Differences in humeral retroversion in dominant and nondominant sides of young baseball players

Bilateral Humeral Retrotorsion Angle Measured Using an Ultrasound-Assisted Technique in Asian Baseball Players

Background

Repetitive pitching is thought to restrict the physiological derotation process of the humeral head. Some studies have reported that side-to-side differences in the humeral retrotorsion angle (ΔHRA) occur between the ages of 9 and 11 years in baseball players. However, it remains unclear whether the ΔHRA in Asian baseball players depends on pitching skill or competitive level.

Purpose

To evaluate the ΔHRA in Asian collegiate and professional baseball players and to determine the effects of pitching activity on the physiological derotation process of the humeral head.

Study Design

Cross-sectional study; Level of evidence, 3.

Methods

We evaluated 128 shoulders in 64 Asian baseball players who were stratified into 4 groups as follows: 13 professional pitchers; 9 professional fielders; 8 collegiate pitchers; and 34 collegiate fielders. The throwing and nonthrowing side HRA was assessed using an ultrasound-assisted technique, and the ΔHRA was compared among the 4 groups. In addition, Pearson correlation analysis was used to assess the relationship between ΔHRA and glenohumeral range of motion, baseball starting age, and fastball velocity in pitchers.

Results

The HRA was significantly greater in the throwing arm than in the nonthrowing arm in each group, with no significant differences among the groups. There was no correlation between ΔHRA and range of motion or fastball velocity. There was a significant negative correlation between baseball starting age and ΔHRA in professional fielders (r = -0.633; P = .036).

Conclusion

The findings of the present study provide evidence that in Asian baseball players, the HRA was significantly greater in the throwing arm than in the nonthrowing arm. There were no clear associations between HRA and pitching ability or competitive level.

Radiographic rotational profiles of the proximal and distal humerus: analysis of 46 computed tomography scans with 3-dimensional simulation

BACKGROUND

To date, no study has investigated the radiographic rotational profiles (RRPs) of the proximal and distal humerus. However, malrotation after minimally invasive surgery for humeral fracture has been an unsolved problem. Therefore, we aimed to investigate the RRPs of the proximal and distal humerus that linearly correlate with rotational status and show significant differences as the rotational status changes.

METHODS

Forty-six computed tomography scans of the humerus were 3-dimensionally reconstructed, and 5 rotational statuses (20° and 10° of internal rotation; neutral; and 10° and 20° of external rotation) were simulated. Seven candidate RRPs of the proximal humerus and 4 candidates of the distal humerus were measured for each rotational status. The overall differences and trends in the RRPs as the rotational status changed were evaluated, and multiple comparisons were performed between the RRPs for each of the 5 rotational statuses. Moreover, the correlations between the RRPs and rotational status with adjustment of retroversion were analyzed. Finally, interobserver and intraobserver reliabilities were evaluated.

RESULTS

The following proximal and distal RRPs were linearly correlated with rotational status, differed significantly between the rotational statuses, and showed a relatively low prediction error and excellent interobserver and intraobserver reliabilities: the distance from the tip of the lesser tuberosity to the lateral margin of the proximal humerus (P_L1) and the medial margin of the head (P_L2), as well as the P_L1 to P_L2 ratio (PR_L), in the proximal humerus; and the distance from the medial margin of the olecranon process to the medial epicondyle (D_OP), the widest width of the overlapped olecranon fossa (D_OF), and the distance from the lateral margin of the capitellum to the lateral epicondyle (D_C) in the distal humerus.

CONCLUSION

Our findings suggest that P_L1, P_L2, and PR_L in the proximal humerus and D_OP, D_OF, and D_C in the distal humerus are potentially useful and reproducible RRPs for restoring the intrinsic rotational alignment in humeral fractures.

