Tantalum trabecular metal - addition of human skeletal cells to enhance bone implant interface strength and clinical application

The osteo-regenerative properties of allograft have recently been enhanced by addition of autogenous human bone marrow stromal cells (HBMSCs). Limitations in the use of allograft have prompted the investigation of tantalum trabecular metal (TTM) as a potential alternative. TTM is already in widespread orthopaedic use, although in applications where there is poor initial stability, or when TTM is used in conjunction with bone grafting, initial implant loading may need to be limited. The aim of this study was to evaluate the osteo-regenerative potential of TTM with HBMSCs, in direct comparison to human allograft and autograft. HBMSCs were cultured on blocks of TTM, allograft or autograft in basal and osteogenic media. Molecular profiling, confocal and scanning electron microscopy (SEM) and biochemical assays were used to characterize cell adherence, proliferation and phenotype. Mechanical testing was used to define the tensile characteristics of the constructs. HBMSCs displayed adherence and proliferation throughout TTM, evidenced by immunocytochemistry and SEM, with significant cellular ingrowth and matrix production through TTM. In contrast to cells cultured with allograft, cell proliferation assays showed significantly higher activity with TTM (p < 0.001), although molecular profiling confirmed no significant difference in expression of osteogenic genes. In contrast to acellular constructs, mechanical testing of cell-TTM constructs showed enhanced tensile characteristics, which compared favourably to cell-allograft constructs. These studies demonstrated the ability of TTM to support HBMSC growth and osteogenic differentiation comparable to allograft. Thus, TTM represents an alternative to allograft for osteo-regenerative strategies, extending its clinical applications as a substitute for allograft.