Skip to content

Clinicians › Shoulder

Os Acromiale

Patient-facing topic on os acromiale — failed fusion of an acromial ossification centre that may cause shoulder pain and contribute to subacromial impingement.

41 citationsUpdated Sep 2026
Illustration: Os Acromiale

For patients: a plain-language version of this topic is available. See the patient guide.

Overview

Os acromiale is an accessory bone at the acromion that is predominantly asymptomatic and requires no treatment in the majority of patients [1]. Diagnosis relies on imaging features rather than age restrictions [3]. The condition is frequently associated with rotator cuff injuries and serves as a co-condition in patients with rotator cuff tears [4, 10]. A multicenter study has examined the prevalence and associated factors of os acromiale within the Japanese population [11].

For symptomatic cases, initial management is nonsurgical [2]. When nonoperative measures fail, surgical intervention predictably leads to decreased symptoms and improved clinical outcomes [5, 6]. Surgical options include arthroscopic sub-total excision, arthroscopic subacromial decompression of stable fragments, and open reduction and internal fixation of unstable fragments [18]. Osteosynthesis to achieve bony union is a safe, effective, and reliable technique for large and unstable symptomatic os acromiale [27]. In athletes, this technique is a predictable and consistent treatment [9]. However, surgical treatment of symptomatic meso-os acromiale with concomitant rotator cuff pathology yielded poorer outcomes, with only 53% achieving satisfactory results overall [16]. Surgical treatment is usually not indicated for os acromiale in the professional tennis player [20], and care should be taken not to perform acromioplasty in the presence of painful os acromiale [21].

In the context of reverse total shoulder arthroplasty, the presence of os acromiale does not appear to have a negative impact on clinical outcomes, and rTSA remains a safe and effective treatment option [8, 17]. Shoulders with os acromiale had a similar overall complication rate compared with matched controls (14% vs. 12%; P = 0.658) [12]. Postoperative local tenderness at the os acromiale can be expected in 1 out of 4 patients but resolves spontaneously over time in the majority of patients [7]. Ipsilateral os acromiale may be a relative contraindication to the clavicle hook plate [24].

Anatomy & Pathophysiology

Bony Anatomy

The acromion develops from three distinct ossification centers: the metacromion at the base, the mesoacromion in the middle, and the preacromion at the tip [41]. Os acromiale is defined as the failure of fusion between these secondary ossification centers, most commonly occurring between the mesoacromion and metacromion [52]. The unfused segment is most frequently the meso-acromion [28]. Anatomically, the acromion, coracoacromial ligament, and coracoid process form the coracoacromial arch, a rigid bony-ligamentous structure that imparts stability to the shoulder girdle [38]. The rotator cuff, subacromial bursa, and subdeltoid bursa pass underneath this arch [38]. The lateral acromion serves as the insertion site for the deltoid muscle [14].

Pathophysiology

Diagnosis of os acromiale is typically incidental, identified on axillary view radiographs of the shoulder [28]. The axillary lateral radiographic view specifically demonstrates the presence of the unfused bone [66]. Primary shoulder pain is usually unrelated to the unfused os acromiale, with no relation between the presence of os acromiale and shoulder pain regardless of diagnosis [28, 13]. When os acromiale drives symptoms, the two principal causes are motion at the non-union site or an impingement-type syndrome resulting from flexion of the os fragment during deltoid contraction and arm elevation [28]. Pain from these mechanisms has been reported in throwing athletes and swimmers [28]. Previously stable non-unions can become unstable following blunt trauma to the region [28].

Extrinsic impingement occurs when the space available for the rotator cuff is diminished, with pathologic os acromiale cited as an example [65]. A tear of the rotator cuff may often be associated with os acromiale, likely due to impingement from abnormal motion at the fibrous union site [15]. One study supports previous findings that os acromiale is associated with rotator cuff injuries [10]. However, the rate of rotator cuff tears for patients with os acromiale was comparable with that of patients without os acromiale, indicating no definitive connection between os acromiale and rotator cuff pathology [14].

Classification

Other Considerations: Meta–os acromiale is the rarest subtype of os acromiale [32]. The rate of rotator cuff tears for patients with os acromiale was comparable with that of patients without os acromiale, indicating that there is no definitive connection between os acromiale and rotator cuff pathology [14].

Clinical Presentation

General Presentation and Prevalence

Primary shoulder pain is usually unrelated to an unfused os acromiale [28]. The prevalence of this condition is reported to range from 1.1% to 15% [67]. In a sample of 1594 skeletons, the overall frequency was 8.34% [19]. Among Korean patients visiting a shoulder outpatient clinic, os acromiale was observed in 7 per 1,000 individuals [14]. Bilateral involvement was found in 15.4% of cases in this Korean patient population [14]. Racial differences in prevalence are consistent, with Black people showing a higher rate (13.2%-18.2%) than white people (5.8%-9.5%) [14].

Symptomatic Presentation

Patients with a symptomatic os acromiale typically present with anterolateral shoulder pain localized to the acromion [67]. Complaints of pain with overhead activities are common [67]. Physical examination may reveal rotator cuff weakness, a positive impingement sign, or decreased forward elevation [67]. Two specific clinical findings aid in diagnosis: tenderness directly over the superior acromion and palpable motion at the pseudarthrosis site [67]. The presence of one or both of these findings is useful for making the correct diagnosis [67].

