Hip Abductor Strength Asymmetry: Relationship to Upper Extremity Injury in Professional Baseball Players.

BACKGROUND: Hip strength is an important factor for control of the lumbo-pelvic-hip complex. Deficits in hip strength may affect throwing performance and contribute to upper extremity injuries. HYPOTHESIS: Deficits in hip abduction isometric strength would be greater in those who sustained an upper extremity injury and hip strength would predict injury incidence. STUDY DESIGN: Prospective cohort study. LEVEL OF EVIDENCE: Level 3. METHODS: Minor League baseball players (n = 188, age = 21.5 ± 2.2 years; n = 98 pitchers; n = 90 position players) volunteered. Hip abduction isometric strength was assessed bilaterally with a handheld dynamometer in side-lying position, expressed as torque using leg length (N·m). Hip abduction strength asymmetry was represented by [(trail leg/lead leg) × 100]. Overuse or nontraumatic throwing arm injuries were prospectively tracked. Poisson regression models were used to estimate relative risk ratios associated with hip asymmetry; confounders, including history of prior overuse injury in the past year, were included. RESULTS: Hip abduction asymmetry ranged from 0.05% to 57.5%. During the first 2 months of the season, 18 players (n = 12 pitchers) sustained an upper extremity injury. In pitchers, for every 5% increase in hip abduction asymmetry, there was a 1.24 increased risk of sustaining a shoulder or elbow injury. No relationship between hip abduction strength and injury was observed for position players. CONCLUSION: Hip abduction asymmetry in pitchers was related to subsequent upper extremity injuries. The observed risk ratio indicates that hip abduction asymmetry may contribute a significant but small increased risk of injury. CLINICAL RELEVANCE: Hip abduction muscle deficits may affect pitching mechanics and increase arm stress. Addressing hip asymmetry deficits that exceed 5% may be beneficial in reducing upper extremity injury rates in pitchers.

Hip Abduction Strength: Relationship to Trunk and Lower Extremity Motion During A Single-Leg Step-Down Task in Professional Baseball Players.

BACKGROUND: The single-leg step down task (SLSD) is a clinical tool to assess movement and control of the lower extremity and trunk. Hip abduction weakness may impact movement quality during the SLSD, however the relationships between movement and strength are unclear. PURPOSE: To determine the relationship between hip abduction isometric strength and movement during the SLSD of trunk lean, pelvic drop, knee valgus, and hip flexion. STUDY DESIGN: Cross sectional, cohort study. METHODS: One hundred-eighteen Minor League baseball players (age=21.6 ± 2.0 years; n=68 pitchers, n=50 position players) participated. Bilateral hip abduction isometric strength was measured using a handheld dynamometer (HHD), and then multiplied by distance from the greater trochanter to the HHD and expressed as hip abduction torque. Video cameras captured the SLSD, with participants standing on one leg while lowering their contralateral heel to touchdown on the floor from a 0.203m (8in.) step. Trunk lean, trunk flexion, pelvic drop, knee valgus, and hip flexion were measured using Dartfish at heel touchdown. A value of 180° indicated no knee valgus. Pearson correlations examined the relationships between hip abduction torque and SLSD motions. RESULTS: There were no significant correlations for position players. For pitchers, on the lead leg increased hip abduction torque weakly correlated with a decrease in knee valgus (r= 0.24, p=0.049). Also for pitchers on the trail leg, increased hip abduction torque weakly correlated with decreased pelvic drop (r= -0.28, p=0.021). CONCLUSION: Hip abduction strength contributes to dynamic control of the trunk and legs. Specifically in pitchers, hip abduction weakness was related to increased movement of the lower extremity and lumbopelvic regions during the dynamic SLSD task. These deficits could translate to altered pitching performance and injury. LEVELS OF EVIDENCE: 2.

The ulnar collateral ligament responds to stress in professional pitchers.

