Superior glenoid impingement

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.

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.

Lower shoulder abduction during throwing motion may cause forceful internal impingement and decreased anterior stability

BACKGROUND

Internal impingement and decreased anterior stability, which result from shoulder capsular loosening, are common shoulder pathologies in throwing athletes. The purpose of this study was to assess the effect of shoulder abduction angle on shoulder internal impingement and anterior shoulder stability during the simulated throwing motion.

METHODS

Eight cadaveric shoulders were tested by simulating the late-cocking and acceleration phases of the throwing motion for intact and thrower's shoulder conditions. The maximal glenohumeral external rotation, anterior translation, location of the rotator cuff insertion with respect to the glenoid, length and site of internal impingement, and glenohumeral contact pressure were measured. All data were compared between shoulder abduction angles of 80°, 90°, and 100°.

RESULTS

Decreasing shoulder abduction in the simulated late-cocking phase shifted the humeral head posteriorly (P < .03) and superiorly (P < .001), decreasing the total internal impingement area between the greater tuberosity and glenoid (P = .04) and increasing the glenohumeral contact pressure during internal impingement (P = .02). In the simulated acceleration phase, anterior glenohumeral translation significantly increased as the shoulder abduction angle decreased (P < .001).

CONCLUSION

Decreasing shoulder abduction significantly increased the contact pressure during internal impingement in the simulated late-cocking phase of the throwing motion. During the simulated acceleration phase of the throwing motion, anterior glenohumeral translation significantly increased as shoulder abduction decreased.

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.

Internal Impingement of the Shoulder: A Risk of False Positive Test Outcomes in External Impingement Tests?

Background

External impingement tests are considered as being particularly reliable for identifying subacromial and coracoid shoulder impingement mechanisms. The purpose of the present study was to evaluate if these tests are likely to provoke an internal shoulder impingement mechanism which, in cases of a pathologic condition, can lead to a positive test result.

Method

In 37 subjects, the mechanical contact between the glenoid rim and the rotator cuff (RC) was measured quantitatively and qualitatively in external impingement test positions using an open MRI system.

Results

Mechanical contact of the supraspinatus with the posterosuperior glenoid was present in 30 subjects in the Neer test. In the Hawkins test, the subscapularis was in contact with the anterosuperior glenoid in 33 subjects and the supraspinatus in 18. In the horizontal impingement test, anterosuperior contact of the supraspinatus with the glenoid was identified in 35 subjects.

Conclusion

The Neer, Hawkins, and horizontal impingement tests are likely to provoke the mechanism of an internal shoulder impingement. A posterosuperior internal impingement mechanism is being provoked predominately in the Neer test. The Hawkins test narrows the distance between the insertions of the subscapularis and supraspinatus and the anterosuperior labrum, which leads to an anterosuperior impingement mechanism.

Pathomechanics and Magnetic Resonance Imaging of the Thrower's Shoulder

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

Stress Distribution in Superior Labral Complex and Rotator Cuff During In Vivo Shoulder Motion: A Finite Element Analysis

PURPOSE

To quantitatively and qualitatively evaluate the impingement behavior between structures within the glenohumeral joint under simulated abduction-external rotation (ABER) motion using finite element analysis.

METHODS

Computed tomography (CT) scanning of 1 shoulder in a volunteer was performed at 0° and 120° of shoulder abduction with external rotation (ABER position), followed by magnetic resonance imaging at 0° of abduction. The CT and magnetic resonance images were then imported into a customized software program to undergo 3-dimensional reconstruction followed by finite element modeling of the bone and soft tissue including the upper part of the rotator cuff and glenohumeral labral complex. Glenohumeral motion from 0° to the ABER position was simulated by CT images in 2 different humeral positions. On the basis of simulated humeral motion with respect to the scapula, we measured the stress value on the biceps-labral complex and upper part of the rotator cuff as a consequence of their structural deformation. In addition, we intended to design 2 types of labra--a normal stable labrum and an unstable posterosuperior labrum--to evaluate the geometric alteration and resulting stress change on the posterosuperior labrum against a compressive force from the humeral head and rotator cuff.

RESULTS

In the ABER position, the posterosuperior labrum was deformed by the humeral head and interposed posterior part of the rotator cuff. When viewed from the rotator cuff, the posterior part of the rotator cuff came into contact with the posterosuperior labrum as external rotation increased. The measured peak contact stress values were 19.7 MPa and 23.5 MPa for the posterosuperior labrum and the upper rotator cuff, respectively. The stress values for both structures decreased to 5.8 MPa and 18.1 MPa, respectively, in the simulated SLAP model. The root of the long head of the biceps became compressed halfway through the range of motion by the humeral head, especially from the part involving horizontal extension and external rotation, resulting in a high stress of 22.4 MPa.

CONCLUSIONS

In this simulated SLAP model, the posterosuperior labrum was medially displaced by the humeral head and upper rotator cuff in the ABER position, causing a functional loss of the spacer effect.

CLINICAL RELEVANCE

In SLAP lesions, the posterosuperior labrum loses its ability to function as a spacer in certain positions (especially ABER) and may decrease the important spacer effect between the humerus and the rotator cuff; this may lead to posterosuperior subluxation of the humeral head or rotator cuff abnormalities and tears during repetitive ABER tasks.

Partial rotator cuff injury in athletes: bursal or articular?

