Is whiplash really a simple muscular injury.
Cervical spine discomfort is a very common complaint following road traffic accidents. Despite the frequency, there is considerable disagreement as to the
exact nature of the injury and consequentially the expected duration of the disability.
Consistent with known biological models injury to bone, joint (discs, facet joints), nerve and the soft tissues of the cervical spine (ligaments, tendons, muscle) are the most likely sources of dysfunction and pain. If the injury pattern was constant, the duration of disability should be predictable but in contrast the literature proposes recovery may occur in two weeks or exceed two years in 19-60% of cases. If the
disability is genuine and the claimant is not misleading the expert, it is probable that not all cervical acceleration deceleration (CAD) injuries are muscular in origin as recovery in such cases would be evident within 3-6 months.
Motion of the neck during the course of the classic rear-impact collision is not (as
previously proposed) a simple exaggeration of the normal flexion or extension. The two injury phases during whiplash are the initial hyperextension at C5-6 and C6-7 with mild flexion at C0-4 followed by the second phase of hyperextension of the entire cervical spine. This non-physiological S-shaped motion subjects the cervical discs, facet joints, paravertebral ligaments and muscle to axial loading, compression,
distraction and shear generating the potential of different injury patterns and consequentially differences in recovery.
Chronic pain associated with cervical strains is most likely to relate to zygapophyseal (facet) joints, intervertebral discs, and upper cervical ligaments. Facet capsular ligaments contain free (nociceptive) nerve endings, and distending these ligaments
by administering facet joint injections have produced whiplash-like pain patterns in
healthy individuals. The C2-3 facet joint is the most common source of referred pain in patients with a dominant complaint of headache. The C5-6 region is the most common source of cervical, axial, and referred arm pain.
A roller coaster ride study of 656 neck and back injuries failed to establish a minimum threshold for spinal injury and concluded that there is individual
susceptibility to injury, which cannot be calculated. This highlights the complexity
of determining prognosis: variables showing significance in one study may be dismissed by other authors.
In general, variables influencing outcome may be allocated to patient/claimant related and accident details. Rear impact collision, seatbelt restraint and lack of impending collision are associated with poor prognosis. A head-turned impact is proposed to generate a dynamic cervical intervertebral narrowing with potential
ganglion compression even in patients with a nonstenotic foramen at C5-6 and C6-7. In patients with stenotic foramen, the risk greatly increases to include C3-4 through C6-7.
In studies, females were more likely to be injured, suggesting genetic, hormonal, structural, or tolerance differences from males. Pre-accident symptoms, degenerative change, early onset of disability with loss of motion or neurological impairment are also associated with poor prognosis.
There is however not sufficient space in this article to discuss all the variables.
CAD injuries are not uniformly muscular injuries and the combination of claimant
and accident variables and the potential of financial gain can make determining duration of disability difficult. As there are no randomised prospective studies to provide a simple solution each individual with disability exceeding the expected
period of recovery needs a thoughtful assessment.
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