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Instability & Dislocation

Traumatic and multidirectional shoulder instability — classification of anterior vs posterior dislocation and the role of glenoid bone loss in recurrence risk.

167 citationsUpdated Sep 2026

Overview

Shoulder instability is a heterogeneous condition where surgical indications are primarily determined by proper evaluation of bone loss, which best dictates operative strategy and outcomes [51]. Posterior instability accounts for 10% of all instability events [17], while anterior instability generally yields superior outcomes across all domains compared to posterior instability following arthroscopic stabilization [18]. Patient selection is critical; better functional results after arthroscopic stabilization are expected in patients over 24 years of age and those with fewer preoperative dislocations [230]. Conversely, the risks of revision stabilization and postoperative dislocation are most influenced by young age (under 20 years) and having had 3 or more preoperative dislocations [27]. For high-risk patients, stabilization surgery helps prevent subsequent dislocation events and minimizes health care costs [24].

Timing of intervention significantly impacts recurrence rates. Immediate surgical stabilization following a first-time dislocation significantly diminishes the risk of recurrent dislocation compared to surgery performed after two dislocation events [29]. Patients with first-time dislocations exhibit lower postoperative instability and reoperation rates than those with recurrent dislocations [15], with long-term benefits in overall stability and functional outcome demonstrated in high-risk patients undergoing arthroscopic Bankart repair for first-time anterior dislocation [13]. However, future studies are needed to ascertain long-term outcomes of surgical stabilization based on preoperative dislocation events [12]. Arthroscopic surgery remains an acceptable treatment if recurrent instability occurs consistently at ≤23.8% [50].

Specific clinical scenarios require tailored approaches. Surgical soft-tissue stabilization might be more aggressively indicated in cases of primary shoulder dislocation, whereas recurrent instability with bone loss should be referred to experienced high-volume specialists [56]. Sensitive patient selection for arthroscopic Bankart repair is recommended, especially in patients with more than five dislocations [57]. In chronic anterior dislocation, the choice of open reduction and stabilization technique was highly variable, leading to wide variation in reported outcomes and a high number of complications such as resubluxation and early arthrosis [25]. Recurrent instability requiring capsular reconstruction seems more prevalent in patients with a previous history of shoulder dislocation in the context of luxatio erecta [26]. No significant differences in outcomes or recurrence rates were found between early and late dislocations following reverse total shoulder arthroplasty [4].

Anatomy & Pathophysiology

Bony Anatomy

The glenohumeral joint is inherently predisposed to instability by its bony architecture [63]. The glenoid cavity is a shallow, convex socket shaped like an inverted pear, approximately one-third the size of the humeral head [72, 73]. The subchondral bone of the glenoid is relatively flat, with the articular concavity augmented by cartilage and a circumferential labrum [75]. The glenoid averages 5° of retroversion relative to the axis of the scapular body [75, 87], with an average inclination of 4.2 degrees (range –7 to 20 degrees) and version averaging 1.5 degrees retroversion (range 10.5 degrees anteversion to 9.5 degrees retroversion) [85]. The glenoid diameter ranges from 18-30 mm superior anteroposterior, 21-35 mm inferior anteroposterior, and 30-48 mm superoinferior height [85]. The glenoid articular surface radius of curvature is 22-28 mm, which is 2 to 3 mm larger than that of the humeral head [85]. The glenoid cartilage thickness is 2.16 mm, and the glenoid surface area is 4-6 mm [85].

The humeral head is spherical with a diameter of 37 to 57 mm and a radius of curvature of approximately 25 mm, slightly larger in men than in women [72, 85]. The articular surface is essentially spherical, with an arc of approximately 160 degrees covered by articular cartilage [85]. The humeral head cartilage thickness is 1.44 mm, and the surface area is 11-19 mm [85]. The humeral head is retroverted an average of 30 degrees relative to the transepicondylar axis [73, 87], with an average version of 29.8 degrees (range 10 to 55 degrees) [72]. The head-shaft angle averages 135 degrees [73], though other measurements report an average of 45 degrees (±5 degrees) with a range of 30 to 50 degrees [85], or 41° of inclination [75]. The most superior portion of the articular surface averages 8 mm above the greater tuberosity [72], with the superior margin normally positioned 8 to 10 mm superior to the top of the greater tuberosity [85]. The head height is approximately 5.6 cm above the superior border of the pectoralis major tendon [87]. The medial (coronal) humeral offset is 4-14 mm, and the posterior (transverse) humeral offset is –2 to 10 mm [85]. A significant decrease in lateral humeral offset reduces the lever arms for the deltoid and supraspinatus muscles, weakening abduction and impairing function [85]. Conversely, a significant increase in lateral humeral offset causes excessive tension on the soft tissues, resulting in loss of motion and likely accelerating polyethylene wear [85].

The anatomic neck of the proximal humerus is located at the junction of the articular surface and the tuberosities [72, 73]. The surgical neck represents an indistinct metadiaphyseal junction below the tuberosities but above the humeral shaft [72, 73]. The greater tuberosity serves as the attachment site for the supraspinatus, infraspinatus, and teres minor tendons [72, 73, 80]. The lesser tuberosity serves as the attachment site for the subscapularis tendon [72, 73, 80]. The bicipital groove lies between the greater and lesser tuberosities and serves as a pathway for the long head of the biceps, with its distal aspect internally rotated with respect to the proximal portion [72].

The scapula is attached to the axial skeleton by the clavicle via the acromioclavicular and sternoclavicular joints [74]. It is separated from the chest wall by thin gliding fibro-fatty tissue, allowing smooth excursion [74]. The scapula spans the second through seventh ribs and serves as an attachment for 17 muscles [87]. It is anteverted on the chest wall approximately 30 degrees relative to the body [87]. The glenoid is connected with the flat body of the scapula by the scapular neck [74]. The hook-shaped coracoid process curves forwards from the superior surface of the scapular neck [74]. The acromion is a flattened bony process that curves forwards from the scapular spine [74]. The distribution of bony mass in the scapula is highly uneven, with the highest concentration in the glenoid, the scapular neck, and the lateral border of the scapular body [74]. Two bony pillars transmit compressive forces from the glenoid fossa: the lateral pillar, which connects the inferior border of the glenoid with the inferior angle, and the spinal pillar, which arises from the central part of the glenoid and continues medially to become part of the base of the scapular spine [74]. The weakest bone in the scapula is located primarily in the central part of the biomechanical body, specifically in the infraspinous fossa, while the weakest area of the circumference of the biomechanical body is the spinomedial angle [74].

The clavicle is the only long bone to ossify by intramembranous ossification [75, 82]. It is the first bone in the body to ossify at 5 weeks gestation and last to fuse with the medial epiphysis at 25 years of age [87]. The medial (sternal) epiphysis of the clavicle is the last ossification center to fuse, at age 20 to 25 years [75]. The primary blood supply to the clavicle is periosteal; no nutrient artery is present [75, 82]. Fracture of the clavicle is the most common musculoskeletal birth injury [87].

The proximal humerus has three centers of ossification: the humeral head (4 to 6 months), the greater tuberosity (1 to 3 years), and the lesser tuberosity (3 to 5 years) [75, 80]. The proximal humeral ossification centers fuse to the shaft at age 17 to 20 years [75], or by 5 to 7 years of age to form the humeral head [80]. The proximal humeral physis closes by 14 to 17 years of age in girls and by 16 to 18 years in boys [80]. Eighty percent of subsequent growth of the humerus comes from the proximal humeral physis [80]. This physis is irregularly shaped, with its apex located on the posteromedial portion of the proximal humerus, where the periosteum is thicker and stronger compared to the anterolateral portion [80]. Humeral retroversion averages 65 degrees in infants and young children and gradually decreases, approaching adult values by 11 years of age [80]. The proximal humerus is primarily cartilaginous at birth, with ossification centers detectable by ultrasonography as early as the 38th week of gestation [80]. The ossification center for the humeral head is usually present at birth [80]. The formation of the humerus begins with the appearance of the cartilage anlage, which is present by the fifth week of gestation, and the primary ossification center appears at about the sixth week [80]. By the time of birth, the entire humeral diaphysis is completely ossified [80].

The acromion has three ossification centers: the metacromion (base), the mesoacromion (middle), and the preacromion (tip) [75]. Failure of fusion of the acromial ossification centers results in os acromiale [75]. The scapula has only one true diarthrodial articulation, the acromioclavicular joint [75]. Normal shoulder motion is approximately two-thirds glenohumeral and one-third scapulothoracic [75]. The sternoclavicular joint is the only true diarthrodial articulation between the upper appendicular and axial skeletons [75]. The acromioclavicular joint is a small diarthrodial joint with an interposed fibrocartilaginous disk [75]. The superior and posterior acromioclavicular ligaments are the primary stabilizers to anterior and posterior translation of the clavicle [75]. The coracoclavicular ligaments (conoid: medial; trapezoid: lateral) are the primary stabilizers to superior translation of the distal clavicle [75, 82]. The posterior sternoclavicular joint capsule and ligaments are the primary stabilizers to anterior and posterior translation of the medial clavicle [75].

The superior shoulder suspensory complex provides a stable connection between the scapula and the axial skeleton [75, 82]. It is composed of the glenoid, the coracoid process, the coracoclavicular ligaments, the distal clavicle, the acromioclavicular joint, and the acromion [75]. The superior strut of this complex comprises the middle clavicle, while the inferior strut comprises the lateral scapular border and spine of the scapula [75]. The coracoid process serves as an attachment for the coracoacromial ligament, coracoclavicular ligaments, conjoined tendon, and pectoralis minor [87]. The coracobrachialis muscle and the short head of the biceps tendon originate from the coracoid process [75]. The pectoralis minor muscle inserts onto the medial coracoid process [75]. The scapular spine is an osseous ridge that separates the supraspinatus and infraspinatus fossae [75].

Evolutionary adaptations have altered scapular morphology. The scapula is suspended by muscles alone and has shifted caudally from the cervical position in lower animals [83]. Broadening of the infraspinatus fossa has changed the vector of muscle pull from the axillary border of the scapula to the glenoid fossa, allowing the infraspinatus and teres minor muscles to be more effective in their roles as depressors and external rotators of the humeral head [83]. The acromion has enlarged over time, reflecting the increasing role of the deltoid muscle in shoulder function, and the coracoid process has undergone an increase in size [83]. 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 [83].

Soft Tissue Anatomy & Ligaments

The rotator cuff is a sheet of conjoined tendons closely applied over the shoulder capsule and inserting mainly into the greater tuberosity of the humerus [81]. It consists of four muscles: the subscapularis, supraspinatus, infraspinatus, and teres minor [73]. The teres major is not a rotator cuff muscle [73]. The cuff is arranged with the subscapularis in front, supraspinatus above, and infraspinatus and teres minor behind [81]. The subscapularis originates from the anterior scapula and inserts anteriorly onto the lesser tuberosity [80, 81]. The greater tuberosity provides attachment superiorly and posteriorly for the supraspinatus, infraspinatus, and teres minor [80]. The rotator cuff has an important function in stabilizing the head of the humerus by pulling it firmly into the glenoid whenever the deltoid lifts the arm forwards or sideways [81]. The cuff muscles serve as depressors of the humeral head to allow the deltoid to efficiently abduct the humerus [73]. The infraspinatus and teres minor are external rotators, while the subscapularis is an internal rotator of the humerus [73].

The deltoid forward flexes and abducts the shoulder and courses from the clavicle and acromion superiorly, coalescing into a common tendinous insertion onto the lateral upper third of the humeral shaft [80]. The pectoralis major powers adduction and internal rotation due to its tendinous insertion anteriorly onto the lateral wall of the bicipital groove [80]. The pectoralis major forms the roof of the distal continuation of the bicipital tunnel, which is a closed space that extends proximally to the glenohumeral joint [80]. The deltoid and pectoralis major muscles, along with the rotator cuff, cause predictable displacement of fractures around the proximal humerus [73].

