Systemically Administered Human Growth Hormone Improves Initial Implant Stability: An Experimental Study in the Rabbit

ABSTRACT Purpose : This study was an investigation to determine whether human growth hormone (hGH) continuously adminis‐ tered to rabbits may improve implant integration in bone. Materials and Methods : Thirty‐two commercially pure titanium (c.P. Ti) implants were inserted in the tibiae of 16 rab‐ bits. Human growth hormone (0.3 U/kg/d) or sodium chloride (NaCl) was administered by subcutaneous pumps. Insulin‐like growth factor‐1 (IGF‐1) levels in blood were measured. Two biomechanical tests were performed (1) every second week resonance frequency analysis (RFA) was used to investigate implant stability or stiffness at the interface and, after 8 weeks of follow‐up, (2) removal torque (a measure of implant integration and stability) was registered. Further evaluation was performed by dual energy x‐ray analysis (DEXA), to evaluate bone mineral density, and histomorphomet‐ ric analysis of tissue‐to‐implant integration on undecalcified cut and ground sections. Results : A difference in implant stability was detected with the RFA technique after 2 weeks and 8 weeks in favor of the hGH‐treated rabbits. No significant differences were detected with removal torque, DEXA, and histomorphometric mea‐ surements. The blood test demonstrated antibody development in the rabbits treated with hGH after 4 weeks. Conclusion : Growth hormone has an initial beneficial effect on implant integration; however, owing to rapid antibody formation, this study did not demonstrate whether this effect remains in the long term.