The collarbone- Anatomy of the clavicle

Hello friend, It is the start of a brand new week, and with it comes a fresh subject that diverges significantly from what I have been writing about in the past. In today's post, I'm going to talk about the collarbone, which is an important component of the pectoral girdle. If you were to look at the characteristics of this bone, you would be amazed because it is such a fascinating structure in the body.

When viewed from a cephalad position, the clavicle is a long bone that has the shape of a sigmoid and has a curved surface along the middle end of the bone. Together with the scapula, it connects the axial and appendicular skeletons. All of these structures make up the pectoral girdle.
Even though they aren't as big as some of the other supporting structures in the body, the clavicular attachments are responsible for a lot of the function and range of motion in the upper extremities. They also protect the neurovascular structures that are in the back. Each individual component of this long bone serves a specific function in relation to the attachments it makes, which in turn influence the pectoral girdle's anatomy and physiology.

When the clavicle connects to the manubrial part of the sternum, it makes the sternoclavicular joint, which is in the middle. This joint is between the clavicle and the sternum. It is surrounded by a fibrous capsule and has a disc inside the joint. The interclavicular ligament, which connects the clavicles on the same side and the opposite side at the top, makes the body more stable.

The acromioclavicular ligament is formed laterally when the clavicle and acromion articulate. The surrounding area serves as an attachment point for the shoulder joint capsule. An intra-articular disc is present in this joint, just like in the SC joint, which is lined by fibrocartilage. The coracoacromial ligament (CA), the coracoclavicular ligament (CC), and the AC ligament are the three primary ligaments that support this joint.

The middle two-thirds and lateral third of the clavicle's real shaft are separated anatomically into two sections. Correct identification of the places where muscles are connected is done using these sites. The sternocleidomastoid (SCM) muscle and subclavius muscle both have attachment sites along the subclavian cleft in the middle two-thirds, which are superiorly and inferiorly positioned, respectively.

The pectoralis major muscle attaches to the anterior surface, and the sternohyoid muscle to the rear side. The SC joint is supported by the costal tuberosity, which is also located on the inferior side. It is where the costoclavicular tendon enters. The deltoid and trapezius muscles have receptors on the lateral third of the collarbone, which is where they are located anteriorly and laterally. Stability is provided between the collarbone and the coracoid process of the scapula inferiorly by the conoid and trapezoid components of the CC ligament.

One of the most frequently broken bones in the human body is the clavicle, which can be broken either directly or by collapsing onto an outstretched hand and transmitting energy. Surgery may be necessary depending on how much the fracture has displaced, and because each accident is unique, the best course of treatment must be chosen individually.

The Roles of Structure and Function

The clavicle, despite its diminutive size, not only enables the upper extremity to function to its full potential but also serves as a protective barrier for the region by reducing the amount of force that is transferred via direct contact. The location of the clavicle also maintains the extremity at a sufficient distance from the thorax, which enables the shoulder to have a range of motion (ROM) that is not restricted in any manner. Because of its strut-like mechanics, the scapula is able to slide effortlessly along the posterior wall, which is essential for complete mobility in the upper extremities. The anatomical position also safeguards neurovascular structures, such as the brachial plexus, subclavian artery, and subclavian vein, which, if disturbed, would significantly increase morbidity. These structures are located in the subclavian region.

Embryology of clavicle

Clavicle - Wikipedia. (2009, July 1). Clavicle - Wikipedia.

It is fascinating to note that the clavicle is the first bone to initiate ossification during the process of embryologic development. The clavicle is a derivation of the lateral mesoderm. During the ossification process, the medial and lateral extremities of the clavicle each go through their own unique set of steps. The development of the middle end takes place through a process known as endochondral ossification. Before mineralization and ossification, an endochondral ossification of a bone structure is preceded by the construction of a cartilaginous model by chondrocytes. This model is then followed by the endochondral ossification of the skeletal structure.

On the other hand, the lateral extremity develops through a process known as intramembranous ossification, which results in woven bone that is created directly without the involvement of cartilage. In either scenario, the structure undergoes remodeling in such a manner that lamellar bone is produced as a final product. In spite of the fact that it is one of the first bones to begin the process of ossification, it is also one of the last bones to finish this process, and the growth plates may not close until somewhere between the twentieth and twenty-fifth years of life.

The blood supply and the Lymphatics

Even though the clavicle is considered to be a long bone, it usually doesn't have a medullary cavity. This is in contrast to the other long bones in the body. According to the findings of studies, there is a blood supply to the bone structure coming from the periosteal arteries, but there is no primary nutrient artery (a.). It has been found that the suprascapular artery, the thoracoacromial artery, and the internal thoracic artery (also called the mammalian artery) all bring blood to the clavicle.

There are muscles that are connected to the collarbone.

The collarbone is attached to a number of different muscles, all of which need to be taken into account when thinking about its anatomy.

