Jan Ekstrand, Håkan Bengtsson, Markus Waldén, Michael Davison, Karim M Khan, Martin Hägglu, http://dx.doi.org/10.1136/bjsports-2021-105407
The recently published paper from Ekstrand et al. describes the incidence of hamstring injuries in male professional football players over consecutive 21 seasons (2001/02 to 2021/22). The authors also analyse the time trends of hamstring muscle injuries over the most recent eight seasons (2014/15 to 2021/22) and in addition, they outline hamstring injury location, mechanism and recurrence rate.
Data was collected from the Elite Club Injury Study (ECIS). The individual player exposure and the time-loss injuries of 3909 players were recorded by the medical staff of 54 football teams from 20 European countries, which all qualified for the UEFA Champions League (UCL) group stage.
A hamstring injury was defined as a ’complaint sustained by a player that resulted from a football match or football training and led to the player being unable to take full part in future football training or match play‘. In the beginning injuries were solely classified by using the Orchard Sports Injury Classification System (OSICS); however, since 2011/12 the Munich Muscle Injury Classification was also used to classify hamstring injuries. Between 2001/02 and 2021/22, 2636 hamstring injuries were documented representing 19 % of all reported injuries. Compared to the first recorded season, the proportion of diagnosed hamstring injuries and the proportion of all injury absence days caused by hamstring injuries have doubled by 2021/22 (from 12 % to 24 % and from 10 % to 20 % respectively). Specifically during the last 8 consecutive seasons the incidence (Number of injuries per 1000 player hours, 6,7 % annually) and the burden (Number of lay-off days per 1000 player hours, 9.0 % annually) of hamstring injuries during training and match play have increased significantly. The hamstring injury incidence was 10 times higher during match play than during training and the median lay-off following a hamstring injury was 13 days. Overall it was reported that during a season 20 % of players missed training or match play due to a hamstring injury and 8 hamstring injuries can be expected in a 25-player squad per season. In addition, there were more structural than functional injuries classified, whereby these structural injuries were associated with a longer lay-off time than the functional ones (median absence 17 vs. 6 days).
In terms of the injury mechanism and location, this study confirmed the existing knowledge that sprinting was the most common mechanism and the biceps femoris injuries were more frequent than semitendinosus and semimembranosus injuries. However, further details concerning which phase of sprinting (i.e., terminal swing, early stance) or which exact part of the biceps femoris (i.e., proximal, distal, T-junction, long/short head or myofascial, myotendinous, or tendinous) were not described. Regarding the recurrence rate, 18 % of all recorded hamstring injuries were recurrences, from which early recurrences (within 2 months) made up 69 %. Recurrences were nine times more likely to occur in matches than in training. An increased recurrence rate specifically within the first 2 months could indicate that return to full training/competition may be too early for some types of injuries. Taking into consideration that the healing time of different kind of tissues takes longer than others (i.e., connective tissue), healing may not be sufficiently completed to sustain certain thresholds of high-speed exposure. The authors hypothesize that the reason for the increasing number of hamstring injuries could be because the intensity of elite’s football matches has significantly increased, which has led to more high intensity activities in professional footballers compared to the past. Another explanation may be related to a more crowded match calendar of players associated with fewer training sessions during the (pre-) season period considering that more training sessions may lower the injury risk. In summary, this publication highlights the increasing burden of hamstring injuries in elite football. More effort is needed to understand better how to prevent the first injury and how to manage injured players more effectively to reduce the risk of re-injuries.
Autoren
is a consultant orthopaedic and trauma surgeon who is currently working as a club doctor at Chelsea Football Club. Prior to joining CFC, he was the medical director of Lanserhof at The Arts Club in London for over 4 years. Before moving to the UK, he worked for several years at ATOS MediaPark Klinik Cologne, MVZ Ortho Königsallee Düsseldorf, Lans Medicum Hamburg and he was a club doctor of Viktoria Köln.