A painful shoulder is a very common complaint among athletes, especially in the case of those in sports involving throwing. Partial lesions of the rotator cuff may be very painful and cause significant functional limitation to athletes’ sports practice. The incidence of partial lesions of the cuff is variable (13–37%). It is difficult to make the clinical and radiological diagnosis, and this condition should be borne in mind in the cases of all athletes who present symptoms of rotator cuff syndrome, including in patients who are diagnosed only with tendinopathy.

Objective

To evaluate the epidemiological behavior of partial lesions of the rotator cuff in both amateur and professional athletes in different types of sports.

Methods

We evaluated 720 medical files on athletes attended at the shoulder service of the Discipline of Sports Medicine at the Sports Traumatology Center, Federal University of São Paulo. The majority of them were men (65%). Among all the patients, 83 of them were diagnosed with partial lesions of the rotator cuff, by means of ultrasonography or magnetic resonance, or in some cases using both. We applied the binomial test to compare the proportions found.

Result

It was observed that intra-articular lesions predominated (67.6%) and that these occurred more frequently in athletes in sports involving throwing (66%). Bursal lesions occurred in 32.4% of the athletes, predominantly in those who did muscle building (75%).

Conclusion

Intra-articular lesions are more frequent than bursal lesions and they occur predominantly in athletes in sports involving throwing, while bursal lesions were more prevalent in athletes who did muscle building.

Effect of posterior shoulder tightness on internal impingement in a cadaveric model of throwing

PURPOSE

Posterior shoulder tightness is common in throwing athletes, especially those with symptomatic shoulder internal impingement. The role of posteroinferior capsular contracture in the pathoetiologies of throwing-related injuries caused by shoulder internal impingement remains unclear. The purpose of this study was to assess effect of posterior shoulder tightness on internal impingement in a cadaveric model of throwing.

METHODS

Seven fresh-frozen cadaveric shoulders were tested with the shoulder abducted to 90° and at maximum external rotation to simulate the late cocking phase of throwing motion. Glenohumeral joint contact pressure and area through internal impingement, humeral head shift, and the maximum humeral rotation angle were measured. Posteroinferior capsular plication was performed to simulate posteroinferior capsular tightness and induce glenohumeral internal rotation deficit.

RESULTS

Following generation of simulated posteroinferior capsular tightness with resultant glenohumeral internal rotation deficit, glenohumeral contact pressure was significantly increased (P < 0.05), the impinged area of rotator cuff tendon was significantly decreased (P < 0.05), and the humeral head shifted posteriorly (P < 0.05) during shoulder internal impingement.

CONCLUSION

Excessive posteroinferior capsular tightness can cause forceful internal impingement of the shoulder at maximum external rotation position.

Association between kyphosis and subacromial impingement syndrome: LOHAS study

BACKGROUND

Kyphosis is a cause of scapular dyskinesis, which can induce various shoulder disorders, including subacromial impingement syndrome (SIS). This study aimed to clarify the impact of kyphosis on SIS with use of cross-sectional data from the Locomotive Syndrome and Health Outcome in Aizu Cohort Study (LOHAS).

METHODS

The study enrolled 2144 participants who were older than 40 years and participated in health checkups in 2010. Kyphosis was assessed by the wall-occiput test (WOT) for thoracic kyphosis and the rib-pelvic distance test (RPDT) for lumbar kyphosis. The associations between kyphosis, SIS, and reduction in shoulder elevation (RSE) were investigated.

RESULTS

Age- and gender-adjusted logistic regression analysis demonstrated significant association between SIS and WOT (odds ratio, 1.65; 95% confidence interval, 1.02, 2.64; P < .05), whereas there was no significant association between SIS and RPDT. Multivariable logistic regression analysis demonstrated no significant association between SIS and both WOT and RPDT, whereas there was significant association between SIS and RSE.

CONCLUSION

RSE plays a key role in the development of SIS, and thoracic kyphosis might influence the development of SIS indirectly by reducing shoulder elevation induced by the restriction of the thoracic spine extension and scapular dyskinesis.

Superficial blood flow of the superior labrum associated with rotator cuff tear using laser Doppler flowmeter

INTRODUCTION

Superior labrum anterior and posterior (SLAP) lesions due to overuse by repeated pitching motion and trauma are often noted and usually. However, shoulder disorders with a chronic course are often accompanied by SLAP lesions. SLAP lesions are frequently observed during arthroscopic surgery of the shoulder joint for rotator cuff tear in middle-aged and elderly individuals, suggesting the involvement of factors other than pitching motion and traumatic events in the pathogenesis. We considered that blood flow in the labrum is altered. The purpose of this study was to clarify the superficial blood flow in the superior labrum during arthroscopic surgery of the rotator cuff tear and investigate whether it is altered with labrum injury.

MATERIALS AND METHODS

We evaluated 33 subjects with a mean age of 55.1 years who underwent arthroscopic surgery for partial or complete rotator cuff tears. The blood flow measurement site for the superior labrum was set at the supraglenoid tubercle attachment site, and blood flow was measured twice using laser Doppler flowmeter. The mean was calculated and compared among the normal labrum and type 1 SLAP lesions.

RESULTS

The morphology of the labrum was normal in 16 subjects, and 17 subjects had type 1 SLAP lesions. The mean blood flow was 1.75 ml/min/100 g in subjects with a normal labrum; however, in subjects with type 1 SLAP lesions, blood flow was 1.32 ml/min/100 g, showing significant differences (P < 0.01).

