Embolization coils are among the most widely used devices in interventional radiology, but not all coils are deployed the same way. Coils generally fall into two broad categories based on how they are released from the delivery system: detachable coils, which offer mechanical control over the exact moment of release, and pushable coils, which are advanced and released simply by the force used to push them out of the catheter. The distinction between detachable vs pushable coils has real implications for procedural control, cost, and how operators approach different clinical scenarios.
How Do Pushable Coils Work?
Pushable coils are deployed by advancing them through a delivery catheter using a guidewire or pusher, and the coil exits the catheter tip and enters the vessel simply through mechanical advancement — there is no separate detachment mechanism. Once the coil has left the catheter, its position is essentially fixed; if the placement is not ideal, retrieving or repositioning a pushable coil is far more difficult than with a detachable system. This straightforward mechanism generally makes pushable coils quicker to deploy and typically less expensive per coil.
How Do Detachable Coils Differ?
Detachable coils remain mechanically or electrolytically attached to a delivery wire even after they have exited the catheter and taken shape within the target vessel. This allows the operator to visualize the coil's position and configuration on imaging before making the final decision to release it. If the position is not satisfactory, a detachable coil can generally be withdrawn back into the catheter and repositioned or removed entirely — a level of control that pushable coils do not offer.
Why Does Detachment Control Matter Clinically?
The ability to reposition or retrieve a coil before final release is particularly valuable in anatomically complex or high-stakes locations, such as near small branch vessels where inaccurate placement could risk non-target embolization, or in vessels where the first coil placed will serve as a "framing" coil that determines how subsequent coils pack into the space. In these situations, the precision offered by detachable coils can reduce the risk of needing to abandon a poorly placed coil or accept a suboptimal result.
When Might Pushable Coils Be Preferred?
Pushable coils remain a reasonable and commonly used choice in situations where precise, individualized placement control is less critical — for example, when filling a relatively large, straightforward vessel where general positioning within the target segment is sufficient, or when procedural efficiency and cost are significant considerations. Since detachable coil systems generally involve a more complex delivery mechanism, they tend to cost more per coil, which factors into an operator's choice, particularly in procedures requiring many coils to achieve adequate packing density.
How Do Operators Decide Which to Use?
The decision between detachable and pushable coils depends on vessel anatomy, the criticality of precise placement, the number of coils anticipated, and clinical judgment about the specific risks in a given case. Many procedures use a combination approach, such as a detachable coil to establish a precisely placed framing coil, followed by pushable coils to fill in the remaining space more efficiently. Neither coil type is universally superior — the appropriate choice is determined by the treating physician based on the specific clinical situation.
Coil Systems From INVAMED
INVAMED manufactures the Spider Peripheral Detachable Coil System, a detachable and pushable coil platform designed for embolization of peripheral aneurysms, AV fistulas, and abnormal vessels, offering stable coil packing with controlled mechanical detachment. Further details are available on the Spider Peripheral Detachable Coil System product page. Device selection should always be guided by the treating physician and the product's Instructions for Use (IFU); availability and indications vary by country.
Device availability and regulatory status vary by country. Please contact INVAMED or your authorized local distributor for current regulatory information applicable to your region.