Forearm Flexor Injuries Among Major League Baseball Players: Epidemiology, Performance, and Associated Injuries

Alterations in pitching biomechanics and performance with an increasing number of pitches in baseball pitchers: A narrative review

In baseball pitchers, the association of fatigue with overuse injury and decline in pitching performance has been discussed frequently, but the scientific data concerning their interrelationships have been inconsistently reported. The purpose of this narrative review is to summarize and explore the evidence regarding acute changes in pitching biomechanics and performance from repetitive throwing motions among baseball pitchers. Muscle fatigue from repetitive throwing not only decreases muscle output but also disturbs the kinetic chain of baseball pitching. In addition, repetitive throwing can impair the proprioceptive and kinesthetic functions needed for accurate joint position sense in the shoulder and elbow. Consequently, these changes negatively affect ball velocity and pitching accuracy, two critical aspects of overall pitching performance. Moreover, the cumulative loading caused by fatigue contributes to the high prevalence of overuse injuries, particularly in the elbow and shoulder joints. Thus it is important to comprehensively understand the relationships among changed pitching mechanics, deteriorated performance, and musculoskeletal injury originating from muscle fatigue due to repetitive pitching.

Upper-Extremity Injuries Have the Poorest Return to Play and Most Time Lost in Professional Baseball: A Systematic Review of Injuries in Major League Baseball

PURPOSE

To summarize the incidence of injuries occurring in professional baseball and compare player outcomes reported in the literature.

METHODS

We conducted a systematic review using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines across 3 databases (PubMed, MEDLINE, Embase). Inclusion criteria were studies of injury incidences and/or injury outcomes on active Major League Baseball (MLB) athletes and studies published in the English language. Exclusion criteria were non-MLB players, case series and case report studies with a cohort of ≤3 players, and/or review articles.

RESULTS

A total of 477 articles were identified from the initial search of 3 databases, with 105 studies meeting inclusion criteria. Among these articles, the most common injuries studied were elbow (38%), shoulder (14%), hip/groin (11%), hand/wrist (7%), head/face (7%), knee (7%), spine (5%), and foot/ankle (3%). Injuries with the greatest incidence included hand/wrist (150.3 per year), hamstring (7.8-73.5 per year), ulnar collateral ligament (UCL) tears (0.23-26.8 per year), gastrocnemius strains (24.2 per year), and concussions (3.6-20.5 per year). Lowest rates of return to play were seen following shoulder labral tears (40%-72.5%), rotator cuff tears (33.3%-87%), and UCL tears (51%-87.9%). The injuries leading to most time away from sport included elbow UCL tears (average 90.3 days treated nonoperatively to 622.8 days following revision reconstruction), shoulder labral tears (average 315-492 days), and anterior cruciate ligament (ACL) tears (average 156.2-417.5 days). Following ACL tears, rotator cuff tears, shoulder labral tears, and hip femoroacetabular impingement requiring arthroscopy, athletes had a significantly lower workloads compared with before injury upon return to play.

CONCLUSIONS

Most published investigations focus on elbow injuries of the UCL, with variable return to play and mixed performance following surgery. UCL tears, shoulder labral tears, and ACL tears result in the most missed time. Upper-extremity injury such as shoulder labral tears, rotator cuff tears, and UCL tears had the poorest return to play rates. Workload was most affected following ACL reconstruction, rotator cuff repair, shoulder labral repair, and hip arthroscopy for femoroacetabular impingement.

LEVEL OF EVIDENCE

IV, systematic review of level II-IV studies.

Relationship between Medial Elbow Pain, Flexor Pronator Muscles, and the Ulnar Nerve in Baseball Players Using Ultrasonography

We aimed to clarify changes cross-sectional area (CSA) in flexor pronator muscles and the ulnar nerve (UN) in players with medial elbow pain between pitching phases. Forty-two male baseball players with and without medial elbow pain during throwing were included in this study. The players were divided into maximum external rotation (MER) and ball release (BR) groups according to the pitching phase in which pain was reported. The imaged region was the flexor digital profundus, flexor carpi ulnaris (FCU), flexor digitorum superficialis, and pronator teres muscles, as well as the UN. CSA at rest and during contraction was assessed using the ultrasonography software tracing function. For statistical analysis, the CSA at rest and at contraction in the healthy group, MER group and BR group was compared using one-way analysis of variance. There was a significant difference in CSA only in the FCU between the healthy (95.4 ± 15.5%) and the MER group (76.6 ± 12.5%) at rest (p = 0.004). There were significant differences in the UN between the healthy (105.0 ± 27.7%) and MER groups (176.4 ± 53.5%), and between the healthy and BR groups (132.9±21.1%) (p = 0.001 and p = 0.038, respectively). Our results suggest that athletes with medial elbow pain during the MER of pitching have ulnar nerve swelling.