CONCLUSION

Superficial blood flow in the superior labrum of the shoulder with rotator cuff tear was measured using laser Doppler flowmetry. The blood flow in type 1 SLAP lesions was lower than that in the normal labrum.

Prevalence of the rotator cuff tear increases with weakness in hemiplegic shoulder

Objective

To investigate the relationship between the rotator cuff tear (RCT) and the muscle strength in hemiplegic side, and the effects of paralysis on the affected shoulders in hemiplegic patients.

Methods

A cross-sectional observational study performed in a university hospital was presented. The study enrolled 55 participants with hemiplegia of diverse degree of motor paresis, excluding those with bilateral lesions, history of major trauma or other co-existing musculoskeletal disorders of the shoulder. The main outcome measurements were muscle strength of the affected upper extremity (based on Medical Research Council scale), RCTs of the bilateral shoulders (by ultrasonography), and presence of shoulder pain, subluxation of the glenohumeral joint, passive range of motions, and subacromial spurs.

Results

Comparing each side of the shoulders, the prevalence of shoulder pain and supraspinatus muscle tear was higher (p<0.0001, p=0.007), and the range of motion was restricted (p<0.0001, p<0.0001, p<0.0001, p<0.0001) in the affected side. There was a significant trend toward higher prevalence of RCT and shoulder subluxation in the weaker shoulder (p=0.019, p<0.0001). In a multivariate analysis, Manual Muscle Test grade of less than three was an independent risk factor for RCT (p=0.025).

Conclusion

RCT in hemiplegia had a linear trend with muscle weakness in the affected side and the degree of weakness was an independent risk factor for the occurrence of RCT. In addition, shoulder pain, limitation of range of motions, and RCT were more frequent on the hemiplegic side of the shoulders. It is the first study to reveal a linear trend between RCT and upper extremity weakness and will provide physicians an insight to the management of RCTs in hemiplegic patients.

Physical tests for shoulder impingements and local lesions of bursa, tendon or labrum that may accompany impingement

BACKGROUND

Impingement is a common cause of shoulder pain. Impingement mechanisms may occur subacromially (under the coraco-acromial arch) or internally (within the shoulder joint), and a number of secondary pathologies may be associated. These include subacromial-subdeltoid bursitis (inflammation of the subacromial portion of the bursa, the subdeltoid portion, or both), tendinopathy or tears affecting the rotator cuff or the long head of biceps tendon, and glenoid labral damage. Accurate diagnosis based on physical tests would facilitate early optimisation of the clinical management approach. Most people with shoulder pain are diagnosed and managed in the primary care setting.

OBJECTIVES

To evaluate the diagnostic accuracy of physical tests for shoulder impingements (subacromial or internal) or local lesions of bursa, rotator cuff or labrum that may accompany impingement, in people whose symptoms and/or history suggest any of these disorders.

SEARCH METHODS

We searched electronic databases for primary studies in two stages. In the first stage, we searched MEDLINE, EMBASE, CINAHL, AMED and DARE (all from inception to November 2005). In the second stage, we searched MEDLINE, EMBASE and AMED (2005 to 15 February 2010). Searches were delimited to articles written in English.

SELECTION CRITERIA

We considered for inclusion diagnostic test accuracy studies that directly compared the accuracy of one or more physical index tests for shoulder impingement against a reference test in any clinical setting. We considered diagnostic test accuracy studies with cross-sectional or cohort designs (retrospective or prospective), case-control studies and randomised controlled trials.

DATA COLLECTION AND ANALYSIS

Two pairs of review authors independently performed study selection, assessed the study quality using QUADAS, and extracted data onto a purpose-designed form, noting patient characteristics (including care setting), study design, index tests and reference standard, and the diagnostic 2 x 2 table. We presented information on sensitivities and specificities with 95% confidence intervals (95% CI) for the index tests. Meta-analysis was not performed.

MAIN RESULTS

We included 33 studies involving 4002 shoulders in 3852 patients. Although 28 studies were prospective, study quality was still generally poor. Mainly reflecting the use of surgery as a reference test in most studies, all but two studies were judged as not meeting the criteria for having a representative spectrum of patients. However, even these two studies only partly recruited from primary care.The target conditions assessed in the 33 studies were grouped under five main categories: subacromial or internal impingement, rotator cuff tendinopathy or tears, long head of biceps tendinopathy or tears, glenoid labral lesions and multiple undifferentiated target conditions. The majority of studies used arthroscopic surgery as the reference standard. Eight studies utilised reference standards which were potentially applicable to primary care (local anaesthesia, one study; ultrasound, three studies) or the hospital outpatient setting (magnetic resonance imaging, four studies). One study used a variety of reference standards, some applicable to primary care or the hospital outpatient setting. In two of these studies the reference standard used was acceptable for identifying the target condition, but in six it was only partially so. The studies evaluated numerous standard, modified, or combination index tests and 14 novel index tests. There were 170 target condition/index test combinations, but only six instances of any index test being performed and interpreted similarly in two studies. Only two studies of a modified empty can test for full thickness tear of the rotator cuff, and two studies of a modified anterior slide test for type II superior labrum anterior to posterior (SLAP) lesions, were clinically homogenous. Due to the limited number of studies, meta-analyses were considered inappropriate. Sensitivity and specificity estimates from each study are presented on forest plots for the 170 target condition/index test combinations grouped according to target condition.

