Balloon dilation + thorn penetration dual mechanism
Reflow Medical’s Spur Stent System, approved by the FDA via the De Novo pathway in May 2025, is the first retrievable peripheral stent system specifically designed to treat primary or restenosis lesions of the below-knee artery (BTK) for patients with chronic limb-threatening ischemia (CLTI).
This system employs a unique “retrievable stent therapy” concept. Unlike traditional permanently implanted stents, Spur can be completely retrieved after lesion treatment, leaving no metal implant in the body, thus preserving the possibility of future treatment of the vessel.
The Spur Stent System consists of three core components: a self-expanding nickel-titanium alloy stent, an integrated semi-compliant balloon catheter, and a radially expandable spur. The system uses an over-the-wire (OTW) delivery method, has an outer diameter of 5.6 Fr (approximately 1.88 mm), and is compatible with 6F sheaths and 0.014-inch guidewires.
The stent body is made of nickel-titanium alloy and features self-expanding properties. The stent has a closed-pore design, providing temporary mechanical support. The stent is designed for retrieval, allowing a single device to be deployed and retrieved up to four times in the same or different vessels. The system is available in two sizes: a 3.0mm diameter (65mm treatment length) for vessels of 2.5-3.49mm and a 4.0mm diameter (60mm treatment length) for vessels of 3.25-4.5mm.
The stent surface is uniformly distributed with 112 radially expandable spikes facing the vessel wall. During balloon inflation, these spikes expand radially, penetrating the plaque and vessel wall, reaching the adventitia. The penetration depth of the spikes is optimized for controlled penetration of the lesion, altering plaque morphology, increasing acute lumen diameter, while simultaneously improving vascular compliance and reducing vascular recoil.
The system integrates a semi-compliant dilatation balloon and employs a “needle-pull” deployment mechanism. The balloon operates at a rated burst pressure (RBP) of 12 atm. At a rated pressure of 6 atm, the diameters are 3.00 mm (3.0 specification) and 4.02 mm (4.0 specification), respectively, expanding to 3.20 mm and 4.23 mm at 12 atm. The distal 30 cm of the catheter has a hydrophilic coating for easy delivery. The effective length of the balloon catheter is 135 cm, meeting the requirements for lower extremity vascular interventional procedures.
The stent is mounted on a balloon catheter and restrained in a folded state by an outer sheath. Upon reaching the lesion site, the outer sheath is retracted to release the stent, and balloon inflation allows the thorn to penetrate the lesion. After balloon retraction, pushing the outer sheath forward recaptures the stent, achieving complete retrieval. This design ensures no metal implant remains in the body after treatment, preserving the vessel’s future treatment potential.
When the thorn penetrates the vessel wall, it disrupts the annular calcification ring (confirmed by IVUS imaging), creating a channel within the plaque. This improves luminal openness and creates better drug penetration conditions for subsequent drug-coated balloon (DCB) treatment. Preclinical studies have shown that the thorn structure promotes the transfer of coated drugs to deeper layers of the vessel wall.
The system is equipped with gold contrast markers for precise intraoperative stent placement and assessment of dilation effectiveness.
The system’s compatibility with 6F sheaths and 0.014-inch guidewires makes it highly operable; the DEEPER REVEAL clinical trial showed a 99.2% success rate.