Our bones provide structural support for our bodies; hence, they must be very strong. The lamellar bone, the base of the structure, consists of a collagen matrix incorporated with the mineral calcium phosphate, allowing it to be strong and hard without being too brittle. The cortical bone(compact bone), forms the outer layer while the cancellous bone(spongy or trabecular bone), forms the inner bone. In cortical bone, the lamellar bones are arranged concentrically around the Haversian systems(minute tubes that form a network in bone and contain blood vessels), while in cancellous bone, the lamellar bones are arranged as rods or plates. The medullary cavity(marrow cavity) contains bone marrow that either has blood stem cells(red bone marrow) or mesenchymal stem cells (yellow bone marrow).
There are many different ways to fracture a bone. Some types include compound fractures (when the bone breaks through your skin), hairline fractures (minute cracks on the bones), and greenstick fractures (small, slender cracks in the bone). Severe fractures may result in heavy bleeding and damage to the surrounding tissues and organs.
There are three general phases in the repair of the broken bone:
The first is the inflammatory phase, which occurs immediately after the fracture. When the bone is fractured, this disrupts the blood vessels, resulting in localized bleeding at the site of the fracture, otherwise known as a hematoma. Eventually, this bleeding results in a blood clot that joins the broken ends and sets the basis for further healing.
The second phase is the repair phase, which can be divided into two stages and starts within the first two weeks of the fracture. The first stage is fibrocartilaginous callus formation or soft callus formation. Platelets will go to the fracture site and signal for other mesenchymal cells and inflammatory cells to come, resulting in a collagen-rich fibrocartilaginous network and angiogenesis. This network, known as a soft callus, replaces the original blood clot at the fracture site. The second stage is the bony callus formation. This is when the soft callus undergoes endochondral ossification, where it gets calcified and replaced by immature bone, which becomes hard. (Sheen, J.R., Garla, V.V. and Mabrouk, A, 2023)
The final one is the remodeling phase, which starts around six weeks after the fracture. Bone remodeling happens throughout one’s life, whether a fracture occurs or not, and ensures that the bone remains strong. Osteoclasts resorb parts of the bone while osteoblasts form new bone, allowing the bone to mature and become stronger.
Casts and splints are used to hold the affected site in place so that these structures can form during the bone healing process. In some cases, rods, screws, and plates would be inserted into the bone. In more severe cases where the broken ends are too far apart for them to heal naturally, a bone graft is used to connect them. These bone grafts can be taken from one’s body; a donor or a synthetic one can be used.
Although most people’s bones are strong enough not to get easily fractured, certain factors and conditions can cause bones to be more fragile. Young children are more likely to get fractures as their bones are still developing, and in the elderly, the bone remodeling process becomes less effective and results in weaker bones. There is also a genetic condition known as Osteogenesis imperfecta, which results in the lack of suitable collagen for bone formation, resulting in weaker bones.
Reference list
Branch, N.S.C. and O. (2023). What Is Bone? [online] National Institute of Arthritis and Musculoskeletal and Skin Diseases. Available at: https://www.niams.nih.gov/health-topics/what-bone#:~:text=Bone%20is%20made%20of%20protein.
Lee, S. (2015). The bones. [online] Canadian Cancer Society. Available at: https://cancer.ca/en/cancer-information/cancer-types/bone-childhood/what-is-childhood-bone-cancer/the-bones#:~:text=The%20medullary%20cavity%20is%20the.
Physiopedia. (n.d.). Bone Cortical And Cancellous. [online] Available at: https://www.physio-pedia.com/Bone_Cortical_And_Cancellous.
Sheen, J.R., Garla, V.V. and Mabrouk, A. (2023). Fracture Healing Overview. [online] PubMed. Available at: https://www.ncbi.nlm.nih.gov/books/NBK551678/.
www.betterhealth.vic.gov.au. (n.d.). Bone fractures | betterhealth.vic.gov.au. [online] Available at: https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/bone-fractures#types-of-bone-fracture.
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