Bony adaptation of the proximal humerus and glenoid correlate within the throwing shoulder of professional baseball pitchers

A narrative review of little league shoulder: proximal humeral physis widening is only one piece of the puzzle, it is time to consider posterior glenoid dysplasia

Baseball athletes across all levels of play are at an increased risk for upper extremity injury due to the supraphysiologic demands on the shoulder and elbow during overhead throwing. Little league baseball players present with a unique subset of injuries that can affect the growth plate, commonly at the shoulder or the elbow. Ascertaining a diagnosis and plan of care for little league shoulder (LLS) historically focuses on the proximal humeral physis in skeletally immature throwing athletes presenting with shoulder pain. However, while not a current standard of care, posterior glenoid dysplasia is often present in youth baseball athletes presenting with LLS, warranting a shift in the way clinicians evaluate for and treat the youth baseball athlete's pathologic shoulder. Therefore, purpose of this narrative review is 2-fold: first, to describe the current standard of care as it relates to a diagnosis of LLS, and second, to critically describe a comprehensive evaluation process for youth throwing athletes with shoulder pain that includes screening for evidence of posterior glenoid dysplasia. This paper summarizes the current state of the available evidence for anatomic considerations of LLS in the baseball athletes throwing shoulder. Additionally, we provide a framework for clinical evaluation using a multidisciplinary approach to evaluate the entire kinetic chain of the youth baseball athlete presenting with LLS and posterior glenoid dysplasia. A case study is presented to describe common presentations, clinical and objective examinations, and a plan of care from time of evaluation to return to throwing.

Adaptive pathology: new insights into the physical examination and imaging of the thrower's shoulder and elbow

Throwing with high velocity requires extremes of glenohumeral external rotation of the abducted arm where particularly high forces in the shoulder and elbow are endured. Repeated throwing leads to dominant-arm bony remodeling of the humerus, glenoid, and elbow, and multiple soft tissue changes that would be considered abnormal. Many of these features are thought to be adaptive and protective. The purpose of this work is to (1) define the concept of adaptive pathology; (2) review the mechanics of the throwing motion; (3) review pertinent physical examination and imaging findings seen in asymptomatic throwers' shoulders and elbows and describe how these changes develop and may be adaptive-allowing the thrower to perform at high levels; and then (4) review the principles of surgical treatment in the throwing athletes, which should focus on reducing symptoms, but not necessarily restoring the thrower's anatomy to normal.

Native Glenoid Depth and Hill-Sachs Lesion Morphology in Traumatic Anterior Shoulder Instability

BACKGROUND

Although Hill-Sachs lesions (HSLs) are assumed to be influenced by glenoid characteristics in the context of bipolar bone loss, little is known about how glenoid concavity influences HSL morphology.

PURPOSE

To investigate the relationship between the native glenoid depth and HSL morphological characteristics.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Computed tomography images of bilateral shoulders from 151 consecutive patients with traumatic unilateral anterior shoulder instability were retrospectively reviewed. Patients were categorized into flat (<1 mm), moderate (1-2 mm), and deep (>2 mm) groups based on the native glenoid depth measured from the contralateral unaffected shoulder. The HSL morphological characteristics included size (depth, width, length, and volume), location (medial, superior, and inferior extent), and orientation (rim and center angle). The glenoid characteristics included diameter, depth, version, and bone loss. The patient, glenoid, and HSL morphological characteristics were compared among the 3 depth groups. Subsequently, the independent predictors of some critical HSL morphological characteristics were determined using multivariate stepwise regression.

RESULTS

After exclusion of 55 patients, a total of 96 patients were enrolled and classified into the flat group (n = 31), moderate group (n = 35), and deep group (n = 30). Compared with those in the flat group, patients in the deep group were more likely to have dislocation (38.7% vs 93.3%; P = .009) at the primary instability and had a significantly larger number of dislocations (1.1 ± 1.0 vs 2.2 ± 1.8; P = .010); moreover, patients in the deep group had significantly deeper, wider, larger volume, more medialized HSLs and higher incidences of off-track HSLs (all P≤ .025). No significant differences were detected among the 3 groups in HSL length, vertical position, and orientation (all P≥ .064). After adjustment for various radiological and patient factors in the multivariate regression model, native glenoid depth remained the strongest independent predictor for HSL depth (β = 0.346; P < .001), width (β = 0.262; P = .009), volume (β = 0.331; P = .001), and medialization (β = -0.297; P = .003).

CONCLUSION

The current study sheds light on the association between native glenoid depth and the morphology of HSLs in traumatic anterior shoulder instability. Native glenoid depth was independently and positively associated with HSL depth, width, volume, and medialization. Patients with deeper native glenoids were more likely to have off-track HSLs and thus require more attention in the process of diagnosis and treatment.

Organizational risk profiling and education associated with reduction in professional pitching arm injuries: a natural experiment

Background

Risk profiling and education are strategies implemented to help reduce injury risk; however, currently. there is little evidence on the effect of these interventions on injury incidence. The purpose of this study was to evaluate the influence of risk profiling and education on upper extremity injury incidence in minor league (MiLB) pitchers and to stratify by injury severity.

Methods

A prospective natural experiment study was conducted from 2013 to 2019 on MiLB pitchers. Beginning in the 2015 season, pitchers were examined and risk profiled for upper extremity injury. Shoulder external, internal, total range of motion, horizontal adduction, and humeral torsion were measured. Organizational risk profiling and education was implemented starting in 2015, based on preseason assessments. Chi-squared test was performed to investigate potential differences between shoulder range of motion risk categories between 2013-2014 (pre) and 2015-2019 (post) seasons. Interrupted time series analyses were performed to assess the association between organizational risk profiling and education on arm injury in MiLB pitchers and were repeated for 7-27 and 28+ day injury severity.

Results

297 pitchers were included (pre: 119, post: 178). Upper extremity injury incidence was 1.5 injuries per 1000 athletic exposures. Pitchers in the 2015-2019 seasons demonstrated increased preseason shoulder injury risk for internal (P = .003) and external (P = .007), while the 2013-2014 seasons demonstrated greater horizontal adduction risk (P = .04). There were no differences between seasons for total range of motion risk (P =.76). Risk profiling and education resulted in an adjusted time loss upper extremity injury reduction for the 2015-2019 seasons (0.68 (95% CI: 0.47, 0.99)), which impacted 7-27 days (0.62 (95% CI: 0.42, 0.93)) but not for 28+ days (0.71 (95% CI: 0.47, 1.06)) time loss. There was no reduction in combined trunk and lower extremity injuries for the 2015-2019 seasons (1.55 (95% CI: 0.79, 3.01)).

Conclusions

Organizational risk profiling and education appear to reduce professional pitching overall and 7-27-day upper extremity injury risk by 33%-38%. There was no difference in trunk and lower extremity injuries over the period, strengthening the reduction in upper extremity injury risk results. This suggests that while injury risk increased over time, organizational risk profiling mitigated the expected increase in upper extremity injury rates. Risk profiling and education can be used as a clinical screening and intervention tool to help decrease upper extremity injuries in professional baseball populations.

Return to Play After Shoulder Surgery in Professional Baseball Players: A Systematic Review and Meta-analysis

Background

The current literature lacks an updated review examining return to play (RTP) and return to prior performance (RTPP) after shoulder surgery in professional baseball players.

Purpose

To summarize the RTP rate, RTPP rate, and baseball-specific performance metrics among professional baseball players who underwent shoulder surgery.

Study Design

Systematic review; Level of evidence, 4.

Methods

A literature search was performed utilizing the PubMed, MEDLINE, and CINAHL databases and according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Inclusion criteria were English-language studies reporting on postoperative RTP and/or RTPP in professional baseball players who underwent shoulder surgery between 1976 and 2016. RTP rates, RTPP rates, and baseball-specific performance metrics were extracted from qualifying studies. A total of 2034 articles were identified after the initial search. Meta-analysis was performed where applicable, yielding weighted averages of RTP and RTPP rates and comparisons between pitchers and nonpitchers for each type of surgery. Baseball-specific performance metrics were reported as a narrative summary.

Results

Overall, 26 studies featuring 1228 professional baseball players were included. Patient-level outcome data were available for 529 players. Surgical interventions included rotator cuff debridement (n = 197), rotator cuff repair (RCR; n = 43), superior labrum from anterior to posterior repair (n = 124), labral repair (n = 103), latissimus dorsi/teres major (LD/TM) repair (n = 21), biceps tenodesis (n = 17), coracoclavicular ligament reconstruction (n = 15), anterior capsular repair (n = 5), and scapulothoracic bursectomy (n = 4). Rotator cuff debridement was the most common surgical procedure, while scapulothoracic bursectomy was the least common (37.2% and 0.8% of interventions, respectively). Meta-analysis revealed that the RTP rate was highest for LD/TM repair (84.5%) and lowest for RCR (53.5%), while the RTPP rate was highest for LD/TM repair (100.0%) and lowest for RCR (27.9%). RTP and RTPP rates were generally higher for position players than for pitchers. Nonvolume performance metrics were unaffected by shoulder surgery, while volume statistics decreased or remained similar.

Conclusion

RTP and RTPP rates among professional baseball players were modest after most types of shoulder surgery. Among surgical procedures commonly performed on professional baseball players, RTP and RTPP rates were highest for LD/TM repair and lowest for RCR.

