Shoulder problem
Shoulder problems are common musculoskeletal conditions, with point prevalence estimates ranging from 7% to 26% in adults, encompassing a broad range of disorders affecting the shoulder joint and surrounding structures, characterized by pain, stiffness, weakness, instability, or limited range of motion, often resulting from injury, repetitive use, inflammation, degenerative changes, or referred pain from other body areas.[1] The shoulder is the most movable joint in the human body, formed by the clavicle, scapula, and humerus, with stability provided by muscles, tendons, and ligaments like the rotator cuff, making it highly susceptible to issues that can impair daily activities such as reaching or lifting.[2][3] Common shoulder problems include rotator cuff injuries, which involve tears or inflammation of the tendons that stabilize the upper arm bone and affect approximately 20% of asymptomatic individuals aged 60-69, with prevalence increasing to around 30% or higher in older age groups; frozen shoulder (adhesive capsulitis), a condition causing gradual loss of motion and severe pain due to thickening of the joint capsule; bursitis and tendinitis, resulting from inflammation of the fluid-filled sacs (bursa) or tendons due to overuse or trauma; osteoarthritis or rheumatoid arthritis, leading to cartilage breakdown and joint degeneration; and acute injuries such as dislocations, where the humerus pops out of the shallow socket, or sprains of the acromioclavicular (AC) joint from falls.[4][5][6][7][8][9] These conditions often present with symptoms like aching or sharp pain exacerbated by overhead movements, night pain disrupting sleep, swelling, or a catching sensation during arm elevation, and they are more prevalent in athletes, older adults, or those with repetitive overhead occupations. Diagnosis of shoulder problems typically begins with a detailed medical history and physical examination to assess range of motion, strength, and provocative tests for specific issues like impingement or instability, followed by imaging such as X-rays to detect bone abnormalities, ultrasound for soft tissue evaluation, or MRI for detailed views of tendons and ligaments. Treatment is tailored to the underlying cause and severity, starting with conservative measures including the RICE protocol (rest, ice, compression, elevation), nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen for pain and swelling relief, and physical therapy to improve strength and flexibility; corticosteroid injections may provide temporary relief for inflammatory conditions, while severe or non-responsive cases may require surgical options such as arthroscopic repair, decompression, or joint replacement. Early intervention is crucial, as many shoulder problems resolve within 6 to 12 months with nonsurgical care, though chronic cases can lead to long-term disability if untreated.[10][3][2]Shoulder Anatomy and Function
Bones and Joints
The shoulder girdle is composed of four primary bones: the scapula, humerus, clavicle, and sternum, which form the skeletal foundation for the region's mobility and stability.[11] The scapula, a flat triangular bone located on the posterior thoracic wall overlying ribs 2 through 7, features the glenoid fossa—a shallow, pear-shaped cavity on its lateral aspect—and the acromion process, a bony projection extending from the scapular spine that forms the superior aspect of the shoulder.[12] The humerus, the long bone of the upper arm, has a rounded humeral head at its proximal end, which is covered by hyaline cartilage and articulates with the glenoid fossa to enable a wide range of motion.[13] The clavicle, an S-shaped long bone, serves as a strut connecting the upper limb to the axial skeleton, with its medial sternal end articulating with the sternum and its lateral acromial end meeting the scapula's acromion.[12] The sternum's manubrium, the uppermost portion of this flat anterior thoracic bone, provides the medial attachment point for the clavicle.[11] These bones articulate to form three main joints: the glenohumeral, acromioclavicular (AC), and sternoclavicular (SC) joints, each contributing uniquely to shoulder stability and function.[11] The glenohumeral joint is a ball-and-socket synovial joint where the convex humeral head fits into the concave glenoid fossa of the scapula, allowing multiaxial movement including flexion, extension, abduction, adduction, and rotation.[12] The AC joint, a plane synovial joint, connects the lateral clavicle to the acromion process, permitting limited gliding and rotation to facilitate scapular motion relative to the thorax.[13] The SC joint, a saddle-type synovial joint, links the medial clavicle to the manubrium of the sternum and the first costal cartilage, serving as the sole direct bony connection between the upper limb and the axial skeleton while enabling elevation, depression, protraction, retraction, and circumduction of the clavicle.