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This is the clinical evidence summary written for health professionals. It is technical, and it lists the research this page was built from. You do not need to read it to understand your treatment or to make a decision about it.

Overview¶

• Chronic subacromial bursitis can present as a soft tissue tumor mimic [1].
• Management of subacromial impingement syndrome includes physical therapy, injections, and surgery for some patients [2].
• There remains a need for high-quality studies of the pathology, etiology, and management of subacromial impingement syndrome [2].
• Current randomized, controlled trial evidence shows no difference in outcomes of shoulder function or pain between surgical and conservative treatment for subacromial impingement syndrome [6].
• Arthroscopic subacromial decompression provided no benefit over diagnostic arthroscopy at 24 months for patients with shoulder impingement syndrome [7].
• Arthroscopic subacromial decompression provided no benefit over diagnostic arthroscopy or exercise therapy at 5 years for patients with shoulder impingement syndrome [10].
• Arthroscopic subacromial decompression provided no benefit over diagnostic arthroscopy or exercise therapy on return to work in patients with shoulder impingement syndrome [11].
• Subacromial pain syndrome should preferably be treated non-operatively [12].
• Subacromial injection with corticosteroids is indicated for persistent or recurrent symptoms of subacromial pain syndrome [12].
• Adding a large dose of shoulder strengthening to current nonoperative care for patients with subacromial impingement did not result in superior shoulder-specific patient-reported outcomes [13].
• For patients who have a long-term disease course, operative treatments may be considered [19].
• Standard ASD surgery is preferred over arthroscopic bursectomy and the open surgical technique for subacromial decompression for patients with a long-term disease course [19].
• Ultrasound guidance is not superior in the subacromial bursa and glenohumeral joint injections in pain or function [21].
• ASD in the treatment of subacromial impingement yields good long-term results [24].
• Ultrasonography provides substantial benefit in detecting and determining the involvement of the shoulder in a patient with septic or tuberculous bursitis of the subacromial bursa [27].
• Five randomized trials found that formal subacromial decompression does not result in improved clinical outcomes up to 2 years after rotator cuff repair [30].
• There is no evidence from the available RCTs for differences in outcome in pain and shoulder function between conservatively and surgically treated patients with subacromial impingement syndrome [31].
• Preserving the subacromial bursa during rotator cuff surgery may lead to better rotator cuff healing when secondary pain is manageable [33].
• Conservative treatment can be recommended as a first choice of treatment of shoulder impingement in first or second grade because of surgery's higher costs and susceptibility for complications compared with costs and risks of conservative treatment [35].
• Surgical groups had better outcomes for shoulder pain and function compared with no treatment, but this difference was not clinically important [37].
• The SUPPORT trial aims to determine how to optimise outcomes for subacromial impingement syndrome through exercise and corticosteroid injection strategies [52].
• Arthroscopic subacromial decompression is a valid treatment, reducing pain and improving quality of life for patients selected for surgery according to the Danish national guidelines [60].
• Arthroscopic subacromial decompression is of little or no benefit over placebo surgery in the treatment of pain due to subacromial impingement [61].
• The surgical option for subacromial impingement should not be ruled out in cases of failure of medical management associated with unfavorable acromion morphology [61].

Anatomy & Pathophysiology¶

Bony Anatomy¶

• The acromion, coracoacromial ligament, and coracoid process form the coracoacromial arch, a rigid bony-ligamentous structure that imparts stability to the shoulder girdle [70].
• The rotator cuff, subacromial bursa, and subdeltoid bursa pass underneath the coracoacromial arch [70].
• The acromion has three ossification centers: the metacromion (base), the mesoacromion (middle), and the preacromion (tip) [73].
• Failure of fusion of the acromial ossification centers results in os acromiale [73].
• The relationship between acromial anatomy and rotator cuff disease remains controversial [73].
• The classification of acromial morphology as flat, curved, or hooked is challenged by poor interobserver reliability [73].
• A system incorporating more objective classification criteria and acknowledging the continuous nature of acromial morphologic types may improve interobserver reliability [51].
• The humeral head averages 19° of retroversion and 41° of inclination (neck-shaft angle) [73].
• The glenoid averages 5° of retroversion in relation to the axis of the scapular body [73].
• The subchondral bone of the glenoid is relatively flat, with the articular concavity augmented by cartilage and a circumferential labrum [73].
• The glenoid is a convex structure of shallow depth shaped like an inverted pear [70].
• The articular head of the humerus is spherical with a diameter of 37 to 57 mm [70].
• The most superior portion of the articular surface of the humeral head averages 8 mm above the greater tuberosity [70].
• The humeral version averages 29.8 degrees, with a range of 10 to 55 degrees [70].
• The head is inclined approximately 130 degrees with respect to the humeral shaft [70].
• The bicipital groove lies between the greater and lesser tuberosities and serves as a pathway for the long head of the biceps [70].
• The distal aspect of the bicipital groove is internally rotated with respect to the proximal portion [70].
• The greater tuberosity serves as the attachment site for the supraspinatus, infraspinatus, and teres minor tendons [70].
• The lesser tuberosity serves as the attachment site for the subscapularis tendon [70].
• The acromion is a massive structure overlying the humeral head in humans, reflecting the increasing role of the deltoid muscle in shoulder function [80].
• The coracoid process has undergone an increase in size over time [80].
• With the shoulder in 90 degrees of abduction, the coracoid extension over the glenohumeral joint can mechanically limit anterior translation of the humerus relative to the glenoid [80].