Disabled Throwing Shoulder 2021 Update: Part 1-Anatomy and Mechanics

The purpose of this article is to provide updated information for sports health care specialists regarding the Disabled Throwing Shoulder (DTS). A panel of experts, recognized for their experience and expertise in this field, was assembled to address and provide updated information on several topics that have been identified as key areas in creating the DTS spectrum. Each panel member submitted a concise presentation on one of the topics within these areas, each of which were then edited and sent back to the group for their comments and consensus agreement in each area. Part 1 presents the following consensus conclusions and summary findings regarding anatomy and mechanics, including: 1) The current understanding of the DTS identifies internal impingement, resulting from a combination of causative factors, as the final common pathway for the great majority of the labral pathoanatomy; 2) intact labral anatomy is pivotal for glenohumeral stability, but its structure does not control or adapt well to shear or translational loads; 3) the biceps plays an active role in dynamic glenohumeral stability by potentiating "concavity compression" of the glenohumeral joint; 4) the ultimate function of the kinetic chain is to optimize the launch window, the precise biomechanical time, and position for ball release to most effectively allow the ball to be thrown with maximum speed and accuracy, and kinetic chain function is most efficient when stride length is optimized; 5) overhead throwing athletes demonstrate adaptive bony, capsular, and muscular changes in the shoulder with repetitive throwing, and precise measurement of shoulder range of motion in internal rotation, external rotation, and external rotation with forearm pronation is essential to identify harmful and/or progressive deficits. LEVEL OF EVIDENCE: Level V, expert opinion.

The Thrower's Shoulder

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The thrower's shoulder has been a subject of great interest for many decades. Different theories have been proposed to clarify the pathophysiology, clinical presentation, and treatment options for this condition. In this review article, we summarize the relevant anatomy and pathophysiology and how these translate into signs, symptoms, and imaging findings. Also, a historical review of the treatment methodologies in the setting of an evolving concept is presented.

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The initial event in the cascade is thickening and contracture of the posteroinferior capsule resulting from repetitive tensile forces during the deceleration phase of throwing. This is known as "the essential lesion" and is clinically perceived as glenohumeral internal rotation deficit (GIRD), and a Bennett lesion may be found on radiographs.

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Change in the glenohumeral contact point leads to a series of adaptations that are beneficial for the mechanics of throwing, specifically in achieving the so-called "slot," which will maximize throwing performance.

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The complexity of the throwing shoulder is the result of an interplay of the different elements described in the cascade, as well as other factors such as pectoralis minor tightness and scapular dyskinesis. However, it is still unclear which event is the tipping point that breaks the balance between these adaptations and triggers the shift from an asymptomatic shoulder to a painful disabled joint that can jeopardize the career of a throwing athlete. Consequences are rotator cuff impingement and tear, labral injury, and scapular dyskinesis, which are seen both clinically and radiographically.

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A thorough understanding of the pathologic cascade is paramount for professionals who care for throwing athletes. The successful treatment of this condition depends on correct identification of the point in the cascade that is disturbed. The typical injuries described in the throwing shoulder rarely occur in isolation; thus, an overlap of symptoms and clinical findings is common.

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The rationale for treatment is based on the pathophysiologic biomechanics and should involve stretching, scapular stabilization, and core and lower-body strengthening, as well as correction of throwing mechanics, integrating the entire kinetic chain. When nonoperative treatment is unsuccessful, surgical options should be tailored for the specific changes within the pathologic cascade that are causing a dysfunctional throwing shoulder.

Comparison of Glenohumeral Range of Motion Deficits in Youth, Collegiate, and Professional Baseball Players

BACKGROUND

Examining range of motion deficits across levels of baseball competition can result in a better understanding of the extent of altered range of motion patterns and identify competition levels that may require preventative interventions that target the deficits.

PURPOSE

The purpose of this study was to compare shoulder range of motion in baseball players across levels of competition and compare the prevalence of glenohumeral internal rotaton deficit (GIRD) and total arc of motion differences (TAMD) between competition levels in pitchers and position players.

STUDY DESIGN

Prospective descriptive cohort.

METHODS

Passive internal and external rotation range of motion was measured bilaterally. Individuals with current pain in the arm, shoulder, elbow or shoulder surgery within the prior two years were excluded. Measurements were taken during pre-season physical examinations. Players were divided into seven groups: 12u (11-12 years; n=30), 14u (13-14 years; n=30), High School 1 (HS 1; 15-16 year; n=42), High School 2 (HS 2; 17-18 years; n=25), College (n=22), Professional 1 (Pro1; 17-22 years; n=37) and Professional 2 (Pro2; 23 and older; n=37). Multiple one-way analyses of variance were performed to determine differences between groups. Tukey test for post-hoc analysis was employed to determine which competition levels were significantly different.

RESULTS

Two-hundred and twenty-three male baseball players ages 11-26 participated. The 12u (53.7°) and 14u (54.2°) groups had significantly less internal rotation than HS1 (65.2°), HS2 (63.9°), College (62.3°), Pro1 (64.9°), and Pro2 (64.5°) players (p<0.0001). The 12u, 14u, HS1, college, and Pro2 groups had greater than 50% of players with total arc of motion differences >5°. Conclusions: Range of motion alterations exist across ages and levels of competition with 12u and 14u players having less internal rotation than the older groups and youth pitchers having less total range of motion than HS1.

LEVEL OF EVIDENCE

2.

Shoulder Range of Motion Deficits in Youth Throwers Presenting With Elbow Pain

BACKGROUND

Glenohumeral internal rotation deficit (GIRD) and total arc of motion difference (TAMD) have been associated with elbow injuries in throwing athletes.

HYPOTHESIS

Youth pitchers with elbow pain will have greater GIRD and TAMD compared with youth pitchers without elbow pain.

STUDY DESIGN

Cross-sectional study.

LEVEL OF EVIDENCE

Level 3.

METHODS

Glenohumeral range of motion of 25 consecutive throwing athletes presenting with elbow pain and that of a matched control group of 18 asymptomatic throwing athletes were compared. Bilateral glenohumeral internal rotation, external rotation, and horizontal adduction at 90° were measured and GIRD and TAMD were then calculated. An analysis of variance was performed to compare range of motion between throwers with and without elbow pain.

RESULTS

The average GIRD of the elbow pain group was 32.7° compared with 14.5° in the control group (P < 0.05). The average TAMD in the elbow pain group was 28.3° compared with 6.7° in the control group (P < 0.05). GIRD and TAMD were present in 88% (22 of 25) and 96% (24 of 25) of the elbow pain group versus 33.3% (6 of 18) and 55.6% (10 of 18) of the control group, respectively.

CONCLUSION

Compared with asymptomatic youth pitchers, those presenting with elbow pain have a statistically significant GIRD and TAMD.

CLINICAL RELEVANCE

This study suggests that a GIRD and TAMD may predispose youth pitchers to present with symptomatic elbow pain.

Does Youth Baseball Result in Morphologic Changes of the Lateral Elbow? A Prospective MRI Study

BACKGROUND

Stress from overhead throwing results in morphologic changes to the shoulder in youth baseball players. With greater valgus torque stresses, the elbow experiences injuries specifically attributed to throwing. However, no previous work that we know of has assessed throwing-related morphologic changes of the elbow without associated conditions.

QUESTIONS/PURPOSES

(1) Do children who play competitive baseball have enlargement or overgrowth of their radial head shape and/or capitellum compared with the nondominant elbow on MRI? (2) Do children who stop playing year-round baseball have less enlargement of the lateral elbow structures than children who maintain a high level of play?

METHODS

A prospective study was conducted between 2015 and 2018 on preadolescent boys who underwent voluntary MRI of their bilateral elbows before the start of the spring baseball season. Twenty-six children agreed to participate out of a four-team league that was asked to participate; their first MRI was obtained at a mean (range) age of 12 years (10 to 13). We also obtained their history related to throwing and performed a physical examination. Players had a mean of 5.6 years of playing before their first MRI, and half the children (13 of 26) were year-round baseball players. Sixty-two percent (16 of 26) reported being either or both a pitcher or catcher as their primary position. No child was excluded from participation. Three years later, these boys were asked to return for repeat MRI and physical examinations. Fifty-eight percent (15 of 26) of players were still playing at the 3-year MRI. Continued play or new onset of pain was documented. Radiographic measurements were then compared between dominant and nondominant arms, and the differences of these changes were compared between those who had continued playing during the study period and those who had quit. The measurements were made in all three planes of the radial head and capitellum, both osseous and cartilaginous. Measurement intrarater and interrater reliability were in the good-to-excellent range (intraclass correlation coefficient 0.77 to 0.98).

RESULTS

When we compared dominant and nondominant arms, we found there was no dominant arm overgrowth (difference between baseline and 3-year measurements) in any measurement; for example, sagittal capitellum measurements in dominant arms were 2.5 ± 1.1 mm versus non-dominant arms: 2.8 ± 1.1 mm (mean difference -0.23 [95% CI -0.55 to 0.08]; p = 0.13). There was only undergrowth of the cartilaginous axial diameter of the radial head (change in dominant: 2.5 ± 1.3 mm; change in nondominant: 3.2 ± 1.7 mm; mean difference -0.64 mm [95% CI -1.2 to -0.06]; p = 0.03). There was no enlargement of the lateral elbow structures when children who continued to play were compared with children who stopped playing; for example, the difference in the bone-only growth ratio of the sagittal radial head to humerus of those still playing was 0.001 ± 0.03 and it was 0.01 ± 0.03 for those not playing (mean difference -0.01 [95% CI -0.04 to 0.01]; p = 0.29).

CONCLUSION

In healthy children who play baseball for multiple years between the ages of 6 to 11 years, continued torque at the elbow from throwing does not result in morphologic changes as it does in the shoulder. Despite evidence that injuries and surgery because of long-term participation in a throwing sport results in a larger radial head and capitellum, our study presents evidence that outside an injured elbow, throwing alone does not appear to change the morphology of the lateral elbow. Therefore, changes to the radial head size could presuppose other elbow pathology and future study could be performed to better evaluate the correlation.

LEVEL OF EVIDENCE

Level I, prognostic study.

Relationship between humeral retroversion and baseball positions during elementary and junior-high school

BACKGROUND

Humeral retroversion is greater in the dominant shoulder than in the nondominant shoulder in baseball players. However, the effect of different baseball positions during childhood on humeral retroversion remains unknown. The purpose of this study was to investigate the following: (1) the relationship between humeral retroversion and baseball positions played during elementary and junior-high schools; (2) the association between humeral retroversion and the prevalence of pain during the medical checkup and self-reported history of injuries in the dominant shoulder or elbow.

