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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.

171 citationsUpdated Oct 2026

Overview

Shoulder instability management relies on precise patient selection and preoperative assessment to optimize surgical outcomes. Young age (under 20 years) and a history of three or more preoperative dislocations are the most influential predictors for revision stabilization and postoperative dislocation risks [24]. Conversely, patients over 24 years of age with fewer preoperative dislocations achieve better functional results following arthroscopic stabilization [243]. Immediate surgical stabilization after a first-time dislocation significantly reduces the risk of recurrence compared to surgery performed after two dislocation events [26], and patients with first-time dislocations exhibit lower postoperative instability and reoperation rates than those with recurrent dislocations [21]. Sensitive selection is particularly recommended for arthroscopic Bankart repair in patients with more than five dislocations [61]. Proper evaluation of bone loss is the primary determinant of surgical indications and outcomes [51], while the Latarjet procedure is indicated based on humeral and glenoid bone loss, symptom duration, dislocation count, and revision status [248]. Arthroscopic surgery remains an acceptable treatment when recurrent instability occurs consistently at ≤23.8% [50].

Surgical technique selection is guided by the specific pathology and patient profile. Soft-tissue stabilization is more aggressively indicated for primary shoulder dislocation, whereas recurrent instability with bone loss should be referred to experienced high-volume specialists [59]. The long head of biceps tendon transfer is indicated for shoulder instability in high-impact athletes combined with capsule-labrum reconstruction, or for poor labral tissue quality in patients with multiple long-term dislocations [56]. Arthroscopic management of failed instability repairs provides success rates similar to open reconstruction when proper indications are selected [53]. In terms of outcomes, anterior instability results are superior to posterior instability across all domains after arthroscopic stabilization [30]. Recurrent instability rates are generally higher with arthroscopic stabilization, accompanied by other complications [60]. However, the posterior bone block procedure carries a low risk of recurrent dislocation for posterior instability [257], and open capsular shift with Achilles allograft augmentation demonstrates low recurrence rates and improved outcomes in high-risk multidirectional instability populations [14].

Stabilization surgery in high-risk patients helps prevent subsequent dislocation events and minimizes health care costs [20]. Long-term benefits in overall stability and functional outcome have been demonstrated for high-risk patients undergoing arthroscopic Bankart repair for first-time anterior dislocation [12]. For chronic locked posterior dislocations, arthroscopically assisted reduction has shown no recurrent dislocation or instability at six-month follow-up [3]. In soccer goalkeepers, surgical arthroscopic repair is feasible for acute or recurrent instability when well-defined exclusion criteria are met [237]. No significant differences in outcomes or recurrence rates exist between early and late dislocations following reverse total shoulder arthroplasty [4]. The choice of open reduction and stabilization technique for chronic anterior dislocation is highly variable, leading to wide outcome variation and high complication rates such as resubluxation and early arthrosis [22]. Thresholds defined in a 2025 study provide guidelines for interpreting outcomes following arthroscopic stabilization for posterior instability, allowing earlier detection of recurrence [250]. Future studies are needed to ascertain long-term outcomes of surgical stabilization based on preoperative dislocation events [11].

Anatomy & Pathophysiology

Bony Anatomy

The glenoid cavity is a shallow, convex socket shaped like an inverted pear, approximately one-third the size of the humeral head [72]. Its subchondral bone is relatively flat, with articular concavity augmented by cartilage and a circumferential labrum [74]. The glenoid averages 5° of retroversion relative to the scapular body axis [74], with specific measurements averaging 1.5 degrees of retroversion (range 10.5-9.5 degrees anteversion) and an inclination of 4.2 degrees (range –7 to 20 degrees) [84]. The glenoid articular surface radius of curvature is 2 to 3 mm larger than that of the humeral head [84], ranging from 22-28 mm [84]. Glenoid dimensions range from 18-30 mm superior anteroposterior, 21-35 mm inferior anteroposterior, and 30-48 mm superoinferior [84], with a surface area of 4-6 mm and cartilage thickness of 2.16 mm [84].

The humeral head is spherical with a diameter of 37 to 57 mm [71] and a radius of curvature of approximately 25 mm, slightly larger in men than in women [84]. The articular surface is covered by cartilage over an arc of approximately 160 degrees [84], with a surface area of 11-19 mm and cartilage thickness of 1.44 mm [84]. The most superior portion of the articular surface averages 8 mm above the greater tuberosity [71], or 8 to 10 mm superior to the top of the greater tuberosity [84]. Humeral version averages 29.8 degrees (range 10 to 55 degrees) [71], with retroversion averaging 30 degrees relative to the transepicondylar axis [72, 86] or 19° [74]. The head-shaft angle averages 135 degrees [72] or 45 degrees (±5 degrees, range 30 to 50 degrees) [84], with inclination ranging from 30-55 degrees [84] or averaging 41° [74]. Medial (coronal) humeral offset ranges from 4-14 mm, and posterior (transverse) offset ranges from –2 to 10 mm [84].

The scapula is suspended by muscles alone and has shifted caudally from the cervical position in lower animals [82]. Broadening of the infraspinatus fossa has altered the vector of muscle pull from the axillary border to the glenoid fossa [82]. The acromion has enlarged to reflect the increasing role of the deltoid, and the coracoid process has increased in size over time [82]. With the shoulder in 90 degrees of abduction, the coracoid extension mechanically limits anterior translation of the humerus relative to the glenoid [82]. The scapula is attached to the axial skeleton by the clavicle via the acromioclavicular and sternoclavicular joints [73]. It is separated from the chest wall by thin gliding fibro-fatty tissue, allowing smooth excursion [73]. The scapula spans second through seventh ribs and serves as an attachment for 17 muscles [86]. It is anteverted on the chest wall approximately 30 degrees relative to the body [86].

The basic part of the scapula is the triangular body, with its base situated superiorly and its apex inferiorly [73]. The glenoid connects to the flat body via the scapular neck [73]. The hook-shaped coracoid process curves forwards from the superior surface of the scapular neck [73]. The scapular spine ends in the flattened acromion, which curves forwards [73]. Bony mass distribution is highly uneven, with the highest concentration in the glenoid, scapular neck, and lateral border of the body [73]. Two bony pillars extend between the glenoid and the scapular body to transmit compressive forces [73]. The lateral pillar connects the inferior border of the glenoid with the inferior angle, while the spinal pillar arises from the central glenoid and continues medially to become part of the base of the scapular spine [73]. These pillars, connected by a markedly thinner medial border, form the basic load-bearing structure of the scapular body [73]. The weakest bone in the scapula is located primarily in the central part of the biomechanical body, specifically in the infraspinous fossa [73]. The weakest area of the circumference of the biomechanical body is the spinomedial angle, where the scapular spine connects to the medial border [73].

The clavicle is the first bone to ossify at the fifth week of gestation and is the only long bone to ossify by intramembranous ossification [74]. It is also 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 [86]. The medial (sternal) epiphysis is the last ossification center to fuse, at age 20 to 25 years [74]. The primary blood supply to the clavicle is periosteal, with no nutrient artery present [74]. Fracture of the clavicle is the most common musculoskeletal birth injury [86].