Os acromiale must be included in the differential diagnosis for swimming athletes presenting with shoulder pain, particularly when there is a failed response to physical therapy, activity modification, or steroid injection [23]. In young athletes, awareness of the condition, appropriate clinical examination, and image studies are crucial to confirm the diagnosis [26].

Imaging and Diagnosis

Anteroposterior, scapular Y, and axillary radiographic views of the shoulder should be routinely obtained to help confirm the diagnosis [67]. The os acromiale can be easily overlooked radiographically and is best visualized on the axillary lateral radiograph [67]. On magnetic resonance images, edema or fluid may be noted at the pseudoarthrosis site in symptomatic cases [67].

Etiology of Symptoms

The etiology of symptoms in symptomatic os acromiale is not definitively understood but has been postulated to arise from two potential causes [67]. One source is a painful inflammatory reaction due to motion at the pseudoarthrosis site [67]. Another source is an impingement-type syndrome resulting from flexion of the os fragment during deltoid contraction and arm elevation [28]. Pain from either motion at the non-union site or impingement has been reported in a variety of sports, particularly among throwing athletes and swimmers [28]. Previously stable non-unions can become unstable following an episode of blunt trauma to the region [28].

Investigations

Plain radiography: Standardized plain films are almost always sufficient for shoulder evaluation, and the temptation to "overimage" should be resisted [31]. The purpose of imaging is to establish the diagnosis, determine pathoanatomy severity, assist in surgical planning, and illustrate the condition to the patient [31]. The standard shoulder series includes orthogonal views: a true AP view in the scapular plane (Grashey view), an AP view with the arm in internal rotation, an axillary view, and a scapular Y view [62, 64]. The Grashey view is oriented to the scapula with the beam centered on the glenohumeral joint line, visualizing the anterior greater tuberosity in profile and revealing proximal humeral migration [62, 64]. The AP view with internal rotation visualizes the posterior aspect of the greater tuberosity and the lesser tuberosity in profile [62]. The axillary view is necessary for evaluating glenohumeral joint instability, determining humeral head position, and assessing glenoid morphology in osteoarthritis [62, 64]. It provides an unambiguous view of anteroposterior glenohumeral alignment and is centered on the epicenter of the humeral head and glenoid [64]. The scapular Y view visualizes the coracoacromial arch, reveals coracoacromial spurs associated with rotator cuff pathology, and serves as a reliable alternative for evaluating subluxation and dislocation [62]. It also shows acromial shape [62]. In patients unable to abduct the arm due to acute injury, a scapular “Y” view must be obtained to evaluate the relationship of the humeral head to the glenoid [64]. A Velpeau view can be obtained in guarding patients with the plate positioned posteriorly and under the shoulder [64]. Modified axillary views include positioning the patient sitting on the table with the arm abducted 60 degrees, or leaning slightly forward with the beam aiming down 45 degrees toward a plate positioned behind the patient, providing greater comfort in acute traumatic dislocation [64]. Special views include the Zanca view (10° cephalic tilt centered over the AC joint) for AC joint evaluation, the Stryker notch view for Hill-Sachs lesions, the West point view for anterior glenoid bone loss, the Apical oblique view for glenoid rim fractures, and the Serendipity view for the sternoclavicular joint [62]. The Stryker Notch, West Point, and Bernageau profile views assist in identifying pathology related to shoulder instability [64]. Conventional radiographs are appropriate for patients with shoulder pain, trauma history, dislocation, night pain, or chronic pain [62]. Normal acromiohumeral distance is 7 to 14 mm, the glenohumeral joint space should be symmetric superiorly and inferiorly, and the coracoclavicular distance is normally 1.1 to 1.3 cm [62]. Neer classified acromial morphology as type I (flat), type II (curved), and type III (hooked); type III morphology correlates with rotator cuff disease, though no direct causal relationship has been demonstrated, and the classification shows relatively poor interobserver reliability [62]. In a systematic review of posterior shoulder dislocations, 73% of patients had a missed initial diagnosis due to the lack of an axillary view, Y view, or CT imaging [64]. Of these, 98% (147/150) had only AP or lateral views [64]. When axillary or Y-view radiographs were made subsequently, the diagnosis was confirmed in 100% of patients [64]. In a comparison of 75 consecutive patients with suspected dislocations, the axillary and scapular “Y” views resulted in the same diagnosis in 92% (69 patients) [64]. 81% of patients preferred the scapular “Y” view due to less pain, and radiology technicians preferred it due to ease of acquisition [64]. The synchondrosis of an os acromiale can be injured following trauma, emphasizing the need for appropriate radiographic investigation including axillary views [33].

