Isolated subacromial bursal fluid on MRI of the shoulder in symptomatic patients: correlation with arthroscopic findings

Fluid in the subacromial bursa (SAB) is a common finding on magnetic resonance (MR) images of the shoulder, and the implications of this finding have not been clarified. We retrospectively reviewed and correlated the MR features with arthroscopic findings in 21 symptomatic patients who had fluid in the SAB on MR imaging without demonstrable rotator cuff tear. Rotator cuff impingement was the most frequent surgical finding (42.9%). Other frequent surgical observations were glenoid labrum abnormality (28.6%), bursitis (19%), and supraspinatus tendinitis (14.3%). Distribution of acromial types was similar to that reported by Bigliani et al., and impingement was evenly distributed among acromial types in our study population. We conclude that in our patient population group the MR finding of isolated SAB fluid in symptomatic patients is highly likely to be associated with the finding of other abnormalities in the shoulder joint at surgery.     

Schulterimpingement

The impingement syndrome is a clinical entity characterized by shoulder pain due to primary or secondary mechanical irritation of the rotator cuff. The primary factors for the development of impingement are a curved or hook-shaped anterior acromion as well as subacromial osteophytes, which may lead to tearing of the supraspinatus tendon. Secondary impingement is mainly caused by calcific tendinopathy, glenohumeral instability, os acromiale and degenerative changes of the acromioclavicular joint. Conventional radiographs are initially obtained, mainly for evaluation of the bony structures of the shoulder. If available, sonography can be used for detection of lesions and tears of the rotator cuff. Finally, MR-imaging provides detailed information about the relationship of the acromion and the acromioclavicular joint to the rotator cuff itself. In many cases however, no morphologic cause for impingement syndrome can be found. While patients are initially treated conservatively, chronic disease usually requires surgical intervention.     

MR imaging of the shoulder: appearance of the supraspinatus tendon in asymptomatic volunteers.

MR imaging has been shown to be accurate in the diagnosis of rotator cuff disruption and tear. Uncertainty remains about the significance of increased signal intensity in the critical zone of the supraspinatus tendon without visible disruption of tendon fibers and about the significance of other secondary findings commonly encountered with rotator cuff abnormalities, such as musculotendinous retraction or obliteration and fluid in the subacromial space. We evaluated proton density-weighted and T2-weighted coronal images (obtained on a 1.5-T superconductive MR imager) of 55 shoulders in 32 asymptomatic volunteers for signal intensity in the supraspinatus tendon, location of the musculotendinous junction, fluid in the subacromial-subdeltoid space, and appearance of the fat plane. In 89% of shoulders, the supraspinatus tendon showed focal, linear, or diffuse increased signal intensity with or without loss of the low-signal-intensity tendon margin on proton density-weighted images. None of these findings were confirmed on T2-weighted images. The musculotendinous junction was always located within an area 15 degrees medial to 30 degrees lateral to the highest point (12 o'clock) on the humeral head convexity. A peribursal fat plane was poorly defined or absent in 49%, and fluid in the subacromial-subdeltoid space was found in 20%. Increased signal intensity in the supraspinatus tendon on proton density-weighted images without a corresponding increase on T2-weighted images, the presence of small amounts of fluid in the subacromial space, and the lack of preservation of the subdeltoid fat plane are common findings in asymptomatic shoulders and by themselves are poor predictors of rotator cuff disease.     

MR findings in asymptomatic shoulders: a blind analysis using symptomatic shoulders as controls.

