Porous bioabsorbable implant

Abstract

An implant for insertion into a breast lumpectomy cavity to serve as a guide for orienting a radiation source relative to the breast lumpectomy cavity, includes a body formed of a bioabsorbable material comprised of chitosan having a porosity sufficient to ensure tissue in-growth before significant bio-absorption of the implant, the body having exterior margins. An interior orientation marker is spaced inwardly from the exterior margins of the body to facilitate relative orientation between the implant and the radiation source.

1 . An implant for insertion into a breast lumpectomy cavity to serve as a guide for orienting a radiation source relative to the breast lumpectomy cavity, comprising:
 a body formed of a bioabsorbable material comprised of chitosan having a porosity sufficient to ensure tissue in-growth before significant bio-absorption of the implant, the body having exterior margins; and   an interior orientation marker spaced inwardly from the exterior margins of the body to facilitate relative orientation between the implant and the radiation source.   
     
     
         2 . The implant of  claim 1  wherein the orientation marker comprises a plurality of radiopaque elements spaced inwardly from the exterior margins of the implant in a predefined pattern. 
     
     
         3 . The implant of  claim 1  wherein the implant has a spongy consistency, and wherein a hardness of the implant is determined by an amount of the chitosan in the implant. 
     
     
         4 . The implant of  claim 1  wherein the bioabsorbable material has an in vivo life of at least two weeks but not more than about twenty weeks. 
     
     
         5 . (canceled) 
     
     
         6 . The implant of  claim 1  comprising a radiopaque imaging agent located at the exterior margins to facilitate imaging of the exterior margins of the implant, the radiopaque imaging agent being selected from the group consisting of Barium Sulfate, Barium Carbonate, Silver Chloride, Silver Iodide, Silver Nitrate, Calcium Carbonate and Zinc Oxide. 
     
     
         7 . The implant of  claim 1  comprising a plurality of radiopaque elements that comprise a metallic material selected from the group consisting of Titanium, Platinum, Gold, Iridium, Tantalum, Tungsten, Silver, Rhenium and non-magnetic stainless steel. 
     
     
         8 . The implant of  claim 1  having maximum transverse dimension between about 0.5 and about 8 cm. 
     
     
         9 . The implant of  claim 1  having maximum transverse dimension between about 2 and about 6 cm. 
     
     
         10 . The implant of  claim 1  wherein the interior orientation marker is comprised of a plurality of radiopaque elements that form a plane within the interior of the implant. 
     
     
         11 . The implant of  claim 1  wherein the interior orientation marker has three radiopaque elements which are located at apices of an equilateral triangle. 
     
     
         12 . The implant of  claim 1  wherein the pore size ranges from about 10 to about 600 micrometers. 
     
     
         13 . The implant of  claim 1  wherein the exterior margin has a pore size ranging from about 20 to about 80 micrometers. 
     
     
         14 . The implant of  claim 1  wherein the implant interior has a pore size from about 50 to about 200 micrometers. 
     
     
         15 - 22 . (canceled) 
     
     
         23 . An implant for insertion into a breast lumpectomy cavity to serve as a guide for orienting a radiation source relative to the breast lumpectomy cavity, comprising:
 a body formed of a porous chitosan having a spongy consistency, the body having an outer surface and an interior within the outer surface; and   an orientation marker spaced inwardly from the outer surface of the body in the interior of the body of the implant and configured to facilitate a relative orientation between the implant and the radiation source.   
     
     
         24 . The implant of  claim 23 , wherein the orientation marker is comprised of a plurality of radiopaque elements located within the interior of the body of the implant and arranged to define a single plane within the interior of the body of the implant. 
     
     
         25 . The implant of  claim 23 , wherein the orientation marker comprises three radiopaque elements located within the interior of the body of the implant and which are located at apices of an equilateral triangle formed within the interior of the body of the implant. 
     
     
         26 . The implant of  claim 23 , wherein the outer surface defines an exterior margin having a pore size ranging from about 20 to about 80 micrometers. 
     
     
         27 . An implant for insertion into a breast lumpectomy cavity to serve as a guide for orienting a radiation source relative to the breast lumpectomy cavity, comprising:
 a body formed of about 67 percent porous chitosan and about 33 percent barium sulfate so as to have a spongy consistency approximating the consistency of breast tissue that surrounds the lumpectomy cavity, the body of the implant having an outer surface and an interior within the outer surface; and   an orientation marker spaced inwardly from the outer surface of the body in the interior of the body of the implant and configured to facilitate a relative orientation between the implant and the radiation source.   
     
     
         28 . The implant of  claim 27 , wherein the orientation marker is comprised of a plurality of radiopaque elements located within the interior of the body of the implant and arranged to define a single plane within the interior of the body of the implant. 
     
     
         29 . The implant of  claim 27 , wherein the orientation marker comprises three radiopaque elements located within the interior of the body of the implant and which are located at apices of an equilateral triangle formed within the interior of the body of the implant.