MRI: MRI is the modality of choice for evaluating the rotator cuff, biceps, and subacromial/subdeltoid bursa [61]. It is useful to identify osteonecrosis of the humeral head, bone tumours, labral tears, and rotator cuff tears [55]. T1-weighted MRI can reveal Hill-Sachs lesions and is often used with MR arthrograms to provide a more detailed picture of joint surfaces [61]. T2-weighted MRI provides better visualization of full-thickness rotator cuff tears [61]. The accuracy for identifying labral and rotator cuff tears is enhanced by combining the scan with arthrography [55]. In a meta-analysis, MR arthrography (MRA) had greater diagnostic test accuracy for detecting glenoid labral lesions than MRI, with MRA sensitivity of 88% and specificity of 93% versus MRI sensitivity of 76% and specificity of 87% [59]. MRA is considered the benchmark for evaluation of labral tears and is rarely indicated for rotator cuff pathology [61]. Abduction and external rotation (ABER) of the arm is an alternative position utilized to increase sensitivity and specificity for detecting anteroinferior labroligamentous injury [59]. Full routine MRI or MRA examination had similar accuracy as the ABER sequence in evaluating the anteroinferior labral–ligamentous complex [59]. The sensitivity of MRA with the ABER position for detecting anteroinferior labral lesions was significantly higher than that of MRA in the neutral position [59]. MRAs can demonstrate a patulous capsule on coronal, sagittal, and axial imaging in patients with multidirectional instability [59]. MRAs can be helpful in evaluating lesions of the rotator interval and other associated findings that may affect the surgical plan [59]. The presence of glenoid dysplasia, increased capsular cross-sectional area, and increased glenoid retroversion have been found to be associated with increased posterior labral tears and symptomatic instability [59]. Glenoid retroversion was significantly increased in patients with symptomatic posterior labral tears, but there was no significant association between instability and increased humeral head subluxation [59]. The diagnosis of multidirectional instability is a clinical one, and the need for expensive and/or invasive imaging should be weighed against the information gained [59]. MRI has a sensitivity of 100%, specificity of 68%, positive predictive value of 85%, negative predictive value of 100%, and accuracy of 89% for the detection of full-thickness rotator cuff tears [62].

CT: CT scans may offer a few degrees of increased precision in the measurement of glenoid version, but this precision does not necessarily improve the quality of the surgery or the clinical outcome [31]. CT is helpful for planning fracture surgery and shoulder joint replacement [55]. CT with three-dimensional reconstructions is the advanced imaging study of choice for determining the extent of glenoid bone loss in the setting of shoulder instability [62]. When MRI or MR arthrography is contraindicated, CT arthrography is indicated [61]. Arthrography involves injection of contrast agent in conjunction with either an MRI or CT scan, enhancing imaging of the joint to enable better identification of normal structures and pathology involving the joint surfaces [61].

Ultrasonography: Ultrasonography is a low-cost alternative to MRI and arthrography for evaluating both skeletal and soft-tissue structures of the shoulder [61]. It can provide immediate, real-time visualization of the rotator cuff, biceps tendon, and calcific deposits [61]. It can be used to measure the subacromial space and detect atrophy of rotator cuff muscles [61]. It can evaluate impingement in various positions and motions due to real-time imaging capabilities [61]. 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 [61]. It 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 [62].

Arthroscopy: Arthroscopy is useful for diagnosing and treating subacromial impingement, intra-articular lesions, detachment of the glenoid labrum, and rotator cuff tears [55].

Other Considerations: Bilateral os acromiale was found in only two cases (15.4%) in the Korean patient study [14]. The prevalence of os acromiale in the Korean study population was very low (less than 1%) as compared with other ethnic groups [14]. Black people consistently showed a higher prevalence of os acromiale (13.2%-18.2%) than white people (5.8%-9.5%), indicating genetic influences in the formation of os acromiale [14].

Treatment

Non-Operative Management

For symptomatic os acromiale, management is initially nonsurgical [2].

Operative Management

Other Considerations: Meta–os acromiale is the rarest subtype of os acromiale, and special consideration must be given to the type of tension-band construct used to achieve adequate compression and fixation [32].

Complications

Other Considerations: Postoperative local tenderness at the os acromiale is expected in 1 out of 4 patients following reverse total shoulder arthroplasty [7]. This tenderness resolves spontaneously over time in the majority of patients [7]. Internal fixation of symptomatic os acromiale is associated with relatively minor complications [36].

Recovery

Other Considerations: Postoperative local tenderness at the os acromiale can be expected in 1 out of 4 patients after reverse total shoulder arthroplasty but resolves spontaneously over time in the majority of patients [7].

