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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

• In appropriately selected patients, in-office needle arthroscopy of the shoulder with subacromial decompression can be performed by a simple technique [1].
• Further studies and clinical trials are needed to evaluate functional results of biplanar acromioplasty [2].
• Computer image-guided precise acromioplasty provides an alternative approach to reduce a large critical shoulder angle to the desired range, especially for patients with rotator cuff tears combined with preoperative CSA greater than 35 degrees [3].
• Despite Clinical Practice Guidelines recommending the nonroutine use of acromioplasty, surgeons continue to perform acromioplasty with rotator cuff repair in most of the cases throughout all subcategorizations analyzed [4].
• The arthroscopic technique described for acromioclavicular joint cysts allows for a minimally invasive, reproducible, and reliable approach for AC cyst decompression [5].

Anatomy & Pathophysiology

Bony Anatomy

• The acromion has three ossification centers: the metacromion (base), the mesoacromion (middle), and the preacromion (tip) [11].
• Failure of fusion of the acromial ossification centers results in os acromiale [11].
• The classification of acromial morphology as flat, curved, or hooked is challenged by poor interobserver reliability [11].
• The relationship between acromial anatomy and rotator cuff disease remains controversial [11].
• The scapula is attached to the axial skeleton by the acromioclavicular (AC) and sternoclavicular (SC) joints [10].
• The scapular spine is an osseous ridge that separates the supraspinatus and infraspinatus fossae [11].
• The glenoid is a convex structure of shallow depth shaped like an inverted pear [8].
• The glenoid averages 5° of retroversion in relation to the axis of the scapular body [11].
• The subchondral bone of the glenoid is relatively flat, and the articular concavity is augmented by cartilage and a circumferential labrum [11].
• The humeral head is spherical with a diameter of 37 to 57 mm [8].
• The most superior portion of the articular surface of the humeral head averages 8 mm above the greater tuberosity [8].
• The humeral version averages 29.8 degrees, with a range of 10 to 55 degrees [8].
• The humeral head is inclined approximately 130 degrees with respect to the humeral shaft [8].
• The neck-shaft angle measures an average of 135 degrees [9].
• The humeral head is retroverted an average of 30 degrees [9].
• The proximal humerus receives its blood supply from the anterior and posterior humeral circumflex branches from the third division of the axillary artery [8].
• The anterior humeral circumflex artery provides vascular inflow to the humeral head by way of its terminal anterolateral branch known as the artery of Laing (also known as the arcuate artery) [8].
• The ascending branch of the anterior humeral circumflex artery courses parallel to the lateral aspect of the long head biceps tendon and enters the humeral head at the interface of the bicipital groove and greater tuberosity [8].
• Injury to the arcuate artery may result in osteonecrosis of the humeral head [8].
• Additional extraosseous collateral branches can permit humeral head perfusion despite complete ligation of the arcuate artery [8].
• The greater tuberosity serves as the attachment site for the supraspinatus, infraspinatus, and teres minor tendons of the rotator cuff [8].
• The lesser tuberosity serves as the attachment site for the subscapularis tendon [8].
• The bicipital groove lies between the greater tuberosity and lesser tuberosity and serves as a pathway for the long head of the biceps [8].
• The distal aspect of the bicipital groove is internally rotated with respect to the proximal portion [8].
• The anatomic neck of the proximal humerus is located at the junction of the articular surface and the tuberosities [8].
• The surgical neck represents an indistinct region (metadiaphyseal junction) below the tuberosities but above the humeral shaft [8].
• Fractures involving the anatomic neck are prognostically worse than fractures involving other regions of the proximal humerus with respect to the potential disruption of the vascular supply to the humeral head and subsequent development of avascular necrosis [8].
• The scapula is separated from the chest wall by thin gliding fibro-fatty tissue, allowing its smooth excursion over the chest wall [10].
• The distribution of bony mass in the scapula is highly uneven, with the highest concentration in the glenoid, the scapular neck (including the base of the coracoid process), and the lateral border of the scapular body [10].
• Two bony pillars extend between the glenoid and the scapular body to transmit compressive forces from the glenoid fossa [10].
• The lateral pillar connects the inferior border of the glenoid with the inferior angle [10].
• The spinal pillar arises from the central part of the glenoid and continues medially to become part of the base of the scapular spine [10].
• The weakest bone in the scapula is located primarily in the central part of the biomechanical body, specifically in the infraspinous fossa [10].
• The weakest area of the circumference of the biomechanical body of the scapula is the connection of the scapular spine and the medial border of the scapula, known as the spinomedial angle [10].

