Implant placement increases bone remodeling transiently in a rat model

Abstract

To examine bone remodeling following implant placement, 88 female Sprague-Dawley rats underwent either sham ovariectomy (sham-ovx) or ovariectomy (ovx) at 4.5 months. At 11 months, 17 baseline control animals were euthanized, while 71 rats received bilateral intramedullary femoral implants. Implanted rats were randomized to 4-, 8-, or 12-week follow-up times. Microcomputed tomography was used to assess cortical area and trabecular architecture in all rats. Dynamic and static histomorphometry were performed in a subset to examine the trabecular and endocortical bone in the distal femoral metaphysis adjacent to the implant and the periosteal surface at the midshaft superior to the implant (n = 59). Implantation did not affect bone volume in either sham-ovx or ovx rats compared to baseline controls. Implant placement significantly increased mineralizing surface, mineral apposition rate, and bone formation rate in both sham-ovx and ovx rats at the trabecular and endocortical surfaces at four and sometimes 8 weeks, with a return to baseline values by 12 weeks. At the periosteal surface, implant placement increased bone formation at 4 weeks with a return to baseline levels by 8 weeks. Thus, implant placement increases bone remodeling transiently without affecting bone volume in sham-ovx and ovx rats.