Femorotibial bone loss during revision total knee arthroplasty.

Bone loss (BL) is frequent during revision total knee arthroplasty (TKA). It is underestimated in X-rays. Most classifications distinguish contained from uncontained BL but the most frequently used classification is that of Engh, which does not take into account this element. Reconstruction should result in resistant support for the revision TKA. It helps correct malalignment, restore satisfactory ligament tension and height of the joint line. Several techniques have been suggested: cement, augments, bone grafts, modular metaphyseal sleeves and cones and megaprostheses. Cement is only used with small BL, especially in elderly patients. Augments allow rapid filling of small peripheral BL with good mid-term results but frequent radiolucent lines. Morselized allografts can be incorporated and remodeled. They are a good alternative in young patients. Structural allografts are resistant but there is a risk of fracture and resorption. Modular metaphyseal sleeves and cones incorporate with host bone and are attached to the prosthesis by a mechanical interface or cement. They may also be more durable. Megaprostheses are only indicated in severe BL in elderly subjects. Reconstruction is just one aspect of revision TKA and it should respect the technical requirements of the procedure in particular fixation with a stem, which is important in determining the outcome of reconstruction.