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

Energy generation, absorption, and transfer at the shoulder and elbow in youth baseball pitchers

Performance during the baseball pitch is dependent on the flow of mechanical energy through the kinetic chain. Little is known about energy flow during the pitching motion and it is not known whether patterns of energy flow are related to pitching performance and injury risk. Therefore, the purpose of this study was to quantify energy generation, absorption, and transfer across the shoulder and elbow during the baseball pitch and explore the associations between these energetic measures, pitch speed, and traditional measures of upper extremity joint loading. The kinematics of 40 youth baseball pitchers were measured in a controlled laboratory setting. Energy flow between the thorax, humerus, and forearm was calculated using a segmental power analysis. Regression analyses revealed that pitch speed was best predicted by arm cocking phase shoulder energy transfer to the humerus and peak elbow valgus torque was best predicted by arm acceleration-phase elbow energy transfer to the forearm. Additionally, energy transfer across the shoulder and elbow generally exhibited the strongest correlations to pitch speed and upper extremity joint loads. These data reinforce the importance of energy transfer through the kinetic chain for producing high pitch speeds and provide descriptive data for energy flow during baseball pitching not previously found in the literature.

Posterior Shoulder Instability in Tennis Players: Aetiology, Classification, Assessment and Management

Background

Micro-traumatic posterior shoulder instability (PSI) is an often missed and misdiagnosed pathology presenting in tennis players. The aetiology of micro-traumatic PSI in tennis players is multifactorial, including congenital factors, loss of strength and motor control, and sport-specific repetitive microtrauma. Repetitive forces placed on the dominant shoulder, particularly combinations of flexion, horizontal adduction, and internal rotation contribute to the microtrauma. These positions are characteristic for kick serves, backhand volleys, and the follow-through phase of forehands and serves. The aim of this clinical commentary is to present an overview of the aetiology, classification, clinical presentation, and treatment of micro-traumatic PSI, with a particular focus on tennis players.

Level of Evidence

5.

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.

Correlation of glenohumeral internal rotation deficit with shear wave ultrasound elastography findings for the posterior inferior shoulder capsule in college baseball players

BACKGROUND

The glenohumeral internal rotation deficit (GIRD), primarily caused by the tightness of the posterior capsule, is a major risk factor for shoulder injuries in overhead throwing athletes. Quantitative evaluation of posterior capsular thickness and tightness can help determine the relationship between the posterior inferior capsule and GIRD. One previous study has assessed posterior capsule tightness using shear wave elastography (SWE), in college baseball players; however, it did not address the cutoff value of capsular elasticity that could be considered as abnormal capsular tightness. We aimed to re-evaluate effectiveness of SWE in quantifying posterior shoulder capsule tightness in college baseball players and determine the cutoff value of abnormal capsular elasticity that can predict impending throwing-related shoulder injuries associated with GIRD.

METHODS

Twenty-four college baseball players were enrolled in this study. External and internal rotation of the shoulder joint was assessed. The participants were classified into the GIRD group if their throwing shoulder showed >20° of internal rotation loss compared with their nonthrowing shoulder. In a longitudinal ultrasonographic scan of the posterior inferior capsule, shear wave (SW) velocity and thickness were measured at the point nearest to the labrum on both shoulders.

RESULTS

Of the 24 subjects, 6 had a GIRD. The mean value of the SW velocity in the throwing shoulder was greater in the GIRD group than in the non-GIRD group (P = .006). The SW velocity difference between the throwing and nonthrowing shoulder was also greater in the GIRD group than in the non-GIRD group (P < .001). There was no significant difference in the thickness of the posterior inferior capsule between both groups. In correlation analysis, the difference in the SW velocity was more strongly correlated with the GIRD than with the SW velocity in the throwing shoulder. When we assume that a 20° GIRD is indicative of a shoulder at risk, the cutoff SW velocity in the throwing shoulder is 4.81 m/s and the SW velocity difference is 0.77 m/s.

CONCLUSION

The SW velocity is closely associated with posterior shoulder capsular tightness and may be of quantitative value in baseball players.

Pitcher Shoulder: Update Article

Most shoulder injuries occur due to repetitive overhead movements. Before studying the treatment of these shoulder injuries, it is paramount that health professionals have an understanding of the etiology of and the underlying mechanisms for shoulder pathologies. The act of overhead throwing is an eloquent full-body motion that requires tremendous coordination from the time of force generation to the end of the pitch. The shoulder is a crucial component of the upper-body kinetic chain, as it transmits force created in the lower body to the arm and hand to provide velocity and accuracy to the pitch.

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.

The throwing shoulder in youth elite handball: soft-tissue adaptations but not humeral retrotorsion differ between the two sexes

PURPOSE

In youth handball players, knowledge about the development of soft-tissue adaptation and humeral retrotorsion is limited. The purpose of this study was to investigate differences in adaptations in the glenohumeral rotational range of motion and humeral retrotorsion of the throwing arm between male and female youth elite handball players.

METHODS

One-hundred and thirty-eight youth elite handball players (mean age: 14.1 ± 0.7 years) were assessed for glenohumeral external (ER) and internal (IR) rotational ranges of motion and humeral retrotorsion (HRT) by means of a manual goniometer and a portable ultrasound device. Sports-specific adaptations between the dominant and non-dominant shoulders and between male and female adolescents were calculated.

RESULTS

Handball players showed side-to-side differences in IR and ER in the throwing shoulder. HRT did not correlate with the measurements of rotational ROM of the throwing arm. Male athletes showed a more pronounced glenohumeral internal rotation deficit than female athletes (13.1° ± 22.8° vs. 5.1° ± 14.0°, p = 0.014). Adaptations in HRT but no sex differences could be seen in the throwing shoulder (16.5° ± 9.6°) compared to the non-throwing shoulder (13.5° ± 9.4°, p < 0.001).

CONCLUSION

Loss of internal rotation and gain in external rotation in youth handball players seem to be more related to adaptive changes in the soft-tissues than to HRT. Male athletes showed stronger throwing-related adaptations in the rotational range of motion but not in humeral torsion in their dominant shoulder than female athletes.

LEVEL OF EVIDENCE

Cross-sectional study, Level II.