Concussion in American Versus European Professional Soccer: A Decade-Long Comparative Analysis of Incidence, Return to Play, Performance, and Longevity

The Effect of Primary ACL Reconstruction on Career Longevity in English Premier League and Championship Soccer Players Compared With Uninjured Controls: A Matched Cohort Analysis

BACKGROUND

Because of the multitude of variables that affect the retirement decisions of professional soccer players, it has proven difficult to isolate the effect of undergoing anterior cruciate ligament (ACL) reconstruction (ACLR) on career longevity.

PURPOSE

To compare the career longevity of professional soccer players after a primary ACLR with that of an uninjured matched control cohort.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A retrospective review of a consecutive series of primary ACLR was performed between 2008 and 2018 in professional male soccer players from the senior author's practice. Each athlete with ACLR was matched to 3 control athletes who had not undergone ACLR according to age, league, playing position, and preinjury game appearances/minutes played. Player career statistics-including league, game appearances, and game minutes-were compiled for each year until retirement or July 1, 2022.

RESULTS

A total of 82 soccer players in the English Premier League or Championship at the time of their primary ACLR were matched to 246 control athletes. The mean career length after ACLR was 6 ± 2.6 years, while that of the matched control athletes was 7.6 ± 2.8 years (P < .001). After primary ACLR, an athlete had a 2 times greater chance of retirement compared with the matched control athlete (hazard ratio, 2.19; P < .001). At 5 years after ACLR, 16% of athletes had retired from professional soccer, while 8.5% of the matched cohort were retired (P = .060). By 10 years, 72% of the ACLR cohort had retired compared with 43% of the matched cohort (P < .001). Forwards were more likely to have shortened careers compared with goalkeepers (P = .021); however, no significant differences were observed between midfielders, defenders, and forwards. Within the ACLR cohort, a contralateral ACL tear during the athlete's career caused a 2.30 times (P = .022) increased chance of retirement compared with athletes with only 1 ACL tear during their career. Mechanism of injury, meniscal pathology, graft rerupture, and chondral lesions did not affect career length.

CONCLUSION

Professional male soccer players who underwent ACLR had decreased career length by approximately 1.6 years compared with a matched player cohort.

A Thirteen-Year Analysis of Facial Fractures among Professional Soccer Players

This study aims to identify the epidemiology and effects of facial fractures on return to play (RTP) in Major League Soccer (MLS) and the English Premier League (EPL). A total of 39 MLS players and 40 EPL players who sustained facial fractures from 2007 to 2019 were identified. Data on player demographics, the injury, and the impact of their injury on RTP were collected. Elbow-to-head was the most common mechanism of injury (20.3%). The most common fracture involved the nasal bone (48.3%). Most players (90%) RTP the same season. Players who sustained nasal fractures missed significantly fewer games (p < 0.001) than those who suffered other craniofacial fractures. Players treated surgically missed significantly more games (3.21 vs. 0.71, p = 0.006) and days (30.1 vs. 8.70, p = 0.002) than those managed nonoperatively. Significantly more EPL players who sustained facial fractures wore headgear upon RTP compared to MLS players (82% vs. 56%, p <0 .01). Most professional soccer players who sustain a facial fracture RTP the same season, but their recovery time can vary depending on the type of fracture, injury management, or injury severity. Our findings can help inform future craniofacial injury management as well as guidelines on player safety and fracture prevention.

Median Time to Return to Sports After Concussion Is Within 21 Days in 80% of Published Studies

PURPOSE

To perform a systematic review of the literature and evaluate the return to play (RTP) time frame after a concussion diagnosis. Our secondary purpose was to analyze and compare different prognostic variables affecting concussions, time to return to school, time to symptom resolution of concussive symptoms, and time each patient spent in the RTP protocol.

METHODS

A PubMed, Scopus, Medline, Embase, and Cochrane Library database literature review was performed in August 2022. The studies needed to report, in days, the length of time a patient/athlete was removed from play due to concussion management. The Risk of Bias in Non-Randomized Studies of Interventions tool was used for risk of bias for each study, and Methodological Index for Non-Randomized Studies criteria were used for quality assessment.

