Low-intensity pulsed ultrasound as a useful adjuvant during distraction osteogenesis: a prospective, randomized controlled trial.

BACKGROUND: Low-intensity pulsed ultrasound (LIPUS) was proven to have a positive impact on bone healing in animal and clinical studies. METHODS: In this prospective, randomized controlled trial the effect of LIPUS during distraction osteogenesis was investigated. Thirty-six patients who underwent distraction osteogenesis (>2 cm) were enrolled. Sixteen patients in the treatment group received LIPUS, and 20 patients as control group did not. Ultrasound treatment device was transcutaneously applied at the distraction gap for 20 minutes daily (frequency 1.5 MHz, signal burst with 200 µs, signal repetition frequency 1.0 kHz, intensity 30 mW/cm(2)). Evaluation of patients was performed by standard radiographs every 3 weeks to 4 weeks. RESULTS: Average transport distance was 7.0 cm in the ultrasound group and 6.3 cm in the control group. Mean Paley index for the ultrasound group was 1.09 mo/cm and 1.49 mo/cm for the control group. Mean distraction consolidation index for the ultrasound group was 32.8 d/cm and 44.6 d/cm for the control group. The calculated indices indicated no significant statistical difference between the two groups (p < 0.116) but the fixator gestation period could be decreased for 43.6 days in the treatment group. CONCLUSIONS: Therapeutic application of LIPUS during callus distraction constitutes a useful adjuvant treatment during distraction osteogenesis and has a positive effect on healing time with no negative effects.

[Surface modification of metal implant materials by low-pressure plasma treatment]. / Oberflächenmodifikation metallischer Implantatmaterialien durch Niederdruckplasmabehandlung / Surface modification of metal implant materials by low-pressure plasma treatment.

BACKGROUND: Plasma treatment leads to a significant change of surface free energy of medical implant materials. These changes strongly influence protein and cell adhesion on the material surface. The aim of the study was to quantify the plasma-induced surface changes and to analyse whether the change of treatment parameters, such as pressure, gas mixture, energy and treatment time, influences the surface free energy of the implant materials. To improve the biocompatibility of the surfaces, polyamino acid coating experiments were performed. MATERIALS AND METHODS: Three different metal implant materials (X2CrNiMo18-15-3, Ti6Al4V, Ti6Al7Nb) were treated with a double-inductively coupled low-pressure plasma. The influence of treatment parameter variation on the surface free energy was evaluated by drop shape analysis. The plasma treated and non-treated materials were incubated in collagen I solution. Afterwards, the coatings were analysed by electron microscopy in terms of structure and adhesion. RESULTS: Drop shape analysis revealed that plasma treatment leads to a significant increase of surface free energy in all groups. Long plasma treatment times and low treatment pressures lead to a significant (p<0.05) extension of the detectable surface free energy increase. Coating experiments showed that only on plasma-treated samples solid and adherent collagen layers could be achieved.

[A double inductively coupled low-pressure plasma for sterilization of medical implant materials]. / Doppelt induktiv gekoppeltes Niederdruckplasma zur Sterilisation von medizinischen Implantatmaterialien.

The potential of plasma treatment in medicine is only slowly gaining acceptance. Inactivation of germs through exposure to UV radiation produced by plasma discharges and sterilization of medical implant devices and instruments is one possible application of this technique. In addition, due to the manifold possibilities of coating through plasma processes, quick sterilization-coating combinations of medical implant devices are possible. To analyze the effectiveness of this sterilization process on different material surfaces, three different alloys (X2CrNiMo18-15-3, Ti6Al7Nb and Ti6Al4V) and one thermoplastic material (ultra-high molecular weight polyethylene, UHMWPE), commonly used in medical implant devices, were examined in the presented study. After spraying Bacillus atrophaeus spores (10(6) CFU) on the surfaces of four different implant materials tested in this study (X2CrNiMo18-15-3, UHMWPE, Ti6Al7Nb and Ti6Al4V), it was demonstrated in each of four gas mixtures used (Ar, Ar:O2, Ar:H2 and Ar:N2) that due to the application of inductively coupled low-pressure plasma technique, plain medical implant materials can be sterilized rapidly, and can be protective and efficient.

