Many might assume significant differences in industrial design methods for addressing human factors associated with handheld devices for surgeons versus a hand held shower spray for the physically impaired. They would be wrong.

While the physical capabilities of each group are diametrically opposed, what is similar is a best-practices approach to human factors research, featurization, and mapping controls. Two product design projects conducted by Tanaka Kapec Design Group (TKDG) Inc, Norwalk, Conn. (tkdg.com), illustrate the point.

A ring-handle instrument was designed for Ethicon, Somerville, N.J. (ethicon.com), for a new generation of disposable, minimally invasive scissors, graspers, and hemostats. It went beyond mechanical and aesthetic solutions. TKDG designers identified other opportunities to help alleviate shoulder, wrist, and elbow pain reported by surgeons performing minimally invasive laparoscopic surgical procedures. The complaints were most common from baby-boomer surgeons transitioning to laparoscopic surgical procedures.

By contrast, the Lumex handheld shower spray device for GF Health Products Inc, Atlanta (grahamfield.com), designed by TKDG, was designed to permit those with little grip strength because of arthritis or other factors, to take showers without assistance. Both projects presented a design need for a device that could be used with a relaxed hand posture.

Eyes on the unseen

Some say that addressing human factors is largely a matter of uncovering uncovered problems. For development of the ring-handle instruments, it was necessary to understand problems associated with the posture surgeons found necessary to use laparoscopic devices. That is, while laparoscopic surgery represented a significant reduction in the application of physical forces, the first generation of disposable instruments was based on what had worked well for conventional open surgery.

Comprehending what surgeons were experiencing required observing operating room procedures to understand differences in the physical and interpersonal dynamics of laparoscopic versus open surgery. In addition to differences in height and position of the operating table, other differences include the posture of fingers, wrists, forearms, elbows, upper arms, and shoulders. In laparoscopic surgery, physical and interpersonal dynamics are based on smaller, more precise constrained movements in the fingers and wrists, coupled with wider rotational swings in the elbows and an exaggerated range of motion in the forearms, upper arms, and shoulders.

While observing one surgeon, we noted the small diameter ring handles that were ideal for open surgery were forcing his fingers to assume a contorted posture while performing a minimally invasive cholectystectomy. The finger contortion was producing pain in the wrist, arm, and elbow.

The second study, a handheld shower spray project, was initiated to create a new product for bathroom safety. Targeted users are challenged by balance, grip strength, and limited range. Just turning on the water while sitting on a tub seat is a serious challenge.

To understand what it feels like to have these mobility, balance, or grip strength challenges, we conducted observations at the Gaylord Hospital, Wallingford, Conn., a rehabilitation hospital that works with patients with brain injuries and other physiological challenges. We learned firsthand that for many prospective users, having an aesthetically pleasing product that did not look like something intended for those with disabilities users was almost as important as being more independent.

These observations were followed by the design team investing themselves in the discovery process. We went into the shower and tried to sit on a stool without touching the wall or grabbing a rail. We tried to do the same thing while standing on only one leg. And we put on large bulky mittens to duplicate physical impairment and then tried to turn on the water and control the temperature.

Common groundhuman factors

The human factors research for the surgeons and physically impaired led to a similar conclusion. Both projects reveal a need for a design form that could be positioned in the hand and used with little or no application of grip force.

Our lab created numerous 3D models for each project and prospective users were asked to experiment with the fabricated models. The same process for analyzing the kinesthetic, tactical, and spatial information gathered in the field was applied and incorporated into the models for each device. We asked subjects to play out tasks with models. We videotaped and charted body posture, limb alignments, and balance. And we used data analysis to visualize concepts for functional attributes.

Feature details and placement of controls in the Lumex and Ethicon projects required significant attention. For the Lumex shower spray, the product had to slide over the hand and stay in place, and with little hand strength. It was designed with a spring-loaded paddle so water would be easy to turn on with minimal effort. For safety, it was designed so the user could brush the handle off their hand to turn off the water if the temperature was too hot.

For the Ethicon surgical devices, we introduced an elongated forward ring now common in laparoscopic instruments. It was a major design departure. By changing the geometry of the ring and adding a larger surface area, the new device lets surgeons straighten their wrists and thumbs. This in turn permits surgeons to drop their elbows, which in turn reduces stress and contraction of the shoulder muscles.

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