A Comparative Evaluation of Commercially Available Cell-Based Allografts in a Rat Spinal Fusion Model

Abstract

Background: To evaluate the comparative abilities of commercially available, viable, cellular bone allografts to promote posterolateral spinal fusion.

Methods: Human allografts containing live cells were implanted in the athymic rat model of posterolateral spine fusion. Three commercially available allogeneic cellular bone matrices (Trinity Evolution, Trinity ELITE and Osteocel Plus) were compared with syngeneic iliac crest bone as the control. All spines underwent radiographs, manual palpation, and micro-computed tomography (CT) analysis after excision at 6 weeks. Histological sections of randomly selected spines were subjected to semiquantitative histopathological scoring for bone formation.

Results: By manual palpation, posterolateral fusion was detected in 40% (6/15) of spines implanted with syngeneic bone, whereas spines implanted with Trinity Evolution and Trinity ELITE allografts yielded 71% (10/14) and 77% (10/13) fusion, respectively. Only 7% (1/14) of spines implanted with Osteocel Plus allografts were judged fused by manual palpation (statistically significantly less than ELITE, P < .0007, and Evolution, P < .0013). The mineralized cancellous bone component of the allografts confounded radiographic analysis, but Trinity Evolution (0.452 ± 0.064) and Trinity ELITE (0.536 ± 0.109) allografts produced statistically significantly higher bone fusion mass volumes measured by quantitative micro-CT than did syngeneic bone (0.292 ± 0.109, P < .0001 for ELITE and P < .003 for Evolution) and Osteocel Plus (0.258 ± 0.103, P < .0001). Semiquantitative histopathological scores supported these findings because the total bone and bone marrow scores reflected significantly better new bone and marrow formation in the Trinity groups than in the Osteocel Plus group.

Conclusions: The Trinity Evolution and Trinity ELITE cellular bone allografts were more effective at creating posterolateral fusion than either the Osteocel Plus allografts or syngeneic bone in this animal model.

Clinical relevance: The superior fusion rate of Trinity cellular bone allografts may lead to better clinical outcome of spinal fusion surgeries.

Keywords: Osteocel Plus; Posterolateral spine fusion; Trinity ELITE; Trinity Evolution; allograft; athymic rat; stem cells.

Conflict of interest statement

Disclosures and COI: This study was funded by a research grant received by B.J. and J.Y. from Orthofix Medical Inc (Lewisville, TX) and MTF Biologics (Edison, NJ). Because MTF Biologics and Orthofix Medical Inc are the manufacturer and distributor of the Trinity spine allografts, we mitigated the potential conflict of interest by blinding every aspect of the study and carrying out the procedures and analyses in this manner before breaking the codes used and examining any differences between the results for the various implants. This process included surgeons not being aware of which allograft they were implanting; randomization of implantation order between each 5-rat batch used for a given implant; manual palpation scoring, x-ray scoring, and micro-CT volume measurements done with all spines randomized and blinding of scorers as to implant type; histology descriptions made by researchers blinded as to implant type. J.T.R., E.I.W., and N.Z. are employees of and own stocks in Orthofix Medical Inc. E.S. and A.D. are employees of MTF Biologics.

©International Society for the Advancement of Spine Surgery 2020.

Figures

Figure 1

Radiographs and micro-CT 3-dimensional reconstructions of Osteocel Plus, Trinity Evolution, and Trinity ELITE implants immediately after implantation (day 0) and at 6 weeks postimplantation (day 42).

Figure 2

Radiographs of (a) syngeneic bone, (b) Osteocel Plus, (c) Trinity Evolution, and (d) Trinity ELITE allografts 6 weeks postimplantation in the athymic rat lumbar spine.

Figure 3

Histology of (a) syngeneic bone (b) Osteocel Plus, (c) Trinity Evolution, and (d) Trinity ELITE allografts 6 weeks postimplantation in the athymic rat lumbar spine (toluidine blue–stained, paraffin-embedded sections).

Figure 4

Semiquantitative histopathological scores for syngeneic bone, Osteocel Plus, Trinity Evolution, and Trinity ELITE allografts 6 weeks postimplantation in the athymic rat lumbar spine.

Figure 5

Volume of fusion masses (mm3) for syngeneic bone, Osteocel Plus, Trinity Evolution, and Trinity ELITE allografts 6 weeks postimplantation in the athymic rat lumbar spine determined from micro-CT images.