Sternoclavicular JointEdit
The sternoclavicular joint (SCJ) is the articulation where the medial end of the clavicle meets the upper part of the sternum, typically near the manubrium and the first costal cartilage. It is a rare but functionally pivotal joint of the shoulder girdle, forming a primary link between the axial skeleton and the upper limb. The joint is a diarthrosis equipped with an articular disc that subdivides the capsule into two synovial cavities, allowing coordinated movement of the clavicle relative to the sternum. Stability derives from a combination of robust ligaments, capsule structure, and muscular attachments surrounding the joint. clavicle sternum articular disc diarthrosis
The SCJ enables movements essential for efficient upper limb function, including elevation and depression, protraction and retraction, and axial rotation of the clavicle as the arm moves through various ranges of motion. Because of its central position and its role in transmitting forces from the arm to the trunk, the SCJ is both highly integrated with surrounding structures and vulnerable to injury when subjected to significant forces. synovial cavity shoulder girdle
Anatomy
Articulation and disc
The SCJ is formed by the medial end of the clavicle and the clavicular notch of the manubrium, with an additional contact surface provided by the first costal cartilage. A fibrocartilaginous articular disc sits between the articulating surfaces, dividing the joint capsule into two synovial compartments. This arrangement helps absorb forces and increases the joint’s stability during shoulder movement. manubrium costoclavicular ligament
Capsule and ligaments
The joint capsule surrounds the SCJ and is reinforced by several key ligaments: - anterior sternoclavicular ligament - posterior sternoclavicular ligament - interclavicular ligament, running between the two clavicles across the superior chest - costoclavicular ligament, which anchors the clavicle to the first rib and adjacent structures These ligaments together limit extreme translations and rotations of the clavicle while allowing the necessary range of motion for arm movement. The capsule and ligaments are further supported by nearby musculature, including tendinous fibers from the sternocleidomastoid and subclavius muscles, which contribute to dynamic stability. anterior sternoclavicular ligament posterior sternoclavicular ligament interclavicular ligament costoclavicular ligament sternocleidomastoid subclavius
Blood supply and innervation
Vascular supply to the SCJ originates from branches of the subclavian and thoracic arteries, distributed around the perijoint tissues. Innervation comes from regional nerves in the area, enabling proprioceptive input and protective reflexes during shoulder movement. subclavian artery thoracic arteries
Function and biomechanics
The SCJ functions as a pivotal link in the shoulder girdle, permitting clavicular motion that accompanies arm elevation and rotation. The joint’s unique combination of disc and ligamentous support allows the clavicle to rotate, tilt, and translate in concert with scapulothoracic motion, facilitating a wide range of arm positions. While the SCJ can move in multiple planes, its intact ligaments constrain excessive movement to protect the mediastinal structures that lie posterior to the joint. This balance between mobility and stability is essential for activities ranging from daily tasks to athletic endeavors. scapulothoracic motion shoulder girdle rotations (anatomy)
Clinical significance
Injuries
Dislocations of the SCJ are uncommon but can be serious. Anterior dislocations are more frequent and often managed conservatively, whereas posterior dislocations pose a risk to mediastinal structures such as major vessels and the trachea and require urgent evaluation and often reduction. Imaging (including computed tomography) is critical in assessing the extent and direction of displacement. dislocation posterior sternoclavicular dislocation anterior sternoclavicular dislocation computed tomography
Fractures involving the SCJ are relatively rare but can occur with high-energy trauma. Treatment depends on the injury pattern and stability, with management ranging from immobilization to surgical stabilization in selected cases. clavicle fracture proximal clavicle fracture
Degenerative and inflammatory conditions
Osteoarthritis of the SCJ can cause pain and limited motion, particularly in older individuals or those with repetitive stress to the joint. Management includes activity modification, physical therapy, and, in some cases, surgical intervention. osteoarthritis joint degeneration
Infections or inflammatory processes affecting the SCJ are uncommon but clinically important due to potential spread from adjacent areas or hematogenous sources. Diagnosis relies on clinical assessment, imaging, and laboratory studies, with treatment guided by the underlying cause. osteomyelitis arthritis
Controversies and debates
In clinical practice, several aspects of SCJ management are debated among experts. For acute posterior dislocations, there is ongoing discussion about the urgency and method of reduction, balancing the need for rapid decompression of mediastinal structures against the risks of anesthesia and hardware-related complications. Some clinicians advocate immediate closed reduction under imaging guidance, while others favor staged approaches in stable patients with careful monitoring. Decisions about surgical reconstruction after recurrent instability or post-traumatic arthritis vary, with options including tendon graft reconstructions, allograft procedures, and, in certain cases, joint fusion. These choices depend on patient factors, activity level, and the presence of comorbidities, and they reflect broader considerations in orthopedic trauma and shoulder reconstruction rather than a one-size-fits-all solution. posterior sternoclavicular dislocation tendon graft reconstructive surgery
In the broader context of the shoulder region, debates over imaging strategies, such as when to use CT versus MRI, revolve around sensitivity for occult injuries and the balance of radiation exposure with diagnostic yield. Evidence-based guidance emphasizes tailored imaging based on the mechanism of injury and clinical suspicion. magnetic resonance imaging computed tomography shoulder imaging