A C L injury risk A C L injury risk Table 1 - Major sports at risk for ACL injury in young males, along with estimated grass profiles for Seasonal and geographical various states of Australia State MAJOR football code(S) PROXIMITY to Grass PROFILE EXAMPLES OF common Grass snowfields TYPE(S) ON commUNITY FIELDS New South Wales Rugby league and union, soccer Close Mainly warm-season Kikuyugrass analysis of acl injury risk in Queensland Rugby league and union, soccer Very distant Warm-season Bermudagrass and Queensland blue couch South Australia Australian football, soccer Distant Mainly cool-season Ryegrass and annual bluegrass Australia John Orchard, Ian Chivers, David Aldous Tasmania Australian football, soccer Distant Cool-season Ryegrass and annual bluegrass Victoria Australian football, soccer Close Mainly cool-season Ryegrass and annual bluegrass 8 There are northern (warm-season) temperature , which is dropping over of ACL injury. As somewhat of a Western Australia Australian football, soccer Very distant Warm-season Kikuyugrass and and early-season biases for ACL the course of the season in outdoor control, the figures for females will be Bermudagrass injuries in the AFL that have been stadiums, but not in indoor stadiums. examined, with the expectation that ACT Rugby league and union, Australian Very close Cool-season Ryegrass, annual bluegrass, revealed by a long-standing reliable any northern (warm-season) state bias football, soccer Kentucky bluegrass, fescues. ACL injuries are particularly common injury surveillance system1-3. Recent would be minimal, as the higher risk Northern Territory Australian football and rugby league Very distant Warm-season Kikuyugrass and in the major football codes (Australian study has suggested that the sports that are popular with females Bermudagrass football, rugby league, rugby union, underlying explanation for these are generally not played on natural soccer) and in snow sports. They trends is the relative predominance of grass. The hypotheses to be tested also occur at a slightly lower rate in high-traction grasses in the northern with respect to the NRL data are that basketball, netball, volleyball and states and early in the football there will be warm-season and early- Comparisons of relative risks Table 2 – Grounds analysed in the NRL martial arts. ACL injuries are thought season3. Little is known about the season biases in a similar fashion to with 99% confidence intervals are to be very common in netball, State GROUND Grass TYPE relative risk of ACL injury at non- the AFL competition. performed using the Taylor series although the likely reason why this NSW Aussie Stadium, Sydney Bermudagrass and ryegrass professional level in Australia or in the expansion method12. is considered a higher risk sport in Telstra Stadium, Homebush Bermudagrass and ryegrass NRL competition. Australia (compared to basketball) is Methods This study also examined ACL Showgrounds, Homebush Bermudagrass and ryegrass Recently, many media commentators that it is played mainly by females, incidence data for natural grass Campbelltown Stadium Bermudagrass and ryegrass have claimed an increase in injuries on who have a much higher relative risk HIC data for cruciate ligament surfaces in the NRL to see whether or Leichhardt Stadium Kikuyugrass dry sporting fields, possibly caused by for ACL injuries than males9, 10. primary reconstructive surgery from not there is a northern (warm-season) OKI Jubilee Stadium, Kogarah Kikuyugrass and ryegrass drought in Australia and subsequent the decade July 1994 to June 2003 in bias, similar to that seen in the AFL. Brookvale Stadium Kikuyugrass and ryegrass The first section of this study water restrictions in major centres4, each Australian state and territory was Penrith Stadium Kikuyugrass and ryegrass examines available data for operations A player status for all first grade 5. Unfortunately there is no national downloaded from the website Energy Australia Stadium, Bermudagrass, ryegrass and performed on the cruciate ligaments players in the NRL was kept by the injury surveillance system in Australia Newcastle Kikuyugrass across Australia to see whether there author over the time period 1999- to investigate these claims. A national http://www.hic.gov.au/statistics/ WIN Stadium, Wollongong Bermudagrass and ryegrass is evidence of any northern (warm- 2004 inclusive, based on media sports injury insurance scheme, the dyn_mbs/forms/mbs_tab4.shtml. Parramatta Stadium Bermudagrass and ryegrass, season) bias at the community level. reports of injuries. Where players 2003-04 some annual bluegrass Accident Compensation Corporation Estimates of the number of ACL injuries The item numbers which were were missing through injuries and (‘poa’) (ACC), exists in New Zealand6. in Australia can be made, as the Health assessed were 49536, 49539 and the diagnosis was available in the Express Advocate Stadium, Bermudagrass and ryegrass Although New Zealand has a superior Insurance Commission (HIC) provides 49542, which cover all primary