RESULTS

There were 65 studies included in the systematic review and a total of 21,966 patients evaluated. The RTP time intervals ranged from 1 to 1,820 days, with 80.7% of the median RTP time frames for each study within 21 days. Preconcussion risk factors for prolonged RTP included female sex, younger age, presence of psychiatric disorders, and history of previous concussion. Postconcussion risk factors included severe symptom scores at initial clinic visit, loss of consciousness, nonelite athletes, and delayed removal from competition. The most common sports resulting in concussion were contact sports, most commonly football and soccer. Median time to return to school was 3 to 23 days. Median time to symptom resolution ranged from 2 to 11 days. Median time in RTP protocol was 1 to 6 days.

CONCLUSIONS

Median time to return to sports after concussion is within 21 days in 80% of published studies.

LEVEL OF EVIDENCE

IV, systematic review of Level I to IV studies.

Incidence of Concussion and Time to Return-to-Play in the National Rugby League

OBJECTIVES

To examine the rates of concussion and recovery time over the course of 2 seasons of the National Rugby League (NRL).

DESIGN

Descriptive cohort study.

SETTING

The NRL match play concussion injury surveillance system.

PARTICIPANTS

All NRL players who participated in the 2017 and 2018 season.

MAIN OUTCOME MEASURES

The (1) frequency of sideline injury surveillance identified head impact events in real-time during the games, (2) frequency of head injury assessments conducted by the medical staff, (3) frequency of medically diagnosed concussions, (4) number of days to medical clearance to return-to-play, and (5) number of games missed after concussion.

MAIN RESULTS

There were 472 head injury assessments conducted during the games and 149 medically diagnosed concussions over the course of 2 NRL seasons (1 concussion every 2.70 games). The median number of days until medical clearance was 6 (M = 6.85, SD = 8.03, interquartile range = 4-7; range = 0-79 days). There was a statistically significant difference in the number of days to be medically cleared to return to full contact or match play between seasons (U = 3517.00, P = 0.001), and the percentage of players medically cleared to return-to-play at 5 days after injury was 60.6% in 2017 and 27.6% in 2018. Most players (87.9%) did not miss a game after injury.

CONCLUSIONS

There is approximately one concussion sustained for every 3 games in the NRL. Most players are medically cleared to return-to-play in 4 to 7 days.

Long-term postural control in elite athletes following mild traumatic brain injury

Background

Traumas to the head and neck are common in sports and often affects otherwise healthy young individuals. Sports-related concussions (SRC), defined as a mild traumatic brain injury (mTBI), may inflict persistent neck and shoulder pain, and headache, but also more complex symptoms, such as imbalance, dizziness, and visual disturbances. These more complex symptoms are difficult to identify with standard health care diagnostic procedures.

Objective

To investigate postural control in a group of former elite athletes with persistent post-concussive symptoms (PPCS) at least 6 months after the incident.

Method

Postural control was examined using posturography during quiet stance and randomized balance perturbations with eyes open and eyes closed. Randomized balance perturbations were used to examine motor learning through sensorimotor adaptation. Force platform recordings were converted to reflect the energy used to maintain balance and spectrally categorized into total energy used, energy used for smooth corrective changes of posture (i.e., <0.1 Hz), and energy used for fast corrective movements to maintain balance (i.e., >0.1 Hz).

Results

The mTBI group included 20 (13 males, mean age 26.6 years) elite athletes with PPCS and the control group included 12 athletes (9 males, mean age 26.4 years) with no history of SRC. The mTBI group used significantly more energy during balance perturbations than controls: +143% total energy, p = 0.004; +122% low frequency energy, p = 0.007; and +162% high frequency energy, p = 0.004. The mTBI subjects also adapted less to the balance perturbations than controls in total (18% mTBI vs. 37% controls, p = 0.042), low frequency (24% mTBI vs. 42% controls, p = 0.046), and high frequency (6% mTBI vs. 28% controls, p = 0.040). The mTBI subjects used significantly more energy during quiet stance than controls: +128% total energy, p = 0.034; +136% low-frequency energy, p = 0.048; and +109% high-frequency energy, p = 0.015.

Conclusion

Athletes with previous mTBI and PPCS used more energy to stand compared to controls during balance perturbations and quiet stance and had diminished sensorimotor adaptation. Sports-related concussions are able to affect postural control and motor learning.

