Dr. Ebraheim's animated educational video describing collagen types.
Approximately 20% of body proteins are made of collagen. There are approximately 20 typoes of collagen. Collagen is tough but flexible framework that mechanically taps the proteoglycans and cells. Collagen is made by fibroblasts.
Type I collagen
The bone is made of type I collagen and so is everything attached to the bone such as ligaments, tendons and menisci. If the cartilage is injured, it gets help from the bone and it heals by fibrocartilage which predominantly types I collagen. All of these structures are predominantly type I collagen. The annulus fibrosus of the intervertebral discs is also typed I collagen (it is attached to the bone). If we have a defect in type I collagen, we may get osteogenesis imperfecta, which means in a simplistic way, fragility bone fractures and a blue sclera. Ehlers danlos syndrome (loose joints, stretchy skin) may also be present. The majority of collagen in the body is type I (approximately 90%).
Type II collagen
You will find type II collagen in the nucleus pulposus of the discs and also in the hyaline cartilage of the joints. Type II collagen is very stable with a very long half-life (approximately 25 years). The cartilage cells do not make new hyaline cartilage. The hyaline cartilage components and framework are supposed to last for a very long time. A genetic defect in type II collagen will give you spondyloepiphyseal dysplasia (SED).
Type III collagen
Found in blood vessels and skin. God created the bone first, followed by cartilage, then followed by skin. The skin is type III collagen. Type III collagen is related to the development of Dupuytren's contracture. With tendon healing, the fibroblasts produce type III collagen in the first 1-7 days. The tissue then remodels and replaces the type III collagen with type I collagen up till 18 months.
Type X collagen
Type X collagen is produced by hypertrophic chondrocytes during endochondral ossification such as in:
•Fracture callus
•The growth plate
•Heterotopic Ossification.
It is associated with calcification of the cartilage (found near the calcified cartilage). Means calcified cartilage. When you have the hard, calcified cartilage, you get ten over ten (type X collagen). When there is a defect in collagen Type X, you will get a Schmid metaphyseal chondrodysplasia.
Type XI collagen
It is an adhesive that holds the collagen lattice or arrangement together.
If you have a fracture that is fixed by a compression plate, what type of collagen do you get?
Type I collagen because the fracture is healing by primary bone healing (There is no cartilage). Primary bone healing (elite bone healing) types I collagen. Bone is created first.
What if you use a rod?
You will get secondary bone healing because there is cartilage in the healing. If you have a cast, brace, external fixator or a bridge plate and not a compression plate, you will get secondary bone healing. You will get an abundance of cartilage and an abundance of callus. With an abundance of cartilage, you will get type II collagen earlier. When this cartilage is calcified or is mineralized, then you will get type X collagen and then the soft callus will become a harder callus. As the soft callus changes completely to a hard callus, you will get an abundance of type I collagen (this means bone).
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