Discussion

The static MRI study revealed that almost half of the 127 rugby players surveyed in the 2002–2003 and 2003–2004 seasons presented abnormalities of the cervical spine, most of which were degenerative discopathies often associated with disc hernia. This result is similar to that obtained with the static component of the second MRI survey conducted on 79 different rugby players in the 2004–2005 and 2005–2006 seasons. Players aged >21 years presented significantly more anatomical abnormalities than younger players in the first study. In the second study, while the point estimate for the relative risk of having anatomical abnormalities for older players was also higher than for younger players, the uncertainty in the estimate meant that the difference between the groups was unclear, and further study with larger samples is required to clarify the extent and direction of the effect. Having a narrower cervical spine canal (MCR>0.6) increased the risk of presenting anatomical abnormalities by up to three times for both static studies. The dynamic component of the second MRI survey, used for the first time in screening of asymptomatic rugby players, showed changes in the proportion of abnormal MCRs compared with the static examination of the same individuals. Dynamic MRI images provided a more detailed analysis of the cervical spine anatomy, with important variations of the MCR observed between flexion and extension as previously demonstrated in patients diagnosed with degenerative cervical spine changes.11

Spinal changes and athlete injuries have been routinely monitored through MRI for the past decade.5 12 13 However, such studies in rugby players have always been conducted using static protocols similar to the one used in the present study.14 The novel dynamic protocol in the second study allowed diagnosis of abnormalities of the spinal canal that were not observed or were inconclusive with the static MRI examination alone. This trend had already been reported in a population of patients with degenerative cervical spine pathology and for whom detection of stenosis using cinematic MRI was increased by 22% in flexion and by 65% in extension.11 To a lesser extent, there were 6% (4/70) more abnormal MCRs measured with the dynamic MRI technique in the present study, and therefore the dynamic MRI technique previously described8 and applied in the present cohort of players provides a sensitive and reproducible method that could be easily set up with any MRI scanner. MCRs obtained with static MRI and considered at the limit of the “normality” criterion for decision making were more sensitively assessed by using the dynamic protocol. It is therefore recommended that MCR measurements between 0.6 and 0.7 for the static protocol be closely reviewed with a combination of clinical investigation (eg, complete neurological examination), including MRI observations of the cervical spine region between flexion and extension to reduce the number of falsely abnormal MCRs.

The proportion of players <21 years diagnosed with a narrow cervical spine canal was clinically important. Although at the beginning of their professional career, these players have been participating in rugby since the age of 12 to 14 years, and therefore, stenosis of the cervical spine cannot be considered exclusively congenital but includes a developmental component as well. Progressive narrowing of the cervical spine has been shown to be induced by biomechanical factors linked to the practice of rugby as opposed to control athletes competing in non-collision sports.5 Rugby players also show reduced cervical mobility compared with non-rugby players, and this abnormality is accentuated between young and older players.15 In addition, an abnormal MCR seems to be more apparent if measured throughout the range of motion of the spine.11 16 Translation of the C2 vertebrae relative to C7 proportionally diminishes throughout the cervical range of motion, and as such, leads to a significant reduction of the physiological lordosis that protects the cervical spine from impacts. Parameters such as angulations between maximal flexion and maximal extension and translation of C2 relative to C7 could help in quantifying abnormalities acquired through professional-level rugby practise, and these players could be regularly monitored throughout their career. In the future, dynamic MRI protocols could be improved by exerting forces onto the players’ cervical spine, in order to recreate game conditions while screening their cervical cord.17 Putting the players’ spines under load could also be done by using a stand-up MRI (Fonar), but this protocol would have a high cost and presents constraining technical conditions such as the magnet’s weight (about 130 tonnes).

Before rugby union became professional in the 1990s, physical impacts to the spine mainly affected the front row players, whose compact physique was valuable for winning the possession of the ball in scrums.18 In contrast, fast-running players like backs would generally avoid tackles from the opposite team, aiming at the score line. The modern rugby game seems to be more physically involved than before the professional era, with more physical confrontations and impacts between players, regardless of the position they hold on the field.19,–,22 In response to rugby becoming more of a collision sport, players’ morphology has evolved, and their average size and weight have significantly increased over the past decade.20 22 More demanding game and training schemes may compromise players’ longevity at a professional level, but more importantly, their ability to recover from injuries and from asymptomatic chronic impacts.5 14 23 24 It is therefore critical to consider previous injuries—as defined by the Rugby Injury Consensus Group21—as well as existing pathology (whether musculoskeletal or systemic) when assessing players’ fitness and their return to play, in order to minimise risks of injury. In France, screening for cervical spine abnormalities is compulsory for professional front row players who are theoretically more at risk of cervical spine acute and chronic impacts, in order to successfully obtain a certificate of “aptitude to play”. However, backline players are increasingly involved in tackles, mauls, clearing-out phases and associated rucks, and they should also be included in screening surveys for cervical spine abnormalities.25 The risk of cervical spine injuries is related to extrinsic factors directly associated with the game, including scrummaging, tackles or foul play, as well as intrinsic factors such as anthropometric identity, physical training, recovery period following injuries and fatigue. All these factors are often difficult to consider simultaneously3 but are essential for the management of injuries in professional rugby.

Serious cervical spine injuries are fortunately rare in rugby union but dramatic when they do occur.26 27 In contrast, chronic degenerative abnormalities induced by repeated injuries are more frequent, and long-term consequences may well be underestimated, although they form the submerged part of the iceberg.28 The prime aim of cervical spine screening is to prevent players with morphological abnormalities from putting themselves at a higher risk of injuries than individuals without such anatomical predisposition. Such assessment uses morphological criteria described by Torg et al,9 and the imaging technique chosen to examine the cervical spine remains a crucial factor in order to provide evidence for players and to some extent coaching teams, to make an informed choice about continuing to play.

Today, sports medicine specialists are primarily guided by clinical examinations, and sensitive imaging screening is only used to advise on the players’ suitability to continue to play rugby or to return to play following injury.29 30 This decision usually belongs to the team management. How a medical contraindication to play is used in the decision-making, especially in the presence of cervical spine pathology, becomes especially important given the availability of improved sensitivity of imaging techniques such as dynamic MRI. Yet, a key question that remains unanswered is the specificity of such tests with respect to predicting which players would go on to sustain permanent functional impairment. In the absence of such evidence, the current guidelines for contraindications to play are largely based on clinical expertise. Therefore, it seems evident that consultation of all parties—team management, physiotherapists and sports medicine clinicians—is essential in arriving at a decision that is in the best interest of the player.