The first detailed case report of a sternoclavicular (SC) joint injury appeared as early as 1843, and numerous related articles were published in the late nineteenth century. However, it was not until the 1920s and 1930s that such articles appeared in the U.S. literature.
Injuries to the SC joint are an uncommon problem, and many authors apologize for reporting only three or four cases. The rarity of these injuries and the lack of standardized methods for treating them, measuring outcomes, and reporting complications increase methodologic flaws in structured literature reviews and often preclude a meaningful meta-analysis. From a literature review and in our combined 50 years of clinical experience, anterior dislocations are best treated nonoperatively, and posterior dislocations, which have accounted for deaths, need to be promptly diagnosed and reduced. Anterior and posterior injuries in adults up to the age of 23 years are usually physeal injuries and heal without specific surgical treatment; however, true posterior dislocations do occur in the skeletally immature population and require similar treatment to their adult counterparts. Special radiographs are usually required to make the diagnosis. In our experience, high-definition computed tomography (CT) images with three-dimensional (3D) reconstructions are the gold standard for evaluating these injuries.
Surgical Anatomy
Because less than half of the medial clavicle articulates with the upper angle of the sternum, the SC joint has the distinction of having the least amount of bony stability of the major joints of the body.
The SC joint is a diarthrodial joint and is the only true articulation between the upper extremity and axial skeleton. The articular surface of the clavicle is much larger than that of the sternum, and both are covered with hyaline cartilage. Articular cartilage covers approximately 67% of the medial end of the clavicle, with coverage only on the anteroinferior aspect of the clavicle and on the underside of the clavicle at its articulation with the manubrial cartilage and first-rib costal cartilage ( Fig. 10-1 ). In 2.5% of patients, there is a small facet on the inferior aspect of the medial clavicle, which articulates with the superior aspect of the first rib at its synchondral junction with the sternum. The enlarged bulbous medial end of the clavicle is concave front to back and convex vertically and thus creates a saddle-type joint with the clavicular notch of the sternum. The clavicular notch of the sternum is curved, and the joint surfaces are not congruent.
Ligaments of the Sternoclavicular Joint
The SC joint has so much incongruity that integrity of the joint must come from its surrounding ligaments; that is, the intra-articular disk ligament, extra-articular costoclavicular ligament (rhomboid ligament), the capsular ligaments, and interclavicular (IC) ligament.
Intra-Articular Disk Ligament
The intra-articular disk ligament is a very dense, fibrous structure that arises from the synchondral junction of the first rib with the sternum and passes through the SC joint. This ligament divides the joint in the sagittal-oblique plane to create two separate joint spaces (medial or sternal and lateral). Anatomic studies have shown that the disk has a robust insertion on the posterosuperior aspect of the clavicle (see Fig. 10-1 ). Anteriorly and posteriorly, the disk blends into the fibers of the capsular ligaments; inferiorly, the disk has a less robust attachment ( Fig. 10-2 ). The diameter and thickness of the articular disk, on average, are 18 mm and 5.4 mm, respectfully. DePalma has shown that the disk is perforated only rarely; the perforation allows free communication between the two joint compartments (see Fig. 10-2 ).
The intra-articular disk acts as a checkrein against medial displacement of the medial clavicle. Histologic studies have demonstrated that the sternal side of the disk is composed of fibrocartilage and dense connective tissue, whereas the clavicular side of the disk is composed of only fibrocartilage. Therefore it is likely the clavicular side of the articular disk that has the function of resisting the compressive load to the clavicular surface.
Costoclavicular Ligament
The costoclavicular ligament, also called the rhomboid ligament , is comprised of an anterior and a posterior fasciculus is the largest ligament of the SC joint. The fibers of the anterior fasciculus arise from the anteromedial surface of the first rib and are directed upward and laterally. The fibers of the posterior fasciculus are shorter and arise lateral to the anterior fibers on the rib and are directed upward and medially. The costoclavicular ligament attaches superiorly to the margins of an impression on the inferior surface of the medial end of the clavicle, sometimes referred to as the rhomboid fossa . Cave showed, in a study of 153 clavicles, that the attachment point of the costoclavicular ligament to the inferior clavicle can be one of three types: (1) a depression, the rhomboid fossa (30%); (2) a flat surface (60%); or (3) an elevation or prominence (10%). More recently, Lee et al. observed that the costoclavicular ligament consistently attached to a palpable tubercle in all of the 11 cadaveric specimens studied, known as the costoclavicular tubercle , which likely corresponds to the “elevation” described by Cave in 1961. The anatomy of the costoclavicular ligament is in many ways similar to the structural configuration of the coracoclavicular ligament on the outer end of the clavicle ( Fig. 10-3 ).
The dimensions of the costoclavicular ligament have also been described. Cave reported that the average length is 1.3 cm, maximum width is 1.9 cm, and average thickness is 1.3 cm. Lee et al. found that on the clavicle, the center of the costoclavicular ligament is on an average 13.8 mm lateral to the inferior SC articular margin, while the most medial fibers are 10.3 mm lateral to the same point of reference. On the first rib cartilage, the center of the insertion was 14.8 mm lateral to the inferior manubrial articular cartilage margin, and the most medial fibers of the ligament were 8.3 mm.
The fibers of the anterior and posterior components cross and allow stability of the joint during rotation and elevation of the clavicle. Bearn has shown experimentally that the anterior fibers resist excessive upward rotation of the clavicle and that the posterior fibers resist excessive downward rotation. In addition, the anterior fibers resist lateral displacement and the posterior fibers resist medial displacement ( Fig. 10-4 ).
