The clavicle, commonly known as the collar bone, is a type of flat bone. Its one end forms a joint with the sternum while the other end forms a joint with the scapula or the shoulder blade. The clavicle, along with the sternum and the scapula, forms the pectoral girdle which gives attachment to multiple muscles controlling the movement of the shoulder and the elbow joints.
Many a times, people notice some abnormal growth on the collar bone. This growth can be a result of multiple causes. Some of them are:
- Poorly healed fracture of the clavicle: This is the commonest cause of a lump on the clavicle. There are times when a small lump may be the only sign of a fractured clavicle. It may be seen in little babies as a result of difficult labor. Or it can be a result of some vigorous exercise or a fall. Whatever be the reason, if the fractured pieces are not aligned properly, a lump may result at the fracture site.
- Lipoma: It is another common reason of a lump on the clavicle. This lump is soft in nature and is a result of deposition of fat tissue at any point on the clavicle.
- Osteoarthritis of acromio-clavicular joint: Osteoarthritis is a degenerative disease of the joints which is usually associated with pain and immobility of the joint. Osteoarthritis of the joint between the clavicle and the shoulder blade (acromio-clavicular joint) may give rise to bony protuberance over the surface of the clavicle, especially on the distal end. These bony protuberances are better known as clavicular spurs. They may impinge upon the free movement of the rotator cuff present between the clavicle and the shoulder. They prevent the free movement of the bursae and tendons and may result in restricted mobility and pain in the shoulder joint. As osteoarthritis is generally a disease of the elderly people, presence of bony spurs on the clavicle should alert the physician about this as a probable diagnosis.
- Osteoarthritis of the sterno-clavicular joint: This condition normally presents as a swelling on the medial end of the clavicle. Most of the patients improve with conservative therapy.
- Condensing osteitis of the clavicle: It is characterized by osteophyte formation at the infero-medial aspect of the clavicle associated with overlying soft tissue swelling. The condition is usually unilateral and is more common in middle-aged women. On x-ray, it can be differentiated from osteoarthritis on account of preservation of the joint space. The most common presenting feature of osteitis is pain which is increased on arm movement and tenderness.
- Postoperative sternoclavicular hypertrophy: There is a bony prominence on the medial side of the clavicle. This condition is commonly seen after homolateral neck dissection for any reason.
- Friedrich disease: It usually affects children and adolescents. There is sclerosis of the medial end of the clavicle.
- Tumors of the clavicle: Last but not the least, tumors of clavicle should also be kept in mind while dealing with bony spurs on the clavicular surface. Benign tumors of clavicle include giant cell tumor, osteochondromas and simple bone cyst. Malignant clavicular tumors include fibrosarcoma, myeloma and osteosarcoma. One must remember that primary bone tumors of clavicle are rare and are usually confined to medial one-third of the bone. As malignant tumors of clavicle are more common than benign ones, aggressively growing bony mass associated with symptoms should cause a suspicion of malignancy and the patient should undergo a MRI scan and biopsy to confirm the diagnosis.
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