Humeral retrotorsion in collegiate baseball pitchers with throwing-related upper extremity injury history

Utilizing the Pronated Forearm Technique for Measuring Glenohumeral External Rotation in Baseball Players

BACKGROUND

Alterations in glenohumeral internal rotation (GIR), glenohumeral external rotation (GER), and total range of motion (TROM) have been linked with increased injury risk. GER capacity has been measured routinely with the forearm in neutral rotation (GERN), but a recent study reported GERN was greater than GER with the forearm in pronation (GERP) in Minor League pitchers. This work has not yet been replicated or extended to other groups.

HYPOTHESIS

GERP would be significantly less than GERN in Independent League baseball pitchers, and there would be no difference in GERP or GERN measurements between this new group and the previous group of Minor League pitchers.

STUDY DESIGN

Cross-sectional study.

LEVEL OF EVIDENCE

Level 3.

METHODS

Goniometric measurements were recorded for bilateral GIR, GERN, and GERP, and resulting TROM for 37 Independent League baseball pitchers. These data were compared with the previous study. All motions were compared individually between groups, between throwing and nonthrowing arm, and both within and between techniques (forearm neutral or pronated).

RESULTS

GERP was significantly less than GERN for both arms within each group tested (P < 0.01). Independent League pitchers had greater between arm differences for GIR (-16.9° vs -6.9°), GERN (+15.1° vs -0.6°), and GERP (+13.1° vs -5.9°) compared with Minor League pitchers. TROM for the Independent League pitchers was not statistically different for either measurement technique, while TROM for the throwing arm of the Minor League pitchers was statistically reduced with varying effect sizes (d = 0.35-0.99) compared with the nonthrowing arm (P < 0.01).

CONCLUSION

This study confirmed earlier findings that the pronated forearm resulted in decreased GER capacity, illustrating the adaptive response to throwing and the need to evaluate for this variable.

CLINICAL RELEVANCE

GERP should be evaluated in all groups of pitchers, but there may be variations within tested groups.

Rehabilitation of the painful shoulder

Managing the painful shoulder in overhead athletes can be difficult because of a lack of time-loss injuries in overhead sports and focusing primarily on either pathoanatomic causes or movement impairments. Although managing the painful shoulder can be challenging, the combination of identifying pathoanatomic causes with movement impairments can provide a more focused rehabilitation approach directed at the causes of shoulder pain. Understanding the potential influence of scapular positioning as well as mobility and/or strength impairments on shoulder pain can help clinicians develop more directed rehabilitation programs. Furthermore, sports-specific methods such as long toss or the use of weighted balls for achieving physiological or performance-based gains have limited empirical evidence regarding their clinical and performance-based benefits, which may impede the rehabilitation process. Applying a comprehensive evaluation approach prior to and throughout the treatment process can assist clinicians with selecting the most appropriate treatment based on patient need. Reconsidering traditional treatments based on existing evidence may help refine the treatment process for overhead athletes with shoulder pain.

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.

Evaluation of glenohumeral range of motion and humeral retroversion at ages after major change and differences in wrestlers

PURPOSE

This study aimed to present the change in humeral retroversion (HR) angle (HRA) that occurs in childhood and young adulthood and the potential developmental difference that is observed in wrestlers.

METHODS

HRA of dominant and non-dominant shoulders (DSHRA and NDSHRA, respectively) were measured using ultrasonography in a group of 30 wrestlers who started wrestling before the age of 13 years (Group 1), a group of 30 young adults, aged between 16-20 years, who were not actively engaged in any branch of overhead sports (Group 2) and a group of children aged between 11-13 years and not actively engaged in any branch of overhead sports (Group 3). Range of motion (ROM) degrees of dominant and non-dominant shoulders in all groups were compared within each group and between the groups.

RESULTS

DSHRA (mean: 88.73°, 88.93° and 89.40°) values were significantly higher than NDSHRA (mean: 81.13°, 81.83° and 84.37°) values (p < 0.001, p < 0.001 and p < 0,05) in Groups I, II and III, respectively. Internal rotation and total ROM degrees of the dominant shoulder in Group 1 and 3 were higher than those in Group 2.

CONCLUSION

There is no significant change in terms of HRA in people aged between 11-13 and 16-20 years because of natural development or wrestling. DSHRA values are higher than NDSHRA ones. In contrast to the shoulders of throwers, the shoulders of wrestlers are characterized by an increase in internal rotation, described as "Wrestler's shoulder."

LEVEL OF EVIDENCE

Level III.

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.

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.

Comparison of the Effects of Static-Stretching and Tubing Exercises on Acute Shoulder Range of Motion in Collegiate Baseball Players

BACKGROUND

The overhead throwing motion repetitively stresses the dominant arm in baseball players, frequently altering normal range of motion (ROM) in multiple directions. Baseball players regularly perform a combination of static stretches (SS) and dynamic tubing (DT) resistance exercises in pre-throwing warm-up routines intended to improve shoulder ROM and reduce injuries.