[11] The articular surfaces of these joints are characterized by their geometry, which influences congruity and range of motion. The glenoid fossa is inherently shallow and smaller in surface area than the humeral head (approximately a 1:4 ratio), providing minimal inherent bony stability but maximal mobility through its shallow design.[13] The glenoid labrum, a fibrocartilaginous rim encircling the glenoid fossa, deepens the socket by about 50% (adding roughly 2.5 mm of depth), improving joint congruity and creating a suction-seal effect that enhances stability during movement.[12] In the AC joint, the flat articular surfaces of the acromion and clavicle allow for smooth gliding with high congruity in neutral positions.[13] The SC joint's saddle-shaped surfaces between the clavicle and manubrium permit greater congruity for load transmission while supporting multiplanar motion.[11] Overall, the bony architecture—particularly the shallow glenohumeral articulation—prioritizes an extensive range of motion (up to 360 degrees of circumduction) over static stability, with joint congruity relying heavily on precise bony fit and labral augmentation to maintain alignment during physiological loads.[12] These skeletal elements interact with surrounding soft tissues to distribute forces across the shoulder complex.[13]Soft Tissue Structures
The rotator cuff consists of four muscles—supraspinatus, infraspinatus, teres minor, and subscapularis—that form a musculotendinous cuff providing dynamic stability to the glenohumeral joint.[14] The supraspinatus originates from the supraspinous fossa of the scapula and inserts via its tendon onto the superior facet of the greater tuberosity of the humerus, blending with the joint capsule to compress the humeral head against the glenoid.[14] The infraspinatus arises from the infraspinous fossa of the scapula and attaches to the middle facet of the greater tuberosity, contributing to the posterior aspect of the cuff.[14] The teres minor originates along the lateral border of the scapula below the glenoid and inserts on the inferior facet of the greater tuberosity, reinforcing the posterior cuff.[14] The subscapularis originates from the subscapular fossa of the scapula and inserts onto the lesser tuberosity of the humerus, forming the anterior portion of the cuff and aiding in anterior stability.[14] Key ligaments of the shoulder include the glenohumeral ligaments, which are thickenings of the anterior joint capsule providing static restraint.[15] The superior glenohumeral ligament extends from the supraglenoid tubercle to the superior aspect of the lesser tuberosity, stabilizing the joint in adduction and limiting inferior translation.[15] The middle glenohumeral ligament runs from the anterior glenoid to the anterior humerus near the lesser tuberosity, reinforcing the anterior capsule.[15] The inferior glenohumeral ligament complex, comprising anterior and posterior bands, arises from the inferior glenoid and attaches to the humerus, serving as a primary anterior stabilizer.[15] The coracohumeral ligament is a broad band from the coracoid process to the greater and lesser tuberosities, supporting the superior capsule and enveloping the long head of the biceps tendon.[15] The coracoacromial ligament forms a triangular arch between the coracoid and acromion, creating an overhead canopy that protects the superior soft tissues.[15] The acromioclavicular (AC) ligament connects the acromion to the clavicle, with superior and inferior components providing horizontal stability to the AC joint.[15] The sternoclavicular (SC) ligaments, including anterior and posterior bands, link the clavicle to the manubrium and first rib, ensuring medial stability.[16] The glenohumeral joint capsule is a fibrous sheath extending from the anatomical neck of the humerus to the glenoid rim, characterized by its looseness to accommodate a wide range of motion.[15] Lined by the synovial membrane, it secretes synovial fluid that lubricates the articular surfaces, reducing friction during joint movement.[15] Bursae in the shoulder minimize friction between moving structures; the subacromial-subdeltoid bursa lies between the rotator cuff and acromion/deltoid, facilitating smooth gliding of tendons.[15] The subscapular bursa, located between the subscapularis tendon and the capsule, reduces friction during internal rotation.[15] The subcoracoid bursa cushions the coracoid process against the subscapularis tendon.[15] Dynamic stabilization is further provided by the long head of the biceps tendon, which originates from the supraglenoid tubercle and superior labrum, traversing the intertubercular groove of the humerus.[17] This groove, situated between the greater and lesser tuberosities, is bridged by the transverse humeral ligament, which secures the tendon and prevents its medial displacement.[17]Biomechanics and Function
