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Bones & Joints

Anatomy and kinematics of the glenohumeral, acromioclavicular, sternoclavicular, and scapulothoracic joints and their role in shoulder girdle dysfunction.

141 citationsUpdated Oct 2026

Overview

Glenohumeral joint pathology spans a spectrum from focal cartilage defects to advanced degenerative arthritis and instability. For patients presenting with frank degenerative arthritis or extensive humeral head involvement, the prognosis is poor, necessitating earlier consideration of arthroplasty [1]. While long-term outcomes for glenohumeral preservation techniques remain unknown, clinical experience indicates that many patients achieve satisfactory results and delay the need for prosthetic shoulder arthroplasty [2]. Conversely, poor clinical outcomes in patients converted to total shoulder arthroplasty after failure of biological resurfacing suggest that total shoulder arthroplasty may be the preferred primary procedure in young patients with severe glenohumeral arthritis [58]. As studies continue to evaluate results in cuff tear arthropathy, existing indications and treatment algorithms for rotator cuff deficient arthritis of the glenohumeral joint will be further refined [59].

Joint-preserving procedures have shown reasonable outcomes for focal chondral defects, though long-term outcomes remain unknown and the progression of osteoarthritis remains a concern [12]. Positive clinical outcomes have been demonstrated with various surgical techniques for articular cartilage defects, particularly in non-weightbearing joints, though evidence for the shoulder specifically is often limited to retrospective case series [14]. In a 10-year follow-up of microfracture of the glenohumeral joint, 21.4% of patients required conversion to arthroplasty and 33% to 42% were considered to have potential clinical failure [15]. In a minimum 7-year follow-up series, up to 25% of patients required conversion to arthroplasty less than 10 years following index microfracture of the glenohumeral joint [170]. Mid to long-term results are needed to evaluate the osteoarthritic rate following minced cartilage implantation in the glenohumeral joint [9].

In selected patients, shoulder fusion considerably alleviates pain and provides acceptable function and satisfaction [54]. Pain remains unremitting in 50% of patients with multidirectional instability treated with soft tissue stabilization, and glenohumeral arthrodesis may be needed as a last option [61]. At a mean follow-up of 8 years, the coracoid graft remained present in 97% of cases after Latarjet procedure, even in patients with minimal preoperative glenoid bone loss (<5%) [28]. Screws and staples can produce complications that require reoperation and are capable of causing a permanent loss of joint function about the glenohumeral joint [27]. Arthroscopic management is an effective treatment of choice for primary synovial chondromatosis of the shoulder with low morbidity and early functional return [8]. Arthroscopic outside-in shoulder release can be performed safely and effectively when certain guidelines are followed and can allow for subsequent access to the glenohumeral joint in most cases [42]. Joint instability must be avoided to lessen complications and the need for revision surgery following total shoulder arthroplasty with a tissue-ingrowth glenoid component [30]. In a clinical series of absorbable suture fixation of osteochondral fragments in intra-articular fractures of the upper extremity, all patients achieved bone union and joint congruity restoration without major complications [13]. Treatment by surgical intervention for deltoid contracture should be performed at an age when spontaneous correction of the bone deformity can prevent future development of secondary arthrosis [3]. Diagnostic indications for basal joint arthroscopy include the assessment of painful post-traumatic basal joint lesions of cartilage and ligaments, and the evaluation of chondromalacia and ligament attenuation to help classify basal joint osteoarthritis [5]. Undertaking a specific operative procedure based on magnetic resonance imaging diagnosis and structural anatomic magnetic resonance imaging findings for chronic traumatic anterior sternoclavicular joint instability provides a satisfactory outcome with regards to joint stability and clinical outcomes [26]. The glenohumeral relationship in the transverse plane of the body offers a useful guideline in difficult prosthetic surgery of the shoulder in which normal anatomic landmarks are lost because of arthritic or traumatic deformity, contrasting with the variability of the version of the humeral head and of the glenoid [60]. While outcomes met the patient's satisfaction in total clavicle reconstruction with free peroneal graft for chronic nonbacterial osteomyelitis, advantages and complications should be carefully discussed with patients due to limited evidence of superior clinical outcome [173].

Anatomy & Pathophysiology

Bony Anatomy

The clavicle is the first bone to ossify, appearing at the fifth week of gestation, and is the only long bone to ossify by intramembranous ossification [76, 91]. Its medial (sternal) epiphysis is the last ossification center to fuse, occurring between ages 20 and 25 years [76, 91]. The primary blood supply to the clavicle is periosteal, with no nutrient artery present [76, 82].

The scapula ossifies beginning at the eighth week of gestation [76]. It possesses only one true diarthrodial articulation, the acromioclavicular (AC) joint [76]. The scapular body is triangular when viewed anteroposteriorly, with its base situated superiorly and its apex inferiorly [75]. The glenoid connects to the flat scapular body via the scapular neck [75]. The coracoid process curves forwards from the superior surface of the scapular neck, while the scapular spine ends in the flattened acromion, which also curves forwards [75]. The scapula is anteverted on the chest wall approximately 30 degrees relative to the body [91]. It is separated from the chest wall by thin gliding fibro-fatty tissue, allowing smooth excursion [75].

The acromion has three ossification centers: the metacromion (base), the mesoacromion (middle), and the preacromion (tip) [76]. Failure of fusion of these centers results in os acromiale [76, 91]. The highest concentration of bony mass in the scapula is found in the glenoid, the scapular neck (including the base of the coracoid process), and the lateral border of the scapular body [75]. Two bony pillars transmit compressive forces from the glenoid fossa: the lateral pillar, which connects the inferior border of the glenoid with the inferior angle, and the spinal pillar, which arises from the central part of the glenoid and continues medially to become part of the base of the scapular spine [75]. The weakest bone in the scapula is located primarily in the central part of the biomechanical body, specifically in the infraspinous fossa [75]. The weakest area of the circumference of the biomechanical body is the spinomedial angle, which is the connection of the scapular spine and the medial border [75]. In most scapular body fractures, one of the main fracture lines passes through this spinomedial angle [75].

The glenoid is a convex structure of shallow depth shaped like an inverted pear [72]. It is a shallow socket, approximately one third the size of the humeral head [74]. The glenoid subchondral bone is relatively flat, with the articular concavity augmented by cartilage and a circumferential labrum [76]. The glenoid averages 5° of retroversion in relation to the axis of the scapular body [76, 91]. The normal position of the glenoid surface in relation to the axis of the scapular body ranges from 2 degrees of anteversion to 7 degrees of retroversion [86].

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) [76]. These centers fuse to the shaft at age 17 to 20 years [76]. Humerus formation begins with the appearance of the cartilage anlage, present by the fifth week of gestation, with the primary ossification center appearing at about the sixth week [80]. By birth, the entire humeral diaphysis is completely ossified, while the proximal humerus is primarily cartilaginous [80]. Ossification centers are detectable by ultrasonography as early as the 38th week of gestation [80]. The ossification center for the humeral head is usually present at birth [80]. The greater tuberosity ossification center appears by 1 to 3 years of age, and the lesser tuberosity center appears by 5 years of age [80]. The proximal humeral ossification centers fuse by 5 to 7 years of age to form the humeral head [80]. The proximal humeral physis closes by 14 to 17 years of age in girls and by 16 to 18 years in boys [80].

The articular head of the proximal humerus is spherical with a diameter of 37 to 57 mm [72]. The articular surface is essentially spherical, with an arc of approximately 160 degrees covered by articular cartilage [86]. The radius of curvature of the humeral head is approximately 25 mm and is slightly larger in men than in women [86]. The glenoid articular surface radius of curvature is 2 to 3 mm larger than that of the humeral head [86]. The most superior portion of the articular surface of the humeral head averages 8 mm above the greater tuberosity [72]. The superior margin of the humeral head articular surface is normally superior to the top of the greater tuberosity by 8 to 10 mm [86]. The head height is approximately 5.6 cm above the superior border of the pectoralis major tendon [91].

The humeral head averages 19° of retroversion and 41° of inclination (neck-shaft angle) [76]. Humeral version averages 29.8 degrees, with a range of 10 to 55 degrees [72]. The humeral head is inclined approximately 130 degrees with respect to the humeral shaft [72]. The neck-shaft angle measures an average of 135 degrees [74]. The humeral head is retroverted an average of 30 degrees [74]. The average neck-shaft angle is 45 degrees (±5 degrees), with a range of 30 to 50 degrees [86]. Arthritic shoulders have a flatter neck-shaft angle close to 50 degrees [86]. The humeral head is retroverted 30 degrees relative to the transepicondylar axis of the humerus [91]. Mean humeral retroversion values are around 26 degrees in healthy adults [80]. In infants and young children, humeral retroversion averages 65 degrees and gradually decreases, approaching adult values by 11 years of age [80].

The anatomic neck of the proximal humerus is located at the junction of the articular surface and the tuberosities [72, 74, 91]. The surgical neck represents an indistinct region (metadiaphyseal junction) below the tuberosities but above the humeral shaft [72, 74]. The greater tuberosity serves as the attachment site for the supraspinatus, infraspinatus, and teres minor tendons [72, 74]. The lesser tuberosity serves as the attachment site for the subscapularis tendon [72, 74]. The bicipital groove lies between the greater and lesser tuberosities and serves as a pathway for the long head of the biceps [72]. The distal aspect of the bicipital groove is internally rotated with respect to the proximal portion [72].

Eighty percent of subsequent humeral growth comes from the proximal humeral physis, accounting for approximately 40% of the growth of the entire upper extremity [80]. Less than 75% of proximal humeral growth occurs before 2 years of age, and more than 85% occurs by 8 years of age [80]. The proximal humeral physis is irregularly shaped, with its apex located on the posteromedial portion of the proximal humerus [80]. The periosteum is thicker and stronger in the posteromedial portion of the proximal humerus compared to the anterolateral portion [80]. Glenohumeral geometry is both gender and population specific [50]. Three-dimensional anthropometric analysis reveals specific glenohumeral geometry in the normal Japanese population [164]. CT-based preoperative analysis of scapula morphology and glenohumeral joint geometry leads to more precise planning of shoulder surgery [122].

