Alicia Filley examines the role of biomechanics in medial tibial stress syndrome. Medial tibial stress syndrome (MTSS – commonly known as shin splints) is not medically serious, yet can suddenly side-line an otherwise healthy athlete. Roughly five percent of all athletic injuries are diagnosed as MTSS(1). The incidence increases in specific populations, accounting for 13-20% of... MORE
Neck assessment and screening
Kay Robinson looks at the mechanics of neck injury and assessment techniques for the clinician
Nearly half the population will experience neck pain at some point during their lives, and with sport accounting for around 10% of all neck injuries1, the cervical spine is an area that warrants more focused attention than it currently gets. The prevalence of neck injuries in sport is thought to be rising, and this is unquestionably partly due to improvements in injury reporting and monitoring. However the increase in the physicality of sport and the growth of ‘extreme sports’ are leaving untrained necks at greater risk of injury.
Working in the sport of skeleton (where athletes sprint on ice and then hurtle head first down the icy, often bumpy track at speeds in excess of 130kph) opened my eyes into the importance of neck training. Neck injuries are common in skeleton, and so an obvious motivation is to prevent this. However, neck training isn’t just about injury-risk mitigation; in a sport where the gold medal can be decided by a single hundredth of a second, training aimed at strengthening the neck so that it can keep the athlete’s chin off the ice, can be the difference between the standing on the podium or applauding from the stands.
In order to reduce the risk of injury, the neck needs to be specifically and strategically trained to ensure its tolerance is greater than the loads that it is exposed to. However, prior to this training program being implemented, it is necessary to accurately evaluate the cervical spine in a comprehensive assessment and screening process. It is this that will be the focus of the first article of this two-part series on neck injury and the cervical spine.
Figure 1: Cervical musculature
How do necks get injured?
Neck injuries are unsurprisingly most common in motorsports, as well as high impact, collision sports such as rugby. The reasons for this injury profile include:
- Acute force exposure through axial loading (compression and distraction)
- Direct blows
- Sudden acceleration/deceleration
Let’s look at the first mechanism. Compression, or axial loading, is the primary mechanism of neck injuries in sport, and most commonly occurs when load is applied, and the neck’s natural lordosis is lost – usually due to excess flexion causing energy dispersal to be compromised2. Acutely, the increased loading can cause severe cervical spine trauma, but chronic exposure can also have a cumulative effect. Situations where this can arise include collapsed scrums in rugby, falls from heights and mistimed manoeuvers in combat sports.
Another neck injury that can arise from axial forces are ‘stingers’ or ‘burners’, which are the frequent result of brachial plexopathy injury or irritation. These can be either compressive or distractive in nature and are most common in tackling sports, or as a result of a fall from a height where the neck is laterally flexed and the shoulder girdle depressed.
Stingers are a result of a downward traction force on the shoulder girdle while the neck is contra-laterally flexed, or the result of compressive forces that close down the ipsilateral posterior elements of the vertebra. Symptoms are often consistent with a ‘dead arm’ and include temporary altered sensation and weakness due to the irritation of the nerve roots – most commonly of the 7th cervical level3. Clinicians need to have a high index of suspicion of spinal cord injury following any compression or distraction injury, and this serious consequence and needs to be cleared by a thorough on-field assessment prior to the athlete being moved.
‘Whiplash Associated Disorders’ (WAD) are commonly seen in the general population. However, they can frequently occur in sports involving sudden acceleration and deceleration, and can also occur following a blow to the trunk or head4. A combination of neck pain, headaches, temporal mandibular dysfunction and referred pain/ neurological symptoms are the result of the forces transferred to the neck causing sudden, uncontrolled movement, which results in damage to the anterior and posterior structure of the cervical spine.
The cervical spine is not just prone to acute injuries however. Chronic force exposure from maintained static positions (such as in sports like archery) or repetitive exposure to gravitational (G) or vibration forces are often implicated in the development of overuse symptoms. As with any area of the body, athletes that are unable to attenuate the forces they are exposed to through their neck will be at a greater risk of injury or dysfunction.
The side effects of chronic G-force exposure include dizziness, disorientation, altered vision, reduced co-ordination, as well as neck pain5. Any of these side effects can not only reduce performance, but also put athletes and opponents at risk, particularly when travelling at high speeds!
Much of the research in this area has been carried out by military air forces, monitoring the effect of G-force on fighter pilots. The symptoms are thought to arise due to a combination of reduced blood flow to the head, visual disturbances and high loads placed on the musculature of the neck6.
G force should also be considered in contact sports, where collisions between players may expose athletes to forces equivalent of those experienced in a car collision7. Long term exposure to G-force is suggested to leave athletes at increased risk of vertebral disc degeneration, therefore exposure should be monitored closely8. This is already commonplace in the world of cccupational health and safety, where machinery operators have limitations on time exposed to vibrational forces to minimise long-term damage.
Assessing the neck
In all sporting environments, basic neck range and strength should be assessed to provide baselines, and to aid return to sport planning – exactly as we would use following any other peripheral joint injury.
Cervical movement and musculature is complex (see figure 1), with vertebral levels contributing to varying degrees of overall neck motion. The change of orientation of the cervical vertebral bodies of the mid to lower cervical spine allow for rotation, flexion and extension. However, this also isolates lateral flexion to the upper portion of the cervical spine. When determining baseline range of movement it is important to recognise that this commonly decreases with age therefore ‘normal’ range will vary between athletes and is likely to change over an athlete’s career.
