How does bone fracture?
What is a fracture?
A fracture is a disruption of the structural integrity of a bone, resulting in a crack or "break." Thus, a "fracture" and a "break" are one and the same. Bones can fracture in different ways and for different reasons. In addition, fractures that occur in children can be quite different than those in adults. To understand how a bone fractures and the different types of fractures, it is important to know what bone is.
What is bone?
Bone is a living organ that includes cells (osteoblasts, osteoclasts, and osteocytes, as well as marrow components that make blood cells), collagen, and mineral. A simple way of understanding bone is to compare it to reinforced concrete. The collagen is a protein that is made into long strands and acts as "rebar" in reinforced concrete. The mineral is the concrete around the rebar. Bone can only have a certain amount of mineral around the collagen. Too little mineral throughout the bones in the body is referred to as osteoporosis.
The cells within the bone help create and remodel the bone. Osteoblasts make new bone. Osteoclasts remove bone. Osteocytes live within the lamellar bone and allow minerals to be deposited and removed as needed by the body. Balanced activity by both osteoblasts and osteoclasts is required for healthy bone.
What are the different types of bone?
While the molecular structure of bone is constant, it can be constructed by the body in different ways to provide different support functions. We often refer to three types of bone microscopically:
Cortical: The thick, hard outside of a bone. Microscopically, this is primarily "lamellar" bone.
Cancellous: The porous insides of a bone usually near the ends where the bone broadens out, called the metaphysis. The porous area is made up of spicules of bone (called trabeculae). Microscopically, these are also primarily lamellar bone.
Woven: Woven bone is always pathologic. It is a healing state of bone when there is poorly developed structure. Fractures begin to heal with woven bone, which is eventually remodeled into either cortical or cancellous bone.
What are different types of fractures?
When you discuss fractures, you will hear terms such as "comminuted," "open," "compound," and "compression." These have particular meanings and some terms are gradually fading from use. For instance, a "compound" fracture is one in which the bone has communication to the outside environment through a laceration of some sort. It is at much higher risk of developing infection and thus the treatment is usually more aggressive than for a closed fracture. The term is antiquated and currently these fractures are referred to as "open."
Fractures are named or described by their particular characteristics and where they occur in the bone. Thus, multiple names may be included, such as "an open, comminuted, fracture of the tibial diaphysis."
1. Simple: only one crack across the bone. May be complete or incomplete/
2. Comminuted: Multiple pieces of bone. Generally related to high energy injuries such as falls from heights or motor vehicle accidents.
3. Transverse: Perpendicular to the longitudinal axis of the bone.
4. Oblique: Angled t o the longitudinal axis of the bone.
5. Compression: Occurs in bones that are composed primarily of cancellous bone (the porous insides of the bones near the metaphyses and in the vertebral bodies). The small pillars inside the cancellous bone, called "trebeculae," collapse.
6. Buckle or Torus fracture: This is a partial failure of bone usually at the metaphysis which results in a cumpling of the cortex. These are usually stable fractures.
7. Stress: Bones microscopic cracks every day. Osteoblasts and osteoclasts repair the bone before there is time for the crack to progress.A stress fracture occurs when repeated injury occurs to the bone and there isn't enough time for the bone to be repaired.
8: Plastic deformation: This occurs in younger children that have particularly porous cortical bone. Instead of a catastrophic failure of the bone across the diaphysis, multiple little cracks occur in the cortex and the bone deforms like a piece of plastic.
9. Pathologic fracture: These are fractures that occur through abnormal bone. Tumor or osteoporosis makes the bone weak and increases the likelihood of a fracture.
So how does it actually happen?
Earlier we described bone as similar to reinforced concrete. Reinforced concrete is very strong in compression. That is why most buildings are built with pillars and structures that bear weight. Like concrete, bone fails in tension. When stressed, the bone begins to bend, creating a tension side and a compression side. The tension side fails first, and the bone is literally pulled apart.
Steven & Alexandra Cohen Children's Medical Center of NY
- Steven and Alexandra Cohen Children\'s Medical Center
A non-profit hospital that is a leader in pediatric care and the only level 1 pediatric trauma center on Long Island.
The Pediatric Orthopaedic Society of North America
- The Pediatric Orthopaedic Society of North America - POSNA
The largest orthopaedic society dedicated to the treatment of children with bone and joint problems.