Category Archives: biomechanics expert

Biomechanics expert Dr. John Lloyd has served attorneys nationwide for 25+ years in biomechanics, human factors, helmet testing and motorcycle accident expert

Brain Injury in Sports

Dr. Lloyd’s research article “Brain Injury in Sports”, co-authored with Dr. Frank Conidi has been published in the Journal of Neurosurgery.

Please email me at DrJohnLloyd@Tampabay.RR.com if you would like to receive a full copy of the published article.

Abstract

BACKGROUND
Helmets are used for sports, military, and transportation to protect against impact forces and associated injuries. The common belief among end users is that the helmet protects the whole head, including the brain. However, current consensus among biomechanists and sports neurologists indicates that helmets do not provide significant protection against concussion and brain injuries. In this paper the authors present existing scientific evidence on the mechanisms underlying traumatic head and brain injuries, along with a biomechanical evaluation of 21 current and retired football helmets.

METHODS
The National Operating Committee on Standards for Athletic Equipment (NOCSAE) standard test apparatus was modified and validated for impact testing of protective headwear to include the measurement of both linear and angular kinematics. From a drop height of 2.0 m onto a flat steel anvil, each football helmet was impacted 5 times in the occipital area.

RESULTS
Skull fracture risk was determined for each of the current varsity football helmets by calculating the percentage reduction in linear acceleration relative to a 140-g skull fracture threshold. Risk of subdural hematoma was determined by calculating the percentage reduction in angular acceleration relative to the bridging vein failure threshold, computed as a function of impact duration. Ranking the helmets according to their performance under these criteria, the authors determined that the Schutt Vengeance performed the best overall.

CONCLUSIONS
The study findings demonstrated that not all football helmets provide equal or adequate protection against either focal head injuries or traumatic brain injuries. In fact, some of the most popular helmets on the field ranked among the worst. While protection is improving, none of the current or retired varsity football helmets can provide absolute protection against brain injuries, including concussions and subdural hematomas. To maximize protection against head and brain injuries for football players of all ages, the authors propose thresholds for all sports helmets based on a peak linear acceleration no greater than 90 g and a peak angular acceleration not exceeding 1700 rad/sec2.

Please call Dr. Lloyd at 813-624-8986 or email DrJohnLloyd@Tampabay.RR.com if you would like to receive a full copy of the published article “Brain Injury in Sports”

Biomechanics

Biomechanics (1899) is derived from the Ancient Greek bios “life” and mēchanikē “mechanics”, to refer to the study of the mechanical principles of living organisms, particularly their movement and structure. The earliest known reference to the study of biomechanics dates back to Aristotle (384– 322 BC), who published ‘De Motu Animalium’ (On the Motion of Animals), in which he presented the mechanical concept ‘Ground Action Force’ as a starting point to deliberate where movement comes from.

The science of biomechanics has come a long way since the days of Aristotle. Contemporary biomechanics involves the application of Newtonian mechanics to determine physical capabilities and limitations of the human body. Trauma biomechanics examines whether mechanical forces acting on and within the human body may be sufficient to cause injury. The science of biomechanics is highly accepted by the courts for the purpose of explaining the mechanical causation of injuries.

Biomechanists posses advanced knowledge of human anatomy, mathematics and physics. We use this knowledge to study failure thresholds of human tissue, bone, ligaments, blood vessels, etc. When applying this knowledge to litigation, a biomechanist will perform a reconstruction to determine the forces acting on the plaintiff during the claimed injury-causing event and relate those forces to thresholds of injury. Biomechanists and Medical Doctors serve complementary roles in the medico-legal system. However a biomechanist is uniquely qualified, based on education, training and experience, to determine injury causation.

The methods that I use in my biomechanical evaluations are similar to methods that have been employed by other researchers and are generally accepted by experts in my field. Such methods have been validated and published in peer-reviewed scientific journals.

Expert in Injury Biomechanics

Dr. John Lloyd has served as a biomechanics expert for both defense and plaintiff’s counsel on hundreds of cases throughout the United States involving automobile collisions, motorcycle accidents, trucking crash as well as slips trips and falls. Dr. Lloyd is available to travel to investigate the causes of such cases. Based on his doctorate in ergonomics with a specialization in biomechanics, Dr. Lloyd can assess whether the claimed injuries meet or exceed known biomechanical thresholds of injury.

Please call Dr. Lloyd at 813-624-8986 or email DrJohnLloyd@Tampabay.RR.com to discuss how he can be of assistance with your case.