AUTHORS' CONCLUSIONS

There is insufficient evidence upon which to base selection of physical tests for shoulder impingements, and local lesions of bursa, tendon or labrum that may accompany impingement, in primary care. The large body of literature revealed extreme diversity in the performance and interpretation of tests, which hinders synthesis of the evidence and/or clinical applicability.

Rotator cuff tears in overhead athletes

The rotator cuff is under significant stress during overhead athletics, which can predictably lead to a certain spectrum of rotator cuff injuries in this population. Although the cause is often multifactorial; tensile overload, outlet impingement, and internal impingement are common causes of cuff pathologic conditions in this group. Identification of symptomatic rotator cuff disease can be challenging in the overhead athlete because abnormalities of the rotator cuff are common in asymptomatic throwers and rotator cuff pathologic conditions often occur in conjunction with other injuries. Although nonoperative options should be exhausted, surgical treatment is typically necessary for any rotator cuff tear for which conservative treatment fails. Tear thickness has been classically used to determine the surgical approach, with tears involving less than 50% of the tendon thickness treated with debridement and more substantial tears treated with formal repair. However, some authors and some noted surgeons with experience in managing this patient population have more recently advocated a higher threshold of tendon involvement before considering formal repair. Multiple repair options have been described, but few reports have focused specifically on the outcomes of rotator cuff surgery in overhead athletes. The limited available data do lead, however, to a few reasonable conclusions. Surgical results typically correlate with tear severity. Partial-thickness tears treated with arthroscopic debridement and management of concomitant pathologic conditions seem to have fairly good outcomes in the literature, with most athletes able to return to activity at their preinjury level. Full-thickness tears, however, have fared much more poorly in the overhead athlete, with largely dismal outcomes after surgical repair. What is abundantly clear is that further refinement of surgical options is necessary to improve patient outcomes after rotator cuff repair in this particularly challenging patient population and to allow more consistent return to sports. Identification of symptomatic rotator cuff disease can be challenging in the overhead athlete because abnormalities of the rotator cuff are common in asymptomatic throwers and rotator cuff pathologic conditions often occur in conjunction with other injuries. Although nonoperative options should be exhausted, surgical treatment is typically necessary for any rotator cuff tear for which conservative treatment fails. Tear thickness has been classically used to determine the surgical approach, with tears involving less than 50% of the tendon thickness treated with debridement and more substantial tears treated with formal repair. However, some authors and some noted surgeons with experience in managing this patient population have more recently advocated a higher threshold of tendon involvement before considering formal repair. Multiple repair options have been described, but few reports have focused specifically on the outcomes of rotator cuff surgery in overhead athletes. The limited available data do lead, however, to a few reasonable conclusions. Surgical results typically correlate with tear severity. Partial-thickness tears treated with arthroscopic debridement and management of concomitant pathologic conditions seem to have fairly good outcomes in the literature, with most athletes able to return to activity at their preinjury level. Full-thickness tears, however, have fared much more poorly in the overhead athlete, with largely dismal outcomes after surgical repair. What is abundantly clear is that further refinement of surgical options is necessary to improve patient outcomes after rotator cuff repair in this particularly challenging patient population and to allow more consistent return to sports.

The relationship between anterior glenohumeral laxity and proprioception in collegiate baseball players

OBJECTIVE

To determine if a relationship exists between anterior glenohumeral (GH) laxity and proprioception.

DESIGN

Cross-sectional study.

SETTING

University biomechanics laboratory.

PARTICIPANTS

Thirty asymptomatic collegiate baseball players.

INDEPENDENT VARIABLES

Anterior GH laxity.

MAIN OUTCOME MEASURES

Proprioception (active joint position sense) at positions of 75 degrees of external rotation, 30 degrees of external rotation, and 30 degrees of internal rotation were measured using an isokinetic dynomometer. Anterior GH laxity was measured using an instrumented arthrometer.

RESULTS

Linear regression analyses showed that there were no relationships between anterior GH laxity and active joint position sense at 30 degrees of GH internal rotation and 30 degrees of GH external rotation (r = 0.21, P = 0.13). However, there was a moderate positive relationship between anterior GH laxity and joint position sense at 75 degrees of shoulder external rotation (r = 0.56, P = 0.001).

CONCLUSIONS

These results suggest that shoulder proprioception in 75 degrees of external rotation decreases as anterior GH laxity increases. These results may prove beneficial in the prevention, evaluation, and treatment of various shoulder injuries associated with GH laxity.

Partial-thickness articular surface rotator cuff tears in patients over the age of 35: Etiology and intra-articular associations

Purpose:

Partial-thickness articular-sided rotator cuff tears have a multifactorial etiology and are associated with degeneration of the tendon. They are often described as an injury of the young athlete, although they are also found in the older population. The aim of this study was to investigate the frequency and associations of partial-thickness articular-sided tears in patients over the age of 35 years.

Design:

Retrospective

Materials and Methods:

A retrospective study of all arthroscopic procedures for rotator cuff pathology in patients over the age of 35 years over a 2-year period by a single surgeon was performed. The included patients were divided into two groups based on the arthroscopic findings: those with a partial-thickness articular-sided rotator cuff tear and those with pure tendinopathy. The groups were then compared to identify the associated pathology with the rotator cuff lesions. 2×2 contingency table analysis and unpaired Student's t-test were used for statistical analysis.

