Pathomechanics and Magnetic Resonance Imaging of the Thrower's Shoulder

The Thrower's Shoulder

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

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

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

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

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

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

Thrower's Shoulder: An Approach to MR Imaging Interpretation

In this article, the authors aim to focus on the challenges of interpreting shoulder MR imaging in the throwing athlete with an approach formed by evidence-based literature and clinical experience, with a particular focus on superior labrum tears.

In situ repair of partial-thickness rotator cuff tears: a critical analysis review

After failed conservative management, operative intervention is typically indicated for patients with partial-thickness rotator cuff tears (PTRCTs) with persistent pain and disability symptoms.

For PTRCTs involving < 50% of the tendon thickness, debridement with or without acromioplasty resulted in favourable outcomes in most studies.

For PTRCTs involving > 50% of the tendon thickness, in situ repair has proven to significantly improve pain and functional outcomes for articular and bursal PTRCTs.

The few available comparative studies in the literature showed similar functional and structural outcomes between in situ repair and repair after conversion to full-thickness tear for PTRCTs.

Most non-overhead athletes return to sports at the same level as previous to the injury after in situ repair of PTRCTs. However, rates of return to preinjury level of competition for overhead athletes have been generally poor regardless of the utilized technique.

During long-term follow-up, arthroscopic in situ repair of articular and bursal PTRCTs produced excellent functional outcomes in most patients, with a low rate of revision.

Cite this article: EFORT Open Rev 2020;5:138-144. DOI: 10.1302/2058-5241.5.190010

Characterization of glenoid bone remodeling in professional baseball pitchers

OBJECTIVE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

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

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

Top 50 cited journal articles on overhead throwing athletes: a bibliographic analysis

Background

The frequency of citations for a journal article is a reflection of its academic impact. The purpose of this study was to identify and characterize the top 50 cited journal articles related to overhead throwing athletes in the published literature.

Methods

The Web of Science database was searched on January 18, 2016, using the terms "throwing athlete," "baseball," and "pitcher" to identify the top 50 cited articles related to overhead throwing athletes using the all-database function. The type of study, country of origin, publishing journal, and year published were reviewed for each article.

Results

The top 50 articles identified were cited between 95 and 471 times and were published in 13 journals between 1969 and 2011. Most of the articles were small case series or nonsystematic literature reviews. The shoulder was the most common body region studied in the top 50 articles (33 of 50 [66%]). Among original studies (n = 43), there was a good representation of surgical management of shoulder and elbow pathology in overhead athletes (9 of 43 [20.9%]); however, most of the articles reported on shoulder and elbow kinematics (19 of 43 [44.2%]) and pathoanatomy (15 of 43 [34.9%]).

Conclusion

The greater prevalence of nonsurgical articles may reflect a continued effort to better understand the different pathologies specific to overhead throwing athletes. An understanding of the variable content and quality of frequently cited articles on overhead throwing athletes may serve as a stepping stone for future studies to advance the diagnosis and management of complex elbow and shoulder injuries in these high functional individuals.

Care of Shoulder Pain in the Overhead Athlete

Shoulder complaints are common in the overhead athlete. Understanding the biomechanics of throwing and swimming requires understanding the importance of maintaining the glenohumeral relationship of the shoulder. Capsular laxity, humeral retrotorsion, glenoid retroversion, glenohumeral internal rotation deficit, and scapular dyskinesis can all contribute to shoulder dysfunction and pain. Injuries are more likely during peak height velocity, especially when coupled with overuse, previous injuries not adequately treated, or change in the demands on the shoulder such as a new technique, bigger field, or longer race. Working with physical therapists, athletic trainers, and coaches to identify and treat the etiology of the shoulder dysfunction will help pediatricians return the athlete to activity and prevent future injury. [Pediatr Ann. 2017;46(3):e112-e119.].