Soft Tissue Anatomy¶

• The rotator cuff consists of four muscles: subscapularis, supraspinatus, infraspinatus, and teres minor [71].
• The rotator cuff serves as depressors of the humeral head to allow the deltoid to efficiently abduct the humerus [71].
• The infraspinatus and teres minor are external rotators, while the subscapularis is an internal rotator of the humerus [71].
• The rotator interval is defined medially by the base of the coracoid, superiorly by the supraspinatus tendon, and inferiorly by the subscapularis tendon [73].
• The rotator interval contains the coracohumeral ligament, the superior glenohumeral ligament, and the intra-articular portion of the long head of the biceps tendon [73].
• Laxity of the rotator interval results in inferior laxity (the sulcus sign) [73].
• Contracture of the rotator interval is seen with adhesive capsulitis [73].
• The coracohumeral ligament restricts external rotation in adduction and is a static restraint to inferior and posterior translation in adduction and external rotation [73].
• The superior glenohumeral ligament is a primary static restraint against anterior translation with the arm at the side [73].
• The superior glenohumeral ligament and coracohumeral ligament form a pulley that provides restraint against medial subluxation of the long head of the biceps tendon [73].
• The middle glenohumeral ligament is a primary static restraint against anterior translation with the arm in external rotation and 45° of abduction [73].
• The anterior band of the inferior glenohumeral ligament is a primary static restraint against anterior-inferior dislocation of the glenohumeral joint in 90° of abduction and external rotation [73].
• The posterior band of the inferior glenohumeral ligament is a primary static restraint against posterior-inferior translation in internal rotation and adduction [73].
• The subscapular bursa lies between the subscapularis tendon and the neck of the scapula [74].
• The subscapular bursa communicates with the joint cavity between the superior and middle glenohumeral ligaments [74].
• The subscapular bursa protects the tendon of the subscapularis at the point where it passes under the base of the coracoid process and over the neck of the scapula [74].
• The subscapular bursa is linked to the coracoid process by a suspensory ligament [74].
• In 28% of dissected specimens, the subscapular bursae merged with the subcoracoid bursae, forming a unique wide bursa [74].
• The subscapular bursa often houses loose bodies in the shoulder [74].
• The subscapular bursa is a region in which synovitis of the shoulder may be most intense [74].
• The humeroscapular motion interface lies between the inner structures of the proximal humerus, rotator cuff, coracohumeral ligament, and biceps tendon sheath and the superficial layer of the acromion, deltoid, coracoacromial ligament, coracoid process, and conjoined tendon [76].
• Smooth, unrestricted motion at the humeroscapular motion interface is vital to shoulder mobility [76].
• The axillary nerve has an intimate relationship within the humeroscapular motion interface [76].
• The axillary nerve is a terminal branch coming off the posterior cord of the brachial plexus just proximal to the coracoid process [76].
• The axillary nerve passes beneath the conjoined tendon anterior to the subscapularis 3 to 5 mm medial to the musculotendinous junction [76].
• The axillary nerve is adjacent to the inferior capsule before entering the quadrilateral space posteriorly [76].
• The axillary nerve splits into anterior and posterior branches within the quadrangular space [76].
• The anterior and middle deltoid muscle receives sole innervation from the anterior branch of the axillary nerve [76].
• The posterior deltoid muscle innervation varies, with supply only from the anterior branch in 2.3% of cases, from the posterior branch in 8.5%, and from both branches in 89.1% [76].
• The posterior branch of the axillary nerve branches to supply the teres minor muscle and then terminates as the superior lateral brachial cutaneous nerve [76].
• The coracoacromial ligament can be anatomically described as two distinct bands - anterolateral and posteromedial - in the majority of cases [119].
• The acromial branch of the thoracoacromial artery runs on the medial aspect of the coracoacromial ligament [84].
• The coracoacromial ligament contributes to anterosuperior stability in rotator cuff deficiency [84].
• The coracoacromial ligament should be preserved with irreparable cuff tears to prevent anterosuperior escape [84].
• The coracoacromial ligament is the arthroscopic landmark for a complete release of the rotator interval for adhesive capsulitis [84].

Bursae and Synovial Structures¶

• The subacromial bursa separates the rotator cuff tendons from the coracoacromial arch, allowing them to glide [78].
• The subacromial bursa receives nociceptive stimuli and proprioception and seems to regulate appropriate shoulder movement [115].
• The subacromial bursa is lined by the humeroscapular motion interface [76].
• Adhesions in the humeroscapular motion interface can limit shoulder mobility, as seen in subacromial adhesions in cuff disease and after proximal humerus fracture [76].
• The subacromial and subdeltoid bursae can become thickened and fibrotic, forming adhesions that limit normal glenohumeral motion [70].
• Pigmented villonodular synovitis of the subacromial bursa is a documented pathology [45].
• Hematogenous abscess of the subacromial/subdeltoid bursa is a documented pathology [63].

