肩峰下撞击综合征的经皮超声引导下肩峰下滑囊造影表现

目的 探讨肩峰下撞击综合征（SIS）的经皮超声引导下肩峰下滑囊造影（PUSB）表现。方法 对150例经临床诊断为SIS患者行PUSB检查,动态观察造影剂在滑囊内的弥散情况及是否进入肩袖、关节腔。结果 53例造影剂在滑囊内呈线状均匀分布,诊断为单纯性肩峰下滑囊炎。97例造影剂在滑囊内分布不均匀,诊断为粘连性肩峰下滑囊炎。40例可见造影剂由滑囊进入肩袖肌腱,但未达肱骨头表面;32例可见造影剂由滑囊进入肩袖肌腱,到达肱骨头表面;78例造影剂未进入肩袖肌腱。结论 PUSB可实时动态评估肩峰下滑囊炎、滑囊粘连、肩袖损伤等情况,对SIS的诊断具有较高的应用价值。     

In vivo dynamic acromiohumeral distance in shoulders with rotator cuff tears

BackgroundThere are no previous studies on the acromiohumeral distance in shoulders with large-to-massive full-thickness rotator cuff tears. In this study, the acromiohumeral distance in rotator cuff tear and healthy shoulders was measured using 3D-to-2D model-to-image registration techniques.MethodsThe dynamic glenohumeral kinematics during scapular plane abduction and axial rotation were analyzed in 11 rotator cuff tear patients and 10 healthy control subjects. Periodic radiographic images of scapular plane abduction and axial rotation were taken using a flat-panel radiograph image detector. Movements of the shoulder joint were assessed using radiographic images and computed tomography-derived digitally reconstructed radiographs. The acromiohumeral distance was defined as the shortest 3D distance between the acromion and the proximal humerus.FindingsFor scapular plane abduction, the rotator cuff tear group had significantly smaller acromiohumeral distance than the control group at 15°, 30°, 45°, 60°, 75°, 135°, and 150° of humeral abduction (P < 0.05 at each measured angle). For axial rotation in the adducted position, the rotator cuff tear group had significantly smaller acromiohumeral distance than the control group at each point between −20° and 40° of glenohumeral external rotation (P < 0.05 at each measured angle).InterpretationThe minimum measured acromiohumeral distance was 0.9 mm in the rotator cuff tear shoulders and 2.1 mm in the healthy shoulders at 90° of scapular plane abduction. The findings are of clinical relevance because quantitative evaluation of the dynamic acromiohumeral distances in rotator cuff tear and healthy shoulders might provide important insight into subacromial impingement.     

肩袖损伤合并肩峰下撞击综合征的MRI表现

目的探讨肩袖损伤合并肩峰下撞击综合征的MRI影像表现。材料与方法对33例X线片无骨折但临床怀疑肩袖损伤或肩峰下撞击综合征的患者,用1.5 T MRI机检查,观察肩袖损伤及肩峰下撞击综合征在MR上的影像特征,分析两者的相关性,并与手术结果对比,计算准确率。结果 33例中肩袖损伤20例(合并肩峰下撞击综合征10例),肩峰下撞击综合征15例(合并肩袖损伤10例)。肩袖损伤和肩峰下撞击综合征术前MR诊断准确率分别约为95.0%、71.3%。结论肩关节MRI扫描对肩袖损伤及肩峰下撞击综合征的诊断有较高的临床应用价值,肩袖损伤者中至少半数合并肩峰下撞击综合征,临床和影像应予重视。     

Comparison of acromiohumeral distance in symptomatic and asymptomatic patient shoulders and those of healthy controls

BackgroundThe reduction of the subacromial space has traditionally been linked to rotator cuff pathology. The contribution of this narrowing, both in the development and maintenance of rotator cuff tendinopathy, is still under debate. The objective of the present study was compare the acromiohumeral distance at 0 and 60 degrees of active shoulder abduction in scapular plane, static position, in both symptomatic and contralateral shoulders, between participants with unilateral rotator cuff related shoulder pain, and in asymptomatic participants.MethodThis was a cross-sectional observational study. Seventy-six participants with chronic shoulder pain were assessed. Forty participants without shoulder pain were also recruited to compare the acromiohumeral distance with symptomatic participants. The acromiohumeral distance was measured at 0 and 60 degrees of active shoulder abduction in all the groups by ultrasound imaging. Mean differences between symptomatic versus contralateral shoulders, and versus healthy controls, were calculated.FindingsThere were no statistical significant differences (p > .05) in the acromiohumeral distance at 0 degrees of shoulder elevation between the groups. However, significant differences were found at 60° between symptomatic and contralateral shoulder groups (0,51 mm; 95% CI: −0.90 to −0.12).InterpretationsDifferences in shoulder pain perception at 0° are not attributable to acromiohumeral distance differences. However, treatments focused on increasing AHD at 60° could be prescribed, as a significantly reduced AHD was found in symptomatic shoulders when compared with contralateral shoulders. Further research is needed to determine, not only static differences in AHD, but also dynamic differences.     