We performed a blind prospective analysis of the shoulders of 20 asymptomatic volunteers, aged 25 to 55 years, to determine the frequency of magnetic resonance (MR) findings considered abnormal in symptomatic patients. Twenty symptomatic patients were used as controls. With regard to the asymptomatic shoulders, all 20 had intact rotator cuff tendons, although six (30%) of the tendons had abnormal internal signal, and one (5%) had abnormal morphology. Subdeltoid and subacromial fat planes were intact in 20 (100%) and 19 (95%) shoulders respectively. Subdeltoid or subacromial fluid was not present in any shoulder. Acromioclavicular osteophytes and supraspinatus depression were seen in seven (35%) and six (30%) respectively. The glenoid labrum was intact in all volunteers, although it had abnormal internal signal in 10 (50%). MR findings of abnormal signal in the glenoid labrum, and of abnormal signal and morphology of the rotator cuff tendons, supraspinatus depression, and acromioclavicular osteophytes have been reported as signs of instability, tendinitis, and impingement. Similar findings were seen in asymptomatic volunteers, indicating that these findings may not be a sign of clinically significant pathology.     

Shoulder impingement syndrome: impingement view and arthrography study based on 100 cases

A prospective evaluation combining the shoulder impingement view and arthrography was made in patients presenting with chronic shoulder pain. Five hundred and twenty-three patients with chronic shoulder pain were X-rayed using conventional views and impingement views. One hundred of these patients (mean age 62 years) had subacromial bony spurs on the impingement view; these underwent arthrography. They were divided into two groups according to the degree of spur formation — whether or not the size of the spur exceeded one half of the acromial width as measured from the outer margin to the acromioclavicular joint. Of the 100 subacromial spurs demonstrated on the impingement view, only 18 were visible on the conventional view as assessed by an independent radiologist. Arthrography showed 35 cases of rotator cuff tear. The size of the bony spur was strongly associated with the incidence of rotator cuff tear (P < 0.02).     

Ultrasound measurement of rotator cuff thickness and acromio-humeral distance in the diagnosis of subacromial impingement syndrome of the shoulder

The usefulness of ultrasound measurements in the diagnosis of the subacromial impingement syndrome of the shoulder was evaluated. Fifty-seven patients with unilateral symptoms of the impingement syndrome underwent ultrasound examination of both shoulder joints, which included assessment of rotator cuff integrity, measurement of rotator cuff thickness and the distance between the infero-lateral edge of acromion and the apex of the greater tuberosity of humerus (AGT distance) in the standard ultrasonographic positions. As a control group, 36 volunteers (72 shoulders) with no history of shoulder pain were examined sonographically. Ultrasonographic assessment of humeral head elevation, measured as the AGT distance, proved to be useful in establishing the diagnosis of the subacromial impingement syndrome of the shoulder. A difference in rotator cuff thickness of more than 1.1 mm and a difference in the AGT distance of more than 2.1 mm between both shoulder joints may reflect dysfunction of rotator cuff muscles.     

The coracoacromial arch: MR evaluation and correlation with rotator cuff pathology

The relative prevalence of various acromial shapes, appearance of the coracoacromial ligament and enthesophytes along the inferior aspect of the acromioclavicular joint in patients with and without rotator cuff tears were evaluated. Of 76 patients with clinical instability and impingement, 31 had a normal rotator cuff and 45 demonstrated a partial or full tear of the supraspinatus tendon at surgery. Results were compared with those from magnetic resonance (MR) scans of 57 asymptomatic volunteers. Of the 45 patients with a supraspinatus tear, 38% (17) had a flat acromial undersurface (type I), 40% (18) had a concave acromial undersurface (type II), 18% (8) had an anteriorly hooked acromion (type III), and 4% (2) had an inferiorly convex acromion (type IV). Among the 31 patients with a normal rotator cuff at surgery and the 57 asymptomatic volunteers, the respective prevalences of the type I acromion were 39% (12) and 44% (25), of type II 48% (15) and 35% (20), type III 3% (1) and 12% (7), and type IV 10% (3) and 9% (5). Shoulders with surgically proven rotator cuff tears showed a tendential association with a type III acromion (8/45) and statistically significant associations with a thickened coracoacromial ligament (17/45) and acromioclavicular enthesophytes (18/45). For the association between inferiorly directed acromioclavicular joint enthesophytes and rotator cuff tears, age appears to be a confounding factor. The type IV acromion, newly classified by this study, does not have a recognizable association with rotator cuff tears. Assessment of the osseous-ligamentous coracoacromial outlet by may prove helpful to the orthopedic surgeon in patients for whom surgical decompression is contemplated.     

