Article

In this article, biomedical engineer, Valentina Ngai discusses the process by which it is possible to reconstruct an incident by examining injury data. In this instance, Dr. Ngai was tasked with determining the way in which the plaintiff fell down a set of stairs.

biomechanical-engineer-stairway-fall-expert

An Unwitnessed Fall Down a Set of Stairs

A patron at a restaurant falls down a set of stairs and suffers fatal injuries. The event is unwitnessed and only audible to others present at the event. How did the person fall? Did they slip, trip or misstep? Were they going up or down the stairs at the time of the fall? Were they using the handrail? There was no dispute that the injuries were related to the incident, but our client’s legal strategy required a detailed understanding of the injury mechanisms (the type and direction of loading necessary to cause the specific injuries), the structures the person falling may have contacted (i.e. the wall, handrail, steps, landing) and the position and orientation at any impacts during the fall in order to determine the fall mechanism.

This type of injury causation analysis falls under the purview of biomechanics. Biomechanics is the science that deals with the time and space response characteristics of biologic solids, fluids and viscoelastic materials to imposed internal and external forces. In more general terms, biomechanics is the science of how the human body responds to applied external and internal forces. Injuries can result due to specific applied loads. A capable biomechanical engineer is able to examine specific injuries and use reverse engineering by applying knowledge of injury mechanisms to determine if the pathologic loading was provided within the event in question to cause the injuries claimed.

As a simplified example, we can look at basic fracture patterns of the bones below. Based on the type of bone fracture and applying knowledge of injury mechanisms, it is then possible to analyze the event to determine if and how the pathological loading was generated to cause the injury.



Transverse - the fracture line is perpendicular to the long axis of the bone. Often results from bending loads due direct trauma at the point of fracture. Oblique - the fracture line is at an angle relative to the long axis of the bone. Often results from a combination of loads including axial compression and bending.

Butterfly - results from a bending load. Characterized by a wedge shaped bone fragment.

Spiral - occurs when a bone is twisted beyond its ultimate strength. Characterized by a helical break about the long axis of the bone.

An injury causation analysis can often determine what happened in an unwitnessed event and can also verify whether or not events took place as described by witnesses. It can also be used to determine if the use/misuse of protective equipment played a role in the cause of an injury.

In the case of the stairway fall, our expert was able to apply knowledge of anthropometrics, the specific stairway dimensions and biomechanics to demonstrate that the person falling was not using the handrail at the time of the fall and likely fell backwards down the stairs in order to sustain the specific injuries. This, in turn, enabled our client to determine whether the fall was due to any structural and maintenance issues of the staircase.

An injury causation analysis can be applied to any type of incident, whether it involves sports, automobile crashes, industrial mishaps, or slips and falls. If your case strategy calls for an understanding of the injury mechanisms, contact Dr. Ngai to discuss your case and how we can help.

Biomechanical Engineering Investigations

The biomechanical experts at Robson Forensic provide scientific and analytical evaluation of injuries to determine causation. Our experts are engaged when the cause or mechanism of an injury is not known, is not understood, or is in dispute.

Injuries tell a story. Could a fall have occurred as testified? Were the forces high enough to have caused the injuries claimed? Was the known mechanism (direction and type of loading) of injury provided in the event? Is the injury consistent with the physical evidence? These are examples of questions our biomechanical experts can help investigate.

For more information visit our Biomechanical Engineering practice page.

 

Featured Expert

Valentina Ngai, Ph.D., P.Eng.

Biomedical Engineer & Biomechanics Expert

Dr. Ngai is an expert in biomechanical engineering. She provides investigations, reports, and testimony toward the resolution of disputes and litigation involving traumatic injuries including medical implants and devices, motor vehicle crashes, premises liability, in addition to workplace and sports injuries.

Dr. Ngai holds a Ph.D. in Bioengineering from the University of Illinois at Chicago. She has been published in the Journal of Biomechanics, Wear, and the Journal of Engineering in Medicine. She has presented her research at numerous international conferences including the Orthopaedic Research Society, Wear on Materials, World Congress of Biomechanics and was an invited speaker at the 10th International Essen Symposium in Germany. Dr. Ngai is a licensed professional engineer in Ontario, Canada and also holds degrees in Civil and Mechanical Engineering.