Clinical assessment of factors associated with subacromial shoulder impingement: a systematic review

Background: Physiotherapists commonly use orthopaedic special tests to reproduce subacromial shoulder impingement (SIS) pain by increasing compression or tension within the subacromial space. However, these tests do not differentiate between purported extrinsic and intrinsic mechanisms associated with SIS.

Objective: To identify, and determine the reliability and validity of clinical tests used to assess extrinsic factors associated with SIS.

Method: A scoping review identified tests for extrinsic SIS. A systematic approach was then used to search six electronic databases in July 2016 to identify clinical tests used to measure (1) posterior shoulder range, (2) cervical and/or thoracic posture, (3) 2D scapula movement, (4) rotator cuff strength. The 14 articles included in the review were assessed using a modified Downs and Black quality assessment tool.

Results: Moderate quality studies investigated 2D scapula measurements (N = 2), resting pectoralis minor length (N = 2) and rotator cuff strength (N = 5). High quality studies measured forward head position and/or thoracic posture (N = 2) and rotator cuff strength (N = 1).

Conclusion: A good level of assessment reliability and significantly less range and strength was identified in those with SIS for: posterior shoulder range (passive shoulder adduction and internal rotation and passive internal rotation in supine); isokinetic peak torque values for internal and external shoulder rotation (isokinetic testing); forward head position (lateral photograph) and thoracic range of motion (tape measure or ultrasound tomography). Good to excellent reliability was reported for lateral scapular slide test positions and resting pectoralis minor muscle length. These clinical tests should be considered for use in SIS assessment.     

The potential role of upper extremity muscle fatigue in the generation of extrinsic subacromial impingement syndrome: a kinematic perspective

Abstract

Background:

Subacromial impingement syndrome (SAIS) of the shoulder has a multi-factorial aetiology which includes both intrinsic and extrinsic mechanisms. Upper extremity muscle fatigue has been proposed as a potential causative factor in extrinsic SAIS development.

Objectives:

This review summarises the current state of knowledge regarding fatigue-induced glenohumeral (GH) and scapulothoracic (ST) kinematic changes as they relate to subacromial space reduction and subsequent SAIS. It specifically addresses evidence for mechanisms including superior humeral head translation and scapular reorientation.

Major findings:

Global upper extremity muscle fatigue elicits GH kinematic changes that increase SAIS risk. Concurrent compensatory ST kinematic alterations, primarily scapular upward rotation (UR), lessen this risk. Additionally, fatiguing protocols aimed to selectively exhaust certain muscles or muscle groups without fatiguing the rotator cuff were unsuccessful, suggesting that rotator cuff fatigue is likely for a wide range of fatiguing upper extremity tasks.

Conclusions:

Despite the compensatory response of scapular reorientation in fatigued conditions, the dimensions of the subacromial space still pose increased risk for SAIS development, and the variability in kinematic responses produces highly differential risk, particularly for those exposed to tasks requiring increased rotator cuff muscle demand.     

Three-dimensional in vivo comparative analysis of the kinematics of normal shoulders and shoulders with massive rotator cuff tears with successful conservative treatment

BackgroundThis study used in vivo three-dimensional to two-dimensional image registration techniques to compare the glenohumeral kinematics of shoulders with massive rotator cuff tears that were successfully treated conservatively and those of normal shoulders.MethodsTen patients (age, 67.4 ± 3.63 years) with massive rotator cuff tears on one side and without contralateral tears were enrolled. We performed computed tomography and fluoroscopy on both shoulder joints and created three-dimensional bone models of the humerus and scapula using image registration techniques. We measured the humeral superoinferior translation, angle of humeral external rotation, scapular upward rotation, scapular anteroposterior tilt, and scapular external rotation of the torn shoulders with good range of motion after effective conservative treatment and compared these measurements to those of the contralateral normal shoulders.FindingsThere was a significant difference in the initial position of the humeral head relative to the glenoid in the tear group; it was 2.0 mm higher than that in the normal group (p < .05). This difference disappeared in the range from 40° to full elevation. The scapular motion of the tear group was significantly more upwardly rotated than that of the normal group: by 9.9° at rest (p < .05) and by 11.6° at terminal elevation (p < .05). No significant differences were detected for humeral head external rotation, scapular anteroposterior tilt, and scapular external rotation between the two groups.InterpretationKinematics of shoulders with massive cuff tears could not be recovered completely even though the patients had no significant symptoms after successful conservative treatment.     

