Sports-related concussions in New Zealand amateur rugby union and league: identification, assessment and impact forces involved
King, Douglas Alistair
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What are the costs and frequency of concussions in sports in New Zealand and how can we identify and measure them? The overarching aim of the thesis was to examine sports-related concussions in New Zealand amateur rugby union and rugby league via identification, assessment and impact forces involved in concussion incidents. Methodological approaches included epidemiological analysis, a survey, prospective cohort analysis utilising data obtained from the King-Devick (K-D) saccadic test, the Sports Concussion Assessment Tool 3rd edition (SCAT3), and impact analyses utilising instrumented mouthguards. Identification of the costs, and epidemiology, of concussions in New Zealand was undertaken by an epidemiological analysis of the Accident Compensation Corporation database, then via a survey of 213 amateur rugby league players. Of 20,902 claims ($NZD 16,546,026) recorded between 1st July 2001 and 30th June 2011, 1,330 (6.4%) were Moderate to Severe Claims. In reviewing 213 amateur rugby league player concussion questionnaires, there were an average of 4.0 ± 2.6 concussive injuries per player in 2010 to 2012. After-match assessment of players with the K-D test identified 22 concussive incidents over a single competition season for senior amateur rugby union. Although five concussive incidents were witnessed, 17 were unrecognised at the time of the event, but identified post-game with the K-D, and later confirmed via medical assessment by a physician. For every 1 point reduction in the post-injury Standard Assessment of Concussion (SAC) components of the SCAT3, there was a corresponding increase (worsening) of K-D test times post-match for changes in orientation (2.9 s), immediate memory (1.8 s), concentration (2.8 s), delayed recall (2.0 s) and SAC total score (1.7 s). Identification of the magnitude, frequency and distribution of head impacts in real-time occurring during rugby union matches was evaluated using an instrumented mouthguard. A total of 20,687 impacts >10g were recorded during matches over the 2013 domestic club competition season. The mean number of impacts per player was 563 ±618 resulting in 95 ±133 impacts to the head per player, per match. While trying to compare the results with other published studies, an issue in the way head impact data were reported was identified. A retrospective review was conducted to compare published data reporting impact thresholds obtained from accelerometer systems with data recorded at the 10g impact threshold obtained from 38 senior rugby players in New Zealand. The comparison was undertaken to identify the percentage, and number, of impacts that were removed with different reporting thresholds. This PhD research has contributed knowledge regarding costs of concussions in seven sporting codes; the percentage of concussions medically managed in a cohort of amateur rugby league players; the benefit of a sideline remove-from-play screening tool for concussions; and a description of the magnitude, frequency and duration of impacts to the head in senior amateur rugby union players. This PhD research also identified the need for a consensus approach to the reporting of impact biomechanics in future studies. As a result of this research a new cyclical model of concussion management has been developed.