Latest research in football - week 51 - 2017

#1 What Performance Analysts Need to Know About Research Trends in Association Football (2012-2016): A Systematic Review
Reference: Sports Med. 2017 Dec 14. doi: 10.1007/s40279-017-0836-6. [Epub ahead of print]
Authors: Sarmento H, Clemente FM, Araujo D, Davids K, McRobert A, Figueiredo A
Summary: Evolving patterns of match analysis research need to be systematically reviewed regularly since this area of work is burgeoning rapidly and studies can offer new insights to performance analysts if theoretically and coherently organized. The purpose of this paper was to conduct a systematic review of published articles on match analysis in adult male football, identify and organize common research topics, and synthesize the emerging patterns of work between 2012 and 2016, according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. The Web of Science database was searched for relevant published studies using the following keywords: 'football' and 'soccer', each one associated with the terms 'match analysis', 'performance analysis', 'notational analysis', 'game analysis', 'tactical analysis' and 'patterns of play'. Of 483 studies initially identified, 77 were fully reviewed and their outcome measures extracted and analyzed. Results showed that research mainly focused on (1) performance at set pieces, i.e. corner kicks, free kicks, penalty kicks; (2) collective system behaviours, captured by established variables such as team centroid (geometrical centre of a set of players) and team dispersion (quantification of how far players are apart), as well as tendencies for team communication (establishing networks based on passing sequences), sequential patterns (predicting future passing sequences), and group outcomes (relationships between match-related statistics and final match scores); and (3) activity profile of players, i.e. playing roles, effects of fatigue, substitutions during matches, and the effects of environmental constraints on performance, such as heat and altitude. From the previous review, novel variables were identified that require new measurement techniques. It is evident that the complexity engendered during performance in competitive soccer requires an integrated approach that considers multiple aspects. A challenge for researchers is to align these new measures with the needs of the coaches through a more integrated relationship between coaches and researchers, to produce practical and usable information that improves player performance and coach activity.


#2 Sleep/Wake Behaviours in Elite Athletes from Three Different Football Codes
Reference: J Sports Sci Med. 2017 Dec 1;16(4):604-605. eCollection 2017 Dec.
Authors: Miller DJ, Sargent C, Vincent GE, Roach GD, Halson SL, Lastella M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5721193/pdf/jssm-16-604.pdf


#3 Do Red and Blue Uniforms Matter in Football and Handball Penalties?
Reference: J Sports Sci Med. 2017 Dec 1;16(4):565-573. eCollection 2017 Dec.
Authors: Krenn B, Pernhaupt N, Handsteiner M
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5721188/pdf/jssm-16-565.pdf
Summary: Past research has revealed ambiguous results on the impact of red uniforms in sports competition. The current study was aimed at analyzing the role of red and blue uniforms in football and handball penalties. Two experiments were conducted using a within subjects design, where participants rated uniform color-manipulated video clips. In the first study, participants (n = 39) watched footage of football players kicking a penalty, whereas in the second study (n = 118) videos of handball penalty takers, handball goalkeepers and football goalkeepers preparing themselves to score/save a penalty were shown. Participants rated player's/goalkeeper's level of confidence and the expected position of the ball crossing the goal line in the first experiment and additionally the probability of scoring the penalty against the goalkeepers in the second experiment. The videos stopped at the point where the ball was leaving the foot and hand respectively. Results did not show any beneficial impact of red uniforms. Rather, football players wearing blue were rated to kick the ball higher. The study contradicts any positive effect of red versus blue uniforms in the context of football and handball penalties, which emphasizes the need of searching for potential moderators of color's impact on human behavior.


