Changes

==Introduction==

==Introduction==

The '''physis''' consists of four zones:

The '''physis''' allows long bones to continue to grow in length after birth and consists of [[Bones - Anatomy & Physiology#Bone Growth|five zones]].

#'''Reserve zone''': adjacent to the epiphysis, where the chondrocytes divide and produce matrix

#'''Proliferating zone''': chondrocyte division produces organised columns extending away from the epiphysis. The true germinal cells of the physis are closest to the epiphysis.

#'''Hypertrophic zone''': chondrocytes increase in volume (80%) a,d ùatrox decreases and undergoes biochemical changes in preparation for calcification.

#'''Provisional calcification zone''': matrix becomes seeded with calcium phosphate.

The physis is weaker than the surrounding ligaments and bone, and therefore most '''susceptible to injury'''.

The physis is weaker than the surrounding ligaments and bone, and therefore most '''susceptible to injury'''.

The physis is weakest at the junction between the proliferative and hypertrophic zones, and the '''hypertrophic zone''' itself is structurally weak due to the large cell:matrix ratio.

The physis is weakest at the junction between the proliferative (aka maturation) and hypertrophic zones, and the '''hypertrophic zone''' itself is structurally weak due to the large cell:matrix ratio.

Physeal fractures involve the '''growth plate''' in all animals, and are classified according to the system described by Salter-Harris.

Physeal fractures involve the '''growth plate''' in all animals, and are classified according to the system described by Salter-Harris.

==Pathophysiology==

==Pathophysiology==

In most physeal fractures, both the hypertrophipc and germinal zones are involved and therefore all types have the potential to produce '''altered growth and limb deformities'''.

In most physeal fractures, both the hypertrophic and germinal zones are involved and therefore all types have the potential to produce '''altered growth and limb deformities'''.

'''Compression''' of the physis is more detrimental than shearing, and this is determined partly by the shape of the growth plate. For example, the distal ulnar physis can easily become compressed.

'''Compression''' of the physis is more detrimental than shearing, and this is determined partly by the shape of the growth plate. For example, the distal ulnar physis can easily become compressed.