Pathophysiology¶

• Subacromial impingement is the most common cause of shoulder pain, accounting for 50%–74% of shoulder cases in general practice [9].
• The pathophysiology of impingement syndrome may have both extrinsic and intrinsic components [46].
• The extrinsic theory of impingement is mechanical and related to the anatomy of the coracoacromial arch [46].
• Patients with a flat (type-I) acromion had better results than those with a curved (type-II) or hooked (type-III) acromion in non-operative treatment [46].
• There was a decreased prevalence of type-I acromial morphology and an increased prevalence of type-III acromial morphology in a population of patients with rotator cuff lesions [46].
• The outcome for patients with a type-II acromion was not significantly different than that for patients with a type-III acromion [46].
• Neer divided the impingement process into three stages [46].
• Stage I of impingement is characterized by acute bursitis with subacromial edema and hemorrhage [46].
• Stage I of impingement is usually observed in patients who are thirty years old or less [46].
• Stage II of impingement is characterized by inflammation of the rotator cuff, with partial-thickness tears possible [46].
• Stage II occurs as the subacromial bursa loses its ability to lubricate and protect the underlying rotator cuff due to continued irritation from abnormal contact with the acromion [46].
• Stage III of impingement results in a full-thickness tear of the rotator cuff due to wear of the anterior aspect of the acromion on the greater tuberosity and supraspinatus tendon [46].
• The progressive process of impingement can be interrupted with an acromioplasty [46].
• Imaging abnormalities of the acromioclavicular joint and subacromial space are common in asymptomatic shoulders [14].
• There is no between-group difference in acromiohumeral distance (AHD) in neutral shoulder position, shoulder abduction at 45° or 60° in adults with subacromial pain syndrome [38].
• The superior migration of the humeral head is a probable result of cuff failure, either partial or complete [124].
• Lack of force on the subscapularis and infraspinatus/teres minor muscles resulted in a significant 61% increase in mean coracoacromial pressures [105].
• Lack of force on all rotator cuff muscles resulted in a significant 35% increase in mean coracoacromial pressures [107].
• Results demonstrated no significant effect of posterior tilting and external rotation on subacromial clearance [112].
• Primary imbalance of rotational musculature of the shoulder is an etiological factor implicated in the impingement syndrome not modified by anterior acromioplasty [111].
• In involved shoulders with impingement syndrome, there was decreased muscle torque in the external rotators in internally rotated positions compared to the uninvolved side [20].
• The aetiology of anterior-superior internal impingement appears to be related to the pulley lesion and instability of the long head of the biceps tendon [53].
• Anterior-superior internal impingement can be caused by trauma or degenerative factors [53].
• Anterior-superior internal impingement produces anterior shoulder pain in middle-aged patients, particularly when performing overhead activities [53].
• Internal impingement between the glenoid and the humeral head may be a significant mechanism in the development of rotator cuff pathosis [117].
• The intraoperative finding of contact of the rotator cuff to the posterosuperior glenoid with the arm in abduction and external rotation can occur in a wide spectrum of shoulder disease and is not limited to the throwing athlete [118].
• Impingement of the undersurface of the cuff on the posterosuperior glenoid labrum may be a cause of painful structural disease of the shoulder in the thrower [132].
• Whether coracoid impingement exists as a distinct syndrome has yet to be fully established [34].
• Lesions of the biceps and the subscapularis should not be attributed to coracoid impingement syndrome [34].
• A weak rotator interval can induce impingement by the soft tissues around the coracoid process [34].
• Closure of the rotator interval, with or without coracoidoplasty, led to improvements in all 14 cases of coracoid impingement studied [34].
• The physiopathologic mechanism for coracoid impingement is not satisfactorily explained [34].
• The physiopathologic mechanism for subacromial impingement is unclear [34].
• Coracoid impingement of the subscapularis tendon seems to be the result of a functional problem, mainly anterior instability of the shoulder joint leading to a functional narrowing of the coracohumeral distance [110].
• Subacromial impingement syndrome is increasingly questioned as a useful diagnosis, with an emerging consensus that symptoms may arise from a number of shoulder pathologies associated with the soft tissues occupying the subacromial space [104].
• Traditionally, extrinsic factors were proposed as causing compression and abrasion of the bursal side of the rotator cuff, mechanically encroached between the acromion (or coracoid) and humeral head [104].
• Intrinsic rotator cuff pathology is suggested as more causative of symptoms than the traditional extrinsic model [104].
• Cadaver studies have demonstrated that rotator cuff pathology occurs more frequently within the internal substance or on the joint side of the tendon [104].
• Lifestyle factors such as sleep behaviors and shoulder usage patterns are associated with subacromial impingement syndrome [66].
• Pain catastrophising levels determine if patients with long-standing subacromial impingement benefit from more resistance exercise [9].

Classification¶

• Stage I of the impingement process is characterized by acute bursitis with subacromial edema and hemorrhage [46].
• Stage I of the impingement process is usually observed in patients who are thirty years old or less [46].
• Stage II of the impingement process is characterized by inflammation of the rotator cuff and possible partial-thickness tears [46].
• Stage III of the impingement process results in a full-thickness tear of the rotator cuff [46].
• The extrinsic theory of impingement syndrome is mechanical and related to the anatomy of the coracoacromial arch [46].
• A comprehensive classification of individualized impingements occurring around the anterior aspect of the shoulder has been proposed to address conflicting theories [5].
• In a study of 552 patients, the impingement group was subdivided into three groups according to severity [49].
• Group 1 in the severity classification consisted of subacromial impingement alone with a positive impingement test, bursitis or cuff tendonitis, but no tear [49].
• Group 2 in the severity classification consisted of partial rotator cuff tears, including bursal-side and joint-side partial tears [49].
• Group 3 in the severity classification consisted of full-thickness rotator cuff tears regardless of size [49].
• Calcium deposits in the shoulder were classified by size, with large deposits defined as 1.5 cm or longer in their greatest profile [120].

Clinical Presentation¶

Epidemiology and Prevalence¶

• Each month, one in every six adults experiences shoulder pain lasting more than 1 week [9].

