Over the course of several decades sports protection technology has been developed and optimized so that the users of various sports products have been offered a means to protect themselves from serious and permanent injuries. However, due to size, weight and shape of helmets and protective gear, the protection, at best, is limited. To date, there have been many attempts to enhance the absorption and dissipation of forces without significantly changing the size of the protective device. One exception that was successful was the flexible facemask patented by C. J. Abraham in 1982 and 1986 that was licensed and manufactured by Riddell (1,2). It is used in the sport of football. The weight and design of this piece of equipment have been significant in changing said facemasks.
At the present time, professionals in football and ice hockey continue to receive head and bodily injuries that force them to prematurely to retire. Amateurs, also incurring similar injuries, are forced out of their respective games as well. The state of technology of protective equipment is at a standstill. No significant improvements have been made to raise the standard of care in order to reduce the number of permanent injuries reported each year. By creating a new standard of care, a reduction in the risk of injury in many sports activities is an obvious and beneficial result.
The undersigned has developed and tested a novel series of designs in protective equipment that absorbs and dissipates more forces than any system available to date. Without optimizing the system, the enhancement in helmets alone, has resulted in the reduction of forces ranging from sixteen (16) to thirty-nine (39) percent, dependent on the type of helmet and area tested.
The designs tested above have applications in many areas. However, the limiting factor in applying the principles and designs is the practical and economical method to manufacture a universal system. A few approaches attempting to solve this problem and tests performed applying these suggestions are demonstrated and discussed.
Over the last twenty years there have been many conferences focusing on helmets, concussions and protective equipment in sports. In addition, there have been numerous presentations and publications covering the classification of head trauma, the definition of a concussion, management of concussions, catastrophic head injuries,, performance testing in head protection and other related topics. Although I have attended a limited number of symposiums, I do not recall one presentation suggesting a method of improving the absorption and dissipation of forces for either headgear or protective equipment.
Even though hematomas are virtually eliminated when certified helmets are worn properly, head traumas continue to occur. Most recently, world-renowned pediatric neurosurgeon, Dr. Fred J. Epstein, received serious head fracture from a bicycle accident. He was injured on the morning of September 30, 2001 while bicycling near his home in Greenwich, Connecticut. He received serious head trauma after he hit a bump in the road and was catapulted over the handlebars. He was wearing a well-known bicycle helmet that cracked upon impact with the pavement. He was in a coma for a month and is now in a wheelchair going through physical therapy. He wears a path over one eye due to double vision. Another individual known personally to the author, and wearing the same helmet, also catapulted over the handlebars landing on his buttocks and right arm first and then his head. The helmet split, his arm was badly fractured, but he did not receive any head injuries from the secondary forces.
Approximately 300,000 sports related concussions occur each year, with 100,000 in football alone. About 900 sports related traumatic brain-injury deaths occur each year, and the risk of concussions is 4-6 times higher in players with previous concussions. Concussions per 100,000 games or practices at college level, by sport are as follows: Football: 27; Ice Hockey: 25; Men's Soccer: 25; Women's Soccer: 24; Wrestling: 20; Women's Basketball: 15; Men's Basketball: 12. One can add a significant number of head injuries from other sports such as in-line roller hockey, motorcycling, scooters, skating, and boxing, (3).
A concussion is a change in mental status caused by a blow to the head. Symptoms include confusion, amnesia, nausea, dizziness, blurred vision, and/or loss of consciousness. At the moment of injury, the brain becomes chemically imbalanced. There are numerous references available on this subject and one can refer to them for an in- depth discussion and analysis.
The list of athletes who have sustained career- ending concussions includes individuals in every major sport. Football and hockey are among the most dangerous, but none are completely safe. Younger athletes are also at risk. While the banging and bashing generally are more subdued in their games, they are less adept at protecting themselves. For example, 46% of injuries among children and adolescents in ice hockey relate to head injuries.
The current designs of protective helmets involve the absorption and dissipation of the primary forces, (translational, rotational, and focal) directly into the shell. The internal padding then absorbs the dissipated forces and distributes said forces directly into the head and brain. Alternative designs of protective systems demonstrated in this paper reduce said forces reducing the probability of head trauma. Because of the diagnostic tools available to measure head trauma, the short term effects may or not be measured.
