Ultrasonographic findings of the shoulder in patients with rheumatoid arthritis and comparison with physical examination

The objectives of this study were: 1) to identify the ultrasonographic (US) abnormalities and 2) to compare the findings of physical examination with US findings in rheumatoid arthritis (RA) patients with shoulder pain. We studied 30 RA patients. Physical examination was performed systemically as follows: 1) area of tenderness; 2) range of passive and active shoulder motion; 3) impingement tests; 4) maneuvers for determining the location of the tendon lesions. US investigations included the biceps, the supraspinatus, infraspinatus, and subscapularis tendons; the subacromial-subdeltoid bursa; and the glenohumeral and acromioclavicular joints. Thirty RA patients with 35 painful and 25 non-painful shoulders were examined. The range of motion affected the most by shoulder pain was abduction. The most frequent US finding of shoulder joint was effusion in the long head of the biceps tendon. Among the rotator cuff tendons, subscapularis was the most frequently involved. Tendon tear was also common among non-painful shoulders. Physical examination used for the diagnosis of shoulder pain had low sensitivity and specificity for detecting abnormalities in the rheumatoid shoulder joint. In conclusion, US abnormalities showed frequent tendon tears in our RA patients. Physical examination had low sensitivity and specificity for detecting rotator cuff tear in the rheumatoid shoulder joint.     

A comprehensive analysis of muscle recruitment patterns during shoulder flexion: an electromyographic study

Although flexion is a common component of the routine clinical assessment of the shoulder the muscle recruitment patterns during this movement are not clearly understood making valid interpretation of potential muscle dysfunction problematic. The purpose of this study was to comprehensively examine shoulder muscle activity during flexion in order to compare the activity levels and recruitment patterns of shoulder flexor, scapular lateral rotator and rotator cuff muscles. Electromyographic (EMG) data were recorded from 12 shoulder muscles sites in 15 volunteers. Flexion was performed in standing in the sagittal plane at no load, 20%, and 60% of each subject's maximum load. EMG data were normalized to maximum values obtained during maximum voluntary contractions. Results indicated that anterior deltoid, pectoralis major, supraspinatus, infraspinatus, serratus anterior, upper, and lower trapezius were activated at similar moderate levels. However, subscapularis was activated at low levels and significantly lower than supraspinatus and infraspinatus. Similar activity patterns across time were demonstrated in the muscles that produce flexion torque, laterally rotate the scapula, as well as supraspinatus and infraspinatus, and did not change as flexion load increased. The onset of activity in supraspinatus and anterior deltoid occurred at the same time and prior to movement of the limb at all loads with infraspinatus activity also occurring prior to movement onset at the medium and high load conditions only. Posterior rotator cuff muscles appear to be counterbalancing anterior translational forces produced during flexion and it would appear that supraspinatus is one of the muscles that consistently "initiates" flexion.     

The moment arms of the muscles spanning the glenohumeral joint: a systematic review

The moment arm of a muscle represents its leverage or torque‐producing capacity, and is indicative of the role of the muscle in joint actuation. The objective of this study was to undertake a systematic review of the moment arms of the major muscles spanning the glenohumeral joint during abduction, flexion and axial rotation. Moment arm data for the deltoid, pectoralis major, latissimus dorsi, teres major, supraspinatus, infraspinatus, subscapularis and teres minor were reported when measured using the geometric and tendon excursion methods. The anterior and middle sub‐regions of the deltoid had the largest humeral elevator moment arm values of all muscles during coronal‐ and scapular‐plane abduction, as well as during flexion. The pectoralis major, latissimus dorsi and teres major had the largest depressor moment arms, with each of these muscles exhibiting prominent leverage in shoulder adduction, and the latissimus dorsi and teres major also in extension. The rotator cuff muscles had the largest axial rotation moment arms regardless of the axial position of the humerus. The supraspinatus had the most prominent elevator moment arms during early abduction in both the coronal and scapular planes as well as in flexion. This systematic review shows that the rotator cuff muscles function as humeral rotators and weak humeral depressors or elevators, while the three sub‐regions of the deltoid behave as substantial humeral elevators throughout the range of humeral motion. The pectoralis major, latissimus dorsi and teres major are significant shoulder depressors, particularly during abduction. This study provides muscle moment arm data on functionally relevant shoulder movements that are involved in tasks of daily living, including lifting and pushing. The results may be useful in quantifying shoulder muscle function during specific planes of movement, in designing and validating computational models of the shoulder, and in planning surgical procedures such as tendon transfer surgery.     