media, a record of injury was kept. Gosford system of monitoring injuries that details of the number of item numbers cruciate ligament reconstructions. Media reports are definitely not 100% Toyota Park, Cronulla Bermudagrass and ryegrass occur in sport, its methods are not claimed for each procedure under Item 49551 was not included, which accurate, yet for serious diagnoses Queensland Suncorp Stadium Bermudagrass and ryegrass perfect because of lack of exposure Medicare in each of the states and is used for revision surgery for 49536, like ACL tears in professional sport ANZ Stadium Bermudagrass and ryegrass data (number of sports participants and territories of Australia each month, 49539 and 49542, where either the the accuracy probably approaches Dairy Farmers Stadium Bermudagrass matches played). There is also little 13 with data going back to July 1994. The first operation has failed or the ACL 100% . ACL injuries are so important ACT Canberra Stadium Ryegrass climatic variation between the different second section of the study examines has been re-injured. and serious (particularly the vast Melbourne Olympic Park Ryegrass regions of New Zealand to test any ACL incidence in the NRL competition Participation figures for various states majority which require immediate New Zealand Ericsson Stadium Bermudagrass. ryegrass and hypothesis based on geographical annual bluegrass to look at both the geographical were taken from the report by the surgical reconstruction) that, if a first differences. and temporal spread of ACL injuries ABS of Participation in Sport and grade player suffers one in a major In the United States, ACL injuries in occurring in first grade matches. Physical Activities 1999-200011. game, it is almost certainly reported the NFL show a strong early-season extensively in the media. Surface One hypothesis to be tested is that Population figures were taken from bias for matches played outdoors on characteristics for each stadium there will be a northern (warm- the Australian Census 2001. Astroturf, but not indoors7. There is were assessed by the primary author season) state bias for number of a small early-season bias for matches The ACT and Northern Territory (who as club doctor for the Sydney reconstructions performed in males, played on natural grass. The Astroturf are territories rather than states, but Roosters visited each ground once due to the popularity and high risk of data is consistent with the observation will be referred to as states for the per year on average) in conjunction the football codes, and the expected that shoe-surface traction on Astroturf purposes the data presentation and with Michael Finch, the ground risk that warm-season grasses in positively correlates with the ambient discussion. manager for Aussie Stadium (Table 2). Australia may pose a greater risk 20 Sport Health VOLUME 23 – ISSUE 4 • SUMMER 2005-06 21 A C L injury risk A C L injury risk Results cooler states of Tasmania, Victoria, season (17.1/1000 games) and Table 3 – Primary cruciate ligament reconstructions performed in the private medical system in Australia over South Australia and the ACT. grounds with a kikuyugrass profile in the decade July 1994 - June 2003 The states and territories of Australia the early season (26.9/1000 games), Table 8 shows the percentage of State NSW VIC QLD SA WA TAS ACT NT AUST are listed in Table 1, along with the although kikuyugrass stadiums had various populations estimated to have Cruciate ligament 18822 12165 8145 5056 5580 671 1423 584 52446 most common football codes played, higher absolute rates of ACL injury. undergone cruciate reconstruction reconstructions proximity to snowfields and expected The relative risk for kikuyugrass over the decade July 1994-June Males aged 15-44 11869 7241 5113 2989 3456 404 794 352 32218 major grass types on football fields. compared to bermudagrass was 1.58 2003. Although there are many Females aged 15-44 5360 4017 2386 1763 1733 232 493 194 16178 (95% CI 0.80-3.11). The number of cruciate ligament assumptions and systematic errors reconstructions performed in the within these estimations, the errors There was however a strong early- Table 4 - Population for states of Australia (by state and for males aged 15-44), 2001 Census private system over the decade may be similar for each state. season bias, with 33 ACL injuries State NSW VIC QLD SA WA TAS ACT NT AUST 1994-2003 are listed in Table 3. The Table 9 shows the risk for each occurring in rounds 1-13 of the NRL Population (total) 6593840 4784260 3592503 1519607 1874670 483666 322089 197780 19368414 majority of these were in people state compared with the Australian season and only 16 occurring in Males aged 15-44 1358610 1006297 763135 307897 405864 91853 72743 51678 4058077 aged 15-44, with reconstructions averages (including 99% confidence rounds 14-26 or the finals (risk ratio Females aged 15-44 1367095 1026791 778122 304903 404386 95058 74477 47754 4098586 more common in males than females. intervals for the rows involving male 2.1, 95% CI 1.1-3.8).