Amee L. Seitz

Mechanisms of rotator cuff tendinopathy: intrinsic, extrinsic, or both?

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.

Shoulder Pain and Mobility Deficits: Adhesive Capsulitis

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 Organizations 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

Effect of Posture on Acromiohumeral Distance With Arm Elevation in Subjects With and Without Rotator Cuff Disease Using Ultrasonography

STUDY DESIGN Controlled laboratory study. OBJECTIVES To examine the effects of altering posture on the subacromial space (SAS) in subjects with rotator cuff disease and subjects without shoulder pain. BACKGROUND 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. METHODS 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. RESULTS 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). CONCLUSION 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.

Ultrasonographic measures of subacromial space in patients with rotator cuff disease: A systematic review

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.

The Scapular Assistance Test Results in Changes in Scapular Position and Subacromial Space but Not Rotator Cuff Strength in Subacromial Impingement

STUDY DESIGN Controlled laboratory study. OBJECTIVES 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). BACKGROUND 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. METHODS 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. RESULTS 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. CONCLUSIONS 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.

Reliability and minimal detectable change in scapulothoracic neuromuscular activity

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.

Validity and reliability of Kinect skeleton for measuring shoulder joint angles: a feasibility study

OBJECTIVE To test the reliability and validity of shoulder joint angle measurements from the Microsoft Kinect™ for virtual rehabilitation. DESIGN Test-retest reliability and concurrent validity, feasibility study. SETTING Motion analysis laboratory. PARTICIPANTS A convenience sample of 10 healthy adults. METHODS 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. MAIN OUTCOME MEASURES 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. RESULTS 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. CONCLUSIONS 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.

Incidence of Shoulder Dislocations and the Rate of Recurrent Instability in Soldiers.

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 ≤2 yr after the initial diagnosis. A Cox proportional hazards model was constructed using demographic variables (age, race, education level, marital status, and sex) to determine incidence rate ratios for risk factors related to shoulder dislocation. Logistic regression was used to calculate odds ratio for risk factors for recurrent injury, including concurrent diagnoses (brachial plexus or peripheral nerve injuries and fractures of the scapula or proximal humerus). RESULTS There were 15,426 incident shoulder dislocations, with a 10-yr incidence rate of 3.13 per 1000 person-year. Soldiers ≤40 yr old showed greater risk for injury compared with those older than 40 yr. The incidence rate ratio for males compared with females was 1.64, 95% confidence interval = 1.55-1.74. Recurrent injury occurred in 28.7% of cases. Concurrent axillary nerve injury (odds ratio = 3.64, 95% confidence interval = 1.56-8.46) and age ≤35 yr were associated with greater risk of recurrence. CONCLUSION Within the active duty U.S. Army, men and younger individuals showed greater risk for shoulder dislocations. Over one-quarter of incident cases became recurrent. Axillary nerve injuries and younger age increased the odds of recurrent injury.

Current Rehabilitation Applications for Shoulder Ultrasound Imaging

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.

Muscle thickness measurements of the lower trapezius with rehabilitative ultrasound imaging are confounded by scapular dyskinesis

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.