Measurement of subacromial impingement of the rotator cuff

Objective: Recent evidence suggests that shoulder impingement syndrome arises from primary rotator cuff pathology and may be related to the inability of the rotator cuff to prevent superior humeral head migration in shoulder elevation. Impingement involves compression of subacromial structures, including the rotator cuff. Previously, clinical tests have been shown to be inaccurate in diagnosing rotator cuff impingement. A lack of anatomical validity might explain the inaccuracy of these tests. This study aimed to clarify the anatomical basis of subacromial compression of the rotator cuff by analysing the compression forces generated and observing the structures impinged in a variety of shoulder positions. Design: This observational case series involved the dissection of nine embalmed cadaveric shoulders. Method: Pressure transducers were placed deep to the coracoid process, coracoacromial ligament, the anterior acromion and the posterior acromion. Shoulders were moved into internal and external rotation from the positions of flexion, abduction and extension. At each position, pressure readings were recorded and structures being compressed observed visually. Results: Highest pressures were recorded in flexion/internal rotation at the coracoacromial ligament, in abduction/internal rotation at the coracoid process (both involving the rotator interval) and in abduction/internal rotation at the coracoacromial ligament (involving supraspinatus). Supraspinatus was also observed to be compressed in extension/external rotation (against the anterior acromion). Infraspinatus was compressed in extension/external rotation (against the posterior acromion), while subscapularis was compressed in flexion/internal rotation and flexion/external rotation (both against the coracoid process). Conclusion: This study identifies shoulder positions likely to impinge particular rotator cuff tendons.     

Full-thickness tears of the rotator cuff of the shoulder: diagnosis with MR imaging.

The purpose of this study was to describe MR findings in full-thickness tears of the rotator cuff. Of 102 shoulders examined by MR imaging, 31 were found to have a full-thickness tendon tear at arthroscopy/bursoscopy (five shoulders) or open surgery (26 shoulders). All shoulders were imaged in oblique coronal and axial planes. MR images of the 102 shoulders were evaluated for (1) the presence of fluid in the subacromial and subdeltoid bursae; (2) abnormal signal of the supraspinatus, subscapularis, infraspinatus, and teres minor tendons; (3) interruption of tendon continuity and thinning of the tendon; and (4) proximal retraction of the junction of the muscle and tendon. The presence or absence of each finding was determined by consensus of two radiologists, who interpreted the images without knowledge of the surgical findings. Results in those 31 shoulders with proved full-thickness tears were: fluid in the subacromial bursae (29 shoulders), interruption of tendinous continuity (22 shoulders), focally increased signal of the tendon equivalent to that of water (27 shoulders), and musculotendinous retraction (24 shoulders). The finding of subacromial fluid was a sensitive indicator (93%) of a full-thickness tear, and interruption of tendinous continuity was a specific finding (96%) in diagnosing a full-thickness tear. Our experience shows interruption of tendon continuity is the most specific MR finding of full-thickness rotator cuff tears, while subacromial fluid is the most common finding.     

Findings of the subcoracoid bursa on MR arthrography and their clinical significance

We studied visualization of the subcoracoid bursa by conducting a retrospective analysis of the MR arthrograms of 101 shoulders with surgical confirmation. MR arthrography showed the subcoracoid bursa in 28 shoulders, among which the bursa was revealed by inadvertent direct injection of contrast material into the bursa in 10 shoulders. Of the remaining 18 shoulders, 16 shoulders had rotator cuff tears, one had shoulder instability, and one had dislocation of the long head of the biceps tendon. Both the subcoracoid and subscapularis bursae are located in the subcoracoid space. The subcoracoid bursa does not communicate with the subscapularis bursa, but occasionally communicates with the subacromial-subdeltoid bursa. On MR arthrography, contrast material in the subcoracoid bursa indicates a pathologic condition such as rotator cuff tear. Careful examination of the subcoracoid bursa on MR arthrography helps to achieve better assessment of the rotator cuff.     