Interclavicular Ligament
The IC ligament connects the superomedial aspect of each clavicle with the capsular ligaments and the upper part of the sternum ( Fig. 10-5 ). Lee et al. found that the IC ligament was the “most readily identified of the SC-associated joint ligaments as a discrete ligament between the two clavicle heads.” The IC ligament attachment is located at the 1:30 o’clock position on the medial clavicle (i.e., right clavicle) (see Fig. 10-1 ).
The IC ligament assists the capsular ligaments in producing shoulder poise , that is, holding the shoulders up. The function of this ligament can be tested by putting a finger in the superior sternal notch; with elevation of the arm, the ligament is quite lax, but as soon as both arms hang at the sides, the ligament becomes tight. Spencer et al. have shown experimentally that the costoclavicular and IC ligaments have little effect on anterior or posterior translation of the SC joint. In an anatomic study, Tubbs et al. found that the IC ligament prevented superior displacement of the clavicle with shoulder adduction and depression.
Capsular Ligament
The capsular ligament covers the anterosuperior and posterior aspects of the joint and represents thickenings of the joint capsule (see Figs. 10-3 and 10-5 ). This structure is the strongest of all the SC ligaments and is the first line of defense against the upward displacement of the medial clavicle caused by a downward force on the superior aspect of the shoulder. We have observed that the clavicular attachment of the ligament is primarily on the epiphysis of the medial clavicle, with some secondary blending of the fibers into the metaphysis. In a more recent anatomic study, Lee et al. found that the anterior SC ligament is an oblique capsular thickening running from inferomedial to superolateral, attaching at the 10 o’clock position on the medial clavicle (i.e., right clavicle). In contrast, the posterior SC ligament appears as a diffuse thickening of the posterior joint capsule with no discrete ligament and a broad footprint on the manubrium and clavicle and attaches at the 4:30 o’clock position on the medial end of the right clavicle (see Fig. 10-1 ).
Although some authors report that the intra-articular disk ligament greatly assists the costoclavicular ligament in preventing upward displacement of the medial clavicle, Bearn has shown that the capsular ligament is the most important structure in preventing upward displacement of the medial clavicle (see Fig. 10-4 ). In an experimental postmortem study, he determined that after cutting the costoclavicular, intra-articular disk, and IC ligaments, they had no effect on clavicle poise. However, the division of the capsular ligament alone resulted in a downward depression of the distal end of the clavicle. Bearn’s findings have many clinical implications for the mechanisms of injury of the SC joint.
Spencer et al. performed a cadaveric study measuring the anterior and posterior translation of the SC joint in both intact specimens and following transection of randomly chosen ligaments about the SC joint. Cutting the posterior capsule resulted in a significant increase in both the anterior and posterior translation. Cutting the anterior capsule produced a significant increase in anterior translation. This study demonstrated that the posterior SC joint capsule is the most important structure for preventing both the anterior and posterior translation of the SC joint, with the anterior capsule acting as an important secondary stabilizer.
Subclavius Muscle
Reis et al. studied the function of the subclavius muscle and found that the basic function of this muscle was to stabilize the SC joint. They also reported that the subclavius could act as a substitute for the ligaments of the SC joint. We believe that this is an important study as it might explain why some people, after loss of the medial clavicle and the supporting SC ligaments, do not have instability of the medial end of the clavicle and provides further support to leave the subclavius muscle intact during operations on the SC joint ( Fig. 10-6 ).
Applied Surgical Anatomy
Surgeons planning an operative procedure on or near the SC joint should be knowledgeable regarding the vast array of anatomic structures immediately posterior to the SC joint. A curtain of muscles—the sternohyoid and sternothyroid—are located posterior to the SC joint and the medial third of the clavicle and block the view of vital structures . The sternohyoid muscle is a thin strap muscle that inserts onto the posterior aspect of the SC joint capsule and medial clavicle. The sternothyroid is located more posterior than the sternohyoid muscle and has a more inferior insertion on the posterior aspect of the sternum and costal cartilage. In addition, there is a fascial attachment between the right and left muscle bellies of both strap muscles with a midline raphe that inserts onto the posterior aspect of the manubrium ( Fig. 10-7 ).
Some of the vital mediastinal structures posterior to the SC joint include the innominate artery (also known as the brachiocephalic trunk), brachiocephalic vein, vagus nerve, phrenic nerve, internal jugular vein, trachea, and esophagus ( Fig. 10-8 ). Ponce et al. used contrast CT in 49 patients without identified injury to the neck or chest to define the proximity of these structures. The mean distance to the nearest anatomic structure deep to the clavicular region of the SC joint was 6.6 mm and was 12.5 mm for the sternal region. The brachiocephalic vein was the closest vital structure to the posterior aspect of both the right (average distance 6.0 ± 2.4 mm) and left (7.0 ± 2.5 mm) SC joint. As a percentage of all the nearest mediastinal structures, 26.0% were within 5 mm, 73.2% were within 10 mm, 87.2% were within 15 mm, and 92.9% were within 20 mm of the posterior SC joint. When operating in the region of the SC joint, it is critical to realize that an avascular plane (i.e., “safe zone”) exists anterior to the fascial layer and muscle bellies of the strap muscles ( Fig. 10-9 ).
