Cervical and Scapula Muscle Dysfunction in Neck Pain – Research Evidence

Following on from the last post where I reviewed some of the literature on Brain Changes in the pain state, I thought it worthwhile to summarise what we know about cervical and scapula muscle dysfunction in neck pain.

What does the research tell us?

Jull (2011)

• Review article.
• A whiplash injury results in reduced range and control of cervical motion and changes in neck muscles’ spatial and temporal relationships as well as strength and endurance.
• The presence or not and magnitude of impairments is highly variable between individuals.
• The effect sizes for current generic exercise programs are modest, suggesting that improvements can be made in exercise prescription.
• Research informs on the need for specificity in exercise prescription to progressively address presenting impairments and exercise programs need to be tailored to the individual.
• Further research is required to determine if specific, individualized exercise programs improves outcomes after a whiplash injury.

O’Leary et al (2009)

• Review article
• Irrefutable evidence of an association between mechanical neck pain (MNP) and dysfunction of the muscles of the cervical spine.
  • Impairments identified include:
    • Changes in the physical structure of muscles (cross-sectional area, fatty infiltration, fiber type).
    • Changes in cervical muscle behaviour (timing and activation level).
      • Such changes suggest an impaired capacity of the cervical muscles to generate, sustain, and maintain precision of the required levels of torque needed for optimal function.
    • While interventions focused on the retraining of cervical muscle function have shown favorable responses in alleviating MNP, the development of best practice strategies for the assessment and management of cervical muscle dysfunction is still a work in progress.
    • As yet, we do not possess the capacity to optimally measure and classify those patients most likely to respond to different methods of training.
    • The ability of a clinician to best identify the need and implement the most appropriate method of training cervical muscle function is still largely dependent on a comprehensive examination of the patient that considers all aspects of the patient’s disorder and functional requirements.

Some of the recent research studies……..

Falla et al (2012)

• Fourteen women with chronic neck pain undertook a 6-week program of specific training that consisted of a craniocervical flexion exercise performed twice per day (10 to 20 min).
• After training, the activation of the deep cervical flexors increased  with the greatest change occurring in patients with the lowest values of deep cervical flexor EMG amplitude at baseline. There was a significant relationship between initial pain intensity, change in pain level with training, and change in EMG amplitude for the deep cervical flexors during craniocervical flexion.
• Specific training of the deep cervical flexor muscles in women with chronic neck pain reduces pain and improves the activation of these muscles, especially in those with the least activation of their deep cervical flexors before training.
• This finding suggests that the selection of exercise based on a precise assessment of the patients’ neuromuscular control and targeted exercise interventions based on this assessment are likely to be the most beneficial to patients with neck pain.

Beer et al (2012)

• This preliminary study investigated the effects of training the DCF with a functional exercise: assumption of an upright lumbo-pelvic and spinal postural position, adding a neck lengthening manoeuvre. The exercise effect was evaluated by changes in sternocleidomastoid (SCM) muscle activity in the cranio-cervical flexion test (CCFT).
• Twenty subjects with neck pain were randomly assigned to an exercise or control group. The exercise group trained for two weeks.
• Results indicated that the exercise improved performance. SCM EMG signal amplitudes decreased across all CCFT stages.
• No differences were evident in the control group.
• There was no difference between groups for pain and disability measures.
• This initial study indicates that a postural exercise, convenient to perform during the working day, improves the pattern of SCM muscle activity in the CCFT.
• Whilst further research is necessary, these observations suggest the worth of such an exercise to augment other training in the rehabilitation of patients with neck pain.

O’Leary et al (2011)

• This study examined the strength of the association between reported levels of pain and disability from 84 individuals (63 women, 21 men) with chronic mechanicalneck pain and levels of electromyographic activity recorded from superficial cervical flexor (sternocleidomastoid; SCM and anterior scalene; AS) muscles during progressive stages of the cranio-cervical flexion muscle test.
• A significant positive association was observed between superficial muscle activity and pain intensity, but not pain duration or perceived disability.
• The strongest relationship between pain intensity and superficial muscle activity occurred at the final increment of the cranio-cervical flexion test (inner-range test position) for both the SCM and AS muscles.
• Although a positive and significant relationship between pain intensity and superficial muscle activity was shown, the relationship was only modest (16% explained variance), indicating that multiple factors contribute to the altered motor function observed in individuals with chronic mechanical neck pain.

O’Leary, Cagnie et al (2011)

• Study investigating the extensor muscles of the cervical spine.
• Data recorded from subjects with chronic mechanical neck pain (n=12; 10 women, 2 men) were compared with previously recorded data from healthy subjects (n=11; 7 men, 4 women).
• While there were observed differences in differential activation of the extensor muscles in participants with mechanical neck pain compared with controls, these differences were only evident for the CCN exercise condition and were only observed for 3 out of the 7 muscle regions of interest during this exercise.
• Results of this study suggest some alteration in the differential activation of the cervical extensors in patients with mechanical neck pain and indicate that further investigation of this muscle group in mechanical neck pain disorders is warranted.

Wegner et al (2010)

• This study compared the activity (surface electromyography) of the three portions of the trapezius in healthy controls (n = 20) to a neck pain group with poor scapular posture (n = 18) during the performance of a functional typing task.
• A scapular postural correction strategy was used to correct scapular orientation in the neck pain group and electromyographic recordings were repeated.
• During the typing task, the neck pain group generated greater activity in the middle trapezius and less activity in the lower trapezius than the control group.
• Following correction of the scapula, activity recorded by the neck pain group was similar to the control group for the middle and lower portions.
• These findings indicate that a scapular postural correction exercise may be effective in altering the distribution of activity in the trapezius to better reflect that displayed by healthy individuals.

Helgadottir et al (2011)

• Altered activity in the axioscapular muscles is considered to be an important feature in patients with neck pain.
• The objectives of this study was to investigate whether there is a pattern of altered activity in the SA and trapezius in patients.
• Study found significantly delayed onset of muscle activation and less duration of muscle activity in the Insidious Onset Neck Pain group, and in the Whiplash Associated Disorder group compared to the asymptomatic group.
• With no interaction, the main effect for the onset of muscle activation and duration of muscle activity for serratus anterior was statistically significant among the groups.
• There were no group main effects or interaction effects for upper, middle and lower trapezius.
• This finding may have implications for scapular stability in these patients because the altered activity in the SA may reflect inconsistent or poorly coordinated muscle activation that may reduce the quality of neuromuscular performance and induce an increased load on the cervical and the thoracic spine.

My views on the above:

• As can be seen there is evidence of all types of muscular dysfunction “across the board” in neck pain patients. They key thing we need to be aware of as clinicians ,as mentioned in Jull (2011) and O’Leary et al (2009), is that:
  • All patients are different and will present with varying types, issues and levels of dominance of various impairments. On top of this the patients may also vary in functional requirements of rehabilitation.
  • Pain, and the experience of pain, is not homogenous. All patients need a highly detailed, and individual, assessment and rehabilitation/treatment regime based on the individual patients presentation, impairments, beliefs, psychosocial elements and goals.
  • Lets also not forget about the previous post on the various potential brain changes!

References:

Jull GA. Considerations in the physical rehabilitation of patients with whiplash-associated disorders. Spine (Phila Pa 1976). 2011 Dec 1;36(25 Suppl):S286-91.