Discussion

Absence due to match injuries was not significantly higher in any of the individual playing positions within the forwards and backs in the current study. This is consistent with other large rugby union epidemiological studies where few differences have also been reported in injury incidence between positions.17 21 22 Nevertheless, players in every position still missed a significant number of days of absence due to match injuries (forwards: 1569 days of absence/1000 player-hours equivalent to 33 days of absence per match due to forwards injuries; backs 1507 days of absence/1000 player-hours equivalent to 28 days of absence per match due to backs injuries). There is a clear need to design and implement injury-prevention programmes for all players to reduce this injury burden.

Three main body locations (the shoulder, knee and ankle/heel) for forwards and three main body locations (the shoulder, hamstring and knee) for backs caused more than 150 days of absence/1000 player-hours; this constituted more than half of all days of absence due to match injuries. As a result, injury-prevention strategies for injuries to these four body regions should be prioritised. Studies implementing injury-prevention interventions in other non-collision sports have been successful at reducing the incidence of injury to all of these lower-limb locations (hamstrings, knees and ankles) by utilising exercises designed to improve parameters such as propriception, core stability and muscle strength.23,–,30 While the need for more research into the effectiveness of injury-prevention interventions in collision sports is recognised, it is likely that interventional approaches used in other sports would be transferrable to the rugby union population. Fewer studies have attempted to prevent shoulder injuries by using controlled injury-prevention interventions, although reducing shoulder capsular tightness31 and eccentric resistance training32 have been highlighted.

Despite the lack of differences in total absence due to injury for each playing position and the identification of three principal body regions for injury-prevention programmes for the majority of forwards and backs, significant differences in injury profile between players in different playing positions were reported. These can be used to focus further on injury-prevention programmes.

Loose-head props and hookers both exhibited similar injury profiles. Cervical injuries, in particular cervical disc/nerve root injuries, caused significantly greater absence compared with other forwards. It has long been established that the risk of sustaining a cervical injury is higher in front-row forwards, in particular during scrummaging;8 11 33,–,36 however, in the current study, tackling was the most common cause of cervical disc/nerve root injuries for these players. Nevertheless, the greater impact forces on scrum engagement and the loads transmitted and absorbed by front-row forwards during scrummaging16 37 may have predisposed these players to cervical injuries. This may have been exacerbated by the greater use of the neck extensors during scrummaging for loose-head props and hookers. Development of the cervical musculature may be of benefit in preventing cervical injuries in these players,38 although the detail of the intervention needs more investigation.

Shoulder rotator cuff injuries also caused significantly more absence in loose-head props and hookers. A large proportion of these injuries to loose-heads were due to scrummaging (66%), although the majority of these were to their right shoulder (75%), which is bound to the hooker rather than the opposition. None of the rotator cuff injuries to hookers were sustained during scrummaging. Factors that might result in these players being more predisposed to rotator cuff injuries14 include rotator cuff weakness,39 fatigue-induced propriception and skill deficits40 41 and suboptimal glenhumeral alignment.42 The high impact forces and loads experienced during scrummaging16 37 and the repetitive demands placed on hookers from throwing the ball into the lineout in matches and training may also increase the risk of injury to these players.

Tight-head props exhibited a different injury profile from the other front-row positions. Lower leg and lumbar spine injuries caused significantly more absence compared with other forwards due to a significantly greater absence from calf muscle strains, lumbar disc/nerve root and lumbar soft tissue injuries; trends that have been identified previously.11 43 The majority of all of these injuries were sustained during scrummaging (54–67%). It has been shown that greater loads are transmitted by tight-head props during scrummaging than by all other forwards.16 The inability of the lumbar spine and calf musculature of tight-head props to adapt to these high loads therefore needs addressing. Improving scrummaging technique to ensure the lumbar spine is maintained in a strong neutral position by improving neuromuscular control44 and specific strength training for the lumbar and calf regions are plausible interventions.45 46 The association between lumbar spine pathology and calf muscle symptoms or strains should also not be overlooked.47

Absence due to lateral ankle ligament injuries was significantly higher in second-rows, and a higher proportion of these injuries were sustained in the lineout (21%) compared with other forwards. This is similar to previous findings15 where inversion ankle injuries on landing from a lineout lift was felt to be a significant risk factor. Landing from a jump is a common cause of ankle injuries in other sports such as soccer48 and volleyball.49 Injury-prevention interventions that have focussed on adopting the correct lower-limb alignment when landing have been successful at reducing the incidence of ankle injuries in other sports.23 27 30

Blind-side flankers had more absence due to thigh injuries than other forwards, in particular due to hamstring muscle injuries. The majority of these injuries were sustained during running (86%), typically during sprinting or running at high speed.28 50 The back-row perform between 1.4 and 2 times as many sprints in a match compared with other forwards.51 52 Eccentric strengthening of the hamstrings,10 24 improving hamstring flexibility53,–,55 and sports-specific conditioning28 have all been successful at reducing the incidence of hamstring injuries.