Range of Motion of the Sternoclavicular Joint
The SC joint is freely movable and functions almost like a ball-and-socket joint in that the joint has motion in all planes, including rotation. The clavicle, and thus the SC joint in normal shoulder motion, is capable of 30 to 35 degrees of upward elevation, 35 degrees of combined forward and backward movement, and 45 to 50 degrees of rotation around its long axis ( Fig. 10-10 ). It is most likely to be the most frequently moved joint of the long bones in the body because almost any motion of the upper extremity is transferred proximally to the SC joint.
Epiphysis of the Medial Clavicle
Although the clavicle is the first long bone of the body to ossify (intrauterine week 5), the epiphysis at the medial end of the clavicle is the last of the long bones in the body to appear and the last epiphysis to close ( Fig. 10-11 ). The medial clavicular epiphysis does not ossify until the 18th to 20th year, and it fuses with the shaft of the clavicle around the 23rd to 25th year. In an extensive cadaveric study of the medial clavicular physis in 605 males and 254 females, Webb and Suchey reported that complete union might not occur until 31 years of age. This knowledge of the epiphysis is important because we believe that many of the so-called SC dislocations in the younger population are fractures through the physeal plate.
Classification of Sternoclavicular Joint Disorders
Classification Based on Etiology
Detailed classifications are confusing and difficult to remember, and the following simple classification and differential diagnosis of SC joint problems is suggested (traumatic versus atraumatic) ( Fig. 10-12 ). This section of the chapter focuses on traumatic injuries to the SC joint.
Traumatic Injury
Traumatic injuries can be further subclassified in terms of severity (sprain, subluxation, dislocation), direction (anterior or posterior), onset (acute or chronic), and age of the patient (skeletally immature or mature). An anterior dislocation is the most common type of SC joint dislocation; the medial end of the clavicle is displaced anteriorly or anterosuperiorly to the anterior margin of the sternum ( Fig. 10-13 ). Posterior SC joint dislocation is uncommon; the medial end of the clavicle is displaced posterior, posteroinferior, or posterosuperior with respect to the sternum.
Because the SC joint is so small and incongruous, one would believe that it would be the most commonly dislocated joint in the body. However, the ligamentous supporting structure is extremely strong and has evolved in such a manner that it is one of the least commonly dislocated joints in the body. Traumatic dislocation of the SC joint usually occurs only after tremendous force, either direct or indirect, has been applied to the shoulder.
Mechanism of Injury
The most common mechanism of injury to the SC joint is an indirect force applied to the anterolateral or posterolateral aspect of the shoulder. Mehta et al. reported that three of four posterior SC dislocations were produced by indirect force, and Heinig reported that indirect force was responsible for eight of nine cases of posterior SC dislocations. Indirect force was the most common mechanism of injury in our series of 185 patients as well. If the shoulder is compressed and rolled forward, an ipsilateral posterior dislocation results; if the shoulder is compressed and rolled backward, an ipsilateral anterior dislocation results ( Fig. 10-14 ). Posterior SC joint injuries can also occur when a significant force is applied directly to the SC joint or the anteromedial aspect of the clavicle from blunt trauma ( Box 10-1 ).
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An athlete lying supine on the ground is jumped on, and the knee of the jumper lands directly on the medial end of the clavicle.
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A kick is delivered to the front of the medial clavicle.
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A person is run over by a vehicle.
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A person is pinned between a vehicle and a wall.
Most Common Cause of Injury to the Sternoclavicular Joint
The most common cause of dislocation of the SC joint in adults is vehicular accidents; the second is an injury sustained during participation in sports. Omer, in his review of patients from 14 military hospitals, found 82 cases of SC joint dislocations. He reported that almost 80% of these occurred because of vehicular accidents (47%) and athletics (31%). In contrast, Tepolt et al. performed a recent meta-analysis of posterior SC joint injuries in the adolescent population (comprising both true dislocations and physeal injuries; mean age, 15.2 ± 1.8 years) and found that 71% of injuries occurred during participation in sports (football, rugby, and wrestling).
Traumatic Injury Subtypes
Sprain or Subluxation
Acute sprains of the SC joint can be classified as mild, moderate, or severe. In a mild sprain (type I), all the ligaments are intact, and the joint is stable. In a moderate sprain (type II), the capsular, intra-articular disk, and costoclavicular ligaments may be partially disrupted, resulting in a subluxation of the SC joint (anterior or posterior).
Acute and Recurrent Dislocation
A severe sprain (type III) involves complete disruption of the capsular and intra-articular ligaments, resulting in a dislocation of the SC joint (anterior or posterior). Occasionally, the costoclavicular ligament is intact but stretched out enough to allow joint dislocation. Isolated dislocations of the SC joint can also occur in skeletally immature patients (i.e., without associated physeal injury). If the supporting ligamentous structures fail to heal following joint reduction, mild-to-moderate force may produce recurrent instability; however, this is rare.
Injuries in the Skeletally Immature
Acute Physeal Fracture. Traditional teaching describes SC injuries in childhood and adolescence as physeal fractures with either anterior or posterior displacement of the medial clavicle, not dislocation of the joint. However, more recent literature has supported the finding that skeletally immature patients may in fact have isolated SC joint dislocation without associated physeal injury, with one such study reporting that both forms of SC injury occur with equal prevalence.