Ossification of the scapular body begins at the eighth week of gestation [74]. The acromion has three ossification centers: the metacromion (base), the mesoacromion (middle), and the preacromion (tip) [74]. Failure of fusion of these centers results in os acromiale, most commonly between the mesoacromion and meta-acromion [74, 86]. The scapula has only one true diarthrodial articulation, the acromioclavicular joint [74]. Normal shoulder motion is approximately two-thirds glenohumeral and one-third scapulothoracic [74].

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) [74]. The formation of the humerus begins with the appearance of the cartilage anlage by the fifth week of gestation [79]. The primary ossification center for the humerus appears at about the sixth week [79]. By birth, the entire humeral diaphysis is completely ossified [79]. The proximal humerus is primarily cartilaginous at birth, with ossification centers detectable by ultrasonography as early as the 38th week of gestation [79]. The ossification center for the humeral head is usually present at birth [79]. The greater tuberosity ossification center appears by 1 to 3 years of age, and the lesser tuberosity center appears by 5 years of age [79]. Proximal humeral ossification centers fuse to the shaft at age 17 to 20 years [74], or by 5 to 7 years of age to form the humeral head [79]. The proximal humeral physis closes by 14 to 17 years of age in girls and by 16 to 18 years in boys [79].

Humeral retroversion averages 65 degrees in infants and young children and gradually decreases, approaching adult values by 11 years of age [79]. Eighty percent of subsequent humeral growth comes from the proximal humeral physis, accounting for approximately 40% of the growth of the entire upper extremity [79]. Less than 75% of humeral growth occurs before 2 years of age, and more than 85% occurs by 8 years of age [79]. The posteromedial metaphysis, a portion of the physis, and the epiphysis are intracapsular [79]. A large part of the proximal humeral physis is extracapsular, making it susceptible to traumatic injury [79]. The proximal humeral physis is irregularly shaped, with its apex located on the posteromedial portion of the proximal humerus [79]. The periosteum is thicker and stronger in the posteromedial portion of the proximal humerus compared to the anterolateral portion [79].

The glenoid labrum increases the depth of the socket by 50% around the humeral head [85]. The glenoid articular surface and labrum combine to create a socket approximately 9 mm deep in the superoinferior direction and 5 mm deep in the anteroposterior direction [85]. Adding the glenoid labrum increases the glenoid surface to 75% of the humeral head vertically and 57% horizontally [85]. The bony anatomy of the shoulder contributes little to stability and has been compared with a golf ball on a tee [85].

The anatomic neck is directly below the humeral head and serves as an attachment for the shoulder capsule [86]. The surgical neck is more distal than the anatomic neck and is more often involved in fractures [86]. Head height is approximately 5.6 cm above the superior border of the pectoralis major tendon [86].

Soft Tissue Anatomy & Ligaments

The rotator cuff is a sheet of conjoined tendons closely applied over the shoulder capsule, inserting mainly into the greater tuberosity of the humerus [80]. It consists of the subscapularis in front, supraspinatus above, and infraspinatus and teres minor behind [80]. The subscapularis is inserted into the lesser tuberosity [80]. The rotator cuff stabilizes the head of the humerus by pulling it firmly into the glenoid whenever the deltoid lifts the arm forwards or sideways [80]. The rotator cuff and periscapular musculature afford dynamic stability to the glenohumeral joint [79].

The coracoacromial arch is a fibro-osseous canopy formed by the acromion process posterosuperiorly, the coracoid process anteriorly, and the coracoacromial ligament joining them [80]. This rigid bony-ligamentous structure imparts stability to the shoulder girdle [71]. The subacromial bursa separates the rotator cuff tendons from the coracoacromial arch and allows them to glide [80]. The rotator cuff, subacromial bursa, and subdeltoid bursa pass underneath the coracoacromial arch [71].

The capsule of the glenohumeral joint extends from the glenoid rim, progressing laterally toward the surgical neck of the humerus and blending with the tendons of the rotator cuff musculature [79]. Static stability of the glenohumeral joint is maintained by capsulolabral attachments and intracapsular ligamentous thickenings of the superior, middle, and inferior glenohumeral ligaments [79].

The coracoid process has attachments to the coracoacromial ligament, coracoclavicular ligaments (conoid and trapezoid), conjoined tendon (coracobrachialis and short head of biceps), and pectoralis minor [86]. The coracobrachialis muscle and the short head of the biceps tendon originate from the coracoid process [74]. The pectoralis minor muscle inserts onto the medial coracoid process [74]. The coracoacromial ligament contributes to anterosuperior stability in rotator cuff deficiency and should be preserved with irreparable cuff tears to prevent anterosuperior escape [86]. The coracoacromial ligament is the arthroscopic landmark for a complete release of the rotator interval for adhesive capsulitis [86].

The greater tuberosity provides attachment superiorly and posteriorly for the supraspinatus, infraspinatus, and teres minor [79]. The subscapularis originates from the anterior scapula and inserts anteriorly onto the lesser tuberosity [79]. The deltoid courses from the clavicle and acromion superiorly, coalescing into a common tendinous insertion onto the lateral upper third of the humeral shaft [79]. The pectoralis major inserts anteriorly onto the lateral wall of the bicipital groove and forms the roof of the distal continuation of the bicipital tunnel [79]. The bicipital tunnel is a closed space that extends proximally to the glenohumeral joint [79]. The transverse humeral ligament is an important stabilizer of the biceps tendon [86].

Classification

Shoulder instability is a complex phenomenon with a variety of clinical presentations that has historically been poorly understood [6]. Since the 1980s, 18 classifications have been developed to define sub-groups of shoulder instability, but none have demonstrated strong measurement properties [36]. The International Classification of Diseases, Ninth Revision (ICD-9) coding system cannot reliably classify shoulder instability [181].

Historical and General Frameworks

Thomas and Matsen: This classification introduced the AMBRI (atraumatic multidirectional instability) versus TUBS (traumatic unidirectional instability) acronyms to distinguish between traumatic and nontraumatic dislocations [36].

Stanmore: Introduced in 2004, this system encompasses Polar type I (true TUBS), Polar type II (true AMBRI), and Polar type III (atraumatic with functional origin) [36].

1995 Classification: This framework for glenohumeral instability is based on trauma, instability, and voluntarism [169].

Modern Classification Systems

FEDS: The Frequency, Etiology, Direction, and Severity (FEDS) system categorizes glenohumeral instability based on frequency, etiology, direction, and severity [76]. Developed using a systematic review of the literature and a survey of the American Shoulder and Elbow Surgeons (ASES) membership to ensure content validity [264], the frequency and etiology components may help identify patients with a higher likelihood of undergoing surgical treatment [195].

ABC: This classification distinguishes three groups of posterior glenohumeral instability with two different subtypes based on pathomechanical type and standard of treatment [9].

Chronologic Classification: Formulated for posttraumatic anterior shoulder instability, this system is based on dynamic pathophysiologic reasoning rather than cataloging complex arthroscopic findings [27].

ISIS: 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 [193]. 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 [215].

Other Considerations

Etiology and Mechanism: Non-traumatic shoulder instability (NTSI) is defined as abnormal movement or position of the shoulder leading to pain, subluxation, or dislocation without a significant history of injury [36]. Variations in the criteria used for the diagnosis of multidirectional instability significantly affect the distribution of patients with that diagnosis [31]. The stated criteria for atraumatic dislocation appear not to be valid or consistent [194]. Multidirectional instability is a complex problem [200].