Absence due to neck injuries, in particular cervical facet joint injuries, was significantly higher in open-side flankers. The tackle is the most common cause of absence due to injury largely because it is the most frequent contact event.56 Open side flankers make more tackles than players in other positions during a match,57 and the majority of open-side neck injuries were sustained in the tackle (63%). Open-side flankers may benefit from gains in cervical musculature strength38 to improve their ability to adapt to high impact forces on their neck, as well as improvements in tackling technique previously advocated.17

The significant differences in the injury profile of the number-8, namely greater absence due to arm and hand injuries and foot injuries, were largely as a consequence of injuries for which injury-prevention strategies are less well validated, namely wrist, hand and foot fractures and biceps muscle injuries.

While absence due to shoulder and knee injuries was high in scrum-halves, as with other backs, absence due to lumbar spine injuries, more specifically lumbar disc/nerve root injuries, caused significantly more days of absence for scrum halves than for other backs. The repeated lumbar flexion and rotation necessary to pass the ball off the ground might predispose these players to lumbar injury. Optimising global and local muscular control of this combined lumbar movements is advocated as a possible injury-prevention strategy.44 45 However, the repeated lumbar flexion and rotation may have positively conditioned the hamstrings of these players by increasing hamstring flexibility53,–,55 and eccentric strength10 24 resulting in the significantly lower absence due to hamstring muscle injuries observed.

Fly-halves had a significantly greater absence due to thigh injuries, specifically hamstring muscle injuries, compared with other backs. A high incidence of hamstring muscle injuries in sports that involve a lot of kicking has been previously reported58,–,60 and the frequency with which fly-halves kick the ball during a match compared with other positions may predispose them to an increased risk of hamstring muscle injury, although this has yet to be confirmed. Greater absence due to arm and hand injuries was largely as a consequence of injuries for which injury-prevention strategies are less well validated, namely elbow joint injuries, while the significantly lower absence from shoulder injuries may be due to fly-halves making fewer tackles in a match compared with other backs.57

The observation that absence due to head injuries, in particular concussions, was significantly higher in centres compared with other backs has been reported previously.13 Absence due to neck and shoulder injuries was also significantly higher in centres compared with other backs, and the most common injury event was tackling (42–68%). High speed going into the tackle, high impact force and contact with the tackler's head and neck have all been identified previously as significant risk factors for tacklers.57 61 Centres tend to make more tackles in a match than other backs57 and have been significantly more prone to injury when tackling than players in other positions.61

While absence due to thigh injuries was high for the majority of backs, it was significantly higher for wingers compared with other backs. One might expect that this greater absence would be due to hamstring muscle injuries because of the greater number of sprints performed in a match by outside backs52 and as a consequence of the faster running speed of these players. While absence due to hamstring muscle injuries was high in wingers, it was the absence due to thigh haematomas that was most significant.

The significant differences in the injury profile of the full-backs, namely greater absence due to groin/hip/buttock injuries and chest injuries, were largely as a consequence of injuries for which injury-prevention strategies are less well validated, namely groin nerve entrapment injuries, costochondral/sternal injuries and rib fractures/contusions.

We believe that this study demonstrates the need for injury-prevention programmes for all players and that playing position should be considered as an independent risk factor for injury and consequently as a driver for individualised injury-prevention programmes. While significant absence due to injury to three body regions was relatively consistent for all positions within the forwards (shoulder, knee and ankle/heel) and the backs (shoulder, hamstring and knee), significant differences in the injury profile between positions demonstrate the need for injury-prevention programmes to be position-specific. Such programmes should also be player-specific and recognise the importance of focusing on a player's previous injury history because of the significantly greater absence due to recurrent injuries compared with new injuries.17 In the future, our understanding of differences in the injury profile between different positions could be further enhanced by a greater understanding of the position-specific demands of the game and the mechanism of injury.