321 - Histopathologic Analysis of a Porous Tantalum Interbody Fusion Device:...

Oral Posters: Innovative Technologies

Presented by: C. Ferry - View Audio/Video Presentation (Members Only)

Author(s):

C. Latimer(1), C. Ferry(1), R. Bloebaum(2), P. Saiz(3)

(1) Zimmer Biomet Spine, Broomfield, CO, United States
(2) University of Utah, Salt Lake City, UT, United States
(3) Las Cruces Orthopaedic Associates, Las Cruces, NM, United States

Abstract

Introduction: Porous metal interbody fusion devices have become increasingly prevalent in spine surgery. As demonstrated through preclinical histological characterization, these devices may possess osteoconductive and osteointegrative capabilities not seen with traditional PEEK devices. However, given the inherent limitations of quantifying such osseous behavior in clinical application, it is not well understood whether extrapolations can be made. The purpose of this study was to assess bone on-growth and in-growth within a human retrieved porous tantalum PLIF implant.

Methods: A porous tantalum PLIF implant (Trabecular Metal TM-500; Zimmer Biomet Spine) was explanted 11mos postoperatively to accommodate a tertiary surgical intervention, unrelated to the implant (Figure 1). The subject (Female, 71yrs old) had initially received the implant for the treatment of L2/3 disc collapse and junctional failure following previous L3-S1 instrumentation. Adjunctive bilateral pedicle screw fixation was utilized. Autologous bone was placed within the graft slot of the implant prior to insertion. Following explantation, the specimen was fixed in 10% neutral buffered formalin, dehydrated in ethanol, infiltrated, and embedded in methyl methacrylate. Once polymerized, 2-3 mm thick sections were made using a high-speed saw. The implant was then histologically analyzed using scanning electron (SEM) and light microscope techniques (Figure 2). Bone percentage within the graft slot and within body of the implant itself were quantified using backscattered electron imaging.

Results: SEM analysis showed that 24±11% of the porous space within the implant body and 59±9% of the graft slot contained cancellous bone. Light microscope analysis showed active remodeling of bone tissue present within the porous implant and graft slot regions. Osteoid, osteoblasts and osteocytes were seen throughout the specimen confirming that the bone tissue was viable within and around the implant.

Conclusions: The presence of healthy viable bone within the graft slot and within the implant body indicated good connectivity with the host vertebrae. Such connectivity provides evidence that the implant was mechanically stable and good skeletal attachment had occurred in-situ. These findings support the postulation that a porous tantalum interbody fusion implant may facilitate osseous on-growth and in-growth while subsequently diminishing the need for adjunctive bone grafting and/or use of biologics. Further characterization within a larger, heterogeneous, cohort is warranted.

Fig 1. Gross Implant; Arrows Indicate Tiissue

Fig 2. SEM Images for % Bone Analysis