The shoulder complex exhibits remarkable mobility, enabling a wide range of motions essential for upper limb function. Normal ranges of motion at the glenohumeral joint include approximately 180° of flexion, 60° of extension, 180° of abduction, 45° of adduction, 70° of internal rotation, and 90° of external rotation.[15] This extensive mobility is achieved through coordinated movement between the glenohumeral and scapulothoracic articulations, known as the scapulothoracic rhythm, which maintains a typical 2:1 ratio of glenohumeral to scapular motion during arm elevation—for instance, 120° of glenohumeral contribution followed by 60° of scapular upward rotation to reach full overhead position.[18] This rhythm optimizes joint congruence and minimizes stress on the glenohumeral ligaments by distributing motion across multiple planes. Stability during these movements relies on precise muscle coordination and force couples that counteract the shoulder's inherent instability arising from its shallow glenoid fossa and large humeral head. The deltoid and rotator cuff muscles form a primary force couple in the coronal plane, where the deltoid provides superior pull on the humeral head while the rotator cuff—infraspinatus, teres minor, subscapularis, and supraspinatus—exerts an inferior and compressive force to center the humeral head in the glenoid during abduction and elevation.[19] Scapular upward rotation is facilitated by balanced activation of the upper and lower trapezius with the serratus anterior, ensuring smooth scapulothoracic gliding and preventing excessive glenohumeral translation.[20] These dynamic stabilizers, working in concert with static ligamentous restraints, maintain joint integrity across the shoulder's high degrees of freedom. Load distribution across the shoulder joints varies significantly during functional activities, highlighting the trade-off between mobility and stability. In overhead reaching, compressive forces on the glenohumeral joint can reach 0.5 to 1 times body weight, with the rotator cuff and deltoid sharing approximately 50-70% of the load to prevent superior humeral migration.[21] During throwing motions, such as in baseball pitching, peak glenohumeral joint forces exceed 100% of body weight at maximum external rotation, primarily distributed through the anterior capsule and labrum, while the scapulothoracic interface absorbs up to 30% of the total kinetic energy to mitigate glenohumeral overload.[22] This high mobility predisposes the shoulder to instability, as the glenohumeral joint's ball-and-socket design prioritizes range over bony congruence, relying heavily on muscular and ligamentous support for load-bearing efficacy.[23] The functional context of shoulder biomechanics is further supported by its vascular and neural supply, which ensures sustained muscle performance. Blood supply derives primarily from branches of the axillary artery, including the subscapular, anterior and posterior circumflex humeral, and thoracoacromial arteries, delivering oxygenated blood to the deltoid, rotator cuff, and scapular stabilizers for efficient force generation during repetitive motions.[24] Innervation arises from the brachial plexus (C5-T1 roots), with the suprascapular nerve (from C5-C6) providing motor supply to the supraspinatus and infraspinatus for initiation of abduction and external rotation, while other branches like the axillary and musculocutaneous nerves coordinate deltoid and biceps activity to maintain force couples.[25]Epidemiology and Risk Factors
Prevalence and Incidence
Shoulder pain is a prevalent musculoskeletal complaint, affecting an estimated 18-26% of adults at any given time in the general population.[26] Annual prevalence rates range from 4.7% to 46.7%, with lifetime prevalence between 6.7% and 66.7%, reflecting variations in study methodologies and populations.[27] In the United States, approximately 4.5 million patient visits occur annually for shoulder-related issues, underscoring its significant public health impact.[28] Incidence rates for specific shoulder problems vary by category and age group. For traumatic injuries, such as glenohumeral dislocations, the overall population incidence is about 36-41 per 100,000 persons annually, but it rises to 1-2% per year among young athletes in contact sports like football and rugby.[29] Degenerative conditions, including rotator cuff tears, show increasing incidence with age; symptomatic tears affect 20-30% of individuals over 60 years, with overall prevalence of rotator cuff pathology reaching 6.8-22.4% in those over 40 and up to 70% in those over 70.