Work Related MSK Disorders

• Work-related Musculoskeletal Disorders (WMSDs)


  Group of painful disorders of muscles, tendons, and nerves

  
• WMSDs


  • Usually develop gradually
  • Caused by overuse of musculoskeletal tissues and nerves
• Traumatic injuries to musculoskeletal tissues and nerves are not considered WMSDs
• Activities that cause WMSDs


  • Frequent and repetitive
  • Have awkward postures
• Most WMSDs affect hands, wrists, elbows, neck, and shoulders because almost all work needs the use of hands and arms
• Work that uses legs can cause WMSD of legs, hips, ankles, and feet
• Back problems can also be a result of repetitive activities
• Other names for WMSDs


  • Repetitive motion injuries
  • Repetitive strain injuries
  • Cumulative trauma disorders
  • Overuse syndrome
  • Regional musculoskeletal disorders
  • Soft tissue disorders

  
• Movements that can cause WMSDs


  • Bending
  • Straightening
  • Gripping
  • Holding
  • Twisting
  • Clenching
  • Reaching
• The movements are not harmful on their own during normal activities of daily living, but become hazardous when continuously repeated, in a forceful manner, quickly, and with little recovery time in between
• Work patterns associated with WMSDs


  • Fixed or constrained body positions
  • Continual repetition of movements
  • Force concentrated on small parts of the body (hand/wrist)
  • Pace of work that doesn't allow sufficient recovery between movements
• WMSDs are a result of a combination of all these factors
• Heat, cold, and vibration contribute to the development of WMSDs
• Muscle injury


  Muscle contraction produces lactic acid as a by-product which is removed by the blood. Muscle contractions that last a long time reduce blood flow, causing an accumulation of irritating substances that leads to pain.
• Tendon injury


  Tendons consist of bundles of fibers that attach to muscles and bones. Tendon disorders related to repetitive/frequent work activities and awkward postures occur in tendons with sheaths (in hand and wrist) and tendons without sheaths (in shoulder, elbow, and forearm).

  
• Tendon injury in tendons with sheaths


  • Repetitive or excessive movement of hand may cause lubrication system to malfunction, creating friction between tendon and sheath, leading to inflammation and swelling of tendon area (tenosynovitis). Repeated inflammation causes fibrous tissue formation, thickening the tendon sheath and hindering tendon movement.

  
• Tendon injury in tendons without sheaths

  • When repeatedly tensed, some fibers may tear apart, causing the tendon to become thick and bumpy, leading to inflammation (tendonitis).

  
• Bursitis


  Inflammation of the bursa, a sac filled with lubricating fluid inserted between tendons and bones to act as an anti-friction device.
• Nerve injury


  Repetitive motions and awkward postures cause swelling in tissues surrounding the nerves, squeezing and compressing the nerves, leading to muscle weakness, sensation of pins and needles, numbness, dryness of skin, and poor circulation to extremities.
• Major categories of risk factors for MSDs

  • Physical hazards
  • Psychosocial hazards
• Sub-categories of physical hazards

  • External loads (heavy lifting, repetitive actions, adverse postures)
• Sub-categories of psychosocial hazards


  • Organizational factors (high workloads, night shifts)
  • Social context (low supervisor support, low recognition)
• The National Institute for Occupational Safety and Health (NIOSH) has developed steps to identify risk factors for WMSDs
• The causation model guides factors screening so we can identify areas to work on through improving or compensating towards the goals of injury prevention programs
• Intrinsic risk factors


  Factors that the individual is born with or acquired before, predisposing the person to injury
• Extrinsic risk factors


  Factors that are applied or exposed to the individual
• Modifiable risk factors


  Risk factors that can be changed
• Non-modifiable risk factors


  Risk factors that cannot be changed
• When intrinsic and extrinsic factors act simultaneously, the individual may be at far greater risk for injury compared to isolation
• Intrinsic and extrinsic risk factors make an individual more susceptible to an inciting event or several inciting events that may lead to injury
• Psychosocial hazards can cause or have a causal impact on MSD risk, and the relative influence of psychosocial vs physical hazards varies widely across different studies but is still substantial

  
• The relationship between factors is not straightforward, and the main goal of an injury prevention program is to screen these factors and identify areas that can be worked on either by improving the factor or working around it in the environment or the individual
• Collecting health and medical evidence is an essential next step in determining the scope and characteristics of the WMSD problem
• Incidence rate


  Calculated by the number of new cases per 100 worker years (200,000 work hours) divided by the total hours worked by all workers for the time period

  
• Prevalence rate


  Calculated when considering all active cases in a given time period regardless of when the case originated

  
• Interviews and symptom surveys are used to identify the onset and nature of possible WMSDs
• Symptom surveys include background information, nature, onset, location, timing, duration, and severity of MSD symptoms, symptoms at previous jobs, difficulty of job tasks, medical history, and a body map
• Surveys are anonymous, voluntary, and completed on work time only, and the data is rank-ordered by frequency and severity of complaints for each body part and averaged for each department/job
• Periodic medical exams designed and administered by a healthcare provider can gather evidence of WMSDs through complete range of motion tests, tenderness tests, and pain reports
• Physicians conducting the medical exams should have no prior knowledge of workers' existing diseases or job titles