Fractures and Dislocations of the Clavicle

Anatomy

The extended mobility of the upper extremity is a result of its “open kinetic chain” nature; the shoulder girdle and the arm work exclusively to allow the hand to take any spatial position. In contrast, at the distal end of the “closed chain” lower extremity, the foot must maintain contact with the ground, and the leg functions as a body support.

The broad tracking of the shoulder blade on the thorax is essential for mobility of the shoulder girdle. Because the scapula is independent and only indirectly connected with the trunk through the clavicular joint, not only are shifts against the thorax possible, but the scapula can also turn in its own plane.

Kapandji appropriately referred to a functional “thoracoscapular joint.” The purpose of the extensive mobility of the scapula is the targeted positioning of the shoulder socket in space.

A number of influences on clavicular length have been investigated. The influence of gender has been clearly shown. In a comparison between African American males and females and white males, Terry demonstrated that male clavicles are longer than female clavicles. Martin and Saller emphasized that male clavicles in all races are longer than those of females. Dzhigora found an average length of 15.6 cm for clavicles of males and 14.3 cm for those of females of Russian ancestry. Investigations looking at body size reveal only the mildest divergence of clavicle length. The left clavicle tends to be longer than the right; this was observed by both Martin and Saller and Dzhigora.

The clavicle is named for its S-shaped curvature with one apex anterior medially and another posterior laterally, resembling the musical symbol, clavicula. The larger medial curvature widens the space for passage of neurovascular structures from the neck into the upper extremity via the costoclavicular interval. Men display significantly more angulation of the clavicle than do women. The etiology for this anatomic phenomenon appears to be the interaction of muscle and bone, as most authors find a positive correlation between increased musculature and clavicular angles. Body side also has significant influence regarding the medial clavicle angle, as confirmed by both Dzhigora and Fick. The increased musculature on the right side in right-handed people most likely determines these effects. However, another plausible explanation for clavicular curvature considers the fact that the clavicle is the first bone ossified during embryonic development (the fifth embryonic week) and later the first bone with which the developing thorax and the developing limbs of the upper extremity must conform. The theory is that the S form develops as a result of these interactions. Because the thoracic diameter is well accepted to be larger in males than in females, this would explain gender differences. However, Kummer and Lohscheidt pointed out Pauwels’ developmental principles of long bones: They are unable to significantly change the axis of an ossified bone. The axes are finished before ossification, in the essential stages of development. Because clavicles ossify early, an essential bone-shape altering factor would have to exist very early in development.

Inman suggested that the curvature of the lateral third of the clavicle contributes to range of motion of the shoulder girdle by allowing approximately 30 degrees of motion between the scapula and clavicle through the acromioclavicular (AC) joint. According to this description, motion occurs via inferior translation of the medial portion of the scapula leading to abduction of the scapula through the AC joint, a motion which might be thought impossible considering the rigid interrelationship between the clavicle and scapula maintained by the stout coracoclavicular ligaments. However, the lateral curvature and 50-degree rotational motion of the clavicle on its longitudinal axis allow for inferior translation of the attachment of the coracoclavicular ligaments onto the posteriorly directed apex of the lateral clavicle along with the scapula. Inman likened this to the action of a crankshaft. Others dispute this description, claiming that little motion occurs at the AC joint and that the scapula actually rotates along with the clavicle ( Fig. 48.1 ).

A clavicle is not beneficial to running and jumping quadruped mammals. In contrast to the quadrupeds, who derive stability and strength from close association of the shoulder girdle with the trunk, in simians, the clavicle enhances upper extremity function for swinging through trees. It holds the glenohumeral joint and the upper extremity away from the trunk in all positions. The clavicle enhances overhead activity (combination of shoulder abduction and elevation), particularly in actions requiring power and stability, and resists those tensile forces that become so prominent in activities required by arboreal mammals. It is not surprising then that in cases of clavicle fractures in humans where there is shortening of the sternum-scapula distance, there is a subsequent limitation in shoulder abduction and elevation. The clavicle also serves as a bony framework for muscular attachments, provides protection for the underlying neurovascular structures, transmits the forces of accessory muscles of respiration (e.g., the sternocleidomastoid) to the upper thorax, and contributes to the aesthetics of the base of the neck.

The clavicle has been considered by some to be an expendable bone. Although children with congenital absence of the clavicle adapt surprisingly well and patients with tumors or infections treated by clavicular resection sometimes function adequately, both have difficulty with overhead activities requiring strength or dexterity. Patients with clavicular resection may also have brachial plexus irritation related to instability of the clavicular fragments. Patients with a trapezius palsy do particularly poorly without a clavicle. We believe that the evolutionary process has determined an important function for the clavicle and always strive to preserve the length and alignment of the clavicle.