Increased external rotation related to the soft tissues is associated with pathologic internal impingement in high-school baseball players

BACKGROUND

Changes in soft-tissue structures such as anterior laxity and posterior tightness are thought to contribute to the development of pathologic internal impingement in baseball players. Although side-to-side differences in shoulder rotational range of motion (ROM) is commonly used in clinical practice to quantify the soft-tissue changes, the ROM does not accurately reflect the soft-tissue changes because the ROM is affected not only by the soft tissues, but also by the bone. Increased retroversion of the humeral head is often observed in the dominant shoulder of throwing athletes. The purpose of this study was to determine the relationship between the soft-tissue-related (STR) ROM and pathologic internal impingement in baseball players.

METHODS

Bilateral humeral retroversion and ranges of glenohumeral external rotation (ER) and internal rotation (IR) were investigated in 81 high-school baseball players. The players were divided into two groups: the internal impingement group (19 players) and the control group (62 players). Humeral retroversion was measured using the ultrasound-assisted technique to assess the bone-related ER and IR. The STR ER and IR were defined as subtracting the amount of humeral retroversion from the measured ER and IR.

RESULTS

The side-to-side difference (throwing shoulder - nonthrowing shoulder) in humeral retroversion showed no significant difference between the internal impingement group (6° ± 10°) and control group (11° ± 11°) (P = .064). The side-to-side difference in STR ER was significantly greater in the internal impingement group (12° ± 12°) than that in the control group (1° ± 14°) (P = .002). No significant difference was observed in the side-to-side difference in STR IR between the internal impingement group (-7° ± 16°) and control group (-5° ± 15°) (P = .696). Pathologic internal impingement was significantly associated with the side-to-side difference of STR ER (odds ratio, 1.06 for increase of 1°; 95% confidence interval, 1.02-1.11; P = .008).

CONCLUSION

In high-school baseball players, the increased STR ER in the throwing shoulder may be associated with pathologic internal impingement. An increase of 10° in side-to-side difference in STR ER would increase the risk of pathologic internal impingement by 1.8 times.

Bilateral glenohumeral internal rotation deficit (GIRD) in elite gymnasts

INTRODUCTION

The "Glenohumeral Internal Rotation Deficit (GIRD)" is known as the difference in internal rotation range of motion (IRRM) between the dominant and non-dominant shoulder of overhead athletes as a result of asymmetric loading. As in contrast loading pattern in gymnastics are quite symmetric and structural changes often occur bilaterally, the question arises if GIRD might develop bilaterally in gymnasts as one source of common bilateral shoulder pathologies and to search for underlying structural adaptations.

MATERIALS AND METHODS

A group of 35 elite gymnasts (8-24 years) were recruited from a local Olympic Training Centre and compared to a paired cohort of 28 non-overhead athletes. Clinical examinations, digital range of motion (ROM)-measurement, ultrasonographic humeral torsion measurement, and standardized MRI scans of both shoulders were obtained and examined for structural pathologies, cross-sectional areas (CSA) of the rotator cuff muscles and capsular thickness.

RESULTS

ROM-measurements showed significant decrease in IRRM in the gymnasts groups by age, with IRRM of 48.6° (SD: 8.4°, CI 95%: 43.0-54.3°) at age group 1 (8-10 years) and IRRM of 10° (SD: 11.4°; CI 95%: 0-22.0°) at age group 4 (18-26 years), that was statistically significant for the entire cohort (p = 0.017) compared to the controls. CSA were not significantly different between the cohorts, while there was a slightly increased humeral retrotorsion in the gymnasts as well as a statistically significant posterior capsular thickening.

CONCLUSION

A new bilateral form of GIRD was identified in higher age groups of youth and senior elite gymnasts enrolled in this study. Despite to former definition of GIRD there was no compensatory increase in external rotation range of motion (ERRM) but an association with posterior capsular thickening, while there was no periscapular muscle hypertrophy. Humeral retrotorsion was also slightly increased in the gymnasts group.

Residual Effects of Glenohumeral Range of Motion, Strength, and Humeral Retroversion on Prior Overhead Athletes After Cessation of Sport

Background:

Research has shown that repetitive stress from playing an overhead (OH) sport can cause musculoskeletal and osseous adaptations to occur on the dominant side. Additionally, there are limited data about the residual effects of these adaptations after the cessation of sports participation.