The coracoacromial arch is a fibro-osseous canopy formed by the acromion process posterosuperiorly, the coracoid process anteriorly, and the coracoacromial ligament joining them [72, 81]. The rotator cuff, subacromial bursa, and subdeltoid bursa pass underneath the coracoacromial arch [72]. The subacromial bursa separates the tendons from the coracoacromial arch and allows them to glide [81]. The coracoacromial ligament contributes to anterosuperior stability in rotator cuff deficiency [87]. The acromial branch of the thoracoacromial artery runs on the medial aspect of the coracoacromial ligament [87].

The glenoid labrum increases the depth of the socket by 50% around the humeral head [86]. 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 [86]. Adding the glenoid labrum increases the glenoid surface to 75% of the humeral head vertically and 57% horizontally [86]. The glenoid labrum provides concavity and up to 50% of marginal glenoid socket depth [75]. The fibrocartilaginous glenoid labrum deepens the socket by 50% and provides a bumper to translation [87]. Labral anatomic variants include the sublabral foramen (anterosuperior) and the Buford complex (absence of anterosuperior labrum and cordlike middle glenohumeral ligament) [87].

The transverse humeral ligament is an important stabilizer of the biceps tendon [87]. The suprascapular artery passes superior to the superior transverse scapular ligament, and the suprascapular nerve passes inferior to the ligament through the suprascapular notch [87]. At the spinoglenoid notch, both the suprascapular artery and nerve are inferior to the inferior transverse scapular ligament [87]. The capsule of the glenohumeral joint extends from the glenoid rim, progressing [80].

Classification

Definitions and Terminology

First-time dislocation is defined as shoulder dislocation in a previously stable joint [6], whereas recurrent dislocation refers to a subsequent episode in a previously dislocated shoulder [6]. Non-traumatic shoulder instability (NTSI) is defined as abnormal movement or position of the shoulder, leading to pain, subluxation or even dislocation and functional discomfort without a significant history of injury [38]. The AMBRI acronym refers to atraumatic multidirectional instability, which is often bilateral and requires rehabilitation and inferior capsular shift [38]. The TUBS acronym refers to traumatic unidirectional instability with a Bankart lesion, which often requires surgery [38].

Classification Systems

The Thomas and Matsen classification introduced the AMBRI versus TUBS dichotomy based on the presence or absence of trauma [38]. The Stanmore classification was introduced in 2004 to encompass Polar type I (true TUBS, traumatic, structural), Polar type II (true AMBRI, atraumatic, structural), and Polar type III (atraumatic with functional origin due to muscle patterning disorders or habitual non-structural) [38]. The ABC classification distinguishes three groups of posterior glenohumeral instability with two different subtypes based on the pathomechanical type of instability and the current standard of treatment [9]. The FEDS system categorizes instability based on frequency, aetiology, direction, and severity [77]. The FEDS classification, particularly the frequency and etiology of the patient's shoulder instability, may be helpful in identifying patients with a higher likelihood of undergoing surgical treatment [185].

The Instability Severity Index Score (ISIS) is highly reliable for grading traumatic anterior instability severity and correlates with the number of prior dislocations and surgical decision-making, but not with patient-reported quality-of-life questionnaires [184]. However, the ISIS failed to predict recurrent instability in a high percentage of cases, as the score was not significantly different between patients with successful and unsuccessful repairs [203].

Clinical Presentation and Prognostic Factors

Shoulder instability is a phenomenon with a variety of clinical presentations, and its complex nature has until recently been poorly understood [5]. A history of multiple instability episodes prior to presentation was the greatest predictor of recurrent instability and failure of nonoperative treatment and progression to surgery [1]. Stabilization after the first-time dislocation achieves better clinical and radiological outcomes than after multiple dislocations [2]. Some risk of recurrent instability is part of the natural history of anterior shoulder dislocation [10]. Characteristics related to a history of instability (age <20 years at first instability episode, larger number of dislocations, ≥2 years between first dislocation and surgery) were found to be risk factors for the development of an off-track HS lesion [11]. Recurrent instability requiring capsular reconstruction seems to be more prevalent in patients with a previous history of shoulder dislocation [26]. Wide-type Hill-Sachs lesions were correlated with more subluxations and dislocations than other types [206]. A history of multiple dislocations and failed soft-tissue surgery should make surgeons consider the possibility of an associated bone deficit [60]. Clustering of thorough history and physical examination findings may identify those with posterior glenohumeral instability and assist in developing management strategies [34]. In a substantial number of patients with a long-standing history of instability, classification of lesions was impossible at arthroscopy because of scar tissue formation and advanced degenerative changes in the labroligamentous complex [197]. Although glenoid version alone does not account for the multifactorial nature of instability, it may serve as a complementary anatomical parameter in future clinical risk-stratification models [196].

Epidemiology and Demographics

The most consistent and significant factor influencing prognosis in shoulder dislocation is the age of the patient at the time of the initial or primary dislocation [8]. The greatest number of primary dislocations occurred for the first time between ten and twenty years of age (ninety-nine primary dislocations) [8]. The next highest number of primary dislocations occurred between fifty and sixty years of age (ninety-three primary dislocations) [8]. Dislocations occurred as frequently after age forty-five (249 dislocations) as before the forty-fifth year (251 dislocations) [8]. In patients with primary dislocation the mean age was forty-eight years, while in patients with recurrent dislocation the mean age was twenty-three years [8]. The recurrence rate in patients under twenty years of age was 83 per cent [8]. Adult shoulder dislocations in the United States showed a bimodal age distribution of under 24 and older than 75 [261]. The incidence of shoulder arthropathy in patients with shoulder instability is difficult to measure given that the majority of shoulder dislocations occur in younger patients [258]. The rate of recurrence seen with shoulder dislocation ranges from 10% to 90% after an initial dislocation [258].

Other Considerations

Shoulder instability cannot reliably be classified using the ICD-9 coding system [175]. Variations in the criteria used for the diagnosis of multidirectional instability significantly affect the distribution of patients with that diagnosis [33]. Since the 1980s, 18 classifications have been developed in an attempt to define the sub-groups of instability, but none of them have demonstrated strong measurement properties [38]. The development of the FEDS system identified 18 different proposed classification systems for glenohumeral instability through a systematic review of the literature [253].

Clinical Presentation

Definitions and Classification

The Thomas and Matsen classification distinguishes between traumatic and nontraumatic dislocations using the acronyms AMBRI (atraumatic multidirectional instability) and TUBS (traumatic unidirectional instability) [38]. The Stanmore classification further categorizes instability into Polar type I (true TUBS, traumatic, structural), Polar type II (true AMBRI, atraumatic, structural), and Polar type III (atraumatic with functional origin due to muscle patterning disorders or habitual non-structural causes) [38]. In a cohort classified by the FEDS system, solitary traumatic anterior dislocation and occasional traumatic anterior dislocation were the most frequently observed patterns [49].

History Taking

The age of the patient at the time of initial dislocation is the most important prognostic factor regarding recurrence, with the highest rate found in patients 30 years and younger [42]. In a cohort of 500 dislocations, the greatest number of primary dislocations occurred between ten and twenty years of age (99 cases), followed by the fifty to sixty years age group (93 cases) [8]. The recurrence rate for patients under twenty years of age with initial dislocation was 83 percent [8]. Characteristics related to a history of instability, including age <20 years at first instability episode, a larger number of dislocations, and ≥2 years between first dislocation and surgery, are risk factors for the development of an off-track Hill-Sachs lesion [11]. Patients presenting with multiple recurrences, more than 2 preoperative dislocations, a duration of instability symptoms of more than 6 months, and identified off-track Hill-Sachs lesions may not be ideal candidates for arthroscopic instability repair due to higher failure rates [48].

History taking should note age at first dislocation, increasing ease of dislocation, frequency of recurrence, duration of symptoms, and the patient's ability to reduce the dislocation himself or herself [111]. Comprehensive history includes age, handedness, sport or recreational activity, unilateral or bilateral complaint, family history of shoulder dislocation, initial traumatic event, position of arm during subluxation or dislocation, number of previous episodes of dislocations or subluxations, whether the dislocation was reduced in the emergency department, interval of time between dislocation and reduction, degree of trauma required for recurrence, voluntary dislocation, dislocation during sleep, presence and location of pain, presence or absence of mechanical symptoms, sensory disturbance or motor weakness, and previous shoulder surgery [146]. 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 [146].

In bony instability, patients may describe dislocation events associated with various activities of daily living or even during sleep, often with the arm in a position of much lower degrees of abduction and external rotation than the well-described “position of athletic function” at 90° of abduction and 90° of external rotation [130]. Multiple dislocation events are often reported in bony instability, with some patients describing “hundreds” of episodes in a short period of time [130]. A past traumatic event involving the shoulder, often higher energy and usually requiring medical treatment for reduction, is a key feature of the history in bony instability [130]. A prior surgical intervention is also a key feature of the history in bony instability [130]. Bony instability may present with complaints such as a “dead arm,” decreased strength or athletic performance, or nonspecific pain dominating the history [130]. The patient typically presents with a history of trauma [111].

Detailed and specific information about prognosis is critical in the management of a first-time anterior shoulder dislocation [35]. Even patients who have experienced a single episode of dislocation may go on to develop long-term sequelae [20]. Extensive labral lesions can occur even in patients with few previous dislocations [108]. In patients with anterior instability, recurrence is 24%, with almost all cases associated with new trauma [115]. Nonoperative treatment was successful in a toddler with rare anterior shoulder dislocation without subsequent instability or re-dislocation [21].

Anterior instability is most common among shoulder instability patients, and most patients undergoing shoulder stabilization are in their early 20s or younger [118]. Traumatic shoulder instability in the older patient may result in a wide array of pathologic findings as well as a diversity of clinical presentations [107]. HAGL lesions are a rare and underdiagnosed cause of anterior shoulder instability that can lead to recurrent dislocations if unaddressed [36]. Recognition and treatment of GAGL lesions should improve surgical outcomes in patients with recurrent dislocations [99]. Lesions associated with traumatic anterior glenohumeral dislocations are more frequent than expected [123]. In a matched cohort, anterior instability outcomes were superior in all domains versus posterior instability after arthroscopic stabilization [18].

Recurrent posterior shoulder instability is an uncommon condition often unrecognized, leading to incorrect diagnoses and delays [19]. Posterior shoulder dislocation is a rare and challenging injury with varied mechanisms of trauma that complicate diagnosis [32]. Posterior shoulder dislocations are less common than anterior dislocations but are more commonly missed [121]. Posterior shoulder dislocations occur rarely but are often missed on initial presentation, resulting in ongoing patient discomfort, long-term morbidity and elevated health care costs [109].

Physical Examination

The apprehension-relocation test (Fowler test) is the most sensitive test, where the arm is placed into abduction and external rotation, the patient experiences a sense of instability, and the examiner places a posterior force on the arm to relieve the sense of instability [111]. The load-and-shift test can be used to classify degrees of instability on the basis of distance of humeral head translation: 1+ is 0 to 1 cm of translation to before glenoid rim, 2+ is 1 to 2 cm of translation to glenoid rim, and 3+ is greater than 2 cm translation or over glenoid rim [111]. An evaluation of generalized laxity should be performed during physical examination [111]. Physical examination should focus on both diagnosis and identification of associated injuries [111].

