Proximal Humerus Fractures: Etiology, Classification, Treatment, and Rehabilitation

Proximal humerus fractures are the second most common fractures of the upper extremity after distal radius fractures. Their incidence is increasing as life expectancy in the general population continues to rise.

Anatomy of Proximal Humerus

Bony Anatomy

The proximal humerus consists of four main anatomical segments: the humeral head, the greater tuberosity, the lesser tuberosity, and the humeral shaft.

The humeral head is almost hemispherical. It articulates with the glenoid fossa of the scapula to form the shoulder joint. The anatomical neck separates the humeral head from the tuberosities. The surgical neck lies at the junction between the metaphysis and the shaft and is a common site of fracture.

The greater tuberosity serves as the attachment site for three of the four rotator cuff muscles: the supraspinatus, infraspinatus, and teres minor. The lesser tuberosity provides attachment for the subscapularis muscle. The intertubercular groove, also known as the bicipital groove, lies between the two tuberosities and contains the tendon of the long head of the biceps brachii muscle.

Blood Supply

The humeral head is supplied mainly by the anterior and posterior circumflex humeral arteries, which are branches of the axillary artery.

Fractures that disrupt these vascular structures carry a higher risk of avascular necrosis of the humeral head. This risk is especially high in displaced anatomical neck fractures and in severely comminuted fractures.

Soft Tissue Structures

The rotator cuff muscles and their tendon attachments play an important role in the pattern of fracture fragment displacement. The supraspinatus, infraspinatus, and teres minor attach to the greater tuberosity, while the subscapularis attaches to the lesser tuberosity. These muscles exert deforming forces on the fracture fragments. The supraspinatus tends to displace the greater tuberosity superiorly and posteriorly. The pectoralis major tends to pull the humeral shaft medially and anteriorly.

The axillary nerve innervates the deltoid and teres minor muscles. It is particularly vulnerable in proximal humerus fractures because it passes around the surgical neck of the humerus.

Etiology and Mechanism of Injury

Influence of Age on Fracture Type

The mechanism of injury in proximal humerus fractures varies considerably depending on the patient’s age and level of physical activity. In older patients, these fractures usually result from low-energy trauma, most often a fall from standing height.

In younger adults, proximal humerus fractures more often occur after high-energy trauma. Common causes include motor vehicle collisions, falls from height, and sports injuries. These mechanisms often produce more complex fracture patterns. They may also be associated with additional injuries to soft tissues, neurovascular structures, or other parts of the skeleton.

Mechanism of Injury

Falls onto an outstretched arm with the shoulder abducted and externally rotated can lead to a wide range of fracture patterns. By contrast, direct blows to the lateral aspect of the shoulder tend to produce more consistent injury patterns. The final fracture configuration depends on several factors. These include the position of the arm at the moment of impact, the direction and magnitude of the force, and the quality of the bone.

Epidemiology

Incidence and Prevalence

Proximal humerus fractures account for approximately 4–6% of all fractures. They are the third most common fracture in older adults after hip fractures and distal radius fractures. The incidence rises sharply with age, with the highest rates observed in people older than 65 years. In the general population, incidence rates range from 60 to 105 per 100,000 people. Among older adults, they exceed 250 per 100,000.

Demographic Features

Proximal humerus fractures have a bimodal distribution. There is a smaller peak among young adults, usually men who sustain high-energy trauma. A much larger peak is seen among older adults, predominantly women with osteoporosis.

There is a clear sex difference in the incidence of proximal humerus fractures. Women are affected approximately three times more often than men. This difference is most pronounced in older age and is mainly explained by the higher prevalence of osteoporosis among postmenopausal women.

Classification of Proximal Humerus Fractures

Neer Classification

The Neer classification system was introduced in 1970 and modified in 1975. It remains one of the most widely used classification systems for proximal humerus fractures. This system is based on the relationship between four main anatomical segments: the humeral head, the greater tuberosity, the lesser tuberosity, and the shaft. A segment is considered a separate “part” if it is displaced by more than 1 cm or angulated by more than 45 degrees.

The Neer classification describes fractures as two-part, three-part, or four-part fractures, depending on the number of displaced fragments. It also includes fracture-dislocations and head-splitting fractures.

The classification has prognostic value because the risk of avascular necrosis increases with the number of displaced fragments. Four-part fractures carry the highest risk of avascular necrosis, estimated at 13–34%.

AO/OTA Classification

The Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association (AO/OTA) classification provides a more detailed and comprehensive approach to proximal humerus fractures. This alphanumeric system classifies fractures according to location, morphology, and severity.

