Development

The embryology of the clavicle is unique in that it is the first bone in the body to ossify (fifth week of fetal life), and is the only long bone to ossify by intramembranous ossification without going through a cartilaginous stage. The ossification center begins in the central portion of the clavicle; this area is responsible for growth of the clavicle until up to about 5 years of age. ^, Epiphyseal growth plates develop at both the medial and lateral ends of the clavicle, but only the sternal ossification center is present radiographically. ^, This medial growth plate of the clavicle is responsible for the majority of its longitudinal growth, and probably contributes as much as 80% of the length of the clavicle. The sternal ossification center appears and fuses relatively late in life, with ossification occurring between the ages of 12 and 19 years and fusion to the clavicle occurring at 22 to 25 years of age. ^, Thus many of the so-called sternoclavicular dislocations in young adults up to 25 years of age are, in fact, epiphyseal fractures, and are a potential source of confusion unless the late sternoclavicular epiphyseal closure is remembered. Computed tomography (CT) scanning can be very useful in this setting.

Morphology and function

The superior surface of the clavicle is essentially subcutaneous over its course, with only the thin platysma providing any muscular coverage and then only to the inner two-thirds of the bone. The supraclavicular nerves, which provide sensation to the overlying skin, are consistently found just deep to the platysma muscle layer, and there are typically two or three major branches. These nerves have been known to cause painful neuromas when damaged by fracture fragments or iatrogenic injury (it is wise to warn the patient that some numbness may occur inferior to the incision if operative intervention is planned) ( Fig. 14.1 ). The clavicle is the sole bony strut connecting the trunk to the shoulder girdle and arm, and it is the only bone of the shoulder girdle that forms a synovial joint with the trunk. Its name is derived from the Latin word clavis (key), the diminutive of which is clavicula, a reference to the musical symbol of similar shape.

Surgical view of the middle branch of the supraclavicular nerve entrapped in the fracture site.

The shape and configuration of the clavicle are not only important for its function but also provide an explanation for the pattern of fractures encountered in this bone. In 1993, Harrington and colleagues described an image-processing system that was used to evaluate the histomorphometric properties of 15 adult male and female human clavicles. Variations in porosity, cross-sectional area, and anatomic and principal moments of inertia were assessed at 2.5% to 5% increments along the length of the bones. The clavicle’s biomechanical behavior (axial, flexural, and proportional rigidity and the critical forceful buckling) was modeled from these data by using beam theory. More than threefold variations in porosity and moments of inertia were found along the length of the S-shaped clavicle, with the greatest porosity and moments of inertia being located in the variably shaped sternal and acromial thirds of the bone, as opposed to the denser, smaller, and more circular central third of the bone. This helps explain why 80% or more of clavicle fractures are seen in the middle third: clavicle orientation, as indicated by the direction of greatest resistance to bending (maximal principal moment of inertia), was found to rotate from a primarily craniocaudal orientation at the sternum to a primarily anteroposterior (AP) orientation at the acromion. Based on cross-sectional geometry, sectional moduli, and estimates of flexural and proportional rigidity, the clavicle was found to be weakest in the central third of its length. These data concur with the fracture location most commonly reported clinically.

An analysis of Euhler buckling predicted a minimal critical force for buckling during axial loading of about two to three body weights for an average adult. Thus buckling, or a combination of axial loading and bending or proportional loading, must be considered as the probable failure mechanism for this commonly injured bone. Although it appears almost straight when viewed from the front, when viewed from above, the clavicle appears as an S-shaped double curve that is concave ventrally on its outer half and convex ventrally on its medial half ( Fig. 14.2 ). Although it remains controversial, modern studies have noted differences in the shape and size of the clavicle in male and female subjects and in the dominant and nondominant arm. This is of significance clinically in the design of anatomic clavicle plates. Most such plate systems have a variety of sizes and curvatures such that individual anatomy can be accommodated to minimize hardware prominence. ^{, , ,}

The clavicle appears as an S-shaped double curve when viewed from above (a). It appears nearly straight when viewed from the front (b). The outer end of the clavicle is flat in cross section but becomes more tubular in its medial aspect (c).

DePalma found that the outer third of the clavicle exhibited varying degrees of anterior torsion, and suggested that changes in torsion might be responsible for the altered stresses that lead to primary degenerative changes in the acromioclavicular joint. The cross section of the clavicle differs in shape along its length; it varies from flat along its outer third to prismatic along its inner third. The exact curvature of the clavicle and its thickness, to a high degree, vary according to the attachments of muscles and ligaments. The flat outer third is most compatible with pull from muscles and ligaments, whereas the tubular medial third is a shape consistent with axial pressure or pull. The junction between the two cross sections varies with regard to its precise location in the middle third of the clavicle. This junction is a weak spot, particularly with axial loading, which may be one of several reasons why fractures occur so commonly at the middle third. Another reason may be that it is an area not reinforced by muscles and ligaments and that it is just distal to the subclavius insertion. ^,

The clavicle articulates with the sternum through the sternoclavicular joint, which has little actual articular contact but very strong ligamentous attachments. The medial end of the clavicle, which is surprisingly thick, is moored firmly against the first rib by the intra-articular sternoclavicular joint cartilage (which functions as a ligament), the oblique fibers of the costoclavicular ligaments, and to a lesser degree, the subclavius muscle. The scapula and clavicle are bound securely by both the acromioclavicular and coracoclavicular ligaments, the mechanism and function of which have been reported extensively; these ligaments contribute significantly to the movement and stability of the entire upper extremity ( Fig. 14.3 ). Despite the strong medial ligamentous attachments, the clavicle itself rotates approximately 45 degrees with respect to the axial skeleton with full forward flexion of the arm.

(A) Clavicle anatomy. (B) Supraclavicular nerve anatomy.

The intimate relationship between the brachial plexus and subclavian vessels is of obvious clinical importance, both in acute fractures, in which direct injury can occur, and especially with fracture sequelae such as malunion, nonunion, or excessive callus production. This can produce symptoms from distortion or compression of the neurovascular structures, which can lead to late symptoms or complicate subsequent operative intervention.

The brachial plexus, at the level at which it crosses beneath the clavicle, consists of three main branches (see Fig. 14.3 ). Of these branches, two are anterior. One (lateral) branch originates from the fifth, sixth, and seventh cervical roots and forms the musculocutaneous nerve and a branch of the median nerve; the other (medial) originates from the eighth cervical and first thoracic roots, and forms another branch of the median nerve, the entire ulnar nerve, and the medial cutaneous nerve. The posterior branch of the plexus forms the axillary and radial nerves. The cord of the brachial plexus that contains the components of the ulnar nerve crosses the first rib directly under the medial third of the clavicle. The other two cords are farther to the lateral side and are further posterior. Therefore, since the fibers that make up the ulnar nerve are closest to the first rib, any deformity or inferior displacement of the limb causes compression or pressure on them and this manifests itself in the patient through typical ulnar nerve symptoms.

The space between the clavicle and the first rib has been called the costoclavicular space. This space has been measured in gross anatomic studies and often appears to be quite adequate. However, it is not as large in a living subject as in a cadaver, possibly because in a living subject, the vessels are distended and the dimensions of the cords of the brachial plexus are larger than in a cadaver. In addition, in a living subject, this space is dynamic, not static, and may be diminished as the first rib elevates because of contraction of the scalenus anticus, or with other motions/positions of the arm. Hence when the distal fragment of the fractured clavicle is depressed, there is much less space between the first rib and the clavicle; the result is that the vessels (especially the subclavian and axillary vessels) and nerves (especially the medial cord/ulnar nerve) are potentially subject to injury, pressure, or irritation. The internal jugular, which is adjacent to the sternoclavicular joint (see Fig. 14.3 ), is not usually injured with middle-third fractures, but has the potential for injury in more medial trauma involving the sternum and sternoclavicular joint. The subclavian vessels, because of their relative proximity to the medial third of the clavicle, can also be injured during operative treatment of clavicle fractures, particularly when dealing surgically with malunion or nonunion when scarring and distortion can alter the position and resilience of these critical structures. The clavicle also appears to be unique as a long bone in that it has only a periosteal blood supply and little, if any, intramedullary (IM) or nutrient arterial blood supply. More important, the periosteal blood supply has been found to be primarily on the anterior and superior surface of the clavicle. This blood supply, coupled with the poor soft tissue coverage of the clavicle, may be an important consideration in fixation of the clavicle, particularly when significant soft tissue stripping has occurred as a result of the injury or is necessary during surgical intervention. ^,

Surgical anatomy

The surgical anatomy relative to the fascial arrangements about the clavicle has been extensively described by Abbott and Lucas. Such knowledge will reduce the risk of damage to neurovascular structures during surgical dissection. It is useful to divide these structures into areas above, below, and behind the clavicle.

Behind the clavicle

A thin but consistent and continuous myofascial layer, which has not been commonly appreciated in surgical anatomy, lies in front of the large vessels and nerves as they pass from the root of the neck to the axilla. From above to below, this layer consists of the omohyoid fascia enclosing the omohyoid muscle and the clavipectoral fascia enclosing the pectoralis minor and subclavius muscles. Behind the medial part of the clavicle and the sternoclavicular joint, the internal jugular and subclavian veins join to form the innominate vein. These veins are covered by the omohyoid fascia and by its extension medially over the sternohyoid and sternothyroid muscles. Behind the clavicle, at the junction between the middle and medial thirds, the junction of the subclavian and axillary veins lies very close to the clavicle and is also protected by this myofascial layer.