Key Evidence

  • [L4] The majority of os acromiale is asymptomatic and requires no treatment. [1] (10.2147/orr.s141480)
  • [L5] For the symptomatic os acromiale, management is initially nonsurgical. [2] (10.5435/00124635-200601000-00004)
  • [L4] The diagnosis of os acromiale should be based on imaging features and not limited by age. [3] (10.1007/s00256-015-2098-4)
  • [L4] Os acromiale is a co-condition in patients with rotator cuff tear. [4] (10.1080/00016470510030643)
  • [L4] Operative management of a symptomatic os acromiale that has failed initial nonoperative treatment leads to decreased symptoms and improvement in clinical outcomes. [5] (10.1016/j.jse.2019.05.047)
  • [L4] Surgical management of symptomatic os acromiale that has failed nonoperative measures may predictably lead to improved outcomes. [6] (10.4103/0973-6042.80461)
  • [L3] Postoperative local tenderness at the os acromiale can be expected in 1 out of 4 patients but resolves spontaneously over time in the majority of patients. [7] (10.1177/2325967120965131)
  • [L4] The presence of os acromiale does not appear to have a negative impact on the clinical outcomes after surgery and rTSA remains a safe and effective treatment option. [8] (10.1016/j.xrrt.2025.01.002)
  • [L4] This technique is a predictable and consistent treatment for symptomatic os acromiale in this population. [9] (10.1016/j.jse.2005.09.019)
  • [L3] The study supports previous findings that os acromiale is associated with rotator cuff injuries. [10] (10.1016/j.jseint.2025.05.015)
  • [L3] This multicenter study aimed to determine the prevalence of and factors associated with os acromiale in the Japanese population. [11] (10.1016/j.jse.2025.01.008)
  • [L3] Shoulders with os acromiale had a similar overall complication rate compared with matched controls (14% vs. 12%; P = 0.658). [12] (10.5435/jaaos-d-25-00614)
  • [L3] There was no relation between the presence of os acromiale and shoulder pain, regardless of diagnosis. [13] (10.1177/23259671221078806)
  • [L4] [14] (10.4055/cios.2013.5.3.202)
  • [L4] A tear of the rotator cuff may often be associated with os acromiale, likely due to impingement from abnormal motion at the fibrous union site. [15] (10.2106/00004623-198466080-00029)
  • [L4] Surgical treatment of symptomatic meso-os acromiale with concomitant rotator cuff pathology yielded poorer outcomes than previously reported, with only 53% achieving satisfactory results overall. [16] (10.1016/j.jse.2005.08.024)
  • [L4] The outcome of RTSA does not seem to be negatively affected by the presence of an os acromiale. [17] (10.1016/j.jse.2017.02.012)
  • [L5] Surgical options for symptomatic os acromiale include arthroscopic sub-total excision, arthroscopic subacromial decompression of stable fragments, and open reduction and internal fixation of unstable fragments. [18] (10.5435/jaaos-d-17-00011)
  • [L4] The overall frequency of os acromiale in the sample of 1594 skeletons was 8.34%. [19] (10.1002/oa.877)
  • [L4] Surgical treatment is usually not indicated for os acromiale in the professional tennis player. [20] (10.1177/2325967118773723)
  • [L4] Care should be taken not to perform acromioplasty in the presence of painful os acromiale. [21] (10.1016/j.otsr.2012.10.020)
  • [L5] An os acromiale should be included in the differential diagnosis of the swimming athlete who presents with shoulder pain, particularly in the setting of a failed response to physical therapy, activity modification, or steroid injection. [23] (10.1177/1941738108326705)
  • [L4] Ipsilateral os acromiale may be a relative contraindication to the clavicle hook plate. [24] (10.1186/s12891-021-04841-1)
  • [L4] Awareness of the os acromiale in the young athlete, appropriate clinical examination, and image studies are crucial to confirm diagnosis. [26] (10.1016/j.jseint.2020.02.008)
  • [Paper] Osteosynthesis to achieve bony union is a safe, effective, and reliable technique for the treatment of large and unstable symptomatic os acromiale, though high-level studies are still needed to compare outcomes between different techniques. [27] (10.1016/j.eats.2017.03.025)
  • [L4] [28] (10.1302/2058-5241.4.180100)
  • [L4] Meta–os acromiale is the rarest subtype of os acromiale, and special consideration must be given to the type of tension-band construct used to achieve adequate compression and fixation. [32] (10.1177/03635465211028238)
  • [L4] This case highlights that the synchondrosis of an os acromiale can be injured following trauma, though rarely, and emphasizes the need for appropriate radiographic investigation including axillary views and a flexible surgical approach. [33] (10.1016/j.jse.2008.02.012)
  • [L4] The procedure eliminates pain, preserves both acromial length and deltoid origin, and is associated with relatively minor complications. [36] (10.1016/j.jse.2004.01.023)
  • [Paper] [67] (10.1016/j.eats.2021.01.016)

See Also

References

[1] Optimal management of symptomatic os acromiale: current perspectives. Orthopedic Research and Reviews. 2018. DOI: 10.2147/orr.s141480

[2] Symptomatic Os Acromiale. Journal of the American Academy of Orthopaedic Surgeons. 2006. DOI: 10.5435/00124635-200601000-00004

[3] Differentiating os acromiale from normally developing acromial ossification centers using magnetic resonance imaging. Skeletal Radiology. 2015. DOI: 10.1007/s00256-015-2098-4

[4] Rotator cuff tears associated with os acromiale. Acta Orthopaedica. 2005. DOI: 10.1080/00016470510030643

[5] Os acromiale: systematic review of surgical outcomes. Journal of Shoulder and Elbow Surgery. 2020. DOI: 10.1016/j.jse.2019.05.047

[6] Systematic review of the surgical treatment for symptomatic os acromiale. International Journal of Shoulder Surgery. 2011. DOI: 10.4103/0973-6042.80461

[7] Os Acromiale in Reverse Total Shoulder Arthroplasty: A Cohort Study. Orthopaedic Journal of Sports Medicine. 2020. DOI: 10.1177/2325967120965131