PURPOSE

The purpose of this study was to compare acute changes in dominant shoulder ROM improvements between SS and DT warm-up exercise protocols. The DT exercises were hypothesized to elicit greater improvements in shoulder ROM.

STUDY DESIGN

Two-way crossover study.

METHODS

Twenty-five healthy collegiate baseball players (mean age = 19.8 ±1.0 years) presenting with glenohumeral internal rotation deficit (GIRD) >20° and total rotational range of motion (TRROM) losses >5° completed the SS and DT interventions on different days. Dominant arm internal rotation (IR), external rotation (ER) and TRROM were measured before, immediately after, 30-minutes after, and 60-minutes after each treatment session. A two-way repeated measures analysis of variance (ANOVA) compared the effect of SS and DT over time on IR, ER and TRROM.

RESULTS

IR improved on average 10.68 ± 0.82° (p < .001) post intervention, 11.18 ± 0.79° (p < .001) 30-min post intervention, and 9.03 ± 0.95° (p < .001) 60-min post intervention. ER improved on average 8.60 ± 0.67° (p < .001) post intervention, 8.25 ± 0.85° (p < .001) 30-min post intervention, and 6.65 ± 0.91° (p < .001) 60-min post intervention. TRROM improved on average 19.28 ± 1.09° (p < .001) post intervention, 19.43 ± 1.36° (p < .001) 30-min post intervention, and 15.68 ± 1.55° (p < .001) 60-min post intervention. There were no significant differences between the main effects of treatment and time for IR, ER, and TRROM. For IR, SS improved by an average of 1.73 ± 0.55° (p = .005) more than DT. For ER and TRROM, there were no differences between SS and DT.

CONCLUSION

Both SS and DT exercises improve glenohumeral IR, ER and TRROM up to one-hour post intervention, with no significant differences noted between interventions for treatment or time. Baseball players can benefit equally from performing SS or DT exercises to acutely improve shoulder ROM.

LEVEL OF EVIDENCE

Level 3.

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.

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.

THE EFFECT OF HUMERAL RETROTORSION ON PITCH VELOCITY IN YOUTH BASEBALL PLAYERS

BACKGROUND

Pitching velocity is a critical measure of performance, but it may also play a role in the development of injury. It has been proposed that increased humeral retrotorsion (HRT) may be an advantageous adaptation among throwers, resulting in increased throwing velocity. However, there is limited published data directly investigating this relationship.

PURPOSE / HYPOTHESIS

The purpose of this study was to examine the effects of HRT on pitching velocity in a group of youth baseball players. We hypothesized that there would be a positive association between pitching velocity and increased humeral retrotorsion.

STUDY DESIGN

Cross-sectional cohort study.

METHODS

Demographic and physical variables that may correlate to pitching velocity (age, height, weight, glenohumeral external rotation (ER) range of motion, dominant arm humeral retrotorsion and shoulder internal rotation (IR) strength) were assessed. Univariate analysis using Pearson correlation coefficients examined the relationship of each variable to pitching velocity. Significant variables were retained and entered into a multivariable regression analysis.

RESULTS

All variables significantly correlated with pitching velocity (p<0.05) with the exception of ER (r = -0.169,p = 0.145). Multivariable regression model was significant and accounted for 81.7% of pitching velocity (R² = 0.817 F(5,70) = 62.59,p<0.001). Player age (B = 1.7,p < 0.001), height (B = 0.225,p = 0.001) and shoulder IR strength (B = 0.622, p < 0.001) significantly contributed to the model. After accounting for all other variables, HRT had a non-significant (B = 0.005,p = 0.884) and very small contribution to pitching velocity adding only .005mph per degree of HRT.

CONCLUSIONS

Pitching velocity in youth baseball players is strongly influenced by age, height and IR strength. In opposition to the hypothesis, the degree of humeral retrotorsion did not have a significant effect on pitching velocity.

LEVEL OF EVIDENCE

Level 3.

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.

Humeral Retroversion and Participation Age in Professional Baseball Pitchers by Geographic Region

CONTEXT

Baseball is played around the world, including in North America and Latin America. The repetitive and stressful act of throwing can lead to adaptations such as increased humeral retroversion (HR) in the throwing arm. This adaptation is often considered beneficial as it allows more glenohumeral external rotation during the cocking phase of pitching without soft tissue stretching. Therefore, it is speculated that throwing should be started at a young age to capitalize on this adaptation. Interestingly, athletes in different geographic regions of the world often begin organized baseball at different ages. However, range of motion (ROM), HR, and the starting age of baseball have never been examined based on geographic region.

OBJECTIVE

To determine if ROM, HR, and the starting age of baseball players differed between professional baseball pitchers from North America and Latin America.