Forensic Biomechanics – The Science of Injury Causation

Human injury is complicated. If we lived our lives inside a protective bubble then, one day experienced an incident, it may be relatively simple to ascribe any injuries to the traumatic event. But that is typically not the case. As an aging nation, our bodies experience mechanical trauma every day – from work, sports, recreation and potential incidents. The question is whether forces and accelerations acting on the body as a result of a traumatic incident, such as an automobile collision, slip and fall, or recreational accident, were the direct and ultimate cause of injuries. Answering those questions is the unique role of forensic biomechanics and is typically beyond the expertise of most medical doctors.

Forensic biomechanics is the study of injury causation by measuring forces acting on and within the human body using methods of mechanics, to determine whether such forces exceed known thresholds of injury. As such, a biomechanist possesses expertise in the fields of both mechanics and human anatomy. Biomechanists and medical doctors serve complementary roles in the medico-legal system. Medical Doctors have specific knowledge to diagnose and treat a patient, however forensic biomechanics is not taught in medical school. Therefore, a biomechanist is required, based on their specialized education, training and experience, to serve as the necessary ‘bridge’ between medicine and engineering by calculating the forces acting on the body as a result of a claimed incident and thereby explaining the diagnosed injuries in terms of mechanical causation.

In a motor vehicle accident case, a biomechanist will assist the trier of fact by relating the impact forces and motions of the vehicles (automobiles, trucks, motorcycles, bicycles or pedestrians) to the resultant motion of occupants or other persons involved (kinematics). and forces they experience (kinetics) due to often multiple impacts within the vehicle interior or ground, then relate those forces to explain the mechanical causation of their medically diagnosed injuries.

Motorcycle, bicycle and pedestrian involved accidents can be substantially more complex, since the vehicles and operators tend to become separated and travel independently to their final rest positions. In Florida and many other states, motorcyclists have the right to choose whether or not to wear a helmet. Dr. Lloyd has conducted and published extensive research on the biomechanics of helmet protection, which shows that while helmets are effective at reducing the risk of penetrating head injury due to skull fracture, helmets do not offer adequate protection against traumatic brain injury, which can occur whether the rider is helmeted or not.

In a recent jury trial, Dr. Lloyd provided expert testimony in the fields of accident reconstruction, biomechanics and human factors on behalf of a plaintiff who suffered traumatic brain injury and a broken neck in a high-speed truck collision when a distracted driver drove through a stop sign. The jury awarded the plaintiff more than $14.5 million in damages.

Forensic biomechanics is also key to the analysis of cases involving slips, trips and falls, which are frequently claimed in all manners of environments, including workspaces, shopping arenas, restaurants, etcetera. Slips may occur whenever the coefficient of friction (CoF) between one’s footwear and flooring surface is too low, often due to the presence of a foreseeable foreign substance, such as a fluid. Whereas a trip may occur whenever the CoF between the footwear and flooring is too great, or unexpected, such as a transition between different surfaces. Unprotected falls can and do generate inordinate forces on the human body caused by acceleration due to gravity. For example, a simple fall from approximately 3 feet can generate an impact velocity of 10 miles per hour! But, more important is how quickly the human body comes to rest upon impact. It has been shown that a simple fall from only 12 inches onto a hard surface, such as concrete, can generate more than 1000 pounds of force on the human head, which is sufficient to cause fatal injury.

One recent slip and fall case in which Dr. Lloyd testified, involved a vascular surgeon, who went to sit down on a ‘budget’ stool to write his post-surgical notes. In that case, it was determined that the choice of casters on the wheeled stool were inappropriate for the environment, causing the stool to slip out from beneath the surgeon, who fell backwards, striking his head on the hard floor, resulting in traumatic brain injury and ongoing epileptic episodes. The surgeon, who suffered severe neurological deficits as a result of the incident was unable to return to work and also suffered many other lifelong effects. At trial the jury awarded the surgeon $10 million for injuries caused by the slip and fall.

In conclusion, a forensic biomechanical analysis may be pertinent to the success of a variety of cases, including: motor vehicle accidents (involving automobiles, trucks, motorcycles, bicycles and pedestrians), recreational accidents (including boating, jet skiing, ATVs, etc.), sports injuries / helmet protection as well as slips, trips and falls. The opinions formulated by Dr. Lloyd and other forensic biomechanists regarding the quantitative accelerations and forces necessary to result in injury are uniquely biomechanical opinions, and no other area of science or medicine is as appropriate to offer such opinions. Neither mechanical engineering nor physics include the prerequisite background concerning human body tissue properties and human anatomy. Similarly, medical training does not provide the necessary understanding of biomechanical principles to identify qualitative relationships between physical trauma and human tissue injury. Thus, a forensic biomechanist serves the legal system by quantifying the forces associated with an incident and comparing those forces against scientifically accepted thresholds of injury thereby explaining the medical diagnosis.

