Can you describe the classification system of osteogenesis imperfecta?
It is complicated with at least 8 subtypes described, and many of the subtypes are difficult to distinguish from one another purely on radiography. It is worth remembering the first three types. Type I - most common and mildest; Type II - most severe leading to perinatal death; Type III - progressive deforming (see related article for more information).
What are the horizontal metaphyseal bands known as and what is their cause?
Zebra stipe sign is due to cyclical bisphosphonate therapy, e.g. pamidronate which results in accentuated mineralisation each time the drug is administered. As most growth is occurring around the knee, this is where the lines are most evident, and furthest appart.
Anterior view of both legs from hip to ankle demonstrates a number of features. Firstly there is evidence of a currently healing fracture of the proximal shaft of right femur, with two medullary pins. There is a degree of varus angulation. An old remodelled fracture of the left femur is also visible, with a minor degree of residual deformity.
The long bones are gracile in shape with bowing most marked of the right tibia, but seen in all bones. Multiple somewhat evenly spaced sclerotic bands are seen in the distal metaphyses of the femurs, and proximal and distal metaphyses of the tibias and fibulas.