Radioprotectant combinations spare radiation-induced damage to the physis more than fractionation alone.
OBJECTIVE
The aim of this study was to determine if fractionation and individual or combinations of radioprotectants could minimize damage to physeal longitudinal growth in an animal model to any greater extent than fractionation alone.


METHODS
Sixty-three weanling male Sprague-Dawley rats were randomized into seven equal groups. Five groups received a total 25 Gy radiation exposure in three equal fractions to the right knee with the left as non-irradiated control. For each group, pentoxifylline, misoprostol, and amifostine were given individually and amifostine was also given in combination with each of the other drugs prior to the radiation fractions. One group each received 25 Gy in one or three fractions without radioprotection. At six weeks, limb lengths and histomorphometry were assessed.


RESULTS
The single fraction of 25 Gy caused a mean tibial length discrepancy of 24.4%. Fractionation decreased this to 18.8% (p < 0.001). Beyond fractionation alone, the mean femoral length discrepancies were significantly decreased by each of the added individual and combination radioprotectant drugs (p < 0.0004). The smallest absolute femoral length discrepancy (11%) was achieved with fractionation and the combination of amifostine and misoprostol.


CONCLUSIONS
Radioprotectants may be beneficial in growth plate radioprotection, alone or in combination.
Spadaro
Joseph A
JA
Musculoskeletal Research Laboratory of Department of Orthopedic Surgery, Institute for Human Performance at SUNY Upstate Medical University, Syracuse, New York 13210, USA.
Horton
Jason A
JA
Margulies
Bryan S
BS
Luther
Jay
J
Strauss
Judith A
JA
Farnum
Cornelia E
CE
Damron
Timothy A
TA
D004999:Amifostine / Q000494:pharmacology*; D000818:Animals; D000897:Anti-Ulcer Agents / Q000494:pharmacology; D001846:Bone Development / Q000528:radiation effects*; D004195:Disease Models, Animal; D019583:Dose Fractionation, Radiation; D007719:Knee Joint / Q000528:radiation effects; D008297:Male; D016595:Misoprostol / Q000494:pharmacology; D010431:Pentoxifylline / Q000494:pharmacology; D011832:Radiation Injuries / Q000517:prevention & control*; D011837:Radiation-Protective Agents / Q000494:pharmacology*; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013977:Tibia / Q000254:growth & development
D000897:Anti-Ulcer Agents; D011837:Radiation-Protective Agents; D016595:Misoprostol; D004999:Amifostine; D010431:Pentoxifylline