An Analysis of Intrapitch Variation in Joint and Segment Velocities With Throwing Arm Kinetics in High School and Professional Baseball Pitchers.

BACKGROUND: Improper sequencing order of maximal joint and segment velocities has been identified as an important predictor for both throwing arm kinetics and ball velocity. PURPOSE: To investigate the intrapitcher variation of maximal segment velocities and the relationship to throwing arm kinetics and ball velocity in high school (HS) and professional (PRO) pitchers. STUDY DESIGN: Descriptive laboratory study. METHODS: HS (n = 59) and PRO (n = 338) pitchers, instructed to throw 8 to 12 fastball pitches, were evaluated with 3-dimensional motion capture (480 Hz). Maximal joint and segment velocities were calculated for each pitch, and the standard deviation of the maxima was calculated per pitcher. These standard deviations were used to classify pitchers as "low variance" or "high variance" for each segmental velocity subgroup, "overall low variance" or "overall high variance" based on cumulative segment velocity variation, or "population," with any pitcher eligible to be included in multiple subcategories. Maximal velocities and throwing arm kinetics were compared among the various subgroups. RESULTS: The HS low-variance shoulder internal rotation velocity subgroup (4949 ± 642 deg/s) had significantly lower maximal shoulder internal rotation velocity compared with HS population (5774 ± 1057 deg/s) (P < .001); similar findings were observed for PROs (5269 ± 835 vs 5824 ± 1076 deg/s; P < .001), as well as lower shoulder superior force compared with the PRO population (14.8% ± 8.8% vs 17.8% ± 8.8% body weight; P = .001). The PRO low-variance lead knee extension velocity subgroup had significantly lower maximal lead knee extension velocity (216 ± 135 vs 258 ± 125 deg/s; P = .001) and shoulder distractive force (111.5% ± 14.4% vs 115.6% ± 15.9% body weight; P = .003) compared with the PRO population. The PRO overall low-variance subgroup had significantly lower shoulder distractive force (111.8% ± 14.1% vs 119.6% ± 15.5% body weight; P = .008) and elbow anterior force (40.6% ± 5.0% vs 43.6% ± 6.2% body weight; P = .008) compared with the PRO overall high-variance subgroup. CONCLUSION: HS and PRO pitchers with low variance for joint and segment velocities achieved significantly lower maximal velocities in the subgroup of interest, while preserving ball velocity. PRO pitchers with overall low variance among multiple maximal joint and segment velocities demonstrated decreased shoulder distractive and elbow anterior force. CLINICAL RELEVANCE: PRO pitchers with low intrapitch variation in maximal joint and segment velocities may be viewed as kinetically conservative throwers. These pitchers with similarly maintained mechanics between pitches may have an increasingly regimented form that preserves kinetic forces about the throwing arm. The opposite may be true for PRO pitchers with increased variability in segmental velocities during their pitching motion, as they showed increased throwing arm kinetics including shoulder distractive and elbow anterior force compared with the overall low-variance group, theoretically increasing their risk of injury.

Incidence of Vitamin D Deficiency in Foot and Ankle Arthrodesis Nonunions.

Background Vitamin D has been found to be crucial in musculoskeletal health. The role of vitamin D levels in orthopedic patients has become a growing area of interest given its negative impact on fracture healing which can contribute to the development of nonunion following surgery. We sought to investigate the incidence of hypovitaminosis D in a cohort of patients who experienced a nonunion following a foot and ankle arthrodesis procedure. Methodology Patients who underwent a major elective foot and ankle arthrodesis procedure and developed a nonunion were given the opportunity to obtain serum vitamin D levels. All vitamin D levels were reported from percutaneous venous blood samples and compared to our institution's range of accepted normal values (25-80 ng/mL). Results A total of 13 patients who developed a nonunion agreed to have a vitamin D level obtained, and 11 of 13 patients had a low vitamin D level (average = 14.6 ng/mL, range = 9-24 ng/mL). Five patients underwent revision arthrodesis after normalization of vitamin D levels, and four out of five patients went on to successful union. Conclusions Hypovitaminosis D may be a modifiable risk factor for nonunion following a major foot and ankle arthrodesis procedure. Orthopedic surgeons should consider vitamin D screening and supplementation in patients undergoing elective arthrodesis procedures.

Kinematic Parameters Predictive of Pitch Velocity in Youth to Professional Baseball Pitchers: A Qualitative Systematic Review.