[8] Clinical implications of reverse total shoulder arthroplasty with an os acromiale: a systematic review. JSES Reviews, Reports, and Techniques. 2025. DOI: 10.1016/j.xrrt.2025.01.002

[9] Painful os acromiale (or unfused acromial apophysis) in athletes. Journal of Shoulder and Elbow Surgery. 2006. DOI: 10.1016/j.jse.2005.09.019

[10] Prevalence and factors associated with os acromiale: a multicenter study. JSES International. 2025. DOI: 10.1016/j.jseint.2025.05.015

[11] The prevalence and associated factors of os acromiale: a multicenter study. Journal of Shoulder and Elbow Surgery. 2025. DOI: 10.1016/j.jse.2025.01.008

[12] The Influence of Os Acromiale on Patient Outcomes After Reverse Total Shoulder Arthroplasty: A Matched Cohort Study. Journal of the American Academy of Orthopaedic Surgeons. 2026. DOI: 10.5435/jaaos-d-25-00614

[13] Prevalence of Os Acromiale in Thai Patients With Shoulder Problems: A Magnetic Resonance Imaging Study. Orthopaedic Journal of Sports Medicine. 2022. DOI: 10.1177/23259671221078806

[14] The Prevalence of Os Acromiale in Korean Patients Visiting Shoulder Clinic. Clinics in Orthopedic Surgery. 2013. DOI: 10.4055/cios.2013.5.3.202

[15] Rotator cuff tears associated with os acromiale.. The Journal of Bone & Joint Surgery. 1984. DOI: 10.2106/00004623-198466080-00029

[16] Surgical treatment of os acromiale with and without associated rotator cuff tears. Journal of Shoulder and Elbow Surgery. 2006. DOI: 10.1016/j.jse.2005.08.024

[17] Reverse shoulder arthroplasty in patients with os acromiale. Journal of Shoulder and Elbow Surgery. 2017. DOI: 10.1016/j.jse.2017.02.012

[18] Symptomatic, Unstable Os Acromiale. Journal of the American Academy of Orthopaedic Surgeons. 2018. DOI: 10.5435/jaaos-d-17-00011

[19] The frequency of os acromiale in the Robert J. Terry Collection. International Journal of Osteoarchaeology. 2006. DOI: 10.1002/oa.877

[20] Os Acromiale in Professional Tennis Players. Orthopaedic Journal of Sports Medicine. 2018. DOI: 10.1177/2325967118773723

[21] Os acromiale, a cause of shoulder pain, not to be overlooked. Orthopaedics & Traumatology: Surgery & Research. 2013. DOI: 10.1016/j.otsr.2012.10.020

[23] Os Acromiale as a Cause for Shoulder Pain in a Competitive Swimmer: A Case Report. Sports Health: A Multidisciplinary Approach. 2009. DOI: 10.1177/1941738108326705

[24] Os acromiale may be a contraindication of the clavicle hook plate: case reports and literature review. BMC Musculoskeletal Disorders. 2021. DOI: 10.1186/s12891-021-04841-1

[26] The unstable os acromiale: a cause of pain in the young athlete. JSES International. 2020. DOI: 10.1016/j.jseint.2020.02.008

[27] Operative Treatment of Symptomatic Meso‐Type Os Acromiale. Arthroscopy Techniques. 2017. DOI: 10.1016/j.eats.2017.03.025

[28] Os acromiale: a review of its incidence, pathophysiology, and clinical management. EFORT Open Reviews. 2019. DOI: 10.1302/2058-5241.4.180100

[31] Rockwood And Matsen S The Shoulder. Arthroscopic Management of Prearthritic and Arthritic Conditions of the Shoulder and the Postarthroplasty Shoulder > Radiographic Evaluation.

[32] Rare Symptomatic Meta–Os Acromiale in an Athlete. The American Journal of Sports Medicine. 2021. DOI: 10.1177/03635465211028238

[33] Fracture of an os acromiale with associated rupture of the coracoclavicular ligaments. Journal of Shoulder and Elbow Surgery. 2008. DOI: 10.1016/j.jse.2008.02.012

[36] Internal fixation of symptomatic os acromiale: a series of twenty-six cases. Journal of Shoulder and Elbow Surgery. 2004. DOI: 10.1016/j.jse.2004.01.023

[38] Rockwood And Matsen S The Shoulder. Shoulder and Elbow Specialty Clinic Workers’ Survey > ANATOMY.

[41] Aaos Comprehensive Orthopaedic Review 3. Anatomy of the Shoulder, Arm, and Elbow > I. Shoulder.

[52] Miller S Review Of Orthopaedics. Genetics of musculoskeletal conditions and abnormalities are summarized in Table 1.27 > UPPER EXTREMITY > SHOULDER.

[55] Apley And Solomon S Concise System Of Orthopaedics And Trauma. INVESTIGATION.

[59] Rockwood And Green S Fractures In Adults. 29: Principles of Nonunion and Bone Defect Treatment > Magnetic Resonance Imaging and Arthrography.

