Objective To elucidate the early detachment of the Solitaire stent during mechanical thrombectomy, we tested the stent in vitro under various conditions and evaluated with microscopy.

Methods A total of five stents were tested. Using a dynamic mechanical analysis machine, we calculated the tensile force needed for separation of the four stents from the pusher wire. Stent Nos 1 and 2 were tested without any prior manipulation. During the retraction test, no sheathing around the stent–wire junction was applied to stent No 1 whereas stent No 2 was partially covered with a sheath in accordance with instructions for use (IFU) recommendations. Stent No 3 was tested after deployment and retrieval were performed three times in an in vitro vascular replica with sheathing during retrieval. Stent No 4 was tested after one deployment and retrieval using the same replica as in stent No 3 without sheathing. In addition, forward pushing force was applied intentionally during retraction to induce excessive bending of the stent. Stent No 5 was pulled apart by both hands. After separation, stent tips and pusher wires were studied for all stents under the microscope.

Results The tensile force needed for separation was about 6 N for stent Nos 1, 2, and 3, and about 4 N for stent No 4. All of the stents showed separation at the proximal marker, not at the detachment zone.

Conclusions Detachment of the Solitaire stent during thrombectomy can be due to separation around or inside the proximal marker. Adherence to the manufacturer's IFU of partial re-sheathing during retraction and not using the device for more than two passes might decrease the possibility of such device failure.