Background: Specific kinematic factors have been found to contribute to faster pitch speeds, with poor mechanics leading to injury. Purpose: To discuss the kinematic parameters that predict faster ball velocity among baseball pitchers. Study Design: Systematic review. Methods: Using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, the authors utilized the Cochrane Database of Systematic Reviews, PubMed (2008-2019), and OVID/MEDLINE (2008-2019) databases. Eligible articles included those that reported on kinematic factors predictive of ball velocity across youth, high school, collegiate, and professional levels of play. The quality of all included studies was evaluated by 2 reviewers using the Appraisal tool for Cross-Sectional Studies (AXIS). The lack of consistent study design or outcome variables precluded meta-analysis. Results: A total of 584 studies were identified from the initial search with 12 included in final analysis (930 pitchers in total; 429 [46.1%] youth, 164 [17.6%] high school, 153 [16.5%] collegiate and 184 [19.8%] professional) with mean ball velocity of 71.1 mph (114.4 km/h). The average AXIS score was 16 out of a possible 20. The shoulder played a significant role in the generation of velocity-induced torques. Hip and shoulder separation was associated with a 2.6 ± 0.5 mph (4.1 ± 0.8 km/h) increase in velocity, whereas increased shoulder movement of the nonthrowing arm was negatively correlated with initial ball velocity (r2 = 0.798). Furthermore, hip/shoulder separation, decreased movement of the nonthrowing shoulder, trunk power and timing of maximum trunk rotation, increased contralateral trunk tilt and increased sagittal-plane trunk tilt, and decreased knee flexion at ball release were all associated with higher fastball speeds. Conclusion: Multiple upper extremity and trunk kinematic parameters affect ball velocity, with significant contributions from the throwing shoulder and trunk, as well as nondominant arm. Understanding kinematic predictors of faster ball velocity can help guide training regimens.

Forearm Pronation at Foot Contact: A Biomechanical Motion-Capture Analysis in High School and Professional Pitchers.

Background: It has previously been speculated that baseball pitchers who display excessive forearm pronation at foot contact (FC) have a higher propensity toward ulnar collateral ligament injury and subsequent surgery. Purpose: To evaluate the association between degree of forearm pronation/supination at FC and throwing arm kinetics in high school and professional pitchers, at both the individual (intrapitcher) and the group (interpitcher) level. Study Design: Descriptive laboratory study. Methods: High school (n = 41) and professional (n = 196) pitchers threw 8 to 12 fastballs while being assessed with a 3-dimensional motion-capture system (480 Hz). Pitchers at each playing level were divided into a supination or pronation subgroup depending on degree of forearm pronation at FC. Regression models were built to observe the relationship between forearm pronation at FC and kinetic and kinematic parameters of interest. Results: At both the individual and the group level of high school and professional pitchers, there was no significant correlation between forearm pronation at FC and elbow varus torque (P min = .21). For every 10° increase in forearm pronation at FC in the individual high school pitcher, elbow flexion at FC decreased by 5°, whereas maximum elbow extension velocity was achieved 0.6% later in the pitch. In addition, elbow medial force increased by 4.1 N and elbow varus torque increased by 0.8 N·m for every 10° increase in forearm supination at FC. For every 10° increase in forearm supination in the individual professional pitcher, ball velocity increased by 0.5 m/s, shoulder external rotation at FC decreased by 11°, and elbow medial force decreased by 5.5 N. Conclusion: Supination- or pronation-predominant forearm motion during the pitch did not significantly differ between playing levels. Excessive forearm pronation at FC was not a significant risk factor for increased throwing arm kinetics for high school or professional pitchers. There was a weak positive association between forearm supination at FC and elbow varus torque in the individual high school pitcher. Ultimately, coaches and pitchers may be better served by redirecting their focus to other mechanical aspects of the pitch that may have stronger associations with injury risk implications as well as performance.

A Systematic Review of Lower-Body Kinematic and Strength Factors Associated With Pitch Velocity in Adult Baseball Pitchers.