DESIGN

Cross-sectional study.

SETTING

Clinical setting.

PATIENTS OR OTHER PARTICIPANTS

Thirty professional pitchers (North American = 19, Latin American = 11) with no current injury or surgery in the previous 6 months.

MAIN OUTCOME MEASURE(S)

Both ROM and HR were measured in the dominant and nondominant shoulder of each participant. The starting age for baseball was self-reported.

RESULTS

The Latin American group had more dominant-arm HR (8.7°; P = .034), more nondominant-arm external rotation (5.3°; P = .049), and a trend toward more nondominant-arm HR (6.5°; P = .058), yet they started playing baseball at a later age (by 3.7 years; P = .021) compared with the North American group.

CONCLUSIONS

Latin American players had greater HR but started playing baseball at an older age. These findings contradict current thinking that HR would be more pronounced if baseball was started at a younger age. Additional research is required to better understand HR and the genetic, environmental, and nutritional factors that contribute to its development.

BASEBALL PLAYERS DIAGNOSED WITH ULNAR COLLATERAL LIGAMENT TEARS DEMONSTRATE GREATER SIDE TO SIDE DIFFERENCES IN PASSIVE GLENOHUMERAL ABDUCTION RANGE OF MOTION COMPARED TO HEALTHY CONTROLS

Background

Numerous studies have shown that baseball players develop range of motion adaptations in their throwing arm. While some of these shoulder range of motion adaptations can lead to greater throwing velocity, excessive changes in shoulder range of motion can increase the risk of injury to the ulnar collateral ligament (UCL).

Purpose/Hypotheses

The purpose of this study was to compare the passive GH-ABD ROM measures of baseball players with a diagnosed UCL tear (UCL group) to a group of age, activity, and position matched healthy controls (CONT group). The primary hypothesis was that baseball players with an UCL tear would have a greater loss of passive glenohumeral abduction range of motion in their throwing shoulder than healthy controls. A secondary hypothesis was that baseball players with an UCL tear would demonstrate similar glenohumeral abduction range of motion in their non-throwing arm and increased side-to-side glenohumeral abduction differences compared to the healthy cohort.

Study Design

Retrospective prospective case-control study.

Results

The UCL group had significantly greater glenohumeral abduction range of motion on their throwing shoulder (132.5 °±8.3 °) than the CONT group (120.19 °±11.2 °, p = 0.000). Similarly, the UCL group had increased glenohumeral abduction range of motion on their non-throwing shoulder (141.2 °±9.5 °) compared to the CONT group (124.1 °±11.4 °, p = 0.000). Additionally, the UCL group had a greater glenohumeral abduction difference (-8.7 °±8.4 °) than the CONT group (-3.8 °±7.7 °, p = 0.001).

Conclusion

In contrast to the original hypotheses, high school and collegiate baseball players that sustained an UCL injury presented with greater glenohumeral abduction range of motion in both their throwing and non-throwing shoulders compared to healthy controls. However, the finding of greater side-to-side glenohumeral abduction range of motion deficits in the UCL group when compared to the matched healthy controls confirms the secondary hypothesis.

Level of Evidence

Level 3.

Humeral retroversion and shoulder muscle changes in infants with internal rotation contractures following brachial plexus birth palsy

AIM

To examine humeral retroversion in infants who sustained brachial plexus birth palsy (BPBI) and suffered from an internal rotation contracture. Additionally, the role of the infraspinatus (IS) and subscapularis (SSc) muscles in the genesis of this bony deformation is explored.

METHODS

Bilateral magnetic resonance imaging (MRI) scans of 35 infants (age range: 2-7 mo old) with BPBI were retrospectively analyzed. Retroversion was measured according to two proximal axes and one distal axis (transepicondylar axis). The proximal axes were: (1) the perpendicular line to the borders of the articular surface (humeral centerline); and (2) the longest diameter through the humeral head. Muscle cross-sectional areas of the IS and SSc muscles were measured on the MRI-slides representing the largest muscle belly. The difference in retroversion was correlated with the ratio of muscle-sizes and passive external rotation measurements.

RESULTS

Retroversion on the involved side was significantly decreased, 1.0° vs 27.6° (1) and 8.5° vs 27.2° (2), (P < 0.01), as compared to the uninvolved side. The size of the SSc and IS muscles on the involved side was significantly decreased, 2.26 cm² vs 2.79 cm² and 1.53 cm² vs 2.19 cm², respectively (P < 0.05). Furthermore, the muscle ratio (SSc/IS) at the involved side was significantly smaller compared to the uninvolved side (P = 0.007).

CONCLUSION

Even in our youngest patient population, humeral retroversion has a high likelihood of being decreased. Altered humeral retroversion warrants attention as a structural change in any child being evaluated for the treatment of an internal rotation contracture.

