which are now reﬂected from either the opposite
cortex (in cases treated without nailing) or the IMN (in cases
treated with nailing).
A fracture will appear as a break in
the otherwise continuous white line (representing the intact
bone cortex), and a second small white line, which is farther
away from the ﬁrst one, appears because of reﬂection of
waves from the IMN.
As a fracture heals, the periosteal
soft callus forms and grows in size and density with time and
bridges the fracture gap.
This periosteal callus appears as
various shades of gray depending on its density and can be
delineated from the surrounding soft tissues because of dif-
fering densities of the two.
The bridging of a fracture gap
by dense periosteal soft callus obscures the passages of waves
through the fracture and hence the visibility of intramedullary
nail decreases with time, until it completely disappears
because of complete coverage of the fracture gap by soft
During US therefore, a decrease in the visibility
of the IMN as compared with previous ultrasonographs and
an increase in the extent and density of periosteal soft callus
across fracture site as compared with previous US indicates