The gold standard for measuring cervical range of movement is radiological examination; however due to expense, this is technique is unlikely to be feasible in the sporting environment. Many clinicians commonly ‘eyeball’ neck motion, but there are in fact a number of more reliable and inexpensive tools that can be used and increase intra-rater reliability. These include the full-circle goniometer, or simply a tape measure to record the distance between anchor points, which can be easily replicated (see table 1).
The primary stabilisers of the neck are collectively known as the deep neck flexors (DNFs – longus capitus, longus colli, rectus capitis anterior and rectus capitis lateralis9. These are difficult to isolate without using EMG resources, but are most active through the commonly prescribed ‘chin tuck’ (craniocervical flexion). The most common assessment used to measure the activation and endurance of the DNFs is the craniocervical flexion test and assessed using a biofeedback device (see figure 2). This assessment is a useful baseline test, and can recognise weakness and movement control dysfuntions. One drawack however is that it lacks normalised data10.
Research tells us that the activity of the stabilisers is significantly decreased and delayed in anyone with neck pain11, and therefore this is a great starting point in all neck rehabilitation to regain stability. Postural assessment is also a key component of neck assessment. The primary purpose of the neck is to optimise head position and equal displacement of the weight of the head (3-6kg) is important in minimising overload to the stabilising muscles. Segarra et al describe a battery of reliable tests to aid assessment of cervical movement control dysfunctions including neck function in four point kneeling and with upper limb movement12.
|Table 1 – Anchor points used to assess Cx range of movement using tape measure|
|Anchor point 1||Tip of chin||Tip of chin||Tragus of ear||Tip of chin|
|Anchor point 2||Manubrium||Manubrium||Acromion process||Acromion process|
Cervical prime mover strength can be assessed in a number of ways including the use of isokinetic and isometric dynamometers, and can be combined with measuring muscle activity using EMG studies to increase validity. Cervical extension is stronger than flexion in general population studies, while lateral side flexion is commonly coupled with extension with a bias towards the subject’s dominant side. In athletes who rely on a dominant side bias (eg racquet and throwing sports) for performance advantage, this asymmetry should be recognised but not necessarily be seen as detrimental.
In the athletic environment without access to isokinetic and EMG equipment, baseline strength can be determined using a handheld dynamometer, ideally mounted to minimise assessor bias. Decisions on which ranges should be tested should remain consistent and accommodate for sport specific positions if required.
To ensure data is normalised the following considerations should be made:
- Torso stabilised
- Minimised lower limb involvement (eg feet on wobble cushion)
- Set appropriate ranges that strength will be measured at/through
- Standardised warm up and testing protocols
The neck does not function in isolation. Strong correlations have been found between neck pain and shoulder dysfuction and vice-versa; therefore the entire kinetic chain should also be considered in neck assessment. With swimmers in particular, shoulder dysfunctions commonly lead to hypertonicity of the cervical muscles, resulting in muscle imbalances, dysfunction and pain, all of which predispose the athlete to further neck injury13.
Figure 2: Cranio-cervical flexion test (Jull et al. 2008)
To perform the cranio-cervical flexion test:
-Patient supine, crook lying with neck in neutral position.
-Uninflated pressure sensor placed behind neck so that it borders the occiput.
-Inflate cuff to 20mmHg.
-Movement is described as ‘a slow head nodding action’.
Patient attempts to sequentially target five 2mmHg progressive pressure increases, with 10sec holds.
Compensation strategies to observe:
-Pressure loss of > 2 mmHg
-Began using superficial neck flexors (palpation)
-Jerked chin down
-Loss of cervical lordosis through retraction.
Neck injuries and concussion
Clinicians should have a high level of suspicion of concussion when treating acute neck injuries due to the high forces translated between the areas. It follows from this neck assessment should be carried out in all athletes following concussion or head trauma. As research into concussion grows there is more focus on the association with neck strength. Collins et al concluded that neck strength was a significant predictor of concussion amongst a large sample of high school athletes and although further research is needed, showed positive outcomes in reducing concussion risk from adopting neck strengthening programs14.
Cervical injuries can occur in a range of sporting environments from the result of acute trauma through axial loading, prolonged position exposure, whiplash and external forces such as vibrations and G forces. All cervical assessments should rule out severe spinal injury and concussion, and also include range of movement measurement and deep neck flexor and prime mover strength assessment. Consideration should also be made for the rest of the kinetic chain – in particular the shoulder girdle – due the high correlation between dysfunctions of the two areas.
In the next article, we’ll discuss management ideas for neck injuries and the phases of rehabilitation, whether it’s to return players to the field post injury or address any dysfunctions found in assessment and screenings.
- Current Review Musculoskeletal Medicine 2008. 1(3-4) 175 – 179
- Clinical Sports Medicine 2003. 22 (427-443)
- Clinical Sports Medicine 2003. 21:493–500
- British Journal of Sports Medicine 2012 46(9):662-663
- Aviat Space Environ Med 2005. 76:496–500
- Aviat Space Environ Med 2005. 76:496–500
- Int J Sports Physiol Perform. 2015. Sep;10(6):681-6
- Aviat Space Environ Med 2013. 84:734–8
- Physical Therapy 2005. 85:1349-1355
- Physiotherapy Research Int 2010. 15; 144-149
- Spine 2004. 29(19):2108-14
- Manual Therapy 2015. 20: 570-579
- Journal of Orthopaedic & Sports Physical Therapy 2012. 42(6):552-558
- Journal of Primary Prevention 2014. 35: 309-319