#4 How Can Governmental Positive Power Decrease Violence in Crime-Oriented Arenas? The Case of English Football
Reference: Int J Offender Ther Comp Criminol. 2017 Jan 1:306624X17694375. doi: 10.1177/0306624X17694375. [Epub ahead of print]
Authors: Guy S, Muchtar O, Ronel N
Summary: This article will survey the dramatic change English football had undergone since the end of the last century. The authors will closely explore the implementation of the Taylor Report recommendations, to convince that which power and management techniques were used to decrease violence in public areas that were previously considered dangerous and crime-oriented. It will be argued that disciplinarian techniques were practiced, much like those described in Foucault's Discipline and Punish, while this very power has proven to be positive and revitalizing. It will be therefore concluded that power is at its most effective when operated via techniques of discipline and social inclusion. These arguments correspond with the positive criminology theory whose popularity within the discipline is gradually increasing.


#5 Eccentric hamstring strength deficit and poor hamstring-to-quadriceps ratio are risk factors for hamstring strain injury in football: A prospective study of 146 professional players
Reference: J Sci Med Sport. 2017 Dec 5. pii: S1440-2440(17)31822-4. doi: 10.1016/j.jsams.2017.11.017. [Epub ahead of print]
Authors: Lee JWY, Mok KM, Chan HCK, Yung PSH, Chan KM
Summary: The purpose of this study was to investigate whether preseason isokinetic strength measures were predictive of future HSI among professional football players. A total of 169 professional players participated in a preseason isokinetic strength screening, followed by a 10-month competitive season. Testing protocol included the concentric performance of both knee flexion and extension at 60degs-1 and 240degs-1 and the eccentric performance of the knee flexor at 30degs-1. Strength deficits, bilateral differences, and hamstring to quadriceps strength ratios were computed. Univariate and multivariate logistic regressions were used to identify potential risk factors of HSI. Receiver operating characteristic (ROC) curves were used to investigate the sensitivity and specificity of the strength measures. Forty-one acute HSIs were sustained, and 12% (n=5) reoccurred within the study period. In the multivariate analysis, we have shown an association between the injury risk and eccentric hamstring peak torque below 2.4Nmkg-1 (OR=5.59; 95% CI, 2.20-12.92); concentric H/Q ratio below 50.5% (OR=3.14; 95% CI, 1.37-2.22); players with previous injury of HSI (OR=3.57; 95% CI, 3.13-8.62). ROC analysis displayed an area under curve (AUC) of 0.77, indicating fair combined sensitivity and specificity of the overall predicting model. Professional football players with significant lower isokinetic hamstring strength, lower hamstring-to-quadriceps strength ratio, and a previous injury of HSI were linked to an increased risk of acute HSI.


#6 Operative Fixation of an Anterior Inferior Iliac Spine Apophyseal Avulsion Fracture Nonunion in an Adolescent Soccer Player: A Case Report
Reference: JBJS Case Connect. 2017 Apr-Jun;7(2):e29. doi: 10.2106/JBJS.CC.16.00167.
Authors: Carr JB 2nd, Conte E, Rajadhyaksha EA, Laroche KA, Gwathmey FW, Carson EW
Summary: A 14-year-old male competitive soccer player presented with a history of recurrent right hip pain for 18 months. He was diagnosed with an anterior inferior iliac spine (AIIS) apophyseal avulsion fracture nonunion with subspinal impingement, which was confirmed by radiographs, computed tomography, and magnetic resonance imaging. The patient underwent surgical fixation and subspinal decompression. He returned to competitive soccer 5 months postoperatively. AIIS apophyseal avulsion fractures occur in adolescent athletes and generally respond to nonoperative treatment. When such management is unsuccessful, surgical fixation can lead to resolution of pain with return of full function.


