PACS: Refining the human-machine interface

Oct 28, 2004

Work-related musculoskeletal disorders (WRMSDs) are not caused by what workers do, but rather by how they do it. The increasing use of technology in the workplace has led to decreased movements to accomplish tasks, creating a "frozen" relationship between the user and the equipment. The resulting postures are not normal for the human body.

A human-machine interface requires that an interaction or pathway be established between the human and the machine being worked with. These pathways can create a reciprocal relationship in which the human gains information provided by the machine, but ultimately the interpretation of the information is dependent on the user's decision.

Technically, machines and technological improvements allow humans to work at greater speeds and with greater precision. However, the interfaces that enable humans to gain information from machines and the machines to translate information to humans hold inherent risks for WRMSDs.

PACS workstations must display information effectively to the operator, and provide an efficient system for inputting information for interpretation. Furthermore, the workstation environment housing the PACS system can be directly related to the operator's risk for WRMSDs.

Computer work is a combination of static and dynamic effort. Dynamic effort uses continuous movement, and produces an alternating contraction and extension of muscles. During a static effort, blood flow to the muscles being utilized is restricted in proportion to the force exerted, creating oxygen deficiency and buildup of lactic acid (Grieco A, Molteni G, DeVito G, et al, "Epidemiology of musculoskeletal disorders due to biomechanical overload," Ergonomics, September 1998, Vol. 41:9, pp. 1253-1260).

While utilizing the keyboard, mouse, and monitor, PACS users sustain static postures with the muscles of the shoulders, arms, and back, along with simultaneous dynamic movement of the hands and fingers. Consequently, the muscles held in static position are at risk for fatigue and overuse syndromes, while those using dynamic effort are at risk for repetitive strain injury.

With their computer setup, PACS operators are highly susceptible to WRMSDs, based on their prolonged duration of fixed postures and repetitive motions. WRMSDs of the neck, shoulder, arms, and hands are likely to increase from positioning errors such as a keyboard placed at too high a level and inadequate forearm support. Risk of injury also grows from increased flexion, extension, or lateral deviation of the wrist or neck.

Incorrect workstation equipment or setup, or improper use of the equipment, can increase the awkward postures associated with WRMSDs. A workstation that provides the opportunity for both sitting and standing allows the use of alternating muscle groups, resulting in variation in nutrient supply to the muscles and intervertebral disks.

Adjustability

Adjustability in the workstation is critical for optimizing the workstation setup for all users. This is particularly important for a workstation that is used by multiple staff members. If the work surface is too high, the shoulders must lift to compensate by contracting the upper trapezius muscles, or by lifting the upper arms (contraction of the deltoid muscles), causing pain in the neck and shoulders.

If the workstation is too low, back pain can result. Since the ideal standing work height is 50-100 mm below elbow level, obtaining the ideal work surface height in a workstation that is used by multiple users with distinctly different body proportions is best achieved with an adjustable workstation.

Due to the nature of ultrasound scanning, filmless radiology, MRI, and CT, radiologists and sonographers are at high risk for developing symptoms of WRMSDs, such as shoulder bursitis, carpal or cubital tunnel syndrome, or degenerative disk disease.

A recent study published in the American Journal of Roentgenology reported a 100% incidence of cubital tunnel syndrome (50% unilateral, 50% bilateral) among the study group of radiologists, as well as a 25% incidence of bilateral carpal tunnel syndrome. Identified risk factors included using systems utilizing a filmless-computer keyboard, mouse or trackball, and/or electronic reporting-editing or approving programs. Additionally, 75% of those symptomatic subjects also performed sonography (July 2003, Vol. 181:1, pp. 37-42).

WRMSDs cost $60 billion overall per year, and costs businesses $5 billion to $20 billion per year in direct costs. These costs include workers' compensation and medical expenses, with the latter increasing 2.5 times faster than any other benefit cost.

Other facts about WRSMD costs:

$1 of every $3 of workers' compensation costs are spent on WRMSDs.
Employers pay $15 billion to $20 billion per year in workers' compensation costs for lost workdays.
Mean cost per cause of upper extremity WRMSDs is $8,070, compared to a mean cost of $4,075 per case for all types of work-related injury.
WRSMD costs include incurred claim costs, such as indemnity and medical payments.
The average cost for all claims equals $10,105.
The average cost for carpal tunnel syndrome equals $13,263.

The indirect costs are three to five times higher, reaching approximately $150 billion per year. These include absenteeism, staff replacement and retraining, and loss of productivity and/or quality of patient care. If a radiologist or sonographer is out due to injury, the loss of chargeable revenue in ultrasound studies alone reaches up to $4,500 per day, or over $20,000 per week.

Ergonomic adaptations

Appropriate ergonomic adaptations have been found to effectively reduce the risk of WRMSD symptoms. Adapting a workstation to each person and his or her work requirements ensures that it functions as intended, increasing productivity.

Taking steps to prevent WRMSDs involves using ergonomically designed equipment so that staff members can optimize the setup of the workstation unique to their physical dimensions and the work being performed. Furthermore, personal awareness and training in the proper adjustment to the work environment will also aid in preventing injury.

Important equipment design features to consider:

PACS and computer equipment: Adjustable monitors and keyboards, and ergonomic mouse to reduce reach.
Desks: Adjustable height, easily accessible controls, and adjustable height/tilting keyboard tray.
Chairs: Adjustable height, footrest, adjustable seat pan, lumbar support, and sit/stand capability for those who need to use viewboxes.

Dollars spent on improving the ergonomic design of the workstation yield an excellent return on investment, leading to improved performance and employee well-being. Technological advances in radiology have provided a means for cost-effective management of data with increasing efficiency.

However, failure to address the ergonomic concerns related to PACS use could negate the cost-saving value of soft-copy reading. Ergonomics provides the foundation for effective management, allowing highly skilled workers to perform at their best level, thus increasing productivity and profits.

By Susan L. Murphey
AuntMinnie.com contributing writer
October 29, 2004

Susan L. Murphey is director of operations at Sound Ergonomics, a consulting firm specializing in ergonomics for allied health professionals.

References

"Good ergonomics is good economics," American Federation of Labor-Congress of Industrial Organizations.

Grieco A, Molteni G, DeVito G, Sias N, "Epidemiology of musculoskeletal disorders due to biomechanical overload," Ergonomics. September 1998, Vol. 41:9, pp. 1253-1260.

Kroemer K.H.E., Grandjean E., Fitting the Task to the Human: A Textbook of Occupational Ergonomics. 5th edition. Taylor & Francis, 1997.

Ruess L, O'Connor SC, Cho KH, et al, "Carpal Tunnel Syndrome and Cubital Tunnel Syndrome: Work Related Musculoskeletal Disorders in Four Symptomatic Radiologists," American Journal of Roentgenology. July 2003, Vol. 181:1, pp. 37-42.

Schneider MF, "Ergonomics and Economics: Why ergonomics makes a lot of sense from a dollar-and-cents standpoint and why it may be inevitable because of legislation," Office Ergonomics, May/June 1985.

U.S. Department of Labor Bureau of Labor Statistics

Webster BS, Snook SH, "The cost of compensable upper extremity cumulative trauma disorders," Journal of Occupational Medicine. July 1994, Vol. 36:7, pp. 713-717.

Managing ultrasound ergonomics, March 26, 2004