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EHS 218 Occupational Ergonomics

EHS 218 Occupational Ergonomics. Risk Factors and Musculoskeletal Disorders. Risk Factor. Risk is the probability or likelihood of injury. A risk factor is any element that contributes to this probability. Personal Risk Factors for Musculoskeletal Disorders. Rheumatoid Arthritis

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EHS 218 Occupational Ergonomics

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  1. EHS 218 Occupational Ergonomics Risk Factors and Musculoskeletal Disorders

  2. Risk Factor • Risk is the probability or likelihood of injury. • A risk factor is any element that contributes to this probability.

  3. Personal Risk Factors for Musculoskeletal Disorders • Rheumatoid Arthritis • Endocrinological Disorders • Acute Trauma (such as burns, lacerations) • Vitamin B6 Deficiency • Wrist size and shape • Obesity

  4. Personal Risk Factors for Musculoskeletal Disorders • Gender and Age • Pregnancy • Oral Contraceptives • Gynecological Surgery • Fitness Level • Certain Medications

  5. Ergonomic Risk Factors for Musculoskeletal Disorders • Repetition • Awkward posture • Force • Vibration • Contact pressure • Cold temperatures

  6. Repetition • Refers to how frequently a task or set of motions is performed • Involves rapid and frequent muscle contractions which subject joints/muscles to high stress without adequate time for recovery

  7. Awkward Posture • Refers to taking the body out of its normal alignment or moving a joint toward the end ranges of motion.

  8. Force • Refers to muscle force exerted by the body and outside forces exerted on the body • Causes deformation of tissues

  9. Vibration • Transmitted to the body via the hand or entire body • It affects the blood vessels, intervertebral disks, and low back • Results in impaired circulation which in turn affects muscle function

  10. Contact Pressure • Produced when soft tissues are squeezed between bone and external objects such as tools, parts, or equipment

  11. Cold Temperatures • Results in circulatory, sensory, and motor impairments that affect manual dexterity and nerve function

  12. Musculoskeletal Disorders

  13. Musculoskeletal Disorders • Tendon disorders • Nerve disorders • Neurovascular disorders • Muscular injuries

  14. Tendon Disorders Tendinitis, Tenosynovitis, DeQuervain’s Tenosynotitis, Trigger Finger, Epicondylitis

  15. Tendinitis • Inflamation of a tendon • Occurs when a muscle/tendon unit is repeatedly contracted • With excessive exertion, some tendon fibers can tear • Tendon can become thickened, bumpy and irregular or calcified • Without rest, the tendon can be permanently weakened

  16. Tenosynovitis • A tendon injury involving the synovial sheath • Excessive synovial fluid is produced, and the sheath becomes swollen and painful

  17. DeQuervain’s Tenosynovitis • A special case of stenosing tenosynovitis • Stenosis is a progressive constriction of the tendon sheath

  18. DeQuervain’s Tenosynovitis • Involves the 2 tendons that abduct and extend the thumb • They run through a common sheath at the side of the wrist • Attributed to repetitive friction b/w these tendons • Clothes-wringing motion

  19. Trigger Finger (Tenosynovitis) • When the tendon sheath becomes sufficiently swollen • The tendon becomes locked inside the sheath

  20. Trigger Finger (Tenosynovitis) • Attempts to move finger cause a snapping/jerking movement • Associated with tools with hard or sharp edges

  21. Ganglion Cyst • The tendon sheath swells up with synovial fluid • Causes a bump under the skin • “Bible bumps”

  22. Epicondylitis • Inflammation of the unsheathed tendons in the elbow joint • Due in part to the imbalance in the elbow between the large forearm muscles and their small insertion areas on the humerous (the epicondyles)

  23. Medial Epicondylitis (Golfer’s Elbow) • Involves the finger flexor tendons located on the medial elbow • When strained or overused, the tendons become irritated and radiate pain from the elbow down the anterior arm • Tasks that require repeated forceful rotation of the forearm and bending of the wrist

  24. Lateral Epicondylitis (Tennis, Pitcher’s, Bowler’s Elbow) • Involves the finger extensor tendons located on the lateral elbow • When strained or overused, the tendons become irritated and radiate pain from the elbow down the posterior forearm • Using the arm for impact or jerky throwing motions