CONTEXT: Ball velocity for baseball pitchers is influenced by a multitude of factors along the kinetic chain. While a vast amount of data currently exist exploring lower-extremity kinematic and strength factors in baseball pitchers, no previous study has systematically reviewed the available literature. OBJECTIVE: The aim of this systematic review was to perform a comprehensive assessment of the available literature investigating the association between lower-extremity kinematic and strength parameters and pitch velocity in adult pitchers. EVIDENCE ACQUISITION: Cross-sectional studies that investigated the association between lower-body kinematic and strength factors and ball velocity in adult pitchers were selected. A methodological index for nonrandomized studies checklist was used to evaluate the quality of all included studies. EVIDENCE SYNTHESIS: Seventeen studies met the inclusion criteria comprising a total of 909 pitchers (65%, professional, 33% college, and 3% recreational). The most studied elements were hip strength and stride length. The mean methodological index for nonrandomized studies score was 11.75 of 16 (range = 10-14). Pitch velocity was found to be influenced by several lower-body kinematic and strength factors including the following: (1) hip range of motion and strength of muscles around the hip and pelvis, (2) alterations in stride length, (3) alterations in lead knee flexion/extension, and (4) several pelvic and trunk spatial relationships throughout the throwing phase. CONCLUSIONS: Based on this review, we conclude that hip strength is a well-established predictor of increased pitch velocity in adult pitchers. Further studies in adult pitchers are needed to elucidate the effect of stride length on pitch velocity given mixed results across multiple studies. This study can provide a basis for trainers and coaches to consider the importance of lower-extremity muscle strengthening as a means by which adult pitchers can improve pitching performance.

Increased Pitch Velocity Is Associated With Throwing Arm Kinetics, Injury Risk, and Ulnar Collateral Ligament Reconstruction in Adolescent, Collegiate, and Professional Baseball Pitchers: A Qualitative Systematic Review.

PURPOSE: To assess the relationship between pitch velocity and throwing arm kinetics, injury, and ulnar collateral ligament reconstruction (UCLr) among high school, collegiate, and professional baseball pitchers. METHODS: The Cochrane Database of Systematic Reviews, the Cochrane Central Register of Controlled Trials, PubMed (2008-2019), and OVID/MEDLINE (2008-2019) were queried for articles that reported on pitch velocity predicting throwing arm kinetics, injury, or UCLr. The Methodological Index for Non-randomized Studies checklist was used to evaluate the quality of all included studies. Descriptive statistics with ranges were used to quantify data where appropriate. RESULTS: A total of 24 studies examining 2,896 pitchers, with Level of Evidence II-V were included. Intergroup analysis noted pitch velocity was significantly correlated with elbow varus torque in high school (R2 = 0.36), collegiate (R2 = 0.29), and professional (R2 = 0.076) pitchers. Elbow distraction force was positively associated with ball velocity in interpitcher analyses of high school (R2 = 0.373), professional (R2 = 0.175), and mixed-cohort evaluations (R2 = 0.624). Intragroup analysis demonstrated a strong association between pitch velocity and elbow varus torque (R2 = 0.922-0.957) and elbow distraction force (R2 = 0.910) in professional pitchers. Faster ball velocity was positively associated with a history of throwing arm injury (R2 = 0.194) in nonadult pitchers. In 2 studies evaluating professionals, injured pitchers had faster pitch velocity before injury compared with uninjured controls (P = .014; P = .0354). The need for UCLr was positively correlated with pitch velocity (R2 = 0.036) in professional pitchers. The consequences of UCLr noted little to no decrease in pitch velocity. CONCLUSIONS: Professional baseball pitchers with faster pitch velocity may be at the greatest risk of elbow injury and subsequent UCLr, potentially through the mechanism of increased distractive forces on the medial elbow complex. When a pitcher ultimately undergoes UCLr, decreases in pitching performance are unlikely, but may occur, which should encourage pitchers to caution against maximizing pitch velocity. LEVEL OF EVIDENCE: Level IV, systematic review of Level II-IV studies.

Lower Extremity Muscle Injuries in the Overhead Athlete.

PURPOSE OF REVIEW: Lower extremity (LE) injuries are a common source of disability and time-loss for overhead athletes, and muscles have been found to be the predominant soft tissue structure affected. The current review highlights the orthopaedic literature examining lower extremity muscle injuries in overhead athletes in regard to epidemiology, diagnosis, and conventional and emerging treatment measures. RECENT FINDINGS: The hamstring muscles have been found to be the most commonly injured lower extremity muscle group in professional baseball, followed by the adductors, quadriceps, iliopsoas, and gastrocnemius-soleus complex. Strains and contusions comprise over 90% of these muscle injuries. Various advanced imaging grading systems have been developed to help characterize the nature of a muscle injury, although a clear and consistent prognostic utility of these systems is still unclear. The vast majority of lower extremity muscle injuries in overhead athletes are managed nonoperatively, and there is promising data on the use of emerging treatments such as platelet-rich plasma and blood flow restriction therapy. Lower extremity muscle injuries-often referred to as strains-are a relatively common issue in high-demand overhead athletes and can be a significant source of time-loss. Within baseball, position players are affected far more often than pitchers, and sprinting and fielding are the most common activities leading to strains. Magnetic resonance imaging (MRI) is considered the gold standard imaging modality to evaluate these muscle injuries and will allow for a detailed assessment of tissue damage. Nonetheless, return-to-play is often dictated by a given athlete's progression through a nonoperative rehabilitation protocol, with surgical intervention reserved for less common, select injury patterns.