The sternoclavicular and AC joints are both diarthrodial articulations (hyaline articular cartilage–covered and synovium-lined mobile joints) with intervening fibrocartilage disks. Both joints lack inherent osseous articular stability and are maintained by strong ligaments. The AC joint is unusual in that negligible motion occurs through the joint and yet degenerative arthritis is common, particularly after trauma. The function of the AC articulation is unclear. Patients with AC or coracoclavicular fusion or coracoclavicular screw fixation have full or nearly full shoulder motion. All the motion between the shoulder girdle and the axial skeleton must therefore occur at the sternoclavicular joint. Motion at this joint is commonly thought to be 35 degrees of elevation-depression, 35 degrees of protraction-retraction, and 50 degrees of rotation, as reported by Inman; however, these figures are inconsistent with the common view that 60 degrees of the 180 degrees of shoulder abduction occurs through the shoulder girdle, which would imply that the sternoclavicular joint provides at least 60 degrees of elevation-depression. The sternal epiphysis does not ossify until the midteenage years and is difficult to visualize on plain radiographs. It closes as late as 25 years in normal adults, and some have argued that many apparent dislocations of the sternoclavicular joint may actually be physeal fractures.

Ligament-cutting studies in cadavers suggest that the coracoclavicular ligaments limit superior displacement of the clavicle and the AC ligaments limit posterior displacement. The capsuloligamentous covering of the AC ligament is most stout superiorly. Because one of the complications of distal clavicular excision is posterior displacement of the clavicle with impingement on the scapular spine, many surgeons emphasize preservation of the AC ligaments, particularly superiorly.

It is not surprising that the middle third is the most common site of clavicular fracture, since the midportion is the thinnest and narrowest portion of the bone; it represents a transitional region of the bone, both in curvature and in cross-sectional anatomy, which makes it a mechanically weak area, and it is the only area of the clavicle that is not supported by ligamentous or muscular attachments. It is possible that this anatomy was selected during evolution because clavicular fracture protects the brachial plexus during difficult births (shoulder dystocia).

In view of the intimate relationship of the clavicle to the brachial plexus, the subclavian artery and vein, and the apex of the lung, it is surprising that injury to these structures in association with fracture of the clavicle is so uncommon. Brachial plexus palsy may develop weeks or years after injury as a result of compromise of the costoclavicular space by hypertrophic callus, with or without malalignment of the fracture fragments. Narrowing of the costoclavicular space because of malunion or nonunion can also lead to dynamic narrowing of the thoracic outlet. Prolonged compression of vascular structures can likewise be problematic.

Sternoclavicular Joint Dislocation

(Content from AO Surgery Reference. Executive Editor: Joseph Schatzker. Authors: Jonas Andermahr, Michael McKee, Diane Nam: https://www2.aofoundation.org )

Key Points: Sternoclavicular Dislocation

• Posterior or superior displaced fracture

• Supporting indications

  • Compression of retrosternal or retroclavicular structures

Injuries to the sternoclavicular joint are unusual. The ligaments that stabilize the joint are so strong that a substantial force is necessary to dislocate it. The most common sources of sternoclavicular dislocation are motor vehicle accidents and sports injuries. The mechanism of injury is believed to be compression of the shoulder (i.e., a direct medial load on the point of the shoulder) with either forced protraction (causing posterior dislocation) or forced retraction (causing anterior dislocation) of the shoulder girdle. Anterior dislocations are much more common than posterior dislocations. A direct blow to the clavicle—such as when one player falls on top of another—can also cause posterior dislocation of the sternoclavicular joint. It is possible that some of these injuries represent physeal fractures because the medial clavicular physis can remain open well into adulthood; however, in practice, this distinction is difficult or impossible to make and does not seem to be important.

Computed tomography should be used to characterize the injury by verifying the direction and displacement of the injury and delineating associated fractures.

Sternoclavicular joint dislocations represent high-energy chest wall injuries. The thorax and shoulder girdle should be inspected for associated injuries, pneumothorax ruled out, and the neurovascular status of the arm carefully evaluated. Inspection for associated injuries is particularly important in posterior dislocations because the medial part of the clavicle is driven backward toward the trachea, esophagus, and major vascular structures. Respiratory problems, shortness of breath, or a sense of asphyxiation can occur.

Although injury to these structures is uncommon, it is wise to have a thoracic surgeon available when reduction is attempted because injury to one of these structures could be catastrophic.