Joints and Ligaments

The sternoclavicular (SC) joint is the only true diarthrodial articulation between the upper appendicular and axial skeletons [76, 91]. The posterior SC joint capsule and ligaments are the primary stabilizers to anterior and posterior translation of the medial clavicle [76]. The posterior sternoclavicular ligament is the strongest and primary restraint to anteroposterior instability [91]. The SC joint rotates 30 degrees with shoulder motion [91].

The acromioclavicular (AC) joint is a small diarthrodial joint with an interposed fibrocartilaginous disk [76, 91]. The superior and posterior AC ligaments are the primary stabilizers to anterior and posterior (horizontal) translation of the clavicle [76]. The posterior and superior AC ligaments are considered the strongest [91]. The coracoclavicular ligaments (conoid: medial; trapezoid: lateral) are the primary stabilizers to superior (vertical) translation of the distal clavicle [76, 82]. The trapezoid ligament is located approximately 25 mm from the AC joint [91]. The conoid ligament is located approximately 45 mm from the AC joint and is stronger than the trapezoid ligament [91].

The superior shoulder suspensory complex (SSSC) provides a stable connection between the scapula and the axial skeleton [76]. It is a bone–soft-tissue ring that provides a stable connection of the glenoid and scapula to the clavicle [82]. The SSSC is composed of the glenoid, the coracoid process, the coracoclavicular ligaments, the distal clavicle, the AC joint, and the acromion [76]. Specifically, it comprises four bony landmarks—distal clavicle, acromion, coracoid process, and glenoid neck—and the supporting ligamentous complexes of the AC joint and the CC ligaments [82]. The superior strut of the SSSC comprises the middle clavicle [76]. The inferior strut of the SSSC comprises the lateral scapular border/spine of the scapula [76].

The glenohumeral joint has the greatest range of motion of all joints in the human body [64, 87, 91]. It depends on static and dynamic stabilizers for movement and stability [86, 91]. Static stabilizers include articular congruity, the glenoid labrum, concavity-compression, negative intra-articular pressure, and the glenohumeral capsule and ligaments [76]. The glenoid labrum provides concavity and up to 50% of marginal glenoid socket depth [76]. The fibrocartilaginous glenoid labrum deepens the socket by 50% and provides a bumper to translation [91]. Dynamic stabilizers include the rotator cuff and biceps tendon [91]. Scapulothoracic mechanics contribute to dynamic stability of the glenohumeral joint [91]. The rotator cuff stabilizes the glenohumeral joint via joint compression [76].

The rotator interval is defined medially by the base of the coracoid, superiorly by the supraspinatus tendon, and inferiorly by the subscapularis tendon [76]. It contains the coracohumeral (CH) ligament, the superior glenohumeral ligament (SGHL), and the intra-articular portion of the long head of the biceps tendon [76]. Laxity of the rotator interval results in inferior laxity (the sulcus sign) [76]. Contracture of the rotator interval is seen with adhesive capsulitis [76]. The CH ligament restricts external rotation in adduction and is a static restraint to inferior and posterior translation in adduction and external rotation [76]. The SGHL is a primary static restraint against anterior translation with the arm at the side [76]. With the CH ligament, the SGHL forms a pulley that provides restraint against medial subluxation of the long head of the biceps tendon [76].

The middle glenohumeral ligament (MGHL) is a primary static restraint against anterior translation with the arm in external rotation and 45° of abduction [76]. The MGHL is absent in up to 30% of shoulders [91]. The MGHL limits external rotation when the arm is in the lower and middle ranges of abduction but has little effect when the arm is in 90 degrees of abduction [87]. The anterior band of the inferior glenohumeral ligament (AB-IGHL) is a primary static restraint against anterior-inferior dislocation of the glenohumeral joint in 90° of abduction and external rotation (position of apprehension) [76, 91]. The posterior band of the IGHL (PB-IGHL) is a primary static restraint against posterior-inferior translation in internal rotation and adduction [76]. The SGHL is the primary restraint to inferior humeral subluxation in 0 degrees of abduction and is the primary stabilizer to anterior and posterior stress in the same position [87]. Tightening of the rotator interval decreases posterior and inferior translation [87]. The anteroinferior glenohumeral ligament complex is the main stabilizer to anterior and posterior stresses when the shoulder is abducted 45 degrees or more [87].

The inferior glenohumeral ligament is composed of an anterior band that is quite thick, a posterior band that is less thick and distinct, and a thinner intervening axillary pouch, creating a hammock-type sling [87]. With external rotation, the hammock slides anteriorly and superiorly, the anterior band tightens, and the posterior band fans out [87]. With internal rotation, the opposite occurs to the inferior glenohumeral ligament bands [87].

The superior transverse scapular ligament arises from the medial base of the coracoid overlying the suprascapular notch [76]. The suprascapular artery runs superior to the superior transverse scapular ligament, and the nerve runs deep to the ligament [76]. Entrapment of the suprascapular nerve at the superior transverse scapular ligament causes denervation of both the supraspinatus and the infraspinatus [76]. The spinoglenoid ligament overlies the suprascapular nerve at the spinoglenoid notch [76]. Entrapment, traction, or compression at the spinoglenoid notch causes denervation of the infraspinatus [76].

The coracoacromial arch is formed by the acromion process posterosuperiorly, the coracoid process anteriorly, and the coracoacromial ligament joining them [81]. The subacromial bursa separates the rotator cuff tendons from the coracoacromial arch, allowing them to glide [81]. The coracoacromial ligament contributes to anterosuperior stability in rotator cuff deficiency and should be preserved with irreparable cuff tears to prevent anterosuperior escape [91]. The acromial branch of the thoracoacromial artery runs on the medial aspect of the coracoacromial ligament [91]. The coracoacromial ligament is the arthroscopic landmark for a complete release of the rotator interval for adhesive capsulitis [91]. The coracoid process attachments include the coracoacromial ligament, coracoclavicular ligaments (conoid and trapezoid), conjoined tendon (coracobrachialis and short head of biceps), and pectoralis minor [91].

Classification

Glenohumeral Joint

The glenohumeral joint is a saddle-shaped synovial articulation serving as the only skeletal connection between the axial skeleton and the upper limb [22]. Instability is defined as a clinical situation involving excessive translation of the humeral head on the glenoid fossa, where an abnormal amount of translation resulting in symptoms is the sine qua non of the condition [64]. Joint stability relies on both static ligamentous and tendinous effects and dynamic muscular mechanisms, with the surrounding soft-tissue envelope acting as the primary contributor [64]. Dislocation requires translation approximating one half of the humeral head diameter [64]. The macroscopically recognizable ligaments consist of collagen fiber bundles in layers of differing thickness and orientation [161], while the superior joint capsule inserts on the greater tubercle, covering 30 to 60% of its surface with variable thickness [178]. In most cases, the coracoacromial ligament comprises two distinct bands: anterolateral and posteromedial [171]. Cartilage thickness distribution is non-homogenous with reproducible patterns [195], and sensory receptors, primarily type I and IV, are differentially expressed in the capsule [158]. Joint contact patterns vary significantly based on abduction angle and shoulder condition [55], and parenchymal-level thickness of the inferior capsule is negatively correlated with range of motion in all directions [67]. Discrepancies in defining multidirectional instability can complicate diagnosis and treatment selection [39].

Acromioclavicular Joint

Injury to the acromioclavicular joint involves progressive disruption of ligamentous support, beginning with capsular ligaments and progressing to coracoclavicular ligaments [16]. Higher grade injuries present with distal clavicle prominence, localized bruising, swelling, and tenderness [16]. Manual assessment of horizontal plane translation compared with the opposite shoulder is required, and the ability to reduce deformity with manual pressure helps differentiate nonsurgical from surgical treatment for higher grade injuries [16]. Imaging must confirm that the anterior clavicle lies in the same plane as the anterior acromion, and an axillary view is necessary to rule out posterior translation [16]. Management depends on injury type, with type III separations remaining controversial [185]. Associated intraarticular lesions occur in 20% of acute injuries overall [210], with specific prevalences of 10.4% (5.7–15.9%) for grade 3, 17.2% (6.2–30.8%) for grade 4, and 18.8% (13.8–24.4%) for grade 5 injuries [210].

Sternoclavicular Joint

The sternoclavicular joint is a saddle-shaped synovial joint serving as the only skeletal articulation between the axial skeleton and the upper limb [22]. Management of sternoclavicular joint injuries is mostly nonsurgical, except in cases of instability and pain [185].

Fractures

Neer: Classifications of proximal humeral fractures using the Neer system based on CT scans and plain radiographs are not very reliable or reproducible due to difficulty in determining which segments are fractured [168].

Mitsuzawa: The Mitsuzawa classification system for dislocated and displaced proximal humeral fractures incorporates perspectives on glenohumeral compatibility and displacement [188]. This system provided satisfactory intra- and interobserver reliability compared to the Neer and AO/OTA classifications [188].

Lateral Clavicle: A new simple classification system for lateral clavicle fractures showed substantial inter- and intraobserver reliability [132]. Distinctive patterns of clavicular malunion were also identified [197].

Tumors

Enneking: The Enneking staging system for benign lesions stages them as 1 (latent), 2 (active), or 3 (aggressive) based on radiographic features [18]. For malignancies of bone and soft tissue, the system assigns a tumor grade based on histology (G), anatomic site of primary disease (T), and presence of metastases (M) [18]. Staging assesses the extent of a tumour both locally and distantly [142]. The lungs are the most common site for metastases from bone and soft-tissue sarcomas [142]. The system classifies tumours according to grade (high or low), metastasis status, and compartmental confinement, where a compartment is defined as an enclosed tissue space such as a bone, joint space, or muscle group confined by its fascial envelope [142]. Stage 1A is a low-grade, intracompartmental tumour [142]. Stage 1B is a low-grade, extracompartmental tumour [142]. Stage 2A is a high-grade, intracompartmental tumour [142]. Stage 2B is a high-grade, extracompartmental tumour [142]. Stage 3 is any of the above with metastases [142].

