Association Between Osteochondritis Dissecans of the Humeral Capitellum and Medial Epicondyle Lesion in Baseball Players

Background: Osteochondritis dissecans (OCD) of the humeral capitellum occurs in adolescent overhead athletes, and medial epicondyle (ME) lesions are also common in this population. Purpose: To evaluate the association between elbow OCD and ME lesions in adolescent baseball players. Study Design: Cross-sectional study; Level of evidence, 3. Methods: This study retrospectively evaluated adolescent baseball players with unstable elbow OCD who underwent surgery between January 2000 and February 2020. Patients were excluded if they had osteoarthritis of the elbow. A total of 139 elbows were included in this study (138 male and 1 female athlete; mean ± SD age, 13.6 ± 1.5 years). The patients were first divided into 2 groups based on OCD location: a central lesion group (72 elbows) and a lateral group (67 elbows). Next, patients were divided according to OCD size into a localized group (56 elbows) and a widespread group (83 elbows). Finally, OCD lesions that were both lateral and widespread were defined as lateral-widespread (60 elbows), resulting in 5 groups. ME apophyseal fragmentation and elongation were evaluated and defined as ME lesions. We then compared the relationship between OCD and ME lesions. Results: Of the 139 elbows, 63 (45.3%) had ME lesions. The prevalence of ME lesion was higher in the lateral group than the central group (56.7% vs 34.7%; P = .009) and higher in the widespread group than the localized group (55.4% vs 30.4%; P = .004). Furthermore, the prevalence ratio of ME lesion was significantly higher in the lateral-widespread group than for other lesions (58.3% vs 35.4%; P = .007). Conclusion: In patients undergoing surgery for capitellar OCD, the presence of ME lesions was more commonly associated with lateral and widespread capitellar lesions when compared with central and localized lesions.

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Osteochondritis Dissecans of the Humeral Capitellum in Young Athletes

Orthopaedic Journal of Sports Medicine ◽

10.1177/2325967117692513 ◽

2017 ◽

Vol 5 (3) ◽

pp. 232596711769251 ◽

Cited By ~ 13

Author(s):

Shiro Kajiyama ◽

Satoshi Muroi ◽

Hiroyuki Sugaya ◽

Norimasa Takahashi ◽

Keisuke Matsuki ◽

...

Keyword(s):

Inclination Angle ◽

Osteochondritis Dissecans ◽

Early Stage ◽

Elbow Flexion ◽

Cross Sectional Study ◽

Level Of Evidence ◽

Full Extension ◽

Cross Sectional ◽

Baseball Players ◽

Computed Tomography Images

Background: Osteochondritis dissecans (OCD) lesions are often observed in the humeral capitellum both in young baseball players and gymnasts. It is generally believed that capitellar OCD in baseball players can be seen on an anteroposterior (AP) radiograph with the elbow in 45° of flexion. However, the mechanism of injury seems to be different in baseball players and gymnasts. Repetitive valgus overload with the elbow in flexion is believed to be the cause of capitellar OCD lesions in baseball players, whereas weightbearing with the elbow in extension may be the cause of OCD in gymnasts. Purpose: To determine the difference in capitellar OCD location between baseball players and gymnasts and to propose the optimal AP radiographic angle of the elbow for visualization of early-stage OCD lesions in adolescent gymnasts. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Subjects consisted of 95 baseball players (95 elbows) and 21 gymnasts (24 elbows) with a mean age of 13.7 years (range, 11-18 years). To localize the lesion, inclination of the affected area in the humeral capitellum against the humeral axis was investigated using sagittal computed tomography images of the elbow. The inclination angle was defined as the angle between the long axis of the humerus and the line perpendicular to a line that connected the anterior and posterior margin of the lesion. The inclination angle in each group was compared and statistically analyzed. Results: The mean inclination angle was 57.6° ± 10.7° in baseball players and 28.0° ± 10.7° in gymnasts. Capitellar OCD lesions were located more anterior in baseball players when compared with gymnasts ( P < .01). Conclusion: Due to differences in applied stress, capitellar OCD lesions in baseball players were located more anteriorly compared with those seen in gymnasts. Therefore, although AP radiographs with the elbow in 45° of flexion are optimal for detecting OCD lesions in baseball players, radiographs with less elbow flexion or full extension are more useful in gymnasts, especially in early-stage OCD.