  25. Shoulder Impingement Syndrome • Recall that the shoulder is a complex joint

  26. Shoulder Impingement Syndrome • Impingement is a rubbing or pinching action • Impingement occurs somewhat during everyday activities when using the arm above shoulder height • Working continuously overhead, repeated throwing, or other repetitive actions can cause impingement to be a problem

  27. Shoulder Impingement Syndrome • Usually there’s adequate space between the acromion and rotator cuff for the tendons to slide easily as the arm is flexed • Some impingement on the tendons and the bursa is normal

  28. Shoulder Impingement Syndrome • Impingement becomes a problem when it irritates or damages the rotator cuff tendons • It’s also related to irritation of the bursa caused by the humerous forced against the acromion

  29. Shoulder Impingement Syndrome • In some people, the space between the acromion and rotator cuff is too small because the acromion is oddly sized

  30. Nerve Disorders Carpal Tunnel Syndrome (CTS) Guynon’s Canal Syndrome Radial Tunnel Syndrome Cubital Tunnel Syndrome

  31. Nerve Disorders • Occur when repeated or sustained work expose the nerves to pressure from hard, sharp edges of work surface, tools, or nearby bones, ligaments and tendons

  32. Carpal Tunnel Syndrome • Tendons that flex the fingers, the median nerve, and blood vessels pass through the carpal tunnel

  33. Carpal Tunnel Syndrome • The tendons, median nerve, and blood vessels are enclosed by the flexor retinaculum (carpal ligament)

  34. Carpal Tunnel Syndrome • If any of the tendon sheaths become swollen in the carpal tunnel, the median nerve may be pinched

  35. Carpal Tunnel Syndrome • Symptoms of CTS includes numbness, tingling, and pain in the thumb, first 2 fingers, and lateral side of the 3rd finger • Symptoms may be most severe while sleeping

  36. Carpal Tunnel Syndrome • Advanced cases of CTS may cause weakness of the thenar muscles at the base of the thumb

  37. Carpal Tunnel Syndrome • Nerve conduction velocity tests are sometimes used to help diagnose CTS • Carpal tunnel release surgery can relieve the pressure

  38. Guyon’s Canal Syndrome • Compression of the ulnar nerve as it passes through the Guyon tunnel at the wrist

  39. Guyon’s Canal Syndrome • Guyon's canal is formed with the pisiform and hamate and the ligament that connects them.  • After passing through the canal, the ulnar nerve branches out to supply feeling to the little finger and half the ring finger. 

  40. Guyon’s Canal Syndrome • Overuse of the wrist, especially flexion and ulnar deviation • Placing constant pressure on the palm • Symptoms are pain, numbness, and tingling in the anterior side of the palm, last finger, and ½ of the ring finger

  41. Radial Tunnel Syndrome • At the lateral elbow, the radial nerve travels in a tunnel formed by the surrounding muscles and bone • Runs below the supinator and down the posterior forearm • Difficult to diagnose; similar to lateral epicondylitis

  42. Cubital Tunnel Syndrome • The cubital tunnel is located on the medial elbow where the ulnar nerve passes • The ulnar nerve enervates the little finger and half the ring finger

  43. Neurovascular Disorders Thoracic Outlet Syndrome Vibration Syndromes

  44. Neurovascular Disorders • Involve nerves and adjacent blood vessels

  45. Thoracic Outlet Syndrome • Compression of the nerves and blood vessels between the neck and shoulder • Abduction causes the brachial plexus to be stretched under the pectoralis muscle

  46. Thoracic Outlet Syndrome • Result is that muscles, tendons and ligaments are deprived of oxygen and nutrition • Symptoms are numbness in the fingers and hand • Frequent reaching above shoulder level

  47. Vibration Syndromes • Hand-arm vibration (Raynaud’s Disease) • Whole-body vibration

  48. Hand-Arm Vibration Raynaud’s Disease • Disorder of the small blood vessels in the skin • During an attack, arteries contract briefly, limiting blood flow (vasospasm) • When the skin is deprived of oxygen, it turns white and then blue • The skin turns red as the arteries relax and blood flows again

  49. Hand-Arm Vibration Raynaud’s Disease • Recurrent episodes can cause complete closure of the arteries • Exposure to cold or vibration may trigger vasospasm in the fingers

  50. Vibration White Finger or Raynaud’s Disease • Forceful gripping and use of vibrating tools • Symptoms: • intermittent numbness and tingling of the fingers • skin that turns pale and cold • eventual loss of sensation and control in the fingers and hand

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