Measurement of 125I-labeled 4-iodoantipyrine (I-Ap) washout is a useful
method to study changes in bone blood flow because it can demonstrate fine
changes in flow, the tracer is not involved in tissue metabolism, and
several measurements can be made in the same subject. In the tibiae of
twenty-one adult dogs there was a significant (p smaller than 0.001)
correlation between I-Ap washout and the deposition of 85Sr, suggesting
that the uptake of 85Sr is related to blood flow. After fracture, blood
flow at the fracture site reached a maximum on the tenth day and then
progressively decreased, but was not back to control values at 112 days. In
the proximal part of the diaphysis, away from the fracture site, flow
reached a maximum at five to twenty-one days and then progressively
decreased to normal.