The clavicle, or collarbone, is a long bone extending between the manubrium of the sternum and the acromion of the scapula. Thin individuals can often feel it through the skin and it has three main functions: to attach the upper limb to the trunk as part of the 'shoulder girdle', to protect the underlying neurovascular structures supplying the upper limb and to transmit force from the upper limb to the axial skeleton. In this article, we shall look at the anatomy of the clavicle - its bony landmarks and clinical correlations.
The clavicle is a slender bone with an 'S' shape. When facing forward, the medial aspect is convex and the lateral aspect is concave. It can be divided into three parts - the sternal end, the shaft and the acromial end.
The sternal end contains a large facet for articulation with the manubrium of the sternum at the sternoclavicular joint. The inferior surface of the sternal end is marked by a rough oval depression for the costoclavicular ligament (a ligament of the SC joint).
The shaft of the clavicle serves as a point of origin and attachment for several muscles, including the deltoid, trapezius, subclavius, pectoralis major, sternocleidomastoid and sternohyoid.
The acromial end has a small facet for articulation with the acromion of the scapula at the acromioclavicular joint. It also serves as an attachment point for two ligaments - the conoid tubercle and the trapezoid line. The conoid tubercle provides the attachment point of the conoid ligament, the medial part of the coracoclavicular ligament, while the trapezoid line provides the attachment point of the trapezoid ligament, the lateral part of the coracoclavicular ligament. The coracoclavicular ligament is a very strong structure, effectively suspending the weight of the upper limb from the clavicle.
The clavicle acts to transmit forces from the upper limb to the axial skeleton. Given its relative size, this makes it more vulnerable to fracture, usually when a person falls onto the shoulder or an outstretched hand. Fractures can typically be divided into thirds: around 15% occur in the lateral third, 80% occur in the middle third and 5% occur in the medial third.
After a fracture, the lateral end of the clavicle is displaced inferiorly by the weight of the arm and displaced medially by the pectoralis major, while the medial end is pulled superiorly by the sternocleidomastoid muscle.
Management of a clavicular fracture can be conservative (e.g. sling immobilization) or operative (e.g. open reduction and internal fixation). The supraclavicular nerves lie in close proximity to the clavicle and can occasionally be sacrificed during a surgical repair, leading to a numb patch over the upper chest and shoulder.
When a clavicular fracture occurs, the lateral end of the clavicle is displaced inferiorly by the weight of the arm, and displaced medially by the pectoralis major. At the same time, the medial end is pulled superiorly as a result of the action of the sternocleidomastoid muscle.
The management of such fractures can vary depending on the situation. One option, known as conservative management, involves the use of a sling for immobilisation, while the other is an operative method which involves open reduction and internal fixation. When pursuing the second option, however, there is a potential risk that the supraclavicular nerves which lie in close proximity to the clavicle may be sacrificed, resulting in a numb patch over the upper chest and shoulder.
Conservative management usually involves the immobilisation of the shoulder and arm with a swathe bandage or brace for a period of four to six weeks. This means that the clavicle is held in place and is not allowed to move, thus allowing for proper healing. During this time, there is a risk of pain in the area due to decreased movement and activity. To reduce the risk of this, medications such as analgesics, anti-inflammatory agents, or muscle relaxants may be prescribed.
When it comes to operative management, open reduction and internal fixation is the most common procedure. It involves making an incision near the fracture and pushing the bones back into place. This is followed by the insertion of screws, plates, or other fixation devices into the clavicle for proper immobilisation. While this method is relatively straightforward and can provide faster results, it carries a higher risk of complications, such as infection or nerve damage.
One potential complication of this procedure is nerve damage. The supraclavicular nerve lies close to the clavicle, and during the process of open reduction and internal fixation, it can be damaged or sacrificed, leading to a numb patch over the upper chest and shoulder. This can lead to decreased sensation in the affected area, tingling, or a burning sensation. To reduce the risk of this, the surgeon performing the procedure must be experienced and thoroughly knowledgeable of the anatomy of the region.
Ultimately, the management of clavicular fractures depends on the severity of the injury and the preference of the patient. Conservative management is generally preferred for younger patients or those with mild fractures. On the other hand, operative management is usually recommended for those with more severe injuries and for older patients.
Regardless of the chosen management method, it is important to follow the advice of a healthcare professional to ensure proper healing and reduce the risk of complication. By taking proper precautions and following the necessary steps, it is possible to recover fully from a clavicular fracture.
