Anatomy of the Clavicle Bone

The clavicle, also referred to as the collarbone, is an elongated, S-shaped bone that sits between the shoulder and sternum at the top of the ribcage.

The clavicle provides structural support between the shoulder and the rest of the skeleton and is the most frequently fractured bone in the human body.

Clavicle Bone Anatomy

The clavicle is considered a long bone, since it's longer than it is wide. Long bones have two main parts. The diaphysis is the central part of the bone and the epiphysis is the rounded end of the bone.

The clavicle can be divided into three parts:

• The sternal (medial) end, located at the front of the chest
• The shaft, the long part of the bone
• The acromial (lateral) end, located at the top of the shoulder

The clavicle joins the scapula, or shoulder blade, and sternum to form two joints on either end of the bone, which are:

• Acromioclavicular (AC) joint: The acromioclavicular joint forms between the acromion of the scapula and clavicle at the top of the shoulder, held together by the acromioclavicular ligament.
• Sternoclavicular joint: The sternoclavicular joint forms between the sternum and clavicle at the front of the chest and is supported by the costoclavicular ligament.
  

The clavicle and scapula together are collectively referred to as the pectoral girdle, or shoulder girdle.

Clavicle Bone Function

The clavicle connects the shoulder to the rest of the skeleton. Its positioning allows for increased range of motion of the shoulder away from the body and helps protect the arm by dispersing force transmitted through direct contact.

The clavicle has a small degree of movement in elevation and depression (upward and downward movement), protraction and retraction (forward and backward movement), and rotation.

Clavicle Muscle Attachments

The clavicle is attached to five different muscles: The subclavius, the trapezius, the anterior deltoid, the sternocleidomastoid, and the pectoralis major muscles.

The subclavius, which means “beneath the clavicle,” is the primary muscle that controls the clavicle. It originates at the first rib and attaches to the underside of the clavicle. When contracted, the subclavius, controlled by the subclavian nerve, causes the clavicle to depress, or move downwards.

The anterior deltoid, trapezius, sternocleidomastoid, and pectoralis major muscles all attach to the clavicle for support and cause a small degree of multidirectional movement as well.

Associated Conditions

The clavicle and associated joints can become damaged from injury or repetitive overuse of the shoulder. Common conditions associated with the clavicle include the following:

Clavicle Fracture (Broken Collarbone)

The relative size of the clavicle leaves it particularly susceptible to fracture. A broken collarbone or clavicle fracture can be caused by direct trauma such as during a fall landing on an outstretched hand or through a direct blow to the shoulder.

The middle third of the clavicle is most commonly fractured, accounting for about 80% of all cases of clavicle fractures.

Symptoms include collarbone pain or shoulder pain as well as pain and difficulty with moving the arm.

Acromioclavicular (AC) Joint Sprain or Separation

Trauma to the acromioclavicular joint, such as a direct blow to the front of the shoulder or falling and landing on an outstretched hand, can injure the ligaments holding the acromion and clavicle together.

This type of trauma can result in either an acromioclavicular joint sprain or separation of the joint. The injury causes pain where the clavicle meets the top of the shoulder.

Sternoclavicular Joint Sprain or Dislocation

A sternoclavicular joint injury can happen when an injury to the front of the shoulder causes the sternoclavicular (SC) joint to become dislocated. The SC joint is the joint between the clavicle and sternum. SC dislocation can cause pain and swelling around the injured area.

Distal Clavicle Osteolysis (Weightlifter’s Shoulder)

The end of the clavicle, or distal portion, which forms the acromioclavicular joint can become irritated and inflamed. Distal clavicle osteolysis, or bone degeneration, can easily occur at the end of the clavicle. This happens when excess stress and repetitive forces are placed on the small surface area of the acromioclavicular joint, especially with heavy lifting such as bench press or military press.

With distal clavicle osteolysis, bone breaks down faster than new bone cells form. Sharp pain commonly occurs with overhead and pushing movements of the arm and shoulder with a dull ache at rest.

Osteomyelitis

This is an infection of the bone that can cause a lump to form on the collarbone. Other symptoms of osteomyelitis can include:

• Bone pain
• Fever, chills, and sweating
• Feeling generally unwell
• An open wound that may ooze pus
  

Acromioclavicular (AC) Joint Arthritis

Aging and repetitive overuse of the shoulder can lead to degeneration of the cartilage and the development of arthritis within the acromioclavicular joint, causing inflammation within the shoulder and AC joint pain with arm movements.

Rehabilitation

Depending on the extent of your condition, rehabilitation for conditions associated with the clavicle or associated joints include the following:

Conservative Treatments

Many injuries to the clavicle will improve with conservative measures such as rest and physical therapy.

• Rest: Avoiding activities that cause increased symptoms for associated conditions of the clavicle is often necessary to allow time for inflammation to decrease and for injured joints to heal. Overhead movements and pulling, pushing, and lifting should be avoided.
• Immobilization: It may be necessary to wear a shoulder sling to protect your clavicle after an injury. For acromioclavicular and sternoclavicular joint sprains or dislocations, you may need to wear a shoulder sling for two to six weeks, depending on the severity of the injury. For a clavicle fracture, you may need to wear a shoulder sling for six to eight weeks until the bone heals.
• Physical therapy: Physical therapy can help rehabilitate the structures surrounding the clavicle after injury to decrease pain, restore range of motion and proper joint mobility, and strengthen the muscles around the shoulders and shoulder blades.

Medication

Pain can be treated with over-the-counter medications or medications prescribed by your healthcare provider:

• Pain relievers: Pain-relieving and anti-inflammatory medications can temporarily be used to manage symptoms after injury.
• Cortisone injections: Cortisone can be injected into the acromioclavicular joint to help decrease pain and inflammation.

Surgery

In some cases, surgery may be needed to correct a problem with the clavicle.

• Arthroscopic surgery: This is commonly performed for active patients with distal clavicular osteolysis who wish to resume weightlifting and athletic activities without pain. A distal clavicle resection is often performed, where a small portion of the end of the clavicle that has become inflamed is removed to increase the space in the acromioclavicular joint and reduce joint compression and degeneration. Arthroscopic surgery may also be performed to manage symptoms of acromioclavicular joint arthritis when other treatment methods have failed to relieve pain.
• Surgical Repair: Surgical repair may be necessary for a significant fracture of the clavicle. An open reduction internal fixation (ORIF) is most commonly performed, during which the broken pieces of the clavicle are repositioned back together, or reduced, and then held together with metal hardware, or internally fixated.

Summary

The clavicle is the long, s-shaped bone located between the shoulder and sternum above the ribcage. It is also known as the collarbone.

The clavicle connects your shoulder to the rest of your skeleton. It helps you move your shoulder away from your body. Clavicle breaks are common; trauma can also cause dislocation of the joints at either end of the clavicle. Other conditions that can affect the clavicle include osteolysis, osteomyelitis, and arthritis.