Introduction: Aseptic loosening of cemented total knee arthroplasties is still an unsolved problem. In this regard the adhesion strength of the metal-bone cement interface is of major interest.

Material und Methods: Cemented tibial components coated with a silica/silane interlayer system (n=8) were dynamically loaded within a knee-simulator (DIN ISO 14243). After loading, the components were cut by “high pressure water jet technique” (Fraunhofer Institute for Production Technology, Aachen, Germany) into 10 slices (thickness 5 mm each) parallel to the shaft axis according to a standardised protocol. To evaluate the metal-bone cement interface with regard to gaps and cement failure, the tibial slices were analysed by light and fluorescent microscopy. These data were matched with uncoated components (n=8).

Results: The coated tibial components yielded a significant reduction of gaps in the metal-bone cement interface (p < 0.05) as well as a highly significant reduction of cement mantle failure (p < 0.001).

Conclusion: With the help of the silica/silane coating, gaps in the metal-bone cement interface with consecutive early cement mantle failure due to mechanical overstressing can be significantly reduced.

Background: The aim of this prospective multi-center study was to evaluate the clinical and radiological results of a total of 314 uncemented femoral stem revisions using the modular MRP-titanium system.

Methods: 305 patients (111 males, 194 females, mean age 67.7) with 314 MRP-titanium systems were followed-up for a meantime of 3.2 years (1 to 9 years). Pre- and post-operatively all patients were clinically documented using the Harris hip score. Radiologically, the preoperative bony defects were assessed by the Paprosky classification. Post-operatively, periprosthetic bone remodeling was evaluated on the basis of radiographic evidence of bone apposition or resorption.

The modular MRP-titanium system has proven to be valuable in quite problematic cases of hip revision arthroplasty with extensive femoral defects. The system allows intraoperative adaptation of implant length and antetorsion angle to the actual situation, a feature not provided by non-modular femoral revision implants.

Two major complications of hip replacement are loosening and infection. Reliable differentiation between these pathological processes is difficult since both may be accompanied by similar symptoms. Our aim was to assess the diagnostic ability of triple-phase bone scanning (TPBS) and positron-emission tomography (PET) to detect and differentiate these complications in patients with a hip arthroplasty. Both TPBS and PET were performed in 63 patients (92 prostheses). The radiotracer for PET imaging was ¹⁸F-fluorodeoxyglucose (FDG). Image interpretation was performed according to qualitative and quantitative criteria although the final diagnosis was based upon either surgical findings or clinical follow-up.

The sensitivity, specificity and accuracy of PET was 0.94, 0.95 and 0.95 respectively, compared with 0.68, 0.76 and 0.74 for TPBS. We found that an image interpretation based exclusively upon quantitative criteria was inappropriate because of its low selectivity. The histological examination indicated that increased periprosthetic uptake of FDG in patients with aseptic loosening was caused by wear-induced polyethylene particles and the subsequent growth of aggressive granulomatous tissue.