Pagkiklik, Pagputok at Instability ng Balikat Impormasyon In-depth

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

Epidemiology and Presentation

• Multidirectional instability (MDI) is characterized by inferior laxity in addition to anterior and/or posterior laxity [23].
• MDI presentations are variable and difficult to quantify [23].
• Symptoms of MDI include pain, weakness, ipsilateral paresthesias, popping or clicking of the shoulder, instability during sleep, difficulty with throwing, and pain when carrying heavy objects [23].
• Differential diagnoses for MDI include unidirectional shoulder instability, cervical disease, brachial plexitis, and thoracic outlet syndrome [23].
• Rotator cuff tendinitis in an individual younger than 20 years should raise concern for MDI [23].
• A previously undescribed group of patients presents with chronic shoulder instability even after surgery to correct the problem, characterized by an axillary index-scar [7].

Pathoanatomy

• Two commonly associated anatomic lesions in MDI are a patulous inferior capsule containing both the anterior and posterior bands of the IGHL and functional deficiency of the rotator interval [23].
• Labral tearing may occur with repeated subluxations or a traumatic event in MDI [23].
• Coracoid morphology differs significantly in patients undergoing posterior shoulder stabilization compared to patients undergoing surgery for anterior instability or a comparison cohort [20].

Evaluation

• Assessment for generalized ligamentous laxity using Beighton criteria is part of the physical examination for MDI [23].
• A positive sulcus sign assesses the competency of the rotator interval in MDI [23].
• Accurate identification of the mechanism of instability is essential for guiding management in dislocated reverse total shoulder arthroplasty [3].

Non-Operative Management

• All patients with MDI should undergo extensive physical therapy for 6 to 9 months prior to consideration of surgical treatment [23].
• Physical therapy for MDI should focus on rotator cuff strengthening, scapular kinematics, and proprioceptive training [23].
• NHL team physicians strongly favor nonoperative management in-season for initial posterior instability events of the shoulder [6].

Operative Management

• Surgery for MDI is appropriate for patients with pain and instability that interferes with normal or sport-related activity who have failed extensive nonsurgical treatment [23].
• Approximately 20% of patients with MDI fail nonsurgical management [23].
• Surgery is contraindicated for voluntary dislocators and patients who have not attempted physical therapy [23].
• Arthroscopic pancapsular plication with or without rotator interval closure is a surgical technique for MDI [23].
• If labral pathology is encountered during MDI surgery, anterior or posterior labral repair is indicated [23].
• Capsulorrhaphy for MDI should address inferior redundancy in a balanced fashion to avoid asymmetric tightening [23].
• Open anterior-inferior capsular shift is a surgical technique for MDI [23].
• The indications for an isolated soft-tissue procedure in anterior shoulder instability are narrower, with the ideal candidate presenting with minimal glenoid bone loss of 13.5% [14].
• Soft-tissue stabilization alone may not be sufficient in patients with substantial bone loss to the posterior glenoid and/or the anterior humeral head [12].
• The Arthroscopic Trillat Procedure resulted in a stable and functional shoulder in 96% (20/21) of patients with recurrent anterior instability associated with massive irreparable cuff, with no patient losing active shoulder motion [1].
• Retroglenoid osteotomy with capsular shift for posterior shoulder instability showed clinical improvements in all patients, with complete resolution of instability symptoms and radiological correction of glenoid retroversion [2].
• Single-portal arthroscopic posterior capsulorrhaphy offers an efficient, reproducible procedure to address posterior shoulder instability pathology [4].
• Open capsular shift with Achilles allograft augmentation demonstrated low rates of recurrent instability and improved clinical outcomes in patients with multidirectional shoulder instability and Ehlers-Danlos Syndrome [9].
• The arthroscopic subscapular sling procedure is proposed as an alternative to existing surgical treatment options for recurrent anterior shoulder instability [15].
• The "Pinch-and-Tuck" arthroscopic technique effectively and safely addresses capsular laxity in patients with posterior shoulder instability [65].
• A complex salvage surgery involving posterior bone block, dynamic anterior stabilization, and modified McLaughlin is presented for patients with multidirectional instability or hyperlaxity with significant posterior erosion and loss of the anterior wall [66].
• The Bristow-Latarjet procedure was associated with significantly higher rates of full return to sport than Bankart repairs in anterior shoulder instability [28].
• The Latarjet procedure leads to similar functional outcomes and failure rates in patients with or without hyperlaxity for recurrent shoulder instability [30].
• Shoulder stabilization using the Latarjet procedure is effective in patients over 50 years old without associated cuff damage, despite a higher complication rate than in the younger population [43].
• Anterior labral reconstruction with biceps autograft for anterior shoulder instability has been performed in a small number of patients, with data inadequate to report on clinical results and recurrent instability risk [10].

Outcomes and Complications

• Recurrence of MDI occurs in 7% of cases for both open and arthroscopic techniques [23].
• Axillary nerve injury is a complication of MDI surgery [23].
• Stiffness is a rare complication of MDI surgery [23].
• Subscapularis insufficiency is a complication after open MDI procedures [23].
• Outcomes for dislocated reverse total shoulder arthroplasty remain variable, and recurrent instability continues to be a major challenge [3].
• At 2 years, 19.1% of patients with 270-360 degree panlabral tears experienced instability and 7.9% underwent reoperation for instability or dislocation [8].
• Patient-reported outcomes decline over time following arthroscopic Bankart repair for anterior shoulder instability [21].
• A high failure rate was found in a high-risk population with traumatic posterior glenohumeral dislocations, with 19 out of 33 shoulders (58%) experiencing structural failure such as recurrent dislocation or revision surgery [31].
• New trauma drives recurrent shoulder instability following primary stabilization surgery in adolescent patients [40].