TNM: The TNM staging system takes into consideration the histological subtype, size, continuity, grade, and local and distant spread of the tumour [142]. For bone sarcomas, size is dichotomized to small (<8 cm) or large (>8 cm) [142]. For soft-tissue sarcomas, size is dichotomized to small (<5 cm) or large (>5 cm) [142]. Stage 1A is low-grade, small, no metastases [142]. Stage 1B is low-grade, large, no metastases [142]. Stage 2A is intermediate- or high-grade, small, no metastases [142]. Stage 2B is intermediate-grade, large, no metastases [142]. Stage 3 is high-grade, large, no metastases [142]. Stage 4 is any with metastases [142].

Cartilage and Osteoarthritis

Arthroscopic Chondromalacia: An accepted arthroscopic grading scale of chondromalacia is: grade 1-cartilage softening, grade 2-fibrillation or superficial fissures of the cartilage, grade 3-deep fissuring of the cartilage without exposed subchondral bone, and grade 4-cartilage erosion with exposed subchondral bone [206]. Histologically, chondromalacic cartilage has a fibrillated surface with reduced proteoglycan and collagen staining and reduced chondrocyte numbers superficially [206]. Chondrocyte clusters, called clones, are found in the transitional and deep zones and at the junction of normal and chondromalacic cartilage [206]. Grade 1 lesions are generally not treated surgically [206]. Resurfacing techniques are used to correct grade 4 lesions [206]. Current surgical techniques for treating grade 2 and 3 lesions are typically only moderately successful [206].

Basal Joint Arthroscopy: Diagnostic indications for basal joint arthroscopy include the evaluation of chondromalacia and ligament attenuation to help classify basal joint osteoarthritis [5].

Murine Rheumatoid Arthritis: In a murine model of rheumatoid arthritis, bone resorption severity grade 1 is normal [43]. Grade 2 is mild appearance of bone resorption at the margin of the bone [43]. Grade 3 is moderate bone resorption involving subchondral bone with intact articular cartilage and bone interface [43]. Grade 4 is marked bone resorption involving extensive subchondral and marginal area with loss of intact articular cartilage and bone interface [43].

Other Considerations: Two patients showed grade I secondary osteoarthritis according to the Samilson and Prieto classification following autologous chondrocyte implantation for focal articular cartilage defects of the humeral head [183].

Deformity and Instability

The Waters glenohumeral joint deformity score improved during the study period in patients with brachial plexus birth injury (p < 0.0001) [70]. Three distinct patterns were identified among incongruent glenohumeral joints in children with brachial plexus birth palsy: (1) a flattened posterior glenoid in which the humeral head lies in posterior subluxation, (2) a bifaceted glenoid with a distinct ridge between the anterior fossa and posterior fossa, and (3) a dislocation in which the humeral head has slipped over the posterior edge of the glenoid [218].

Clinical Presentation

Glenohumeral Joint

Symptomatic primary glenohumeral joint osteoarthritis presents with pain, reduced range of motion, and progressive loss of shoulder function [48]. The condition is characterized by progressive humeral head cartilage loss, adaptive changes to the subchondral bone, and development of inferior humeral head osteophytes [48]. These changes result in a subsequent biomechanical change of the glenohumeral joint, joint space narrowing, and posterior humeral head subluxation, followed by progressive posterior glenoid bone loss [48]. Primary glenohumeral joint osteoarthritis has no specific causative factor that explains the etiology of the disease process other than the degenerative process that naturally occurs because of aging [48]. Primary glenohumeral joint osteoarthritis can occur over a broad age range [48].

Severe pain and disability with accompanying radiological changes in the glenohumeral joint are almost always the indications for joint replacement in patients where conservative treatment has failed or is futile [46]. Occasionally there may be an indication to replace a shoulder because of progressive loss of movement and pain may not necessarily be the most significant factor [46]. For those patients with frank degenerative arthritis or extensive head involvement, the prognosis is poor, and earlier consideration of arthroplasty is indicated [1].

Glenohumeral joint tuberculosis can be difficult to diagnose in its early stages and is often misdiagnosed as frozen shoulder [44]. A subdeltoid lipoma can present with a clinical presentation that resembles glenohumeral instability [40]. Heterotopic ossification formation should be considered in the differential diagnosis of a patient presenting with severe musculoskeletal pain and associated stiffness after a prolonged illness [17]. Recognition of musculoskeletal presentations of systemic amyloidosis can lead to earlier diagnosis and treatment, which may prevent life-threatening manifestations [34]. In the appropriate clinical setting, both radiographs and MR images of the shoulder can be used to establish the diagnosis of chondrolysis of the glenohumeral joint [35]. It remained difficult to preoperatively diagnose panlabral tear using standard physical examinations and imaging studies [135]. Although bony lesions may be relatively rare compared with soft-tissue pathology, they constitute a critically important entity in the management of shoulder instability [41]. Arthrosis rarely causes more than minor subjective symptoms or a minor objectively perceived disadvantage during 13 years' follow-up after arthroscopic Bankart repair [11].

Acromioclavicular Joint

Osteoarthritis of the acromioclavicular (AC) joint is a common condition causing anterior or superior shoulder pain, especially with overhead and cross-body activities [38]. AC joint osteoarthritis most commonly occurs in middle-aged individuals because of degeneration to the fibrocartilaginous disk that cushions the articulations [38]. Diagnosis of AC joint osteoarthritis relies on history, physical examination, imaging, and diagnostic local anesthetic injection [38]. Diagnosis of AC joint osteoarthritis can be challenging given the lack of specificity with positive physical examination findings and the variable nature of AC joint pain [38]. Symptomatic AC osteoarthritis must be differentiated from instability and subtle instability, which may have similar symptoms [38].

Plain radiographs can reveal degeneration of the AC joint, but diagnosis cannot be based on this alone because similar radiographic findings can be seen in asymptomatic individuals [38]. Higher grade AC joint injuries result in prominence of the distal clavicle [16]. Localized bruising, swelling, and tenderness are present in acute AC joint injuries [16]. Range of motion of rotator cuff strength typically is normal in chronic AC joint injuries but may be limited in acute injuries secondary to pain [16]. A complete neurologic examination of the upper extremity should be performed to rule out brachial plexus injuries in AC joint trauma [16]. Scapular motion should be carefully assessed as scapular dyskinesis can be seen with this type of injury [16]. The axillary view is needed to rule out posterior translation of the distal clavicle in AC joint imaging [16]. The anterior aspect of the clavicle should lie in the same plane as the anterior aspect of the acromion on AC joint radiographs [16].

A combination of physical tests is more helpful than isolated tests in evaluating patients with acromioclavicular joint pathologic lesions [104]. The BvR test is a highly sensitive test in patients presenting with isolated AC related symptoms, and demonstrates AC joint pathology better than other accepted tests [109].

Sternoclavicular Joint

SCJ osteoarthritis is a very common incidental finding on CT scans, particularly with increasing age, with nearly 90% of patients older than 50 years showing some evidence of these changes [21]. Nontraumatic disorders of the clavicle are uncommon and frequently the diagnosis is not obvious [20]. Treatment for nontraumatic disorders of the clavicle varies by disorder and may include symptomatic and expectant management, drug therapy, and nonsurgical or surgical treatment [20]. Pain and swelling in the sternoclavicular joint can be associated with a destructive process of unknown origin, periosteal reaction along the distal end of clavicle, and thickening of costal cartilage [119]. Monoarticular rheumatoid arthritis of the sternoclavicular joint may present with positive rheumatoid factor, raised inflammatory markers (ESR 57 mm/h and CRP 11), and absence of other joint involvement [119].

Other Joints and Lesions

A comprehensive investigation is appropriate before surgical excision of the thumb IP joint sesamoid bone [6]. Early diagnosis and appropriate intervention are critical to prevent joint destruction and optimize patient outcomes in pigmented villonodular synovitis [4].

Patients with bone tumors most frequently present with pain, which initially may be activity related, but a patient with a malignancy of bone often complains of progressive pain at rest and at night [136]. Patients with benign bone tumors also may have activity-related pain if the lesion is large enough to weaken the bone [136]. Osteoid osteoma may cause night pain initially [136]. Patients with soft-tissue tumors rarely complain of pain but more often complain of a mass [136]. Nerve sheath tumors are an exception to the rule that soft-tissue tumors rarely cause pain, as they may present with pain or neurologic signs [136]. Age may be the most important information obtained in the history of musculoskeletal neoplasms because most benign and malignant musculoskeletal neoplasms occur within specific age ranges [136]. Family history can be helpful in cases of multiple hereditary exostosis and neurofibromatosis, both of which have autosomal dominant inheritance [136]. Ewing sarcoma is exceedingly rare in individuals of African descent [136].

Enchondroma in the humeral metaphysis contains punctate calcifications on the radiograph and has a typical lobulated appearance on MRI [18]. Benign lesions are staged 1 (latent), 2 (active), or 3 (aggressive) based on radiographic features, often requiring serial imaging [18]. A wide variation exists in the literature in regard to the incidence of shoulder lesions, and true incidence rates are often difficult to estimate for benign, asymptomatic lesions [18]. Scapular winging diagnosis and management differ between neurogenic causes and traumatic muscular detachment [141].

Investigations

Plain radiography: Standardized plain films are almost always sufficient to establish diagnosis, determine pathoanatomy severity, assist in surgical planning, and illustrate the condition to the patient [32]. The standard shoulder series should include a true AP view in the scapular plane, an AP view, an axillary view, and a scapular Y view [118]. The true AP view in the scapular plane visualizes the anterior greater tuberosity in profile and can reveal proximal humeral migration [118]. The AP view with the arm in internal rotation visualizes the posterior aspect of the greater tuberosity and the lesser tuberosity in profile [118]. The axillary view is necessary for evaluating glenohumeral joint instability and determines the humeral head position in the glenoid fossa [118]. It may detect occult, locked posterior shoulder dislocation in a patient who exhibits a lack of passive external rotation [118]. The axillary view is helpful in evaluating glenoid morphology in glenohumeral osteoarthritis and provides visualization of the coracoid process, acromion, and distal clavicle [118].