[30][31] Demographic patterns highlight disparities in shoulder problem occurrence. Prevalence is higher in older adults, with nearly 20% of those aged 65 and older reporting shoulder pain, escalating to 21-27% in the elderly population overall.[32][33] Males experience elevated rates of traumatic injuries like dislocations, while females have a 1.5-1.8 times higher risk for adhesive capsulitis, with an overall incidence of 2-5% in the general population but disproportionately affecting women aged 40-60.[34] Occupational risks amplify these trends, with manual laborers facing 2-3 times higher prevalence of shoulder disorders due to repetitive overhead work and heavy lifting compared to non-manual workers.[35] Globally, shoulder problems are on the rise as of 2025, driven by aging populations and increased sports participation, contributing to musculoskeletal disorders surpassing chronic conditions like diabetes in economic burden.[36] Community prevalence medians stand at 16% worldwide, with higher incidences in industrialized nations linked to occupational exposures.[37]Predisposing Factors
Shoulder problems can arise from a combination of non-modifiable and modifiable predisposing factors that increase susceptibility to various disorders. Non-modifiable factors include age, genetics, and sex. Advancing age, particularly beyond 40 years, is associated with degenerative changes in shoulder structures due to cumulative biomechanical stress and reduced tissue resilience, elevating the risk for conditions like rotator cuff pathology and osteoarthritis.[26] Genetic predispositions, such as those seen in hyperlaxity syndromes like Ehlers-Danlos syndrome, contribute to joint instability by altering connective tissue integrity and increasing capsular laxity.[38] Regarding sex, males exhibit a higher risk for traumatic shoulder issues due to greater exposure to high-impact activities, whereas females face elevated susceptibility to inflammatory conditions, including frozen shoulder, potentially linked to hormonal and biomechanical differences.[39] Modifiable factors encompass lifestyle, occupational, and behavioral elements that can be addressed to mitigate risk. Occupational overuse, particularly repetitive overhead activities such as those in construction or assembly work, imposes sustained biomechanical strain on the shoulder, significantly heightening the likelihood of tendinopathies and impingement syndromes.[26] In sports, overhead throwing athletes, like baseball pitchers, experience markedly increased vulnerability to labral tears owing to repetitive high-velocity motions that exceed normal joint tolerances.[40] Poor posture and scapular dyskinesis further predispose individuals by disrupting normal scapulohumeral rhythm, leading to compensatory overload on shoulder stabilizers and a 43% higher risk of future pain in asymptomatic cases.[41] Smoking exacerbates this by impairing tendon vascularity and healing, thereby promoting degenerative processes in shoulder tissues.[42] Systemic conditions also play a critical role in predisposing individuals to shoulder problems. Diabetes mellitus substantially elevates the risk for frozen shoulder, with affected patients facing approximately 2.3 times the odds compared to non-diabetics, likely due to glycemic effects on collagen cross-linking and capsular fibrosis.[39] Obesity contributes similarly by increasing mechanical load on the shoulder and promoting inflammatory pathways that correlate with higher rates of pain and dysfunction.[43] Previous injuries often result in residual instability, creating a cycle of vulnerability where initial trauma compromises joint congruence and muscle balance, thereby amplifying the chance of recurrent issues.[44] Environmental factors, such as acute trauma mechanisms, serve as precursors to shoulder problems by directly overwhelming joint defenses. Falls onto an outstretched arm or direct blows to the shoulder can initiate structural damage, particularly in those with underlying vulnerabilities, underscoring the interplay between external forces and intrinsic risks.[44]Diagnosis
History Taking and Physical Examination