Supraspinatus outlet view in the diagnosis of stages II and III impingement syndrome

Purpose: To compare supraspinatus outlet view (SOV) findings at different stages of the impingement syndrome (IS) with findings in asymptomatic age- and sex-matched controls.Material and Methods: Pre-operative SOVs were obtained of 37 shoulders of patients scheduled for unilateral open repair of a full-thickness rotator cuff tear (stage III IS) and 74 shoulders of patients scheduled for open (n=46) or arthroscopic (n=28) acromioplasty for tendinitis (stage II IS). Each view of a patient's shoulder was paired with a control view obtained from an age- and sex-matched person with no shoulder problems (n=111).Results: There were no significant differences in acromial morphology as evaluated on the scale devised by Bigliani et al. or in the tilt, slope or length of the acromion between the study groups and their controls. However, hooked acromion seemed to be more common in the patients. The thickness of the anterior part of the acromion at the tendinitis stage and the acromial angle at the tear stage of IS were the only parameters that showed significant differences between patients and controls.Conclusion: Variation of the morphology of the acromion as evaluated on a basis of the SOV is associated with IS, but the association is weak and its value in the diagnosis of IS is therefore only as an adjunctive to other diagnostic modalities.     

Rotator cuff coactivation ratios in participants with subacromial impingement syndrome

Coactivation of the rotator cuff is vital to glenohumeral joint stability by centralising the humeral head within the glenoid fossa. Yet in individuals with subacromial impingement, it is hypothesised that rotator cuff coactivation abnormalities are present that could contribute to their shoulder pain. The purpose of this study was to determine if abnormal rotator cuff coactivation and deltoid activation patterns exist in participants with subacromial impingement. Rotator cuff (supraspinatus, infraspinatus, and subscapularis) coactivation and middle deltoid activation was assessed during an elevation task. ANOVA models were used to compare muscle activation patterns in 10 participants with subacromial impingement and 10 control participants. Participants with impingement exhibited decreased rotator cuff coactivation (subscapularis–infraspinatus and supraspinatus–infraspinatus) and increased middle deltoid activation at the initiation of elevation (0–30° of humeral elevation). The participants with impingement also had higher subscapularis–infraspinatus and supraspinatus–infraspinatus coactivation above the level of the shoulder where pain is typically present (90–120° of humeral elevation). The results indicate that individuals with subacromial impingement exhibit rotator cuff muscle coactivation and deltoid activation abnormalities during humeral elevation that might contribute to the encroachment of the subacromial structures associated with subacromial impingement.     

Alterations in the supraspinatus tendon at MR imaging: correlation with histopathologic findings in cadavers

To determine the histopathologic correlates of alterations in the rotator cuff at magnetic resonance (MR) imaging, 13 cadaveric shoulders (in subjects aged 26-83 years at the time of death) underwent MR imaging in the coronal oblique plane at 1.5 T with proton-density- and T2-weighted spin-echo sequences. Areas corresponding to sites of MR imaging alterations were then examined histologically. Increased signal intensity on proton-density-weighted images (without further increased signal intensity on T2-weighted images) and an indistinct margin at the articular side of the supraspinatus tendon corresponded to eosinophilic, fibrillar, and mucoid degeneration and scarring. Areas of increased signal intensity on T2-weighted images were associated with severe degeneration and disruption of the supraspinatus tendon. Although other authors have suggested that certain MR findings are indicative of tendinitis, the histologic data in this study were not those of active inflammation but rather tendon degeneration.     