Direction and Prevalence: Posterior instability represents 10% of all instability events [23]. Bony evidence of posterior pathologic condition is more common than usually seen in clinical reports, where posterior dislocations are conceived to be rare events composing 1.5% to 3.8% of all shoulder dislocations [44]. In a study of 50 patients, 96% presented with traumatic unidirectional anterior instability [275].

Severity and Progression: The dynamic progression of labral and ligamentous pathology in dislocation and subluxation disorders suggests a time-dependent, recurrence-dependent worsening [27]. Posttraumatic-progressive anterior shoulder instability is a developing process that can lead to anatomical instability without adequate treatment [192]. 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 [208].

Clinical Presentation

Shoulder instability presents with diverse clinical manifestations and has historically been poorly understood due to its complex nature [6]. Anterior instability is the most common form, with most patients undergoing stabilization in their early 20s or younger [122]. Posterior dislocations are less common but more frequently missed on initial presentation, resulting in ongoing discomfort, long-term morbidity, and elevated health care costs [125, 111]. Posterior shoulder dislocation is a rare and challenging injury with varied trauma mechanisms that complicate diagnosis [89]. Recurrent posterior instability is an uncommon condition often unrecognized, leading to incorrect diagnoses and delays [15]. Management of locked posterior dislocations is difficult, particularly because late diagnosis is not uncommon [5]. Traumatic instability in patients older than 35 years may result in a wide array of pathologic findings and diverse clinical presentations [109]. Even patients with a single episode of dislocation may develop long-term sequelae [16]. Non-traumatic shoulder instability is defined as abnormal movement or position of the shoulder leading to pain, subluxation, or dislocation without a significant history of injury [36].

History Taking

Patients typically present with a history of trauma [113]. History taking should note the age at first dislocation, increasing ease of dislocation, frequency of recurrence, duration of symptoms, and the patient's ability to reduce the dislocation themselves [113]. A history of multiple instability episodes prior to presentation is the greatest predictor of recurrent instability and failure of nonoperative treatment [2]. Characteristics related to a history of instability, including age under 20 years at the first episode, a larger number of dislocations, and a duration of at least 2 years between the first dislocation and surgery, are risk factors for the development of an off-track Hill-Sachs lesion [10]. 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 [49]. All parameters related to history taking, physical exam, and imaging studies should be considered according to the patient's age and the number of dislocation episodes [39]. Detailed and specific information about prognosis is critical in the management of a first-time anterior shoulder dislocation [33]. The age of the patient at the time of the initial dislocation is the most consistent and significant factor influencing prognosis, with recurrence rates of 83% in patients under twenty years and 12% in patients over fifty years [17]. 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 [41]. Stabilization after the first-time dislocation achieves better clinical and radiological outcomes than after multiple dislocations [1]. In patients with anterior instability, recurrence is 24%, with almost all cases associated with new trauma [118].

Physical Examination

Physical examination should focus on both diagnosis and identification of associated injuries [113]. An evaluation of generalized laxity should be performed during physical examination [113]. Clustering of thorough history and physical examination findings may identify those with posterior glenohumeral instability and assist in developing management strategies [32]. Alteration of scapular position and motion is common in association with symptoms and dysfunction from glenohumeral instability [48]. The main symptom of recurrent true posterior dislocation is dislocation, defined by total loss of contact requiring reduction by external maneuver [127]. 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].

Special Tests: * Apprehension-relocation test (Fowler test): The most sensitive test, where the arm is placed into abduction and external rotation to elicit a sense of instability that is relieved by a posterior force [113]. * Load-and-shift test: Classifies degrees of instability based on the distance of humeral head translation: 1+ for 0 to 1 cm of translation to before the glenoid rim, 2+ for 1 to 2 cm of translation to the glenoid rim, and 3+ for greater than 2 cm translation or over the glenoid rim [113]. * Posterior instability tests: Showed high sensitivity but low specificity, leading to over-diagnosis [40].

Imaging & Diagnostic Findings

The diagnosis of anterior-inferior glenohumeral instability is made on the basis of a combination of signs and symptoms, including patient description of dislocation or looseness, pain or apprehension on instability tests, radiographic evidence, and arthroscopic findings [91]. Lesions associated with traumatic anterior glenohumeral dislocations are more frequent than expected [128]. There is wide variation in pathology after anterior dislocation [120]. Bony evidence of instability is more common than the reporting of clinical cases, with a prevalence figure of 5.4% demonstrated in one study [44]. Posterior pathologic condition is more common in skeletal specimens than is usually seen clinically [44]. Statistical reports suggest posterior dislocations compose from 1.5% to 3.8% of all shoulder dislocations [44].

Specific Lesions: * HAGL lesions: A rare and underdiagnosed cause of anterior shoulder instability that can lead to recurrent dislocations if unaddressed [34]. * GAGL lesions: Recognition and treatment should improve surgical outcomes in patients with recurrent dislocations [99]. * Extensive labral lesions: Can occur even in patients with few previous dislocations, and clinical outcomes can be excellent with appropriate treatment [110].

Imaging Modalities: * MRI: Has proven to be useful in identifying capsulolabral avulsions (HAGL and reverse HAGL lesions) and rotator cuff pathology, which is common in patients over 40 years old with glenohumeral dislocation [149]. This review describes the pathologic MR features of posterior instability and the underlying joint abnormalities predisposing to this condition [35]. * Computed Tomography: Allows for a more precise quantification of bone loss compared to plain radiography [149].

Bone Loss Metrics: * Glenoid bone loss greater than 18% to 25% of the glenoid surface area increases the risk of failure of nonoperative and operative management that does not address the bone loss [149]. * A 1.5-mm osseous lesion corresponds to 5% glenoid bone loss [149].

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].

Investigations

Plain radiography: Conventional radiography remains the initial imaging study for evaluating patients with persistent shoulder pain and instability [249]. Standardized plain films are almost always sufficient to garner the information needed for shoulder evaluation [29]. At least two X-ray views should be obtained: an anteroposterior in the plane of the glenoid and an axillary projection with the arm in abduction to show the relationship of the humeral head to the glenoid [95]. The axillary view is a necessary view in evaluation of glenohumeral joint instability and enables determination of the humeral head position in the glenoid fossa [133]. It may detect occult, locked posterior shoulder dislocation in a patient who exhibits a lack of passive external rotation [133]. The scapular Y view is a reliable alternative for evaluation of glenohumeral subluxation and dislocation [133].

Specific views are indicated for targeted pathology: a Stryker notch view evaluates Hill-Sachs lesions after dislocation, a West Point view evaluates anterior glenoid bone loss, and an apical oblique view evaluates glenoid rim fracture in instability [133]. Focal cortical bone loss at the inferior aspect of the glenoid is a radiographic sign of anterior shoulder instability of traumatic origin [288]. In patients with suspected posterior glenohumeral instability, imaging can show abnormalities of the bone, labrum, and joint capsule [293]. The standardized axillary view taken with the arm in the functional position of elevation is referred to as the “truth view” because it demonstrates the glenohumeral relationships in the functional position of elevation [29]. This view can show posterior subluxation or “functional decentering” that is not evident in images taken with the arm at the side [29]. The degree of posterior subluxation can be measured as the position of the center of the humeral head in relation to the plane of the scapula, the position of the center of the humeral head in relation to the glenoid face, or the point of contact of the humeral articular surface on the glenoid articular surface [29]. The point of contact reflects the degree of centering of the net humeral joint reaction force on the glenoid [29]. Malcentering of the joint reaction force leads to posterior instability, posterior glenoid wear, and “rocking horse” loosening of prosthetic glenoid components [29].

