epifysial

Epifysial, more commonly spelled epiphyseal in English, is an adjective relating to the epiphysis, the end portion of a long bone. In developing skeletons, each long bone has an epiphysis at its ends and a diaphysis along the shaft; between them lies the epiphyseal plate, also called the growth plate, a hyaline cartilage region that enables longitudinal bone growth during childhood and adolescence. In adults, the growth plate closes and is replaced by an epiphyseal line.

Growth and structure: The epiphyseal plate allows bones to lengthen through endochondral ossification. It comprises several zones, including reserve chondrocytes, proliferative chondrocytes, hypertrophic chondrocytes, and a calcification/ossification zone. Chondrocyte activity drives lengthening until the plate ossifies and the epiphysis fuses with the metaphysis.

Regulation and timing: Growth is controlled by hormones such as growth hormone and thyroid hormone, with sex steroids accelerating eventual plate closure during puberty. Estrogen and testosterone influence the timing of fusion, which varies by bone and individual.

Clinical relevance: Growth plate injuries are a common consideration in pediatric fractures. Disruption of the epiphyseal plate can impair normal growth and lead to limb length discrepancies or angular deformities. The Salter-Harris system classifies physeal fractures based on the involvement of the growth plate and surrounding bone.

Imaging and terminology: Open epiphyseal plates appear as radiolucent lines on X-ray in children; MRI can assess cartilage when necessary. The term epifysial is a variant spelling found in some texts, though epiphyseal is the standard English form.