Low Back Injuries

1. Low Back Injuries TM 655 Summer 2008 Carter J. Kerk, PhD, PE, CSP, CPE

2. Outline • Concepts • A Systems Approach • Risk Factor Model • ID, Evaluation, Control • Identification: Checklists • Evaluation • Force • Posture • Repetition

3. Stover Snook At any time, 15 to 20% of adults, evenly split between men and women, experience low back symptoms.

4. Stover Snook 35% of adults say they’ve had low back pain in the past month, 50% in the last year.

5. Stover Snook About two-thirds of all back pain develops gradually without any trauma or precipitating event.

6. US Bureau of Labor Statistics For employees who miss work time due to back problems, the median time away from the job is between 6 and 7 days.

7. National Research Council In the US, employers in private industry report around 7 million cases of work-related musculoskeletal injuries each year, with 25% of these leading to lost working days and restricted activities. It is estimated that 5 to 6 million of these cases are work-related back pain leading to 100 million working days lost.

8. Risk Factor Model for Potential Development of Cumulative Trauma Disorders,Including Low Back Pain Lack of Rest Work/Rest Ratio Shift Length Environment Sustained Repetition Occupational Vibration Non-Occupational Temperature Posture Physical & Temporal Risk Factors Force Personal Psychosocial Compounding Risk Factors

9. Attacking Hazards • Identification • Evaluation • Control

10. Control of Hazards • Engineering Controls • Administrative Controls • Personal Protective Equipment

11. Identification • Body Part Discomfort Survey • Quick Exposure Checklist (QEC) • Pareto Analysis

12. Body Part Discomfort Survey • Ask employee to shade in areas of discomfort • Rate each shaded area on a scale

13. Quick Exposure Checklist (QEC) Quickly assess the exposure to risks for work-related musculoskeletal disorders See http://www.geocities.com/qecuk

14. Quick Exposure Checklist (QEC) Steps • Self-Training • Observer’s Assessment Checklist • Worker’s Assessment Checklist • Calculation of Exposure Scores • Consideration of Actions

15. Quick Exposure Checklist (QEC) A1 A2 A3

16. Quick Exposure Checklist QEC Observer Assessment Worker Assessment

17. Quick Exposure Checklist QEC E(%) = X/Xmax x 100%

18. Use of Checklists • Preliminary screening • Before and after analysis • Relative comparison among tasks

19. Pareto Analysis • The Powerful Few - Group A – 10% of the tasks produce 70% of injuries – focus on these • The Insignificant Many - Group C – 65% of tasks produce <10% of injuries

20. Evaluation of Force • Direct force measurement • Force gauge, scale • NIOSH Lifting Guide • Psychophysical Tables

21. NIOSH Lifting Equation • Recommended Weight Limit • Load that nearly all healthy workers could perform over a substantial period of time without an increased risk of developing lifting-related low back pain • RWL = LC x HM x VM x DM x AM x FM x CM • Lifting Index • Estimate of physical stress • LI = Load Weight / RWL

22. NIOSH Lifting Equation RWL = LC x HM x VM x DM x AM x FM x CM • LC = 51 lb = 23 kg • HM = Horizontal Multiplier • VM = Vertical Multiplier • DM = Distance Multiplier • AM = Asymmetric Multiplier • FM = Frequency Multiplier • CM = Coupling Multiplier • Each multiplier ranges from 0 to 1

23. NIOSH Lifting Equation Determination of H and V

24. NIOSH Lifting Equation Determination of Asymmetry (A)

25. NIOSH Lifting Equation Does Not Apply When Lifting or Lowering • One hand • Over 8 hours • While seated or kneeling • In a restricted work space • Unstable objects • While carrying, pushing, pulling • Wheelbarrows, shovels • High speed (>30 inches / sec) • Slippery floors

26. NIOSH Lifting Equation

27. NIOSH Lifting Equation • Horizontal Multiplier • Metric • HM = 25/H • US Customary Units • HM = 10/H • Or Use Table 1

29. Evaluation of Force • Direct force measurement • Force gauge, scale • NIOSH Lifting Guide • Psychophysical Tables

30. Psychophysical Tables • How much should a worker be required to lift or lower or push or pull or carry? • How much is too much? • These tables are the culmination of 25 years of experiments at the Liberty Mutual Research Center

31. Psychophysical Table: Lifting, Males

32. Psychophysical Table: Pushing, Females, Initial Force

33. Evaluation of Posture • Photography / Videotaping • RULA • Rapid Upper Limb Assessment • REBA • Rapid Entire Body Assessment

34. Photography / Videotaping • Capture and evaluate entire work cycles • Freeze frame postures • Measure body angles • Protractor / Goniometer • Combine with force measurement • Combine with frequency evaluation

35. RULA • Rapid Upper Limb Assessment • Used to assess the posture, force, and movement associated with sedentary tasks • Including computer workstation tasks, manufacturing and retail tasks where the worker is seated or standing without moving about

36. REBA • Rapid Entire Body Assessment • Whole body • Posture is static or dynamic • Frequent or infrequent load handling

37. REBA • Steps • Observe the task • Select the postures for assessment • Score the postures • Process the scores • Establish the REBA score • Confirm action level and urgency

38. REBA • Selecting postures for assessment • Most frequently repeated postures • Longest maintained postures • Posture requiring greatest forces • Posture known to cause discomfort • Extreme, unstable, or awkward postures

39. REBA

40. REBA – Trunk Scoring

41. REBA – Neck Scoring

42. REBA – Leg Scoring

43. REBA – Scoring Group A

44. REBA – Load / Force Score

45. REBA – Action Levels

46. Evaluation of Repetition • Tools: Stopwatch, Videotape • Methods: Work Measurement Skills • Calculate repetitions: e.g., lifts per minute • Document the work cycles

47. Biomechanics • Advanced Technique • Uses elements of analysis from • Force and Posture • Requires knowledge of • Anatomy, Anthropometry, Statics, Dynamics

48. Gender and Posture Differences • Strength testing shows there are significant differences in lifting capability due to gender and posture • These concepts are critical in job analysis and job design

49. Squat Lift vs. Stoop Lift • Normally a squat lift is recommended over a stoop lift - “Lift with your legs, not your back” • But, if you cannot fit the load between your knees then a stoop lift becomes less stressful than a squat lift

50. Lifting Analysis • This type of analysis helps to understand the strength required throughout the lift at the elbow, shoulder, and hip. • The most stressful points can be identified.