I thought bones were fully developed by age 18 for boys. But when I dislocated my collarbone where it attaches to the breast bone this year, the radiologist who read the X-rays and CT scans said my bone wasn’t fully “ossified”. They explained ossified means the bone is fully hardened. Am I unusual or just a late bloomer?

Bone growth is usually completed in girls by age 16 and in boys around age 18 to 20. But there are always people who complete the growth process later than expected. Males especially can continue gaining heighth into their early 20s.

One area of the body where bone growth and ossification (hardening) isn’t complete until age 18 to 20 is the end of the clavicle (collarbone). The growth plate here (called the physis) does not close with fusion of all layers of the clavicle until around age 23 to 25.

Dislocations of the sternoclavicular (SC) joint (where the collarbone attaches to the breastbone or sternum) are rare. The soft tissue structures in this area are very strong. It takes a great force to overcome resistance and stability provided by the shape, size, and strength of the ligaments.

Car accidents and sports injuries account for most of the reasons why the SC joint might dislocate. And even athletic events have to be pretty extreme to dislodge this joint. For example, dislocation can occur to a player lying on the field who is then subjected to the force of another player falling or jumping on his or her clavicle. Or taking a direct hit or kick to the clavicle can also dislodge the SC joint.

We don’t know your situation exactly but it sounds like you may be in that in-between age group for this particular injury. Your surgeon will be able to advise you regarding the best plan of care given your injury, chronological age, and bone age.