. While the
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Fig. 2. Load cell normal (Z) force (top) and Z-direction (axial) neck force (bottom) time histories from all four subjects.
Fig. 1. Lateral view images from the test on subject 516. Video times are taken from initial contact (top), time of first peak load cell force (next), time of load cell minimum between peaks (next), and time of the second (next), and peak load cell force (bottom).
current study utilized whole body PMHS, and the tests by Nightingale et al. (1997) utilized only PMHS components, it was hypothesized that the conditions were comparable. However, there were several differences in the forces response and injury values. While two of the three subjects in the Nightingale et al. (1997) study clearly showed the same bimodal shape of head force as three of the four subjects in the current study,
there were several differences in timing and magnitude. The first peak in the Nightingale tests occurred approximately 10 ms later (15.8-23.5 ms, avg. 20.1 ms) than in the current study. This suggests that there was a difference in the stiffness of the foam between the two studies. There were similar values for the averaged peak head force magnitude between the two studies (4495 N vs. 4433 N for the three subjects in Nightingale), which suggests that the portion of mass coupled well enough to the head to be decelerated during the time of the initial force peak was similar between the tests. However, the second peak force was substantially higher in the current study than in the previous study (2970 N vs. 1925 N), which suggests that the 16 kg used in the Nightingale study to represent the portion of the torso mass that serves to compress the spine in such an impact is an underestimate of the real mass. The time difference between the two peaks was longer in the current study (27.9 ms, or 32 ms if subject 552 is not counted) than in the Nightingale study (17.4 ms). The reason for this is not clear, but it may be related to the constraint on T1 in the Nightingale study, which may have caused different vertebral kinematics subsequent to the first impact than in the current study. Injuries in the current study were much less severe than in the Nightingale study. Subjects from tests N03, D40, and N02 sustained seven fractures, five intervertebral/facet joint
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Short Communications disruptions (including one case of bilateral facet dislocation), and four generally unstable injuries. In the current study, there was only one fracture that appeared to be related to the loading that occurred during the first 100 ms after impact (C4 chip fracture in 631). Even if the C7 fractures in 552 were not iatrogenic, there is a substantial difference in the injury severity between the current study and previous studies, especially given the relatively low bone quality of the subjects in the current study (as indicated by DEXA T-scores). Nightingale et al. (1997) and others have indicated that producing such severe bilateral fractures requires at least near-perfect alignment of the load vector and vertebral bodies. While it is possible that such severe fractures were not produced in the current study because of slight variations in the alignment, much more severe injuries, including some that were similar to those produced by Nightingale et al. (1997), were produced in the subjects tested by Nusholtz et al. (1983) in impacts between 4.4 and 5.9 m/s. In the current study, sensor data showed that T1 translates and rotates substantially during even the initial phase of loading (first 20-40 ms). It is thus hypothesized that constraining T1 motion to restrict transverse translations and rotations results in an artificial boundary condition that subjects the cervical spine to a lower fracture tolerance than would exist in the absence of such a constraint. Cervical spine boundary conditions have been shown to have a substantial effect on the injury type and tolerance in compressive loading (Myers et al. 1991). While T1 was more constrained in the Nightingale et al. (1997) tests than it is when a living human is in a rollover crash, it seems possible that the active musculature in a living human provides more constraint on T1’s motion than a PMHS model can accurately reproduce. Lastly, data from the current study suggest that Nij injury criteria for compressive loading should be reconsidered. While other tests have been performed to evaluate Hybrid III crash dummy response (Frechede et al. 2009 and others) in inverted impacts, two tests performed as part of the current study showed that the peak upper neck compressive load recorded by the Hybrid III in a 3.1 m/s impact was between 9200 N and 11800 N (depending on head/neck/chest orientation). Thus, in impacts that resulted in only minor or no injury in PMHS with low bone quality, the Hybrid III dummy predicts a force that is between 230% and 296% of the compressive limit, and 140% to 180% of the compression intercept for Nij. As discussed by other authors, this is because the dummy spine (cervical and thoracic) is far too stiff to accurately represent human response in an inverted impact, and thus will likely need to be modified to accurately predict neck injuries in rollover crash tests.
Conclusions The current study was an initial step in determining injury criteria for the cervical spine to predict severe injuries like those that occur in rollover crashes. The current study showed:
269 • inverted head/ground impacts at 3.1 m/s are not sufficient to cause severe cervical spine injury; • the combination of constraining T1 and using 16 kg to estimate the portion of the torso that serves to compress the spine in an inverted head/ground impact results in a response that has different dynamics than when an unconstrained whole body cadaver is subjected to a similar impact; and • the T1 vertebra undergoes substantial translation and rotation during the axial compressive loading that occurs subsequent to an inverted head/ground impact.
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