BACKGROUND: Our purpose with this study was to determine the response of the ulnar collateral ligament (UCL) in professional pitchers after exposure to a season of pitching and to rest during an off-season. METHODS: In a prospective study supported by Major League Baseball, all pitchers within a single professional baseball club were enrolled. An ultrasound of the ligament was then performed by a single fellowship-trained ultrasonographer at the beginning of the season (T1), the end of the season (T2), and the beginning of the following season (T3). We measured the UCL thickness and ulnotrochlear joint opening at 30° of flexion with and without stress. Two ultrasound images were saved. Inter- and intra-rater reliability were determined. A multivariable analysis was conducted. RESULTS: A total of185 total pitchers were included: 94 pitchers at T1, 83 at T2, and 118 at T3. These pitchers had 12 [7, 15] (median [interquartile range]) years of pitching experience and had a peak velocity of 95 [93, 97] miles/hour. Intra- and inter-rater reliability were excellent. The baseline UCL thickness was associated with peak velocity (P = .031) and prior UCL reconstruction (P = .024). After accounting for pitching experience, peak velocity, and prior UCL reconstruction, thickness increased during the season (P = .002) and decreased during the off-season (P = .001). After accounting for these same variables, valgus laxity at 30° increased during the season (P = .002) and decreased during the off-season (P = .029). CONCLUSION: The UCL responds to stress in professional pitchers by becoming thicker and more lax, and responds to rest by becoming thinner and less lax.

Ultrafine- and uniform-grained biodegradable Zn-0.5Mn alloy: Grain refinement mechanism, corrosion behavior, and biocompatibility in vivo.

An ultrafine- and uniform-grained Zn-0.5Mn alloy (D3 alloy, stands for deformation rate of 99.5%) is fabricated via multi-pass drawing. The alloy features excellent ductility and elongation properties (up to 245.0% ± 9.0% at room temperature). Zn-0.5Mn alloys are composed of two phases, namely, Zn and MnZn13. The MnZn13 phase confers multiple effects during refinement by inducing and pinning low-angle boundaries within grains. Meanwhile, the presence of these phases along grain boundaries prevents the growth of new refined grains. D3 shows uniform corrosion behaviors in c-SBF solution on account of the even distribution of the MnZn13 phase in its microstructure. Animal implantation experiments indicate that D3 has good biocompatibility; it does not cause damage to bone tissue or other organs. Taking the results together, D3 may be developed into a new type of biodegradable material with remarkable elongation and corrosion properties and satisfactory biocompatibility for medical applications.

Human activity pattern implications for modeling SARS-CoV-2 transmission.

BACKGROUND AND OBJECTIVES: SARS-CoV-2 emerged in December 2019 and rapidly spread into a global pandemic. Designing optimal community responses (social distancing, vaccination) is dependent on the stage of the disease progression, discovery of asymptomatic individuals, changes in virulence of the pathogen, and current levels of herd immunity. Community strategies may have severe and undesirable social and economic side effects. Modeling is the only available scientific approach to develop effective strategies that can minimize these unwanted side effects while retaining the effectiveness of the interventions. METHODS: We extended the agent-based model, SpatioTemporal Human Activity Model (STHAM), for simulating SARS-CoV-2 transmission dynamics. RESULTS: Here we present preliminary STHAM simulation results that reproduce the overall trends observed in the Wasatch Front (Utah, United States of America) for the general population. The results presented here clearly indicate that human activity patterns are important in predicting the rate of infection for different demographic groups in the population. CONCLUSIONS: Future work in pandemic simulations should use empirical human activity data for agent-based techniques.

PREVALENCE OF HAMSTRING INJURIES IN SUMMER LEAGUE BASEBALL PLAYERS.

BACKGROUND AND PURPOSE: Hamstring injuries (HSI) occur more commonly in baseball than are often appreciated and can impact the potential career of a player. Little is known about the historical incidence of these injuries in summer league players preparing for their upcoming collegiate season or being drafted by major league team(s). Summer league baseball players have a high historical incidence of HSI which are often unknown at the start of their summer league play. The purpose of this study was to administer a validated questionnaire to assess various factors regarding the prevalence of prior hamstring injuries, current symptoms of posterior thigh pain or hamstring injuries in amateur summer league baseball players, and to provide details on the injury history, time lost from injury, injury reocurrence, position, individual player physical characteristics and physical activities that might be associated with those injuries. STUDY DESIGN: Cross-sectional Observational Study. METHOD: A self-reported, validated questionnaire regarding the history, prevalence, reoccurrence and functional impact of HSI and posterior thigh pain was administered to and completed by 201 out of 251 summer league baseball players associated with the Cape Cod League and the Northwoods League at the start of the 2013-2015 seasons. The questionnaire was administered by certified athletic trainers associated with each team. Participation was voluntary and informed consent was obtained from all players. RESULTS: Forty seven out of 201 players surveyed reported a HSI history. Sixty-six percent of these players (N = 31) reported unilateral injuries and 34% (N = 16) reported bilateral injuries. Reoccurrence rate was 27.7% across all players. Approximately 1/3rd of all position players (catchers 33.3%, infielders 32.6% and outfielders 31.6%) reported a HSI history compared to 12.9% of all pitchers. Significant differences (p<.05) existed between the HSI and Non-HSI groups for self-reported symptoms, soreness, and pain, as well as function and quality of life. Within the HSI history group, players who batted left and threw right reported the most injuries. CONCLUSION: A large number of position players and pitchers who report for summer league baseball have a history of posterior thigh pain and HSI. Those with prior injuries have a high reoccurrence rate. Position players have a higher incidence of injury than do pitchers. LEVEL OF EVIDENCE: 3.