Post-Concussive Vestibular Dysfunction Is Related to Injury to the Inferior Vestibular Nerve

Symptoms of vestibular dysfunction such as dizziness and vertigo are common after sports-related concussions (SRC) and associated with a worse outcome and a prolonged recovery. Vestibular dysfunction after SRC can be because of an impairment of the peripheral or central neural parts of the vestibular system. The aim of the present study was to establish the cause of vestibular impairment in athletes with SRC who have persisting post-concussive symptoms (PPCS). We recruited 42 participants-21 athletes with previous SRCs and PPCS ≥6 months and 21 healthy athletic age- and sex-matched controls-who underwent symptom rating, a detailed test battery of vestibular function and 7T magnetic resonance imaging with diffusion tensor imaging (DTI) and diffusion kurtosis imaging (DKI) of cerebellar white matter tracts, and T1-weighted imaging for cerebellar volumetrics. Vestibular dysfunction was observed in 13 SRC athletes and three controls (p = 0.001). Athletes with vestibular dysfunction reported more pronounced symptoms on the Dizziness Handicap Inventory (DHI; p < 0.001) and the Hospital Anxiety and Depression Scale (HADS; p < 0.001). No significant differences in DTI metrics were found, while in DKI two metrics were observed in the superior and/or inferior cerebellar tracts. Cerebellar gray and white matter volumes were similar in athletes with SRC and controls. Compared with controls, pathological video head impulse test results (vHIT; p < 0.001) and cervical vestibular evoked myogenic potentials (cVEMP; p = 0.002) were observed in athletes with SRC, indicating peripheral vestibular dysfunction and specifically suggesting injury to the inferior vestibular nerve. In athletes with persisting symptoms after SRC, vestibular dysfunction is associated with injury to the inferior vestibular nerve.

Lower Extremity Injury After Return to Sports From Concussion: A Systematic Review

Background:

Recent studies have suggested increased rates of lower extremity (LE) musculoskeletal injury after a diagnosed concussion, although significant heterogeneity exists.

Purpose:

To examine the current body of research and determine whether there is an increased risk for LE musculoskeletal injury after a concussion and to identify populations at an increased risk.

Study Design:

Systematic review; Level of evidence, 3.

Methods:

A systematic review of current literature using MEDLINE and PubMed databases was performed. Keywords included concussion, athlete, lower extremity injury, and return to sport. Inclusion criteria required original research articles written in the English language examining the rate of LE injuries after a diagnosed concussion.

Results:

A total of 13 studies involving 4349 athletes (88.1% male and 11.9% female; mean age, 19.8 years) met inclusion criteria. Athletes were classified as high school (46.1%), collegiate (17.0%), or professional (36.9%). Of the 13 studies, 4 demonstrated an increased risk of LE injury within 90 days of a diagnosed concussion (odds ratio [OR], 3.44; 95% CI, 2.99-4.42), and 6 revealed an elevated risk of injury within 1 year of concussion (OR, 1.85; 95% CI, 1.73-2.84). Increased risk was seen in professional (OR, 2.49; 95% CI, 2.40-2.72) and collegiate (OR, 2.00; 95% CI, 1.96-2.16) athletes compared with high school athletes (OR, 0.97; 95% CI, 0.89-1.05). A stepwise increase in risk of sustaining an LE injury was observed with multiple concussions, with increasing risk observed from ≥2 (OR, 2.29; 95% CI, 1.85-2.83) to ≥3 (OR, 2.86; 95% CI, 2.36-3.48) career concussions.

Conclusion:

An increased incidence of LE injuries was observed at 90 days and 1 year after the diagnosis of a concussion. Higher levels of competition, such as at the collegiate and professional levels, resulted in an increased risk of sustaining a subsequent LE injury after a diagnosed concussion. These results suggest an at-risk population who may benefit from injury prevention methods after a concussion. Future studies should focus on identifying which injuries are most common, during what time period athletes are most vulnerable, and methods to prevent injury after return to sports.

Development of a Machine-Learning-Based Classifier for the Identification of Head and Body Impacts in Elite Level Australian Rules Football Players

Background: Exposure to thousands of head and body impacts during a career in contact and collision sports may contribute to current or later life issues related to brain health. Wearable technology enables the measurement of impact exposure. The validation of impact detection is required for accurate exposure monitoring. In this study, we present a method of automatic identification (classification) of head and body impacts using an instrumented mouthguard, video-verified impacts, and machine-learning algorithms.

