What is the metaphysis of long bones?

The metaphysis is a small portion that appears between the epiphysis and the diaphysis of the long bones of the body, both in large long bones, such as the femur, tibia, fibula, humerus, ulna, radius or some ribs, as well as in small long bones, such as the phalanges, metacarpals or metatarsals.

The metaphysis is very important during childhood and adolescence, because in this area the cartilage or growth plate that makes possible the bone elongation and the growth of the individual.

General characteristics

In a long bone three parts are distinguished, the epiphysis, the diaphysis and the metaphysis:

  • epiphysis: each of the flared ends on each side of a long bone.
  • Diaphysis: is the middle portion of the bone, longer and narrower than the epiphysis.
  • metaphysis: transition zone between the diaphysis and the epiphysis.

Anatomically, the metaphysis can be divided into three components based on the type of tissue present:

  • cartilaginous component: forms the epiphyseal plate, growth plate or physis.
  • bone component: is the metaphysis itself.
  • Fibrous component: surrounds the periphery of the growth plate.

In large long bones, two metaphyses appear, one distal and one proximal, for example in the femur, tibia or fibula. In small long bones, for example the phalanges, there is only one metaphysis.

Metaphyseal development and bone growth

The growth plate is a disc of hyaline cartilage in which the synchronization chondrogenesis or cartilage formation, with the osteogenesis or bone formation. Cartilage connects the epiphysis and diaphysis, making bone elongation and growth possible.

The growth plate can be found in children and adolescents, while in adults the cartilaginous tissue replaced by cancellous bone tissuepreventing the bone from continuing to grow longitudinally, which occurs around the age of 18 in women and 21 in men.

From this moment on, the area of ​​union between the epiphysis and the diaphysis is known as epiphyseal line.

Thus, if in children and adolescents the metaphysis allows bone growth, in adults its main function is load transfer and distribution from the joints to the diaphysis.

medical implications

Among other possible clinical implications, the metaphysis is involved in the following cases:

  • Due to its role in bone growth, the metaphysis has a rich blood supply, which makes it prone to Hematogenous spread of infectious osteomyelitis in children.
  • The metaphysis can be affected by cancer and tumors, such as osteosarcoma, chondrosarcoma, fibrosarcoma, osteoblastoma, or enchondroma, as well as other conditions such as fibrous dysplasia or various types of bone cysts, such as simple bone cyst and aneurysmal bone cyst.
  • The observation of hollow or worn metaphyses on X-ray radiographs is a frequently observed clinical symptom in children with rickets.
  • The lead poisoning It usually causes metaphysis with a dense appearance under X-rays due to the accumulation of this metal.
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