228 - Fortifying the Bone-Implant Interface: An In Vivo Evaluation of 3D-pri...

Oral Posters: Innovative Technologies

Presented by: D. Lindsey - View Audio/Video Presentation (Members Only)

Author(s):

R. MacBarb(1), D. Lindsey(1), S. Woods(2), P. Lalor(3), M. Gundanna(4), S. Yerby(1)

(1) SI-BONE, Inc., San Jose, CA, United States
(2) MPI Research, Mattawan, MI, United States
(3) Histion LLC, Everette, WA, United States
(4) Brazos Spine, College Station, TX, United States

Abstract

Introduction: Chronic low back pain (LBP) is a public health burden that, when conservative approaches fail, may require surgical treatment. Minimally invasive surgical fusion of the sacroiliac (SI) joint using machined solid triangular titanium implants with a titanium plasma spray (TPS) coating has demonstrated positive clinical outcomes in patients with SI joint pain. The recent advent of additive manufacturing, i.e. 3D-printing, allows for fabrication of implants with complex geometries and intricate surface features that mimic bone morphology. SI joint implants made using additive manufacturing may further optimize biological fixation and biomechanical stability compared to implants made from traditional manufacturing processes, such as TPS-coating.

Purpose: This in vivo study evaluated the bone-implant interface of additive manufactured (AM) fenestrated titanium implants with a porous surface, with and without nanocrystalline hydroxyapatite (HA) coating or autograft, and compared the bone-implant interface to that of FDA-cleared solid TPS-coated SI joint implants.

Methods: Triangular 45mm long implants were machined with a 0.75mm thick TPS-coating (SI-BONE, Inc., San Jose, CA) or additive manufactured to have a fenestrated structure with a printed 0.75mm thick porous surface designed to emulate cancellous bone (Figure 1). Implants were placed bilaterally in an ovine distal femoral defect model. Four implant groups (n = 6/group/time-point) were included: 1) TPS-coated, 2) AM, 3) AM+HA, and 4) AM+Auto. The bone-implant interfaces of 6- and 12-week specimens were investigated via radiographic, microcomputed tomographic, biomechanical, and histomorphometric methods.

Results: Radiographic images showed peri-implant bone formation around all implants. Push-out testing demonstrated no significant differences among groups. TPS implants, however, were observed to fail primarily at the bone-implant interface, whereas failure in the AM groups occurred ~2-3mm away from the implant surfaces within the surrounding host bone (Figure 2A). Quantitative histomorphometry found no significant differences in the amount of bone contacting the surface among groups. The AM implants, however, had significantly more area filled with bone than the TPS-coated implants (p< 0.0001). Of the three AM groups, the AM+Auto implants had the greatest total bone area (Figure 2B, p< 0.002).

Conclusions: Both TPS and AM implants exhibited substantial bone growth onto and into their porous surfaces, and through the central core of the AM implants, forming strong and stable interfaces with host bone. While HA-coating did not further enhance results compared to uncoated AM implants, the addition of autograft potentially promoted additional osteointegration. Taken together, the AM implants displayed similar, if not enhanced, biomechanical stability and bone integration, and therefore may be an attractive alternative to TPS-coating for SI joint implants.

Figure 1

Figure 2