Methods: Time series data were collected via the Nexus A9 mouthguard from 60 elite level men (mean age = 26.33; SD = 3.79) and four women (mean age = 25.50; SD = 5.91) from the Australian Rules Football players from eight clubs, participating in 119 games during the 2020 season. Ground truth data labeling on the captures used in this machine learning study was performed through the analysis of game footage by two expert video reviewers using SportCode and Catapult Vision. The visual labeling process occurred independently of the mouthguard time series data. True positive captures (captures where the reviewer directly observed contact between the mouthguard wearer and another player, the ball, or the ground) were defined as hits. Spectral and convolutional kernel based features were extracted from time series data. Performances of untuned classification algorithms from scikit-learn in addition to XGBoost were assessed to select the best performing baseline method for tuning.

Results: Based on performance, XGBoost was selected as the classifier algorithm for tuning. A total of 13,712 video verified captures were collected and used to train and validate the classifier. True positive detection ranged from 94.67% in the Test set to 100% in the hold out set. True negatives ranged from 95.65 to 96.83% in the test and rest sets, respectively.

Discussion and conclusion: This study suggests the potential for high performing impact classification models to be used for Australian Rules Football and highlights the importance of frequencies <150 Hz for the identification of these impacts.

Observable player behaviours and playing performance following helmet strikes in elite cricket

OBJECTIVES

Investigate the observable player behaviours and features of both concussive (HS-C) and non-concussive (HS-NC) helmet strikes and describe their impact on playing performance.

METHODS

Elite male cricketers sustaining helmet strikes between the 2016 and 2018 seasons were identified by the England and Wales Cricket Board. Medical records identified players sustaining a concussion and those in whom concussion was excluded. Retrospective cohort analysis was performed on batting and bowling performance data available for these players in the 2 years prior to and 3 months post helmet strike. Video analysis of available incidents was conducted to describe the characteristics of the helmet strike and subsequent observable player behaviours. The HS-C and HS-NC cohorts were compared.

RESULTS

Data were available for 194 helmet strikes. 56 (29%) resulted in concussion. No significant differences were seen in playing performance in the 3 months post concussive helmet strike. However, a significant decline in batting performance was seen in this period in the HS-NC group (p<0.001).Video features signifying motor incoordination were most useful in identifying concussion post helmet strike, however, typical features suggesting transient loss of consciousness were not seen. Features such as a longer duration pause prior to the batsman resuming play and the level of concern shown by other players were also useful features.

CONCLUSION

HS-NC may be more significant for player performance than previously thought. Guidance for using video replay to identify concussion in cricket may need to be modified when compared with other field sports.

Heads-Up: Risk-Specific Neurodegenerative Mortality and Years-Saved Analysis on the US Olympian Cohort

Purpose: This study aimed to identify the risk of neurodegenerative death (ND) that former Olympians endure due to their participation in sports grouped based on presumed repeated shocks to the head, and to understand the impact of their participation in such elite sports on their total longevity.

Materials and Methods: The cohort included all former US Olympians, who participated in the Olympic Games (OG) between 1948 and 1972, and whose vital status and causes of death were verified (n = 2,193). Olympic sports were classified into three categories of exposure: Collision (the highest presumed risk of repeated shocks to the head), Contact, and No-Contact. The Fine-Gray competing risk regression model was used to compare the risk of ND where the No-Contact category was a reference group. The years-saved analysis was performed to quantify the number of years saved or lost to ND and total longevity compared with the US general population.

Results: A total of 65 NDs were identified. Collision sports Olympians had a 3.11 (95% CI: 1.31–7.40) higher risk of ND while the Contact group showed a risk of 0.56 (95% CI: 0.21–1.48) compared with the No-Contact sports Olympians. Compared with the general population, the Collision group lost 0.61 (95% CI: -1.16—0.06) years of life from ND, while the Contact group saved 0.4 (95% CI: 0.26–0.54) and the No-Contact group saved 0.09 (-0.09–0.28) years of life up to the age of 90. Regarding the total longevity, Collision, Contact, and No-Contact groups saved 4.67 (95% CI: 3.13–6.22), 5.8 (95% CI: 4.93–6.67), and 6.24 (95% CI: 5.57–6.92) years of life, respectively, from all causes of death.

