Humerus fracture
A humerus fracture is a break in the humerus, the long bone of the upper arm that connects the shoulder to the elbow, and it can occur in the proximal (upper) portion near the shoulder, the shaft (middle) section, or the distal (lower) portion near the elbow.[1] These fractures represent approximately 4-6% of all fractures in younger patients and 1-3% in the elderly, with higher incidence in young men due to high-energy trauma and in older women from low-energy falls.[1] Causes of humerus fractures typically involve direct trauma, such as falls onto an outstretched hand or elbow, sports-related impacts, motor vehicle accidents, or direct blows to the arm.[2] In older adults, underlying conditions like osteoporosis weaken the bone, increasing susceptibility to fractures from minor falls or ground-level impacts.[3] Pathologic fractures may also arise from bone tumors or metastatic disease, compromising the bone's integrity without significant trauma.[1] Symptoms commonly include severe pain at the injury site that intensifies with movement, swelling, bruising, and tenderness, often accompanied by an inability to lift the arm or rotate the forearm.[2] Deformity may be visible if the bone is displaced, and in distal fractures, stiffness, instability, or bruising around the elbow can occur.[3] Nerve involvement, such as radial nerve palsy in shaft fractures, may cause weakness or numbness in the hand.[1] Diagnosis begins with a physical examination to assess pain, swelling, and neurovascular status, followed by X-rays in multiple views (anteroposterior, lateral, and axillary) to confirm the fracture location, displacement, and type.[1] Advanced imaging like CT scans is used for complex or intra-articular fractures to evaluate fragmentation and plan treatment.[1] Treatment varies by fracture location and severity, with many cases managed nonoperatively using immobilization such as a sling for proximal fractures or a functional brace for shaft fractures, promoting healing through the bone's good vascularity and non-weight-bearing nature.[1] Surgical intervention, including open reduction and internal fixation (ORIF) with plates and screws, is indicated for displaced, open, or unstable fractures, particularly in distal cases where elbow stability is crucial.[3] In severe proximal or distal fractures in older patients, options like hemiarthroplasty or total elbow replacement may be employed to restore function.[1] Complications can include nerve injuries (e.g., axillary or radial nerve damage), blood vessel disruption leading to compartment syndrome—an emergency requiring prompt fasciotomy—and joint stiffness from prolonged immobilization.[2] Long-term issues may involve malunion, nonunion, or temporary disability, though most fractures heal well with appropriate care.[1]Clinical Presentation
Signs and Symptoms
A humerus fracture typically presents with severe pain at the site of injury, which is often immediate and intensifies with any movement of the arm.[2] This pain can radiate along the upper arm and significantly limits the patient's ability to use the affected limb, such as lifting or rotating the arm.[4] Patients frequently report a grinding or crunching sensation during attempted motion, reflecting the mechanical disruption of the bone.[4] Swelling and bruising, known as ecchymosis, commonly develop around the fracture site in the upper arm, often extending to adjacent areas like the shoulder or elbow.[5] The affected area becomes tender to touch, contributing to further discomfort and reluctance to manipulate the limb.[2] These soft tissue changes arise from local hemorrhage and inflammation following the bone break.[5] Functional impairment is prominent, with decreased range of motion and inability to perform routine tasks like raising the arm overhead or supporting weight.[1] In severe cases, visible deformity may occur, such as shortening, angulation, or an abnormal contour of the upper arm due to bone displacement.[2] If neurovascular structures are compromised by the fracture fragments or associated hematoma, patients may experience numbness, tingling, or weakness in the arm or hand, indicating potential nerve or vascular involvement.[4] Symptoms can vary modestly by fracture location along the humerus, but the primary manifestations of pain, swelling, and limited function are consistent across cases.[5]Physical Examination
The physical examination of a suspected humerus fracture begins with a systematic assessment to identify deformity, associated soft tissue injury, and neurovascular compromise, while minimizing patient discomfort. Inspection reveals swelling, ecchymosis, and potential skin tenting or open wounds indicating an open fracture, with ecchymosis often extending to the chest, arm, or forearm in proximal injuries due to hematoma spread. Deformity may present as shortening, varus angulation, or rotational malalignment, particularly in shaft fractures distal to the deltoid insertion, where the arm appears shortened and adducted. Skin integrity is evaluated for lacerations or punctures, as these suggest contamination and necessitate urgent intervention. Palpation is performed gently along the humerus to