Diagnostic Challenges and Comorbidities¶

• Patients presenting with signs and symptoms of subacromial pain syndrome have a high prevalence of conflicting and concomitant diagnoses [4].
• Examination of the cervical spine in patients with subacromial shoulder pain is variable in randomized controlled trials [55].
• Night pain is a common complaint of patients presenting with impingement of the shoulder but cannot be used in isolation as a diagnostic predictor for the presence of a rotator cuff tear [100].
• Accurate diagnosis of the etiology of a patient's shoulder pain and proper injection technique are important in achieving satisfactory clinical outcomes [54].

Clinical Testing and Physical Examination¶

• A Cochrane review includes 33 studies evaluating a total of 4002 shoulders in 3852 patients regarding physical tests for shoulder impingements and local lesions of bursa, tendon or labrum [3].
• The provocative tests for subacromial impingement also appear to elicit contact consistent with internal impingement [109].
• A quantified measurement test enables the clinician to quantify the subacromial space [28].
• In the involved shoulders of patients with impingement syndrome, there was decreased muscle torque in the external rotators in internally rotated positions compared to the uninvolved side [20].

Imaging and Pathology¶

• Supraspinatus pathology as defined by magnetic resonance imaging indicates that these pathologic conditions are nonspecific findings related to age and not to shoulder impingement [15].
• The subacromial space width is smaller in nearly all rotator cuff pathologies, but becomes even smaller as the severity of the condition increases and is smaller in the case of a complete cuff tear [57].
• Women aged between 30 and 60 years with subacromial pain syndrome and a calcific deposit of >1.5 cm in length have the highest chance of suffering from symptomatic calcific tendinopathy of the rotator cuff [40].
• Synovitis in the subacromial space was milder and not associated with any clinical parameters in patients with rotator cuff tears [16].
• Subacromial osteolysis has a relatively high and variable incidence, and the primary factor influencing the reported incidence is the radiological assessment method [23].
• Detailed diagnoses could be made as patients were kept at rest by subacromial blocking during MRI by infusing mylocain and Gd-DTPA into the subacromial bursa [36].

Atypical Presentations¶

• Chronic subacromial bursitis can present as an unusual case mimicking a soft tissue tumor [1].
• Two cases of synovial chondromatosis of the subacromial bursa were documented in patients who had undergone years of daily work that involved positioning the arms overhead, which may have created persistent subacromial impingement [29].

Investigations¶

Clinical Examination and Diagnostic Challenges¶

• A Cochrane review of physical tests for shoulder impingements and local lesions included 33 studies evaluating a total of 4002 shoulders in 3852 patients [3].

Plain Radiography¶

• At least two X-ray views should be obtained for shoulder imaging: an anteroposterior in the plane of the glenoid and an axillary projection with the arm in abduction to show the relationship of the humeral head to the glenoid [87].
• The standard shoulder series should include orthogonal views of the shoulder, including a true AP view in the scapular plane, an AP view, an axillary view, and a scapular Y view [95].
• The true AP view in the scapular plane visualizes the anterior greater tuberosity in profile and can reveal proximal humeral migration [95].
• The axillary view enables determination of the humeral head position in the glenoid fossa and may detect occult, locked posterior shoulder dislocation [95].
• The scapular Y view provides visualization of the coracoacromial arch and can reveal coracoacromial spurs, which have been closely associated with the presence of rotator cuff pathology [95].
• The acromiohumeral distance is normally 7 to 14 mm [95].
• Neer classified acromial morphology as type I (flat), type II (curved), and type III (hooked) [95].
• Type III acromial morphology has been shown to have a correlation with the presence of rotator cuff disease, although no direct causal relationship has been demonstrated [95].
• The Neer classification of acromial morphology has shown relatively poor interobserver reliability [95].
• Due to the low certainty of evidence and significant variation among study populations, further research is needed to clarify prevalence estimates of imaging abnormalities in asymptomatic shoulders [14].

Magnetic Resonance Imaging (MRI)¶

• MRI is the modality of choice for evaluating the rotator cuff, biceps, and subacromial/subdeltoid bursa [94].
• T2-weighted MRI provides better visualization of full thickness rotator cuff tears [94].
• MR imaging in shoulder abduction can be a help in evaluating the pathoanatomy of impingement syndrome [58].
• In a study of patients with impingement syndrome, the subacromial space was significantly smaller than in healthy persons [130].
• Supraspinatus pathology as defined by magnetic resonance imaging is a nonspecific finding related to age and not to shoulder impingement [15].
• The acromiohumeral distance is significantly smaller on MRI compared to AP radiographs in shoulders with an intact rotator cuff [125].
• The acromiohumeral distance on MRI should not be used as a decision criterion to assess glenohumeral centering or subacromial space width in shoulders with an intact rotator cuff [125].
• No correlation was found between abnormal findings on MR images of the shoulder after surgery and the postoperative clinical presentation of patients [128].
• MRI accuracy in identifying labral and rotator cuff tears in the literature ranges from 70% to 100% [92].
• Magnetic resonance arthrography (MRA) has greater diagnostic test accuracy for glenoid labral lesions than MRI, with MRA sensitivity of 88% and specificity of 93% versus MRI sensitivity of 76% and specificity of 87% [92].
• MRA is considered the benchmark for evaluation of labral tears and is rarely indicated for evaluation of rotator cuff pathology [94].
• When MRI or MR arthrography is contraindicated, CT arthrography is indicated [94].

