Hazard Analysis — Awkward neck postures

Neck pain and disorders

Neck pain is among the most common health complaints in working-aged populations worldwide.  Studies from Canada, the United Kingdom, and the Netherlands have shown the annual incidence of new neck pain to be as high as 15-18% among working-age adults.  Furthermore, studies have shown that neck pain is persistent and up to 50% adults will have symptoms one year later.  Numerous studies have shown women are at a greater risk for neck pain than men.  Neck pain is characterized by having pain in the soft tissues of the neck and shoulder girdle.  Neck pain can be accompanied by tingling or numbness into the arms, wrists, and hands.   
Work-Related Risk Factors
Awkward neck postures may be more harmful if they are combined with the following:
•    Static loading of neck or shoulder muscles
•    Repetitive movements of the shoulder or wrist
•    Awkward trunk postures (bending and twisting)
•    Psychosocial factors including job demand, control over work, support at work, and job strain

Development and Progression

The neck is the most mobile and least stable portion of the spine, which makes it susceptible to ligament, muscle, and intervertebral disc injury.  Neck pain can occur from inflammation, trauma, myofascial pain syndrome, intervertebral disc disorders, and osteoarthritis.  

The intervertebral disc  is composed of an outer ring of fibers surrounding a sac of gel-like material.  The ring of fibers can be damaged from a sudden stress, such as a fall, or cumulative stress.  When the fibers can no longer contain the fluid, small leaks or bulges (herniations) can occur or the disc may flatten.  Disc problems may lead to a compressed nerve (Figure A).
 
Figure A. A herniated disc.   The picture on the left depicts a normal disc and the picture on the right is a herniated disc.

Picture taken from http://myhealth.ucsd.edu/library/healthguide/en-us/images/media/medical/hw/n1926.jpg

The cause for the majority of episodes of neck pain remains unknown.  Once serious medical problems have been ruled out, patients are seldom given an accurate diagnosis.  Because of the difficulty to diagnose neck problems most are classified as either being related to the disc or to “mechanical neck disorders”.  Mechanical neck disorders are those related to improper movement or function of the neck tissues.

Common Symptoms

Neck pain is often accompanied by headaches or radiating pain into the upper back, shoulders, arms, and hands.   Point tenderness and trigger points (knots) in the neck and shoulder muscles are common in patients with neck disorders.  Limited range of motion is common in patients with neck pain.

Common Treatment

Initial treatment for most episodes of neck pain includes avoidance of stressful activities and use of nonsteroidal anti-inflammatory medications (NSAIDs, e.g. Advil ® or Aleve®).  Medical practitioners will often prescribe stronger drugs (muscle relaxants or narcotics) for more severe, acute pain.  Other treatment options may include application of heat and cold, spinal manipulation, traction, injections, and physical therapy.  Current evidence suggests the most appropriate interventions focus on strengthening the neck and shoulder muscles, and increasing mobility of the spine and surrounding soft tissues.  Some neck pain cases may require surgery (e.g. ruptured disc or severe trauma cases).

Most workers with occupational neck pain get better with minimal treatment.  However, a significant portion of workers will develop chronic neck pain.  At least 42% of workers will miss at least 1 week of work and 37% will still have symptoms after one year.  In the general population, 5% of people with neck pain become disabled.

The Rapid Entire Body Assessment (REBA) is a quick tool to assess worker exposure to several risk factors, including neck posture.  Awkward neck postures combined with flexion of the trunk and legs increases worker risk.

The Rodger’s Muscle Fatigue Index is also a useful tool to assess exposure to risk factors[DCA1]  involving the neck.  This observation method can be used to assess the amount of fatigue that accumulates in a muscle during 5 minutes of work.  The premise is that fatigued muscles are more susceptible to injury.  Using this tool, a safety manager can assess which tasks are potentially harmful for the neck, and prioritize tasks that could be modified.

The Washington Industrial Safety and Health Act (WISHA) provides a checklist to determine which risk factors are present in work activities.  Included in the checklist is an assessment of neck postures.  According to the checklist, flexion angles of the neck greater than 30 degrees for 2 hours of the day is considered cautionary.  Angles greater than 45 degrees for more than 4 hours a day is considered hazardous. 

All three assessment tools above can be accessed at Thomas Bernard’s website:

http://personal.health.usf.edu/tbernard/ergotools/index.html