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Scapular Dyskinesis in Young, Asymptomatic Elite Swimmers

Orthopaedic Journal of Sports Medicine ◽

10.1177/2325967117750814 ◽

2018 ◽

Vol 6 (1) ◽

pp. 232596711775081 ◽

Cited By ~ 5

Author(s):

Jacopo Preziosi Standoli ◽

Francesco Fratalocchi ◽

Vittorio Candela ◽

Tiziano Preziosi Standoli ◽

Giuseppe Giannicola ◽

...

Keyword(s):

Sagittal Plane ◽

Dynamic Test ◽

Cross Sectional Study ◽

Type I ◽

Scapular Dyskinesis ◽

Long Distance ◽

Level Of Evidence ◽

Cross Sectional ◽

Overhead Athletes ◽

Elite Swimmers

Background: Overhead athletes are at a greater risk of developing scapular dyskinesis (SD). Although swimming is considered an overhead sport, information regarding SD in these athletes is scarce. Purpose: To determine the prevalence of SD in young, asymptomatic elite swimmers. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 661 asymptomatic elite swimmers were enrolled in this study (344 male, 317 female; mean age, 15.83 ± 2.20 years). Anthropometric characteristics, training routine, and stroke specialty were recorded. SD was assessed using a dynamic test consisting of an examination of the shoulder blades throughout synchronous forward flexion motion in the sagittal plane and was deemed to be either present or absent. Each movement was repeated 5 times. These evaluations were performed with athletes at rest, before any training or competition. Statistical analysis was performed. Results: SD was detected in 56 (8.5%) participants. Type I SD was the most common (46.5%); male participants were 2 times as likely to have SD as female participants (39 male, 17 female; P < .01). No correlation was found between the dominant limb and side affected ( P = .258); rather, a correlation was found between the breathing side and side affected, in that swimmers with a preferred breathing side were more prone to develop SD in the opposite shoulder ( P < .05). Swimmers involved in long-distance races were found to have a greater risk of developing SD ( P = .01). Conclusion: SD may be an asymptomatic condition in elite young swimmers and is present in 8.5% of these athletes. Early diagnosis may be useful for asymptomatic athletes with SD and to avoid its possible evolution to a symptomatic condition.

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Relationship Between Lower Limb Tightness and Practice Time Among Adolescent Baseball Players With Symptomatic Osgood-Schlatter Disease

Orthopaedic Journal of Sports Medicine ◽

10.1177/2325967119847978 ◽

2019 ◽

Vol 7 (5) ◽

pp. 232596711984797 ◽

Cited By ~ 2

Author(s):

Takuya Omodaka ◽

Takashi Ohsawa ◽

Tsuyoshi Tajika ◽

Hiroyuki Shiozawa ◽

Syogo Hashimoto ◽

...

Keyword(s):

Range Of Motion ◽

Lower Limb ◽

Cross Sectional Study ◽

Tibial Tuberosity ◽

Lower Limbs ◽

Level Of Evidence ◽

Cross Sectional ◽

Baseball Players ◽

Ankle Joints ◽

Practice Time

Background: Osgood-Schlatter disease (OSD) is characterized by traction apophysitis of the tibial tuberosity. Few studies on symptomatic and asymptomatic OSD have correlated findings with clinical examination. Purpose: To investigate the relationship between lower limb tightness and practice time among adolescent baseball players with symptomatic OSD. Study Design: Cross-sectional study; Level of evidence, 3. Methods: The study participants were 402 male baseball players (N = 804 knees) with a mean ± SD age of 10.9 ± 1.5 years (range, 7-14 years). Participant age, height, body weight, body mass index, practice time per week, range of motion of the hip and ankle joints, heel-buttock distance (HBD), and straight-legged raise angle were evaluated. Tibial tuberosity development, as assessed with ultrasonography, was classified into 4 stages: cartilaginous, apophyseal, epiphyseal, and bony. Knees that were classified as apophyseal or epiphyseal were investigated. Participants were divided into 3 groups: non-OSD, asymptomatic OSD, and symptomatic OSD. Results: Of 400 knees in the apophyseal and epiphyseal stages, 23 knees had asymptomatic OSD, and 11 had symptomatic OSD. Players with symptomatic OSD practiced for significantly longer than the non-OSD group ( P = .001) and asymptomatic OSD group ( P = .001). Players with symptomatic OSD also had a larger HBD ( P = .006) and smaller range of motion regarding internal rotation of hip ( P = .023) and dorsiflexion of the ankle ( P = .013) than the non-OSD group. Conclusion: Players with symptomatic OSD had longer practice times than the non-OSD and asymptomatic OSD players. Symptomatic OSD was also associated with tightness of the lower limbs as assessed by the HBD and range of motion in the hip and ankle joints.