Ultrasonography¶

• Ultrasonography is a simple and accurate test for identifying rotator cuff tears and calcific tendinitis [87].
• Ultrasonography is a low-cost alternative to MRI and arthrography for evaluating both skeletal and soft-tissue structures of the shoulder [94].
• Ultrasonography can provide immediate, real-time visualization of the rotator cuff, biceps tendon, and calcific deposits [94].
• Ultrasonography can be used to measure the subacromial space and detect atrophy of rotator cuff muscles [94].
• Ultrasonography can evaluate impingement in various positions and motions due to real-time imaging capabilities [94].
• Ultrasonography is highly operator dependent and is not as useful for evaluating labral tears or rotator cuff tears that are very small or larger than 3 cm [94].
• The subacromial space width is smaller in nearly all rotator cuff pathologies, becoming even smaller as the severity of the condition increases and smallest in the case of a complete cuff tear [57].
• Ultrasonography is not superior to non-guided techniques for subacromial bursa and glenohumeral joint injections in terms of pain or function [21].
• Ultrasonography is superior to non-guided techniques for bicipital groove injections [21].
• A machine learning-based ultrasomics approach may be helpful in the preliminary screening of shoulder pain [67].
• Ultrasonography has a sensitivity of 98%, specificity of 80%, positive predictive value of 90%, negative predictive value of 95%, and accuracy of 94% for the detection of full-thickness rotator cuff tears [95].
• Ultrasonography is useful in detecting and determining the involvement of the shoulder in patients with septic or tuberculous bursitis of the subacromial bursa [27].
• MRI showed no rotator cuff tear and localized subacromial hemorrhage in a patient on anticoagulation therapy [134].

Arthroscopy and Other Modalities¶

• Arthroscopy is useful for diagnosing and treating subacromial impingement, intra-articular lesions, detachment of the glenoid labrum, and rotator cuff tears [87].
• Both changes in the acromion showed impingement at both sites in 13 shoulders during bursoscopy [8].
• The presence of subacromial plicae observed in living subjects at bursoscopy is in agreement with previously published anatomic studies [22].
• Subacromial friction could be seldom observed in shoulder disease except in pure impingement syndrome [18].
• Detailed diagnoses could be made using MRI by infusing mylocain and Gd-DTPA into the subacromial bursa as patients were kept at rest by subacromial blocking [36].
• A test enabling the clinician to quantify the subacromial space has been described [28].
• Subacromial osteolysis following hook plate fixation for acromioclavicular dislocation has a relatively high and variable incidence, with the primary factor influencing the reported incidence being the radiological assessment method [23].

Treatment¶

Non-Operative Management¶

• Conservative treatment can be recommended as a first choice of treatment for shoulder impingement in first or second grade due to surgery's higher costs and susceptibility for complications [35].
• Conservative treatment is considered the first choice in the treatment of subacromial impingement syndrome, with complaints relieved when conservative methods are regularly applied [26].
• Most UK management regimes for subacromial impingement employ a minimum period of 12 weeks of conservative management incorporating physiotherapy and at least 2 subacromial steroid injections [17].
• A systematic review found no clinically meaningful differences in pain or function at any 3-, 6-months, 1-, 2-, 5- or ≥10-years follow up when comparing surgery plus physiotherapy versus physiotherapy alone [50].
• The level of pain catastrophising determines if patients with long-standing subacromial impingement benefit from more resistance exercise [9].

Injections¶

• Ultrasound guidance is not superior in subacromial bursa and glenohumeral joint injections regarding pain or function [21].
• A systematic review indicates there is little reproducible evidence to support the efficacy of subacromial corticosteroid injection in managing rotator cuff disease [108].

Operative Management¶

• Arthroscopic subacromial decompression is of little or no benefit over placebo surgery in the treatment of pain due to subacromial impingement, although the surgical option should not be ruled out in cases of failure of medical management associated with unfavorable acromion morphology [61].
• For patients who have a long-term disease course, operative treatments may be considered, with standard ASD surgery preferred over arthroscopic bursectomy and the open surgical technique for subacromial decompression [19].
• Major improvements in pain/function were seen at mid- to long-term after isolated arthroscopic subacromial decompression and combined decompression/rotator cuff repair [41].
• Subacromial continuous infusion of local anesthetic does not provide a clinically significant benefit compared with placebo as part of a multimodal analgesia regime after arthroscopic subacromial surgical procedures [123].

Complications¶

Diagnostic and Pathologic Mimics¶

• Synovial chondromatosis of the subacromial bursa is a documented complication associated with persistent overhead work [29].
• Pigmented villonodular synovitis of the subacromial bursa is a rare pathological entity [45].
• Pseudotumoral calcified bursitis of the shoulder can occur in patients with hemodialysis [62].
• Subacromial plicae are present in living subjects and have been described as a cause of impingement [22].

Imaging and Diagnostic Findings¶

• Supraspinatus pathology defined by magnetic resonance imaging is a nonspecific finding related to age rather than shoulder impingement [15].
• Subacromial synovitis is milder and not associated with any clinical parameters in the context of rotator cuff tears [16].

Post-Surgical Complications¶

• Subacromial osteolysis following hook plate fixation for acromioclavicular dislocation has a relatively high and variable incidence [23].
• The primary factor influencing the reported incidence of subacromial osteolysis following hook plate fixation is the radiological assessment method [23].
• Subacromial notching following reverse shoulder arthroplasty with a 135° inlay humeral component and a lateralized glenoid is not associated with functional outcomes or range of motion at short-term follow-up [39].
• Subacromial pain pumps used for arthroscopic shoulder procedures are safe in the short-term [131].