Physical examination for shoulder instability includes inspection, constitutional ligamentous laxity (e.g., Marshall test, Beighton score), neck range of motion and Spurling’s maneuver, shoulder range of motion and scapular symmetry, strength testing of shoulder girdle muscles, lift-off and belly press tests, sulcus sign, anterior apprehension test and position of arm (including evaluation for mid-range instability), relocation test, load and shift (anterior and posterior), jerk test, O’Brien’s active compression test, Hawkin’s and Neer’s impingement tests, and cross-body adduction [146]. An examination under anesthesia is critical to the success of arthroscopic stabilization and is more sensitive for determining both the degree and direction of instability [146]. The axial load test or load-and-shift test conducted under anesthesia notes translation in the anterior, inferior, and posterior directions [146]. Grading of instability under anesthesia reflects the degree of humeral head translation: Grade 1+ corresponds to the translation of the humeral head to the edge of the glenoid, 2+ if the humeral head can be subluxated over the glenoid rim but reduces spontaneously, and 3+ if a frank dislocation of the humeral head over the glenoid rim does not reduce spontaneously [146].

Posterior instability tests showed high sensitivity but low specificity, leading to over-diagnosis [41]. Many different diagnostic examinations for assessing shoulder instability are used and a high variety is seen in the use of diagnostic tools [125]. In a study of arthroscopic and open stabilization, all patients had an anterior apprehension sign positive for pain and apprehension [124]. In a study of arthroscopic and open stabilization, three patients in the arthroscopic group had a positive sulcus sign, while no patients in the open group demonstrated a sulcus sign [124]. In a study of arthroscopic and open stabilization, 13 patients in the arthroscopic group reported feeling instability with sports, 15 reported instability with activities of daily living, and 2 reported awakening because of instability during sleep [124]. In a study of arthroscopic and open stabilization, all 20 patients in the open group had complaints consistent with instability associated with sports and activities of daily living, and no patients reported any symptoms in their sleep [124].

Patients with multidirectional instability demonstrate painful, excessive translation of the humeral head anteriorly, inferiorly, and posteriorly on physical examination [91]. Patients with posterior instability demonstrate painful, excessive translation posteriorly and often inferiorly but not anteriorly [91]. The diagnosis of anterior-inferior glenohumeral instability is made on the basis of a combination of signs and symptoms: (1) the patient’s description of shoulder dislocation or a sensation of looseness and slipping, (2) pain or apprehension, or both, on anterior-inferior instability tests, (3) radiographic evidence of glenohumeral instability, and (4) findings during the arthroscopic operation that documented anterior-inferior glenohumeral instability [91].

The recurrence of instability was considered a failure if it involved any postoperative dislocation or any subjective complaint of occasional to frequent subluxation [98]. The recurrence of instability as determined by either a subjective sense of subluxation or objective documentation of dislocation was considered a failure [117]. In a review of nonsurgical management, the variability in recurrent instability as an outcome may depend on whether authors defined it as a recurrent frank dislocation, apprehension on physical examination or self-reported subluxation [113]. In a review of nonsurgical management, male gender was found to be a predictor of recurrence, though this could have occurred if the majority of young patients were male, as younger age was also found to be a predictor of recurrence [113]. In a review of nonsurgical management, the association between a concurrent fracture and older age confers protection against recurrent dislocation [113]. In a review of nonsurgical management, younger age is associated with activity level or sport [113]. In a review of nonsurgical management, most recurrences are thought to occur within the first 2 years [113].

In a study of arthroscopic treatment for anterior-inferior instability, the inclusion criterion was a preoperative diagnosis confirmed at the time of the arthroscopic operation [91]. In a study of arthroscopic treatment for anterior-inferior instability, exclusion criteria included multidirectional instability, posterior instability, a prior operation for instability, and repair of a full-thickness rotator-cuff tear [91]. In a study of arthroscopic treatment for anterior-inferior instability, patients with multidirectional instability demonstrated painful, excessive translation of the humeral head anteriorly, inferiorly, and posteriorly on physical examination [91]. In a study of arthroscopic treatment for anterior-inferior instability, patients with posterior instability demonstrated painful, excessive translation posteriorly and often inferiorly but not anteriorly [91]. In a study of arthroscopic treatment for anterior-inferior instability, thirty-one patients who were receiving Workers’ Compensation were excluded because of various issues that adversely affected the outcome [91]. In a study of arthroscopic treatment for anterior-inferior instability, Misamore et al. and other investigators have documented inferior results following shoulder operations in the Workers’ Compensation population [91]. In a study of arthroscopic treatment for anterior-inferior instability, sixty-four patients met the criteria for inclusion [91]. In a study of arthroscopic treatment for anterior-inferior instability, no attempt was made to exclude patients who had particular lesions of the shoulder [91]. In a study of arthroscopic treatment for anterior-inferior instability, each shoulder was evaluated for lesions at the time of the operation, and specific approaches were selected to treat the different lesions that were encountered [91]. In a study of arthroscopic treatment for anterior-inferior instability, the diagnosis was made on the basis of a combination of signs and symptoms: (1) the patient’s description of shoulder dislocation or a sensation of looseness and slipping, (2) pain or apprehension, or both, on anterior-inferior instability tests, (3) radiographic evidence of glenohumeral instability, and (4) findings during the arthroscopic operation that documented anterior-inferior glenohumeral instability [91]. In a study of arthroscopic treatment for anterior-inferior instability, the inclusion criterion was a preoperative diagnosis of anterior-inferior glenohumeral instability that was confirmed at the time of the arthroscopic operation [91]. In a study of arthroscopic treatment for anterior-inferior instability, the exclusion criteria included multidirectional instability (thirty-eight patients), posterior instability (twelve patients), a prior operation for instability (twenty-six patients), and repair of a full-thickness rotator-cuff tear (two patients) [91]. In a study of arthroscopic treatment for anterior-inferior instability, thirty-one patients who were receiving Workers’ Compensation also were excluded because of various issues that adversely affected the outcome [91]. In a study of arthroscopic treatment for anterior-inferior instability, Misamore et al. and other investigators have documented inferior results following shoulder operations in this population [91].

Investigations

Plain radiography: Standard radiographs serve as the initial imaging study for patients with persistent shoulder pain and instability, providing an overview of bony anatomy, humeral head orientation, and initial assessment for bony Bankart and Hill–Sachs lesions [236, 135]. The standard shoulder series includes a true AP view in the scapular plane, an AP view, an axillary view, and a scapular Y view [127]. The axillary view is necessary to evaluate glenohumeral joint instability and determine humeral head position within the glenoid fossa [127]. It may detect occult, locked posterior shoulder dislocation in patients exhibiting a lack of passive external rotation [127]. In a systematic review of posterior shoulder dislocations, 73% of patients had a missed initial diagnosis due to the lack of an axillary view, Y view, or CT imaging [135]. Of the 150 patients with missed initial diagnoses, 98% had only AP or lateral views [135]. When axillary or Y-view radiographs were subsequently obtained, the diagnosis of posterior dislocation was confirmed in 100% of patients [135]. In patients unable to abduct the arm due to injury acuity, a scapular "Y" view must be obtained to evaluate the relationship of the humeral head to the glenoid [135]. Specific views are indicated for targeted pathology: the Stryker Notch view evaluates Hill–Sachs lesions after dislocation, the West Point view evaluates anterior glenoid bone loss, and the apical oblique view evaluates glenoid rim fracture in instability [127]. The axillary view taken with the arm in the functional position of elevation is referred to as the "truth view" because it demonstrates glenohumeral relationships in that position [31]. This standardized view can show posterior subluxation or "functional decentering" that is not evident in images taken with the arm at the side [31]. Radiographs do not accurately measure glenoid bone loss in anterior shoulder instability [290]. Standardized plain films are almost always sufficient to garner the information needed for shoulder care, helping establish the diagnosis, determine pathoanatomy severity, assist in surgical planning, and illustrate the condition to the patient [31].

CT: CT imaging is frequently used to assess for bony lesions in recurrent instability cases [116]. 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 [127]. CT and MRI (2D or 3D) accurately measure glenoid bone loss in anterior shoulder instability [290]. Three-dimensional imaging serves as an integral component of the evaluation for accurate characterization of glenoid and humeral bone loss [283]. CT imaging proved to be more important than MRI for glenoid defects in recurrent anterior shoulder instability [289]. CT scans may offer increased precision in the measurement of glenoid version, but this precision does not necessarily improve the quality of surgery or clinical outcome [31]. CT scans have the disadvantage of being taken with the arm in the adducted position, unlike the axillary truth view [31].

MRI: MRI is useful to identify osteonecrosis of the humeral head, bone tumours, labral tears, and rotator cuff tears [95]. MRI is the modality of choice for evaluating the rotator cuff, biceps, and subacromial/subdeltoid bursa [116]. T1-weighted MRI can reveal Hill–Sachs lesions and is often used with MR arthrograms to provide a more detailed picture of joint surfaces [116]. T2-weighted MRI provides better visualization of full-thickness rotator cuff tears [116]. Magnetic resonance accuracy in identifying labral and rotator cuff tears ranges from 70% to 100% [103]. Capsular injury is commonly seen in magnetic resonance imaging of patients with anterior shoulder instability [254]. Patients who undergo MRI greater than 6 months from the time of primary shoulder dislocation demonstrate a greater incidence and severity of intra-articular pathology including SLAP tears, posterior labral tears, and anterior glenoid cartilage damage [28]. Patients who undergo MRI greater than 6 months from the time of primary or initial shoulder dislocation had significantly more recurrent shoulder instability events [255]. Routine MRI has similar diagnostic value to MR arthrogram for measuring labral tear extent up to approximately 2 weeks postacute shoulder dislocation [275]. After approximately 2 weeks postacute shoulder dislocation, routine MRI significantly loses accuracy and precision for measuring labral tear extent compared to MR arthrogram [275]. MRI is able to reliably diagnose and predict the structural soft tissue damage associated with chronic traumatic sternoclavicular joint instability [264]. In patients with suspected posterior glenohumeral instability, imaging of the affected shoulder can show abnormalities of the bone, labrum, and joint capsule [282]. The superior-capsular elongation and its diagnostic criteria of measurements by MR arthrography can serve as references for diagnosing atraumatic posteroinferior shoulder instability [288].

Magnetic resonance arthrography: Magnetic resonance arthrography has been firmly established as the imaging modality of choice for demonstrating specific soft tissue abnormalities associated with glenohumeral instability [236]. MR arthrography is considered the benchmark for evaluation of labral tears [116]. MR arthrography increases both sensitivity and specificity in detecting injuries to the capsulolabral–ligamentous complex compared to traditional MRI [103]. In a meta-analysis of 4,667 shoulders, MRA had a sensitivity of 88% and specificity of 93% for glenoid labral lesions, compared to MRI sensitivity of 76% and specificity of 87% [103]. MR arthrogram outperforms standard MRI for labral tear diagnosis, particularly as time from dislocation increases [260]. Magnetic resonance angiography has a high sensitivity when used to identify associated injuries in shoulder dislocation [257]. In 8 patients (13%) undergoing comparison of MRA and arthroscopy for anterior shoulder dislocations, arthroscopy identified an additional injury not seen on MRA [257]. Identification of critical radiographic variables on magnetic resonance arthrography assists in the accurate diagnosis and management of clinically significant posterior shoulder instability [249]. MR arthrography is identified as the main tool in diagnosing shoulder instability injuries [270]. Abduction and external rotation (ABER) positioning is utilized to increase the sensitivity and specificity for detecting anteroinferior labroligamentous injury [103]. The sensitivity of MRA with the ABER position for detecting anteroinferior labral lesions is significantly higher than that of MRA in the neutral position [103]. MRA with the ABER position is more effective than neutral position MRA in identifying Perthes lesions [103]. MRAs can demonstrate a patulous capsule on coronal, sagittal, and axial imaging in patients with multidirectional instability [103]. Glenoid dysplasia, increased capsular cross-sectional area, and increased glenoid retroversion have been found to be associated with increased posterior labral tears and symptomatic instability [103]. Substantial variability was observed in the scoring of important elements in the radiological report for the evaluation of anterior shoulder instability, regardless of modality [277].