Variability in Pitch Count Limits and Rest Day Requirements by State: Implications of Season-Long Pitch Counts in High School Baseball Pitchers.

BACKGROUND: It is unknown how different pitch count limits and rest day requirements affect cumulative pitch counts during a baseball season. PURPOSE: To determine (1) the variability of pitch count rules in high school baseball and (2) the theoretical effect of different pitch count limits and rest day combinations on game, weekly, and seasonal pitch totals in high school baseball pitchers. STUDY DESIGN: Cross-sectional study. METHODS: Pitch count rules for the 2019-2020 academic year for 48 sanctioned states were recorded from each state's athletic association website. Maximum pitch count limits were recorded along with the number of pitches allowed before requiring 0 to 5 rest days before the next pitching outing. Rules were also analyzed for several distinctions, including the athlete's level of competition, age, and grade. To determine the effect of pitch count rules and rest days, a theoretical 3-month season was calculated in the following scenarios: (1) variable maximum pitch count limits with a universal 3-day rest requirement, (2) universal 110 pitch count limit with variable rest day requirements (3, 4, or 5 days), and (3) actual pitch count limits and required rest days for every state assuming pitchers throw as many pitches as allowed. Analysis of variance and Student t tests were used to compare between-group and intragroup seasonal pitch totals based on variations in required rest days. RESULTS: The most common maximum pitch count limit for a varsity high school athlete was 110 pitches (range, 100-125 pitches) with 4 rest days (range, 0-5 days). We found that 23 states (48%) did not make distinctions for pitch count rules based on the athlete's level of competition, age, or grade. We noted a 25% increase in total seasonal pitch counts between the smallest and largest pitch count limit when assuming constant 3-day rest. We found a 53% difference in total seasonal pitch count when rest days varied between 3 and 5 days with a constant 110-pitch limit. Allowing 140 pitches in a 4-day span without a specific rest day requirement resulted in the highest seasonal pitch count (Nevada). There was a 49% difference in maximum seasonal pitch counts between the most and least restrictive states (P < .001). Submaximum pitch limits resulted in higher seasonal pitch counts than maximum pitch limits in 56% of states. CONCLUSION: Pitch count rules vary widely by state. Required rest days influenced total seasonal pitch counts more than maximum or submaximum pitch count limits.

Interval Throwing Programs at Distances Beyond 150 Feet Can Be Equivalent to Pitching Over Five Innings.

PURPOSE: To determine the cumulative elbow varus torque (EVT) experienced during created interval throwing programs (ITP) and derive innings pitched equivalent for each step. METHODS: High school pitchers wearing the motusBASEBALL sensor who had at least 50 throws at 90, 120, 150, and 180 ft and game pitches were included in this analysis. Means for EVT per throw and torque per minute were calculated at each distance. Three throwing programs were created using a template of 1 phase at each distance with 2 steps per phase. Programs varied only by number of throws per set (20, 25, and 30 throws for Program A, B, and C, respectively). Total EVT for each step, phase, and program were calculated using mean EVT per throw at each distance. Total EVT for each step and program were converted to a mean inning pitched equivalent (IPE) and maximum pitch count equivalent (MPE), respectively, using in-game pitching torque values and expected mean pitch counts (15 pitches/inning and maximum 105 pitches/game). RESULTS: In total, 3,447 throws were analyzed from 7 subjects (16.7 years ± 0.8 years). EVT per throw increased at each distance (range 36.9-45.5 N·m), comparable to game pitches (45.7 N·m). Mean EVT per minute was highest for 90 ft throws (193.4 N·m/min) and lowest for game pitches (125 N·m/min). Throwing Program A had the lowest range of IPE (Step 1: 2.0 and Step 8: 3.7), and Program C had the highest range (Step 1: 3.0 and Step 8: 5.6). The phases of Program A never exceeded 1MPE. Program B exceeded this threshold after Phase 1, and Program C exceeded 1MPE at every phase. Total program MPE ranged from 3.5 to 5.2 (Program A and C, respectively). CONCLUSIONS: Programs requiring 25 or more throws per set reached approximately 5 IPE per day. Increasing throwing repetitions by 10 throws resulted in a nearly 50% increase in IPE and MPE. LEVEL OF EVIDENCE: IV, retrospective cohort study.

