The Duck Test

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Johann F. Szautner, PE, Civil Engineer ::::

Case Synopsis: On a February evening, a lady went to a hospital to visit a friend. She mistakenly entered the emergency area in lieu of the hospital lobby and was directed to an exterior stairway leading to the lobby. While descending the stairs, she stepped off the bottom step, lost her balance and fell. She claimed that she slipped on ice; her allegation apparently passed the duck test and the hospital was sued. During the investigation, it was quickly discovered that this fall event failed the duck test, as the facts revealed a classic “everything is not what it seems to be” case.

Expert Analysis: Plaintiff testified that when she stepped off the bottom step with her left foot, her right foot landed on what she perceived to be marble sized rock salt. As her left foot landed on the described substance, it slipped and she fell forward, injuring her left knee. She further testified that her fall happened so quickly that she didn’t remember what part of her body hit the ground first as she landed, but she definitely remembered falling forward.

Normal human ambulation is achieved by pushing off with the ball of one foot, swinging the other leg forward and landing that leg on the heel. In this process, a horizontal force component, related to the person’s weight and walking speed, is transmitted to the walking surface. The walking surface has to have sufficient friction resistance to overcome the force transmitted by the walking person or a slip will occur. Heel slips typically result in a backward fall injuring one or a combination of these body parts; the lower back, hip, neck and head. Attempts at breaking a fall often result in injuries to elbows and wrists.

In descending steps, the gait still encompasses a toe-off, a swing phase, first contact, and a stance phase. At first contact, the leading foot is lowered onto the next step or landing, but with the foot roughly horizontal. The ball of the foot is usually placed well forward on the tread, and the heel may or may not be placed on the tread. There is some risk of under-stepping, missing the next step entirely or slipping off the edge because not enough of the foot has been placed on the step, actions that are likely to make us lose our equilibrium, resulting in a fall. A common stair descent misstep is when the foot with which we push off from the higher step had landed too close to the step’s edge and as we push off, the heel gets arrested by the step edge.

During the investigation it was determined that the stairs met all dimensional building code requirements and were well maintained. On the evening of the accident, maintenance personnel had applied calcium chloride on the steps, based on the weather forecast. The plaintiff did not slip and fall, she lost her equilibrium for unknown reasons and fell forward and landed on her left knee.

Result: The case settled.

Johann F. Szautner, PE is a Civil Engineer with DJS Associates and can be reached via email at experts@forensicDJS.com or via phone at 215-659-2010.

Civil Engineer | Johann F. Szautner | Trip

 

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