Increased pitch velocity and workload are common risk factors for ulnar collateral ligament injury in baseball players: a systematic review

Importance

Ulnar collateral ligament (UCL) injuries commonly occur in baseball players. Strategies for injury prevention have long been accepted without clinical data informing which risk factors lead to serious injury.

Objective

The objective of this study was to systematically review the impact of various pitching-related risk factors for UCL injury in baseball players from all levels of play.

Evidence review

The electronic databases MEDLINE, EMBASE and PubMed were systematically searched until 4 March 2018, and pertinent data were abstracted by two independent reviewers. Search terms included ‘ulnar collateral ligament’, ‘medial ulnar collateral ligament’, ‘Tommy John’, ‘risk’ and ‘association’. Inclusion criteria were English-language studies, level of evidence I–IV and studies reporting risk factors for UCL injury of the elbow in baseball players. Study quality was assessed using the methodological index for non-randomised studies (MINORS) criteria. The results are presented in a narrative summary.

Findings

Pitching practices (workload and pitch characteristics) were reported in 9/15 studies. Specifically, three of four studies (n=1810) reported increased pitch workload as a risk factor for native UCL injury (p<0.001 to 0.02). The most common pitch characteristic reported was pitch velocity with four of five studies showing increased velocity being significantly associated with native UCL injury (p<0.01 to 0.02). Biomechanical risk factors reported were increased humeral retrotorsion (two studies; n=324), poor lower extremity and trunk balance (one study; n=42) and loss of total arc of shoulder motion (two studies; n=118), all significantly associated with UCL injury (p<0.0001 to 0.05). One of three studies assessing pitch workload as a risk factor for re-rupture of UCL reconstruction found a significant association (p<0.01).

Conclusions and relevance

Pitching practices, reflected by increased pitch workload and velocity, were most commonly associated with UCL injury; however, the definition of workload (number of pitches per game, inning or season) was inconsistently reported. Biomechanical risk factors were less commonly reported and lack sufficient evidence to recommend preventative strategies. More quality data is needed to refine the current recommendations for injury prevention in baseball players.

Level of evidence

III.

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.

Reliability and Validity of a 1-Person Technique to Measure Humeral Torsion Using Ultrasound

CONTEXT

  Knowledge of the bilateral difference in humeral torsion (HT) enables clinicians to implement appropriate interventions for soft tissue restrictions of the shoulder to restore rotational motion and reduce injury risk. Whereas the current ultrasound method for measuring HT requires 2 assessors, a more efficient 1-person technique (1PT) may be of value.

OBJECTIVE

  To determine if a 1PT is a reliable and valid alternative to the established 2-person technique (2PT) for indirectly measuring HT using ultrasound.

DESIGN

  Descriptive laboratory study.

SETTING

  Biomechanics laboratory.

PATIENTS OR OTHER PARTICIPANTS

  A convenience sample of 16 volunteers (7 men, 9 women; age = 26.9 ± 6.8 years, height = 172.2 ± 10.7 cm, mass = 80.0 ± 13.3 kg).

MAIN OUTCOME MEASURE(S)

  We collected the HT data using both the 1PT and 2PT from a total of 30 upper extremities (16 left, 14 right). Within-session intrarater reliability (intraclass correlation coefficient; ICC [3,1]) and standard error of measurement (SEM) were assessed for both techniques. Simple linear regression and Bland-Altman analysis were used to examine the validity of the 1PT when compared with the established 2PT.

RESULTS

  The 1PT (ICC [3,1] = 0.992, SEM = 0.8°) and 2PT (ICC [3,1] = 0.979, SEM = 1.1°) demonstrated excellent within-session intrarater reliability. A strong linear relationship was demonstrated between the HT measurements collected with both techniques ( r = 0.963, r² = 0.928, F_1,28 = 361.753, P < .001). A bias of -1.2° ± 2.6° was revealed, and the 95% limits of agreement indicated the 2 techniques can be expected to vary from -6.3° to 3.8°.

CONCLUSIONS

  The 1PT for measuring HT using ultrasound was a reliable and valid alternative to the 2PT. By reducing the number of testers involved, the 1PT may provide clinicians with a more efficient and practical means of obtaining these valuable clinical data. ^a.

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.

Physical and Functional Differences in Youth Baseball Players With and Without Throwing-Related Pain

Background:

Identifying risk factors that contribute to shoulder and elbow pain within youth baseball players is important for improving injury prevention and rehabilitation strategies.

Hypothesis:

Differences will exist between youth baseball players with and without a history of upper extremity pain on measures related to growth, shoulder performance, and baseball exposure.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

A total of 84 youth baseball players were divided into 2 groups based on self-reported history of throwing-related arm pain. Group differences for growth-related, shoulder performance, and baseball exposure variables were analyzed by use of parametric and nonparametric tests, as appropriate. Multivariate logistic regression was used to assess variables most predictive of pain.

