Total knee replacement with ceramic components: Evaluation, material characteristics and clinical performance

Abstract

Since the first clinical use of ceramics in total joint arthroplasty, the material properties, manufacturing methods and implant design have been improved. This led to the development of a total knee replacement (TKR) system with a monobloc ceramic femoral component. Ahead of clinical implementation, new ceramic implants for total joint replacements require a series of preclinical testing under standard ISO and worst-case conditions to provide a high level of implant safety. In this context, by means of a finite-element-analysis (FEA) of the in situ situation considering different cement layer thicknesses and slightly tilted implant position, no critical stress amounts within the ceramic material were found. The dynamic modelling of intraoperative impaction behaviour revealed higher stresses in the ceramic material than in metallic components when the implant was hit using an impaction hammer. However, stresses were beneath critical values. An additional analysis could highlight the influence of the distal femur resection geometry. Inadequate preparation of the distal femur, especially the anterior and posterior resection caused by deflection of the sawblades, led to bending (wedge load) of the femoral component resulting in critical stresses. Hence, according to clinical observations, preparation of the distal femur must be carried out very carefully, at best using an additional resection template for an accurate anterior and posterior resection plane. Furthermore, impaction must be realized by hand including usage of a guided instrument to reduce stress peaks caused by an impulse and tilting. The wear simulator tests demonstrate that abrasive wear of polyethylene inserts under third-body wear conditions in combination with ceramic femoral components was significantly lower than with metallic femoral components with identical design. In clinical observation, the functional and radiological results are encouraging for a long-term survival of the ceramic femoral component. Therefore, ceramic implants could be a promising solution not only for patients with allergies against metallic implant materials but also for 'normal' osteoarthritic patients.