For proximal humerus fractures, the recommended series is the Neer trauma series, consisting of an AP view, a lateral view in the scapular plane, and a Velpeau modified axillary view [101]. The axillary view is important for evaluating the glenoid articular surface and the relationship of the humeral head anteriorly and posteriorly [101]. On occasion, CT scanning for detailing bony anatomy may be necessary for proximal humerus fractures [101]. The purpose of imaging of the shoulder is to help establish the diagnosis, determine the severity of the pathoanatomy, assist in surgical planning, and enable the surgeon to illustrate the condition of the shoulder to the patient [29]. The temptation to “overimage” should be resisted, obtaining only the scans or reconstructions that are necessary for the care of the patient [29].

CT: CT imaging is frequently used to assess for bony lesions in recurrent instability cases [119]. 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 [133]. 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 [294]. 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 [276]. CT scans may offer a few degrees of increased precision in the measurement of glenoid version, but this precision does not necessarily improve the quality of the surgery or the clinical outcome [29].

MRI: Magnetic resonance arthrography has been firmly established as the imaging modality of choice for demonstrating specific soft tissue abnormalities associated with glenohumeral instability [249]. MR-arthrography is identified as the main tool in diagnosing shoulder instability injuries [283]. MRI is useful to identify osteonecrosis of the humeral head, or a bone tumour [95]. MRI can identify labral tears and rotator cuff tears, although the accuracy for these is enhanced by combining the scan with arthrography [95]. Traditional magnetic resonance imaging (MRI) is utilized for evaluation of soft tissues in anterior shoulder instability with high contrast and spatial resolution [104]. MR accuracy in identifying labral and rotator cuff tears in the literature ranges from 70% to 100% [104].

MR arthrography (MRA) increases the sensitivity for detecting tears and other lesions by distending the joint capsule with contrast [104]. In the acute dislocation setting, a joint effusion with distension of the joint may outline structures similarly, making the arthrogram unnecessary [104]. MRA has proven utility by increasing both sensitivity and specificity in detecting injuries to the capsulolabral–ligamentous complex as compared to traditional MRI [104]. A meta-analysis found greater diagnostic test accuracy for MRA over MRI in the detection of glenoid labral lesions, with MRA sensitivity of 88% and specificity of 93% versus MRI sensitivity of 76% and specificity of 87% [104]. Abduction and external rotation (ABER) of the arm is an alternative MRI position utilized to increase the sensitivity and specificity for detecting anteroinferior labroligamentous injury [104]. Limited range of motion or pain may prohibit patients from performing the ABER provocative maneuver [104]. Full routine MRI or MRA examination had similar accuracy as the ABER sequence in evaluating the anteroinferior labral–ligamentous complex [104]. The sensitivity of MRA with the ABER position for detecting anteroinferior labral lesions was significantly higher than that of the MRA in neutral position and more effective in identifying Perthes lesions [104].

MRAs can demonstrate a patulous capsule on the coronal, sagittal, and axial imaging in patients with multidirectional instability [104]. MRAs can be helpful in evaluating lesions of the rotator interval and other associated findings that may affect the eventual surgical plan [104]. The presence of glenoid dysplasia, increased capsular cross-sectional area, and increased glenoid retroversion have all been found to be associated with increased posterior labral tears and symptomatic instability [104]. Glenoid retroversion was significantly increased in patients with symptomatic posterior labral tears, but there was no significant association between instability and increased humeral head subluxation [104]. The diagnosis of multidirectional instability is a clinical one, and the need for expensive and/or invasive imaging should be weighed against the information that will be gained [104].

MRI is the modality of choice for evaluating the rotator cuff, biceps, and subacromial/subdeltoid bursa [119]. T1-weighted MRI can reveal Hill-Sachs lesions and is often used with magnetic resonance (MR) arthrograms to provide a more detailed picture of the joint surfaces [119]. T2-weighted MRI provides better visualization of full thickness rotator cuff tears [119]. MR arthrography is considered the benchmark for evaluation for labral tears and rarely is indicated for evaluation of rotator cuff pathology [119]. When MRI or MR arthrography is contraindicated, CT arthrography is indicated [119].

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 [25]. 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 [266]. MR arthrogram outperforms standard MRI for labral tear diagnosis, particularly as time from dislocation increases [273]. 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 [289]. Identification of critical radiographic variables on magnetic resonance arthrography assists in the accurate diagnosis and management of clinically significant posterior shoulder instability [261]. Capsular injury is commonly seen in magnetic resonance imaging of patients with anterior shoulder instability [265]. 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 [268]. MRI is a simple, non invasive method for acute first time traumatic shoulder dislocation evaluation [272]. CINE MRI is a reproducible technique to evaluate normal capsular attachments to the glenoid and confirms diagnosis of anterior and posterior shoulder instability [271]. MRI is able to reliably diagnose and is a good predictor of the structural soft tissue damage associated with chronic traumatic sternoclavicular joint instability [278]. Substantial variability was observed in the scoring of important elements in the radiological report for the evaluation of anterior shoulder instability, regardless of modality [291].

Ultrasonography: Ultrasonography is a simple and accurate test for identifying rotator cuff tears and calcific tendinitis [95]. It can be useful in guiding injections or barbotage (aspirating calcific deposits in the rotator cuff) [95]. Ultrasonography is a low-cost alternative to MRI and arthrography for evaluating both skeletal and soft-tissue structures of the shoulder [119]. It can provide immediate, real-time visualization of the rotator cuff, biceps tendon, and calcific deposits [119]. Ultrasonography can be used to measure the subacromial space and detect atrophy of rotator cuff muscles [119]. As a result of providing images in real-time, ultrasonography can evaluate impingement in various positions and motions [119]. 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 [119]. The most commonly performed joint examination using ultrasonography is the shoulder examination [93]. Accuracy of shoulder ultrasonography depends on the skill of the scanner operator and an awareness of pitfalls that are encountered [93].

Other Considerations: Recurrent posterior shoulder instability is an uncommon condition often unrecognized, leading to incorrect diagnoses and delays [15]. The management of a locked posterior dislocation can be difficult, especially as late diagnosis is not uncommon [5]. In the setting of ongoing pain or instability, further imaging should be performed [284]. The diagnosis of a stiff shoulder depends on awareness of the problem, with history and physical examination being paramount and ancillary studies helpful in certain circumstances [28].

Treatment

Non-Operative

Nonoperative management of anterior shoulder instability is associated with high rates of recurrent instability and pain at long-term follow-up, with a high rate of poor outcomes observed at 17 years [18]. Primary non-operative management is a prominent risk factor for recurrence [166]. In patients aged over 50 years with anterior shoulder instability, operative treatment is associated with a decreased risk of recurrent dislocation compared with non-operative treatment [2]. For posterior shoulder instability, nonoperative treatment is commonly unsuccessful in active patients [224], and long-term follow-up demonstrates that nearly 40% of patients treated non-operatively eventually require surgery [19]. However, recent studies continue to demonstrate a role for nonoperative treatment in the successful long-term management of anterior glenohumeral instability [55]. 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 [225]. 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 strategy [218].

