Porous composite biomaterials and related methods

Abstract

Synthetic composite materials for use, for example, as orthopedic implants are described herein. In one example, a composite material for use as a scaffold includes a thermoplastic polymer forming a porous matrix that has continuous porosity and a plurality of pores. The porosity and the size of the pores are selectively formed during synthesis of the composite material. The example composite material also includes a plurality of a anisometric calcium phosphate particles integrally formed, embedded in, or exposed on a surface of the porous matrix. The calcium phosphate particles provide one or more of reinforcement, bioactivity, or bioresorption.

1 . A porous composite material, comprising:
 a thermoplastic polymer forming a porous matrix having continuous porosity and a plurality of pores, wherein the porosity and the size of the pores are selectively formed during synthesis of the composite material;   a plurality of anisometric calcium phosphate particles integrally formed, embedded in, or exposed on a surface of the porous matrix, wherein the calcium phosphate particles provide one or more of reinforcement, bioactivity, or bioresorption.   
     
     
         2 . A porous composite material as described in  claim 1 , wherein the porosity and the size of the pores are selectively formed by the inclusion of a porogen material during synthesis of the composite material. 
     
     
         3 . A porous composite material as described in  claim 2 , wherein the porogen material is leached from the composite material during the synthesis of the composite material. 
     
     
         4 . A porous composite material as described in  claim 1 , wherein the porous matrix includes a plurality of composite struts. 
     
     
         5 . A porous composite material as described in  claim 4 , wherein the plurality of composite struts form a continuous body of the porous scaffold apparatus. 
     
     
         6 . A porous composite material as described in  claim 1 , wherein the pore sizes of the matrix range between 100 to 500 μm. 
     
     
         7 . A porous composite material as described in  claim 1 , further comprising fractions of microporosity having a pore sizes less than 10 μm. 
     
     
         8 . A porous composite material as described in  claim 1 , wherein the matrix porosity ranges between 1 to 95 percent by volume. 
     
     
         9 . A porous composite material as described in  claim 1 , wherein the polymer comprises a non-degradable polymer. 
     
     
         10 . A porous composite material as described in  claim 1 , wherein the polymer comprises a biosorbable or biodegradable polymer. 
     
     
         11 . A porous composite material as described in  claim 1 , wherein the composite material is injectable to cure or harden in vivo. 
     
     
         12 . A porous composite material as described in  claim 1 , wherein the polymer comprises polyaryletherketone, polyetheretherketone, polyetherketonekteone, polyetherketone, polyethylene, high density polyethylene, ultra high molecular weight polyethylene, low density polyethylene, polyethylene oxide, polyurethane, polypropylene, polypropylene oxide, polysulfone, polymethylmethacrylate, and other polyacrylics from monomers such as bisphenol a hydroxypropylmethacrylate (bis-GMA) and/or tri(ethylene glycol) dimethacrylate, polypropylene, poly(DL-lactide), poly(L-lactide), poly(glycolide), poly(ε-caprolactone), poly(dioxanone), poly(glyconate), poly(hydroxybutyrate), poly(hydroxyvalerate, poly(orthoesters), poly(carboxylates), poly(propylene fumarate), poly(phosphates), poly(carbonates), poly(anhydrides), poly(iminocarbonates), poly(phosphazenes), copolymers thereof, or blends thereof. 
     
     
         13 . A porous composite material as described in  claim 1 , wherein the calcium phosphate reinforcement particles comprise single crystals or dense polycrystals. 
     
     
         14 . A porous composite material as described in  claim 1 , wherein the reinforcement particles have a mean aspect ratio (length along c-axis/length along a-axis) of greater than 1 and less than 100. 
     
     
         15 . A porous composite material as described in  claim 1 , wherein the size of the reinforcement particles ranges between 20 nm and 2 mm. 
     
     
         16 . A porous composite material as described in  claim 1 , wherein the reinforcement particle volume fraction is between 1 and 60 percent by volume. 
     
     
         17 . A porous composite material as described in  claim 1 , wherein at least a portion of the calcium phosphate reinforcement particles are shaped like whiskers. 
     
