Zeitschriften

Ohne Zusammenfassung     

Zeitschriften

Ohne Zusammenfassung     

Zeitschriften

Ohne Zusammenfassung     

Zeitschriften

Ohne Zusammenfassung     

Zeitschriften

Ohne Zusammenfassung     

Serial proton MR spectroscopy of contrast-enhancing multiple sclerosis plaques: absolute metabolic values over 2 years during a clinical pharmacological study

BACKGROUND AND PURPOSE: The time courses of total creatine (Cr), N-acetylaspartate (NAA), choline (Cho), and myo-inositol have not previously been investigated in the follow-up of contrast-enhancing multiple sclerosis (MS) plaques. Therefore, over a period of 2 years, we compared the absolute concentrations of these metabolites between patients treated with a placebo or 15 +/- deoxyspergualin (DSG) and between clinical groups with relapsing-remitting or secondary-progressive MS. METHODS: Sixteen patients, recruited from a pharmacological study of DSG, and 11 healthy control subjects were investigated by a stimulated-echo acquisition mode sequence (TR/TE = 3000/20). The selected volume initially contained a contrast-enhancing plaque, which was followed up for a period of 2 years. RESULTS: In contrast-enhancing plaques, Cho was significantly elevated and showed a significant reduction after both 3 and 12 months. The initially normal Cr significantly increased between 3 and 12 months, and was negatively correlated with plaque volume on T1-weighted MR images. NAA initially showed normal values, a significant decrease at 1 month, and a slow recovery over 2 years. Myo-inositol did not show a clear tendency. The placebo group did not differ from the treated group, nor did the relapsing-remitting group differ from the secondary-progressive group. CONCLUSION: The contradictory time courses of Cr and NAA show that an absolute quantification in proton MR spectroscopy in MS is necessary to avoid a false interpretation of reduced NAA/Cr ratios. The increase in Cr is probably due to remyelination. The initial dip and later recovery of NAA seem to be related to diminishing edema and remyelination.     

The predictive value of transcutaneous oxygen tension measurement in diabetic lower extremity ulcers treated with hyperbaric oxygen therapy: a retrospective analysis of 1144 patients

The objective of this retrospective analysis was to determine the reliability of transcutaneous oxygen tension measurement (TcPO2) in predicting outcomes of diabetics who underwent hyperbaric oxygen therapy for lower extremity wounds. Six hyperbaric facilities provided TcPO2 data under several possible conditions: breathing air, breathing oxygen at sea level, and breathing oxygen in the chamber. Overall, 75.6% of the patients improved after hyperbaric oxygen therapy. Baseline sea-level air TcPO2 identified the degree of tissue hypoxia but had little statistical relationship with outcome prediction because some patients healed after hyperbaric oxygen therapy despite very low prehyperbaric TcPO2 values. Breathing oxygen at sea level was unreliable for predicting failure, but 68% reliable for predicting success after hyperbaric oxygen therapy. TcPO2 measured in chamber provides the best single discriminator between success and failure of hyperbaric oxygen therapy using a cutoff score of 200 mmHg. The reliability of in-chamber TcPO2 as an isolated measure was 74% with a positive predictive value of 58%. Better results can be obtained by combining information about sea-level air and in-chamber oxygen. A sea-level air TcPO2 < 15 mmHg combined with an in-chamber TcPO2 < 400 mmHg predicts failure of hyperbaric oxygen therapy with a reliability of 75.8% and a positive predictive value of 73.3%.     

Biomechanical comparison of tension band- and interfragmentary screw fixation with a new implant in transverse patella fractures

Aim

The aim of the present study was to compare the primary fixation stability and initial fixation stiffness of two established fixation techniques, the tension band wiring technique and interfragmentary screw fixation, with a mini-screw fragment fixation system in a model of transverse patella fracture. It was hypothesised that the biomechanical loading performance of the fragment fixation system would not significantly differ from the loading characteristics of the two established methods currently investigated.

Materials and methods

Ninety-six calf patellae were used in this biomechanical model. A standardized transverse patella fracture was induced and three different fixation methods, including the modified tension band wiring technique, interfragmentary screw fixation, and the mini-screw fragment fixation system, were used for fragment fixation. Specimens were mounted to a loading rig which was secured within a material testing machine. In each fixation group, eight specimens were loaded to failure at a simulated knee angle of either 0° or 45°. Another eight specimens were submitted to a polycyclic loading protocol consisting of 30 cycles between 20 N and 300 N at a simulated knee angle of 0° or 45°. The residual displacement between the first and the last cycle was recorded. Differences in the biomechanical performance between the three fixation groups were evaluated.

Results

No significant differences between the three fixation groups were observed in the parameters maximum load to failure and linear fixation stiffness with monocyclic loading. Specimens being loaded at 45° showed significantly lower maximum failure loads and linear stiffness when compared with 0°. During polycyclic loading, no significant differences in the residual displacement were observed between the groups at 0° loading angle, while at 45°, residual displacement was significantly higher with tension band fixation when compared with interfragmentary screw fixation or the fragment fixation system.

Conclusion

The biomechanical performance of the fragment fixation system was comparable to interfragmentary screw fixation and superior to the tension band wiring technique. Given the advantages of a system which provides interfragmentary compression and which simplifies fracture fixation after open or closed reduction, we believe the fragment fixation system to be an adequate alternative in the osteosynthesis of transverse patella fractures.