METHODS

We enrolled 149 male high-school baseball players who started playing baseball in elementary school. The subjects were classified into 3 groups according to their baseball positions in elementary and junior-high schools. All participants completed questionnaires regarding their current and past positions, current incidence and history of injuries in their shoulder or elbow joints, and the age they started playing baseball. Shoulder range of motion, humeral retroversion on ultrasonographic-assisted measurement, and the association between humeral retroversion and shoulder and elbow pain were evaluated.

RESULTS

Humeral retroversion was significantly greater in the dominant shoulder than in the nondominant shoulder in all groups (P < .001). In addition, humeral retroversion in the dominant shoulder was significantly greater in players who were pitchers in both elementary and junior-high schools than in those who were fielders during both periods (96.2° and 89.4°, respectively; P = .02). Humeral retroversion in the dominant shoulder was positively correlated (P = .005, r = 0.23) with the length of career as a pitcher during elementary and junior-high schools. Humeral retroversion was not correlated with the prevalence of pain during the medical checkup or self-reported history of injuries in the dominant shoulder or elbow (P values ranging from 0.09-0.99).

CONCLUSION

These results suggest that playing baseball as a pitcher during elementary school and junior-high school affects the increase in humeral retroversion in the dominant shoulder. Increased humeral retroversion in the dominant shoulder by repetitive throwing motion is an adaptive change, rather than a pathologic change.

DESCRIPTIVE PROFILE OF SHOULDER RANGE OF MOTION AND STRENGTH IN YOUTH ATHLETES PARTICIPATING IN OVERHEAD SPORTS

Background

The unilateral and repetitive nature of overhead sports, often result in a biomechanical overload of the upper extremity. Understanding the musculoskeletal shoulder range of motion (ROM) and strength patterns in the youth sports of baseball, softball, and tennis could assist injury prevention screening and further the development of conditioning and rehabilitation programs.

Purpose

To generate a descriptive profile of shoulder musculoskeletal characteristics and determine whether bilateral differences in shoulder ROM exist in youth baseball, softball, and tennis athletes. A secondary aim was to determine whether shoulder rotational adaptations are correlated with playing position, sport, or years of experience.

Study Design

Descriptive Laboratory.

Methods

A total of 136 competitive youth overhead athletes (baseball: n = 51,12.8 ± 0.9yrs; softball: n = 63,12.3 ± 1.1yrs; and tennis: n = 22,12.5 ± 0.9yrs) participated. Bilateral shoulder internal (IR) and external (ER) passive ROM and external rotation strength were measured using an inclinometer and handheld dynamometer.

Results

Significant differences (p<.001) in bilateral shoulder ROM and ER strength were found between the athletes in the three sports. Post-hoc test revealed tennis athletes had greater bilateral shoulder ROM than both baseball and softball athletes, but baseball and softball athletes had greater bilateral ER strength than tennis athletes. There were no differences between baseball and softball athletes. Additionally, tennis athletes had greater bilateral internal rotation and total ROM but less ER strength than baseball pitchers, baseball positional athletes, softball pitchers, and softball positional athletes. There were no significant differences between positions and baseball and softball athletes. There were no significant correlations between playing position, sport, or years of experience.

Conclusion

The results of this study showed differences in shoulder passive ROM and strength adaptations between youth tennis, baseball, and softball athletes. The descriptive nature of this study is impactful as it presents specific ROM adaptions seen in this population. Future research is needed to further evaluate if the "at risk" ROM identified in older populations holds true in the youth population.

Level of Evidence

Diagnosis, Level 3b.

Three-dimensional geometry of the normal shoulder: a software analysis

BACKGROUND

Three-dimensional (3D) geometry of the normal glenohumeral bone anatomy and relations is poorly documented. Our aims were (1) to determine the 3D geometry of the normal glenohumeral joint (GHJ) with reference to the scapular body plane and (2) to identify spatial correlations between the orientation and direction of the humeral head and the glenoid.

METHODS

Computed tomographies (CTs) of the normal, noninjured GHJ were collected from patients who had undergone CTs in the setting of (1) polytrauma, (2) traumatic head injury, (3) chronic acromioclavicular joint dislocations, and (4) unilateral trauma with a contralateral normal shoulder. We performed 3D segmentation and measurements with a fully automatic software (Glenosys; Imascap). Measurements were made in reference to the scapular body plane and its transverse axis. Geometric measurements included version, inclination, direction, orientation, best-fit sphere radius (BFSR), humeral subluxation, critical shoulder angle, reverse shoulder angle, glenoid area, and glenohumeral distance. Statistical correlations were sought between glenoid and humeral 3D measurements (Pearson correlation).

RESULTS

A total of 122 normal GHJs (64 men, 58 women, age: 52 ± 17 years) were studied. The glenoid BFSR was always larger than the humerus BFSR (constant factor of 1.5, standard deviation = 0.2). The mean glenoid version and inclination were -6° ± 4° and 7° ± 5°, respectively. Men and women were found to have significantly different values for inclination (6° vs. 9°, P = .02), but not for version. Humeral subluxation was 59% ± 7%, with a linear correlation with glenoid retroversion (r = -0.70, P < .001) regardless of age. There was a significant and linear correlation between glenoid and humeral orientation and direction (r = 0.72 and r = 0.70, P < .001).

CONCLUSION

The 3D geometry of the glenoid and humeral head present distinct limits in normal shoulders that can be set as references in daily practice: version and inclination are -6° and 7°, respectively, and humeral posterior subluxation is 59%; interindividual variations, regardless of the size, are relative to the scapular plane. There exists a strong correlation between the position of the humeral head and the glenoid orientation and direction.

Influence of a Pre-throwing Protocol on Range of Motion and Strength in Baseball Athletes

Though chronic overhand throwing is known to result in range of motion and strength adaptations, there is limited research regarding interventions for maintenance of these characteristics. Therefore, the purposes of this study were to explore the use of a pre-throwing protocol focusing on lumbopelvic-hip complex musculature in high school baseball players and examine its effects on shoulder and hip range of motion and isometric strength over the course of a season. Four exercises were added to the intervention team's warm-up routine. The control and intervention teams' passive bilateral hip and shoulder range of motion and isometric strength were assessed pre/post-season. A multivariate analysis of variance revealed significant differences in delta scores between the teams for multiple shoulder and hip range of motion and isometric strength variables. Key results were the intervention team lost significantly more stride hip external rotation but gained more isometric strength than the control team. The intervention team was also able to better maintain shoulder range of motion than the control team. Practitioners should use the results of this study and consider incorporating exercises that target lumbopelvic-hip complex musculature into their current training program.

Risk Factors of Overuse Shoulder Injuries in Overhead Athletes: A Systematic Review

CONTEXT

Shoulder injuries are highly prevalent in sports involving the upper extremity. Some risk factors have been identified in the literature, but consensus is still lacking.

OBJECTIVES

To identify risk factors of overuse shoulder injury in overhead athletes, as described in the literature.

DATA SOURCES

A systematic review of the literature from the years 1970 to 2018 was performed using 2 electronic databases: PubMed and Scopus.

STUDY SELECTION

Prospective studies, written in English, that described at least 1 risk factor associated with overuse shoulder injuries in overhead sports (volleyball, handball, basketball, swimming, water polo, badminton, baseball, and tennis) were considered for analysis.

STUDY DESIGN

Systematic review.

LEVEL OF EVIDENCE

Level 3.

DATA EXTRACTION

Data were extracted from 25 studies. Study methodology quality was evaluated using the Modified Coleman Methodology Score.

RESULTS

Intrinsic factors, previous injury, range of motion (lack or excess), and rotator cuff weakness (isometric and isokinetic) highly increase the risk of future injuries. Additionally, years of athletic practice, body mass index, sex, age, and level of play seem to have modest influence. As for the effect of scapular dysfunction on shoulder injuries, it is still controversial, though these are typically linked. Extrinsic factors, field position, condition of practice (match/training), time of season, and training load also have influence on the occurrence of shoulder injuries.

CONCLUSION

Range of motion, rotator cuff muscle weakness, and training load are important modifiable factors associated with shoulder injuries. Scapular dysfunction may also have influence. The preventive approach for shoulder injury should focus on these factors.

Does humeral torsion play a role in shoulder and elbow injury profiles of overhead athletes: a systematic review

BACKGROUND

Humeral retrotorsion (HRT) is one bony adaptation that occurs in overhead athletes. This bony adaptation often leads to bilateral changes in range of motion at the glenohumeral joint. Because HRT can create different stress environments on the surrounding tissue, it may play a role in upper-limb injury and pain profiles. Therefore, the aim of this review was to examine whether HRT plays a role in shoulder and elbow injury profiles.

METHODS

Two separate critical appraisal tools were administered: the Newcastle-Ottawa Scale (case control) and the Appraisal Tool for Cross-sectional Studies. The primary author extracted all data and obtained means and standard deviations for each outcome. Cohen d effect sizes (ESs) were calculated (ES [95% confidence interval]) for all HRT measurements including nondominant, dominant, and side-to-side differences. Finally, the Strength of Recommendation Taxonomy was used to evaluate the overall strength of the recommendation.

RESULTS

Nine articles were included in this review. Large ESs were present in 2 studies on examination of symptomatic and asymptomatic dominant HRT and ranged between 0.83 (0.08-1.55) and -2.57 (-3.66 to 1.99). The majority of all ESs for all HRT measurements were moderate or low, rendering comparisons between asymptomatic and symptomatic cohorts that were not clinically meaningful.

CONCLUSION

The Strength of Recommendation Taxonomy rating was C based on inconsistent findings. Differences in sports populations and definitions of injuries across studies may be one reason for the varying ESs. HRT does occur in the overhead population, but the degree to which this HRT starts to affect upper-limb injury is unknown and is more than likely player specific and multifactorial.