The cornerstone of treatment for instability remains immobilization followed by rehabilitation [42]. The optimal nonoperative treatment of a shoulder dislocation is still unknown and deserves further study [42]. For patients who choose nonsurgical treatment for a first-time dislocation, the shoulder is immobilized until pain resolves and early motion is initiated [123]. Physical therapy focuses on regaining motion, strengthening the rotator cuff and periscapular muscles, and proprioceptive training [123]. Initial immobilization in external versus internal rotation may better reduce the torn labrum to the anterior-inferior glenoid [123]. A meta-analysis showed no benefit in rates of recurrence or validated outcomes with external rotation bracing compared to other methods [123]. Immobilization with an external rotation brace was similar to an internal rotation sling [241]. The position of external rotation immobilization does not offer any obvious clinical advantage over an arm placed in internal rotation in a traditional sling [241]. A comprehensive program that includes appropriate immobilization (minimum three weeks) followed by intensive strengthening to restore the balance and stability of the shoulder musculature appears to be the optimal approach for conservative management [242].

Nonsurgical treatment should always be attempted first for posterior instability [38]. After a single traumatic posterior injury, the arm should be immobilized in neutral rotation with the elbow in adduction for 1 to 2 weeks followed by therapy [38]. Nonsurgical treatment including physical therapy, activity modification, and anti-inflammatory agents should be considered for patients with minimal symptoms of posterior instability [165]. Nonsurgical treatment is the treatment of choice for voluntary posterior dislocators, in whom surgical intervention is contraindicated because of an extremely high failure rate [165]. Nonoperative management of posterior instability begins with immobilization until pain resolution allows the start of a physical therapy program [171]. Rehabilitation protocols for posterior instability should focus on proprioception training as well as strengthening of the rotator cuff and scapulothoracic musculature [171]. Multidirectional instability is initially treated nonoperatively with a focus on intense physical therapy to strengthen the rotator cuff, deltoid, and periscapular musculature [170]. Surgical intervention for multidirectional instability should only be considered if patients fail to improve after a lengthy course of glenohumeral and scapular stabilization therapy [170]. Multidirectional instability should be initially treated with conservative treatment [174]. Nonoperative treatment was successful in a toddler with rare anterior shoulder dislocation without subsequent instability or re-dislocation [45]. 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 [229].

Operative

Indications: Surgical stabilization helps prevent subsequent dislocation events and minimizes health care costs for patients with a high risk for recurrent instability [20]. Patients with first-time dislocations had lower postoperative instability rates and reoperation rates when compared with patients with recurrent dislocations before surgery [21]. This study demonstrates a long-term benefit in overall shoulder stability and functional outcome in high-risk patients who have undergone arthroscopic Bankart repair for first-time anterior dislocation [12]. 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 [154]. Early operative stabilization of Bankart lesions in young patients offers a significant reduction in the risk of recurrent instability compared to non-operative management [172]. 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 [168]. Arthroscopic stabilisation resulted in a significantly lower rate of recurrent instability compared with non-operative management in young, active patients, particularly military cadets [65]. 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 [219]. 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 [123]. Surgery resulted in lower costs and higher patient satisfaction, but overall outcomes were related to shoulder stability, not necessarily the surgery itself [123]. Patients in the repair group had a higher rate of return to contact sports [123]. A systematic review of level I and II studies demonstrated decreased recurrence of instability following arthroscopic Bankart repair when compared with physical therapy and sham surgery [123]. 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 [123]. 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 [123]. Radiographic evidence of dislocation arthropathy was reported in 41% of patients 8 years after arthroscopic Bankart repair [123]. The presence of radiographic arthritis did not correlate with outcome scores [123].

Surgical Approach / Technique: Open Bankart repair has historically provided good results for shoulder stability [123]. 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° [123]. 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 [123]. 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 [123]. Ninety-four percent of patients resumed athletic activity, 75% of those at their original level of competition [123]. 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) [123]. The highest rate of recurrence was noted in males younger than 25 years with Hill-Sachs lesions [123]. 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 [123]. A systematic review of more recent meta-analyses demonstrated no difference in recurrence between open and arthroscopic techniques [123]. 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 [123]. Most shoulder specialists consider arthroscopic anterior stabilization as the first-line treatment for recurrent glenohumeral instability [112]. Successful arthroscopic management of posttraumatic unidirectional instability must be able to independently address the Bankart lesion, ALPSA lesion, HAGL lesion, and capsular attenuation [112]. An anteroinferior Bankart labral detachment is present in the majority of recurrently unstable shoulders after an initial traumatic dislocation [112]. Most of these shoulders have a certain degree of coexisting capsular redundancy at the time of surgery [112]. As the acute dislocation evolves into chronic, recurrent instability, further capsular attenuation is likely to occur [112]. In this setting, isolated labral reattachment is usually inadequate and results in failure [112]. 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 [112]. With advances in suture anchor technology, clinical outcomes have improved significantly [112]. Arthroscopic techniques have the advantage of approximating the methods routinely used during open shoulder stabilization [112]. Anchors can be placed more precisely at the margin of the articular surface and the glenoid neck to anatomically recreate the labrocapsuloligamentous origin [112]. Suture anchor techniques are biomechanically the strongest of eight repair techniques in a canine Bankart model [112]. 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 [112]. 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 [112]. Recurrent dislocation occurred in two of 18 athletes involved in collision sports at 22 and 60 months postoperatively after return to sport [112]. 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 [112]. Advanced arthroscopic techniques include double-row labral repair, postero-inferior capsulolabral repair, and remplissage [112]. Recent cadaveric studies have shown that double-row fixation may better restore normal anatomy [112]. These techniques may be indicated in the setting of small (<20%) bony Bankart lesions as well [112]. 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 [112]. The purpose of this article is to define the complications associated with anterior instability repair and provide recommendations on techniques that may be used to help avoid them [63]. 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 [59].

Other Considerations: The success of treating anterior glenohumeral instability relies on multiple factors, including glenoid bone loss [143]. 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 [146]. 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%) [213]. 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 [160]. 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 [160]. Open Bankart repair was previously considered the gold standard for treatment of traumatic anterior shoulder instability with recurrence rates of typically less than 10% [160]. 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 [160]. 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 [160]. 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 [160]. An assessment of the 2004 to 2009 U.S. national insurance database showed that arthroscopic Bankart repairs accounted for 84% of shoulder stabilization surgeries [160]. Arthroscopic Bankart repair can minimize much of the morbidity associated with open surgery such as subscapularis weakness with possible rupture and arthrofibrosis [160]. Modern techniques utilizing suture anchors and capsular plication have achieved recurrence rates similar to open repairs of 8% to 11% in selected patients [160]. 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 [160]. 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 [160]. Surgical stabilization provides the best stability to the shoulder among all the treatment options [148]. The number of patients needing surgical stabilization after an initial dislocation is calculated to be 7.0 for the general population and 2.6 for high-risk patients [148]. If you perform surgical stabilization in all patients after an initial dislocation, you will end up doing unnecessary surgery in 60% to 85% of them [148]. A surgery for an initial dislocation is a preventive surgery for chronic instability, which may or may not occur [148]. Discretion is required when selecting a surgical procedure for a patient with an initial dislocation [148]. Bipolar lesions of the shoulder (glenoid bony defect and Hill-Sachs lesion) are very common and are observed in 81% of patients with recurrent anterior dislocation of the shoulder [148]. The critical size of a glenoid defect is reported to be 25% to 26% of the glenoid width [148]. The acceptable defect size is less than 17% and the unacceptable defect size more than 25% [148]. The size between 17% and 25% remains a gray zone [148]. The decision whether to perform a bone graft for a gray-zone bony defect depends on the patient’s background, including age, gender, joint laxity, sports involved, daily activity level, and occupation [148]. The risk of engagement depends on the relative margin of the Hill-Sachs lesion to the anterior rim of the glenoid [148]. The glenoid track is the zone of contact between the glenoid and the humeral head during arm movement along the posterior end-range of motion [148]. If the Hill-Sachs lesion stays within the glenoid track, there is no chance that it will engage with the anterior rim of the glenoid [148]. If the medial margin of the Hill-Sachs lesion travels outside the glenoid track, there is a risk of engagement [148]. A Hill-Sachs lesion that stays on the glenoid track is an “on-track” lesion, while one that goes outside the glenoid track is an “off-track” lesion [148]. For an on-track Hill-Sachs lesion, soft tissue repair alone, such as arthroscopic Bankart repair, is sufficient [148]. For an off-track lesion, if the glenoid defect is smaller than the critical size, remplissage may be indicated [148]. The Latarjet procedure may be preferable in the case of a throwing athlete or with high risks of recurrence as in a collision athlete [148].