AO/OTA Classification of Proximal Humerus Fractures

3D Models of Proximal Humerus Fractures:

Bifocal Comminuted Fracture of Surgical Neck of Humerus

Fracture of Greater Tuberosity of Humerus

Unifocal Fracture of Surgical Neck of Humerus

Isolated Fracture of Anatomical Neck of Humerus

Other Classification Systems

• The Codman classification preceded the Neer system. It identifies four anatomical segments of the proximal humerus and describes fractures according to the number and location of fracture lines. This classification formed the basis for later classification systems.
• The Codman-Hertel classification is designed to assess the risk of ischemia and avascular necrosis. It evaluates the integrity of the medial hinge and the length of the posteromedial metaphyseal extension of the fracture line. These features provide valuable prognostic information about vascular compromise.

Clinical Assessment and Diagnosis of Fractures

Initial Assessment

Pain, swelling, ecchymosis, and deformity in the shoulder region are common clinical signs. Patients usually support the injured arm with the opposite hand and hold it adducted against the body. Crepitus may be felt with gentle palpation. However, excessive manipulation should be avoided because it may worsen soft-tissue injury or cause neurovascular compromise.

Neurovascular Status

A comprehensive neurovascular assessment is necessary in all cases of proximal humerus fracture. The axillary nerve is the most commonly injured nerve. The incidence of axillary nerve injury may reach 30%, depending on the fracture pattern.

Assessment of axillary nerve function includes evaluation of deltoid muscle contraction and sensation over the lateral aspect of the shoulder. This sensory area is known as the “regimental badge” area.

Other nerves at risk include the musculocutaneous, radial, median, and ulnar nerves. However, injuries to these structures are less common.

Vascular injuries are rare but may occur, especially after high-energy trauma or fracture-dislocations. The examination should include assessment of distal pulses, capillary refill, and signs of vascular compromise.

Radiologic Methods

Standard radiographic evaluation includes several shoulder views: an anteroposterior (AP) view, a scapular Y view, and an axillary lateral view. Together, these orthogonal views allow accurate fracture assessment and classification.

Computed tomography (CT) with three-dimensional reconstruction is valuable in the evaluation of complex proximal humerus fractures. It is especially useful for surgical planning because it allows assessment of the size and position of fracture fragments.

Magnetic resonance imaging (MRI) may be useful in selected cases to evaluate associated soft-tissue injuries. These include rotator cuff tears, labral injuries, and occult fractures. MRI can also help assess the vascularity of the humeral head.

Treatment Methods for Proximal Humerus Fractures

Medical therapy

Many proximal humerus fractures can be managed without surgery, especially when they are minimally displaced or stable. Approximately 80% of these fractures have minimal displacement and respond well to conservative management.

Treatment usually begins with a short period of immobilization, typically lasting 1–2 weeks. This is followed by early mobilization and a gradual rehabilitation program.

This approach is appropriate for fractures with minimal displacement, defined as less than 1 cm of displacement and less than 45 degrees of angulation. It may also be used for impacted fractures in stable valgus alignment, as well as in patients with significant comorbidities or low functional demands. In older patients with low functional demands, even some three-part and four-part fractures may be managed conservatively with acceptable functional outcomes.

Open Reduction and Internal Fixation

Open reduction and internal fixation (ORIF) with locking plates is widely used for displaced proximal humerus fractures. One commonly used implant is the Proximal Humerus Internal Locking System (PHILOS) plate. Locking plate technology provides angular stability and improves fixation in osteoporotic bone compared with conventional plates.

ORIF is usually indicated for displaced two-part and three-part fractures in young, active patients. It may also be considered in selected older patients with good bone quality. The procedure allows anatomical reduction of the fracture fragments, restoration of humeral head height and inclination, and stable fixation for early mobilization.

In older patients with osteoporosis, augmentation may be used to improve screw purchase in bone. Common augmentation options include polymethyl methacrylate, calcium phosphate bone cement, and fibular strut grafts.

Intramedullary Fixation

Intramedullary fixation is an alternative surgical option for proximal humerus fractures. Its potential advantages include a minimally invasive technique, preservation of soft tissues, and biomechanical stability.

This method is mainly used for two-part and three-part fractures, especially when the fracture extends into the humeral shaft. It is less suitable for fractures with marked metaphyseal comminution or tuberosity involvement. In these situations, the nail may not provide adequate control of the fracture fragments.