The relationship of acromial architecture to rotator cuff disease

Variations in the architecture of the coracoacromial arch can lead to a clinically symptomatic rotator cuff lesion. Differences in the development and morphology of the acromion, and the presence of anterior acromial spurs and inferior acromioclavicular osteophytes decrease the volume of the subacromial space, leading to impingement. Recent anatomic, radiographic, biomechanical, and SPG studies have confirmed these architectural variations and their effects on the contents of the subacromial space. Abnormal contact between the acromion and these soft tissues can lead to pathologic lesions. Surgical procedures should be directed at increasing the space beneath the coracoacromial arch to reduce wear on the rotator cuff.     

肩关节冈上肌出口位X线摄影在肩峰下撞击综合征中的应用价值

目的:探讨肩关节冈上肌出口位X线摄影所示肩峰形态、肩峰下间隙与肩峰下撞击综合征(shoulder impingement syndrome,SIS)的相关性,总结其临床应用价值。方法:回顾性分析60例经临床证实的SIS患者的临床及影像资料,对X线摄影所示的肩峰形态及肩峰下间隙进行分型、测量,并与MRI所见进行对照,分析肩峰形态及肩峰下间隙与SIS的相关性。结果:60例患者中,肩峰平坦形(Ⅰ型)8例、弧形(Ⅱ型)10例、钩状(Ⅲ型)42例。冈上肌出口位X线摄影所示肩峰下间隙为(1.21±0.36)cm,MRI所示肩峰下间隙值为(1.10±0.18)cm,两者差异无统计学意义(P0.05)。肩袖损伤MRI分级Ⅰ级27例,Ⅱ级20例,Ⅲ级13例。肩峰下间隙值与肩袖损伤MRI分级呈正相关(P0.05)。结论:肩关节冈上肌出口位X线摄影所示肩峰形态、肩峰下间隙与SIS发生密切相关;当肩峰形态为钩状及肩峰下间隙值1cm,强烈提示SIS可能,对于无MRI的基层医院诊断SIS临床意义明显,值得临床应用。     

Ultrasonographic rotator-cuff changes in veteran tennis players: the effect of hand dominance and comparison with clinical findings

The aim of this study was to correlate sonographic abnormalities of the rotator cuff with clinical findings in veteran tennis players. One hundred fifty individuals playing competition-level tennis, aged from 35 to 77 years (mean age 55 years), underwent physical and US examinations of their shoulders. The US abnormalities found in the dominant shoulder were compared with those observed in the non-dominant shoulder and in different subsets of players defined by the absence or presence of former and/or current pain. Tears of the long head of the biceps tendon were seen only in dominant shoulders (n=8), and tears (23 complete and 20 partial) of the supraspinatus tendon were observed in 43 dominant vs 16 (3 complete and 13 partial) contralateral shoulders (p<0.001). Subscapularis tendon calcifications were depicted in 23 dominant vs 12 contralateral shoulders (p<0.05). Seventy players had no pain, 49 had former-but-not-current pain, and 31 had current pain. Abnormal thickening (>2 mm) and effusion of the subacromial–subdeltoid bursa and complete tear of the supraspinatus tendon were more frequent in the latter two groups (p<0.001 and p<0.05), respectively. Although 90% of the players with a complete supraspinatus tear had experienced former pain, no relationship was found between current pain and the presence of a supraspinatus tear or tendon calcification. The rotator cuff may present important asymptomatic lesions, such as complete tears of the supraspinatus tendon or calcifications, that do not prevent the playing competitive tennis. The only US abnormality associated with pain was subacromial–subdeltoid bursa effusion.     

