Abstract
Despite the potential for growth factor delivery strategies to promote orthopedic implant healing, there is a need for growth factor delivery methods that are controllable and amenable to clinical translation. We have developed a modular bone growth factor, herein termed “modular bone morphogenetic peptide (mBMP)”, which was designed to efficiently bind to the surface of orthopedic implants and also stimulate new bone formation. The purpose of this study was to coat a hydroxyapatite-titanium implant with mBMP and evaluate bone healing across a bone-implant gap in the sheep femoral condyle. The mBMP molecules efficiently bound to a hydroxyapatite-titanium implant and 64% of the initially bound mBMP molecules were released in a sustained manner over 28 days. The results demonstrated that the mBMP-coated implant group had significantly more mineralized bone filling in the implant-bone gap than the control group in C-arm computed tomography (DynaCT) scanning (25% more), histological (35% more) and microradiographic images (50% more). Push-out stiffness of the mBMP group was nearly 40% greater than that of control group whereas peak force did not show a significant difference. The results of this study demonstrated that mBMP coated on a hydroxyapatite-titanium implant stimulates new bone formation and may be useful to improve implant fixation in total joint arthroplasty applications.
Highlights
Total joint replacement surgeries have been performed popularly because these surgeries can successfully relieve pain and improve functional outcomes
Calculation of new bone formation in Goldner’s trichrome stained images demonstrated a significant increase in new bone formation in the middle section and in the inner/ middle/outer section levels combined for modular bone morphogenetic peptide (mBMP) coated implants when compared to controls (p,0.05) (Fig. 6)
Mechanical Testing Results The results of mechanical push-out testing demonstrated that the stiffness of the mBMP-treated group (21576651.9 N/mm) was significantly greater than that of control group (15456480.5 N/ mm) (p,0.05), whereas there was no significant difference in peak force between the mBMP-treated group (10226371.4 N) and the control group (682.26269.3 N) groups (p.0.05)
Summary
Total joint replacement surgeries have been performed popularly because these surgeries can successfully relieve pain and improve functional outcomes. There is a need to develop novel biomaterials to increase replacement success rate and reduce revision rate, and to promote successful bone healing after revision surgery. Besides improving surgery techniques [2], the key factor for successfully improving implant-bone healing in joint replacement is the ability to encourage new bone formation at the implant-native bone interface [3]. Several groups have begun to explore the use of pro-osteogenic growth factors to induce new bone formation on implant surfaces. Lamberg et al stated that transforming growth factor-b1 (TGF-b1) and insulinlike growth factor-1 (IGF-1) enhanced the mechanical fixation and osseointegration of titanium implants in cancellous bone in a dog model [5]
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