American Journal of Sports Medicine http://ajs.sagepub.com Living with artificial grass: A knowledge update: Part 1: Basic science I. Martin Levy, Mary Louise Skovron and Julie Agel Am. J. Sports Med. 1990; 18; 406 DOI: 10.1177/036354659001800413 The online version of this article can be found at: http://ajs.sagepub.com/cgi/content/abstract/18/4/406 Published by: http://www.sagepublications.com On behalf of: American Orthopaedic Society for Sports Medicine Additional services and information for American Journal of Sports Medicine can be found at: Email Alerts: http://ajs.sagepub.com/cgi/alerts Subscriptions: http://ajs.sagepub.com/subscriptions Reprints: http://www.sagepub.com/journalsReprints.nav Permissions: http://www.sagepub.com/journalsPermissions.nav Citations (this article cites 23 articles hosted on the SAGE Journals Online and HighWire Press platforms): http://ajs.sagepub.com/cgi/content/abstract/18/4/406#BIBL Downloaded from http://ajs.sagepub.com by CRAIG C MCKIRGAN on April 27, 2008 © 1990 American Orthopaedic Society for Sports Medicine. All rights reserved. Not for commercial use or unauthorized distribution. Living with artificial grass: A knowledge update Part 1: Basic science I. MARTIN LEVY,*† MD, MARY LOUISE SKOVRON,‡ DrPH, AND JULIE AGEL,* ATC From the * Sports Medicine Service, Department of Orthopaedic Surgery, Montefiore Medical Center, Division of Albert Einstein College of Medicine, Bronx, New York, and ‡ Hospital for Joint Diseases/Orthopaedic Institute, New York, New York ABSTRACT artificial grass field more attractive. In contrast are the concerns over alterations in field characteristics as well as a two reviews the Part I of this part study development concern that playing on artificial grass will increase the risk and characteristics of artificial grass, and the influence for injury. Studies quantifying the physical effects of artifi- on of this surface the American football player. cial grass on athletes have been undertaken, but the conclu- Artificial grass was initially developed to provide city sions reached have been inconsistent. and thus enable children with increased play space The goals of this Phase I report are two-fold. In Part 1, them to maintain a fitness level to their in equal peers we shall review the development, material characteristics, more artificial fields allow for rural locales. Today, grass mechanical properties, and costs of artificial grass. In Part use when field is or for a increased availability limited, 2, we shall review all available epidemiologic studies of the where will not grass substitute grass grow. However, effect of artificial grass on American football players. With studies that there is an in- epidemiologic suggest this review we have been able to form a knowledge base that risk lower to the football creased of extremity injury can be used to clarify the key issues concerning artificial on an field. athlete playing artificial grass By reviewing grass and can serve as a starting point for future epidemio- available studies, a knowledge base can be formed that logic investigations. can serve to direct future investigations concerning the influence of artificial grass surfaces and injury and, ultimately, how that influence can be affected. HISTORY After the Korean War, the Ford Foundation evaluated the factors that influenced the physical well-being of young Twenty-five years ago a field made of a grass substitute was people. A review of military induction examinations from installed in a covered sport facility for the first time.4’ Today American recruits indicated that rural inductees were in artificial grass is played on throughout the world by profes- better physical condition than their urban counter- sional and amateur athletes. after a cen- 37, 47 However, quarter parts.l8~ 28, It was concluded that this difference was due of artificial has not been it tury use, grass totally accepted; to a lack of suitable play areas for urban children.4’ In 1960, Whether or not it is has been both praised and maligned. the Educational Facilities Laboratory (EFL) was created by safe for the athlete, or influences the games played on it, is the Ford Foundation to pioneer work in school-plant devel- still a subject of controversy. opment.47 Led by Harold Gores, the EFL began to evaluate Artificial grass has undeniable advantages. Where land is methods for the construction of rooftop playgrounds. Mon- limited, field use is high, or the climate is harsh, artificial santo, Minnesota Mining & Manufacturing (3M; St. Paul, use better than natural When funds grass withstands grass.