Anatomy & Pathophysiology

Bony Anatomy

• The glenoid cavity is a shallow socket approximately one-third the size of the humeral head [69].
• The glenoid is a convex structure of shallow depth shaped like an inverted pear [68].
• The subchondral bone of the glenoid is relatively flat, with articular concavity augmented by cartilage and a circumferential labrum [70].
• The glenoid averages 5° of retroversion in relation to the axis of the scapular body [70].
• The humeral head is spherical with a diameter of 37 to 57 mm [68].
• The most superior portion of the articular surface of the humeral head averages 8 mm above the greater tuberosity [68].
• Humeral version averages 29.8 degrees, with a range of 10 to 55 degrees [68].
• The humeral head is inclined approximately 130 degrees with respect to the humeral shaft [68].
• The neck-shaft angle measures an average of 135 degrees [69].
• The humeral head is retroverted an average of 30 degrees [69].
• The humeral head averages 19° of retroversion and 41° of inclination (neck-shaft angle) [70].
• The proximal humerus has three ossification centers: the humeral head (4 to 6 months), the greater tuberosity (1 to 3 years), and the lesser tuberosity (3 to 5 years) [70].
• The proximal humeral ossification centers fuse to the shaft at age 17 to 20 years [70].
• The proximal humeral physis closes by 14 to 17 years of age in girls and by 16 to 18 years in boys [74].
• Humeral retroversion averages 65 degrees in infants and young children, gradually decreasing to approach adult values by 11 years of age [74].
• The articular surface of the humeral head is essentially spherical, with an arc of approximately 160 degrees covered by articular cartilage [77].
• The radius of curvature of the humeral head is approximately 25 mm and is slightly larger in men than in women [77].
• The glenoid articular surface radius of curvature is 2 to 3 mm larger than that of the humeral head [77].
• The average neck-shaft angle is 45 degrees (±5 degrees), with a range of 30 to 50 degrees [77].
• The superior margin of the humeral head articular surface is normally superior to the top of the greater tuberosity by 8 to 10 mm [77].
• The distance from the lateral base of the coracoid process to the lateral margin of the greater tuberosity is called the lateral humeral offset [77].
• A significant decrease in lateral humeral offset reduces the lever arms for the deltoid and supraspinatus muscles, weakening abduction and impairing function [77].
• A significant increase in lateral humeral offset causes excessive tension on the soft tissues ("overstuffing" of the joint), resulting in loss of motion and likely accelerating polyethylene wear [77].
• Humeral articular malposition of more than 4 mm led to increased subacromial contact [77].
• Offset of 8 mm in any direction significantly decreased passive range of motion [77].
• Proximal humeral retroversion is highly variable, ranging from 0 to 55 degrees depending on the method used for measurement [77].
• The glenoid diameter ranges from 18-30 mm (superior anteroposterior), 21-35 mm (inferior anteroposterior), and 30-48 mm (superoinferior height) [77].
• The glenoid inclination averages 4.2 degrees, with a range of –7 to 20 degrees [77].
• The glenoid version averages 1.5 degrees retroversion, with a range of 10.5-9.5 degrees anteversion [77].
• The glenoid surface area is 4-6 mm, while the humeral head surface area is 11-19 mm [77].
• Glenoid cartilage thickness is 2.16 mm, and humeral head cartilage thickness is 1.44 mm [77].
• The glenoid radius of curvature is 22-28 mm, and the humeral head radius of curvature is 23-28 mm [77].
• Medial (coronal) humeral offset ranges from 4-14 mm, and posterior (transverse) offset ranges from –2 to 10 mm [77].
• The coracoid process has undergone an increase in size over evolutionary time [75].
• 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 [75].
• Coracoid morphology differs significantly in patients undergoing posterior shoulder stabilization when compared to patients undergoing surgery for anterior instability or a comparison cohort [20].
• Antero-inferior glenohumeral instability is associated with an abnormal position of the coracoid process [32].
• The overall bony concavity of the glenoid may play an inherent role regarding stability [110].
• Labral morphology does not compensate for reduced bony glenoid concavity in clinically stable shoulders [91].
• The scapula is anteverted on the chest wall approximately 30 degrees relative to the body [79].
• The scapula spans the second through seventh ribs and serves as an attachment for 17 muscles [79].
• The clavicle is the first bone to ossify (fifth week of gestation) and is the only long bone to ossify by intramembranous ossification [70].
• The medial (sternal) epiphysis of the clavicle is the last ossification center to fuse, at age 20 to 25 years [70].
• The primary blood supply to the clavicle is periosteal, with no nutrient artery present [70].
• The acromion has three ossification centers: the metacromion (base), the mesoacromion (middle), and the preacromion (tip) [70].
• Failure of fusion of the acromial ossification centers results in os acromiale [70].
• The relationship between acromial anatomy and rotator cuff disease remains controversial [70].
• The classification of acromial morphology (flat, curved, or hooked) is challenged by poor interobserver reliability [70].
• The relationship between coracoid morphology and subscapularis tears is controversial [70].
• The coracoacromial ligament contributes to anterosuperior stability in rotator cuff deficiency and should be preserved with irreparable cuff tears to prevent anterosuperior escape [79].
• The acromial branch of the thoracoacromial artery runs on the medial aspect of the coracoacromial ligament [79].
• The coracoacromial ligament is the arthroscopic landmark for a complete release of the rotator interval for adhesive capsulitis [79].
• The humeral head receives its blood supply from the anterior and posterior humeral circumflex branches from the third division of the axillary artery [68].
• The anterior humeral circumflex artery (AHCA) arises from the axillary artery at the inferior border of the subscapularis and 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) [68].
• The ascending branch of the AHCA 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 [68].
• Injury to the arcuate artery may result in osteonecrosis of the humeral head [68].
• Additional extraosseous collateral branches can permit humeral head perfusion despite complete ligation of the arcuate artery [68].
• The anterolateral ascending branch of the anterior humeral circumflex artery provides the primary blood supply to the humeral head [70].
• The terminal intraosseous portion of the artery enters at the proximal aspect of the intertubercular groove as the arcuate artery [70].
• Recent quantitative assessment has shown that 64% of the humeral head blood supply arises from the posterior humeral circumflex artery [74].
• The transverse humeral ligament is an important stabilizer of the biceps tendon [79].
• The bicipital groove lies between the greater and lesser tuberosities and serves as a pathway for the long head of the biceps [68].
• The distal aspect of the bicipital groove is internally rotated with respect to the proximal portion [68].
• The anatomic neck of the proximal humerus is located at the junction of the articular surface and the tuberosities [68].
• The surgical neck represents an indistinct region (metadiaphyseal junction) below the tuberosities but above the humeral shaft [68].
• A fracture involving the anatomic neck is 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 [68].
• The greater tuberosity serves as the attachment site for the supraspinatus, infraspinatus, and teres minor tendons of the rotator cuff [68].
• The lesser tuberosity serves as the attachment site for the subscapularis tendon [68].
• The glenoid is a convex structure of shallow depth shaped like an inverted pear that articulates with the humeral head and serves as the attachment for the labrum and joint capsule [68].
• The acromion, the coracoacromial ligament, and the coracoid process form the coracoacromial arch, a rigid bony-ligamentous structure that imparts stability to the shoulder girdle [68].
• The rotator cuff, subacromial bursa, and subdeltoid bursa pass underneath the coracoacromial arch [68].
• Displaced proximal humeral fractures can impede normal movement of structures passing under the coracoacromial arch, causing impingement and disruption of normal glenohumeral motion [68].
• The superior shoulder suspensory complex (SSSC) provides a stable connection between the scapula and the axial skeleton [70].
• The SSSC is composed of the glenoid, the coracoid process, the coracoclavicular ligaments, the distal clavicle, the AC joint, and the acromion [70].
• The superior strut of the SSSC comprises the middle clavicle [70].
• The inferior strut of the SSSC comprises the lateral scapular border/spine of the scapula [70].
• The scapula has only one true diarthrodial articulation, the acromioclavicular (AC) joint [70].
• Normal shoulder motion is approximately two-thirds glenohumeral and one-third scapulothoracic [70].
• Ossification of the scapular body begins at the eighth week of gestation [70].
• The scapular spine is an osseous ridge that separates the supraspinatus and infraspinatus fossae [70].
• The coracobrachialis muscle and the short head of the biceps tendon originate from the coracoid process [70].
• The pectoralis minor muscle inserts onto the medial coracoid process [70].
• The superior transverse scapular ligament arises from the medial base of the coracoid overlying the suprascapular notch [70].
• The suprascapular artery runs superior to the superior transverse scapular ligament, and the nerve runs deep to the ligament [70].
• Entrapment of the suprascapular nerve at the superior transverse scapular ligament causes denervation of both the supraspinatus and the infraspinatus [70].
• The spinoglenoid ligament overlies the suprascapular nerve at the spinoglenoid notch [70].
• Entrapment, traction, or compression of the suprascapular nerve at the spinoglenoid notch causes denervation of the infraspinatus [70].

Soft Tissue Anatomy & Ligaments

• The glenohumeral joint depends on static and dynamic stabilizers for movement and stability [77].
• The rotator cuff stabilizes the glenohumeral joint while allowing greater freedom of motion and fixes the fulcrum of the upper extremity against which the deltoid can contract and elevate the humerus [77].
• The rotator cuff must act simultaneously and synergistically with the deltoid muscle for normal function [77].
• The bony anatomy contributes little to stability and has been compared with a golf ball on a tee [78].
• The glenoid is encircled by the labrum, composed of dense fibrocartilaginous tissue, which increases the depth of the socket by 50% around the humeral head and increases stability [78].
• The glenoid articular surface and the labrum combine to create a socket that is approximately 9 mm deep in the superoinferior direction and 5 mm deep in the anteroposterior direction [78].
• Adding the glenoid labrum increases the glenoid surface to 75% of the humeral head vertically and 57% horizontally [78].
• The labrum affects the distribution of contact stresses when a compressive load is applied to the shoulder at 90 degrees of abduction [78].
• Most stability of the shoulder is provided by the surrounding muscles and ligaments due to very little bony constraint [78].
• The ligamentous constraints are the primary stabilizers at extremes of motion [78].
• The superior glenohumeral ligament is the primary restraint to inferior humeral subluxation in 0 degrees of abduction [78].
• The superior glenohumeral ligament is the primary stabilizer to anterior and posterior stress in 0 degrees of abduction [78].
• Tightening of the rotator interval decreases posterior and inferior translation [78].
• The middle glenohumeral ligament limits external rotation when the arm is in the lower and middle ranges of abduction but has little effect when the arm is in 90 degrees of abduction [78].
• The inferior glenohumeral ligament is composed of an anterior band that is quite thick, a posterior band that is less thick and distinct, and a thinner intervening axillary pouch, creating a hammock-type sling [78].
• With external rotation, the inferior glenohumeral ligament hammock slides anteriorly and superiorly, the anterior band tightens, and the posterior band fans out [78].
• With internal rotation, the inferior glenohumeral ligament hammock slides posteriorly and inferiorly, the posterior band tightens, and the anterior band fans out [78].
• The anteroinferior glenohumeral ligament complex is the main stabilizer to anterior and posterior stresses when the shoulder is abducted 45 degrees or more [78].
• The extrinsic muscles primarily control movement of the scapula and include the rhomboids, levator scapulae, trapezius, and serratus anterior [78].
• The intrinsic muscles control the glenohumeral joint and include the rotator cuff muscles (subscapularis, supraspinatus, infraspinatus, and teres minor), the deltoid, the pectoralis major, the teres major, the latissimus dorsi, and the biceps brachii [78].
• The extrinsic muscles dynamically position the scapula to place the glenoid opposite the humeral head as the shoulder moves [78].
• Ligament stiffness and torsional rigidity are increased with concomitant muscle activity [78].
• Rotator cuff activity and biceps activity have been shown to stiffen the capsule and decrease glenohumeral translation [78].
• Intrinsic and extrinsic muscles serve as fine tuners of motion and power movers by working in "force couples" [78].
• The most important force couple involves the subscapularis and posterior rotator cuff, providing a compressive force that centers the humeral head in the glenoid cavity [78].
• The teres minor has heightened attention to its contribution to rotator cuff function, particularly when the other cuff tendons fail [78].
• The tendinous insertions of the rotator cuff muscles, the articular capsule, the coracohumeral ligament, and the glenohumeral ligament complex blend into a confluent sheet before insertion into the humeral tuberosities [78].
• The tendons of the infraspinatus and supraspinatus muscles join approximately 15 mm proximal to their insertion and cannot be readily separated by blunt dissection [78].
• The infraspinatus and teres minor fuse near their musculotendinous junctions [78].
• The supraspinatus and subscapularis tendons join as a sheath that surrounds the biceps tendon at the entrance of the bicipital groove [78].
• The roof of the biceps sheath consists of a portion of the supraspinatus tendon, and a sheet of the subscapularis tendon forms the floor [78].
• The coracohumeral ligament is a thick band of fibrous tissue extending from the coracoid process along