A thorough history taking is essential in evaluating shoulder problems, beginning with the onset of symptoms to distinguish between acute traumatic events and insidious onset suggestive of degenerative or overuse conditions. Clinicians inquire about the timing and mechanism of pain initiation, such as sudden injury versus gradual development during repetitive activities.[45] Pain characteristics are detailed, including location (anterior, posterior, or diffuse), quality (sharp, aching, or burning), severity, duration, and radiation patterns, which help narrow differential diagnoses. Aggravating and relieving factors are explored, such as overhead motions worsening impingement-like symptoms or rest alleviating inflammatory pain, alongside functional limitations like difficulty with dressing or sleep disturbances due to night pain. A review of trauma history, previous episodes, treatments attempted, occupational or recreational demands, and comorbidities (e.g., diabetes or cervical spine issues) provides context for underlying etiologies.[46] The physical examination commences with inspection to identify visible abnormalities, including asymmetry, swelling, deformity, atrophy, or skin changes such as bruising or erythema. Palpation follows, systematically assessing bony landmarks like the acromion, clavicle, and scapula, as well as soft tissues including the rotator cuff insertions and biceps tendon for tenderness or crepitus. Range of motion is evaluated through active and passive testing in forward flexion, extension, abduction, adduction, internal and external rotation, assessing for pain, crepitus, or end-range restrictions that may indicate capsular tightness or mechanical blocks. Strength testing is performed against resistance for key muscle groups, such as abduction for deltoid and supraspinatus, external rotation for infraspinatus and teres minor, and internal rotation for subscapularis, using standardized positions to isolate functions and detect weakness.[47][48] Special tests are incorporated to provoke specific pathologies without relying on interpretive outcomes for definitive diagnosis. For potential impingement, maneuvers like the Neer impingement sign (passive forward flexion to elicit subacromial pain) and Hawkins-Kennedy test (forward flexion with internal rotation) are performed to assess subacromial space compression. Instability evaluation includes the apprehension test (abduction and external rotation to provoke subluxation fear) and sulcus sign (inferior traction to check for humeral head depression), aiding in identifying laxity directions. These tests, when combined with history and basic exam findings, guide further diagnostic steps such as imaging.[49] Red flags during history and examination warrant urgent investigation to rule out serious non-musculoskeletal causes. Systemic symptoms like unexplained weight loss, fever, night sweats, or new respiratory issues may indicate malignancy, infection, or referred pain from visceral sources such as cardiac or pulmonary conditions. A history of cancer (e.g., lung or breast) or acute trauma with severe movement restriction raises concern for fracture or metastasis. Examination findings including a hot, erythematous joint, palpable mass, profound weakness, or bilateral involvement suggesting inflammatory arthropathy (e.g., polymyalgia rheumatica) necessitate prompt referral.[50]Imaging Modalities
X-rays remain the initial imaging modality for evaluating shoulder problems, providing essential information on bony structures. Standard views include the anteroposterior (AP) view to assess overall alignment and joint space, the axillary view to evaluate glenohumeral joint positioning and detect dislocations, and the scapular Y (lateral scapula) view to confirm humeral head position relative to the glenoid. These projections are particularly useful for identifying fractures, dislocations, and degenerative changes such as joint space narrowing.[51][52] Ultrasound offers a dynamic, real-time assessment of shoulder soft tissues and is cost-effective for initial evaluation. It excels in detecting tendinopathy, bursitis, and joint effusions through probe manipulation to visualize tendon motion and fluid collections during movement. As an operator-dependent technique, its accuracy relies on the examiner's expertise, but it serves as a reasonable first-line option after radiography for soft tissue pathology.[53][54] Magnetic resonance imaging (MRI) is the gold standard for detailed soft tissue evaluation in shoulder disorders. It provides high-contrast images of rotator cuff tears, labral injuries, and capsular thickness, with sensitivity exceeding 90% for full-thickness rotator cuff tears. Specialized protocols like MR arthrography, involving intra-articular contrast injection, enhance visualization of glenohumeral instability by delineating labroligamentous complexes more clearly than conventional MRI.[53][55] Computed tomography (CT) scans are reserved for complex bony injuries, offering superior detail on fractures and deformities through multiplanar reformations and 3D reconstructions. They are particularly valuable for preoperative planning in proximal humerus fractures, where they improve classification accuracy over plain radiographs. However, radiation exposure limits their routine use, favoring them in cases of suspected intra-articular fragments or subtle displacements.[56][57] Emerging techniques as of 2025 include ultrasound-guided injections for therapeutic applications, such as subacromial corticosteroid administration, which improve pain relief and function in impingement syndromes with real-time needle placement. Additionally, AI-enhanced MRI and ultrasound leverage deep learning for automated segmentation and early pathology detection, achieving diagnostic accuracies comparable to expert radiologists while reducing interpretation time.[58][59]Laboratory and Other Tests
