PGE2 induces regional remodeling changes in haversian envelope: a histomorphometric study of fractured ribs in beagles.

A histomorphometric study was carried out in the region of healing defects in the ribs of Beagles. A transverse fracture was made in the left 9th and 10th ribs. Eleven Beagles received either ethanol vehicle (n = 6) or PGE2 orally (n = 5) for the 30 day period from surgery to time of necropsy. Double-pulsed labels were given with each of two fluochrome markers, calcein prior to surgical treatment and oxytetracycline hydrochloride prior to euthanasia. The objectives were to determine the effects of fracture on regional remodeling in the haversian envelope; to determine the effects of PGE2 on the regional remodeling changes in the haversian envelope; and to determine the systemic effects of PGE2 on remodeling changes of the contralateral matching sites. The remodeling changes after surgically induced fracture were relatively insignificant between the injured and uninjured sides in the non-treated dogs as well as in the PGE2 treated group. This may be attributable to the global effect of a fracture. However, there were significantly slower rates of mineral apposition (P less than 0.05) and a longer period for osteon formation time (P less than 0.05) on the injured side compared to the uninjured side of the PGE2 treated dogs. The remodeling activities were increased on both sides in the PGE2 treated dogs when compared to the non-treated ones with more remodeling sites per unit cortical area (P less than 0.01), and a higher turnover rate (shorter total remodeling period in days) with a faster resorption rate and a net increase in mineral apposition rates at the end of the experiment (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)