Biomechanics and Motion Analysis

Canine Carpal Joint Fusion: A Model of Four-Corner Arthrodesis Using a Porous Tantalum Implant

Principal Investigator: Scott P. Steinman, M.D.
Project Coordinator: Kristin Zhao — zhao.kristin@mayo.edu

Figure 1: Canine forepaw detailing the site of the "three-corner fusion". The tantalum dowel was cylindrical measuring 10.5 mm x 5.0 mm.

In this study, we investigated use of a porous tantalum metal implant as a prosthetic bone graft substitute in a canine model of wrist arthrodesis. This porous tantalum implant promoted bony union of the experimental arthrodesis site, which would otherwise fail to heal. A cylindrical defect was created at the junction of the radiocarpal, ulnocarpal, and IV carpal bones, a site analogous to the four-corner fusion site in humans. A tantalum cylinder was press-fit into the defect and stabilized with K-wire fixation (Fig. 1). Controls were represented by creating the defect without interposition of any implant. Animals were sacrificed at 4-, 8-, and 12-weeks postoperatively. Histological analysis demonstrated bony ingrowth into the implant as early as 4- weeks post implantation, and mechanical testing revealed progressively increasing strength of the fusion construct over time. The controls failed to achieve union at any time point. This highly porous metal implant served as a prosthetic alternative to bone graft in this canine model of four-corner arthrodesis of the wrist. The results of this study are promising and may indicate a novel application of this material in the treatment of a wide variety of orthopedic conditions where bone grafts have been used.