Ultrasonography: Ultrasonography is a simple and accurate test for identifying rotator cuff tears and calcific tendinitis [95]. Ultrasonography is a low-cost alternative to MRI and arthrography for evaluating both skeletal and soft-tissue structures of the shoulder [116]. Ultrasonography can provide immediate, real-time visualization of the rotator cuff, biceps tendon, and calcific deposits [116]. The most commonly performed joint examination using ultrasonography is the shoulder examination [93]. 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 [116]. Accuracy of shoulder ultrasonography depends on the skill of the scanner operator and an awareness of pitfalls encountered [93].

Other Considerations: Advanced imaging modalities are essential for identifying associated lesions in shoulder instability [263]. In the setting of ongoing pain or instability after traumatic inferior shoulder dislocation, further imaging should be performed [271]. Posterior instability tests showed high sensitivity but low specificity, leading to over-diagnosis in rugby players [41]. The diagnosis of a stiff shoulder depends on awareness of the problem, with history and physical examination being paramount [30].

Treatment

Non-Operative

Nonoperative management of anterior shoulder instability carries a high risk of recurrent instability and pain at long-term follow-up, with poor outcomes observed in 17-year follow-up data [22]. Primary non-operative management is a prominent risk factor for recurrence [163]. However, nonoperative treatment remains a preferred strategy when the likelihood of recurrence is low or when an informed patient has an aversion to surgery [207]. It is specifically favoured for first-time dislocators, particularly those with multi-directional instability, soft-tissue laxity, older patients, or younger patients not engaged in overhead activities [214]. Recent studies continue to demonstrate a role for nonoperative treatment in the successful long-term management of anterior glenohumeral instability [54]. For displaced anterior glenoid rim fractures without dislocation in elderly patients, nonoperative management provides satisfactory functional and radiographic outcomes with no evidence of subsequent instability [221].

For patients choosing nonsurgical treatment for a first-time dislocation, the shoulder is immobilized until pain resolves, followed by early motion [119]. Physical therapy focuses on regaining motion, strengthening the rotator cuff and periscapular muscles, and proprioceptive training [119]. While initial immobilization in external rotation may better reduce the torn labrum to the anterior-inferior glenoid [119], meta-analyses show no benefit in recurrence rates or validated outcomes with external rotation bracing compared to other methods [119]. Specifically, external rotation immobilization offers no obvious clinical advantage over internal rotation in a traditional sling for younger patients with first-time dislocation [229]. Compliance with external rotation braces is poor in younger age groups, as patients often feel better after one week, making three-to-four-week sling use challenging [229].

Nonsurgical treatment is the initial approach for posterior instability, involving immobilization in neutral rotation with the elbow in adduction for 1 to 2 weeks followed by therapy [40]. For patients with minimal symptoms of posterior instability, nonsurgical treatment including physical therapy, activity modification, and anti-inflammatory agents should be considered [162]. Nonsurgical treatment is the treatment of choice for voluntary posterior dislocators, as surgical intervention is contraindicated due to an extremely high failure rate [162]. However, long-term follow-up demonstrates that nearly 40% of patients treated non-operatively for posterior shoulder instability eventually require surgery [23]. Nonoperative treatment is commonly unsuccessful in active patients with posterior instability, and surgical stabilization can be considered in patients who do not respond [213].

Multidirectional instability should be initially treated with conservative treatment [169]. The goal is to restore joint stability and decrease pain, accomplished through nonoperative means with physical therapy, patient education, and avoidance of aggravating activities for most patients [167]. Patients with multidirectional instability often manifest as bilateral shoulder subluxations in a susceptible patient and should be treated with an extended course of physical therapy [43]. In contrast, nonoperative management of perilunate fracture-dislocations results in progressive arthritis and poor long-term outcomes [218]. The cornerstone of treatment for instability remains immobilization followed by rehabilitation, though the optimal nonoperative treatment of a shoulder dislocation is still unknown and deserves further study [43].

Operative

Indications: Surgical treatments are more effective than conservative options in preventing recurrent instability in adolescents and young adults under 40 years of age with first-time anterior shoulder dislocation [165]. Arthroscopic stabilization of traumatic, first-time anterior shoulder dislocations is an effective and safe treatment that significantly reduces the recurrence rate in young athletes compared with conventional nonoperative treatment [151]. Early arthroscopic stabilization by anterior capsule-labrum reinsertion after initial anterior shoulder dislocation is associated with a low 10-year recurrence rate of 35% compared to non-operative management [208]. First-time dislocators who underwent surgical stabilization had better outcomes than recurrent dislocators regarding the need for additional surgery for recurrent dislocation (7% versus 32%) [119]. Physicians must maintain a sense of urgency toward surgical treatment, particularly in young, high-demand athletes with persistent instability; while it is not necessary to fix the shoulder after the first anterior dislocation, it should definitely be done before the second [210]. Early arthroscopic stabilization can decrease recurrence rates and improve functional outcomes in young (>25 years old), high-risk patients with first-time anterior dislocations and an associated Bankart lesion [43]. In the absence of severe capsular laxity or bony deficiency, arthroscopic stabilization is considered a first-line therapy in recurrent anterior and posterior instability of traumatic origin [43]. Patients aged >50 years with anterior shoulder instability have a decreased risk of recurrent dislocation after operative treatment compared with non-operative treatment [1]. While there are indications that quality of life is better in the stabilized group, definitive conclusions on how to treat first-time traumatic dislocations require further waiting [194].

Surgical Approach / Technique: Arthroscopic Bankart repair has become common because it allows excellent visualization of the entire joint and is minimally invasive; it is now the treatment of choice among new surgeons in the United States [119]. In a double-blind, randomized clinical trial evaluating arthroscopic Bankart repair versus sham surgery, patients with a first-time dislocation had decreased recurrence of instability and improved outcome scores after repair [119]. A systematic review of only level I and II studies demonstrated decreased recurrence of instability following arthroscopic Bankart repair when compared with physical therapy and sham surgery, both together and in isolation [119]. The patients in the repair group were noted to have one-fifth the rate of recurrent instability and improved Western Ontario Shoulder Instability Index (WOSI) scores [119]. Surgery resulted in lower costs and higher patient satisfaction, but overall outcomes were related to shoulder stability, not necessarily the surgery itself [119]. Patients in the repair group also had a higher rate of return to contact sports [119].

Most shoulder specialists consider arthroscopic anterior stabilization as the first-line treatment for recurrent glenohumeral instability [110]. Successful arthroscopic management of posttraumatic unidirectional instability must independently address several coexisting pathologic entities: the Bankart lesion (labral detachment), anterior labroligamentous periosteal sleeve avulsion (ALPSA lesion), HAGL lesion, and capsular attenuation [110]. An anteroinferior Bankart labral detachment is present in the majority of recurrently unstable shoulders after an initial traumatic dislocation [110]. Most of these shoulders have a certain degree of coexisting capsular redundancy at the time of surgery [110]. As the acute dislocation evolves into chronic, recurrent instability, further capsular attenuation is likely to occur [110]. In this setting, isolated labral reattachment is usually inadequate and results in failure [110]. Patients with more than two or three instability episodes and/or significant capsular attenuation require capsular shifting in conjunction with Bankart repair to regain and maintain stability [110].

With advances in suture anchor technology, clinical outcomes have improved significantly [110]. Arthroscopic techniques have the advantage of approximating the methods routinely used during open shoulder stabilization [110]. Anchors can be placed more precisely at the margin of the articular surface and the glenoid neck to anatomically recreate the labrocapsuloligamentous origin [110]. McEleney et al. demonstrated that suture anchor techniques are biomechanically the strongest of eight repair techniques (including single and multiple tacks, sutures, and transglenoid sutures) in a canine Bankart model [110]. Early clinical outcomes of suture anchor repair were promising and realized similar results to open stabilization, even in high demand athletes, with redislocation rates of 6% and an 85% return to previous level of sporting activity [110]. Over a mean follow-up period of 46 months, the overall recurrence rate was 10%, while in 90% of cases the subjective outcome measures were graded as good to excellent [110]. Recurrent dislocation occurred in two of 18 athletes involved in collision sports at 22 and 60 months postoperatively after return to sport [110]. The variables associated with successful outcomes were use of a low anterior portal (5 o'clock position), repair of tear extension into the superior labrum, and placement of the suture anchors 2 mm in on the glenoid face articular cartilage [110].

Advanced arthroscopic techniques include double-row labral repair, postero-inferior capsulolabral repair, and remplissage [110]. While arthroscopic single row techniques are commonly employed for primary surgical management in patients with capsulolabral avulsions, recent cadaveric studies have shown that double-row fixation may better restore normal anatomy [110]. These techniques may be indicated in the setting of small (<20%) bony Bankart lesions as well [110]. Arthroscopic approaches to shoulder stabilization may benefit from use of these advanced techniques in the clinical setting of the high-risk male athlete; however, their superiority over traditional techniques has not been evaluated in comparative clinical studies [110].

Open Bankart repair has historically provided good results for shoulder stability [119]. The procedure requires transection, or splitting, of the subscapularis tendon, and mild losses in forward elevation and external rotation can occur, typically between 8° and 10° [119]. In a series of 49 patients, including 31 elite rugby players, 16% had recurrence of instability during the 26-year follow-up period after open Bankart repair [119]. Of these patients, 65% had radiographic evidence of arthritis at final follow-up, most of which was considered mild, and 80% reported being pain free [119]. Ninety-four percent of patients resumed athletic activity, 75% of those at their original level of competition [119]. In a randomized clinical trial comparing open versus arthroscopic Bankart repair, an increased rate of recurrence was noted after arthroscopic repair (23% versus 11% in open repair) [119]. The highest rate of recurrence was noted in males younger than 25 years with Hill-Sachs lesions [119]. In a trial of isolated Bankart lesions randomized to arthroscopic versus open repair, improved Disability of the Arm, Shoulder and Hand scores were noted in the arthroscopic group, with no substantial difference in recurrence noted [119]. A systematic review of more recent meta-analyses demonstrated no difference in recurrence between the two techniques, but noted that the analyses performed before 2007 favored open surgery with regard to recurrence rates [119].

Open Bankart repair was previously considered the gold standard for treatment of traumatic anterior shoulder instability with recurrence rates of typically less than 10% [157]. The advantages of open surgery include a more secure repair, a greater ability to reduce capsular redundancy, and achieving adequate tension of the capsuloligamentous complex, which may be challenging in chronic instability cases [157]. The known disadvantages of open Bankart repair include restriction of glenohumeral motion following surgery, particularly external rotation, which may lead to secondary arthritis and muscle weakness [157]. As a result of the potential morbidity involved in open Bankart repair and improvement in implant and instrumentation, arthroscopic Bankart repair has supplanted open repair as the treatment of choice for most common anterior instability injuries [157]. An assessment of the 2004 to 2009 U.S. national insurance database showed that arthroscopic Bankart repairs accounted for 84% of shoulder stabilization surgeries [157]. Arthroscopic Bankart repair can minimize much of the morbidity associated with open surgery such as subscapularis weakness with possible rupture and arthrofibrosis [157]. Modern techniques utilizing suture anchors and capsular plication have achieved recurrence rates similar to open repairs of 8% to 11% in selected patients [157].

Implant Selection: Patients achieved good-to-excellent functional outcomes, supporting the efficacy of knotless anchors as an alternative to knot-tying anchors for arthroscopic anterior labral repair of recurrent anterior shoulder dislocation [143].

Alignment / Balancing Strategy: The overall goal of surgical treatment for anterior shoulder instability is to restore glenohumeral stability through either repair of the capsuloligamentous complex and/or enhanced stability through bony augmentation in cases of significant anterior glenoid deficiency [157]. The success of treating anterior glenohumeral instability relies on multiple factors, including glenoid bone loss [140]. 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%) [201]. Indications for the Latarjet were humeral and glenoid bone loss, duration of symptoms, number of dislocations, and revision stabilizations [64]. Free bone block procedures are considered safe and clinically effective for the management of anterior shoulder instability with glenoid bone loss [147].