Results:

One hundred patients were included in the study of whom 62 had a partial articular-sided tear. Those with a partial articular-sided tear were older (P=0.0001), were more commonly associated with a documented injury (P=0.03), and more commonly had biceps degeneration (P=0.001) and synovitis (P=0.02) within the joint.

Conclusion:

Partial-thickness articular-sided tears are a common occurrence in patients requiring arthroscopic surgery for rotator cuff pathology over the age of 35 years. This probably reflects an injury in an already degenerate cuff. This would support the theory of intrinsic degeneration of the tendon in this age group and probably represent a different etiology to those seen in the young athletes.

Level of Evidence:

Level 3

Effect of scapular orientation on shoulder internal impingement in a cadaveric model of the cocking phase of throwing

BACKGROUND

Although deviations in scapular orientation are thought to predispose to shoulder injuries in throwing athletes, the biomechanical mechanism underlying shoulder injuries in throwing athletes with an altered scapular orientation remains unclear.

METHODS

Seven fresh-frozen cadaveric shoulders were evaluated at 90° of abduction, with the humerus externally rotated from 90° to the maximum angle, to simulate the late cocking phase of the throwing motion. Loads were applied to the deltoid, pectoralis major, latissimus dorsi, teres major, and all rotator cuff muscles. Contact pressure in the glenohumeral joint was measured with use of a pressure sensor. The area of internal impingement was calculated on the basis of three-dimensional position data. Glenohumeral contact pressure and the area of impingement were compared between 20°, 30°, and 40° of internal scapular rotation; between 20°, 30°, and 40° of upward scapular rotation; and between 0° and 10° of anterior scapular tilt. Data were analyzed with use of repeated-measures analysis of variance with the Tukey post hoc test.

RESULTS

Contact pressure was at its maximum in the posterior aspect of the glenohumeral joint. The glenohumeral contact pressure and internal impingement area increased with increasing internal scapular rotation. The glenohumeral contact pressure at 40° of internal scapular rotation was significantly (43.4%) greater than that at 20° of internal scapular rotation (p < 0.01), and the impingement area at 40° of internal scapular rotation was significantly (43.1%) greater than that at 20° of internal scapular rotation (p < 0.05). Decreasing upward scapular rotation resulted in an increase in internal impingement area. The internal impingement area at 40° of upward motion was 38.1% less than that at 20° of upward rotation (p < 0.001) and 28.9% less than that at 30° of upward rotation (p < 0.01).

CONCLUSIONS

Increasing internal scapular rotation and decreasing upward scapular rotation significantly increase glenohumeral contact pressure and the area of impingement of the rotator cuff tendon between the greater tuberosity and glenoid during simulated throwing motion.

Percutaneous SLAP lesion repair technique is an effective alternative to portal of Wilmington

Athletes with superior labral tear from anterior to posterior (SLAP) lesions place large demands on their rotator cuff and often have partial articular-sided rotator cuff tears as part of an internal impingement process. A percutaneous technique that facilitates SLAP repair may decrease the rotator cuff morbidity associated with establishment of the standard Wilmington portal. The current study reports the clinical outcome of patients with SLAP lesions treated with a percutaneous repair technique. Twenty-two patients with SLAP lesions underwent percutaneous repair. Mean patient age was 26.9 years. Standard posterior viewing and anterior working portals were used. Anchor placement and suture passing were performed with a 3-mm percutaneous and transtendinous approach to the superior labrum. Knot tying was performed via the standard anterior working portal. Clinical outcomes were assessed with validated shoulder evaluation instruments. Mean follow-up was 31.1 months (±6.6 months). Improvement of shoulder evaluation scores from pre- to postoperative were as follows: American Shoulder and Elbow Surgeons score improved from 49.5 to 83.6, visual analog scale improved from 5.4 to 1.5, and Simple Shoulder Score improved from 6.4 to 11.0. All were significant improvements (P<.05). There was no significant difference in functional scores between Type II lesions versus combined lesions, or between patients with or without a concurrent low-grade rotator cuff tear. Ninety percent of athletes were able to return to sport at pre-injury level of function. Percutaneously-assisted arthroscopic SLAP lesion repair may minimize surgical morbidity to the rotator cuff and provides excellent results.

Management of the throwing shoulder: cuff, labrum and internal impingement

Repetitive throwing or other overhead activity places great stress on the shoulder. As a result, the shoulder is a common site of injury in athletes. Addressing throwing-related injuries requires an understanding of throwing biomechanics and pathology. Nonoperative treatment is directed at restoring strength, flexibility, and neuromuscular control to the entire kinetic chain. Surgery is indicated when nonoperative treatment fails, and is directed at correcting labral, capsular, and rotator cuff pathology.

Effect of rotator cuff muscle imbalance on forceful internal impingement and peel-back of the superior labrum: a cadaveric study

BACKGROUND

Throwing athletes with shoulder pain have been shown to have decreased rotator cuff muscle strength. Shoulder internal impingement and labral peel-back mechanism, as may occur during the late cocking phase of throwing motion, are thought to cause rotator cuff injury and type II superior labrum anterior and posterior lesions. Therefore, the objective of this study was to assess the effect of rotator cuff muscle force on internal impingement and the peel-back of the superior labrum by quantifying maximum external rotation, glenohumeral contact pressure, and position of the cuff insertion relative to the glenoid.