The Most Common Type, Severity, and Expected Frequency of Injuries Vary by Defensive Position in Professional Baseball Players.

BACKGROUND: Location, frequency, and severity of in-game injuries by defensive position played have never been determined in professional baseball players. HYPOTHESIS: Catchers would have a higher frequency of hip and knee injuries; infielders and outfielders would have a higher frequency of general lower extremity injuries; and pitchers would have a higher frequency and severity of shoulder and elbow/forearm injuries. STUDY DESIGN: Descriptive epidemiology study. METHODS: The Major League Baseball Health and Injury Tracking System database was queried for all injuries in Major League Baseball and Minor League Baseball during the 2011-2019 seasons. Injuries were stratified by the following variables: athlete's level of play at the time of injury, anatomic region injured, whether the injury occurred during a game, and position played at the time of injury (infielder, outfielder, catcher, or pitcher). Number of days missed from competition immediately after an injury was used as a surrogate for injury severity: mild (0 days missed), moderate (1-5 days), and severe (>5 days). Observed versus expected injury ratios were calculated for each anatomic region based on position played, and ratios were adjusted by the number of players per position type during a standard inning of play. RESULTS: A total of 112,405 work-related injuries were reported, with the majority of injuries (86,520; 77%) occurring in Minor League Baseball athletes. Injuries to the leg, hand, shoulder, torso, and foot were the most common for athletes in both leagues, while hip/groin injuries were the least common. Catchers sustained the most in-game defensive head/neck injuries, while infielders and outfielders had the highest number of knee injuries. Starting and relief pitchers had the greatest total proportion of in-game defensive injuries across every other body region. Infielders and outfielders sustained injuries less frequently than expected across all body regions, while pitchers experienced more injuries than expected for all body parts. Catchers experienced more injuries than expected to the head/neck, hand, hip/groin, knee, and foot, and were more likely than other position players to sustain a knee injury that was categorized as severe based on time missed. CONCLUSION: The location, severity, and frequency of injuries vary by defensive position among professional baseball players.

Seasonal and monthly trends in elbow ulnar collateral ligament injuries and surgeries: a national epidemiological study.

Background: Monthly incidence of elbow ulnar collateral ligament (UCL) injuries and surgeries is relatively unknown. Defining seasonal peaks of UCL injuries and surgeries may identify opportunities for injury-prevention strategies. The purpose of this study is to analyze seasonal and monthly variations in UCL injuries and surgeries across the United States with emphasis on the timing of baseball season. Methods: The Truven Health MarketScan database (2013-2015) was queried for patients younger than 40 years with a diagnosis code of elbow UCL sprain and a procedural code for UCL repair or reconstruction. Differences in patient characteristics were evaluated using chi-square and Mann-Whitney U-tests. Negative binomial regression models were calculated for UCL injuries and surgeries to assess monthly trends. Results: UCL injuries were sustained by 13,894 patients, with 1404 (10.1%) patients having undergone surgery. The median age at first diagnosis was 17 years, and the median age of patients requiring surgery decreased from 20 to 18 years from 2013 to 2015 (P = .75). Most UCL injuries (n = 3785) and surgeries (n = 438) occurred during the spring season (March 21-June 20), and spring injuries were most likely to result in surgical management (11.6%). During the baseball season (March to September), the number of UCL injuries peaked in April/May, then declined, except for a second peak in September/October (incidence rate ratio 0.97; confidence interval 0.95, 0.99; P = .01). The number of UCL surgeries steadily increased from March (n = 116) to June (n = 152), followed by a gradual decline (incidence rate ratio 1.00; confidence interval 0.96, 1.04; P = .99). Conclusion: Athletes frequently experienced UCL injuries and surgeries in the early months (April-June) of the baseball season. More emphasis should be paid to rehabilitative strategies at the beginning of a baseball season to help mitigate injury risk.

Decreased Trunk Rotation at Foot Contact in Professional Baseball Pitchers With Prior Conservatively Managed SLAP Tears: A Propensity Score-Matched Analysis.