Sites of flexor-pronator muscle injury and relationship between ulnar collateral ligament injury and flexor-pronator muscle injury in baseball players: a retrospective cohort study

BACKGROUND

Ulnar collateral ligament (UCL) and flexor-pronator muscle (FPM) injuries are common in baseball players. However, the sites of FPM injuries and the relationship between UCL and FPM injuries in baseball players have not been fully clarified. The purpose of this study was to identify the sites of FPM injuries and to determine the relationships of location and severity of UCL injury with the presence of FPM injuries in baseball players.

METHODS

UCL and FPM injuries were diagnosed using magnetic resonance imaging in 99 baseball players. The sites of FPM injuries were identified on coronal, sagittal, and axial images. UCL injury severity was classified into four grades: chronic changes, low-grade partial tear, high-grade partial tear, and complete tear. UCL injury location was classified as proximal UCL tear or distal UCL tear. All images were assessed by a musculoskeletal radiologist and an orthopedic surgeon.

RESULTS

Combined UCL and FPM injuries were observed in 45 of 99 players, of which 40 of 45 (89%) involved injury of the flexor digitorum superficialis (FDS). All FDS injuries were in the deep layer of the muscle belly. There was no significant difference between the severity of UCL injury and presence of FPM injuries (P = .352). There was a significant association of distal UCL tears with FPM injuries (P < .001).

CONCLUSION

FDS injury occurs most commonly in the muscle belly of the second and fifth digits. There may be no relationship between the severity of UCL injury and presence of FPM injury in baseball players. FPM injuries may be a contributing factor in the failure of nonoperative management of distal UCL tears in baseball players.

Pectoralis muscle injuries in Major and Minor League Baseball

BACKGROUND AND HYPOTHESIS

Although shoulder and elbow injuries in professional baseball players have been thoroughly studied, little is known about the frequency and impact of pectoralis muscle injuries in this population. The purpose of this study was to use the official league injury surveillance system to describe pectoralis muscle injuries in professional baseball players in Major League Baseball (MLB) and Minor League Baseball (MiLB). Specifically, (1) player demographic characteristics, (2) return to play (RTP), (3) injury mechanism, (4) throwing- and batting-side dominance, and (5) injury rate per athlete exposure (AE) were characterized to guide future injury prevention strategies.

METHODS

The MLB Health and Injury Tracking System database was used to compile all pectoralis muscle injuries in MLB and MiLB athletes in the 2011-2017 seasons. Injury-related data including diagnosis (tear or rupture vs. strain), player demographic characteristics, injury timing, need for surgical intervention, RTP, and mechanism of injury were recorded. Subanalyses of throwing- and batting-side dominance, as well as MLB vs. MiLB injury frequency, were performed.

RESULTS

A total of 138 pectoralis muscle injuries (32 MLB and 106 MiLB injuries) were reported in the study period (5 tears or ruptures and 133 strains), with 5 of these being recurrent injuries. Operative intervention was performed in 4 athletes (2.9%). Of the 138 injuries, 116 (84.1%) resulted in missed days of play, with a mean time to RTP of 19.5 days. Starting pitchers sustained the greatest proportion of pectoralis injuries (48.1%), with pitching being the most common activity at the time of injury (45.9%). A majority of injuries (86.5%) were sustained during non-contact play. Overall, 87.5% of injuries occurred on the player's dominant throwing side and 81.3% occurred on the player's dominant batting side. There was no significant difference in the rate of pectoralis injuries in the MLB regular season (0.584 per 10,000 AEs) vs. the MiLB regular season (0.425 per 10,000 AEs) (P = .1018).

