Absorbable anchor for hernia mesh fixation

Abstract

A method of forming and deploying an improved absorbable anchor for hernia mesh fixation is disclosed. The absorbable anchor of the present invention functions to securely fasten tough, non macro-porous, and relative inelastic mesh to soft tissue. The anchor is formed from co-polymers of lactide and glycolide.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The present application is a Divisional Application claiming the benefit of and priority to U.S. patent application Ser. No. 10 / 907,834, filed on Apr. 18, 2005, which is a Continuation-in-Part Application claiming the benefit of and priority to U.S. patent application Ser. No. 10 / 905,020, filed on Dec. 10, 2004 (now abandoned), the entire contents of which are hereby incorporated by reference.[0002]U.S. application Ser. No. 10 / 907,834 is also a Continuation-in-Part Application claiming the benefit of and priority to U.S. patent application Ser. No. 10 / 709,297, filed on Apr. 27, 2004 (now U.S. Pat. No. 7,758,612), the entire contents of which are hereby incorporated by reference.BACKGROUND OF THE INVENTION[0003]This invention relates to surgical fasteners and their associated applicators, and more particularly, surgically fastening material to tissue and their method of use.[0004]In laparoscopic repair of hernias surgical fasteners have be...

AI Technical Summary

Benefits of technology

The present invention relates to a method of producing a bio-absorbable hernia mesh fixation anchor and its delivery device. The anchor has a threaded portion and a slotted portion, and can be sterilized and packaged for implantation. The anchor can be made from d, l-lactide and glycolide co-polymers, which have a critical absorption time of 4-13 months. The anchor has a threaded section that easily penetrates tough, non-macro porous mesh and pulls the tissue towards the head of the anchor, firmly anchoring the mesh to the abdomen. The delivery device includes a housing, a delivery tube, an actuator, flexible anchor reaction members, a reciprocating anchor carrier, and a queuing spring to urge the anchors distally. The anchor has a centered internal channel through which the anchor carrier passes. The anchor is equipped with rigid barbs that expand the tissue to secure the anchor in place. The invention provides a method for producing a reliable and effective hernia mesh fixation anchor with good mechanical properties.

Problems solved by technology

Hernias of this type can be a congenital defect or can be caused by straining or lifting heavy objects.

The protrusion results in an unsightly bulge in the groin area often causing pain, reduced lifting ability, and in some cases, impaction of the bowel.

Phillips depicts the installed device returning to the H shape but he fails to teach how to generate enough spring action from the device to overcome the high radial forces generated by the tissue.

The primary problem with these prior art fasteners is that the mesh is attached to body tissue in as many as 100 places for large ventral hernias.

This results in a large quantity of metal remaining in the body as permanent implants, even though after the ingrowth phase the fasteners serve no useful purpose.

Compounding this problem the distal ends of the fasteners are sharp pointed and thus pose a continued pain or nerve damage hazard.

These materials require special attention to many design details that are much more demanding than their counterparts in metallic fixation devices such as applicator tool design, sterilization processes, and packaging.

Materials of appropriate strength are generally limited to synthetic materials.

Unfortunately, however, the optimum values of each of these properties are not available in any one of these materials so that it is necessary to make performance tradeoffs.

Because of the lower strength of absorbable material this requirement imposes severe design constraints on both the applier and the anchor.

It can fracture, separating the mesh holding feature from the tissue-snaring feature, or it can pull out of the tissue owing to inadequate tissue snaring.

Ory discloses adequate fixation strengths but the applicator device required to insert his anchor is necessarily 10 mm in diameter thereby causing the procedure to be more invasive than necessary.

Homo crystalline PG and PL generally require greater than 6 months to absorb and thus are not optimum materials for hernia mesh fixation.

However, mesh migration and mesh contraction can occur for more than two months if not adequately stabilized.

Bio-absorbable polymers degrade when exposed to high humidity and temperature.

High doses of gamma radiation or electron beam radiation (E Bream), both accepted methods of sterilization for many devices, could weaken the mechanical properties of PG, PL and their co-polymers.

Criscuolo suggests the use of PG and PL with an absorption time of 2-3 weeks but does not disclose a method of forming the device that results in such an absorption time.

Loss of fixation after 2 to 3 weeks could well lead to hernia recurrence.

Hernia mesh such as PTFE based mesh manufactured by W. L. Gore is difficult to penetrate since the material is tough, non macro-porous, and relative inelastic.

There are several problems associated with the prior art.

The helical fastener, however, does not have a head or stop on the proximal end so that it can often be screwed all the way through the mesh and into the tissue and thus providing no fastening support for the mesh.

This configuration can cause permanent pain for some placements of the fastener and sometimes results in the need for the fastener to be excised from the body in a subsequent surgical procedure.

Both the Phillips dart and H shape fastener must be placed in soft enough tissue that will allow the anchor members to deploy or else the holding strength is severely compromised.

The Ethicon device is very complex and expensive to manufacture owing to the delivery mechanism and the cost of the super elastic fastener material.

In addition the proximal end of the fastener is not symmetric so that care must be taken to orient it correctly so that both proximal leg members contact the mesh, since fasteners are almost always deployed near the edges of the mesh.

Another problem with the Ethicon device is that the delivery tube is 5 mm in diameter and the surgeon must hold a counter force with the palm of the hand on the handle to hold the delivery tube against the mesh while simultaneously applying an oppositely directed force to the trigger (actuator) with his fingers of the same hand.

These two dynamic countervailing force requirements from the same hand sometimes causes the surgeon to apply too much handle pressure resulting in the 5 mm delivery tube puncturing the tissue causing excess bleeding and other trauma.

These fasteners can touch or penetrate nerves and cause severe pain that is more or less permanent unless they are removed in subsequent surgical procedures.

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