Manipulative reduction is usually successful if performed within 48 hours after the injury. General anesthesia and complete muscle paralysis are needed to overcome muscle spasm associated with pain. With the patient supine, a roll is placed between the scapulae to facilitate retraction of the shoulder girdle. Lateral traction is applied to the arm with the shoulder in 90 degrees of abduction while an assistant places countertraction on the torso. The arm is then extended to retract the shoulder girdle. Reduction usually creates an audible pop and is obvious. It is occasionally necessary to grasp the clavicle and manipulate it directly, particularly with posterior dislocations. The skin can be cleansed and a sterile towel clip applied if the clavicle is difficult to grasp with the hand.

When manipulative reduction is successful, the shoulder girdle is immobilized in a sling or figure-of-eight bandage for 6 weeks while the ligaments begin to heal. If open reduction is required, some surgeons favor stabilizing the joint, whereas others suggest resecting the medial part of the clavicle and securing it to the first rib. Reduction and reconstruction with semitendinosus or fascia lata graft, using a subclavian technique, or reconstruction with polydiaxanone suture (PDS) cord are possible.

Regardless of which approach is selected, smooth wires should not be used to stabilize the joint because of the potential for migration of these wires into the thorax.

Problems after this injury include instability and arthrosis of the sternoclavicular joint. Reconstructions using fascia lata, the subclavius tendon, or other tendon grafts have been suggested for instability. Painful arthrosis of the sternoclavicular joint has been treated with medial clavicular excision.

Shoulder Suspensory Complex

Although most isolated fractures of the clavicle and scapula are thought to be relatively straightforward to treat effectively, combined injuries are regarded as more troublesome and are more readily considered for operative treatment. An anatomic concept that has been developed to facilitate understanding of these issues is the superior shoulder suspensory complex. This complex consists of two struts (the clavicle and the lateral portion of the scapular body) linked by a combined bony and soft tissue ring ( Fig. 48.2 ). The ring is composed of the coracoid process, coracoclavicular ligaments, distal end of the clavicle, AC ligaments, acromion, and glenoid process. It is argued that disruption of this complex at two sites will be far more problematic than disruption at one site. Common examples of double disruptions include complete AC dislocation (e.g., disruption of the coracoclavicular and AC ligaments), a displaced fracture of the lateral aspect of the clavicle (i.e., coracoclavicular ligament injury and fracture of the distal part of the clavicle), and fracture of the clavicle associated with fracture of the glenoid neck or scapulothoracic dislocation. Although the role of operative treatment of these injuries is debated, each poses more substantial risk to shoulder function than do injuries that disrupt only one aspect of the shoulder suspensory complex.

The outcomes for fractures of the scapular processes associated with disruption of the scapular suspensory system have been less well documented even though the spectrum of these fractures may comprise up to 28% of all scapular fractures. The clinical behavior of lateral clavicular fractures and AC joint disruptions is similar to the mechanism of injury, the reasons for failures of treatment, and the functional and clinical outcomes are similar. A system of classification that recognized this logical concurrence would be useful in clinical practice. Concepts that help to understand the mechanism of injury and the associated patterns of disruption of the shoulder girdle assist decision making in treatment, which is principally aimed at the restoration of the orientation of the glenoid fossa in relation to the body axis. Specific components of a complex disruption of the suspensory system of the scapula are currently separately classified (as an example, a lateral clavicular fracture with a coracoid base fracture and an associated glenoid fracture could be classified separately by the Neer, Ogawa et al., and Ideberg et al. classifications, whereas assessment of the whole injury would theoretically guide improved treatment algorithms). For this reason, a systematic approach to the classification of disruptions of the components of the suspension system of the scapula was developed. This system, developed as described by the Arbeitsgemeinschaft für Osteosynthesefragen (AO) Classification Advisory Group, has been expanded into a comprehensive system to support more detailed morphologic classification of scapular fractures for clinical research and surgical decision making.

The lateral scapular suspension system (LSSS) is classified according to three failure conditions according to the AO classification system. Within each of the S1 and S2 categories, failures are further subdivided into three groups: S0, clavicle fracture medial to the LSSS; S1, incomplete LSSS failures; and S2, complete failure of the LSSS ( Fig. 48.3 ).

Acromioclavicular Joint Dislocation

Dislocations of the AC joint represent varying degrees of disruption of the ligamentous connections between the clavicle and scapula. Treatment considerations focus on the potential for symptoms related to arthrosis of the AC joint or displacement and instability of the clavicle. Nonoperative treatment is favored in most cases because patients with complete loss of ligamentous association between the clavicle and scapula and complete displacement of the AC joint usually have excellent shoulder girdle function.