Other Considerations: Patient selection, including careful consideration of patient and injury characteristics (i.e., chronicity, number of dislocations, capsular insufficiency, and bony deficiencies), is paramount to achieving success with arthroscopic surgery [157]. It is important to remember that while arthroscopic Bankart repair is suitable for most patients with anterior instability, there are certain factors that should prompt consideration of an open or bony procedure [157]. Early surgical stabilization after traumatic anterior shoulder instability injuries has been shown to reduce the frequency of recurrent instability and improve functional outcome in young individuals engaged in physical activities [157]. In the interim, surgical soft-tissue stabilization might be more aggressively indicated in cases of primary shoulder dislocation, whereas recurrent instability with bone loss should be referred to experienced high-volume specialists [56].

First-time dislocators may have more bone loss than originally thought, with one prospective military study reporting that first-time dislocators had an average glenoid bone loss of 6.8% at the time of initial injury [119]. This study demonstrates a long-term benefit in overall shoulder stability and functional outcome in high-risk patients who have undergone ABR for first-time anterior dislocation [13]. Arthroscopic stabilisation resulted in a significantly lower rate of recurrent instability compared with non-operative management in young, active patients, particularly military cadets [62]. There is no significant difference of recurrence rate and functional outcome between the surgical group and the nonoperative groups with recurrent dislocation undergoing arthroscopic stabilization at the final follow up [46]. Recurrent shoulder subluxation also displayed similar functional outcomes and failure rate after arthroscopic stabilization procedures as recurrent dislocation [52].

When patients were treated with an open or arthroscopic procedure for acute irreducible shoulder dislocations, recurrence was low, with none reporting recurrent dislocation in limited follow-up [190]. Athletes may return to play after a shoulder dislocation or after stabilization surgery when strength and mobility have normalized [43]. Recent evidence also suggests that participation in a contact sport is not a contraindication to arthroscopic stabilization [43]. Proper mobilization of capsulolabral tissue, placement of an accessory portal low and lateral to aid in placement of suture anchors, and addressing the associated capsular injury are critical to results of arthroscopic surgery using modern suture-anchor techniques and shoulder-specific instrumentation have yielded results comparable to those of open surgery [43]. Many believe that open surgery has a slightly lower recurrence rate at the cost of some loss of external rotation [43]. Open surgery should also be strongly considered in cases of severe capsular laxity or deficiency, glenoid or humeral bone loss, avulsion of the capsule from the humeral side, documented connect

Complications

Recurrence and Instability

Risk Factors: A history of multiple instability episodes prior to presentation is the greatest predictor of recurrent instability and failure of nonoperative treatment [1]. Multivariate regression identified an increased risk of recurrence associated with having multiple dislocations (P .03; OR, 2.4; 95% CI, 1.3 to 43.3) [199]. Younger patients, particularly those ≤15 and 16 to 20 years of age, were more likely to have experienced multiple instability events at the time of initial evaluation, require surgery, and experience recurrent instability compared with older patients [66]. In the twelve to twenty-two-year age-group, recurrent dislocation occurred in ten of fourteen shoulders that had had the initial dislocation after trivial trauma [231]. Preoperative risk factors for recurrent anterior glenohumeral instability following a primary Latarjet procedure included history of bilateral shoulder instability and atraumatic mechanism of dislocation [219]. Patients undergoing open stabilization for posterior shoulder instability were more likely to have a higher number of instability events prior to surgery and a history of previous arthroscopic stabilization [250].

Incidence and Outcomes: The recurrence rate for patients under twenty years of age with primary dislocation was 83% [8]. Recurrent instability occurred in 2 of 26 patients who had 2 to 5 preoperative instability episodes and 5 of 10 patients who had more than 5 episodes [199]. Recurrence of posterior instability occurred in 5 cases (18%), all of which were recurrent subluxations with no dislocations [7]. Overall recurrent instability occurred in 100 of 1658 cases (6.0%±1.2%) following open coracoid transfer procedures [244]. Recurrent dislocation occurred in 46 of 1658 cases (2.8%±0.8%) and recurrent subluxation occurred in 54 of 1658 cases (3.3%±0.9%) following open coracoid transfer procedures [244]. Instability-related complications occurred only in the capsulabral group, and the incidence increased with time [181]. Recurrence rate and complications were noted for subluxation and dislocation in a multicentric prospective study on gender and recurrent shoulder instability [235].

Surgical Timing and Technique: Immediate surgical stabilization following a 1st time dislocation significantly diminishes the risk of recurrent dislocation in comparison to those who undergo surgery following two dislocation events [29]. Patients with first-time dislocations had lower postoperative instability rates and reoperation rates compared with patients with recurrent dislocations before surgery [15]. While younger age and a higher number of preoperative dislocations were potential risk factors for recurrence, a shorter interval between the first dislocation and surgery was associated with improved clinical outcomes [252]. In the 14- to 17-year-old adolescents with traumatic primary dislocations in whom imaging studies show Bankart lesions, there is an indication for prophylactic stabilizing surgery at the time of the initial injury [69]. The study demonstrated low rates of recurrent instability in patients with Ehlers-Danlos syndrome treated with open capsular shift and Achilles allograft augmentation [16].

Etiology of Recurrence: Of the 46 recurrent dislocations following open coracoid transfer, 17 were as a result of an additional traumatic episode of varying severity [244]. Of the 46 recurrent dislocations following open coracoid transfer, 12 were ascribed to a technical error [244]. Of the 46 recurrent dislocations following open coracoid transfer, 1 was attributed to the surgery having been done in a patient with multidirectional instability [244]. Recurrent instability might result from new trauma even if a long time has passed since the open modified inferior capsular shift procedure [232]. Factors associated with poor results in open revision stabilization surgery include an atraumatic cause of failure, voluntary dislocations, and multiple prior stabilization attempts [234].

Arthropathy and Structural Pathology

The natural history of the first time shoulder dislocations is bound up with arthropathy [53].

Other Considerations

Patients with a history of shoulder instability or replacement are at risk for shoulder dislocation during common elbow and hand procedures [217]. Short-term outcomes for pre-shaped allograft glenoid reconstruction are reassuring, but more research is needed to study long-term graft union, graft resorption, glenohumeral arthritis, and patient outcomes including recurrent shoulder instability [65].

Recovery

Prognostic Factors and Natural History: Age at the time of initial dislocation is the most consistent and significant factor influencing prognosis in shoulder dislocation [8]. Specifically, age at the time of primary shoulder dislocation is the most significant prognostic factor for the rate of recurrence [292]. The mean age for patients with primary dislocation was forty-eight years, while the mean age for patients with recurrent dislocation was twenty-three years [8]. Characteristics related to a history of instability, including age <20 years at first instability episode, larger number of dislocations, and ≥2 years between first dislocation and surgery, are risk factors for the development of an off-track Hill-Sachs lesion [11]. The natural history of first-time shoulder dislocations is bound up with arthropathy [53].

Outcomes by Dislocation History: Recurrent shoulder subluxation displayed similar functional outcomes and failure rate after arthroscopic stabilization procedures as recurrent dislocation [52]. The number of episodes of dislocation before surgery and the delayed surgical intervention did not increase the recurrent anterior shoulder instability rates postoperatively [272]. In a high-demand population, there is no significant difference of recurrence rate and functional outcome between the surgical group and the nonoperative groups with recurrent dislocation undergoing arthroscopic stabilization at the final follow up [46]. The most significant predictors for optimal observed outcome following surgical treatment of anterior shoulder instability included shorter time to presentation and history of subluxations over frank dislocations pre-operatively [267].

Operative Outcomes and Complications: The 1-year outcomes in a prospective study suggest superiority of operative over non-operative treatment for posterior shoulder instability [61]. Recurrence of posterior instability occurred in 5 cases (18%) following all-arthroscopic posterior bone block procedure; all had recurrent subluxations, with no dislocations [7]. The authors followed up a patient with chronic locked posterior shoulder dislocation treated with arthroscopically assisted reduction for 6 months and found no recurrent dislocation or instability [3]. The study demonstrated low rates of recurrent instability and improved clinical outcomes in a high-risk population with Ehlers-Danlos Syndrome treated with open capsular shift with Achilles allograft augmentation [16]. Surgical stabilization appears to restore the rate and timing of instability to that of players with no prior history of instability in professional football players [278]. The long-term data suggest that the benefits of the Latarjet procedure are durable, and it should be considered as a viable and reliable treatment option for anterior glenohumeral instability [222]. The Latarjet procedure provides excellent long-term outcomes in the treatment of recurrent anterior glenohumeral instability [227]. 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 arthroscopic and open Bankart repair approaches [68]. Short-term outcomes for pre-shaped allograft for glenoid reconstruction are reassuring, but more research is needed to study long-term graft union, graft resorption, glenohumeral arthritis, and patient outcomes including recurrent shoulder instability [65].

