The radial head is a round, disc-shaped top to the radius bone (the smaller of two bones in the forearm). The radial head sits next to and articulates (moves) with the lower portion of the humerus (upper arm bone). The position of the radius is on the outside of the elbow (side away from the body).
The mechanism of injury for radial neck fractures is usually a fall on an outstretched arm. The force of the impact can be enough to snap the top of the radius right off. If the broken piece shifts away from the main bone, it is considered a displaced fracture. If the radial head moves off to the side and away from the shaft of the bone, it is a translation of the head in relation to the shaft.
If the radial head tips over and forms an angle with the radial shaft, it is considered both displaced and angulated. The amount of angulation will be an indication of severity of the fracture and also direct treatment. Angulation is easier to treat than translation. In younger children (up to age six), angulated radial neck fractures correct by themselves during the healing process.
General guidelines are: 1) less than 30 degrees of angulation can correct in children of all ages. 2) Displacement less than two millimeters does not require surgery. 3) More than 60 degrees of angulation must be treated surgically no matter how young the child is. 4) Angulation between 30 and 60 degrees is a gray area. There are nio clear guidelines. In general, the younger the child, the greater the chances for healing and correction.
How does this happen exactly? The remodeling process of bone in children is not completely understood. But because they are not skeletally mature (bone is still growing), the body has a way of producing bone and shaping it according to the needs of the child.
In the case of bone fracture, enough bone is laid down around the fracture site to form a callus. Often this is much more bone than is actually needed. Once the fracture site is stable, then the body goes about the business of remodeling the callus. In the end, there is usually just enough change in the bone to see on X-ray that there was a break but it can be very subtle.
Conservative care with cast immobilization is still needed to allow the healing process to complete itself uninterrupted. Outside forces and even the stress and load of normal movement could disrupt the healing process. It usually takes about four to six weeks for complete bone healing in children. Many will show a solid union in two to three weeks.