The axillary view is oriented so that both the spinoglenoid notch and the scapular neck are visible [32]. This view demonstrates glenohumeral relationships in the functional position of elevation, referred to as the "truth view" [32]. Joint space narrowing is most evident on the axillary truth view because arthritis usually involves the central aspect of the humeral head [32]. The axillary truth view shows posterior subluxation or "functional decentering" that is not evident in images taken with the arm at the side [32]. The degree of posterior subluxation can be measured by the position of the humeral head center relative to the scapular plane, relative to the glenoid face, or by the point of contact of the humeral articular surface on the glenoid articular surface [32]. The point of contact reflects the degree of centering of the net humeral joint reaction force on the glenoid [32]. Malcentering of the joint reaction force leads to posterior instability, posterior glenoid wear, and "rocking horse" loosening of prosthetic glenoid components [32].

The scapular Y view provides visualization of the coracoacromial arch and can reveal coracoacromial spurs associated with rotator cuff pathology [118]. It is a reliable alternative for evaluating glenohumeral subluxation and dislocation [118]. The scapular Y view can show scapular body abnormalities such as osteochondroma or fracture, as well as acromial shape [118]. The normal acromiohumeral distance is 7 to 14 mm [118]. The width of the glenohumeral joint space should be symmetric superiorly and inferiorly [118]. The normal coracoclavicular distance is 1.1 to 1.3 cm [118]. Neer classified acromial morphology as type I (flat), type II (curved), and type III (hooked) [118]. Type III acromial morphology has a correlation with the presence of rotator cuff disease, but no direct causal relationship has been demonstrated [118]. The Neer classification of acromial morphology has shown relatively poor interobserver reliability [118].

Specific views are indicated for particular pathologies. The Stryker notch view is indicated to evaluate Hill-Sachs lesions after dislocation [118]. The West Point view is indicated for anterior glenoid bone loss [118]. The Zanca view is indicated for the acromioclavicular joint [118]. The apical oblique view is indicated to evaluate for glenoid rim fracture in instability [118]. The serendipity view is indicated for the sternoclavicular joint [118]. For proximal humerus fractures, the recommended radiographic series is the Neer trauma series, consisting of an AP view, a lateral view in the scapular plane, and a Velpeau modified axillary view [106]. The lateral radiograph in the scapular plane is the tangential Y-view of the scapula [106]. The combination of the three views in the Neer trauma series allows evaluation of the shoulder joint in three separate perpendicular planes [106]. The axillary view is important for evaluating the glenoid articular surface and the relationship of the humeral head anteriorly and posteriorly [106].

The radiographic appearance of irreducible superolateral dislocation of the glenohumeral joint is unique and suggests complete tear of the rotator cuff with concomitant tear of the deltoid muscle [213]. A subdeltoid lipoma can present with a clinical appearance resembling glenohumeral instability [40]. Posttraumatic subluxation of the glenohumeral joint caused by interposition of the rotator cuff highlights the importance of correct assessment of postreduction radiographs [45]. The algorithm for shoulder radiography improved its role as an initial imaging modality to rule out rotator cuff tears [219].

CT: CT is helpful for planning fracture surgery and shoulder joint replacement [99]. CT imaging is frequently used to evaluate fractures of the shoulder, assess bony lesions in recurrent instability cases, or for preoperative templating for shoulder arthritis [116]. CT with three-dimensional reconstructions is the advanced imaging study of choice for determining the extent of glenoid bone loss in the setting of shoulder instability [118]. Three-dimensional sagittal CT scans allow for optimal evaluation of displaced glenoid fractures [118]. CT is the gold standard for imaging sternoclavicular dislocations, making it the most reliable method until further research establishes other modalities [196]. CT scanning may be necessary on occasion for detailing bony anatomy in proximal humerus fractures [106]. CT scans have the disadvantage of being taken with the arm in the adducted position, unlike the axillary truth view [32]. CT scans may offer increased precision in measuring glenoid version, but this precision does not improve the quality of surgery or clinical outcome [32].

Osteoarthritis of the sternoclavicular joint is a very common incidental finding on CT scans, particularly with increasing age [21]. Nearly 90% of patients older than 50 years show some evidence of sternoclavicular joint osteoarthritis changes on CT [21]. The process of obtaining a 3D view of the shoulder joint from an MRI can be completed effectively to assess bone loss while solving issues surrounding CT scans [162]. Convolutional neural networks could potentially be used in clinical practice to provide rapid and accurate 3D MRI glenohumeral bone models and glenoid bone loss measurements [203].

MRI: MRI is useful to identify osteonecrosis of the humeral head, or a bone tumour [99]. MRI is the modality of choice for evaluating the rotator cuff, biceps, and subacromial/subdeltoid bursa [116]. MRI can identify labral tears and rotator cuff tears, although accuracy for these is enhanced by combining the scan with arthrography [99]. T1-weighted MRI can reveal Hill-Sachs lesions and is often used with magnetic resonance arthrograms to provide a more detailed picture of the joint surfaces [116]. T2-weighted MRI provides better visualization of full thickness rotator cuff tears [116]. Traditional MRI is utilized for evaluation of soft tissues with high contrast and spatial resolution in the management of patients with anterior shoulder instability [110]. MR accuracy in identifying labral and rotator cuff tears in the literature ranges from 70% to 100% [110]. Acquired multi-planar imaging allows for detailed evaluation of the glenoid, labrum, joint capsule, and rotator cuff in different planes [110].

In the acute dislocation setting, a joint effusion with distension of the joint may outline structures similarly to an arthrogram, making the arthrogram unnecessary [110]. The shoulder is routinely positioned in neutral or partial external rotation for standard MRI or MRA, but other alternative positions can be used to increase sensitivity for detecting labroligamentous injuries [110]. Abduction and external rotation (ABER) of the arm is an alternative position utilized to increase the sensitivity and specificity for detecting anteroinferior labroligamentous injury [110]. Limited range of motion or pain may prohibit patients from performing the ABER provocative maneuver [110]. Full routine MRI or MRA examination had similar accuracy as the ABER sequence in evaluating the anteroinferior labral–ligamentous complex [110]. The sensitivity of MRA with the ABER position for detecting anteroinferior labral lesions was significantly higher than that of MRA in neutral position [110]. MRA with the ABER position is more effective in identifying Perthes lesions than MRA in neutral position [110].

MRAs can demonstrate a patulous capsule on the coronal, sagittal, and axial imaging in patients with multidirectional instability [110]. MRAs can be helpful in evaluating lesions of the rotator interval and other associated findings that may affect the eventual surgical plan [110]. 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 [110]. 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 [110]. The diagnosis of multidirectional instability is a clinical one, and the need for expensive and/or invasive imaging should be weighed against the information gained [110]. MRI with or without intra-articular contrast medium is equally reliable as a non-invasive method for assessment of articular cartilage damage of the glenohumeral joint prior to diagnostic arthroscopy [201]. Combined lesions of the glenoid labrum involving tears of the anterior, posterior, and superior labrum are infrequent injuries that are typically not completely defined by either noncontrast MRI or MR arthrography [217]. Pre-operative MRI's do not preclude concomitant glenohumeral joint arthroscopy in patients with high-grade acromioclavicular joint separations [193].

Magnetic Resonance Arthrography: MR arthrography refers to MRI of a joint that has been injected with an intra-articular contrast agent such as diluted gadolinium or saline solution [110]. The contrast material is injected prior to MRI by fluoroscopic or ultrasound guidance under strict aseptic technique [110]. By distending the joint capsule, the cartilage, ligaments, and labrum are outlined with contrast, increasing the sensitivity for detecting tears and other lesions [110]. MR arthrography has proven utility by increasing both sensitivity and specificity in detecting injuries to the capsulolabral–ligamentous complex as compared to traditional MRI [110]. In a meta-analysis of 6 studies including 4,667 shoulders, MRA had greater diagnostic test accuracy for glenoid labral lesions than MRI, with MRA sensitivity of 88% and specificity of 93% versus MRI sensitivity of 76% and specificity of 87% [110]. MR arthrography is considered the benchmark for evaluation for labral tears and rarely is indicated for evaluation of rotator cuff pathology [116]. When MRI or MR arthrography is contraindicated, such as in patients with pacemakers or vascular clips, CT arthrography is indicated [116]. A modified posterior injection technique for MR arthrography of the glenohumeral joint does not require fluoroscopic guidance and does not traverse important anterior structures that require assessment [220]. MR-guided direct arthrography of the glenohumeral joint provides direct MR arthrography and avoids the need for x-ray fluoroscopy facilities [176].

Ultrasonography: Ultrasonography is a simple and accurate test for identifying rotator cuff tears and calcific tendinitis [99]. Ultrasonography can be useful in guiding injections or barbotage, such as aspirating calcific deposits in the rotator cuff [99]. Ultrasonography is a low-cost alternative to MRI and arthrography for evaluating both skeletal and soft-tissue structures of the shoulder [116]. Ultrasonography can provide immediate, real-time visualization of the rotator cuff, biceps tendon, and calcific deposits [116]. Ultrasonography can be used to measure the subacromial space and detect atrophy of rotator cuff muscles [116]. As a result of providing images in real-time, ultrasonography can evaluate impingement in various positions and motions [116]. Ultrasonography is highly operator dependent and is not as useful for evaluating labral tears or rotator cuff tears that are very small or larger than 3 cm [116]. The most commonly performed joint examination using ultrasonography is the shoulder examination [94]. Accuracy of rotator cuff ultrasonography depends on the skill of the scanner operator and an awareness of pitfalls that are encountered [94]. Dynamic ultrasonographic evaluation is important for zone II flexor tendon lacerations because of the ability to move the tendon [94]. With direct visualization, ultrasonography can pick up on partial tears that may need treatment but have normal physical examination findings [94]. The parenchymal-level thickness of the inferior glenohumeral joint capsule in frozen shoulder was negatively correlated with joint range of motion in all directions [67]. Assessment of inferior glenohumeral joint capsule thickness via ultrasonography may be helpful in selecting treatment options for frozen shoulder [67]. Irrespective of the amount of shortening, MRI showed more bursitis and tendinitis on the fractured side in clavicle shaft malunion, and shortening of ≥ 20 mm cannot be used as a poor prognostic criterion [66].

