Copper complexes as a source of redox active MRI contrast agents

The study reports an advance in designing copper-based redox sensing MRI contrast agents. Although the data demonstrate that copper(II) complexes are not able to compete with lanthanoids species in terms of contrast, the redox-dependent switch between diamagnetic copper(I) and paramagnetic copper(II) yields a novel redox-sensitive contrast moiety with potential for reversibility

Biomechanical evaluation of location and mode of failure in three screw fixations for a comminuted transforaminal sacral fracture model

Background: Pelvic ringecomminuted transforaminal sacral fracture injuries are rotationally and vertically unstable and have a high rate of failure. Objective: Our study purpose was to use three-dimensional (3D) optical tracking to detect onset location of boneeimplant interface failure and measure the distances and angles between screws and line of applied force for correlation to strength of pelvic fracture fixation techniques. Methods: 3D relative motion across sacralerami fractures and screws relative to bone was measured with an optical tracking system. Synthetic pelves were used. Comminuted transforaminal sacralerami fractures were modelled. Each pelvis was stabilised by either (1) two iliosacral screws in S1, (2) one transsacral screw in S1 and one iliosacral screw in S1 and (3) one trans-alar screw in S1 and one iliosacral screw in S1; groups 4e6 consisted of fixation groups with addition of anterior inferior iliac pelvic external fixator. Eighteen-instrumented pelvic models with right ilium fixed simulate single-leg stance. Load was applied to centre of S1 superior endplate. Five cycles of torque was initially applied, sequentially increased until permanent deformation occurred. Five cycles of axial load compression was next applied, sequentially increased until permanent deformation occurred, followed by axial loading to catastrophic failure. A Student t test was used to determine significance (p < 0.05). Results: The model, protocol and 3D optical system have the ability to locate how subcatastrophic failures initiate. Our results indicate failure of all screw-based constructs is due to localised bone failure (screw pull-in push-out at the ipsilateral iliumescrew interface, not in sacrum); thus, no difference was observed when not supplemented with external fixation. Conclusion: Inclusion of external fixation improved resistance only to torsional loading. Translational Potential of this Article: Patients with comminuted transforaminal sacral eipsilateral rami fractures benefit from this fixation

Biomechanical evaluation of location and mode of failure in three screw fixations for a comminuted transforaminal sacral fracture model

Background: Pelvic ring–comminuted transforaminal sacral fracture injuries are rotationally and vertically unstable and have a high rate of failure. Objective: Our study purpose was to use three-dimensional (3D) optical tracking to detect onset location of bone–implant interface failure and measure the distances and angles between screws and line of applied force for correlation to strength of pelvic fracture fixation techniques. Methods: 3D relative motion across sacral–rami fractures and screws relative to bone was measured with an optical tracking system. Synthetic pelves were used. Comminuted transforaminal sacral–rami fractures were modelled. Each pelvis was stabilised by either (1) two iliosacral screws in S1, (2) one transsacral screw in S1 and one iliosacral screw in S1 and (3) one trans-alar screw in S1 and one iliosacral screw in S1; groups 4–6 consisted of fixation groups with addition of anterior inferior iliac pelvic external fixator. Eighteen-instrumented pelvic models with right ilium fixed simulate single-leg stance. Load was applied to centre of S1 superior endplate. Five cycles of torque was initially applied, sequentially increased until permanent deformation occurred. Five cycles of axial load compression was next applied, sequentially increased until permanent deformation occurred, followed by axial loading to catastrophic failure. A Student t test was used to determine significance (p < 0.05). Results: The model, protocol and 3D optical system have the ability to locate how sub-catastrophic failures initiate. Our results indicate failure of all screw-based constructs is due to localised bone failure (screw pull-in push-out at the ipsilateral ilium–screw interface, not in sacrum); thus, no difference was observed when not supplemented with external fixation. Conclusion: Inclusion of external fixation improved resistance only to torsional loading. Translational Potential of this Article: Patients with comminuted transforaminal sacral–ipsilateral rami fractures benefit from this fixation. Keywords: bone–implant failure, external fixator, fracture stabilisation, pelvic ring injury, pelvic screws, transforaminal sacral fractur

Hybrid instrumentation in lumbar spinal fusion : a biomechanical evaluation of three different Instrumentation techniques

Study Design Ex vivo human cadaveric study. Objective The development or progression of adjacent segment disease (ASD) after spine stabilization and fusion is a major problem in spine surgery. Apart from optimal balancing of the sagittal profile, dynamic instrumentation is often suggested to prevent or impede ASD. Hybrid instrumentation is used to gain stabilization while allowing motion to avoid hypermobility in the adjacent segment. In this biomechanical study, the effects of two different hybrid instrumentations on human cadaver spines were evaluated and compared with a rigid instrumentation. Methods Eighteen human cadaver spines (T11-L5) were subdivided into three groups: rigid, dynamic, and hook comprising six spines each. Clinical parameters and initial mechanical characteristics were consistent among groups. All specimens received rigid fixation from L3-L5 followed by application of a free bending load of extension and flexion. The range of motion (ROM) for every segment was evaluated. For the rigid group, further rigid fixation from L1-L5 was applied. A dynamic Elaspine system (Spinelab AG, Winterthur, Switzerland) was applied from L1 to L3 for the dynamic group, and the hook group was instrumented with additional laminar hooks at L1-L3. ROM was then evaluated again. Results There was no significant difference in ROM among the three instrumentation techniques. Conclusion Based on this data, the intended advantage of a hybrid or dynamic instrumentation might not be achieve