Figure 1.1
The Salter-Harris classification (Reprinted with permission from Rockwood and Wilkins’ Fractures in Children Lippincott Williams & Wilkins, 2010)
1.6 Physeal Injuries and Arrest
1.6.1 Epidemiology
Physeal injuries are common, representing 20–30% of childhood injuries, with the largest proportion of these being in the phalanges.
The incidence of growth arrest is approximately 1%.
1.6.2 Mechanism
The physis has only a limited ability to repair, depending on the level of cellular injury within the physis. Partial growth arrest can result from injuries that affect part of the physis but leave the uninjured physis to grow normally. The potential consequences of physeal growth disturbance include the development of angular deformity, limb length inequality and epiphyseal distortion.
The mechanisms include disruption to the physeal architecture or the formation of bony bridges or physeal bars. This occurs whenever a bridge of bone develops across a portion of physis, tethering the metaphysis and epiphysis. Physeal bars usually require preventative or corrective treatment to minimise long term sequelae.
Causes of growth disturbance, other than trauma include:
Infection.
Blount’s disease.
Irradiation.
Enchondroma.
1.6.3 Anatomy of the Physis
The physis is arranged in columns of cells or layers. The different layers are:
The reserve zone – this is the layer immediately adjacent to the epiphysis. Cells typically store lipids, glycogen and proteoglycan aggregates for later growth and matrix production. Due to the relatively low cellular activity the oxygen tension is typically low.
The proliferative zone – this has the highest rate of metabolic activity. It is the zone in which chondrocyte proliferation and stacking takes place, and accompanying the high level of metabolic activity an increased oxygen tension.
The hypertrophic zone – this zone is itself split into maturation, degeneration and provisional calcification zones.
Maturation zone: preparation of matrix for calcification and chondrocyte growth.Related posts:
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