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Youth Single-Sport Specialization in Professional Baseball Players

Orthopaedic Journal of Sports Medicine ◽

10.1177/2325967120907875 ◽

2020 ◽

Vol 8 (3) ◽

pp. 232596712090787

Author(s):

Patrick S. Buckley ◽

Michael C. Ciccotti ◽

Meghan Bishop ◽

Patrick Kane ◽

Stephen Selverian ◽

...

Keyword(s):

Athletic Trainers ◽

The United States ◽

Cross Sectional Study ◽

Professional Baseball ◽

Level Of Evidence ◽

Cross Sectional ◽

Baseball Players ◽

Current Trends ◽

Youth Baseball ◽

The Us

Background: An increasing number of youth baseball athletes are specializing in playing baseball at younger ages. Purpose: The purpose of our study was to describe the age and prevalence of single-sport specialization in a cohort of current professional baseball athletes. In addition, we sought to understand the trends surrounding single-sport specialization in professional baseball players raised within and outside the United States (US). Study Design: Cross-sectional study; Level of evidence, 3. Methods: A survey was distributed to male professional baseball athletes via individual team athletic trainers. Athletes were asked if and at what age they had chosen to specialize in playing baseball at the exclusion of other sports, and data were then collected pertaining to this decision. We analyzed the rate and age of specialization, the reasons for specialization, and the athlete’s perception of injuries related to specialization. Results: A total of 1673 professional baseball athletes completed the survey, representing 26 of the 30 Major League Baseball (MLB) organizations. Less than half (44.5%) of professional athletes specialized in playing a single sport during their childhood/adolescence. Those who reported specializing in their youth did so at a mean age of 14.09 ± 2.79 years. MLB players who grew up outside the US specialized at a significantly earlier age than MLB players native to the US (12.30 ± 3.07 vs 14.89 ± 2.24 years, respectively; P < .001). Additionally, MLB players raised in the US recalled a significantly higher incidence of sustaining an injury attributed to specializing in baseball than MLB athletes raised outside the US (27.7% vs 20.6%, respectively; P = .05). Conclusion: This study challenges the current trends toward early youth sport specialization, finding that the majority of professional baseball athletes studied did not specialize as youth and that those who did specialize did so at a mean age of 14 years. With the potential cumulative effects of pitching and overhead throwing on an athlete’s arm, the trend identified in this study toward earlier specialization within baseball is concerning.

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Site and Severity of the Increased Humeral Retroversion in Symptomatic Baseball Players

The American Journal of Sports Medicine ◽

10.1177/0363546516638331 ◽

2016 ◽

Vol 44 (7) ◽

pp. 1825-1831 ◽

Cited By ~ 6

Author(s):

Yasuo Itami ◽

Teruhisa Mihata ◽

Koji Shibano ◽

Kazuomi Sugamoto ◽

Masashi Neo

Keyword(s):

Cross Sectional Study ◽

Mirror Image ◽

3D Ct ◽

Shoulder Injury ◽

Level Of Evidence ◽

Cross Sectional ◽

Baseball Players ◽

Elbow Injury ◽

Humeral Retroversion ◽

Dominant Side

Background: Humeral retroversion in baseball players is greater in the dominant shoulder than in the nondominant shoulder. However, the site and severity of the humeral rotational deformity remain unclear. Purpose: To evaluate the site of side-to-side differences in humeral retroversion in baseball players and the severity of these changes through 3-dimensional computed tomographic (3D CT) bone models. Study Design: Cross-sectional study; Level of evidence, 3. Methods: From 2008 to 2014, we studied 25 baseball players (12 pitchers, 13 fielders) who underwent surgery for throwing-related injuries (shoulder injury, 15 players; elbow injury, 10 players). The mean age (±SD) at the time of surgery was 20.0 ± 5.9 years. A reconstructed 3D CT model of the entire humerus was divided into 15 segments of equal height (overall mean, 21.4 ± 1.0 mm). The side-to-side difference in humeral retroversion in each segment was calculated by superimposing the model of the dominant side over the mirror-image model of the nondominant side. Results: The overall mean increase in humeral retroversion was 13.0° ± 6.2° on the dominant side. Significant side-to-side differences in retroversion were present throughout the humerus. The largest side-to-side difference in humeral retroversion was seen at the insertions of the internal rotator muscles (2.5° ± 4.3°) and around the proximal physis (2.5° ± 1.4°). At the insertions of shoulder capsule and rotator cuff tendons, the superior half of the humeral head was more retroverted than the inferior half ( P < .0001). The side-to-side difference in humeral retroversion was significantly greater in the pitchers (16.2° ± 5.1°) than in the fielders (10.0° ± 5.7°) ( P = .009), particularly at the proximal physis. Conclusion: Baseball players exhibited significant side-to-side differences in humeral retroversion at multiple sites throughout the humerus, including the proximal humerus near the epiphyseal plate and at the insertions of the internal rotator muscles, the middle of the humeral shaft, and the distal third of the humerus. Therefore, the increased humeral retroversion at multiple sites throughout the humerus needs to be considered when we perform physical examinations, provide treatment, or undertake biomechanical studies for any throwing-related injuries.