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 [2]. Multivariate regression identifies an increased risk of recurrence associated with having multiple dislocations (P .03; OR, 2.4; 95% CI, 1.3 to 43.3) [210]. Other significant predictors include young age (under 20 years), having had 3 or more preoperative dislocations [24], and a history of bilateral shoulder instability or an atraumatic mechanism of dislocation following a primary Latarjet procedure [228]. 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 [10]. Younger patients, particularly those ≤15 and 16 to 20 years of age, are more likely to have experienced multiple instability events at the time of initial evaluation, require surgery, and experience recurrent instability compared with older patients [232].

Incidence and Timing: 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 [210]. Recurrences occurred in 2 of 16 patients who underwent surgery within 3 months of the initial injury, 2 of 16 patients who had surgery between 4 months and 1 year after the initial injury, and 3 of 21 patients who had surgery between 1 and 6 years after the initial injury (P > .05) [210]. Of 1658 cases of open coracoid transfer procedures, overall recurrent instability occurred in 100 (6.0%±1.2%), recurrent dislocation occurred in 46 (2.8%±0.8%), and recurrent subluxation occurred in 54 (3.3% 0.9%) [259]. Recurrence of posterior instability occurred in 5 cases (18%), all of which were recurrent subluxations with no dislocations, following an all-arthroscopic posterior bone block procedure [8].

Etiology and Revision: Of the 46 recurrent dislocations following open coracoid transfer, 17 were as a result of an additional traumatic episode of varying severity, 12 were ascribed to a technical error (in addition to a traumatic episode in 1), and 1 was attributed to the surgery having been done in a patient with multidirectional instability [259]. Factors associated with poor results in open revision stabilization surgery for recurrent anterior glenohumeral instability include an atraumatic cause of failure, voluntary dislocations, and multiple prior stabilization attempts [247]. Recurrent instability might result from new trauma even if a long time has passed since the open modified inferior capsular shift procedure [245]. Recurrent instability requiring capsular reconstruction seems to be more prevalent in patients with a previous history of shoulder dislocation following luxatio erecta [198].

Non-Operative Management Outcomes

Natural History and Prognosis: The natural history of the first time shoulder dislocations is bound up with arthropathy [54]. At long-term follow-up of 17 years, a high rate of poor outcomes was observed following nonoperative management of anterior shoulder instability [18]. The frequency of recurrence was based on the age of the patient at the time of the initial dislocation, with a recurrence rate of 90% in patients less than 20 years old, 60% in patients 20 through 40 years old, and only 10% in patients over 40 years of age [258]. In the 12 to 22-year age-group, recurrent dislocation occurred in ten of fourteen shoulders that had had the initial dislocation after trivial trauma, compared with fifty-five of eighty-five shoulders that had had the initial dislocation after a traumatic event [244].

Surgical Timing and Patient Profile: Early surgery can lower the recurrence rate compared with nonoperative treatment [69]. It was reported that more than 6 months between initial dislocation and surgical stabilization significantly increased the postoperative risk of redislocation, but other authors did not confirm this correlation [69]. Patients with recurrent shoulder instability reported a more extensive history of instability, were more likely to have severe bone loss, and required more invasive stabilization procedures [256]. Patients undergoing open stabilization for posterior shoulder instability were more likely to be older, have a higher number of instability events prior to surgery, and have a history of previous arthroscopic stabilization [262]. Glenohumeral instability without overt dislocation (recurrent subluxation) can be a very disabling condition and may occur with or without a history of actual dislocation [258].

Specific Clinical Scenarios and Outcomes

Adolescents and High-Risk Populations: 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 [68]. 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 [26]. The study demonstrated low rates of recurrent instability and improved clinical outcomes in this high-risk population with Ehlers-Danlos Syndrome treated with open capsular shift with Achilles allograft augmentation [14].

Special Mechanisms and Outcomes: None of the patients had a recurrence of the dislocation following an operative technique for recurrent shoulder dislocations in older patients [7]. At 3-year follow-up, the shoulders were stable and revealed no recurrent instability in a case of bilateral luxatio erecta [57]. At her most recent follow-up, a patient with bilateral posterior shoulder dislocations following seizure denied any apprehension or instability in either shoulder and had no further dislocations [236].

Other Considerations

Comparative Outcomes and Adjacent Risks: 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 [67]. The prevalence of subjects with past or present recurrent dislocations in the male population 22 to 33 years old was found to be approximately .5% [253]. Some risk of recurrent instability is part of the natural history of anterior shoulder dislocation [47]. Instability-related complications occurred only in the capsulabral group, and the incidence increased with time in patients returning to professional Australian Rules Football after surgery for traumatic anterior shoulder instability [188]. Patients with a history of shoulder instability or replacement are at risk for shoulder dislocation during common elbow and hand procedures [226].

Recovery

Prognostic Factors and Natural History: The age of the patient at the time of initial dislocation is the most consistent and significant factor influencing prognosis, with recurrence rates of 83% in patients under twenty years and 12% in patients over fifty years [17]. This age factor remains the most influential variable for prognosis [298]. Characteristics related to a history of instability, including age <20 years at the first instability episode, a larger number of dislocations, and ≥2 years between the first dislocation and surgery, are risk factors for the development of an off-track HS lesion [10]. The dynamic progression of labral and ligamentous pathology in dislocation and subluxation disorders is time-dependent and recurrence-dependent [27].

Non-Operative Management Outcomes: In a high-demand population, there is no significant difference in 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].

Operative Management Outcomes: Surgical intervention 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 [12]. Patients aged >50 years with anterior shoulder instability have a decreased risk of recurrent dislocation after operative treatment compared with non-operative treatment [2]. One-year outcomes in a prospective study suggest superiority of operative over non-operative treatment for posterior shoulder instability [64]. In one cohort, recurrence of posterior instability occurred in 5 cases (18%); all had recurrent subluxations, with no dislocations [8]. Following arthroscopically assisted reduction in a chronic locked posterior shoulder dislocation, a 6-month follow-up found no recurrent dislocation or instability [3]. In patients with Ehlers-Danlos Syndrome, open capsular shift with Achilles allograft augmentation demonstrated low rates of recurrent instability and improved clinical outcomes [14].