Judge Healey of the State of Florida First District Court of Appeals (Case No. 1D11-4210) recently upheld the importance of forensic biomechanics testimony in his ruling, which stated that “a biomechanics expert is qualified to offer an opinion as to causation if the mechanism of injury falls within the field of biomechanics” and as such is “relevant to establishing a reasonable hypothesis … that the victim’s injuries were consistent with … trauma”.

Ultimately, the success of any expert lies in their ability to convey often complex matters to a jury. Based on over 20 years of experience as an expert, during which time Dr. Lloyd has provided testimony at trial or in deposition more than 80 occasions, he has become highly proficient in using methods that express complex matters in simplistic terms for the purpose of educating the jury as to the facts of a case.

Publications

Why all head protection is in need of a redesign

The humble helmet dates back nearly 3000 years and though it has been used prolifically in warfare, it is now most commonly used to provide head protection outside the combat arena.

However, although applications might have diversified, it is still fundamentally designed and used to provide the same thing.

So when this most traditional of objects is combined with modern sensor technologies, greater test data resolution and analysis, there is bound to be fresh insight.

And this is the case for many conventional designs where sensors, test and measurement technologies are changing conventional thinking into how something has been designed, to how it should be designed.

It sets the scene and means helmet design is on a collision course for further impact protection, specifically in preventing serious brain injury by giving helmet designers greater clarity in to the mechanical forces at play in any particular scenario.

It was this, along with a lifetime of comprehensive knowledge, which enabled biomechanist Dr John Lloyd, research director of BRAINS, to start up a company dedicated to improving current helmet technology and ultimately improve protection for wearers. He aims to shed new light on helmet design, and improve protection against the fundamental causes of concussion and brain injury.

“There are two key forces at play during a head impact,” said Dr Lloyd, speaking at this year’s National Instruments Week in Austin, Texas. “Firstly there are linear forces, these are the ones that cause visible injuries such as bruising and skull fractures. However, the second is the rotational forces. These are the ones that cause invisible injuries such as concussion and brain injury.

“Current helmet testing technologies measure the linear forces. However, at this time, they do not measure the rotational forces, so consequently we have helmets for many sports that do not test against their ability to provide protection against concussions and brain injury.”

Whether it is for riding a bike, horse riding, skiing or indeed for the soldier in the field, the effect of rotational movement is the same. Yet, it is rarely tested for, and even less frequently measured, to see how effective any helmet is in rotation force protection.

Dr Lloyd modified the standard apparatus used for testing helmets (see the rig on page 28), where a head section is raised 2m on a rig and dropped under gravity before it hits a striking plate with an impact force in the region of 4500N. However, instead of using a standard head form, Dr Lloyd replaced it with a standard automotive crash test dummy head and neck section. This way, when the head impacts the striking plate at the bottom of the test rig it will rotate, and the movement measured.

“We had multiple sensors embedded in the centre of mass of this head form,” explained Lloyd. “So, during the impact we were able to measure the linear acceleration as well as the angular motion of the head.

“My measuring apparatus includes sensors from several manufacturers.. The angular rate sensor, for example, that is used to measure the rotational forces is a highly specialised sensor. And, as a result, has its own data acquisition hardware and software.”

Simplifying synchronisation
Trying to integrate all this data from different sensors was a challenge at best. And to make matters more complicated, the peak linear acceleration and peak angular acceleration actually happen at different points in time.

“So while you can just line up the data,” he said, “there is a lag between them. So we need to measure that lag, which is a critical measurement in the research.”

To resolve the problem, Dr Lloyd uses both the National Instruments LabView graphical software and a CompactDAQ to interface with the sensors and provide the necessary synchronisation between the various sensors.

Dr Lloyd modified his apparatus for testing helmets used by American footballers in the National Football League (NFL), to develop understanding of the how spinal and head injuries are caused and improve the design of the standard helmet.

“The results are pretty alarming in terms of how little protection they provide against concussions and traumatic brain injuries,” he said.

