Sport Trauma 2015 - Lunds tekniska högskolabme.lth.se/.../Biomekanik/Sport_Trauma_2015.pdfmater, is observed as a result of trauma to the skull and the underlying meningeal vessels.

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Trauma and Sport Biomechanics

Trauma biomechanics

h:ps://www.youtube.com/watch?v=d7iYZPp2zYY

Crash dummies

•  Dummies are developed from measurements of sub-‐injury crash simulaMons and simulaMons with post mortem human and animal subjects

•  Dummies are instrumented with load-‐cells, accelerometers, gyros, infra red devices for measuring chest pressure, belt movement sensors, strain gauges

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Head injuries 64 Head Injuries

Fig. 3.1 Anatomy of the head: bony structures of the skull (top), the meninges(middle), and the brain (bottom) [adapted from Sobotta 1997].

64 Head Injuries


64 Head Injuries


The anatomy of the head

The meninges (hjärnhinnor) The brain

Possible head injuries 66 Head Injuries

laceration but are generally regarded to be of minor importance. Likewisefacial injuries, to the eyes or ears for example are considered minor injuriesand therefore are mainly rated as AIS1 or AIS2. These injuries will not bediscussed here.

More severe head injuries can arise from fractures. Facial fracturesinclude fracture of the nasal bone, which occurs most frequently, andmaxillary fractures. The latter are considered serious with AIS grades of upto 3. Figure 3.3. shows the LeFort classification that is used to categorisemaxillary fractures. Examples of head injuries classified according to theAIS scale are presented in Table 3.1.

With respect to the skull, fractures are divided into basilar and vaultfractures (i.e. all other fractures not occurring at the basis of the skull). Itshould be noted that basilar fractures may be difficult to visualise usingconventional radiographic methods, so that diagnosis can be difficult.

Injuries to the brain are clinically classified into two broad categories:diffuse injuries and focal injuries. Diffuse brain injuries form a spectrumranging from mild concussion to diffuse white matter injuries. The mostcommon form of such brain injury is mild concussion (fully reversible, noloss of consciousness). Particularly in sports, mild traumatic brain injury

Fig. 3.2 Possible injuries to the head.

Fig. 3.3 Three types of facial fractures as classified by LeFort [adapted from Vetter2000].

68 Head Injuries

significant than coup-contusions [Melvin and Lighthall 2002]. As forhematoma, three different types are distinguished depending on the site ofthe bleeding: epidural hematoma, subdural hematoma and intracerebralhematoma (Figure 3.4). Epidural hematoma, i.e. bleeding above the duramater, is observed as a result of trauma to the skull and the underlyingmeningeal vessels. It is therefore not due to brain injury. Usually skullfracture is associated, but an epidural hematoma may also occur in theabsence of fracture. If the hematoma is found below the dura mater, it iscalled a subdural hematoma. Three sources were identified for subdural

Fig. 3.4 Bleeding into the epidural space is calledan epidural hematoma and can cause braincontusion [adapted from Vetter 2000].

Fig. 3.5 Possible mechanisms for head injury.

Epidural hematomea

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72 Head Injuries

acceleration for shorter durations.The WSTC is supported by experiments conducted in Japan which led to

the Japan Head Tolerance Curve (JHTC) [Ono et al. 1980]. JHTC wasmainly obtained from experiments with primates and scaling of results tohumans. Differences between the WSTC an JHTC are negligible for timeintervals up to 10 ms, and only minor differences exist for longer durations.

When the WSTC is plotted in a logarithmic scale, it becomes a straightline with a slope of -2.5. Based on this finding, Gadd et al. (1961) proposeda first head injury criterion, the severity index (SI). A modified form of thiscriterion is still in use today (see section 3.4.1).

Using the WSTC or any criterion developed thereof, restrictions thatarise from the test conditions have to be considered. The paucity of data

Table 3.3 Test conditions of the experiments the WSTC is based upon.

pulse duration

test objects test set-up response measured injury criterion

2 - 6 ms cadavers drop test acceleration at the back of the head

skull fracture

6- 20 ms

cadavers and animals

impact test acceleration of skull, brain pressure

pathological changes

> 20 ms volunteers sled tests whole body acceleration without head impact

concussion, state of consciousness

Fig. 3.7 The Wayne State Tolerance Curve (acceleration vs. duration ofacceleration pulse) [adapted from Krabbel 1997].

Wayne State Tolerance curve

Mechanical response of the head 73

points, the position of the accelerometer (back of the head), the fact that therotational acceleration is not considered, and the techniques used to scalethe animal data are, for instance, major limitations. However, from abiomechanical point of view the main criticism concerns thecorrespondence of skull fracture and brain injury that was assumed. Thishypothesis remains to be verified, as there was no direct demonstration offunctional brain damage in an experiment in which biomechanicalparameters sufficient to determine a failure mechanism in the tissue weremeasured [Melvin and Lighthall 2002].