Chronic Physeal Fracture. Similar to SC dislocations, physeal fractures of the SC joint are at risk for being missed on initial presentation, and unfortunately, a delayed presentation is not uncommon. In the skeletally immature population, posterior SC joint injury may be missed in nearly 25% of patients on initial presentation. Delayed diagnosis affects treatment options because successful closed reduction after 48 hours is rarely reported in the literature.
Incidence of Injury to the Sternoclavicular Joint
The incidence of SC dislocation, based on the series of 1,603 injuries of the shoulder girdle reported by Cave et al., is 3% (specific incidences of dislocation in this study were glenohumeral, 85%; acromioclavicular [AC], 12%; and SC, 3%). In the series by Cave et al., and in our experience, dislocation of the SC joint is not as rare as posterior dislocation of the glenohumeral joint.
In a study of 3,451 injuries during alpine skiing, Kocher and Feagin showed that injuries involving the shoulder complex accounted for 39.1% of upper extremity injuries and 11.4% of all alpine skiing injuries. Of the 393 injuries involving the shoulder complex, SC separations accounted for 0.5%.
The largest published series from a single institution was reported by Nettles and Linscheid, who studied 60 patients with SC dislocations (57 anterior and 3 posterior). However, in our series of 185 traumatic SC injuries, 135 patients had anterior dislocation and 50 patients had posterior dislocation.
Orthopedic Injuries Associated With the Sternoclavicular Joint
Bilateral Dislocations
In 1896, Hotchkiss reported a bilateral traumatic dislocation of the SC joint. The senior author (C.A.R.) has treated four cases of bilateral SC dislocation. Bilateral traumatic anterior SC joint dislocations have also been reported following a motorcycle accident in a 28-year-old male. In 2010, Baumann et al. reported the first case of a bilateral traumatic posterior physeal fracture dislocation in a 15-year-old boy who fell forward on his chest while downhill skiing. Closed reduction under anesthesia with a clamp was initially successful; however, recurrent instability occurred just 2 days later as confirmed on repeat CT, necessitating open reduction and internal fixation with transosseous sutures.
Dislocations of Both Ends of the Clavicle
Dislocation of both ends of the clavicle is a rare, high-energy injury with fewer than 30 cases reported in the literature. In 1990, the senior author reported six patients who sustained a dislocation of both ends of the clavicle (anterior dislocation of the SC joint and posterior dislocation of the AC joint). Two patients who had fewer demands on the shoulder did well with only minor symptoms after nonoperative management. The other four patients had persistent symptoms that were localized to the AC joint. Each of these patients underwent reconstruction of the AC joint that resulted in painless full range of motion and return to normal activity.
Combined Sternoclavicular Joint Injury and Fractures of the Clavicle
Elliott reported on a tripartite injury about the clavicular region in which the patient sustained an anterior subluxation of the right SC joint, a type II injury to the right AC joint, and a fracture of the right midclavicle. Velutini and Tarazona reported a unusual case of posterior dislocation of the left medial clavicle, the first rib, and a section of the manubrium. Others have reported fracture of the clavicle associated with anterior SC joint subluxation, and injury to the long thoracic nerve. All of these combined injuries were associated with severe trauma to the shoulder region (e.g., the involved shoulder struck an immovable object or was severely compressed) ( Fig. 10-15 ).
Combined Sternoclavicular Joint Dislocation and Scapulothoracic Dissociation
Tsai et al. reported a patient with an SC dislocation associated with a scapulothoracic dissociation. The patient had also sustained a transection of the axillary artery, an avulsion of the median nerve, and a complete brachial plexopathy. Surgical management included vascular repair and an above-elbow amputation.
Signs and Symptoms of Injuries to the Sternoclavicular Joint
Traumatic Subluxation
In a mild sprain (type I injury), the patient complains of mild-to-moderate pain, particularly with movement of the upper extremity. The joint may be slightly swollen and tender to palpation, but instability is not noted. A moderate sprain or subluxation of the SC joint (type II injury) often results in swelling, and pain is marked, particularly with any movement of the arm. Anterior or posterior subluxation may not be obvious to the examiner when the injured joint is compared with the normal SC joint.
Signs Common to Anterior and Posterior Dislocations
The patient with an SC dislocation has severe pain that is increased with any movement of the arm, particularly when the shoulders are pressed together by a lateral force. The patient usually supports the injured arm across the trunk with the normal arm. The affected shoulder appears to be shortened and thrust forward when compared with the normal shoulder. The head may be tilted toward the side of the dislocated joint, and discomfort increases when the patient is placed in the supine position.
Signs and Symptoms of Anterior Dislocations
With an anterior dislocation, the medial end of the clavicle is visibly prominent anterior to the sternum and can be palpated anterior to the sternum. The clavicle may be fixed or quite mobile.
Signs and Symptoms of Posterior Dislocations
The patient with a posterior dislocation has more pain than a patient with an anterior dislocation. The anterosuperior fullness of the chest produced by the clavicle is less prominent and visible when compared with the normal side. The medial end of the clavicle is displaced posteriorly, and the corner of the sternum is more prominent but this is usually difficult to appreciate because of swelling. Venous congestion may be present in the neck or in the upper extremity. Symptoms can also include a dry, irritating cough and hoarseness. Breathing difficulties or shortness of breath may be secondary to a pneumothorax. Circulation to the ipsilateral arm may be decreased. The patient might complain of difficulty swallowing, a tight feeling in the throat, or a choking sensation. The distal neurologic examination may reveal diminished sensation or weakness secondary to brachial plexus compression. Complete nerve deficits suggest more severe injury patterns.