Shoulder kinematics impact subacromial proximities: a review of the literature

BackgroundAlterations in glenohumeral and scapulothoracic kinematics have been theorized to contribute to rotator cuff pathology by impacting the magnitude of the subacromial space.ObjectiveThe purpose of this review is to summarize what is currently known about the relationship between shoulder kinematics and subacromial proximities.ConclusionsA variety of methods have been used to quantify subacromial proximities including photographs, MR imaging, ultrasonography, and single- and bi-plane radiographs. Changes in glenohumeral and scapulothoracic kinematics are associated with changes in subacromial proximities. However, the magnitude and direction of a particular motion's impact on subacromial proximities often vary between studies, which likely reflects different methodologies and subject populations. Glenohumeral elevation angle has been consistently found to impact subacromial proximities. Plane of humeral elevation also impacts subacromial proximities but to a lesser degree than the elevation angle. The impact of decreased scapulothoracic upward rotation on subacromial proximities is not absolute, but instead depends on the angle of humerothoracic elevation. The effects of scapular dyskinesis and humeral and scapular axial rotations on subacromial proximities are less clear. Future research is needed to further investigate the relationship between kinematics and subacromial proximities using more homogenous groups, determine the extent to which compression and other factors contribute to rotator cuff pathology, and develop accurate and reliable clinical measures of shoulder motion.     

The specificity of fatiguing protocols affects scapular orientation: Implications for subacromial impingement

Background

Shoulder impairments are often associated with altered scapular kinematics. As muscles control scapular movement, functionally altering muscle performance through fatigue may produce scapular kinematics that mimic those of injured patients. The aim of this study was to examine if changes in scapular tilt, rotation and pro/retraction following two different upper extremity fatiguing protocols have any implications with respect to subacromial impingement.

Methods

Scapular orientation was monitored during posturally constrained static holds (at 0°, 45° and 90° of humeral elevation) before and after two fatiguing protocols, one global and one local. Both protocols are associated with producing changes in shoulder skeletal arrangement.

Findings

Following the global fatiguing protocol, there was significantly more scapular posterior tilt (P < 0.01) and upward rotation (P < 0.02), particularly at 90° humeral elevation. No changes in scapular orientation occurred following the local fatiguing protocol.

Interpretation

Scapular orientation changes following muscle fatigue acted to increase the subacromial space. Thus, the rotator cuff muscles, not the scapular stabilizers, have more influence on actively preventing mechanical subacromial impingement. The lack of evidence of reduction of the subacromial space thus implicates superior humeral head translation as a more likely primary mechanism of the initiation of subacromial impingement.     

Decreasing glenoid inclination improves function in shoulders with simulated massive rotator cuff tears

BACKGROUND: A massive rotator cuff tear leads to poor shoulder function as evidenced by diminished glenohumeral abduction and superior translation of the humeral head compared to its normal position. The inclination angle of the glenoid has been associated with rotator cuff tears. The objective of this study was to quantify the effect of a decreased glenoid inclination angle on glenohumeral kinematics during active abduction in shoulders with a simulated, massive rotator cuff tear. METHODS: Eight fresh-frozen full upper extremities were tested using a dynamic shoulder testing apparatus. After recording the kinematics of the intact shoulder, a massive rotator cuff tear was surgically simulated. An osteotomy of the glenoid was then performed and the inclination angle was decreased by 30 degrees . The translation of the humeral head during abduction and the maximum abduction angle were recorded. FINDINGS: With an intact rotator cuff minimal humeral head translation on the glenoid occurred and the maximum abduction angle was mean 85.5 degrees (SD 7.4 degrees ). A massive rotator cuff tear resulted in superior translation of the humeral head with impingement on the acromion. The maximum abduction angle was mean 15.5 degrees (SD 9.4 degrees ). Decreasing the inclination angle of the glenoid resulted in a significant reduction of superior humeral head translation during abduction and there was no impingement on the acromion. The maximum abduction achieved was mean 28.5 degrees (SD 17.0 degrees ). INTERPRETATION: From a clinical perspective the reduced superior translation may decrease shoulder pain since the humeral head no longer impinges on the acromion. Further investigations are necessary to assess if the improvement in abduction is clinically significant.     