Blood tests play a crucial role in evaluating systemic or inflammatory contributions to shoulder problems. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are key inflammatory markers used to detect elevated inflammation suggestive of arthritis or infection affecting the shoulder joint.[60] These tests measure the rate at which red blood cells settle and the levels of a liver-derived protein, respectively, providing non-specific indicators of ongoing inflammatory processes.[61] For suspected autoimmune involvement, rheumatoid factor (RF) and antinuclear antibody (ANA) tests are performed to identify antibodies associated with conditions like rheumatoid arthritis that can manifest as shoulder pain and stiffness.[62] The RF test detects immunoglobulins that target the body's own tissues, while ANA identifies antibodies attacking cell nuclei, aiding in the diagnosis of autoimmune joint disorders.[63] Positive results, when correlated with clinical symptoms, support targeted autoimmune evaluation.[64] Metabolic screening includes fasting glucose and hemoglobin A1c (HbA1c) levels to assess diabetes risk, as hyperglycemia is linked to increased susceptibility to shoulder pathologies such as adhesive capsulitis.[65] Elevated HbA1c, reflecting average blood sugar over 2-3 months, correlates with higher prevalence of prediabetes (37.3%) and diabetes (46.2%) in patients with idiopathic frozen shoulder, highlighting its utility in risk stratification.[65] Electrodiagnostic studies, such as electromyography (EMG) and nerve conduction studies (NCS), are indicated for assessing neuropathic or brachial plexus-related shoulder issues. EMG evaluates muscle electrical activity to detect denervation or reinnervation patterns, while NCS measures nerve signal speed and strength to localize lesions in the brachial plexus.[66] These tests differentiate pre-ganglionic from post-ganglionic injuries and guide prognosis in cases of trauma or idiopathic neuritis.[67] Arthrocentesis, or joint aspiration, provides synovial fluid for laboratory analysis to confirm crystalline arthropathies like gout or infectious processes in the shoulder. The procedure involves needle insertion into the glenohumeral joint to extract fluid, which is then examined for urate crystals via polarized light microscopy or cultured for pathogens.[68] This test is particularly valuable when septic or inflammatory arthritis is suspected based on clinical findings.[69] Nuclear medicine bone scans are employed to identify osteolysis or occult fractures in the shoulder, revealing areas of increased radionuclide uptake indicative of bone resorption or stress injuries.[70] Dual-energy X-ray absorptiometry (DEXA) scans assess bone mineral density to evaluate osteoporosis, a risk factor for fragility fractures in the proximal humerus or clavicle, with T-scores below -2.5 standard deviations confirming the diagnosis.[71] Functional assessments quantify impairments in shoulder mechanics through goniometry, which measures range of motion (ROM) in degrees—for instance, normal shoulder abduction reaches 150 degrees with full girdle contribution—and isokinetic dynamometry, which evaluates muscle strength at controlled speeds to detect rotator cuff deficits.[72] Optimal isokinetic testing occurs in supine positions at 45-90 degrees abduction for reliable peak torque measurements.[73] These tests are ordered when physical examination suggests ROM limitations or weakness, complementing diagnostic efforts.[74]Traumatic Injuries
Glenohumeral Dislocation
Glenohumeral dislocation refers to the displacement of the humeral head from the glenoid fossa, making it the most common type of joint dislocation, with anterior dislocations accounting for approximately 95-96% of cases, while posterior and inferior dislocations are rare, comprising 2-4% and less than 1%, respectively.[75][76] Anterior dislocations typically result from a traumatic mechanism involving forced abduction and external rotation of the arm, often seen in contact sports or falls onto an outstretched hand, whereas posterior dislocations arise from axial loading on an adducted and internally rotated arm, such as during seizures or electric shocks.[75][77] Inferior dislocations, known as luxatio erecta, occur due to hyperabduction forces and represent the least common variant.