On the superior surface, the anterior deltoid muscle, which helps to flex the shoulder, originates on the anterior aspect, and one of the insertion locations for the trapezius muscle is situated on the posterior aspect. The majority of the work that is done to stabilize the scapula is done by the trapezius muscle.

inferior surface: the subclavius muscle is located in the subclavian groove of the collarbone. Its job is to draw the clavicle anteroinferiorly as well as compress the shoulder. Laterally, you'll find the coracoacromial ligament, which receives support from the coracoid bone that's situated below it. The conoid ligament is the part of the CA ligament that is located in the middle and it attaches onto the conoid tubercle. The trapezoid ligament is the part of the CA ligament that is located on the side and it inserts onto the trapezoid line.

The clavicular portion of the pectoralis major muscle originates anteriorly from the medial collarbone. This is the surface that faces the front of the chest. The movement of the humerus in the direction of bending, horizontal adduction, and inward rotation is aided by the clavicular head.

On the posterior surface, the trapezius muscle attaches in a posterosuperior position on the collarbone, as was previously stated. The clavicular head of the sternocleidomastoid muscle (also known as the SCM) is located in a comparable region, but it can be found along the middle third of the collarbone. When the SCM contracts on its own, it forces the cranium to rotate to the opposing side and bend laterally to the ipsilateral side. The cranium bends forward as a result of contractions in both SCM.

Along with fibers originating from the manubrium and the posterior sternoclavicular ligament, the sternohyoid muscle also has fibers that originate inferomedially along the posterior portion of the collarbone. The sternohyoid muscle contraction results in depression of the hyoid bone.

Clavicle - Wikipedia. (2009, July 1). Clavicle - Wikipedia.

Variations in Clavicles

When compared to other long bones, the clavicle has been found to display a greater variety of characteristics. Both thickness and length can change depending on a person's gender, with males typically possessing longer and more robust bone characteristics than females do. In addition to this, the bone in males has a greater degree of deformation than the bone in females. Studies conducted on cadavers also demonstrated that left clavicles were noticeably lengthier than their contralateral counterparts. Cleidocranial dysplasia is a genetic condition that is uncommon but clinically significant. It can manifest itself with missing or partially absent clavicles on both sides of the body. Other symptoms that may be present in this illness include dental abnormalities, delayed fontanel closure, and cranial sutures that have failed to join.

Fractures of the clavicle

Fractures are a type of disease that can happen to the clavicle. Fractures are usually caused by damage or other types of trauma. This can happen as a result of things like vehicle collisions or playing sports that involve physical contact, both of which put the clavicle in danger of being compressed by powerful impacts. A clavicle fracture can also be caused by a fall, especially if the person lands directly on their shoulder or collapses with their arm out in front of them. Clavicle fractures can also happen during childbirth if there are any complications that develop while the newborn is making their way through the delivery canal.

Some of the symptoms of a broken collarbone are as follows:

• Extreme discomfort caused by any movement of the arm or shoulder
• Bruising, discomfort, and swelling over the fractured region
• A sagging appearance of the shoulder in both the anterior and posterior directions

Treatment for clavicle fractures can involve either:
Technique that does not involve surgery, which is the method of choice in cases where the fractured clavicle can still be aligned appropriately. The fracture can mend naturally without the need for invasive procedures if a simple arm sling is used to keep the clavicle fragments in position while the fracture is healing.

surgically, which is the only option when the fragments of the shattered clavicle are not in the correct alignment. In this method of treatment, the broken fragments are secured to a metal frame using screws so that they remain in their proper positions while the fracture heals. Pins, which can be removed at a later time, are used to substitute the metal plate and fasteners that were used initially while the clavicle was healing.

References

• Clavicle - an overview | ScienceDirect Topics. n.d. Clavicle - an overview | ScienceDirect Topics. https://doi.org/10.1016/B978-0-323-29731-8.00008-8.

• Clavicle Fracture (Broken Collarbone) - OrthoInfo - AAOS. 2022, April 1. Clavicle Fracture (Broken Collarbone) - OrthoInfo - AAOS. https://www.orthoinfo.org/en/diseases--conditions/clavicle-fracture-broken-collarbone/.

• Clavicle. n.d. Clavicle: Anatomy and clinical notes | Kenhub. https://www.kenhub.com/en/library/anatomy/the-clavicle.

• “Clavicle - Wikipedia.” Clavicle - Wikipedia, 1 July 2009, en.wikipedia.org/wiki/Clavicle.

• Hyland, Scott, et al. “Anatomy, Shoulder and Upper Limb, Clavicle - StatPearls - NCBI Bookshelf.” Anatomy, Shoulder and Upper Limb, Clavicle - StatPearls - NCBI Bookshelf, 25 July 2022, www.ncbi.nlm.nih.gov/books/NBK525990/#:~:text=The%20clavicle%20is%20a%20sigmoid,structures%20forms%20the%20pectoral%20girdle.

• Clavicle - Structures, Muscle Attachments, 3D Model | AnatomyZone. n.d. AnatomyZone. https://anatomyzone.com/upper-limb/pectoral-girdle-and-shoulder/clavicle/.

• The Clavicle - Functions - Landmarks - Fractures - TeachMeAnatomy. n.d. The Clavicle - Functions - Landmarks - Fractures - TeachMeAnatomy. https://teachmeanatomy.info/upper-limb/bones/clavicle/.

• Clavicle. n.d. Physiopedia. https://www.physio-pedia.com/Clavicle.