PURPOSE: To compare kinematic and kinetic parameters between a cohort of fully recovered professional pitchers with prior shoulder injury treated conservatively and a cohort with no prior shoulder injury. METHODS: Twenty-six fully recovered professional baseball pitchers with a history of shoulder injury treated conservatively pitched 8 to 10 fastball pitches using 3-dimensional motion capture (480 Hz). All shoulder injuries occurred within a 1- to 4-year time span from biomechanical evaluation and were severe enough to prevent pitchers from playing for between 1 and 12 months. These pitchers were propensity score matched by age, height, weight, handedness, and ball velocity to pitchers with no prior injury history (control) at a ratio of 1:4. We compared 21 kinematic and 11 kinetic parameters between groups using appropriate parametric testing. Subanalysis comparisons of pitchers with prior SLAP injury as well as rotator cuff tendinitis were also performed. RESULTS: SLAP tears (n = 11, 42.3%) were the most frequently reported injury, followed by rotator cuff tendinitis and/or shoulder impingement (n = 7, 26.9%). Compared with the control group, the 26 pitchers with prior injury showed no significant differences across the kinematic and kinetic factors. However, the SLAP tear subgroup did show significantly less trunk rotation at foot contact compared with controls (34.1° ± 4.9° vs 39.2° ± 10.2°, P = .0075). CONCLUSIONS: Fully recovered professional baseball pitchers with shoulder injuries treated conservatively showed no significant differences in kinetics or kinematics compared with their propensity score-matched counterparts, suggesting that shoulder injury alone may not greatly alter pitching mechanics. However, whereas prior groups have shown a decrease in trunk rotation at foot contact after surgical repair for SLAP tears, our study suggests that this kinematic change may alternatively originate with the injury itself. CLINICAL RELEVANCE: Understanding the cause of biomechanical adaptations by pitchers after injury can better aid clinicians and coaching staff in providing individualized and specific care to the throwing athlete.

Increased Shoulder Distraction Force and Shoulder Horizontal Abduction in Professional Baseball Pitchers With Discordant Torso Rotation Order.

BACKGROUND: Inefficient energy transfer from the pelvis and trunk has been shown to increase compensation at the level of the shoulder. Kinetic chain sequencing of the core segments is underexamined in professional baseball pitchers, especially as it relates to changes in upper extremity kinetics. PURPOSE: To evaluate elbow and shoulder kinetics in a cohort of professional pitchers differentiated by instances of discordant pelvic to upper torso sequencing during the pitch. STUDY DESIGN: Descriptive laboratory study. METHODS: 285 professional baseball pitchers were evaluated using 3D motion capture (480 Hz). Pitchers were divided into "chronological" and "discordant" groups based on whether maximum pelvic rotation velocity occurred before (chronological) or after (discordant) maximum upper torso rotation velocity during the pitch motion. Pelvic, upper torso, and shoulder kinematic parameters, shoulder distraction force, shoulder internal rotation torque, and pitch efficiency (PE) were compared between groups. RESULTS: Pitchers with discordant torso sequencing (n = 30; 110 pitches) had greater shoulder horizontal adduction at maximum external rotation (mean difference, 3.6°; 95% CI, -5.2° to -2.0°; t = -4.5; P < .001) and greater maximum shoulder external rotation (mean difference, 3.7°; 95% CI, 5.7° to 1.5°; t = -3.5; P < .001) than chronological pitchers (n = 255; 2974 pitches). PE did not differ between groups (P = .856), whereas ball velocity was significantly faster in the discordant group (mean difference, 0.6 m/s; 95% CI, -1.1 to -0.3 m/s; t = -3.3; P = .0012). Chronological pitchers had significantly reduced shoulder distraction force (mean difference, -4.7% body weight (BW); 95% CI, -7.9% to -1.5% BW; t = -2.9; P = .004) with no difference in shoulder internal rotation torque (P = .160). These kinematic and kinetic differences were not observed when accounting for interpitcher variability. CONCLUSION: Between pitchers, those who had a discordant pelvic to upper torso sequence experienced significantly greater shoulder distraction forces, potentially compensating by increasing maximum shoulder external rotation and horizontal abduction. Achieving maximal pelvic rotation velocity before maximal rotation velocity may be advantageous in preventing compensation at the upper extremity and excessive throwing arm loading. CLINICAL RELEVANCE: Identifying risk factors for increased upper extremity forces has potential implications in injury prevention. Specifically, mitigating shoulder distraction forces may be beneficial in reducing risk of injury.

Editorial Commentary: Platelet-Rich Plasma Shows Promise for Improving Shoulder Tendinopathy.

