Disturbances of the ossification

Among the diseases that affect ossification, a distinction is made between diseases that alter normal ossification and diseases that lead to excessive ossification. A typical disorder of ossification is achondroplasia, which leads to premature closure of the epiphyseal joints. The absence of cartilage in the long bones prevents the bone from growing in length due to the lack of cartilage cells.

However, the thickness growth of the bone is not impaired in achondroplasia, as perichondral growth does not require cartilage cells as a precursor. The tubular bones therefore grow predominantly in width in patients with achondroplasia. Since the skull bones are formed by desmal ossification, the growth of the skull is unaffected, so that the head reaches a normal size and appears too large compared to the extremities.

The vertebrae and ribs are also not affected by achondroplasia, so that those affected usually reach almost a normal sitting height. A pathological ossification is the so-called heterotopic ossification, where “heterotopic” means “occurring at a different location”. It therefore ossifies areas that should normally be connective tissue.

This heterotopic ossification often occurs after severe injuries. It is irrelevant here whether the injury was caused by an accident or an operation. The tissue damage stimulates the body to produce messenger substances that stimulate precursor cells of bone in the tissue to develop from cartilage to bone.

This process is usually noticed one to two weeks after an operation by pain and redness without any evidence of inflammation in the blood. After one month, the new bones can be seen in an X-ray. However, most bone formations in this way do not cause any complaints in the long term and are not noticed.

On the other hand, larger bones in particular can, by themselves, mechanically reduce the range of motion of joints considerably. Whether or not such excessive ossification occurs depends on the severity of the injury: Patients with multiple injuries are more prone to this than patients with simple fractures, patients with hip joint replacement more than those with shoulder operations. Infections and bruises also appear to increase the ossification.