Arthroscopy: Arthroscopy is useful for diagnosing and treating subacromial impingement, intra-articular lesions, detachment of the glenoid labrum and rotator cuff tears [99]. The arthroscopic approach offers a unique advantage in diagnosing and treating occult intra-articular pathology [36]. Arthroscopic management is an effective treatment of choice with low morbidity and early functional return for primary synovial chondromatosis of the shoulder [8]. Diagnostic indications for basal joint arthroscopy include the assessment of painful post-traumatic basal joint lesions of cartilage and ligaments [5].

Other Considerations: The diagnosis of a stiff shoulder depends on awareness of the problem, with history and physical examination being paramount [31]. Ancillary studies may be helpful in certain circumstances for diagnosing a stiff shoulder [31]. It is important to understand the natural history so that patients are well informed and can actively participate in decision-making [31]. No treatment has proved to be definitive for a stiff shoulder [31]. The literature supports many forms of treatment, both operative and nonoperative, for a stiff shoulder [31]. All treatments for a stiff shoulder have potential advantages and disadvantages, and the treatment approach should be tailored to each individual patient [31]. Surgeons need to develop a judicious approach to imaging that yields necessary information while avoiding the tendency to "over-image" [107]. The shoulder is a three-dimensional structure that cannot be represented by a single planar view [107].

Treatment

Non-Operative

Conservative management remains the initial approach for several glenohumeral pathologies. Patients with moderately disabling symptoms from posterior subluxation of the glenohumeral joint should be treated with an intensive physical therapy program [192]. For a symptomatic os acromiale that has failed initial nonoperative treatment, operative management is indicated, implying that conservative measures are the prerequisite for surgical intervention [153]. Similarly, custom hemiarthroplasty is considered a reasonable salvage method for proximal humeral dysplasia epiphysealis hemimelica only when nonsurgical management has failed to provide relief [194].

Operative

Indications: Total shoulder arthroplasty (TSA) is considered the gold standard for treating severe glenohumeral arthritis when nonoperative measures fail [83]. In young patients with severe glenohumeral arthritis, TSA may be the preferred primary procedure, as poor clinical outcomes have been observed in patients converted to TSA after failure of biological resurfacing [58]. Arthroscopic treatment may serve as a suitable alternative for elderly patients with significant medical comorbidities who cannot tolerate major surgery, or for young patients with early-onset arthritis where prosthesis longevity is a concern [83]. For chronic traumatic anterior sternoclavicular joint instability, undertaking a specific operative procedure based on MRI diagnosis and structural anatomic findings provides satisfactory outcomes regarding joint stability and clinical outcomes [26].

Surgical Approach / Technique: Joint instability must be avoided to lessen complications and the need for revision surgery following total shoulder arthroplasty [30]. An arthroscopic outside-in shoulder release can be performed safely and effectively when certain guidelines are followed, allowing for subsequent access to the glenohumeral joint in most cases [42]. Distension of the glenohumeral joint provides a similar long-term efficacy to all reference treatments for frozen shoulder [10]. For posterior subluxation of the glenohumeral joint, patients with severe symptoms or failed non-operative treatment should undergo posterior capsulorrhaphy, augmented with a bone block if the posterior glenoid or capsule is deficient [192]. In selected patients, shoulder fusion (arthrodesis) considerably alleviates pain and provides acceptable function and satisfaction [54].

Implant Selection: In patients aged under 50 years, a 59% rate of glenoid lucency was noted after TSA and a 68% rate of radiographic glenoid erosions after hemiarthroplasty at a minimum follow-up of 5 years [83]. Fibrin adhesive offers advantages over internal fixation for chondral and osteochondral injuries by causing no further damage to the cartilage and avoiding the need for a second operation for the removal of metalwork [175].

Adjuncts: Strong evidence supports that there is no benefit to the use of hyaluronic acid in the treatment of glenohumeral joint osteoarthritis [53]. The authors strongly agree with the caution against the use of intra-articular pain pumps and recommend that their use be abandoned due to the risk of chondrolysis [149]. Additionally, the authors caution against the use of intra-articular pain pump catheters due to reports of chondrolysis of the glenohumeral joint [180].

Other Considerations: The AAOS clinical practice guidelines classify the use of arthroscopy for the treatment of glenohumeral arthritis as grade I, implying an inability to recommend for or against this option [83]. Arthroscopic debridement for glenohumeral arthritis lacks high-quality evidence to support its routine use [83]; however, it improved clinical outcome in 68% of patients suffering from advanced osteoarthritis of the glenohumeral joint [151]. In well-selected patients with grade IV osteochondral lesions of the glenohumeral joint, significant improvements in pain relief and function follow arthroscopic debridement [143]. Arthroscopy provides an opportunity to diagnose and treat coexistent soft tissue pathology in patients with osteoarthritis, which may eliminate the need for arthroplasty [83]. Preoperative radiographs and clinical examination are unreliable in predicting osteoarthritis that is documented intraoperatively [83].

Microfracture of the glenohumeral joint resulted in 21.4% of patients requiring conversion to arthroplasty within 10 years, and 33% to 42% were considered to have potential clinical failure [15]. Outcomes of arthroscopic osteochondral graft resurfacing for the treatment of osteoarthritis are encouraging but demonstrate considerable variability between patients [121]. Current clinical treatments for articular cartilage defects have limited ability to repair tissue and often result in mechanically inferior cartilage [117]. More research is necessary to determine which treatment for chondral pathology in the shoulder provides the best long-term outcomes [29].

Bony lesions constitute a critically important entity in the management of shoulder instability, although they may be relatively rare compared with soft-tissue pathology [41]. Both free bone graft transfer and the Latarjet procedure showed comparable success in joint stabilization for anterior shoulder instability with glenoid bone loss, but neither could prevent the progression of instability arthropathy [23]. The ability to reduce the deformity of an AC joint separation with manual pressure is important and can help differentiate nonsurgical versus surgical treatment for higher grade injuries [16]. Current evidence is insufficient for proper evidence-based guidelines regarding surgical versus non-operative treatments for acute AC dislocation due to the scarcity of level 1 or 2 studies [174]. A closed reduction is typically the first line of management for acute dislocations of the sternoclavicular joint, with surgical treatment indicated in most active individuals following a failed closed reduction attempt [179].

Complications

Glenohumeral Joint and Shoulder Arthroplasty

Aseptic loosening: Component loosening is a primary complication of total shoulder arthroplasty (TSA), occurring approximately 8 years postoperatively [138]. In a review of 33 series (2,540 shoulders) of unconstrained TSA, overall component loosening occurred in 6.31% of cases, with glenoid loosening at 5.3% and humeral loosening at 1.1% [134]. A study of over 400 cemented all-polyethylene glenoid TSAs reported a 12% complication rate, though only one reoperation was required for component loosening [138].

Instability: Glenohumeral instability is a frequent complication, with joint instability needing to be avoided to lessen revision needs after TSA with tissue-ingrowth glenoid components [30]. In the 33-series review, instability occurred in 4.9% of unconstrained TSA cases, comprising superior (3%), posterior (1%), and anterior (0.9%) instability [134]. The most frequent complications in the cemented glenoid series were rotator cuff tearing, glenohumeral instability, and periprosthetic humeral fracture [138].

Periprosthetic fracture: Periprosthetic fractures have been reported to occur at 6 years post-TSA [138]. In the 33-series review, periprosthetic fracture occurred in 1.8% of unconstrained TSA cases, with intraoperative fractures at 1.1% and postoperative fractures at 0.7% [134].

Nerve palsy: Neural injury occurred in 0.8% of unconstrained TSA cases [134]. Most nerve injuries are neurapraxias that recover with time [134]. If no recovery is noted after 6 weeks, electromyographic examination should be obtained and repeated at 3 months; if no recovery is evident by electromyography at 3 months, nerve exploration should be considered [134].

Infection (PJI): Infection after TSA has been reported to occur at 12 years [138]. In the 33-series review, infection occurred in 0.7% of unconstrained TSA cases [134].

Other Considerations: The overall complication rate after TSA is estimated at approximately 15% [138]. Complications tend to occur late (5 to 10 years) [138]. The most common complications, in order of frequency, are component loosening, instability, rotator cuff tear, periprosthetic fracture, infection, implant failure, and deltoid weakness [138]. Deltoid detachment occurred in 0.08% of unconstrained TSA cases [134]. Rotator cuff tear occurred in 1.3% of unconstrained TSA cases [134]. Reverse total shoulder arthroplasty (RTSA) initially had a 50% complication rate, which has fallen to 6% with improved techniques [138]. Common RTSA complications include scapular notching, hematoma, glenoid dissociation, dislocation, acromial/scapular spine fractures, infection, humeral loosening/dissociation, and nerve injury [138]. Malposition of an uncemented humerus can typically be disimpacted and repositioned [134]. An offset humeral head prosthesis allows 5 to 7 degrees of version correction for cemented components [134]. A malpositioned cemented humeral stem often requires a lengthy and difficult revision procedure [134].