Treatment-Related Outcomes and Risks¶

• Surgical treatment carries higher costs and susceptibility for complications compared with conservative treatment [35].
• Arthroscopic subacromial decompression provided no benefit over diagnostic arthroscopy at 24 months [7].
• Formal subacromial decompression does not result in improved clinical outcomes up to 2 years after rotator cuff repair [30].
• There is no evidence from available randomized controlled trials for differences in outcome in pain and shoulder function between conservatively and surgically treated patients with subacromial impingement syndrome [31].
• Adding a large dose of shoulder strengthening exercises to nonoperative care for 16 weeks did not significantly improve long-term outcomes in terms of shoulder disability, health-related quality of life, sick leave, or surgery rates at 1 year [64].
• There was no significant difference regarding shoulder function or adverse effects between intra-articular and subacromial corticosteroid injection in frozen shoulder [44].

Recovery¶

Non-Operative Management¶

• Conservative treatment is considered the first choice for subacromial impingement syndrome, with complaints relieved when conservative methods are regularly applied [26].
• Scapular focused interventions showed a between-group difference in shoulder abduction range of motion in the short term only [56].

Operative Management¶

• For patients with a long-term disease course, operative treatments may be considered, with standard ASD surgery preferred over arthroscopic bursectomy and the open surgical technique for subacromial decompression [19].
• Major improvements in pain and function were seen at mid- to long-term after isolated arthroscopic subacromial decompression and combined decompression/rotator cuff repair [41].

Post-Operative Complications and Findings¶

• Subacromial osteolysis has a relatively high and variable incidence following hook plate fixation for acromioclavicular dislocation, with the primary factor influencing the reported incidence being the radiological assessment method [23].
• When subacromial notching occurs following reverse shoulder arthroplasty, it is not associated with functional outcomes or range of motion at short-term follow-up [39].
• There was no evidence of progression of intrinsic rotator cuff pathologic conditions at a mean follow-up of 4.5 years after acromioplasty without repair for partial-thickness rotator cuff tears [69].

Clinical Presentation and Diagnosis¶

• Less than half of patients in secondary care adhere to clinical guidelines for subacromial pain syndrome and have acceptable symptoms after treatment [25].
• There was no between-group difference in acromiohumeral distance in neutral shoulder position, shoulder abduction at 45° or 60° in adults with subacromial pain syndrome [38].

