SAE 1999-13-0010 Relationship between Localized Spine Deation and Cervical Vertebral Motions for Low Speed Rear Impacts Usin.docx

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1、.1999-13-0010Relationship between Localized Spine Deformation andCervical Vertebral Motionsfor Low Speed Rear Impacts Using Human VolunteersKoshiro Ono*, Satoshi Inami*, Koji Kaneoka*, Tukasa Gotou* Yoshikatu Kisanuki*, Shigeru Sakuma*, and Kazuo Miki* *Japan Automobile Research Institute, *Universi

2、ty of Tsukuba*Tokyo Kosei-Nekin Hospital, *Toyota Central R&D Labs., Inc.ABSTRACTIt is important to more clearly identify the relationship among the ramping- up motion, straightening of the whole spine, and cervical vertebrae motion in order to clarify minor neck injury mechanism. The aim of the cur

3、rent study is to verify the influence of the change of the spine configuration on human cervical vertebral motion and on head/neck/torso kinematics under low speed rear-end impacts. Seven healthy human volunteers participated in the experiment under the supervision of an ethics committee. Each subje

4、ct sat on a seat mounted on a sled that glided backward on rails and simulated actual car impact acceleration. Impact speeds (4, 6, and 8 km/h), and seat stiffness (rigid and soft) without headrest were selected. During the experiment, the change of the spine configuration (measured by a newly devel

5、oped spine deformation sensor with 33 paired set strain gauges and placed on the skin) and the interface load-pressure distribution was recorded. This was measured by means of a Tekscan system at a rate of 100 f/s, placed between the seat and subject. The cervical vertebrae motion was also recorded

6、by 90 f/s cineradiography. Furthermore, analysis was made to quantify the relationship between the cervical vertebrae motion and the change of the spine configuration.The localized straightening of the lumbar spine starts at around 30 ms with the rigid seat. The localized straightening of the thorac

7、ic spine reaches the maximum at around 80 ms when the load-pressure distribution is at its peak value due to the interaction between the shoulder and the seatback. On the other hand, for the softer seat, the pelvis starts to sink into the seat back and cushion at around 70 ms. As for such seat the l

8、oad-pressure is distributed over a large area, the localized straigthening of the middle thoracic spine occurred together with deflection of seatback itself at around 120 ms. The results of this study can help clarify the relationship between the localized straightening of the spine and cervical ver

9、tebrae motion with respect to the difference in seat characteristics.149THE HYPEREXTENSION OF NECK was pointed out as a major factor to cause neck injuries (including whiplash) sometime ago. The authors (Ono et al. 1993, 1997-1, 1997-2, 1998, Kaneoka et al. 1998), however, identified anotherIRCOBI C

10、onference - Sitges (Spain), September 1999interface load-pressure distribution shows that region between thoracic vertebrae T11 and T12 acts as the pivot for the interaction between the subjects back and the seatback, and that lumbar vertebrae beneath the pivot travel backward together with the pelv

11、is due to the femoral inertia caused by the impact, resulting in flexions of lumbar vertebrae (L1-L3). On the other hand, the thoracic vertebrae (T1-T5) flex on the pivotal region between T6 and T8, resulting in the backward travel of(.号)soobueMuo 一急OH158IRCOBI Conference _ Sitges (Spain), September

12、 1999Time (ms)Figure 19. Time-histories of interface pressure distribution divided into 6 blocks of sheet mat (The initial load is set to zero and curves are shown separately. Rigid seat; 8 km/h)159upper torso. Around 60 ms after impact, the upper torso vertebrae-T1 in particular -extend and rotate

13、on the pivotal region between the thoracic spines T6-T10, as the region around the shoulder blades interacts intensely with the seatback, resulting in the push-up motion and extension against the cervical vertebral lower region (C7-C6). In terms of changes in relative rotation angles of individual s

14、pine vertebrae, the rotation angles become larger for lumbar vertebrae (L4- L1) and thoracic spines (T2-T6, T10-T12). It can be said from the foregoing results that the rotation of the first thoracic spine (T1) is the direct reflection of the rotation of thoracic spine upper region (T5-T6).For stand

15、ard seat, Figure 20 shows the change in rotation angle of each vertebral segment. Figure 21 shows the spine extension derived from the changeof linear distance between the neck-torso joint and the iliac crest. Figure 22 shows the calculated rotation angles which correspond to the measured rotation a

16、ngles of individual sacra, lumbar and thoracic spines that occurred on the standard seat. Figure 23 shows the angle of sacra, lumbar and thoracic vertebral segments relative to lower segment. Figure 24 shows the time-histories of each divided block of interface pressure distribution.In comparison wi