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Prevalence and Consequences of Sport Specialization Among Little League Baseball Players

Sports Health A Multidisciplinary Approach ◽

10.1177/1941738120970956 ◽

2021 ◽

pp. 194173812097095

Author(s):

Eric G. Post ◽

Michael D. Rosenthal ◽

Andrew T. Pennock ◽

Mitchell J. Rauh

Keyword(s):

Cross Sectional Study ◽

Patient Reported Outcome ◽

Online Questionnaire ◽

Level Of Evidence ◽

Cross Sectional ◽

Baseball Players ◽

Little League ◽

Patient Reported ◽

Youth Baseball ◽

Level 3

Background: Baseball is one of the most popular boy’s youth sports, and there has been a rise in the rates of certain overuse injuries among players. Specialization has been identified as a risk factor for overuse injury in high school athlete populations, but there is little understanding of the prevalence or consequences of sport specialization in Little League baseball players. Hypothesis: Sport specialization will be highly prevalent among Little League baseball players and specialization will be associated with worse throwing arm health. Study Design: Cross-sectional study. Level of Evidence: Level 3. Methods: A total of 246 Little League baseball players (male; N = 241; age, 9.5 ± 1.6 years) between 7 and 12 years old completed an anonymous, online questionnaire with their parent’s assistance. The questionnaire consisted of participant demographics and baseball participation information, including sport specialization status and the Youth Throwing Score (YTS), a valid and reliable patient-reported outcome measure for youth baseball players. Results: Only 29 (11.8%) players met the criteria for high specialization. Approximately one-third of all players (n = 77; 31.3%) reported participating in baseball year-round or receiving private coaching outside of their league (n = 81; 32.9%). Highly specialized athletes demonstrated worse scores on the YTS on average compared with low-specialization athletes (mean [SE]: 56.9 [1.6] vs 61.1 [1.2]; P = 0.01). Similarly, pitching in the previous year ( P < 0.01) or traveling overnight regularly for showcases ( P = 0.01) were associated with a worse score on the YTS. Conclusion: While the prevalence of high sport specialization was low among Little League baseball players, other behaviors associated with specialization such as year-round play and the receiving of private coaching were more common. Highly specialized Little League players demonstrated worse throwing arm health compared with low-specialization players. Clinical Relevance: Little League players and their parents may represent a potential target audience for dissemination campaigns regarding sport specialization.

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Pitching Behaviors in Youth Baseball: Comparison With the Pitch Smart Guidelines

Orthopaedic Journal of Sports Medicine ◽

10.1177/23259671211050127 ◽

2021 ◽

Vol 9 (11) ◽

pp. 232596712110501

Author(s):

Justin J. Greiner ◽

Cameron A. Trotter ◽

Brian E. Walczak ◽

Scott J. Hetzel ◽

Geoffrey S. Baer

Keyword(s):