localize point tenderness, elicit crepitus from bone ends rubbing together, and assess abnormal mobility by rotating the humeral shaft while palpating the proximal or distal segments for unified motion. In proximal fractures, palpation of the humeral head during gentle rotation helps determine stability and detect crepitus, while shaft fractures often show focal tenderness and deformity at the mid-humerus. Distal fractures may exhibit tenderness over the elbow with crepitus in the olecranon fossa. Range of motion testing is limited by pain, with active and passive abduction, flexion, and rotation eliciting severe discomfort, particularly in proximal injuries where shoulder motion is restricted. Neurovascular examination is critical, as up to 18% of shaft fractures involve radial nerve injury, manifesting as wrist drop (weakness in wrist and finger extension) and sensory loss over the dorsal hand first web space. The axillary nerve is most commonly affected in proximal fractures, tested by deltoid contraction and sensation over the lateral shoulder, while distal fractures risk median, ulnar, or radial nerve deficits, assessed via motor function (e.g., thumb opposition for median) and sensory testing in dermatomes. Vascular status includes palpation of brachial, radial, and ulnar pulses, with comparison to the contralateral side and monitoring for capillary refill; absent pulses warrant immediate imaging or exploration.Etiology and Risk Factors
Mechanisms of Injury
Humerus fractures result from biomechanical forces that exceed the bone's structural integrity, typically involving direct trauma, indirect forces, or a combination thereof, leading to stress concentrations that propagate cracks in transverse, oblique, spiral, or comminuted patterns depending on the loading direction and magnitude.[6] Direct trauma applies localized perpendicular force, often causing transverse fractures through bending stress at the impact site, while indirect mechanisms like axial loading or torsion generate oblique or spiral patterns due to shear and twisting stresses along the bone's longitudinal axis.[7] High-energy mechanisms, such as motor vehicle accidents, produce comminuted fractures with multiple fragments from explosive force distribution, whereas low-energy events like ground-level falls result in simpler patterns, particularly in osteoporotic bone.[8] For proximal humerus fractures, the most common mechanism is a low-energy fall onto an outstretched hand (FOOSH) with the arm in abduction and external rotation, transmitting axial compression and varus stress to the humeral head, often in elderly patients.[7] In younger individuals, high-energy direct impacts from sports or vehicular collisions cause similar compression but with greater displacement.[8] A specific example is avulsion of the greater tuberosity, resulting from sudden contraction of the rotator cuff muscles (supraspinatus and infraspinatus) during forceful abduction or external rotation, often associated with anterior shoulder dislocation, where tensile stress pulls the tuberosity fragment away from the humerus.[9] Humeral shaft fractures predominantly arise from direct blows to the mid-arm, such as in assaults or falls onto the lateral humerus, generating transverse fracture lines perpendicular to the force vector due to localized bending stress concentration in the diaphysis.[10] Indirect mechanisms include FOOSH with the elbow extended, driving the distal humerus proximally and creating oblique or impacted patterns from axial compression.[11] High-energy scenarios like motor vehicle accidents account for about 30% of cases, leading to comminuted or segmental fractures from combined bending and torsional forces, while low-energy ground-level falls comprise 60%, typically yielding simpler transverse or spiral configurations.[10] Distal humerus fractures often stem from high-energy direct trauma in younger adults, such as dashboard impacts in motor vehicle collisions compressing the elbow posteriorly, resulting in supracondylar or intercondylar patterns with posterior displacement from varus or valgus stress.[12] Low-energy FOOSH in the elderly transmits axial load through the olecranon, hyperextending the elbow and fracturing the supracondylar region via tension on the anterior cortex and compression posteriorly.[13] Indirect varus or valgus forces from falls with the forearm twisted can isolate medial or lateral columns, producing T- or Y-shaped intra-articular fractures due to uneven stress distribution across the trochlea.[14]Predisposing Factors
