Introduction: In an already published prospective and randomised study the positioning of TKA with and without a navigation device was analyzed. The results with navigation were significantly better than free hand surgery. The issue of this study was to find out if navigation can improve MIS in TKA.

Materials and methods: A three arm study was designed by the National Institute of Rheumatology. The study was prospective and externely evaluated. 30 persons have got TKA in an open technique with navigation, 30 cases have got MIS and another 30 MIS and navigation. Operation time, blood loss, early outcome and accuracy of the implantation was measured and compared.

Results: MIS increases the operation time and leads to a significant better early outcome within the first ten days. The accuracy of the implantation is poorer in comparison to open techniques. Navigation doesn‘t improve the results because the malpositioning is caused by the final surgical step of impaction. This was verified by a radiological score analysis using a score developed in our hospital for the postoperative X-rays.

Aims: The purpose of this study was to find out if navigation devices can improve the alignement of knee arthroplasties even in experience surgeons. Methods: An external group of investigators – members of the Department of Epidemiology of the German Research Institute of Rheumatology – designed a prospective randomized study for the anlayzes of the alignement of knee implants with and without the support of a navigation device. Long standing X-rays before and after surgery were performed. The analyzes of X-rays was done in an external department of radiology. The analyzing radiologers didn’t know to which group the X-rays belonged. In total 120 patients with and 120 patients without the use of the Stryker navigation device were analyzed. The results were compared with the Qui square test. Results: There was a significant difference between the group of non navigated and navigated total knee arthroplasties. In the group without navigation system between 3 and 6% of the implants were positioned in mal-alignement of more than 3°. In the navigated group there was no case which differed to far from the ideal mechanical line. Conclusions: Even in the hands of very experienced surgeons the use of a navigation device can improve the alignment of implants. This study could prove it in concern of varus/valgus-position of the femoral and tibial component but also in the flexion/extension-position of the femoral component and the slope of the tibia component. The positioning was much more accurate in the navigated group. There was no case in the navigated group with wrong alignement.

Aims: The purpose of this study was to þnd out if an open navigation system is useful in early revision cases of TKA. We used an open navigation device which was developed in our hospital. The question was to þnd out if the mal positioning of the implants can be analyzed by the navigation device. Methods: 41 early revision cases were performed with the support of our navigation device. All these cases came to the hospital because of pain or swelling, there was now infection and now loosening in this group. We analyzed the positioning of the implant by cinematic navigation that means pre-operative CT and other preparations were not necessary. We measured the position of the implants and compared it to the ideal position which was calculated by the navigation device. Results: The need of early revision in total knee arthroplasty is caused by mal-positioning of the implants. The mal-positioning leads to a mal alignment and to a soft tissue imbalance. The most common failure in Germany is a wrong internal rotation of the femur component. This is causing overload of the medium side of the polyethylene and an instability of the lateral side. Often mal tracking of the patella is caused by mal rotation of the femur component. In all these cases the navigation device could lead the surgeon to the right position of the implant in revision surgery. Conclusions: A development of open navigation systems is necessary for the use of these systems in revision surgery. Revision surgery needs from time to time the intraoperative calculation of the positioning because early revisions are always caused by mal alignments. Therefore the use of a navigation device can improve the knowledge of the surgeon and help to perform the revision surgery in an excellent way.

Introduction

Severe acetabular bone stock loss compromises the outcome in primary and revision total hip arthroplasty. This acetabular deficienca occurs very often in Rheumatoid Arthritis.

In 1979 a biologic method was introduced with tightly impacted cancellous allograft in combination with a cemented polyethylene cup for acetabular reconstruction. With this technique it is possible to replace the loss of bone and restore hip function with a standard implant.

Because of the poor long term results and our own experience with large solid grafts we started in 1998 to use the impaction grafting in primary and revision hip replacements in Osteoarthritis and Rheumatoid Arthritis.

Materials and Methods

Between 1998 and 2001 35 acetabular reconstructions were performed in 29 patients with rheumatoid arthritis. 3 Patients were lost to follow up.

24 primary and 11 Revision Arthroplasties were performed. The average age was 55( 22-73. 29 female, 6 male.

58 Patients had additional dysplasia.

We had cavitary, segmental and also combined defects.

Femoral head autografts were used in all primaries, allografts were used in revision surgery.

Firstly the peripheral and central segmental defects were close with a metal mesh, so that only a cavitary defect remained. The cavity was filled with bone chips which were impacred layer by layer. To strabilize these reconstruction cement was used in direct contact with the graft.

In the Merle d’ Aubigne Score an improvement in pain, walking ability and function were observed. We had 1case of aseptic loosening, in a 73 year old female.

After 10 month the grafts were incorporated.

Our results are short term results- compared to the international literature ( Rosenberg et al. ) Nevertheless we can confirm the technique can be used with good results in cases with severe acetabular defects due to rheumatoid arthritis.