Proximal humeral fractures are common, with low-energy injuries occurring in the elderly population and less frequent high-energy fractures striking young people. This article discusses the anatomy, clinical evaluation, and treatment of these fractures.
Key points
- •
Proximal humeral fractures are common.
- •
Classification systems have evolved to develop treatment guidelines.
- •
Bone quality must be considered for treatment.
- •
Surgical stabilization may require augmentation.
- •
Arthroplasty must be considered especially in the elderly.
Introduction
Proximal humeral fractures are common, with low-energy injuries occurring in the elderly population and less frequent higher-energy fractures striking young people. The decision to pursue operative or nonoperative treatment is driven by the functional goals and the degree of displacement of the proximal humeral anatomic parts. Operative management is based on the ability to obtain and maintain reduction, vascularity of the articular segment, quality of soft-tissue attachments, and bone porosity. Despite much study, the optimal treatment of significantly displaced fracture patterns remains controversial.
Introduction
Proximal humeral fractures are common, with low-energy injuries occurring in the elderly population and less frequent higher-energy fractures striking young people. The decision to pursue operative or nonoperative treatment is driven by the functional goals and the degree of displacement of the proximal humeral anatomic parts. Operative management is based on the ability to obtain and maintain reduction, vascularity of the articular segment, quality of soft-tissue attachments, and bone porosity. Despite much study, the optimal treatment of significantly displaced fracture patterns remains controversial.
Epidemiology
Fractures of the proximal humerus are common, occurring in 4% of the population. They are most commonly attributed to low-energy falls, with a smaller subset of high-energy injuries affecting a younger population, but overall incidence increases as bone mineral density decreases. Proximal humeral fractures are the third most common osteoporotic extremity fracture after hip fractures and distal radius fractures. Greater than 70% of these fractures occur in patients older than 60 years, with a 4:1 female/male ratio and an incidence steadily increasing after the age of 40 years.
Independent risk factors for proximal humeral fractures include a recent decline in health status, insulin-dependent diabetes mellitus, infrequent walking, indicators of neuromuscular weakness, diminished femoral neck bone density, height/weight loss, previous falls, impaired balance, and maternal history of hip fractures. In a 3-decade population-based study of osteoporotic proximal humeral fractures, Palvanen and colleagues found that the incidence in patients older than 60 years increased by 13.7% per year of age. When adjusted for age, the incidence of proximal humeral fracture increased in women by 243% and in men by 153%. This increase was attributed to the expanding elderly population as well as the increasing incidence in the risk factors mentioned previously. Based on the observed trends, they calculated that the incidence of proximal humeral fractures would triple by 2030.
Anatomy
The 4 basic osseous structures that serve as the basis for restoration of normal anatomy after reduction are the articular surface proximal to the anatomic neck, greater tuberosity, lesser tuberosity, and humeral shaft. The articular segment has no muscular attachments. The supraspinatus, infraspinatus, and teres minor muscles attach to the greater tuberosity; the subscapularis attaches to the lesser tuberosity; and the deltoid, pectoralis major, teres major, and latissimus dorsi attach to the humeral shaft. The normal osseous relationships define goals for reduction. In the coronal plane the humeral head is inclined to the shaft by a neck shaft angle of 130° to 150°. The humeral head center is offset medially 4 to 14 mm from the center of the shaft and −2 to 10 mm posteriorly. The most proximal aspect of the humeral head articular surface is 8 mm from the tip of the greater tuberosity. In the sagittal plane, the humeral head is retroverted to the shaft by 0° to 55°.
