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TECHNICAL PAPERS

Novel Stent for Dacryocystorhinostomy (DCR) and Other Surgical Applications

[+] Author and Article Information
David R. Wulfman

Department of Mechanical Engineering,  University of Minnesota, Minneapolis, MN 55455

Andrew R. Harrison

Department of Ophthalmology, University of Minnesota, Minneapolis, MN 55455

Dave Hultman

Departments of Electrical Engineering and Aerospace Engineering, University of Minnesota, Minneapolis, MN 55455

J Biomech Eng 127(6), 952-955 (Jul 12, 2005) (4 pages) doi:10.1115/1.2049338 History: Received April 08, 2005; Revised July 12, 2005

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Copyright © 2005 by American Society of Mechanical Engineers
Topics: Surgery , stents
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Figures

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Figure 1

Obstructed tear duct and illustration of surgical repair. (a) Tear duct obstruction results in interruption of tear flow through the lacrimal system. (b) A new passage (osteotomy) is surgically formed approximately across from the common canaliculus. Tube like stents are threaded through the canaliculi, new osteotomy, and tied off in the nasal passage. Stent remains 3–6months after surgery.

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Figure 2

Stent design and function (general): Image of the general design of new stent. The sleeve balloon is everted over the thicker via wall. A needle driven through the thick wall acts as an inflation line for the balloon.

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Figure 3

Stent placement in the osteotomy. Stent is placed in the surgically formed osteotomy such that its medial portion serves as a bridge between the nasal cavity and tear sac. Upon proper placement, the stent is inflated, lodging itself within the new surgical incision. The softness of the balloon conforms within the irregularities of the new passage. Like current stents, the new stent is designed to remain implanted for 3–6months after surgery. The stent is removed by deflating the balloon via a nasal approach.

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Figure 4

Typical mold assembly for stent. Silicone is injected into mold body, then the plunger is driven in place as shown, forming the geometry of the stent. Body wall, plunger proportions, and geometry can be varied to change geometry and inflation profile of the final stent.

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Figure 5

Illustration of stent assembly process. As shown, the stent is inserted within an assembly tube after the clamping ring is stretched over a conical shoe. The ring is then inverted over the outside wall of the assembly tube forming cavity. When compressed air is applied through the assembly tube, the balloon is partially inflated and the stent body is driven into the balloon.

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Figure 6

Detail of stent inflation. A needle is driven into the stent body wall forming an inflation line to the surrounding balloon. Through use of a syringe (as shown) or other pumping device, saline is driven through the inflation line, expanding the balloon. After the balloon is inflated, the needle is removed. The inflation line seals in the needle’s wake due to compressive hoop stresses resultant from the inflation pressure of the balloon.

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Figure 7

Assembled and inflated stents shown with a dime

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Figure 8

Illustration of lacrimal stent with introducer. The inner segment of the introducer is driven into the inside diameter of the stent body while the outer segment rests against the stent’s proximal end. As shown, the introducer accommodates an inflation line. The outer segment is scaled such that its outside diameter is the same as that of the stent. The introducer permits placement and inflation of the stent through the nose. The stent is released from the introducer by applying antagonistic finger force between the inner and outer segments, pulling the inner segment out of the stent body.

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