Classification

• Posterior shoulder instability (PSI) is categorized into first-time (Type A), dynamic (Type B), and static (Type C) [13].
• Type B of the ABC-Classification for posterior shoulder instability is further divided into functional (B1) and structural (B2) dynamic instability [13].
• The B1 subtype of dynamic posterior shoulder instability is characterized by a pattern in which instability is caused by pathological activation of the rotator cuff and periscapular muscles [13].
• Kim’s lesion of the shoulder is characterized by incomplete tearing of the junction between the posteroinferior labrum and the glenoid, with the superficial labral tissue remaining intact [25].
• Kim’s lesion represents an under-reported subtype of posterior labral injury and a source of activity-related posterior shoulder discomfort and instability [25].
• Kim’s lesions are frequently observed in young, active individuals involved in overhead and contact sports [25].
• Kim’s lesions often result from traumatic mechanisms with the shoulder in flexion and adduction, as well as from repetitive microtrauma and overuse [25].
• Patients with Kim’s lesions often present with posterior or posteroinferior instability and discomfort with provocative physical examination maneuvers stressing the posterior labrum [25].
• Patients with Kim’s lesions often present with pain during activities of daily living and/or sports [25].
• Shoulder instability in skeletally immature patients can be caused by an acute traumatic event or by chronic repetitive trauma [17].
• Patients with shoulder instability can be divided into those who are skeletally immature and those who are skeletally mature [17].
• The indications for an isolated soft-tissue procedure in anterior shoulder instability are now narrower, with the ideal candidate presenting with minimal glenoid bone loss (13.5%) [14].
• Current classifications exhibit poor reliability in categorizing glenoid defects post-reverse shoulder arthroplasty removal [117].
• Among patients requiring shoulder arthroplasty after anterior shoulder instability surgery, 55.1% exhibited A1-type OA, 18.4% A2, 16.3% B1, and 10% B2 according to the Walch Classification [119].
• Pathologies reported at the time of conversion to shoulder arthroplasty included avascular necrosis, large engaging Hill-Sachs lesions, rotator cuff tears, and graft dislocation in coracoid transfer cases [119].
• The Gerber and Nyffeler classification of glenohumeral joint instability is cited as a reference for multidirectional instability [121].
• The Gerber and Nyffeler classification of glenohumeral joint instability is cited as a reference for posterior shoulder instability [62].

Clinical Presentation

History and Mechanism

• The evaluation of a patient suspected of having a bony Bankart lesion begins with a comprehensive history including a description of the mechanism of injury, direction of force applied to the shoulder, direction of perceived instability, history of previous dislocations, whether manual reduction has ever been required, and any history of surgery for shoulder instability [11].
• The history should define the mechanism of the injury, including the position of the arm, the amount of force applied, and the point of force application [96].
• Injury with the arm in extension, abduction, and external rotation favors anterior dislocation [96].
• Electoshock, seizures, or a fall on the flexed and adducted arm are commonly associated with posterior dislocation [96].
• If the instability is recurrent, the history defines the initial injury, the position or action that results in instability, how long the shoulder stays out, whether radiographs are available with the shoulder out of joint, and what means have been necessary to reduce the shoulder [96].
• The history also solicits evidence of neurologic or rotator cuff problems after previous episodes of shoulder instability [96].
• Previous treatment of the recurrent instability, as well as the effectiveness of this treatment, should be documented [96].
• A thorough history and physical examination should allow the examiner to understand the etiology, direction, degree, and frequency of a patient’s shoulder instability [106].
• Risk factors associated with treatment failure include age, gender, presence of osseous Bankart, and/or large Hill-Sachs lesions, participation in competitive collision or forced overhead sports, hypermobility, time lapse between dislocation and reduction, and the number of instability episodes prior to operation [106].
• In throwers, a detailed history with the chronology of symptoms is essential [104].
• Pitchers commonly complain of loss of pitch control and loss of velocity and also describe symptoms distant from the shoulder joint [104].
• Instability often exists in overhead athletes, but they do not present with symptoms of frank subluxation or dislocation [104].
• The throwing phase in which the pain occurs gives direct clues to the underlying pathoanatomy [104].
• Pain during cocking is often a result of instability or internal impingement with a type II SLAP lesion [104].
• Pain during follow-through arises from rotator cuff or posterior capsular problems [104].
• Swimmers will often complain of pain during the catch or the recovery, when the shoulder is more often in the provocative impingement position [104].
• In swimmers, instability is often the principal culprit, exacerbating symptoms of impingement [104].
• For athletes with gross instability, determining the onset of the symptoms is critical to distinguish between traumatic and atraumatic instability [104].
• Symptoms elicited with the arm in adduction and internal rotation may suggest posterior instability [104].
• Symptoms reproduced by holding objects with the arms at the sides often indicate inferior instability [104].
• The location of pain or instability, its duration, and response to prior treatment should be noted for all athletes [104].
• Kim’s lesions are frequently observed in young, active individuals involved in overhead and contact sports, often resulting from traumatic mechanisms with the shoulder in flexion and adduction, as well as from repetitive microtrauma and overuse [25].
• Patients with Kim’s lesions often present with posterior or posteroinferior instability and discomfort with provocative physical examination maneuvers stressing the posterior labrum, accompanied by pain during activities of daily living and/or sports [25].
• Repetitive microtrauma is the most prevalent inciting cause of posterior shoulder instability in athletes [24].
• Athletes who experience instability because of repetitive overhead motion or microtrauma to the posterior capsule are more likely to encounter recurrent posterior shoulder subluxation, where the humeral head does not fully dislocate [24].
• Repeated stress on the glenohumeral joint can tear or stretch the posterior capsule, eventually resulting in persistent posterior shoulder instability [24].
• Athletes with pre-existing shoulder instability face a higher risk of subluxation or dislocation as they rely more heavily on their static stabilizers while still demanding a wide range of motion from the shoulder [24].
• Multidirectional instability symptoms include pain, weakness, ipsilateral paresthesias, popping or clicking of the shoulder, instability of the shoulder during sleep, difficulty with throwing, and pain when carrying heavy objects [23].
• Differential diagnoses for multidirectional instability include unidirectional shoulder instability, cervical disease, brachial plexitis, and thoracic outlet syndrome [23].
• Clinicians should maintain a high index of suspicion in young patients presenting with traumatic shoulder pain, even in the absence of perceived instability [39].
• A previously undescribed group of patients presents with chronic shoulder instability, even after surgery to correct this problem, and who accordingly present with an axillary index-scar [7].
• Frozen shoulder is a common epidemiological affliction that does not resolve spontaneously in a large number of patients [5].

Physical Examination: Inspection and General

• An acutely dislocated shoulder is usually very painful, and muscles are in spasm in an attempt to stabilize the joint [96].
• The humeral head may be palpable anteriorly in an anteriorly dislocated shoulder [96].
• The posterior and lateral aspect of the shoulder shows a hollow beneath the acromion in an anteriorly dislocated shoulder [96].
• The arm is held in slight abduction in an anteriorly dislocated shoulder [96].
• Passive and active motions are limited by pain in an anteriorly dislocated shoulder [96].
• Recognition of a posterior dislocation may be impaired by the lack of a striking deformity of the shoulder and by the fact that the shoulder is held in the traditional sling position of adduction and internal rotation [96].
• Limited external rotation of the shoulder, often to <0 degrees, is a classic feature of posterior dislocation [96].
• Limited elevation of the arm, often to <90 degrees, is a classic feature of posterior dislocation [96].
• Posterior prominence and rounding of the shoulder in comparison to the normal side is a classic feature of posterior dislocation [96].
• Flattening of the anterior aspect of the shoulder is a classic feature of posterior dislocation [96].
• Prominence of the coracoid process on the dislocated side is a classic feature of posterior dislocation [96].
• Asymmetry of the shoulder contours can often best be visualized by viewing the shoulders from above while standing behind the patient [96].
• With long-standing disuse of the muscles about the shoulder, atrophy will be present, which accentuates the flattening of the anterior portion of the shoulder, the prominence of the coracoid, and the fullness of the posterior portion of the shoulder [96].
• In the interval before the diagnosis of posterior dislocation of the shoulder is made, the injury may be misdiagnosed as a frozen shoulder for which vigorous therapy may be mistakenly instituted in an attempt to restore range of motion [96].
• The patient’s general posture, any bone/soft-tissue deformity, incisions/scars, regions of swelling or erythema, muscle atrophy, and any asymmetry are noted during general inspection [107].
• The scapulae are examined bilaterally for resting attitude and winging/dyskinesia with movement of the shoulder through its range of motion [107].