肩袖全层撕裂的MRI表现

目的 总结肩袖全层撕裂的MRI表现。材料与方法 回顾性分析21例肩关节MR造影证实的肩袖全层撕裂的MR图像。结果 21例肩袖全层撕裂均发生在冈上肌腱。在T2W序列上,6例（28．9％）表现为冈上肌腱断裂并断裂端的回缩;12例（57．1％）表现为冈上肌腱变薄或增粗并伴有贯穿冈上肌腱全层的高信号;1例（4．7％）表现为冈上肌腱增厚并未贯穿全层的下表面高信号;2例（9．3％）冈上肌腱的形态和信号未见异常。结论 冈上肌腱的断裂并回缩以及冈上肌腱形态增粗或变细并伴 有贯穿肌腱全层的异常高信号为全层撕裂的主要MRI表现。     

The shoulder impingement syndrome: prevalence of radiographic findings and correlation with response to therapy

The shoulder impingement syndrome is believed to be caused by compression of the rotator cuff tendons and subacromial bursa between the humeral head and structures that make up the coracoacromial arch. Plain film findings were tabulated for 36 patients, 22-81 years old, who had signs and symptoms of an acute impingement syndrome. The most common radiographic abnormalities were subacromial bony proliferation in 68%, degenerative changes in the greater tuberosity of the humerus in 66%, and degenerative joint disease in the acromioclavicular joint in 66%. There was evidence of calcium deposition in the rotator cuff in 37%, inferiorly oriented acromioclavicular osteophytes in 32%, and degenerative changes of the lesser humeral tuberosity in 29%. The acromiohumeral space was narrowed in only 21%. The radiographic findings were scored blindly and compared to the treatment outcome of 6 weeks of medical therapy. There was no statistically significant correlation between any of the radiographic findings and the response to medical therapy. The results suggest that radiographic findings are extremely common in patients with the acute impingement syndrome, but that they are not useful as prognostic indicators of the short-term response to medical treatment.     

直接数字X线摄影对肩峰下撞击综合征的诊断价值

目的探讨肩关节正位、轴位、肩峰出口位直接数字X线摄影(DR)在肩峰下撞击综合征诊断中的意义。方法选取以肩部疼痛及活动受限为主诉的患者20例进行分析,其中男性13例,女性7例,右肩15例,左肩5例,分别摄取肩关节正位、轴位、肩峰出口位DR片,20例患者均行患肩关节磁共振成像(MRI)检查。结果 DR检查9例阳性患者,磁共振成像(MRI)检查均可见肩袖表面毛糙、部分或全层撕裂,而DR检查阴性患者仅1例可见肩袖损伤。结论肩关节正位、轴位、肩峰出口位DR对诊断肩峰下撞击综合征具有病因学意义。     

Acromial morphology in patients with calcific tendinitis of the shoulder

Purpose

The purpose of this study was to evaluate whether the morphology of the acromion in calcific tendinitis differs from controls without subacromial pathology and matches subacromial impingement.

Methods

Digital radiographs of 150 shoulders were evaluated with the open source DICOM-Viewer OsiriX. 50 patients had symptomatic calcific tendinitis of the shoulder, 50 had subacromial impingement without calcifications or rotator cuff tears, 50 with bruised shoulder that were previously asymptomatic served as controls. Acromial shape according to Bigliani et al. acromial tilt (AT) according to Kitay et al. and Aoki et al. acromion index (AI) according to Nyffeler et al. and lateral acromial angle (LAA) according to Banas et al. were measured.

Results

Both calcific (0.72; P = 0.001) and impingement groups (0.73; P = 0.008) were significantly different from controls (0.67) using AI measure, while only the calcific group (79.5°) was different from controls (84.1°) using LAA (P < 0.001), and only the impingement group (32.9°) was different from controls (29.2°) using AT (P < 0.001). An LAA <70° only occurred in two patients with calcific tendinitis.

Conclusion

The hypothesis of this study was that the morphology of the acromion in calcific tendinitis differs from controls without subacromial pathology and matches subacromial impingement was only confirmed for the AI. The AI of shoulders with calcific tendinitis is comparable to that of shoulders with subacromial impingement.

Level of evidence

IV.