#7 Effect of Boards in Small-Sided Street Soccer Games on Movement Pattern and Physiological Response in Recreationally Active Young Men
Reference: J Strength Cond Res. 2017 Dec 11. doi: 10.1519/JSC.0000000000002401. [Epub ahead of print]
Authors: Randers MB, Brix J, Hagman M, Nielsen JJ, Krustrup P.
Summary: The present study investigated whether street soccer might be proposed as an alternative to recreational small-sided games on grass as a health-enhancing activity, and specifically the effects of the boards surrounding the pitch. Eleven recreationally active young males (28.4±4.2 (±SD) yrs, 19.9±4.2% body fat, 47.7±6.0 mlminkg), after familiarization, completed one to two sessions of 20x13-m 3v3 street soccer games with boards (WB) and one to two sessions without boards (WOB) in a randomized order. Movement pattern was measured using GPS and heart rate recordings, blood sampling and RPE scales were used to evaluate exercise intensity and physiological strain. Total number of accelerations (19%) and Player Load (18%) were higher (p < 0.05) in WB than in WOB, whereas total distance covered (12%), high-speed running (59%) and peak speed (11%) were lower (p < 0.05) in WB than in WOB. Moreover, HRmean was higher in WB than in WOB (85.7±5.4 vs. 81.3±8.2%HRmax, p = 0.012, ES = 0.64), whereas time with HR>90%HRmax did not differ between WB and WOB (42±34 vs. 32±30%, p = 0.243, ES = 0.32). Plasma ammonia increased more in WB than in WOB, with no differences found in mean and peak blood lactate. RPE was higher after WB than after WOB (7.1±1.0 vs. 5.5±1.2, p < 0.001, ES = 1.39). In conclusion, intensity was sufficiently high in both game formats to expect short- and long-term health improvements as a result of regular participation. Boards affected movement pattern and physiological demands, producing higher number of accelerations, Player Load, average heart rate, plasma ammonia, and rating of perceived exertion, but lower total distance, number of intense runs and peak speed.


#8 Surgical treatment of rectus femoris injury in soccer playing athletes: report of two cases
Reference: Rev Bras Ortop. 2017 Jan 17;52(6):743-747. doi: 10.1016/j.rboe.2017.01.001. eCollection 2017 Nov-Dec.
Authors: Shimba LG, Latorre GC, Pochini AC, Astur DC, Andreoli CV
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5720843/pdf/main.pdf
Summary: Muscle injury is the most common injury during sport practice. It represents 31% of all lesions in soccer, 16% in track and field, 10.4% in rugby, 17.7% in basketball, and between 22% and 46% in American football. The cicatrization with the formation of fibrotic tissue can compromise the muscle function, resulting in a challenging problem for orthopedics. Although conservative treatment presents adequate functional results in the majority of the athletes who have muscle injury, the consequences of treatment failure can be dramatic, possibly compromising the return to sport practice. The biarticular muscles with prevalence of type II muscle fibers, which are submitted to excentric contraction, present higher lesion risk. The quadriceps femoris is one example. The femoris rectus is the quadriceps femoris muscle most frequently involved in stretching injuries. The rupture occurs in the acceleration phase of running, jump, ball kicking, or in contraction against resistance. Although the conservative treatment shows good results, it is common that the patient has lower muscle strength, difficulty in return to sports, and a permanent and visible gap. Surgical treatment can be an option for a more efficient return to sports.