Physical Examination: Specific Tests and Signs

• Assessment of the neurovascular status of the upper extremity and charting of the findings before reduction is an essential part of the physical examination of an anteriorly dislocated shoulder [96].
• A positive sulcus sign assesses the competency of the rotator interval in multidirectional instability [23].
• Rotator cuff tendinitis in an individual <20 years should raise concern for multidirectional instability [23].
• Constitutional ligamentous laxity is assessed using the Marshall test or Beighton score [106].
• The anterior apprehension test and position of arm, including evaluation for mid-range instability, are part of the physical examination for shoulder instability [106].
• The relocation test is part of the physical examination for shoulder instability [106].
• The load and shift test (anterior and posterior) is part of the physical examination for shoulder instability [106].
• The jerk test is part of the physical examination for shoulder instability [106].
• O’Brien’s active compression test is part of the physical examination for shoulder instability [106].
• Hawkin’s and Neer’s impingement tests are part of the physical examination for shoulder instability [106].
• Cross-body adduction is part of the physical examination for shoulder instability [106].
• The axial load test or load-and-shift test is conducted during examination under anesthesia to note translation in the anterior, inferior, and posterior directions [106].
• Grading of instability during examination under anesthesia reflects the degree of humeral head translation anterior and posterior to the glenoid rim [106].
• Grade 1+ corresponds to the translation of the humeral head to the edge of the glenoid [106].
• Grade 2+ corresponds to the humeral head being subluxated over the glenoid rim but reducing spontaneously [106].
• Grade 3+ corresponds to a frank dislocation of the humeral head over the glenoid rim that does not reduce spontaneously [106].
• The subscapularis muscle can be tested with the belly-press, lift-off, and bear-hug tests [107].
• The belly-press maneuver is performed with the patient’s hand pressing on the upper abdomen, with the elbow anterior to the wrist in the coronal plane [107].
• The lift-off test is performed with the shoulder rotated internally and the dorsum of the patient’s hand resting against the patient’s ipsilateral sacroiliac joint [107].
• The bear-hug test requires the patient to place the palm of the hand on the opposite shoulder, with the elbow anterior to the body [107].
• The supraspinatus muscle is evaluated with the empty can and champagne toast tests [107].
• The infraspinatus muscle is tested with the shoulder abducted 20° in the scapular plane and the elbow at 90° of flexion [107].
• The teres minor muscle is isolated with the elbow flexed to 90° and the arm in 90° of external rotation and 90° of abduction [107].
• A positive external rotation “lag” or “dropping” sign indicates insufficiency of the infraspinatus muscle [107].
• A positive “hornblower” sign indicates teres minor insufficiency [107].
• Clinical examination should assess range of motion in multiple planes, documenting forward elevation, external and internal rotation, and abduction for dynamic posterior shoulder instability [58].
• Particular attention should be given to posterior subluxation or dislocation occurring during forward elevation, as this clinical sign is highly relevant for surgical indication in dynamic posterior shoulder instability [58].
• A thorough clinical exam is the most important factor when determining indication for shoulder instability surgery [37].
• The evaluation of the overhead athlete requires the close integration of history and physical examination findings while utilizing a systematic approach [104].
• Many of the traditional examination tests of the shoulder have not been validated or critically evaluated to a significant extent and should therefore be used only as an adjunct to a wider global assessment [104].
• The precise pathophysiology of many shoulder conditions remains unknown, leaving the interpretation of some examination maneuvers uncertain [104].
• A sport-specific approach should be used when evaluating the shoulder in an athlete [104].
• A preseason examination is critical to document baseline shoulder stability, strength, and ROM, which can be used as a reference when evaluating a mid-season injury [104].
• The joint may catch, pinch, or lock in the quadrant position of abduction and external rotation where capsular length must be sufficient to allow glide of the humerus [18].
• In subtle cases of anterior-inferior capsular length insufficiency, symptoms may only occur when the patient is performing tasks requiring maximal effort [18].
• The combined movement of abduction and external rotation with an excessively tight anterior band of the inferior glenohumeral ligament complex will cause excessive glide of the humeral head on the glenoid in the posterior and superior direction [18].
• This compression will begin near 150° of flexion and will occur earlier if elevation of the humerus is performed in greater amounts of horizontal abduction as greater capsular length is required [18].
• Rotator cuff dysfunction with inadequate humeral head depression will cause excessive superior translation [18].
• Motion asymmetry due to rotator cuff insufficiency usually presents early in the elevation attempt due to the nearly vertical force the deltoid exerts to overcome gravity [18].
• The Western Ontario Shoulder Instability Index (WOSI) includes items assessing pain, aching or throbbing, weakness, fatigue, clicking/cracking/snapping, stiffness, neck discomfort, instability/looseness, compensation, and loss of range of motion [55].
• The Western Ontario Rotator Cuff Index (WORC) includes items assessing sharp pain, constant nagging pain, weakness, stiffness, clicking/grinding/crunching, and neck discomfort [100].
• Functional assessment for dynamic posterior shoulder instability typically includes standardized outcome measures such as the American Shoulder and Elbow Surgeons score, the Western Ontario Shoulder Instability index, and the visual analog scale for pain [58].

Investigations

Clinical Evaluation and History

• The evaluation of a patient suspected of having a bony Bankart lesion begins with a comprehensive history including the mechanism of injury, direction of force applied, direction of perceived instability, history of previous dislocations, whether manual reduction has ever been required, and any history of surgery for shoulder instability [11].
• The diagnosis of a stiff shoulder depends on awareness of the problem, with history and physical examination being paramount [46].
• Clinical examination for dynamic posterior shoulder instability should assess range of motion in multiple planes, with particular attention to posterior subluxation or dislocation occurring during forward elevation [58].
• The authors define a group of patients who present with chronic shoulder instability, even after surgery to correct this problem, and who present with an axillary index-scar [7].
• Historically, the absence of structural pathology on diagnostic imaging in dynamic-functional posterior instability frequently led to the dismissal of this subtype as attention-seeking or psychiatric behavior [13].
• Surgical stabilization is generally not recommended for dynamic-functional instability, as it is associated with poor outcomes [13].

Plain Radiography

• The purpose of imaging of the shoulder 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 [47].
• Standardized plain films are almost always sufficient to garner the information needed for shoulder evaluation [47].
• The first key radiographic view is the anteroposterior (AP) in the plane of the scapula, which shows the superoinferior position of the humeral head relative to the glenoid, presence of osteophytes, narrowing of the joint space, degree of medial displacement of the humerus, quality of bone, presence of loose bodies, and whether there is humeral head collapse or deformity [47].
• 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, which shows the amount of glenoid bone, 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 [47].
• The standardized axillary view is referred to as the “truth view” because it demonstrates the glenohumeral relationships in the functional position of elevation [47].
• The axillary truth view can show posterior subluxation or “functional decentering” that is not evident in images taken with the arm at the side [47].
• 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, the position of the center of the humeral head in relation to the glenoid face, or the point of contact of the humeral articular surface on the glenoid articular surface [47].
• 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 [87].
• The axillary view is a necessary view in evaluation of glenohumeral joint instability and enables determination of the humeral head position in the glenoid fossa [87].
• The axillary view may detect occult, locked posterior shoulder dislocation in a patient who exhibits a lack of passive external rotation [87].
• 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 [87].
• The scapular Y view is a reliable alternative for evaluation of glenohumeral subluxation and dislocation [87].
• The West Point view is indicated for evaluating anterior glenoid bone loss [87].
• The Stryker notch view is indicated to evaluate Hill-Sachs lesion after dislocation [87].
• The apical oblique view is indicated to evaluate for glenoid rim fracture in instability [87].
• The acromiohumeral distance is normally 7 to 14 mm [87].
• The width of the glenohumeral joint space should be symmetric superiorly and inferiorly [87].
• The coracoclavicular distance is normally 1.1 to 1.3 cm [87].
• Neer classified acromial morphology as type I (flat), type II (curved), and type III (hooked) [87].
• 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 [87].
• Initially, all patients are usually asked to have AP and lateral plain radiographs of the shoulder related to their chief report [86].
• These images are often the only required studies needed for assessing acute shoulder trauma, including fractures or dislocations [86].
• Arthritis, calcific tendinitis, and osteolysis of the distal clavicle can be observed on plain radiograph [86].
• Healing or failure of a bony Bankart repair may be evaluated on plain radiographs primarily with axillary views, which should demonstrate union by 12 weeks [135].
• Postoperative radiographic evaluation at 7-month follow-up for anterior capsular reconstruction with dermal allograft augmentation demonstrated a concentrically reduced glenohumeral joint [27].

Computed Tomography (CT)

• CT imaging is frequently used to evaluate fractures of the shoulder, to assess for bony lesions in recurrent instability cases, or for preoperative templating for shoulder arthritis [86].
• 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 [87].
• CT provides accurate quantification of glenoid version using standardized methods, including Friedman and Hoenecke techniques [58].
• Although CT scans may offer a few degrees of increased precision in the measurement of glenoid version, this precision does not necessarily improve the quality of the surgery or the clinical outcome [47].
• CT scans have the disadvantage of being taken with the arm in the adducted position [47].
• In the future, CT is expected to be superseded by MRI in anterior shoulder instability [125].