Radiographic Findings of Injury to the Sternoclavicular Joint
Anteroposterior Views
Occasionally, routine radiographs of the chest or SC joint suggest that something is wrong with one of the clavicles, because it appears to be displaced compared with the normal side ( Fig. 10-16 ). For example, a difference in the relative craniocaudal position of the medial clavicle greater than 50% of the width of the clavicular head suggests dislocation. It would be ideal to take a view at right angles to the anteroposterior (AP) plane, but because of the complex 3D anatomy, it is impossible to take a true 90-degree cephalic-to-caudal lateral view. Regardless of a clinical impression that suggests an anterior dislocation, a CT scan must be obtained to confirm one’s suspicions.
Heinig View
For the Heinig view, with the patient in a supine position, the x-ray tube is placed approximately 30 inches from the involved SC joint and the central ray is directed tangential to the joint and parallel to the opposite clavicle. The cassette is placed against the opposite shoulder and centered on the manubrium ( Fig. 10-17 ).
Hobbs View
For the Hobbs view, the patient is seated at the x-ray table, high enough to lean forward over the table. The cassette is on the table, and the lower anterior rib cage is against the cassette ( Fig. 10-18 ). The patient leans forward so that the base of the neck is almost parallel to the table. The flexed elbows straddle the cassette and support the head and neck. The x-ray source is above the nape of the neck, and the beam passes through the cervical spine to project the SC joints onto the cassette.
Serendipity View
The senior author accidentally found that the next best thing to having a true cephalocaudal lateral view of the SC joint was a 40-degree cephalic tilt view; hence, the serendipity view . The patient is positioned supine on the x-ray table. The tube is tilted at a 40-degree angle off the vertical, and is centered directly on the sternum ( Fig. 10-19 ).
Computed Tomography Scans
Lucet et al. used CT scans to evaluate the SC joints in 60 healthy subjects homogeneously distributed in terms of gender and decade of life from 20 to 80 years old. They reported that 98% of the subjects had at least one sign of abnormality, such as sclerosis, osteophytes, erosion, cysts, or joint space narrowing. The number of signs increased with age, and the number of signs in the clavicle was greater than those in the sternum. Similarly, Tuscano et al. obtained CT scans from 104 healthy subjects free from SC joint symptoms, and demonstrated that greater than 10% of patients show substantial asymmetry in the SC joints (i.e., SC joint space and distance between the manubrium and anterior margin of clavicular head), which may be interpreted as pathologic. These authors suggest exercising caution in attributing a disease state to asymmetry because of the frequency of this finding in the asymptomatic population. These findings become clinically useful in the setting of chronic subluxation or dislocation of the SC joint.
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) has been correlated with anatomic sections of SC joints, and is an excellent method for evaluating the anatomy of the SC joint and surrounding soft tissues in great detail. The sagittal plane is useful to assess the integrity of the costoclavicular ligament and the attachments of the intra-articular disk to the SC ligaments. This view is also helpful in assessing the location of the great vessels, trachea, and esophagus. T2-weighted images were superior to T1-weighted images in depicting the intra-articular disk. MR arthrography has the added advantage of delineating perforations in the intra-articular disk and more subtle injuries to the capsular ligaments. In children and young adults, MRI is especially helpful in distinguishing between a dislocation of the SC joint and a physeal injury ( Fig. 10-20 ). MRI is far superior to CT in its ability to detect bone marrow abnormalities, cartilage injury, effusions, and the surrounding soft tissues.
Ultrasound
The role of ultrasound is limited in comparison to CT and MRI except in the case of intraoperative evaluation, where it can be nearly impossible to precisely determine the adequacy of reduction. In this setting, the value of ultrasound is unsurpassed in accurately confirming whether a closed reduction has been successful. However, sonography is dependent on operator experience and knowledge of regional anatomy. In 2012, Sullivan et al. described the use of an O-arm intraoperative CT system to verify reduction in two cases of posterior SC joint dislocation. Lastly, duplex ultrasonography can be helpful for diagnosing thrombosis and vessel occlusion in cases where vascular insult is suspected. However, the role for advanced vascular imaging such as CT angiography cannot be understated and should be performed if vascular injury is present or suspected acutely to define the location and extent of vascular injury. CT angiography should also be considered for all chronic or late presentations of posterior SC joint injury.
Atraumatic Disorders of the Sternoclavicular Joint
Like other diarthrodial joints, the SC joint is also susceptible to the normal spectrum of inflammatory and degenerative diseases, as well as a number of other disorders that are specific to the SC joint (see Fig. 10-13 ). Such disorders can present either acutely or insidiously with localized pain, swelling, and even subluxation or enlargement of the joint. A simple algorithm is outlined that reviews the clinical approach to a patient who presents with such complaints without a history of trauma ( Fig. 10-21 ).
Spontaneous Subluxation and Dislocation
This condition typically occurs in women during their late teens or young adult life, and usually occurs in patients who have generalized ligament laxity of other joints. Although both SC joints can be affected, usually the dominant side is more symptomatic ( Fig. 10-22 ). As the patient raises the arm forward, the medial clavicle spontaneously displaces anteriorly and superiorly, and, when the arm is returned to the patient’s side, the medial clavicle is reduced. Atraumatic subluxation and dislocation are usually anterior, and are usually not associated with a great deal of pain. In some patients, the anterior subluxation of the SC joint is painful and is associated with mechanical symptoms (e.g., a snap or pop) as the arm is both elevated overhead and again lowered to the patient’s side. In middle-aged women, spontaneous anterior or anterosuperior subluxation can be associated with condensing osteitis of the clavicle.