Anatomy and function of the subdeltoid bursa

An anatomical study was undertaken on 40 non-embalmed normal cadaver shoulders to determine the attachments, boundaries and macroscopic nerve supply of the subdeltoid bursa. Two areas of attachment were observed, one (proximal and superficial) along the free border of the coracoacromial ligament and adjacent deep surface of deltoid, the other (distal and deep) to the humerus distal to the supraspinatus tendon there were no posterior or anterior attachments. In addition, two blind pouches were observed, one proximal under the coracoacromial ligament and the other beyond the distal attachment. The continuity observed between the lateral border of the coracoacromial ligament and the subdeltoid bursa provides a smooth surface, thereby casting doubt on the aggressive action of the ligament on the rotator cuff.     

Shoulder measurements on MRI: Statistical analysis of patients without and with rotator cuff tears and predictive modeling

This study aims to determine significant differences between various measurements of shoulder structures and relationships in patients with and without rotator cuff tears and identify a subset of these measurements that may merit further investigation. Shoulder MRIs of 120 patients with rotator cuff tears (RCT group) and 80 patients with normal examinations (No RCT group) were retrospectively identified. Numerous measurements of shoulder anatomy and relationships and pathology characterization were performed for each study. The mean and ranges of measurements for each group were identified, and P-values were calculated to assess differences between the two groups. Classification and Regression Tree (CART) identified prediction models for separating the two groups based on these shoulder MRI measurements. Statistically significant differences were observed for 9 of 18 of the shoulder measurements between the two groups (P < 0.05). Using long head of biceps tendon tear, tendinosis, and subacromial–subdeltoid bursal fluid, the prediction model from CART demonstrated 99.5% accuracy in separating the two groups. Subacromial distance, subacromial spur size, and acromioclavicular osteophyte could also separate the two groups with 97.5% accuracy. Other measures less commonly associated with impingement and rotator cuff tears could also be used to separate the two groups with up to 81.5% accuracy. This study introduces new measures and clarifies ranges for existing measurements on shoulder MRI. Abnormalities of some of these measurements may be associated with subacromial impingement, and combinations of these parameters may be useful for separating patients with or without rotator cuff tears. Clin. Anat. 33:173–186, 2020. © 2019 Wiley Periodicals, Inc.     

Infraspinatus and Supraspinatus Tendon Strain Explained Using Multiple Regression Models

Supraspinatus tendon tears are complex yet common. We have shown that the supraspinatus and infraspinatus tendons interact, indicated by parallel changes in strain in the supraspinatus and infraspinatus with increasing size of supraspinatus tear, load applied to the supraspinatus, and changes in glenohumeral rotation but not abduction angle, suggesting disruption in the interaction between the two tendons with increase in abduction angle. While considering these factors individually is valuable, the contribution of each factor in the context of all others on strain in the supraspinatus, or on the interaction between the two tendons is unknown and has important implications in the management of rotator cuff tears. In this study, regression models using least-square estimation with backward and forward elimination were used to predict strains in the infraspinatus and supraspinatus from joint position, supraspinatus load, and supraspinatus tear size or repair. Interestingly, despite previous findings showing that supraspinatus tear size significantly affects infraspinatus strain, tear size was not a significant predictor of infraspinatus strain, emphasizing the importance of other factors evaluated such as joint position and shoulder loading in management of cuff tears and postoperative care. A better understanding of the loading environment in rotator cuff tendons necessitates multifactorial complex models.     

