EFFECT OF THERAPEUTIC ULTRASOUND ON ENDOCHONDRAL OSSIFICATION

The effect of therapeutic doses of ultrasound was tested on endochondr al ossification of in vitro developing metatarsal long bone rudiments of 16- and 17-day-old fetal mice. Bone growth, calcification and resor ption following exposure to several doses of pulse-wave (PW) or contin uous-wave (CW) ultrasound were examined. PW was applied at intensities between 0.1 W cm(-2) and 0.77 W cm(-2) (I-satp) and CW intensities we re 0.1 W cm(-2) or 0.5 W cm(-2) (I-sata). After 1 week of culture, the metatarsal long bone rudiments were fixed and paraffin sections were prepared for histological evaluation and for measurement of the relati ve contribution of the various cartilage zones to the total bone lengt h. In contrast to treatment with CW ultrasound, treatment of 16-day-ol d metatarsal long bone rudiments with PW ultrasound resulted after 4 d ays of culture in significantly increased longitudinal growth. Histolo gy revealed a significant increased length of the proliferative zone, whereas the length of the hypertrophic cartilage zone was unaltered. T his might indicate that proliferation of the cartilage cells is stimul ated without influence on cell differentiation.