Assistive Technology:Assistive Technology:Hand ControlsHand Controls

AgrAbility WebinarAgrAbility Webinar22 February, 201022 February, 2010

Robert W. StuthridgeRobert W. Stuthridge B.Sc., M.ScB.Sc., M.Sc..Purdue UniversityPurdue University

National AgrAbility ProjectNational AgrAbility Project

Agenda

• The need for hand-operated (AT) controls

• Design options

• Hazards and risks

• Design considerations

• Usage considerations

• Hazard and risk assessments

Need for hand-operated (AT) controls

• US Ag. high rate of permanent disability (Deboy 2008; NIOSH 2009)

• Types of disabilities (through AgrAbility) (Willcomm, 2004)

• 23% Orthopedic (including musculoskeletal).• 16% Amputation. • 13% Neuromuscular.• 21% Spinal Cord injury. • 27% Other.

• Any of these may involve reduced lower-limb functionality.

Need for hand-operated (AT) controls

• Over 70% of agricultural workers with disabilities continue to work by modifying their work environment using ‘assistive technology devices’ (Gruver at al. 1997)

Hazards and risks

• AT may increase primary user’s risk of developing “secondary injuries” (Willkomm 1997; Yoder,

Kingman et al. 2001; Willkomm 2004; Mathew 2009). • AT injuries may occur as a consequence of

inappropriate design of AT, preceded by incidents such as: • Slips• Trips• Falls• Incidental contact with AT (Willkomm 1997).

Hazards and risks• May also increase risk of similar injuries for

secondary users (family members, other employed workers including seasonal/casual) (Willkomm 2004; Mathew 2009).

• Slips, falls and incidental contact result in acute injury.

• Possible to attribute injury to immediately precedent event.

• May lead to: • Redesign of AT• Limitation or cessation of use of AT • Change in workers’ behavior when using AT

Hazards and risks

• Most agricultural injuries are not acute - no clear cause effect relationship between an incident and an injury (Walker-Bone and Palmer 2002).

• Work-related musculoskeletal disorders WMSD are most prevalent form of agricultural injury (Walker-Bone and Palmer 2002).

• WMSD arise from repeated or prolonged exposure to occupational hazards such as: • whole body vibration, • segmental (e.g. hand-arm) vibration, • awkward working postures, • heavy lifting, and • use of excessive force (Mehta, et. al., 2000; Muzammil et.al., 2004;

Rautiainen, et.al., 2004; O'Sullivan, et. al., 2009).

Design considerations

Design Considerations: Wrist Posture

• Handles designed to promote neutral wrist/arm postures

Design Considerations: Force

Nonslip cushioned grips must be suited to all likely climatic conditions.

Don’t make handles too large in diameter:

Optimum handle span largely dependent on hand lengthhand length.Small hands Small hands <6.7 inches long and medium hands medium hands 6.7-7.5 inches long exert most force at ≤2.0 inch handle span.Large hands Large hands >7.5 inches long exert most force at 2.4 inch handle span.

Usage considerations

Usage Considerations: Repetition

• Even initially ‘comfortable’ postures and forces can cause pain with enough duration or repetition, e.g. laying, sitting, standing.

• Need to balance mobility/movement with a need to avoid repetitive movements.

• Variation of posture is key.• Rest/recovery pauses and

breaks.

Steering Ball can provide postural options…suitable for fitting to steering wheels of tractors and other vehicles.

Hazard and risk assessment

Definition of Terms Used• “Assistive Technology (AT)” means “technology designed to be utilized in an assistive technology device or

assistive technology service.” Assistive Technology Act (1998). Assistive Technology Act of 1998. 105-394, S.2432. US Congress. Washington DC.

– “Assistive Technology Device”: “The term `assistive technology device' means any item, piece of equipment, or product system, whether acquired commercially, modified, or customized, that is used to increase, maintain, or improve functional capabilities of individuals with disabilities.” Assistive Technology Act (1998). Assistive Technology Act of 1998. 105-394, S.2432. US Congress. Washington DC.

– “Assistive technology service”: The term `assistive technology service' means “any service that directly assists an individual with a disability in the selection, acquisition, or use of an assistive technology device. .” Assistive Technology Act (1998). Assistive Technology Act of 1998. 105-394, S.2432. US Congress. Washington DC.