The author has been involved with the development of many products and patents over the last thirty-five years. A few of the products involved safety in sports. The facemask for football changed the sport significantly and, from the first date of use to the present time, no injuries have been reported relating to that product. Most recently, an investigation was made with the objective of performing a worldwide search in determining the present state of technology in energy absorbing systems in order to develop a unique universal protective system that can be applied to headgear, protective body protectors, mats, arena boards, and footgear used in a variety of sports.
The parameters that one looks for in developing a novel shock attenuating properties are the following:
In order to create a novel shock absorbing system and meet the parameters listed above, the following approaches were proposed:
Patent and worldwide searches uncovered many approaches in enhancing the shock absorbing characteristics of protective equipment including footwear (4-36). Although the objective for each of the patents was to create a safer energy absorbing system, there are limitations with each of them in significantly enhancing the attenuation of the preexisting energy absorbing system.
One of the objectives of the present inventions was to reduce the risks of concussion and head trauma by enhancing the protective headgear in every sport using the pre-existing helmets for both contact and non-contact sports activities. The absorption and dissipation of forces is significantly enhanced with minimal cost to the manufacturer and to the consumer. Past attempts to improve the design have involved varying the shape of the plastic shell and modifying the type of padding. The amount of concussions and serious head traumas have not been reduced in number up to the present time.
Because of the advances in sport shoe technology, this author has examined some of them made over the years. The current designs and use of different energy absorbing systems such as foamed polymers, viscoelastic materials, gases, gels, air, silicone spheres and springs have been applied to protective equipment in order to enhance the performance.
In the sport shoe industry, it is known that cushioned soles redistribute the load of the foot, reduce peak pressures on the plantar surface and attenuate the impact shock wave transmitted to the skeleton. Similarly, design features such as varus wedges, variable density cushioning systems and mechanical stiffening elements can be used to control subtalor joint pronation. Such features have directly intervened in the putative mechanisms of patello-femoral pain, Achilles tendonitis, stress fractures and other lower extremity joints.
Although a large variety of energy absorbing materials have been incorporated into the systems of the modern running shoe, the principles of cushioning is common to all of them. For example, the addition of a layer of compliant material between the foot and the ground distributes impact forces, both temporally (reducing peak forces) and spatially (reducing peak pressures). The basic mechanics of cushioning is further demonstrated when one compares the results of testing a hard and a soft cushioning system. The more compliant shoe will undergo a greater deformation when impacted increasing the duration of the impact, assuming that the system does not bottom out. The redistribution of the impact force also results in lower peak forces and the peak rate force is also lowered.
The impact between the foot and the ground during a running step has a peak force magnitude of two times the athlete's bodyweight and generates a shock wave that is transmitted through the musculo-skeletal system. The impact shock wave has a typical magnitude of between 5 and 15 times the acceleration due to gravity (5-15gs) at the level of the tibia, but is attenuated to between 1 and 3gs at the level of the head.
Polymeric materials are used in an attempt to absorb and dissipate a certain percentage of the forces. If one first looks at the shock mitigation characteristics in thermoplastic polymers, the kinetic energy from an incoming mass is mostly dissipated in the foam. This results in little reverse throwback of the mass from the foam. At very low compressions in the range of 5%, for example, the foam acts as a Hookean elastic spring. The compression is directly proportional to the applied stress with a proportionality constant being the modulus of the foam. The modulus of the foam is directly related to the modulus of the polymer and the ratio of the squares of the foam density and polymer density.
At compressions approximating 65%, which would be considered a high compression, the foam cells collapse to a point where the strut supports are interfering with one another. Resistance to further compression is mostly related to the compressive character of the polymer itself and not that of the compressive nature of the foam.
At low compressive forces, the compressive nature of the foam is given as a combination of the bending and/or the buckling characteristics of the strut supports and the compressive nature of the gas in the foam cells.
The ideal situation is when the impact loading does not compress the foam greater than the 65% or into the region where the stress strain curve begins to turn up. Compression usually occurs only in the impact region of the incoming mass and then in a plane essentially parallel to the foam surface in that region. Continued compression will force weaker cell walls in other portions of the foam to collapse.