Negative Binomial ◽

Negative Binomial Regression ◽

High Volume ◽

Cross Sectional Study ◽

Level Of Evidence ◽

Cross Sectional ◽

Baseball Players ◽

Binomial Regression ◽

Youth Baseball ◽

Rate Ratios

Background: The Pitch Smart guidelines aim to limit youth baseball pitching behaviors associated with overuse injuries. Despite many youth baseball leagues being compliant with the guidelines, during tournaments, pitch count restrictions or guidelines are often not followed. Purpose: To perform a quantitative analysis of pitch counts in youth baseball players and evaluate compliance with regard to the Pitch Smart guidelines in the tournament setting. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Included in the analysis were 100 youth baseball teams that competed in the 8-and-under to 14-and-under age divisions during the 2019 tournament season. Pitching data were compared with the Pitch Smart guidelines. Violations were identified as (1) exceeding maximum daily pitch count, (2) inadequate rest between pitching events, and (3) pitching more than 1 event on the same day. Pitcher and game factors were analyzed for possible relationships to guideline violations using mixed-effects negative binomial regression models, with comparisons of violations using rate ratios (RRs). Results: Analysis included 1046 pitchers and 2439 games. There were 1866 total Pitch Smart guideline violations, with 48.6% of pitchers having at least 1 violation. Inadequate rest was the most common reason for violation, with noncompliance occurring in 43.3% of pitchers. The highest rate of any violation (0.32 per appearance) occurred in the 8-and-under age division. High-volume pitchers had increased violation rates in each category compared with low-volume pitchers ( P < .001). Violation rates were increased more than twice the rate when pitchers participated in ≥5 consecutive games without a rest day when compared with a single game (RR, 2.48; P < .001). Conclusion: Noncompliance with Pitch Smart guidelines in tournament settings occurred in more than 90% of teams and almost half of all pitchers. Factors associated with noncompliance included younger pitcher age, high-volume pitching, and pitching in multiple consecutive games. Education of tournament directors, coaches, parents, and athletes regarding pitching guidelines is warranted in order to limit the risk of injury.

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Lipophilic Statin Use and Suicidal Ideation in a Sample of Adults With Mood Disorders

Crisis ◽

10.1027/0227-5910/a000260 ◽

2014 ◽

Vol 35 (4) ◽

pp. 278-282 ◽

Cited By ~ 14

Author(s):

Karen M. Davison ◽

Bonnie J. Kaplan

Keyword(s):

Suicidal Ideation ◽

Mood Disorders ◽

Prevalence Ratio ◽

Cross Sectional Study ◽

Community Based ◽

Cross Sectional ◽

Symptom Scores ◽

Unit Increase ◽

Predominantly Female ◽

Lipophilic Statin

Background: Mood disorders are associated with a high risk of suicide. Statin therapy has been implicated in this relationship. Aims: To further clarify reported associations between suicide and cholesterol in mental health conditions, we conducted an analysis of dietary, clinical, and suicidal ideation measures in community-living adults with mood disorders. Method: Data were used from a cross-sectional study of a randomly selected community-based sample (> 18 years; n = 97) with verified mood disorders. Dietary (e.g., fat, iron, vitamin intakes), clinical (e.g., current depression and mania symptoms, medications), and sociodemographic (age, sex, and income) measures were analyzed using bivariate statistics and Poisson regression with robust variance. Results: Participants were predominantly female (71.1%) with bipolar disorder (59.8%); almost one-third (28.9%) were taking lipophilic statins. The prevalence of suicidal ideation was more than 2.5 times in those taking statins, PR = 2.59, 95% CI 1.27–5.31, p < .05. The prevalence ratio for suicidal ideation was 1.10, 95% CI 1.06–1.15, p < .001, for each unit increase in mania symptom scores. No associations between suicidal ideation and dietary intake measures were identified. Conclusion: Individuals with mood disorders may be susceptible to neuropsychiatric effects of cholesterol-lowering drugs, which warrants further research.

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Prevalence of Morphological Variations Associated With Femoroacetabular Impingement According to Age and Sex: A Study of 1878 Asymptomatic Hips in Nonprofessional Athletes

Orthopaedic Journal of Sports Medicine ◽

10.1177/2325967120977892 ◽

2021 ◽

Vol 9 (2) ◽

pp. 232596712097789

Author(s):

Rodolfo Morales-Avalos ◽

Adriana Tapia-Náñez ◽

Mario Simental-Mendía ◽

Guillermo Elizondo-Riojas ◽

Michelle Morcos-Sandino ◽

...