Ligaments and Soft Tissue Structures

• The acromion, the coracoacromial ligament, and the coracoid process form the coracoacromial arch [8].
• The coracoacromial arch is a rigid bony-ligamentous structure that imparts stability to the shoulder girdle [8].
• The rotator cuff, subacromial bursa, and subdeltoid bursa pass underneath the coracoacromial arch [8].
• The superior shoulder suspensory complex (SSSC) provides a stable connection between the scapula and the axial skeleton [11].
• The SSSC is composed of the glenoid, the coracoid process, the coracoclavicular ligaments, the distal clavicle, the AC joint, and the acromion [11].
• The superior strut of the SSSC comprises the middle clavicle [11].
• The inferior strut of the SSSC comprises the lateral scapular border/spine of the scapula [11].
• The coracoclavicular ligaments (conoid: medial; trapezoid: lateral) are the primary stabilizers to superior (vertical) translation of the distal clavicle [11].
• The superior and posterior AC ligaments are the primary stabilizers to anterior and posterior (horizontal) translation of the clavicle [11].
• The glenoid labrum provides concavity and up to 50% of marginal glenoid socket depth [11].
• The rotator interval is defined medially by the base of the coracoid, superiorly by the supraspinatus tendon, and inferiorly by the subscapularis tendon [11].
• The rotator interval contains the coracohumeral (CH) ligament, the superior glenohumeral ligament (SGHL), and the intra-articular portion of the long head of the biceps tendon [11].
• Laxity of the rotator interval results in inferior laxity (the sulcus sign) [11].
• Contracture of the rotator interval is seen with adhesive capsulitis [11].
• The CH ligament restricts external rotation in adduction and is a static restraint to inferior and posterior translation in adduction and external rotation [11].
• The SGHL is a primary static restraint against anterior translation with the arm at the side [11].
• With the CH ligament, the SGHL forms a pulley that provides restraint against medial subluxation of the long head of the biceps tendon [11].
• The middle glenohumeral ligament (MGHL) is a primary static restraint against anterior translation with the arm in external rotation and 45° of abduction [11].
• The anterior band of the inferior glenohumeral ligament (AB-IGHL) is a primary static restraint against anterior-inferior dislocation of the glenohumeral joint in 90° of abduction and external rotation [11].
• The posterior band of the IGHL (PB-IGHL) is a primary static restraint against posterior-inferior translation in internal rotation and adduction [11].
• The superior transverse scapular ligament arises from the medial base of the coracoid overlying the suprascapular notch [11].
• The suprascapular artery runs superior to the superior transverse scapular ligament, and the nerve runs deep to the ligament [11].
• Entrapment of the suprascapular nerve at the superior transverse scapular ligament causes denervation of both the supraspinatus and the infraspinatus [11].
• The spinoglenoid ligament overlies the suprascapular nerve at the spinoglenoid notch [11].
• Entrapment, traction, or compression of the suprascapular nerve at the spinoglenoid notch causes denervation of the infraspinatus [11].

Bursae

• The subacromial bursa has clinical importance in the shoulder region [12].
• The subscapular bursa lies between the subscapularis tendon and the neck of the scapula [12].
• The subscapular bursa communicates with the joint cavity between the superior and middle glenohumeral ligaments [12].
• 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 [12].
• The subscapular bursa is linked to the coracoid process by a suspensory ligament [12].
• In 28% of specimens dissected by Colas and colleagues, the subscapular bursae merged with the subcoracoid bursae, forming a unique wide bursa in this region [12].
• The subscapular bursa often houses loose bodies in the shoulder [12].
• The subscapular bursa is a region in which synovitis of the shoulder may be most intense, where small fringes, or villi, can project into the joint cavity [12].
• A soft tissue sheath consistently covers the long head of the biceps tendon to the level of the proximal margin of the pectoralis major tendon and contributes to the roof of the bicipital tunnel [12].
• The fibro-osseous bicipital tunnel consists of three distinct anatomic zones [12].
• Zone 1 of the bicipital tunnel represents the traditional bony bicipital groove beginning at the articular margin and ending at the distal margin of the subscapularis tendon [12].
• Zone 2 of the bicipital tunnel extends from the distal margin of the subscapularis tendon to the proximal margin of the pectoralis major tendon and represents a "no man's land" because it is not viewable from arthroscopy above or from subpectoral exposure below [12].
• Zone 3 of the bicipital tunnel is distal to the proximal margin of the pectoralis major tendon and represents the subpectoral region [12].

