Kontrastmittelgestützte Magnetresonanzangiographie mit Eisenoxidpartikeln

Das superparamagnetische T2-Kontrastmittel (KM) Resovist zeigt unter T1-gewichteten Sequenzen niedrig dosiert ein positives und hoch dosiert ein negatives Signalverhalten. In der mit Resovist durchgeführten T1-gewichteten MRA konnte zwar ein intravasaler Signalanstieg, jedoch keine nutzbare Verlängerung der Bluthalbwertszeit (BHWZ) erzielt werden. Daraufhin wurde experimentell getestet, bei welchem Partikel-Durchmesser (DM) von Resovist (65-21nm), bei welcher Konzentration und welchen Sequenzen sich der T1-Effekt der KM diagnostisch nutzen lassen könnte. Unter Berücksichtigung dieser Ergebnisse wurde in der Tierstudie der Einfluss von Partikel-DM und Dosis für die T1-gewichtete MRA ermittelt. Abnehmender Partikel-DM und zunehmende KM-Dosis zeigten eine Signalverstärkung und eine verlängerte BHWZ. Die kleinste Resovist-Fraktion (21nm) erzielte neben der stärksten Signalerhöhung auch die längste BHWZ, sodass aussagekräftige MRA bis über 25 Minuten nach KM-Gabe angefertigt werden konnten

Biomechanical evaluation of combined short segment fixation and augmentation of incomplete osteoporotic burst fractures

Background: Treating traumatic fractures in osteoporosis is challenging. Multiple clinical treatment options are found in literature. Augmentation techniques are promising to reduce treatment-related morbidity. In recent years, there have been an increasing number of reports about extended indication for augmentation techniques. However, biomechanical evaluations of these techniques are limited. Methods: Nine thoracolumbar osteoporotic spinal samples (4 FSU) were harvested from postmortem donors and immediately frozen. Biomechanical testing was performed by a robotic-based spine tester. Standardized incomplete burst fractures were created by a combination of osteotomy-like weakening and high velocity compression using a hydraulic material testing apparatus. Biomechanical measurements were performed on specimens in the following conditions: 1) intact, 2) fractured, 3) bisegmental instrumented, 4) bisegmental instrumented with vertebroplasty (hybrid augmentation, HA) and 5) stand-alone vertebroplasty (VP). The range of motion (RoM), neutral zone (NZ), elastic zone (EZ) and stiffness parameters were determined. Statistical evaluation was performed using Wilcoxon signed-rank test for paired samples (p = 0.05). Results: Significant increases in RoM and in the NZ and EZ (p < 0.005) were observed after fracture production. The RoM was decreased significantly by applying the dorsal bisegmental instrumentation to the fractured specimens (p < 0.005). VP reduced fractured RoM in flexion but was still increased significantly (p < 0.05) above intact kinematic values. NZ stiffness (p < 0.05) and EZ stiffness (p < 0.01) was increased by VP but remained lower than prefracture values. The combination of short segment instrumentation and vertebroplasty (HA) showed no significant changes in RoM and stiffness in NZ in comparison to the instrumented group, except for significant increase of EZ stiffness in flexion (p < 0.05). Conclusions: Stand-alone vertebroplasty (VP) showed some degree of support of the anterior column but was accompanied by persistent traumatic instability. Therefore, we would advocate against using VP as a stand-alone procedure in traumatic fractures. HA did not increase primary stability of short segment instrumentation. Some additional support of anterior column and changes of kinematic values of the EZ may lead one to suppose that additive augmentation may reduce the load of dorsal implants and possibly reduce the risk of implant failure.<br

Experimentally induced incomplete burst fractures - a novel technique for calf and human specimens

Background: Fracture morphology is crucial for the clinical decision-making process preceding spinal fracture treatment. The presented experimental approach was designed in order to ensure reproducibility of induced fracture morphology. Results: The presented method resulted in fracture morphology, found in clinical classification systems like the Magerl classification. In the calf spine samples, 70% displayed incomplete burst fractures corresponding to type A3.1 and A3.2 fractures. In all human samples, superior incomplete burst fractures (Magerl A3.1) were identified by an independent radiologist and spine surgeon. Conclusions: The presented set up enables the first experimental means to reliably model and study distinct incomplete burst fracture patterns in an in vitro setting. Thus, we envisage this protocol to facilitate further studies on spine fracture treatment of incomplete burst fractures