There has been a considerable amount of work published on predicting prognosis following whiplash injury, and the leading researcher in this field is Professor Michele Sterling, Associate Director of the Rehabilitation Sciences Program at ‘Recover Injury Research Centre’, Queensland, Australia.
Professor Sterling and her team were among the first researchers to prospectively study a cohort of whiplash injured people from the first few weeks following injury up to two years later. The individuals in their studies were comprehensively examined with batteries of questionnaires assessing their psychological state, in combination with cutting edge lab-based investigations of muscle and motor performance and assessments of sensory change (i.e hypersensitivity to mechanical or thermal stimulus).
In this way they were able to follow up those people that failed to improve at two years post injury – and who had persistent pain problems – and see what was different about them in the first few weeks following the collision. Suffice to say that the findings strongly implicate a person’s physiological and psychological stress response as a key marker in predicting poor recovery following whiplash injury.
In this the first of three blog posts on predicting and managing risk of poor recovery, I will attempt to answer the following question: ‘what should I note from the history and clinical examination that will help me in evaluating an individual’s prognosis following whiplash injury?’ So I will cover what questions we should be asking and what tests we should be performing.
In the second blog post I review the literature on psychological factors associated with poor recovery (here). The third blog post brings together current thinking around managing individuals at risk of poor recovery (here). Note that my thoughts on pathology and how it impacts prognosis in whiplash can be found here.
Prognosis: history and clinical examination
The prognostic role of pre-injury neck pain remains unclear (Carroll et al. 2008) and those reviews that have demonstrated an effect for the presence of pre-injury neck pain have described it as, ‘small but significant’ (Walton et al. 2013). The effect size for history of headache suggests no significant risk of persistent problems (Walton et al. 2013). Carroll et al. (2008) found, ‘no scientifically admissible’ studies which addressed the impact of disc degeneration on recovery from whiplash injury.
A one year prospective study demonstrated that pre-existing degeneration on magnetic resonance imaging (MRI) was not associated with prognosis (Kongsted et al. 2008).
The evidence varies on the role of age and gender as a prognostic factor for recovery following whiplash injury, however in those reviews that have identified older age and gender as prognostic for poor recovery, the effects are negligible to modest (Walton et al. 2013, Carroll et al. 2008) with the prognosis for females being slightly worse (female OR = 1.64) (Walton et al. 2013).
Having less than post-secondary education has been associated with poor prognosis (Walton et al. 2013). Additionally the relationship between compensation-related factors, symptoms and outcome is currently unclear (Spearing and Connelly 2010) due in part to what Spearing (2012) has termed ‘reverse causation bias’ i.e. the likelihood that poor health influences the decision to pursue compensation.
Crash related factors
Crash related factors include collision direction, use and type of head restraints, speed of impact, awareness of collision, position in seat and whether the person’s head was turned at the time of the accident. Whilst experimental data has suggested that having a rotated neck position at the time of impact doubles the strain through the facet capsule (Siegmund et al. 2008, Winkelstein et al. 2000) clinically orientated systematic reviews have identified few crash related factors that have predictive utility.
Carroll et al (2008) concluded there was no association between crash related factors and outcome, except for a modest effect for those injured while driving a vehicle fitted with a tow bar having a poorer prognosis. Not wearing a seat belt at the time of the collision appears to lead to a two-fold increase in the risk of developing whiplash related pain and disability at 12 month follow up (Walton et al. 2009).
Sterling makes the interesting point that this factor (‘I was not wearing my seatbelt’) is likely to be under reported in jurisdictions where compulsory seat belt use is legislated, so the risk associated with this factor may be even higher (Sterling and Kenardy 2011).
More recently Walton et al (2013) utilising rigorous inclusion criteria in a systematic review and meta-analysis concluded that parameters of the collision show no predictive ability in identifying risk of poor outcome. Variables with strong evidence of no effect include, ‘unprepared for collision,’ no head restraint in use and vehicle stationary when hit (Walton et al. 2009).
In an attempt to explain the lack of evidence, some authors have noted that crash related factors rely heavily upon the self-report of the injured individual making them highly susceptible to both recall bias and desirability bias (secondary motive influencing reports) (Walton et al. 2013).
Presenting signs and symptoms
Initial post injury pain intensity, number and severity of injury related symptoms and the presence of radicular signs or symptoms appear to be substantial predictors of recovery (Carroll et al. 2008, Walton et al. 2009, Walton et al. 2013).
Walton et al (2013) recently found a six-fold increase in risk of persistent pain or disability at follow up in those complaining of high neck pain intensity (defined as a score of five and a half out of ten on a Visual Analogue Scale or VAS).
Self-reported headache at inception is associated with a significant increase in the risk of reporting persistent problems at follow-up and reports of low back pain also demonstrate a small but significant risk for persistent problems (Walton et al. 2013).
In one cohort, 30% of acute whiplash patients presented with a neuropathic pain component, as measured by the Leeds Assessment of Neuropathic Symptoms and Signs pain scale (S-LANSS) (Sterling and Pedler 2009) a score of > 12 on this scale predicted poor recovery.
The most commonly used measure of disability in whiplash is the Neck Disability Index (NDI) (Vernon and Mior 1991). The NDI is a 10-item questionnaire that allows scoring of activities of daily living pertaining to the neck region from 0 to 5. The scores are summed to give a total of 50 or multiplied by 2 to give a percentage score.
Scores on this instrument are predictive of poor recovery: 30% or higher in one meta-analysis (Walton et al. 2013). In a more recent study designed to establish a clinical prediction rule for use following whiplash injury a score of > 40% predicted chronic moderate/severe disability with a score < 32% predicting recovery (Ritchie et al. 2013). The latter study also included age and a measure of post-traumatic stress response in the clinical prediction rule (this will be discussed in the second blog post in this series).