[75] Clinically, patients present with a characteristic squared-off shoulder deformity due to the loss of the normal rounded deltoid contour, and the affected arm is often held in slight abduction and external rotation to minimize discomfort.[75] A palpable bulge may be felt anteriorly in anterior dislocations or posteriorly in rare posterior cases, accompanied by significant pain and restricted active shoulder motion.[75] Neurovascular assessment is critical, as axillary nerve palsy occurs in 10-40% of cases, manifesting as numbness over the lateral shoulder and weakness in deltoid abduction, while vascular injuries like axillary artery damage are less common but must be ruled out through pulse checks.[75][78] Diagnosis is primarily confirmed with plain radiographs, including anteroposterior, lateral, and axillary views, which demonstrate the abnormal position of the humeral head relative to the glenoid.[79] For associated soft tissue injuries, magnetic resonance imaging (MRI) is recommended to identify Bankart lesions (anterior labral tears) or Hill-Sachs lesions (posterolateral humeral head impaction fractures), which are present in up to 70-100% of initial anterior dislocations and contribute to instability.[80][81] Initial management involves prompt closed reduction under sedation or analgesia, using techniques such as the Stimson method (gravity-assisted with the patient prone) or traction-countertraction, with post-reduction radiographs to verify joint congruence.[75] Immobilization in a sling for 3-4 weeks follows, typically with the arm in internal rotation to promote coaptation, though external rotation bracing may reduce recurrence risk in select cases.[79] For first-time dislocations in older patients, conservative care suffices, but recurrent instability affects over 50% of young patients (under 20 years), necessitating surgical stabilization via arthroscopic Bankart repair to reattach the labrum and restore stability.[79][82]Clavicle and Scapular Fractures
Clavicle fractures represent a significant portion of shoulder girdle injuries, accounting for approximately 2.6% to 3.3% of all orthopedic fractures and up to 10% in pediatric populations.[83][84] Midshaft fractures constitute the majority, comprising about 80% to 82% of cases, and typically result from direct falls onto the shoulder or outstretched hand.[85] Distal clavicle fractures, which often involve the acromioclavicular (AC) joint, account for around 10% to 15% and are associated with similar mechanisms but may lead to instability due to ligamentous disruption.[86] These injuries are most prevalent in young males and athletes, with falls being the dominant cause followed by motor vehicle accidents (MVAs).[87] Scapular fractures, in contrast, are relatively uncommon, representing 0.4% to 1% of all fractures and 3% to 5% of shoulder girdle fractures.[88] They usually occur in high-energy trauma scenarios, such as MVAs or falls from height, and are frequently accompanied by other injuries including pulmonary contusions or head trauma.[89] Body fractures of the scapula make up the largest subset (about 45%), while glenoid fractures, which involve the articular surface, are less common (25% to 30%) but carry higher functional implications due to potential joint incongruity.[90] Patients with clavicle or scapular fractures commonly present with acute pain localized to the shoulder region, swelling, bruising, and crepitus at the fracture site; the affected arm is often held adducted against the body to minimize movement.[83][91] Neurovascular compromise, such as brachial plexus injury, is rare (occurring in 1% to 3% of cases) but must be assessed, particularly in displaced midshaft clavicle fractures where posterior fragment displacement may compress the plexus.[92] For glenoid-involving scapular fractures, pseudoparalysis—marked limitation in shoulder elevation due to pain and instability—may be evident, distinguishing it from isolated soft tissue injuries.[93] Diagnosis begins with anteroposterior (AP) and lateral radiographs of the clavicle and scapula, often requiring multiple views (e.g., axillary or scapular Y-view) to assess displacement and alignment.[94] Computed tomography (CT) is recommended for intra-articular glenoid fractures or complex scapular patterns to evaluate fragment displacement and associated injuries.[89] In pediatric patients, Salter-Harris classification is applied to physeal injuries of the distal clavicle or scapular apophyses to guide prognosis and management.[83] Management of clavicle fractures prioritizes nonoperative approaches for undisplaced or minimally displaced midshaft fractures, using a sling or figure-of-eight brace for 4 to 6 weeks, achieving union rates of approximately 91% to 97% within 6 to 12 weeks.[95] Open reduction and internal fixation (ORIF) with plates is indicated for significantly displaced fractures (>2 cm shortening), distal types with AC instability, or open injuries, reducing nonunion risk to under 3%.[96] Scapular fractures are managed conservatively in over 90% of cases with sling immobilization for 2 to 4 weeks followed by pendulum exercises, as most body and neck fractures heal without intervention.[97] Surgical fixation is reserved for comminuted glenoid fractures with >2 mm step-off, displaced neck fractures (>40° angulation or >1 cm displacement), or those with neurovascular compromise, typically via ORIF to restore glenohumeral stability.[89][98]Acromioclavicular Joint Separation