HYPOTHESIS

A change in rotator cuff muscle force will lead to increased external rotation, glenohumeral contact pressure, and overlap of the cuff insertion relative to the glenoid.

STUDY DESIGN

Controlled laboratory study.

METHODS

Eight fresh-frozen cadaveric shoulders were tested at the simulated late cocking position. Glenohumeral contact pressure, location of the cuff insertion relative to the glenoid, and maximum humeral external rotation angle were measured. The forces of the supraspinatus, subscapularis, and infraspinatus muscles were determined based on published clinical electromyographic data. To assess the effect of cuff muscle imbalance, each muscle force was varied. Horizontal abduction positions of 20 degrees , 30 degrees , and 40 degrees with respect to the scapular plane were tested.

RESULTS

Decreased subscapularis strength resulted in a significant increase in maximum external rotation (P <.001) and increased glenohumeral contact pressure (P <.01). The cuff insertion overlapped the edge of the glenoid at 30 degrees and 40 degrees of horizontal abduction for all muscle loading conditions.

CONCLUSION

Decreased subscapularis muscle strength in the position simulating the late cocking phase of throwing motion results in increased maximum external rotation and also increased glenohumeral contact pressure.

CLINICAL RELEVANCE

Athletes with decreased subscapularis muscle strength, such as fatigue with repetitive throwing, may be more susceptible to rotator cuff tears and type II superior labrum anterior and posterior lesions. Subscapularis muscle strengthening exercises may be beneficial for preventing these injuries.

Fluoroscopic assessment of rotator cuff fatigue on glenohumeral arthrokinematics in shoulder impingement syndrome

BACKGROUND

Although prior researchers have assessed glenohumeral arthrokinematics using isometrically held arm postures with standard radiographs, dynamic assessment of glenohumeral arthrokinematics has been limited. This study utilized video fluoroscopy to analyze superior inferior glenohumeral migration during dynamic arm elevation in individuals with outlet impingement syndrome, before and after fatigue of the rotator cuff.

HYPOTHESIS

Prior to the study, it was hypothesized that during the pre-fatigue state, glenohumeral migration would be in the superior direction, and that post-fatigue there would be a significant increase in superior migration.

MATERIALS AND METHODS

Digital fluoroscopic videos (30 Hz) were used to analyze 20 male volunteers (27.7 +/- 7.3 years) with right shoulder outlet impingement syndrome during concentric elevation of the arm in the plane of the scapula, both before and after fatigue of the rotator cuff.

RESULTS

During concentric arm elevation, there was superior glenohumeral migration (1.6 mm) between 45 degrees and 90 degrees of arm elevation, regardless of fatigue-state (P = .02). After rotator cuff fatigue, the humeral head was positioned more superiorly on the glenoid fossa (P = .03). The position of the humeral head was 0.4 mm more superior than that reported in a previous study on healthy individuals.

CONCLUSION

These results support prior findings that suggest superior glenohumeral migration during arm elevation is influenced both by shoulder pathology and the state of fatigue of the rotator cuff musculature. Future research should examine the effects of physical therapy and surgical interventions on glenohumeral arthrokinematics to better determine the most effective treatment methods for outlet impingement.

LEVEL OF EVIDENCE

Controlled laboratory study.

Internal impingement of the shoulder

Internal impingement of the shoulder is a pathologic condition characterized by excessive or repetitive contact of the greater tuberosity of the humeral head with the posterosuperior aspect of the glenoid when the arm is abducted and externally rotated. This arm positioning leads to rotator cuff and glenoid labrum impingement by the bony structures of the glenohumeral joint. Although some degree of contact between these structures occurs under normal conditions, to date most of the orthopaedic literature has focused on internal impingement as a disease state that affects overhead athletes and is characterized by the development of articular-sided rotator cuff tears and posterosuperior labral lesions. The precise cause of these impingement lesions remains unclear. However, it is believed that varying degrees of glenohumeral instability, posterior capsular contracture, and scapular dyskinesis may play a role in the development of symptomatic internal impingement. The purpose of this article is to review the pathomechanics, clinical complaints, physical examination findings, and imaging findings that are associated with internal impingement. The results of treatment will be reviewed, and a diagnostic and therapeutic algorithm for the management of internal impingement is presented.

Shoulder injuries in the throwing athlete

Pathologic conditions in the shoulder of a throwing athlete frequently represent a breakdown of multiple elements of the shoulder restraint system, both static and dynamic, and also a breakdown in the kinetic chain. Physical therapy and rehabilitation should be, with only a few exceptions, the primary treatment for throwing athletes before operative treatment is considered. Articular-sided partial rotator cuff tears and superior labral tears are common in throwing athletes. Operative treatment can be successful when nonoperative measures have failed. Throwing athletes who have a glenohumeral internal rotation deficit have a good response, in most cases, to stretching of the posteroinferior aspect of the capsule.

MRI of impingement syndromes of the shoulder

The diagnosis of shoulder impingement is primarily a clinical one. Imaging has a role in assisting clinicians in developing a treatment strategy by identifying and characterizing the cause of shoulder impingement. In this review, the relevant anatomy, cause/pathomechanics, clinical features, and magnetic resonance imaging (MRI) findings of the different types of impingement syndromes are presented.

