Customized implants for bone replacement

Abstract

The present invention relates to customized implants for bone replacement that are prepared from poly(ether ketone ketone) or PEKK, and to a computer-based imaging and rapid prototyping (RP)-based manufacturing method for the design and manufacture of these customized implants. The PEKK customized implants made using rapid prototyping demonstrate biomechanical properties similar (if not identical) to that of natural bone even when prepared without the use of processing aids such as carbon black and aluminum powder.

1 . A customized implant or scaffold for bone replacement comprising poly(ether ketone ketone) (PEKK). 
     
     
         2 . The customized implant or scaffold of  claim 1  modified to add at least one feature selected from the group consisting of a) openings to encourage bone, vascular and nerve in-growth, b) adding surface pores to hold therapeutic agents, and c) adding surface anchors and/o threaded holes. 
     
     
         3 . The customized implant or scaffold of  claim 2  wherein said surface pores hold one or more therapeutic agents selected from the group consisting of antibiotics, anti-coagulants, anti-inflammatory, anti-metabolites, antivirals, bone morphogenic proteins, cell adhesion molecules, growth factors, healing promotors, immunosuppressants, vascularizing agents, and topical anesthetics/analgesics; said therapeutic agents optionally being present in or on a carrier for controlled release. 
     
     
         4 . The customized implant or scaffold of  claim 3 , wherein said carrier is encapsulated in a biocompatible or biodegradable polymer, or in a bioadhesive gel. 
     
     
         5 . The customized implant or scaffold of  claim 1 , comprising a rigid implant having an inner core with a low porosity of 10 percent or less pores, and an outer layer, said implant having a compressive strength (ASTM #D695) of from 100 to greater than 200 megapascals (Mpa) and a flexural modulus (ASTM #D570) of greater than 3.5 GPa. 
     
     
         6 . The customized implant or scaffold of  claim 5  wherein said implant replaces a load-bearing bone. 
     
     
         7 . The customized implant or scaffold of  claim 6 , wherein said load-bearing bone is selected from the spine, a long bone of the arms or legs, and a hip bone. 
     
     
         8 . The customized implant or scaffold of  claim 7 , wherein at least 95 percent of pores have a diameter of 1-500 microns, and may or may not be connected. 
     
     
         9 . The customized implant or scaffold of  claim 1  comprising a substantially uniform cross-sectional morphology having a porosity of greater than about 35 percent, wherein the pores are interconnected and have an average diameter of 50-250 microns, and wherein said implant or scaffold has a compressive strength (ASTM #D695) of from 10 to 200 megapascals (Mpa) and a flexural modulus (ASTM #D570) of from 0.5 to greater than 4.5 GPa. 
     
     
         10 . The customized implant or scaffold of  claim 9 , comprising a bone replacement scaffolding for ongrowth/ingrowth of tissues, or as a support for stem cells. 
     
     
         11 . The customized implant or scaffold of  claim 9  comprising a three-dimensional lattice structure having a plurality of bars crossing each other in a plurality of zones, the bars being fused in each of these zones, wherein the interstitial spaces between adjacent bars define a plurality of interconnected pores or channels in lattice structure. 
     
     
         12 . A laser sinterable composition comprising poly(ether ketone ketone) (PEKK) powder, wherein said powder has an average particle size of from 10-150 microns, and is either a) semi-crystalline, having at least 10% crystallinity by weight as measured by DSC, or said powder is b) quasi-amorphous, at most 2% crystallinity as measured by DSC. 
     
     
         13 . The laser sinterable composition of  claim 12 , wherein said composition further comprises one or more fillers selected from the group consisting of glass, carbon, mineral fillers, surface-bioactive ceramics, hydroxyapatite (HAp), biologically active glass, resorbable bioactive ceramics, α-tricalcium phosphate (α-TCP),β-TCP), solids that will render the implant or scaffold radioopaque, and barium sulfate (BaSO 4 ). 
     
     
         14 . The laser sinterable composition of  claim 12  having an average particle size of from 20-100 microns. 
     
     
         15 . The laser sinterable composition of  claim 12  wherein said semi-crystalline powder has 15-90% crystallinity as measured by DSC. 
     
     
         16 . The laser sinterable composition of  claim 12  having an average particle size of from 50-70 microns. 
     
     
         17 . The laser sinterable composition of  claim 12  wherein said semi-crystalline powder has 15-35% crystallinity as measured by DSC. 
     
     
         18 . A process for producing a customized implant or scaffold for bone replacement comprising the steps of :
 (a) scanning a patient in an area requiring bone repair or replacement to obtain tomographic information;   (b) designing a bone implant model using computer aided design from the tomographic information obtained from the patient;   (c) optionally, modifying the bone implant model by one or more of the following steps: adding suture anchors, threaded holes, mating surfaces and textures, open cell regions for scaffolding, surface pores to carry antibiotics, and/or varying density or porosity levels so as to vary stiffness or rigidity; and   (d) forming a bone implant or scaffold using a solid free-form fabrication method from the bone implant model, the bone implant comprising sequential layers of biocompatible poly(ether ketone ketone) (PEKK) powder.   
     
     
         19 . The process of  claim 18 , wherein said fabrication method in step (d) is by selective laser sintering (SLS), fused deposition modeling (FDM) or selective mask sintering (SMS). 
     
     
         20 . The process of  claim 18 , wherein the PEKK powder has an average particle size of from 10 to 150 microns. 
     
     
         21 . The process of  claim 18 . wherein said PEKK powder further comprises from 5 to 40 weight percent of additives, based on the weight of PEKK. 
     
     
         22 . The process of  claim 21 , wherein said additives are selected from the group consisting of surface-bioactive ceramics, resorbable bioactive ceramics, solids to render the implant or scaffold radioopaque.