Results:

The group of athletes with pain (n = 16) were taller and heavier, played more baseball per year, and had greater pitching velocity. Athletes with pain also had greater loss of internal rotation range of motion and greater side-to-side asymmetry in humeral retrotorsion (HRT), attributable to lower degrees of HRT within the nondominant humerus. Multivariate analysis revealed that player height was most predictive of pain, with a 1-inch increase in height resulting in a 77% increased risk of pain.

Conclusion:

Vertical growth that accompanies adolescence increases the risk of experiencing throwing-related pain in youth baseball players. Players who are taller, particularly those with faster pitching velocities, are at the greatest risk for developing pain and should be more carefully monitored for resultant injury. The degree of nondominant HRT may have a relationship to the development of pain, but further research is required to better understand the implications of this observation.

Preseason screening of shoulder range of motion and humeral retrotorsion does not predict injury in high school baseball players

BACKGROUND

Shoulder and elbow injuries are commonplace in high school baseball. Although altered shoulder range of motion (ROM) and humeral retrotorsion angles have been associated with injuries, the efficacy of preseason screening of these characteristics remains controversial.

METHODS

We conducted preseason screenings for shoulder internal and external rotation ROM and humeral retrotorsion on 832 high school baseball players and tracked their exposure and incidence on throwing-related shoulder and elbow injuries during a subsequent season. Poisson regression with robust error variance was used to determine whether preseason screening could identify injury risk in baseball players and whether the injury risk was higher for pitchers compared with players who do not pitch.

RESULTS

Shoulder rotation ROM or humeral retrotorsion at preseason did not predict the risk of throwing-related upper extremity injury (P = .15-.89). Injury risk was 3.84 higher for baseball players who pitched compared with those who did not (95% confidence interval, 1.72-8.56; P = .001).

DISCUSSION

Preseason measures of shoulder ROM and humeral retrotorsion may not be effective in identifying players who are at increased injury risk. Because shoulder ROM is a measure that fluctuates under a variety of influences, future study should investigate whether taking multiple measurements during a season can identify at-risk players. The usefulness of preseason screening may also depend on rigor of participation in sports. Future studies should investigate how preseason shoulder characteristics and participation factors (ie, pitch count and frequency, competitive level, pitching in multiple leagues) interact to predict injury risk in baseball players.

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

BACKGROUND

The relationship between the disabled throwing shoulder and humeral retroversion has recently attracted a great deal of attention. However, none of the previous studies clarified when the side-to-side difference of humeral retroversion in young baseball players would start. This study aimed to clarify when the difference of humeral retroversion in the dominant and nondominant sides appeared in baseball players.

METHODS

The bicipital-forearm angle in bilateral shoulders of 172 elementary school baseball players was measured by ultrasound. The bicipital-forearm angle was defined as an angle between the perpendicular line to the bicipital groove and the ulnar long axis with the elbow flexed at 90°. The correlation between the bicipital-forearm angle and the grade and the difference of the bicipital-forearm angle between the dominant and nondominant sides were analyzed.

RESULTS

In the nondominant shoulders, the bicipital-forearm angle increased with the grade in school (r = 0.32, P < .0001), but this was not observed in the dominant shoulders. In the fourth to sixth graders, the bicipital-forearm angles were significantly smaller in the dominant shoulders than in the nondominant shoulders.

CONCLUSION

Our findings indicated that humeral retroversion decreased with age in the nonthrowing side but not in the throwing side and that the side-to-side difference of humeral retroversion in the baseball players became obvious from the fourth grade. We assume that the repetitive throwing motion restricts the physiologic humeral derotation process and the difference became apparent from the fourth grade when the growth spurt begins in boys.

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.

Site and Severity of the Increased Humeral Retroversion in Symptomatic Baseball Players: A 3-dimensional Computed Tomographic Analysis

BACKGROUND

Humeral retroversion in baseball players is greater in the dominant shoulder than in the nondominant shoulder. However, the site and severity of the humeral rotational deformity remain unclear.

PURPOSE

To evaluate the site of side-to-side differences in humeral retroversion in baseball players and the severity of these changes through 3-dimensional computed tomographic (3D CT) bone models.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

From 2008 to 2014, we studied 25 baseball players (12 pitchers, 13 fielders) who underwent surgery for throwing-related injuries (shoulder injury, 15 players; elbow injury, 10 players). The mean age (±SD) at the time of surgery was 20.0 ± 5.9 years. A reconstructed 3D CT model of the entire humerus was divided into 15 segments of equal height (overall mean, 21.4 ± 1.0 mm). The side-to-side difference in humeral retroversion in each segment was calculated by superimposing the model of the dominant side over the mirror-image model of the nondominant side.