Magnetic Resonance Imaging (MRI) and Arthrography

• MRI is the modality of choice for evaluating the rotator cuff, biceps, and subacromial/subdeltoid bursa [86].
• T1-weighted MRI can reveal Hill-Sachs lesions and is often used with magnetic resonance arthrograms to provide a more detailed picture of the joint surfaces [86].
• T2-weighted MRI provides better visualization of full thickness rotator cuff tears [86].
• MR arthrography is considered the benchmark for evaluation for labral tears and rarely is indicated for evaluation of rotator cuff pathology [86].
• When MRI or MR arthrography is contraindicated, CT arthrography is indicated [86].
• Magnetic resonance imaging and magnetic resonance arthrography are recommended to rule out associated pathology such as labral injuries or rotator cuff tears in dynamic posterior shoulder instability [58].
• Posterior subluxation of the humeral head can be quantified with the glenohumeral and scapulohumeral indices on MRI [58].
• Complementary radiographic parameters, such as posterior acromial coverage, sagittal tilt, and the cross-sectional area (CSA), should be assessed to determine morphological contributors to instability [58].
• The study investigated and compared morphological factors on magnetic resonance imaging between pain-predominant (UPS) and apprehension-dominant (ASI) instability presentations [59].
• The study investigated whether unstable painful shoulder (UPS) and anterior instability (AI) are associated with differences in scapula morphology using magnetic resonance imaging [134].
• Automated 3D analysis of glenoid bone loss using deep learning may improve prognostic analysis of anterior shoulder instability and will facilitate measurement on MRI, which rarely includes the contralateral shoulder [36].
• Including the whole scapula on MRI, especially in advanced levels of tear retraction, may allow a more representative assessment [123].
• In a selected cohort with post-operative imaging, no consistent MRI evidence of subscapularis atrophy or fatty infiltration was identified following either open or arthroscopic stabilization [138].
• The authors recommend strong consideration of performing arthroscopy prior to open Latarjet if a preoperative MRI is not obtained or if a preoperative MRI identifies additional intra-articular pathology [137].

Ultrasonography

• Ultrasonography is a low-cost alternative to MRI and arthrography for evaluating both skeletal and soft-tissue structures of the shoulder [86].
• Ultrasonography can provide immediate, real-time visualization of the rotator cuff, biceps tendon, and calcific deposits [86].
• Ultrasonography can be used to measure the subacromial space and detect atrophy of rotator cuff muscles [86].
• As a result of providing images in real-time, ultrasonography can evaluate impingement in various positions and motions [86].
• 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 [86].

Diagnostic Considerations and Limitations

• Clinicians should interpret findings with caution when using systematic reviews to guide management of anterior shoulder instability [19].
• Soft-tissue stabilization alone may not be sufficient in patients who present with substantial bone loss to the posterior glenoid and/or the anterior humeral head [12].
• Two cases document an unusual injury pattern in which a posterior glenohumeral dislocation occurred in association with a (posterior) acromion fracture [29].

Treatment

Non-Operative Management

• All patients with multidirectional instability should undergo extensive physical therapy for 6 to 9 months prior to consideration of surgical treatment [23].
• Physical therapy for multidirectional instability should focus on rotator cuff strengthening, scapular kinematics, and proprioceptive training [23].
• Nonsurgical treatment should always be attempted first for posterior glenohumeral instability [105].
• After a single traumatic injury causing posterior instability, the arm should be immobilized in neutral rotation with the elbow in adduction for 1 to 2 weeks, followed by therapy [105].
• Conservative treatment is preferred in most cases of Type II SLAP lesions, with surgical treatment undertaken when conservative treatment does not meet expectations [33].
• For patients with Kim’s lesion who have persistent discomfort and/or instability despite nonoperative management, arthroscopic fixation is generally recommended [25].
• Frozen shoulder does not resolve spontaneously in a large number of patients [5].

Surgical Indications and Contraindications

• Surgery is appropriate for patients with multidirectional instability who have pain and instability interfering with normal or sport-related activity and have failed extensive nonsurgical treatment [23].
• Approximately 20% of patients with multidirectional instability fail nonsurgical management [23].
• Surgery is contraindicated for voluntary dislocators and patients who have not attempted physical therapy for multidirectional instability [23].
• Surgical intervention is indicated for patients with posterior instability who have symptoms interfering with activities or athletics and have failed nonsurgical management [105].
• Surgery is contraindicated for voluntary dislocators with posterior instability [105].
• If chronic instability develops, surgery could be considered [16].
• Surgery is considered for the patient who fails conservative treatment with persistent or worsening symptoms of at least 6 months’ duration [101].
• Recurrence rates increase with posterior glenoid bone loss >20%, which should be considered a contraindication to arthroscopic soft-tissue stabilization alone [105].

Anterior Instability Procedures

• The Arthroscopic Trillat Procedure resulted in 96% (20/21) of patients having a stable and functional shoulder with no loss of active shoulder motion [1].
• The Latarjet procedure leads to similar functional outcomes and failure rates in patients with or without hyperlaxity for recurrent instability [30].
• The subscapular sling procedure is proposed as an alternative to existing surgical treatment options for recurrent anterior shoulder instability [15].
• The flipped Latarjet procedure aims to anteriorly stabilize the shoulder by transferring the coracoid to the deficient glenoid without splitting the subscapularis muscle while keeping the benefits of a sling effect of the conjoined tendon [136].
• The subscapularis and capsule augmentation is a safe and relatively easy technique for the treatment of shoulder instability [118].
• The arthroscopic congruent-arc distal tibial allograft bone augmentation technique aims to address anterior shoulder instability with bone loss by creating a bony 'ramp' that prevents anterior translation [26].
• Anterior labral reconstruction with biceps autograft has been performed in a small number of patients, and data are inadequate to report on clinical results and recurrent instability risk [10].
• At 2 years, 19.1% of patients experienced instability and 7.9% underwent reoperation for instability or dislocation following arthroscopic treatment of 270-360 degree panlabral tears [8].
• Patients should be counseled pre-operatively on the expected outcomes over time following arthroscopic Bankart repair of anterior shoulder instability [21].

Posterior Instability Procedures

• Retroglenoid osteotomy with capsular shift showed clinical improvements in all patients, with complete resolution of instability symptoms and radiological correction of glenoid retroversion [2].
• The modified Kouvalchouk procedure provides good results in the stabilization of recurrent posterior unstable shoulders in traumatic cases and patients without previous surgery [64].
• Portal closure after segmental posterior labral repair aims to potentially decrease the likelihood of recurrent instability or failure by addressing a potential cause of residual posterior laxity [67].
• The arthroscopic posterior bone block procedure with two cortical buttons fixation and specific glenoid guide is a technique for posterior shoulder instability [62].
• A thorough clinical exam is the most important factor when determining indication for shoulder instability surgery, with no difference in outcomes for posterior shoulder instability surgery in patients with a normal vs. pathological radiologist reported magnetic resonance arthrogram study [37].
• Recurrence is the most common complication of posterior instability surgery, reported to be 8.5% in the general population [105].
• Recurrence rates for posterior instability are highest in overhead athletes [105].
• Overtightening of the posterior capsule can lead to anterior subluxation or coracoid impingement [105].
• Shoulder stiffness or adhesive capsulitis is a concern with rotator interval plication for posterior instability [105].
• In arthroscopic labral repair for posterior instability, a high lateral portal provides better access than a standard posterior portal [105].
• Postoperatively for posterior instability, the shoulder should be placed in a rigid immobilizer with the arm abducted to 30° in neutral rotation [105].
• Strengthening for posterior instability should begin at 12 weeks postoperatively [105].
• Patients may return to heavy labor or contact sports 6 months after posterior instability surgery [105].
• The pooled published rate of return to any sport after posterior instability surgery is 91% [105].
• The pooled published rate of return to preinjury level of sport after posterior instability surgery is 67% [105].

Multidirectional Instability Procedures

• Open capsular shift with Achilles allograft augmentation demonstrated low rates of recurrent instability and improved clinical outcomes in patients with multidirectional instability, including those with Ehlers-Danlos Syndrome [9].
• Arthroscopic pancapsular plication ± rotator interval closure is a surgical technique for multidirectional instability [23].
• If labral pathology is encountered during multidirectional instability surgery, anterior or posterior labral repair is indicated [23].
• To avoid asymmetric tightening in multidirectional instability surgery, capsulorrhaphy should address the inferior redundancy in a balanced fashion [23].
• Open anterior-inferior capsular shift is a surgical technique for multidirectional instability [23].
• Recurrence of multidirectional instability is 7% for both open and arthroscopic techniques [23].
• Axillary nerve injury is a complication of multidirectional instability surgery [23].
• Stiffness is a rare complication of multidirectional instability surgery [23].
• Subscapularis insufficiency is a complication after open multidirectional instability procedures [23].
• The zip-tie technique for multidirectional instability allows for greater control over tensioning while preserving joint access throughout the repair [54].
• The zip-tie technique addresses shortcomings of traditional suture-based methods where premature capsular tightening can create unnecessary tension and reduce surgical flexibility [54].
• Anterior capsulolabral allograft reconstruction is a reproducible way to improve shoulder stability and obtain good postoperative outcome measures for patients with recurrent multidirectional instability [57].

