The periphysis and its effect on the metaphysis: I. Definition and normal radiographic pattern.

The zone of Ranvier and the ring of LaCroix, together with the membranous bone bark they produce, are termed the periphysis in order to emphasize their normal effect (the metaphyseal collar) on the metaphysis of the infant and young child. In the first 7 years of life, the normal collar at the wrist is 1-3 mm wide. The step-off between the metaphyseal collar and the curvilinear metaphysis, at the margin of the periphysis, should not be mistaken for abuse fracture. The periphyseal bone bark may be radiologically visible at the edge of the physis at the distal ulna in 9% of infants and should not be mistaken for fracture or rickets.