The long-term data suggest that the benefits of the Latarjet procedure are durable, and the procedure should be considered as a viable and reliable treatment option for anterior glenohumeral instability [233]. The Latarjet procedure provides excellent long-term outcomes in the treatment of recurrent anterior glenohumeral instability [239]. The number of episodes of dislocation before surgery and delayed surgical intervention did not increase the recurrent anterior shoulder instability rates postoperatively following an open Latarjet-Bristow procedure [285]. In professional football players, surgical stabilization appears to restore the rate and timing of instability to that of players with no prior history of instability [292]. At 3-year follow-up, the shoulders were stable and revealed no recurrent instability in cases of luxatio erecta of bilateral shoulders [57]. None of the patients has had instability after an average follow-up of 26 months following treatment for humeral and glenoid detachment of the anterior inferior glenohumeral ligament [230].

Other Considerations: The most significant predictors for the optimal observed outcome following surgical treatment of anterior shoulder instability included shorter time to presentation and history of subluxations over frank dislocations pre-operatively [280]. Short-term outcomes for pre-shaped allograft for glenoid reconstruction in anterior shoulder instability are reassuring, but more research is needed to study long-term graft union, graft resorption, glenohumeral arthritis, and patient outcomes including recurrent shoulder instability [231].

Key Evidence

• [L4] Stabilization after the first-time dislocation achieves better clinical and radiological outcomes than after multiple dislocations. [1] (10.1177/0363546516675145)
• [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. [2] (10.1016/j.asmr.2023.03.014)
• [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)
• [L4] The management of a locked posterior dislocation can be difficult, especially as late diagnosis is not uncommon. [5] (10.1016/s1058-2746(96)80191-1)
• [L5] Shoulder instability is a phenomenon with a variety of clinical presentations, and its complex nature has until recently been poorly understood. [6] (10.1016/j.cuor.2004.04.002)
• [L4] None of the patients had a recurrence of the dislocation. [7] (10.1016/s1058-2746(99)90075-7)
• [L4] Recurrence of posterior instability occurred in 5 cases (18%); all had recurrent subluxations, with no dislocations. [8] (10.1016/j.jseint.2025.101473)
• [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)
• [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. [10] (10.1177/23259671231213858)
• [L2] Future studies are needed to ascertain long-term outcomes of surgical stabilization based on preoperative dislocation events. [11] (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. [12] (10.2106/jbjs.19.00858)
• [L4] The study demonstrated low rates of recurrent instability and improved clinical outcomes in this high-risk population. [14] (10.1016/j.jse.2026.05.024)
• [L5] Recurrent posterior shoulder instability is an uncommon condition often unrecognized, leading to incorrect diagnoses and delays. [15] (10.5435/00124635-200608000-00004)
• [L5] Even patients who have experienced a single episode of dislocation may go on to develop long-term sequelae. [16] (10.1308/003588409x359123)
• [L4] The age of the patient at the time of the initial dislocation is the most consistent and significant factor influencing prognosis, with recurrence rates of 83% in patients under twenty years and 12% in patients over fifty years. [17] (10.2106/00004623-195638050-00001)
• [L4] At long-term follow-up of 17 years, a high rate of poor outcomes was observed following nonoperative management of anterior shoulder instability. [18] (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. [19] (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. [20] (10.1016/j.jseint.2020.04.023)
• [L3] Patients with first-time dislocations had lower postoperative instability rates and reoperation rates when compared with patients with recurrent dislocations before surgery. [21] (10.1177/0363546517698692)
• [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. [22] (10.1016/j.jse.2020.10.010)
• [L2] Posterior instability represents 10% of all instability events. [23] (10.1177/0363546513501508)
• [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. [24] (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. [25] (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. [26] (10.1177/2325967121s00713)
• [L3] [27] (10.1016/s1058-2746(99)90058-7)
• [L2] Anterior instability outcomes in this matched cohort were superior in all domains versus posterior instability after arthroscopic stabilization. [30] (10.1177/0363546518819199)
• [L3] Variations in the criteria used for the diagnosis of multidirectional instability significantly affect the distribution of patients with that diagnosis. [31] (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. [32] (10.1177/1941738117752306)
• [L2] Detailed and specific information about prognosis is critical in the management of a first-time anterior shoulder dislocation. [33] (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. [34] (10.1016/j.eats.2020.10.053)
• [L5] This review describes the pathologic MR features of posterior instability and the underlying joint abnormalities predisposing to this condition. [35] (10.1016/j.mric.2019.12.005)
• [L5] [36] (10.1177/17585732251320070)
• [L2] All parameters related to history taking, physical exam and imaging studies should be considered according to the patient's age and the number of dislocation episodes. [39] (10.1002/ksa.70336)
• [L3] Posterior instability tests showed high sensitivity but low specificity, leading to over-diagnosis. [40] (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. [41] (10.1007/bf00431367)
• [L4] [44] (10.1016/s1058-2746(96)80056-5)
• [L4] Nonoperative treatment was successful in this patient without subsequent instability or re-dislocation. [45] (10.1007/s00402-007-0546-x)
• [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)
• [L4] Some risk of recurrent instability is part of the natural history of anterior shoulder dislocation. [47] (10.1016/j.jor.2015.01.030)
• [Paper] Alteration of scapular position and motion is common in association with symptoms and dysfunction from glenohumeral instability. [48] (10.1097/00132589-200309000-00001)
• [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. [49] (10.1016/j.arthro.2018.06.021)
• [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] Arthroscopic management of a failed instability repair provides similar success to open reconstruction if one selects proper indications. [53] (10.1097/00132589-200212000-00008)
• [Abstract] The natural history of the first time shoulder dislocations is bound up with arthropathy. [54] (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. [55] (10.1007/s12178-017-9432-5)
• [L5] Its main indications are for shoulder instability in high-impact athletes, together with a capsule-labrum reconstruction, and poor tissue quality of the labrum in patients with multiple long-term dislocations. [56] (10.1097/bte.0000000000000153)
• [L5] At 3-year follow-up, the shoulders were stable and revealed no recurrent instability. [57] (10.1067/mse.2001.115987)
• [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. [59] (10.1016/j.arthro.2016.06.032)
• [Paper] Rates of recurrent instability in published reports are generally higher with arthroscopic stabilization, and other complications occur. [60] (10.1016/s0278-5919(05)70182-4)
• [L4] Sensitive patient selection for arthroscopic Bankart repair is recommended especially in patients with more than five dislocations. [61] (10.1186/2047-783x-14-1-18)
• [L5] The purpose of this article is to define the complications associated with anterior instability repair and provide recommendations on techniques that may be used to help avoid them. [63] (10.1016/j.arthro.2009.03.009)
• [L3] The 1-year outcomes in this prospective study suggest superiority of operative over non-operative treatment for posterior shoulder instability. [64] (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. [65] (10.1136/jisakos-2016-000091)
• [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. [67] (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. [68] (10.1067/mse.2000.108385)
• [L4] [69] (10.1016/j.jse.2012.07.006)
• [L5] The system categorizes instability based on frequency, aetiology, direction, and severity. [76] (10.1136/bjsm.2009.071183)
• [L4] Posterior shoulder dislocation is a rare and challenging injury with varied mechanisms of trauma that complicate diagnosis. [89] (10.5435/jaaos-22-03-145)
