The field of nanoparticle related research for the diagnosis and therapy of diseases evolves rapidly. Magnetic nanoparticles in combination with magnetizable implant materials for the treatment of implant related infections present a possible implementation in orthopedics. Magnetic nanoporous silica nanoparticles (MNPSNPs) were developed and equipped with fluorescent dyes. In vitro/in vivo biocompatibility and in vivo biodistribution were examined to appraise their potential applicability. Cell culture tests with NIH-3T3 and HepG2 cell lines indicated a good in vitro biocompatibility. Ferritic and titanium alloy (control) plates were implanted subcutaneously at the hind legs of Balb/c mice. Immediately after i.v. or s.c. injection of MNPSNPs, the caudal half of the mice was placed between the poles of an electro magnet. Exposure to the electromagnetic field of approx. 1.7 T was maintained for 10 minutes. 10 animals each were euthanized at days 0, 1, 7, 21 or 42, respectively. Quantity of MNPSNPs in liver, spleen, kidney, lung and skin/muscle samples was assessed by fluorescent microscopic methods. MNPSNP existence on the implant surface was also appraised after several steps of detachment. MNPSNPs showed a time-dependent accumulation in the organs after i.v. injection with initial accumulation in the lungs followed by redistribution to liver and spleen. After s.c. injection no systemic distribution but local appearance of MNPSNPs could be found. First histological evaluation showed no pathological changes after i.v. injection. With good in vivo biocompatibility, future focus will be laid on increasing circle life time of MNPSNPs and evaluation in an infection model.

After the implantation of endoprotheses or osteosynthesis devices, implant-related infections are one of the major challenges. The surface of implants offers optimal conditions for the formation of a biofilm. Effective carrier systems for the delivery of adequate therapeutics would reduce the concentrations needed for successful treatment and improve cure rates. In cancer diagnosis and therapy, magnetic nanoparticles are concentrated in the target area by an external magnetic field. For orthopaedic applications, in vitro examinations showed that the addition of a magnetic implant in combination with an external magnetic field could increase the amount of MNPSNPs that accumulated in direct vicinity to the implant. The present examinations implemented an electromagnet to increase magnetic field strength and should show if the in vitro set up can be transferred to an in vivo mouse model. Additionally, the loading capacity of the MNPSNPs with enrofloxacin and its release kinetics were determined.

Fluorescein-isothiocyanate (FITC) was covalently attached to MNPSNPs. For the in vitro set up, a peristaltic pump was used to establish a closed circuit which contained the MNPSNP dispersion and a magnetic platelet. After 5 minutes fluid samples were taken from the area around the magnetic platelet and analysed using a microplate reader. For the in vivo set up, a BALB/c mouse was implanted subcutaneously with the metallic platelet at the hind leg. The MNPSNP dispersion was injected into the tale vein and the hind leg of the mouse was placed immediately in a magnetic field of 1.9 T. After one week the implant was retrieved and examined by confocal laser scanning microscopy (CLSM). Liver, spleen and kidneys of the mouse were examined by magnetic resonance imaging (MRI). The loading capacity of the MNPs with enrofloxacin was examined by quantification of the enrofloxacin content in the incubation and washing solution after incubation. The release kinetics weres tested in PBS using UV/Vis-spectrometry.

The solution in the remaining tube contained no detectable MNPs while the concentration in the vicinity of the platelet was 150 µg/ml. The mouse showed no clinical adverse effects. The CLSM examination revealed a considerable accumulation of the MNPs at the implant surface. MRI could show neither accumulated MNPs nor changes of organ structure. The loading capacity of the MNPs for enrofloxacin was approximately 95 µg/mg. A burst release of nearly a third of the loaded antibiotic occurred within the first 6 hours followed by a further steady release.

Autologous matrix-induced chondrogenesis (AMIC) is a new treatment option for full-thickness cartilage defect repair using the well-known microfracturing technique combined with a porcine collagen type I/III matrix implant and partially autologous fibrin sealant.

A retrospective study has being carried out to investigate the objective and subjective clinical outcome of this procedure over a period of up to 2 years after the operation. 18 patients (10 male, 8 female) with localised cartilage defects were treated with AMIC.

The mean age was 37 13 years. Defects treated were localised retropatellar (6), on the medial femoral condyle (7), on the lateral femoral condyle (2) and multiple lesions (3). During the clinical follow-up these patients were evaluated with the help of 3 different scores (IKDC score, Cincinnati score, Lysholm-Gillquist score).

For the collective of 18 patients, one or more years had elapsed since the operation at the time this study was completed. 10 patients were included into the 2-year evaluation. The IKDC Score showed a mean improvement from 28 to 58 out of 100 at 1-year and from 25.5 to 69 out of 100 at 2-years post-operative. The Cincinnati and Lysholm-Gillquist scores showed the same tendency with an improvement of about 40 pecent at 1 year and about 55 percent at 2 years compared to pre-operative value. The improvement in the IKDC Score as well as the Cincinnati and Lysholm-Gillquist suggest that AMIC is a promising alternative in the treatment of local cartilage defects in the knee with good short and possibly mid-term results.

Further follow up will reveal, if the good results are durable and AMIC, as matrix enhanced microfracturing technique can become a valuable, recognised cartilage repair technique.

Introduction: We developed a new treatment option for localized articular cartilage defects: the matrix-induced, autologous chondrocyte transplantation (MACT) in which we seeded autologous chondrocytes on porcine porous matrices of type I/III collagen (Chondro-Gide®, Geistlich Biomaterials, Wolhusen, Switzerland) instead of a periosteum flap.The target of this clinical prospective study was to evaluate the outcome for a follow up period of five years after transplantation.

Methods: Between 1998 and 2001 we treated 38 patients (19 male and 19 female) with localized cartilage defects (Outerbridge grade three to four). Within the follow up time of this study until October 2002 the patients were assessed clinically 3, 6, 12, 18, 24, 36 and 60 month after the transplantation using four different standard rating scales: the Meyers-score, the Tegner/Lysholm-score, the Lysholm/Gilquist-score and the ICRS-score as well as MRI. Results were documented and compared with the pre operatives. Furthermore histological stainings of four patients were assessed.

Results: Mean patient age was 35 years (19 to 58 years). Average defect size was 5,6 qcm, 10 defects localized patellar, 16 femoral medial,3 femoral lateral and 9 combined. Two years after operation 66,7% (n=25) of the patients rated the function of their knee as much better or better than before in the subjective evaluation. After five years the percentage decreased to 57,1% (n=10). Up to a follow-up time of 24 month the clinical outcome of all four scores illustrated an significant improvement. Five years after transplantation two scores still showed significant improvement (Meyers-score: p= 0,02; Lysholm-Gilquist-Score: p=0,02). The other two scores showed improvement which turned out to be non significant (Tegner-Lysholm-Score: p=0,19; ICRS-Score: p=0,06) MRI scanning results after one year could not detect the quality of cartilage defect repair. Histological evaluation of four patients might not identify any association between the quality of the tissue and the clinical outcome

Conclusion: Five years results in two scores (Meyer- and Lysholm-Gilquist-Score) still showing significant improvement imply that MACT has turned out to be an acceptable alternative for the treatment of localized cartilage defects in the knee.