Effect of FK-506 (tacrolimus) therapy on bone healing of titanium implants: a histometric and biomechanical study in mice.

Immunosuppressive agents have been recognized as a factor affecting bone metabolism. The aim of the present study was to evaluate the influence of FK-506 administration on the healing of bone around titanium implants. Thirty-two male mice were randomly allocated to two groups: the FK-506 group (n = 16 mice), which received subcutaneous administration of FK-506 (1 mg kg-1 d-1 ); and the control group (n = 16 mice), which received saline solution by the same route of administration. After 2 wk, one titanium implant with sandblasted/acid-etched surface was placed in the femur. The therapy continued until the mice were killed 2 and 4 wk after surgery. The femurs with implants were evaluated by biomechanical testing and histologic analysis. The bone-implant contact (BIC) and bone volume (BV/TV) within a 100-μm-wide circumferential zone lateral to the implant surface were histomorphometrically analyzed. Compared with the control group, the FK-506 group showed significantly lower BIC and BV/TV at both 2 and 4 wk. Biomechanical tests showed that FK-506 significantly impaired the strength of bone-implant integration at both 2 and 4 wk postoperatively. Our data indicate that immunosuppressive therapy with FK-506 negatively affects the fixation of titanium implants.