Hamstring Injury Trends in Major and Minor League Baseball: Epidemiological Findings From the Major League Baseball Health and Injury Tracking System.

BACKGROUND: Hamstring strains are the most common injury for professional baseball players and can result in significant time on the disabled list. To date, no study has reported the current trends in hamstring strains in professional baseball. HYPOTHESIS: Professional baseball players would have an increased incidence of hamstring strains from 2011 through 2016. STUDY DESIGN: Descriptive epidemiology study. METHODS: Injury data were prospectively collected from 2011 through 2016 for every Major League Baseball (MLB) and Minor League Baseball (MiLB) team and was recorded in the MLB Health and Injury Tracking System. Data collected for this study included date of injury, activity during injury, time lost, primary injury or reinjury status, and imaging findings as well as player demographic information related to level of play, age, and position for all hamstring injury events. Injury rates were reported as hamstring injuries per number of games. RESULTS: From 2011 to 2016, there were 2633 hamstring strains in professional baseball players. The rate of hamstring strains increased in MLB from a low of 1 injury every 39 games in 2011 to a high of 1 injury every 30 games in 2016. In MiLB, there were 2192 hamstring strains, with 1 injury every 35 games in 2011 compared with 1 injury every 30 games in 2016. The majority of injuries occurred in the infielder positions (37.5%) and resulted from base running (>50%), most commonly from home to first base. The most common hamstring injury was a grade 2 injury to the distal biceps femoris. The mean time missed after a hamstring injury was 14.5 days. Grade 3 and grade 2 hamstring strains resulted in significantly more days missed compared with grade 1 injuries (P = .005 and P = .002, respectively). The rate of recurrent hamstring injuries was 16.3% for MLB and 14.2% for MiLB. Recurrent hamstring injuries resulted in more time lost than primary injuries (mean, 16.4 vs 14.5 days, respectively; P = .02). A total of 42 injuries were treated with platelet-rich plasma, and 19 were treated with surgery. The number of injuries treated with platelet-rich plasma increased in successive years. CONCLUSION: The rate of hamstring strains in professional baseball players has increased over the past 6 years and has resulted in a significant loss of playing time. Study results indicated that these injuries are affected by injury characteristics, position played, running to first base, seasonal timing, and history of hamstring injuries.

Intertester reliability and validity of motion assessments during lumbar spine accessory motion testing.

BACKGROUND AND PURPOSE: Posterior-anterior (PA) assessment of the lumbar spine correlates with radiographic signs of instability and can guide treatment choices, yet studies of the validity of lumbar PA assessments have not been conducted in vivo. The purposes of this study were to determine the intertester reliability of the PA examination in assessing intersegmental lumbar spine motion and to evaluate the validity of this procedure in vivo with dynamic magnetic resonance imaging (MRI). SUBJECTS: Twenty-nine subjects with central lumbar pain participated in this study. METHODS: Two physical therapists independently identified each subject's most and least mobile lumbar segments using the PA procedure. Midsagittal lumbar images were obtained simultaneously during one examiner's assessment. Lumbar segmental mobility was quantified from magnetic resonance images as the change in the intervertebral angle between the resting position and the end range of the PA force application. For each vertebral level tested, maximal sagittal-plane segmental motion was determined. RESULTS: The intertester reliability for identifying the least mobile segment was good (agreement=82.8%, kappa=.71, 95% confidence interval [CI]=.48 to .94), but it was poor for identifying the most mobile segment (kappa=.29, 95% CI=-.13 to .71), despite good agreement (79.3%). The level of agreement between the PA assessments and intervertebral motion measured by MRI was poor (kappa=.04, 95% CI=-.16 to .24, and kappa=.00, 95% CI=-.09 to .08, for the least and most mobile segments, respectively). DISCUSSION AND CONCLUSION: Despite good intertester reliability for identifying the least mobile segment, PA assessments of lumbar segmental mobility did not agree with sagittal-plane motion measured by dynamic MRI. This finding calls into question the validity of the PA procedure for assessing intervertebral lumbar spine motion.