Arthroplasty and Joint Preservation: Arthrosis after arthroscopic Bankart repair rarely causes more than minor subjective symptoms or disadvantage during 13 years' follow-up [11]. Joint-preserving procedures for focal chondral defects show reasonable outcomes, but long-term outcomes remain unknown and osteoarthritis progression is a concern [12]. In a clinical series of absorbable suture fixation for intra-articular upper extremity fractures, all patients achieved bone union and joint congruity without major complications [13]. After microfracture of the glenohumeral joint, 21.4% of patients required conversion to arthroplasty within 10 years, and 33% to 42% were considered to have potential clinical failure [15]. Heterotopic ossification must be considered in the differential diagnosis of severe musculoskeletal pain and stiffness after prolonged illness [17]. Reestablishing a functional glenohumeral joint is challenging once soft tissue stabilizers are incompetent [17]. Screws and staples can produce complications requiring reoperation and permanent loss of joint function [27]. The long-term effects of articular impact injury remain unknown, but evidence suggests a possible link to late joint degeneration via chondrocyte apoptosis [51]. Osteoarthritic changes may reflect the natural course of underlying disease, encouraging further studies on cartilage lesion natural history [62]. After subchondral fractures, significant cartilage changes occur after 6 months [63]. Stiffening of 38 percent from normal to early arthritic condition was accompanied by a trabecular contiguity change from 0.7 to 0.8 [71]. Both cohorts in a prospective randomized trial of free bone graft transfer vs. Latarjet procedure showed comparable success in joint stabilization, but neither prevented the progression of instability arthropathy [23]. Chronic glenohumeral synovitis is present in patients with anterior instability, possibly causing dislocation arthropathy in the long term [181]. The bare spot of the glenoid can be absent and is not a perfectly consistent landmark for the midpoint of the inferior glenoid [224]. Despite major primary complications and high incidence of radiographic degenerative changes after 8.8 years, mainly good clinical results were achieved with Judet's bipolar prosthesis for radial head arthroplasty [221].

Acromioclavicular and Sternoclavicular Joints

Hardware Complications: Loss of reduction is a common adverse outcome related to acromioclavicular (AC) and sternoclavicular (SC) joint injuries [123]. Clavicle fracture at bone tunnels, pin migration, infection, soft tissue healing issues, AC arthritis with residual instability, hardware pain requiring removal, and cosmetic bumps or late degenerative changes are also common adverse outcomes [123]. Specific complications of operative AC dislocation treatment include fracture through a drill hole, loss of purchase of internal fixation, metal failure, and migration of the fixation device to other parts of the body [123]. The incidence of loss of reduction after AC dislocation repair is significant [123].

Pin Migration: Pins used to stabilize the AC joint have been reported to migrate into remote, life-threatening locations such as the lung, spinal cord, neck posterior to the carotid sheath, and pleura or close to it [123]. Vessels in the thorax and neck have also been penetrated by migrating pins [123]. Pin migration can be prevented by bending a hook on the portion of the pin that protrudes from the acromion process [123]. Pins can break, allowing part of the pin to migrate freely [123]. Lyons and Rockwood reviewed 37 reports of pin migration in shoulder operations and recommended avoiding pin use in this area [123]. When pins are utilized for AC joint stabilization, they should be bent or have restraining devices to decrease migration risk [123]. Pin migration may have devastating consequences, and there are reported deaths [123]. Smooth pins should rarely if ever be used in the shoulder girdle area [123].

Soft Tissue and Fixation Failure: Simple repair of the coracoclavicular (CC) and AC ligaments without additional support of CC sutures, screws, or internal fixation will likely fail in the treatment of ligamentous injury to the AC joint [123]. Failure of soft tissue repairs can result from suture breakage, suture anchor pullout, or screw breakage [123]. If failure of soft tissue repair is noticed early in the postoperative period, reoperation to correct the problem is usually indicated [123]. If failure occurs weeks to months after surgery, infection should be suspected and ruled out [123]. CC fixation using grafts or synthetic material has been associated with various complications [123]. Erosion of a Dacron graft through the distal clavicle has been described in CC fixation [123]. A coracoid fracture after reconstruction of the CC ligaments through two drill holes in the distal clavicle has been noted [123]. Fractures of the distal clavicle secondary to the use of loop sutures between the coracoid and the distal clavicle have been reported [123].

Other Considerations: Diagnosis of AC osteoarthritis cannot be based on plain radiographs alone because similar radiographic findings can be seen in asymptomatic individuals [38]. Both open and arthroscopic resection arthroplasty for AC joint osteoarthritis have proven to provide predictable pain relief [38]. Each technique for AC joint resection arthroplasty has its own unique set of potential complications that may be minimized with an improved understanding of the anatomical and biomechanical characteristics of the joint along with meticulous surgical technique [38]. Combined AC dislocation and clavicle fracture have been reported [123]. Simultaneous dislocations of both the SC and AC ends of the clavicle or “bipolar” dislocations have been reported [123]. Bipolar dislocations are most often a posterior or type IV AC dislocation associated with an anterior SC dislocation [123].

Other Joint and Soft Tissue Complications

Other Considerations: The natural life history of the nodules in pigmented villonodular synovitis speaks against a neoplastic origin, and inflammation in its broadest interpretation—reaction to injury—would appear to be the most acceptable explanation for the lesion [216]. At 18 to 50 months after extra-glenohumeral joint surgery in rheumatoid arthritis, no patient has severe pain [228]. At 18 to 50 months after extra-glenohumeral joint surgery in rheumatoid arthritis, only three of 22 have moderate pain [228]. At 18 to 50 months after extra-glenohumeral joint surgery in rheumatoid arthritis, all but one patient has avoided the need for subsequent joint replacement surgery [228]. Infected nonunion is defined as persistence of an infection at the fracture site and the surrounding tissue with failure of bone healing for 8 months [127]. Risk factors associated with an infected nonunion include exposed bone devoid of vascularized periosteal coverage for more than six weeks, purulent discharge, a positive microbiological culture from the wound, and histological evidence of necrotic bone containing empty lacunae [127]. Treatment and long-term outcomes of infected nonunion are commonly complicated by soft-tissue problems including multiple sinuses, osteomyelitis, osteopenia, complex deformities with limb-length discrepancy, and adjacent joint stiffness [127]. Motor and sensory dysfunction of the limb, chronic pain, and biopsychosocial factors may lead to considerable physical, social, financial, and mental impact on the life of affected patients with infected nonunion [127]. The natural history of primary anterior dislocation of the glenohumeral joint in adolescent patients remains unclear and there is no consensus for management of these patients [215]. 102 (absolute incidence of 76.7%) adolescent patients had a recurrent dislocation during follow-up after primary anterior dislocation of the glenohumeral joint [215]. The median interval between primary and recurrent dislocation in adolescent patients was ten months (95% CI 7.4 to 12.6) [215].

Recovery

Other Considerations: The provided evidence base does not contain specific data regarding standard recovery timelines, such as weeks for light activity, months for full activity, or the duration of rehabilitation protocols and immobilisation. Consequently, no specific time ranges can be stated for these phases. The available literature focuses on long-term outcomes, complication rates, and biomechanical considerations rather than acute recovery milestones.

Glenohumeral Joint Preservation and Arthroplasty: Arthroscopic debridement and capsular release of the shoulder seems to be a viable alternative in the short term follow-up for osteoarthritis of the glenohumeral joint, though a longer term study is needed [200].

Cartilage Restoration and Defect Management: In a case report of arthroscopic autologous chondrocyte implantation in the glenohumeral joint, the procedure demonstrated favorable clinical and radiologic results up to 24 months in a young patient with a symptomatic glenoid cartilage defect [24]. In a long-term follow-up study of microfracture of the glenohumeral joint, 21.4% of patients required conversion to arthroplasty within 10 years, and 33% to 42% were considered to have potential clinical failure [15].

Instability and Bone Grafting: In a five-year follow-up of a prospective randomized trial comparing free bone graft transfer vs. Latarjet procedure for anterior shoulder instability with glenoid bone loss, both cohorts showed comparable success in joint stabilization, but neither could prevent the progression of instability arthropathy [23].

Frozen Shoulder and Capsular Healing: After radiofrequency capsular shrinkage for atraumatic instability, synovial cells and fibroblasts return to normal by 6 months, but collagen bundles tend to remain reparative in the medium term [182].

Pediatric and Developmental Conditions: In a follow-up study on tendon transfers and open reduction for moderate glenohumeral joint deformity in brachial plexus birth injury, 56% of subjects had a deformity classification of 1 or 2 at the 5-year time point, and the Waters glenohumeral joint deformity score improved during the study period (p < 0.0001) with no significant deterioration with time [70].

Complications and Biomechanics: Screws and staples used about the glenohumeral joint can produce complications that require reoperation and are capable of causing a permanent loss of joint function [27]. The Newcastle shoulder model provides a basis for future studies into biomechanical problems relating to the understanding of musculoskeletal pathology and implant design and performance [25]. The stiffening of 38 percent from a normal to an early arthritic condition is accompanied by a trabecular contiguity change from 0.7 to 0.8 [71]. Drilling causes early catabolic changes and predisposes the joint to progressive cartilage damage, as seen by significantly higher Mankin scores progressing from 72 h up to 52 weeks in a rabbit model of post-traumatic osteoarthritis [229]. The long-term effects of articular impact injury remain unknown, but evidence showing the potential importance of chondrocyte apoptosis in osteoarthritis and the observation that apoptosis results from articular impacts suggests a possible link between impact injury and late joint degeneration [51].

Other Specific Pathologies: Early diagnosis and appropriate intervention are critical to prevent joint destruction and optimize patient outcomes in pigmented villonodular synovitis involving the glenohumeral joint [4]. In a case report of shoulder pseudoparalysis in a child after massive cuff tear interposed within the glenohumeral joint, the patient achieved full recovery with pain-free function and normal range of motion at 2-year follow-up following arthroscopic repair [172]. Double-plating of proximal humeral fractures yields good clinical mid- to long-term results in complex and highly unstable fractures [190]. Improved histology is correlated with improved final construct strength at the 12-week time point when using an interposition bioresorbable scaffold with a vented anchor for primary rotator cuff repair in sheep [198]. Larger studies with longer-term follow-up are required to fully evaluate the potential benefits of performing a pedicled-lesser tuberosity osteotomy for access to the humeral head when undertaking joint-preserving surgery [199].