Between the omohyoid fascia posteriorly and the investing layer of cervical fascia anteriorly is a space, described by Grant, in which the external jugular vein usually joins the subclavian vein at its confluence with the internal jugular vein. Before this junction, the external jugular is joined on its lateral aspect by the transverse cervical and scapular veins and on its medial aspect by the anterior jugular vein. This anastomosis usually lies just behind the fascial envelope and the angle formed by the posterior border of the sternocleidomastoid muscle and clavicle.

These neurovascular structures are at risk for injury at the time of a clavicle fracture. Recent studies have shown that these structures, especially the subclavian vein, are at risk for injury during plate fixation of the clavicle, with the subclavian vein being an average of only 4.8 mm from the undersurface of the medial clavicle ( Fig. 14.4 ). Furthermore, damage to the subclavian vessels from the initial injury or subsequent surgical intervention can result in pseudoaneurysm formation, hemorrhage, and even death. This may be more likely to occur with the surgical treatment of malunion and nonunion, for the reasons described above. ^,

The relationship of a medial drill relative to the vascular structures below the medial clavicle. The dangerous trajectory is in the central third of the clavicle. AC, Acromioclavicular joint; BP, brachial plexus; CL, clavicle; SA, subclavian artery; SV, subclavian vein.

(From Sinha A, Edwin J, Sreeharsha B, et al. A radiological study to define safe zones for drilling during plating of clavicle features. J Bone Joint Surg Br . 2011;93[9]:1247–1252.)

Power and stability of the arm

The clavicle, by serving as a bony link from the thorax to the shoulder girdle, provides a stable linkage of the arm-trunk mechanism, and contributes significantly to the power and stability of the arm and shoulder girdle, especially in movement above shoulder level. It transmits the support and force of the trapezius muscle to the scapula and arm via the coracoclavicular ligaments.

Although patients with cleidocranial dysostosis and absence of the clavicle do not appear to have significantly decreased range of motion and can, in fact, have an increase in protraction and retraction of the scapula (because of the absence of the clavicle), they can exhibit weakness in supporting a load overhead, and have significant endurance strength deficits. This limitation further suggests that the clavicle adds stability to the extremity under load in extreme ranges of motion.

The clavicle is predominantly supported and stabilized by passive structures, particularly the sternoclavicular ligaments. ^, Although evidence of trapezius muscle activity at rest has been demonstrated electromyographically, thus suggesting a role for that muscle in the support of the clavicle, other authors have not been able to demonstrate that muscle activity plays any role in supporting the clavicle and thus is not clinically relevant.

Motion of the shoulder girdle

When the arm is elevated 180 degrees, the clavicle angles upward 30 degrees and backward 35 degrees at the sternoclavicular joint. It also rotates upward on its longitudinal axis approximately 45 degrees. During combined glenohumeral, acromioclavicular, and sternoclavicular movement, the humerus moves approximately 120 degrees at the glenohumeral joint, and the scapula moves along the chest wall approximately 60 degrees. The commonly used clinical correlate is that, in the normal situation, the glenohumeral joint accounts for two-thirds of shoulder motion and the scapulothoracic articulation for one-third. These complex and combined simultaneous movements of the joints and their articulating bony structures (scapula, humerus, and clavicle) seem to imply an important role for the clavicle in the range of motion of the arm. This role is debatable, however, because it has been observed by some that loss of the clavicle does not in fact impair abduction of the arm at all ^, and that excision of the clavicle can permit range of motion just as well. While loss of the clavicle results in some loss of function, especially weakness and drooping of the arm, it may be a reasonable salvage operation in those patients with intractable pain, chronic infection, or residual clavicle stump instability that can be seen after multiple failed operative procedures (see Figs. 14.5 and 14.6 ).

It has been stated that its contribution to motion may be the most important function of the clavicle, and that this role is related to its curvature, especially its lateral curvature. The 50-degree rotation of the clavicle on its axis appears to be important for free elevation of the extremity. In fact, a direct relationship has been found among the line of attachment of the coracoclavicular ligaments, the amount of clavicular rotation, the extent and relative lengthening of the ligaments, and scapula rotation itself. Of the total 60 degrees of scapular rotation, the first 30 degrees is due to elevation of the clavicle as a whole by movement of the sternoclavicular joint, and the second 30 degrees is permitted through the acromioclavicular joint by clavicular rotation and elongation of the coracoclavicular ligaments. Thus the lateral curvature of the clavicle permits it to act as a crankshaft, effectively allowing half of the scapular movement.

The smooth, rhythmic movement of the shoulder girdle is a complex interaction of muscle groups acting on joints and both the subacromial and scapulothoracic spaces. Although it is difficult to break down all the contributions of the clavicle to the total motion of the shoulder, it appears that its geometric and kinematic design, by permitting rotation, maximizes the stability of the upper limb against the trunk while permitting mobility, particularly of the scapula along the chest wall. The practical result is that the glenoid fossa continually moves, facing and contacting the humeral head as the arm is used overhead.

Nonunion and malunion can cause significant alterations in the orientation of the scapula and glenohumeral joint ( Figs. 14.7 and 14.8 ). ^, While the obvious deformity is inferior (drooping) and medial (shortening) translation, there is also a significant anteromedial and inferior rotational deformity that typically occurs: that is, the shoulder protracts, or rolls forward. This results in a change in the orientation of the scapula and the resting length of the muscles around the shoulder, with a negative functional effect on patients. Basamania and McKee and colleagues found significant weakness in the affected limbs of patients with clavicle malunion, regardless of the length of time since their injury. This weakness was corrected with the surgical correction of the clavicle to its normal position, despite no formal physical therapy. Additionally, this characteristic deformity is consistent and was defined in a three-dimensional CT study by Ristevski and colleagues ( Fig. 14.9 ).

(A) Clinical appearance of a patient with clavicle malunion. (B) Note the drooping of the right shoulder and loss of forward flexion.

Computed tomography scan of clavicular malunion reveals significant shoulder asymmetry with shortening of the affected shoulder girdle, protraction of the scapula, and prominence of the vertebral border of the scapula (winging).

Muscle attachments

The clavicle also acts as a bony framework for muscle origin and insertion. The upper third of the trapezius inserts on the superior surface of the outer third of the clavicle, opposite the site of origin of the clavicular head of the deltoid along its anterior edge. The clavicular head of the sternocleidomastoid muscle arises from the posterior edge of the inner third of the clavicle. The clavicular head of the pectoralis major muscle arises from the anterior edge of the clavicle. During active elevation of the arm, these muscles contract simultaneously. It has been suggested that in theory, the muscles above the clavicle could be directly attached to the muscles below the clavicle as a continuous muscular layer without an interposed bony attachment, but the stable bony framework clearly provides the advantage of a solid foundation for muscle attachment, in addition to the strut function of the clavicle, ensuring proper muscle length and tension.

The other muscle that inserts on the clavicle is the subclavius muscle. After it arises from the first rib anteriorly at the costochondral junction, it proceeds obliquely and posteriorly into a groove on the undersurface of the clavicle. This muscle appears to aid in depressing the middle third of the clavicle. Fractures of the clavicle often occur at the distal portion of its insertion. In midclavicular fractures, this muscle can offer some protection to the neurovascular structures beneath; however, it can also become entrapped within the fracture site and delay or inhibit healing.

Protection of neurovascular structures

The clavicle also provides skeletal protection for adjacent neurovascular structures and the superior aspect of the lung. The subclavian and axillary vessels, the brachial plexus, and the lung are directly behind the medial third of the clavicle. The tubular cross section of the medial third of the clavicle increases its strength and adds to its protective function at this level. The anterior curve of the medial two-thirds of the clavicle provides a rigid arch beneath which the great vessels pass as they move from the mediastinum and thoracic outlet to the axilla. It has been shown that during elevation of the arm, the clavicle, as it rotates upward, also moves backward, with the curvature providing increased clearance for the vessels. Loss of the clavicle eliminates this bony barrier against external trauma. In addition, loss of the clavicle or mal- or nonunion in an inferiorly translated position can cause exacerbation of thoracic outlet symptoms because of the drooping of the shoulder and the resultant draping of the brachial plexus over the first rib.

Respiratory function

Elevation of the lateral part of the clavicle results in increased pull on the costoclavicular ligament and subclavius muscle. Because of the connection between the clavicle and the first rib and between the first rib and the sternum, elevation of the shoulder girdle brings about a cephalad motion of the thorax corresponding to an inspiration. This relationship is used in some breathing exercises and in some forms of artificial respiration.

Cosmesis

By providing a graceful curve to the base of the neck, the smooth, subcutaneous bony clavicle provides body symmetry and serves a cosmetic function. Traditionally, cosmesis has not been a priority for orthopedic fracture surgeons but there is increasing recognition that it is an issue that patients focus on. There is a negative effect on cosmesis following a displaced fracture that results in malunion or nonunion with deformity. There can be an unsightly lump or prominence at the fracture site, obvious shoulder asymmetry, and problems with apparel. For example, female patients have trouble keeping their bra or swimsuit strap on their affected shoulder because of this drooping, and military personnel, skiers, or bikers have problems keeping a backpack strap on the affected side ( Fig. 14.10 ). This can be a significant issue for a soldier wearing an 80-pound pack all day. This effect, a type of functional cosmesis, can be a serious issue for some patients. A randomized trial that compared nonoperative to operative treatment (plate fixation) for displaced clavicle fractures found that significantly more patients in the operative group were pleased with the final appearance of their shoulder compared to the nonoperative group.