Platelet-rich plasma (PRP) injections continue to be used at increasing rates to treat common musculoskeletal conditions. PRP has a low-risk profile and emerging in vitro evidence to support its positive effects on soft-tissue healing. PRP has been shown to be of benefit for knee osteoarthritis, but less has been published regarding the shoulder. PRP delivers a high concentration of growth factors, cytokines, and other important inflammatory modulators. Its use is appealing for treating partial-thickness rotator cuff tears, subacromial bursitis, and rotator cuff tendinopathy since rotator cuff tendons often have poor healing capacity due to intrinsic degeneration. PRP has been shown to increase cell proliferation and matrix synthesis in tenocytes, which may aid tendon regeneration and healing. Adult tendons also contain a small amount of tendon progenitor cells, which can be induced to an active state by PRP. In addition, PRP is an autologous biologic agent and easy to acquire and administer in an outpatient clinical setting. Clinical studies continue to lag and are often heterogenous in quality and in results. PRP can vary widely based on multiple intrinsic and extrinsic factors, including patient age, sex, activity level, centrifugation speed, and number of centrifugation cycles. Thus, quality research methods should include reporting using the PAW (platelets/activation/white blood cells) system. Clinicians should remain cautiously optimistic about the future role of PRP injections in the shoulder.

Association of Pitch Timing and Throwing Arm Kinetics in High School and Professional Pitchers.

BACKGROUND: Understanding the relationship between the temporal phases of the baseball pitch and subsequent joint loading may improve our understanding of optimal pitching mechanics and contribute to injury prevention in baseball pitchers. PURPOSE: To investigate the temporal phases of the pitching motion and their associations with ball velocity and throwing arm kinetics in high school (HS) and professional (PRO) baseball pitchers. STUDY DESIGN: Descriptive laboratory study. METHODS: PRO (n = 317) and HS (n = 54) baseball pitchers were evaluated throwing 8 to 12 fastball pitches using 3-dimensional motion capture (480 Hz). Four distinct phases of the pitching motion were evaluated based on timing of angular velocities: (1) Foot-Pelvis, (2) Pelvis-Torso, (3) Torso-Elbow, and (4) Elbow-Ball. Peak elbow varus torque, shoulder internal rotation torque, and shoulder distraction force were also calculated and compared between playing levels using 2-sample t tests. Linear mixed-effect models with compound symmetry covariance structures were used to correlate pitch velocity and throwing arm kinetics with the distinct temporal phases of the pitching motion. RESULTS: PRO pitchers had greater weight and height, and faster ball velocities than HS pitchers (P < .001). There was no difference in total pitch time between groups (P = .670). PRO pitchers spent less time in the Foot-Pelvis (P = .010) and more time in the Pelvis-Torso (P < .001) phase comparatively. Shorter time spent in the earlier phases of the pitching motion was significantly associated with greater ball velocity for both PRO and HS pitchers (Foot-Pelvis: B = -6.4 and B = -11.06, respectively; Pelvis-Torso: B = -6.4 and B = -11.4, respectively), while also associated with increased shoulder proximal force (Pelvis-Torso: B = -76.4 and B = -77.5, respectively). Decreased time in the Elbow-Ball phase correlated with greater shoulder proximal force for both cohorts (B = -1150 and B = -645, respectively) with no significant correlation found for ball velocity. CONCLUSION: Significant differences in temporal phases exist between PRO and HS pitchers. For all pitchers, increased time spent in the final phase of the pitching motion has the potential to decrease shoulder distraction force with no significant loss in ball velocity. CLINICAL RELEVANCE: Identifying risk factors for increased shoulder and elbow kinetics, acting as a surrogate for loading at the respective joints, has potential implications in injury prevention.

The association of stride length to ball velocity and elbow varus torque in professional pitchers.

Professional basebal pitchers (n =315) were divided into quartiles based on increasing stride length and random intercept linear mixed-effect models were used to correlate stride length with ball velocity, pelvis and trunk rotation at foot contact, and throwing arm kinetics. Average stride length among all pitchers was 78.3±5.3%body height (%BH). For every 10% increase in stride length, ball velocity increased by 0.9 m/s (B =0.089, ß =0.25, p <0.001) and trunk rotation initiation occurred 4.23 ms earlier (B =-0.42, ß =-0.14, p <0.001). When divided into quartiles pelvis rotation was less towards home plate in Q1 compared to Q3 and Q4 (70.0±10.7° vs. 60.9±8.9° and 58.6±9.1°, p <0.001). No significant differences in shoulder internal rotation torque (p =0.173) or elbow varus torque (p =0.072) were noted between quartiles. Professional baseball pitchers who reached stride lengths of 80%BH or greater achieved faster ball velocity without an increase in elbow varus torque. This may, be a byproduct of rotating the pelvis for a greater proportion of the pitching motion and thereby more effectively utilising the lower extremities in the kinetic chain. Encouraging players to achieve this threshold of stride length may enhance ball velocity outcomes.