CONCLUSION

Pectoralis muscle injuries are most frequently non-contact injuries, most commonly sustained by pitchers. An understanding of these injuries can guide athletic trainers and management in expectation management and decision making, in addition to directing future efforts at injury prevention.

The 532 nm Laser Treatment Promotes the Proliferation of Tendon-Derived Stem Cells and Upregulates Nr4a1 to Stimulate Tenogenic Differentiation

Objective: This study aimed to verify the effect of photobiomodulation therapy (PBMT) with a wavelength of 532 nm on the proliferation and differentiation of tendon-derived stem cells (TDSCs) of Sprague-Dawley (SD) rats. Background: The combination of PBMT and stem cell transplantation with TDSCs provides a new treatment strategy for tendon injury. Nevertheless, the effect of PBMT on the biological behavior of TDSCs and its internal mechanisms remain unclear. Methods: TDSCs were isolated from Achilles tendons of SD rats and identified by cell morphology and flow cytometric analysis. Energy density gradient experiment was performed to determine the ideal energy. Then, TDSCs were treated with PBMT using a wavelength of 532 nm at a fluence of 15 J/cm² in 532 nm laser group, and the TDSC in control group were not treated with 532 nm laser. Cell response after irradiation was observed to ascertain cell morphology and cell proliferation in the 532 nm laser group and the control group. The RNA expression levels of the key genes of TDSC differentiation, including scleraxis (Scx), tenomodulin (Tnmd), Mohawk homeobox (Mkx), Decorin (Dcn), peroxisome proliferator-activated receptor gamma (PPARγ), SRY-box transcription factor 9 (Sox9), and RUNX family transcription factor 2 (Runx2), were detected by reverse transcription-polymerase chain reaction. Then, gene chip microarray was used to detect the expression of differential genes after 532 nm laser intervention in TDSCs, and the target genes were screened out to verify the role in this process in vitro and in vivo. Results: When the 532 nm laser energy density was 15 J/cm², the proliferation capacity of TDSCs was improved (2.73 ± 0.24 vs. 1.81 ± 0.71, p < 0.05), and the expression of genes related to tenogenic differentiation of TDSCs was significantly increased (p < 0.01). After RNA sequencing and bioinformatics analyses, we speculated that nuclear receptor subfamily 4 group A member 1 (Nr4a1) was involved in the tenogenic differentiation process of TDSCs regulated by 532 nm laser treatment. Subsequent experiments confirmed that Nr4a1 regulated the expression of the tenogenic differentiation genes Scx and Tnmd in TDSCs. Conclusions: A 532 nm laser with 15 J/cm² regulated the process of TDSC proliferation and upregulated Nr4a1 to stimulate tenogenic differentiation.

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.

Using Advanced Data to Analyze the Impact of Injury on Performance of Major League Baseball Pitchers: A Narrative Review

Major league baseball (MLB) pitchers are at risk of numerous injuries during play, and there is an increasing focus on evaluating their performance in the context of injury. Historically, performance after return to play (RTP) from injury has focused on general descriptive statistics, such as innings or games played, or rate statistics with inherent variability (eg, earned run average, walks and hits per inning pitched, strikeouts per 9 innings, or walks per 9 innings). However, in recent years, MLB has incorporated advanced technology and tracking systems in every stadium, allowing for more in-depth analysis of pitcher-specific data that are captured with every pitch of every game. This technology allows for the ability to delve into the pitching performance on a basis that is more specific to each pitcher and allows for more in-depth analysis of different aspects of pitching performance. The purpose of this narrative review was to illustrate the current state of injury recording for professional baseball pitchers, highlight recent technological advances in MLB, and describe the advanced data available for analysis. We used advanced data in the literature to review the current state of performance analysis after RTP in MLB pitchers after injury. Finally, we strived to provide a framework for future studies to more meticulously assess RTP performance given the current available resources for analysis.

Current State of Data and Analytics Research in Baseball

PURPOSE OF REVIEW

Baseball has become one of the largest data-driven sports. In this review, we highlight the historical context of how big data and sabermetrics began to transform baseball, the current methods for data collection and analysis in baseball, and a look to the future including emerging technologies.

RECENT FINDINGS

Machine learning (ML), artificial intelligence (AI), and modern motion-analysis techniques have shown promise in predicting player performance and preventing injury. With the advent of the Health Injury Tracking System (HITS), numerous studies have been published which highlight the epidemiology and performance implications for specific injuries. Wearable technologies allow for the prospective collection of kinematic data to improve pitching mechanics and prevent injury. Data and analytics research has transcended baseball over time, and the future of this field remains bright.

