Exponent Article

By: Michael Prange and Ray Daniel, Exponent Inc.

Concussions and the role of a biomechanical engineer

In the past decade, there has been a general increase in awareness and emphasis on concussions. Overall, the diagnosis of concussions has increased over the years but it is unclear if this is due to an actual increase in incidences or a result of the increase in awareness and the evolution to the definition of concussion. In the past, loss of consciousness or amnesia was considered a necessary symptom. However, the American Association of Neurological Surgeons currently defines a concussion as a “clinical syndrome characterized by immediate and transient alteration in brain function, resulting from mechanical force or trauma.” Objective clinical evidence of concussions can be difficult to obtain as there currently are limited empirical tests for this type of injury such as blood tests or radiological studies. As such, medical doctors sometimes diagnose this injury based on the patient’s description of symptoms and their history of an event. Some instances of concussion can be straightforward such as a loss of consciousness after a severe blow to the head. However, not all instances of concussion are so obvious. Many times, the specifics of the incident such as the number of impacts sustained, direction, or severity of a specific impact are impossible for a medical doctor to quantify. In these situations, a biomechanical engineer can help understand the severity of the incident and the associated risk of concussion.

Although biomechanical engineers can assist in understanding the associated risk of concussion during specific events, it is often the job of a medical doctor to correctly identify that the injury sustained was in fact a concussion. The Kentucky’s Medical Practice Act defines the practice of medicine or osteopathy as the “diagnosis, treatment, or correction of any and all human conditions, ailments, diseases, injuries, or infirmities by any and all means, methods, devices, or instrumentalities.” In other words a medical doctor is a professional who diagnoses and treats a variety of conditions. In contrast, biomechanical engineers examine the relationships between the forces applied to the human body, the motions of the human body, and the physical mechanical damage to structures of the body. A biomechanical engineer evaluates the incident to determine the forces and motions on an individual’s body and if the tissues of the body have reached their biomechanical limit. A medical doctor determines exactly the pathology created and/or the medical reason for the symptoms (diagnosis) then addresses these through medical interventions (treatment). Biomedical engineers are specifically trained to understand the circumstances that lead to a traumatic injury while the medical doctor’s role typically starts after the injury has occurred. The human body, like any other structure, has material properties that affect its behavior when exposed to mechanical loading. A biomechanical engineer can evaluate the forces and motions generated in a specific situation and compare those mechanics to data of the tolerance of the biological structures involved. This analysis differs from that of a medical doctor as a physician’s analysis is focused on diagnosing and treating injuries and medical conditions.

In regards to concussions, biomechanical engineers have a number of tools to evaluate the mechanism of this injury. These tools include numerous peer-reviewed research studies conducted using various techniques such as field incident data, human surrogates, anthropomorphic test devices (ATDs or crash test dummies), and biomechanical models. This research has resulted in the development of correlations between head motion (kinematics) and the risk of brain injury. Biomechanical engineers then can determine the head motions during a subject event based on the laws of physics and

techniques such as quantification and modeling of video evidence, ATD testing and reconstructions, and non-injurious volunteer testing. Utilizing these data, the head accelerations and other injury metrics can be compared to published incidence of concussion, risk curves, and injury thresholds. Based on these relationships reported in the biomechanical literature, including tens of thousands of recorded impacts, the risk of concussion and brain injury can be determined for a subject incident. The severity of a specific event can also be compared to levels reported during non-injurious activities such as hopping off a step, plopping down in a chair, impact from a pillow, or to a child jumping rope. All this data helps to understand how the subject event compares to injurious and non-injurious activities and the risk of concussion associated with that specific situation.

With the increased emphasis on the occurrence and consequences of concussion, there have been questions about the protective ability that helmets provide regarding concussions. For the majority of helmets, the performance standards more directly address the risk of skull fracture but this does not necessarily mean that helmets do not assist in the mitigation of concussions. In general, a helmet can reduce the severity of an impact in several ways such as absorbing the impact energy and distributing contact forces. These design features can also reduce the risk of concussion as shown in several studies that demonstrated that the injury metrics correlated with concussions were reduced with the use of a helmet. However, it should be noted that while helmets can mitigate concussive impacts in many cases, not all concussions can be prevented by a helmet. Biomechanical engineers can evaluate any potential benefits a helmet could offer individuals who were not wearing a helmet during a specific incident.

In conclusion, both medical doctors and biomechanical engineers play a role in evaluating incidents that lead to injury of human beings. However, these roles are different between the two professionals. While a medical doctor focuses on diagnosing the injury and treating the associated symptoms, a biomechanical engineer evaluates the specific event and the mechanism of the injury. For concussions, a biomechanical engineer can analyze the severity of a head impact by applying the laws of physics and principals of mechanics, conducting tests and incident reconstructions, analyzing past research studies, and creating biomechanical models to simulate a subject event. This information along with the associated risk of injury puts the severity of the subject event into perspective. By performing these types of analyses, biomechanical engineers can provide a unique and important role in evaluating claims of concussion.

Categories: Volume 7 #1

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