Purpose:

To investigate the effects of prior participation in an OH sport versus not participating in an OH sport on glenohumeral range of motion (ROM), isometric strength, and humeral retroversion (HR).

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

Forty-eight college-aged individuals participated. Participants were split into 2 groups: (1) individuals who previously participated in an OH sport (n = 20; age, 20.3 ± 1.1 years; height, 166.3 ± 15.27 cm; weight, 72.2 ± 13.5 kg) and (2) individuals who previously did not play an OH sport (n = 28; age, 20.6 ± 0.9 years; height, 168.8 ± 6.3 cm; weight, 68.1 ± 15.1 kg). After completing a health history questionnaire, the following were measured: side-to-side shoulder internal rotation (IR) and external rotation (ER) ROM via an inclinometer, isometric shoulder strength via a handheld dynamometer, and HR using an ultrasound imaging machine. A Mann-Whitney U test was used to determine group differences, and a Wilcoxon t test was used to analyze side-to-side differences within each group.

Results:

The Mann-Whitney U test revealed a statistically significant group difference for dominant shoulder ER ROM (U = 162.00, P = .014). Specifically, the prior OH group had significantly more ER than the control group. Within the prior OH group, testing revealed that athletes had significantly more HR (Z =–2.782, P = .005), ER ROM (Z =–1.979, P = .048), and ER isometric strength (Z =–2.763, P = .006) on their dominant than nondominant shoulder and significantly less IR ROM (Z =–3.099, P = .002) on their dominant than nondominant shoulder.

Conclusion:

Prior OH sports participation may have residual osseous and musculoskeletal effects that remain after cessation of the sport.

Chronic adaptations of the long head of the biceps tendon and groove in professional baseball pitchers

BACKGROUND AND HYPOTHESIS

The long head of the biceps tendon (LHBT) plays a significant shoulder stabilizing role during pitching, with the large forces and repetitions involved in overhead throwing likely contributing to LHBT pathology. Determining whether the LHBT undergoes adaptive changes in baseball pitchers and how these changes relate to bicipital groove morphology can improve our understanding of the biceps function at the glenohumeral joint. Therefore, the purpose of this study was to determine the chronic adaptations of the bicipital groove morphology and the LHBT in professional baseball pitchers, with a secondary purpose of evaluating biceps integrity as it relates to torsional changes of the bicipital groove. We hypothesized that the throwing arm of professional baseball pitchers would exhibit chronic adaptations of the LHBT compared with their nonthrowing arm, and that these adaptations would be related to the bicipital groove morphology.

MATERIALS AND METHODS

Fifty-three professional baseball pitchers were enrolled at the beginning of the 2015 Major League Baseball spring training. Ultrasound was used to bilaterally measure humeral retroversion and to capture images of the bicipital groove and the LHBT. MATLAB software was used to calculate the area of the bicipital groove, and ImageJ software was used to quantify the area, echogenicity, and circularity of the LHBT.

RESULTS

The dominant arm LHBT cross-sectional area was significantly smaller than the nondominant arm (9 mm² vs. 10 mm²; P = .011), whereas the dominant arm LHBT echogenicity was significantly higher than the nondominant arm (65 optical density vs. 59 optical density; P = .002). Pitchers with more bicipital groove rotational adaptation (more retroversion) had significantly more LHBT echogenicity adaptation compared with pitchers with less bicipital groove rotational adaptation (12 vs. 2; P = .023).

CONCLUSION

There are significant bilateral differences in the LHBT of professional baseball pitchers. An adaptation in bony rotation was associated with a larger bilateral difference in LHBT echogenicity but was not related to bilateral differences in LHBT area or circularity. Therefore, the bilateral difference in echogenicity is impacted by bony morphology, whereas the bilateral difference in cross-sectional area may be independent of bony morphology in this healthy population.

Relationship of clinical measures with humeral torsion in young adults: a pilot study

PURPOSE

Humeral retroversion alters range of motion and has been linked to injury risk. Clinically,palpation of the bicipital groove is used to quantify humeral torsion, but the accuracy of this procedure has not been fully examined. The purpose of this study was to investigate the relationship between clinical and diagnostic ultrasound (US) assessment of humeral torsion while considering shoulder position of the participant and clinical expertise of the examiner.