Bearing in mind that the WSTC is based on direct frontal impact tests,the results can, strictly speaking, not be applied to non-contact loadingconditions and to other impact directions, respectively. Nonetheless, WSTCis still the most important data source with respect to the linear accelerationresponse of the head.

Further experimental studies addressed rotational accelerations whichmay cause diffuse brain injury and subdural hematoma. Besides volunteersand cadavers, primates were subjected to head rotation, where the rotationalacceleration was measured and the resulting degree of injury was assessed[e.g. Ommaya et al. 1967, Hirsch et al. 1968, Gennarelli et al. 1972]. It wasfound that the angular acceleration and the according injury thresholds arerelated to the mass of the brain. Thus, the tolerance limit for the human wasobtained by scaling the results from the primate tests (Figure 3.8). Table 3.4gives tolerance values that are commonly used. However, additional studieson volunteers suggest that much higher tolerance values up to 25000 rad/s2

may be possible for short durations [Tarriere 1987].

Fig. 3.8 Results from experiments and scaling addressing tolerance towardsrotational acceleration [adapted from Krabbel 1997].

Tolerance against rotaMonal acceleraMon (extrapolated to humans)

Head Injury Criterion

Injury criteria for head injuries 75

3.4 Injury criteria for head injuries

Although great progress in passive safety, such as the introduction ofadvanced restraint systems, was made in the last couple of years to reducethe number and severity of head injuries, there is only one injury criteria inwide use, the Head Injury Criterion (HIC), which was developed more thanthirty years ago. Besides the HIC and its European equivalent, the HeadProtection Criterion (HPC), the “3 ms criterion” and the GeneralisedAcceleration Model for Brain Injury Threshold (GAMBIT) are presented.However, it should be noted that all these criteria are based on accelerationresponse only. Consequently, injuries that are related to impact force ratherthan acceleration are not addressed by these criteria. In other words, thosecriteria do not allow an evaluation of the injury risk of sustaining fracturesof the bony structures of the head. The only dummy capable of measuring aforce response to facial impact is the THOR dummy (see section 2.6.1), butthis dummy is not included in recent crash test standards. More recentattempts on improving head injury criteria include a criterion based on thetotal change of kinetic energy of the head during impact (HIP, Newman etal. 2000), or employ e.g. finite element models to predict shear strain in thebrain tissue, thus bypassing the discussion on whether rotational ortranslational accelerations are more important (Willinger and Baumgartner2001, Takhounts et al. 2003, 2008). Such criteria, however, requireextensive calculation and modelling steps after e.g. a crash test.

3.4.1 Head Injury Criterion (HIC)

The Head Injury Criterion has a historical basis in the work of Gadd (1961),who used the Wayne State Tolerance Curve (WSTC) (see section 3.3) todevelop the so-called severity index (SI). In 1971, Versace (1971) proposeda version of the HIC as a measure of average acceleration that correlateswith the WSTC. The actual version of HIC was then proposed by the USNational Highway Traffic Safety Administration (NHTSA) and is includedin FMVSS 208. HIC is computed based on the following expression:

(3.1)

where t2 and t1 are any two arbitrary time points during the accelerationpulse. Acceleration is measured in multiples of the acceleration of gravity

HIC max 1t2 t1–--------------- a t( ) td

t1

t2

³2,5

t2 t1–( )=

76 Head Injuries

[g] and time is measured in seconds. The resultant acceleration is used forthe calculation. FMVSS 208 requires t2 and t1 not to lay more than 36 msapart (thus called HIC36) and the maximum HIC36 not to exceed a value of1000 for the 50th percentile male. In 1998 NHTSA also introduced theHIC15, i.e. the HIC evaluated over a time interval of 15 ms [Kleinberger etal. 1998]. As for the according threshold value, a maximum of 700 wassuggested for the 50th percentile male.

To determine the relationship between HIC and injuries of the skull andbrain, available test data was analysed statistically by fitting normal, lognormal, and two-parameter Weibull cumulative distributions to the data set,using the Maximum Likelihood method to achieve the best fit for eachfunction [Hertz 1993]. The best fit of the data was achieved with the lognormal curve (Figure 3.9).

The probability of skull fracture (AIS ≥ 2) is given by the formula

(3.2)

where N( ) is the cumulative normal distribution, µ = 6.96352 and σ =0.84664.

Since the data used to establish this risk analysis consists of shortduration impacts of typically less than 12 milliseconds, the HIC curve isapplicable to both HIC15 and HIC36. Thus, the probability of skull fracture(AIS ≥ 2) associated with a HIC15 threshold value of 700 for a mid-sizedmale is 31% and for a limit of 1000 for HIC36 (50th percentile male) it is

p fracture( ) NHIC( ) µ–ln

σ----------------------------------© ¹§ ·=

Fig. 3.9 Probability of skull fracture (AIS ≥ 2) in relation to the HIC asdetermined by Hertz (1993).

