The effect of a novel pillar surface morphology and material composition demonstrates uniform osseointegration

• Published in: Journal of the mechanical behavior of biomedical materials Vol. 123; p. 104775
• Main Authors: Causey, Gregory C., Picha, George J., Price, Jamey, Pelletier, Matthew H., Wang, Tian, Walsh, William R.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2021
• Subjects: Bone remodeling; Continuous bone ingrowth; Discontinuous surface; Histology; Osteointegration; Ovine model; Pillar surface morphology; Pushout; μCT; Osteointegration; μCT; Ovine model; Continuous bone ingrowth; Discontinuous surface; Histology; Pushout; Bone remodeling; Pillar surface morphology
• ISSN: 1751-6161; 1878-0180
• DOI: 10.1016/j.jmbbm.2021.104775

Long-term survival of orthopedic implants requires a strong and compliant interface between the implant and surrounding bone. This paper further explores the in-vivo response to a novel, macro-scale osseointegration surface morphology. In this study, we examine the effects of material composition on osseointegration in relation to the controlled surface geometry. The pillared surface is constructed of discontinuous surface geometry which creates an open space for unencumbered bone migration. In creating an open, macro-scale morphology we have demonstrated a bone migration and integration that is less dependent on the underlying implant material and is substantially driven thru surface geometry. In this in-vivo study an established ovine model was used to examine the effects of implant material composition on bone ingrowth and mechanical performance. Cortical and cancellous sites in the tibia and distal femur were examined at 6 and 12 weeks with μCT, histology, histomorphometry, and mechanical performance. Implant materials tested included PEEK (Evonik, VISTAKEEP®), PEEK HA (Invibio, PEEK-OPTIMA HA Enhanced), Titanium coated PEEK, Titanium (Ti–6Al–4V, Grade 5), and Ultra-High Molecular Weight Polyethylene (UHMWPE). Extensive bone ingrowth was noted in all implant materials at 12 weeks with maturation of the bone within the pillar structure from 6 weeks to 12 weeks. Histology demonstrated little fibrous deposition at the implant interface with no adverse cellular reactions. Histomorphometric review of cortical sites revealed greater than 60% bone ingrowth at 6 weeks increasing to nearly 80% by the 12 week timepoint. Cancellous sites yielded a mean of 30% ingrowth at 6 weeks increasing to 35% by 12 weeks. Pushout testing of cortical site samples demonstrated increase in pushout force between the 6 and 12 week timepoints. Increases were significant in all but the UHMWPE samples. Stiffness likewise increased in all samples between the two times. These results demonstrated the effectiveness of the pillar morphology with full integrating from the surrounding bony tissue regardless of the material. In-Vivo study using a common Ovine model examining bone ingrowth into a novel, macro-scale osseointegration surface morphology. 6 Geometrically similar implants were manufactured utilizing different materials and coatings configurations and were tested at 6 and 12 weeks. Post-sacrifice analysis reviewed μCT, histologic response, bone ingrowth via histomorphometry, and mechanical pushout (modified from G. C. Causey et al., "In-Vivo response to a novel pillared surface morphology for osseointegration in an ovine model," JMBBM, V119, 2021. https://doi.org/10.1016/j.jmbbm.2021.104462.). [Display omitted] •Pillared surface supports robust bone ingrowth independent of implant material.•In-vivo osseointegration testing in an Ovine model with PEEK, PEEK-HA, Ti coated PEEK, Titanium, and UHMWPE.•Bone ingrowth from 20 to 45% in cancellous bone and nearly 80% cortical bone at 12 weeks.•Mechanical testing of cortical samples at 12 weeks demonstrated robust resistance to pushout in all implant materials.•Mature bone ingrowth in at 12 weeks with fully formed vascularity and no fibroplasia or adverse cellular reaction in any group.