Significant cosmetic and functional deficits in a patient following nonoperative treatment of a displaced right midshaft clavicular fracture.

Craig’s classification

In 1990, Craig introduced a more detailed classification of clavicle fractures that was based on the variable fracture patterns seen within the three broad groups of Allman’s clavicle fracture classification ( Box 14.1 ).

Group II (distal third) fractures

Group II fractures account for 12% to 15% of all clavicle fractures and are subclassified according to the location of the coracoclavicular ligaments relative to the fracture fragments. Neer first pointed out the importance of this fracture while subdividing it into four types.

Type I fractures are the most common, by a ratio of 4:1. In this type of fracture, the ligaments remain intact to hold the fragments together and prevent rotation, tilting, or significant displacement. This fracture is an interligamentous fracture that occurs between the conoid and the trapezoid or between the coracoclavicular and acromioclavicular ligaments ( Fig. 14.11 ).

Type I fracture of the distal end of the clavicle (group II). The intact ligaments hold the fragments in place.

(From Rockwood CA, Green DP, eds. Fractures , 2nd ed. Philadelphia: JB Lippincott; 1984.)

In type II distal clavicle fractures, the coracoclavicular ligaments are detached from the medial segment. Both the conoid and trapezoid ligaments may be on the distal fragment (IIA) ( Figs. 14.12 and 14.13 ), or the conoid ligament may be ruptured while the trapezoid ligament remains attached to the distal segment (IIB) ( Fig. 14.14 ). There is really no functional difference between these two fractures. The high rate of nonunion in these fractures may be secondary to excessive motion at the fracture site. These fractures are equivalent to a serious acromioclavicular separation in which the normal constraints to anteromedial rotation of the scapula relative to the clavicle are lost.

Type II distal clavicle fracture. In type IIA, both the conoid and trapezoid ligaments are on the distal segment, and the proximal segment, without ligamentous attachments, is displaced.

(From Rockwood CA, Green DP, eds. Fractures , 2nd ed. Philadelphia: JB Lippincott; 1984.)

Anterior posterior radiograph of a type IIA fracture of the distal clavicle.

Type IIB fracture of the distal part of the clavicle. The conoid ligament is ruptured, and the trapezoid ligament remains attached to the distal segment. The proximal fragment is displaced.

(From Rockwood CA, Green DP, eds. Fractures , 2nd ed. Philadelphia: JB Lippincott; 1984.)

Four forces that may impair healing and may be contributing factors to the reported high incidence of nonunion act on this fracture. When the patient is erect, the outer fragment, which retains the attachment of the trapezoid ligament to the scapula through the intact acromioclavicular ligaments, is pulled downward and forward by the weight of the arm; the pectoralis major, pectoralis minor, and latissimus dorsi draw the distal segment downward and medially, thereby causing overriding and shortening. The trapezius muscle attaches to the entire outer two-thirds of the clavicle, whereas the sternocleidomastoid muscle attaches to the medial third, and these muscles act to draw the clavicular segment superiorly and posteriorly, often into the substance of the trapezius muscle.

Type III distal clavicle fractures involve the articular surface of the acromioclavicular joint alone. Although type II fractures can have intra-articular extension, type III fractures are characterized by a break in the articular surface without a ligamentous injury. A type III injury may be subtle, and may be confused with a first-degree acromioclavicular separation, and can require special views to visualize. In fact, it may be manifested as late degenerative joint arthrosis of the acromioclavicular joint. In addition, it has been suggested that “weightlifter’s clavicle,” a resorption or osteolysis of the distal end of the clavicle, might occur from increased vascularity secondary to the microtrauma or microfractures that lead to such resorption. ^,

In certain pediatric fractures, bone displacement occurs as a result of deforming muscle forces, but the coracoclavicular ligaments remain attached to bone or periosteum. These injuries have been classified as type IV fractures and may be confused with complete acromioclavicular separation ( Fig. 14.15 ). Known as pseudodislocation of the acromioclavicular joint, these fractures typically occur in children younger than 16 years. The distal end of the clavicle is fractured, and the acromioclavicular joint remains intact. In children and young adults, the attachment between the bone and the periosteum is relatively loose. The proximal fragment ruptures through the thin periosteum and may be displaced upward by muscular forces. The coracoclavicular ligaments remain attached to the periosteum or may be avulsed with a small piece of bone. This can result in an interesting appearance radiographically, with a bifid distal clavicle consisting of the reconstituted inferior periosteal sleeve and the original shaft superiorly ( Fig. 14.16 ). ^{, ,}

Type IV fracture occurring in children that has been called a pseudodislocation of the acromioclavicular joint. The coracoclavicular ligaments remain attached to the bone or the periosteum, and the proximal fragment ruptures through the thin superior periosteum and may be displaced upward by muscle forces.

(From Rockwood CA, Green DP, eds. Fractures , 2nd ed. Philadelphia: JB Lippincott; 1984.)

An unusual radiographic appearance of a “bifid” clavicle. Following a pediatric distal clavicle fracture, the shaft is disrupted superiorly and the thick, strong periosteum remains attached inferiorly to both the conoid and trapezoid ligamentous connections. The periosteum subsequently reconstitutes a “new” shaft.

Group III (medial third) fractures

Group III fractures, or fractures of the inner third of the clavicle, are rare, and constitute 5% to 6% of all clavicle fractures. As with distal clavicle fractures, they can be subdivided according to the integrity of the ligamentous structures. If the costoclavicular ligaments remain intact and attached to the outer fragment, little or no displacement develops. ^, When these lesions occur in children, they are usually epiphyseal fractures. In adults, articular surface injuries can also lead to degenerative changes. ^, Based on their observations of 57 medial fractures, Throckmorton and Kuhn classified medial fractures into five different types based on their fracture patterns ( Fig. 14.17 ). It is of interest to note that in their medial clavicle fracture series, 22% of the fractures could only be seen on CT scan.

Classification of medial clavicle fractures.

(From Throckmorton T, Kuhn JE. Fractures of the medial end of the clavicle. J Shoulder Elbow Surg . 2007;16[1]:49–54.)

This emphasizes the importance of obtaining a CT scan in settings in which a medial fracture is anticipated. Panclavicular dislocation, or a bipolar clavicle injury, is neither a clavicle fracture nor an isolated sternoclavicular or acromioclavicular separation. In this injury, both sternoclavicular ligaments and the coracoclavicular and the acromioclavicular ligamentous structures are disrupted. This is typically treated operatively, as significant disruption and functional deficit can result in this condition if left untreated.

Robinson’s classification

The classification proposed by Robinson and colleagues ( Fig. 14.18 ) is the only validated classification system in terms of correlating the type of fracture with the typical outcome. Their system was based on the observation of 1000 adult clavicle fractures, and takes into account the anatomic site, extent of displacement, comminution, and articular extension and stability of the fracture.

Robinson classification of clavicle fractures.

(From Robinson CM. Fractures of the clavicle in the adult. Epidemiology and classification. J Bone Joint Surg Br . 1998;80:476–484.)

The primary anatomic sites are medial (type 1), middle (type 2), and lateral (type 3). Displacement further subdivides these primary groups if they are displaced less than 100% (subgroup A) or more than 100% (subgroup B). Types 1 and 3 fractures are subdivided with regard to their articular involvement, with subgroup 1 having no intra-articular involvement and subgroup 2 having intra-articular extension. Type 2 fractures are subdivided with regard to their comminution. Simple or wedge comminution is classified into subgroup 1, and segmental or comminuted fractures are classified into subgroup 2.

By combining these groups and subgroups, virtually all fractures can be described. For example, a comminuted, displaced midshaft fracture is described as a type 2B2 fracture, and a nondisplaced intra-articular lateral clavicle fracture is a type 3A2 . Robinson found that both displacement and comminution were associated with an increased risk of delayed union or nonunion.

Trauma in children

Fractures of the clavicle in children share many of the same mechanisms of injury as in adults and can result from a direct blow to the clavicle or the point of the shoulder or from an indirect blow such as a fall on the outstretched hand. However, other features are unusual and unique to children, including obstetric fracture of the clavicle and plastic bowing injury.

