Biomechanical Engineering & Injury Investigation

Biomechanical engineering is simply the application of mechanical engineering principles to biological systems, most often the human body. At its essence, biomechanical engineering seeks to understand the forces and motions experienced by the human body. Injury biomechanics, a sub discipline of biomechanical engineering, seeks specifically to understand the forces and motions associated with injury causation. 

Amongst the applications of injury biomechanics is the design of orthopedic fracture fixation devices, design of safety equipment, and automotive safety system design. After all, how can one design systems that prevent injury if they don’t understand what causes them in the first place? The field of injury biomechanics can also be applied to real-world events to better understand what happened during an injurious incident. More specifically, the field of forensic biomechanics can be used to determine what happened during a specific real-world event in order to shine light on issues arising in civil or criminal litigation.

The Expertise of a Biomechanical Engineer

Biomechanical engineering is a complex and often cross-disciplinary field. When applied to litigation, biomechanical engineers are often brought in to supplement or challenge the testimony of physicians who specialize in “diagnosis (identification) of injuries and their treatment, not necessarily a detailed assessment of the physical forces and motions that created injuries during a specific event”, according to the Reference Manual on Scientific Evidence, used by Federal judges to determine admissibility in court cases.

Biomechanical engineers often have advanced degrees or training in mechanical engineering along with laboratory experience related to testing biological tissues or experience with computer modeling, especially as it relates to human motion or tissue damage. Technical publications in the field of biomechanical engineering can be used to support their experience. 

The Application of Biomechanical Engineering to Injury Investigation

In general, biomechanical engineering can be used to answer a variety of questions related to injury investigation:

  • Are the alleged injuries consistent with the forces and motions (i.e., dynamics) experienced by an individual during an accident?
  • Can the injuries be used to reconstruct specific elements of an event?
  • Can determinations on the effectiveness of safety devices, such as helmets, seatbelts, and airbags, be made?

The basic process for applying biomechanical engineering to answering these questions is different based on the particular question at hand. However, a few key elements of the process typically remain constant. Specifically, it is common that the biomechanical engineer will want to fully characterize the injuries per the available medical records and imaging (see image of 3D reconstruction of a brain injury). Additionally, once characterized, a biomechanical engineer will want to determine the known biomechanical mechanisms (forces and motions) associated with the causation of those injuries.


Once these two elements have been determined, the biomechanical engineer can engage in answering the specific question at hand. For example, in instances involving a question as to whether or not an alleged injury occurred in an event, the biomechanical engineer will need to compare the forces and motions experienced by an individual in the event to the forces and motions associated with the causation of the injury. If these turn out to be one in the same, then the obvious conclusion is that the incident was most likely causative of the injury. Conversely, if the forces and motions experienced by the individual were not consistent with the known, generally accepted, and peer-reviewed mechanism of the injury, then the obvious conclusion is that the event was most likely not responsible for the medical condition.

In situations involving traumatic injury with a lack of understanding of the associated circumstances, a biomechanical analysis can help fill in the blanks. Specifically, when determining whether or not the source of an injury was from a motor vehicle collision or assault, a biomechanical analysis can compare the most likely forces resulting from either event and provide a comparison. Depending on the injury, a clear delineation can be drawn. 


For example, a person’s head impacting a windshield during a frontal collision that results in a change of velocity of approximately 20 MPH can result in an acceleration of the head during the impact of as much as 60 g’s of acceleration (1 g of acceleration is equivalent to 32 feet per second squared). Conversely, a fall from a standing height on concrete can result in head accelerations on the order of 400 g’s. The resulting skull and brain injury risk is very different at these two disparate severities.

Finally, evaluating the effectiveness of seatbelt use is a common question asked of forensic biomechanical engineers (depending on the laws in a given state). In order to perform this type of analysis, a thorough determination of the vehicle’s impact dynamics is typically performed. These dynamics are used to fully characterize the unrestrained occupant’s forces and motions, which should be consistent with their documented injuries. Finally, a hypothetical situation in which the occupant was restrained can be performed in order to determine the potential loading and injuries that would occur during restraint use. These data can be used to reach a conclusion regarding the effectiveness of restraint use in mitigating injuries.


Real-world Applications of Biomechanical Engineering

In addition to the examples above, you can review some of the ways that Explico has deployed our expertise when it comes to biomechanical engineering and forensic engineering on our case studies page.

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