Increasing angulation decreases measured aortic stent graft pullout forces

Area of Science:

• Biomedical Engineering
• Medical Device Testing
• Vascular Surgery

Background:

• Experimentally measured pullout forces for stent grafts (SGs) are crucial for clinical and computational studies.
• Previous studies primarily assessed SG pullout in a straight caudal direction.
• Clinical and numerical evidence suggests displacement forces on SGs are often directed anteriorly.

Purpose of the Study:

• To experimentally measure stent graft (SG) pullout forces as a function of angulation.
• To test the hypothesis that SG pullout forces decrease with increasing angulation.

Main Methods:

• Six different SG models were deployed in bovine aortas and pulled out using an electronic motor at 1 mm/s.
• Tension force was continuously measured with a digital load cell as SG angulation varied from 0 to 90 degrees.
• Tests were conducted in a 37°C saline bath, with at least three repetitions per device/angle.

Main Results:

• A total of 310 valid pullout tests were analyzed across six SG devices.
• All tested SGs exhibited a decrease in average pullout force from 0 to 90 degrees angulation.
• For example, Bolton Treovance force decreased from 39.3 N to 23.9 N; Cook Zenith LP from 50.3 N to 41.8 N.

Conclusions:

• This study is the first to report changes in stent graft (SG) pullout force with varying angulation.
• Results demonstrate a general trend of decreasing pullout force with increasing angulation.
• The findings provide updated benchmark data for clinical discussions, computational modeling, and future SG design.