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The osteochondral fracture occurs on the weight-bearing portion of the lateral condyle. Typically, the condyle will fracture (and the patella may dislocate) as a result of severe impaction from activities such as downhill skiing and parachuting. [1] Open reduction and internal fixation surgery is typically used to repair an osteochondral fracture.
The initiation of endochondral ossification starts by proliferation and condensation of mesenchymal cells in the area where the bone will eventually be formed. Subsequently, these mesenchymal progenitor cells differentiate into chondroblasts, which actively synthesize cartilage matrix components.
These cellular units will then develop into skeletal and other tissues, such as cartilage, tendon, ligament and muscle tissue. [ citation needed ] Osteoprogenitor cell condensations can aggregate, dissipate or condense depending on the signals present, however these still remain largely unknown.
Diagram showing stages of endochondral ossification. Endochondral ossification is the formation of long bones and other bones. This requires a hyaline cartilage precursor. There are two centers of ossification for endochondral ossification. The primary center. In long bones, bone tissue first appears in the diaphysis (middle of shaft).
An ossification center is a point where ossification of the hyaline cartilage begins. The first step in ossification is that the chondrocytes at this point become hypertrophic and arrange themselves in rows. [1] The matrix in which they are imbedded increases in quantity, so that the cells become further separated from each other.
The cartilage cells or chondrocytes are contained in cavities in the matrix, called cartilage lacunae; around these, the matrix is arranged in concentric lines as if it had been formed in successive portions around the cartilage cells. This constitutes the so-called capsule of the space.
In cartilage, the lacunae and hence, the chondrocytes, are isolated from each other. Materials picked up by osteocytes adjacent to blood vessels are distributed throughout the bone matrix via the canaliculi. Diameter of canaliculi in human bone is approximately 200 to 900 nm. [1]
Diagram of cartilage cells called chondroblasts. Date: 30 July 2014 (released by CRUK) Source: Original email from CRUK: Author: Cancer Research UK: Permission (Reusing this file) This image has been released as part of an open knowledge project by Cancer Research UK. If re-used, attribute to Cancer Research UK / Wikimedia Commons