Arthritis
Osteoarthritis
Osteoarthritis represents the most frequent cause of pain and swelling of the SC joint, and is characterized by narrowing of the joint space, osteophytes, subchondral sclerosis, and cysts on both sides of the joint. Because hyaline cartilage covers only the anteroinferior aspect of the medial clavicle, most of degenerative changes occur in this region of the joint. The sometimes discrete degenerative changes are best seen on CT scans ( Fig. 10-23 ). The swelling may be asymptomatic; however, a symptomatic joint is characteristically painful on abduction or forward elevation of the shoulder beyond the horizontal plane. Other findings on clinical examination include prominence at the medial end of the clavicle (caused by osteophytes), a fixed subluxation, or crepitus with range of motion. Most often, there is no history of previous injury to the joint. High-risk groups include postmenopausal women, patients with chronic SC joint instability, and manual laborers. Sternoclavicular joint arthritis and hypertrophy can also develop after radical neck surgery, particularly when the spinal accessory nerve is sacrificed. The mechanism for this is believed to be the result of chronic downward and forward position of the shoulder that results after denervation of the trapezius muscle. The incidence of SC joint arthritis in such circumstances is reported to be as high as 54%.
Sadr and Swann reported on 22 patients with postmenopausal arthritis involving the SC joint. The majority of cases involved the SC joint of the dominant arm, and were believed to be the result of normal degeneration of a frequently moved joint. The majority of patients are asymptomatic; a lump develops at the SC joint and, occasionally, a vague ache will develop when the joint is stressed. Patients have no previous history of injury or disease. Radiographs reveal sclerosis and enlargement of the medial end of the clavicle, reactive sclerosis of the sternum, and subluxation of the joint. The pathologic changes are those of degenerative arthritis.
In a recent report, Sternheim et al. identified a group of 25 female patients (mean age, 59 years; range, 50–71 years) with monoarticular arthritis of the SC joint that had a benign, self-limiting clinical course. The patients presented with complaints of pain (72%), local swelling (88%), and redness (8%) that progressed over a 4-week period. The physical examination revealed tenderness (84%), swelling (88%), and limited range of motion (16%), which persisted for a median of 5 months. All patients underwent blood work to rule out infection and inflammatory arthritis, which was normal. Plain radiographs revealed arthritic changes in only five patients (25%); however, of the six patients who underwent advanced imaging such as CT, five patients (83%) had joint space narrowing, sclerosis, and subchondral cysts. Pain resolved spontaneously in all patients, leaving only swelling in nine patients and tenderness in one patient. The authors described this clinical entity as transient sternoclavicular joint arthritis .
Rheumatoid Arthritis
Rheumatoid arthritis (RA) is a chronic, systemic inflammatory disorder of unclear etiology characterized by an erosive, symmetrical polyarthritis of synovial joints. RA is the most common form of inflammatory arthropathy; the estimated prevalence is 1% worldwide, with a female-to-male ratio of 3 : 1 that diminishes with age. Approximately 91% of patients with longstanding RA (>5 years’ duration) develop glenohumeral joint symptoms ; however, symptomatic SC joint involvement is less common, ranging from 19% to 30%. Like RA involvement of other joints, RA of the SC joint is characterized by osteopenia, soft tissue swelling and synovitis, and periarticular erosions ( Fig. 10-24 ).
Seronegative Spondyloarthropathies
These inflammatory arthropathies include a heterogeneous group of diseases characterized by axial spine involvement (e.g., ankylosing spondylitis), asymmetric peripheral arthritis (e.g., psoriatic arthritis), enthesopathy, inflammatory eye (e.g., Reiter syndrome), and bowel (e.g., colitic arthritis) disease occurring in the absence of serum rheumatoid factor and association with HLA-B27. These arthritides may also destroy articular cartilage but characteristically are more destructive toward collagen and fibrocartilage. Limited published studies have assessed the SC joint involvement in this group of arthropathies. Emery et al. reported involvement of the SC joint in only 2 of 52 (4%) patients with ankylosing spondylitis. In contrast, Taccari et al. found that the SC joint was clinically symptomatic in 5 of 10 patients (50%) with severe psoriatic arthritis.
Crystal Arthropathy
Crystal deposition disease has been described in multiple joints, including the SC joint. Identification of calcium pyrophosphate dihydrate (CPPD) crystals or monosodium urate crystals in synovial fluid, articular tissue, and rarely, the periarticular tissue, allows one to differentiate between crystal deposition disease and other inflammatory and degenerative arthritides. Examination of joint fluid with a polarizing light microscope reveals characteristic positive (pseudogout) or negative (gout) birefringent crystals. CPPD crystal deposition disease may be asymptomatic or may cause an acute, gout-like attack of inflammation and pain, referred to as pseudogout ( Fig. 10-25 ). In a recent study, Shirazian et al. retrospectively evaluated CT studies of the cervical spine in 209 patients that were free of SC joint symptoms; the overall prevalence of CPPD crystal deposition in the SC joint was 17.2% (36 of 209 patients). The rarest manifestation of CPPD deposition is tophaceous pseudogout, which is characterized by a mass containing CPPD crystals arising within or adjacent to the SC joint. Richman et al. have reported a case of tophaceous pseudogout extending posteriorly and inferiorly from the left SC joint, causing a mass effect on the adjacent brachiocephalic vein requiring excision.
