Injectable resorbable bone graft material, powder for forming same and methods relating thereto for treating bone defects

Abstract

An injectable resorbable bone graft material, and methods of using the same, provide increased compressive strength after injection in a bone defect. The bone graft material is made from calcium sulfate hemihydrate having a thick stubby rod-like crystalline structure and low water-carrying capacity.

1 . A method for treating bone defects comprising the steps of:
 mixing a powder comprising calcium sulfate hemihydrate with a diluent to produce a bone graft material in the form of a paste; and   applying the bone graft material to a bone defect, the bone graft material having a compressive strength in excess of 15 MPa within one hour after said applying step.   
     
     
         2 . The method of  claim 1 , wherein the bone graft material has a compressive strength of approximately 45-49 MPa within one hour after said applying step. 
     
     
         3 . The method of  claim 1 , wherein the bone graft material has a compressive strength exceeding approximately 50 MPa within one hour after said applying step. 
     
     
         4 . The method of  claim 1 , wherein the bone graft material has a compressive strength of at least 6 MPa within 20 minutes after said applying step. 
     
     
         5 . The method of  claim 1 , wherein the bone graft material has a compressive strength of at least 35 MPa within 24 hours after said injecting step. 
     
     
         6 . The method of  claim 5 , wherein the bone graft material has a compressive strength of approximately 56 MPa within 24 hours after said injecting step. 
     
     
         7 . The method of  claim 1 , wherein the diluent is water or a solution comprising an inorganic salt or a cationic surface active agent. 
     
     
         8 . The method of  claim 1 , wherein the calcium sulfate hemihydrate is formed by immersing calcium sulfate dihydrate in a solution of water and an inorganic salt to form a mixture, and heating the mixture to substantially its boiling point at atmospheric pressure such that the calcium sulfate dihydrate is converted to calcium sulfate hemihydrate. 
     
     
         9 . The method of  claim 1 , wherein the bone graft material has a working time of at least 5 minutes following mixing. 
     
     
         10 . The method of  claim 1 , wherein the bone graft material further comprises an accelerant. 
     
     
         11 . The method of  claim 10 , wherein the accelerant is selected from the group consisting of calcium sulfate dihydrate, calcium sulfate dihydrate coated with sucrose, potassium sulfate, and sodium sulfate. 
     
     
         12 . The method of  claim 1 , wherein the bone graft material further comprises one or more additives selected from the group consisting of bone marrow aspirate, platelet concentrate, blood, antibiotics, chemotherapeutic agents, growth factors, and analgesics. 
     
     
         13 . The method of  claim 1 , wherein the diluent to powder weight ratio is 0.19:1 to 0.31:1. 
     
     
         14 . The method of  claim 1 , wherein the powder comprises between about 99.8 to 100 percent by weight calcium sulfate hemihydrate. 
     
     
         15 . The method of  claim 1 , wherein the calcium sulfate hemihydrate consists of thick, stubby, rod-like crystals having a low water carrying capacity. 
     
     
         16 . The method of  claim 1 , wherein the applying step comprises injecting the paste into a bone defect. 
     
     
         17 . A method for preparing a bone graft material for treating bone defects comprising the step of mixing a powder comprising calcium sulfate hemihydrate with a diluent to produce a bone graft material in the form of a paste, wherein when undergoing dry-testing, the bone graft material has a compressive strength of approximately 88 MPa within 24 hours after said mixing step. 
     
     
         18 . The method of  claim 17 , wherein the bone graft material has a compressive strength exceeding approximately 106 MPa within 24 hours after said mixing step. 
     
     
         19 . The method of  claim 17 , wherein the diluent is water or a solution comprising an inorganic salt or a cationic surface active agent. 
     
     
         20 . The method of  claim 17 , wherein the calcium sulfate hemihydrate is formed by immersing calcium sulfate dihydrate in a solution of water and an inorganic salt to form a mixture, and heating the mixture to substantially its boiling point at atmospheric pressure such that the calcium sulfate dihydrate is converted to calcium sulfate hemihydrate. 
     
     
         21 - 47 . (canceled)