[61] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Shoulder Anatomy and Biomechanics, Clinical Evaluation, Imaging > Clinical Evaluation > Imaging.

[62] Aaos Comprehensive Orthopaedic Review 3. Imaging of the Shoulder and Elbow > I. Shoulder.

[64] Rockwood And Green S Fractures In Adults. 29: Principles of Nonunion and Bone Defect Treatment > Radiography.

[65] Campbell S Operative Orthopaedics 4 Volume Set. ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION WITH BONE-PATELLAR TENDON-BONE GRAFT > Developmental Stages of Impingement Syndrome.

[66] Campbell S Operative Orthopaedics 4 Volume Set. ARTHROSCOPIC REPAIR OF POSTERIOR HUMERAL AVULSION OF THE GLENOHUMERAL LIGAMENT > SUBACROMIAL IMPINGEMENT SYNDROME.

[67] Arthroscopic “Wallow” Procedure for Resection of Symptomatic Os Acromiale Pseudoarthrosis. Arthroscopy Techniques. 2021. DOI: 10.1016/j.eats.2021.01.016

Creative Commons BY-NC 4.0

CC Creative Commons licence
BY Attribution — you must credit the source
NC NonCommercial — not for commercial use

Attribution-NonCommercial 4.0 International

Creative Commons Corporation ("Creative Commons") is not a law firm and does not provide legal services or legal advice. Distribution of Creative Commons public licenses does not create a lawyer-client or other relationship. Creative Commons makes its licenses and related information available on an "as-is" basis. Creative Commons gives no warranties regarding its licenses, any material licensed under their terms and conditions, or any related information. Creative Commons disclaims all liability for damages resulting from their use to the fullest extent possible.

Using Creative Commons Public Licenses

Creative Commons public licenses provide a standard set of terms and conditions that creators and other rights holders may use to share original works of authorship and other material subject to copyright and certain other rights specified in the public license below. The following considerations are for informational purposes only, are not exhaustive, and do not form part of our licenses.

Considerations for licensors: Our public licenses are intended for use by those authorized to give the public permission to use material in ways otherwise restricted by copyright and certain other rights. Our licenses are irrevocable. Licensors should read and understand the terms and conditions of the license they choose before applying it. Licensors should also secure all rights necessary before applying our licenses so that the public can reuse the material as expected. Licensors should clearly mark any material not subject to the license. This includes other CC- licensed material, or material used under an exception or limitation to copyright. More considerations for licensors: wiki.creativecommons.org/Considerations_for_licensors

Considerations for the public: By using one of our public licenses, a licensor grants the public permission to use the licensed material under specified terms and conditions. If the licensor's permission is not necessary for any reason--for example, because of any applicable exception or limitation to copyright--then that use is not regulated by the license. Our licenses grant only permissions under copyright and certain other rights that a licensor has authority to grant. Use of the licensed material may still be restricted for other reasons, including because others have copyright or other rights in the material. A licensor may make special requests, such as asking that all changes be marked or described. Although not required by our licenses, you are encouraged to respect those requests where reasonable. More considerations for the public: wiki.creativecommons.org/Considerations_for_licensees

Creative Commons Attribution-NonCommercial 4.0 International Public License

By exercising the Licensed Rights (defined below), You accept and agree to be bound by the terms and conditions of this Creative Commons Attribution-NonCommercial 4.0 International Public License ("Public License"). To the extent this Public License may be interpreted as a contract, You are granted the Licensed Rights in consideration of Your acceptance of these terms and conditions, and the Licensor grants You such rights in consideration of benefits the Licensor receives from making the Licensed Material available under these terms and conditions.

Section 1 -- Definitions.

a. Adapted Material means material subject to Copyright and Similar Rights that is derived from or based upon the Licensed Material and in which the Licensed Material is translated, altered, arranged, transformed, or otherwise modified in a manner requiring permission under the Copyright and Similar Rights held by the Licensor. For purposes of this Public License, where the Licensed Material is a musical work, performance, or sound recording, Adapted Material is always produced where the Licensed Material is synched in timed relation with a moving image.

b. Adapter's License means the license You apply to Your Copyright and Similar Rights in Your contributions to Adapted Material in accordance with the terms and conditions of this Public License.

c. Copyright and Similar Rights means copyright and/or similar rights closely related to copyright including, without limitation, performance, broadcast, sound recording, and Sui Generis Database Rights, without regard to how the rights are labeled or categorized. For purposes of this Public License, the rights specified in Section 2(b)(1)-(2) are not Copyright and Similar Rights.

d. Effective Technological Measures means those measures that, in the absence of proper authority, may not be circumvented under laws fulfilling obligations under Article 11 of the WIPO Copyright Treaty adopted on December 20, 1996, and/or similar international agreements.

e. Exceptions and Limitations means fair use, fair dealing, and/or any other exception or limitation to Copyright and Similar Rights that applies to Your use of the Licensed Material.

f. Licensed Material means the artistic or literary work, database, or other material to which the Licensor applied this Public License.

g. Licensed Rights means the rights granted to You subject to the terms and conditions of this Public License, which are limited to all Copyright and Similar Rights that apply to Your use of the Licensed Material and that the Licensor has authority to license.