肩部撞击综合征的发生机制和影像学表现

肩部撞击综合征是临床上常见的引起肩关节疼痛和活动障碍的一组疾病,以肩袖、肱二头肌肌腱等结构的炎症及损伤为主要病理改变.广义的肩部撞击综合征包括肩峰下撞击、喙突下撞击和内撞击三型,对其发生机制尚存在争议,本文就肩部撞击的发生机制和影像学表现进行综述.     

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 impingement syndrome: relationships between clinical, functional, and radiologic findings

OBJECTIVE: Although there has been much research about imaging methods for shoulder impingement syndrome, the clinical information and upper limb level of disability have been generally ignored. The purpose of this study was to detect the relationships between clinical, functional, and radiologic variables in patients with shoulder impingement syndrome. DESIGN: A cross-sectional, clinical, and radiologic study was planned and 59 shoulders of 58 consecutive patients waiting for physical therapy because of a clinically suspected shoulder impingement syndrome were included into this study. Comprehensive clinical examination, radiography, shoulder ultrasonography, and magnetic resonance imaging were performed in the same month. RESULTS: Despite the high sensitivities of ultrasonography for diagnosing rotator cuff tears (98.1%) and biceps pathologies (100%), magnetic resonance imaging was superior to ultrasonography in many important shoulder structures such as a glenoid labral tear and subacromial bursal effusion/hypertrophy (P < 0.01). These structures were the determinants of the shoulder's disability measured by disabilities of the arm, shoulder, and hand questionnaire. CONCLUSION: Ultrasonography and magnetic resonance imaging had comparable high accuracy for identifying the biceps pathologies and rotator cuff tears. The basic clinical tests had modest accuracy in both disorders. The choice of which imaging test to perform should be based on the patient's clinical information (regarding lesion of glenoid labrum, joint capsule, muscle, and bone), cost, and imaging experience of the radiology department.     

In vivo measurement of subacromial space width during shoulder elevation: technique and preliminary results in patients following unilateral rotator cuff repair

BACKGROUND: The shoulder's subacromial space is of significant clinical interest due to its association with rotator cuff disease. Previous studies have estimated the subacromial space width to be 2-17 mm, but no study has measured in vivo subacromial space width during shoulder motion. The purpose of this study was to measure the in vivo subacromial space width during shoulder elevation in patients following rotator cuff repair. METHODS: Biplane X-ray images were collected during shoulder elevation of 11 patients who had undergone rotator cuff repair. Glenohumeral joint motion was measured from the biplane X-ray images for each subject's repaired and asymptomatic, contralateral shoulders. The joint motion data were combined with subject-specific CT models to measure the subacromial space width during shoulder motion. FINDINGS: Subacromial space width decreased with shoulder elevation, ranging from 2.3 to 7.4 mm in the repaired shoulder and 1.2-7.1 mm in the contralateral shoulder. Subacromial space width in the repaired shoulder was only 0.5 mm less than the contralateral shoulder when averaged over 10-60 degrees of glenohumeral elevation. INTERPRETATION: The results indicate that the humerus in the repaired shoulder is positioned more cranially on the glenoid than in the contralateral shoulder. It is unclear if these subtle differences in subacromial space width are due to the surgical procedure or post-operative stiffness, or if subacromial impingement contributed to the development of the rotator cuff tear. Future research will ascertain if these results represent a transient response to the surgery or a more fundamental difference in rotator cuff function between repaired and contralateral shoulders.     