Special Populations and Specific Pathologies

• Anchorless labral repair is a technique described for recurrent shoulder instability in the skeletally immature to avoid potential damage to the glenoid physis [17].
• In younger skeletally immature patients, recurrence rates for shoulder instability can be in excess of 70% [17].
• The value of new trauma driving recurrent instability in adolescents is on the lower end of the currently reported range [40].
• Accurate identification of the mechanism of instability is essential for guiding management of dislocated reverse total shoulder arthroplasty, but outcomes remain variable and recurrent instability continues to be a major challenge [3].
• Removal of the torn or degenerated intra-articular disk along with a capsulorrhaphy can improve pain and eliminate mechanical symptoms of popping and grating in chronic dislocation [101].
• Complications when attempting to stabilize an anterior injury include recurrent instability, loss of motion, and pain [101].
• The acromioclavicular harness has been used with good results in treating twenty cases of acromioclavicular dislocation, maintaining reduction and bringing about permanent healing [22].
• The triple anatomical technique for acromioclavicular joint reconstruction enables early recovery and return to sports by biologically restoring joint anatomy and kinematics [50].
• Type II SLAP lesions are frequently observed in throwers who may complain of intermittent clicking or mechanical symptoms in the shoulder, particularly during the cocking phase [33].
• Recurrence rates following arthroscopic surgery for Type II SLAP lesions are reported to be around 10% to 30% [33].
• Recurrence rates after arthroscopic repair for Type II SLAP lesions have recently decreased to 5.3% [33].
• Arthroscopic treatment is more effective in relieving pain than open surgery for Type II SLAP lesions [33].
• The incidence of scapulohumeral periarthritis is lower after arthroscopic surgery than open surgery for Type II SLAP lesions [33].
• Kim’s lesion is characterized by incomplete tearing of the junction between the posteroinferior labrum and the glenoid, with the superficial labral tissue remaining intact [25].
• Patients with Kim’s lesion often present with posterior or posteroinferior instability and discomfort with provocative physical examination maneuvers stressing the posterior labrum [25].
• Bony Bankart lesion evaluation begins with a comprehensive history including mechanism of injury, direction of force, direction of perceived instability, history of previous dislocations, manual reduction history, and history of surgery for shoulder instability [11].
• The evaluation of a patient suspected of having a bony Bankart lesion includes a description of the mechanism of injury [11].
• The evaluation of a patient suspected of having a bony Bankart lesion includes the direction of force applied to the shoulder [11].
• The evaluation of a patient suspected of having a bony Bankart lesion includes the direction of perceived instability [11].
• The evaluation of a patient suspected of having a bony Bankart lesion includes history of previous dislocations [11].
• The evaluation of a patient suspected of having a bony Bankart lesion includes whether manual reduction has ever been required [11].
• The evaluation of a patient suspected of having a bony Bankart lesion includes any history of surgery for shoulder instability [11].
• Clinicians should interpret findings from systematic reviews comparing Bankart repair with remplissage versus the Latarjet procedure with caution when using them to guide management of anterior shoulder instability [19].
• Recent randomized trials and systematic reviews have not shown the superiority of modern arthroscopic techniques compared with open repairs for shoulder instability [108].
• Open repair resulted in a significantly lower risk of recurrence than arthroscopic repair in terms of patient quality of life [108].
• Secondary outcome data suggest that open surgical repair may be recommended to reduce the risk of recurrent instability in younger male patients with a Hill-Sachs lesion [108].
• Arthroscopic and open repair techniques for the treatment of recurrent traumatic shoulder instability yield comparable results if the procedure is selected on the basis of the pathologic findings at the time of surgery [108].
• Available evidence indicates that arthroscopic approaches are not as effective as open approaches in preventing recurrent instability or enabling patients to return to work [108].
• Misplaced suture anchors can give rise to secondary degenerative joint disease or "anchor arthropathy" [108].
• Use of intra-articular infusion of local antibiotics via a pain pump after arthroscopic instability repairs results in a risk of glenohumeral chondrolysis [108].
• The healing time for a labral reattachment is likely to be the same as the time to heal a subscapularis tenotomy, so the time to return to activity should not be different with arthroscopic versus open approaches [108].
• The routine use of bone transfers for glenohumeral instability in the absence of major glenoid bone loss is not advisable because of the increased risk of arthritis, screw-related problems, damage to the subscapularis, and difficulty in revision [108].
• For AMBRI type instability, the surgeon can use the redundant capsule to augment the labrum, creating a deeper stabilizing concavity, rather than risking overtightening with capsular plication [108].
• Rotator interval closure may be another useful adjunct in managing shoulders with the AMBRI type of instability [108].
• Historically, the absence of structural pathology on diagnostic imaging coupled with limited success of conventional treatments led to the dismissal of dynamic-functional posterior instability as attention-seeking or psychiatric behavior [13].
• This misconception delayed appropriate care and increased the disease burden and social stigmatization for affected patients [13].
• The current gold standard for dynamic-functional instability focuses on normalizing pathological muscle activation pattern through specific interventions [13].
• The pectoralis major stabilizes the glenohumeral joint by resisting superior migration of the humeral head and enhancing scapulothoracic stabilization of the latissimus dorsi and deltoid muscles [13].
• Dysfunction of the pectoralis major may compromise glenohumeral stability [13].
• Existing literature primarily associates pectoralis major abnormalities with anterior or multidirectional shoulder instability [13].
• Posterior shoulder instability in athletes is often caused by repetitive microtrauma, which is the most prevalent inciting cause [24].
• Athletes with pre-existing shoulder instability face a higher risk of subluxation or dislocation as they rely more heavily on their static stabilizers while demanding a wide range of motion [24].
• A stark dislocation of the shoulder causes damage to the posterior capsule and can lead to repeated instability events [24].
• Patients with bony abnormalities such as glenoid dysplasia may suffer from posterior shoulder instability even without a history of trauma [24].
• Multidirectional instability is characterized by inferior laxity in addition to anterior and/or posterior laxity [23].
• Two commonly associated anatomic lesions in multidirectional instability are a patulous inferior capsule containing both the anterior and posterior bands of the IGHL and functional deficiency of the rotator interval [23].
• Labral tearing may occur with repeated subluxations or a traumatic event in multidirectional instability [23].
• Symptoms of multidirectional instability include pain, weakness, ipsilateral paresthesias, popping or clicking of the shoulder, instability during sleep, difficulty with throwing, and pain when carrying heavy objects [23].
• Assessment for generalized ligamentous laxity using Beighton criteria is part of the physical examination for multidirectional instability [23].
• Rotator cuff tendinitis in an individual younger than 20 years should raise concern for multidirectional instability [23].
• Posterior glenohumeral instability accounts for 2% to 5% of all glenohumeral instability [105].
• Up to 50% of traumatic posterior shoulder dislocations are undiagnosed upon presentation to hospital emergency departments [105].
• Traumatic posterior glenohumeral dislocation or recurrent instability can cause posterior labral tearing or disruption of the posterior IGHL [105].
• A compression fracture of the anterosuperior portion of the humeral head (a reverse Hill-Sachs) may be present in posterior instability [105].
• Posterior glenoid bone loss may be present in cases of recurrent posterior instability [105].
• An acute posterior dislocation presents with a prominent posterior shoulder and anterior coracoid and a limited ability to externally rotate the shoulder [105].
• Posterior instability can lead to compensatory scapular winging [105].
• Specialized tests to assess posterior stability include the posterior stress test

Complications

Recurrent Instability and Failure Rates

• In a cohort of 270-360 degree panlabral tears treated arthroscopically, 19.1% of patients experienced instability at 2 years [8].
• In the same cohort of 270-360 degree panlabral tears, 7.9% of patients underwent reoperation for instability or dislocation at 2 years [8].
• In a high-risk population with traumatic posterior glenohumeral dislocations, 58% (19/33) of shoulders experienced structural failure such as recurrent dislocation or revision surgery [31].
• Following all-arthroscopic posterior bone block procedure for recurrent posterior shoulder instability, recurrence occurred in 5 cases (18%), all presenting as recurrent subluxations with no dislocations [42].
• In patients with multidirectional shoulder instability treated with open capsular shift and Achilles allograft augmentation, low rates of recurrent instability were demonstrated [9].
• The Latarjet procedure for recurrent anterior shoulder instability in patients over 50 years old is effective despite a higher complication rate than in the younger population [43].
• In recurrent shoulder instability, the Latarjet procedure leads to similar functional outcomes and failure rates in patients with or without hyperlaxity [30].
• For dislocated reverse total shoulder arthroplasty, recurrent instability continues to be a major challenge with variable outcomes [3].
• Patient-reported outcomes following arthroscopic Bankart repair for anterior shoulder instability decline over time [21].
• Contemporary studies show comparable instability and functional outcomes between arthroscopic and open Bankart repair, whereas historical differences were driven primarily by earlier studies [45].
• In a study of 21 patients with recurrent anterior instability associated with massive irreparable cuff treated with the Arthroscopic Trillat Procedure, 96% (20/21) had a stable and functional shoulder [1].
• No patient in the Arthroscopic Trillat Procedure cohort lost active shoulder motion [1].
• Retroglenoid osteotomy with capsular shift for posterior shoulder instability resulted in complete resolution of instability symptoms in all patients [2].
• A local vascularized scapula bone graft for posterior glenohumeral instability resulted in a posteriorly stable glenohumeral joint at two-year follow-up [60].
• Anterior capsular reconstruction with dermal allograft augmentation for multidirectional shoulder instability demonstrated a concentrically reduced glenohumeral joint at 7-month follow-up [27].