h. Licensor means the individual(s) or entity(ies) granting rights under this Public License.

i. NonCommercial means not primarily intended for or directed towards commercial advantage or monetary compensation. For purposes of this Public License, the exchange of the Licensed Material for other material subject to Copyright and Similar Rights by digital file-sharing or similar means is NonCommercial provided there is no payment of monetary compensation in connection with the exchange.

j. Share means to provide material to the public by any means or process that requires permission under the Licensed Rights, such as reproduction, public display, public performance, distribution, dissemination, communication, or importation, and to make material available to the public including in ways that members of the public may access the material from a place and at a time individually chosen by them.

k. Sui Generis Database Rights means rights other than copyright resulting from Directive 96/9/EC of the European Parliament and of the Council of 11 March 1996 on the legal protection of databases, as amended and/or succeeded, as well as other essentially equivalent rights anywhere in the world.

l. You means the individual or entity exercising the Licensed Rights under this Public License. Your has a corresponding meaning.

Section 2 -- Scope.

a. License grant.

1. Subject to the terms and conditions of this Public License, the Licensor hereby grants You a worldwide, royalty-free, non-sublicensable, non-exclusive, irrevocable license to exercise the Licensed Rights in the Licensed Material to:

a. reproduce and Share the Licensed Material, in whole or in part, for NonCommercial purposes only; and

b. produce, reproduce, and Share Adapted Material for NonCommercial purposes only.

2. Exceptions and Limitations. For the avoidance of doubt, where Exceptions and Limitations apply to Your use, this Public License does not apply, and You do not need to comply with its terms and conditions.

3. Term. The term of this Public License is specified in Section 6(a).

4. Media and formats; technical modifications allowed. The Licensor authorizes You to exercise the Licensed Rights in all media and formats whether now known or hereafter created, and to make technical modifications necessary to do so. The Licensor waives and/or agrees not to assert any right or authority to forbid You from making technical modifications necessary to exercise the Licensed Rights, including technical modifications necessary to circumvent Effective Technological Measures. For purposes of this Public License, simply making modifications authorized by this Section 2(a) (4) never produces Adapted Material.

5. Downstream recipients.

a. Offer from the Licensor -- Licensed Material. Every recipient of the Licensed Material automatically receives an offer from the Licensor to exercise the Licensed Rights under the terms and conditions of this Public License.

b. No downstream restrictions. You may not offer or impose any additional or different terms or conditions on, or apply any Effective Technological Measures to, the Licensed Material if doing so restricts exercise of the Licensed Rights by any recipient of the Licensed Material.

6. No endorsement. Nothing in this Public License constitutes or may be construed as permission to assert or imply that You are, or that Your use of the Licensed Material is, connected with, or sponsored, endorsed, or granted official status by, the Licensor or others designated to receive attribution as provided in Section 3(a)(1)(A)(i).

b. Other rights.

1. Moral rights, such as the right of integrity, are not licensed under this Public License, nor are publicity, privacy, and/or other similar personality rights; however, to the extent possible, the Licensor waives and/or agrees not to assert any such rights held by the Licensor to the limited extent necessary to allow You to exercise the Licensed Rights, but not otherwise.

2. Patent and trademark rights are not licensed under this Public License.

3. To the extent possible, the Licensor waives any right to collect royalties from You for the exercise of the Licensed Rights, whether directly or through a collecting society under any voluntary or waivable statutory or compulsory licensing scheme. In all other cases the Licensor expressly reserves any right to collect such royalties, including when the Licensed Material is used other than for NonCommercial purposes.

Section 3 -- License Conditions.

Your exercise of the Licensed Rights is expressly made subject to the following conditions.

a. Attribution.

1. If You Share the Licensed Material (including in modified form), You must:

a. retain the following if it is supplied by the Licensor with the Licensed Material:

i. identification of the creator(s) of the Licensed Material and any others designated to receive attribution, in any reasonable manner requested by the Licensor (including by pseudonym if designated);

ii. a copyright notice;

iii. a notice that refers to this Public License;

iv. a notice that refers to the disclaimer of warranties;

v. a URI or hyperlink to the Licensed Material to the extent reasonably practicable;

b. indicate if You modified the Licensed Material and retain an indication of any previous modifications; and

c. indicate the Licensed Material is licensed under this Public License, and include the text of, or the URI or hyperlink to, this Public License.

2. You may satisfy the conditions in Section 3(a)(1) in any reasonable manner based on the medium, means, and context in which You Share the Licensed Material. For example, it may be reasonable to satisfy the conditions by providing a URI or hyperlink to a resource that includes the required information.

3. If requested by the Licensor, You must remove any of the information required by Section 3(a)(1)(A) to the extent reasonably practicable.

4. If You Share Adapted Material You produce, the Adapter's License You apply must not prevent recipients of the Adapted Material from complying with this Public License.

Section 4 -- Sui Generis Database Rights.

Where the Licensed Rights include Sui Generis Database Rights that apply to Your use of the Licensed Material:

a. for the avoidance of doubt, Section 2(a)(1) grants You the right to extract, reuse, reproduce, and Share all or a substantial portion of the contents of the database for NonCommercial purposes only;

b. if You include all or a substantial portion of the database contents in a database in which You have Sui Generis Database Rights, then the database in which You have Sui Generis Database Rights (but not its individual contents) is Adapted Material; and

c. You must comply with the conditions in Section 3(a) if You Share all or a substantial portion of the contents of the database.