Posterior Labral Injury and Glenohumeral Instability in Overhead Athletes: Current Concepts for Diagnosis and Management

Posterior glenohumeral instability in overhead athletes presents a unique set of challenges for both diagnosis and treatment. Although a great deal of attention has been focused on the management of injuries to the biceps-labrum complex and rotator cuff in throwers, comparatively less has been written about posterior glenohumeral instability within this unique cohort. Historically, posterior instability has been observed secondary to either acute trauma or repetitive microtrauma, usually among collision athletes, weight lifters, and rowers. However, posterior glenohumeral instability resulting from pathology of the posterior capsulolabral tissues in throwers is a different entity, and the clinical assessment begins with an accurate differentiation between adaptive capsular laxity and labral injury with pathologic instability. Some posterior capsule labrum tears confirmed on arthroscopy will require nothing more than débridement. However, for more extensive lesions, surgical treatment must balance the necessity to repair torn capsulolabral tissues with the tendency to over constrain the shoulder. The literature provides mixed results regarding the likelihood of overhead athletes with posterior glenohumeral instability and labral injury treated surgically returning to their preinjury level of sport performance.

The Relationship Between Humeral Torsion and Arm Injury in Baseball Players: A Systematic Review and Meta-analysis

CONTEXT

Humeral torsion (HT) has been linked to various injuries and benefits. However, the exact interplay between HT, shoulder range of motion (ROM), competition level differences, and injury risk is unclear.

OBJECTIVE

To determine the relationship between HT, ROM, and injury risk in baseball players. Secondarily, to determine HT based on competition level.

DATA SOURCES

PubMed, Embase, Web of Science, CINAHL, and Cochrane databases were searched from inception until November 4, 2018.

STUDY SELECTION

Inclusion criteria consisted of (1) HT measurements and (2) arm injury or shoulder ROM.

STUDY DESIGN

Systematic review.

LEVEL OF EVIDENCE

Level 3.

DATA EXTRACTION

Two reviewers recorded patient demographics, competition level, HT, shoulder ROM, and injury data.

RESULTS

A total of 32 studies were included. There was no difference between baseball players with shoulder and elbow injuries and noninjured players (side-to-side HT difference: mean difference [MD], 1.75 [95% CI, -1.83 to 2.18]; dominant arm: MD, 0.17 [95% CI, -1.83 to 2.18]). Meta-regression determined that for every 1° increase in shoulder internal rotation (IR), there was a subsequent increase of 0.65° in HT (95% CI, 0.28 to 1.02). HT did not explain external rotation (ER ROM: 0.19 [95% CI, -0.24 to 0.61]) or horizontal adduction (HA ROM: 0.18 [95% CI, -0.46 to 0.82]). There were no differences between HT at the high school, college, or professional levels.

CONCLUSION

No relationship was found between HT and injury risk. However, HT explained 65% of IR ROM but did not explain ER ROM or HA ROM. There were no differences in HT pertaining to competition level. The majority of IR may be nonmodifiable. Treatment to restore and maintain clinical IR may be important, especially in players with naturally greater torsion. HT adaptation may occur prior to high school, which can assist in decisions regarding adolescent baseball participation.

Characterization of glenoid bone remodeling in professional baseball pitchers

OBJECTIVE

To characterize the appearance, location, severity, and prevalence of focal glenoid retroversion on shoulder MRI in professional baseball pitchers versus age-matched controls.

MATERIALS AND METHODS

In this retrospective review, two musculoskeletal radiologists evaluated shoulder MRI examinations from 40 professional baseball pitchers and 40 age-matched controls. Images were scored for the presence of a focal posterior glenoid convexity and the clock face positions involved. A consensus interpretation was also performed. A third reader identified the presence of additional shoulder abnormalities.

RESULTS

After consensus, 60% (24/40) of pitchers were found to have focal glenoid retroversion versus 20% (8/40) of controls (p = 0.001). The most apparent location was posterior or posterior-superior, from 7.75 o'clock to 10.5 o'clock (median, 9.75 o'clock; interquartile range, 9.25-10 o'clock). The median clock angle of involvement was greater in pitchers than in controls (30° vs. 0°; p < 0.001). Interreader agreement regarding the presence or absence of focal glenoid retroversion was moderate (Cohen's kappa, 0.49). Focal glenoid retroversion was more prevalent among subjects with additional shoulder abnormalities (p = 0.014).

CONCLUSIONS

Glenoid remodeling occurs in the throwing shoulder of professional baseball pitchers and manifests as focally convex morphology of the posterior or posterior-superior glenoid. This type of remodeling does not appear to be associated with a lower prevalence of injuries related to posterior-superior impingement.

Review of Shoulder Range of Motion in the Throwing Athlete: Distinguishing Normal Adaptations from Pathologic Deficits

PURPOSE OF REVIEW

Overhand (OH) throwers demonstrate a unique motion profile of the shoulder joint complex. This manuscript reviews normal adaptations in the OH thrower and contrast findings with pathologic motion deficits.

RECENT FINDINGS

Multiple adaptations in range of motion have been associated with increased risk for arm injury. The use of a more conservative cutoff value for glenohumeral internal rotation deficit and horizontal adduction in younger throwers may help reduce injury risk. Deficits in glenohumeral internal rotation, total range of motion, shoulder flexion, and external rotation insufficiency have all been proposed as means to identify OH throwers at risk for arm injury, but conflicting evidence exists. Understanding normal adaptation due to repetitive stress of throwing is essential to effective management of these athletes. Adaptive change in bone and soft tissues is normal and contributes to the unique motion profiles expected in throwers. The causative link between normal adaptation and shoulder and elbow injury remains uncertain.

Relationship between bilateral humeral retroversion angle and starting baseball age in skeletally mature baseball players-existence of watershed age

BACKGROUND

Repetitive pitching in childhood was thought to restrict the physiological derotation process of the humeral head. Some studies reported that the side-to-side differences of humeral retroversion in baseball players occurred between the age of 9 and 11 years. The present study investigated the relationship between bilateral humeral retroversion angle and starting baseball age in skeletally mature baseball players.

METHODS

One hundred and seventeen male baseball players, who belonged to a college or amateur team, were investigated. Bilateral humeral retroversion was assessed using an ultrasound-assisted technique as described by previous studies. All players were divided into four groups: players who had started playing baseball before the age of 6 years, between 7 and 8 years, between 9 and 10 years and after 11 years. Bilateral humeral retroversion angle was compared among the four starting age groups.

RESULTS

All players started playing baseball between 5 and 12 years. Comparing the throwing arm, humeral retroversion in starting age group 11-12 (72°) was significantly smaller than the other 3 groups (81°, 82°, and 80° for groups 5-6, 7-8, and 9-10, respectively). Comparing the non-throwing arm revealed no significant differences among the 4 starting age groups (71°, 72°, 70°, and 66° for groups 5-6, 7-8, 9-10, and 11-12, respectively).

CONCLUSIONS

Skeletally mature baseball players who started playing baseball after 11 years had significantly smaller humeral retroversion in the throwing arm than those who started baseball before 11 years.

High incidence of posterior glenoid dysplasia of the shoulder in young baseball players

BACKGROUND

Rounding of the posterior glenoid rim is observed in young throwing athletes with internal shoulder impingement and is considered developmental dysplasia of the glenoid. The aim of our study was to determine the incidence rate of dysplastic changes of the glenoid within a group of 92 young baseball players.

METHODS

The study group included 92 male baseball players, with a mean age of 14.63 years. Of these patients, 30 were diagnosed with Little Leaguer's shoulder and 62 with a painful baseball-throwing shoulder with no abnormal findings on x-ray. The posterior glenoid rim of the affected shoulder was compared with the contralateral nonpainful shoulder, with the 2 following outcomes measured on radiographs obtained using the modified Bernageau imaging method: the distance between the anterior and posterior glenoid rims and the presence or absence of dysplasia of the posterior glenoid rim.

RESULTS

The mean distance between the anterior and posterior glenoid rims was significantly shorter in the painful shoulders (mean, 26 mm) than in the nonpainful shoulders (mean, 29 mm; P < .0001). Dysplasia of the posterior glenoid rim was identified in 89 painful shoulders (96.7%), with 9 cases (9.7%) identified on the unaffected contralateral side (P < .001). The presence of dysplasia was not correlated with the age at which baseball playing began.

CONCLUSION

The incidence of dysplasia of the posterior glenoid rim is high (96.7%) among young baseball players with a painful shoulder. The identified dysplasia may be related to impaired development of the inferior peripheral secondary glenoid ossification center due to repetitive throwing.

Shoulder Range of Motion and Baseball Arm Injuries: A Systematic Review and Meta-Analysis

OBJECTIVE

Arm injuries in baseball players are a common problem. The identification of modifiable risk factors, including range of motion (ROM), is essential for injury prevention. The purpose of this review was to assess the methodologic quality and level of evidence in the literature and to investigate the relationship between shoulder ROM and the risk of arm injuries in baseball players.

DATA SOURCES

Relevant studies in PubMed, CINAHL, Embase, and SPORTDiscus published from inception to August 1, 2017.

STUDY SELECTION

Only studies that encompassed healthy baseball cohorts who were assessed for shoulder ROM and prospectively evaluated for injuries throughout a baseball season or seasons were included.

DATA EXTRACTION

Six articles met the search criteria. Only 3 studies were included in the meta-analysis due to disparate participant groups.

DATA SYNTHESIS

The modified Downs and Black scale (0-15 points) was used to analyze methodologic quality. Study quality ranged from 11 to 14. Four studies received high-quality (≥12) and 2 studies received moderate-quality (≥10) scores. The overall pooled analysis demonstrated that absolute and internal-rotation deficits (-5.93 [95% confidence interval {CI} = -9.43, -2.43], P < .001 and 4.28 [0.71, 7.86], P = .02, respectively) and absolute total ROM (TROM; -6.19 [95% CI = -10.28, -2.10]; P = .003) were predictors of injury, and these data exhibited homogeneity (absolute IR P value = .77, I² = 0%; IR deficit P value = .41, I² = 0%; absolute TROM P value = .78, I² = 0%). No significance was observed for absolute external rotation (-2.86 [95% CI = -6.56, 0.83], P = .13), which had data with high heterogeneity ( P = .003; I² = 83%). A deficit in horizontal adduction was a predictor of injury (-8.32 [95% CI = -12.08, -4.56]; P < .001); these data were homogeneous but yielded a moderate heterogenic effect ( P = .16; I² = 50%).

