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PURPOSE Glenohumeral instability accounts for 23% of all shoulder injuries among collegiate athletes. The apprehension position-combined shoulder abduction and external rotation-commonly reproduces symptoms in athletes with instability. Rehabilitation aims to increase glenohumeral stability by strengthening functional positions. However, it is unclear how much glenohumeral stability increases with muscle contraction in the apprehension position. The purpose of this study was to determine whether the ability to increase translational glenohumeral stiffness, a quantitative measure of glenohumeral stability, with muscle contraction is reduced in the apprehension position. METHODS Seventeen asymptomatic adults participated. A precision-instrumented robotic system applied pseudorandom, anterior-posterior displacements to translate the humeral head within the glenoid fossa and measured the resultant forces as participants produced isometric shoulder torques. Measurements were made in neutral abduction (90° abduction/0° external rotation) and apprehension (90° abduction/90° external rotation) positions. Glenohumeral stiffness was estimated from the relationship between applied displacements and resultant forces. The ability to increase glenohumeral stiffness with increasing torque magnitude was compared between positions. RESULTS On average, participants increased glenohumeral stiffness from passive levels by 91% in the neutral abduction position and only 64% in the apprehension position while producing 10% of maximum torque production. The biggest decrease in the ability to modulate glenohumeral stiffness in the apprehension position was observed for torques generated in abduction (49% lower, P < 0.001) and horizontal abduction (25% lower, P < 0.001). CONCLUSION Our results demonstrate that individuals are less able to increase glenohumeral stiffness with muscle contraction in the apprehension position compared with a neutral shoulder position. These results may help explain why individuals with shoulder instability more frequently experience symptoms in the apprehension position compared with neutral shoulder positions.

Background Clinicians of many specialties within sports medicine care for athletes with shoulder instability, but successful outcomes are inconsistent. Consistency across specialties in the diagnosis of shoulder instability is critical for care of the athlete, yet the extent of divergence in its diagnosis is unknown. Hypothesis Physicians differ from rehabilitation providers in which findings they deem clinically important to differentiate shoulder instability from impingement, and in how they diagnose athlete scenarios with atraumatic shoulder instability. Study Design Cross-sectional study. Methods Physicians (orthopaedic surgeons, primary care sports medicine physicians) and rehabilitation providers (physical therapists, athletic trainers) were asked via an online survey to rate clinical factors used to diagnose shoulder instability. Clinicians were also asked to diagnose two athlete scenarios with concurrent clinical findings of atraumatic shoulder instability and impingement, differentiated by the absence or presence of a positive sulcus sign. Results Responses were recorded from 888 clinicians. Orthopaedic surgeons (N=170) and primary care sports medicine physicians (N=108) ranked physical examination factors as more important for the diagnosis of shoulder instability than patient history factors, whereas physical therapists (N=379) and athletic trainers (N=231) preferred patient history factors. Orthopaedic surgeons differed from physical therapists and athletic trainers in their clinical diagnoses for both scenarios (P≤0.001). Conclusion A lack of consistency exists among sports medicine clinicians in recognizing which clinical factors are important when used to diagnose shoulder instability and in diagnoses given with concurrent findings of impingement. Level of Evidence Level 3.

Subacromial pain syndrome (SPS) accounts for as much as 44% of shoulder pain encountered by physical therapists. Thoracic spine thrust manipulation (TSTM) is effective in the short term for improving pain and function in individuals with SPS, but its mechanisms remain elusive. Furthermore, it is unknown whether individuals with SPS respond differently based on the TSTM technique received.To compare the immediate effects of a supine TSTM, seated TSTM, and sham manipulation on the primary outcomes of self-reported pain, function, and satisfaction and secondary biomechanical impairments examined in individuals with SPS.Participants in this randomized clinical trial were randomized to receive a seated TSTM (n = 20), supine TSTM (n = 20), or sham manipulation (n = 20). The primary outcomes of self-reported pain, function, and satisfaction were measured via the Penn Shoulder Score. Secondary outcomes were changes in scapular upward rotation and posterior tilt; peak force generated in tests for the middle trapezius, lower trapezius, and serratus anterior; and pectoralis minor muscle length. Impairment measures were immediately reassessed, and the Penn Shoulder Score was reassessed after 48 hours.There were no significant between-group differences in immediate or short-term follow-up outcomes.Two TSTM techniques resulted in no differences in pain, satisfaction, and function when compared to a sham manipulation. Thoracic spine thrust manipulation did not have an immediate effect on the scapular impairments examined.Therapy, level 1.

