characterization of the pediatric shoulder’s...
TRANSCRIPT
IntroductionMotor vehicle crashes, especially side impacts, are a leading cause of death and disability to the
pediatric population as they account for approximately 50% of pediatric trauma [1]. Sixteen percent
of children were non-fatally injured while 32% of children have died as a result of vehicle side
impacts [2]. According to the Crash Injury Research Engineering Network (CIREN), children
involved in side impact crashes are more likely to suffer severe injuries to the head and thorax [1].
The placement of the head and thorax during impact has been shown to be heavily dependent on the
response of the shoulder mechanism [3].
Due to the need to increase safety in automobiles, the automotive community has been actively
researching methods to prevent injury during car accidents. Potential improvements must first be
tested to verify that they reduce injury. This is done through the use of anthropomorphic test
devices (ATDs), which provide a method for analyzing the injuries involved in a vehicle crash [1].
However, the data used to design pediatric ATDs is derived and scaled from adults and animal
surrogates and it is uncertain whether they are accurate for the child population [4]. In addition, the
dynamic response of the pediatric shoulder, which plays an important role in the response of the
head and neck during impact, has not been researched and modeled into pediatric ATDs.
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Objectives• Perform quasi-static, noninvasive shoulder displacements on adult volunteers to define the
adult shoulder’s stiffness
• Perform quasi-static shoulder stiffness testing and dynamic, noninvasive impacts on adult post
mortem human subjects
• Perform quasi-static shoulder stiffness testing on pediatric volunteers
• Define a correlation between quasi-static and dynamic stiffnesses and find the pediatric shoulder’s
response to dynamic loading conditions
MethodsThe right shoulders of six adult volunteers were quasi-statically displaced in four directions:
medially, anteromedially, posteromedially, and inferiorly. A combination of motion testing using a
point-cluster technique to measure 6-degree-of-freedom motion of the shoulder; resistive loading
using a load cell to measure the shoulder’s resistance to quasi-static loading; and electromyography
(EMG) recordings to measure the activation of the shoulder muscles during loading was utilized.
In each subject, reflective markers were placed on the upper right arm, both acromions, the
manubrium, and the medial and lateral epicondyles of the right elbow. Surface electrodes were
applied to the latissimus dorsi, upper trapezius, anterior and posterior deltoids, biceps brachii, and
pectoralis major. The right shoulders of each subject were quasi-statically displaced using a hand-
held force applicator. A load cell attached to the applicator recorded the forces during the motion
while an 8-camera Vicon motion capture system tracked and recorded the shoulder’s motion.
During the test, electrodes measured the activity of the shoulder muscles during loading.
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Characterization of the Pediatric Shoulder’s Resistance to Lateral, Anterolateral,
Posterolateral, Inferior, and Superior Loading Conditions
Brian Suntay1, Kevin Moorhouse2, Ajit Chaudhari1, John Borstad1, John Bolte IV1
1The Ohio State University, 2National Highway Traffic Safety Administration
-0.5 0 0.5 1 1.5 2 2.5-10
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Displacement (mm)
Fo
rce
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Subject 1
Subject 2
Subject 3
Subject 5
Subject 6
-20 0 20 40 60 80-20
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Displacement (mm)
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rce
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Subject 2
Subject 3
-5 0 5 10 15 20 25-5
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Displacement (mm)
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rce
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Subject 2
Subject 3
Subject 4
Subject 5
Subject 6
-1 0 1 2 3 4 5-10
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Displacement (mm)
Fo
rce
(N
)
Subject 1
Subject 2
Subject 3
Subject 4
Subject 5
Subject 6
-5 0 5 10 15-5
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Displacement (mm)
Fo
rce
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)
Subject 1
Subject 2
Subject 3
Subject 4
Subject 5
Subject 6
Figure 1. Force applicator and guide that can
be adjusted to the four desired directions.
Figure 3. (Top) Subject 3 seated on the bench. Force applicator and guide set to the medial/lateral
direction; (Bottom Left) Close up view of subject 3 upper arm reflector cluster, acromion marker,
manubrium marker, and anterior deltoid and biceps brachii EMG electrodes; (Bottom Right) Close
up view of the posterior shoulder of subject 3.
Results and Discussion
Figure 2. Electrode placement: latissimus,
trapezius, deltoid, biceps, pectoralis.
Figure 4. Plot of force vs. deflection for the
purely medial loading condition.
Figure 5. Plot of force vs. deflection for the
inferior loading condition.
Figure 6. Plot of force vs. deflection along
the x-axis for the posteromedial loading
condition.
Figure 7. Plot of force vs. deflection along
the y-axis for the posteromedial loading
condition.
Figure 8. Plot of force vs. deflection along
the x-axis for the anteromedial loading
condition.
LAT INF PM PM AM
Y-Axis Z-Axis X-Axis Y-Axis X-Axis
Subject 1 20.58 1.616 3.519 10.33 1.769
Subject 2 26.32 1.318 2.416 9.209 2.041
Subject 3 17.41 0.9067 1.383 8.455 1.430
Subject 4 1.545 12.16 1.392
Subject 5 19.87 1.783 9.250 1.263
Subject 6 17.40 0.7784 2.834 0.9818
Table 1. Stiffnesses (N/mm) for the subjects’
shoulders calculated as the slope of the linear
fit to the force-displacement curves.
Stiffnesses were calculated for the shoulders
for each of the loading conditions.
The response of each subject’s shoulders appear to follow a similar pattern. The force-
displacement curves of the shoulders appear to be almost linear and there is little variation in
the stiffness of each subject’s shoulder, with the exception of subject 6. The inferior loading
condition data for subjects 4-6 has not yet been processed. An abnormal curve was observed in
subject 4’s lateral data and was omitted. The abnormality of the curve’s shape might be due to
an error in the tracking of the reflective markers.
ConclusionThe method for quasi-statically and noninvasively measuring the force-displacement
characteristics of the shoulder seems promising. However, more subjects need to be tested
before moving on to pediatric subjects.
References1.Brown, J. K., Jing, Y., Wang, S., & Ehrlich, P. F. (2006). Patterns of severe injury in pediatric car crash victims: Crash Injury Research
Engineering Network database. Journal Of Pediatric Surgery, 41(2), 362-367.
2.Klinich, K. D., & Burton, R. W. (1993). Injury patterns of older children in automotive accidents.
3.Neale, M. S., Hardy, B. J., & Lawrence, G. J. L. (2005). Development and evaluation of a biofidelic shoulder for the IHRA (JARI)
pedestrian model.
4.Franklyn, M., Peiris, S., Huber, C., & Yang, K. H. (2007). Pediatric material properties: a review of human child and animal surrogates.
Critical Reviews in Biomedical Engineering, 35(3-4), 197-342.