Specific Complications and Adverse Events

• In a study of 46 anterior shoulder reconstructions, 31 remained unstable due to uncorrected defects, failure to recognize posterior dislocation, or further violence [129].
• Pain following anterior shoulder reconstruction can result from late arthritis caused by over-shortening of the capsule in front [129].
• Frozen shoulder is a common condition that does not resolve spontaneously in a large number of patients [5].
• Two cases documented an unusual injury pattern where a posterior glenohumeral dislocation occurred in association with a posterior acromion fracture [29].
• In patients with epilepsy, 60% of identified shoulder dislocations were anterior, 30% were posterior, and 10% were bidirectional [44].
• In patients with epilepsy, 51% of identified shoulder dislocations were first-time and 49% were recurrent [44].

Risk Factors and Predispositions

• Adolescent athletes with a history of anterior shoulder instability have a high incidence of bipolar bone loss [41].
• The indications for an isolated soft-tissue procedure in anterior shoulder instability are narrower, with the ideal candidate presenting with minimal glenoid bone loss (13.5%) [14].
• Athletes with pre-existing shoulder instability face a higher risk of subluxation or dislocation as they rely more heavily on static stabilizers while demanding a wide range of motion [24].
• Repeated stress on the glenohumeral joint can tear or stretch the posterior capsule, resulting in persistent posterior shoulder instability [24].
• Dynamic-functional posterior instability is associated with poor outcomes from surgical stabilization [13].
• Historically, the absence of structural pathology in dynamic-functional posterior instability led to its dismissal as attention-seeking or psychiatric behavior, delaying appropriate care [13].

Recovery

Operative Outcomes and Recurrence

• 96% (20/21) of patients treated with the arthroscopic Trillat procedure for recurrent anterior instability associated with massive irreparable cuff had a stable and functional shoulder and were satisfied with the procedure [1].
• No patient lost active shoulder motion following the arthroscopic Trillat procedure for recurrent anterior instability associated with massive irreparable cuff [1].
• Retroglenoid osteotomy with capsular shift for posterior shoulder instability resulted in clinical improvements in all patients, with complete resolution of instability symptoms and radiological correction of glenoid retroversion [2].
• Outcomes for the management of dislocated reverse total shoulder arthroplasty remain variable, and recurrent instability continues to be a major challenge [3].
• At 2 years, 19.1% of patients treated with arthroscopic treatment for 270-360 degree panlabral tears experienced instability [8].
• At 2 years, 7.9% of patients treated with arthroscopic treatment for 270-360 degree panlabral tears underwent reoperation for instability or dislocation [8].
• Open capsular shift with Achilles allograft augmentation for multidirectional shoulder instability demonstrated low rates of recurrent instability and improved clinical outcomes in patients with Ehlers-Danlos Syndrome [9].
• Data are inadequate to report on clinical results and recurrent instability risk for anterior labral reconstruction with biceps autograft for anterior shoulder instability [10].
• Postoperative radiographic evaluation at 7-month follow-up for anterior capsular reconstruction with dermal allograft augmentation for multidirectional shoulder instability demonstrated a concentrically reduced glenohumeral joint [27].
• The Latarjet procedure leads to similar functional outcomes and failure rates in patients with or without hyperlaxity for recurrent instability of the shoulder [30].
• In a high-risk population with traumatic posterior glenohumeral dislocations, 19 out of 33 shoulders (58%) experienced structural failure such as recurrent dislocation or revision surgery [31].
• Contemporary studies show comparable instability and functional outcomes between arthroscopic and open Bankart repair for anterior shoulder instability [45].
• The two-year follow-up of a local vascularized scapula bone graft for posterior glenohumeral instability led to a posteriorly stable glenohumeral joint and a persisting vital bone graft [60].
• Long-term reoperation rates and failures are not reported for arthroscopic subscapularis repair with preserved biceps anatomy [142].

Patient-Reported Outcomes and Subjective Symptoms

• Patient-reported outcomes may decline over time following arthroscopic Bankart repair for anterior shoulder instability in patients who experience recurrent anterior shoulder instability and undergo isolated arthroscopic Bankart repair compared to arthroscopic Bankart repair with remplissage [140].
• The duration of subjective shoulder instability following anterior stabilization was similar between Latarjet and Bankart repair techniques [141].
• The presence of subjective shoulder instability following anterior stabilization was not associated with an increased risk of dislocation [141].

Non-Operative and Conservative Management

• If chronic instability develops after traumatic shoulder dislocation, surgery could be considered [16].
• The acromioclavicular harness has been used with good results in treating twenty cases, maintaining reduction and bringing about permanent healing [22].

Pathomechanisms and Diagnostic Considerations

• Accurate identification of the mechanism of instability is essential for guiding management of dislocated reverse total shoulder arthroplasty [3].
• A previously undescribed group of patients presents with chronic shoulder instability, even after surgery to correct this problem, and presents with an axillary index-scar [7].
• Historically, the absence of structural pathology on diagnostic imaging for dynamic-functional posterior instability, coupled with the limited success of conventional treatments, frequently led to the dismissal of this subtype as attention-seeking or psychiatric behavior [13].
• The current gold standard for dynamic-functional posterior instability focuses on normalizing the pathological muscle activation pattern [13].
• Rotator cuff dysfunction with inadequate humeral head depression causes excessive superior translation [18].
• The combined movement of abduction and external rotation with an excessively tight anterior band of the inferior glenohumeral ligament complex causes excessive glide of the humeral head on the glenoid in the posterior and superior direction [18].
• Posterior and superior compression of the suprahumeral space begins near 150 degrees of flexion and occurs earlier if elevation of the humerus is performed in greater amounts of horizontal abduction [18].
• Addressing cartilage injury in the setting of first-time anterior shoulder instability can be beneficial and may alter recovery and longer-term shoulder joint outcomes [35].
• Adolescent athletes who present with a history of anterior shoulder instability have a high incidence of bipolar bone loss [41].
• In patients with epilepsy, 60% (43/72) of identified shoulder dislocations were anterior, 30% (22/72) were posterior, and 10% (7/72) were bidirectional [44].
• In patients with epilepsy, 51% (37/72) of identified shoulder dislocations were first-time and 49% (35/72) were recurrent [44].
• Further biomechanical studies and long-term follow-up are essential to validate the efficacy of arthroscopic autologous iliac crest bone grafting using 3 suture-loaded anchors for recurrent anterior shoulder instability with critical glenoid bone loss [56].
• Cost-effectiveness analyses comparing distal tibial allograft versus the Latarjet procedure for anterior shoulder instability do not account for long-term outcomes such as the development of glenohumeral arthritic changes [139].