METHODS

Seventeen participants (34 shoulders, 16/17 right handed, 10/17 history of throwing) were recruited. US was assessed by an experienced assessor. Two clinical assessments of humeral torsion were performed by two assessors of different experience (expert and novice). Humeral torsion was assessed at 90 degrees shoulder abduction (Palp90) and 45 degrees shoulder abduction (Palp45). Within assessor intraclass correlation coefficients (ICC (3, 1) were calculated. Correlation coefficients (Pearson's) were generated to determine relationship between clinical and US examination findings.

RESULTS

Intra-rater reliability for clinical tests were good (ICCs .73 - .92) for both raters. Of the palpation tests, only the expert assessor was significantly correlated to the US measurement (p<.001) at Palp45 (r = .64) and Palp90 (r = .62). For the expert, there was a significantly lower angle calculated for Palp45 compared to Palp90 (p<.001).

CONCLUSION

The accuracy of both palpation methods for assessing humeral retrotorsion may depend on the training background of the assessor. Further, the glenohumeral position of the patient during palpation should be consistent for the purposes of repeated testing.

Junior and Collegiate Tennis Players Display Similar Bilateral Asymmetries of Humeral Retroversion

CONTEXT

Overhead throwing athletes consistently display significant bilateral differences in humeral retroversion (HRV). However, there is limited evidence regarding HRV asymmetries in tennis players despite similarities between the overhead throw and tennis serve.

OBJECTIVE

To determine if junior and collegiate tennis players demonstrate bilateral differences in HRV, and whether the magnitude of the side-to-side difference (HRVΔ) was similar across different age groups.

DESIGN

Cross-Sectional Study Setting: Field-Based Patients or Other Participants: Thirty-nine healthy tennis players were stratified into three age groups: Younger Juniors (n = 11; age = 14.5 ± 0.5 years), Older Juniors (n = 12; age = 17.1 ± 0.9 years), and Collegiate (n = 16; age = 19.6 ± 1.2 years).

MAIN OUTCOME MEASURES

Three-trial means were calculated for HRV for the dominant and nondominant limbs, and HRVΔ was calculated by subtracting the mean of the nondominant side from the dominant side. Paired-sample t-tests were utilized to determine bilateral differences in HRV, while a one-way ANOVA was used to compare HRVΔ between groups.

RESULTS

For all three groups, HRV was significantly greater in the dominant arm compared to the nondominant arm (Younger Juniors: dominant = 62.8° ± 9.1° vs nondominant = 56.3° ± 6.8°, P = .039; Older Juniors: dominant = 75.5° ± 11.2° vs nondominant = 68.6° ± 14.2°, P = .043; Collegiate: dominant = 71.7° ± 8.5° vs nondominant = 61.2° ± 6.9°, P = .001). However, no significant differences were detected in HRVΔ when compared across age groups (P = .511).

CONCLUSIONS

Consistent with studies involving overhead throwing athletes, tennis players demonstrated significantly greater measures of HRV in the dominant limb. Further, the development of HRV asymmetries appear to have occurred prior to the teenage years as no changes were observed in HRVΔ between age groups.

Effect of Younger Starting Pitching Age on Humeral Retrotorsion in Baseball Pitchers With an Ulnar Collateral Ligament Injury

BACKGROUND

Increased humeral retrotorsion (HRT) has been found to be a risk factor for ulnar collateral ligament (UCL) tears in baseball players. Recent work has demonstrated the age of 11 years as a potential watershed age for HRT development.

HYPOTHESIS

In a group of baseball pitchers with UCL injuries, athletes who started pitching before the age of 10 years will demonstrate significantly more dominant limb humeral retrotorsion (DHRT) when compared with a group of baseball pitchers who reported starting pitching at 10 years or older.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A total of 84 baseball pitchers with a diagnosed UCL injury were divided into 2 groups based upon the age at which participants began pitching: 33 players reporting a starting pitching age of 10 years or older (group 1) were compared with 51 baseball pitchers reporting a starting pitching age under 10 years (group 2). Participants' DHRT and nondominant limb humeral retrotorsion (NDHRT) were measured using diagnostic ultrasound. Independent t tests were run to compare mean group differences of all patient data, starting pitching age, age at time of injury, DHRT, NDHRT, and humeral retrotorsion difference (HRTdiff).