17、th the rigid seat, the standard seat reveals that the lower lumbar spines (S1 to L5) and the upper thoracic spines (T1-T4) extend around 40 ms, while the upper lumbar spines (L1-L4) and the lower thoracic spines (T8-T12) flex slightly. The lower lumbar spines (S1 to L5) extend as the hips and the th

18、ighs sink into the seatback and seat cushion due to inertia, and rotate around thepivotal region of the lower lumbar spines (L4) at around 70 ms. The upper thoracic spines (T1-T5) rotate and extend backward with a region around the shoulder blades acting as the pivot. The upper lumbar spines (L1-L4)

19、 and the lower thoracic spines (T8-T12) flex slightly with a region around T7 acting as the pivot. In terms of changes in relative rotation angles of individual spine vertebrae, some motions are found in the regions of lumbar spines (L5-L2) and thoracic spines (T4-T6, T7- T8). It can be said that th

20、e rotation of T1 is the direct significant reflection of rotations of lower spinal vertebrae such as the middle thoracic and lumbar spinal vertebrae.IRCOBI Conference - Sitges (Spain), September 1999DISCUSSIONFLEXIBILITY OF SPINAL VERTEBRAE AND ACCURACY - According to the spinal deformations and sea

21、tback interface load-pressure distributions(.MSP) Sague -Buonsox160IRCOBI Conference Sitges (Spain), September 1999Time (ms)Figure 24. Time-histories of interface pressure distribution divided into 6 blocks of sheet mat (The initial load is set to zero and curves are shown separately. Standard seat;

22、 8 km/h)Panjabi (1990). These data and those obtained in this study (Figures 18 and 23) are compared in the following. In case of rigid seat, the following were found: L3-L4: 7 degrees (flexion: F); T12-L1: 12 deg. (extension: E); T5-T6: 8 deg. (E), showing that the rotation angles of upper lumbar s

23、pines are large but within the normal physiological range, while those of thoracic spines (T4- T5 and T5-T6) are twice larger than the normal physiological values. In case of standard seat, on the other hand, the following were found: L2-L3: 8 degrees (E); L3-L4:11 deg. (F); L4-L5: 9 deg. (F);Inters

24、paceCombined Fkxion/Extension (4/- y-axis rotation)Limits of Ranges (degrees)Representative Angle (degrees)Thoracic SpineT1-T2T2-T5势4,44官笔秀4一E 二为.4愣曾M5付出6总r枚tio3-S6TTOTO4149TTPTil不勿“T2* T12-L16-2012Lumbar SpineL1-L2316口8-iS14L工L46-i715L4-13*期16L5-S110-2417Table 4. Limits and Representative Values of

25、 Ranges of Rotationmeasured on each subjects skin, it is found that the relative rotational angles of individual spinal vertebrae in rear impact are large not only for lumbar spines but also for lower and upper thoracic spines (T2-T6, T10-T12), though they may vary according to the seat stiffness. N

26、o studies were available in the past regarding dynamic measurements of spinal deformation and rotation angles of individual spinal vertebrae of volunteers. In this study, the flexibility (range of motion) in rotation angles of spinal vertebrae was compared with the flexibility in static state report

27、ed by Lumsden et al. (1968), White and Panjabi (1990), and the dynamic flexibility was also studied according to the data measured and analyzed in this study. The accuracy of measured and analyzed data on the rotation angles of individual spinalvertebrae according to measurements ofspinal deformatio

28、ns was also clarified. It was done by installing the tape sensors onto each subject and conducting X-ray under both standing and sitting positions of the subject. Then each spinal vertebral location defined by the tape sensor andthe motion of each spinal vertebra at the sitting and standing position

29、s were compared, and the error was approximately +/- 5 %. However, cineradiography in dynamic conditions could not be done, which calls for further studies.Table 4 shows an extract of combined flexion/extension data of thoracic andlumbar spines shown in a paper presented by Lumsden et al. (1968), Wh

30、ite and161IRCOBI Conference - Sitges (Spain), September 1999T4-T5: 9 deg. (E), showing that the rotation angles of lower lumbar vertebrae are also large but within the normal physiological range, while those of thoracic spines (T4-T5) are twice larger than the normal physiological values. It can be

31、deduced from the foregoing data that the upper thoracic spines moved beyond the physiological range, with its influence transmitted to the lower cervical vertebrae.INFLUENCES OF SPINAL MOTIONS ON CERVICAL VERTEBRAL MOTIONS -The authors have suggested in an earlier study (Ono et al. 1993, 1997-1,1997

32、-2,1998, Kaneoka et al. 1998) that cervical vertebrae would exceed the normal physiological range in rear impact, showing abnormal motion with the upward travel of rotational axis, and that the straightening of spinal vertebrae and the torso ramping-up motion would influence markedly.Assuming that t

