Background:
During elective orthopedic surgery or fracture repair, tourniquet ischaemia of osteoporotic bones may carry the risk of postischaemic inflammatory complications. We previously demonstrated that exogenous estrogen and ischaemic preconditioning (IPC) ameliorates periosteal inflammatory reactions induced by limb ischaemia−reperfusion (IR). In the present experiments, the effect of IPC in these reactions was examined during experimental osteoporosis.

Material and Methods:
Three−month old female Sprague−Dawley rats were bilaterally ovariectomized (OVX) or sham−operated (SH). 12 weeks later, the periosteal microcirculatory consequences (neutrophil leukocyte−endothelial interactions) of 60−min complete limb ischaemia and 180 min reperfusion were examined by fluorescence intravital microscopy in sham−operated (SH+IR) and OVX animals (OVX+IR). In further groups, limb IPC (2 × 10’/10” I−R) was elicited before I−R in sham−operated (SH+IPC+IR) and OVX rats (OVX+IPC+IR) (n=6−9). In another series, intravascular neutrophil leukocyte activation (CD11b adhesion molecule expression) changes were assessed by flow cytometry (n=7−9).

Result:
Rolling and adhesion of leukocytes to the periosteal postcapillary venules and leukocyte CD11b expression were increased after limb IR; these reactions were attenuated by IPC. In OVX animals, the number of rolling leukocytes was moderately reduced, but adherent leukocyte numbers and CD11b expression were not affected by IPC.

Conclusions:
Our data shows that the ameliorating effects of IPC against limb IR−induced inflammatory complications are partially lost in the presence of chronic estrogen withdrawal. These data suggest a limited efficacy of IPC to improve the postischaemic microcirculatory inflammatory consequences of tourniquet ischaemia in osteoporotic situations. Supported by: OTKA K104656, TÁMOP 4.2.4. A/2−11−1−2012−0001, TÁMOP 4.2.2A−11/1/KONV−2012−0035, TÁMOP 4.2.2A−11/1/KONV−2012−0073.