Search

Purpose: Bone marrow aspirate has been successfully used alongside a variety of grafting materials to clinically augment spinal fusion. However, little is known about the fate of these transplanted cells. Herein, we develop a novel murine model for the in vivo monitoring of implanted bone marrow cells (BMCs) following spinal fusion., Methods: A clinical-grade scaffold was implanted into immune-intact mice undergoing spinal fusion with or without freshly isolated BMCs from either transgenic mice which constitutively express the firefly luciferase gene or syngeneic controls. The in vivo survival, distribution and proliferation of these luciferase-expressing cells was monitored via bioluminescence imaging over a period of 8 weeks and confirmed via immunohistochemistry. MicroCT imaging was performed 8 weeks to assess fusion., Results: Bioluminescence imaging indicated transplanted cell survival and proliferation over the first 2 weeks, followed by a decrease in cell numbers, with transplanted cell survival still evident at the end of the study. New bone formation and increased fusion mass volume were observed in mice implanted with cell-seeded scaffolds., Conclusions: By enabling the tracking of transplanted bone marrow-derived cells during spinal fusion in vivo, this mouse model will be integral to developing a deeper understanding of the biological processes underlying spinal fusion in future studies. These slides can be retrieved under Electronic Supplementary Material.

Study Design: A posterolateral rabbit spinal fusion model was used to evaluate the effects of recombinant human bone morphogenetic protein-2 (rhBMP-2) and teriparatide (PTH [1-34]) used individually and in combination on spinal fusion outcomes., Objective: To test the efficacy of parathyroid hormone on improving spinal fusion outcomes when used with BMP-2., Summary of Background Data: Of the more than 250,000 spinal fusion surgical procedures performed each year, 5% to 35% of these will result in pseudarthrosis. Growing controversy on the efficacy and cost of rhBMP-2 for improving spinal fusion outcomes has presented a challenge for clinicians. Research into PTH as an adjunct therapy to rhBMP-2 for spinal fusion has not yet been investigated., Methods: Forty-eight male New Zealand white rabbits underwent bilateral posterolateral intertransverse process arthrodesis surgery at the L5-L6 level. Animals were divided into 6 groups. Two groups were treated with autograft alone or autograft and PTH (1-34), whereas the other 4 groups were treated with low-dose rhBMP-2 alone, high-dose rhBMP-2 alone, or either dose combined with PTH (1-34). All animals were euthanized 6 weeks after surgery. The L4-L7 spinal segment was removed and assessed using manual palpation, computed tomography (CT), and biomechanical testing., Results: CT assessments revealed fusion in 50% of autograft controls, 75% of autograft PTH (1-34) animals, 87.5% in the 2 groups treated with low-dose rhBMP-2, and 100% in the 2 groups treated with high-dose rhBMP-2. CT volumetric analysis demonstrated that all groups treated with biologics had fusion masses that were on average significantly larger than those observed in the control group (P < 0.0001). Biomechanical data demonstrated no statistical difference between controls, PTH (1-34), and low-dose rhBMP-2 in any testing orientation. PTH (1-34) did not increase bending stiffness when used adjunctively with either low-dose or high-dose rhBMP-2., Conclusion: Although intermittent teriparatide administration results in increased fusion mass volume, it does not improve biomechnical stiffness over use of autograft alone. When delivered concurrently with high- and low-dose rhBMP-2, teriparatide provided no statistically significant improvement in biomechanical stiffness., Level of Evidence: N/A.