     
         18 . A porous composite material as described in  claim 1 , wherein at least a portion of the calcium phosphate reinforcement particles are shaped like platelets. 
     
     
         19 . A porous composite material as described in  claim 1 , wherein the anisometric calcium phosphate particles comprises hydroxyapatite, hydroxyapatite whiskers, carbonated calcium hydroxapatite, beta-tricalcium phosphate (beta-TCP), alpha-tricalcium phosphate (alpha-TCP), amorphous calcium phosphate (ACP), octacalcium phosphate (OCP), tetracalcium phosphate, biphasic calcium phosphate (BCP), anhydrous dicalcium phosphate (DCPA), dicalcium phosphate dihydrate (DCPD), anhydrous monocalcium phosphate (MCPA), monocalcium phosphate monohydrate (MCPM), or combinations thereof. 
     
     
         20 . A porous composite material as defined in  claim 1 , further comprising a carrier material containing a growth factor agent, wherein the carrier material and growth factor material are incorporated into the pore space of the porous matrix. 
     
     
         21 . A method of forming an porous composite material, the method comprising:
 providing a thermoplastic polymer powder and anisometric calcium phosphate particles;   mixing the polymer powder and the calcium phosphate particles with a fluid;   selectively varying the porosity and/or the pore size;   consolidating and drying the mixture;   deforming or densifying the mixture under uniaxial compression to form the porous composite; and   leaching a material from the porous composite.   
     
     
         22 . A method as described in  claim 21 , wherein selectively varying the porosity comprises adding a porogen material to the mixture. 
     
     
         23 . A method as described in  claim 22 , wherein selectively varying the size of the pores comprises sieving the porogen material to a desired size prior to mixing. 
     
     
         24 . A method as described in  claim 22 , wherein leaching a material from the porous composite comprises leaching the porogen material from the porous composite. 
     
     
         25 . A method as described in  claim 21 , wherein deforming or densifying the mixture comprises compression molding the mixture to form the porous composite. 
     
     
         26 . A method as described in  claim 21 , further comprising selectively varying the mechanical properties of the implant device by varying the calcium phosphate reinforcement volume fraction, aspect ratio, size and orientation, the amount of the polymer powder, or the size, volume fraction, shape and directionality of the void space and/or porosity of the implant device. 
     
     
         27 . The method as described in  claim 21 , further comprising adding a surface-active agent. 
     
     
         28 . An implantable orthopedic device, comprising:
 a porous body, wherein the body comprises a thermoplastic polymer forming a porous matrix having continuous porosity and a plurality of pores, wherein the porosity and the size of the pores are selectively formed during synthesis of the composite material, and a plurality of a anisometric calcium phosphate particles integrally formed, embedded in, or exposed on a surface of the porous matrix, wherein the calcium phosphate particles provide one or more of reinforcement, bioactivity, or bioresorption.   
     
     
         29 . An implantable device as described in  claim 28 , wherein the porosity is present throughout the body, localized within regions of the body, or functionally graded in any material or implant direction from a highly porous region to a relatively dense region. 
     
     
         30 . An implantable device as described in  claim 28 , wherein the porosity and the size of the pores are selectively formed by the inclusion of a porogen material during synthesis of the implantable device, and wherein the porogen material is leached from the implantable device. 
     
     
         31 . An implantable device as described in  claim 28 , wherein the pores accommodate or deliver bone morphogenetic protein, growth factors, transcription factors, matrix metalloproteinases, peptides, proteins, bone cells, progenitor cells, blood plasma, bone marrow aspirate, or combinations thereof. 
     
     
         32 . An implantable device as described in  claim 28 , wherein the polymer comprises a radiolucent polymer. 
     
     
         33 . An implantable device as described in  claim 28 , wherein the calcium phosphate reinforcement particles comprise single crystals or dense polycrystals. 
     
     
         34 . An implantable device as described in  claim 28 , wherein the body further includes a roughened surface that comes into contact with adjacent bodies in order to prevent movement after implantation. 
     
     
         35 . An implantable device as described in  claim 28 , wherein the implant device comprises an interbody spinal fusion cage, bone ingrowth scaffolding for implant fixation, fracture fixation, synthetic bone graft substitute, or a tissue engineering scaffold.