CONCLUSIONS

High-quality evidence demonstrated that deficits in throwing-arm TROM and IR were associated with upper extremity injury in baseball players. Heterogeneity across studies for horizontal adduction suggested that this may be a modifiable risk factor for injury, but it requires further research.

Unravelling the hip pistol grip/cam deformity: Origins to joint degeneration

This article reviews a body of work performed by the investigators over 9 years that has addressed the significance of cam morphology in the development of hip osteoarthritis (OA). Early hip joint degeneration is a common clinical presentation and preexisting abnormal joint morphology is a risk factor for its development. Interrogating Hill's criteria, we tested whether cam-type femoroacetabular impingement leads to hip OA. Strength of association was identified between cam morphology, reduced range-of-movement, hip pain, and cartilage degeneration. By studying a pediatric population, we were able to characterize the temporality between cam morphology (occurring 1st) and joint degeneration. Using in silico (finite element) and in vivo (imaging biomarkers) studies, we demonstrated the biological plausibility of how a cam deformity can lead to joint degeneration. Furthermore, we were able to show a biological gradient between degree of cam deformity and extent of articular damage. However, not all patients develop joint degeneration and we were able to characterize which factors contribute to this (specificity). Lastly, we were able to show that by removing the cam morphology, one could positively influence the degenerative process (experiment). The findings of this body of work show consistency and coherence with the literature. Furthermore, they illustrate how cam morphology can lead to early joint degeneration analogous to SCFE, dysplasia, and joint mal-reduction post-injury. The findings of this study open new avenues on the association between cam morphology and OA including recommendations for the study, screening, follow-up, and assessment (patient-specific) of individuals with cam morphology in order to prevent early joint degeneration. Statement of significance: By satisfying Hill's criteria, one can deduct that in some individuals, cam morphology is a cause of OA. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:3125-3135, 2018.

Changes in humeral retrotorsion and the development of little league shoulder: A case study

OBJECTIVE

To present the case of a 15 year-old baseball player with Little League Shoulder (LLS) and describe how developmental changes in the angle of humeral retrotorsion (HRT) may contribute to the underlying pathology of this condition.

DESIGN

Case report.

SETTING

Two years earlier, the patient had participated in a healthy player screening program at which time measurements of height, weight, shoulder motion, and HRT were obtained. These same measures were obtained during the initial evaluation after injury. Between measurements, the patient grew more than 12 cm in height and demonstrated a large shift in proximal humeral torsional alignment with a change of 13° and 19° of HRT in the dominant and non-dominant sides respectively.

PARTICIPANT

15 year-old male (1.88 m, 79.8 kg), right hand dominant baseball pitcher and 3rd baseman diagnosed with right LLS.

CONCLUSION

The pathoanatomical factors contributing to LLS are not well understood. The degree of HRT is a developmental characteristic that changes over the course of physiological maturation. The large changes in HRT seen in this case, may implicate rapid changes in HRT angle create a window of increased susceptibility to physeal damage, and contribute to the development of LLS.

Shoulder Injuries in the Overhead-Throwing Athlete: Epidemiology, Mechanisms of Injury, and Imaging Findings

The unparalleled velocity achieved by overhead throwers subjects the shoulder to extreme forces, resulting in both adaptive changes and pathologic findings that can be detected at imaging. A key biomechanical principle of throwing is achieving maximum external rotation, which initially leads to adaptive changes that may result in a pathologic cascade of injuries. In addition to the well-established concepts of glenohumeral internal rotation deficit and internal impingement, osseous and soft-tissue injuries of the shoulder unique to overhead athletes are illustrated. The epidemiology and biomechanics of throwing injuries are reviewed, and examples from the authors' institutional experience with competitive, collegiate, and professional baseball players are provided to demonstrate the constellation of unique imaging findings seen in overhead throwing athletes. Given the widespread popularity of baseball, and other sports relying on overhead throwing motions at all playing levels from recreational to professional, it is important for radiologists in various practice settings to be familiar with the special mechanisms, locations, and types of shoulder injuries seen in the overhead throwing population. ^© RSNA, 2018.

Humeral Retroversion and Capsule Thickening in the Overhead Throwing Athlete: A Systematic Review

PURPOSE

To investigate the humeral and soft-tissue adaptations, including humeral retroversion, range of motion, and posterior capsule changes, in overhead throwing athletes.

METHODS

We performed a systematic review in accordance with Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. PubMed, MEDLINE, CENTRAL (Cochrane Central Register of Controlled Trials), and Embase were searched from January 1, 2011, through April 23, 2017, by 2 reviewers independently and in duplicate. The methodologic quality of all included articles was assessed using the Methodological Index for Non-randomized Studies criteria. Interobserver agreement for assessments of eligibility was calculated with the Cohen κ statistic. Descriptive statistics and raw counts were used to summarize data.

RESULTS

We identified 14 studies (6 Level IV and 8 Level III) including 1,152 overhead throwing athletes. The mean age of the included athletes was 18.37 years (standard deviation, 1.52 years), with 59% of the athletes being pitchers and 41% being position players. Significantly greater humeral retroversion was found across all studies evaluating bony morphology in the dominant arm of overhead throwing athletes (range of mean differences, 9.6°-25.8°). Each of these studies also found decreased internal rotation in the dominant arm (range of mean internal rotation differences, -28° to -7.8°). Five studies found a significant negative correlation between the difference in humeral retroversion between the 2 arms and the difference in internal rotation (range of Pearson correlation coefficients, -0.56 to -0.35). Soft-tissue adaptations were assessed in 5 studies, with 4 identifying significantly thicker posterior capsules and 2 identifying significantly stiffer posterior capsules (P < .05).

CONCLUSIONS

Overhead throwing athletes consistently show several distinct changes in their dominant shoulder. These include increased humeral retroversion and the presence of a thickened and stiff posterior capsule. Concomitantly, there is often reduced internal rotation and increased external rotation of the dominant arm.

LEVEL OF EVIDENCE

Level IV, systematic review of Level III and IV studies.

Many Shoulder MRI Findings in Elite Professional Throwing Athletes Resolve After Retirement: A Clinical and Radiographic Study

BACKGROUND

Anatomic findings on MRI scans of the shoulder likely affect patients differently based on their physical demands and fitness levels. The natural history of these anatomic findings once professional overhead athletes retire remains unclear. A better understanding of what happens with these findings after retirement may influence how we manage shoulder problems in athletes.

PURPOSE

(1) What is the natural history of MRI-observed findings in the throwing and nonthrowing shoulders of professional European handball players after retirement from the sport? What proportion of these individuals have diagnosable findings on MRI, and do these findings disappear after retirement? (2) Do clinical findings such as Constant and Murley score and shoulder ROM change after retirement in these professional overhead athletes?

METHODS

The inception cohort of this series consisted of the entire Swiss National European handball team except the goalkeepers. These 30 professional players also played in the highest Swiss handball league in 2001. None of these players previously had shoulder surgery. During their career, they had a clinical assessment and bilateral shoulder MRI as part of an earlier study. We sought to evaluate the players who had retired and did not have a history of shoulder surgery, to evaluate the natural history of MRI-observed findings made in the initial study during their professional career. Of the 30 players, 10 were excluded (four continued to play professionally, four declined participation, and two had surgery after the initial study), leaving 20 (66%) for analysis at a mean of 6 years (SD, 3 years) after retirement. To gain a better understanding of the evolution of these MRI findings in the longer-term, we also evaluated 18 additional former professional European handball players who did not have any history of shoulder surgery, had all played in the highest Swiss league and for the National Team, and had terminated their career at a mean of 15 years (SD, 3 years) ago. All the subjects in both study groups (those at 6 and 15 years after retirement) underwent a detailed interview, standardized clinical examination including ROM measurements, collection of the Constant and Murley scores and the subjective shoulder value of both shoulders, and bilateral shoulder MRI. MRI findings (consisting of abnormalities and normal variations) were reported as radiographic diagnoses, independent of the potential that these findings could be considered normal variations in people in this age group.

RESULTS

At the initial MRI evaluation, the proportion of active professional European handballers with diagnosable MRI findings in the throwing shoulder was 19 of 20 (95%) and for the handballers with nonthrowing shoulders was 17 of 20 (85%), while 15 years after retirement, both shoulders of all subjects showed MRI findings. None of the rotator cuff tears progressed to full-thickness tears after retirement. In the throwing shoulders, we observed fewer individuals with ganglion cysts larger than 5 mm (initial followup: six of 20 [30%] versus 6 years after retirement: 0 of 20 (0%); odds ratio, 14.5; [95% CI, 0.7-283]; p = 0.044). The Constant and Murley score increased in the throwing shoulder from 93 points (SD, 6 points) at initial followup to 98 points (SD, 3 points) at a mean of 6 years after retirement (mean difference, 5 points; SD, 5 points; 95% CI, 2.5-7.4; p < 0.001), and to 97 points (SD, 3 points) at a mean of 15 years after retirement. However these differences are below the typically reported minimum clinically important difference for the Constant and Murley score, and so are unlikely to be clinically relevant. External rotation in 90° abduction remained increased in the throwing shoulder compared with the nonthrowing shoulder up to 15 years after retirement (initial followup: mean difference, 8°; p = 0.014; 15 years after retirement: mean difference, 4°; SD, 15; p = 0.026). Internal rotation remained decreased in the throwing compared with the nonthrowing shoulders (during the career: mean difference, 5° [SD, 10°], p = 0.036; 15 years after retirement: mean difference, 3° [SD, 4°], p = 0.021).

CONCLUSIONS

Our data suggest that findings of the throwing shoulder like partial rotator cuff tears, bony cysts and ganglions do not progress after retirement, and sometimes they resolve. Because of this and because many MRI changes correlate poorly with clinical symptoms, the indication for surgical treatment of these findings should be questioned very carefully.

LEVEL OF EVIDENCE

Level II, prognostic study.