#9 Isokinetic knee muscle strength profile in Brazilian male soccer, futsal and beach soccer players: A cross-sectional study
Reference: Int J Sports Phys Ther. 2017 Dec;12(7):1103-1110.
Authros: de Lira CAB, Mascarin NC, Vargas VZ, Vancini RL, Andrade MS
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5717486/pdf/ijspt-12-1103.pdf
Summary: Anterior cruciate ligament injury is higher in soccer athletes as compared to athletes of other sports. Risk factors for anterior cruciate ligament injury include low knee hamstring/quadriceps strength ratio and bilateral strength deficits. The purpose was to investigate isokinetic thigh muscles strength, hamstring/quadriceps strength ratio, and bilateral strength comparisons in athletes who participate in professional soccer, futsal, and beach soccer. Brazilian professional soccer (n=70), futsal (n=30), and beach soccer (n=12) players were isokinetically assessed to examine strength of knee extensors and flexors at 60 degrees/second in concentric mode, to measure peak torque of dominant and non-dominant limbs. In the dominant limb, for extensors muscles, futsal players presented significantly lower peak torque values (223.9 ± 33.4 Nm) than soccer (250.9 ± 43.0 Nm; p=0.02) and beach soccer players (253.1 ± 32.4 Nm; p=0.03). Peak torque for extensor muscles in the non-dominant limb was significantly lower in futsal (224.0 ± 35.8 Nm) than in beach soccer players (256.8 ± 39.8 Nm; p=0.03). Hamstring/quadriceps strength ratio for dominant limbs for futsal (57.6 ± 10.1%), soccer (53.5 ± 8.8%), and beach soccer (56.3 ± 8.4%) players presented no significant differences between groups; however, the mean values were lower than recommended values found in the literature. There were no strength deficits for any of the evaluated groups when compared bilaterally. Futsal athletes presented lower values for quadriceps strength than soccer and beach soccer athletes. Futsal, soccer, and beach soccer players presented no strength asymmetries, but they presented with strength imbalance in hamstring/quadriceps strength ratio.


#10 Collegiate male soccer players exhibit between-limb symmetry in body composition muscle strength and range of motion
Reference: Int J Sports Phys Ther. 2017 Dec;12(7):1087-1094.
Authors: DeLang MD, Kondratek M, DiPace LJ, Hew-Butler T
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5717484/pdf/ijspt-12-1087.pdf
Summary: Functional and structural asymmetries attributed to limb dominance are equivocal in soccer players. Previous authors hypothesize the existence of between-limb asymmetry secondary to the repetitive unilateral nature of kicking. However, symmetry is often present, particularly in measures of muscle strength. The purpose of the present study was to determine if lateral dominance is accompanied by corresponding between-limb asymmetries in a comprehensive assessment of body composition, muscle strength, and range of motion in healthy soccer players. 17 healthy male NCAA Division One collegiate soccer players participated (age 19.6 ± 1.5 years; BMI 23.9 ± 1.4 kg/m2). Footedness was attained via participant self-report. Lower limb muscle strength (hand held dynamometry), range of motion (goniometry), and body composition (dual energy x-ray absorptiometry scan) were measured. Lower-leg symmetry was analyzed comparing the dominant versus non-dominant limb using paired t-tests. Comparisons revealed no statistically different differences in outcomes, indicating remarkable symmetry in all measures of body composition, muscle strength, and range of motion (p>0.05) between the dominant and non-dominant lower limbs. The authors speculate the prevalence of running versus kicking, the longitudinal effects of playing careers, and/or functional compensation attenuates the expected asymmetries in healthy male collegiate soccer players.


#11 Injuries in Japanese Junior Soccer Players During Games and Practices
Reference: J Athl Train. 2017 Dec 11. doi: 10.4085/1062-6050-52.12.23. [Epub ahead of print]
Authors: Kuzuhara K, Shibata M, Uchida R
Summary: Soccer is the most popular junior sport in the world. In junior sports, injury analysis and injury-prevention measures for players, especially those under 12 years of age, are urgently needed. The purpose was to prospectively study the incidence, sites, types, and mechanisms of injuries in elementary school-aged junior soccer players during games and practices. Eighty-nine players in 5 community-based club teams of junior soccer (U-12, age range =11-12 years; U-11, age range =10-11 years; U-10, age ≤10 years). Data on all game and practice injuries for the 2013-2014 season were collected using an injury report form. Injury rates were calculated according to injury site, type, and mechanism. The overall injury rate was 2.59/1000 athlete-hours (AHs). The game injury rate (GIR; 6.43/1000 AHs) was higher than the practice injury rate (PIR; 1.49/1000 AHs; P < .05). The most common anatomical areas of injury during games and practices were the lower limbs (62.5% and 4.02/1000 AHs versus 38.5% and 0.57/1000 AHs, respectively). Contusions (27.6%, n = 8) were the most frequent type of overall injuries. Most game injuries resulted from body contact (43.8%, 2.81/1000 AHs), wherease most practice injuries resulted from other types of contact (53.8%, 0.83/1000 AHs). The GIRs were higher than the PIRs in Japanese junior soccer players. A lower overall PIR suggested that players in the U-12 age group practiced under appropriate conditions. However, the higher GIR in this age category needs to be decreased.