RESULTS

The overall mean increase in humeral retroversion was 13.0° ± 6.2° on the dominant side. Significant side-to-side differences in retroversion were present throughout the humerus. The largest side-to-side difference in humeral retroversion was seen at the insertions of the internal rotator muscles (2.5° ± 4.3°) and around the proximal physis (2.5° ± 1.4°). At the insertions of shoulder capsule and rotator cuff tendons, the superior half of the humeral head was more retroverted than the inferior half (P < .0001). The side-to-side difference in humeral retroversion was significantly greater in the pitchers (16.2° ± 5.1°) than in the fielders (10.0° ± 5.7°) (P = .009), particularly at the proximal physis.

CONCLUSION

Baseball players exhibited significant side-to-side differences in humeral retroversion at multiple sites throughout the humerus, including the proximal humerus near the epiphyseal plate and at the insertions of the internal rotator muscles, the middle of the humeral shaft, and the distal third of the humerus. Therefore, the increased humeral retroversion at multiple sites throughout the humerus needs to be considered when we perform physical examinations, provide treatment, or undertake biomechanical studies for any throwing-related injuries.

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.

Adaptations of the Shoulder to Overhead Throwing in Youth Athletes

CONTEXT

The high number of repetitions and high forces associated with overhead throwing lead to anatomical adaptations, such as humeral retrotorsion and posterior-capsule thickness, in elite and professional baseball athletes. However, little is known about the origin and progression of these changes that may account for the increasing trend of chronic shoulder injuries in youth baseball and precipitate subsequent pathologic conditions throughout a young athlete's lifetime.

OBJECTIVE

To investigate the relationship of age and upper extremity dominance on humeral retrotorsion, posterior-capsule thickness, and glenohumeral range of motion.

DESIGN

Cross-sectional study.

SETTING

Research laboratory, local baseball fields, and training facilities.

PATIENTS OR OTHER PARTICIPANTS

Thirty-six boys (mean age = 10.94 ± 1.34 years, height = 151.31 ± 12.17 cm, mass = 42.51 ± 10.32 kg) ranging in age from 8 to 12 years and involved in organized youth baseball.

MAIN OUTCOME MEASURE(S)

Diagnostic ultrasound was used to determine humeral retrotorsion and posterior-capsule thickness. Glenohumeral internal rotation and external rotation were measured using a handheld inclinometer. We used 2 × 2 mixed-model analyses of variance to compare the influence of limb dominance and age on the dependent variables of humeral retrotorsion, posterior-capsule thickness, internal rotation, and external rotation.

RESULTS

The dominant shoulders of youth throwers exhibited less glenohumeral internal rotation but greater humeral retrotorsion, posterior-capsule thickness, and glenohumeral external rotation than the nondominant shoulders. Dominant internal rotation was greater in the 8- to 10-year-old group than in the 11- to 12-year-old group, and results trended toward a difference (F1,33 = 4.12, P = .05). Correlations existed between humeral retrotorsion and range of motion (P < .05).

CONCLUSIONS

The structural adaptations in the dominant shoulders of younger baseball players were similar to adaptations observed in older baseball athletes, indicating that more examination is needed in younger athletes. We are the first to demonstrate greater posterior-capsule thickness in the dominant shoulders of youth baseball athletes.

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.

Assessing biological maturity: chronological age and the pubertal development scale predict free testosterone in adolescent males

BACKGROUND

Pubertal development status has implications for development of physical characteristics, performance, and injury risk in school-aged athletes.

OBJECTIVE

The objective of this study was to evaluate the ability of non-invasive measures of biological maturity to predict salivary free testosterone.

PARTICIPANTS

A total of 61 physically active males (ages 6-16) participated in this study.

METHODS

Participants had their anthropometrics measured, completed the Pubertal Development Scale (PDS), and reported their birthdays and the heights of their biological parents. Exact chronological age and percent of predicted height were calculated. Resting salivary samples were collected and assessed for free testosterone levels using enzyme-linked immunosorbent assay procedures. Variables were entered into a stepwise linear regression to predict free testosterone.

RESULTS

The regression model was statistically significant (R²=0.716, F₂,₆₁=74.2, p<0.005) with chronological age (β=0.66, t₆₀=7.587, p<0.005) and PDS (β=0.26, t₆₀=3.02, p=0.004) remaining as significant predictors of free testosterone.

CONCLUSIONS

Chronological age and PDS adequately predict salivary free testosterone levels in school-aged males and may be an appropriate tool to evaluate physical maturity in school-aged males quickly, cheaply, and accurately.

