155- How to explain the radiological abnormalities in rickets?
The earliest radiologic feature in rickets is appearance of indistinct margins and
fraying of metaphysis. This is due to impingement of metaphysis along the
longitudinal axis by proliferating hypertrophic chondrocytes. The unrestricted
proliferation of hypertrophic chondrocytes results in expansion of growth plate
which is visualized as increased distance between epiphysis and metaphysis.
Later, weight bearing on unmineralized osteoid at metaphysis leads to splaying
and cupping of metaphysis. These alterations in growth plate (physis) and
metaphysis clinically manifest as widening of end of long bones, typically at
wrist. The changes in the diaphysis and epiphysis reflect poor mineralization
due to low calcium-phosphorus solubility product.- What is pseudo-fracture?
Pseudo-fractures or Looser’s zone is visualized as a thin transverse band of
rarefaction oriented perpendicular to the long-axis of bone. They are charac-
teristic of rickets/osteomalacia; however, they can also be seen in Paget’s dis-
ease and osteogenesis imperfecta. Looser’s zone occurs due to mechanical
stress of arterial pulsations on poorly mineralized bone and represents corti-
cal stress fractures, which are filled with poorly mineralized callus, osteoid,
and fibrous tissue. These lesions heal with optimal therapy of underlying
disease.- What are the differences between true fracture and pseudo-fracture?
The differences between true fracture and pseudo-fractures are summarized in
the table given below.Parameters True fracture Pseudo-fracture
History of trauma Usually present Absent
Symmetry Usually unilateral Bilateral and symmetrical
Sites Any Inner margin of femoral neck
Axillary margin of scapula
Pubic and ischial rami
Ribs
Involvement of bone Through and through Incomplete
Direction Can be oblique/
perpendicularPerpendicular to the long axis of boneVisible callus (on
X-ray)Present Absent5 Rickets–Osteomalacia