Quantitative morphology of full thickness rotator cuff tears

The occurrence of full thickness rotator cuff tears (RCTs) at time of death, the size and distribution of those tears among the tendons of the rotator cuff, and the anterior to posterior and medial to lateral dimensions of the RCTs were determined. A subset of 57 shoulders from a group of 414 were found to have full thickness rotator cuff tears. The three-dimensional coordinates of specific bony landmarks and points defining the circumference of the RCT were digitized using a Flock of Birds DC electromagnetic tracking device. Bony landmarks were used to determine the separation between adjacent tendons of the rotator cuff. Points describing the circumference of the RCT were used to calculate the area of the tear. The majority of tears occurred in the supraspinatus tendon alone (25), or in both the supraspinatus and infraspinatus tendons (22). The areas of the RCTs ranged from 0.07 cm(2) to 19.17 cm(2) with an average of 4.43 cm(2). The mean anterior to posterior length was 1.95 cm. The mean medial to lateral length was 1.98 cm.     

Lines of action and stabilizing potential of the shoulder musculature

The objective of the present study was to measure the lines of action of 18 major muscles and muscle sub‐regions crossing the glenohumeral joint of the human shoulder, and to compute the potential contribution of these muscles to joint shear and compression during scapular‐plane abduction and sagittal‐plane flexion. The stabilizing potential of a muscle was found by assessing its contribution to superior/inferior and anterior/posterior joint shear in the scapular and transverse planes, respectively. A muscle with stabilizing potential was oriented to apply more compression than shear at the glenohumeral joint, whereas a muscle with destabilizing potential was oriented to apply more shear. Significant differences in lines of action and stabilizing capacities were measured across sub‐regions of the deltoid and rotator cuff in both planes of elevation (P < 0.05), and substantial differences were observed in the pectoralis major and latissimus dorsi. The results showed that, during abduction and flexion, the rotator cuff muscle sub‐regions were more favourably aligned to stabilize the glenohumeral joint in the transverse plane than in the scapular plane and that, overall, the anterior supraspinatus was most favourably oriented to apply glenohumeral joint compression. The superior pectoralis major and inferior latissimus dorsi were the chief potential scapular‐plane destabilizers, demonstrating the most significant capacity to impart superior and inferior shear to the glenohumeral joint, respectively. The middle and anterior deltoid were also significant potential contributors to superior shear, opposing the combined destabilizing inferior shear potential of the latissimus dorsi and inferior subscapularis. As potential stabilizers, the posterior deltoid and subscapularis had posteriorly‐directed muscle lines of action, whereas the teres minor and infraspinatus had anteriorly‐directed lines of action. Knowledge of the lines of action and stabilizing potential of individual sub‐regions of the shoulder musculature may assist clinicians in identifying muscle‐related joint instabilities, assist surgeons in planning tendon reconstructive surgery, aid in the development of rehabilitation procedures designed to improve joint stability, and facilitate development and validation of biomechanical computer models of the shoulder complex.     

Localized Rotator Cuff Tendon Degeneration for Cadaveric Shoulders with and Without Tears Isolated to the Supraspinatus Tendon

Localized differences in tissue degeneration throughout intact and torn rotator cuff tendons have not been well quantified. The objective of this study was to investigate histological differences in localized degeneration in tendons with and without rotator cuff tears isolated to the supraspinatus tendon. Four intact shoulders and four shoulders with rotator cuff tears isolated to the supraspinatus tendon were dissected down to the infraspinatus and supraspinatus tendons. Biopsies were taken throughout the tendon insertion, mid-substance, myotendinous junction, and around the tear if present. Samples were stained with hematoxylin and eosin and tendon degeneration was graded based on collagen fiber organization, nuclei shape, cellularity, and lipoid degeneration. Comparisons in degeneration parameters were made based on the tendon type (supraspinatus vs. infraspinatus), location within the tendon, and presence of a tear. Supraspinatus tendons exhibited more degeneration than the infraspinatus tendon (P < 0.05). Significant increases in lipoid degeneration were found near the myotendinous junction compared to the rest of the tendon (P < 0.001). Tendons with rotator cuff tears showed greater amounts of lipoid degeneration compared to intact tendons (P = 0.03). A strong negative correlation was found between lipoid degeneration and collagen fiber organization (r = −0.922, P = 0.001). No differences in degeneration were found between medial, anterior, and posterior edges of the tear. The study highlights specific factors of tendon degeneration contributing to the local differences in tendon degeneration. By understanding local differences in tendon degeneration, surgical protocols for repair can be improved. Clin. Anat., 33:1007–1013, 2020. © 2019 Wiley Periodicals, Inc.     