“Based on lessons learned from that study, I have developed a new ‘football’ helmet prototype. This uses a patent pending matrix of non-Newtonian materials and when we tested the prototype helmet, on the same apparatus, the result blew me away. Not only did these materials reduce the linear forces but compared to the standard football helmet they actually reduced the rotational forces that cause concussion and brain injury by an amazing 50%.”

The non-Newtonian materials Lloyd has in mind are inexpensive and produce a helmet that is considerably lighter and even said to be more comfortable for those wearing them.

Dr Lloyd is now expanding the concept of reducing rotation forces in helmets in every application and said it can be applied to almost any helmet design to help reduce concussion and brain injuries from sports to leisure and even back to warfare.

Building a rig and conducting the test
A modification to the US National Operating Committee on Standards for Athletic Equipment (NOCSAE) standard test apparatus was used by Dr John Lloyd, research director of US helmet research start-up, BRAINS.

He developed and validated a new helmet test rig to measure the impact of protective headwear to include measurements of both linear and angular kinematics. This apparatus consists of a twin wire fall test system equipped with a drop arm that incorporates a 50th percentile Hybrid III head and neck assembly from HumaneticsATD crash test dummy, as used in the automotive industry.

The aluminium fly arm runs on Teflon sleeves through parallel braided stainless steel wires, which are attached to mounting points in the building structure and anchored into the concrete foundation. The anvil, onto which the head drop systems impacts, consists of a 350mm x 350mm steel based plate.

Both the standard Riddell Revolution Speed US university football helmet, and the prototype BRAINS helmet that incorporates a non-Newtonian matrix, were dropped from a height of 2m onto a flat steel anvil, in accordance with American Society for Testing and Materials (ASTM) standards. This generated an impact velocity of 6.2 m/s (13.9 mph).

Instrumentation:
A triaxial accelerometer from PCB Piezotronics and three DTS-ARS Pro 18k angular rate sensors (Diversified Technical Systems) were affixed to a tri-axial block installed at the centre of mass in the Hybrid III head form. Data from the accelerometer and angular rate sensors were acquired using National Instruments compactDAQ hardware.

Analysis:
Data from the analogue sensors were acquired at 10,000Hz, per channel, using LabView and then filtered in Matlab using a phaseless 4th order Butterworth filter with a cut off frequency of 1650Hz. Angular acceleration values were derived from the angular velocity data based on a 5-point least squares quartic equation.

Result:
The result of the new helmet design shows significant improvement in rotational acceleration exerted on the head and neck, cutting the overall force by nearly 50%.

Author
Justin Cunningham

– See more at: http://www.eurekamagazine.co.uk/design-engineering-features/technology/why-all-head-protection-is-in-need-of-a-redesign/66493/#sthash.6Tv5duXE.dpuf

Motorcycle Accident Expert in Biomechanics and Human Factors

Motorcycle Accident Expert

Motorcycle collision analysis is a highly specialized discipline in which Dr. Lloyd is eminently qualified as a motorcycle accident expert. In addition to holding a PhD in Ergonomics (Human Factors), with a specialization in Biomechanics, John has more that 20 years and 200,000 miles of experience riding motorcycles. Dr. Lloyd has completed numerous advanced programs, including Motorcycle Safety Foundation (MSF), Experienced Rider Course and Total Rider Tech Advanced training.

Motorcycle Helmets and Brain Injury

To consider whether a motorcycle helmet might reduce the risk of brain trauma in a motorcycle accident it is first important to understand the two primary mechanisms associated with traumatic brain injury – impact loading and impulse loading.

Impact loading involves a direct blow transmitted primarily through the center of mass of the head, resulting in extracranial focal injuries, such as contusions, lacerations and external hematomas, as well as skull fractures. Shock waves from blunt force trauma may also cause underlying focal brain injuries, such as cerebral contusions, subarachnoid hematomas and intracerebral hemorrhages. Whereas, impulse or inertial loading caused by sudden movement of the brain relative to the skull, produces cerebral concussion. Inertial loading at the surface of the brain can cause subdural hemorrhage due to bridging vein rupture, whereas if affecting the neural structures deeper within the brain can produce diffuse axonal injury (DAI).

Holbourn was the first to cite angular / rotational acceleration as an important mechanism in brain injury. Gennarelli, Thibault, and colleagues, in a series of studies using live primates and physical models investigated the role of rotational acceleration in brain injury. They concluded that angular acceleration contributes more than linear acceleration to brain injuries, including concussion, axonal injury, and subdural hematoma.