Trends in Medial Ulnar Collateral Ligament Repair and Reconstruction From 2007 to 2016: A Population-Based Study of a Large Private Insurance Database

Background: Ulnar collateral ligament (UCL) reconstruction and UCL repair of the elbow are commonly performed procedures, resulting in high return-to-play rates. Whether the incidence rate of UCL reconstruction vs UCL repair has changed over time is not currently known. Purpose/Questions: We sought to assess temporal trends in the incidence rates of UCL repair and UCL reconstruction and to identify factors associated with UCL reconstruction. We hypothesized that UCL repair would demonstrate an increased incidence overall in recent years with an associated decline in UCL reconstruction rates. Methods: Using the PearlDiver Research Program to query the Humana administrative claims database, we identified patients who had undergone UCL repair and/or reconstruction from 2007 to 2016. Patients were stratified by age (15-19; 20-29; 30-49 years), sex, and year (2007-2011 vs 2012-2016). Poisson regression analysis (continuous variables) was used to calculate the incidence risk ratio (IRR); chi-square tests were performed for categorical variables, and odds ratios were calculated with 95% confidence intervals (CI). Results: The incidence rate of UCL repair was greater in 2012-2016 than in 2007-2011 (IRR: 1.86, 95% CI: 1.16-2.96). The incidence rate of UCL reconstruction vs UCL repair was greater for patients aged 15 to 19 years (IRR: 3.37, 95% CI: 1.97-5.77) but not patients aged 20 to 29 years (IRR: 0.89, 95% CI: 0.49-1.59) as compared with patients aged 30 to 49. Males aged 19 years were more likely than females to undergo UCL reconstruction (IRR: 10.09, 95% CI: 1.37-3.45). Conclusion: While UCL procedures are becoming more popular, our retrospective analysis showed that young males are preferentially treated with UCL reconstruction, warranting further investigation into these trends.

Effect of COVID-19 on Ulnar Collateral Ligament Reconstruction in Major League Baseball Pitchers

Background:

The coronavirus disease of 2019 (COVID-19) pandemic led to the suspension and shortening of the 2020 Major League Baseball (MLB) season from 162 to 60 regular season games. The effect of this disruption on injury rates, specifically injury to the ulnar collateral ligament (UCL), has not been quantified.

Purpose/Hypothesis:

The purpose of this study was to compare the rate of UCL reconstruction (UCLR), surgery timing, and pitching workload in MLB pitchers from before and after the COVID-19 pandemic lockdown. We hypothesized that UCLR rates relative to games played would be increased and pitching workload would be decreased in 2020 compared with previous seasons.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

An extensive online search using publicly available data was conducted to identify all MLB pitchers who underwent UCLR between January 1, 2017, and December 31, 2020. Only pitchers who were competing at the MLB level when undergoing reconstruction were included. Player characteristics and surgery date, as well as career and season of surgery pitching workload, were collected for all included pitchers. All data were compared as a pooled sample (2017-2019 vs 2020).

Results:

A similar number of pitchers underwent UCLR during or after the 2020 regular season (n = 18) compared with the 2017-2019 seasons (n = 16, 20, and 16, respectively). However, after accounting for the decrease in games played during the 2020 regular season, an MLB pitcher was 2.9 times more likely to undergo surgery per game after the COVID-19 lockdown compared with the previous years (P < .001). MLB pitchers who underwent surgery in 2020 threw fewer preseason innings than did pitchers who underwent surgery between 2017 and 2019 (5.98 vs 9.39; P = .001).

Conclusion:

MLB pitchers were almost 3 times more likely to undergo UCLR per game after the COVID-19 lockdown. A decreased preseason pitching workload because of the COVID-19 lockdown may have had an effect on per game UCLR rates.

Forearm flexor injury is associated with medial ulnar collateral ligament injury in throwing athletes

BACKGROUND

Elbow ulnar collateral ligament (UCL) injuries have become increasingly common in throwing athletes. The forearm flexors (FF) have been studied as biomechanical stabilizers for the medial elbow. However, there are no studies investigating the association of concomitant UCL injuries and FF injuries in throwing athletes.