33、he spinal vertebrae are one flexible rod, the occupants back -seatback interface load-pressure increases at some local regions upon contact. Shen, et al. (1998) also reported the localized force of seatback. The seatback constitutes the acting point of the force against the occupants back, which is

34、characterized by the concentration of the force mainly on the upper torso and the lumbar, though it may differ according to the seat stiffness. Shen, et al. (1998) analyzed the force, focusing mainly on the function of localized loading point but have not analyzed how the difference in loading point

35、 influences the occupants head and neck. Furthermore, biomechanical experimental data regarding rear impact are not available, as pointed out by Kroonenberg, et al. (1997), and the validation of data is lagging.The lumbar spinal motions are as follows. First, thighs travel backward with inertia duri

36、ng impact, then the pelvis (around S1-L5) interacts with the seatback, and the thigh motion turns into rotation against the pelvis. As a result, lumbar spines flex or extend. It may be said that the question of whether flexion or extension occurs depends on whether or not the pelvis sinks into the s

37、eat cushion - in other words, it depends on the seat cushion property.Motions of the lower thoracic spines consist of the backward travel of the torso (T6-T8) with inertia, and the interaction between the torso and seatback resulting in the flexion or extension of the lower thoracic spines (T10-T12)

38、.Motions of the upper thoracic spines are as follows. The head, neck and torso travel backward first with inertia by impact, then the shoulders including arms travel backward as the torso gets in contact with the seatback, followed by the backward extension of the head with inertia, resulting in the

39、 extension of the upper thoracic spines as the upper torso arches upward. At the same time, spinal vertebrae also extend. The pivotal region for the seatback force at this moment is nearT6-T10.162It may be said that the foregoing results represent the mechanism of spinal straightening. That is, it c

40、an be deduced that the neck is pushed up due to the straightening of spinal vertebrae (lumbar and thoracic spines), and the motions of lower cervical vertebrae are transmitted to the upper cervical vertebrae, which may result in the impingement of synovial fold due to the upward travel of the instan

41、taneous axis of rotation of the cervical vertebra.IRCOBI Conference Sitges (Spain), September 1999Therefore, for the evaluation of seat properties aiming at the reduction of such neck injuries, it would be indispensable to develop proper anthropometric dummies and models with the human spine charact

42、eristics incorporated accordingly.CONCLUSIONIn this study, spinal deformations of volunteers and seatback interface loadpressure distributions have been measured for the first time, in addition to the low speed rear impact experiments conducted on volunteers by means of cineradiography. The aim of t

43、his study was to verify the influences of seatbacktorso interaction and the spine straightening on human cervical vertebral motions as described below.1) In case of the rigid seat, the localized straightening of lumbar spines started around 30 ms after impact, and the localized straightening of thor

44、acic spines occurred around 80 ms where the interaction between the seatback and the subjects shoulders became maximum.2) With the standard seat, the pelvis started to sink around 70 ms, resulting in the localized straightening of the thoracic spine around 120 ms where the interaction between the se

45、atback and the subjects shoulders became maximum.3) For rigid seat, the rotation angles of the thoracic spines (T4-T5 and T5-T6) became about twice larger than the physiological range, although the rotation angles of the lower lumbar spines were roughly within the normal physiological range.4) For s

46、tandard seat, the rotation angles of the thoracic spines (T4-T5) exceeded the physiological range by two-folds, as in the case of rigid seat, although the rotation angles of the lower lumbar spines were roughly within the normal physiological range.5) It can be deduced that such localized deformatio

47、ns of spines are likely to occur not only in the lumbar spines but also in the thoracic spines.The influences of seat stiffness on the localized spinal deformations are deduced as follows.6) The question whether the lumbar spines flex or extend depends on how the pelvis and the thigh sink into the s

48、eat cushion - namely, it depends on the seat stiffness.7) The localized extension of upper thoracic spines is caused by the backward travel of the shoulders including arms, as the torso interacts with the seatback by inertia, and the upper torso arches upward. In other words, it is important to cont

49、rol the upper torso motion properly.It can be said according to the foregoing findings that it is vital to incorporate proper parameters - components ofT1 translation and rotation which are necessary inputs related with the spinal straightening - in the analysis of cervical vertebrae.163IRCOBI Confe

50、rence - Sitges (Spain), September 1999REFERENCESDavidsson J., Ono K., Lovsund P., and Svensson M. : A Comparison between Volunteer and BioRID P3 Performance in Rear-End Sled Collisions Impacts, Proc, of IRCOBI Conference, in Press, 1999Ishiyama S., Tsukada K., Nishigaki H., Ikeda Y., and Sakuma S.:

