Trapezius Myalgia

Definition
Trapezius Myalgia is chronic pain of the upper trapezius muscle, most frequent is neck pain. It is a complex and multifactorial condition. Musculoskeletal pain is often intensifying by mental and social stress at home or work. A biopsychosocial model plays an important role in the clinical management of chronic pain. It is a complex of different factors such neurobiological, psychological, coping styles, and contextual factors that contributes to the development and maintenance of chronic pain states12-13.

Clinically relevant anatomy
The trapezius muscle consists of 3 parts.

1. Trapezius pars descendens
2. Trapezius pars transversa
3. Trapezius pars ascendens

It is the upper part of the muscle, Trapzius pars descendens, that is painfull. The origin is found on the external occipital protuberance, Nuchal ligament and spinonus processes of 7th cervical and all thoracic vertebrae. The insertion is on the lateral third of the clavicula and acromion and spine of the scapula.

The function of the muscle is upward rotation of the glenoid cavity. The cranial fibers elevate the acromial end of the clavicula causing the glenoid cavity of the scapula to rotate upward (cranially).
Upward rotation of the scapula.
Extension of the head and to stabilize the scapula.

Epidemiology/ Etiology

At the moment a large and increasing collection of epidemiologic findings has shown strong and consistent links between musculoskeletal disorders and several occupational ergonomic exposures like forceful exertions, highly repetitive motions, sustained static muscle loading, lack of sufficient rest, awkward body postures, localized mechanical stress and features of the work environment such as restrictive, high demand-low control jobs. However there is still less consensus about nature of the epidemiologic findings and the physical examination findings.

There has been done a lot of research on the aetiology of work related neck and shoulder disorders. Researchers agree that the disorders arise from both biomechanical and psychosocial factors. Within the biomechanical dimension the m. Trapezius plays an important role. This type of neck pain called ‘trapezius myalgia’ may be associated with a lot of changes. These changes can take place at both the peripheral and central level and can interact resulting in muscle pain and fatigue.2

At the peripheral level the changes occur at the muscular level. There have been seen mitochondrial disturbances in the type I fibres and also reduced capillary density and circulation.5,7 These changes can possibly cause interferences in the oxidative metabolism of the muscles. There has also been described transformations of oxidative type I fibres to quick-acting glycolytic type IIb fibres.12 These changes can explain the muscle fatigue and pain. In one study they also found a larger cross-sectional area of the type I one fibres of the upper trapezius which demonstrates a higher load of these fibres.6

At the central level a reorganization of the neuromotor control strategies takes place. This can be illustrated in the cervical flexors by a dysfunction of the deeper flexors and a loss of force and endurance of these muscles.10 Persons with complaints also show a delayed activation of the muscles of the neck with arm movements.4 The superficial cervical flexors show a higher muscle activation and are faster fatigued, which demonstrate a less efficient function of the stabilization mechanism of the neck.3 This phenomenon is also seen in the cervical extensors where the superficial upper trapezius shows a higher activation then the erector spinae. Szeto et al. (2005) demonstrate in their study that the greater recruitment of type II fibres in symptomatic persons could possibly explain the muscle fatigue. These patients also show a diminished ability to relax the trapezius muscle after work.11 Another study showed a higher EMG-activity and an impaired relaxation time in symptomatic persons.9

Not only the biomechanical factors play an important role in het onset of trapezius myalgia. In the literature an causal relationship has been described between psychosocial factors and the occurrence of neck and shoulder disorders. There is some evidence for a link between disorders and high quantitative and qualitative demands, lack of support of colleagues, low job control and low influence.1 They also demonstrated a relationship between mental stress at work and disorders.11

Characteristics/ clinical presentation

The clinical presentation of Trapezius myalgia is chronic neck pain, pain, spasms and tenderness in the upper trapezius. The trigger points in the muscle results in painfull headarches behind the eye, into the temple and in the back of the neck.

Diagnostic procedures

The basis for diagnostic criteria of neck and shoulder myalgia is not very clear, and the diagnostic terminology and methods for assessment are variable. This indicates that several more or less specific and partly overlapping diagnoses exist. Progressing neck and shoulder pain accompanied with no other symptoms or signs (red flags) does not require specific investigations like radiography, magnetic resonance imaging, electromyography or nerve conductance testing. A standardized clinical examination for the clinical diagnosis of neck and shoulder myalgia contains questions on pain, tiredness and stiffness on the day of examination and physical tests. These test measure range of motion and tightness of muscles, pain threshold and sensitivity, muscle strength and palpation tender points.8
Possible risk factors
In the review of Larsson et al. an overview is given of the possible risk factors for work-related upper-extremity disorders. The conclusion stated that strong evidence was found for a causal relationship between neck disorders and highly repetitive work, forceful exertions, high level of static contractions, prolonged static loads and extreme postures as well as combinations of these previously named factors. But there was insufficient evidence for vibration as a risk factor. Also gender seems to play an important role in the development of neck disorders, since the prevalence is much higher among women. This difference can possibly explained with the fact that women’s jobs involve more work tasks with static load on the neck muscles, high repetitiveness, low control and high mental demands which are all risk factors for developing neck-shoulder pain. After the biomechanical and individual factors there are also psychosocial factors that have a causal relationship with the occurrence of neck and shoulder disorders.8 There is some evidence for a link between disorders and high quantitative and qualitative demands, lack of support of colleagues, low job control and low influence. They also demonstrated a relationship between mental stress at work and disorders.1
It seems logical, as we see all of the risk factors, that there is evidence for an increased risk for development of upper-extremity disorders among computer users. It was suggested that this could be due to constrained postures, constant force and highly repetitive movements as well as psychosocial factors such as time constraints and high quantitative demands.8

Physical Therapy Management
• Biofeedback
• Specific Strength training: 1-arm row, shoulder abduction, shoulder elevation, reverse flies and upward row.
• General endurance training
• Manual techniques: ischemic compression, transverse friction massage, stretching
• Tens
• Laser therapie

Prevention:
Prolonged stress in the upper trapezius muscle can activate latent trigger points or maintain pain in active trigger points. Biofeedback in the form of EMG of the upper trapezius muscle during work leeds to significant less activity and more rest pauses of the specific muscle. Therefore biofeedback might be useful in the treatment of trapezius myalgia.

Physical exercise:
Exercise seems to have beneficial effects on patients suffering from work related trapezius myalgia. Both general fitness training and specific strength training generate significant effects on diminishing pain. However strength training has proven to be even more effective compared to general fitness training. Prolonged effects 10 weeks after intervention were found. Other studies noted that long-term effects after 3 years disappeared.

Manual therapies:
Ischemic compression, stretch of the upper trapezius muscle, transverse friction massage are manual techniques to help patients with trapezius myalgia. These techniques appear to have instant improvement on pain. Long-term effects have not yet been well investigated.

Physical applications:
Transcutaneous Electro Nerve Stimulation (TENS) and laser therapy seemed to have positive short-term effects. However, more investigation on the long-term effect of these applications are needed. Also the most efficient type, frequency and duration of laser therapy require additional research.