Cervical spine loads and intervertebral motions during whiplash.
OBJECTIVE
To quantify the dynamic loads and intervertebral motions throughout the cervical spine during simulated rear impacts.


METHODS
Using a biofidelic whole cervical spine model with muscle force replication and surrogate head and bench-top mini-sled, impacts were simulated at 3.5, 5, 6.5, and 8 g horizontal accelerations of the T1 vertebra. Inverse dynamics was used to calculate the dynamic cervical spine loads at the centers of mass of the head and vertebrae (C1-T1). The average peak loads and intervertebral motions were statistically compared (P < 0.05) throughout the cervical spine.


RESULTS
Load and motion peaks generally increased with increasing impact acceleration. The average extension moment peaks at the lower cervical spine, reaching 40.7 Nm at C7-T1, significantly exceeded the moment peaks at the upper and middle cervical spine. The highest average axial tension peak of 276.9 N was observed at the head, significantly greater than at C4 through T1. The average axial compression peaks, reaching 223.2 N at C5, were significantly greater at C4 through T1, as compared to head-C1. The highest average posterior shear force peak of 269.5 N was observed at T1.


CONCLUSIONS
During whiplash, the cervical spine is subjected to not only bending moments, but also axial and shear forces. These combined loads caused both intervertebral rotations and translations.
Ivancic
Paul C
PC
Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, New Haven, Connecticut 06520-8071, USA. paul.ivancic@yale.edu
Panjabi
Manohar M
MM
Ito
Shigeki
S
D000054:Acceleration; D000063:Accidents, Traffic; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002102:Cadaver; D002574:Cervical Vertebrae / Q000293:injuries*; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000293:injuries*; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular; D012399:Rotation; D014911:Whiplash Injuries / Q000503:physiopathology*