The medical term ossification refers to the growth of bone, also called bone formation. A synonym is ossification. It is the formation of bone tissue during the growth phase and in the callus (scar tissue to bridge the fracture gap) in secondary fracture healing in bone fractures.
What is ossification?
The medical term ossification refers to the growth of bone, also known as bone formation. Medical professionals distinguish between two types of bone formation. In desmal ossification, bone forms from connective tissue; in chondral ossification, bone forms from pre-existing cartilage. In a normal course, ossification is a natural process of bone formation that builds up the not yet fully formed skeleton, especially in childhood. In an abnormal course, there is increased bone formation. Bones form where they were not intended to.
Function and task
Bones develop either from connective tissue (desmal, cranial, clavicular) or from cartilage precursor (perichondral ossification). During the growth phase, bones form at the boundary between the metaphysis (length growth) and the epiphysis (growth area of the long bones). In adult humans, bones renew regularly through the activity of osteoblasts (bone-forming cells) and osteoclasts (bone-degrading cells). Ossification takes place due to an acquired (surgery, accident, injury) or congenital (autosomal inherited dwarfism) malformation of the skeleton due to impaired bone formation. Overused muscles and metabolic dysregulation can also be a cause. Sometimes ossification develops ideopathically (without a reason). It develops in the cartilaginous epiphyseal joints that form the center of enchondral ossification. The bones of the human skeleton are formed in different shapes. There are elongated tubular bones. Their head is called epiphysis, and the transition to the actual tubular form is called metaphysis. The tube as such is called diaphysis. Typical representatives of this type of bone are the upper arm bones (humerus) and the thigh bones (femur). The bones of the skull are flat. A third type of bone is formed by the rounded sesamoid bones (kneecap, hand bones). The air-filled bones are the bones of the facial skull, such as the sinuses. Each bone is surrounded by a fine periosteum. Inside is a dense bone structure (compacta, corticalis) that gives the bone strength. Uniformly aligned fibers reinforce the tissue. Bones are composed of organic collagen in the form of protein, bone and fat marrow, water, phosphate and calcium. Between the bone tissue are the osteoblasts and osteoclasts in the form of small cells. The osteoblasts are connected by fine channels and produce the bone substance. The osteoclasts, as counterparts, break down the bone again. The uniformly arranged lamellar bones are responsible for the typical bone structure. If a bone fracture is present, a meshwork bone with fibers without any structure is formed, which grows haphazardly. Only with the healing process does a structured, stable lamellar bone develop again. Desmal ossification develops from connective tissue formed by mesenchymal cells. As the bone grows, the cells lie close together and are well supplied with blood. The mesenchymal cells are stimulated to become osteoblasts, which produce new bone. More osteoblasts attach to this new, very small bone, which also form bone material, so that the bone grows appositionally by apposition. Skull bones typically form through this desmal process of bone growth. In chondral ossification, bones are created as cartilage in the first step. Only in the course of this indirect (enchondral) ossification does bone develop from the cartilage material. From about the age of 19, perichondral bone growth is complete. The cartilage cells become larger and calcify, and osteoblasts enter the process at this point, acting as anabolic cells to ensure bone growth.
Diseases and ailments
Medicine distinguishes between diseases that affect regular ossification and diseases that cause excessive ossification.In patients with achondroplasia (small bone growth), the long bones grow in width instead of length because the bone growth leads to premature closure of the epiphyseal joints. The cartilage cells become larger and calcify. Since there are no more cartilage cells in the affected bone, it cannot grow in length. Vertebrae, ribs, and cranial bones are not affected by achondroplasia, so these bones form normally but appear larger than they are when compared to the shortened extremities. In heterotopic ossification, areas ossify where connective tissue is normally found. The medical term heterotopic in this process stands for “occurring in a different location.” The tissue damage gives the body false signals and causes it to produce messenger substances that lead to ossification of cartilage tissue. Larger bones affected by excessive ossification cause discomfort in mechanical motion. The range of motion of the affected joints is considerably restricted. Smaller bone neoplasms usually do not cause discomfort because they are too minor. Bone fractures are the most common cause of this irregular bone growth. The more complicated the fractures, the more likely there is to be ossification. Patients with multiple injuries are more likely to have excessive ossification than patients with a simple injury. Patients with hip replacements, for example, are more often affected than people with shoulder surgery. Bruising and infection may favor the progression of excessive ossification. There is no known basic prevention. Orthopedic treatment starts with the axis deviations. Vitamin D deficiency in newborns severely impairs normal bone formation. Rickets is the most common ossification disorder in newborns. An undersupply of vitamin D automatically leads to calcium deficiency. Since bones are largely composed of calcium, this deficiency leads to impaired bone growth. Therefore, newborns are often given vitamin D.