For the avoidance of doubt, this Section 4 supplements and does not replace Your obligations under this Public License where the Licensed Rights include other Copyright and Similar Rights.

Section 5 -- Disclaimer of Warranties and Limitation of Liability.

a. UNLESS OTHERWISE SEPARATELY UNDERTAKEN BY THE LICENSOR, TO THE EXTENT POSSIBLE, THE LICENSOR OFFERS THE LICENSED MATERIAL AS-IS AND AS-AVAILABLE, AND MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND CONCERNING THE LICENSED MATERIAL, WHETHER EXPRESS, IMPLIED, STATUTORY, OR OTHER. THIS INCLUDES, WITHOUT LIMITATION, WARRANTIES OF TITLE, MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, NON-INFRINGEMENT, ABSENCE OF LATENT OR OTHER DEFECTS, ACCURACY, OR THE PRESENCE OR ABSENCE OF ERRORS, WHETHER OR NOT KNOWN OR DISCOVERABLE. WHERE DISCLAIMERS OF WARRANTIES ARE NOT ALLOWED IN FULL OR IN PART, THIS DISCLAIMER MAY NOT APPLY TO YOU.

b. TO THE EXTENT POSSIBLE, IN NO EVENT WILL THE LICENSOR BE LIABLE TO YOU ON ANY LEGAL THEORY (INCLUDING, WITHOUT LIMITATION, NEGLIGENCE) OR OTHERWISE FOR ANY DIRECT, SPECIAL, INDIRECT, INCIDENTAL, CONSEQUENTIAL, PUNITIVE, EXEMPLARY, OR OTHER LOSSES, COSTS, EXPENSES, OR DAMAGES ARISING OUT OF THIS PUBLIC LICENSE OR USE OF THE LICENSED MATERIAL, EVEN IF THE LICENSOR HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH LOSSES, COSTS, EXPENSES, OR DAMAGES. WHERE A LIMITATION OF LIABILITY IS NOT ALLOWED IN FULL OR IN PART, THIS LIMITATION MAY NOT APPLY TO YOU.

c. The disclaimer of warranties and limitation of liability provided above shall be interpreted in a manner that, to the extent possible, most closely approximates an absolute disclaimer and waiver of all liability.

Section 6 -- Term and Termination.

a. This Public License applies for the term of the Copyright and Similar Rights licensed here. However, if You fail to comply with this Public License, then Your rights under this Public License terminate automatically.

b. Where Your right to use the Licensed Material has terminated under Section 6(a), it reinstates:

1. automatically as of the date the violation is cured, provided it is cured within 30 days of Your discovery of the violation; or

2. upon express reinstatement by the Licensor.

For the avoidance of doubt, this Section 6(b) does not affect any right the Licensor may have to seek remedies for Your violations of this Public License.

c. For the avoidance of doubt, the Licensor may also offer the Licensed Material under separate terms or conditions or stop distributing the Licensed Material at any time; however, doing so will not terminate this Public License.

d. Sections 1, 5, 6, 7, and 8 survive termination of this Public License.

Section 7 -- Other Terms and Conditions.

a. The Licensor shall not be bound by any additional or different terms or conditions communicated by You unless expressly agreed.

b. Any arrangements, understandings, or agreements regarding the Licensed Material not stated herein are separate from and independent of the terms and conditions of this Public License.

Section 8 -- Interpretation.

a. For the avoidance of doubt, this Public License does not, and shall not be interpreted to, reduce, limit, restrict, or impose conditions on any use of the Licensed Material that could lawfully be made without permission under this Public License.

b. To the extent possible, if any provision of this Public License is deemed unenforceable, it shall be automatically reformed to the minimum extent necessary to make it enforceable. If the provision cannot be reformed, it shall be severed from this Public License without affecting the enforceability of the remaining terms and conditions.

c. No term or condition of this Public License will be waived and no failure to comply consented to unless expressly agreed to by the Licensor.

d. Nothing in this Public License constitutes or may be interpreted as a limitation upon, or waiver of, any privileges and immunities that apply to the Licensor or You, including from the legal processes of any jurisdiction or authority.

Creative Commons is not a party to its public licenses. Notwithstanding, Creative Commons may elect to apply one of its public licenses to material it publishes and in those instances will be considered the “Licensor.” The text of the Creative Commons public licenses is dedicated to the public domain under the CC0 Public Domain Dedication. Except for the limited purpose of indicating that material is shared under a Creative Commons public license or as otherwise permitted by the Creative Commons policies published at creativecommons.org/policies, Creative Commons does not authorize the use of the trademark "Creative Commons" or any other trademark or logo of Creative Commons without its prior written consent including, without limitation, in connection with any unauthorized modifications to any of its public licenses or any other arrangements, understandings, or agreements concerning use of licensed material. For the avoidance of doubt, this paragraph does not form part of the public licenses.

Creative Commons may be contacted at creativecommons.org.