• [L3] [91] (10.2106/00004623-200007000-00011)
• [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. [109] (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. [110] (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. [111] (10.1007/s11739-007-0017-y)
• [L4] In patients with anterior instability, recurrence is 24%, with almost all cases associated with new trauma. [118] (10.1177/2325967126s00536)
• [L4] We found that there is wide variation in pathology after anterior dislocation. [120] (10.1016/j.jse.2004.07.002)
• [L4] Anterior instability is most common among shoulder instability patients, and most patients undergoing shoulder stabilization are in their early 20s or younger. [122] (10.1177/0363546518755752)
• [L4] Posterior shoulder dislocations are less common than anterior dislocations but are more commonly missed. [125] (10.1177/2325967114s00196)
• [L5] [127] (10.1016/j.otsr.2024.104061)
• [L3] Lesions associated with traumatic anterior glenohumeral dislocations are more frequent than expected. [128] (10.1007/s00264-015-2862-z)
• [L5] The success of treating anterior glenohumeral instability relies on multiple factors, including glenoid bone loss. [143] (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. [146] (10.1007/s00167-020-06057-7)
• [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. [154] (10.1177/03635465020300041801)
• [L2] Primary non-operative management is a prominent risk factor for recurrence of shoulder instability. [166] (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. [168] (10.1016/j.arthro.2025.07.044)
• [L4] This classification is very useful to compare pathogenesis and results of treatment in patients with glenohumeral instability. [169] (10.1016/s1058-2746(05)80051-5)
• [L1] Early operative stabilization of Bankart lesions in young patients offers a significant reduction in the risk of recurrent instability compared to non-operative management. [172] (10.1111/j.1758-5740.2010.00083.x)
• [Paper] Multidirectional instability should be initially treated with conservative treatment, and newer arthroscopic techniques may now approach the success rates of traditional open treatments. [174] (10.1016/j.csm.2013.07.010)
• [L1] Shoulder instability cannot reliably be classified using the ICD-9 coding system. [181] (10.1016/j.jse.2008.10.005)
• [L3] Instability-related complications occurred only in the capsulabral group, and the incidence increased with time. [188] (10.1177/03635465211029022)
• [L4] This kind of instability is a developing process and without adequate treatment can lead to anatomical instability. [192] (10.1016/s1058-2746(96)80239-4)
• [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. [193] (10.1177/0363546512470815)
• [L4] The stated criteria for atraumatic dislocation appear not to be [valid/consistent]. [194] (10.1016/s1058-2746(96)80314-4)
• [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. [195] (10.1177/2325967115607434)
• [L4] Recurrent instability requiring capsular reconstruction seems to be more prevalent in patients with a previous history of shoulder dislocation. [198] (10.1016/j.jse.2009.07.062)
• [L4] Multidirectional instability is a complex problem. [200] (10.2174/1874325001711010812)
• [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. [208] (10.1148/radiol.2372041429)
• [L4] [210] (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%). [213] (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. [215] (10.1016/j.jse.2014.06.009)
• [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. [218] (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. [219] (10.1016/j.otsr.2015.09.029)
• [L4] Nonoperative treatment is commonly unsuccessful in active patients, and surgical stabilization can be considered in patients who do not respond. [224] (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. [225] (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. [226] (10.1016/j.jse.2020.04.012)
• [L3] Preoperative risk factors included history of bilateral shoulder instability and atraumatic mechanism of dislocation. [228] (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. [229] (10.1186/s12891-025-08947-8)
• [L4] None of the patients has had instability after an average follow-up of 26 months. [230] (10.1016/s1058-2746(97)90064-1)
• [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. [231] (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. [232] (10.1177/0363546519886861)
• [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. [233] (10.1016/j.jseint.2025.04.033)
• [L5] At her most recent follow-up, she denied any apprehension or instability in either shoulder and had no further dislocations. [236] (10.1097/bte.0000000000000175)
• [L4] Surgical arthroscopic repair was possible in all cases of acute or recurrent instability with well-defined exclusion criteria. [237] (10.1055/s-0032-1327656)
• [L4] The Latarjet procedure provides excellent long-term outcomes in the treatment of recurrent anterior glenohumeral instability. [239] (10.1016/j.jse.2014.02.015)
• [L1] [241] (10.2106/jbjs.9616.ebo209)
• [L2] [242] (10.1197/j.jht.2004.02.010)
• [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. [243] (10.1007/s00167-015-3785-3)
• [L2] [244] (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. [245] (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. [247] (10.1177/03635465000280020401)
• [L2] Indications for the Latarjet were humeral and glenoid bone loss, duration of symptoms, number of dislocations, and revision stabilizations. [248] (10.1016/j.arthro.2019.02.035)
• [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. [249] (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. [250] (10.1016/j.jseint.2025.08.006)
• [L4] The prevalence of subjects with past or present recurrent dislocations in the male population 22 to 33 years old was found to be approximately .5%. [253] (10.1016/s1058-2746(98)90011-8)
• [L3] Correspondingly, they reported a more extensive history of instability, were more likely to have severe bone loss, and required more invasive stabilization procedures. [256] (10.1177/2325967119841079)
• [L4] The risk of recurrent dislocation is low following this procedure. [257] (10.1007/s00167-007-0316-x)
• [L3] [258] (10.1177/036354658401200103)
• [L1] [259] (10.1016/j.jse.2012.02.008)
• [L3] Identification of these critical radiographic variables on magnetic resonance arthrography assists in the accurate diagnosis and management of clinically significant posterior shoulder instability. [261] (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. [262] (10.1177/17585732221117103)
• [L2] [264] (10.1016/j.jse.2010.10.027)
• [L1] Capsular injury is commonly seen in magnetic resonance imaging of patients with anterior shoulder instability. [265] (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. [266] (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. [268] (10.1007/s00256-014-2080-6)
• [Paper] CINE MRI is a reproducible technique to evaluate normal capsular attachments to the glenoid and confirms diagnosis of anterior and posterior shoulder instability. [271] (10.1016/s1058-2746(96)80178-9)
• [L4] MRI is a simple, non invasive method for acute first time traumatic shoulder dislocation evaluation. [272] (10.1016/s1058-2746(96)80273-4)
• [L3] MR arthrogram outperforms standard MRI for labral tear diagnosis, particularly as time from dislocation increases. [273] (10.1016/j.arthro.2024.02.020)
• [L3] [275] (10.1097/corr.0000000000002320)
• [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. [276] (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. [278] (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. [280] (10.1177/2325967123s00069)
• [L5] MR-arthrography is identified as the main tool in diagnosing shoulder instability injuries. [283] (10.21037/qims.2017.08.05)
• [L4] In the setting of ongoing pain or instability, further imaging should be performed. [284] (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. [285] (10.1016/j.jseint.2022.12.003)
• [L4] These findings suggest that this radiographic change should be regarded as a new sign of anterior shoulder instability of traumatic origin. [288] (10.1016/1058-2746(92)90092-h)
• [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. [289] (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. [291] (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. [292] (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. [293] (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. [294] (10.5435/jaaos-d-22-00016)
• [L3] The age of the patients when the primary dislocation occurred was the most influential factor for prognosis. [298] (10.1016/s1058-2746(96)80363-6)

See Also

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

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