Primary complex total knee replacement – surgical principles for knee deformities

To determine total knee replacement (TKR) surgical principles for extra- and intra-articular knee deformities. Causes for extra-articular deformities includes posttraumatic or congenital deformity, prior osteotomy, osteomyelitis, metabolic bone diseases of lower limb. These are relatively infrequent clinical problems. Preoperative planning rules for extra-articular deformities are clinical examination, radiological examination includes long leg standing x-rays with extremity in neutral rotation, anatomical axis of femur is measured in sagital plane to determine deformity angle and level, resection level of femoral bone cuts not extends above the level of epicondyles. Extra-articular femoral deformities can be corrected by compensatory intra-articular distal femur resections. Magnitude of correction can be assesed by digital templating based on mechanical axis devination. Extra-articular tibial deformities can be corrected by compensatory intra-articular tibial resection, but it can lead to Līgament instability. Angular deformity correction in cases of extra-articular deformities – if if deformity is more than 10-15° varus or valgus, or more than 20° in sagittal plane, plan osteotomy at apex of deformation and axis correction before TKR as two stage treatment. Causes for intra-articular deformities are avascular necrosis of femoral or tibial condyles, previous Līgament damage, prior arthroscopy, intra-articular fractures, congenital deformities, patellofemoral subluxation. Usually they are combinationof intra-articular bone loss and simoutaneous Līgament contracture. Preoperative planning rules for intra-articular deformity are clinical examination, weight-bearing long leg standing x-rays, AP view with knee in extension, in cases of valgus knee deformity - 30° of flexion and with knee in 90° flexion. Tibial resection level depends on magnitude of defect. Complex primary TKR in cases of intra- and extra-articular deformities requires surgeons experience and understanding of surgical principles. Preoperative clinical examination and x-ray digital planning is essencial. For major femoral or tibial angular deformities two stage surgical plan could be the optimal choice.