Key Evidence¶

• [L5] This article documents an unusual presentation of chronic subacromial bursitis. [1] (10.1016/s1058-2746(00)90014-4)
• [L5] Management of subacromial impingement syndrome includes physical therapy, injections, and surgery for some patients, but there remains a need for high-quality studies of the pathology, etiology, and management of the condition. [2] (10.5435/00124635-201111000-00006)
• [L1] The review includes 33 studies evaluating a total of 4002 shoulders in 3852 patients. [3] (10.1002/14651858.cd007427.pub2)
• [L3] Patients presenting with signs and symptoms of subacromial pain syndrome have a high prevalence of conflicting and concomitant diagnoses. [4] (10.1177/23259671251332942)
• [L4] The article proposes a comprehensive classification of all individualized impingements occurring around the anterior aspect of the shoulder, including newly described entities, to address conflicting theories and improve understanding of their etiologic factors, diagnosis, and treatment. [5] (10.1007/s00264-017-3515-1)
• [L1] Current randomized, controlled trial evidence shows no difference in outcomes of shoulder function or pain between surgical and conservative treatment for subacromial impingement syndrome. [6] (10.2106/jbjs.9202.ebo579)
• [L1] In this controlled trial involving patients with a shoulder impingement syndrome, arthroscopic subacromial decompression provided no benefit over diagnostic arthroscopy at 24 months. [7] (10.1136/bmj.k2860)
• [L4] Both changes in the acromion showed impingement at both sites in 13 shoulders. [8] (10.1016/s1058-2746(96)80549-0)
• [L1] [9] (10.1136/bjsports-2022-106383)
• [L1] Arthroscopic subacromial decompression provided no benefit over diagnostic arthroscopy or exercise therapy at 5 years for patients with shoulder impingement syndrome. [10] (10.1136/bjsports-2020-102216)
• [L1] Arthroscopic subacromial decompression provided no benefit over diagnostic arthroscopy or exercise therapy on return to work in patients with shoulder impingement syndrome. [11] (10.1186/s12891-021-04768-7)
• [Paper] SAPS should preferably be treated non-operatively, with subacromial injection with corticosteroids indicated for persistent or recurrent symptoms. [12] (10.3109/17453674.2014.920991)
• [L1] Adding a large dose of shoulder strengthening to current nonoperative care for patients with subacromial impingement did not result in superior shoulder-specific patient-reported outcomes. [13] (10.1177/03635465211016008)
• [L2] Due to the low certainty of evidence and significant variation among study populations, further research is needed to clarify these prevalence estimates and to guide evidence-based management of shoulder abnormalities. [14] (10.1186/s13018-024-05378-4)
• [L4] This finding indicates that these pathologic conditions are nonspecific findings related to age and not to shoulder impingement. [15] (10.1016/s1058-2746(99)90090-3)
• [L4] Synovitis in the subacromial space was milder and not associated with any clinical parameters. [16] (10.1177/23259671231207818)
• [L4] Variation exists in the management regimes offered to patients with subacromial impingement, but most employ a minimum period of 12 weeks of conservative management incorporating physiotherapy and at least 2 subacromial steroid injections. [17] (10.1177/1758573215571010)
• [Paper] Consequently, the subacromial friction could be seldom observed in the shoulder disease except pure impingement syndrome. [18] (10.1016/s1058-2746(98)90106-9)
• [L1] For patients who have a long-term disease course, operative treatments may be considered, with standard ASD surgery preferred over arthroscopic bursectomy and the open surgical technique for subacromial decompression. [19] (10.1097/md.0000000000000510)
• [L4] In the involved shoulders there was also a decreased musle torque in the externa? rotators in internally rotated positions compared to the uninvolved side. [20] (10.1016/s1058-2746(96)80130-3)
• [L1] Ultrasound guidance is not superior in the subacromial bursa and glenohumeral joint injections in pain or function. [21] (10.1016/j.arthro.2021.12.013)
• [L4] The findings of this study, describing the presence of subacromial plicae observed in living subjects at bursoscopy, are in agreement with previously published anatomic studies. [22] (10.1016/j.jse.2006.03.009)
• [L1] Subacromial osteolysis has a relatively high and variable incidence, and the primary factor influencing the reported incidence is the radiological assessment method. [23] (10.1016/j.jse.2024.03.018)
• [L3] ASD in the treatment of subacromial impingement yields good long-term results. [24] (10.1016/j.jse.2007.06.020)
• [L3] [25] (10.1016/j.msksp.2021.102322)
• [L4] We believe that conservative should be the first choice in the treatment of subacromial impingement syndrome and we noted that the complaints were relieved when the conservative treatment methods are regularly applied. [26] (10.1016/s1058-2746(96)80423-x)
• [L5] This case illustrates the substantial benefit of ultrasonography in detecting and determining the involvement of the shoulder in a patient with septic or tuberculous bursitis of the subacromial bursa. [27] (10.1016/s1058-2746(03)00093-4)
• [L4] This test enables the clinician to quantify the subacromial space. [28] (10.1016/s1058-2746(03)00038-7)
• [L5] Both patients had undergone years of daily work that involved positioning the arms overhead, which may have created persistent subacromial impingement. [29] (10.1067/mse.2001.111964)
• [L1] Five randomized trials found that formal subacromial decompression does not result in improved clinical outcomes up to 2 years after rotator cuff repair. [30] (10.1016/j.arthro.2012.06.003)
• [L1] According to the best-evidence synthesis, there is no evidence from the available RCTs for differences in outcome in pain and shoulder function between conservatively and surgically treated patients with SIS. [31] (10.1016/j.jse.2009.01.010)
• [L5] Preserving the subacromial bursa during rotator cuff surgery may lead to better rotator cuff healing when secondary pain is manageable. [33] (10.1530/eor-2024-0183)
• [L4] [34] (10.1016/s1058-2746(99)90005-8)
• [L1] Because of surgery's higher costs and susceptibility for complications compared with costs and risks of conservative treatment, conservative treatment can be recommended as a first choice of treatment of shoulder impingement in first or second grade. [35] (10.3109/09638288.2014.907364)
• [L4] Detailed diagnoses could be made as the patients were kept at rest by subacromial blocking. [36] (10.1016/s1058-2746(95)80307-6)
• [L1] Surgical groups had better outcomes for shoulder pain and function compared with no treatment but this difference was not clinically important. [37] (10.1016/s0140-6736(17)32457-1)
• [L1] There was no between group difference in acromiohumeral distance (AHD) in neutral shoulder position, shoulder abduction at 45° or 60°. [38] (10.1038/s41598-020-76704-z)
• [L3] When subacromial notching occurs, it is not associated with functional outcomes or range of motion at short-term follow-up. [39] (10.1016/j.jseint.2024.01.009)
• [L3] This study demonstrates that women aged between 30 and 60 years with subacromial pain syndrome and a calcific deposit of >1.5 cm in length have the highest chance of suffering from symptomatic calcific tendinopathy of the rotator cuff. [40] (10.1016/j.jse.2015.02.024)
• [L3] Major improvements in pain/function were seen at mid- to long-term after isolated arthroscopic subacromial decompression and combined decompression/rotator cuff repair. [41] (10.1016/j.jor.2018.03.004)