Shoulder MRI Abnormalities in Asymptomatic Little League Baseball Players

Background:

Youth baseball is extremely popular in the United States, but it has been associated with shoulder pain and injury. The incidence of shoulder abnormalities in this athletic population has yet to be defined.

Purpose:

To examine abnormalities noted on magnetic resonance imaging (MRI) in the shoulders of asymptomatic Little League baseball players and to correlate these findings with the players’ throwing history and physical examinations.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

A total of 23 Little League baseball players aged 10 to 12 years were recruited. All players underwent a comprehensive physical examination and responded to a questionnaire addressing their playing history and any arm or shoulder pain. Bilateral shoulder MRIs were performed and read in a blinded manner by 2 radiologists. Responses on the questionnaire and physical examination findings were compared between participants with and without positive MRI findings through use of chi-square test and analysis of variance.

Results:

The dominant arm was 8.5 times more likely to have an abnormality on MRI compared with the nondominant arm. In all, 12 players (52%) had 17 positive MRI findings in their throwing shoulder that were not present in their nondominant shoulder. These findings included edema or widening of the proximal humeral physis (n = 5), labral tear (n = 4), partial rotator thickness tear (n = 4), acromioclavicular joint abnormality (n = 2), subacromial bursitis (n = 1), and cystic change of the greater tuberosity (n = 1). Two primary risk factors were associated with an abnormal MRI: year-round play and single-sport athletes focusing solely on baseball (P < .05). Players with no risk factors, 1 risk factor, and both risk factors had a 25%, 71%, and 100% chance, respectively, of having an abnormal MRI. A majority of players (61%) had previously experienced shoulder pain, especially pitchers throwing curveballs and sliders (P < .05), but this was not associated with an abnormal MRI.

Conclusion:

Abnormalities seen on MRI involving the shoulder are common in Little League baseball players, especially those who are single-sport athletes playing year-round.

Left-handed skeletally mature baseball players have smaller humeral retroversion in the throwing arm than right-handed players

BACKGROUND

It is known that the humeral retroversion of baseball players is greater in the throwing arm than in the nonthrowing arm. An investigation measuring dry bone specimens also showed that the right humerus had greater retroversion than the left. Considering these facts, it was hypothesized that humeral retroversion would differ between right- and left-handed players. This study aimed to compare the bilateral humeral retroversion between right- and left-handed skeletally mature baseball players.

METHODS

We investigated 260 (196 right-handed and 64 left-handed) male baseball players who belonged to a college or amateur team. Bilateral humeral retroversion was assessed using an ultrasound-assisted technique (humeral torsion angle [HTA]) as described by previous studies. Analysis of covariance, adjusted for handedness and baseball position, assessed the effect of throwing arm dominance on HTA.

RESULTS

In comparison of the throwing arm, HTA was significantly smaller in left-handed (left humerus) than in right-handed (right humerus) players (77° vs. 81°; P < .001). In comparison of the nonthrowing arm, HTA was significantly greater in left-handed (right humerus) than in right-handed (left humerus) players (73° vs. 69°; P < .001). The mean side-to-side difference of HTA was significantly smaller in left-handed than in right-handed players (3° vs. 12°; P < .001).

CONCLUSIONS

Humeral retroversion of left-handed skeletally mature baseball players was significantly smaller in the throwing arm, greater in the nonthrowing arm, and smaller in side-to-side differences than that of right-handed players. These findings may be key to understanding some of the biomechanical differences between right- and left-handed baseball players.

Upper Extremity Range of Motion and Pitching Profile of Baseball Pitchers in Japan

BACKGROUND

Shoulder range of motion and pitch count in baseball pitchers have been linked to pitching-related upper extremity injury.

PURPOSE

To investigate upper extremity range of motion and pitching profiles in baseball pitchers in Japan as well as to make a comparison between injured and noninjured pitchers.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Forty-one Little League to college-level baseball pitchers were measured for bilateral shoulder and elbow range of motion, including shoulder internal rotation (IR), external rotation (ER), shoulder horizontal adduction (HAD), and elbow extension (EXT). They were also asked to answer a simple questionnaire regarding their past pitching-related medical history and pitching profile. Additionally, 28 participants with baseball-related upper extremity injuries (injury group) were compared with 13 participants without injury (no-injury group) for the same parameters. Collected data were analyzed using analysis of variance.

RESULTS

Significant limb differences (dominant vs nondominant side) were noted for ER (117.2° vs 109.8°, P = .02), IR (53.5° vs 61.9°, P = .007), HAD (28.3° vs 32.8°, P = .03), and EXT (1.0° vs 4.6°, P = .01). A significant between-group difference (injury vs no-injury group) was observed for IR in both the dominant (55.4° vs 45.6°, P = .03) and nondominant shoulder (65.3° vs 55.0°, P = .01). Participants in the injury group pitched more games in a season and more innings per game started.

CONCLUSION

Japanese baseball pitchers displayed adaptive changes in upper extremity range of motion similar to American pitchers when compared bilaterally. Injured pitchers exhibited greater IR range of motion in their pitching arm compared with noninjured pitchers.

Humeral Retrotorsion and Glenohumeral Motion in Youth Baseball Players Compared With Age-Matched Nonthrowing Athletes

BACKGROUND

Baseball players exhibit a more posteriorly oriented humeral head in their throwing arm. This is termed humeral retrotorsion (HRT) and likely represents a response to the stress of throwing. This adaptation is thought to occur while the athlete is skeletally immature, however currently there is limited research detailing how throwing activity in younger players influences the development of HRT. In addition, it is presently unclear how this changing osseous orientation may influence shoulder motion within young athletes.

PURPOSE

To determine the influence of throwing activity and age on the development of side-to-side asymmetry in HRT and shoulder range of motion (ROM).

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Healthy athletes (age range, 8-14 years) were categorized into 2 groups based upon sports participation; throwers (n = 85) and nonthrowers (n = 68). Bilateral measurements of HRT, shoulder external rotation (ER), internal rotation (IR), and total range of motion (TROM) at 90° were performed using diagnostic ultrasound and a digital inclinometer. Side-to-side asymmetry (dominant minus nondominant side) in HRT and in shoulder ER, IR, and TROM were assessed. Statistical analysis was performed with 2-way analysis of variance and Pearson correlation coefficients.

RESULTS

Throwers demonstrated a larger degree of HRT on the dominant side, resulting in greater asymmetry compared with nonthrowers (8.7° vs 4.8°). Throwers demonstrated a gain of ER (5.1°), a loss of IR (6.0°), and no change in TROM when compared with the nondominant shoulder. Pairwise comparisons identified altered HRT and shoulder ROM in all age groups, including the youngest throwers (age range, 8-10.5 years). A positive correlation existed between HRT and ER ROM that was stronger in nonthrowers ( r = 0.63) than in throwers ( r = 0.23), while a negative correlation existed with IR that was stronger in throwers ( r = -0.40) than in nonthrowers ( r = -0.27).

CONCLUSION

Throwing activity causes adaptive changes in HRT and shoulder ROM in youth baseball players at an early age. Other factors in addition to HRT influence shoulder motion within this population.

Baseball Players With an Ulnar Collateral Ligament Tear Display Increased Nondominant Arm Humeral Torsion Compared With Healthy Baseball Players

BACKGROUND

Previous work has suggested that an increase in the amount of developmentally acquired, dominant arm humeral retrotorsion (D HRT) in the thrower's shoulder may be a potentially protective mechanism. Although the relationship between HRT and shoulder injuries has been reported, the relationship between HRT and ulnar collateral ligament (UCL) tears in baseball players is not known.

PURPOSE

To determine whether D HRT and nondominant arm HRT (ND HRT) measurements in baseball players with a UCL tear differ statistically from a matched healthy cohort.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

D HRT and ND HRT were measured in 112 male competitive high school and collegiate baseball players seen over an 18-month period from 2013 to 2015. A total of 56 participants with a clinical and magnetic resonance imaging-confirmed diagnosis of a throwing-arm UCL tear (UCLInj group) were compared with 56 healthy baseball players with no history of an elbow injury who were matched for age, experience, and position (NUCLInj group). The mean ages in the UCLInj and NUCLInj groups were 17.9 ± 2.2 and 17.6 ± 2.8 years, respectively. Using a previously validated ultrasound method, D HRT and ND HRT were measured in the supine position, and the HRT side-to-side difference (D HRT - ND HRT) was calculated. A 1-way multivariate analysis of variance was used to determine the mean statistical differences between groups ( P < .05).

RESULTS

Baseball players with a UCL tear displayed significantly more humeral torsion (ie, less retrotorsion) in their nondominant arm compared with healthy baseball players (UCLInj = 33.27° ± 10.27°, NUCLInj = 27.82° ± 10.88°; P = .007). Baseball players with a UCL tear did not display any differences in D HRT compared with healthy baseball players (UCLInj = 18.67° ± 9.41°, NUCLInj = 17.09° ± 9.92°; P = .391). Significant side-to-side differences in HRT existed between groups (UCLInj = -14.60° ± 6.72°, NUCLInj = -10.72° ± 6.88°; P = .003).

CONCLUSION

There was a significant increase in mean nondominant arm humeral torsion (ie, less retrotorsion) in the UCL tear group, but there was no significant difference in the mean D HRT between the injured and uninjured groups. A greater HRT side-to-side difference was displayed in the UCL tear group. The extent to which a thrower has developmentally acquired both D HRT and ND HRT may affect elbow UCL tear risk. Furthermore, it is possible that the extent of genetically predisposed ND HRT may influence the throwing-related increase in D HRT.

The Relationship Between Humeral Retrotorsion and Shoulder Range of Motion in Baseball Players With an Ulnar Collateral Ligament Tear

BACKGROUND

Humeral retrotorsion has been investigated in relation to shoulder range of motion (ROM) in healthy baseball players. Currently, there is limited information on the osseous anatomy and development of ulnar collateral ligament (UCL) tears.