Birth fractures

In 15,000 deliveries from 1954 to 1959, Rubin found that fractures of the clavicle were the most common injury at birth. Although it has been stated that intrapartum traumatic injuries are decreasing as a result of improvements in obstetric care, ^, the incidence of clavicle fracture remains quite high, and in infants, it might actually be increasing. Moir and Myerscough found an incidence of clavicle fractures of 5 per 1000 vertex births, which increased to 160 per 1000 with breech presentation. The mechanism of injury in a full-term newborn infant delivered vaginally, when the baby is in a cephalic presentation, is compression of the leading clavicle against the maternal symphysis pubis. ^, In a breech delivery, direct traction can occur and produce the same bone injury as the obstetrician tries to depress the shoulders and free the arm during delivery of the head. ^, Breech deliveries are much less common now in North America and Europe since several prospective trials demonstrated superior outcomes with C-sections compared to vaginal deliveries in breech presentations. This theoretically will decrease the rate of clavicular fracture in newborns, since this injury is very rare in C-section cases. The overall incidence of fracture of the clavicle during birth is approximately 0.5 to 7.2 per 1000 births. In addition to the presentation of the infant, several factors appear to be involved. Birth weight clearly plays a role because the incidence of fractures of the clavicle increases with increasing birth weight and in larger babies. ^, Babies who weigh 3800 to 4000 g or measure 52 cm or longer seem to be at higher risk for fracture. Increased maternal age has likewise been shown to be a risk factor for birth fracture. The experience of the physician is likely also related. Cohen and Otto reported an increased incidence of fractures of the clavicle when babies were delivered by less experienced residents, and a decrease in incidence was noted for each year of obstetrics experience. On the other hand, Balata et al. noted no fractures in babies delivered by cesarean section.

Fracture of the clavicle does not seem to be related to the type of anesthesia, length of active labor, length of second-stage labor, Apgar score, or parity of the mother. The exact anatomy of fractures that occur during delivery varies, and incomplete, greenstick, and bicortical disruptions with or without displacement have all been reported. In one study, boys were more commonly affected than girls, and the right clavicle was fractured more often than the left clavicle. In 1992, a study suggested a relationship between fractures of the clavicle and mothers who had a second child.

Injuries in infancy and childhood

Fractures of the clavicle are particularly common in childhood, and almost half occur in children younger than 7 years. Fractures commonly result from a fall on the point of the shoulder or on an outstretched hand. In younger children, such a fall can be from a highchair, bed, or changing table. The fracture is occasionally caused by a direct violent force applied from the front of the clavicle; like other fractures of long bones, fractures of the clavicle may be one of several signs of trauma in a physically abused child.

Unlike the situation in adults, direct and indirect trauma to a child’s clavicle can result in incomplete or greenstick fractures rather than displaced fractures. In addition, trauma to a child’s clavicle can result in plastic bowing alone without evident cortical disruption. Despite an initial appearance of only bowing, on later examination these injuries usually show evidence of healing of complete fractures, with obvious callus visible on radiographs. It is also important to remember that considerable remodeling of completely displaced fractures of the clavicle can occur in children. ^,

Trauma in adults and adolescents

The incidence of fractures of the clavicle in adults appears to be increasing because of several factors, including the occurrence of many more high-velocity vehicular injuries and the increase in the popularity of contact sports. The mechanism of injury of fractures of the clavicle in adults has been widely reported to consist of either direct or indirect force. It has generally been assumed that the most common mechanism of fractures in adults is a direct blow or fall onto the outstretched hand. In a large series of fractures of the clavicle (342 patients) studied by Sankarankutty and Turner, 91% sustained a fall or blow to the point of the shoulder, whereas only 1% had a fall onto the outstretched hand.

In 1994, Nordqvist and Petersson investigated the incidence of fractures of the clavicle. They reviewed 2035 fractures that occurred between 1952 and 1987. The fractures were classified into three groups according to the Allman system. Each group was further divided into nondisplaced fracture subgroups, with an extra subgroup of comminuted midclavicle fractures in group I. Of the fractures, 76% were classified as Allman group I. The median age of the patients in this group was 13 years. Significant differences in age- and gender-specific incidence were noted between the nondisplaced, displaced, and comminuted fracture subgroups. Allman group II accounted for 21% of the fractures. The median age of these patients was 47 years, and no difference in age was found between the subgroups with nondisplaced and displaced fractures. Three percent of the fractures were classified as Allman group III, and the median age of the patients in this group was 59 years. All three groups were characterized by a significant preponderance of male patients.

A study by Nowak in 2000 showed that the incidence of clavicle fractures in Uppsala, Sweden, was 50 per 100,000 population; however, the incidence in male patients was 71 per 100,000, and the incidence in female patients was 30 per 100,000. ^, Bicycle accidents were the most common cause of injury, and male patients tended to be younger and to have more comminuted, high-energy injuries. Most (75%) of the injuries were midshaft fractures, and the nonunion rate was 5%.

More recently, Stanley and colleagues studied a consecutive series of 150 patients with fractures of the clavicle; 81% of the patients described the mechanism of injury. The researchers found that 94% had fractured the clavicle from a direct blow on the shoulder, whereas only 6% had fallen onto an outstretched hand. Further biomechanical analysis of the force involved in the fracture of the clavicle by this group revealed that direct injury produces a critical buckling load that is exceeded at a compression force equivalent to body weight, and thereby results in the fracture of the bone. When force is applied along the axis of the arm, the buckling force is rarely reached in the clavicle. These investigators recorded fractures at every site along the clavicle with a direct injury to the point of the shoulder and found little support for Allman’s concept that fractures at different anatomic sites have different mechanisms of injury. In addition, they theorized that a direct blow to the shoulder might even be the mechanism of injury in those who described a fall on the outstretched hand: as the hand makes contact with the ground, the patient’s body weight and falling velocity are such that the fall continues, with the shoulder becoming the upper limb’s next point of contact with the ground.

Harnroongroj and colleagues found that when clavicles were axially loaded, they tended to fracture at the middle third of the clavicle in the region where the curve of the lateral aspect of the clavicle changes to the curve of the medial aspect of the clavicle. The force required to fracture the clavicle was 1526.19 N, and the ratio of the lateral fragment to the total length of the clavicle was 0.49.

Another indirect mechanism of fracture of the clavicle is a direct force applied to the top of the shoulder; the clavicle is forced against the first rib, and a spiral fracture of the middle third is often produced. Another variation of this mechanism is what we refer to as seatbelt fractures. The shoulder strap from the seatbelt acts as a fulcrum, typically at the midpoint of the clavicle, and the forward force of the clavicle against this fulcrum causes the clavicle to fracture in a transverse or oblique pattern, with little or no comminution. It appears that this fracture is more prone to nonunion than more typical fractures ( Fig. 14.19 ) perhaps due to the increased amount of energy required to cause a transverse fracture.

Atrophic midshaft clavicular nonunion 18 months after a seatbelt injury.

Stress fractures

Stress fractures of the clavicle have been reported in athletes. They have been seen in a variety of sports, including baseball, diving, gymnastics, and cheerleading. ^, It appears that the mechanism of injury is repeated axial loading of the clavicle in all the activities except cheerleading. These fractures tend to be more medial and should be suspected in patients with chronic clavicular pain associated with overuse. Although plain radiographs can appear normal, magnetic resonance imaging can readily detect these injuries and rule out pathologic fractures. Most of these fractures occur after changes or an increase in the athlete’s training routine, and typically heal uneventfully with rest and activity modification. Stress fractures have also been reported in conjunction with coracoclavicular cerclage fixation of acromioclavicular joint separation.

Nontraumatic fractures

It is well recognized that the clavicle can be the site of neoplastic or infectious destruction of bone, and a fracture can occur after relatively minor trauma. Certainly, lack of a traumatic episode should lead the clinician to focus on the possibility that a long bone fracture has occurred in pathologic bone. In addition to both malignant and benign lesions producing pathologic fractures of the clavicle, ^, pathologic fracture has also been described in association with arteriovenous malformation, and underlying spontaneous infection ( Fig. 14.20 ).

(A) This 58-year-old man sustained a spontaneous clavicle fracture while doing a push-up. An anterior posterior radiograph reveals a displaced fracture with a lytic lesion in the distal fragment. (B) Increasing displacement and deformity and ongoing pain at 6 weeks postinjury prompted surgical intervention. (C) The fracture was treated with irrigation and debridement and open reduction and internal fixation with a precontoured plate. Cultures of the lesion at the time of surgery grew C. acnes . Uneventful healing followed.

Atraumatic stress fractures have also been reported in the clavicle. In addition, spontaneous fracture of the medial end of the clavicle has been reported as a pseudotumor after radical neck dissection. Atraumatic clavicular stress fractures have also been reported after reverse total shoulder arthroplasty ( Fig. 14.21 ).

Clavicle stress fracture seen after a reverse total shoulder arthroplasty.

(From Anakwenze OA, Pifer MA, Singh A. Clavicle stress fracture after reverse shoulder arthroplasty. J Shoulder Elbow Surg . 2014;23[7]:e170–e172.)

The synthetic material used to treat coracoclavicular disruption has also been reported to produce stress fractures in the clavicle, with subsequent nonunion. Nonunion of the clavicle has occurred after the use of polyester mesh (Mersilene) tape and polyethylene (Dacron) to repair a grade III dislocation of the acromioclavicular joint. Such nonunion is likely the result of the differential motion between the clavicle and the scapula with normal arm motion. When the tape or suture is passed over the clavicle, the differential motion can result in the tape sawing through the clavicle. Fig. 14.22 shows an axillary view of a patient who had undergone nonabsorbable suture fixation around the clavicle and coracoid for a distal clavicle fracture.

Erosion of the coracoid and clavicle seen after stabilization of a distal-third fracture using nonabsorbable sutures.

Birth fractures

Two clinical manifestations of birth fractures appear to predominate: clinically unapparent and clinically apparent (pseudoparalysis).