BACKGROUND: Fatty infiltration of the rotator cuff evaluated with CT has been associated with asymmetric glenoid wear and humeral head subluxation in patients with glenohumeral arthritis. The relationship between rotator cuff pathologic findings and abnormal glenoid wear plays an important role in determining the optimal surgical management of advanced glenohumeral osteoarthritis. Compared with CT, MRI has increased sensitivity for identifying rotator cuff conditions; therefore, prior studies using CT may have underestimated the association between fatty infiltration of the rotator cuff and abnormal glenoid wear. QUESTIONS/PURPOSES: (1) Compared with Type A glenoids, which muscles in which Walch subtypes have a greater degree of fatty infiltration using Goutallier scores? (2) What glenoid type is associated with greater imbalance in fatty infiltration, as measured by comparing Goutallier scores between the posterior and anterior rotator cuff muscles? (3) What is the correlation between glenoid version and fatty infiltration of the rotator cuff muscles? (4) Comparing Type B2 and B3 glenoids with Type A glenoids, after accounting for age and sex, is there an increase in fatty infiltration of the infraspinatus muscle? METHODS: A total of 129 shoulders from 129 patients undergoing anatomic total shoulder arthroplasty to treat primary glenohumeral osteoarthritis were retrospectively reviewed. Patients had an average age of 66.4 ± 9.3 years and an average BMI of 30.6 ± 6.7 kg/m(2), and 53% (69 of 129) were men. All patients underwent MRI within 12 months before total shoulder arthroplasty to assess glenoid morphology and rotator cuff pathologic findings. Three reviewers assessed the images, and glenoid morphology was assigned using the modified Walch classification system (Types A1, A2, B1, B2, B3, C, and D). Fatty infiltration of the rotator cuff was classified using Goutallier scores. The examiners demonstrated moderate-to-good reliability using these classification systems; the Walch classification system had interrater reliability kappa coefficients (κ) from 0.54 to 0.69 and intrarater reliability κ from 0.60 to 0.64. Goutallier scores using the simplified classification system had interrater reliability κ from 0.64 to 0.68 and intrarater reliability κ from 0.64 to 0.79. Thirty-six percent (46 of 129) of the shoulders had posterior wear patterns (18% [23] were Type B2 glenoids; 18% [23] were Type B3 glenoids). The average Goutallier scores for each rotator cuff muscle were determined, and the amount of fatty infiltration was compared between the various Walch subtypes using independent t-tests. Axial-plane imbalance in fatty infiltration of the rotator cuff was assessed by determining the difference in the average fatty infiltration of the posterior rotator cuff muscles (infraspinatus and teres minor) and anterior rotator cuff muscles (subscapularis) and comparing the differences among the Walch subtypes using independent t-tests. The association between glenoid version and fatty infiltration was assessed using Pearson correlations. Finally, a multivariate logistic regression model was used to assess fatty infiltration of the rotator cuff among the various Walch subtypes while accounting for patient age and sex. RESULTS: Compared with Type A1 glenoids, Type B2 and B3 glenoids had an increased amount of fatty infiltration of the infraspinatus (1.6 ± 0.7 versus 0.7 ± 0.4; mean difference 0.9 [95% CI 0.7-1.2]; p < 0.001 and 1.8 ± 0.4 versus 0.7 ± 0.4; mean difference 1.1 [95% CI 0.9-1.4]; p < 0.001, respectively) and teres minor (1.3 ± 0.7 versus 0.6 ± 0.5; mean difference 0.7 [95% CI 0.4-1.0]; p < 0.001 and 1.6 ± 0.6 versus 0.6 ± 0.5; mean difference 1.0 [95% CI 0.7-1.2]; p < 0.001, respectively). There was greater imbalance in fatty infiltration between the posterior and anterior rotator cuff muscles for Type B2 (0.5 ± 0.3) and B3 (0.6 ± 0.5) glenoids than for Type A1 (0.1 ± 0.3) and A2 (0.1 ± 0.6) glenoids (p < 0.001). Only the infraspinatus’s fatty infiltration was strongly correlated with glenoid version (r = 0.64; p < 0.001), while fatty infiltration of the other muscles only correlated weakly or moderately. After accounting for age and sex, fatty infiltration in the infraspinatus was associated with Type B2 (OR 66.1 [95% CI 7.6-577.9]; p < 0.001) and Type B3 glenoids (OR 59.5 [95% CI 5.4-661.3]; p < 0.001) compared with Type A glenoids. CONCLUSION: Compared with concentric wear, posteriorly worn glenoids had an imbalance in axial-plane rotator cuff fatty infiltration and an increased amount of fatty infiltration of the infraspinatus and teres minor compared with the subscapularis. These imbalances may contribute to the higher rates of failure after anatomic total shoulder arthroplasty in patients with posterior wear compared with those with concentric wear. Future research should be directed toward investigating the temporal relationship of these findings, as well as understanding the clinical outcomes for patients undergoing anatomic total shoulder arthroplasty who have posteriorly worn glenoids with a high degree of fatty infiltration of the posterior rotator cuff musculature. CLINICAL RELEVANCE: Providers should consider the increased likelihood of higher-grade fatty infiltration of the posterior rotator cuff in the setting of posteriorly worn glenoids, particularly when treating patients without using MRI. These patients have higher rates of failure postoperatively and may benefit from closer monitoring and altered postoperative rehabilitation protocols that target the posterior rotator cuff.

Recent evidence suggests an inhomogeneous distribution of intramuscular rotator cuff fat infiltration (FI) in a small sample of individuals with rotator cuff tears, yet clinically just a few slices at the scapular Y-view are used to evaluate FI in patients with rotator cuff tears. The purpose of this study was to determine if assessment of FI using the scapular Y-view is representative of the entire muscle in patients with full-thickness rotator cuff tears, and whether this varies by tear size.Patients (N = 25) diagnosed with full-thickness rotator cuff tear and confirmed with magnetic resonance imaging (MRI) were included. Fat-water sequences were used to objectively quantify mean FI (%) in the entire 3D muscle and the mean from 3 slices at the Y-view. Mixed-model 2 × 2 ANOVAs were used to assess for differences between methods, and if results vary by tear-size.There were no statistically significant differences between mean amount of FI of the entire 3D muscle and mean Y-view in the supraspinatus or infraspinatus muscles (p 0.05). Additionally, this did not differ across tear size groups (p 0.05).Results of this study suggest FI assessed in the Y-view is not different (mean difference 1.0%) from FI of the entire 3D muscle in patients with full-thickness rotator cuff tears. Therefore, the clinical utility of evaluating rotator cuff intramuscular fat infiltration with the Y-view is further supported in patients with full-thickness rotator cuff tears across tear sizes.

Shoulder instability has varying mechanisms of injury, direction, and severity. Classification systems based on clustering signs and symptoms have been developed to define subgroups of shoulder instability. Despite this attempt at homogeneity, multidirectional instability (MDI) suffers from the same lack of diagnostic clarity as low back pain. In this Viewpoint, the authors outline 3 key areas to address when diagnosing MDI: patient interview, medical comorbidities, and specific shoulder tests and measures. J Orthop Sports Phys Ther 2020;50(2):52-54. doi:10.2519/jospt.2020.0602.

Daily tasks rely on our ability to generate multi-dimensional shoulder torques. When function is limited, strength assessments are used to identify impairments and guide treatment. However, these assessments are often one-dimensional and limited in their sensitivity to diagnose shoulder pathology. To address these limitations, we have proposed novel metrics to quantify shoulder torque capacity in all directions. To quantify the feasible torque space of the shoulder, we measured maximal volitional shoulder torques in 32 unique directions and fit an ellipsoid model to these data. This ellipsoid model was used to quantify overall strength magnitude, strength balance, and the directions in which participants were strongest and weakest. We used these metrics to characterize three-dimensional shoulder strength in healthy adults and demonstrated their repeatability across days. Finally, using musculoskeletal simulations, we showed that our proposed metrics can distinguish between changes in muscle strength associated with aging or rotator cuff tears and quantified the influence of altered experimental conditions on this diagnostic capacity. Our results demonstrate that the proposed metrics can robustly quantify the feasible torque space of the shoulder and may provide a clinically useful description of the functional capacity of the shoulder in health and disease.