RESULTS

There were no significant differences between groups with regard to age at time of injury, height, weight, or playing years' experience. There was a statistically significant difference in the participant-reported starting pitching age. Significant differences between groups were noted for DHRT (group 1: 20.0°± 9.4°, group 2: 14.5°± 10.3°, P = .015) and for NDHRT (group 1: 38.6°± 8.8°, group 2: 32.9°± 9.5°, P = .007). No significant differences between groups were found for HRTdiff (P = .940).

CONCLUSION

Baseball pitchers with a UCL injury who reported a starting pitching age younger than 10 years demonstrated significantly greater DHRT and NDHRT when compared with UCL-injured baseball pitchers who reported a starting pitching age at 10 years or later. The results of this study demonstrate that a younger starting pitching age results in increased HRT in players with UCL injuries.

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.

Characteristics of Femoral Torsion Angles and Relationships Between Femoral Torsion Angles and Hip Rotational Motion Variables in Adult Baseball Players

Background:

Abnormalities in hip rotational motion (HRM) are risk factors for throwing injuries. To evaluate hip rotational motion, it is necessary to assess the torsion angle. However, no studies have investigated the femoral torsion angle (FTA) in baseball players.

Purpose:

To investigate differences in hip FTA of adult baseball players through use of ultrasonography to evaluate the relationship between the FTA and HRM.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

A total of 149 elite male baseball players (mean age, 20.0 ± 1.8 years; 64 pitchers, 85 position players) were enrolled in this study. Ultrasonographic assessment of FTA was performed based on the tilting angles of the anterior surface of the femoral neck and condylar axis. The hip internal rotation (HIR) and hip external rotation (HER) were assessed at 0° and 90° of flexion. Data related to FTA and HRM were compared between hips and between pitchers and position players.

Results:

No significant difference was observed in the FTAs between hips for any player (lead hip, 20.5° ± 9.2°; trail hip, 19.6° ± 9.8°; P = .276). No significant difference was observed in FTAs of both hips between pitchers and position players (lead hip, 20.1° ± 9.4° and 20.9° ± 9.0°, respectively, P = .957; trail hip, 19.5° ± 9.8° and 19.7° ± 9.8°, P = .999). In terms of HER in 90° of hip flexion in both hips, significant differences were observed in HRM variables between pitchers and position players (lead hip, 33.0° ± 8.9° and 37.5° ± 9.8°, respectively, P = .024; trail hip, 35.6° ± 9.6° and 40.4° ± 10.2°, P = .035). Linear regression analysis revealed a significant agreement between the FTA and HIR at both 0° (R = 0.298, P < .001) and 90° of hip flexion (R = 0.279, P < .001).

Conclusion:

Our findings indicated that FTAs were not different between the hips of elite baseball players. Abnormalities of the HRM are not caused by differences in the FTA but rather involve soft tissue tightness around the hip area or other bony morphologic factors in the hip joint.

Pediatric Sports Injuries

With increasing pediatric participation in organized sport and the early specialization of children in single sports, the number of injuries seen in the pediatric and adolescent athletic population continues to increase. Children experience acute traumatic injuries during practice and competition as well as chronic overuse injuries secondary to the repetitive stress on their developing bodies. The unique nature of the pediatric patient often requires a different diagnostic, prognostic, and treatment approach to sports injuries compared with their adult counterparts.

