Midterm Results of Proximal Aneurysm Sealing With the Ovation Stent-Graft According to On- vs Off-Label Use.

PURPOSE: To compare the use of the Ovation stent-graft according to the ≥7-mm neck length specified by the original instructions for use (IFU) vs those treated off-label (OL) for necks <7 mm long. METHODS: A multicenter retrospective registry (TriVascular Ovation Italian Study) database of all patients who underwent endovascular aneurysm repair with the Ovation endograft at 13 centers in Italy was interrogated to identify patients with a minimum computed tomography (CT) follow-up of 24 months, retrieving records on 89 patients (mean age 76.4±2.4 years; 84 men) with a mean follow-up of 32 months (range 24-50). Standard CT scans (preoperative, 1-month postoperative, and latest follow-up) were reviewed by an independent core laboratory for morphological changes. For analysis, patients were stratified into 2 groups based on proximal neck length ≥7 mm (IFU group, n=57) or <7 mm (OL group, n=32). Outcome measures included freedom from type Ia endoleak, any device-related reintervention, migration, and neck enlargement (>2 mm). RESULTS: At 3 years, there was no aneurysm-related death, rupture, stent-graft migration, or neck enlargement. There were no differences in terms of freedom from type Ia endoleak (98.2% IFU vs 96.8% OL, p=0.6; hazard ratio [HR] 0.55, 95% CI 0.02 to 9.71 or freedom from any device-related reintervention (92.8% IFU vs 96.4% OL, p=0.4; HR 2.42, 95% CI 0.34 to 12.99). In the sealing zone, the mean change in diameters was -0.05±0.8 mm in the IFU group and -0.1±0.5 mm in the OL group. CONCLUSION: Use of the Ovation stent-graft in patients with neck length <7 mm achieved midterm outcomes similar to patients with ≥7-mm-long necks. These midterm data show that the use of the Ovation system for the treatment of infrarenal abdominal aortic aneurysm is not restricted by the conventional measurement of aortic neck length, affirming the recent Food and Drug Administration-approved changes to the IFU.

Inexplicable late type Ia endoleak associated with the low-profile Ovation endograft in a patient with favorable neck anatomy: treatment with transcaval coil embolization.

PURPOSE: To report an unusual late type Ia endoleak after endovascular aneurysm repair with a low-profile sealing ring endograft and its treatment with transcaval sac embolization. CASE REPORT: An 82-year-old man was treated for a 47-mm abdominal aortic aneurysm associated with a 35-mm left common iliac artery aneurysm using an Ovation Abdominal Stent Graft System. Correct endograft placement was documented at 3-month follow-up. Seven months after the repair, the patient was admitted to the emergency department with acute left inguinal pain. Computed tomography showed aneurysm sac enlargement (57 mm) and a contained rupture of the left common iliac artery due to a late type Ia endoleak. The endoleak was embolized with coils and thrombin via a transcaval approach. Sac shrinkage without signs of endoleak was observed at 12-month follow-up. CONCLUSION: In this case, late endograft failure with sealing ring collapse created an inflow channel into the aneurysm sac, with massive type Ia endoleak.

Effect of Geometric Error on Friction Behavior of Cylinder Seals.

The tribological characteristics of the cylinder directly affect the operation accuracy of the pneumatic servo system. However, the geometric error has a significant effect on its tribological behavior and the related research is insufficient. Thus, the dynamic friction process of rubber seals has been investigated considering the influence of geometric errors. Firstly, based on the self-made friction test platform, the friction force of the rubber seals was studied and the influence law of geometric error on the contact area of the rubber seal ring was revealed. Secondly, the numerical model of the friction and contact of the rubber seals for the cylinder segment was developed by using the finite element simulation method and the influence laws of machining errors, such as roundness and straightness on the friction characteristics, were revealed. Finally, synergy effects of roundness and straightness in the friction behavior of rubber seals considering geometric errors was investigated, which lays a foundation for the accurate prediction of cylinder dynamic mechanical properties.