Keyword(s):

Femoroacetabular Impingement ◽

Alpha Angle ◽

Cross Sectional Study ◽

Level Of Evidence ◽

Crossover Sign ◽

Cross Sectional ◽

Radiographic Findings ◽

Morphological Variations ◽

Pelvic Radiographs ◽

Center Edge

Background: Radiographic findings related to the cam and pincer variants of femoroacetabular impingement (FAI) include measurements of the alpha angle and lateral center-edge angle (LCEA). The function of these radiographic findings has been put into question because of high heterogeneity in reported studies. Purpose: The aim of this study was 3-fold: (1) to determine the prevalence of cam and pincer variants according to sex and age on anteroposterior (AP) pelvic radiographs from an asymptomatic nonathletic population, (2) to identify the most common radiographic signs of cam- and pincer-type variants, and (3) to determine if there are variations in the prevalence of these radiographic signs according to sex and age. Study Design: Cross-sectional study; Level of evidence, 3. Methods: There were 3 independent observers who retrospectively analyzed the 939 AP pelvic radiographs (1878 hips) of patients aged 18 to 50 years who did not have hip symptoms and who were not professional athletes. The prevalence of the cam and pincer variants according to the alpha angle and LCEA, respectively, and the presence of other radiographic signs commonly associated with these variables were determined in the overall population and by subgroup according to sex and age group (18-30, 31-40, and 41-50 years). Descriptive and inferential statistics were used to analyze the study sample. Results: The mean age of the included population was 31.0 ± 9.2 years, and 68.2% were male. The prevalence of the cam-type variant was 29.7% (558/1878), and that of the pincer-type variant was 24.3% (456/1878). The radiographic signs that were most associated with the cam and pincer variants were a pistol-grip deformity and the crossover sign, respectively. Significant differences ( P < .001) in the prevalence of these variants were identified between men and women in both variants. No differences were observed in the alpha angle or LCEA according to sex or age. Conclusion: Radiographic findings suggestive of FAI had significant variations with respect to sex and age in this study sample. This study provides information to determine the prevalence of these anatomic variants in the general population.

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Head Impact Biomechanics in Youth Flag Football: A Prospective Cohort Study

The American Journal of Sports Medicine ◽

10.1177/03635465211026643 ◽

2021 ◽

pp. 036354652110266

Author(s):

Landon B. Lempke ◽

Rachel S. Johnson ◽

Rachel K. Le ◽

Melissa N. Anderson ◽

Julianne D. Schmidt ◽

...

Keyword(s):

Mixed Model ◽

Linear Acceleration ◽

Cross Sectional Study ◽

Head Impact ◽

Rotational Acceleration ◽

Event Type ◽

Level Of Evidence ◽

Cross Sectional ◽

Head Impact Biomechanics ◽

Impact Biomechanics

Background: Youth flag football participation has rapidly grown and is a potentially safer alternative to tackle football. However, limited research has quantitatively assessed youth flag football head impact biomechanics. Purpose: To describe head impact biomechanics outcomes in youth flag football and explore factors associated with head impact magnitudes. Study Design: Cross-sectional study; Level of evidence, 3. Methods: We monitored 52 player-seasons among 48 male flag football players (mean ± SD; age, 9.4 ± 1.1 years; height, 138.6 ± 9.5 cm; mass, 34.7 ± 9.2 kg) across 3 seasons using head impact sensors during practices and games. Sensors recorded head impact frequencies, peak linear ( g) and rotational (rad/s2) acceleration, and estimated impact location. Impact rates (IRs) were calculated as 1 impact per 10 player-exposures; IR ratios (IRRs) were used to compare season, event type, and age group IRs; and 95% CIs were calculated for IRs and IRRs. Weekly and seasonal cumulative head impact frequencies and magnitudes were calculated. Mixed-model regression models examined the association between player characteristics, event type, and seasons and peak linear and rotational accelerations. Results: A total of 429 head impacts from 604 exposures occurred across the study period (IR, 7.10; 95% CI, 4.81-10.50). Weekly and seasonal cumulative median head impact frequencies were 1.00 (range, 0-2.63) and 7.50 (range, 0-21.00), respectively. The most frequent estimated head impact locations were the skull base (n = 96; 22.4%), top of the head (n = 74; 17.2%), and back of the head (n = 66; 15.4%). The combined event type IRs differed among the 3 seasons (IRR range, 1.45-2.68). Games produced greater IRs (IRR, 1.24; 95% CI, 1.01-1.53) and peak linear acceleration (mean difference, 5.69 g; P = .008) than did practices. Older players demonstrated greater combined event–type IRs (IRR, 1.46; 95% CI, 1.12-1.90) and increased head impact magnitudes than did younger players, with every 1-year age increase associated with a 3.78 g and 602.81-rad/s2 increase in peak linear and rotational acceleration magnitude, respectively ( P≤ .005). Conclusion: Head IRs and magnitudes varied across seasons, thus highlighting multiple season and cohort data are valuable when providing estimates. Head IRs were relatively low across seasons, while linear and rotational acceleration magnitudes were relatively high.

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