Percutaneous Fixation

Percutaneous fixation with Kirschner wires (K-wires) or cannulated screws is a minimally invasive option for selected fracture patterns. It is most suitable for two-part fractures with minimal comminution and adequate bone quality. The main advantages are limited soft tissue disruption, preservation of blood supply, and shorter operative time.

However, this technique has important limitations. Pin migration is a common complication and may occur in up to 30% of cases. It can lead to neurovascular injury or soft tissue irritation. Malunion is also more common than after open reduction and internal fixation (ORIF), which may result in deformity, pain, and functional impairment.

Arthroplasty

Arthroplasty procedures include hemiarthroplasty (HA) and reverse shoulder arthroplasty (RSA). They are usually reserved for fractures with a high risk of avascular necrosis, severe comminution that prevents stable fixation, or fracture-dislocations with significant damage to the articular surface.

Hemiarthroplasty

Hemiarthroplasty involves replacement of the humeral head while preserving the patient’s native glenoid. Historically, it was the main arthroplasty option for complex proximal humerus fractures. The procedure requires anatomical reconstruction and secure fixation of the tuberosities to restore rotator cuff function.

Outcomes after hemiarthroplasty for fractures are variable. Tuberosity union is a key factor that determines functional recovery. If the tuberosities heal in an anatomical position, shoulder function may be satisfactory. However, tuberosity nonunion or malunion occurs in 15–30% of cases and can significantly impair shoulder function.

Reverse Shoulder Arthroplasty

Reverse shoulder arthroplasty (RSA) has become the preferred arthroplasty option for complex proximal humerus fractures in older patients. The reverse design uses a glenosphere and a concave humeral component. This configuration provides stability and allows functional shoulder movement even when rotator cuff function is absent.

RSA is particularly useful when tuberosity reconstruction is unreliable or when preexisting rotator cuff disease is present. Unlike hemiarthroplasty, functional recovery after RSA does not depend on tuberosity healing. This makes it a more predictable option for older patients.

Treatment Decision-Making Algorithm

The choice of treatment depends on several factors, including fracture pattern, patient age, bone quality, functional demands, comorbidities, and patient preferences.

International Treatment Selection Protocol

Note:

* Risk of avascular necrosis.

Rehabilitation After Proximal Humerus Fractures

Principles of Rehabilitation

Rehabilitation is an essential part of recovery after proximal humerus fractures, whether treatment is conservative or surgical. Its main goals are to restore shoulder range of motion, strength, and function. It also helps reduce the risk of complications, such as stiffness and adhesive capsulitis.

Early mobilization is the standard of care for most proximal humerus fractures. Gentle passive range-of-motion exercises are usually started within the first 1–2 weeks after injury or surgery. This early movement is a key element of recovery.

Rehabilitation Protocols

Rehabilitation protocols usually progress through several phases.

Note:

** Specific timelines and rehabilitation progression should be individualized according to the fracture pattern, treatment method, bone quality, and patient-related factors.

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Prognosis and Outcomes of Proximal Humerus Fractures

Factors Affecting Prognosis

The pattern and complexity of the fracture have a major impact on prognosis. Minimally displaced fractures usually have an excellent prognosis with conservative management. In contrast, complex four-part fractures carry a higher risk of complications and poorer functional outcomes, regardless of the treatment method. Comminution, involvement of the articular surface, and metaphyseal extension negatively affect prognosis.

Osteoporotic bone increases the risk of fixation failure, loss of reduction, and poor functional outcomes after open reduction and internal fixation.

Adherence to rehabilitation is closely associated with functional recovery. Patients who actively participate in structured rehabilitation programs tend to achieve better range of motion, strength, and overall function than those with poor adherence.

Functional Outcomes

Studies of conservative management for minimally displaced fractures report good to excellent outcomes in 70–85% of patients. Even some displaced three-part and four-part fractures may achieve acceptable functional results when treated conservatively in older patients with low physical demands.

Open reduction and internal fixation with locking plates achieves good to excellent outcomes in 70–88% of appropriately selected patients. Results are generally better in younger patients with good bone quality and less complex fractures. Functional improvement may continue for 12–24 months after the injury.

Reverse shoulder arthroplasty for complex fractures in older patients provides good to excellent results in 75–85% of cases.

Return to Daily Activities

Return to daily activities is an important outcome measure, especially in older patients. Most patients regain independence in basic self-care within 3–6 months, although more complex activities may take longer.

For young, active patients, return to work and sport is a key consideration. Light work and low-demand activities may be possible within 3–4 months. Return to heavy labor or contact sports may require 6–12 months or longer.