Possibly less important, but nonetheless interesting, is the difference brought about by professionalization in rugby union. Another 2014 BJSM paper examines the injuries to the shoulders of French Rugby Union players for 2008-2013. The paper presents a fascinating range of comparisons. For example, professional rugby players that suffer a shoulder injury during a tackle with an opponent differ from non-professionals. In professional rugby it is the tackler that is likely to suffer whereas it is the tackled player that suffers more injuries outside the professional game. Yohan Bohn (Racing-Metro 92) and his co-authors show that the incidence and severity of shoulder injuries increases with age. The relative importance of shoulder injuries also vary with gender.
In terms of positions on the rugby team, the positions most likely to suffer shoulder injuries are third row (back row) forwards, front row forwards, and centres. The presentation of the injuries by positions is slightly misleading because there are three front row forwards, three back row forwards, but only two centres. Therefore, it is not surprising to find that the positions with the lowest incidence of injuries have only one player - full back, scrum-half, and fly half. It is a pity the injuries were not listed by player number/position for all fifteen players. This is done for front-row forwards and it shows that players wearing number 1 have the highest shoulder incidence among front row forwards. Next up is the player wearing number 3 and then the player carrying number 2.
The player carrying number 2 is the hooker. Number 1 is known as a loose-head prop and number 3 is known as a tight-head prop. As the players lock heads, the hooker and tight-head prop have an opponents head to either side. The loose-head prop is bound by only one other player.
At scrum time the hooker is positioned in the middle of the three front row forwards as they collide with the opposition. It seems this position protects the hooker from injury at scrum time according to a third BJSM paper. Alison Taylor, Simon Kemp, Grant Trewartha and Keith Strokes examined scrum injury risk in English professional rugby. The hooker sustained 15% of the reported scrum injuries. However, the average for the other two front row forwards was 36.5% each. This is a massive 88% of reported scrum injuries falling on 3 of the 8 players involved in the scrum. The most interesting fact of all is the coincidence between injury, player position and whether the scrum collapsed or not. Almost 91% of the injuries to loose-head prop forwards were associated with collapsed scrums. By contrast, 62.5% of injuries to tight-head props, and 83.3% of injuries to hookers, occurred when the scrum did not collapse. As to the reason for this difference, the authors call for more research. It is a pity they did not speculate on the reasons.