Given the propensity for avascular necrosis of the humeral head after proximal humeral fracture, the perfusion of this area has been the focus of much study. The primary vascular supply to the humeral head is through the anterior humeral circumflex artery. In a latex injection dissection study, Gerber and colleagues showed the anterior humeral circumflex artery to originate from the axillary artery at 1 cm distal to the pectoralis major, running between the short head of the biceps and the coracobrachialis and reaching the surgical neck of the humerus at the inferior border of the subscapularis. The most important branch, the anterolateral branch, traverses under the long head of the biceps adjacent to the lateral border of the intertubercular groove, entering the head at the transition of the intertubercular groove and the greater tuberosity. Once the vessel penetrates the head, it runs as the arcuate artery, posteromedially within the epiphysis, supplying all but a small portion of the posteroinferior portion of the epiphysis and the adjacent posterior portion of the greater tuberosity. The posterior humeral circumflex artery arises from the axillary artery and perfuses the posteroinferior portion of the epiphysis and the posterior greater tuberosity anastomosing with the anterior humeral circumflex artery in the region of the joint capsule and greater tuberosity.
Further study into the humeral head blood supply after fracture shows that, although the anterior humeral circumflex artery is the main blood supply, the head may stay perfused despite its frequent disruption. The anterior humeral circumflex artery is disrupted in 80% of fractures, whereas the posterior humeral circumflex is intact in 85%. In magnetic resonance imaging angiography studies, Hettrich and colleagues showed that the posterior humeral circumflex artery may perfuse up to 64% of the humeral head, which explains the clinical finding of perfusion after fracture. Studies using different evaluation tools have shown contradicting findings, but there seems to be fracture-specific predictors of humeral head ischemia. Hertel and colleagues showed that humeral head ischemia could be predicted with a 97% positive predictive value when the metaphyseal head extension length was less than 8 mm, when there was disruption of the medial hinge between the humeral head and shaft, and when there was an anatomic neck component ( Fig. 1 ).
Evaluation
Mechanism of Injury
History reveals one or a combination of mechanisms occurring to produce a fracture of the proximal humerus: (1) direct blows in the setting of high-energy trauma, (2) falls from standing height, (3) axial loads, (4) excessive internal rotation and adduction forces.
Clinical Evaluation
After evaluation for concomitant upper extremity, neck, and chest wall injuries, as may be present in high-energy trauma, a thorough neurovascular examination is performed. Motor evaluation of the brachial plexus innervation is performed by evaluating the deltoid, biceps, triceps, and wrist flexors/extensors and hand intrinsics motor examination. So-called pseudoparalysis, thought to be secondary to swelling and pain, may make this examination difficult, and the presence of deltoid function does not always rule out an axillary nerve injury. Axillary nerve neuropraxia is the most common deficit in the setting of proximal humeral fracture. Sensation is evaluated through dermatomal light touch examination, and careful evaluation of perfusion to the hand should be documented as well.
Associated Injury
Vascular injury to the axillary artery, although rare, may have devastating consequences if not identified. It may present as obvious acute ischemia or subtly as increasing pain, loss of sensation, and axillary swelling with ecchymosis. The axillary artery is at risk as it crosses medial to the head and surgical neck of the humerus and may be damaged by direct laceration from displaced fracture fragments or by traction to the upper extremity. Prompt arteriography and subsequent repair is necessary and may be timed with fracture fixation to prevent further injury.
A significant factor in the outcome of proximal humeral fractures is associated injury to the brachial plexus. Neurologic injury associated with proximal humeral fracture is most common in the axillary nerve distribution. Large fracture fragment displacement with associated hematoma development and older age show increasing incidences of axillary nerve injury. Complete evaluation of neurologic injury is often difficult secondary to pain and swelling associated with the fracture. Most associated neurologic injuries partially or completely resolve within 4 months.
Rotator cuff injury is common after proximal humeral fractures with rates of 29% to 40%. The severity of the tear correlates with increasing Neer and AO-OTA (AO-Orthopaedic Trauma Association) classification and subsequent displacement of the greater tuberosity fragment. The role of the rotator cuff tear in the functional recovery of proximal humeral fractures is incompletely defined. Two reports on the functional outcome in conservatively treated proximal humeral fractures with rotator cuff tears are inconclusive with respect to outcome; therefore, advanced imaging for complete evaluation of the rotator cuff in the setting of proximal humeral fracture cannot be recommended at this time.
