 available for analysis due to the poor quality of the video footage. On the basis of the 10 injury events (5 tackle events—4 tackler injured and 1 ball-carrier injured; 4 ruck and 1 aerial collision), 83 non-injury events were identified (19 tackle, 61 ruck and 3 aerial collisions). The concussion event was first analysed in a similar fashion to that by Hutchison et al,13 using descriptors specific to concussion. Thereafter, both the injury and non-injury events were analysed using coding variables for each phase of play, and for general playing situational variables as outlined by to Hendricks et al.19 ,20 The authors were granted access to these databases by SARU and the UCT Human Research Ethics Committee (injury database HREC Ref: 438/2011; video database HREC Ref: R042/2013).
Injury data collection
The under-18 Craven Week tournament is an annual fixture aimed at showcasing the country's top schoolboy rugby players. Often a precursor to provincial and national selection, these tournaments are highly contended and thought to be associated with a high injury incidence.15 Details about each injury sustained during the tournaments were recorded on an injury collection form that was designed on the basis of the Consensus Statement for injury surveillance.21 Information collected included the player's team, body height, body weight, age, whether the player had medical insurance or not, and the presence or absence of protective gear during the inciting event. Written informed consent allowing for the analysis of recorded information was provided prior to the tournament by all players and by the player's parent or legal guardian in the event of the player being younger than 18 years of age. In addition, assent was required by the injured player or by the player's parent or legal guardian at the time of recording the injury. If a player, by virtue of the nature of their injury on the day, was unable to give written assent, verbal assent was acquired after an explanation of the nature of the study was given.
Data were 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 conc