To determine which normalization method may best account for confounding individual factors, such as age or BMI, when quantifying fat infiltration on MRI in patients with rotator cuff tears, the effects of normalization using three different muscles (teres major; triceps brachii; teres minor) were compared. Thirty-seven consecutive patients diagnosed with rotator cuff pathology were included. MRI fat–water sequences were used to quantify rotator cuff intramuscular fat (%fat). Three reference muscles (teres major, triceps, teres minor) were used to derive normalized %fat. Relationships between intramuscular %fat and tear size, age, and BMI in each rotator cuff muscle, before and after normalization, were compared with Fisher transformations (α = 0.05). Normalization with teres major ameliorated confounding relationships of age and BMI on rotator cuff %fat. In contrast, normalization with triceps maintained the confounding relationships between %fat and age in supraspinatus (p = 0.03) and infraspinatus/teres minor (p = 0.028). Normalization with teres minor maintained the confounding relationship between %fat and BMI in subscapularis (p = 0.039). Normalization with teres major best-maintained relationships between tear size and infraspinatus/teres minor %fat (p = 0.021). In contrast, normalization with triceps or teres minor eliminated all significant relationships with tear size. Results of this pilot study suggest normalization to teres major using MRI-based %fat quantification methods can effectively control for individual factors, such as BMI or age, and may have utility in evaluating and monitoring rotator cuff fat infiltration attributed specifically to a tendon tear.

Background Psychosocial factors are key determinants of health and can influence patient-reported outcomes after rotator cuff tears. However, to our knowledge, a systematic review of published studies has not been conducted to determine the degree of consistency and strength of the relationship between psychosocial factors and patient-reported outcomes in this patient population. Questions/purposes (1) Are psychosocial factors associated with patient-reported measures at initial clinical presentation in patients with rotator cuff tears? (2) Are psychosocial factors associated with patient-reported outcomes after treatment in patients with rotator cuff tears? Methods A systematic review of cross-sectional and prospective observational studies was performed in MEDLINE/PubMed, EMBASE, CINAHL, PsycINFO, and Web of Science from each database's inception to June 2016. We included studies examining associations between psychosocial factors and patient-reported measures in patients with rotator cuff tears. We excluded studies not reporting on this relationship, involving patients with nonspecific shoulder pain, and written in a language other than English. Two independent reviewers performed the search, extracted information, and assessed methodological quality. Study quality was assessed using the Methodological Items for Non-Randomized Studies (MINORS) criteria. The primary outcomes for the review were associations between each psychosocial factor and patient-reported measures of function or disability, pain, or quality of life. Associations were interpreted based on significance, strength, and direction of the relationship. A total of 10 studies (five cross-sectional and five prospective) in 1410 patients (age range, 46-62 years, 60% [571 of 958] men) were included in the review. Pooling of results for meta-analyses was not possible as a result of study heterogeneity. Results Weak to moderate cross-sectional associations were found for emotional or mental health with function or disability and pain in multiple studies. Lower emotional or mental health function was associated with greater pain or disability or lower physical function at initial evaluation. Only one psychosocial factor (patient expectation) was weak to moderately associated with patient-reported outcomes after treatment in more than one study. In the two studies that examined expectations, the higher the expectation of benefit, the greater the perceived benefit after surgical intervention. Conclusions At the initial evaluation of patients with rotator cuff tear, there was an association between self-reported function and pain and emotional or mental health. However, these factors were not associated with patient-reported outcomes after intervention. This finding could be attributed to the lack of large prospective studies in this area or complex phenotypes within this patient population. Preoperative patient expectation is an important predictor of patient-reported outcomes in patients after rotator cuff surgery and may be a modifiable target for enhancing recovery. Level of evidence Level III, therapeutic study.

There is no established consensus regarding the optimal rehabilitation protocol following rotator cuff repair, including duration of immobilization, timing to initiate range of motion and resistance exercises, and the importance of supervised, formal therapy. The purpose of this study was to determine agreement in opinion regarding rotator cuff rehabilitation between orthopedic surgeons and physical therapists (PTs).A 50-question survey was created on a secure data capture system and distributed via e-mail to members of professional organization affiliations. Surgeon participants were recruited from the American Shoulder and Elbow Surgeons, and PTs were recruited from the American Society of Shoulder and Elbow Therapists and the Academy of Orthopaedic Physical Therapy of the American Physical Therapy Association. Survey responses were analyzed for interprofessional differences in majority opinion and distribution of answer choices.A total of 167 surgeons and 667 PTs responded to the survey. Of the 39 questions evaluated, surgeons and PTs reached intraprofessional majority agreement in 26 (67%) and 28 (72%) statements, respectively, with agreements matching in 17 instances and differing in 4. The 2 groups had different answer preferences in 32 questions (82%). PTs were more likely to support shorter immobilization intervals (P.001), earlier strengthening (P.001), and more frequent home exercises (P = .002), whereas surgeons endorsed more conservative weight-bearing restrictions (P.001), time-based phase transitions (P.001), and web-based technological platforms for rehabilitation (P.001).Our findings show that although significant discrepancy of opinion exists within professions, greater differences in preferences exist between surgeons and PTs regarding rotator cuff repair rehabilitation.

Background Intramuscular fat infiltration is a critical factor in surgical decision-making and is the most important factor used to prognosticate surgical repair outcomes in patients with rotator cuff tears. Quantitative 3D assessment of total rotator cuff fat infiltration in patients with rotator cuff tears has been realized. However, a reproducible method to evaluate 3D spatial distribution of rotator cuff intramuscular fat has not been established. The objective of this study was to establish the reproducibility, change detectable beyond error, and concurrent validity of a semi-automated method to evaluate the 3D spatial distribution of fat infiltration and muscle volume in patients with rotator cuff tears. Methods Thirteen consecutive patients diagnosed with symptomatic rotator cuff pathology and 3.0 T MRI confirmation at a single center were included. Fat-water imaging was used to quantify 3D intramuscular fat (%fat) in sagittal oblique sequences and intramuscular spatial distribution with the semi-automated technique. Each rotator cuff muscle was manually segmented yielding %fat in four axial intramuscular quartile-regions (superior-inferior; Q1–4) and three sagittal (medial/ intermediate/ lateral) regions. Reliability and concurrent validity of %fat and whole muscle volume were calculated with intraclass correlation coefficients (ICC). Results Intra-rater reliability for intramuscular sagittal divisions (ICC = 0.93–0.99) and axial divisions (ICC = 0.78–0.99) was good/excellent. Inter-rater reliability for %fat (ICC = 0.82–0.99) and volume (ICC = 0.92–0.99) was good/excellent. Concurrent validity with commercialized software showed good/excellent agreement (ICC = 0.66–0.99). Conclusions A new semi-automated method to assess 3-dimensional intramuscular distribution of fat infiltration in patients with rotator cuff tears using advanced MR imaging demonstrates high intra and inter-rater reliability and good concurrent validity. Minimal detectable change thresholds established facilitate clinical interpretation for future clinical application of this technique to assess change and treatment efficacy in patients with rotator cuff tears.

