Aim

We present the greatest study of patients with proximal fibula resection. Moreover we describe a new classification system for tumour resection of the proximal fibula independent of the tumour dignity.

The use of megaprostheses is accompanied with periprosthetic infection in up to 15% of cases. Among metals with antimicrobial activity, silver has raised the interest of investigators because of its good antimicrobial activity. The aim of this study was to determine the infection rate of silver-coated megaprostheses in comparision to uncoated titanium prostheses.

We prospectively identified 40 patients who were treated with a silver-coated proximal femur (n=17) or proximal tibia (n=23) replacement (Mutars^®, Implantcast, Germany). Patients with a silver-coated tumor endoprosthesis were compared with 74 (proximal femur replacement n=33, proximal tibia n=41) retrospectively assessed patients with a titanium endoprosthesis regarding the number of infections.

In the titanium group a proximal femur replacement was associated with the highest infection rate (18.2%; time of infection in mean 15 months postoperatively). In the silver-group infection could be reduced to 5.9% (time of infection 12 months postoperatively). In patients with a proximal tibia replacement the infection rate could be reduced from 17.1% (time of infection in mean 28 months postoperatively) to 4.3% (time of infection 4 months postoperatively) in the silver group.

Regarding the final, successful treatment of infection it can be stated that in the silver group the patients could be treated either by intravenous antibiotics only or by a one-stage exchange of the prosthetic body. In the titanium group seven patients (53%) were treated by a two-stage reimplantation of the prosthesis, in 4 patients (31%) an amputation and in one patient rotationplasty was performed.

We conclude that silver-coated megaendoprostheses can reduce the risk of infection on a short-term followup. Importantly, minor revisions in the case of infection in patients with a silver-coated prostheses were more often successful. Further studies with more patients and a longer followup are necessary in order to evaluate the possible benefit of silver exactly.

Megaendoprotheses are widely used in the reconstruction of large bone defects in orthopaedic tumour surgery. The major complications (up to 36%) are periprosthetic infections. Persisting periprosthetic infections lead to secondary amputation up to 37% of the cases. One underestimated reason for persisting infections are subpopulations of S. aureus called “small colony variants” (SCVs). Aim of this study was to evaluate that silver ions might prevent or cure a periprosthetic infection caused by SCVs.

For testing the antimicrobial activity of silver-coated titanium we used a technique introduced by Bechert et al. Therefore an adhesion and proliferation assay was performed with clinical isolates of S. aureus SCV (A22616/3). We tested the adhesion and proliferation properties of S aureus SCV on stainless steel (steel), Cobalt-Chrome-Molybdenum-alloy (CoCrMo), Titan-Aluminium-Vanadium-alloy (TiAlVa) and silver-coated Titan-Aluminium-Vanadium-alloy (scTiAlVa).

Adhesion of S. aureus SCV is significantly reduced on scTiAlVa vs. steel (p> 0001). We could also demonstrate that the proliferation rate of scTiAlVa vs. all tested materials is significant (p> 0001) lower.

We concluded that silver-coating has an effective antimicrobial activity against S. aureus SCVs. Thus silver-coated megaendoprostheses are a good prophylaxis against persisting infections caused by S. aureus SCVs.

A revision of a first generation KMFTR prosthesis due to stem breakage is a problem oncologic surgeons are regularly faced with. We designed an adapter which allows us to connect new MUTARS components to the original KMFTR devices. Thus it is possible to bypass an exchange of the whole prosthesis.

We used this adapter in 10 patients. Time of revision was in average 16.6 years after primary implantation of the KMFTR prostheses. Reasons for revision were femoral stem breakage (n = 5), breakage of the tibial component (n = 3) and periprosthetic fracture (n = 2, one femoral, one tibial).

The femoral stem (3 cases) and the tibial stem (2 cases) as well as the tibial plateau and body (2 cases) could be replaced by MUTARS parts and conjoined with the remaining KMFTR devices. Three cases were converted to MUTARS total femur.

Postoperative complications were one aseptic loosening and one cone-dislocation. Pre-incidence function was restored in all cases. The average Musculoskeletal-Tumour-Society-Score was 82.9% of normal function.

The results show that the new adapter facilitates to restore pre-incidental extremity function by performing a relatively modest revision.

Chondrosarcoma are rare malignant tumors. About the biological characteristics of chondrosarcoma is little-known [2]. Endothelin and its receptors are involved in regulating angiogenesis and metastatic dissemination [1]. The aim of this study is first to identify if chondrosarcoma are expressing endothelin-1 (ET-1) and the endothelin-receptors and thereupon to identify potential molecular markers for new target therapies. Another aim is to determine if endothelin is a prognostic factor in chondrosarcoma.

32 cases were investigated clinically and histopathologically. The expression of vascular endothelial growth factor (VEGF), Endothelin-1, Endothelin-Receptor-A (ETR-A) and Endothelin-Receptor-B (ETR-B) were determined. All data were analyzed by Fisher’s exact test (p< 0,05). All tumors show an expression of either ET-1, ETR-A or ETR-B. Chondrosarcomas with grade (G) I are mostly expressing less than 10-% ET-1 in cells, Chondrosarcomas G II are expressing in most cases between 10–50% and nearly all Chondrosarcoms G III more than 50%. In addition ET-1-expression is correlating with the histological grading. The patients also show a significant high metastatic dissemination probability at the time when tumor samples present more than 10%-storing ET-1-cells. The intensity of ET-1-expression is correlating with VEGF, which is the most important angiogenetic factor in tumors.

Chondrosarcomas are expressing ET-1, ETR-A and ETR-B. ET-1 seems to play a role in the angiogenesis of chondrosarcoma. Increased expression of ET-1 is accompanied with a high probability of metastatic dissemination. Endothelin receptor antagonists, which are used for example in prostate and breast cancer, can represent a potential therapy for chondrosarcoma [1]. Experiments on animals and clinical studies are required.