Pathophysiology and Biomechanics

• Stability and function of the glenohumeral joint is provided by the interaction of structures that promote a near global range of motion and purposeful function [8].
• External loads transferred to the shoulder girdle are initially offset by joint surface anatomy, joint volume, atmospheric pressure, and joint fluid cohesion and adhesion [8].
• Moderate and large loads are counterbalanced by the deltoid and rotator cuff and by the capsulolabral and bone structures, respectively [8].
• Proximal humeral fractures alter complex interactions in the shoulder girdle, resulting in pain, decreased range of motion and stiffness, and disability [8].
• Displaced proximal humeral fractures can impede normal movement of the rotator cuff, subacromial bursa, and subdeltoid bursa, causing impingement and disruption of normal glenohumeral motion [8].
• In proximal humeral fractures, the subdeltoid and subacromial bursae can become thickened and fibrotic, forming adhesions that can limit normal glenohumeral motion [8].
• Early range of motion exercises after a fracture have been hypothesized to decrease the formation of such adhesions [8].
• The rotator cuff muscles serve as depressors of the humeral head to allow the deltoid to efficiently abduct the humerus [9].
• The infraspinatus and teres minor are external rotators, while the subscapularis is an internal rotator of the humerus [9].
• The glenoid cavity is a shallow socket, approximately one third the size of the humeral head [9].
• Stability of the glenohumeral joint depends on capsule, ligament, and muscle [9].
• A redundant capsule allows for motion in the glenohumeral joint [9].
• The pathogenesis of shoulder stiffness is still elusive, but ongoing basic science research has provided insight into the cellular and biochemical pathways that result in shoulder stiffness [6].
• No treatment for a stiff shoulder has proved to be definitive [6].
• The literature supports many forms of treatment for a stiff shoulder, both operative and nonoperative [6].
• The treatment approach for a stiff shoulder should be tailored to each individual patient to ensure the best possible outcome [6].

Classification

• In appropriately selected patients, in-office needle arthroscopy of the shoulder with subacromial decompression can be performed [1].
• Computer image-guided precise acromioplasty is an alternative approach to reduce a large critical shoulder angle to the desired range, especially for patients with rotator cuff tears combined with preoperative critical shoulder angle greater than 35 degrees [3].
• The arthroscopic technique described allows for a minimally invasive, reproducible, and reliable approach for acromioclavicular cyst decompression [5].

Clinical Presentation

• Computer image-guided precise acromioplasty is an alternative approach to reduce a large critical shoulder angle to the desired range [3].
• Computer image-guided precise acromioplasty is especially for patients with rotator cuff tears combined with preoperative critical shoulder angle greater than 35 degrees [3].
• Surgeons continue to perform acromioplasty with rotator cuff repair in most of the cases throughout all subcategorizations analyzed [4].
• Clinical Practice Guidelines recommend the nonroutine use of acromioplasty [4].