Reliability of and the relationship between ultrasound measurement and three clinical assessments of humeral torsion

PURPOSE/BACKGROUND

Differences in humeral torsion have been observed between overhead athletes and non-athletes. Although humeral torsion may be an adaptive process for athletic performance, it may be associated with injury. Methods for measuring humeral torsion have consisted of radiography, computer tomography, and ultrasound imaging. However, diagnostic imaging may be costly and not available to all clinicians. The implementation of clinical assessments may be an alternative way to measure humeral torsion. Before clinical measures can be recommended, these assessments need to be evaluated for validity and reliability of each test. The purpose of this study was to assess the intratester and intertester reliability of three clinical tests, intratester reliability of ultrasound measures, and the validity of each clinical test to ultrasound measures.

METHODS

Thirty participants (male: 12, female: 18; age: 20±2 years; height: 174.24±9.35 cm; mass: 70.53±11.06 kg; body mass index: 23.13±2.47 kg/m(2); years in sport: 9±4 years) with experience in overhead sports were assessed for humeral torsion, bilaterally. Humeral torsion was assessed using musculoskeletal ultrasound by a single assessor, and using three separate clinical assessments by two independent assessors. Clinical assessments included the angle of rotation during both the bicipital tuberosity palpation with the shoulder abducted at 90 degrees (Palp90) or 45 degrees (Palp45), and the angle of external rotation during horizontal adduction (HADD).

RESULTS

Intratester reliability for the ultrasound measure was good (ICC=0.907), along with intratester reliability for both assessors across each clinical assessment (ICC's > 0.769). Poor to moderate reliability was observed between assessors for each clinical assessment (ICC=0.256 Palp90, ICC=0.419 Palp45, ICC=0.243 HADD. Only the Palp90 measure had a fair but significant (r=0.326, p=0.011) relationship with ultrasound measures.

CONCLUSION

Individual assessors can achieve reliable ultrasound, bicipital tuberosity palpation and HADD values across multiple trials; however, these measures are not consistent between assessors. Additionally, only one clinical test had a fair but significant relationship with ultrasound measures. Improved testing procedures may be needed to increase between assessor reliability and strength of relationships to ultrasound measures. Current application of clinical assessments to measure humeral torsion is limited.

LEVEL OF EVIDENCE

3b; Grade of Recommendation C.

Dominant-limb range-of-motion and humeral-retrotorsion adaptation in collegiate baseball and softball position players

CONTEXT

Biomechanically, the motions used by baseball and softball pitchers differ greatly; however, the throwing motions of position players in both sports are strikingly similar. Although the adaptations to the dominant limb from overhead throwing have been well documented in baseball athletes, these adaptations have not been clearly identified in softball players. This information is important in order to develop and implement injury-prevention programs specific to decreasing the risk of upper extremity injury in softball athletes.

OBJECTIVE

To compare range-of-motion and humeral-retrotorsion characteristics of collegiate baseball and softball position players and of baseball and softball players to sex-matched controls.

DESIGN

Cross-sectional study.

SETTING

Research laboratories and athletic training rooms at the University of North Carolina at Chapel Hill.

PATIENTS OR OTHER PARTICIPANTS

Fifty-three collegiate baseball players, 35 collegiate softball players, 25 male controls (nonoverhead athletes), and 19 female controls (nonoverhead athletes).

INTERVENTION(S)

Range of motion and humeral retrotorsion were measured using a digital inclinometer and diagnostic ultrasound.

MAIN OUTCOME MEASURE(S)

Glenohumeral internal-rotation deficit, external-rotation gain, total glenohumeral range of motion, and humeral retrotorsion.

RESULTS

Baseball players had greater glenohumeral internal-rotation deficit, total-range-of-motion, and humeral-retrotorsion difference than softball players and male controls. There were no differences between glenohumeral internal-rotation deficit, total-range-of-motion, and humeral-retrotorsion difference in softball players and female controls.

CONCLUSIONS

Few differences were evident between softball players and female control participants, although range-of-motion and humeral-retrotorsion adaptations were significantly different than baseball players. The throwing motions are similar between softball and baseball, but the athletes adapt to the demands of the sport differently; thus, stretching/strengthening programs designed for baseball may not be the most effective programs for softball athletes.

Increase in humeral retrotorsion accounts for age-related increase in glenohumeral internal rotation deficit in youth and adolescent baseball players

BACKGROUND

Glenohumeral internal rotation deficit (GIRD) is the difference in internal rotation range of motion (IRROM) between the dominant and nondominant limbs. Pathological GIRD of greater than 15° to 25° has previously been linked to shoulder and elbow injuries in baseball players. Because of its relationship to shoulder and elbow disorders, research has focused on understanding the underlying factors that contribute to changes in IRROM and ultimately GIRD. The rotation deficit reportedly increases during adolescence, but it remains unclear whether this change is caused by changes in osseous properties or soft tissue tightness.

