Musculoskeletal and Neurovascular Disorders

1. Musculoskeletal and NeurovascularDisorders IENG 321 – Ergonomics and Human Factors Engineering Spring 2010

2. Lack of Rest Work/Rest Ratio Shift Length Environment Sustained Repetition Occupational Vibration Non-Occupational Temperature Physical & Temporal Risk Factors Posture Force Personal Psychosocial Compounding Risk Factors Risk Factor Model

3. Common Occupational Risk Factors • Awkward Posture • Force • Repetition • Duration • Contact Stress • Vibration • Temperature

4. Awkward Posture • Awkward Posture • Body postures determine which joints and muscles are used and the amount of force or stresses that are capable or tolerable • Greater deviations from neutral postures increase risk of MSDs

12. Combination of risk factors has a compounding effect

13. Force • Tasks requiring forceful exertions place higher loads on the muscles, tendons, ligaments, and joints. • Prolonged or recurrent force may leave inadequate time for recovery. May increase with: • Weight and bulkiness of the load handled or lifted • Awkward posture • Low friction of objects to be handled (requiring increased grip force) • Vibration (i.e., localized vibration from power hand tools leads to use of an increased grip force) • Use of the index finger and thumb to forcefully grip an object (i.e., a pinch grip compared to hand grip) • Small or narrow tool handles that lower grip capacity.

14. Repetitive motions • If motions are repeated frequently (e.g., every few seconds) and for prolonged periods such as an 8-hour shift, fatigue and muscle-tendon strain can accumulate. • Tendons and muscles can often recover from the effects of stretching or forceful exertions if sufficient time is allotted between exertions. • Effects of repetitive motions from performing the same work activities are increased when awkward postures and forceful exertions are involved. • Repetitive actions as a risk factor can also depend on the body area and specific act being performed.

15. Duration • Duration refers to the amount of time a person is continually exposed to a risk factor. • Job tasks that require use of the same muscles or motions for long durations increase the likelihood of both localized and general fatigue. • In general, the longer the period of continuous work (e.g., tasks requiring sustained muscle contraction), the longer the recovery or rest time required.

16. Contact Stress • Repeated or continuous contact with hard or sharp objects such as non-rounded desk edges or unpadded, narrow tool handles may create pressure over one area of the body (e.g., the forearm or sides of the fingers) that can inhibit nerve function and blood flow.

19. Vibration • Exposure to local vibration occurs when a specific part of the body comes in contact with a vibrating object, such as a power hand tool. • Exposure to whole-body vibration can occur while standing or sitting in vibrating environments or objects, such as when operating heavy-duty vehicles or large machinery.

20. Hot/Cold Temperatures • Hot temperature exposure can lead to annoyance, discomfort and health risks. • Cold temperatures are associated with discomfort in the hands, face and feet. • Manual dexterity is affected as temperatures drop below 60 F. • Sensitivity and strength are also affected in cold temperatures. • This will be covered in more detail later

21. Often used interchangeably, not necessarily the case Musculoskeletal & Neurovascular Disorders • Musculoskeletal Disorders (MSDs) • Disorders of muscles, joints, tendons, ligaments, cartilage • Cumulative Trauma Disorders (CTD) • Repeated Motion Injury (RMI) • Musculoskeletal Disorders (MSD) • Neurovascular • Disorders of nervous, blood vessels • Usually a gradual buildup of stress to the musculoskeletal system and neurovascular system • Diagnosis by a qualified medical expert • Most common in upper extremities and spine

23. Categories of Upper Extremity CTDs • Tendon disorders • Nerve disorders • Neurovascular disorders

24. Tendon Disorders • Tendonitis • Lateral epicondylitis (tennis elbow) • Medial epicondylitis (golfer’s elbow) • Rotator cuff tendonitis • Tenosynovitis • Stenosing tenosynovitis crepitans (trigger finger) • De Quervain’s disease • Ganglionic cyst (Bible Bumps)

29. Nerve Disorders • Cubital tunnel syndrome • Pressure on the ulnar nerve behind the funny bone causing numbness and tingling in the ring and small fingers of the hand. • Carpal tunnel syndrome (CTS)

30. Neurovascular Disorders • Thoracic outlet syndrome • Vibration syndrome • White finger or Raynaud’s phenomenon

33. Low Back Pain (LBP) Categories • Muscular / Ligamentous • strain • Structural • overloading trauma, degenerative disease, facet dysfunction, osteoporosis, scoliosis • Discogenic • herniation, nerve irritation • Others • infections, congenital disorders