Background The goal of therapeutic exercise is to facilitate a neuromuscular response by increasing or decreasing muscular activity in order to reduce pain and improve function. It is not clear what dosage of exercise will create a neuromuscular response. Purpose The purpose of this study was to assess the effects following a three-week home program of a daily single exercise, the prone horizontal abduction exercise (PHA), on neuromuscular impairments of motor control as measured by scapular muscle EMG amplitudes, strength, and secondarily outcomes of self-reported pain and function between individuals with and without subacromial pain syndrome. Study Design Prospective Case-Control, Pilot Study. Methods Twenty-five individuals participated; eleven with shoulder pain during active and resistive motions (Penn Shoulder Score: 77 ± 11) and 14 matched healthy controls (Penn Shoulder Score: 99 ± 27) (p

AB Purpose: Shoulder dislocations present a potentially debilitating injury for soldiers and other groups of physically active adults. The purpose of this study was to determine the 10-yr incidence rate of shoulder dislocations in soldiers, the percentage with recurrent instability, and risk factors for these injuries. Methods: This retrospective cohort study used medical encounter data from U.S. Army soldiers to calculate the 10-yr incidence rate for shoulder dislocations and the percentage of chronic or recurrent injuries >3 months and

This study examines the association between strength measurements and supraspinatus tear in patients with shoulder pain. This study characterized determinants of abduction strength among patients with tears.A total of 208 patients with shoulder pain were recruited. Strength was tested using a handheld dynamometer. Supraspinatus tears were diagnosed by combination of clinical assessment and blinded magnetic resonance imaging review. Associations of supraspinatus tear with patient characteristics and strength measurements (abduction, internal rotation and external rotation) were assessed using multivariable logistic regression models.Patients with supraspinatus tear had decreased abduction strength (P = 0.02) and decreased external rotation strength (P0.01). When adjusted for age, sex, tear laterality, and body mass index, decreased abduction strength (odds ratio, 1.18/kg; 95% confidence interval, 1.06-1.32) and decreased external rotation strength (odds ratio, 1.29/kg; 95% confidence interval, 1.14-1.48) were associated with supraspinatus tear. In patients with tear, age 60 yrs or older, female sex, and visual analog scale pain score were significantly associated with decreased abduction strength but tear size, fatty infiltration, and atrophy were not.Decreased abduction and external rotation strength were associated with supraspinatus tear in patients with shoulder pain. In this cohort, the abduction strength of patients with tears was influenced by demographic factors but not tear characteristics.

Background Individuals with subacromial pain present with a variety of contributing impairments related to the movement problem. The scapular assistance test (SAT) and scapula reposition test (SRT) are proposed to identify shoulder pain related to abnormal scapular movement or position. It remains unknown if scapular movement related impairments are present in those with positive tests. Objectives To determine if scapular motion related impairments differ based on the result of the SAT or SRT in individuals with subacromial pain syndrome. Design Cross-sectional Method Sixty individuals with subacromial pain syndrome were included. Prior to obtaining results of the SAT and SRT, a single examiner measured scapular upward rotation and posterior tilt active and passive motion, pectoralis minor length, and strength of the middle trapezius, lower trapezius, and serratus anterior. Dynamic scapular motion was qualitatively assessed with the Scapular Dyskinesis Test. The Mann-Whitney U test assessed for differences based on the outcome of the SAT and SRT. Results There was a significant difference (P = .023) in pectoralis minor length for the SAT. Participants with a positive SAT had decreased muscle length compared to those who tested negative. There were no significant differences in scapular motion or strength based on the result of either the SAT or SRT. Conclusions A positive SAT was associated with greater pectoralis minor length impairment, but not muscle strength or mobility. The SRT did not identify greater impairments in any of the scapular movement related impairments assessed. Individuals may vary in contributing impairments related to SAT or SRT results.

OBJECTIVE The study aim was to evaluate subacromial and internal impingement risk between shoulders (dominant/nondominant) during dynamic motion using subject-specific anatomy and precise in vivo kinematics. DESIGN In a prospective cross-sectional study, nine subjects underwent bilateral magnetic resonance (N = 18 shoulders) and fluoroscopic imaging during elevation and external rotation at 90 degrees of abduction. Subject-specific bone models were created and distances from footprint to (a) acromion and (b) glenoid were measured to evaluate risk. RESULTS Throughout elevation, subacromial impingement risk was greater in the dominant shoulder (P = 0.0178). Regardless of side, high subacromial impingement risk occurred at 30% (78 degrees), 50% (101 degrees), and 70% (57 degrees) of the elevation cycle (P < 0.0001). High subacromial impingement risk also occurred at 30% (94 degrees), 50% (120 degrees), and 70% (63 degrees) of the external rotation motion cycle (P < 0.0001). Throughout both motions, internal impingement risk was not observed; however, the footprint and glenoid were closest at 50% of the elevation (101 degrees) and external rotation (120 degrees) cycles (P < 0.0001). CONCLUSIONS During elevation, subacromial impingement risk is greatest at lower arm positions (30% cycle, 78 degrees) and is greater in the dominant shoulder. High subacromial impingement risk also occurs with external rotation (63-120 degrees). Internal impingement risk does not occur with maximal elevation (101 degrees) or external rotation at 90-degree abduction but is more closely approached with elevation.

