The Pitch is a new, recurring feature on OpNotes in which we invite a manufacturer to fill out a standard questionnaire about a novel device, and we then independently choose an expert user to comment. If you would like your device to be featured on The Pitch, please e-mail editor (at) opnotes.com.

In this edition of The Pitch, we take a look at the NGage Nitinol Stone Extractor by Cook Medical (Spencer, Indiana). 

FROM THE MANUFACTURER

Description of novel features or technologies
NGage is not a grasper or stone basket, but a whole new category in the evolution of stone extraction. The patented design enables the physician to engage, reposition, release, or extract stones from within the urinary tract.

Does this device replacing an existing device?
No 

Advantages over existing products
The challenge with traditional stone graspers is the ability to retain stone fragments in difficult anatomy. Tests have shown that NGage has 50% greater retention strength than traditional graspers. Stone release is also difficult with baskets, and may even pose some problems for advanced nitinol stone extractors. In a calyceal model, the NGage demonstrated a superior ability to release stone fragments when compared with both standard and multi wire nitinol baskets.

FROM THE EXPERT USER 

The expert: Dr. Margaret Pearle (Professor of Urology, University of Texas Southwestern; internationally known expert in endourology and kidney stone disease)

Her take:  As an endourologist who has seen too many referrals and legal cases due to complications from basket injuries, I am a firm believer in the use of reversible retrieval devices in the ureter or across the ureteropelvic junction.

Don’t get me wrong: I routinely use tipless nitinol baskets for diplacing stones from the lower to upper pole calyces, for retrieving stones with a flexible nephroscope during percutaneous nephrolithotomy, and for retrieval of small fragments during ureteroscopy when an access sheath is in the renal pelvis.

My ability to judge when a stone can be safely withdrawn, however, is not fool-proof, and as such I prefer to use a safe retrieval device that will release a stone fragment before avulsing the ureter. Although I love my 3Fr wire-pronged grasper for that reason, it has a relatively large caliber relative to the current 1.7-2.4F nitinol baskets, which causes reduced visibility and irrigant flow. The device also releases stone fragments a bit sooner than desired from a safety standpoint.

The N-gage device addresses many of these concerns. The 1.7F version allows for excellent visibility and irrigant flow, and deflection is virtually uncompromised. It also holds fragments securely, but releases them reliably without one needing to disassemble the device.

A device of this size is perfect for retrieving fragments that are about 2-6 mm. It doesn’t do quite as well with very small fragments (1-2 mm) as the wire-pronged grasper, and I do like to retrieve every last fragment from the kidney. In most cases, however, this is not really an issue.

Our work using a tensiometer in vitro to measure retention strength showed that the Ngage did retain beads better than a wire-pronged grasper, particularly smooth, round beads with which the wire-pronged grasper was deficient.

It does take a little practice to get the hang of using it. I open the device and drive it straight onto the fragment with my ureteroscope, encircling it in the wires. In that regard, perhaps it isn’t quite as efficient at grasping fragments in the fornices as a nitinol basket.

Overall I find the N-gage a very useful device. Although it may not replace other retrieving devices, it certainly works for the majority of stone fragments.

If you have used this device, please share your experiences using the comment form below.