Effect of rotator cuff dysfunction on the initial mechanical stability of cementless glenoid components

The functional outcome of shoulder replacement is related to the condition of the rotator cuff. Rotator cuff disease is a common problem in candidates for total shoulder arthroplasty; this study relates the functional status of the rotator cuff to the initial stability of a cementless glenoid implant. A 3D finite element model of a complete scapula was used to quantify the effect of a dysfunctional rotator cuff in terms of bone-implant interface micromotions when the implant is physiologically loaded shortly after surgery. Four rotator cuff conditions (from fully intact to progressively ruptured rotator cuff tendons) as well as two bone qualities were simulated in a model. Micromotions were significantly larger in the worst modeled cuff dysfunction (i.e. the supraspinatus and infraspinatus tendons were fully dysfunctional). Micromotions were also significantly different between conditions with healthy and poor bone quality. The implant’s initial stability was hardly influenced by a dysfunctional supraspinatus alone. However, when the infraspinatus was also affected, the glenohumeral joint force was displaced to the component’s rim resulting in larger micromotions and instability of the implant.     

Rotator cuff muscles perform different functional roles during shoulder external rotation exercises

The aim of this study was to compare activity in shoulder muscles during an external rotation task under conditions of increasing arm support to investigate whether changing support requirements would influence muscle recruitment levels, particularly in the rotator cuff (RC) muscles. Electromyographic recordings were collected from seven shoulder muscles using surface and indwelling electrodes. The dominant shoulder of 14 healthy participants were examined during dynamic shoulder external rotation performed at 90° abduction with the arm fully supported, partially supported, and unsupported. Linear regressions between arm support load and the averaged muscle activity across participants for each muscle showed infraspinatus predominantly contributing to rotating the shoulder whilst supraspinatus, deltoid, upper trapezius, and serratus anterior were predominantly functioning in support/stabilization roles. During dynamic shoulder external rotation in mid‐range abduction, the RC muscles perform different functional roles. Infraspinatus is responsible for producing external rotation torque, supraspinatus is playing a larger joint stabilizer role, and subscapularis is contributing minimally to joint stability. The results also indicate that increasing support load requirements during an external rotation task may be a functionally specific way to retrain the stabilization function of axioscapular muscles. Manipulating joint stabilization requirements while maintaining constant rotational load is a novel method of investigating the differential contribution of muscles to joint movement and stabilization during a given task. Clin. Anat. 2013. © 2012 Wiley Periodicals, Inc.     

Rotator cuff tendinosis in an animal model: role of extrinsic and overuse factors

The rat shoulder animal model has been used previously to study the role of intrinsic injury (modeled as an acute insult to the tendon), extrinsic injury (modeled as external subacromial impingement), and overuse factors on rotator cuff tendinosis. These studies demonstrated that it is possible to produce rotator cuff tendinosis with any one of these factors in isolation. The current study uses the rat shoulder model to study the roles of extrinsic compression, overuse, and overuse in combination with extrinsic compression, on the development of rotator cuff tendinosis. The results of this study demonstrate that the injury created by overuse plus extrinsic compression is greater than the injuries created by overuse or extrinsic compression alone, particularly when important biomechanical variables are considered. While ineffective in causing a change in supraspinatus tendon properties in animals with normal cage activity, extrinsic compression had a significant and dramatic effect when it was combined with overuse activity. Without an additional factor, such as overhead activity, the extrinsic compression alone may be insufficient to cause tendinosis. The results of the present study support the role of multiple factors in the etiology of some rotator cuff injuries. © 2002 Biomedical Engineering Society. PAC2002: 8719Rr, 8719St     

Clinical anatomy of the subacromial and related shoulder bursae: A review of the literature

