Surgical planning and procedures for difficult total knee arthroplasty.

Most total knee arthroplasties (TKAs) are performed for minimal knee joint deformities with standard techniques and instrumentation. However, patients with extra-articular deformities, severe varus and valgus deformities, and posttraumatic arthrosis pose unique challenges to surgeons. Each deformity requires different modifications of surgical technique or prosthesis used to successfully perform TKA and optimize postoperative results. The surrounding tissues connect the femur and the tibia at the anterior, posterior, medial, and lateral walls of the knee joint. The medial soft tissues should be released for varus deformities and lateral soft tissues should be released for valgus deformities. The posterior soft tissue may be released for flexed deformities. The anterior quadriceps and patellar tendon may be adjusted while approaching the knee joint for posttraumatic arthrosis. A more constrained knee prosthesis may be needed for more severe deformities.