Gout is a heterogeneous group of diseases resulting from monosodium urate crystal deposition in tissues or from supersaturation of uric acid in extracellular fluids. The initial episode of acute gout usually follows decades of asymptomatic hyperuricemia, and is predominantly a disease of adult men, with incidence peaking in the fifth decade of life. However, gout involving the SC joint has been described in limited reports and in less predictable clinical circumstances, including a case in an 18-year-old female.
Less Common Forms of Arthritis
Neuropathic arthropathy is a destructive arthritis characterized by fracture, subluxation, and dislocation of articular structures in the setting of neurologic damage to the involved joint. Syringomyelia is the most common cause of neuropathic arthropathy in the upper limb; only two cases of SC joint involvement have been reported in the literature. Other uncommon conditions that cause erosive changes to the medial clavicle include the systemic inflammatory syndrome of polymyalgia rheumatica, hemophilic pseudotumors, and hyperparathyroidism. Hemodialysis-related deposition of amyloid (β 2 -microglobulin) in the SC joint in long-term hemodialysis patients has been described. The clinical and imaging features may be similar to that of infection, warranting synovial biopsy and specific staining for the β 2 -microglobulin component of amyloid.
Infection
Spontaneous, unilateral, painful, and erythematous swelling of the SC joint with the appearance of joint subluxation should be considered an infectious etiology until proven otherwise. Such clinical presentations may be associated with acute, subacute, or chronic bacterial arthritis; however, it is important to recognize that such clinical signs and symptoms may be absent in the elderly or immunocompromised patient. Predisposing conditions include intravenous (IV) drug addiction, distant site infection and bacteremia, RA, diabetes mellitus, alcoholism, chronic diseases, and human immunodeficiency virus (HIV) infection. Sternoclavicular joint sepsis and osteomyelitis have also been reported in patients undergoing invasive procedures in the region of the SC joint including subclavian vein catheterization, coronary angiography, tracheostomy tube placement, and other head and neck surgical procedures of the larynx, pharynx, and esophagus. However, one must recognize that SC joint infection can occur in otherwise healthy adults without identifiable risk factors. Ancillary investigations such as CT are very helpful in making an early diagnosis of a septic SC joint ( Fig. 10-26 ); however, MRI has been shown to be more sensitive than CT in diagnosing septic arthritis and osteomyelitis of the SC joint ( Fig. 10-27 ). The typical findings on imaging include joint capsular distension of 10 mm or greater over both the clavicle and sternum, and adjacent bone marrow fluid signal on MRI. Regardless of the advanced imaging modality used, definitive diagnosis of SC joint infection requires image-guided aspiration or open biopsy followed by consultation with an infectious disease specialist to ensure that appropriate laboratory evaluation of the specimen is undertaken. The joint fluid should also be analyzed to rule out crystal-induced monoarthritis.
In 2004, Ross and Shamsuddin summarized the findings of 180 cases of septic SC joint arthritis published between 1970 and 2004. The mean age of the patients was 45 years (range, 11–88 years) and the majority were male (73%). Presenting symptoms included chest pain (78%) and shoulder pain (24%); painless swelling was the presenting complaint in only 4% of patients, including 50% of those diagnosed with tuberculous arthritis. Only 65% of the patients were febrile. Laboratory investigations revealed an elevated white blood cell count in only 56% of the patients (erythrocyte sedimentation rate and C-reactive protein values were not reported); bacteremia was demonstrated in 62% of the patients. When needle aspiration was performed, cultures were positive in 50 of 65 patients (77%). Eighty-seven of 102 (85%) initial plain radiographs were normal, whereas all 95 patients (100%) who underwent CT scans demonstrated at least one abnormality, including osteomyelitis (69%), chest wall abscess (57%), joint space widening (25%), mediastinitis (20%), and extrapleural abscess (1%). The most common risk factor was IV drug use (21%), followed by infection at a distant site (15%), diabetes mellitus (13%), trauma (12%), and infected central lines (9%). Staphylococcus aureus was responsible for 49% of the cases. Other common and uncommon pathogens that have been reported include Streptococcus pyogenes , methicillin-resistant S. aureus, Neisseria gonorrhoeae , and Salmonella . Atypical infections such as Pseudomonas aeruginosa and Candida albicans have been previously reported in IV drug users; however, in the review by Ross and Shamsuddin and in more recent reports, methicillin-sensitive S. aureus was still the most prevalent organism isolated in this patient group.
In developing countries, there have been reports of joint infection from Mycobacterium tuberculosis . Richter et al. reported on nine patients with infection of the SC joint secondary to tuberculosis. The average time from onset of the disease to diagnosis was 1.4 years. Higoumenakis has stated that unilateral enlargement of the SC joint is a diagnostic sign of congenital syphilis. The enlargement of the SC joint can be mistaken for an anterior dislocation. He reported the sign to be positive in 170 of 197 patients with congenital syphilis. The enlargement is attributed to hyperostosis of the medial aspect of the clavicle occurring in the SC joint of the dominant extremity, which reaches its permanent stage and size at puberty. Joint enlargement has also been seen in leprosy.