Diagnosis of clinically unapparent fracture may be very difficult because of the presence of few clinical symptoms. A crack heard during the delivery may be the only clue to fracture of the clavicle. Whether the lesion in this group of fractures is truly asymptomatic and is overlooked in the neonatal examination is uncertain, but Farkas and Levine emphasized that many of these fractures are not initially diagnosed. Of the five cases of fracture of the clavicle in 355 newborns in their series, none were suspected after routine physical examination in the delivery room and newborn nursery. On reexamination, however, crepitus could usually be demonstrated at the fracture site. Thus it appears that fractures can easily be overlooked. However, because they are generally unilateral, close examination can reveal asymmetry of clavicular contour or shortening of the neckline. The fracture is often first recognized by the mother after noticing the swelling, which is caused by fracture callus, and typically appears 7 to 11 days after the fracture.

The infant with a clinically apparent fracture is disinclined or unwilling to use the extremity, and clinicians note a unilateral lack of movement of the whole upper limb either spontaneously or during elicitation of the Moro reflex. ^, Because these fractures are often complete, local swelling, tenderness, and crepitus can suggest the diagnosis. This injury must be distinguished from other conditions that can make the infant disinclined or unable to use the extremity, such as birth brachial plexus injury, separation of the proximal humeral epiphysis, and acute osteomyelitis of the clavicle or proximal end of the humerus. It is important to remember that a fractured clavicle and a brachial plexus injury can coexist.

Fractures in children

Almost half of fractures of the clavicle in children occur in those younger than 7 years. Because clavicle fractures in these young children may be incomplete or of the greenstick variety, they might not be obvious, and thus may be overlooked. The mother of the infant might notice that the baby cries after being picked up and appears to be hurt. The baby does not seem to use the arm naturally and cries when the arm is used for any activities or is moved during dressing. On palpation, a tender, uneven upper border of the clavicle may be felt that is asymmetric when compared with the contralateral side. As with a newborn, the mother may take the baby to the pediatrician because of the “sudden” appearance of a lump ( Fig. 14.23 ).

Clavicle fracture in a 2-year-old child. Prominent callus formation is evident and is manifested clinically as a bump.

However, if the fracture is complete in children who are ambulatory and verbal, the diagnosis is usually obvious. In addition to the child’s complaints of pain localized to the clavicle, when these fractures are displaced, a typical deformity caused by muscle displacement of the fracture fragments is apparent. The shoulder on the affected side can appear lower and droop forward and inward. The child splints the involved extremity against the body and supports the affected elbow with the contralateral hand. Due to the pull of the sternocleidomastoid muscle on the proximal fragment, the child tilts the head toward and the chin away from the side of the fracture in an effort to relax the pull of this muscle ( Fig. 14.24 ). Physical examination reveals tenderness, crepitus, and swelling, which are typical for this fracture at any age.

Clinical manifestation of a displaced clavicle fracture in a child. The shoulder on the affected side appears lower and droops forward and inward. The child splints the involved extremity against the body, supports the affected elbow with the contralateral hand, and tilts the head toward and the chin away from the site of the fracture to relax the pull of the sternocleidomastoid muscle.

Complete acromioclavicular separations are very unusual in children younger than 16 years. What may be evident clinically as a high-riding clavicle above the acromioclavicular joint and an apparent acromioclavicular separation is often either a transperiosteal distal clavicle fracture or, more commonly, a rupture through the periosteum plus a distal clavicle fracture, with the coracoclavicular ligaments remaining behind attached to the periosteum.

Similarly, because the sternal epiphysis is the last epiphysis of the long bones to fuse with the metaphysis (fusion usually occurs from ages 22 to 25 years), the sternoclavicular joint may be subject to the usual types of epiphyseal injury. Many misdiagnosed sternoclavicular dislocations are, in fact, fracture-dislocations through the medial clavicular epiphysis. In this situation, CT scanning is the diagnostic imaging procedure of choice ( Fig. 14.25 ). Occasionally, sternoclavicular separations occur with adjacent clavicle fractures in children. ^,

Computed tomography scanning is the radiographic investigation of choice for complex injuries of both the medial and lateral clavicle. This scan reveals a medial clavicular displaced fracture-dislocation.

It should be pointed out that, although the clavicle is the last bone to stop growing, there is probably very little potential for remodeling after the age of 9 years in females and 12 years in males ( Fig. 14.26 ). Furthermore, although younger patients can remodel an angular deformity, there is little possibility of remodeling shortening.

Growth of the clavicle in females and males from less than 1 to 18 years of age.

(From McGraw MA, Mehlman CT, Lindsell CJ, et al. Postnatal growth of the clavicle: birth to 18 years of age. J Pediatr Orthop . 2009;29:937–943.)

Fractures in adults

Because of the characteristic clinical features in adults, displaced fractures of the clavicle present little difficulty with diagnosis if the patient is seen soon after injury. The patient usually provides a clear history of some form of either direct or indirect injury to the shoulder. The clinical deformity is obvious, with the proximal fragment displaced upward and backward, and possibly tenting the skin. Compounding of this fracture is unusual but can occur. The patient is usually splinting the involved extremity at the side because any movement elicits pain. The involved arm droops forward and down because of the weight of the arm and the pull of the pectoralis minor muscle. This drooping further accentuates the posterosuperior angulation seen in most clavicle fractures. Although the initial deformity may be obvious later, acute swelling of the soft tissue and hemorrhage may obscure it.

Examination of the patient reveals tenderness directly over the fracture site, and any movement of the arm is painful. Ecchymosis may be noted over the fracture site, especially if severe displacement of the bone fragments has produced associated tearing of the soft tissue. Patients might angle the head toward the injury in an attempt to relax the pull of the trapezius muscle on the fragment. As in children, the patient may be more comfortable with the chin tilted to the opposite side. Gentle palpation and manipulation usually produces crepitus and motion, and the site of the fracture is easily palpable because of the subcutaneous position of the bone. The skin over the clavicle, the scapula, or the chest wall might give a clue to the mechanism of injury and might indicate other areas to be evaluated for associated injuries. The lungs must be examined for the presence of symmetrical breath sounds to rule out pneumothorax, and the whole extremity must be examined carefully. A careful neurological examination is mandatory.

A pan-clavicular or bipolar dislocation is typically produced by extreme and forceful protraction of the shoulder ( Fig. 14.27 ). This injury is usually the result of a major traumatic episode such as a high-speed motor vehicle accident, a fall from a height, or a very heavy object falling on the shoulder, although it has been reported after a minor fall at home. Clinically, patients usually have bruising over the spine of the scapula, and swelling and tenderness at both ends of the clavicle. This injury is associated with anterosuperior sternoclavicular dislocation and either posterosuperior or subjacent displacement of the clavicle. The whole clavicle may be freely mobile and may feel as though it is floating. The investigation of choice is a CT scan of both the medial and lateral ends of the clavicle, and surgical intervention is usually indicated.

(A) This 62-year-old woman sustained a severe shoulder girdle injury in a motor vehicle accident. There is an anterior dislocation of the clavicle at the sternoclavicular joint, and a posterior dislocation at the acromioclavicular joint. (B) Profile clinical photograph reveals the significant anterior prominence of the clavicle and the disruption of the shoulder girdle. (C) Three-dimensional computed tomography scan confirms a “bipolar” dislocation of the clavicle. Surgical intervention is indicated in these individuals.

Associated injuries

In 1830, Gross reported that “fractures of the clavicle usually assume a mild aspect, being seldom accompanied by any serious accident.” Although statistically, most clavicle fractures are relatively innocuous injuries, serious associated injuries can occur, and a delay in treatment may be potentially life-threatening. ^, Therefore, in a patient with a clavicle fracture, it is critical that a careful examination of the entire upper extremity be performed, with particular emphasis on neurovascular status, in addition to careful examination of the lungs.

Furthermore, although open fractures of the clavicle are rare, they are often associated with significant and potentially life-threatening pulmonary and cranial injuries, with concomitant neurovascular injuries being an uncommon finding. Associated injuries accompanying acute fractures of the clavicle may be divided into associated skeletal injuries (including scapula, ribs, spine, craniofacial), injuries to the lung and pleura, injuries to the brain, vascular injuries, and brachial plexus injuries. Disruption of the superior shoulder suspensory complex consisting of multiple lesions are an associated injury with clavicle fractures that are associated with a high rate of nerve injury and muscle atrophy if not recognized.

Associated skeletal injuries can include sternoclavicular or acromioclavicular separations or fracture-dislocations through these joints ( Fig. 14.28 ). ^, As might be anticipated with ipsilateral sternoclavicular or acromioclavicular joint injuries, closed reduction of the ligamentous injury is usually impossible because of the accompanying clavicle fracture. ^,

An unusual case of a fracture of the clavicle associated with complete acromioclavicular separation. The associated clavicle fracture makes treatment of the ligamentous injury very difficult.

Head and neck injuries may be present, especially with displaced distal clavicle fractures. In one series, 10% of the patients were comatose.

Fractures of the ipsilateral ribs are common and may be overlooked, although they are readily seen if displaced ( Fig. 14.29 ). ^, These rib fractures may be directly responsible for accompanying lung, brachial plexus, or subclavian vein injury. First-rib fractures, whether ipsilateral or contralateral, may be under-recognized because they are not easily seen on standard chest radiographs. Weiner and O’Dell recommended either an AP view of the cervical spine or an AP view of the thoracic spine associated with a lateral view of the thoracic spine to decrease the likelihood that this injury would be overlooked.

