Dose-dependent new bone formation by extracorporeal shock wave application on the intact femur of rabbits

Background: Whereas various molecular working mechanisms of shock
waves have been demonstrated, no study has assessed in detail the
influence of varying energy flux densities (EFD) on new bone
formation in vivo. Methods: Thirty Chinchilla bastard rabbits were
randomly assigned to 5 groups (EFD 0.0, 0.35, 0.5, 0.9 and 1.2
mJ/mm(2)) and treated with extracorporeal shock waves at the distal
femoral region (1,500 pulses; 1 Hz frequency). To investigate new
bone formation, animals were injected with oxytetracycline at days
5-9 after shock wave application and sacrificed on day 10.
Histological sections of all animals were examined using broad-band
epifluorescent illumination, contact microradiography and
Giemsa-Eosin staining. Results: Application of shock waves induced
new bone formation beginning with 0.5 mJ/mm(2) EFD and increasing
with 0.9 mJ/mm(2) and 1.2 mJ/mm(2). The latter EFD resulted in new
bone formation also on the dorsal cortical bone; cortical fractures
and periosteal detachment also occurred. Conclusion: Here, for the
first time, a threshold level is presented for new bone formation
after applying shock waves to intact bone in vivo. The findings of
this study are of considerable significance for preventing unwanted
side effects in new approaches in the clinical application of shock
waves. Copyright (c) 2008 S. Karger AG, Basel.