Spectrum of shoulder injuries in the baseball pitcher

This review describes a range of shoulder injuries experienced by baseball pitchers. It is estimated that more than 57% of pitchers suffer some form of shoulder injury during a playing season. Knowledge of the overhead throwing cycle is crucial for our understanding of these shoulder injuries. Baseball pitchers are prone to rotator cuff tears from tensile overload and impingement. Glenoid labrum degeneration or tears are also common, due to overuse syndrome (micro-instability), internal impingement and microtrauma. An understanding of the lesions involved in overhead throwing is crucial in baseball pitchers, as long-term disability can result from these injuries, sometimes with severe financial consequences to the player.

Variations in the superior capsuloligamentous complex and description of a new ligament

Although the rotator cuff interval and the adjacent ligaments are gaining interest because of their importance for glenohumeral instability and adhesive capsulitis, there seems to be some confusion about their anatomy. This study reinvestigates the superior capsular structures in 110 cadaveric shoulders by a combination of arthroscopy, dissection, histology, and functional analysis. The structure of the superior capsule was found to be more complex than suspected until now. The coracohumeral, coracoglenoid, and superior glenohumeral ligaments joined with a circular transverse band to form the anterior limb of a suspension sling. This was 9 to 26 mm wide at its midportion. In 90% of the specimens, there also was a posterior limb composed of a broad fibrous sheet, 6 to 26 mm wide at its midportion. This hitherto unrecognized posterosuperior glenohumeral ligament joined posterolaterally with the circular transverse band. Four types of configuration for the superior complex could be identified. The suspension sling formed by the superior complex functions in the same way as the hammock formed by the inferior glenohumeral ligament complex. The posterior limb seems to restrict internal rotation, like the anterior limb restricts external rotation. The expanded knowledge of the superior capsular complex increases the understanding of the pathology involved in anterosuperior and posterosuperior impingement, as well as articular-sided rotator cuff tears. It also has clinical implications for rotator cuff interval and biceps pulley lesions, because these areas are bordered by the anterior limb of the superior complex, as well as for adhesive capsulitis, where we can now understand why internal rotation is limited and why the release needs to be extended posterosuperiorly.

Shoulder MR arthrography of the posterior labrocapsular complex in overhead throwers with pathologic internal impingement and internal rotation deficit

PURPOSE

To determine if overhead-throwing athletes with internal impingement pain and internal rotation deficit have thickening of the posterior inferior labrocapsular complex on MR arthrogram images.

MATERIALS AND METHODS

This study was approved and a waiver of consent granted by our institutional review board. Twenty-six overhead-throwing athletes with internal impingement pain and internal rotation deficit, and 26 controls who had undergone MR arthrograms, were retrospectively examined. The MR studies were combined and read in a blind fashion. On an axial image through the posteroinferior glenoid rim, the readers measured the labral length, capsule-labrum length, and the posterior recess angle. A t-test was used to determine statistical significance.

RESULTS

The mean labral length was 4.9 mm [standard deviation (SD) 1.4 mm] for the controls, and 6.4 mm (SD 1.6 mm) for the athletes (P = 0.001). The mean capsule-labrum length was 5.4 mm (SD 2.1 mm) for the controls, and 8.8 mm (SD 2.9 mm) for the athletes (P < 0.001). The mean posterior recess angle measured 65 degrees (SD 27 degrees) for the controls and 94 degrees (SD 38 degrees) for the athletes (P = 0.002).

CONCLUSIONS

Overhead-throwing athletes with internal impingement pain and internal rotation deficit tend to have a thicker labrum and a shallower capsular recess in the posterior inferior shoulder joint than do non-overhead-throwing athletes. In many, the posteroinferior capsule is also thickened. These MR findings should alert the radiologist to closely inspect the posterior cuff and posterosuperior labrum for the tears associated with internal impingement.

Shoulder adaptive changes in youth baseball players

Shoulder adaptive changes in response to overhand throwing have been observed in adults, but the age of onset and progression of these adaptive changes have not been established. Two-hundred ninety-eight youth baseball players (8- to 28-year-olds) were studied to determine whether shoulder range of motion and laxity differences between the dominant and non-dominant shoulders exist between different age groups. The subjects were separated into 3 different age groups of 100 8- to 12-year-olds (Group 1), 100 13- to-14 year-olds (Group 2), and 98 15- to 28-year-olds (Group 3). For dominant shoulder external rotation with the humerus in abduction, all groups were significantly different from each other, with Group 2 having the greatest range and Group 1 having the smallest range (P < .05). When comparing dominant shoulder internal rotation in abduction among different groups, Group 3 and Group 2 motion was significantly less than that for Group 1 (P < .05.) When comparing dominant to non-dominant shoulder motion within each group, a significant increase in dominant shoulder external rotation in abduction was found in all 3 age groups (P < .05). Comparison of the differences in external rotation in abduction between the dominant and non-dominant shoulders demonstrated an increase with increasing age, Group 1 (1.5 +/- 6.8 degrees), Group 2 (9.6 +/- 15.3 degrees), and Group 3 (15.0 +/- 11.2 degrees; P < .05). Comparison of differences in internal rotation in abduction between dominant and non-dominant shoulders demonstrated a decrease with increasing age, Group 1 (4.6 +/- 8.2 degrees), Group 2 (8.4 +/- 14.5 degrees), and Group 3 (15.5 +/- 11.7 degrees; P < .05). For shoulder laxity, Groups 2 and 3 had significantly more inferior shoulder laxity when compared to Group 1. In summary, our results indicate that shoulder range of motion and laxity of youth baseball players are caused by adaptive changes that manifest during adolescence.

