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==Introduction==
==Introduction==
The '''physis''' consists of four zones:
The [[Bones - Anatomy & Physiology#Bone Growth|'''physis''']] allows long bones to continue to grow in length after birth and consists of [[Bones - Anatomy & Physiology#Bone Growth|five zones]]. It is is weaker than the surrounding ligaments and bone, and therefore most '''susceptible to injury'''. 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.
#'''Provisional calcification zone''': matrix becomes seeded with calcium phosphate.
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.
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.
'''K-wire''' fixation is used in most cases in a variety of ways:
'''K-wire''' fixation is used in most cases in a variety of ways:
:'''rush pins''': theoretically allowed continued growth as the pins run along the endosteal surface of the cortex rather than penetrating it.
:'''rush pins''': theoretically allow continued growth as the pins run along the endosteal surface of the cortex rather than penetrating it.
:'''cross pins''': two wires are placed from the medial and lateral surface of the epiphysis to cross the fracture line, and then each other just proximal to the fracture line, before penetration the opposite cortex in the metaphysis. These prevent further growth unless they are removed.
:'''cross pins''': two wires are placed from the medial and lateral surface of the epiphysis to cross the fracture line, and then each other just proximal to the fracture line, before penetration the opposite cortex in the metaphysis. These prevent further growth unless they are removed.
:'''parallel wires''': theoretically will allow continued growth.
:'''parallel wires''': theoretically will allow continued growth.
These are '''intra-articular fractures''', and therefore repair should follow certain principles:
These are '''intra-articular fractures''', and therefore repair should follow certain principles:
:'''Anatomic reduction and alignement''': avoid steps in the joint surface and exposure of the fracture to synovial fluid
:'''Anatomic reduction and alignement''': avoid steps in the joint surface and exposure of the fracture to synovial fluid
:'''Rigid stabilisation with compression''': to achieve direct bone healing. A '''lag screw''' is the idea method of fixation, as it will compress and provide rigid stability. A second point of fixation such as a K-wire or a second screw will add rotational stability. Rigid fixation also allow '''early limb use''' and helps maintain joint function and range of motion
:'''Rigid stabilisation with compression''': to achieve direct bone healing. A '''lag screw''' is the ideal method of fixation, as it will compress and provide rigid stability. A second point of fixation such as a K-wire or a second screw will add rotational stability. Rigid fixation also allows '''early limb use''' and helps maintain joint function and range of motion.
:'''Post-operative management''': cold compresses, good analgesia, exercise restriction and physiotherapy
:'''Post-operative management''': cold compresses, good analgesia, exercise restriction and physiotherapy
:'''Avoid prolonged immobilisation''' of the joint.
:'''Avoid prolonged immobilisation''' of the joint.
Post-traumatic '''osteoarthritis''' is inevitable even with a perfect repair. Areas of damage tend to be replaced by biomechanically inferior fibrocartilage.
Post-traumatic '''[[osteoarthritis]]''' is inevitable even with a perfect repair. Areas of damage tend to be replaced by biomechanically inferior fibrocartilage.
==Prognosis==
In general, as these are young growing animals, '''fracture healing is rapid''' and often complete within '''3-4 weeks'''. Although removal of the implants when fracture healing is complete would facilitate further growth where the potential exists, in most cases they are '''left in-situ''' unless they are expected to cause problems.
In general, as these are young growing animals, '''fracture healing is rapid''' and often complete within '''3-4 weeks'''. Although removal of the implants when fracture healing is complete would facilitate further growth where the potential exists, in most cases they are '''left in-situ''' unless they are expected to cause problems.
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[[Category:Bones - Degenerative Pathology]]
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