Acromioclavicular joint separation, also known as acromioclavicular (AC) joint injury, occurs when the ligaments stabilizing the joint between the acromion of the scapula and the distal clavicle are damaged, leading to partial or complete disruption. This injury is commonly seen in contact sports such as football, hockey, and rugby, where it accounts for 40% to 50% of all shoulder injuries, often resulting from a direct blow to the superolateral aspect of the shoulder with the arm in an adducted position or from a fall onto the outstretched hand or elbow.[99][100] The Rockwood classification system categorizes AC joint separations into six types based on the extent of ligamentous injury, degree of joint displacement, and involvement of surrounding structures, guiding diagnosis and treatment decisions. Type I involves a simple sprain of the AC ligaments with no increase in the coracoclavicular (CC) distance and no joint displacement. Type II features a complete tear of the AC ligaments with a sprain of the CC ligaments, resulting in subluxation and less than 25% increase in CC distance. Type III represents complete tears of both AC and CC ligaments with 25% to 100% increase in CC distance and clavicular elevation. Type IV includes posterior displacement of the clavicle through the trapezius muscle. Type V shows superior displacement with more than 100% increase in CC distance and deltotrapezial fascia disruption. Type VI is characterized by inferior displacement of the clavicle below the coracoid or acromion.[100][99] Patients typically present with acute pain and tenderness localized to the AC joint, exacerbated by shoulder movement or cross-body adduction. Swelling, ecchymosis, and limited range of motion may occur, with a palpable or visible step deformity evident in types III and higher due to superior clavicular displacement, sometimes described as a "piano key" sign from clavicular prominence. The cross-arm adduction test, where the arm is actively adducted across the chest, reproduces pain at the AC joint and is positive in affected individuals.[100][99] Diagnosis relies on a combination of clinical evaluation and imaging to confirm injury severity and rule out associated fractures or soft-tissue damage. Standard anteroposterior radiographs of both shoulders are initial imaging, with the Zanca view (15° cephalic tilt) used to assess AC joint alignment and measure CC distance, where normal is 11 to 13 mm and widening indicates higher-grade injury. Stress views, obtained by weighting the arm or comparing loaded versus unloaded positions, evaluate dynamic instability but are not routinely recommended due to pain and limited reliability. Advanced imaging such as MRI may be employed if diagnosis remains uncertain or to evaluate concomitant injuries.[100][99] Management is stratified by Rockwood type and patient factors such as activity level and symptoms. Types I and II are treated nonoperatively with a sling for comfort (typically 3 to 7 days), ice application, analgesics, and early initiation of physical therapy to restore range of motion and strength, yielding good outcomes in most cases. Type III injuries are often managed conservatively initially, though surgery may be considered for high-demand athletes or persistent symptoms after 3 to 6 months. Types IV, V, and VI, along with acute type III in high-demand patients, require surgical intervention to restore anatomy and stability; common procedures include the Weaver-Dunn reconstruction, which transfers the coracoacromial ligament to the clavicle, or CC ligament reconstruction using techniques like endobuttons, grafts, or hook plates.[100][99]| Rockwood Type | AC Ligament | CC Ligament | Displacement | Treatment Approach |
|---|---|---|---|---|
| I | Sprain | Intact | None | Nonoperative (sling, PT)[100] |
| II | Torn | Sprain | <25% CC widening | Nonoperative (sling, PT)[100] |
| III | Torn | Torn | 25-100% CC widening | Nonoperative initial; surgery if high-demand[99] |
| IV | Torn | Torn | Posterior through trapezius | Surgical (reconstruction)[100] |
| V | Torn | Torn | >100% CC widening | Surgical (reconstruction)[100] |
| VI | Torn | Torn | Inferior | Surgical (reconstruction)[100] |