#12 Aerodynamic effects of dimples on soccer ball surfaces
Reference: Heliyon. 2017 Oct 31;3(10):e00432. doi: 10.1016/j.heliyon.2017.e00432. eCollection 2017 Oct.
Authors: Hong S, Asai T
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5714554/pdf/main.pdf
Summary: Recently, the shape and design of the panel on the official ball used in the FIFA World Cup was considerably different from that of a conventional soccer ball (having 32 pentagonal and hexagonal panels). Depending on the number of different panels and their orientation, the aerodynamic force experienced by a ball is believed to change, which in turn changes the ball trajectory. However, not much is known about the impact of the surface forms of a ball on its aerodynamics. Therefore, in the present study, 10 different types of soccer balls were produced and their aerodynamic properties were studied by wind tunnel experiments. The results confirmed that the aerodynamic force acting on the ball varied considerably depending on the existence of dimples on the ball surface. In addition, the 4 types of soccer balls, which had different kinds of roughness, revealed that even balls having the same number and shapes of panels experienced greatly varying aerodynamic forces depending on the surface form of the balls.


Australian Football
#1 Physical demands and technical performance in Australian Football League Women's (AFLW) competition match-play
Reference: J Sci Med Sport. 2017 Dec 5. pii: S1440-2440(17)31823-6. doi: 10.1016/j.jsams.2017.11.018. [Epub ahead of print]
Authors: Clarke AC, Ryan S, Couvalias G, Dascombe BJ, Coutts AJ, Kempton T
Summary: The purpose was to compare positional differences in the physical and technical demands of Australian Football League Women's (AFLW) match-play. A secondary aim was to examine the time course changes in activity profiles during AFLW match-play. Global positioning system data were collected from 26 players (6 positional groups) from the same club during seven AFLW matches. Absolute and relative physical performance data were categorised into total distance, high-speed running (>14.4kmh-1, HSR), very high-speed running (>18.0kmh-1, VHSR), and sprinting distance (>20.0kmh-1, Sprint). Technical performance data was obtained from a commercial statistics provider. A mixed model analysis was used to examine differences between positional groups and playing quarters. Absolute measures of running performance did not differ between position groups. Relative total distance was moderately greater (ES=∼0.80, p<0.05) for midfielders, small backs and small forwards (125-128mmin-1) than tall backs and tall forwards (102-107mmin-1). Relative HSR distance was greater (ES=∼0.73) for midfielders and small backs (∼28mmin-1) than tall backs (17mmin-1). Analysis of technical performance indicators showed: midfielders and small forwards had the most inside 50s; tall backs had the highest number of rebound 50s; tall forwards scored more goals; while midfielders made more tackles (p<0.05). All relative running performance measures were reduced in the fourth quarter when compared to the first and second quarters (ES=0.32-0.77). These data can be used as benchmarks for temporal analysis of AFLW match demands and assist in developing specific training strategies.


