Recent studies have shown osteogenic effects of high-frequency mechanical s
timuli. The purpose of this study was whether externally applied, high-freq
uency, low-magnitude interfragmentary movements affect the process of bone
healing. In 12 sheep, a transverse osteotomy with a 3-mm gap was created in
the right metatarsus and externally stabilized by a rigid circular fixator
, External stimulation was performed in six sheep with the use of ground-ba
sed vibration, The sheep were standing with their hind limbs on a platform
that produced vertical movements resulting in interfragmentary movements of
approximately 0.02 mm magnitude at 20 Hz frequency, The other six sheep re
mained rigidly stabilized by external fixation during the 8-week study and
served as a control group. Healing was assessed postmortem by densitometric
and mechanical examinations, No significant differences were found between
the two groups, although callus formation was slightly enhanced (11%) in t
he stimulated group compared with the control group. Mechanical stimuli att
ributable to weightbearing in the control group were sufficient enough to i
nitiate callus formation even under rigid, external fixation, Thus, externa
l mechanical stimulation with the stimulation design described in the curre
nt study might not be indicated for improvement of bone healing.