Sternoclavicular Joint

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SCJ Gray.png
Sternoclavicular Joint
Primary Type Saddle joint"Saddle joint" is not in the list (Synovial Joint, Cartilaginous Joint, Fibrous Joint, Compound Joint) of allowed values for the "Has joint type" property.
Secondary Type
Bones Manubrium, proximal clavicle"Proximal clavicle" is not in the list (Vertebra, Sacrum, Coccyx, Scapula, Clavicle, Humerus, Radius, Ulna, Scaphoid, Lunate, ...) of allowed values for the "Has joint bones" property., cartilage of first rib"Cartilage of first rib" is not in the list (Vertebra, Sacrum, Coccyx, Scapula, Clavicle, Humerus, Radius, Ulna, Scaphoid, Lunate, ...) of allowed values for the "Has joint bones" property.
Ligaments Sternoclavicular, costoclavicular, interclavicular ligs.
Muscles
Innervation Medial supraclavicular (C3-4) and subclavian (C5-6) nn.
Vasculature Internal thoracic and suprascapular aa. (branches of the subclavian a.)
ROM 35° in the horizontal and coronal planes, 70° range of motion anteroposteriorly, 50° of rotation along its long axis.
Volume
Conditions Sternoclavicular Joint Pain and Instability


The sternoclavicular joint (SCJ) is a diarthrodial, multi-axial saddle joint, and consists of the articulation between the manubrium sterni, the proximal clavicle, and the cartilage of the first rib. The articular surfaces are covered by hyaline cartilage. The joint has an intraarticular disc or meniscus that is made of fibrocartilage. It is attached to the joint capsule anteriorly and posteriorly, first costal cartilage inferiorly and the clavicle superiorly.

Ligaments

The joint has limited osseous restraint and is primarily stabilised by the following ligaments.

Ligament Description Function
Sternoclavicular ligament This consists of the anterior, posterior, superior, and inferior sternoclavicular ligaments. It attaches the manubrium sterni to the clavicle The posterior component, provides primary anteroposterior stabilisation of the SCJ. The anterior ligament also stabilises the SCJ and prohibits excessive superior displacement
Costoclavicular ligament Attaches the cartilage of the first rib to the clavicle. Twisted cord like appearance. Strongest of all ligaments. Mediates bilateral clavicle and anterior first rib stability. By anchoring the inferior surface of the sternal end of the clavicle to the first rib, it serves as the primary restraint for the SCJ. Anterior portion resists upward rotation and lateral clavicular movement. Posterior portion resists downward rotation and medial clavicular movement.
Interclavicular ligament Attaches the proximal end of one clavicle to the other. It also attaches to the superior manubrium sterni. Facilitates medial traction of both clavicles, resisting upward movement of the medial clavicle in response to axial load to the shoulder and distal clavicle.
Intra-articular disc ligament Dense and fibrous. Originates from the chondral joint of the first rib, passes vertically through the SCJ creating two distinct joint areas. Attachments on both the superior and posterior clavicular aspects. Integrates with the capsular ligament Resists medial displacement upon compressive forces applied to the clavicle
Capsular ligament (anterior and posterior) Thickenings around the joint capsule which enshrouds the external portion of the SCJ Resists upward movement of the medial clavicle in response to axial load placed on the distal clavicle. Anterior and posterior stability.

The subclavius muscle also functions to provide joint stability.

Biomechanics

The SCJ is only of five articulations that allow fluid shoulder girdle movement. It provides 35° range of motion for movement in the horizontal and coronal planes and 70° range of motion antero-posteriorly. It also provides 50° of rotation along its long axis. Movement of the shoulder girdle influences movement of the SCJ. With humeral elevation of up to 90°, there is 4° of clavicular elevation about the SCJ with every 10°of humeral elevation. Rigid fixation of the SCJ therefore results in inadequate mobility.

There are no muscles that immediately act on the SCJ. SCJ motion primarily depends on the motion of the scapula and shoulder girdle, including the clavicle. Muscles that insert on the clavicle that influence SCJ movement are the deltoid, pectoralis major, trapezius, and sternocleidomastoid muscles.

Motion Muscles Innervation
Elevation levator scapulae, upper trapezius, rhomboid major and minor muscles dorsal scapular nerve, C5 ventral ramus, C3-C4 ventral rami
Depression pectoralis minor, lower trapezius, serratus anterior and inferior muscles medial pectoral nerve, spinal accessory nerve, long thoracic nerve
Protraction pectoralis minor, serratus anterior muscles medial pectoral nerve, long thoracic nerve
Retraction middle trapezius, latissimus dorsi, rhomboid major and minor muscles spinal accessory nerve, thoracodorsal nerve, dorsal scapular nerve
Rotation via elevation of the glenoid cavity upper and lower trapezius, serratus anterior and inferior muscles suprascapular nerve, axillary nerve, long thoracic nerve
Rotation via depression of the glenoid cavity levator scapulae, latissimus dorsi, pectoralis minor, rhomboid major and minor muscles dorsal scapular nerve, thoracodorsal nerve, medial pectoral nerve, dorsal scapular nerve

Relations

There are several vital structures directly posterior to the SCJ. This includes the brachiocephalic trunk, internal jugular vein, common carotid artery, vagus nerve, phrenic nerve, trachea, and oesophagus. These structures may be as close as 1mm to the joint. They are susceptible to injury with posterior dislocation and surgical procedures.

SCJ relations.jpg

Variants

In a small portion of cases there is a facet that articulates with the first rib.

See Also

References

  • Epperson & Varacallo. Anatomy, Shoulder and Upper Limb, Sternoclavicular Joint. 2021. . PMID: 30725943.
  • Garcia et al.. Sternoclavicular Joint Instability: Symptoms, Diagnosis And Management. Orthopedic research and reviews 2020. 12:75-87. PMID: 32801951. DOI. Full Text.
  • Sewell et al.. Instability of the sternoclavicular joint: current concepts in classification, treatment and outcomes. The bone & joint journal 2013. 95-B:721-31. PMID: 23723264. DOI.