Conclusion: There is an elevated risk of ND among US Olympians, who engaged in sports with the highest presumed risk of repeated shocks to the head compared with those exposed to no such hazard. Such risk does not jeopardize the total longevity among Olympians in Collision sports.

Participation in pre-injury level sport one-year following sport-related concussion: A prospective, matched cohort study

OBJECTIVES

To estimate the times taken to receive clearance to return to sporting activity and to return to pre-injury level of sport competition following sport-related concussion, and to estimate the proportion of athletes who were participating at their pre-injury level of sport competition six months and one-year following sport-related concussion.

DESIGN

Prospective cohort study.

METHODS

Amateur, adult athletes (16-38 years old) were diagnosed with sport-related concussion at a university-affiliated hospital emergency department. Participants were assessed within one-week, upon medical clearance to return to sporting activity, two weeks following return to sporting activity, six months, and 12 months following sport-related concussion. We assessed sex-, age-, and activity-matched non-injured, control participants at matched time-points. Participants were asked during each study assessment whether they were participating in any sport, in a different sport than before their sport-related concussion, in the same sport but at a lower level of competition than before their sport-related concussion, or in the same sport at the same level of competition than before their sport-related concussion.

RESULTS

Fifty concussed participants and 50 non-injured, control participants completed the study. The median times taken to receive clearance to return to sporting activity and to return to pre-injury level of sport competition following sport-related concussion were 13 days (95%CI=12,16) and 31 days (95%CI=28,32), respectively. One-year following sport-related concussion, 52% of participants reported that they were no longer participating in the same sport and at the same level of competition as they were before their sport-related concussion, compared with only 24% of participants in the non-injured, control group (p=0.003).

CONCLUSIONS

A greater percentage of athletes in the concussion group were not participating at their perceived pre-injury level of sport competition one-year following sport-related concussion compared with a non-injured control group. Factors that explain the lower proportion of amateur athletes participating at their pre-injury level of sport competition one-year after sport-related concussion are likely multifaceted and should be considered in future investigations.

Clinical versus Functional Reaction Time: Implications for Postconcussion Management

PURPOSE

This study aimed to examine the association between clinical and functional reaction time (RT) assessments with and without simultaneous cognitive tasks among healthy individuals.

METHODS

Participants (n = 41, 49% female; 22.5 ± 2.1 yr; 172.5 ± 11.9 cm; 71.0 ± 13.7 kg) completed clinical (drop stick, Stroop) and functional (gait, jump landing, single-leg hop, anticipated cut, unanticipated cut) RT assessments in random order. All RT assessments, except Stroop and unanticipated cut, were completed under single- (movement only) and dual-task conditions (movement and subtracting by 6s or 7s). Drop stick involved catching a randomly dropped rod embedded in a weighted disk. Stroop assessed RT via computerized neurocognitive testing. An instrumented walkway measured gait RT when center-of-pressure moved after random stimulus. All other functional RT assessments involved participants jumping forward and performing a vertical jump (jump landing), balancing on one leg (single-leg hop), or a 45° cut in a known (anticipated cut) or unknown (unanticipated cut) direction. RT was determined when the sacrum moved following random visual stimulus. Pearson correlation coefficients and a 5 × 2 repeated-measures ANOVA compared RT assessments and cognitive conditions.

RESULTS

Stroop RT outcomes did not significantly correlate with functional RT assessments (r range = -0.10 to 0.24). A significant assessment by cognitive task interaction (F4,160 = 14.01; P < 0.001) revealed faster single-task RT among all assessments compared with dual-task (mean differences, -0.11 to -0.09 s; P < 0.001), except drop stick (P = 0.195). Single-leg hop (0.58 ± 0.11 s) was significantly slower compared with jump landing (0.53 ± 0.10 s), anticipated cut (0.49 ± 0.09 s), gait (0.29 ± 0.07 s), and drop stick (0.21 ± 0.03 s; P values ≤ 0.001). Dual-task assessments were significantly slower than single-task assessments (mean difference, 0.08 s; P < 0.001).

CONCLUSIONS

Clinical and functional RT assessments were not correlated with each other, suggesting that sport-like RT is not being assessed after concussion. Functional and dual-task RT assessments may add clinical value and warrant further exploration after concussion.