The objective of this prospective duo-center study was to evaluate the clinical and radiological outcome of the unconstrained Multigen Plus total knee system (Lima Lto, San Daniele, Italy) with the new BIOLOXÒ Delta ceramic femoral component.

40 patients underwent cemented total knee arthroplasty in two university hospitals. Clinical evaluations were undertaken preoperatively and at 3 as well as 12 months postoperatively using the HSS-Score, WOMAC-Score and SF-36-Score. The radiological investigations included ant-post. radiographs (whole leg in two leg stance and lateral view of the knee) and patella tangential radiographs (Merchant view).

During 12 months follow-up three patients underwent revision surgery. One patient had to be revised due to infection after postoperative opening of the knee joint due to direct trauma. One patient sustained an osteosynthetic procedure due to periprosthetic fracture after trauma. In one patient a retropatellar replacement was inserted one year postoperatively. Implant related complications were not found. The mean preoperative HSS-Score amounted to 57.8±11.7 points. At 3 and 12 month follow-up the mean HSS-Score was 76.0±12.3 and 83.3±11.9 points respectively.

Therefore HSS, as well as WOMAC and SF-36 Score improved significantly from preoperativly to both postoperative evaluations (Wilcoxon-Test p< 0.002). Radio-lucent lines around the femoral ceramic component were found in six cases.

However, subsequent long-term studies must be carried out in order to prove the good early clinical results and to clarify if progression of radiolucent lines may influence the clinical outcome of the presented newly ceramic total knee system.

Introduction: Total knee replacement has become a common procedure with good clinical results. Today many different designs of the femoral component of bicondylar endoprostheses are offered by industry. The femoral components show similar designs however different angles and length of the cross sections are specific. Because of these design differences the preoperative planning and sparing bone resection are difficult at the revision surgery. The aim of this experimental study was to compare the design of femoral components at their cross section contours to find congruence and differences of common bicondylar endoprostheses to prove the possibility of design exchange during revision surgery.

Material and method: Ten femoral components (e.motion^®, Genesis II, Genia^®, Innex^®, LCS^®, Multigen Plus, NexGen^®, P.F.C.^®, Scorpio^®, Vanguard^®) of similar implant size were analysed with regard to their cross section design. Therefore the constructional properties of the inner surface (direction and length of cross sections) of the components were determined. The components were scanned with a three-dimensional laser scanner and were transferred to two dimensional CAD models to the lateral and frontal view in order to compare the inner contours. The contours of the cross sections were overlaid with congruence of the posterior and anterior cross section of all components at lateral view.

Results: Four of the ten analysed femoral components showed good congruence of the cross sections. Here, only a few additional bone resections or extra bone cement have to be done at the diagonal cross sections to change the femoral design among each other. Four other components show wide differences between the inner contours in comparison to the first four components especially at their posterior and diagonal cross sections. Two components can not be compared with the others due to their diagonal distal cross section.

Discussion: The numerical results shows good congruence of cross section contours of some analysed femoral components. Furthermore there were clear design differences which complicate the exchange of the femoral component at revision surgery. The use of an elementary inner contour of femoral components of bicondylar endoprostheses could be an advantage for revision arthroplasty in regard to bone sparing surgical treatment.