#2 Oculomotor cognitive control abnormalities in Australian rules football players with a history of concussion
Reference: J Neurotrauma. 2017 Dec 11. doi: 10.1089/neu.2017.5204. [Epub ahead of print]
Authors: Clough M, Mutimer S, Wright DK, Tsang A, Costello D, Gardner A, Stanwell P, Mychasiuk R, Sun M, Brady RD, McDonald SJ, Webster KM, Johnstone M, Fielding J, Semple B, Agoston DV, White OB, Frayne R, O'Brien TJ, Shultz SR
Summary: This study used oculomotor, cognitive, and multimodal magnetic resonance imaging (MRI) measures to assess for neurological abnormalities in current asymptomatic amateur Australian rules footballers (i.e., Australia's most participated collision sport) with a history of sports-related concussion (SRC). Participants were 15 male amateur Australian rules football players with a history of SRC greater than 6 months previously, and 15 sex-, age- and education-matched athlete control subjects that had no history of neurotrauma or participation in collision sports. Participants completed a clinical interview, neuropsychological measures and oculomotor measures of cognitive control. MRI investigation involved structural imaging, as well as diffusion tensor imaging and resting state functional MRI sequences. Despite no group differences on conventional neuropsychological tests and multimodal MRI measures, Australian rules football players with a history of SRC performed significantly worse on an oculomotor switch task: a measure of cognitive control that interleaves the response of looking towards a target (i.e., a prosaccade) with the response of looking away from a target (i.e., an antisaccade). Specifically, Australian footballers performed significantly shorter latency prosaccades and found changing from an antisaccade trial to a prosaccade trial (switch cost) significantly more difficult than control subjects. Poorer switch cost was related to poorer performance on a number of neuropsychological measures of inhibitory control. Further, when comparing performance on the cognitively more demanding switch task with performance on simpler, antisaccade/prosaccades tasks which require a single response, Australian footballers demonstrated a susceptibility to increased cognitive load, compared to the control group who were unaffected. These initial results suggest that current asymptomatic amateur Australian rules football players with a history of SRC may have persisting, subtle, cognitive changes, which are demonstrable on oculomotor cognitive measures. Future studies are required in order to further elucidate the full nature and clinical relevance of these findings.


American Football
#1 Game Schedules and Rate of Concussions in the National Football League
Reference: Orthop J Sports Med. 2017 Nov 28;5(11):2325967117740862. doi: 10.1177/2325967117740862. eCollection 2017 Nov.
Authors: Teramoto M, Cushman DM, Cross CL, Curtiss HM, Willick SE
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5714093/pdf/10.1177_2325967117740862.pdf
Summary: Concussion prevention in the National Football League (NFL) is an important priority for player safety. The NFL now has modified game schedules, and one concern is that unconventional game schedules, such as a shortened rest period due to playing on a Thursday rather than during the weekend, may lead to an increased risk of injuries. The hypothesis is that unconventional game schedules in the NFL are associated with an increased rate of concussion. This study analyzed concussions and game schedules over the NFL regular seasons from 2012 to 2015 (4 years). Documented numbers of concussions, identified by use of the online database PBS Frontline Concussion Watch, were summarized by regular-season weeks. Association of days of rest and game location (home, away, or overseas) with the rate of concussion was examined by use of the χ2 test. Logistic regression analysis was performed to examine the relationships of days of rest and home/away games to the risk of repeated concussions, with adjustment for player position. A total of 582 concussions were analyzed in this study. A significantly greater number of concussions occurred in the second half of the season (P < .01). No significant association was found between the rate of concussion and the days of rest, game location, or timing of the bye week by the team or the opponent (P > .05). Game schedules were not significantly associated with the occurrence of repeat concussions (P > .05). Unconventional game schedules in the NFL, including playing on Thursday and playing overseas, do not seem to put players at increased risk of concussions.