The effect of a rotator cuff tear and its size on three-dimensional shoulder motion

BackgroundRotator cuff-disease is associated with changes in kinematics, but the effect of a rotator cuff-tear and its size on shoulder kinematics is still unknown in-vivo.MethodsIn this cross-sectional study, glenohumeral and scapulothoracic kinematics of the affected shoulder were evaluated using electromagnetic motion analysis in 109 patients with 1) subacromial pain syndrome (n = 34), 2) an isolated supraspinatus tear (n = 21), and 3) a massive rotator cuff tear involving the supraspinatus and infraspinatus (n = 54). Mixed models were applied for the comparisons of shoulder kinematics between the three groups during abduction and forward flexion.FindingsIn the massive rotator cuff-tear group, we found reduced glenohumeral elevation compared to the subacromial pain syndrome (16°, 95% CI [10.5, 21.2], p < 0.001) and the isolated supraspinatus tear group (10°, 95% CI [4.0, 16.7], p = 0.002) at 110° abduction. Reduced glenohumeral elevation in massive rotator cuff tears coincides with an increase in scapulothoracic lateral rotation compared to subacromial pain syndrome (11°, 95% CI [6.5, 15.2], p < 0.001) and supraspinatus tears (7°, 95% CI [1.8, 12.1], p = 0.012). Comparable differences were observed for forward flexion. No differences in glenohumeral elevation were found between the subacromial pain syndrome and isolated supraspinatus tear group during arm elevation.InterpretationThe massive posterosuperior rotator cuff-tear group had substantially less glenohumeral elevation and more scapulothoracic lateral rotation compared to the other groups. These observations suggest that the infraspinatus is essential to preserve glenohumeral elevation in the presence of a supraspinatus tear. Shoulder kinematics are associated with rotator cuff-tear size and may have diagnostic potential.     

Online Information About the Effectiveness of Shoulder Surgery Is Not Based on the Best Available Evidence: A Content Analysis

ObjectiveTo summarize the proportion of consumer webpages on subacromial decompression and rotator cuff repair surgery that make an accurate portrayal of the evidence for these operations (primary outcome), mention the benefits and harms of surgery, outline alternatives to surgery, and make various surgical recommendations.DesignContent analysis.SettingOnline consumer information about subacromial decompression and rotator cuff repair surgery. Webpages were identified through (1) Google searches using terms synonymous with “shoulder pain” and “shoulder surgery” and searching “orthopedic surgeon” linked to each Australian capital city and (2) websites of relevant professional associations (eg, Australian Orthopaedic Association). Two reviewers independently identified webpages and extracted data.ParticipantsNot applicable.InterventionsNot applicable.Main Outcome MeasuresWhether the webpage made an accurate portrayal of the evidence for subacromial decompression or rotator cuff repair surgery (primary outcome), mentioned benefits and harms of surgery, outlined alternatives to surgery, and made various surgical recommendations (eg, delay surgery). Outcome data were summarized using counts and percentages.ResultsA total of 155 webpages were analyzed (n=89 on subacromial decompression, n=90 on rotator cuff repair, n=24 on both). Only 18% (n=16) and 4% (n=4) of webpages made an accurate portrayal of the evidence for subacromial decompression and rotator cuff repair surgery, respectively. For subacromial decompression and rotator cuff repair, respectively, 85% (n=76) and 80% (n=72) of webpages mentioned benefits, 38% (n=34) and 47% (n=42) mentioned harms, 94% (n=84) and 92% (n=83) provided alternatives to surgery, and 63% (n=56) and 62% (n=56) recommended delayed surgery (the most common recommendation).ConclusionsMost online information about subacromial decompression and rotator cuff repair surgery does not accurately portray the best available evidence for surgery and may be inadequate to inform patient decision making.     

The Aetiology of Subacromial Impingement Syndrome

Subacromial impingement syndrome is one of the most common causes of shoulder pathology (Jobe and Jobe, 1983; Kessel and Watson, 1977) with reference to the condition appearing in the literature approximately 150 years ago (Adams, 1852). The pain and dysfunction associated with SIS are generally considered to occur when the shoulder is placed in positions of elevation, an activity commonplace during many sporting and vocational pursuits, as well as during the activities involved in daily living.Although it has been popular to assign blame for this condition on the acromion, considerable evidence suggests that SIS is of multifactorial aetiology. Other factors include rotator cuff over-use and degen-eration, glenohumeral hypermobility and instability, restrictive processes of the shoulder, functional scapular instability as well as poor posture. Many of these models of impingement still remain hypothetical and require confirmation.Further, many other structures may refer symptoms to the shoulder and may mimic the symptoms of SIS. Each category of subacromial impingement may require its own specific treatment and rehabilitation programme. At present there is not enough evidence in the literature to determine the most appropriate assessment methods or treatment strategies for each category of impingement. Key Messages

▪ Subacromial impingement syndrome has been described as the most common form of shoulder pathology.