Alterations in scapular muscle activity have been theorized to contribute to abnormal scapular motion and shoulder pain, but pose challenges to quantify in the clinic. Rehabilitative Ultrasound Imaging (RUSI) has proved useful identifying dysfunction of lumbar regional stabilizing muscle activity, specifically contractile behavior. Although, recent examinations of scapular stabilizing trapezius muscle function using RUSI did not detect alterations individuals with shoulder pain or differences in muscle thickness between varying external loads in asymptomatic individuals, a potential confounder to prior results, scapular dyskinesis has not been controlled. It is unknown if dyskinesis alters scapular muscle thickness during activation measured with RUSI. Thus, the purpose of this study was to compare change in scapular muscle thickness between individuals with and without scapular dyskinesis. Thirty-nine asymptomatic adults with (n = 19) and without (n = 20) scapular dyskinesis, defined with a reliable and validated method, participated. Two separate ultrasound images of the serratus anterior (SA) and lower trapezius (LT) were captured under two randomized conditions, rest and isometric contraction against gravity, and saved for blinded measurement. Change in thickness with contraction was calculated and expressed as a percentage. The dyskinesis group demonstrated a greater increase (p = 0.005) in LT thickness with the isometric contraction than the group without (mean difference = 31.6%; 95%CI = 10.3, 53.0). No differences in SA or resting thickness of either muscle were found between groups. The presence of scapular dyskinesis alters thickness changes of the lower trapezius during activation. Furthermore, potential underlying reasons beyond muscle contractile behavior must be considered.

Synopsis The available body of knowledge on shoulder ultrasound imaging has grown considerably within the past decade, and physical therapists are among the many health care professions currently exploring the potential clinical integration of this imaging technology and the knowledge derived from it. Therefore, the primary purpose of this commentary was to review the recent evidence and emerging uses of ultrasound imaging for the clinical evaluation of shoulder disorders. This includes a detailed description of common measurement techniques along with their known clinimetric properties. Specifically provided are critical appraisals of the existing measures used to estimate soft tissue and bony morphometry, muscle contractile states, and lean muscle density. These appraisals are intended to help clinicians clarify the scope of physical therapy practice for which these measurement techniques are effectively utilized and to highlight areas in need of further development. J Orthop Sports Phys Ther 2015;45(5)...

A high prevalence of neovascularity in lower extremity tendinopathies has been reported. Neovascularity in those with rotator cuff tendinopathy exclusively has not been examined. The objective was to determine the prevalence of neovascularization in patients with rotator cuff tendinopathy compared with asymptomatic controls.Single-blind cross-sectional study.Research laboratory.Participants (n = 40; age = 44.9 years, 23-62 years; 20 females) with rotator cuff tendinopathy (n = 20) but without full-thickness rotator cuff tears, and asymptomatic controls that were age, gender, and hand dominance matched (n = 20) to the patients.The participants laying in supine had their shoulder positioned in internal rotation and extension. Ultrasound images were collected of the supraspinatus tendon and subacromial bursae in the transverse and longitudinal planes using a linear transducer in color Doppler mode.Images were assessed for neovascularization by 2 trained raters who were blinded to group (rotator cuff tendinopathy or asymptomatic group).No statistically significant difference in neovascularization was identified between participants with and without rotator cuff tendinopathy (χ = 0.13, df = 1, P = 0.72). Neovascularization was identified in 6 of 20 patients with rotator cuff tendinopathy (30%) and 5 of 20 asymptomatic control participants (25%).The authors found no differences in neovascularization rate in patients with rotator cuff tendinopathy (30%) and asymptomatic controls (25%). The study indicates that neovascularization is not related to presence of symptomatic tendinopathy in those with rotator cuff tendinopathy. Neovascularization may not be a relevant sonographic finding to aid the clinical assessment of those with rotator cuff tendinopathy.

The Orthopaedic Section of the American Physical Therapy Association (APTA) has an ongoing effort to create evidence-based practice guidelines for orthopaedic physical therapy management of patients with musculoskeletal impairments described in the World Health Organization's International Classification of Functioning, Disability, and Health (ICF). The purpose of these clinical practice guidelines is to describe the peer-reviewed literature and make recommendations related to adhesive capsulitis. J Orthop Sports Phys Ther 2013;43(5):A1–A31. doi:10.2519/jospt.2013.0302

Study Design Cross-sectional cohort. Introduction Tendon collagen organization can be estimated by peak spatial frequency radius (PSFR) on ultrasound images. Characterizing PSFR can define the contribution of collagen disruption to shoulder symptoms. Purpose of the Study The purpose of this was to characterize the (1) supraspinatus tendon PSFR in participants with subacromial pain syndrome (SPS) and healthy controls; (2) PSFR between participants grouped on a tendon visual quality score; and (3) relationship between PSFR with patient-reported pain, function, and shoulder strength. Methods Participants with SPS ( n = 20) and age, sex, and arm-dominance–matched healthy controls ( n = 20) completed strength testing in scaption and external rotation, and patient-reported pain, and functional outcomes. Supraspinatus tendon ultrasound images were acquired, and PSFR was calculated for a region of interest 15 mm medial to the supraspinatus footprint. PSFR was compared between groups using an independent t -test and an analysis of variance to compare between 3 groups for visually qualitatively rated tendon abnormalities. Relationships between PSFR with pain, function, and strength were assessed using Pearson correlation coefficient. Results Supraspinatus tendon PSFR was not different between groups ( P = .190) or tendon qualitative ratings ( P = .556). No relationship was found between PSFR and pain, functional loss, and strength ( P > .05). Conclusions Collagen disruption (PSFR) measured via ultrasound images of the supraspinatus tendon was not different between participants with SPS or in those with visually rated tendon defects. PSFR is not related to shoulder pain, function, and strength, suggesting that supraspinatus tendon collagen disorganization may not be a contributing factor to shoulder SPS. However, collagen disruption may not be isolated to a single region of interest. Level of Evidence 3b: case-control study.

Alterations in scapular muscle activity, including excess activation of the upper trapezius (UT) and onset latencies of the lower trapezius (LT) and serratus anterior (SA) muscles, are associated with abnormal scapular motion and shoulder impingement. Limited information exists on the reliability of neuromuscular activity to demonstrate the efficacy of interventions. The purpose of this study was to characterize the reproducibility of scapular muscle activity (mean activity, relative onset timing) over time and establish the minimal detectable change (MDC). Surface electromyography (sEMG) of the UT, LT, SA and anterior deltoid (AD) muscles in 16 adults were captured during an overhead lifting task in two sessions, one-week apart. sEMG data were also normalized to maximum isometric contraction and the relative onset and mean muscle activity during concentric and eccentric phases of the scapular muscles were calculated. Additionally, reliability of the absolute sEMG data during the lifting task and MVIC was evaluated. Both intrasession and intersession reliability of normalized and absolute mean scapular muscle activity, assessed with intraclass correlation coefficients (ICC), ranged from 0.62 to 0.99; MDC values were between 1.3% and 11.7% MVIC and 24 to 135 mV absolute sEMG. Reliability of sEMG during MVIC was ICC = 0.82-0.99, with the exception of intersession upper trapezius reliability (ICC = 0.36). Within session reliability of muscle onset times was ICC = 0.88-0.97, but between session reliability was lower with ICC = 0.43-0.73; MDC were between 39 and 237 ms. Small changes in scapular neuromuscular mean activity (11.7% MVIC) can be interpreted as meaningful change, while change in muscle onset timing in light of specific processing parameters used in this study is more variable.

