Management of bone loss in revision TKA: it's a changing world

Bone deficiency represents a common theme in revision total knee arthroplasty (TKA). The etiology of bone deficiency may be aseptic loosening resulting in direct mechanical bone loss, osteolysis, stress shielding, septic loosening, or iatrogenic resulting from implant removal. Not all revisions are created equal. The surgeon must assess the degree of complexity and have a broad armamentarium available. Principles to consider in bone loss management are defect size and location and patient demographics, including body mass index, activity level, age, and life expectancy. Treatment options include polymethylmethacrylate (PMMA) with or without reinforcing screws; modular TKA systems including optional stems, wedges, and metal augments; orthopedic salvage systems such as mega- or tumor prostheses; autograft; and morselized or structural allograft. Morselized allograft is better suited for reconstitution of contained deficits and may be associated with a higher rate of incorporation. Disadvantages of allograft include late resorption, fracture or nonunion of structural allograft, and risk of disease transmission. A recent innovation has been a variety of augments and cones fabricated in the new ultraporous metals to address structural defects in revision TKA. Recommendations for bony reconstruction include: for deficits <5 mm, PMMA fill; for deficits 5 to 10 mm and <50% of the femoral condyle or tibial plateau, PMMA with reinforcing screws; for contained deficits >5 mm, morselized allograft; for noncontained deficits 5 to 15 mm and >50% of the femoral condyle and tibial plateau, TKA modular systems with stems and augments; and for noncontained deficits >15 mm, structural allografts, megaprostheses, and ultraporous metal augments.