• “Disability”: This presentation uses the definition applied by the Americans with Disabilities Act, As Amended, 2008 ADA (2008). Americans With Disabilities Act of 1990 As Amended 2008 42.126.12101 P.L. 110-325 US Congress, Washington DC. The ADA defines "disability" with respect to an individual as:

– A physical or mental impairment that substantially limits one or more major life activities of such individual;– A record of such an impairment; or– Being regarded as having such an impairment.– In determining whether a person is disabled within the meaning of the Act, ‘major life activities’ are defined as follows:

“Major Life Activities include, but are not limited to, caring for oneself, performing manual tasks, seeing, hearing, eating, sleeping, walking, standing, lifting, bending, speaking, breathing, learning, reading, concentrating, thinking, communicating, and working. A major life activity also includes the operation of a major bodily function, including but not limited to, functions of the immune system, normal cell growth, digestive, bowel, bladder, neurological, brain, respiratory, circulatory, endocrine, and reproductive functions” ADA (2008). Americans With Disabilities Act of 1990 As Amended 2008. 42.126.12101 P.L. 110-325,. US Congress. Washington DC,..

– Disabilities may arise due to trauma, disease, aging, genetic conditions (Deboy et al, 2008).• “ Hand Controls” here infers only equipment controls modified for operation with the hands or arms, where

the operation would not ordinarily involve the use of the hands or arms. It specifically includes for this presentation only those controls modified to meet the needs of agricultural workers with disabilities.

• “Secondary injury” is an injury “caused wholly or partially by limitations associated with disability conditions and/or resulting from the use of modified practices or AT to compensate for disabling conditions. The cause of the original disability can be a previous injury or any other condition.” Mathew, S. N. (2009).

References• Deboy, G. R., Jones, P.J., Field, W.E., Metcalf, J.M. and Tormoehlen, R.L. (2008) "Estimating the Prevalence of Disability

within the U.S. Farm and Ranch Population." Journal of Agromedicine 13(3 ): 175-189.• Gruver, M.L., Allen, P. B., Field, W. E., Schweitzer, J. (1997) Potential health and safety risks of farming/ranching with a

disability. In Plowshares #27. 1997, Breaking New Ground Resource Center, Purdue University: West Lafayette, IN..• Mathew, S. N. (2009). “An assessment process to estimate the secondary injury potential of assistive technology adopted

by farmers with disabilities.” (PhD Thesis). West Lafayette, IN., Purdue University.• Mehta, C.R., Shyam, M., Singh, P., Verma, R.N., (2000) Ride vibration on tractor-implement system. Applied Ergonomics,

2000. 31(3): p. 323-8.• Muzammil, M.S., Siddiqui S.S. and F. Hasan, (2004) Physiological effect of vibrations on tractor drivers under variable

ploughing conditions. Journal of Occupational Health., 2004. 46(5): p. 403-9.• NIOSH (2009). "Agricultural Safety." NIOSH Safety and Health Topic http://www.cdc.gov/niosh/topics/aginjury/default.html • Rautiainen, R.H., Lange, J.L., Hodne, C.J., Schneiders, S., Donham, K.J., (2004) Injuries in the Iowa Certified Safe Farm

Study. Journal of Agricultural Safety and Health, 2004. 10(1): p. 51-63.• Walker-Bone, K. and K. T. Palmer (2002). "Musculoskeletal disorders in farmers and farm workers." Occup Med (Lond)

52(8): 441-450.• Willkomm, T. (1997). “Risks in using modified tractors by operators with spinal cord injuries and their co-workers.” PhD

Thesis. Pittsburgh, PA, University of Pittsburgh.• Willkomm, T. (2004) "Farming and Ranching with a Disability

http://nasdonline.org/static_content/documents/1832/d001767.pdf."• Yoder, A., Kingman, D.M., Field, W.E. (2001) Influences of disabling conditions on the nature and frequency of farm/ranch-

related injuries. National Ag Safety Database 2001 11/27/2009; Available from: http://nasdonline.org/document/1833/d001768/influences-of-disabling-conditions-on-the-nature-and.html.