The subacromial bursa (SAB) is the main bursa of the shoulder. It facilitates normal movement and is also commonly involved in shoulder disorders. Other shoulder bursae have been described but their anatomy has not been well studied. Anatomical variation of shoulder bursae has been suggested and this has implications for clinical practice. This article reviews current knowledge of the normal anatomy of the SAB and related shoulder bursae. A systematic review of the English and German literature was conducted using databases and a hand search of reference lists focusing on the clinical anatomy of the SAB, coracobrachial and subcoracoid bursae and subtendinous bursa of subscapularis. Twenty‐four original sources and 13 textbooks were identified. Fifteen studies described the general morphology of the shoulder bursae using cadaveric specimens, eight examined innervation, and one provided information about the blood supply of the SAB. The literature agrees that the SAB is consistent and well innervated with a lateral subdeltoid part and a variable subcoracoid portion. There is variability regarding the consistency, location, and communications of the coracobrachial and subcoracoid bursae and the superior part of the subtendinous bursa of subscapularis, and little information on their nerve and blood supply. Several bursae are present around the shoulder joint. Further research is warranted to understand the precise attachments, dimensions, and communications of the bursae, as well as their nerve and blood supply. This information will improve understanding of the clinical relevance of these bursae and inform appropriate assessment and treatment. Clin. Anat. 30:213–226, 2017. © 2017 Wiley Periodicals, Inc.     

Relationship between humeral geometry and shoulder muscle power among suspensory, knuckle-walking, and digitigrade/palmigrade quadrupedal primates

Shoulder morphology is functionally related to different patterns of locomotion in primates. To investigate this we performed a quantitative analysis of the relationship between cortical bone thickness (Cbt) of the muscle/tendon attachment site on the humerus and physiological cross-sectional area (PCSA) of the shoulder muscle in primates with different locomotory habits. The deltoid, subscapularis, supraspinatus, and infraspinatus were investigated. A chimpanzee, a gibbon, a baboon, two species of macaque, a lutong, a capuchin, and a squirrel monkey were included in the study. The total length of the humerus was measured and the values were converted into three-dimensional reconstructed data on a computer by computed tomography. The Cbt values were obtained from the volumes divided by the areas of the muscle/tendon attachment sites of the humerus by computer analysis. Muscle mass, muscle fascicle length, and muscle pennation angle were measured and PCSA was calculated using these parameters. A relatively high Cbt and small PCSA were characteristic of the gibbon. The gibbon's high Cbt suggests that passive tension in the muscle/tendon attachment site of suspensory primates (brachiators) may be greater than that of quadrupedal primates, whereas the relatively small PCSA indicates an association with a large amount of internal muscle fascia to endure the passive stress of brachiation. Although chimpanzees undertake some suspensory locomotion, the results for this species resemble those of the digitigrade/palmigrade quadrupedal primates rather than those of the suspensory primate. However, the deltoid and subscapularis in chimpanzee differ from those of the other primates and appear to be affected by the peculiar locomotion of knuckle-walking, i.e. the moment arm of forelimb in chimpanzees is relatively longer than that of digitigrade/palmigrade quadrupedal primates. Hence, a large PCSA in the deltoid and subscapularis may contribute to sustaining the body weight during locomotion. On the other hand, a thin cortical bone relative to a large PCSA was a feature of the cercopithecids, indicating that digitigrade/palmigrade quadrupedal locomotion produces less tension at the muscle/tendon attachment sites compared with that produced by brachiators.     

肩峰下脂肪垫的断层解剖与MRI观测及临床意义

目的　为肩峰撞击征的诊断和治疗提供断层解剖学基础。 方法　（1）取15例女性标本进行肩关节的断层切割观察;(2)运用MRI技术对10例女性健康人的肩峰下脂肪垫进行测量。 结果　（1）肩峰下脂肪垫上方为斜方肌,下方为冈上肌,在肩峰下面与肩峰下三角肌滑膜囊相邻,在横断面上呈方形,在斜矢状断面和斜冠状断面上呈长条形;肩峰下脂肪垫长度为（48.91±7.5）mm, 宽度为（28.0±4.7）mm,肩峰下脂肪垫厚度在冈上肌中部为（11.5±1.9）mm,在肩峰外缘为（3.1±0.8）mm。（2）MRI轴位、斜矢状位、斜冠状位可清楚显示肩峰下脂肪垫,肩峰下脂肪垫长度（49.8±7.0）mm, 宽度为(28.7±5.2)mm,肩峰下脂肪垫厚度在冈上肌中部为(12.5±1.5)mm,在肩峰外缘为(3.2±0.8)mm。（3）断层肩峰下脂肪垫长度、宽度、厚度观测值数据和MRI数据分别进行t检验结果无差异(P>0.05)。 结论　MRI的肩峰下脂肪垫测量可以为肩峰撞击症早期诊断提供解剖学依据。     