Key Evidence

• [L4] Overall, 96% (20/21) of the patients had a stable and functional shoulder and were satisfied with the procedure; no patient lost active shoulder motion. [1] (10.1016/j.jseint.2024.08.149)
• [L4] This study showed clinical improvements in all patients, with the complete resolution of instability symptoms and radiological correction of glenoid retroversion. [2] (10.1186/s12891-026-09524-3)
• [L4] Accurate identification of the mechanism of instability is essential for guiding management, but outcomes remain variable and recurrent instability continues to be a major challenge. [3] (10.1177/17585732261472448)
• [L5] All in all, this technique offers an efficient, reproducible procedure to address posterior shoulder instability pathology. [4] (10.1016/j.eats.2022.05.004)
• [L4] Frozen shoulder is a common epidemiological affliction that does not resolve spontaneously in a large number of patients. [5] (10.3389/fmed.2021.663703)
• [L4] NHL team physicians strongly favor nonoperative management in-season for initial posterior instability events of the shoulder. [6] (10.1177/23259671261440208)
• [L5] The authors define a previously undescribed group of patients who present with chronic shoulder instability, even after surgery to correct this problem, and who accordingly present with an axillary index-scar. [7] (10.1016/s0020-1383(00)00127-3)
• [L3] At 2 years, 19.1% of patients experienced instability and 7.9% underwent reoperation for instability or dislocation. [8] (10.1177/2325967126s00513)
• [L4] The study demonstrated low rates of recurrent instability and improved clinical outcomes in this high-risk population. [9] (10.1016/j.jse.2026.05.024)
• [L4] This technique has been performed in a small number of patients, and the data are inadequate to report on clinical results and recurrent instability risk. [10] (10.1016/j.eats.2024.102935)
• [L4] [11] (10.2106/jbjs.rvw.23.00200)
• [L5] Soft-tissue stabilization alone may not be sufficient in patients who present with substantial bone loss to the posterior glenoid and/or the anterior humeral head. [12] (10.2106/jbjs.rvw.23.00243)
• [L5] [13] (10.1016/j.xrrt.2026.100861)
• [Paper] The indications for an isolated soft-tissue procedure in anterior shoulder instability are now narrower; the ideal candidate presents with minimal glenoid bone loss (13.5%). [14] (10.2106/jbjs.rvw.26.00033)
• [L5] The authors propose the arthroscopic subscapular sling procedure as an alternative to existing surgical treatment options for recurrent anterior shoulder instability. [15] (10.1016/j.eats.2021.03.027)
• [L1] If chronic instability develops, surgery could be considered. [16] (10.1136/bjsports-2017-098539)
• [L5] [17] (10.1016/j.eats.2022.08.005)
• [L4] [18] (10.2519/jospt.1996.23.3.216)
• [L1] Clinicians should interpret these findings with caution when using systematic reviews to guide management of anterior shoulder instability. [19] (10.1016/j.jse.2026.06.027)
• [L3] Coracoid morphology differs significantly in patients undergoing posterior shoulder stabilization when compared to patients undergoing surgery for anterior instability or a comparison cohort. [20] (10.1177/03635465261421534)
• [L3] Patients should be counseled pre-operatively on the expected outcomes over time following ABR of anterior shoulder instability. [21] (10.1177/2325967126s00552)
• [L4] The acromioclavicular harness has been used with good results in treating twenty cases, maintaining reduction and bringing about permanent healing. [22] (10.2106/00004623-195234010-00032)
• [L5] [24] (10.2106/jbjs.rvw.25.00098)
• [Paper] [25] (10.2106/jbjs.rvw.25.00126)
• [L5] The technique aims to address anterior shoulder instability with bone loss by creating a bony 'ramp' that prevents anterior translation. [26] (10.1016/j.eats.2024.103344)
• [L5] Postoperative radiographic evaluation at 7-month follow-up demonstrated a concentrically reduced glenohumeral joint. [27] (10.1002/atn2.70104)
• [L3] The Bristow-Latarjet procedure was associated with significantly higher rates of full RTS than Bankart repairs in anterior shoulder instability, despite variability in patient indications across procedures. [28] (10.1177/23259671261450204)
• [L4] Two cases document an unusual injury pattern in which a posterior glenohumeral dislocation occurred in association with a (posterior) acromion fracture. [29] (10.1016/j.xrrt.2025.09.006)
• [L4] In recurrent instability of the shoulder, the Latarjet procedure leads to similar functional outcomes and failure rates in patients with or without hyperlaxity. [30] (10.1016/j.jseint.2024.08.174)
• [L4] The study found a high failure rate in both cohorts, with 19 out of 33 shoulders (58%) experiencing structural failure such as recurrent dislocation or revision surgery. [31] (10.1016/j.jseint.2026.101773)
• [L3] [32] (10.1016/j.jseint.2026.101785)
• [L5] [33] (10.1016/j.eats.2023.10.002)
• [L5] The authors conclude that addressing the cartilage injury can be beneficial and may alter recovery and longer-term shoulder joint outcomes. [35] (10.1002/arj.70461)
• [Paper] Such methods may improve prognostic analysis of anterior shoulder instability and will facilitate measurement on MRI, which rarely includes the contralateral shoulder. [36] (10.1016/j.jseint.2025.101506)
• [L3] A thorough clinical exam is the most important factor when determining indication for shoulder instability surgery. [37] (10.1016/j.xrrt.2026.100675)
• [L3] Clinicians should maintain a high index of suspicion in young patients presenting with traumatic shoulder pain, even in the absence of perceived instability. [39] (10.1177/23259671251414851)
• [L4] This value is on the lower end of the currently reported range and we believe this to be very accurate as this study contains the largest and most heterogenous population of pediatric shoulder instability patients in the literature. [40] (10.1177/2325967126s00536)
• [L4] Adolescent athletes who present with a history of anterior shoulder instability have a high incidence of bipolar bone loss. [41] (10.1177/2325967126s00146)
• [L4] Recurrence of posterior instability occurred in 5 cases (18%); all had recurrent subluxations, with no dislocations. [42] (10.1016/j.jseint.2025.101473)
• [L4] Despite a higher complication rate than in the younger population, shoulder stabilization using the Latarjet procedure is effective in patients over 50 without associated cuff damage. [43] (10.1016/j.jseint.2025.101518)
• [L4] A total of 72 shoulder dislocations were identified: 60% anterior (43/72), 30% posterior (22/72), and 10% bidirectional (7/72); 51% were first-time dislocations (37/72) and 49% recurrent (35/72). [44] (10.1186/s12891-026-10180-w)
• [L4] Publication period subgroup analysis suggests that historical instability differences were driven primarily by earlier studies, whereas contemporary studies show comparable instability and functional outcomes between approaches. [45] (10.1177/03635465261443999)
• [L5] It enables early recovery and return to sports by biologically restoring joint anatomy and kinematics. [50] (10.1016/j.eats.2025.103595)
• [L5] [54] (10.1016/j.eats.2025.103762)
• [L5] However, further biomechanical studies and long-term follow-up are essential to validate the efficacy of this technique. [56] (10.1016/j.eats.2025.103705)
• [L5] This technique can be a reproducible way to improve shoulder stability and obtain good postoperative outcome measures for patients with recurrent MDI. [57] (10.1016/j.eats.2025.103500)
• [L5] [58] (10.1002/atn2.70026)
• [L4] The study investigated and compared morphological factors on magnetic resonance imaging between pain-predominant (UPS) and apprehension-dominant (ASI) instability presentations. [59] (10.1016/j.xrrt.2026.100810)
• [L5] The two-year follow-up of the performed surgical procedure led to a posteriorly stable glenohumeral joint and a persisting vital bone graft. [60] (10.1016/j.xrrt.2026.100772)
• [L4] [62] (10.1016/j.eats.2023.05.023)
• [L4] The modified Kouvalchouk procedure provides good results in the stabilization of recurrent posterior unstable shoulders in traumatic cases and patients without previous surgery, with the advantage of local harvesting of a bone block and a potential sling effect. [64] (10.1016/j.jseint.2026.101681)
• [L5] The article presents an alternative technique for capsular plication that effectively and safely addresses capsular laxity in patients with posterior shoulder instability. [65] (10.1016/j.eats.2025.103794)
• [L5] A complex salvage surgery with multiple procedures is presented for patients with multidirectional instability or hyperlaxity, with an important posterior erosion component (mainly glenoid dysplasia) and loss of the anterior wall in previous surgical procedures to theoretically reduce recurrent dislocation rates. [66] (10.1016/j.eats.2024.103115)
• [L5] The technique aims to potentially decrease the likelihood of recurrent instability or failure by addressing a potential cause of residual posterior laxity. [67] (10.1016/j.eats.2022.12.002)
• [L4] This study demonstrates that labral morphology does not compensate for reduced bony glenoid concavity in clinically stable shoulders. [91] (10.1016/j.jseint.2025.101422)
• [L3] These findings suggest that the overall bony concavity of the glenoid may play an inherent role regarding stability. [110] (10.1016/j.arthro.2020.12.046)
• [Paper] Current classifications exhibit poor reliability in categorizing glenoid defects post-reverse shoulder arthroplasty removal. [117] (10.1016/j.jseint.2024.08.170)
• [Paper] The subscapularis and capsule augmentation is a safe and relatively easy technique for the treatment of shoulder instability. [118] (10.1016/j.eats.2024.103313)
• [L4] [119] (10.1177/23259671261451245)
• [L5] [121] (10.1016/j.eats.2023.03.020)
• [Paper] Including the whole scapula on MRI, especially in advanced levels of tear retraction, may allow a more representative assessment to the [123] (10.1016/j.jseint.2024.08.135)
• [L4] In the future, we expect CT to be superseded by MRI in anterior shoulder instability. [125] (10.1016/j.jseint.2025.101440)
• [L4] [129] (10.1016/0020-1383(86)90252-4)
• [L3] The study investigated whether unstable painful shoulder (UPS) and anterior instability (AI) are associated with differences in scapula morphology using magnetic resonance imaging (MRI). [134] (10.1016/j.jse.2026.04.009)
• [L5] Healing (or failure) may be evaluated on plain radiographs primarily with axillary views, which should demonstrate union by 12 weeks. [135] (10.1016/j.eats.2023.02.024)
• [L5] The aim of the flipped Latarjet procedure is to facilitate a safe and reliable arthroscopic operation to anteriorly stabilize the shoulder by transferring the coracoid to the deficient glenoid without splitting the subscapularis muscle while keeping the benefits of a sling effect of the conjoined tendon. [136] (10.1016/j.eats.2023.102899)
• [L4] The authors recommend strong consideration of performing arthroscopy prior to open Latarjet if a preoperative MRI is not obtained or if a preoperative MRI identifies additional intra-articular pathology. [137] (10.1177/23259671261415839)
• [L4] In this selected cohort with post-operative imaging, no consistent MRI evidence of subscapularis atrophy or fatty infiltration was identified following either open or arthroscopic stabilization. [138] (10.1016/j.xrrt.2026.100824)
• [Paper] Notably, this analysis does not account for long-term outcomes such as the development of glenohumeral arthritic changes, which may influence the relative value of each procedure over time. [139] (10.1177/2325967126s00557)
• [L4] PROs may decline over time following ABR for anterior shoulder instability for patients who experience recurrent anterior shoulder instability and undergo isolated ABR compared to ABR with remplissage. [140] (10.1016/j.xrrt.2026.100719)
• [L3] Its duration was similar between techniques, and its presence was not associated with an increased risk of dislocation. [141] (10.1177/23259671261470584)
• [L5] The limitations of this technique description are largely confined to the nature of the study in that long term reoperation rates and failures are not reported. [142] (10.1016/j.eats.2023.02.047)

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[125] MRI augmented with novel artificial intelligence system is superior to CT in shoulder instability. JSES International. 2026. DOI: 10.1016/j.jseint.2025.101440

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