MRI of internal impingement of the shoulder

OBJECTIVE

Internal impingement is a condition that occurs in athletes in which the shoulder is put in extreme abduction and external rotation during overhead movements. During this motion, the posterior fibers of the supraspinatus tendon, anterior fibers of the infraspinatus tendon, or both can get impinged between the humeral head and the posterior glenoid. The purpose of this study was to evaluate the ability of MRI to show the findings of internal impingement of the shoulder.

CONCLUSION

As opposed to our six patients with clinically and surgically diagnosed internal impingement, the control patients had isolated pathology in the rotator cuff, labrum, or humeral head. We found that the constellation of findings of undersurface tears of the supraspinatus or infraspinatus tendon and cystic changes in the posterior aspect of the humeral head associated with posterosuperior labral pathology is a consistent finding diagnostic of internal impingement.

Subacromial impingement syndrome: the role of posture and muscle imbalance

Changes in upper body posture, colloquially termed forward head posture (FHP), are considered to be an etiologic factor in the pathogenesis of subacromial impingement syndrome (SIS). The literature suggests that postural deviations associated with FHP follow distinct patterns involving an increase in the thoracic kyphosis angle and a downwardly rotated, anteriorly tilted, and protracted scapula, which in turn leads to increased compression in the subacromial space. These postural changes are thought to occur concurrently with an imbalance of the musculature, and conservative rehabilitation commonly involves addressing both posture and muscle imbalance. There is a paucity of evidence supporting the hypothesis that posture and muscle imbalance are involved in the etiology of SIS. The purpose of this study was to investigate whether FHP was associated with an increased thoracic kyphosis, an altered position of the scapula; and a reduction in glenohumeral elevation range. Selected sagittal and frontal plane postural measurements were made in 60 asymptomatic subjects and 60 subjects with SIS. The findings suggested that upper body posture does not follow the set patterns described in the literature, and further research is required to determine whether upper body and scapular posture and muscle imbalance are involved in the pathogenesis of SIS.

Subacromial impingement syndrome: the effect of changing posture on shoulder range of movement

STUDY DESIGN

Random allocation of subjects into a placebo-controlled, crossover study.

OBJECTIVES

To investigate the effect of changing thoracic and scapular posture on shoulder flexion and scapular plane abduction range of motion in asymptomatic subjects, and in subjects with subacromial impingement syndrome.

BACKGROUND

Changes in upper body posture and concomitant imbalance of the muscle system have been proposed as one of the etiological mechanisms leading to subacromial impingement syndrome. Although clinicians commonly assess posture and devise rehabilitation programs to correct posture, there is little evidence to support this practice.

METHODS AND MATERIALS

Selected postural, range of movement, and pain measurements were investigated in 60 asymptomatic subjects and 60 subjects with subacromial impingement syndrome, prior to and following thoracic and scapular taping intended to change their posture.

RESULTS

Changing posture had an effect on all components of posture measured (P<.001) and these changes were associated with a significant increase (P<.001) in the range of motion in shoulder flexion and abduction in the plane of the scapula. Changing posture was not found to have a significant effect on the intensity of pain experienced by the symptomatic subjects, although the point in the range of shoulder elevation at which they experienced their pain was significantly higher (P<.001).

CONCLUSIONS

The findings of this investigation suggest that changing 1 or more of the components of posture may have a positive effect on shoulder range of movement and the point at which pain is experienced.

Rotator Cuff Impingement

OBJECTIVE

To present a case of shoulder impingement syndrome managed with a conservative multimodal treatment approach.

CLINICAL FEATURES

A patient had anterior shoulder pain and a diffuse ache in the right upper arm, with tenderness in the shoulder region on palpation. Shoulder range of motion was limited with pain and catching, coupled with limited and painful cervical motion. After physical and orthopedic examination, a clinical diagnosis of shoulder impingement syndrome was made.

INTERVENTIONS AND OUTCOME

The patient underwent a multimodal treatment protocol including soft tissue therapy, phonophoresis, diversified manipulation; and rotator cuff and shoulder girdle muscle exercises. Outcomes included pain measurement; range of motion of the shoulder, and return to normal daily, work, and sporting activities. At the end of the treatment protocol the patient was symptom free with all outcome measures normal. The patient was followed up at 4 and 12 weeks and continued to be symptom free with full range of motion and complete return to normal daily and pre-treatment activities.

CONCLUSION

This case report shows the potential benefit of a multimodal chiropractic protocol in resolving symptoms associated with shoulder impingement syndrome.

Ergonomic Pain--Part 2: Differential Diagnosis and Management Considerations

Work-related musculoskeletal disorders (MSDs) can produce ergonomic pain in several different regions of the body, including the shoulder, elbow, wrist and hand, lumbar spine, knee, and ankle/foot. Each family of disorders is distinctive in presentation and requires diagnosis-specific interventions. Because of the complex nature of these disorders, management approaches may not always eliminate symptoms and or completely restore patient function to a level found prior to symptom onset. As a consequence, ergonomic measures should be implemented to reduce the overload on tissue and contribute to patient recovery. However, functional limits may persist and the clinician must make further decisions regarding a person's functional status in the chronic stages of the patient's care.