Multiplanar cervical spine injury due to head-turned rear impact.
METHODS
Head-turned whole cervical spine model was stabilized with muscle force replication and subjected to simulated rear impacts of increasing severity. Multiplanar flexibility testing evaluated any resulting injury.


OBJECTIVE
To identify and quantify cervical spine soft tissue injury and injury threshold acceleration for head-turned rear impact, and to compare these data with previously published head-forward rear and frontal impact results.


BACKGROUND
Epidemiologically and clinically, head-turned rear impact is associated with increased injury severity and symptom duration, as compared to forward facing. To our knowledge, no biomechanical data exist to explain this finding.


METHODS
Six human cervical spine specimens (C0-T1) with head-turned and muscle force replication were rear impacted at 3.5, 5, 6.5, and 8 g, and flexibility tests were performed before and after each impact. Soft tissue injury was defined as a significant increase (P < 0.05) in intervertebral flexibility above baseline. Injury threshold was the lowest T1 horizontal peak acceleration that caused the injury.


RESULTS
The injury threshold acceleration was 5 g with injury occurring in extension or axial rotation at C3-C4 through C7-T1, excluding C6-C7. Following 8 g, 3-plane injury occurred in extension and axial rotation at C5-C6, while 2-plane injury occurred at C7-T1.


CONCLUSIONS
Head-turned rear impact caused significantly greater injury at C0-C1 and C5-C6, as compared to head-forward rear and frontal impacts, and resulted in multiplanar injuries at C5-C6 and C7-T1.
Biomechanics Research Laboratory, Department of Orthopedics and Rehabilitation, Yale University School of Medicine, New Haven, CT 06520-8071, USA. manohar.panjabi@yale.edu
Manohar M
MM
Panjabi
Paul C
PC
Ivancic
Travis G
TG
Maak
Yasuhiro
Y
Tominaga
Wolfgang
W
Rubin
D000063:Accidents, Traffic; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002574:Cervical Vertebrae / Q000293:injuries* / Q000503:physiopathology; D005260:Female; D019416:Head Movements; D006801:Humans; D008297:Male; D008954:Models, Biological; D016059:Range of Motion, Articular; D017695:Soft Tissue Injuries / Q000209:etiology / Q000503:physiopathology; D013124:Spinal Injuries / Q000209:etiology* / Q000503:physiopathology