Bone health issues, particularly osteoporosis and osteopenia, significantly increase the susceptibility to humerus fractures, especially fragility fractures of the proximal humerus in older adults.[7] Osteoporosis weakens bone density, making it more prone to low-energy trauma such as falls from standing height, and is particularly prevalent among postmenopausal women due to estrogen deficiency accelerating bone loss.[15] Similarly, osteopenia represents a precursor state that heightens fracture risk without the full severity of osteoporosis.[16] Age-related factors contribute distinctly across life stages, with higher incidence of proximal humerus fragility fractures in the elderly over 65 years due to cumulative bone loss and reduced muscle strength.[7] In children, particularly those aged 5 to 7 years, distal humerus fractures like supracondylar or greenstick types are more common, predisposed by the flexibility of immature bones with thicker periosteum that favors incomplete fractures during falls.[17] Comorbidities such as neurological conditions, including stroke, elevate fracture risk through impaired balance and increased fall propensity, with stroke survivors facing 1.4 to 7 times higher odds of humerus fractures compared to the general population.[18] Malignancy-related pathologic fractures of the humerus often stem from metastatic bone lesions weakening the cortex, commonly from primaries like breast, lung, or prostate cancer.[19] Lifestyle factors impairing bone integrity include chronic alcoholism and smoking, which reduce bone mineral density and healing capacity, thereby increasing humerus fracture susceptibility; for instance, alcohol consumption exceeding moderate levels disrupts calcium absorption, while smoking inhibits osteoblast activity.[20] Participation in high-risk activities, such as contact sports, predisposes individuals to humerus shaft fractures via direct impact or torsional forces. Anatomical variations, including pre-existing deformities or prior fractures, compromise bone strength and elevate the risk of subsequent humerus fractures by creating stress risers or altering load distribution.[21]Types and Classification
Proximal Humerus Fractures
Proximal humerus fractures involve the upper end of the humerus, including the humeral head, anatomic neck, surgical neck, greater tuberosity, and lesser tuberosity. These fractures are common in older adults due to osteoporosis and in younger patients from high-energy trauma. They are classified primarily using the Neer classification system, which divides the proximal humerus into four segments: the humeral head, shaft, greater tuberosity, and lesser tuberosity. A segment is considered displaced if separation exceeds 1 cm or angulation is greater than 45 degrees.[22]- One-part fractures: Nondisplaced or minimally displaced, involving any number of segments without significant separation; these represent the majority of cases and often include impacted fractures.
- Two-part fractures: Displacement of one segment, such as surgical neck, anatomic neck, greater tuberosity, or lesser tuberosity fractures.
- Three-part fractures: Displacement of two segments, typically involving the surgical neck plus one tuberosity.
- Four-part fractures: Displacement of all four segments, often with high risk of avascular necrosis due to disrupted blood supply to the humeral head; includes head-split and valgus impaction variants.
Humeral Shaft Fractures
Humeral shaft fractures occur in the diaphysis, defined as the region from the proximal surgical neck to approximately 5 cm proximal to the olecranon fossa in the distal humerus. These represent about 3-5% of all fractures and are often transverse, oblique, spiral, or comminuted, resulting from direct trauma or torsional forces. They are subclassified by location (proximal third, middle third, distal third) and pattern, with Holstein-Lewis fractures (distal third spiral) at higher risk for radial nerve injury.[10] The primary classification is the AO/OTA system (code 12), which categorizes based on fracture morphology:- Type A (simple fractures): Single fracture line, including spiral (A1), oblique (A2), or transverse (A3) patterns.
- Type B (wedge fractures): Multifragmentary with an intact wedge, subdivided into intact wedge (B1), fragmented wedge (B2), or bending wedge (B3).
- Type C (multifragmentary/complex fractures): Irregular, highly comminuted without a defined wedge, including segmental (C2) or highly irregular (C3) subtypes.
Distal Humerus Fractures
Distal humerus fractures involve the metaphysis and/or articular surface of the lower humerus, from 5 cm above the olecranon fossa to the supracondylar ridges. These account for 2% of fractures in adults and up to 60% in children (primarily supracondylar), often from falls or varus/valgus stresses. They are intra-articular in 50-70% of adult cases, complicating management due to elbow joint involvement.[26] Adult distal humerus fractures are classified using the AO/OTA system (code 13):- Type A (extra-articular): Supracondylar or transcondylar fractures without joint involvement, including simple (A1), wedge (A2), or complex (A3) metaphyseal patterns.
- Type B (partial articular): Involves part of the articular surface, such as lateral/medial condyle (B1), transcondylar (B2), or frontal plane (capitellar/trochlear, B3).
- Type C (complete articular): Fracture lines separate the articular surface from the shaft and cross both columns, with simple (C1), simple articular/simple metaphyseal (C2), or complex (C3) variants.
- Type I: Nondisplaced or minimally angulated (<5 degrees).
- Type II: Displaced with intact posterior cortex (IIa: angulated without rotation; IIb: with rotation).
- Type III: Completely displaced, unstable in all planes.
- Type IV: Unstable after reduction, with multidirectional instability.