Morphological characterization and in vitro biocompatibility of a porous nickel-titanium alloy.

Disks consisting of macroporous nickel-titanium alloy (NiTi, Nitinol, Actipore) are used as implants in clinical surgery, e.g. for fixation of spinal dysfunctions. The morphological properties were studied by scanning electron microscopy (SEM) and by synchrotron radiation-based microtomography (SRmuCT). The composition was studied by X-ray diffractometry (XRD), differential scanning calorimetry (DSC), and energy-dispersive X-ray spectroscopy (EDX). The mechanical properties were studied with temperature-dependent dynamical mechanical analysis (DMA). Studies on the biocompatibility were performed by co-incubation of porous NiTi samples with isolated peripheral blood leukocyte fractions (polymorphonuclear neutrophil granulocytes, PMN; peripheral blood mononuclear leukocytes, PBMC) in comparison with control cultures without NiTi samples. The cell adherence to the NiTi surface was analyzed by fluorescence microscopy and scanning electron microscopy. The activation of adherent leukocytes was analyzed by measurement of the released cytokines using enzyme-linked immunosorbent assay (ELISA). The cytokine response of PMN (analyzed by the release of IL-1ra and IL-8) was not significantly different between cell cultures with or without NiTi. There was a significant increase in the release of IL-1ra (p<0.001), IL-6 (p<0.05), and IL-8 (p<0.05) from PBMC in the presence of NiTi samples. In contrast, the release of TNF-alpha by PBMC was not significantly elevated in the presence of NiTi. IL-2 was released from PBMC only in the range of the lower detection limit in all cell cultures. The material, clearly macroporous with an interconnecting porosity, consists of NiTi (martensite; monoclinic, and austenite; cubic) with small impurities of NiTi2 and possibly NiC(x). The material is not superelastic upon manual compression and shows a good biocompatibility.

Inhibition of PMN apoptosis after adherence to dip-coated calcium phosphate surfaces on a NiTi shape memory alloy.

Nickel-titanium shape-memory alloys (NiTi-SMA) were coated with calcium phosphate by dipping in oversaturated calcium phosphate solution (CaP-coating). Polymorphonuclear neutrophil granulocytes (PMN) belong to the first cells which will adhere to implant materials. We analyzed the apoptosis of isolated human PMN after cell culture on non-coated and CaP-coated NiTi-SMA by light and scanning electron microscopy (cell morphology) and by flow cytometry (DNA-fragmentation). In contrast to PMN adherent to non-coated NiTi-SMA, the apoptosis of PMN adherent CaP-coated samples was inhibited. Cell culture media obtained from cultured leukocytes with CaP-coatings (conditioned media, CM) were able to transfer the apoptosis inhibiting activities to freshly isolated PMN. There was a significant (p<0.01) increase in GM-CSF, IL-8, IL-6, and TNF-alpha within CM obtained from coated versus non-coated NiTi-SMA as was determined by ELISA.

Calcium phosphate coating of nickel-titanium shape-memory alloys. Coating procedure and adherence of leukocytes and platelets.

Nickel-titanium shape-memory alloys (NiTi-SMA) were coated with calcium phosphate by dipping in oversaturated calcium phosphate solution. The layer thickness (typically 5-20 micrometer) can be varied by choice of the immersion time. The porous nature of the layer of microcrystals makes it mechanically stable enough to withstand both the shape-memory transition upon cooling and heating and also strong bending of the material (superelastic effect). This layer may improve the biocompatibility of NiTi-SMA, particulary for osteosynthetic devices by creating a more physiological surface and by restricting a potential nickel release. The adherence of human leukocytes (peripheral blood mononuclear cells and polymorphonuclear neutrophil granulocytes) and platelets to the calcium phosphate layer was analyzed in vitro. In comparison to non-coated NiTi-SMA, leukocytes and platelets showed a significantly increased adhesion to the coated NiTi-SMA.