51、Development of an Abdominal Deformation Measuring System for Hybrid III Dummy, 38th Stapp Car Crash Conferenceproceedings, SAE No. 942223, pp. 265-279, 1994Kahane C. J.: An Evaluation of Head Restraints; Federal Motor Vehicle Safety Standard 202. NHTSA Technical Report DOT HS-806-108, February 1982

52、Kaneoka K. and Ono K.: Human Volunteer Studies on Whiplash Injury Mechanisms, Frontiers in Head and Neck Trauma: Clinical and Biomechanical, Publisher JOS Press, Harvard, MA, 1998, pp. 313-325Kroonenberg A., Thunnissen J., and Wismans J.: A Human Model for Low-severity Rear-Impacts, Proc, of IRCOBI

53、Conference, Hannover, Germany, 1997, pp. 117-132Lumsden R. M., and Morris J. M. : An In Vivo Study of Axial Rotation and Immobilization at the Lumbosacral Joint. J. Bone Joint Surg., 50 A:1591, 1968Nygren A.: Injuries to Car Occupants. Some Aspects of Interior Safety of Cars - A Study of 5 years Mat

54、erial from an Insurance Company, Acta Otolaryngol Suppl (Stockholm) 1984 : (Suppl 395)Ono K. and Kanno M.: Influences of the Physical Parameters on the Risk to Neck Injuries in Low Impact Speed Rear-end Collisions, Proceedings of the International IRCOBI Conference on the Biomechanics of Impact. Ein

55、dhoven, 1993: pp. 201-212.Ono K, and Kaneoka K.: Motion Analysis of Human Cervical Vertebrae during Low Speed Rear Impacts By the Simulated Sled, Proc, of IRCOBI Conference, Hannover, Germany, 1997, pp. 223-237Ono K., Kaneoka K., Wittek A., and Kajzer J.: Cervical Injury Mechanism Based on the Analy

56、sis of Human Cervical Vertebral Motion and Hed-Neck-Torso Kinematics During Low Speed Rear Impacts, Proc, of 41st Stapp Car Crash Conference SAE P-315, Paper No. 973340, Florida, Nov. 13-14,1997, pp. 339-356Ono K., Kaneoka K., and Inami S.: Influence of Seat Properties on Human Cervical Vertebral Mo

57、tion and Head/Neck/Torso Kinematics During Rear-end Impacts, Proc, of IRCOBI Conference, Gothenberg, Sweden, 1998, pp. 303-318Shen W., Wiklund K., Frid S., Swamy B., Nilson G., and Humer M.: Pressure and Load Patterns on Seat Interface: A Comparison between Human Subjects and Crash Test Dummies, Pro

58、c, of IRCOBI Conference, Gothenberg, Sweden, 1998, pp. 453-464WHO/CIOMS Proposed Guidelines for Medical Research Involving Human Subjects, and the Guidelines on the Practice of Ethics Committees Published by the Royal College of Physicians, The Lancet, November 12, 1988, pp. 1128-1131White III A. an

59、d Panjabi M.: Clinical Biomechanics of the Spine, Second Edition, Publisher: J. B. Lippincott Company, 1990. pp. 86-120164IRCOBI Conference _ Siiges (Spain), September 1999factors that may lead to the neck injuries even if the hyperextension does not take place. Although the mechanism of the so-call

60、ed whiplash has not been completely identified, phenomena observed in impact are well recognized. They can be divided into the following (Figure 1).1) Initial Impact Response Phase: Neck is pushed up due to torso ramping-up motion and spine straightening. The occupants spine, normally curved, starts

61、 to be pushed against the seatback, and the torso ramps up and pushes the neck upward at the same time.2) Middle Phase - Head rapid backward motion (S-shape deformation): The head inclines rapidly backward relative to the torso, resulting in a significant retraction between the head and neck.3) Fina

62、l Phase - Head backward inclination: The neck rotates as the head inclines markedly relative to the torso.The headrest installation was made obligatory, and the use of headrest is common because of the recognition that it is a crucial mean to reduce neck injuries in the final phase of impact. Severa

63、l reports (Kahane 1992, Nygren 1984) have shown that the so-called whiplash injuries caused by the hyperextension of neck have been reduced significantly by the above. However, the question of how the occupants motions in the initial impact phase - spine straightening in particular - influence the o

64、ccurrence of neck injury have not been answered yet.In this regard, spinal deformation and seatback load-pressure measurements have been conducted in this study. This is in addition to the low speed rear impact tests conducted on volunteers by means of cineradiography done in the past. Spinal deform

65、ation and seatback load-pressure measurements were done with the following goals:1) to determine influences of seatback and the seat stiffness on human head/ neck/torso kinematics and on the change of spinal cofiguration.2) To determine the influence of spine strightening on the cervical vertebrae motion.METHODS OF EXPERIMENTSThe test apparatus, measurement method, etc. are the same as those described in the paper presented by the authors (Ono