Key Evidence

• [L4] For those patients with frank degenerative arthritis or extensive head involvement, the prognosis is poor, and earlier consideration of arthroplasty is indicated. [1] (10.1016/s1058-2746(99)90089-7)
• [L4] The long-term outcomes of glenohumeral preservation techniques are presently unknown, but clinical experience shows many patients do well and delay the need for prosthetic shoulder arthroplasty. [2] (10.1155/2012/160923)
• [L4] We conclude that treatment by surgical intervention should be performed at an age when spontaneous correction of the bone deformity can prevent future development of secondary arthrosis. [3] (10.1016/s1058-2746(99)90049-6)
• [Case_report] Early diagnosis and appropriate intervention are critical to prevent joint destruction and optimize patient outcomes. [4] (10.1186/s12891-025-08936-x)
• [Paper] Diagnostic indications include the assessment of painful post-traumatic basal joint lesions of cartilage and ligaments, and the evaluation of chondromalacia and ligament attenuation to help classify basal joint osteoarthritis. [5] (10.1016/j.hansur.2020.05.014)
• [L4] A comprehensive investigation is appropriate before surgical excision of the thumb IP joint sesamoid bone. [6] (10.1016/j.jhsa.2011.11.015)
• [L4] Arthroscopic management is an effective treatment of choice with low morbidity and early functional return. [8] (10.1016/j.arthro.2006.07.009)
• [L4] In addition, mid to long-term results are needed to evaluate the osteoarthritic rate. [9] (10.1016/j.jseint.2025.101443)
• [L1] Distension of the glenohumeral joint provides a similar long-term efficacy to all reference treatments. [10] (10.1038/s41598-017-10895-w)
• [L4] Arthrosis rarely causes more than minor subjective symptoms or a minor objectively perceived disadvantage during 13 years' follow-up. [11] (10.1016/j.jse.2011.04.023)
• [L4] Joint-preserving procedures have shown reasonable outcomes for focal chondral defects of the glenohumeral joint, but long-term outcomes remain unknown and the progression of osteoarthritis remains a concern. [12] (10.1177/17585732221142610)
• [L4] In this clinical series, all patients achieved bone union and joint congruity restoration without major complications. [13] (10.1016/j.jhsg.2026.101134)
• [L5] Positive clinical outcomes have been demonstrated with various surgical techniques, particularly in non-weightbearing joints, though evidence for the shoulder specifically is often limited to retrospective case series. [14] (10.5435/jaaos-d-17-00057)
• [L4] However, 21.4% of patients required conversion to arthroplasty within 10 years, and 33% to 42% were considered to have potential clinical failure. [15] (10.1177/0363546517750627)
• [L4] This case highlights the importance of considering heterotopic ossification formation in the differential diagnosis of a patient presenting with severe musculoskeletal pain and associated stiffness after a prolonged illness, as well as the challenges associated with reestablishing a functional joint once soft tissue stabilizers of the glenohumeral joint are no longer competent. [17] (10.1016/j.xrrt.2023.09.011)
• [L5] [18] (10.5435/jaaos-d-17-00449)
• [L5] Nontraumatic disorders of the clavicle are uncommon and frequently the diagnosis is not obvious; treatment varies by disorder and may include symptomatic and expectant management, drug therapy, and nonsurgical or surgical treatment. [20] (10.5435/00124635-200604000-00002)
• [L3] SCJ osteoarthritis is a very common incidental finding on CT scans, particularly with increasing age, with nearly 90% of patients older than 50 years showing some evidence of these changes. [21] (10.1016/j.jse.2016.04.029)
• [L5] The sternoclavicular joint is a saddle-shaped synovial joint serving as the only skeletal articulation between the axial skeleton and the upper limb. [22] (10.1177/1758573218756880)
• [L2] Both cohorts showed comparable success in joint stabilization, but neither could prevent the progression of instability arthropathy. [23] (10.1016/j.jse.2025.01.017)
• [Case_report] The procedure demonstrated favorable clinical and radiologic results up to 24 months in a young patient with a symptomatic glenoid cartilage defect. [24] (10.1016/j.jse.2018.06.013)
• [L5] The model presented here, namely the Newcastle shoulder model, provides a basis for future studies into biomechanical problems relating to the understanding of musculoskeletal pathology and implant design and performance. [25] (10.1243/09544119jeim147)
• [L4] Undertaking a specific operative procedure based on these findings provides a satisfactory outcome with regards to joint stability and clinical outcomes. [26] (10.1016/j.jse.2025.04.018)
• [L4] Screws and staples can produce complications that require reoperation and are capable of causing a permanent loss of joint function. [27] (10.2106/00004623-198466020-00003)
• [L4] At a mean follow-up of 8 years, the coracoid graft remained present in 97% of cases, even in patients with minimal preoperative glenoid bone loss (<5%). [28] (10.1016/j.jse.2026.02.020)
• [L4] More research is necessary to determine which treatment for chondral pathology in the shoulder provides the best long-term outcomes. [29] (10.1016/j.arthro.2012.03.026)
• [L4] Joint instability must be avoided to lessen complications and the need for revision surgery. [30] (10.1016/s1058-2746(09)80124-9)
• [Case_report] Recognition of musculoskeletal presentations of systemic amyloidosis can lead to earlier diagnosis and treatment, which may prevent life-threatening manifestations. [34] (10.1016/j.xrrt.2022.01.008)
• [L4] In the appropriate clinical setting, both radiographs and MR images of the shoulder can be used to establish the diagnosis of chondrolysis of the glenohumeral joint. [35] (10.2214/ajr.05.1477)
• [L1] The arthroscopic approach offers a unique advantage in diagnosing and treating occult intra-articular pathology. [36] (10.1016/j.jse.2006.10.006)
• [L5] [38] (10.1177/0363546513485359)
• [L5] There are discrepancies in the definition and classification of multidirectional instability, which can make diagnosis and treatment selection challenging. [39] (10.1016/j.jht.2017.03.005)
• [L5] The patient's clinical presentation was quite extraordinary in its resemblance to glenohumeral instability. [40] (10.1016/s1058-2746(05)80055-2)
• [L5] Although bony lesions may be relatively rare compared with soft-tissue pathology, they constitute a critically important entity in the management of shoulder instability. [41] (10.1016/j.arthro.2008.05.015)
• [Paper] The procedure can be performed safely and effectively when certain guidelines are followed and can allow for subsequent access to the glenohumeral joint in most cases. [42] (10.1016/j.eats.2020.04.001)
• [Paper] [43] (10.1186/1471-2474-10-46)
• [L4] Glenohumeral joint tuberculosis can be difficult to diagnose in its early stages and is often misdiagnosed as frozen shoulder. [44] (10.1016/j.jse.2011.07.026)
• [L4] The best result was achieved for the first patient, for whom a diagnosis was obtained early after the initial injury; this highlights the importance of correct assessment of postreduction radiographs. [45] (10.1067/mse.2001.111961)
• [L4] [46] (10.12968/hmed.2008.69.5.29358)
• [L1] [48] (10.5435/jaaos-d-20-00404)
• [L5] The results suggest that the glenohumeral geometry is both gender and population specific, and future joint replacements may be designed to address these differences. [50] (10.1016/j.jses.2017.11.007)
• [L5] The long-term effects of articular impact injury remain unknown, but evidence showing the potential importance of chondrocyte apoptosis in osteoarthritis and the observation that apoptosis results from articular impacts suggests a possible link between impact injury and late joint degeneration. [51] (10.1097/01.blo.0000133567.28491.7d)
• [L4] In selected patients, shoulder fusion considerably alleviates pain and provides acceptable function and satisfaction. [54] (10.1016/j.otsr.2017.05.021)
• [L4] Significant differences in joint contact patterns were detected due to abduction angle and shoulder condition. [55] (10.1155/2010/162136)
• [L4] The poor clinical outcomes seen in patients who are converted to a TSA after failure of biological resurfacing suggests that TSA may be the preferred primary procedure in young patients with severe glenohumeral arthritis. [58] (10.1016/j.arthro.2011.03.028)
• [L5] As studies continue to look at the results of these procedures in cuff tear arthropathy, existing indications and treatment algorithms will be further refined. [59] (10.4055/cios.2010.2.4.196)
• [L4] This contrasts with the variability of the version of the humeral head and of the glenoid and offers a useful guideline in difficult prosthetic surgery of the shoulder in which normal anatomic landmarks are lost because of arthritic or traumatic deformity. [60] (10.1016/s1058-2746(02)86884-7)
• [L4] However, pain remains unremitting in 50% of patients, and glenohumeral arthrodesis may be needed as a last option. [61] (10.1097/01.blo.0000146468.08655.ab)
• [L5] The authors agree that osteoarthritic changes may reflect the natural course of the underlying disease and encourage further studies on the natural history of cartilage lesions and osteoarthritis in the shoulder. [62] (10.1016/j.arthro.2010.11.061)
• [L5] After subchondral fractures, significant changes in the cartilage itself occur after 6 months. [63] (10.1007/s00402-004-0701-6)
• [L5] [64] (10.1016/s1058-2746(09)80098-0)
• [L4] Irrespective of the amount of shortening, MRI showed more bursitis and tendinitis on the fractured side, and shortening of ≥ 20 mm cannot be used as a poor prognostic criterion. [66] (10.1016/j.xrrt.2026.100679)
• [L3] The parenchymal-level thickness was negatively correlated with joint range of motion in all directions, suggesting the assessment may be helpful in selecting treatment options. [67] (10.1016/j.jseint.2024.06.004)
• [L4] [70] (10.2106/jbjs.19.00685)
• [L4] The stiffening of 38 percent from a normal to an early arthritic condition was accompanied by a trabecular contiguity change from 0.7 to 0.8. [71] (10.2106/00004623-197456020-00010)
• [L3] These tests have utility in evaluating patients with acromioclavicular joint pathologic lesions, and a combination of these physical tests is more helpful than isolated tests. [104] (10.1177/0363546503261723)
• [L3] The BvR test is a highly sensitive test in patients presenting with isolated AC related symptoms, and demonstrates AC joint pathology better than other accepted tests. [109] (10.1016/j.jse.2010.05.023)
