Head, neck, and mandible dynamics generated by 'whiplash'

Area of Science:

• Biomechanics
• Orthopedics
• Traumatology

Background:

• The link between low-velocity rear-end collisions and temporomandibular joint (TMJ) injuries has been hypothesized for over 50 years.
• Previous research proposed various injury mechanisms for the TMJ during whiplash maneuvers.
• Forces at the TMJ during an 8.0 km/h impact velocity change are considered within typical physiologic ranges.

Purpose of the Study:

• To apply current head/neck dynamic data to model forces experienced at the TMJ during rear-end collisions.
• To investigate the relationship between impact velocity changes and forces generated at the TMJ.
• To assess the potential for TMJ injury and neck movement abnormalities in low-velocity impacts.

Main Methods:

• Conducted 14 motor vehicle test collisions involving 7 live subjects at impact velocities ranging from 3.9 to 10.9 km/h.
• Utilized linear and angular accelerometers and high-speed cameras to record vehicle and subject responses.
• Measured head accelerations, TMJ forces, and mandibular opening responses; monitored for neck hyperflexion/hyperextension.

Main Results:

• Head accelerations and TMJ forces showed a generally linear relationship with impact velocity changes.
• No instances of neck hyperflexion or hyperextension were observed in any subject.
• All subjects experienced transient neck muscle strain (1-3 days); no TMJ symptoms were reported.

Conclusions:

• Head, neck, and mandible motions in whiplash are more complex than previously understood.
• The cervical muscle injury threshold appears to be reached around 8.0 km/h.
• Low-velocity rear-end impacts (<11.0 km/h) do not seem to cause injurious forces at the TMJ.