#2 Posterior Cruciate Ligament Injuries of the Knee at the National Football League Combine: An Imaging and Epidemiology Study
Reference: Arthroscopy. 2017 Dec 7. pii: S0749-8063(17)31163-5. doi: 10.1016/j.arthro.2017.08.304. [Epub ahead of print]
Authors: Logan CA, Beaulieu-Jones BR, Sanchez G, Chahla J, Kennedy NI, Cinque ME, LaPrade RF, Whalen JM, Vopat BG, Price MD, Provencher MT
Summary: The purpose was to determine the epidemiology by player position, examination, imaging findings, and associated injuries of posterior cruciate ligament (PCL) injuries in players participating in the National Football League (NFL) Combine. All PCL injuries identified at the NFL Combine (2009-2015) were reviewed. Data were obtained from the database organized by the NFL medical personnel for the compilation of the medical and physical performance examination results of NFL Draftees participating in the NFL Combine from 2009 to 2015. Inclusion criteria were any player with clinical findings or a previous surgery consistent with a PCL injury who participated in the NFL Combine. Of the 2,285 players who participated in the NFL Combine between 2009 and 2015, 69 (3%) had evidence of a PCL injury, of which 11 players (15.9%) were managed surgically. On physical examination, 35 players (52%) had a grade II or III posterior drawer. Concomitant injuries were present frequently and included medial collateral ligament (MCL; 42%), anterior cruciate ligament (ACL; 11.6%), and chondral injuries (31.8%), especially in the lateral tibiofemoral compartment. Three percent of the players at the NFL Combine presented with a PCL injury, with a significant amount being either running backs (14/69, 20.2%) or offensive linemen (14/69, 20.2%). Approximately half of the players with a PCL tear had a residual grade II or III posterior drawer after sustaining a PCL injury. Concomitant injuries were present frequently and included MCL (42%), ACL (11.6%), and chondral injuries (31.8%), especially in the lateral tibiofemoral compartment. For those players with clinical concern for PCL ligamentous laxity, there should be a complete comprehensive workup that includes plain and PCL stress view radiographs, and magnetic resonance imaging.


#3 Symptomatic Focal Knee Chondral Injuries in National Football League Combine Players Are Associated With Poorer Performance and Less Volume of Play
Reference: Arthroscopy. 2017 Dec 7. pii: S0749-8063(17)31159-3. doi: 10.1016/j.arthro.2017.08.300. [Epub ahead of print]
Authors: Provencher MT, Chahla J, Cinque ME, Sanchez G, Kennedy NI, Haber DB, Tisosky AJ, Beaulieu-Jones BR, Price MD, Whalen JM, Moatshe G, LaPrade RF
Summary: The purpose was to (1) describe the magnetic resonance imaging (MRI) characteristics of knee chondral injuries identified at the National Football League (NFL) Combine and (2) assess in-game performance of prospective NFL players with previously untreated knee chondral injuries and compare it with matched controls. All players with knee chondral injuries identified at the NFL Combine (2009-2015) were retrospectively reviewed. Players with prior knee surgery were excluded. A knee MRI for each player was reviewed; location, modified International Cartilage Repair Society (ICRS) grade (I-IV), and associated compartment subchondral edema were documented. Position, respective NFL Draft pick selection number, games started, played, snap percentage, and position-specific performance metrics during the first 2 NFL seasons were recorded for the injury and injury-free control group composed of players with (1) no prior knee injury, (2) no significant missed time prior to the NFL (≤2 total missed games in college), (3) no history of knee surgery, and (4) drafted in the respective NFL Draft following the NFL Combine. Of the 2,285 players reviewed, 101 (4.4%) had an injury without prior knee surgery. The patella (63.4%) and trochlea (34%) were most commonly affected. Defensive linemen were at highest risk for unrecognized injuries (odds ratio 1.8, P = .015). Players with previously untreated injuries, compared with controls, were picked later (mean pick: 125.8) and played (mean: 23) and started (mean: 10.4) fewer games during the initial 2 NFL seasons (P < .001 for all). Particularly, subchondral bone edema and full-thickness cartilage injuries were associated with fewer games played (P = .003). The patellofemoral joint was most commonly affected in NFL Combine participants. Previously untreated knee articular injuries in players at the NFL Combine are associated with poorer early NFL performance in comparison to uninjured players. Subchondral bone edema and full-thickness cartilage injury on MRI were associated with fewer games played during the initial NFL career.