Disorders Specific to the Sternoclavicular Joint
Condensing Osteitis of the Medial Clavicle
This condition has also been termed hypertrophic osteitis. In 1974, Brower et al. first described the clinical entity of condensing osteitis of the medial clavicle in two young adult women. Since this original report, there have been fewer than 50 cases of condensing osteitis of the medial clavicle published in the English literature. This rare condition usually affects women in their fourth and fifth decades of life (range, 20–65 years) ; only three reports in men have been published. Most cases involve the medial end of one clavicle; only two cases of bilateral condensing osteitis have been reported. The etiology of condensing osteitis is unknown, and is likely to be multifactorial. Brower et al. hypothesized that the histopathologic changes of the medial clavicle (increased number and thickness of trabeculae combined with obliteration of marrow space) was probably a reaction to abnormal repetitive mechanical stress; however, only 2 of 11 cases (18%) reviewed by Outwater and Oates had a history of occupational or athletic-related recurrent stress. Other etiologies have been proposed and some investigators believe condensing osteitis represents low-grade osteonecrosis. In children, condensing osteitis most likely represents chronic recurrent multifocal osteomyelitis.
The clinical signs and symptoms consist of intermittent or constant pain of variable intensity that is localized to the medial clavicle that radiates to the supraclavicular fossa and ipsilateral anterior chest and shoulder. By the time patients first seek medical attention, the symptoms usually will have been present for months to years. There is often swelling and tenderness over the medial clavicle, and pain is reproduced with shoulder abduction or forward elevation; however, the swelling may be painless.
Radiographs show sclerosis and slight expansion of the inferior margin of the medial third of the clavicle. Occasionally, there is an inferior osteophyte present, but the joint space is preserved. The changes in the inferior-medial clavicle are best detected by CT (sclerosis and marrow cavity obliteration). Radionuclide studies reveal increased uptake of the isotope. The differential diagnosis includes Paget disease, SC hyperostosis, Friedrich disease, infection, Tietze syndrome, and osteoarthritis. Several authors have described the use of MRI as an adjunctive method for diagnosing this entity. In some cases, a biopsy may be required to differentiate this entity from primary or metastatic bone tumors.
Friedrich Disease
Aseptic osteonecrosis of the medial end of the clavicle, also known as Friedrich disease, was first described in 1924. Friedrich wrote that this disease shares some similar characteristics with Perthes disease, Köhler disease, Kienböck disease, and Preiser disease. Since this original report, there have been fewer than 25 cases of Friedrich disease published in the English literature; even fewer cases have been confirmed by histopathology with the pathognomonic finding of osteonecrosis (i.e., devitalized bone) surrounded by normal intact bone. Some authors believe it is difficult to differentiate cases of condensing osteitis from Friedrich disease, and postulate that both conditions may be one of the same that follow along a spectrum of disease.
The majority of reported cases are in female patients, both children and adults, although cases have been reported in men. It is usually unilateral; we are aware of only one bilateral case. This condition usually presents with swelling and tenderness over the medial end of the clavicle; however, some patients present with a painless swelling as their primary complaint. Similar to condensing osteitis, laboratory tests for inflammatory and rheumatologic markers are normal. Radiographs and CT reveal irregularity and bony deformity of the sternal end of the clavicle ; MRI may demonstrate necrotic islands of bone in the metaphysis. The symptoms are usually self-limiting, and complete resolution with remodeling of the medial end of the clavicle typically occurs over a period of 12 to 18 months.
Synovitis Acne Pustulosis Hyperostosis Osteitis (SAPHO) Syndrome
Starting in the 1960s, there have been reports of an association between cutaneous lesions and musculoskeletal manifestations such as peripheral synovitis or aseptic osteitis affecting the anterior chest wall. Since then, more than 50 designations have been used to describe these combinations, including one of the more common terms, sternocostoclavicular hyperostosis (SCCH). In 1987, a group of French researchers who suspected that these disorders might share common characteristics coined the acronym SAPHO. The complete syndrome described by the acronym is not common; the dermatologic manifestations are not frequently concomitant with the joint symptoms. In one of its rarest presentations, Tamai and Saotome described a patient with palmar and plantar lesions associated with bilateral osseous fusion of both the AC and SC joints.
SAPHO syndrome affects predominantly children and adults, and is not common in individuals older than 60 years; chronic recurrent multifocal osteomyelitis is considered the pediatric equivalent of SAPHO syndrome. There is no predilection for gender, except for the male predominance in patients with severe acne. The etiology remains unknown, and its consideration as a variant of the spondyloarthropathies is controversial and not definitively established. Others have theorized that SAPHO may be the result of an autoimmune process following long-term persistence of low-virulence organisms such as Propionibacterium acnes ; this pathogen has been identified in bone biopsies of the affected chest wall, and in spinal and peripheral lesions. Enthesitis can represent an initial symptom of SAPHO syndrome in some patients. Inflammatory enthesopathies can cause ossification, contributing to the formation of bone bridges; the painful swelling of the anterior chest wall is caused by hyperostosis and osteitis. The anterior chest wall (i.e., sterno-costo-clavicular junction) is involved in 60% to 95% of patients with SAPHO syndrome. The characteristic skin changes include severe acne and palmoplantaris pustulosis, which have been found in approximately 25% and 50% to 75% of patients with SAPHO, respectively ( Fig. 10-28 ). Such dermatologic changes may precede or follow the osteoarticular manifestations. The high variability in the clinical and imaging presentation depends on the stage of the lesions and the imaging method used.
