Locally delivered TGF-β1 and IGF-1 enhance the fixation of titanium implants: A study in dogs

Abstract

Background Osteogenic growth factors have been suggested to enhance the fixation of implants used in joint replacement. We examined the effect of locally delivered transforming growth factor-β1 and insulin-like growth factor-1 in a biodegradable poly (D, L-lactide) coating. Material and methods In a paired study using 9 dogs, unloaded titanium implants surrounded by a 1-mm gap were inserted into the proximal humerus. The growth factors were incorporated in a poly (D, L-lactide) coating at a 1% (w/w) ratio of TGF-β1 and a 5% (w/w) ratio of IGF-1. Control implants were uncoated. After 4 weeks, the implants were evaluated by mechanical push-out test and by histomorphometry. Results A twofold increase was seen in mechanical fixation (strength, stiffness, energy absorption) for the growth factor-treated implants (p = 0.04). Similar results were seen in histomorphometry, as bone ongrowth was 2.5 times higher (p = 0.02), and gap healing was 30–110% higher (p = 0.04) for the growth factor-treated implants than for the control implants. Ongrowth of fibrous tissue was eliminated by the treatment. Interpretation TGF-beta-1 and IGF-1, locally delivered in a biodegradable poly(D,L-lactide) coating, enhance the mechanical fixation and osseointegration of titanium implants in cancellous bone, and no fibrous tissue is produced in the growth factor treated implants.