An anterior chest radiograph reveals a displaced midshaft clavicle fracture in addition to multiple lateral displaced rib fractures and an underlying pneumothorax.

Rib fractures are usually detected on the thoracic CT scan that is performed on most trauma patients presenting with high-energy mechanisms of injury. Weiner and O’Dell have outlined how several of these types of rib fractures occur. The scalenus anticus muscle attaches on a tubercle of the first rib. On either side of this tubercle lies a groove for the subclavian vein anteriorly and the subclavian artery posteriorly. Posterior to the groove for the subclavian artery lies a roughened area for attachment of the scalenus medius muscle. These two muscles elevate the rib during inspiration. The serratus anterior muscle arises from the outer surfaces of the upper eight ribs and fixes the rib posteriorly during inspiration. These structures can interact to contribute to the occurrence of fractures of the first rib as the clavicle is fractured.

Three basic mechanisms have been theorized to be responsible for this combination of injuries: indirect force transmitted via the manubrium, avulsion fracture at the weakest portion of the rib by the scalenus anticus, and injury to the lateral portion of the clavicle, causing an acromioclavicular separation that leads to indirect force from the subclavius muscle to the costal cartilage and the anterior aspect of the first rib. ^, Because of the loss of the suspensory function of the clavicle and splinting secondary to pain from the clavicle and rib fractures, care should be taken to monitor respiratory function, especially in those with already compromised function, such as patients with chronic obstructive pulmonary disease. These patients can easily decompensate unless given appropriate respiratory and analgesic support. In addition, if there is the presence of a flail segment, fixation of the ribs may be warranted ( Fig. 14.30 ).

(A) After a polytraumatic event, this patient suffered severe bilateral flail chest injuries with a displaced left clavicular fracture. (B) These injuries were treated with open reduction and plate fixation of the clavicle and ribs.

Fractures of the clavicle may also be associated with dissociation-disruption of the scapulothoracic articulation manifested as swelling of the shoulder, lateral displacement of the clavicle, severe neurovascular injury, and fracture of the clavicle or the acromioclavicular or sternoclavicular joints. This injury often occurs as a result of a distraction force on the arm, such as occurs when it is caught in a winch or in industrial machinery. The key feature of this injury is distraction at the site of the clavicle fracture or acromioclavicular joint injury. While most clavicle fractures shorten or medialize, the fracture associated with scapulothoracic dissociation are gapped or distracted, and this is an obvious clue to a potentially limb- or life-threatening underlying injury.

In a combination injury, the floating shoulder consists of fractures of both the clavicle and the scapula and is associated with an extremely unstable shoulder girdle. In this injury, sequelae such as a drooping shoulder and limited range of motion can develop if this fracture is treated conservatively. The primary indication for internal fixation of the scapula is to reduce and internally stabilize a grossly displaced intra-articular fracture of the glenoid fossa. ^, Stabilization of the clavicle alone has been shown to produce good and excellent functional results. ^, In a case of multiple trauma, Herscovici and colleagues recommended internal fixation of only the clavicle fracture. ^,

Other authors have suggested that although operative fixation does give good results, most cases of floating shoulder are not really unstable, and can be managed with nonoperative treatment. Williams and colleagues studied double disruptions of the superior suspensory mechanism, and did not find any significant loss of stability unless the coracoacromial and acromioclavicular ligaments were disrupted in addition to fractures of the clavicle and glenoid neck. Mulawka and colleagues examined triple and quadruple disruptions of the superior shoulder suspensory complex and found that high-energy mechanisms consisting of open-cockpit collisions (motorcycle, snowmobile) were the most common causes, followed by motor vehicle accidents. They demonstrated an 87% rate of concomitant nerve injury in this patient population. A number of authors have commented on the potentially serious complication of associated pneumothorax or hemothorax with fractures of the clavicle because the apical pleura and upper lung lobes lie adjacent to this bone. Rowe reported a 3% incidence of pneumothorax in a series of 690 clavicle fractures, but did not comment on how many had associated rib or scapular fractures. ^{, ,} It is essential that a careful physical examination of the lung be undertaken at the initial evaluation and that the presence and symmetry of breath sounds be identified. In addition, an upright chest film appears to be important in the assessment of all patients with fractures of the clavicle who have decreased breath sounds or other physical findings that suggest pneumothorax, with particularly close attention paid to the outline of the lung. Such assessment is especially necessary in multiply traumatized or unconscious patients who have neither obvious blunt chest trauma nor any external signs of trauma to the chest that might yield a clue to potential lung or pleural complications. ^{, ,}

Although nerve injuries are rare with clavicle fractures, acute injuries to the brachial plexus do occur. The neurovascular bundle emerges from the thoracic outlet under the clavicle on top of the first rib. As it passes under the clavicle, it is protected to a certain extent by the thick medial clavicular bone; considerable trauma is usually necessary to damage the brachial plexus and break the clavicle at the same time. When the force is severe enough to break the clavicle and injure the brachial plexus, a subclavian vascular injury often occurs concomitantly ( Fig. 14.31 ). The force resulting in nerve injury usually comes in a direction from above downward or from in front downward. As the force is applied, the nerves may be stretched, with the fulcrum of maximal tension being the transverse process of the cervical vertebra. The roots can also be torn above the clavicle, or they may be avulsed from their attachment to the spinal cord. Although the posterior periosteum, subclavius muscles, and bone offer some protection to the underlying plexus, the plexus may be injured directly by the fragments of bone. Depending on the direction of the deforming force, a variety of brachial plexus injuries can result, including “upper trunk” lesions that leave a well-functioning hand but a flail shoulder, “lower trunk” injuries that affect predominantly hand function, mixed lesions, and “complete” injuries (that have the worst prognosis). Acute vascular injuries are unusual because of many of the same local anatomic factors that protect the nerves from direct injury. The subclavius muscle and the thick, deep cervical fascia also act as barriers against direct injury to the vessels. If the initial displacement of the fracture fragment has not injured the adjacent vessels, they are unlikely to be injured further, because the distal fragment is pulled downward and forward by the weight of the limb and the proximal fragment is pulled upward and backward by the trapezius muscle. Thus, as with acute nerve injury, a major injury is usually required to produce an acute vascular insult. Nevertheless, injury has been reported, even with greenstick fractures. In addition, acute vascular compression resulting from fracture angulation and/or malunion has been described ( Fig. 14.32 ).

As the clavicle fractures and displaces, the subclavian vessels immediately posterior to the clavicle may be injured by sharp shards of bone.

Subtraction arteriogram showing nearly complete cutoff of the left subclavian artery after a clavicle malunion.

When they occur, vascular injuries include laceration, occlusion, spasm, or acute compression; the vessels most commonly injured are the subclavian artery, subclavian vein, and internal jugular vein. The subclavian vein is particularly vulnerable to tearing due to its thinner wall and the fact that it is fixed to the clavicle by a fascial aponeurosis. ^, Injuries to the suprascapular and axillary arteries have also been reported. ^, Laceration can result in life-threatening hemorrhage, whereas arterial thrombus and occlusion can lead to distal ischemia. Damage to the arterial wall can, in addition, lead to aneurysm formation and late embolic phenomena. Venous thrombosis may be problematic as well; although it does not typically threaten life or limb, it has the potential for pulmonary embolism, which can constitute a threat.

Clinical recognition of an acute vascular injury may be difficult, particularly in an unconscious patient or one in shock. Although a complete laceration can cause life-threatening hemorrhage or result in an extremity that is cold, pulseless, and pale, a partial laceration is more likely to be manifested as uncontrolled bleeding and life-threatening blood loss. The color and temperature of the extremity may be normal, but the absence of a pulse, the presence of a bruit, or a pulsatile hematoma (as the hematoma is walled off or produces a false aneurysm) should make the clinician strongly suspect a major vascular injury. If blood flow is significantly obstructed, the injured limb is usually colder than the uninjured limb, but there might also be a difference in blood pressure between the two. Vascular contusion or spasm can result in thrombotic and, later, thromboembolic phenomena. It is sometimes difficult to recognize the difference between arterial spasm and interruption or occlusion, and it may be reasonable to consider a sympathetic block to help distinguish a spasm from a more serious injury.

If major injury to a vessel is suspected, an arteriogram or CT angiogram should be performed. In the rare event of a tear of a large vessel, surgical exploration by a surgeon with vascular expertise is mandatory. To gain adequate exposure, the clavicle may be osteotomized to provide as much exposure as needed to isolate and repair the injured major vessel, and a team approach is very useful in this regard. Although the vessel may be ligated in a life-threatening situation, ligation of a major vessel may critically impair survival of the limb if there is inadequate collateral circulation to the extremity.

Of particular importance is the association of medial clavicle fractures with the occurrence of almost all of these injuries. Medial clavicle fractures are relatively uncommon in comparison to midshaft and lateral fractures, but they have been associated with a very high incidence of pulmonary problems such as pneumothorax, hemothorax, or hemopneumothorax and pulmonary contusion, as well as head, face, and cervical injuries. Most impressive is the very high mortality rate found in association with medial clavicle injuries. Throckmorton and Kuhn found that 20% of patients with medial clavicle fractures died as a result of their associated injuries.