▪ The pain of subacromial impingement is generally experienced around the anterolateral aspect of the shoulder during activities involving shoulder elevation.

▪ The aetiology of subacromial impingement syndrome is multifactorial. Each potential cause may act independently or in combination with one another.

Immediate effects of kinesiotaping on acromiohumeral distance and shoulder proprioception in individuals with symptomatic rotator cuff tendinopathy

BackgroundKinesiotaping is widely used for the rehabilitation of rotator cuff tendinopathy. It has been argued to reduce symptoms and functional limitations through improvement of proprioceptive feedback. In addition, kinesiotaping has been reported to increase the subacromial space in healthy subjects. However, its effects on the acromiohumeral distance and shoulder proprioception of individuals with rotator cuff tendinopathy have not been ascertained. This study investigated the immediate effects of kinesiotaping on the acromiohumeral distance and shoulder proprioception in individuals with rotator cuff tendinopathy.MethodsTwenty-two individuals with chronic rotator cuff tendinopathy were included. The acromiohumeral distance was measured using an ultrasound scanner at rest and 60° shoulder abduction. Proprioception was measured through active joint repositioning in low- (45°–65°) and mid-amplitude (80°–100°) of shoulder flexion and abduction. A wireless inertial measurement unit system was used to quantify shoulder angles. First, measurements were taken without kinesiotaping. Thereafter, kinesiotaping was applied on the symptomatic shoulder, and the same measurements were retaken. Repeated measures ANOVAs were used for statistical analyses.FindingsKinesiotaping induced a significant increase in acromiohumeral distance at 60° abduction (∆AHD = 0.94 mm; 95%CI: 0.50–1.38, p < 0.001), exceeding the minimal detectable change (0.70 mm). No significant difference was observed in acromiohumeral distance at rest or in proprioception during active joint repositioning in both low- and mid-amplitude (p > 0.05).InterpretationKinesiotaping led to an immediate increase in acromiohumeral distance at 60° of abduction that, although it seems a minor change (↑10.5%), it may be significant for symptomatic patients, whereas it had no immediate effect on active joint repositioning.     

Validation of Ultrasound Measurement of the Subacromial Space Using a Novel Shoulder Phantom Model

Ultrasound has a high degree of diagnostic accuracy in the assessment of rotator cuff tendons. Increasingly, ultrasound is being used to measure other parameters of rotator cuff pathology, including the size of the subacromial space, or acromiohumeral distance (AHD). Although this measure has been found to be clinically reliable, no assessment of its validity has been carried out. This technical study reports on the development of a novel ultrasound phantom of the shoulder and its use in validation of ultrasound measurement of AHD. There was a close agreement between AHD measures using ultrasound and the true subacromial space of the phantom model, providing support for the construct validity of this measurement. The phantom model has good potential for further development as a training tool for shoulder ultrasound and guided injections.     

Three-dimensional scapular morphology is associated with rotator cuff tears and alters the abduction moment arm of the supraspinatus

BackgroundNumerous studies have reported an association between rotator cuff injury and two-dimensional measures of scapular morphology. However, the mechanical underpinnings explaining how these shape features affect glenohumeral joint function and lead to injury are poorly understood. We hypothesized that three-dimensional features of scapular morphology differentiate asymptomatic shoulders from those with rotator cuff tears, and that these features would alter the mechanical advantage of the supraspinatus.MethodsTwenty-four individuals with supraspinatus tears and twenty-seven age-matched controls were recruited. A statistical shape analysis identified scapular features distinguishing symptomatic patients from asymptomatic controls. We examined the effect of injury-associated morphology on mechanics by developing a morphable model driven by six degree-of-freedom biplanar videoradiography data. We used the model to simulate abduction for a range of shapes and computed the supraspinatus moment arm.FindingsRotator cuff injury was associated with a cranial orientation of the glenoid and scapular spine (P = .011, d = 0.75) and/or decreased subacromial space (P = .001, d = 0.94). The shape analysis also identified previously undocumented features associated with superior inclination and subacromial narrowing. In our computational model, warping the scapula from a cranial to a lateral orientation increased the supraspinatus moment arm at 20° of abduction and decreased the moment arm at 160° of abduction.InterpretationsThree-dimensional analysis of scapular morphology indicates a stronger relationship between morphology and cuff tears than two-dimensional measures. Insight into how morphological features affect rotator cuff mechanics may improve patient-specific strategies for prevention and treatment of cuff tears.