How Does Weight Bearing Influence The Bone Repair Process You Described Above

half dozen.5 Fractures: Os Repair

Learning Objectives

Past the end of this section, you lot will be able to:

Explain how bone repairs itself after a fracture

Differentiate amid the unlike types of fractures
Describe the steps involved in bone repair

A fracture is a broken bone. It will heal whether or not a physician resets (places) it in its anatomical position. If the bone is not reset correctly, the healing process will rebuild new bone just keep the bone in its plain-featured position.

When a cleaved bone is manipulated and fix into its natural position without surgery, the process is chosen a closed reduction. Open reduction requires surgery to expose the fracture and reset the bone. While some fractures can be minor, others are quite severe and result in grave complications. For case, a fractured diaphysis of the femur has the potential to release fatty globules into the bloodstream. These can become lodged in the capillary beds of the lungs, leading to respiratory distress and if not treated quickly, decease (this is called a pulmonary embolism).

Types of Fractures

Fractures are classified by their complexity, location, and other features (Effigy 6.5.1). Table 6.4 outlines mutual types of fractures. Some fractures may be described using more one term considering it may have the features of more than one type (e.g., an open transverse fracture).

In this illustration, each type of fracture is shown on the right femur from an anterior view. In the closed fracture, the femur is broken in the middle of the shaft with the upper and lower halves of the bone completely separated. However, the two halves of the bones are still aligned in that the broken edges are still facing each other. In an open fracture, the femur is broken in the middle of the shaft with the upper and lower halves of the bone completely separated. Unlike the closed fracture, in the open fracture, the two bone halves are misaligned. The lower half is turned laterally and it has protruded through the skin of the thigh. The broken ends no longer line up with each other. In a transverse fracture, the bone has a crack entirely through its width, however, the broken ends are not separated. The crack is perpendicular to the long axis of the bone. Arrows indicate that this is usually caused by compression of the bone in a superior-inferior direction. A spiral fracture travels diagonally through the diameter of the bone. In a comminuted fracture, the bone has several connecting cracks at its middle. It is possible that the bone could splinter into several small pieces at the site of the comminuted fracture. In an impacted fracture, the crack zig zags throughout the width of the bone like a lightning bolt. An arrow indicates that these are usually caused by an impact that pushes the femur up into the body. A greenstick fracture is a small crack that does not extend through the entire width of the bone. The oblique fracture shown here is travelling diagonally through the shaft of the femur at about a thirty degree angle. — **Figure 6.5.one – Types of Fractures:** Compare healthy bone with different types of fractures: (a) open fracture, (b) closed fracture, (c) oblique fracture, (d) comminuted fracture, (eastward) spiral fracture , (f) impacted fracture, (g) greenstick fracture, and (h) transverse fracture.

Types of Fractures (Table six.four)
Type of fracture	Description
Transverse	Occurs straight across the long centrality of the bone
Oblique	Occurs at an angle that is not 90 degrees
Spiral	Bone segments are pulled autonomously every bit a result of a twisting move
Comminuted	Several breaks upshot in many small pieces between two large segments
Impacted	One fragment is driven into the other, usually every bit a outcome of pinch
Greenstick	A partial fracture in which merely one side of the bone is broken, frequently occurs in the young

Blazon of Fracture	Description
Open (or compound)	A fracture in which at least one terminate of the broken bone tears through the peel; carries a high adventure of infection
Airtight (or elementary)	A fracture in which the skin remains intact

Bone Repair

Depending on the type, severity of the fracture and distance between bone fragments, bones may heal directly by edifice new os onto the fracture site (directly os healing or contact healing) or may heal in a procedure like endochondral os formation (indirect bone healing). Direct bone healing is essentially bone remodeling in which osteoblasts and osteoclasts unite broken structures. With indirect bone healing the process is more than complicated and like to endochondral bone germination in which broken basic class cartilaginous patches earlier regrowing new bone. In this process, blood released from broken or torn vessels in the periosteum, osteons, and/or medullary cavity clots into a fracture hematoma (Figure 6.5.2a). Though broken vessels promote an increase in nutrient delivery to the site of vessel injury (come across inflammation procedure in blood vessel chapter), the disruption of blood menses to the bone results in the death of bone cells effectually the fracture.

Within about 48 hours after the fracture, stalk cells from the endosteum of the bone differentiate into chondrocytes which then secrete a fibrocartilaginous matrix between the 2 ends of the broken os; gradually over several days to weeks, this matrix unites the opposite ends of the fracture into an internal callus (plural = calli or calluses). Additionally, the periosteal chondrocytes course and working with osteoblasts, create an external callus of cartilage and bone, respectively, around the outside of the break (Figure vi.5.iib). Together, these temporary soft calluses stabilize the fracture.

Over the next several weeks, osteoclasts resorb the expressionless bone while osteogenic cells become active, split, and differentiate into more than osteoblasts. The cartilage in the calluses is replaced by trabecular bone via endochondral ossification (destruction of cartilage and replacement by bone) (Figure 6.five.twoc). This new bony callus is also chosen the hard callus.

Over several more weeks or months, compact bone replaces spongy bone at the outer margins of the fracture and the bone is remodeled in response to strain (Figure half dozen.5.2d). Once healing and remodeling are complete a slight swelling may remain on the outer surface of the bone, but quite frequently, no external evidence of the fracture remains. This is why os is said to be a regenerative tissue that tin completely supervene upon itself without scars.

External Website

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Section Review

Fractures are classified by their complexity, location, and other features. Common types of fractures are transverse, oblique, spiral, comminuted, impacted, greenstick; they may also be classified equally open (or chemical compound), and closed (or unproblematic). During indirect bone healing, fracture repair begins with the formation of a hematoma, followed by cartilaginous internal and external calluses. Osteoclasts resorb dead bone, while osteoblasts create new bone that replaces the cartilage in the calluses. Calluses eventually unite, and os remodeling occurs to consummate the healing procedure.

Review Question

Critical Thinking Questions

1. What is the difference between closed reduction and open reduction? In what type of fracture would closed reduction most likely occur? In what type of fracture would open reduction about likely occur?

ii. In terms of origin, composition and cells involved, what are the differences between an internal callus and an external callus?

Glossary

airtight reduction: manual manipulation of a cleaved bone to set it into its natural position without surgery

external callus: collar of cartilage and bone that forms around the outside of a fracture

fracture: cleaved bone

fracture hematoma: blood clot that forms at the site of a broken bone due to cleaved blood vessels

internal callus: fibrocartilaginous matrix, in the endosteal region, between the ii ends of a broken bone

open reduction: surgical exposure of a bone to reset a fracture

Solutions

Answers for Critical Thinking Questions

In closed reduction, the broken ends of a fractured os can be reset without surgery. Open reduction requires surgery to return the broken ends of the bone to their correct anatomical position. A partial fracture would likely require closed reduction. A compound fracture would require open reduction.
The internal callus is produced by cells in the endosteum and is composed of a fibrocartilaginous matrix. The external callus is produced by cells in the periosteum and consists of hyaline cartilage and bone. Both types are formed by stem cells that differentiate into chondroblasts (chondrocytes), but in different locations.