Key Evidence

• [L3] A history of multiple instability episodes prior to presentation was the greatest predictor of recurrent instability and failure of nonoperative treatment and progression to surgery. [1] (10.1016/j.asmr.2023.03.014)
• [L4] Stabilization after the first-time dislocation achieves better clinical and radiological outcomes than after multiple dislocations. [2] (10.1177/0363546516675145)
• [Paper] The authors followed up the patient for 6 months and found no recurrent dislocation or instability. [3] (10.1016/j.eats.2019.03.015)
• [L4] No significant differences in outcomes or recurrence rates were found between early and late dislocations. [4] (10.1016/j.jse.2016.12.073)
• [L5] Shoulder instability is a phenomenon with a variety of clinical presentations, and its complex nature has until recently been poorly understood. [5] (10.1016/j.cuor.2004.04.002)
• [L2] [6] (10.1002/ksa.70336)
• [L4] Recurrence of posterior instability occurred in 5 cases (18%); all had recurrent subluxations, with no dislocations. [7] (10.1016/j.jseint.2025.101473)
• [L4] [8] (10.2106/00004623-195638050-00001)
• [L5] The ABC classification distinguishes three groups of posterior glenohumeral instability with two different subtypes based on the pathomechanical type of instability and the current standard of treatment. [9] (10.1007/s11678-017-0404-6)
• [L4] Some risk of recurrent instability is part of the natural history of anterior shoulder dislocation. [10] (10.1016/j.jor.2015.01.030)
• [L3] Characteristics related to a history of instability (age <20 years at first instability episode, larger number of dislocations, ≥2 years between first dislocation and surgery) were found to be risk factors for the development of an off-track HS lesion. [11] (10.1177/23259671231213858)
• [L2] Future studies are needed to ascertain long-term outcomes of surgical stabilization based on preoperative dislocation events. [12] (10.1016/j.jse.2017.10.041)
• [L1] This study demonstrates a long-term benefit in overall shoulder stability and functional outcome in high-risk patients who have undergone ABR for first-time anterior dislocation. [13] (10.2106/jbjs.19.00858)
• [L3] Patients with first-time dislocations had lower postoperative instability rates and reoperation rates when compared with patients with recurrent dislocations before surgery. [15] (10.1177/0363546517698692)
• [L4] The study demonstrated low rates of recurrent instability and improved clinical outcomes in this high-risk population. [16] (10.1016/j.jse.2026.05.024)
• [L2] Posterior instability represents 10% of all instability events. [17] (10.1177/0363546513501508)
• [L2] Anterior instability outcomes in this matched cohort were superior in all domains versus posterior instability after arthroscopic stabilization. [18] (10.1177/0363546518819199)
• [L5] Recurrent posterior shoulder instability is an uncommon condition often unrecognized, leading to incorrect diagnoses and delays. [19] (10.5435/00124635-200608000-00004)
• [L5] Even patients who have experienced a single episode of dislocation may go on to develop long-term sequelae. [20] (10.1308/003588409x359123)
• [L4] Nonoperative treatment was successful in this patient without subsequent instability or re-dislocation. [21] (10.1007/s00402-007-0546-x)
• [L4] At long-term follow-up of 17 years, a high rate of poor outcomes was observed following nonoperative management of anterior shoulder instability. [22] (10.1016/j.jse.2021.07.016)
• [L3] Long-term follow-up demonstrates that nearly 40% of patients treated non-operatively for posterior shoulder instability eventually require surgery. [23] (10.1177/2325967118s00098)
• [L4] For patients with a high risk for recurrent instability, stabilization surgery would help prevent subsequent dislocation events and minimize health care costs. [24] (10.1016/j.jseint.2020.04.023)
• [L4] The choice of open reduction and stabilization technique for chronic anterior dislocation was highly variable and led to a wide variation in reported outcomes with a high number of complications such as resubluxation and early arthrosis. [25] (10.1016/j.jse.2020.10.010)
• [L4] Recurrent instability requiring capsular reconstruction seems to be more prevalent in patients with a previous history of shoulder dislocation. [26] (10.1016/j.jse.2009.07.062)
• [L3] The risks of revision stabilization and postoperative dislocation were most influenced by young age (under 20 years) and having had 3 or more preoperative dislocations. [27] (10.1177/0363546513492952)
• [L3] Patients who undergo MRI greater than 6 months from the time of primary shoulder dislocation demonstrate a greater incidence and severity of intra‐articular pathology including SLAP tears, posterior labral tears and anterior glenoid cartilage damage. [28] (10.1177/2325967117s00360)
• [L3] Immediate surgical stabilization following a 1st time dislocation significantly diminishes the risk of recurrent dislocation in comparison to those who undergo surgery following two dislocation events. [29] (10.1177/2325967121s00713)
• [L4] Posterior shoulder dislocation is a rare and challenging injury with varied mechanisms of trauma that complicate diagnosis. [32] (10.5435/jaaos-22-03-145)
• [L3] Variations in the criteria used for the diagnosis of multidirectional instability significantly affect the distribution of patients with that diagnosis. [33] (10.2106/00004623-200311000-00011)
• [L4] Clustering of thorough history and physical examination findings, including the aforementioned tests, may identify those with posterior glenohumeral instability and assist in developing management strategies. [34] (10.1177/1941738117752306)
• [L2] Detailed and specific information about prognosis is critical in the management of a first-time anterior shoulder dislocation. [35] (10.1016/j.jse.2010.10.037)
• [Paper] HAGL lesions are a rare and underdiagnosed cause of anterior shoulder instability that can lead to recurrent dislocations if unaddressed. [36] (10.1016/j.eats.2020.10.053)
• [L5] [38] (10.1177/17585732251320070)
• [L3] Posterior instability tests showed high sensitivity but low specificity, leading to over-diagnosis. [41] (10.1177/17585732221092025)
• [L3] The age of the patient at the time of initial dislocation is the most important prognostic factor regarding recurrence, with the highest rate found in patients 30 years and younger. [42] (10.1007/bf00431367)
• [L3] In addition, there is no significant difference of recurrence rate and functional outcome between the surgical group and the nonoperative groups with recurrent dislocation undergoing arthroscopic stabilization at the final follow up. [46] (10.1016/j.fjmd.2010.12.010)
• [L5] Patients who present with multiple recurrences, more than 2 preoperative dislocations, a duration of instability symptoms of more than 6 months, and identified off-track Hill-Sachs lesions may not be ideal candidates for arthroscopic instability repair due to higher failure rates. [48] (10.1016/j.arthro.2018.06.021)
• [L4] Solitary, traumatic, anterior dislocation and occasional, traumatic, anterior dislocation were the most frequently observed in our cohort. [49] (10.1016/j.jse.2018.08.014)
• [L2] Arthroscopic surgery is an acceptable treatment if recurrent instability occurs consistently at ≤23.8%. [50] (10.1177/2325967115618161)
• [L5] Proper evaluation of bone loss best determines shoulder instability surgical indications and outcomes. [51] (10.1016/j.arthro.2021.01.004)
• [L4] Recurrent shoulder subluxation also displayed similar functional outcomes and failure rate after arthroscopic stabilization procedures as recurrent dislocation. [52] (10.1016/j.arthro.2016.08.019)
• [Abstract] The natural history of the first time shoulder dislocations is bound up with arthropathy. [53] (10.1016/j.jse.2007.02.100)
• [L4] Recent studies continue to demonstrate a role for nonoperative treatment in the successful long-term management of anterior glenohumeral instability. [54] (10.1007/s12178-017-9432-5)
• [L5] In the interim, surgical soft-tissue stabilization might be more aggressively indicated in cases of primary shoulder dislocation, whereas recurrent instability with bone loss should be referred to experienced high-volume specialists. [56] (10.1016/j.arthro.2016.06.032)
• [L4] Sensitive patient selection for arthroscopic Bankart repair is recommended especially in patients with more than five dislocations. [57] (10.1186/2047-783x-14-1-18)
• [L5] The essential statements on which the experts reached consensus included the following: A history of multiple dislocations and failed soft-tissue surgery should make surgeons consider the possibility of an associated bone deficit. [60] (10.1016/j.arthro.2020.12.237)
• [L3] The 1-year outcomes in this prospective study suggest superiority of operative over non-operative treatment for posterior shoulder instability. [61] (10.1016/j.otsr.2017.08.004)
• [L2] Arthroscopic stabilisation resulted in a significantly lower rate of recurrent instability compared with non-operative management in young, active patients, particularly military cadets. [62] (10.1136/jisakos-2016-000091)
• [L4] The glenohumeral joint is inherently predisposed to instability by its bony architecture. [63] (10.1007/s12178-011-9092-9)
• [L2] Indications for the Latarjet were humeral and glenoid bone loss, duration of symptoms, number of dislocations, and revision stabilizations. [64] (10.1016/j.arthro.2019.02.035)
• [Paper] Short-term outcomes are reassuring, but more research is needed to study long-term graft union, graft resorption, glenohumeral arthritis, and patient outcomes including recurrent shoulder instability. [65] (10.1016/j.eats.2017.10.007)
• [L3] Younger patients, particularly those ≤15 and 16 to 20 years of age, were more likely to have experienced multiple instability events at the time of initial evaluation, require surgery, and experience recurrent instability compared with older patients. [66] (10.1177/0363546519886861)
• [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. [68] (10.1177/03635465261443999)
• [L4] In the 14- to 17-year-old adolescents with traumatic primary dislocations in whom imaging studies show Bankart lesions, there is an indication for prophylactic stabilizing surgery at the time of the initial injury. [69] (10.1067/mse.2000.108385)
• [L5] The system categorizes instability based on frequency, aetiology, direction, and severity. [77] (10.1136/bjsm.2009.071183)
• [L3] [91] (10.2106/00004623-200007000-00011)
• [L4] [98] (10.2106/jbjs.e.00817)
• [L4] Recognition and treatment of GAGL lesions should improve surgical outcomes in patients with recurrent dislocations. [99] (10.1016/j.arthro.2010.06.005)
• [L4] Traumatic shoulder instability in the older patient may result in a wide array of pathologic findings as well as a diversity of clinical presentations. [107] (10.1177/2325967115584318)
• [L3] Extensive labral lesions can occur even in patients with few previous dislocations, and clinical outcomes can be excellent with appropriate treatment. [108] (10.1007/s00167-012-2045-z)
• [L5] Posterior shoulder dislocations occur rarely but are often missed on initial presentation, resulting in ongoing patient discomfort, long-term morbidity and elevated health care costs. [109] (10.1007/s11739-007-0017-y)
• [L1] [113] (10.1016/j.arthro.2016.05.039)
• [L4] In patients with anterior instability, recurrence is 24%, with almost all cases associated with new trauma. [115] (10.1177/2325967126s00536)
• [L4] [117] (10.1016/j.arthro.2008.01.017)
• [L4] Anterior instability is most common among shoulder instability patients, and most patients undergoing shoulder stabilization are in their early 20s or younger. [118] (10.1177/0363546518755752)
• [L4] Posterior shoulder dislocations are less common than anterior dislocations but are more commonly missed. [121] (10.1177/2325967114s00196)
• [L3] Lesions associated with traumatic anterior glenohumeral dislocations are more frequent than expected. [123] (10.1007/s00264-015-2862-z)
• [L3] [124] (10.1177/0095399703258747)
• [L4] Many different diagnostic examinations for assessing shoulder instability are used and a high variety is seen in the use of diagnostic tools. [125] (10.1007/s00402-016-2443-7)
• [L5] [130] (10.1016/j.arthro.2008.05.015)
• [L5] The success of treating anterior glenohumeral instability relies on multiple factors, including glenoid bone loss. [140] (10.1016/j.arthro.2021.09.002)
• [L3] Patients achieved good-to-excellent functional outcomes, supporting the efficacy of knotless anchors as an alternative to knot-tying anchors for arthroscopic anterior labral repair of recurrent anterior shoulder dislocation. [143] (10.1007/s00167-020-06057-7)
• [L4] They are considered safe and clinically effective for the management of anterior shoulder instability with glenoid bone loss. [147] (10.5435/jaaos-d-22-00837)
• [L1] Arthroscopic stabilization of traumatic, first-time anterior shoulder dislocations is an effective and safe treatment that significantly reduces the recurrence rate of shoulder dislocations in young athletes when compared with conventional, nonoperative treatment. [151] (10.1177/03635465020300041801)
• [L2] Primary non-operative management is a prominent risk factor for recurrence of shoulder instability. [163] (10.1136/bjsports-2016-096895)
• [L1] Surgical treatments are more effective than conservative options in preventing recurrent instability in adolescents and young adults under 40 years of age with first-time anterior shoulder dislocation. [165] (10.1016/j.arthro.2025.07.044)
• [Paper] Multidirectional instability should be initially treated with conservative treatment, and newer arthroscopic techniques may now approach the success rates of traditional open treatments. [169] (10.1016/j.csm.2013.07.010)
• [L1] Shoulder instability cannot reliably be classified using the ICD-9 coding system. [175] (10.1016/j.jse.2008.10.005)
• [L3] Instability-related complications occurred only in the capsulabral group, and the incidence increased with time. [181] (10.1177/03635465211029022)
• [L2] The ISIS is highly reliable for grading traumatic anterior instability severity and correlates with the number of prior dislocations and surgical decision-making, but not with patient-reported quality-of-life questionnaires. [184] (10.1177/0363546512470815)
• [L2] The FEDS classification, particularly the frequency and etiology of the patient's shoulder instability, may be helpful in identifying patients with a higher likelihood of undergoing surgical treatment. [185] (10.1177/2325967115607434)
• [L4] When patients were treated with an open or arthroscopic procedure, recurrence was low, with none reporting recurrent dislocation in limited follow-up. [190] (10.1177/23259671221121633)
• [L5] We cannot yet answer this question definitively; while there are indications that quality of life is better in the stabilized group, the authors state we must wait before deciding definitely on how to treat first-time traumatic dislocations. [194] (10.1007/s00167-003-0357-8)
• [L3] Although version alone does not account for the multifactorial nature of instability, it may serve as a complementary anatomical parameter in future clinical risk-stratification models. [196] (10.1186/s12891-026-09594-3)
• [L2] In a substantial number of patients with a long-standing history of instability, classification of lesions was impossible at arthroscopy because of scar tissue formation and advanced degenerative changes in the labroligamentous complex. [197] (10.1148/radiol.2372041429)
• [L4] [199] (10.1016/j.arthro.2013.09.008)
• [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%). [201] (10.2106/jbjs.rvw.26.00033)
• [L3] The Instability Severity Index Score (ISIS) failed to predict recurrent instability in a high percentage of cases, as the score was not significantly different between patients with successful and unsuccessful repairs. [203] (10.1016/j.jse.2014.06.009)
• [L3] Wide-type lesions were correlated with more subluxations and dislocations than other types. [206] (10.1016/j.jse.2016.10.017)
• [L3] In clinical settings where the likelihood of recurrent instability is low after nonoperative care or when an informed patient has an aversion to surgery, nonoperative treatment may be the preferred treatment strategy. [207] (10.1016/j.jse.2011.01.031)
• [L2] Early arthroscopic stabilization by anterior capsule-labrum reinsertion after initial anterior shoulder dislocation is associated with a low 10-year recurrence rate of 35% compared to non-operative management. [208] (10.1016/j.otsr.2015.09.029)
• [L5] Physicians must maintain a sense of urgency toward surgical treatment, particularly in young, high-demand athletes with persistent instability; you don't have to fix the shoulder after the first anterior dislocation, but you should definitely do it before the second! [210] (10.1016/j.arthro.2022.11.014)
• [L4] Nonoperative treatment is commonly unsuccessful in active patients, and surgical stabilization can be considered in patients who do not respond. [213] (10.1177/1941738116672446)
• [L4] Non-operative management is favoured for first-time dislocators, particularly those with multi-directional instability, soft-tissue laxity, older patients, or younger patients not engaged in overhead activities. [214] (10.1302/2058-5241.2.160018)
• [Case_report] Patients with a history of shoulder instability or replacement are at risk for shoulder dislocation during common elbow and hand procedures. [217] (10.1016/j.jse.2020.04.012)
• [L3] Preoperative risk factors included history of bilateral shoulder instability and atraumatic mechanism of dislocation. [219] (10.1177/2325967120s00378)
• [L4] Nonoperative treatment of displaced anterior glenoid rim fractures without dislocation in elderly patients provides satisfactory functional and radiographic outcomes, with no evidence of subsequent instability. [221] (10.1186/s12891-025-08947-8)
• [L4] The long-term data suggest that these benefits are durable, and the Latarjet procedure should be considered as a viable and reliable treatment option for anterior glenohumeral instability. [222] (10.1016/j.jseint.2025.04.033)
• [L4] Surgical arthroscopic repair was possible in all cases of acute or recurrent instability with well-defined exclusion criteria. [225] (10.1055/s-0032-1327656)
• [L4] The Latarjet procedure provides excellent long-term outcomes in the treatment of recurrent anterior glenohumeral instability. [227] (10.1016/j.jse.2014.02.015)
• [L1] [229] (10.2106/jbjs.9616.ebo209)
• [L2] Better functional results following arthroscopic stabilization can be expected in patients over 24 years of age and in those with a fewer number of dislocations preoperatively. [230] (10.1007/s00167-015-3785-3)
• [L2] [231] (10.2106/00004623-199611000-00006)
• [L4] Recurrent instability might result from new trauma even if a long time has passed since the open modified inferior capsular shift procedure, so follow-up should be continued as long as possible after surgery. [232] (10.1016/j.jse.2021.07.021)
• [L4] However, the results are not as predictable as for primary surgery, with factors associated with poor results including an atraumatic cause of failure, voluntary dislocations, and multiple prior stabilization attempts. [234] (10.1177/03635465000280020401)
• [L3] Recurrence rate and complications were noted for subluxation and dislocation. [235] (10.1016/j.jseint.2024.08.120)
• [L5] Conventional radiography remains the initial imaging study for evaluating patients with persistent shoulder pain and instability, while magnetic resonance arthrography has been firmly established as the imaging modality of choice for demonstrating specific soft tissue abnormalities associated with glenohumeral instability. [236] (10.1177/03635465000280032501)
• [L4] The thresholds defined in this study can provide a guideline for interpreting patient outcomes following arthroscopic stabilization for posterior shoulder instability, allowing for earlier detection of recurrent posterior instability. [237] (10.1016/j.jseint.2025.08.006)
• [L4] The risk of recurrent dislocation is low following this procedure. [242] (10.1007/s00167-007-0316-x)
• [L1] [244] (10.1016/j.jse.2012.02.008)
• [L2] Ranges of recurrent instability measures, including recurrent dislocation rates, are higher in patients undergoing isolated Bankart repair in comparison to Bankart repair augmented with remplissage. [246] (10.1016/j.arthro.2024.04.036)
• [L3] Identification of these critical radiographic variables on magnetic resonance arthrography assists in the accurate diagnosis and management of clinically significant posterior shoulder instability. [249] (10.1177/0363546516660076)
• [L3] Patients undergoing open stabilization were more likely to be older, have a higher number of instability events prior to surgery, and have a history of previous arthroscopic stabilization. [250] (10.1177/17585732221117103)
• [L4] While younger age and a higher number of preoperative dislocations were potential risk factors for recurrence, a shorter interval between the first dislocation and surgery was associated with improved clinical outcomes. [252] (10.1177/03635465251351293)
• [L2] [253] (10.1016/j.jse.2010.10.027)
• [L1] Capsular injury is commonly seen in magnetic resonance imaging of patients with anterior shoulder instability. [254] (10.1016/j.xrrt.2024.08.004)
• [L3] Patients who undergo MRI greater than 6 months from the time of primary or initial shoulder dislocation had significantly more recurrent shoulder instability events and demonstrated a greater incidence and severity of intra-articular abnormalities, including SLAP tears, posterior labral tears, and anterior glenoid cartilage damage. [255] (10.1177/2325967117728019)
• [L4] Magnetic resonance angiography has a high sensitivity when used to identify associated injuries in shoulder dislocation, although in 8 patients (13 %) arthroscopy identified an additional injury. [257] (10.1007/s00256-014-2080-6)
• [L4] [258] (10.1016/j.csm.2004.08.010)
• [L3] MR arthrogram outperforms standard MRI for labral tear diagnosis, particularly as time from dislocation increases. [260] (10.1016/j.arthro.2024.02.020)
• [L3] [261] (10.1002/arj.70010)
• [Paper] Advanced imaging modalities are essential for identifying associated lesions, and bony reconstruction procedures should be considered for patients with significant glenoid bone loss or recurrent instability after soft tissue reconstruction. [263] (10.1016/j.csm.2014.06.006)
• [L4] MRI is able to reliably diagnose and is a good predictor of the structural soft tissue damage associated with chronic traumatic SCJ instability. [264] (10.1016/j.jse.2025.04.018)
• [L3] The most significant predictors included shorter time to presentation and history of subluxations over frank dislocations pre-operatively. [267] (10.1177/2325967123s00069)
• [L5] MR-arthrography is identified as the main tool in diagnosing shoulder instability injuries. [270] (10.21037/qims.2017.08.05)
• [L4] In the setting of ongoing pain or instability, further imaging should be performed. [271] (10.1007/s00068-017-0854-y)
• [L4] The number of episodes of dislocation before surgery and the delayed surgical intervention did not increase the recurrent anterior shoulder instability rates postoperatively. [272] (10.1016/j.jseint.2022.12.003)
• [L3] Routine MRI has similar diagnostic value to MR arthrogram for measuring labral tear extent up to approximately 2 weeks postacute shoulder dislocation, after which it significantly loses accuracy and precision. [275] (10.1177/2325967124s00075)
• [L5] Substantial variability was observed in the scoring of important elements in the radiological report for the evaluation of anterior shoulder instability, regardless of modality. [277] (10.1016/j.jseint.2024.03.012)
• [L3] Surgical stabilization appears to restore the rate and timing of instability to that of players with no prior history of instability. [278] (10.1177/1941738112472156)
• [L5] In patients with suspected posterior glenohumeral instability, imaging of the affected shoulder can show abnormalities of the bone, labrum, and joint capsule. [282] (10.2214/ajr.07.3849)
• [L5] Accurate characterization of glenoid and humeral bone loss is essential for preoperative planning to minimize the risk of recurrent dislocation, with three-dimensional imaging serving as an integral component of this evaluation. [283] (10.5435/jaaos-d-22-00016)
• [L3] The superior-capsular elongation as well as its diagnostic criteria of measurements by MR arthrography revealed in the present study could serve as references for diagnosing atraumatic posteroinferior shoulder instability and offer insight into the spectrum of imaging findings corresponding to the pathologies encountered at clinical presentation. [288] (10.3109/02841850903524421)
• [L3] Despite the advantages of MRI in the detection of soft tissue damages in recurrent anterior shoulder instability CT imaging proved to be more important for glenoid defects. [289] (10.1007/s00402-012-1656-7)
• [L4] CT and MRI (2D or 3D) accurately measure glenoid bone loss in anterior shoulder instability, but radiographs do not. [290] (10.2214/ajr.18.20504)
• [L2] Three-dimensional MRI (FRACTURE) is equivalent to 3D CT in quantifying bone loss in patients with shoulder dislocation and measuring shoulder morphologic parameters. [291] (10.1016/j.arthro.2023.12.016)
• [L3] Age at the time of primary shoulder dislocation is the most significant prognostic factor for the rate of recurrence. [292] (10.1007/s00264-006-0183-y)

