Evaluation of lumbar spinal fusion utilizing recombinant human platelet derived growth factor‐B chain homodimer (rhPDGF‐BB) combined with a bovine collagen/β‐tricalcium phosphate (β‐TCP) matrix in an ovine model

BACKGROUND CONTEXT: While the clinical effectiveness of recombinant human Platelet Derived Growth Factor‐B chain homodimer combined with collagen and β‐tricalcium phosphate (rhPDGF‐BB + collagen/β‐TCP) treatment for indications involving hindfoot and ankle is well‐established, it is not approved for use in spinal interbody fusion, and the use of autograft remains the gold standard. PURPOSE: The purpose of this study was to compare the effects of rhPDGF‐BB + collagen/β‐TCP treatment on lumbar spine interbody fusion in an ovine model to those of autograft bone and collagen/β‐TCP treatments using biomechanical, radiographic, and histological assessment techniques. STUDY DESIGN: Thirty‐two skeletally mature Columbian Rambouillet sheep were used to evaluate the safety and effectiveness of rhPDGF‐BB + collagen/β‐TCP matrix in a lumbar spinal fusion model. Interbody polyetheretherketone (PEEK) cages contained either autograft, rhPDGF‐BB + collagen/β‐TCP, collagen/β‐TCP matrix, or left empty. METHODS: Animals were sacrificed 8‐ or 16‐weeks post‐surgery. Spinal fusion was evaluated via post‐sacrifice biomechanical, micro‐computed tomography (μCT), and histological analysis. Outcomes were statistically compared using a two‐way analysis of variance (ANOVA) with an alpha value of 0.05 and a Tukey post‐hoc test. RESULTS: There were no statistically significant differences between groups within treatment timepoints for flexion‐extension, lateral bending, or axial rotation range of motion, neutral zone, neutral zone stiffness, or elastic zone stiffness. μCT bone volume fraction was significantly greater between treatment groups independent of timepoint where Autograft and rhPDGF‐BB + collagen/β‐TCP treatments demonstrated significantly greater bone volume fraction as compared to collagen/β‐TCP (P = .026 and P = .038, respectively) and Empty cage treatments (P = .002 and P = .003, respectively). μCT mean bone density fraction was most improved in rhPDGF‐BB + collagen/β‐TCP specimens at the 8 week and 16‐week timepoints as compared to all other treatment groups. There were no statistically significant differences in histomorphometric measurements of bone, soft tissue, or empty space between rhPDGF‐BB + collagen/β‐TCP and autograft treatments. CONCLUSIONS: The results of this study indicate that the use of rhPDGF‐BB combined with collagen/β‐TCP promotes spinal fusion comparable to that of autograft bone. CLINICAL SIGNIFICANCE: The data indicate that rhPDGF‐BB combined with collagen/β‐TCP promotes spinal fusion comparably to autograft bone treatment and may offer a viable alternative in large animal spinal fusion. Future prospective clinical studies are necessary to fully understand the role of rhPDGF‐BB combined with collagen/β‐TCP in human spinal fusion healing.