&dquo; MN) and Cabin Crafts Carpets (Dalton, GA) were given are limited, decreased maintenance costs may make an design parameters for the construction of the rooftop play areas.4’ Chemstrand (Pensacola, FL), a subsidary of Mon- had been with fibers for t Address correspondence and reprnt requests to I Martin Levy, MD, The santo, already working synthetic Center for Sports Trauma, 2330 Eastchester Road, Bronx, NY 10469 use in carpeting to be installed in schools and other public 406 Downloaded from http://ajs.sagepub.com by CRAIG C MCKIRGAN on April 27, 2008 © 1990 American Orthopaedic Society for Sports Medicine. All rights reserved. Not for commercial use or unauthorized distribution. 407 buildings. From this work they developed an artificial sur- faces have been in use across the United States since 1982.’ face, ChemGrass. With a $200,000 grant from the EFL, an Today, AstroTurf and All-Pro Athletic Surfaces are those experimental ChemGrass field was installed in the field- most widely used, but other companies continue to find house of the Moses Brown School in Providence, Rhode places in the American market. Island, in 1964.18,28,37,47 This was the first artificial indoor surface and it is still in use. ARTIFICIAL TURF CHARACTERISTICS The Astrodome in Houston, Texas, was completed in 1965. Because the glare from the roofs skylights was blind- Fiber ribbons and wear surfaces ing Houston Astros’ outfielders, the skylights were painted The fibers that make the surface of an over. Without sunlight, the grass inside the Astrodome died, collectively up and the playing surface turned into hard dirt.51 To resolve artificial playing field are most effectively produced from an extruded monofilament ribbon.49 The of these fi- this dilemma a medium-pile, artificial surface, Monsanto majority bers are in cross-section. Two AstroTurf, was laid over the dirt floor. The surface was rectangular thermoplastics are used for the formation of the ribbon and modified a year later, in 1967, when a rubber pad was placed principally between the synthetic turf and the floor.51 Outdoor artificial ultimately the structural fiber: nylon and polypropylene.26, 49 is a linear of surfaces were first installed in 1967 by Monsanto at High Nylon thermoplastic polyamide capable a fiber.49 To it its resistance to the School Memorial Stadium in Seattle, Washington, and at forming help improve Indiana State University in Terre Haute, Indiana. 17,5’ By environment, nylon is usually modified by additives.49 Pig- ments are added to the fiber the desired color. 1980, AstroTurf (Appendix 1) had been installed in over 300 give is a linear For out- fields in the United States as well as abroad. 18,30,46 Polypropylene hydrocarbon polymer.49 door use, it requires both stabilizers and antioxidants. After In 1960, 3M had begun research on an all-weather track the final compound is formed, it is extruded a slit for horse racing.28 While not successful as a surface for horse through dye, forming a film. Tapes of the appropriate width are racing, the track was modified slightly and put to use as a produced by multiple blade slitters or air knives. The tapes running surface called Tartan Track. This surface was used are then stretched. This orients and influences the for the track events in the 1968 Olympic Games in Mexico them, of City. Tartan Turf (Appendix 1), designed for field sports, degree crystallinity.49 Once a suitable fiber is created it is into the became the next entrant in the artificial surface market. It incorporated wear surface system by merging it with the carpet backing. was initially installed at university playing fields in Tennes- This final product can be knitted, woven, or tufted. Knitted see and Wisconsin. 41 In 1974, 3M abandoned the production carpets are formed by tying each fiber into the carpet back- of its Tartan products because of increasing production ing. 1’, &dquo; The knitted fiber, and its backing, in effect become costs, limited markets, limited revenues, and negative pub- a single unit. A woven carpet backing is created by interlac- licity concerning the risk to athletes playing on the surface.28 ing warp and filler threads while the pile fibers are inserted PolyTurf (Appendix 1) was created by American Bilt-Rite along the warp threads. A tufted surface is formed by passing (Wellesley, MA). One of its earliest installations was in the pile fiber through a separately prepared backing.49 The Miami’s Orange Bowl followed by Foxboro Stadium, Spring- fiber is fixed to the backing by applying a binder coating of field College, Cornell University, Tulane University, and polyurethane or a synthetic rubber to lock the fiber in place. Boston Not long after its installation, the surface College. 17 The resistance of a pile fiber to pullout (tuft lock) from a at the Bowl suffered from with Orange problems plasticizer knitted carpet construct is excellent, and may exceed the and seams.28 American Bilt-Rite ceased pro- migration split tensile strength of the fiber. A woven system’s resistance to duction of in as Polyturf 1973, claiming only unprofitability pile pullout is less than that of a knitted system and is the reason for discontinuance. dependent on the type of weave employed.