No effect of autologous growth factors (AGF) around ungrafted loaded implants in dogs

Abstract

Autologous growth factors (AGF) is a growth-factor-rich concentrate of platelets, white blood cells and fibrinogen. Application of AGF was presumed to improve implant fixation and gap healing of non-grafted, loaded implants. We inserted one loaded titanium implant intra-articularly in each medial femoral condyle of eight dogs. Each implant was surrounded by a 0.75 mm gap. One implant in each dog was coated with AGF prior to implantation whereas the contralateral implant served as a control. AGF was prepared by isolating the buffy-coat from blood and further concentrated using an Interpore Cross UltraConcentrator. Platelet counts were increased from a median baseline of 168x10(3)/microl to 1003x10(3)/microl in AGF. However, AGF had no significant effect on implant fixation or bone formation. Even though AGF increased ultimate shear strength and energy absorption by approximately 50%, these differences had a p-value less than 0.05. The sample size in this study was small and any negative conclusions should be taken with caution due to low statistical power. We have previously demonstrated that AGF significantly improves fixation and incorporation of grafted implants. AGF might require mixing with an osteoconductive grafting material in order to provide a scaffold on which to foster bone growth and to keep the growth factors on location for a prolonged period.

Fig. 1

The implant device was inserted in the medial condyle of both knees. a Anchorage screw with a threaded piston. b Test implant mounted on the piston. c Titanium ring. d Polyethylene (PE) plug (diameter 4.5 mm) which protrudes so that load from the proximal tibia can be transmitted to the implant device. A gap of 0.75 mm between surface of the implant and border of the drill hole was either left empty or treated with autologous growth factors (AGF)

Fig. 2

a Section from an autologous growth factor (AGF) treated implant. The implant (a) is seen to the left. Woven bone is in contact with the implant surface and is seen throughout the gap. Lamellar bone (c) is found outside the original 0.75 mm gap (100X magnification, light-green, basic fucsin staining). b Section from the group with no gap treatment. The implant (a) is covered by a thick fibrous membrane (b). Woven bone (c) is seen in the gap but it is not in contact with the implant. Lamellar bone (d) is found outside the original 0.75 mm gap (100X magnification, light-green, basic fucsin staining)