[Modular revision systems in total knee arthroplasty. Possibilities and techniques].

This paper deals with surgical techniques in revision total knee arthroplasty. The principles of exploring the knee joint, removing the implant, and implanting modular revision systems using a three-step technique are described. The opportunities of modern revision systems for reconstruction of bone defects and ligament instabilities are demonstrated. By means of modularity, the implant can be adapted to individual specifications for bone quality, bone defects, and soft tissue conditions. Modular stems allow an additional diaphyseal load transfer. Uncontained bone defects are reconstructed by metal wedges and blocks. By using the range from cruciate-retaining to condylar-constrained systems, the different degrees of instability can be substituted with the least constrained prosthesis. Totally constrained hinge knee prostheses should be used only in extreme cases such as complete loss of collateral ligaments or inability to correct flexion-extension gap mismatches. The results with modular revision systems described in the literature are reviewed.