Fractures of the shaft

With most clavicular shaft fractures, the diagnosis is not in doubt because of the clinical deformity and confirmatory radiographs. Historically, many physicians have obtained only an AP radiograph of the shoulder to image clavicle fractures. Because of the multiplanar nature and the unusual sigmoid shape of the clavicle, it is difficult to accurately determine fracture displacement and angulation on a single AP radiograph. The primary problem is that the plane of the fracture is oblique to the plane of the x-ray beam. Therefore, what is measured as displacement or shortening on an AP radiograph is really equivalent to the base of a triangle, but the true amount of shortening is really the hypotenuse of the triangle ( Fig. 14.33 ). The clavicle not only shortens but also becomes angulated inferiorly and rotated medially, producing a complex three-dimensional deformity. Aside from using a three-dimensional Cartesian coordinate system, it is very difficult, if not impossible, to characterize the true deformity on plain radiographs. Furthermore, it is important to obtain standing radiographs of the clavicle because supine radiographs will diminish the effects of gravity on the displacement of the lateral fragment. It is important to note in this regard that CT scans of the clavicle are performed in a supine position. It is also important to note that displacement can worsen with time due to the downward gravitational pull on the shoulder and also the deforming forces of the muscles around the shoulder. Even if the initial radiographic evaluation suggests minimal deformity, patients treated nonoperatively should receive follow-up radiographs. Significant displacement has been shown to occur in up to 60% of patients initially believed to be nonoperative candidates due to minimal displacement on initial radiographs ( Fig. 14.34 ). ^, This is especially true when the initial diagnosis of a clavicle fracture is made in a supine trauma patient based on an AP chest radiograph. To obtain as accurate an evaluation of fragment position as possible, at least two projections of the clavicle historically have been obtained: an AP view and a cephalic tilt view (with the tube angled between 20 and 45 degrees cephalad). In the former, the proximal fragment is typically displaced upward and the distal fragment is displaced downward ( Fig. 14.35 A). In the latter, the tube is directed from below upward and more accurately assesses the AP relationship of the two fragments (see Fig. 14.35 B). Displacement of the fracture is best assessed on the cephalic tilt projection. An axillary view with the beam angled slightly cephalad can also help determine fracture displacement in the antero-posterior plane and can be useful in assessing possible nonunion ( Figs. 14.36 and 14.37 ). Historically, in 1926, Quesana recommended two views at right angles to each other, a 45-degree angle superiorly and a 45-degree angle inferiorly, to assess the extent and displacement of fractures of the clavicle.

Shortening cannot be determined on standard radiographs because the deformity is not orthogonal to the x-ray beam. The beam is represented by the long dashed line and the apparent shortening by the short solid line . The true shortening (short dotted line) is really the hypotenuse of the triangle and is longer than the apparent shortening.

(A) Initial radiographs of this patient’s clavicle revealed only a subtle deformity during initial hospital stay. (B) Radiographs taken 10 days later revealed significant subsequent displacement of the fracture. While initial supine chest radiographs may not reveal any significant displacement, up to 60% of trauma patients show subsequent displacement of their fracture.

(A) Anteroposterior radiograph of an acute midshaft left clavicle fracture sustained in a mountain bike accident. It appears to be relatively nondisplaced on this view. (B) A 45-degree cephalic tilt radiograph of the clavicle showing marked displacement and a transversely oriented butterfly fragment.

Anteroposterior radiograph of a clavicle nonunion. On this view, the fracture appears to be healed in acceptable alignment and has adequate callus.

Axillary radiograph of the same patient in Fig. 14.36 . The nonunion is obvious, with significant shortening at the fracture site.

Furthermore, in addition to the amount of displacement, shortening of the clavicle shaft fracture is an important factor in determining whether or not to operate. Recently, the PA 15-degree caudad view has been shown to be more accurate than the AP 15-degree cephalad view in determining shortening in clavicle fractures. Sharr and colleagues determined the true length of a skeletal clavicle to be 124 mm using utilizing metallic markers and multiple radiographs. However, when utilizing a standard AP image, the clavicle length was 149 mm with up to 19 mm of variation on oblique views, compared to a length of 130 mm with only 4 mm of maximum variation with a PA 15-degree caudad view. In comparing the injured clavicle to the uninjured contralateral clavicle, they found less than 5 mm of difference in length in 84% of diaphyseal fractures.

Despite numerous studies examining various imaging modalities in determining the most accurate and reproducible methods to measure shortening of clavicle shaft fractures, there still has not been an accepted consensus. A recent systematic review found that the studies in current literature ranged from poor to fair quality, and thus a definite conclusion could not be made. Any determination of clavicular shortening or deformity should always include a careful examination and measurement of the patient’s clavicle.

The configuration of the fracture is also important to assess because it can give clues as to the presence of associated injuries. The usual clavicular shaft fracture in adults is slightly oblique; fractures that are more comminuted, especially if fragments are projecting in a superior-to-inferior direction, have generally resulted from a greater force, and can alert the surgeon to the potential for associated neurovascular or pulmonary injuries. These could be identified with an AP radiograph to include the upper third of the humerus, the shoulder girdle, and the upper lung fields, as suggested by Rowe.

Children’s fractures may be greenstick or nondisplaced, or they can appear only as bony bowing, and thus the diagnosis of shaft fractures may be more difficult to make ( Fig. 14.38 ), especially in newborns or infants, in whom the clinical findings may be difficult to assess. Movement by the child or bone overlap can obscure radiographic detail, and an incomplete fracture might not be recognized. However, the surrounding soft tissues of the clavicle are normally displayed as parallel shadows above the body of the clavicle, which is invariably present on most radiographs. Suspicion of fractures of the clavicle should be aroused by loss of the accompanying shadow unilaterally. If there is any doubt about the presence of a fracture in a child, a repeat radiograph taken 5 to 10 days after the injury will usually reveal callus formation.

Greenstick fracture of the left clavicle in a 14-year-old patient. In such a patient, diagnosis may be more difficult.

In 1988, the technique of ultrasonography was described for the evaluation of clavicular birth fractures. These birth fractures can easily be overlooked and may be confused clinically with birth palsy. In their study, Katz et al. noted no difference in diagnostic accuracy between ultrasonography and plain radiography.

With either plain radiography or ultrasonography, it may be difficult to differentiate congenital pseudarthrosis from an acute fracture. However, the radiographic features, the lack of trauma, and the absence of callus usually help distinguish an atraumatic condition such as congenital pseudarthrosis from a birth fracture ( Fig. 14.39 ).

This anterior posterior radiograph of the clavicle was taken following a minor motor vehicle accident in an 18-year-old female. The significant separation of the proximal and distal fragments, the chronic morphologic changes, especially of the distal fragment, and the rounded-off atrophic nature of the fragments indicates a chronic, not acute condition. This radiograph is consistent with congenital pseudarthrosis of the clavicle.

Fractures of the distal third

In both children and adults, the usual radiographic views obtained for shaft fractures are inadequate to accurately assess distal clavicle fractures. The standard exposure for evaluation of shoulder or shaft fractures overexposes the distal end of the clavicle and is not centered over the site of injury. The usual exposure for the distal part of the clavicle should be approximately one-third that used for the shoulder joint, centered distally ( Fig. 14.40 ).

This anterior posterior radiograph of the clavicle reveals significantly displaced type II distal clavicle fracture. Although the shaft is significantly displaced, separate fragments can be seen held in place by the intact conoid and trapezoid ligaments.

To accurately assess the extent of the injury and the presence or absence of associated ligamentous damage in type II distal clavicle fractures, a standard AP view and 20 degrees upshot or Zanca view with appropriate penetration and centering are indicated. Posterior displacement of type II distal clavicle fractures is best assessed with an axillary radiograph.

Articular surface fractures of the distal end of the clavicle are easily overlooked unless high-quality radiographs are obtained. A Zanca view with a 15-degree cephalic tilt and soft tissue technique can detect intra-articular fractures much better than standard radiographs can. A CT scan is indicated for more complex injuries or those in which definition of the fracture remains obscure despite standard radiographs ( Fig. 14.41 ).

Computed tomographic scan of a right clavicle fracture. The scan confirms the site of fracture at the distal end of the clavicle and identifies a previously unsuspected intra-articular extension of the distal clavicle fracture.

Fractures of the medial third

These fractures may be particularly difficult to detect by routine radiographs because of the overlap of ribs, vertebrae, and mediastinal shadows. One study showed that over 20% of medial-third fractures can be missed on plain radiographs. A high index of suspicion is appropriate, especially in high-energy injuries such as motor vehicle accidents. However, a cephalic tilt view of 40 to 45 degrees or a serendipity view often reveals the fracture, whether in a child or an adult. In children particularly, fractures of the medial end of the clavicle are often misdiagnosed as sternoclavicular dislocations when in fact they are usually epiphyseal injuries. As with distal clavicular fractures, CT scanning has become the standard of care in the management of these injuries due to the difficulty in obtaining clear plain radiographs (see Fig. 14.9 ).

