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.
NextHippocrates 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 four parts on the basis of epiphyseal lines. In 1970, Neer's classification expanded on the four-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]
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.
A conservative estimate is that proximal humerus fractures account for approximately 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.
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.
In attempting to reduce tuberosity fragments, it is vital to take into account the regional differences in the proximal humerus. 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 is being reconsidered. Neer's four-part classification, with modifications of the four-part valgus impacted type being separated from four-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, humeral head replacement, and reverse shoulder arthroplasty.[4] Fracture patterns best suited for arthroplasty are four-part fractures, fracture dislocations, head-splitting fractures, impaction fractures, humeral head fractures with involvement of more than 50% of the articular surface, and three-part fractures in elderly patients with osteoporotic bone. However, heterogeneity of fracture patterns is observed within these groups.
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.
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 computed tomography (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.
Diagnostic evaluation of proximal humerus fractures is critical in assessing treatment choices. Initially, plain radiographs of good quality that include Neer's trauma series are used to define the extent of injury. These fractures can be classified with the Neer or AO/ASIF classification systems. Each of these methods has certain advantages, but they also share some common problems.
Because both classification systems have limited reliability, reproducibility among observers, and consistency in findings by the same observer at different times, the initial radiographs cannot be relied upon entirely to make a treatment decision. Even if CT scans and three-dimensional (3D) images are added, reliability and reproducibility are limited. However, an understanding of fracture type gives the physician essential information on prognosis and treatment options.
The Neer classification system is based on displacement criteria of 1 cm or fragment angulation of 45°. The type of fracture then is divided into the following four segments:
The basis for the AO/ASIF classification is predicated on disruption of the blood supply to the articular segment, thereby increasing the likelihood of avascular necrosis. These fractures are deemed least ideally suited for internal fixation.
The treatment objective in proximal humerus fractures is to allow bone and soft-tissue healing that maximizes function of the upper extremity while minimizing risk. Displaced fractures, if left untreated, have the greatest likelihood of limited functional outcomes. Most fractures are extra-articular and are minimally displaced; these fractures may be treated with supportive treatment only. Persons with stable fractures can begin rehabilitation early and typically have superior functional outcomes.
Indications for treatment are displaced articular fractures and periarticular fractures. However, the "personality" of the fracture (eg, bone quality, fracture orientation, concomitant soft-tissue injuries), the personality of the patient (eg, compliant, realistic, mental status), and the personality of the surgeon (eg, surgical experience, technical familiarity, available resources) all have a tremendous effect on specific treatment indications.
The most common definition of displacement is 1 cm or more between fracture fragments or 45° of angulation or more between fragments. The segments that most commonly produce these fragments are the humeral articular surface, the greater and lesser tuberosities, and the surgical neck. Currently, a greater tuberosity that is displaced 5 mm or more is commonly considered a fragment that should be reduced.
The anatomy of the proximal humerus is quite variable. Multiple cadaveric studies have been performed to compare anatomic relations that are constant among individuals. Unfortunately, few exist. The critical anatomic relations of the proximal humerus are those of the articular segment to the shaft and the tuberosities. These include retroversion, inclination angle, and translation of the head relative to the shaft, as well as the relation of the head to the greater tuberosity.
On average, the articular segment is retroverted 30° relative to the forearm. The range is quite large (0-70°) and can vary from one side to the other. Inclination of the articular segment also can vary (from 120-140°).
The head segment can lie directly over the medullary canal but often is translated either posteriorly or medially. Therefore, if a prosthetic replacement is placed in the intramedullary canal, a resultant shift in position of the articular segment can occur unless some design feature of the prosthesis allows for a simultaneous shift in the prosthetic head position. Finally, the proper anatomic relations of the prosthetic head must be reconstructed meticulously to avoid overreducing the tuberosity to the head height.[5]
The articular head always lies above the greater tuberosity, but the difference can range from 3 to 20 mm. The biceps groove at the level of the articular surface has a constant relation to the version of a prosthetic articular surface in relation to the fins of the prosthetic body. If the anterior fin is placed at the biceps groove, the articular segment will be in 30° of retroversion. If the posterior fin is placed 8 mm posterior to the biceps groove, the same degree of retroversion will be recreated.
Injury to the blood supply of the proximal humerus has been implicated in the development of avascular necrosis.[6] The ascending branch of the anterior circumflex humeral artery (artery of Liang) has been demonstrated by Gerber to provide most of the blood flow to the articular segment. If the medial calcar of the humerus is spared by the fracture, the vessel will be spared.
The rotator cuff is the critical structure that must be reconstructed following proximal humerus fracture. The initial fracture pattern, displacement of the fracture fragments, reduction maneuvers, and fixation techniques used to oppose the displacement forces are dependent on the rotator cuff forces that produced the fracture.[7]
The supraspinatus attaches to the greater tuberosity at the superior facet and the superior half of the middle facet. Avulsion-type forces from this muscle produce a short transverse fracture of the greater tuberosity that displaces primarily superiorly. Straight abduction helps reduce the fragment, and tension band fixation neutralizes initial displacement forces.
If the infraspinatus, which attaches to the entire middle facet of the greater tuberosity, also is involved, the fracture fragment is larger, and the fragment is displaced posterosuperiorly. In addition to a vertical tension band to neutralize displacement forces, horizontal fixation helps neutralize rotational forces from the infraspinatus.
The subscapularis inserts onto the lesser tuberosity. These fractures avulse the lesser tuberosity anteromedially. Horizontal fixation best neutralizes these fractures. In four-part fractures, the tuberosities are displaced, and the supportive structures of the articular segment are removed. Therefore, this fragment tilts superiorly and subsides. If the forces then axially load the shaft against this head segment, it can extrude laterally, disrupting the medial calcar and its blood supply.
From 21% to 36% of proximal humerus fractures are associated with neurovascular injuries; 8%result in permanent motor loss. The axillary nerve is the nerve most commonly injured. The fracture pattern most commonly associated with axillary nerve injury is an anterior fracture dislocation with a displaced greater tuberosity. Loss of sensation over the lateral deltoid should alert the examiner to possible axillary nerve injury. Isometric contraction of the deltoid should also be tested.
The suprascapular, radial, and musculocutaneous nerves also are at risk. Vascular injuries occur rarely, but 27% of axillary artery injuries may have palpable pulses due to scapular collateral circulation. Associated paresthesias and an enlarging mass must be viewed with caution. Most vascular injuries (84%) occur in patients older than 50 years; 53% are associated with brachial plexus injuries.
Contraindications for repair of proximal humerus fractures include inability to tolerate the procedure medically and lack of clearance for surgery through the primary care physician or specialty consultants (ie, cardiologist, vascular specialist).
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