Excerpt from Proximal Humerus Fractures

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Successful treatment of fractures of the proximal humerus (ie, that portion involving the glenohumeral articulation) presents a challenge for physicians. Many factors must be considered when developing a treatment plan. Accurate assessment of the fracture, patient compliance, medical comorbidities, and time from injury to treatment are critical factors affecting outcome. Additionally, technical factors in the reconstruction of these fractures require surgical experience that few surgeons have the opportunity to develop.

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History of the Procedure

Hippocrates first documented a proximal humerus fracture in 460 BC and treated it with traction. In 1869, to improve treatment, Krocher classified fractures of the proximal humerus. In 1934, Codman developed a classification that divided the proximal humerus into 4 parts, based on epiphyseal lines. In 1970, Neer‘s classification expanded on the 4-part concept and included anatomic, biomechanical, and treatment principles, providing clinicians with a useful framework to diagnose and treat patients with these fractures.¹ Treatment initially consisted of closed reduction, traction, casting, and abduction splints.

In the early 1930s, operative treatment for displaced fractures gained popularity, which continued in the 1940s and 1950s. Humeral head replacement for severely displaced fractures of the proximal humerus was introduced the 1950s. In the 1970s, the AO/ASIF (Arbeitsgemeinschaft für osteosynthesefragen/Association for the Study of Internal Fixation) group popularized plates and screws for fracture fixation, and humeral head prostheses were redesigned. Currently, fixation methods that involve limited fixation and limited dissection are becoming more popular, and prosthetic replacement for severe fracture is being refined further.^{2, 3}

Problem

The shoulder links the upper extremity to the thorax. Optimal functioning of the upper extremity requires mobility and power that allow a range of performance, from powerful, explosive movements (eg, throwing a baseball 100 mph) to very accurate, fine movements (eg, performing microsurgery, playing the violin). Tasks of daily independence require the ability to position the hand throughout the range of an imaginary sphere.

In addition to limiting function, disorders of the shoulder can cause pain, which, in turn, can affect the patient's work and sleep. Therefore, fractures of the proximal humerus can be devastating to quality of life. These fractures can also cost society a significant loss of productivity from otherwise viable members of the workforce.

Frequency

Proximal humerus fractures have been estimated conservatively to account for 5% of all fractures. These fractures occur primarily in older patients, many of whom are osteoporotic. Like hip fractures, proximal humerus fractures are a major cause of morbidity in the elderly population. As the population base ages, the incidence of these fractures will continue to increase.

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Etiology

The most common mechanism for proximal humerus fractures is a fall on an outstretched hand from a standing height. In younger patients, high-energy trauma is a more frequent cause, and the resultant injury is more devastating. Additional mechanisms include violent muscle contractions from seizure activity, electrical shock, and athletic injuries. Finally, a direct blow to the proximal humerus may also lead to fracture.

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Pathophysiology

The regional differences in the proximal humerus must be taken into account when attempting to reduce tuberosity fragments. The cortex of the proximal humerus near the greater tuberosity becomes progressively thicker distally. The exact location of the fracture line depends on the mechanism of, and energy from, the injury. In fractures in the thinnest cortical bone, the fracture lines can be difficult to appose. These fractures are produced by low-energy forces, occur in porotic bone, and typically are comminuted. Conversely, the denser cortical bone near the biceps groove, and more distally on the shaft, provides an easier surface to approximate fracture lines. Fractures in this area are produced by high-energy forces; the fracture pattern depends on the applied force.

Indirect forces cause most shoulder fractures. The predominant force can cause predictable fracture patterns. Such injury forces are tension, axial compression, torsion, bending, and axial compression with bending. The primary fracture patterns from these forces are transverse, oblique, and spiral. For each fracture pattern, a preferred method of fixation has been developed to resist displacement forces. Unfortunately, these patterns have not been well described in the shoulder. The orientation of the fracture pattern as a result of tension depends on the muscle-tendon unit that produced most of the displacement force. Treatment recommendations for these fractures are based on factors such as patient motivation, medical history, coexisting medical morbidities, and the most influential factor, the fracture type.

Fracture classification has recently been reconsidered. Neer's 4-part classification, with modifications of the 4-part valgus impacted type being separated from 4-part fractures in which the humeral head has been extruded laterally, is used primarily to separate these fractures into treatment groups. The majority of fractures are nondisplaced, and nonoperative treatment usually is appropriate. With fracture displacement, operative intervention typically is necessary.

Operative treatment includes closed reduction with percutaneous fixation, open reduction and internal fixation, and humeral head replacement. Fracture patterns best suited for arthroplasty are 4-part fractures, fracture dislocations, head-splitting fractures, impaction fractures, humeral head fractures with involvement of more than 50% of the articular surface, and 3-part fractures in elderly patients with osteoporotic bone. However, heterogeneity of fracture patterns exists within these groups.

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Clinical

Most patients with fractures of the proximal humerus present to an acute care facility with pain following trauma. Pain and loss of function with swelling of the involved extremity are the most common symptoms on initial presentation. Document symptoms of paresthesias or weakness in the involved extremity.

Obtain a detailed history of the mechanism of injury (eg, whether the injury was the result of a direct impact to the lateral shoulder or the result of an indirect mechanism, as in a fall onto an outstretched hand). Indirect causes of proximal humerus fractures result in greater degrees of fracture displacement. Determine whether seizure or electrical shock was involved, as these indirect mechanisms are associated with posterior dislocations.

Obtain the medical history, and stabilize any problems, if possible, prior to proceeding with operative management.

Physical examination

Swelling and ecchymoses usually are present about the shoulder and upper arm. Extensive ecchymosis may become visible 24-48 hours following injury. It may spread to the chest wall and flank, and may involve the entire extremity. Palpate the entire upper extremity and chest wall to evaluate for associated injuries.

To determine fracture stability, gently rotate the humeral shaft while palpating the humeral head to assess whether unified motion is present. Note any movement or crepitus. In high-energy injuries, inspect the skin closely for any disruptions that may allow fracture contamination (ie, open wounds). Pulsatile or expanding hematomas may indicate a vascular lesion.

It is essential to determine the presence of any associated neurovascular injury. The axillary nerve is the nerve most commonly injured in proximal humerus fracture. Carefully assess sensation over the deltoid muscle and isometric deltoid motor function. Additionally, perform distal neurological testing for brachial plexus injuries.

Examination of peripheral pulses is helpful, but does not exclude axillary disruption, because distal pulses may be intact due to collateral circulation around the scapula. Inspect the proximal shoulder girdle for an expanding mass, which may be the only sign of arterial rupture. If vascular injury is suspected, obtain an angiogram and vascular surgery consultation immediately.
 
Evaluate associated injuries (eg, pneumothorax, other traumatized areas) with radiographic studies. Radiographic examination of the shoulder should include Neer's trauma series, which consists of a true anteroposterior (AP) view of the glenohumeral joint, y-view, and axillary view. Modifications of the axillary view, such as a Velpeau view or CT scan, can be obtained to evaluate the relationship of the humeral head to the glenoid. It is estimated that the initial treating physician nevertheless misses 50% of all fracture dislocations.

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