Investigations

Plain Radiography

• The purpose of shoulder imaging is to help establish the diagnosis, determine the severity of the pathoanatomy, assist in surgical planning, and enable the surgeon to illustrate the condition of the shoulder to the patient [7].
• Unless a specific research protocol is in place, the temptation to “overimage” should be resisted, obtaining only the scans or reconstructions that are necessary for the care of the patient [7].
• Standardized plain films are almost always sufficient to garner the information needed for shoulder evaluation [7].
• Proper radiographic technique is as important as proper surgical technique to achieve the desired outcome [7].
• The first key radiographic view is the anteroposterior (AP) view taken in the plane of the scapula such that the x-ray beam passes through the glenohumeral joint [7].
• The AP view in the plane of the scapula shows the superoinferior position of the humeral head relative to the glenoid, the presence of osteophytes on the humeral head and glenoid, narrowing of the joint space, and the degree of medial displacement of the humerus in relation to the lateral acromial line [7].
• The AP view also shows the quality of the humeral and glenoid bone, the presence of loose bodies, and whether there is humeral head collapse or deformity [7].
• The second key radiographic view is the axillary view taken with the arm in the functional position of elevation in the plane of the scapula [7].
• The axillary view is oriented so that both the spinoglenoid notch and the scapular neck are visible [7].
• The axillary view shows a different perspective of the humeral anatomy, the amount of glenoid bone, the shape of the glenoid, its version in relation to the plane of the scapula, and the relationship of the humeral head to the glenoid fossa [7].
• The standardized axillary view is referred to as the “truth view” because it demonstrates the glenohumeral relationships in the functional position of elevation [7].
• CT scans have the disadvantage of being taken with the arm in the adducted position, unlike the axillary truth view which is taken in elevation [7].
• When taken properly, standardized anteroposterior and axillary views indicate the thickness of the cartilage space between the humerus and the glenoid, relative positions of the humeral head and glenoid, presence of osteophytes, degree of osteopenia, and extent of bony deformity and erosion [7].
• Joint space narrowing is most evident on the axillary truth view as opposed to images made with the arm at the side [7].
• The axillary truth view shows posterior subluxation or “functional decentering” that is not evident in images taken with the arm at the side [7].
• The degree of posterior subluxation can be measured as the position of the center of the humeral head in relation to the plane of the scapula [7].
• The degree of posterior subluxation can be measured as the position of the center of the humeral head in relation to the glenoid face [7].
• The degree of posterior subluxation can be measured as the point of contact of the humeral articular surface on the glenoid articular surface [7].
• The point of contact of the humeral articular surface on the glenoid articular surface reflects the degree of centering of the net humeral joint reaction force on the glenoid [7].
• Malcentering of the joint reaction force leads to posterior instability, posterior glenoid wear, and “rocking horse” loosening of prosthetic glenoid components [7].
• At least two X-ray views should be obtained: 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 [16].

Computed Tomography

• CT scans may offer a few degrees of increased precision in the measurement of glenoid version [7].
• Increased precision in glenoid version measurement via CT does not necessarily improve the quality of the surgery or the clinical outcome [7].
• Three-dimensional reconstructions can reveal fine details of the shoulder anatomy, but this additional information rarely changes the planning or conduct of the arthroplasty [7].
• Computed tomography (CT) is helpful for planning fracture surgery and shoulder joint replacement [16].

Magnetic Resonance Imaging

• Magnetic resonance imaging (MRI) is useful to identify osteonecrosis of the humeral head, or a bone tumour [16].
• MRI can identify labral tears and rotator cuff tears [16].
• The accuracy of MRI for identifying labral tears and rotator cuff tears is enhanced by combining the scan with arthrography [16].

Ultrasonography

• Ultrasonography is a simple and accurate test for identifying rotator cuff tears and calcific tendinitis [16].
• Ultrasonography can be useful in guiding injections or barbotage (aspirating calcific deposits in the rotator cuff) [16].
• The most commonly performed joint examination using ultrasonography is the shoulder examination [14].
• Accuracy of shoulder ultrasonography depends on the skill of the scanner operator and an awareness of pitfalls that are encountered [14].

Arthroscopy

• Arthroscopy is useful for diagnosing and treating subacromial impingement, intra-articular lesions, detachment of the glenoid labrum and rotator cuff tears [16].
• The arthroscopic technique for acromioclavicular joint cyst decompression allows for a minimally invasive, reproducible, and reliable approach [5].

