e obtained from the annual SARU injury surveillance project that forms part of the BokSmart National Rugby Safety Programme.18 Video footage containing the concussion events at the under-18 Craven Week tournament was also accessed for analysis from the SARU video database.
Before every tournament, all tournament doctors were informed of the most recent concussion protocols and consensus documents to evaluate and manage concussion. World Rugby (then called IRB) Regulation 10 (http://www.worldrugby.org) and SARU Concussion management protocols (http://www.boksmart.com) were initially used in 2011 and 2012; these were based on the previous 2008 Concussion Consensus Statement.22 From 2013 onwards, the updated 2012 Concussion Consensus Statement,1 World Rugby Regulation 10 and SARU Concussion protocols were used. These were circulated to the tournament doctors and discussed with them.
Video footage was analysed using Sports Code elite V.6.5.1, using an Apple iMac (Apple, USA) positioned at eye level. The analysis software allows control over the time lapse during each movement, and the recording and saving of each coded instance into a database. During the analysis, the analyst is at liberty to pause, rewind and watch the footage in slow motion. The highest frequency the analyst was able to slow down the motion of the footage was 25 Hz (25 frames per second).
Each concussion was analysed using a list of concussion descriptors that were specific to describing the injury mechanism of concussion but non-specific to the phase of play (tables 1 and 2). For example, acceleration of the head, head position precontact and whether the contact was an anticipated hit. The list was largely adapted from the ‘heads-up checklist (HUC)’, a standardised observational tool designed to describe situational factors and injury mechanisms related to concussion in ice hockey.12 Subsequent to the specific analyses of the mechanism of concussion injury, descriptors for the phase of play (ie, tackle, ruck or aerial collision) in which the concussion occurred were analysed. Tackle descriptors were analysed in similar manner to Hendricks et al.19 ,20 Video analysis research for the ruck and aerial collision is limited, and therefore descriptors for the ruck and aerial collision were based on coaching resources and consultations with rugby coaches, sports scientists and rugby administrators. Depending on the phase of play in which the injury occurred (eg, tackle, ruck or aerial collision), all the player's previous non-injury situations in the same phase of play, within the same match and previous matches were identified and analysed as controls. Match situational variables were analysed for all injury and non-injury events.
Statistical analyses was performed by STATA V.12. Given the small sample size, descriptive statistics are reported. Frequency percentage tables were generated for each descriptor under injury and non-injury events. Concussion incidence rate was based on the player match-exposure and the number of concussion events and reported per 1000 player match-hours with corresponding 95% CIs.
Three players were randomly selected using a random number generator (http://www.random.org/). Each player's injury and non-injury events were coded on two separate occasions, separated by at least 1 week. The κ statistics were used to test the intrareliability of the coder for each of the three players. For concussion variables κ=0.92, for match situation κ=0.98 and for ruck κ=0.96. For the tackle, precontact κ=0.77, contact κ=0.74, postcontact κ=0.91, and performance outcome κ=1. The κ values between 0.81 and 0.99 represent ‘excellent agreement’, and values between 0.61 and 0.80 represent ‘substantial agreement’.
The average (±SD) age, height, mass and body mass index of the concussed players was 18.1±0.4 years, 183.2±7.9 cm, 90.2±10.1 kg and 26.9±2.6 kg/m², respectively. For the 10 players analysed in this study, 5 of the concussed players were not wearing protective gear (ie, neither a mouthguard nor a scrum cap), 4 players were using a mouthguard and 