PURPOSE

To determine the relationship between humeral retrotorsion and shoulder ROM in baseball players with a UCL tear.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Fifty-four baseball players (mean age, 18.5 ± 2.0 years) with a UCL tear volunteered for this study. Participants were measured bilaterally for shoulder internal (IR) and external rotation (ER) ROM and humeral retrotorsion. Differences between sides (involved to uninvolved) were used to calculate the glenohumeral internal rotation deficit (GIRD), external rotation ROM difference (ERDiff), total rotational motion difference (TRM), and humeral retrotorsion difference (HTDiff). A multivariate regression analysis was performed with GIRD, ERDiff, and TRM regressing on HTDiff. Univariate analysis was performed to further evaluate the effect of the predictors on each outcome separately. To control for the effect of age, weight, duration of symptoms, and years of experience, the variables were included as covariates. An a priori level was set at P < .05.

RESULTS

There was a statistically significant relationship between the GIRD, ERDiff, and TRM results compared with HTDiff (P = .003). Independent analysis revealed a statistically significant relationship between GIRD and HTDiff (P = .004) and between ERDiff and HTDiff (P = .003) but no significant relationship between TRM and HTDiff (P = .999). After adjusting for age, weight, duration of symptoms, years of experience, dominant arm, and position, a significant relationship was found between GIRD and HTDiff (P = .05) and between ERDiff and HTDiff (P = .01). No significant relationship was found between TRM and HTDiff (P = .54). Adjusted univariate regression analysis determined that HTDiff explains approximately 16% of the variance in GIRD (r² = 0.158) and approximately 24% of the variance in ERDiff (r² = 0.237).

CONCLUSION

In baseball players with a UCL tear, approximately 16% of the variance in GIRD and 24% of the variance in ERDiff can be attributed to differences found in humeral retrotorsion between sides. This indicates that humeral retroversion contributes significantly to GIRD and increased ER ROM in baseball players. Recognition of differences in humeral retrotorsion between the dominant and nondominant upper extremities may help explain some but not all of the changes in shoulder ROM commonly seen in baseball players.

Pathomechanics and Magnetic Resonance Imaging of the Thrower's Shoulder

Repetitive, high-velocity overhead throwing can lead to several adaptive changes in the throwing shoulder, which over time lead to structural microtrauma and eventually overt injury. MR imaging is a useful imaging modality to evaluate these changes and to characterize their acuity and severity. Understanding the throwing motion and the effects of this motion on the structures of the shoulder can help radiologists to recognize these findings and provide useful information to referring physicians, which may affect the treatment of these athletes. This article reviews shoulder pathomechanics and MR imaging findings in overhead throwing athletes.

Isolated glenohumeral range of motion, excluding side-to-side difference in humeral retroversion, in asymptomatic high-school baseball players

PURPOSE

Glenohumeral range of motion is correlated with shoulder capsular condition and is thus considered to be predictive of shoulder pathology. However, in throwing athletes, a side-to-side difference in humeral retroversion makes it difficult to evaluate capsular condition on the basis of glenohumeral range of motion measured by using the conventional technique. The purpose of this study was to measure isolated glenohumeral rotation, excluding side-to-side differences in humeral retroversion, in asymptomatic high-school baseball players.

METHODS

A total of 195 high-school baseball players (52 pitchers and 143 position players; median age, 16 years) and 20 high-school non-throwing athletes (median age, 16 years) without any shoulder symptoms were enroled in this study. Glenohumeral external and internal rotations were measured by using both a conventional technique and our ultrasound-assisted technique. This technique, neutral rotation, was standardized on the basis of the ultrasonographically visualized location of the bicipital groove to exclude side-to-side differences in humeral retroversion from the calculated rotation angle. Intra- and inter-observer agreements of rotational measurements were evaluated by using intra-class correlation coefficients (ICCs).

RESULTS

Isolated glenohumeral rotation measurements, excluding side-to-side differences in humeral retroversion, demonstrated excellent intra-observer (ICC > 0.89) and inter-observer (ICC > 0.78) agreements. Isolated glenohumeral internal rotation was significantly less in the dominant shoulder than in the non-dominant shoulder in asymptomatic baseball players (P < 0.001). Isolated glenohumeral external rotation in baseball players was significantly greater than in non-throwing athletes (P < 0.05). In the baseball players, humeral torsion in the dominant shoulder was significantly greater than that in the non-dominant shoulder (P < 0.001), indicating that the retroversion angle was greater in dominant shoulders than in non-dominant shoulders.

CONCLUSIONS

Isolated glenohumeral external and internal rotations can be measured with high intra- and inter-observer reliability with the exclusion of side-to-side differences in humeral retroversion. Capsular and muscular changes in the throwing shoulder may be better evaluated by using our ultrasound-assisted technique.

LEVEL OF EVIDENCE

Cross-sectional study, Level III.

Preseason Assessment of Radiographic Abnormalities in Elbows of Little League Baseball Players

BACKGROUND

Youth baseball has been associated with elbow pain and elbow abnormalities, leading to the implementation of throwing and pitching guidelines. The purpose of the current study was to examine elbow abnormalities on magnetic resonance imaging (MRI) in asymptomatic Little League baseball players and to correlate these findings with the players' throwing history and physical examinations.

METHODS

A prospective study of Little League players who were 10 to 13 years of age was performed. Players were recruited prior to the start of the season and underwent bilateral elbow MRI. All players underwent a physical examination and responded to a questionnaire addressing their playing history and any arm pain. The MRIs were read by 2 radiologists. Responses on the questionnaire and physical examination findings were compared between subjects with and without positive MRI findings utilizing chi-square and analysis of variance techniques.

RESULTS

Twenty-six players were enrolled. The majority (77%) were right-handed and 14 (54%) were a pitcher and/or catcher. Nine players (35%) had 12 positive MRI findings: 7 findings of edema or signal change of the medial epicondyle apophysis, 2 findings of fragmentation of the medial epicondyle, and 3 findings of edema or signal change of the sublime tubercle. The prevalence of positive MRI findings and a history of arm pain were not greater in pitchers and catchers compared with other players. Players with a positive MRI finding demonstrated greater reduction in shoulder internal rotation (12°) compared with the nondominant arm (3°) (p = 0.04). The two factors associated with a positive MRI finding were year-round play (47% of year-round players compared with 11% of non-year-round players; p < 0.01) and working with a private coach (71% compared with 21%; p = 0.02). Additionally, a history of pain was associated with year-round play and a private coach (p < 0.05).

CONCLUSIONS

MRI abnormalities involving the medial aspect of the elbow are common in year-round Little League baseball players, especially those with internal rotation deficits and private coaches. Although Little League guidelines potentially lessen abnormalities seen in pitchers, further refinement of these guidelines addressing year-round play, pain, and private coaching should be considered.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Bennett lesions in baseball players detected by magnetic resonance imaging: assessment of association factors

BACKGROUND

The purpose of this study was to evaluate the characteristics of Bennett lesions in baseball players compared with those without a Bennett lesion and to identify other possible factors associated with Bennett lesions on magnetic resonance imaging (MRI).

METHODS

We investigated 388 male baseball players with a career >1 year. Demographic factors and a routine physical examination, including glenohumeral internal rotation difference, scapular dyskinesis, and various pathologic changes, were reviewed on MRI to identify relative factors for Bennett lesions.

RESULTS

Of the 388 patients evaluated, 125 (32.2%) were diagnosed with Bennett lesions of the shoulder. No significant differences were observed between the groups in demographic factors, physical examination results, visual analog scale score, American Shoulder and Elbow Surgeons score, or prevalence of concomitant diseases. However, players with Bennett lesions had played baseball longer than those without the lesions (P < .001).

CONCLUSION

An association was found between Bennett lesions and the length of time that a patient with a Bennett lesion had played baseball. The prevalence of pathologic lesions detected on MRI and the physical examination results were not different between players with and without Bennett lesions.

The Development of Humeral Retrotorsion and Its Relationship to Throwing Sports

Context:

Several investigations have noted that throwing athletes exhibit a more posteriorly oriented humeral head (humeral retrotorsion) in the dominant arm. This asymmetry is believed to represent an adaptive response to the stress of throwing that occurs during childhood. The significance of this alteration and factors that affect its development are currently not clear.

Evidence Acquisition:

Basic science, research studies, and review articles were searched through PubMed with search terms including humeral torsion, humeral retrotorsion, and with 1 of the following: pediatric, adult, baseball, pitching, shoulder, and range of motion. The references from each article were reviewed for further inclusion. This review included articles through March 2015.

Study Design:

Clinical review.

Level of Evidence:

Level 4.

Results:

The throwing motion creates stressors that result in bony adaptations that occur while skeletally immature. These osseous changes likely contribute to the observed shift in the arc of rotational range of motion noted in throwing athletes and may play a protective role against injury. However, too much or too little retrotorsion may predispose the shoulder to injury. The degree of “optimal” humeral retrotorsion and factors that influence its development are not fully understood.

Conclusion:

Evidence supports the assertion that the throwing motion creates stressors that alter bony anatomy while young. It is important to determine what specific factors affect this adaptation and its relationship to injury.

Professional Pitchers With Glenohumeral Internal Rotation Deficit (GIRD) Display Greater Humeral Retrotorsion Than Pitchers Without GIRD

BACKGROUND

Dominant shoulder glenohumeral internal rotation deficit (GIRD) has been associated with pitching arm injuries. The relationship of humeral torsion on development of GIRD is not clear.

HYPOTHESIS

Pitchers displaying GIRD will display greater humeral retrotorsion when compared with those without GIRD.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Humeral torsion and shoulder range of motion (ROM) were measured in 222 professional pitchers before spring training from 2009 to 2012. Shoulder external rotation (ER) and internal rotation (IR) ROM were assessed in 90° of abduction with the scapula stabilized. Humeral torsion was measured via ultrasound using previously described and validated methods. Side-to-side differences in total arc of motion (ER + IR), ER, and IR ROM and humeral torsion were calculated as nondominant minus dominant arm measures for analysis. Pitchers were classified as having GIRD if their dominant arm displayed an IR deficit ≥15° concomitant with a total arc of motion deficit ≥10° compared with their nondominant arm. A mixed-model analysis of variance (side × GIRD) was used to compare dominant and nondominant humeral torsion between pitchers with GIRD (n = 60) and those without GIRD (n = 162). Independent t tests were used to compare the side-to-side difference in humeral torsion between pitchers with GIRD and those without GIRD (α = 0.05).