General Imaging Principles

• The shoulder is a three-dimensional structure that cannot be represented by a single planar view [18].
• Critical relationships—such as the degree of centering of the humeral head—change with the position of the arm [18].
• Shoulder pathology may be found in a large number of different bones and soft tissues [18].
• Overlying and superimposed structures as well as metallic implants may complicate imaging the structures of interest [18].
• Surgeons need to develop a judicious approach to imaging that yields the information necessary to treat the patient while avoiding the tendency to "over-image" [18].

Treatment

• Computer image-guided precise acromioplasty provides an alternative approach to reduce a large critical shoulder angle (CSA) to the desired range, especially for patients with rotator cuff tears combined with preoperative CSA greater than 35 degrees [3].

Complications

• Further studies and clinical trials are needed to evaluate functional results of the biplanar acromioplasty technique [2].
• Computer image-guided precise acromioplasty is considered an alternative approach to reduce a large critical shoulder angle to the desired range, especially for patients with rotator cuff tears combined with preoperative CSA greater than 35 degrees [3].

Recovery

• Computer image-guided precise acromioplasty is believed to provide an alternative approach to reduce a large critical shoulder angle to the desired range, especially for patients with rotator cuff tears combined with preoperative CSA greater than 35 degrees [3].

Key Evidence

• [L5] In appropriately selected patients, in-office needle arthroscopy of the shoulder with subacromial decompression can be performed by this simple technique. [1] (10.1016/j.eats.2023.04.012)
• [L5] Further studies and clinical trials are needed to evaluate functional results of this technique. [2] (10.1016/j.eats.2023.04.006)
• [L5] They believe that the introduction of this technique will provide an alternative approach to reduce a large CSA to the desired range, especially for patients with rotator cuff tears combined with preoperative CSA greater than 35 degrees. [3] (10.1016/j.eats.2022.06.026)
• [L4] Despite Clinical Practice Guidelines recommending the nonroutine use of acromioplasty, surgeons continue to perform acromioplasty with rotator cuff repair in most of the cases throughout all subcategorizations analyzed. [4] (10.5435/jaaosglobal-d-22-00075)
• [L5] The arthroscopic technique described allows for a minimally invasive, reproducible, and reliable approach for AC cyst decompression. [5] (10.1016/j.eats.2025.103680)

References

[1] In‐Office Nano‐Arthroscopy of the Shoulder with Acromioplasty. Arthroscopy Techniques. 2023. DOI: 10.1016/j.eats.2023.04.012

[2] Biplanar Acromioplasty: An Arthroscopic Spur Removal Technique Based on Original Bony Landmarks. Arthroscopy Techniques. 2023. DOI: 10.1016/j.eats.2023.04.006

[3] Computer Image‐Guided Precise Acromioplasty for Reducing the Critical Shoulder Angle. Arthroscopy Techniques. 2022. DOI: 10.1016/j.eats.2022.06.026

[4] Trends in Acromioplasty Utilization During Arthroscopic Rotator Cuff Repair: An Epidemiological Study of 139,586 Patients. JAAOS: Global Research and Reviews. 2022. DOI: 10.5435/jaaosglobal-d-22-00075

[5] Arthroscopic Decompression of Acromioclavicular Joint Cysts. Arthroscopy Techniques. 2025. DOI: 10.1016/j.eats.2025.103680

[6] Rockwood And Matsen S The Shoulder. Arthroscopic Management of Prearthritic and Arthritic Conditions of the Shoulder and the Postarthroplasty Shoulder > SUMMARY.

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

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

[9] A Lange Medical Book Current Diagnosis Treatment In Orthopedics Fifth Edition. 2Musculoskeletal Trauma Surgery > SHOULDER AND ARM INJURIES.

[10] Rockwood And Green S Fractures In Adults. 29: Principles of Nonunion and Bone Defect Treatment > Applied Anatomy Related to Scapular Fractures.

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

[12] Rockwood And Matsen S The Shoulder. Developmental Anatomy of the Shoulder and Anatomy of the Glenohumeral Joint > Bursae.

[14] Orthopaedic Knowledge Update Sports Medicine 6. Diagnostic Ultrasonography and Ultrasonography-­Guided Procedures > Annotated References.

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

[18] Rockwood And Matsen S The Shoulder. Developmental Anatomy of the Shoulder and Anatomy of the Glenohumeral Joint > SENIOR EDITOR COMMENTARY.