Ultrasonographic Assessment of Femoral Torsion Angle Based on Tilting Angles of Femoral Neck and Condylar Axis

Femoral anteversion has been assessed with ultrasound using femoral neck tilting angle (FN-TA); however, femoral torsion angle (FTA), which is defined using FN-TA and condylar axis tilting angle, has not been assessed with ultrasound. This study aimed to establish the ultrasonographic assessment of FTA (US-FTA) by comparing data obtained through US-FTA and computed tomography (CT). Twenty-one patients (age range, 38-82 y) with 21 intact hips were included. In the US-FTA, the femoral head and anterior tubercle of the greater trochanter were used as bony landmarks. The intra-rater and inter-rater reliabilities and standard error of measurement (SEM) of US-FTA were 0.994 (SEM 0.93) and 0.994 (SEM 0.94), respectively. A strong agreement was found between FTA variables obtained with ultrasound and CT (R = 0.939, p < 0.001). Ultrasound is useful and can be a valid alternative to CT for the evaluation of the femoral torsion angle without radiation exposure.

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.

The differences of humeral torsion angle and the glenohumeral rotation angles between young right-handed and left-handed pitchers

BACKGROUND

The differences between young right-handed and left-handed baseball players are not well known. This study compared the range of the shoulder motion and humeral torsion angle (HTA) between right-handed and left-handed young baseball pitchers.

METHODS

A total of 65 young baseball pitchers (age, 9-12 years; 46 right-handed throwers, R group; and 19 left-handed throwers, L group) were analyzed. The glenohumeral internal rotation (IR) angle and external rotation (ER) angle were measured at 90° shoulder abduction, and HTA was assessed using indirect ultrasonographic techniques. The side-to-side difference in HTA (d-HTA), glenohumeral ER difference (GERD), and glenohumeral IR deficit (GIRD) were calculated. The adjusted GIRD and adjusted GERD were defined as the angles obtained by subtracting d-HTA from GIRD and GERD, respectively, to exclude the influence of humeral retrotorsion difference.

RESULTS

HTA and ER of the throwing limb were significantly greater than those of the nonthrowing limb in the R group (HTA: 84° vs. 77°; P < .001, ER: 116° vs. 111°; P < .001), but no significant differences were observed in the L group (HTA: 79° vs. 77°, P = .103; ER: 113° vs. 114°, P = .380). Compared with the R group, the L group showed a significantly smaller d-HTA (2° vs. 8°, P < .001) and GERD (5° vs. -2°, P = .004), but no significant difference was observed in adjusted GERD between the groups (-3° vs. -4°, P = .690).

CONCLUSION

Compared with the right-handed pitchers, the side-to-side differences of glenohumeral external rotation angle and humeral torsion angle were significantly smaller in the left-handed pitchers at a young age.

What's New in Pediatric Upper Extremity Sports Injuries?

BACKGROUND

Sports injuries are common in pediatric and adolescent patients and the evaluation and treatment of these injuries continues to evolve. The purpose of this review is to provide a comprehensive appraisal of the most recent literature, highlighting updates on sports-related upper extremity injuries in pediatric patients.

METHODS

An electronic search of the PubMed, EMBASE, and Google Scholar databases was performed for keywords related to pediatric overhead athletes, osteochondritis dissecans (OCD) of the capitellum, medial epicondyle fractures, shoulder instability, and clavicle fractures. Search results were filtered by publication date to yield articles published electronically or in print on or after January 1, 2013 to May 30, 2017. Papers were selected based on expert opinion and consensus by the authors and included if deemed to have contributed important findings to the above topics.

RESULTS

A total of 51 articles were deemed to have contributed significant findings to the literature: 11 overhead athlete, 9 OCD of the capitellum, 6 medial epicondyle fractures, 17 shoulder instability, and 8 clavicle fractures. The level of evidence for most studies was either Level III or IV.

CONCLUSIONS

Overuse and traumatic conditions of the pediatric elbow including UCL tear, capitellar OCD, and medial epicondyle fractures represent a significant portion of injuries in the overhead athlete. Research in the prevention and treatment of primary and recurrent shoulder instability in young athletes continues to evolve. The operative treatment of clavicle fractures in adolescents has been increasing without a commensurate increase in the level of evidence supporting such treatment. Advances have been made in the treatment of sports-related upper extremity injuries in pediatric patients, however, high-level, comparative outcomes research in many areas is lacking and this review may help inform topics for future study.

LEVEL OF EVIDENCE

Level IV-Literature review.

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.