HIC-‐criterion: acceleraMon measured in mulMples of g and Mme in seconds, t2 and t1 should be less than 36 ms apart

Probability of skull fractures

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80 Head Injuries

since repeated MT

BI is believed to result in chronic degenerative brain

damage [e.g. B

ailes and Cantu 2001, B

iasca et al. 2006a, b, Delaney et al.

2006]. Therefore it is recom

mended to docum

ent every MT

BI.

Several studies are presented that investigate head loading and address

Table 3.5 Head impact data related to the risk of sustaining concussion/MTBI.

sport translational acceleration [g]

rotational acceleration [rad/s2]

HIC [-]

delta-v [m/s]

comment/references

football (professional)

< 85 < 6000 240 (HIC15)

- threshold values for reversible brain injury, computer simulationZhang et al. 2004


98 ± 28 6432 ± 1813 381 ± 197 7.2 ± 1.8 concussion, data from video analysis/reconstrucion using Hybrid III dummiesPellman et al. 2003 and Viano et al. 2007

football (college)

60.5 - 168.7 - - - concussion, accelerometers embedded in helmetsGuskiewicz et al. 2007

football (college)

81 - 200 - concussion (one observation),in-helmet accelerometersDuma et al. 2005

football (college)

32 ± 25 2020 ± 2042 y-axis

26 ± 64 - average of 3311observations,in-helmet accelerometersDuma et al. 2005

Head Injuries in Sports H

ead injuries in sports 81

possible injury

criteria and

thresholds for

concussion and

MB

TI,

respectively. The techniques used to investigate the loading of the head

range include video analysis, reconstruction of head impacts using crash

test dumm

ies, measuring loads by instrum

ented helmets and com

puter

Table 3.5 ctd Head impact data related to the risk of sustaining concussion/MTBI.

sport translational acceleration [g]

rotational acceleration [rad/s2]

HIC [-]

delta-v [m/s]

comment/references


60 ± 23 4235 ± 1716 121 ± 64 5.0 ± 1.1 no injury, data from video analysis/reconstruction using Hybrid III dummiesPellman et al. 2003

football (college)

21-23 - - - no concussion, accelerometers embedded in helmetsMihalik et al. 2007

footballhockeysoccer

29.2 ± 1.035.0 ± 1.754.7 ± 4.1

- 22.5 ± 3.613.5 ± 1.848.5 ± 7.0

- no incidents of concussion, accelerometer placed on helmet Naunheim et al. 2000

boxing 58 ± 13 6343 ± 1789 71 ± 49 - punches to a Hybrid III dummy headWalilko et al. 2005

boxing <43.6 <675.9 - - below MTBI injury level, values determined for different punchesSmith et al. 1988

boxing (hook)

71.2 ± 32.2 9306 ± 4485 - - non-injurious, punches to a Hybrid III dummy headViano et al. 2005

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Sport biomechanics

•  Measuring-‐techniques of moMons •  EvaluaMon of moMons •  PrevenMon of injuries •  Anthropometry

Anthropometry

Body mass index, BMI BMI = mass/(length^2)

in kg/m2

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Kenyan runners ”Even the Gardeners Here Are Faster Than Me” Peter Vigneron, Marathon runner, USA, on tour in Kenya I’m staying at Silgich Hill Academy now, where even the gardener is a be:er runner than I am. On my morning run Sunday, as on many of my morning runs since I’ve come to Kenya, a group of children playing near the road fell in alongside me as I passed by. This morning one boy raced me, and he almost won. Before he dropped I was wondering how long I would last if he didn’t get Mred very quickly. I realized when I finished that since my arrival to Kenya in early March, this boy, this nameless, anonymous child, is the first Kenyan who couldn’t hang with my pace. I don’t think he was older than 12.

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ExcepMons… Stefan Holm, Sweden •  Length: 1.81 m •  Personal record: 2.40 m

Javier Sotomayor, Cuba •  Length: 1.95 m •  Personal record: 2.45 m WR

h:p://www.youtube.com/watch?v=ZG3_I3zFB0U h:p://www.youtube.com/watch?v=qMKoyWi7vps&feature=fvwp

RelaMve length of segments

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Length, mass, moment of inerMa

Body shape

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Conclusion: It is about the anatomy of the human body! •  Skeletal bones

(length, width, proportions) •  Ligaments

(stability around joints) •  Muscles

(size and composition of fibres) •  Joints

(motion range)

A lot about motivation!!

Moment of inerMa and rotaMon

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Squat jump vs counter movement jump

Squat jump

Counter movement jump

Sport Trauma 2015 - Lunds tekniska högskolabme.lth.se/.../Biomekanik/Sport_Trauma_2015.pdfmater, is observed as a result of trauma to the skull and the underlying meningeal vessels.

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