Résumé·s
When bone implants are loaded, they are inevitably subjected to displacement relative to bone. Such micromotion
generates stress/strain states at the interface that can cause beneficial or detrimental sequels. The objective
of this study is to better understand the mechanobiology of bone healing at the tissue-implant interface
during repeated loading. Machined screw shaped Ti implants were placed in rat tibiae in a hole slightly bigger
than the implant diameter. Implants were held stable by a specially-designed bone plate that permits controlled
loading. Three loading regimens were applied, (a) zero loading, (b) one daily loading session of 60 cycles with an
axial force of 1.5 N/cycle for 7 days, and (c) two such daily sessions with the same axial force also for 7 days.
Finite element analysis was used to characterize the mechanobiological conditions produced by the loading
sessions. After 7 days, the implants with surrounding interfacial tissue were harvested and processed for histological,
histomorphometric and DNA microarray analyses. Histomorphometric analyses revealed that the
group subjected to repeated loading sessions exhibited a significant decrease in bone-implant contact and increase
in bone-implant distance, as compared to unloaded implants and those subjected to only one loading
session. Gene expression profiles differed during osseointegration between all groups mainly with respect to
inflammatory and unidentified gene categories. The results indicate that increasing the daily cyclic loading of
implants induces deleterious changes in the bone healing response, most likely due to the accumulation of tissue
damage and associated inflammatory reaction at the bone-implant interface.