Dizziness appears to be a common yet overlooked symptom following whiplash injury.
In one cohort of whiplash injuries as many as 75% of subjects complained of dizziness (Treleaven et al 2003). The unsteadiness that can occur following whiplash injury is hypothesised to arise from injury and disruption to the deep muscle spindles of the cervical spine and – probably less so – the mechanoreceptors of the facet joint capsule.
One theory suggests that distortion of the afferent signals from the muscle spindles leads to a conflict of information in the dense anatomical reflex connections between the muscle spindles, the eyes (cervico-ocular reflex) and the vestibular system (vestibulo-ocular reflex) (Treleaven et al. 2008).
Indeed, there is increasing objective evidence of disturbances to smooth pursuit eye movement control, proprioception of the head and neck, and postural instability following whiplash injury (Treleaven et al 2005, 2006, Field et al 2008) however these sensorimotor signs and symptoms, including smooth pursuit eye movement tests, do not appear to be useful as predictive factors following whiplash injury (Kongsted et al. 2008).
Cervical range of motion has been found to have no significant effect on recovery (Williams et al. 2007) with a meta-analysis confirming these findings, (Walton et al. 2009) despite its apparent continued use as the sole ‘objective’ prognostic measure in whiplash injury medico-legal reporting. Interestingly ‘motor control’ factors such as altered activity in trapezius (reduced activity) and sternomastoid (increased activity) – although persisting in those with ongoing pain – also have no association with recovery (Daenen et al 2013).
Widespread sensory change has been identified in a sub-group of 20% of whiplash injured subjects (Sterling et al 2006). This manifests as reduced pressure pain thresholds (‘PPT’ the threshold at which pressure becomes pain) at areas removed from the site of injury and a heightened sensitivity to a cold stimulus, both indicative of augmented central pain processing that has also been identified in fibromyalgia.
Walton et al (2011) have demonstrated that PPT’s at a site over the anterior shin (tibialis anterior muscle) significantly predicted the variance in short term outcome in individuals with acute whiplash injury. The authors concluded that PPT’s represent a, ‘promising addition’ to the clinical assessment of traumatic neck pain.
In one systematic review cold hyperalgesia (a lowered cold pain threshold) was found to be associated with a poorer outcome (Williams et al. 2007).
Screening for risk of poor recovery in the clinic
So, here’s what you need to take note of: Table 1 (below) lists those factors – from the history and clinical examination – that appear to be predictive of poor recovery following whiplash injury.
|Post injury pain > 5.5/10
Number and severity of injury related symptoms
Presence of radicular signs and symptoms
Post injury headache
Post injury low back pain
Neck Disability Index score > 40%
Reduced pressure pain threshold at shin
Cervical spine cold hyperalgesia
Table 1: Risk factors for poor recovery following whiplash injury.
Subjective self-report aspects (eg pain levels, sites of injury etc.) are easily assessed in the clinical setting. Assessing disability levels (Neck Disability Index) and screening for neuropathic pain (S-LANSS) can involve the use of questionnaires.
If you want to get technical – in terms of assessing pressure pain thresholds – a relatively inexpensive hand held device an, ‘algometer’ that reliably quantifies tenderness by measuring the precise force required to produce the first sensation of pain can be utilised.
There has been data published in acute and sub-acute neck pain, with lower scores (0-25th quartile range from <1.5 Kg/f in the upper trapezius and <2.5Kg/f at the Tibialis Anterior site) increasing the risk of ongoing disability at 1 to 3 months (Walton et al. 2011).
Whilst local, mechanical hyperalgesia is a common finding in the majority of individuals with neck pain, increased tenderness at a location removed from the area of trauma – as stated above, the shin is commonly used in the research setting – strongly suggests the presence of widespread mechanical hyperalgesia.
Again on a more technical note, a thermoroller cooled to 15°C can be used to examine for signs of cold hyperalgesia. Recent work has suggested a simpler method that involves applying an ice pack to the posterior aspect of the cervical spine for 10 seconds (Maxwell and Sterling 2013) which, if the resulting sensation is rated as < 5/10 on the VAS, strongly suggests the presence of cold hyperalgesia. If scores are < 1/10 on the VAS, this strongly suggests the absence of cold hyperalgesia.
Take Home Massages
From the history and clinical examination alone we can propose a partial evidence based pathway for screening for poor recovery:
- Neck Disability Index Score > 40%
- Widespread hyperalgesia (Pressure Pain Threshold at shin – algometer)
- Cold hyperalgesia at the neck (Thermoroller / ice pack)
Before we finish let’s step back and look at the bigger picture: factors with strong evidence of no relationship with recovery include degenerative changes in the neck, crash related factors and range of motion. Those factors that do appear to be related to recovery include high initial pain intensity, high levels of disability, widespread hyperalgesia and a lowered cold pain threshold at the neck.
You can see that from the history and clinical examination alone there is a strong sense that factors relating to the physical mechanical insult are not associated with recovery. Let’s also remind ourselves of findings from imaging studies in acute whiplash that demonstrate insignificant pathological changes (see here for my summary).
Interestingly the critical prognostic factors following whiplash that can be identified from the history and clinical examination appear to relate to ‘sensitivity of the nervous system’. I will discuss this further when we look at the role of psychological factors in recovery.
Now, before you head on over to amazon.co.uk for an algometer and a thermoroller, why not wait until you have read the second blog post here, where I review the role of psychological factors in recovery from whiplash injury? It might just save you a few bob (i.e. dollar)!
Photo credit of lovely wizard with crystal ball: Tomasz Lusiak
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