RESULTS

Pitchers with GIRD displayed significantly less humeral torsion (ie, greater retrotorsion) in their dominant arm as compared with those without GIRD (GIRD = 4.5° ± 11.8°, no GIRD = 10.4° ± 11.7°; P = .002). Pitchers with GIRD also displayed a greater side-to-side difference in humeral torsion (GIRD = 19.5° ± 11.9°, no GIRD = 12.3° ± 12.4°; P = .001). However, pitchers with GIRD did not display an increase in dominant ER ROM (dominant ER = 131.8° ± 14.3°, nondominant ER 126.6° ± 13.1°) when compared with those without GIRD (dominant ER = 132.0° ± 14.2°, nondominant ER 122.6° ± 13.1°; P = .03). Pitchers with GIRD displayed expected alterations in ROM (IR = 28.8° ± 9.6°, total arc = 160.6° ± 15.4°; P < .01 for both) when compared with those without GIRD (IR = 39.9° ± 9.9°, total arc = 171.2° ± 15.5°).

CONCLUSION

Pitchers with GIRD displayed greater side-to-side differences and dominant humeral retrotorsion as compared with those without GIRD. The greater humeral retrotorsion may place greater stress on the posterior shoulder resulting in ROM deficits. Pitchers with greater humeral retrotorsion appear to be more susceptible to developing ROM deficits associated with injury and may need increased monitoring and customized treatment programs to mitigate their increased injury risk.

Reliability and validity in measurement of true humeral retroversion by a three-dimensional cylinder fitting method

HYPOTHESIS AND BACKGROUND

Humeral retroversion is defined as the orientation of the humeral head relative to the distal humerus. Because none of the previous methods used to measure humeral retroversion strictly follow this definition, values obtained by these techniques vary and may be biased by morphologic variations of the humerus. The purpose of this study was 2-fold: to validate a method to define the axis of the distal humerus with a virtual cylinder and to establish the reliability of 3-dimensional (3D) measurement of humeral retroversion by this cylinder fitting method.

METHODS

Humeral retroversion in 14 baseball players (28 humeri) was measured by the 3D cylinder fitting method. The root mean square error was calculated to compare values obtained by a single tester and by 2 different testers using the embedded coordinate system. To establish the reliability, intraclass correlation coefficient (ICC) and precision (standard error of measurement [SEM]) were calculated.

RESULTS

The root mean square errors for the humeral coordinate system were <1.0 mm/1.0° for comparison of all translations/rotations obtained by a single tester and <1.0 mm/2.0° for comparison obtained by 2 different testers. Assessment of reliability and precision of the 3D measurement of retroversion yielded an intratester ICC of 0.99 (SEM, 1.0°) and intertester ICC of 0.96 (SEM, 2.8°).

DISCUSSION AND CONCLUSION

The error in measurements obtained by a distal humerus cylinder fitting method was small enough not to affect retroversion measurement. The 3D measurement of retroversion by this method provides excellent intratester and intertester reliability.

Conventional Humeral Retroversion Measurements Using Computed Tomography Slices or Ultrasound Images Are Not Correlated With the 3-Dimensional Humeral Retroversion Angle

Background:

Humeral retroversion angles determined by previous techniques are varied and/or biased by morphologic variations of the proximal and distal humerus, and their validity should be revisited. To overcome the limitations of previous studies associated with 2-dimensional (2D) images and the reference axes, a 3-dimensional (3D) measurement of humeral retroversion is required. However, comparisons of 2D imaging methods with the 3D computed tomography (CT) measurement as a reference standard have not been heretofore performed.

Purpose:

To determine whether the 3D CT humeral retroversion angle in baseball players is correlated with conventional humeral retroversion measurements.

Study Design:

Cohort study (diagnosis); Level of evidence, 2.

Methods:

A total of 28 humeri from 14 male baseball players were used for measuring humeral retroversion. Participants underwent CT scans, and geometric bone models were created for measuring the 3D CT humeral retroversion angle. Using CT slices, the 2D CT humeral retroversion angle was also determined. Bicipital forearm angle was assessed using the indirect ultrasound technique. Linear regressions and Bland-Altman plots were used to determine whether there were agreements among 3 variables: the 3D CT retroversion, 2D CT retroversion, and bicipital forearm angles.

Results:

In linear regression analyses, the 3D humeral retroversion angle was not predicted by the 2D CT retroversion (R = 0.167, R² = 0.028, P = .395) or the bicipital forearm angle (R = 0.049, R² = 0.002, P = .805). The bias of these 2 methods was 20.9° and –15.3°, respectively. Regression analysis demonstrated that the bicipital forearm angle was a significant predictor of the 2D CT retroversion angle (R = 0.632, R² = 0.400, P < .001).

Conclusion:

The 3D CT humeral retroversion angle was found to be underestimated by the 2D CT retroversion angle and overestimated by the bicipital forearm angle obtained by the indirect ultrasound, although a previously observed relationship between the 2D CT retroversion and bicipital forearm angles was confirmed.

Clinical Relevance:

Precise measurement of humeral retroversion angle is important because retroversion has been linked to upper extremity disorders, including throwing-related shoulder and elbow disorders in baseball players.

The thrower's shoulder

Throwers, or athletes who engage in repetitive overhead motions, are a unique subset of athletes that experience distinct shoulder injuries. Athletes engaged in baseball comprise the majority of patients seeking orthopedic care for throwing related injuries. Injuries specific to throwers most commonly involve the labrum and the undersurface of the rotator cuff. In addition, tissue changes in both the anterior and posterior glenohumeral capsule are common with repetitive overhead motions. These capsular changes alter. This article will examine the pathomechanics of injuries to throwers, elaborate means of diagnoses of cuff and labral injury and discuss recent advances in both non-operative and operative interventions, including preventative principles.

Three-dimensional humeral morphologic alterations and atrophy associated with obstetrical brachial plexus palsy

BACKGROUND

Obstetrical brachial plexus palsy (OBPP) is a common birth injury, resulting in severe functional losses. Yet, little is known about how OBPP affects the 3-dimensional (3D) humeral morphology. Thus, the purpose of this study was to measure the 3D humeral architecture in children with unilateral OBPP.

METHODS

Thirteen individuals (4 female and 9 male patients; mean age, 11.8 ± 3.3 years; mean Mallet score, 15.1 ± 3.0) participated in this institutional review board approved study. A 3D T1-weighted gradient-recalled echo magnetic resonance image set was acquired for both upper limbs (involved and noninvolved). Humeral size, version, and inclination were quantified from 3D humeral models derived from these images.

RESULTS

The involved humeral head was significantly less retroverted and in declination (medial humeral head pointed anteriorly and inferiorly) relative to the noninvolved side. Osseous atrophy was present in all 3 dimensions and affected the entire humerus. The inter-rater reliability was excellent (intraclass correlation coefficient, 0.96-1.00).

DISCUSSION

This study showed that both humeral atrophy and bone shape deformities associated with OBPP are not limited to the axial plane but are 3D phenomena. Incorporating information related to these multi-planar, 3D humeral deformities into surgical planning could potentially improve functional outcomes after surgery. The documented reduction in retroversion is an osseous adaptation, which may help maintain glenohumeral congruency by partially compensating for the internal rotation of the arm. The humeral head declination is a novel finding and may be an important factor to consider when one is developing OBPP management strategies because it has been shown to lead to significant supraspinatus inefficiencies and increased required elevation forces.

Return to sport following shoulder surgery in the elite pitcher: a systematic review

Context:

The ability to return to elite pitching, performance, and clinical outcomes of shoulder surgery in elite baseball pitchers are not definitively established.

Objective:

To determine (1) the rate of return to sport (RTS) in elite pitchers following shoulder surgery, (2) postoperative clinical outcomes upon RTS, and (3) performance upon RTS and to compare RTS rates in different types of shoulder surgery.

Data Sources:

Using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and checklist, Medline, SciVerse Scopus, SportDiscus, and Cochrane Central Register of Controlled Trials were searched.

Study Selection:

Levels I-IV evidence were eligible for inclusion if performance-based (eg, RTS) and/or clinical outcome–based reporting of outcomes were reported following surgical treatment of shoulder pathology in elite pitchers (major or minor league or collegiate).

Data Extraction:

Subject, shoulder, and pre- and postoperative performance-based variables of interest were extracted. All shoulder surgery types were potentially inclusive (eg, open, arthroscopic, rotator cuff, labrum, biceps, acromioclavicular joint, fracture). Study methodological quality was analyzed using the Modified Coleman Methodology Score (MCMS).

Results:

Six studies were analyzed (287 elite male pitchers [mean age, 27 years] who underwent shoulder surgery, with 99% on the dominant, throwing shoulder). MCMS was 38 (poor). Most pitchers were professional, with a mean career length of 6.58 years and postoperative clinical follow-up of 3.62 years. In 5 of 6 studies, multiple diagnoses were addressed concomitantly at surgery. Rate of RTS was 68% at mean 12 months following surgery. Twenty-two percent of Major League Baseball (MLB) pitchers never RTS in MLB. Overall performance did improve following surgery; however, this did not improve to pre-injury levels.

Conclusion:

In this systematic review, the rate of return to elite baseball pitching following surgery was established. Performance tended to decrease prior to surgery and gradually improve postoperatively, though not reaching pre-injury levels of pitching.

Level of Evidence:

IV (systematic review of studies level I-IV evidence), therapeutic.

Axillary artery thrombosis in a major league baseball pitcher: a case report and rehabilitation guide

This case study describes a Major League Baseball player who was diagnosed with an axillary artery thrombosis due to arterial compression from throwing. The purpose of this article is to create awareness as to the signs and symptoms associated with arterial positional compression and the rehabilitative implications to surgical intervention.