Using Cones and Augments with Bone Defects in Revision TKA

    Nearly a decade ago, porous tantalum cones and augments were developed because of orthopaedic surgeons’ dissatisfaction with the options they had for managing some of the tibial and femoral bone defects they were encountering in their revision total knee arthroplasty (TKA) patients.

    Not that other options, such as cancellous bone grafting, structural allografts, and modular stem extensions, weren’t effective, said David Lewallen, MD, at ICJr’s annual Winter Hip and Knee Course. They were, and in fact, they are still being used today. But their “batting average” could be improved, he said.

    For example, Dr. Lewallen cited data from his institution – Mayo Clinic in Rochester, Minnesota – in which 75% of structural allografts used in revision TKAs with bone loss were still functioning at 8 years post-surgery. The question is, he said, can we improve on the other 25%?

    That’s the goal of the augments, which are designed to provide a platform in the metaphysis so that off -the-shelf, standard revision components can be used to reconstruct the knee. These augments come in a variety of shapes that have been modified over the years to better fit different bone defects.

    For example, smaller sizes have recently been introduced to address intermediate-sized defects. This is important, Dr. Lewallen said, because they are the defects in which the implants are typically more likely to loosen and fail clinically.

    Poor fixation of damaged bone is the issue. Dr. Lewallen said the key may be to obtain bony in-growth and a living interlock to an appropriately sized augment to prevent loosening and possibly extend the durability of the overall reconstruction.

    During his lecture at the Winter Hip & Knee Course, Dr. Lewallen offered tips and tricks for working with porous tantalum cones and augments in revision TKA, including showing videos in which he and his partner, Dr. Arlen Hanssen, are fitting and fixing these augments.

    Dr. Lewallen’s presentation can be found here.