Context:The literature does not present a consistent pattern of altered scapular kinematics in patients with shoulder-impingement syndrome (SIS).Objectives:To perform meta-analyses of published comparative studies to determine the consistent differences in scapular kinematics between subjects with SIS and controls. In addition, the purpose was to analyze factors of the data-collection methods to explain the inconsistencies in reported kinematics. The results of this study will help guide future research and enable our understanding of the relationship between scapular kinematics and SIS.Evidence Acquisition:A search identified 65 studies; 9 papers met inclusion criteria. Sample sizes, means, and SDs of 5 scapular-kinematic variables were extracted or obtained from each paper’s lead author. Standard difference in the mean between SIS and controls was calculated. Moderator variables were plane of arm elevation, level of arm elevation (ARM) and population (POP).Evidence Synthesis:Overall, the SIS group had less scapular upward rotation (UR) and external rotation (ER) and greater clavicular elevation (ELE) and retraction (RET) but no differences in scapular posterior tilt (PT). In the frontal plane, SIS subjects showed greater PT and ER, and in the scapular plane, less UR and ER and greater ELE and RET. There was also greater ELE and RET in the sagittal plane. There was less UR at the low ARM and greater ELE and RET at the high ARM with SIS. Athletes and overhead workers showed less UR, while athletes showed greater PT and workers showed less PT and ER. The general population with SIS had greater ELE and RET only.Conclusions:Subjects with SIS demonstrated altered scapular kinematics, and these differences are influenced by the plane, ARM, and POP. Athletes and overhead workers have a different pattern of scapular kinematics than the general population. The scapular plane is most likely to demonstrate altered kinematics. These factors should be considered when designing futures studies to assess the impact of altered kinematics in patients with SIS.

Background Scapular dyskinesis is an abnormal scapular motion or position during active arm elevation. Dyskinesis is theorized to contribute to impingement syndrome by decreasing the subacromial space. A corrective maneuver of the scapular assistance test (SAT) proposes to increase scapular upward rotation and posterior tilt to increase the subacromial space. The purpose of this study is to determine the influence that 1) scapular dyskinesis and 2) passive manual correction with the SAT have on subacromial space and 3-dimensional (3-D) scapular kinematics. Materials and methods Forty asymptomatic participants were classified with either obvious dyskinesis (n = 20) or normal motion (n = 20) using the scapular dyskinesis test. The anterior outlet of the subacromial space was measured via the acromiohumeral distance using ultrasound imaging and 3-D scapular orientation was assessed with electromagnetic motion analysis, with the arm at rest 45° and 90° of active elevation with and without the SAT, respectively. Results There were no differences in acromiohumeral distance or scapular kinematics with static active arm elevation between groups. The SAT increased scapular upward rotation, posterior tilt, and acromiohumeral distance in both groups. Participants with dyskinesis demonstrated greater scapular mobility in upward rotation with the SAT, but no additional increase in acromiohumeral distance. Conclusion Scapular dyskinesis identified during active motion did not result in different 3-D scapular orientation or acromiohumeral distance during active arm elevation in static positions; however, the SAT altered scapular kinematics and increased acromiohumeral distance. The SAT may be helpful to identify individuals where subacromial compression is producing symptoms, regardless of dyskinesis.

Context:Differences in 3-dimensional (3D) scapular motion have been reported between healthy baseball position players and healthy nonoverhead athletic controls, as well as players diagnosed with shoulder impingement syndrome. These alterations are theorized to be the result of adaptations due to the demands of repetitive throwing. However, comparisons between the throwing and nonthrowing shoulders are commonly used to infer normal motion.Objective:The purpose of this study was to compare 3D scapular kinematics between the throwing and nonthrowing shoulders in asymptomatic professional male baseball pitchers.Design:Cross-sectional study.Setting:Laboratory.Participants:45 asymptomatic professional baseball pitchers participating without restrictions during preseason training.Interventions:An electromagnetic tracking system was used to assess 3D scapular orientation at rest and during weighted (2.3-kg) shoulder flexion across discrete humeral-flexion angles (rest, 30°, 60°, 90°, 120°, and maximum).Main Outcome Measure:3D scapular upward/downward rotation (UR/DR), anteroposterior (AP) tilt, and internal/external rotation (IR/ER). Separate mixed-model ANOVAs (Side × Angle) for each scapular motion were used to compare the throwing and the nonthrowing shoulder across all angles.Results:There were significant side-to-side differences with scapular UR/DR (P < .001), AP tilt (P < .001), and IR/ER (P < .001). The throwing scapula displayed greater mean UR (increase = 3.6°, SE = 0.50) and anterior/posterior tilt (increase = 2.1°, SE = 0.60) and less mean IR (decrease = 2.1°, SE = 0.66) than the nonthrowing shoulder averaged across all arm angles.Conclusions:In asymptomatic professional pitchers, the throwing shoulder’s scapular position differs across all arm angles from that of the nonthrowing shoulder, but the motion does not differ. Scapular asymmetry that is consistent throughout arm elevation may be indicative not of pathology but, potentially, of a normal adaptation of the pitching shoulder.

The etiology of rotator cuff tendinopathy is multi-factorial, and has been attributed to both extrinsic and intrinsic mechanisms. Extrinsic factors that encroach upon the subacromial space and contribute to bursal side compression of the rotator cuff tendons include anatomical variants of the acromion, alterations in scapular or humeral kinematics, postural abnormalities, rotator cuff and scapular muscle performance deficits, and decreased extensibility of pectoralis minor or posterior shoulder. A unique extrinsic mechanism, internal impingement, is attributed to compression of the posterior articular surface of the tendons between the humeral head and glenoid and is not related to subacromial space narrowing. Intrinsic factors that contribute to rotator cuff tendon degradation with tensile/shear overload include alterations in biology, mechanical properties, morphology, and vascularity. The varied nature of these mechanisms indicates that rotator cuff tendinopathy is not a homogenous entity, and thus may require different treatment interventions. Treatment aimed at addressing mechanistic factors appears to be beneficial for patients with rotator cuff tendinopathy, however, not for all patients. Classification of rotator cuff tendinopathy into subgroups based on underlying mechanism may improve treatment outcomes.