PURPOSE

To evaluate the influence of age group on GIRD, humeral retrotorsion, retrotorsion-adjusted GIRD, and total range of motion (TROM) in healthy baseball players.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Four groups of healthy baseball players participated in the study: 52 youth (aged 6-10 years), 52 junior high school (JH) (aged 11-13 years), 70 junior varsity (JV) (aged 14-15 years), and 113 varsity (aged 16-18 years) players. Internal rotation range of motion, external rotation range of motion (ERROM), and humeral retrotorsion were measured bilaterally using a digital inclinometer and diagnostic ultrasound. Retrotorsion-adjusted IRROM was calculated as the available IRROM from the humeral retrotorsion position; TROM was calculated as the sum of IRROM and ERROM; and GIRD, the difference in humeral retrotorsion between limbs, adjusted GIRD, and the difference in TROM between limbs were calculated as the difference between the dominant and nondominant sides. Four separate analyses of variance were used to compare these variables between age groups.

RESULTS

There was a significant group difference in GIRD (F3,284 = 8.957; P < .001) and a difference in humeral retrotorsion between limbs (F3,284 = 9.688; P < .001). Also, GIRD was greater in varsity participants compared with youth (mean difference [MD], 5.05°) and JH (MD, 4.95°) participants and in JV participants compared with JH (MD, 5.36°) and youth (MD, 5.47°) participants. The difference in humeral retrotorsion between limbs was greater in varsity participants compared with youth (MD, 8.79°) and JH (MD, 5.52°) participants and in JV participants compared with youth participants (MD, 7.88°). There were no significant differences in adjusted GIRD (F3,284 = 1.136; P = .335) or TROM (F3,284 = 1.214; P = .305).

CONCLUSION

Glenohumeral internal rotation deficit and humeral retrotorsion increased with age in youth/adolescent baseball players, while retrotorsion-adjusted GIRD and TROM remained unchanged. An age-related increase in GIRD is primarily attributed to humeral retrotorsion rather than soft tissue tightness.

CLINICAL RELEVANCE

While there was an increase in GIRD from youth league to high school participants, TROM and retrotorsion-adjusted GIRD remained constant across the age groups, indicating that this increase between the age groups is not pathological GIRD and may not contribute to an increased injury risk.

Changes in humeral torsion and shoulder rotation range of motion in high school baseball players over a 1-year period

BACKGROUND

The torsional stress on a baseball player's throwing limb has been theorized to affect humeral retrotosion during skeletal maturity. This study investigated 1) changes in humeral retrotorsion and shoulder rotation range of motion over a 1-year period in high school baseball players, and 2) relationship between a 1-year change in dominant limb retrotorsion and the number of seasons participants played on organized baseball teams.

METHODS

Humeral retrotorsion and shoulder range of motion were measured a year apart in a total of 138 high school baseball players. Baseball participation history over the year was captured using a questionnaire. Changes in bilateral humeral retrotorsion and range of motion over a year and effects of baseball participation on changes in humeral retrotorsion and range of motion were assessed using analysis of variance models.

FINDINGS

Humeral retrotorsion did not significantly change over the year regardless of the number of seasons participants played baseball (P>0.05). The participants' dominant limb internal rotation range of motion decreased slightly over a year (2.0°, P=0.015), while external rotation (7.8°, P<0.01) and total rotation (11.9°, P<0.01) range of motion decreased bilaterally among the participants who only played baseball in 1 season.

INTERPRETATION

Adaptation in humeral retrotorsion seems to occur prior to high school age. Our observations suggest that change in shoulder range of motion in high school baseball players are attributed to soft tissue contracture. This provides a support that stretching exercises should be implemented when significant changes in range of motion are identified in high school baseball players.

Ultrasonographic assessment of humeral retrotorsion in baseball players: a validation study

BACKGROUND

Recently, clinicians and researchers started using diagnostic ultrasound to measure humeral torsion as an alternative to radiological assessments in overhead-throwing athletes and other clinical populations. Ultrasound appears to be a reliable, nonradiological alternative, but ultrasound assessment has not been validated against computed tomography (CT), the current gold standard.

PURPOSE

This study aimed to establish the validity of an ultrasound assessment of humeral torsion by comparing data obtained using both ultrasound and CT, the current standard.

STUDY DESIGN

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

METHODS

Humeral torsion was measured using both ultrasound and CT in 24 collegiate-aged baseball players. Comparisons between the assessments were made using both regression and Bland-Altman plots. Reliability and precision were also established.

RESULTS

A strong relationship existed between humeral torsion variables obtained with ultrasound and CT (R = .797, R (2) = .635, P < .001). The ultrasound assessment yielded reliability coefficients ranging from .991 to .997, with approximately 1° of measurement error. The CT method's reliability coefficients ranged from .805 to .933, with approximately 3.5° of measurement error.

CONCLUSION

There was a strong relationship between humeral torsion obtained with ultrasound and CT, the current standard of assessment. Ultrasound provides a reliable, valid alternative to CT for obtaining an indication of the amount of humeral torsion in the upper extremity.