Implantable medical device with varied composition and porosity, and method for forming same

Inventors

FARRIS, Jeffery A. • Brown, Kevin Lee • Snell, Douglas B. • Roeder, Ryan K. • MESSMAN, Mark G.

Assignees

Happe Spine LLC

Abstract

A method for forming a thermoplastic body having regions with varied material composition and/or porosity. Powder blends comprising a thermoplastic polymer, a sacrificial porogen and an inorganic reinforcement or filler are molded to form complementary parts with closely toleranced mating surfaces. The parts are formed discretely, assembled and compression molded to provide a unitary article that is free from discernible boundaries between the assembled parts. Each part in the assembly has differences in composition and/or porosity, and the assembly has accurate physical features throughout the sections of the formed article, without distortion and nonuniformities caused by variable compaction and densification rates in methods that involve compression molding powder blends in a single step.

Core Innovation

The invention relates to forming a unitary article by using at least two different powder blends that differ in polymer powder content, porogen powder content, inorganic particle powder content, or a combination thereof. Each powder blend is dispensed into at least one mold, compacted into two or more preforms, and machined into two or more parts with complementary mating surfaces. The parts are assembled into an article assembly before compression molding to form a unitary article.

After compression molding, the unitary article is formed free from discernible boundaries between portions derived from the complementary mating surfaces of the assembled parts. The article can be optionally formed to include additional features, and porogen is leached from the unitary article. Leaching the porogen creates porous regions including portions corresponding to the regions formed from the parts that included porogen.

The described approach forms components with varied material composition and varied porosity by sequentially preparing powder blends, machining complementary mating surfaces, assembling, and then compression molding into a single unitary monolithic article. This staged formation and assembly is described as preventing distortion and nonuniformities that would otherwise arise from different compaction/densification behavior versus single-step molding into regions.

The document further describes that the unitary article can be a biomedical implant, including an interbody spinal fusion implant, and that the porous structure can include through porosity and exposed reinforcement surfaces. In addition, it describes use of polymer powders selected from PEEK/PEAK/PEKK types and bioactive inorganic reinforcements such as hydroxyapatite (HA), with porogen such as sacrificial porogen.

Claims Coverage

The partial content provides three independent claims directed to forming a unitary article free from discernible boundaries by using powder blends with differing polymer/porogen/inorganic content, machining complementary mating surfaces, assembling, compression molding, and leaching porogen; the claims include medicinal-implant oriented limitations for some variants.

Across the independent claims, the inventive coverage centers on producing a unitary article by combining multiple powder blends, forming parts with complementary mating surfaces via compacting and machining, assembling the parts, and compression molding to eliminate discernible boundaries, followed by leaching porogen; additional coverage specifies porogen-containing parts and boundary-free formation, and also covers discretely formed parts and interfitting machined complementary surfaces.

Stated Advantages

Documented Applications