Motorcycle Helmet Testing

Traditional testing of motorcycle helmets focuses on reducing the effect of linear impact forces by dropping them from a given height onto an anvil and measuring the resultant peak linear acceleration. According to the Federal Motor Vehicle Safety Standard (FMVSS) 218, commonly known as the DOT helmet standard, the test involves dropping a motorcycle helmet onto a flat steel and hemispherical anvil at an impact velocity of 6.0 m/s (13.4mph). In general, if peak linear acceleration is less than 400g, the helmet is considered acceptable. Current motorcycle helmet testing standards do not incorporate measures of angular acceleration and therefore do not address whether any helmets can provide adequate protection against catastrophic brain injuries, such as concussion, axonal injury and subdural hematoma.

In 1995, the European Commission Directorate General for Energy and Transport initiated a Cooperative Scientific and Technical Research (COST) program to investigate Motorcycle Safety Helmets. Several agencies from Finland, the United Kingdom, France and Germany participated in this study, which compiled and analyzed data from 4,700 motorcycle fatalities in Europe, each year. The COST report documents that 75% of all fatal motorcycle accidents involve head injury. Linear forces were present in only 31% of fatal head injuries, while rotational forces were found to be the primary cause in over 60% of cases. Within the scope of this study experiments were performed using drop tests with accelerometers to measure linear and rotational accelerations of the brain and skull mass associated with different types of impacts. These tests confirmed rotational acceleration to be a primary cause of brain injury in helmeted motorcycle accidents.

Rotational forces acting on the brain are the underlying cause of traumatic brain injuries.
Motorcycle helmets, including those certified under DOT and SNELL standards are designed to mitigate forces associated with linear acceleration.
Motorcycle helmets are not currently certified under either DOT or SNELL standard against their ability to protect against the angular / rotational forces.
Epidemiologic evidence from the COST-327 report indicates that motorcycle helmets do not provide adequate protection against closed head and brain injuries

Human Factors of Motorcycle Accidents

Human factors in vehicle collisions include all factors related to drivers and other road users that may contribute to a collision. Examples include driver behavior, visual and auditory acuity, decision-making ability, and reaction speed. A 1985 report based on British and American crash data found driver error, intoxication and other human factors contribute wholly or partly to about 93% of crashes.

Motorcycle Inspection

Motorcycle accident analysis often requires involves a teardown and careful inspection of the machine to investigate for possible contributing factors. Our engineers have a combined 70 years experience with motorcycle mechanics.

A thorough evaluation includes inspection of tires, brakes, suspension setup, electrical components as well as any aftermarket parts.

NI Week features John Lloyd football helmet expert

Football helmet expert, Dr. John Lloyd, had the privilege to present his research on football helmets as part of the Keynote address at the National Instrument conference in Austin, TX this week. The audience of 5,000+ attendees learned about Dr. Lloyd’s research into biomechanics of the brain.

It has been said that helmets cannot prevent concussions. I disagree.

As a biomechanist I have dedicated my career to studying the biomechanics of brain injuries. There are two key mechanical forces that give rise to head and brain injuries (1) linear forces, which are responsible for visible injuries, including bruising and skull fractures, and (2) rotational forces, which cause invisible injuries, such as concussion and brain injury.

Since helmets are currently designed to pass testing standards that focus on linear forces only, it is no surprise that helmets have limited benefit in preventing concussions. Through advances in medicine we have learned that concussions can potentially have life-long neurological consequences, including memory impairement and personality changes / behavioral effects.

Over the past years I have developed and validated a testing method to evaluate helmets in terms of their ability to protect against both linear and rotational forces. Using this apparatus I characterized football helmets, results of which have been submitted to Science for publication.

Based on lessons learned from my biomechanical evaluation of various sports helmets, I have devised a matrix of shear-thickening non-Newtonian materials. A prototype helmet was constructed using this matrix liner, results of which show that rotational forces that cause concussion and other brain injuries are reduced by up to 50% compared to a leading football helmet, while also reducing linear forces.

helmet prototype reduces concussion risk

It is my goal and my passion to work with leading helmet companies to make this technology available to players and sports participants of all aged to enhance their protection against brain trauma. I am looking to collaborate with one manufacturer in each sport to offer an exclusive license patent-pending technology.

Dr. John Lloyd | Motorcycle Crash, Biomechanics, Human Factors Expert

813-624-8986 | John@DrBiomechanics.com