See Also

• Shoulder Instability
• Total shoulder arthroplasty
• Os Acromiale
• Rotator Cuff
• Fractures
• Calcific Tendinitis
• Latarjet Procedure

References

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[108] Relationship between the extent of labral lesions and the frequency of glenohumeral dislocation in shoulder instability. Knee Surgery, Sports Traumatology, Arthroscopy. 2012. DOI: 10.1007/s00167-012-2045-z

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

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[118] Descriptive Epidemiology of the MOON Shoulder Instability Cohort. The American Journal of Sports Medicine. 2018. DOI: 10.1177/0363546518755752

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[124] Comparison of Shoulder Stabilization Using Arthroscopic Transglenoid Sutures versus Open Capsulolabral Repairs. The American Journal of Sports Medicine. 2004. DOI: 10.1177/0095399703258747

[125] International survey and surgeon’s preferences in diagnostic work-up towards treatment of anterior shoulder instability. Archives of Orthopaedic and Trauma Surgery. 2016. DOI: 10.1007/s00402-016-2443-7

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[140] Editorial Commentary: Recurrent Anterior Shoulder Instability With Glenoid Bone Loss Requires Restoring the Bone. Arthroscopy. 2022. DOI: 10.1016/j.arthro.2021.09.002

[143] Comparable clinical outcomes using knotless and knot‐tying anchors for arthroscopic capsulolabral repair in recurrent anterior glenohumeral instability at mean 5‐year follow‐up. Knee Surgery, Sports Traumatology, Arthroscopy. 2020. DOI: 10.1007/s00167-020-06057-7

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[147] Free Bone Block Procedures for Glenoid Reconstruction in Anterior Shoulder Instability. Journal of the American Academy of Orthopaedic Surgeons. 2023. DOI: 10.5435/jaaos-d-22-00837

[151] A Prospective, Randomized Evaluation of Arthroscopic Stabilization versus Nonoperative Treatment in Patients with Acute, Traumatic, First-Time Shoulder Dislocations. The American Journal of Sports Medicine. 2002. DOI: 10.1177/03635465020300041801

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[163] Recurrence and return to play after shoulder instability events in young and adolescent athletes: a systematic review and meta-analysis. British Journal of Sports Medicine. 2016. DOI: 10.1136/bjsports-2016-096895

[165] Surgical Treatment Is Superior to Conservative Options in Preventing Recurrence of First-Time Anterior Shoulder Dislocation in Adolescents and Adults Under 40 Years of Age: A Systematic Review and Network Meta-analysis. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2025. DOI: 10.1016/j.arthro.2025.07.044

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[169] Pediatric and Adolescent Shoulder Instability. Clinics in Sports Medicine. 2013. DOI: 10.1016/j.csm.2013.07.010

[175] Intraobserver and interobserver agreement of International Classification of Diseases, Ninth Revision codes in classifying shoulder instability. Journal of Shoulder and Elbow Surgery. 2009. DOI: 10.1016/j.jse.2008.10.005