Radiographic Evaluation
Radiographic evaluation with 3 views of the shoulder is critical to successful diagnosis, classification, and treatment. Anteroposterior (AP), axillary lateral, and scapular Y views of the shoulder are obtained in a trauma series. The true AP view (Grashey view) shows the articular surface and defines the main fracture line between the head, neck and shaft, the head/neck shaft angle, the glenohumeral relationship, and the varus/valgus displacement in the coronal plane. The axillary lateral view defines the relationship of the humeral head with respect to the glenoid in the axial plane, allowing evaluation of glenohumeral dislocation as well as AP translation of the head to the shaft. The glenoid should be well visualized, and scapular pathologic findings may be identified with proximal humeral fractures, particularly in high-energy injuries. The scapular Y view gives information on the displacement of the humeral head relative to the shaft in the sagittal plane, as well as greater tuberosity displacement, but the superimposed scapula may obscure fracture anatomy ( Fig. 2 ).
The major fracture fragment relationships may not be clearly defined in multifragmentary fracture patterns. The indications for computed tomographic (CT) examination vary widely but include cases in which fracture overlap and low-quality axillary lateral views may obscure relevant pathoanatomy. CT axial cuts show the glenohumeral relationship when an axillary lateral is unobtainable. Both 2-dimensional cuts and 3-dimensional reconstructions demonstrate major fracture fragment relationships better than plain radiography. CT is also useful when humeral head involvement is suspected, such as humeral head impaction or head-splitting fractures.
Classification
The Neer classification system is based on fragment displacement rather than fracture lines and depicts the pathoanatomy of the soft tissues as well as the bone ( Fig. 3 ). The 4 segments are Codman major fragments, including the anatomic neck, surgical neck, and greater and lesser tuberosities. The fracture classification comprises 18 fracture patterns in 4 categories based on number and displacement of segments, called parts. A part is defined as displacement of a fragment by at least 1 cm or rotation of at least 45°. Articular surface and head-splitting fractures are 2 subcategories that do not fit neatly in these categorizations.
A proximal humeral fracture that does not have displacement of a single part, regardless of fracture lines, is considered a 1-part fracture. These fractures are held together by soft-tissue attachments or are minimally affected.
Two-Part Fractures
Anatomic neck 2-part fractures are rare and consist of the articular surface rotated or displaced into varus as the tuberosities prevent valgus displacement. Surgical neck 2-part fractures occur with the shaft displaced anteriorly and rotated inwardly from the articular surface and tuberosities. Impacted 2-part fractures usually are displaced apex anterior with a periosteal hinge posteriorly. Nonimpacted 2-part surgical neck fractures have shaft displacement anteromedially, with the articular fragment in neutral rotation. Comminuted 2-part surgical neck fractures usually have an anteromedially displaced shaft fragment, with the head in neutral rotation. Greater tuberosity 2-part fractures tend to occur after anterior glenohumeral dislocations, and the tuberosity is displaced superior and posterior along the path of the superior rotator cuff muscles. Lesser tuberosity 2-part fractures tend to occur after forceful muscle contraction of the subscapularis, as in seizures, and the tuberosity displaces medially.
Three-Part Fractures
When 3-part fractures occur, 1 tuberosity remains attached to the articular surface and rotates around a nonimpacted surgical neck fragment. When the lesser tuberosity is displaced, the head rotates externally. When the greater tuberosity is displaced, the head rotates internally.
Four-Part Fractures
Four-part fractures occur in 2 patterns, valgus impacted 4-part fractures and lateral displacement fracture dislocations. Neer described the valgus impacted 4-part fracture as a borderline lesion with less lateral displacement than a true 4-part fracture. In the valgus impacted fracture the tuberosities displace away from the articular segment, allowing it to impact on the shaft. The articular segment rotates at least 45° but does not displace laterally and may have an intact medial periosteal hinge. In the lateral displacement 4-part fracture, the articular segment displaces allowing for varus deformity ( Fig. 4 ). When the articular segment is not in congruity with the glenoid, it is considered a fracture dislocation and may be present in any subcategory but is always present in true 4-part fractures. Fracture dislocations are named according to the direction of displacement of the articular fragment.