• [L1] There was no significant difference regarding the shoulder function or adverse effects. [44] (10.1016/j.ijsu.2019.06.008)
• [L5] At a 3 1/2 year follow-up the patient was functioning well, although she still reported occasional discomfort and had shoulder elevation to 160°. [45] (10.1016/s1058-2746(97)90010-0)
• [L3] [46] (10.2106/00004623-199705000-00013)
• [L3] [49] (10.1197/j.jht.2006.11.009)
• [L1] [50] (10.1371/journal.pone.0216961)
• [L4] It is concluded that a system that incorporates more objective classification criteria and acknowledges the continuous nature of acromial morphologic types may improve interobserver reliability and validate the system's use in making clinical and surgical judgments. [51] (10.1016/s1058-2746(05)80037-0)
• [L2] This protocol paper presents the rationale, design, methods, and operational aspects of the SUPPORT trial, which aims to determine how to optimise outcomes for subacromial impingement syndrome through exercise and corticosteroid injection strategies. [52] (10.1186/1471-2474-15-81)
• [L4] [53] (10.1007/s00167-010-1232-z)
• [L5] Accurate diagnosis of the etiology of a patient's shoulder pain and proper injection technique are important in achieving satisfactory clinical outcomes. [54] (10.1016/j.jse.2007.07.009)
• [L1] Examination of the cervical spine in patients with subacromial shoulder pain is variable in randomized controlled trials. [55] (10.1177/1758573218798023)
• [L1] A between-group difference in shoulder abduction ROM in the short term only was found. [56] (10.1080/09593985.2018.1423656)
• [L4] The subacromial space width is smaller in nearly all rotator cuff pathologies, but becomes even smaller as the severity of the condition increases and is smaller in the case of a complete cuff tear. [57] (10.1016/j.ultras.2003.11.015)
• [L4] MR imaging in shoulder abduction can be a help in evaluating the pathoanatomy of impingement syndrome. [58] (10.1016/s1058-2746(96)80509-x)
• [L4] Arthroscopic subacromial decompression is a valid treatment, reducing pain and improving quality of life for patients selected for surgery according to the Danish national guidelines. [60] (10.1016/j.jse.2017.03.028)
• [L1] Arthroscopic subacromial decompression is of little or no benefit over placebo surgery in the treatment of pain due to subacromial impingement, although the surgical option should not be ruled out in cases of failure of medical management associated with unfavorable acromion morphology. [61] (10.1016/j.otsr.2019.10.002)
• [L5] After 2 years of follow-up, the patient had regained full use of the shoulder and there was no sign of recurrence. [62] (10.1016/s1058-2746(98)90041-6)
• [L5] The patient had full shoulder mobility and strength at 6 months and no symptoms, recurrence, or abnormal x-ray evaluation five years later. [63] (10.1016/s1058-2746(98)90228-2)
• [L1] Adding a large dose of shoulder strengthening exercises to nonoperative care for 16 weeks did not significantly improve long-term outcomes in terms of shoulder disability, health-related quality of life, sick leave, or surgery rates at 1 year. [64] (10.1177/23259671251374314)
• [L1] This evidence supports the development of strategies aimed at improving sleep behaviors and optimizing shoulder usage patterns as effective measures to prevent SIS. [66] (10.1186/s12891-024-07345-w)
• [L4] This noninvasive and low-cost approach may be helpful in the preliminary screening of shoulder pain. [67] (10.1002/jum.15914)
• [L4] There was no evidence of progression of intrinsic rotator cuff pathologic conditions at a mean follow-up of 4.5 years. [69] (10.1177/03635465020300021801)
• [L3] Night pain is a common complaint of patients presenting with impingement of the shoulder but cannot be used in isolation as a diagnostic predictor for the presence of a rotator cuff tear. [100] (10.1111/j.1758-5740.2011.00133.x)
• [L1] [104] (10.1177/1758573216660038)
• [L5] Lack of force on the subscapularis and infraspinatus/teres minor muscles resulted in a significant sixty-one percent increase in mean coracoacromial pressures. [105] (10.1016/s1058-2746(95)80184-7)
• [L5] Lack of force on the subscapularis and infraspinatus/teres minor muscles resulted in a significant 61% increase in mean coracoacromial pressures, while lack of force on all rotator cuff muscles resulted in a significant 35% increase. [107] (10.1016/s1058-2746(05)80039-4)
• [L1] This systematic review of the available literature indicates that there is little reproducible evidence to support the efficacy of subacromial corticosteroid injection in managing rotator cuff disease. [108] (10.5435/00124635-200701000-00002)
• [L5] The provocative tests for subacromial impingement also appear to elicit contact consistent with internal impingement. [109] (10.1016/s1058-2746(00)90008-9)
• [L5] Instead, it seems to be the result of a functional problem, mainly anterior instability of the shoulder joint leading to a functional narrowing of the coracohumeral distance. [110] (10.1016/j.jse.2003.12.007)
• [L4] These data demonstrate primary imbalance of rotatotional musculature of the shoulder is an etiological factor implicated in the impingement syndrome not modified by anterior acromioplasty. [111] (10.1016/s1058-2746(95)80091-3)
• [L5] Results demonstrated no significant effect of posterior tilting and external rotation on subacromial clearance. [112] (10.1016/j.jse.2004.09.001)
• [L5] The subacromial bursa receives nociceptive stimuli and proprioception and seems to regulate appropriate shoulder movement. [115] (10.1016/s1058-2746(96)80069-3)
• [L5] It appears that internal impingement between the glenoid and the humeral head may also be a significant mechanism in the development of rotator cuff pathosis. [117] (10.1067/mse.2000.105449)
• [L3] The intraoperative finding of contact of the rotator cuff to the posterosuperior glenoid with the arm in abduction and external rotation can occur in a wide spectrum of shoulder disease and is not limited to the throwing athlete. [118] (10.1016/s1058-2746(99)90076-9)
• [L5] In the majority of cases, the coracoacromial ligament can be anatomically described as two distinct bands - anterolateral & posteromedial. [119] (10.1016/s1058-2746(96)80286-2)
• [L4] [120] (10.1001/jama.1941.02820220019004)
• [L1] Subacromial continuous infusion of local anesthetic does not provide a clinically significant benefit compared with placebo as part of a multimodal analgesia regime after arthroscopic subacromial surgical procedures. [123] (10.1016/j.jse.2019.11.010)
• [L4] The superior migration of the humeral head is a probable result of cuff failure, either partial or complete. [124] (10.1016/s1058-2746(05)80004-7)
• [L4] The acromiohumeral distance is significantly smaller in the MRI in comparison to AP radiographs in shoulders with an intact rotator cuff and should not be used as a decision criterion on MRI to assess glenohumeral centering or subacromial space width. [125] (10.1007/s00167-020-06090-6)
• [L4] No correlation was found between the abnormal findings on the MR images of the shoulder after surgery and the postoperative clinical presentation of the patients. [128] (10.1016/s1058-2746(96)80212-6)
• [L4] In this study evidence was found that the subacromial space of patients with impingment syndrome is significantly smaller than in healthy persons. [130] (10.1016/s1058-2746(95)80066-2)
• [L4] Subacromial pain pumps used for arthroscopic shoulder procedures are safe in the short-term. [131] (10.1016/j.jse.2008.03.011)
• [L4] [132] (10.1016/s1058-2746(09)80065-7)
• [L5] The MRI showed no rotator cuff tear and localized the subacromial hemorrhage. [134] (10.1067/mse.2000.109411)

References¶

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