Full and hollow stems were implanted in the right and left tibiae of f
ive rabbits to study the effects of the implant shape on revasculariza
tion and remodelling of the bone after 6 months. No significant differ
ence of periosteal and endosteal circumference was observed when the l
eft and right tibiae of each group were compared. Medullary area was,
not surprisingly, significantly smaller in the full stem implanted tib
iae. The cortical bone area result was significantly higher in the hol
low stem group. In hollow stems, vessels were present both inside and
outside the implant with connections through the holes of the implant.
The observed differences of cortical bone area can be explained in te
rms of increased vascular spaces inside the cortical bone of full stem
implanted tibiae. This supports the hypothesis that hollow implants p
rovide more space for medullary revascularization and are consequently
capable of inducing less endosteal remodelling. Cementless prostheses
rely for mechanical fixation on a large interface of the implant with
bone. Two factors, i.e. revascularization of the medullary canal and
stiffness of the stem, can have a relevant effect on the quality of in
terface. This non-weight-bearing model suggests the relevance of vascu
lar factors.