27.12.2012 Views

ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

nearly no tension occurred for the ligamentum flavum (LF) and inter spinous ligament<br />

(ISL) since only obvious extension was observed in the lower segments under rear<br />

impact. It was obvious that the CL was the most possible to be injured under impact<br />

because the peak strain value of CL under any simulated impact condition was predicted<br />

to be higher than its failure limit ( 1 . 16 ± 0.<br />

20)<br />

reported by Yoganandan et al. [23]. In<br />

addition, the strain magnitude of ISL was also above its failure limit ( 0 . 68 ± 0.<br />

14 ) under<br />

front impact. The ligament strain data obtained from other levels showed similar results.<br />

When further investigate the effect of impact direction on the peak strain values of<br />

capsular ligament, it was found that the side and oblique impacts may cause higher<br />

capsular tension than direct impacts (Figure 5R).<br />

Rotational Angle (Deg.)<br />

80<br />

60<br />

40<br />

20<br />

0<br />

0.00 0.05 0.10 0.15 0.20<br />

-20<br />

Time (s)<br />

-40<br />

-60<br />

-80<br />

Rear<br />

Front<br />

Side<br />

Rear-Side<br />

Front-Side<br />

L<br />

Rotational Angle (Deg.)<br />

40<br />

30<br />

20<br />

10<br />

0<br />

0.00<br />

-10<br />

0.05 0.10 0.15 0.20<br />

Time (s)<br />

-20<br />

-30<br />

Side<br />

Rear-Side<br />

Front-Side<br />

M<br />

Rotational Angle (Deg.)<br />

40<br />

30<br />

20<br />

10<br />

0<br />

0.00<br />

-10<br />

0.05 0.10 0.15 0.20<br />

Time (s)<br />

-20<br />

-30<br />

Side<br />

Rear-Side<br />

Front-Side<br />

Fig.4. Predicted overall rotational angles of C0 respect to C7 under various impact<br />

conditions. (L) Sagittal plane; (M) Frontal plane; (R) Transverse plane.<br />

L<br />

R<br />

Fig.5. (L) Predicted peak ligament strains in C6-C7 segment and (R) peak capsular<br />

ligament strains under simulated five impact directions<br />

DISCUSSION<br />

Strain<br />

2<br />

1.5<br />

1<br />

0.5<br />

0<br />

Rear<br />

Front<br />

Side<br />

Rear-side<br />

Front-side<br />

CL ALL PLL ISL LF<br />

A detailed 3-D C0-T1 FE model was developed and used to characterize the<br />

biomechanical response of the cervical spine in various simulated impact vectors.<br />

Under the low-speed rear impact condition, the predicted rotations of each motion<br />

segment during the first 150ms after impact were compared with the experimental<br />

corridors obtained by Stemper et al. [14], the basic variations of intervertebral rotational<br />

angle and head motions were in similar trends and consistent with experimental<br />

observations. Further validations were conducted by comparing the predicted peak<br />

segmental rotational angles against the mean value from experimental studies under<br />

both rear-end and side impacts [27,28].<br />

To simulate rear impact condition, some assumptions in current study may make the<br />

results different from those obtained under actual impact conditions. Firstly, only the<br />

horizontal acceleration acting on T1 vertebra bottom was considered. In real car impact<br />

condition, interaction of the occupant with the seatback may result in secondary thoracic<br />

motions include superiorly directed acceleration and extension rotation of the upper<br />

Strain<br />

2.5<br />

2<br />

1.5<br />

1<br />

0.5<br />

0<br />

Rear<br />

Frontal<br />

side<br />

Rear-Side<br />

Front-Side<br />

C23 C34 C45 C56 C67<br />

R

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!