Multiplanar Cervical Spine Injury
Due to Head-Turned Rear Impact

This section is compiled by Frank M. Painter, D.C.
Send all comments or additions to:    Frankp@chiro.org

FROM:   Spine (Phila Pa 1976) 2006 (Feb 15); 31 (4): 420—429

Panjabi, Manohar M. PhD; Ivancic, Paul C. MPhil; Maak, Travis G. BS;
Tominaga, Yasuhiro MD, PhD; Rubin, Wolfgang Dipl-Ing (FH)

Biomechanics Research Laboratory,
Department of Orthopedics and Rehabilitation,
Yale University School of Medicine,
New Haven, CT 06520-8071, USA.
manohar.panjabi@yale.edu

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STUDY DESIGN:   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.

OBJECTIVES:   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.

SUMMARY OF BACKGROUND DATA:   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.

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