Controlled laboratory study.To examine the effects of altering posture on the subacromial space (SAS) in subjects with rotator cuff disease and subjects without shoulder pain.Poor upper quadrant posture has been linked to altered scapular mechanics, which has been theorized to excessively reduce SAS. However, no study has examined the direct effects of altering upper quadrant posture on SAS. We hypothesized that upright posture would increase and slouched posture would decrease the SAS, as compared to a normal posture, when measured both with the shoulder at rest along the side of the trunk and when maintained in 45° of active shoulder abduction.Participants included 2 groups: the subjects with shoulder pain and rotator cuff disease, as diagnosed via magnetic resonance imaging (n = 31), and control subjects without shoulder pain (n = 29). The SAS was imaged with ultrasound using a 7.5-MHz linear transducer placed in the coronal plane over the posterior to midportion of the acromion. The SAS was measured on ultrasound images using the acromiohumeral distance (AHD), defined as the shortest distance between the acromion and the humerus. The AHD was measured in 2 trials at 2 arm angles (at rest along the trunk and at 45° of active abduction) and across 3 postures (normal, slouched, and upright), and averaged for data analysis.Two mixed-model analyses of variance, 1 for each arm angle, were used to compare AHD across postures and between groups. There was no interaction between group and posture, and no significant main effect of group for either arm position. There was no significant main effect of posture for the arm at rest (P = .26); however, there was a significant main effect of posture on AHD at the 45° abduction arm angle (P = .0002), with a significantly greater AHD in upright posture (mean AHD, 9.8 mm), as compared to normal posture (mean AHD, 8.6 mm).The effect of posture on SAS, as measured by the 2-dimensional AHD using ultrasound of the posterior to middle aspect of the SAS, is small. The AHD increased with upright posture by 1.2 mm compared to normal posture, when the arm was in 45° active abduction.

The present study aimed to test the validity of upper extremity joint angle measurements with the Microsoft Kinect for shoulder rehabilitation. Results indicate that there are large discrepancies in measured shoulder angles from the Kinect compared to the gold standard (magnetic tracker) and the clinical standard (goniometer). Before the Kinect can be used to measure movements for clinical rehabilitation, understanding its limitations in precision and accuracy of measuring specific joint motions is imperative.

To test the reliability and validity of shoulder joint angle measurements from the Microsoft Kinect™ for virtual rehabilitation.Test-retest reliability and concurrent validity, feasibility study.Motion analysis laboratory.A convenience sample of 10 healthy adults.Shoulder joint angle was assessed in four static poses, two trials for each pose, using: (1) the Kinect; (2) a three-dimensional motion analysis system; and (3) a clinical goniometer. All poses were captured with the Kinect from the frontal view. The two poses of shoulder flexion were also captured with the Kinect from the sagittal view.Absolute and relative test-retest reliability of the Kinect for the measurement of shoulder angle was determined in each pose with intraclass correlation coefficients (ICCs), standard error of the measure and minimal detectable change. The 95% limits of agreement (LOA) between the Kinect and the standard methods for measuring shoulder angle were computed to determine concurrent validity.While the Kinect provided to be highly reliable (ICC 0.76-0.98) for measuring shoulder angle from the frontal view, the 95% LOA between the Kinect and the two measurement standards were greater than ±5° in all poses for both views.Before the Kinect is used to measure movements for virtual rehabilitation applications, it is imperative to understand its limitations in precision and accuracy for the measurement of specific joint motions.

To characterize the supraspinatus tendon thickness, subacromial space, and the relationship between tendon thickness and subacromial space to further elucidate the mechanisms of subacromial impingement syndrome.In a single-blind cross-sectional study, subjects were recruited with subacromial impingement syndrome (n = 20) and asymptomatic controls (n = 20) matched for age, gender, and hand dominance. Ultrasound images were collected using a 4-12-MHz linear transducer in B-mode of the supraspinatus tendon in the transverse (short axis) and the anterior aspect of the subacromial space outlet. Using image callipers, measurements of tendon thickness were taken at 3 points along the tendon and averaged for a single thickness measure. The subacromial space outlet was measured via the acromiohumeral distance (AHD) defined by the inferior acromion and superior humeral head. The occupation ratio was calculated as the tendon thickness as a percentage of AHD.The subacromial impingement syndrome group had a significantly thicker tendon (mean difference = 0.6 mm, p = 0.048) and a greater tendon occupation ratio (mean difference = 7.5 %, p = 0.014) compared to matched controls. There were no AHD group differences.The supraspinatus tendon was thicker and occupied a greater percentage of AHD, supporting an intrinsic mechanism. An extrinsic mechanism of tendon compression is theoretically supported, but future imaging studies need to confirm direct compression with elevation. Treatment to reduce tendon thickness may reduce symptoms, and surgical intervention to increase subacromial space may be considered if tendon compression can be verified.

In rehabilitation, exercise instructions are multi-modal and can include a focus of increasing mean activity of a target muscle and inhibiting aberrant synergistic muscle activity, particularly during shoulder exercises, such as the prone horizontal abduction (PHA). The objective was to compare the immediate effects and short-term retention of multi-modal exercise instruction by a physical therapist written only instruction on normalized mean upper and lower trapezius muscle activity during three phases (concentric/isometric/eccentric) versus of an isotonic PHA exercise between participants with and without shoulder pain. Surface electromyography (EMG) was recorded from fourteen healthy participants and twelve participants with shoulder pain during the PHA exercise under two conditions: (1) written only instructions and (2) multi-modal instruction. Retention of multi-modal instruction on muscle activity was assessed one week later. Results demonstrate 12.8–16.0% increase in lower trapezius muscle activity during the concentric and isometric phases with multi-modal instructions in both groups. Inhibition of the upper trapezius did not occur in either group. Facilitation effects were maintained in short-term follow-up. Findings suggest that regardless of shoulder pain, multi-modal instruction by a physical therapist facilitates greater neuromuscular activity of a targeted muscle compared to written instructions alone and these effects are retained.