Dimensions of forelimb muscles in orangutans and chimpanzees

Eight forelimbs of three orangutans and four chimpanzees were dissected and the muscle mass, fascicle length and physiological cross-sectional area (PCSA) of all forelimb muscles were systematically recorded to explore possible interspecies variation in muscle dimensions. Muscle mass and PCSA were divided by the total mass and total PCSA of the entire forelimb muscles for normalization. The results indicate that the mass and PCSA ratios of the monoarticular elbow flexors ( M. brachialis and M. brachioradialis ) are significantly larger in orangutans. In contrast, the mass ratios of the biarticular muscles in the upper arm (the short head of M. biceps brachii and the long head of M. triceps brachii ) are significantly larger in chimpanzees. For the rotator cuff muscles, the force-generating capacity of M. subscapularis is significantly larger in orangutans, whereas the opposite rotator cuff muscle, M. infraspinatus , is larger in chimpanzees. These differences in forelimb muscle dimensions of the two species may reflect functional specialization for their different positional and locomotor behaviors.     

Innervation of the scapular muscles and its morphological significance in man

The origin, course and distribution of the nerves supplying the supraspinatus, infraspinatus, subscapularis, teres minor, deltoid, teres major and latissimus dorsi were examined in 40 human body-halves. All the nerves supplying these 7 muscles derive from the brachial plexus between the upper trunk and the posterior cord. Within the plexus the nerves originate in the following order: the suprascapular nerve in the most cranial and ventral position followed caudally and dorsally the superior subscapular nerve, the axillary nerve, the inferior subscapular nerve and the thoracodorsal nerve. The superior subscapular nerve tends to innervate the upper and middle (thoracic) portions of the subscapularis. Both the axillary and inferior subscapular nerves tend to innervate the lower (axillary) portion of the subscapularis as well as the teres minor and deltoid, and the teres major, respectively. The subscapularis can be regarded as the compound muscle deriving from the components supplied by these nerves, 4 segmental nerves from C5 to C8 innervate the 7 muscles: C5, and (C6) innervate the supraspinatus; C5, and C6 the infraspinatus, the thoracic portion of the subscapularis, and the teres minor; C5, C6, and (C7) the deltoid; (C5), C6, and (C7) the axillary portion of the subscapularis; (C5), C6, and C7 the teres major; and (C6), C7, and C8 the latissimus dorsi. The relationships between the nerves and muscles suggest that these 7 muscles morphologically belong to the same group, the second group of the dorsal musculature attached to the shoulder girdle and limb. The probable process of formation of these muscles from the cervical myotoms is proposed.     

肩袖损伤诊断与治疗方法的选择

目的 探讨肩袖损伤的临床诊断及治疗方法,并评价治疗效果。 方法 选择我院2004年7月~2008年7月收治的48例肩袖损伤患者,依患者分类采用非手术综合治疗及手术治疗。非手术综合治疗组17例,采取休息制动、中药或非甾体抗炎药口服、外用药物、封闭、牵引等方法。手术组31例采用肩关节外侧切口,切除喙肩韧带,肩峰成形,探查修整肩袖,褥式缝合冈上肌腱、冈下肌腱及肩胛下肌腱,术后肩关节外展位石膏固定。 结果 48例均得到半年以上随访,平均随访13个月,采用UCLA评分系统评价,其中手术治疗组中优20例,良10例,差1例,术后优良率96.8％,非手术综合治疗组优8例,良6例,差3例,优良率82.4%。 结论 对于NeerⅡ、Ⅲ期应积极采用手术治疗,是提高效果的关键。