OBJECTIVE

To determine if throwing athletes with a complete UCL injury had a greater likelihood of concomitant FF injury than those with a partial UCL injury.

DESIGN

Descriptive retrospective epidemiological study.

SETTING

Academic, tertiary care medical center.

PATIENTS

Throwing related UCL injuries in patients aged 12-24 years.

INTERVENTIONS/METHODS

Electronic medical records and key word searches identified all patients from January 1, 2010 to December 31, 2019. A board certified and fellowship trained musculoskeletal radiologist reviewed all advanced imaging studies.

RESULTS

Fifty-four patients (46 male, 8 female, mean age 17.1 years, SD 2.3) were included. Fifty-four UCL injuries (21 complete ruptures, 16 proximal partial injuries, 17 distal partial injuries) were confirmed by magnetic resonance imaging (MRI). Twenty-eight FF injuries (22 strains, 6 tears) were diagnosed with MRI and/or MRI-arthrogram. There was a significant association between sustaining a FF injury and UCL reconstruction (UCL-R) (X² = [1, N = 54], = 3.97, P = .046) (15/22, 68.2%), as well as FF injury and UCL injury location (X² = [1, N = 33], = 3.86, P = .049) (10/17, distal partial UCL injury, 58.8%). Analysis of FF injury and complete UCL tear is not significant (X² = [1, N = 54], = 3.02, P = .08) (14/21, 66.7%).

CONCLUSIONS

The data indicate that FF injury is associated with UCL injury in throwing athletes. Future prospective studies should investigate causation versus correlation of FF and UCL injury in throwing athletes. The results of this study have applications to multiple sports medicine areas that include but are not limited to surgical, nonsurgical, prehabilitation, rehabilitation, and sports performance. This study reveals a strongly significant association between FF injury and concomitant UCL injury in throwing athletes.

Ulnar Collateral Ligament Reconstruction

Ulnar collateral ligament (UCL) injuries can significantly impair the overhead athlete. Reconstruction of the anterior bundle of the UCL (UCL-R) has allowed a high proportion of these individuals to return to their previous level of play. Several techniques for UCL-R are described that produce acceptable results with an overall low complication rate. Transient ulnar neuritis is the most common complication following UCL-R. The rate of UCL injury in young athletes is rising with increased youth involvement and year-round participation in overhead sports. The sports medicine community must broaden its focus to not only treat UCL injuries but also prevent them.

Injuries and Conditions Affecting the Elbow Flexor/Pronator Tendons

Common flexor-pronator tendon injuries and medial epicondylitis can be successfully treated nonoperatively in most cases. Operative treatment is reserved for patients with continued symptoms despite adequate nonoperative treatment or in high-level athletes with complete rupture of the common flexor-pronator tendon. The physical examination and workup of patients with flexor-pronator tendon injuries should focus on related or concomitant pathologies of the medial elbow. The gold standard for surgical treatment of flexor-pronator tendon ruptures or medial epicondylitis includes tendon debridement and reattachment.

On-field Management of Shoulder and Elbow Injuries in Baseball Athletes

PURPOSE OF REVIEW

The goal of this review article is to help medical personnel of all levels and backgrounds identify and appropriately manage on-field acute shoulder and elbow injuries in the baseball athlete. This article discusses the most common acute shoulder and elbow injuries in baseball players along with recommendations for appropriate on-field management.

RECENT FINDINGS

Shoulder and elbow injuries are very common in baseball players and can be problematic because of the unique demands placed on the shoulder and elbow during the throwing and swinging motions. While many shoulder and elbow injuries in baseball players are chronic, some acute injuries, including dislocations and fractures, require urgent on-field management. Evaluation should begin with a broad assessment to rule out life-threatening emergencies prior to performing a neurovascular evaluation of the affected extremity. Red-flag signs during examination, such as difficulty breathing, asymmetric pulses, weakness, and limb discoloration, require emergent treatment. In the absence of an emergency, the evaluating medical team should complete a basic neurovascular exam before performing any further on-field care. Contusions, dislocations, and fractures are the most commonly seen acute shoulder and elbow injuries in baseball athletes. Athletic trainers and physicians caring for these athletes should be familiar with these injuries and their appropriate on-field management.