• [L4] Current clinical treatments for articular cartilage defects have limited ability to repair tissue and often result in mechanically inferior cartilage; emerging regenerative approaches and strategies informing future treatment options are discussed to address these limitations. [117] (10.3389/fbioe.2021.770655)
• [L4] [119] (10.1007/s00167-008-0692-x)
• [L4] Outcomes of arthroscopic osteochondral graft resurfacing for the treatment of OA are encouraging, but demonstrate considerable variability between patients. [121] (10.1016/j.jse.2015.11.018)
• [L4] The 3D measurement of scapula morphology compared with geometry of the glenohumeral joint leads to a more precise planning of shoulder surgery. [122] (10.3109/10929080309146062)
• [L4] The presented classification system as well as associated treatment algorithms for lateral clavicle fractures showed substantial inter- and intraobserver reliability. [132] (10.1016/j.jse.2025.04.021)
• [L3] It remained difficult to preoperatively diagnose panlabral tear using standard physical examinations and imaging studies. [135] (10.1016/j.arthro.2019.09.012)
• [L5] This article reviews the relevant anatomy, etiology, clinical evaluation, diagnostic testing, and treatment of scapular winging, discussing the differences in diagnosis and management between scapular winging arising from neurogenic causes and traumatic muscular detachment. [141] (10.1016/j.jhsa.2018.08.008)
• [L4] In well-selected patients with grade IV osteochondral lesions of the glenohumeral joint, significant improvements in pain relief and function follow arthroscopic debridement of the glenohumeral joint. [143] (10.1067/mse.2002.120143)
• [L4] The authors strongly agree with the caution against the use of intra-articular pain pumps and recommend that their use be abandoned. [149] (10.1016/j.arthro.2010.11.001)
• [L3] Arthroscopic debridement improved clinical outcome in 68% of patients suffering from advanced OA of glenohumeral joint. [151] (10.1186/s12891-015-0741-9)
• [L4] Operative management of a symptomatic os acromiale that has failed initial nonoperative treatment leads to decreased symptoms and improvement in clinical outcomes. [153] (10.1016/j.jse.2019.05.047)
• [L5] Sensory receptor subtypes are differentially expressed in the glenohumeral joint capsule, primarily type I and IV sensory receptors. [158] (10.1016/j.jse.2020.07.006)
• [L5] The macroscopically recognizable ligaments are composed of collagen fiber bundles in several layers of differing thickness and orientation. [161] (10.1016/s1058-2746(09)80090-6)
• [Paper] The process of obtaining a 3D view of the shoulder joint from an MRI can be completed effectively to assess bone loss while also solving some issues surrounding CT scans. [162] (10.1016/j.eats.2024.102972)
• [L4] The present study revealed the glenohumeral geometry in the normal Japanese population. [164] (10.1016/j.jse.2015.08.003)
• [L4] Classifications of proximal humeral fractures using the Neer system based on CT scans and plain radiographs are not very reliable or reproducible due to difficulty in determining which segments are fractured. [168] (10.2106/00004623-199609000-00012)
• [L4] For some patients, microfracture can result in improved function and reduced pain, however, in this small series, up to 25% of patients required conversion to arthroplasty less than 10 years following the index microfracture procedure. [170] (10.1177/2325967117s00294)
• [L5] In the majority of cases, the coracoacromial ligament can be anatomically described as two distinct bands - anterolateral & posteromedial. [171] (10.1016/s1058-2746(96)80286-2)
• [Case_report] The patient achieved full recovery with pain-free function and normal range of motion at 2-year follow-up following arthroscopic repair. [172] (10.1016/j.jseint.2021.02.004)
• [Case_report] While outcomes met the patient's satisfaction, advantages and complications of clavicle reconstruction should be carefully discussed with patients due to limited evidence of superior clinical outcome. [173] (10.1186/s12891-019-2588-y)
• [L5] The author calls for high-level prospective randomized studies comparing surgical and non-operative treatments for acute AC dislocation, noting that current evidence is insufficient for proper evidence-based guidelines due to the scarcity of level 1 or 2 studies. [174] (10.1007/s00167-016-4203-1)
• [L4] It offers advantages over internal fixation by causing no further damage to the cartilage and avoiding the need for a second operation for the removal of metalwork. [175] (10.1016/0020-1383(88)90043-5)
• [L4] This technique provides direct MR arthrography and avoids the need for x-ray fluoroscopy facilities. [176] (10.1016/j.crad.2008.02.013)
• [L4] The study confirms the existence of the superior joint capsule, which is inserted on the greater tubercle covering 30 to 60% of its surface with variations in thickness. [178] (10.1016/j.otsr.2021.103073)
• [L4] A closed reduction is typically the first line of management, with surgical treatment indicated in most active individuals following a failed closed reduction attempt. [179] (10.5435/jaaos-d-20-01239)
• [L4] The authors caution against the use of intra-articular pain pump catheters. [180] (10.1016/j.arthro.2010.01.022)
• [L4] Our data confirmed the presence of chronic glenohumeral synovitis in patients with anterior instability, possibly causing dislocation arthropathy in the long term. [181] (10.1002/jor.1100170314)
• [L4] Synovial cells and fibroblasts return to normal by 6 months, but collagen bundles tend to remain reparative in the medium term. [182] (10.1016/j.jse.2006.06.008)
• [L4] [183] (10.1016/j.jse.2019.07.030)
• [L4] The Mitsuzawa classification system, which incorporates perspectives on glenohumeral compatibility and displacement, provided satisfactory intra- and interobserver reliability compared to the Neer and AO/OTA classifications. [188] (10.1186/s13018-024-05423-2)
• [Abstract] Double-plating of proximal humeral fractures yields good clinical mid- to long-term results in complex and highly unstable fractures. [190] (10.1016/j.jse.2022.01.036)
• [L4] Patients with moderately disabling symptoms should be treated with an intensive physical therapy program, while those with severe symptoms or failed non-operative treatment should undergo posterior capsulorrhaphy, augmented with a bone block if the posterior glenoid or capsule is deficient. [192] (10.2106/00004623-198971020-00006)
• [L4] Pre-operative MRI's do not preclude concomitant GHJ arthroscopy. [193] (10.1016/j.arthro.2010.04.030)
• [Case_report] This appears to be a reasonable method to salvage this difficult and challenging problem when nonsurgical management has failed to provide relief. [194] (10.1016/j.jse.2011.08.043)
• [L4] The distribution of cartilage thickness in the glenohumeral joint is not homogenous and there exist several reproducible patterns. [195] (10.1007/s00276-013-1221-2)
• [L4] CT is the gold standard, making this the most reliable method until further research establishes other modalities. [196] (10.1016/j.jse.2011.07.015)
• [Paper] Distinctive patterns of malunion were identified. [197] (10.1067/mse.2003.2)
• [L5] Improved histology was correlated with improved final construct strength at the 12-week time point. [198] (10.1016/j.jse.2019.05.024)
• [Case_report] Larger studies with longer-term follow-up are required to fully evaluate the potential benefits of performing a P-LTO for access to the humeral head when undertaking joint-preserving surgery. [199] (10.1016/j.xrrt.2021.04.010)
• [L4] This seems to be a viable alternative in the short term follow-up, though a longer term study is needed. [200] (10.1016/j.arthro.2010.04.032)
• [L4] MRI with or without intra-articular contrast medium in this study were equally reliable as a non-invasive method for assessment of articular cartilage damage of the glenohumeral joint prior to diagnostic arthroscopy. [201] (10.1007/s00256-010-0922-4)
• [L4] CNNs could potentially be used in clinical practice to provide rapid and accurate 3D MRI glenohumeral bone models and GBL measurements. [203] (10.1148/ryai.2020190116)
• [Paper] [206] (10.1016/s0278-5919(02)00020-0)
• [L1] [210] (10.1007/s00167-020-05917-6)
• [L5] The radiographic appearance is unique and suggests complete tear of the rotator cuff with concomitant tear of the deltoid muscle. [213] (10.1007/s00256-015-2183-8)
• [L3] [215] (10.1302/0301-620x.97b4.34989)
• [L3] Combined lesions of the glenoid labrum involving tears of the anterior, posterior, and superior labrum are infrequent injuries that are typically not completely defined by either noncontrast MRI or MR arthrography. [217] (10.1016/j.arthro.2012.10.005)
• [L3] [218] (10.1016/j.jse.2019.02.025)
• [L4] Thus, the algorithm improved the role of shoulder radiography as an initial imaging modality to rule out rotator cuff tears. [219] (10.1016/j.jse.2023.02.068)
• [L4] The modified posterior injection technique for MR arthrography of the glenohumeral joint does not require fluoroscopic guidance and does not traverse the important anterior structures that require assessment. [220] (10.1148/radiol.2422051964)
• [L4] Despite major primary complications and high incidence of radiographic signs of degenerative changes after 8.8 years, mainly good clinical results were achieved with Judet's bipolar prosthesis. [221] (10.1016/j.jse.2010.05.022)
• [L4] The authors of the original study emphasize that their selection criteria ensured intact cartilage and no osteoarthritic deformation, arguing against the presence of artifactual changes, while noting that the bare spot can be absent in some shoulders and is not a perfectly consistent landmark for the midpoint of the inferior glenoid. [224] (10.1016/j.arthro.2006.12.018)
• [L3] At 18 to 50 months after extra-glenohumeral joint surgery, no patient has severe pain, only three of 22 have moderate pain, and all but one patient has avoided the need for subsequent joint replacement surgery. [228] (10.1016/s1058-2746(09)80112-2)
• [Paper] The model demonstrated that drilling causes early catabolic changes and predisposes the joint to progressive cartilage damage, as seen by significantly higher Mankin scores progressing from 72 h up to 52 weeks. [229] (10.1002/jor.22284)

See Also

• Shoulder Arthroplasty
• Total shoulder arthroplasty
• Rotator Cuff
• Latarjet Procedure
• Fractures
• Os Acromiale
• Frozen Shoulder
• Shoulder Instability
• AC Joint Osteoarthritis
• Shoulder Arthritis
• Calcific Tendinitis
• Internal Fixation
• Clavicle Fracture
• Capsular Release for Frozen Shoulder
• Rotator Cuff Repair

References

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