The patient enablement instrument for back pain: reliability, content validity, construct validity and responsiveness.

BACKGROUND: Currently, there are no outcome measures assessing the ability of people with non-specific low back pain to self-manage their illness. Inspired by the 'Patient Enablement Instrument', we developed the Patient Enablement Instrument for Back Pain (PEI-BP). The aim of this study was to describe the development of the Patient Enablement Instrument for Back Pain (PEI-BP) and investigate content validity, construct validity, internal consistency, test-retest reliability, measurement error, responsiveness and floor and ceiling effects. METHODS: The PEI-BP consists of 6 items that are rated on a 0-10 Numeric Rating Scale. Measurement properties were evaluated using the COSMIN taxonomy and were based on three cohorts from primary care with low back pain: The content validity cohort (N = 14) which participated in semi-structured interviews, the GLA:D® Back cohort (N = 272) and the test-retest cohort (N = 37) which both completed self-reported questionnaires. For construct validity and responsiveness, enablement was compared to disability (Oswestry Disability Index), back pain beliefs (Brief Illness Perception Questionnaire), fear avoidance (Fear-Avoidance Beliefs Questionnaire-physical activity), mental health (SF-36), educational level and number of previous episodes of low back pain. RESULTS: The PEI-BP was found to have acceptable content validity, construct validity, reliability (internal consistency, test-retest reliability and measurement error) and responsiveness. The Smallest Detectable Change was 10.1 points illustrating that a patient would have to change more than 1/6 of the scale range for it to be a true change. A skewed distribution towards the high scores were found at baseline indicating a potentially problematic ceiling effect in the current population. CONCLUSIONS: The PEI-BP can be considered a valid and reliable tool to measure enablement on people seeking care for non-specific LBP. Further testing of the PEI-BP in populations with more severe LBP is recommended. TRIAL REGISTRATION: Not applicable.

New optional IVC filter for percutaneous retrieval--in vitro evaluation of embolus capturing efficiency.

PURPOSE: In-vitro evaluation of a new caval filter (Cook Celect Filter) developed for delayed percutaneous retrieval in comparison to the Gunther Tulip filter. MATERIALS AND METHODS: The new Celect filter is constructed on the basis of the Tulip filter and consists of 4 primary anchoring legs and additional 8 thinner secondary wires to stabilize the filter and to guarantee adequate filtering efficiency. The filtering wires are of the same amount and equal distribution as the filtering wires of the Tulip filter. The secondary wires are arranged in such a way that percutaneous filter retrieval should be possible even if the wires are incorporated into the caval wall. In a flow model (tube size ø15-, ø22- and ø30 mm), the filter was exposed to single and multiple emboli (blood clots) of different sizes (3 x 5, 3 x 10, 5 x 10, 3 x 20, 5 x 20, 7 x 10, 7 x 20 to 10 x 24 mm) to analyse the embolus capturing efficiency under different conditions including eccentric and concentric, horizontal and vertical positions in comparison to the Tulip filter. All testing was carried out in SPSS analytic software; statistical significance was assumed for p-values < 0.05. RESULTS: The in-vitro embolus capturing efficiency of the Celect filter proved to be equivalent to the Tulip filter. In the single-embolus test, 91.6 % of the clots were captured by the Celect filter and 87.2 % by the Tulip filter (p = 0.042). Large clots ranging from 7 x 10 to 10 x 24 mm were captured in all cases, whereas the capture rates for the 3 x 5-mm and 3 x 10-mm clots were lower. The filters captured significantly more clots in the concentric than in the eccentric location. There was no significant difference between the overall capture rates of the two filters in the multi-clot test (72.2 % vs. 75.1 %), which showed deterioration of filter function during multiple clot exposure. With the 15-mm tube, the Celect filter had a significantly higher capture rate than the Tulip filter, whereas it was lower with the ø30-mm tube. There was no significant difference between the filters in a ø22-mm tube. The pressure gradient across the filters when exposed to blood clots ranged from 4.9 - 7.4 mm Hg for the Celect filter and 5.7 - 6.8 mm Hg for the Tulip filter in the single-embolus testing. There was no significant difference in the multi-clot tests. CONCLUSION: The new Celect filter showed similar in-vitro capture properties as the Gunther Tulip filter and deserves further in-vivo testing.

Real-time MR fluoroscopy for MR-guided iliac artery stent placement.

The purpose of this study was to test the feasibility of real-time magnetic resonance (MR) guidance of iliac artery stent placement. Radial scanning together with the sliding window reconstruction technique was implemented on a 1.5 T magnet, yielding a frame rate of 20 images per second. Seven prototype nitinol ZA stents were deployed in iliac arteries of living pigs under MR control. All stents were well visualized on the radial MR images, allowing depiction of the mounted stents as well as stent deployment without anatomy-obscuring artifacts. Stent placement was sucessful in all cases and took 6 minutes on average. The position of the stents was correctly visualized by real-time radial MR scanning, as proved by digital subtraction X-ray angiography. Combined radial scanning and the sliding window reconstruction technique allow real-time MR-guided stent placement in iliac arteries.

[Stent placement with real time MRI guidance: initial animal experiment experiences]. / Stentplazierung unter Echtzeit-MR-Kontrolle: erste tierexperimentelle Erfahrungen.

PURPOSE: The aim of this study was to test the feasibility of iliac artery stent placement under MR guidance with real-time MR radial scanning in an animal model. MATERIALS AND METHODS: The experiments were performed on three pigs in a 1.5 T scanner. Radial scanning with a gradient echo technique (TR 8.4 ms, TE 3.6 ms, flip angle 10 degrees) was used. A dedicated backprojector performed the reconstruction of the raw data in real-time. The resulting MR-images were displayed on LCD screens beside the magnet. The sliding window reconstruction technique allowed image acquisition at a frame rate of 16 images per second. MR-compatible self-expanding stents with a diameter of 8 mm and a length of 3 cm were placed into the left iliac artery. Their positions were verified by digital subtraction angiography (DSA) and compared to MRI. RESULTS: All stents were successfully placed. Stent positions as monitored by real-time MR were identical to those seen on DSA images. The time needed for exact positioning of the scan plane ranged from 15 to 30 minutes. Stent placement itself took 8 minutes on average. CONCLUSION: Radial scanning applied together with the sliding window reconstruction technique allows placement of stents in iliac arteries under real-time MR control.