Controlled laboratory study.To determine the effect of the modified scapular assistance test (SAT) on 3-dimensional shoulder kinematics, strength, and linear measures of subacromial space in patients with subacromial impingement syndrome (SAIS).Abnormal scapular kinematics have been identified in patients with SAIS. Increased scapular upward rotation and posterior tilt, as induced with manual assistance using the SAT, have been theorized to increase subacromial space and may alter shoulder strength.Forty-two subjects (21 with SAIS and 21 controls) participated in this study. The anterior outlet of the subacromial space, measured via the acromiohumeral distance on ultrasound images, and 3-dimensional scapular kinematics, measured using motion analysis, were determined with the arm at rest, and at 45° and 90° of active elevation with and without the SAT. A dynamometer was used to measure isometric shoulder strength. Full factorial mixed-model analyses of variance evaluated the effects of the SAT on variables between groups.There was an increase in scapular posterior tilt at all angles, upward rotation at rest and 45° of elevation, and acromiohumeral distance at 45° and at 90° with the SAT. The SAT did not alter normalized isometric strength. There were no differences in response to the SAT between the SAIS and control groups.Manual scapular assistance using the SAT influences factors associated with SAIS, such as subacromial space and potentially scapular orientation during static arm elevation, but not more so in individuals with SAIS than in healthy individuals. The SAT performed statically may be a way to identify potential subgroups of individuals with SAIS for whom subacromial space narrowing may be a contributing factor.

Reference/Citation: Kuhn JE. Exercise in the treatment of rotator cuff impingement: a systematic review and a synthesized evidence-based rehabilitation protocol. J Shoulder Elbow Surg. 2009;18(1):138–160. Clinical Question: What is the role of exercise in the treatment of rotator cuff impingement syndrome (RCIS), and what evidence-based exercises can be synthesized into a criterion-standard exercise rehabilitation protocol? Data Sources: Investigations were identified by PubMed, Ovid, the Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, American College of Physicians Journal Club, and Database of Abstracts of Reviews of Effects. The search terms included shoulder, impingement, rotator cuff, rehabilitation, physical therapy, physiotherapy, and exercise. Additional searches were performed with bibliographies of retrieved studies. Study Selection: To qualify for inclusion, studies had to be level 1 or level 2 (randomized controlled trials); had to compare rehabilitation interventions, such as exercise or manual therapy, with other treatments or placebo; had to include validated outcome measures of pain, function, or disability; and had to be limited to individuals with diagnosed impingement syndrome. Impingement syndrome was determined by a positive impingement sign per Neer or Hawkins criteria, or both. Articles were excluded if they addressed other shoulder conditions (eg, calcific tendinosis, full-thickness rotator cuff tears, adhesive capsulitis, osteoarthritis), addressed postoperative management, were retrospective studies or case series, or used other outcome measures. Data Extraction: An evidence-based journal club of 9 faculty members and fellows reviewed the articles and extracted and tabulated the data. Individual outcomes for pain, range of motion (ROM), strength, and function were organized. Intragroup and between-groups outcomes were assessed for the effectiveness of treatment, and statistical outcomes were recorded when available. Clinical importance was determined when statistical value was P < .05 and the effect size or difference between treatments was 20% or more. Sixa major categories were created to organize the components of the physical therapy programs used in each study: ROM, flexibility and stretching, strengthening techniques, therapist-driven manual therapy, modalities, and schedule. Components from these categories were used to create a synthesized physical therapy program. Main Results: The searches identified 80 studies, of which 11 met the inclusion criteria. In 5 studies, the diagnosis of RCIS was confirmed using an impingement test consisting of lidocaine injected into the subacromial space and elimination of pain with the impingement sign. Randomization methods were used in 6 studies, and blinded, independent examiners were involved in follow-up data collection in only 3 studies. Validated outcome measures were used in all studies. Follow-up was very good in 10 studies and was less than 90% in only 1 study. The specific exercise programs varied among studies. However, general treatment principles were identified among the different studies and included frequency, ROM, stretching or flexibility, strengthening, manual therapy (joint and/or soft tissue mobilizations), modalities, and others. The findings indicated that exercise improves outcomes of pain, strength, ROM impairments, and function in patients with impingement syndrome. In 10 studies, investigators reported improvements in pain with supervised exercise, home exercise, exercise associated with manual therapy, and exercise after subacromial decompression. Of the 6 studies in which researchers compared pre-exercise pain with postexercise pain, 5 demonstrated that exercise produced statistically significant and clinically important reductions in pain. Two studies demonstrated improvements in pain when comparing exercise and control groups. In 1 study, investigators evaluated bracing without exercise and found no difference in pain between the brace and exercise groups. Investigators evaluated exercise combined with manual therapy in 3 studies and demonstrated improvement in pain relief in each study and improvement in strength in 1 study. In most studies, exercise also was shown to improve function. The improvement in function was statistically significant in 4 studies and clinically meaningful in 2 of these studies. In 2 studies, researchers compared supervised exercise with a home exercise program and found that function improved in both groups but was not different between groups. This finding might have resulted from a type II statistical error. In 4 studies, researchers did not find differences between acromioplasty with exercise and exercise alone for pain alone or for outcomes of pain and function. Conclusions: Findings indicated that exercise is beneficial for reducing pain and improving function in individuals with RCIS. The effects of exercise might be augmented with implementation of manual therapy. In addition, supervised exercise might not be more effective than a home exercise program. Many articles had methodologic concerns and provided limited descriptions of specific exercises, which made comparing types of exercise among studies difficult. Based on the results, Kuhn generated a physical therapy protocol using evidence-based exercise that could be used by clinicians treating individuals with impingement syndrome. This evidence-based protocol can serve as the criterion standard to reduce variables in future cohort and comparative studies to help find better treatments for patients with this disorder.

Purpose. Recently sonography (US) has been used to measure the subacromial space outlet with a linear measurement of the acromiohumeral distance (AHD). The purpose of this article is to systematically review the literature on the influence of rotator cuff disease (RCD) on AHD using US. Methods. Computer-aided searches of databases were performed to identify comparative studies that measured US-generated AHD in adults with symptomatic RCD. Results. Five studies met the inclusion/exclusion criteria. Conclusions. US images of AHD are smaller in patients with full-thickness tears than healthy individuals and subjects with subacromial impingement. AHD is potentially useful to prognosticate outcome in patients with subacromial impingement. © 2010 Wiley Periodicals, Inc. J Clin Ultrasound, 2011