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  Anatomy Basics »  Viewing AO Fractures Classification     [Image 1 of 24]  :: Jump To  
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AO Fractures Classification.jpg - nov 22, 2004
Basic * Regions and Bones of the BodyThis image presents the basic anatomic regions and bones of the human body. To see more details please look further for more images.

De Humani Corporis Fabrica * Title page from De Humani Corporis Fabrica
For a long period of time, the knowledge of anatomy was a hidden treasure waiting to be explored. The invention of printing in the 15th century made it possible to publish multiple copies of illustrated studies of anatomy, to teach anatomy and to eradicate previous errors. One of the most popular studies of the time was Andreas Vesalius’s De Humani Corporis Fabrica (1543), which marked a revolutionary step forward in anatomy. Vesalius was able to correct most errors in ancient writings and anatomic illustrations by his studies of dissection. De Humani Corporis Fabrica became the founding text of modern anatomy, and inspired many scientists, who compared their results with existing texts, corrected errors, and produced new texts with illustrations. The production of images based on dissection became a central component of scientific anatomy.

Development of Bones * Development of long bones
Image based on a template from the LifeART Collection, Lippincott Williams & Wilkins, ©1989- 2001
The arrows show the direction of endochondral ossification within a hyaline cartilage model, which provides a template of the shape of the bone to be formed. In the next step, the cartilage is replaced by bone. This type of ossification is found in long and short bones, but not in flat bones (which are formed by the intramembranous ossification in membranes of fibrous connective tissue).

Diaphysis * Diaphysis of a Long BoneDiaphysis is the shaft of long bones. It is located between both Metaphyses and consists of compact bone walls and an inner cavity (Cavitas medullaris), filled with the yellow (fatty) bone marrow. The external surface of the Diaphysis is covered by the Periosteum.

Osteology 1 * Frontal section through the head of Femur (thigh- bone)
Photography by Pekny P., ©2003

Two different bone components can be found (macroscopically) in human bones: one is dense in texture (Substantia compacta or compact bone tissue) found in the outer parts of bones (thick wall at the shaft of long bones, thin layer at the ends), the other consists of thin fibers and sheets of bone, (trabeculae) which form a reticular, sponge- like network at the ends of long bones and in vertebrae (Substantia spongiosa, trabecular or cancellous bone tissue).
Substantia compacta (cortical bone) is found primarily in the shafts of long bones and forms the outer shell around Substantia spongiosa (cancellous bone) at the end of the joints. The inner parts of the head are filled with spongy bone tissue.

Image: Classification of fractures:
The first step in the therapy of every patient is the accurate diagnosis. The diagnosis is bound to a special classification (for example the international classification of disease or ICD). To bring a clinical example, we will take a closer look on the international classification of fractures, based on the anatomic location and the morphological characteristic (severity) of a fracture. It is also called the AO- classification after the founding swiss group Arbeitsgemeinschaft fur Osteosynthesefragen.
The AO- coding of fractures is an alpha- numeric system, which describes the location of the fracture with first two numbers, followed by a letter and two numbers, which describe the morphological characteristic of the fracture:

Location: The first number describes the bone (see the next image), for example:
1- Humerus
2- Radius/ Ulna
3- Femur
4- Tibia/ Fibula
5- Vertebral column
6- Pelvis
7- Hand
8- Foot

The second number describes the fracture's location more specific by dividing the long bones into three (or four) segments:
1- The proximal segment of a long bone
2- The diaphyseal segment of a long bone
3- The distal segment of a long bone
4- The malleolar segment of Tibia/ Fibula

Morphology: The letter, which follows the first two numbers, describes the morphological characteristic of a fracture:
The diaphyseal fracture characteristics depend on the amount of fragments and on the possibility to achieve a contact of the major fragments after the reposition.
A- Single fragment/ simple fracture
B- More fragments, but contact of all fragments after reposition is possible to achieve
C- More than three fragments, contact of all fragments after reposition is not possible to achieve.
Page last updated on nov 23, 2004