Editorial Commentary: Shoulder Rotator Cuff Tendon Repair Using Bone Marrow Aspirate: Stem Cell Quantity Does Not Equal Quality.

The use of biological agents in orthopaedic surgery is rapidly evolving. The potential to augment the healing environment at a surgical repair site is an especially exciting possibility. There are a few popular biological agents, including platelet-rich plasma, concentrated bone marrow aspirate (BMA), and adipose-derived connective tissue progenitor cells. BMA is an especially appealing biological agent because it can be harvested from a variety of sources, including the iliac crest, distal femur, and proximal humerus. As a result, BMA is readily accessible with minimal added surgical time and morbidity during surgical procedures on the hip, knee, and shoulder. In particular, the surgically repaired rotator cuff tendon is a prime candidate for biological augmentation, and the proximal humerus is an appealing source of concentrated BMA given its ease of access and low harvesting morbidity at the time of arthroscopic repair. The nucleated cell count may be considered a surrogate for the quality of BMA and can be readily calculated at the time of harvest. However, the quantity of nucleated cells does not necessarily equate to the quality of nucleated cells as colony-forming units after cell culture, nor do we know how ex vivo cell culture correlates with in vivo stem cell proliferation and healing. Most of all, future research must determine what factors (if any) do positively correlate with the number of colony-forming units.

Trends in Patient, Physician, and Public Perception of Ulnar Collateral Ligament Reconstruction Using Social Media Analytics.

BACKGROUND: Social media posts regarding ulnar collateral ligament (UCL) injuries and reconstruction surgeries have increased in recent years. PURPOSE: To analyze posts shared on Instagram and Twitter referencing UCL injuries and reconstruction surgeries to evaluate public perception and any trends in perception over the past 3 years. STUDY DESIGN: Cross-sectional study. METHODS: A search of a 3-year period (August 2016 and August 2019) of public Instagram and Twitter posts was performed. We searched for >22 hashtags and search terms, including #TommyJohn, #TommyJohnSurgery, and #tornUCL. A categorical classification system was used to assess the sentiment, media format, perspective, timing, accuracy, and general content of each post. Post popularity was measured by number of likes and comments. RESULTS: A total of 3119 Instagram posts and 267 Twitter posts were included in the analysis. Of the 3119 Instagram posts analyzed, 34% were from patients, and 28% were from providers. Of the 267 Twitter posts analyzed, 42% were from patients, and 16% were from providers. Although the majority of social media posts were of a positive sentiment, over the past 3 years, there was a major surge in negative sentiment posts (97% increase) versus positive sentiment posts (9% increase). Patients were more likely to focus their posts on rehabilitation, return to play, and activities of daily living. Providers tended to focus their posts on education, rehabilitation, and injury prevention. Patient posts declined over the past 3 years (-28%), whereas provider posts increased substantially (110%). Of posts shared by health care providers, 4% of posts contained inaccurate or misleading information. CONCLUSION: The majority of patients who post about their UCL injury and reconstruction on social media have a positive sentiment when discussing their procedure. However, negative sentiment posts have increased significantly over the past 3 years. Patient content revolves around rehabilitation and return to play. Although patient posts have declined over the past 3 years, provider posts have increased substantially with an emphasis on education.

Efficacy of Arm Care Programs for Injury Prevention.

PURPOSE OF REVIEW: Arm care programs for baseball players are an increasingly popular area of interest for players, parents, coaches, sports performance staff, and team physicians. Once a general afterthought, the design of arm care programs is now heavily scrutinized in order to maximize performance and help reduce injury risk. Given the recent spike in interest for arm care programs for baseball players of all ages, the purpose of this work is to review the relevant literature regarding the efficacy of arm care programs and to discuss the authors' preferred, evidence-based principles for arm care programs. RECENT FINDINGS: Arm care programs appear to provide favorable results for performance, maintenance of strength and flexibility, and reduced injury risk. These programs should be tailored to the demands of the athlete, which can change based on the time of year and physical demands of the player's position. A good program will incorporate flexibility, strengthening, proprioception, and joint mobility for the entire kinetic chain. Appropriate warm-up and cool-down periods are also important. Arm care programs should start with basic movement patterns before progressing to more advanced, coordinated exercises. Arm care programs are an important piece of a holistic approach to caring for the throwing arm of baseball athletes. In general, they appear to be a safe and efficacious way to help prevent a portion of throwing arm injuries. Further research is needed to determine the optimal arm care program for each athlete.