When the foam starts to collapse, the idea of using some type of spring in conjunction with the polymeric cushioning which could be applied to offset the limitations of the polymeric system looks promising. The characteristics of springs, if one can come up with the ideal design, are as follows:
One of the earliest manufacturers of shoes to incorporate a ribbon spring in the heel of its sport shoe was ShoeSpring of El Paso, Texas. They have lines of shoes for walking, working, hiking, basketball and running. Ray Frederickson, president of Sports Biomedics stated, "They've designed a better trampoline under the foot." There is one large ribbon spring in the center covering part of the heel. This system would not be acceptable for protective equipment.
The Nike running shoe claims they use four highly resilient columns work in conjunction with a "Pebax" moderator top plate to cushion the foot and act like a trampoline propelling the athlete into the next stride. Qualitative use tests performed by the author did not indicate any significant difference in Nike's energy absorption against a competitor's shoe designed with an air-pressured heel. Nor was there any measurable difference substituting Robatex's 310 one-half inch vinyl/nitrile polymer. The differences over extended usage were not measured for any of the shoes.
One of the objectives of the author is to develop an absorption and dissipation of energy system that will not have a trampoline effect. What the trampoline effect does is absorb some energy and store it. As one releases the stored energy, the amount that is stored reduces the amount required to rebound up again. This quality may be acceptable for sport shoes, but it is not for protective materials used for helmets, shoulder and chest pads, etc. In addition, there is a question concerning the legality of using spring assisted sport shoes in basketball, track and other sports. Examining the methods that the sport shoe companies use in reducing the forces acting on the body is a good start in attempting to solve the problem in creating a universal system.
It is important to note that the study undertaken by the author was made to demonstrate the feasibility of enhancing the absorption and dissipation of forces in all types of sports equipment, including sports shoes. There was no attempt to optimize any of the systems proposed and/or tested.
The thickness of the "preformed break-a-way" padding in the testing was Rubatex's 310-V (R 310V) and was 1/4 of an inch thick. The preformed padding is connected to the various designated parts of the outside of the shell by a system that can break-away. Velcro is one example. The use of the attachment has a two-fold purpose: (1) for attachment and, (2) to release if the glancing blow is greater than the force of the Velcro attachment. The latter sacrificial detachment is an additional benefit for the absorption and dissipation of forces. The padded sacrificial padding can be either replaced or put back where it came off.
The amount of energy absorption and dissipation of the forces depends on the thickness and type of pre-formed break-a-way padding applied. The end result is that the resultant forces to the head and brain are reduced significantly. This approach is directed to the reduction of the risk of injuries in both contact and non-contact sports that can be utilized in protective equipment such as shoulder pads as well as the boards surrounding an indoor arena.
The additional benefits of the proposed innovation invention are as follows:
The tests results, proving the feasibility of significantly improving the energy attenuating system are shown in Figure 1 [not reproduced]. What this demonstrates is that without optimizing the energy absorbing system the risk of injuries can be reduced significantly for many products involving protective systems. This relatively simple and inexpensive system can be applied to helmets of all types, protective equipment such as shoulder pads and the upper part of the boards around the rink. The end result is that a higher standard of care could be obtained reducing the risk of injury.
United States Patent 6,272,692 titled "Apparatus For Enhancing Absorption And Dissipation Of Impact Forces For All Protective Headgear" was issued on August 14, 2001 that covered the method of protection described above.
Static compression tests were performed on a Nike sneaker in the heel area. This was also done with one of the hockey helmets. A one-half inch diameter probe was used to apply an increasing load to the subject material in the heel area. The sneakers were tested up to 250 pounds. The helmet bottomed out at a 100-pound load. The sneaker was made of compressible foam material with numerous strategically shaped and placed, embedded plastic air bladders. (See Figure 2 and 3; not reproduced).
The static testing did show that the feasibility of using a spring type mechanism in conjunction with a cushioning polymeric material shows some potential. The static testing indicates some correlation with the dynamic testing. At the lower loads, there was no evidence of the springs bottoming out.