Fractures of the Clavicle

The traditional orthopaedic complacency regarding fracture of the clavicle has been displaced by a growing awareness that some fractures do not heal and others represent malunions with consequent shoulder girdle malfunction. Fracture of the clavicle is common, and it has long been thought that the bone's inherent reparative capacity leads to rapid healing with little more than symptomatic treatment. Deformity was considered merely a cosmetic concern because function is satisfactory despite malunion. It has long been held that primary operative intervention is meddlesome and only makes things worse. Despite the proximity of major vascular, nervous, and cardiopulmonary structures, associated injury is uncommon.

There is now sufficient evidence to consider operative treatment for midshaft clavicle fractures with greater than 100% displacement or greater than 2 cm of shortening. It is now well established that displaced fractures of the middle portion of the clavicle, particularly those with comminution, are associated with an approximately 10% to 15% risk of nonunion as well as a risk of symptomatic malunion with consequent shoulder deformity, pain, impaired function, and neurovascular compromise.

It is quite interesting that, as the pendulum swings in favor of considering primary operative treatment of midshaft clavicle fractures, it now swings toward operative treatment of displaced lateral clavicle fractures. This is a particularly interesting phenomenon, since the risk of problems leading to operative treatment after initial nonoperative treatment was reported as approximately 11% in a recent large series (with another 21% having a nonunion). This percentage of patients requesting operative treatment, which is used to argue in favor of primary operative treatment at the shaft level, has been used to argue against primary operative treatment in this context. Clearly surgeons and patients need to consider the risks and benefits of operative and nonoperative treatments and make the decision that they feel most comfortable with.

Classification

The traditional division of the clavicle into thirds (Allman, Nordqvist, and Petersson) seems arbitrary given that most fractures occur near the junction of the middle and distal thirds. Other authors (Robinson) have suggested division of the clavicle into fifths, with the middle three-fifths representing midclavicular fractures and the lateral fifths representing distal clavicular fractures. The use of fractional divisions may not adequately distinguish fractures with injury to the coracoclavicular ligaments.

Neer defined fractures of the lateral aspect of the clavicle as being lateral to the medial limit of the trapezoid ligament. Neer distinguished fractures of the distal end of the clavicle with intact coracoclavicular ligaments (type 1) from those associated with tearing of these ligaments and wide displacement of the fracture fragments (type 2). The wide displacement and instability of type 2 fractures place them at greater risk for nonunion ( Fig. 48.7 ).

Distinction of distal third fractures with intact (type IIA) or disrupted (type IIB) coracoclavicular ligaments is confusing because of the lack of a clear distinction between type IIA fractures and more distal midclavicle fractures. In unusual instances, fractures of the distal end of the clavicle may be unstable in the absence of ligamentous injury. This situation occurs when both of the coracoclavicular ligaments remain attached to an inferior fracture fragment that lacks attachment to either of the primary medial or lateral fragments. Neer noted in his initial report that distal clavicular fractures are occasionally associated with extension into the AC joint, and he classified such fractures as type III.

Fractures of the medial end of the clavicle are uncommon and, almost without exception, are treated symptomatically. As evidence of how poorly these fractures are understood, one recent paper associated medial fractures with older age and osteoporosis, while in another, they were associated with high-energy injury and a high mortality rate. Fractures in this region of the clavicle are so uncommon that the patterns of medial clavicular injury have rarely been described and studied, and it remains unclear how different fracture patterns influence treatment and prognosis.

During a 6-year period in Edinburgh, the incidence of medial fifth clavicle fractures was 1 per 100,000 per year as compared with 20 for midclavicular and 8 for lateral clavicular fractures. Midclavicular fractures were more often than not displaced by a ratio of 2.7 to 1, and lateral clavicular fractures were more frequently displaced by a ratio of nearly 2 to 1.

Fractures occurring between the medial limit of the coracoclavicular ligaments and the lateral limit of the costoclavicular ligaments represent by far the most common type of clavicular fracture. These fractures have not to this point been subclassified in a universally acceptable manner. Current publications use the basic AO/Orthopaedic Trauma Association (OTA) classification : Type A fractures are simple transverse fractures; type B fractures are wedge fractures; and type C fractures are those in which the main fragments are separated by a zone of comminution and have no contact. This classification turns out to be very useful for the decision of which operative procedure should be carried out (plate vs. intramedullary nail) ( Fig. 48.8 ).