Differential diagnosis

In adults, fractures of the shaft of the clavicle are not usually confused with any other diagnosis, although pathologic fractures are occasionally difficult to recognize as such. However, fractures of the distal or medial end of the clavicle can clinically appear to be complete acromioclavicular or sternoclavicular separations, although these injuries rarely cause confusion once a CT scan has been performed. In children, it can be easy to confuse injuries to the clavicle with other entities, including congenital disorders and other traumatic conditions.

Congenital pseudarthrosis

When recognized at birth or shortly thereafter, congenital pseudarthrosis may be confused with either cleidocranial dysostosis or a birth fracture, especially if some trauma has been associated with the delivery. However, birth fractures unite rapidly and leave no disability. The deformity of congenital pseudarthrosis can become more conspicuous as the child grows. Clinically, the lump is painless; the child usually has no history of injury, pain, or disability with this lesion. ^, The lump is invariably in the lateral portion of the middle third of the clavicle, and usually affects the right clavicle except in children with dextrocardia, in which case it can occur on the left side. ^, Bilateral congenital pseudarthrosis has been reported, particularly in the presence of bilateral cervical ribs. The cause of this entity is unclear. Although a family history is not typical, some reports have noted a familial incidence, thus raising the question of genetic transmission.

Although there may be a history of trauma with the birth, it is probably incidental; most investigators now agree that congenital pseudarthrosis is not a nonunion of normal bone after trauma. It is probable that abnormal intrauterine development plays the primary role in its appearance, and it has been suggested that pressure from the subclavian artery as it arches over the first rib and under the clavicle may be a primary factor in its development. ^, The cervical ribs can also displace the subclavian artery and cause pressure in the same area of the clavicle.

Radiographically, characteristic changes can be noted in congenital pseudarthrosis (see Fig. 14.39 ). The sternal fragment, which consists of the medial third of the clavicle, is larger and protrudes forward and upward, whereas the lateral half is situated below, points upward and backward, and ends in a bulbous mass at the pseudarthrosis site. Other identifying features are an increase in the deformity with age, the proximity of the bone ends to one another, and a large lump palpable clinically. These findings contrast quite markedly with cleidocranial dysostosis.

Cleidocranial dysostosis

Cleidocranial dysostosis is a hereditary abnormality of membranous bone, such as the skull, and the clavicle is the bone most commonly involved. The abnormality varies from a central defect in the clavicle to complete absence of the clavicle; the most common manifestation is absence of the distal portion of the clavicle. ^, Radiographically, it is distinguished from congenital pseudarthrosis by the larger gap between the bone ends and by the tapered ends of the clavicle rather than the larger bulbous ends. It is more clearly aplastic bone. In addition, multiple membranous bones are involved, and they can each have their own clinical manifestations. Some children have bossing or other skull defects, smallness of the facial bones, scoliosis, abnormal epiphyses of the hands or feet, and deficiencies of the pelvic ring. Usually, a familial history of bone disorders can be elicited. ^,

Sternoclavicular dislocation

Epiphyseal fractures of the medial end of the clavicle can mimic sternoclavicular separations in children because of the late closure of the sternal epiphysis. If it is important to distinguish between these two entities, CT scanning is the imaging study of choice.

Acromioclavicular separation

Fracture of the lateral aspect of the clavicle in children can also be identical to a complete acromioclavicular separation both clinically and radiographically. If plain radiography does not identify the small fracture fragment, a CT scan usually will. However, because the coracoclavicular ligaments remain attached to the periosteal tube in children and healing is uneventful, it is difficult to justify these more elaborate diagnostic modalities with increased radiation exposure and cost in children with this injury, who are typically treated nonoperatively in any event.

Nonunion

Although most clavicles do heal with nonoperative treatment, the incidence of nonunion in modern prospective studies is much higher than previously described ( Fig. 14.42 ). Nonunion of nonoperated shaft fractures had a reported incidence of 0.9% to 4%. ^{, ,} However, more recent research suggests that the actual nonunion rate is higher than previously thought, with an incidence of 15% to 25% for completely displaced midshaft fractures. ^, A review at one of our institutions showed a 10% nonunion rate of fractures that were treated nonoperatively. However, 40% of the fractures in this series were treated acutely with surgery, which means that it could be assumed that the more serious fractures were treated operatively and that this 10% nonunion rate was seen in less severe injuries. A systematic review also showed that the risk of nonunion was related to fracture displacement (relative risk = 2.3), fracture comminution (relative risk = 1.4), female gender (relative risk = 1.4), and advancing age as shown in Table 14.1 .

A midshaft atrophic nonunion of the clavicle following a sports-related injury 6 months previously in an otherwise healthy young female patient.

Most authors consider clavicular nonunion as failure to show clinical or radiographic progression of healing at 4 to 6 months postinjury, ^, although there is some temporal difference between atrophic and hypertrophic nonunion. Manske and Szabo reported that bone ends that were tapered, sclerotic, and atrophic at 16 weeks were unlikely to unite, whereas they classified other fractures as delayed union at the 16-week point as long as some potential for healing was present. ^,

Although nonunion of the clavicle is predominantly a problem after fracture in adults, it has been described in children ( Fig. 14.43 ). It should be remembered that apparent nonunion in a child may be congenital pseudarthrosis. Several factors appear to predispose to nonunion of the clavicle: inadequate immobilization, severity of the trauma, and associated injuries, especially ipsilateral rib fractures, refracture, location of the fracture (outer third), and degree of displacement (marked displacement).

This patient presented following a motor vehicle accident with an open fracture of the clavicle. It is typically the proximal fragment which penetrates the skin. This is an important consideration at the time of debridement, as the surgeon should focus on the proximal, as opposed to the distal, fragment for cleaning and debriding.

Predisposing factors

Refracture

A number of studies have identified refracture of a previously healed clavicle fracture as a factor contributing to the development of nonunion. In Wilkins and Johnston’s series, seven of 31 nonunions occurred in such patients. Although previously there appeared to be no relationship among the length of time between injuries, the age of the patient, the duration of immobilization of the original fracture, or the severity of the initial or subsequent traumatic injuries and the complication of nonunion after refracture, new information suggests that certain fracture patterns may predispose to repeat fracture and potential nonunion. It has been theorized that because the vascular anatomy of a fractured bone remains altered for a long period even after fracture union, reinjury might in some way prevent this altered blood supply from reacting to the new fracture. Additionally, the altered biomechanics of a malunited fracture, especially apex superior angulation, may predispose to repeated reinjury ( Fig. 14.44 , see also Fig. 14.3 ). ^,

Shoulder strength following clavicular malunion compared to the opposite side. The graph demonstrates significant decreases in objectively measured maximal and endurance strength following clavicular malunion. ER, External rotation; IR, internal rotation.

Refracture can also occur after primary operative fixation of displaced fractures. If the refracture is displaced, then operative repair, with spanning of the original fracture line, is usually indicated ( Fig. 14.45 ).

(A) This 45-year-old patient had a previous distal clavicular fracture fixation. He reinjured himself skiing by falling directly on the shoulder. A peri-implant fracture, medially, is seen. (B) Revision fixation was performed with lag screw fixation and anterior plating using a precontoured clavicular plate. Rapid union ensued. Most peri-implant fractures, if they are displaced, require operative intervention.

Primary open reduction

Earlier studies that associated primary open reduction of acute clavicular shaft fractures with an increased incidence of nonunion had a clear selection bias, in which only the more severe fractures received internal fixation. In addition, earlier methods of operative fixation were suboptimal at best ( Fig. 14.46 ). Rowe reported an incidence of nonunion of 0.8% in fractures treated nonoperatively, which rose to 3.7% in those treated operatively. Neer had a similar experience, with a nonunion rate of 0.1% in fractures treated nonoperatively and 4.6% when the initial fracture was treated surgically. Schwartz and Leixnering reported a nonunion rate of 13% in patients with clavicle fractures treated by primary open reduction, although they suggested that inadequate internal fixation might have played a prominent role in this high incidence. Poigenfurst and colleagues reported a complication rate of 10%, with four nonunions in 60 fresh clavicle fractures that were plated. Zenni and colleagues reported a series of 25 acute clavicle fractures treated by primary open reduction with IM pins or cerclage suture and bone grafting, all of which healed without complication. Modern randomized prospective series comparing nonoperative treatment to primary plate or nail fixation for completely displaced midshaft fractures of the clavicle have consistently shown a significant decrease in nonunion rate from 15% to 20% with nonoperative care to 1% to 3% with surgery.

Failure of fixation in a midshaft clavicle fracture.

One cannot overlook the fact that most of the surgical complications previously reported were related to poor fixation techniques, and it is not the concept of surgical treatment that is the problem, but rather the choice of fixation (see Fig. 14.46 ). Recent studies using precontoured plates or modern IM devices for the primary fixation of displaced midshaft clavicle fractures have consistently shown a very high union rate with a low serious adverse event rate, with the main reason for repeat intervention being simple hardware removal ( Fig. 14.47 ).

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related

Related posts:

Developmental anatomy of the shoulder Tendon tears in athletes: Pectoralis major, and latissimus dorsi and teres major General principles of shoulder stiffness Open management of traumatic disorders of the sternoclavicular joint: Indications, techniques, and outcomes Posterior instability: Open and bone augmentation surgery Opinion editorial—concavity compression

Stay updated, free articles. Join our Telegram channel

Join