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Bone fracture healing: how does it work?

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Let us start from the basics: what are bones made of? The main component of a bone is bone matrix, which is a mixture of a fibrous protein called collagen and an inorganic compound mostly made of calcium and phosphate. All bones have an outer surface called periosteum, a very thin membrane with nerves (that feel pain) and blood in it. The compact bone is the smooth and very hard part of the bone; it’s what we see when looking at the skeleton. The spongy bone is lighter than the compact bone, but still very strong. The inside of a bone is hollow,and filled with a jelly called bone marrow.

What’s the difference between kid bones and adult bones?

  • Your baby has tiny hands, little feet, small limbs and an overall tiny body. As he/she grows up, everything becomes gradually bigger, including his/her bones. An infant has about 300 bones at birth; while growing, they fuse together to form the 206 bones that an adult has. Some of your baby’s bones are totally made of a special, soft and flexible material called cartilage; some others are partly made of cartilage. Cartilage is replaced by hard bone matrix as the bones reach their full size. By the time he/she is about 25 years old, this process will be complete and the bones are as big and long as they will ever be. All together they form a skeleton that is light but also strong and very resistant.
  • Children have open growth plates (called epiphysis) located at the end of the long bones. This is the area where the bone grows. Injury to the growth place can cause limb length discrepancies or angular deformities.
  • Small children are more likely to have incomplete fractures, that go partially through the bone, because their soft bones – which are still growing – often bend or buckle instead of completely breaking.

How are bones classified?

The bones of a human skeleton are classified in two major types: the axial skeleton and the appendicular skeleton. Put simply, the axial skeleton includes the bones of the head and torso, and the appendicular skeleton means the appendage or limb bones. Axial skeleton has about 80 bones and appendicular skeleton has 126 bones. The main functions of the skeleton are to give shape to our body, provide attachment for muscles and produce red blood cells.
The longest, largest and hardest bone is the thigh bone, also known as Femur:

  • it is located between the knee and the hip;
  • it makes up one-fourth of an individual’s overall height;
  • it is a weight-bearing bone;
  • it is very light in weight, but it is considered stronger than concrete;
  • it is connected with the hip by a ball and socket joint that allows for freedom of movement.

How many types of bones are there?

There are 5 types of bones in the human body:

  • Long bones provide length to the body, support weight, facilitate movement and provide shock absorption (g. Femur, Humerus and Tibia).
  • Short bones provide support and stability with little movements (g. Carpals, Tarsal, Metacarpal, Metatarsal, Phalanges).
  • Flat bones provide protection to our vital organs and are a base for muscular attachment (g. Scapula, Sternum, Cranium, Pelvis and Ribs).
  • Irregular bones protect the internal organs and have a complex shape (g. Vertebrae, Sacrum, Mandible).
  • Sesamoid bones are short and irregular bones that provide protection to tendons (g. Patella “the knee cap”, Pisiform).

How do fractures heal?

Fractures heal at different rates, depending on the age of the child and type of fracture, but in general a child’s bone heals faster than an adult, due to some differences in the bone structure. In children the periosteum is thicker, stronger and more active to better supply oxygen and nutrients to the growing bones, and this helps rebuild the bone in case of fracture. Its inner part contains very vital cells able to produce new bone.