The cushioning in the heel was removed and replaced with a 4" X 4" R-310V as described above in both hockey helmets and the sport shoes. The initial testing incorporated the use of a simple compression spring that is an open-coil helical spring that offers resistance to a compressive force applied axially. The compression spring was coiled with a constant-diameter cylinder. They were stress-relieved to remove residual forming stresses produced by the coiling operation. They were also designed and manufactured so that they could compressed without permanent set.
ASTM 1045 protocol was applied to the hockey helmets tested. The impact was made at the ear area. The head form was dropped at an average rate of 4.52 meters per second on a MEP pad with a Shore A60 hardness.. The results are shown in Figure 4 [not reproduced].
What is important to note is that:
The cylindrical steel springs bottomed out. This was not because of the K factor. They bottomed out due to the fact that there was not sufficient room for the system to travel. The only way to overcome this problem is to switch to conical springs. Unlike the cylindrical spring, the conical spring is a variable spring that gets stiffer at the end of the travel distance and will be able to easily handle the forces applied. References 39 and 40 describes the use and application of conical springs in conjunction with the polymeric cushioning.
Testing of the latest proposed system was not completed for the present study. Conical springs were made as well as prototypes for running shoes and helmets. A cursory preliminary evaluation allows one to easily predict that the alternating conical spring design will work because: (1) more springs per unit area can be used relative to the cylindrical springs, and (2) the more accommodating fit of alternating the conical springs and the polymer allows for significantly more interaction between the springs and the polymer. This design alone allows one to easily conclude that the problem presented can be solved.
For the first time in the application of polymeric materials used as energy absorbing materials, the feasibility of a method of enhancing the levels of performance has been demonstrated and tested. The system, as of this date, has not been optimized.
A new standard of care may be necessitated if it is foreseeable that there is technology available that will minimize and/or eliminate injuries that are occurring and, foreseeable will occur in the future. Consideration of a risk/utility analysis and cost must also be part of the analysis. The technology must be practical and not be cost prohibitive.
It is accepted that the present designs of hockey helmets has eliminated subdural hematomas in that contact sport. The current testing protocol followed by the CSA, ASTM and ISO are adequate and, in the opinion of the author, modification of the test methods involved along with the certification programs do not need any changes. However, the application of the unique energy absorbing systems described in this paper can change the levels of acceptance for certification.
The energy absorbing system incorporating the conical spring systems in conjunction with the polymeric cushioning materials can be extremely beneficial to the sport shoe markets. The time for recovery after each impact is instantaneous. In addition, the technology can be applied to all protective equipment in every sport such as helmets, shoulder pads, shin pads, elbow protection, crash mats, gym mats, wrestling mats, landing mats, as well as swimming pools, dasher boards and kick plates. The technology will not change the design of the present molds and, therefore, there will be minimal cost to each of the manufacturers to enhance their product lines.
Additional advantages are realized when there is a collision between, for example, the helmet of one player and the shoulder pads of another player. If both of the players were wearing the enhanced protective equipment, the dissipation of forces would be significantly less than the current systems resulting in a much lower probability and risk of head injury. Another example of where the risk of injury would be reduced is when there is impact between the shoulder of the hockey player and the boards.
A prima facie case for product defect can be established through proof of defect, safer alternative design, and risk-utility analysis. One can now establish and present evidence in impact injury cases that (1) the design involved did not produce sufficient protection during foreseeable uses, (2) a safer alternative design exists, and (3) the risk of harm presented by the design outweighed its utility. For example, there is no question that there would have been minimal or no injury to Dr. Epstein had his helmet incorporated the technology demonstrated in this feasibility study. It is more probable than not, and within scientific certainty, that the helmet would not have split and the forces it was exposed to would have been dissipated.
If a helmet manufacturer can document the fact that it has a superior system to the ones suggested in this paper through testing, then any injured party would have little recourse to bring an action against the manufacturer.
Dr. Carl J. Abraham has over Over thirty years of international experience consulting to insurance companies, municipalities, government agencies, and the legal profession in the areas of new product development, manufacturing, packaging, warnings and instructions.
See his Listing on Experts.com.
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