Risk Factors for Injury

The following article was published by the spine research Institute of San Diego.  The Author, Arthur C. Croft, DC, MS, mph, Faco, FACFE is a renowned researcher on the effects of whiplash disorders.

by Arthur C. Croft, DC, MS, MPH, FACO, FACFE

Director – Spine Research Institute of San Diego

Repeated research studies have shown that, in healthy males who are prepared for the collision, without any of the following risk factors present, the lower limit for cervical spine soft tissue injury is a delta-V at or below 5mph.  Recent findings indicate that this lower limit could be as low as 2.5 mph.

 Risk for Acute Injury

  1. Alcohol intoxication.
  2. Low body mass index/head neck index (i.e. decreased risk with increasing mass and neck size)
  3. Crash speed under 10mph.
  4. Female gender.
  5. Having the head turned at impact.
  6. History of neck injury.
  7. Impact by vehicle of greater mass (i.e. >25% greater).
  8. Inclined head position.
  9. Increasing age (i.e. middle age and beyond).
  • Non-awareness of impending impact.
  • Non-failure of seat back.
  • Occupant in a minicar or subcompact.
  • Out of position occupant (e.g., leaning forward/slumped)
  • Poor head restraint geometry/tall occupant (e.g. > 80th percentile male).
  • Rear impact (vs. other impact vectors).
  • Use of seat belt shoulder harness (i.e., standard three-point restraints).


Risk for Late Whiplash Syndrome

Victims with the following characteristics have a higher risk of developing Late Whiplash Syndrome:

  1. A loss of, or reversal of the cervical lordosis (curve).
  2. Low body mass index in females only.
  3. Canal stenosis.
  4. Cigarette smoking.
  5. Clinically significant nutritional or endocrine disorders, e.g. diabetes.
  6. Continued alcohol consumption.
  7. Early onset of numbness.
  8. Emotional stress caused by persistent symptoms.
  9. Female gender.
  10. Front seat position.
  11. Greater number of initial symptoms.
  12. Greater subjective cognitive impairment.
  13. Headrest distance greater than 10 cm.
  14. Immediate/early onset of symptoms (i.e., within 12 hours) and/or severe initial symptoms.
  15. Increasing age (i.e., middle age and beyond).
  16. Initial back pain.
  17. Initial degenerative changes seen on radiographs.
  18. Initial neurological symptoms.
  19. Initial physical findings of limited range of motion.
  20. Ligamentous instability.
  21. Mass ratios, with smaller vehicles being worse.
  22. Multiple injuries.
  23. Need to resume physical therapy more than once.
  24. Non-awareness of impending impact.
  25. Out of position occupant (e.g., leaning forward/slumped).
  26. Past history of neck pain or headache.
  27. Persistence of symptoms beyond 3 months.
  28. Previous whiplash injury.
  29. Prolonged use of cervical collar.
  30. Rear impact (vs. other impact vectors).
  31. Sharp reversal of cervical curve.
  32. Time off work.
  33. Use of seat belt/shoulder harness – for neck (not back) pain.(non-use has a protective effect.)


 Comparison of Occupants Who Reports Symptoms Following Rear-End Crashes


Men (about 50% fewer claims).
Aware of impending impact and has time to brace self (primarily muscle injury).
High or fixed back seats.
Seatback breaks (less neck-axial, more low back pain).
Sitting with head positioned straight ahead.
Now wearing seat belt (i.e. 3-point restraint).
Young occupant.
Shorter occupant.
Occupant in larger vehicle or collision in which there are similar mass ratios for vehicles.
Properly positioned occupants to seat/restraint.
Rear-seated occupants (rigid seatbacks).
Spine joints and soft tissues in good health.



Women (neck longer and has smaller diameter).
Unaware of impending impact with no time to brace self (involves ligaments and disc).
Low, absent, or adjustable head restraint.
Seat does not break.
Head rotated at time of impact.
Wearing seat belt (neck and back injuries).
Elderly occupant.
Taller occupant.
Occupant in smaller vehicle or collision in which mass rations differ significantly.
Abnormally positioned occupant.
Front-seated passenger (elastic seatback).
Pre-existing degenerative joint disease or significant fibromyalgia).