Agnieszka Kierzkowska

Characteristics of anodic layer on Ti6Al4V ELI alloy after bending

The behaviour of the anodised titanium alloy Ti6Al4V ELI deformed by bending was characterised in mechanical and electrochemical tests. The deformation zones formed by tensile and compressive stresses were recognised by Finite Element Method analysis. Relevant deformed surface zones were characterised by microhardness and roughness measurements and electrochemical testing (Ecorr, anodic polarisation, EIS) in air-saturated Ringers solution. The effect of deformation on properties of bent implant rods was investigated. Bending affected mostly the properties of material in the tensile zone of the specimen, whereas the properties of surface layer in the compressive zone and in tensile zone after rebending are comparable and not so severe. Studies in static conditions will be followed by fatigue studies. Results are important in surgical practice the evaluation of the effect of shaping applied during preoperative procedures on the performance of spinal implant systems. Studies are the basis for in vivo studies. [Received 31 April 2006, Accepted 19 March 2007]

In vitro simulation of intraoperative vertebroplasty applied for pedicle screw augmentation. A biomechanical evaluation

BACKGROUND AND PURPOSEnThe purpose of this study was to evaluate the effect of an in vitro simulation of intraoperative vertebroplasty on embedded pedicle screws resistance to pullout. This method involved an application of acrylic cement into the vertebral bodies only after pedicle screws implementation.nnnMATERIALS AND METHODSnFor the purpose of conducting this research, the authors used the spines of fully-grown pigs. The procedure was as follows: firstly, the pedicle screws were bilaterally implemented in 10 vertebrae; secondly, cancellous bone was removed from vertebral bodies selected for screws augmentation and lastly it was replaced by polymethylmethacrylate (PMMA). Six vertebrae with implemented pedicle screws served as a control group. The pullout strength of thirty-two screws (20 augmented and 12 control) was tested. All screws were pulled out at a crosshead speed of 5mm/min.nnnRESULTSnThe PMMA-augmented screws showed a 1.3 times higher average pullout force than the control group: respectively 1539.68N and 1156.59N. In essence, no significant discrepancy was determined between average pullout forces of screws which were pulled as first when compared with consecutive contralateral ones.nnnCONCLUSIONSnAn in vitro simulation of intraoperative injection of PMMA in the vertebral body instrumented with screws (intraoperative vertebroplasty) resulted in enhancing its pullout strength by 33%. Pulling of one of the pedicular screws from the augmented vertebral body did not affect the pullout resistance of the contralateral one.

The Use of Incremental Technology to Produce 3D-Truss Ti6Al4V Implants which Improves the Spinal Treatment Effectiveness

In the study the impact of manufacturing technology of alloy Ti6Al4V implants on the effectiveness of fusion, treatment on the defined tissue biocompatibility and on the osseointegration with the bone” was analyzed. Models and samples made by material removal processing and electron beam technology EBT were tested in vitro biological and in vivo animals tests with histopathological assessment of tissues. The results confirmed the biocompatibility of the Ti6Al4V 3D-T alloy, and thus safety in bone surgery. On the basis of CTt examinations of preparates taken from animals after 3÷4M implantation it has been shown a very good osseointegration of truss structures with the bone. The introduction of EBT technology extends the capabilities of designing of a safe implant which is matched to the anatomy, exhibits complex spatial structure and surfaces that are conducive to the propagation of union/overgrowth of bone in accordance with the proposed hypothesis: Ivy-like mechanism.