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.

What is claimed is: 
     
         1 . A method of forming an implant for use in a mammal, the method comprising the steps of:
 providing a model of an implant;   providing a powder comprising polyetherketoneketone (PEKK) and excluding calcium phosphate;   forming the implant by selective laser sintering the powder in accordance with the model of the implant.   
     
     
         2 . The method of  claim 1 , wherein the step of forming the implant by selective laser sintering comprises the steps of:
 applying a layer of the powder on a bed of a laser sintering machine;   solidifying selected points of the applied layer of powder by irradiation in accordance with a corresponding layer of the model;   successively repeating the step of applying the powder and the step of solidifying the applied layer of powder until a plurality of cross sections of the implant are solidified.   
     
     
         3 . The method of  claim 2 , wherein the selective laser sintering further comprises the step of:
 maintaining a bed temperature between 280 degrees Celsius and 350 degrees Celsius during the successive steps of powder application and solidification.   
     
     
         4 . The method of  claim 2 , wherein the powder comprises a semi-crystalline PEKK powder having a crystallinity between 15% and 90% as determined by DSC and an average particle size between 10 to 150 microns. 
     
     
         5 . The method of  claim 4 , wherein the powder has a crystallinity between 15% and 35% as determined by DSC and an average particle size between 50 to 70 microns. 
     
     
         6 . The method of claim of  claim 2 , wherein the powder comprises a quasi-amorphous PEKK powder having a crystallinity of 2% or less as determined by DSC, and wherein the powder has an average particle size between 50 to 70 microns. 
     
     
         7 . The method of  claim 6 , wherein the selective laser sintering further comprises the step of maintaining a bed temperature between 280 degrees Celsius and 350 degrees Celsius during the successive steps of powder application and solidification. 
     
     
         8 . The method of  claim 2  wherein the step of selectively laser sintering forms a mechanical fastener interface in a surface of the implant. 
     
     
         9 . The method of  claim 2  wherein the powder consists essentially of PEKK. 
     
     
         10 . The implant of  claim 2 , wherein the implant replaces a load-bearing bone. 
     
     
         11 . The implant  2 , wherein the implant replaces a portion of a spine, a long bone of an arm or a leg, a hip bone, or a cranial bone. 
     
     
         12 . The method of  claim 2 , wherein the step of providing the model comprises the steps of:
 (a) scanning a patient to obtain tomographic information;   (b) designing a bone implant model using from the tomographic information obtained from the patient.   
     
     
         13 . A method of forming an implant for use in a mammal, the method comprising the steps of:
 providing a model of an implant;   providing a powder for manufacturing the implant, the powder comprising a a semi-crystalline polyetherketoneketone PEKK powder having a crystallinity between 15% and 90% and excluding calcium phosphate, the powder having an average particle size of between 50 to 70 microns;   forming the implant by selective laser sintering the powder in accordance with the implant model, the step of forming the implant by selective laser sintering comprises the following steps:
 applying a layer of the powder on a bed of a laser sintering machine; 
 solidifying selected points of the applied layer of powder by irradiation in accordance with a corresponding layer of the model; 
 successively repeating the step of applying the powder and the step of solidifying the applied layer of powder until a plurality of cross sections of the implant are solidified; 
 maintaining a bed temperature between 280 degrees Celsius and 295 degrees Celsius during the successive steps of powder application and solidification. 
   
     
     
         14 . The method of  claim 13  wherein the step of selectively laser sintering forms a mechanical fastener interface in a surface of the implant. 
     
     
         15 . The method of  claim 13  wherein the powder consists essentially of PEKK. 
     
     
         16 . The method of  claim 13 , wherein the implant replaces a spine bone or a cranial bone. 
     
     
         17 . An implant for use in a mammal, the implant comprising laser sintered polyetherketoneketone (PEKK) and excluding calcium phosphate. 
     
     
         18 . The implant of  claim 17 , wherein the laser sintered PEKK is prepared by applying a layer of the powder on a bed of a laser sintering machine, solidifying selected points of the applied layer of powder by irradiation in accordance with a corresponding layer of a model, successively repeating the step of applying the powder and the step of solidifying the applied layer of powder until a plurality of cross sections of the implant are solidified. 
     
     
         19 . The implant of  claim 18 , wherein a bed temperature between 280 degrees Celsius and 295 degrees Celsius is maintained during the successive steps of powder application and solidification. 
     
     
         20 . The implant of  claim 19  wherein the implant comprises a mechanical fastener interface in a surface of the implant.