17 Sternoclavicular and Acromioclavicular Dislocations

10.1055/b-0040-176958

17 Sternoclavicular and Acromioclavicular Dislocations

Raymond Pensy

Introduction

Sternoclavicular (SC) Dislocations

Dislocations of the SC joint are uncommon injuries which can result in significant complications. These injuries cross a wide range of age categories and injury mechanisms. In general, these dislocations occur either in an anterior or posterior direction, with the latter carrying more immediate risk and possibly warranting open treatment. Anterior dislocations carry less acute risk, but can result in significant functional impairment if recurrent instability ensues. Both injuries require vigilance, as the initial diagnosis is frequently delayed.

Acromioclavicular (AC) Dislocations

AC injuries are one of the most common injures in orthopaedics. These injuries are, by and large, treated nonoperatively. Injuries involving severe displacement, or comminution of the lateral clavicle, may require operative treatment to reduce the incidence of nonunion, symptomatic prominence, or in rare cases, stabilization of scapula–thoracic dislocation.

I. Preoperative Steps of Sternoclavicular Dislocations

History
1. Typically, these injuries result from a lateral compression force: hockey, wrestling, football, and other contact sports can cause a significant compressive vector which forces the SC joint to dislocate anteriorly; a force applied to the medial clavicle directed posteriorly can also result in posterior dislocation.
2. In high-energy trauma, T-bone motor vehicle collisions (MVCs) or roll-over accidents will similarly result in lateral compression of the chest, causing dislocation.
3. The initial amount of displacement, reflective of the severity and magnitude of the imparted force, will manifest as varying degrees of soft tissue injury and stripping, represented by varying degrees of swelling, ecchymosis, and deformity.
Physical examination
1. Swelling and deformity of the anterior, upper, and midline chest.
2. Pain with attempted range of motion of the affected shoulder.
3. Guarding against range of motion of the cervical spine, secondary to the injury to the origin of the sternal and clavicular heads of the sternocleidomastoids.
4. A “fullness” or difficulty in swallowing or speaking, which is in severely displaced posterior dislocations (dysphagia, dysphonia).
5. Rare neurologic compromise or swelling of the affected side, subsequent to neurologic compression and venous return.
6. Associated chest wall tenderness and contusion, secondary to the lateral compression injury.
7. Marked tenderness to palpation over the affected SC joint.
Anatomy
1. In the axial plane, the SC joint is sloped in an oblique manner, such that in a pure compressive force, the clavicle tends to dislocate posteriorly (▶ Fig. 17.1 ).
  
  Fig. 17.1 ‘*’ demonstrates the normal left sternoclavicular joint. Note the sloped nature of the joint in the axial plane. ‘+’ demonstrates the right posteriorly dislocated sternoclavicular joint.
2. The joint is synovial, with an intra-articular disc, and described as a saddle joint. It is relatively flat and nonconstrained, lending to intrinsic instability without the support of the robust ligamentous capsule.
3. The medial clavicular epiphysis is the last to close, generally in the mid-to-late 20s. Physeal fractures are therefore common in young adults.
4. The SC joint lies immediately upon the brachiocephalic veins on the right and left. These structures pass behind the clavicles, but are anterior to the respective first ribs (▶ Fig. 17.2 ).
  
  Fig. 17.2 (a, b) Effacement of the brachiocephalic vein by the posteriorly dislocated right sternoclavicular joint.
5. The relevant muscular anatomy includes the pectoralis major, sternocleidomastoids, and subclavius.
6. The SC joint itself is made of both extrinsic and intrinsic ligaments. The extrinsic ligaments include the costoclavicular and interclavicular ligaments, whereas the intrinsic ligaments are part of the anterior and posterior joint capsule. The posterior capsular ligaments represent the strongest and most important of the SC joint stabilizers.
7. The clavicle can rotate as much as 40 degrees along its axial plane throughout a full arc of shoulder rotation.
Imaging
1. Plain films of the chest demonstrate inadequate sensitivity for diagnosis. Asymmetry can, however, be recognized, and offers clues to the diagnosis.
2. Although dedicated Serendipity or Henig views have been described, with any degree of suspicion, a computed tomography (CT) scan should confirm diagnosis. Serendipity views—with the patient supine, an anteropoterior (AP) of the medial clavicle is obtained with a 40-degree cephalic tilt of the X-ray beam (▶ Fig. 17.3 ).
  
  Fig. 17.3 Serendipity view.
3. CT scan should be used as the first line of imaging, which permits determination of the direction of displacement, as well as injury or effacement of retrosternal structures.
4. Axial images will depict, in most cases, clear evidence of either anterior or posterior dislocation.
5. Intravenous (IV) contrast can be helpful in discerning injury or effacement to the retrosternal structures particularly that of the brachiocephalic vein (▶ Fig. 17.2 ).
6. Three-dimensional imaging can be helpful in establishing additional vertical displacement (▶ Fig. 17.4 ).
  
  Fig. 17.4 (a, b) Three-dimensional CT reconstruction of the right posteriorly dislocated sternoclavicular joint.
Classification
1. These injuries are broadly classified temporally as acute, subacute, or chronic. Chronic injuries may manifest as either of the following:
  1. Complete, irreducible dislocations.
  2. Recurrent instability, which in some cases can be voluntary or involuntary through muscle contraction, or shoulder range extremes.