[181] Return to Professional Australian Rules Football After Surgery for Traumatic Anterior Shoulder Instability. The American Journal of Sports Medicine. 2021. DOI: 10.1177/03635465211029022

[184] Validation of the Instability Shoulder Index Score in a Multicenter Reliability Study in 114 Consecutive Cases. The American Journal of Sports Medicine. 2012. DOI: 10.1177/0363546512470815

[185] Predictors for Surgery in Shoulder Instability. Orthopaedic Journal of Sports Medicine. 2015. DOI: 10.1177/2325967115607434

[190] A Systematic Review of Acute Irreducible Shoulder Dislocations in the 21st Century. Orthopaedic Journal of Sports Medicine. 2022. DOI: 10.1177/23259671221121633

[194] Should first‐time traumatic shoulder dislocations undergo an acute stabilization procedure?. Knee Surgery, Sports Traumatology, Arthroscopy. 2003. DOI: 10.1007/s00167-003-0357-8

[196] Glenoid version and recurrent anterior shoulder dislocation: a case–control study. BMC Musculoskeletal Disorders. 2026. DOI: 10.1186/s12891-026-09594-3

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[199] Return to Sports After Arthroscopic Anterior Stabilization in Patients Aged Younger Than 25 Years. Arthroscopy. 2013. DOI: 10.1016/j.arthro.2013.09.008

[201] Current Approaches to Arthroscopic Management of Anterior Shoulder Instability. JBJS Reviews. 2026. DOI: 10.2106/jbjs.rvw.26.00033

[203] Long - Term Outcome of Segmental Reconstruction of the Humeral Head for the Treatment of Locked Posterior Dislocation of the Shoulder. Journal of Shoulder and Elbow Surgery. 2014. DOI: 10.1016/j.jse.2014.06.009

[206] Hill-Sachs lesion classification under arthroscopic findings. Journal of Shoulder and Elbow Surgery. 2017. DOI: 10.1016/j.jse.2016.10.017

[207] Operative versus nonoperative treatment after primary traumatic anterior glenohumeral dislocation: expected-value decision analysis. Journal of Shoulder and Elbow Surgery. 2011. DOI: 10.1016/j.jse.2011.01.031

[208] Ten-year follow-up of acute arthroscopic Bankart repair for initial anterior shoulder dislocation in young patients. Orthopaedics & Traumatology: Surgery & Research. 2015. DOI: 10.1016/j.otsr.2015.09.029

[210] Editorial Commentary: Urgency Toward Arthroscopic Bankart Repair Is Essential for Anterior Shoulder Dislocation: You Don’t Have to Fix After the First Dislocation, but Definitely Before the Second!. Arthroscopy. 2023. DOI: 10.1016/j.arthro.2022.11.014

[213] Posterior Shoulder Instability. Sports Health: A Multidisciplinary Approach. 2016. DOI: 10.1177/1941738116672446

[214] Management of the first episode of traumatic shoulder dislocation. EFORT Open Reviews. 2017. DOI: 10.1302/2058-5241.2.160018

[217] Intraoperative anterior shoulder dislocation during ulnar nerve transposition: a case report. Journal of Shoulder and Elbow Surgery. 2020. DOI: 10.1016/j.jse.2020.04.012

[218] Chapter 24 Carpal Instability. 2019.

[219] Risk Factors for Recurrent Anterior Glenohumeral Instability Following a Primary Latarjet Procedure: A Prospective Analysis of 358 Patients. Orthopaedic Journal of Sports Medicine. 2020. DOI: 10.1177/2325967120s00378

[221] Outcomes of nonoperative treatment of displaced anterior glenoid rim fractures without dislocation in the elderly: should instability be a concern?. BMC Musculoskeletal Disorders. 2025. DOI: 10.1186/s12891-025-08947-8

[222] Long-term outcomes of the Latarjet procedure in a North American population. JSES International. 2025. DOI: 10.1016/j.jseint.2025.04.033

[225] Arthroscopic Treatment of Glenohumeral Instability in Soccer Goalkeepers. International Journal of Sports Medicine. 2012. DOI: 10.1055/s-0032-1327656

[227] Long-term results of the Latarjet procedure for anterior instability of the shoulder. Journal of Shoulder and Elbow Surgery. 2014. DOI: 10.1016/j.jse.2014.02.015

[229] Immobilization with an External Rotation Brace Was Similar to an Internal Rotation Sling for Shoulder Dislocation. Journal of Bone and Joint Surgery. 2014. DOI: 10.2106/jbjs.9616.ebo209

[230] Predictors of functional outcomes and recurrent shoulder instability after arthroscopic anterior stabilization. Knee Surgery, Sports Traumatology, Arthroscopy. 2015. DOI: 10.1007/s00167-015-3785-3

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[232] Long-term outcomes of open modified inferior capsular shift for traumatic anterior shoulder instability: over 20 years of follow-up. Journal of Shoulder and Elbow Surgery. 2022. DOI: 10.1016/j.jse.2021.07.021

[234] Open Revision Stabilization Surgery for Recurrent Anterior Glenohumeral Instability. The American Journal of Sports Medicine. 2000. DOI: 10.1177/03635465000280020401

[235] Does Gender Maters In Recurrent Shoulder Instability? Results Of A Multicentric Prospective Study. JSES International. 2024. DOI: 10.1016/j.jseint.2024.08.120

[236] Imaging Techniques for the Evaluation of Glenohumeral Instability. The American Journal of Sports Medicine. 2000. DOI: 10.1177/03635465000280032501

[237] Defining clinical significance following primary stabilization of posterior shoulder instability. JSES International. 2025. DOI: 10.1016/j.jseint.2025.08.006

[242] Posterior bone block procedure for posterior shoulder instability. Knee Surgery, Sports Traumatology, Arthroscopy. 2007. DOI: 10.1007/s00167-007-0316-x

[244] Complications associated with open coracoid transfer procedures for shoulder instability. Journal of Shoulder and Elbow Surgery. 2012. DOI: 10.1016/j.jse.2012.02.008

[246] Lower Range of Recurrent Instability Rates Following Bankart Repair and Remplissage Compared to Isolated Bankart Repair in Patients With “Nonengaging/On‐Track” Hill‐Sachs Lesions and <20% Glenoid Bone Loss. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2024.04.036

[249] Critical Findings on Magnetic Resonance Arthrograms in Posterior Shoulder Instability Compared With an Age-Matched Controlled Cohort. The American Journal of Sports Medicine. 2016. DOI: 10.1177/0363546516660076

[250] Trends in the surgical treatment of posterior shoulder instability in the United States from 2016 to 2020. Shoulder & Elbow. 2022. DOI: 10.1177/17585732221117103

[252] Long-term Outcomes of a Contemporary Arthroscopic Bankart Repair Technique in Patients With Traumatic Anterior Shoulder Instability: A Minimum 10-Year Follow-up. The American Journal of Sports Medicine. 2025. DOI: 10.1177/03635465251351293

[253] Development and reliability testing of the frequency, etiology, direction, and severity (FEDS) system for classifying glenohumeral instability. Journal of Shoulder and Elbow Surgery. 2011. DOI: 10.1016/j.jse.2010.10.027

[254] Glenohumeral capsular injury rate in patients with glenohumeral instability: a systematic review and meta-analysis. JSES Reviews, Reports, and Techniques. 2024. DOI: 10.1016/j.xrrt.2024.08.004

[255] Acute Versus Delayed Magnetic Resonance Imaging and Associated Abnormalities in Traumatic Anterior Shoulder Dislocations. Orthopaedic Journal of Sports Medicine. 2017. DOI: 10.1177/2325967117728019

[257] A comparison of magnetic resonance arthrography and arthroscopic findings in the assessment of anterior shoulder dislocations. Skeletal Radiology. 2014. DOI: 10.1007/s00256-014-2080-6

[258] Osteoarthritis Following Shoulder Instability. Clinics in Sports Medicine. 2005. DOI: 10.1016/j.csm.2004.08.010

[260] Magnetic Resonance Arthrogram Outperforms Standard Magnetic Resonance Imaging 2 Weeks After First Shoulder Dislocation for Labral Tear Diagnosis. Arthroscopy. 2024. DOI: 10.1016/j.arthro.2024.02.020

[261] Adult Shoulder Dislocations in the United States Showed Higher Frequency in Males With a Bimodal Age Distribution of Under 24 and Older Than 75. Arthroscopy. 2026. DOI: 10.1002/arj.70010

[263] Shoulder Instability in the Military. Clinics in Sports Medicine. 2014. DOI: 10.1016/j.csm.2014.06.006

[264] Surgical stabilization of chronic traumatic anterior sternoclavicular joint instability based on magnetic resonance imaging diagnosis and structural anatomic magnetic resonance imaging findings. Journal of Shoulder and Elbow Surgery. 2026. DOI: 10.1016/j.jse.2025.04.018

[267] Paper 43: Defining and Predicting the “Optimal Observed Outcome” Following Surgical Treatment of Anterior Shoulder Instability: A Machine Learning Clustering Analysis of 200 patients with 11-year mean follow up.. Orthopaedic Journal of Sports Medicine. 2023. DOI: 10.1177/2325967123s00069

[270] Imaging of shoulder instability. Quantitative Imaging in Medicine and Surgery. 2017. DOI: 10.21037/qims.2017.08.05

[271] Traumatic inferior shoulder dislocation: a review of management and outcome. European Journal of Trauma and Emergency Surgery. 2017. DOI: 10.1007/s00068-017-0854-y

[272] Quality of life following an open Latarjet-Bristow procedure in a general population with recurrent anterior shoulder instability. JSES International. 2023. DOI: 10.1016/j.jseint.2022.12.003

[275] Poster 105: MRI Demonstrates Similar Diagnostic Value to MR Arthrogram for Determining Labral Tear Extent up to 2 Weeks Following Shoulder Dislocation. Orthopaedic Journal of Sports Medicine. 2024. DOI: 10.1177/2325967124s00075

[277] Substantial variability in what is considered important in the radiological report for anterior shoulder instability: a Delphi study with Dutch musculoskeletal radiologists and orthopedic surgeons. JSES International. 2024. DOI: 10.1016/j.jseint.2024.03.012

[278] Shoulder Instability in Professional Football Players. Sports Health: A Multidisciplinary Approach. 2013. DOI: 10.1177/1941738112472156

[282] Imaging Signs of Posterior Glenohumeral Instability. American Journal of Roentgenology. 2009. DOI: 10.2214/ajr.07.3849

[283] Evaluating Bone Loss in Anterior Shoulder Instability. Journal of the American Academy of Orthopaedic Surgeons. 2022. DOI: 10.5435/jaaos-d-22-00016

[288] Superior-capsular elongation and its significance in atraumatic posteroinferior multidirectional shoulder instability in magnetic resonance arthrography. Acta Radiologica. 2010. DOI: 10.3109/02841850903524421

[289] The importance of CT for the pre-operative surgical planning in recurrent anterior shoulder instability. Archives of Orthopaedic and Trauma Surgery. 2012. DOI: 10.1007/s00402-012-1656-7

[290] Imaging Quantification of Glenoid Bone Loss in Patients With Glenohumeral Instability: A Systematic Review. American Journal of Roentgenology. 2019. DOI: 10.2214/ajr.18.20504

[291] Three‐Dimensional Magnetic Resonance Imaging Fast Field Echo Resembling a Computed Tomography Using Restricted Echo‐Spacing Sequence Is Equivalent to 3‐Dimensional Computed Tomography in Quantifying Bone Loss and Measuring Shoulder Morphology in Patients With Shoulder Dislocation. Arthroscopy. 2023. DOI: 10.1016/j.arthro.2023.12.016

[292] Has the management of shoulder dislocation changed over time?. International Orthopaedics. 2006. DOI: 10.1007/s00264-006-0183-y