|M.Sc Student||Segev Yakir|
|Subject||The Effect of Growth Hormone on Osseointegration of|
Endosteal Titanium Alloy Implants in the Rat Femur
|Department||Department of Medicine||Supervisor||Dr. Anna Weiss|
Biological fixation of uncemented implants requires de novo bone formation, a process named osseointegration. Growth hormone (GH) is anabolic for bone, and is known to exert both direct and indirect effects, by stimulating hepatic secretion and local production of IGF-1. The aim of this research was to study systemic and local effects of GH on implants fixation, by implanting Ti-6Al-4V pins in the distal femurs of adult female rats, for a period of one month. Animals in the systemic GH treatment group received daily 1 mg/kg body weight of rat GH; in the local application group, GH was adsorbed onto pins. GH adsorption was verified by SDS-PAGE electrophoresis. IGF-1 levels in serum were determined by radioimmunoassay, no significant differences between groups were found. Two parameters of osseointegration: bone volume (BV) and bone-implant contact (BIC) were measured on scanning electron microscope images of cross-sections from femoral epiphyses and diaphyses. In all animals the implants underwent fixation in bone. BV and BIC were increased in both the systemic GH treatment and in the GH adsorption groups in comparison to the controls. To evaluate mineralization, animals received oxytetracycline 72 hrs before sacrifice; the results indicated an increase in mineralization rate in GH treatment groups in comparison to controls. The activities of alkaline phosphatase - a marker of bone formation and tartrate resistant acid phosphatase- a marker of bone resorption, were increased in the GH treated animals, indicating an overall increase in bone remodeling.
In conclusion, our findings revealed that GH enhances implant osseointegration in adult rats. GH was more effective when applied locally than systemically. Local administration of GH by adsorption directly onto the implants may improve implant fixation and prevent unwanted systemic effects of GH.