Method for resecting the knee using a resection guide and provisional prosthetic component

Abstract

A method and apparatus for knee replacement surgery wherein a femoral provisional component is provided which corresponds to a permanent component to be implanted in a human and which includes means for establishing the correct fit and position of such a component, prior to its implantation, in relation to the soft tissues of the knee before final resection of the anterior femoral surface. The provisional component further includes cutting guide means for such anterior surface resection such that accurate cuts may be made with the provisional component in place. The method involves preparing the distal femoral surface using the femoral intramedullary canal as a constant reference point for posterior and distal cutting guides followed by locating the provisional component by means of a provisional intramedullary stem so that the relationship with the soft tissues of the knee may be accurately established.

1. A method of knee joint arthroplasty comprising preparing a distal femur to accept a femoral component in knee replacement surgery wherein the femoral intramedullary canal is used as the reference point for all resection cuts comprising the steps of:
 i. incrementally reaming the intramedullary canal out to cortical bone with a reamer means;  
 ii. leaving said reamer means in place and attaching thereto a distal cutting guide;  
 iii. resetting medial and lateral distal surfaces of said femur along said distal cutting guide;  
 iv. replacing said distal cutting guide with a posterior cutting guide and resetting medial and lateral posterior condylar surfaces of said femur along said posterior cutting guide;  
 vi. removing said posterior cutting guide and reamer, attaching a provisional intramedullary stemattaching to a provisional femoral component to a distal femur surface what has been preliminarily resected, which said provisional femoral component including an anteriorincludes a cutting guide formed therein and an outer surface replicatingthat replicates the size of a permanent femoral component, and inserting said stem into said intramedullary canal ;  
 viii. evaluating flexion/extension gaps of the knee and patella tracking relative to said provisional femoral component and establishing correct gaps and soft tissue balance of said knee relative to the anatomical size of said knee;  
 viiiii. resetting an anterior surface of said femur surface along said anterior cutting guide of said provisional femoral component; and  
 viiiiv. removing said provisional stem and provisional femoral component and insertingreplacing it with a permanent femoral component correspondingthat corresponds to said provisional component.  
 
     
     
       2. The method of  claim 1  wherein said provisional femoral component comprises an anterior flange, first and second posterior condylar flanges and an intermediate distal femoral joint portion, said flanges and distal femoral joint portion being formed as a single element having a continuous joint surface around its outer perimeter. 
     
     
       3. The method of  claim 2  wherein said provisional femoral component further comprises said anterior resection cutting guide, said guide comprising means relative to said anterior flange for guiding a bone saw in resection of said anterior femoral surface. 
     
     
       4. The method of  claim 3  wherein said guide means relative to said anterior flange comprises at least one slot formed in and through said provisional femoral component posteriorly of said anterior flange and extending inward from an edge thereof to a point adjacent a center line of said component, said slot having an angle relative to said component corresponding to that of an anterior flange of a permanent femoral knee joint prosthesis component. 
     
     
       5. The method of  claim 2  further comprising adjusting said flexion/extension gaps and thereby the position of said provisional component by interposing provisional augment means between said component and said femur. 
     
     
       6. The method of  claim 5  wherein said provisional augment means comprise distal and posterior portions having an angular relationship corresponding to that of said posterior condylar flanges and said intermediate distal femoral joint portion. 
     
     
       7. The method of  claim 6  wherein said provisional augment means are temporarily interposable between said component and said femur and may be removed therefrom and permanently adhered to a permanent implant component. 
     
     
       8. The method of  claim 1  wherein resection cuts made to said distal femur have constant angular characteristics relative to said intramedullary canal irrespective of the anatomical size of the knee on which said arthroplasty is conducted. 
     
     
       9. The method of  claim 8  wherein resection cuts are determined by geometric constants defining the construction of a set of permanent femoral components from which said permanent component corresponding to said provisional component is selected. 
     
     
       10. A method of knee joint arthroplasty for revision surgery of a human knee wherein resection of a distal femur preparatory to implantation of a femoral component employs the femoral intramedullary canal as the reference point for all resection cuts, comprising:
 i. removing an existing femoral component;  
 ii. fitting a cutting guide means to said femur by a means extending into said femoral intramedullary canal and first resetting medial and lateral distal surfaces of said femur and medial and lateral posterior condylar surfaces of said femur; 
 iiiii. removing said cutting guide means and fitting a provisional femoral knee component onto to said distal femur surface, said provisional component having an anteriora cutting guide means formed therein and an outer surface replicatingthat replicates the size of a permanent femoral component, and wherein said provisional component comprises an intramedullary stem which is inserted into said intramedullary canal ;  
 iv. evaluating and adjusting flexion and extension gaps of the knee and patella tracking relative to said provisional femoral component and establishing correct gaps and soft tissue balance of said knee relative to the anatomical size of said knee followed byiii. resecting an anteriorthe surface of said distal femur along said anterior cutting guide;  
 viv. removing said provisional femoral knee component and inserting a permanent femoral component corresponding to said provisional component; wherein,  
 said anterior resection of said femur comprises an anterior flange cut and an anterior chamfer cut, said cuts having constant angular characteristics relative to said intramedullary canal irrespective of the anatomical size of the knee on which said arthroplasty is performed .  
 
     
     
       11. The method of  claim 10  wherein said provisional femoral component comprises an anterior flange, first and second posterior condylar flanges and an intermediate distal femoral joint portion, said flanges and distal femoral joint portion being formed as a single element having a continuous joint surface around its outer perimeter. 
     
     
       12. The method of  claim 11  wherein said constant angular characteristics of said anterior resection cuts correspond to and are determined by a stem/anterior flange distance and a stem/anterior cortex angle which are constant for all sizes of provisional components. 
     
     
       13. A method of preparing a distal femur to accept a femoral component in knee replacement surgery wherein the femoral intramedullary canal is used as the reference point for all resection cuts, the method comprising the steps of:
 i. fitting a first cutting guide means to said distal femur by a means extending into said intramedullary canal and performing a first resection of the medial and lateral distal surfaces of said femur and the medial and lateral condylar surfaces of said femur;  
 ii. removing said first cutting guide means;  
 iiii. providingfitting a provisional femoral component for connection to said resecteda distal femur to measure the correct size of a permanent component to use with the resected femur,surface that has been preliminarily resected, said provisional component including an inner surface that is engageable with thesaid resected distal femur surface and has an outer surface replicatingthat replicates the size of thesaid permanent femoral component, andthat includes at least one slot extending from thesaid provisional component outer surface to receive a cutting tool for further resection of thesaid distal femur surface to prepare thesaid distal femur surface for connection with said permanent femoral component;  
 ivii. fitting said provisional femoral component to said further resected distal femur surface, evaluating and adjusting flexion and extension of the knee and patella tracking relative to said provisional femoral component, and performing a second resection of said distal femur using said at least one slot of said provisional femoral component as a guide means; and  
 viii. removing said provisional femoral component and insetting in its place a permanent femoral component corresponding to said provisional femoral component.  
 
     
     
       14. The method of  claim 13  wherein said second resection comprises resection of the anterior surface of the distal femur and is performed at angles having constant characteristics relative to said intramedullary canal irrespective of the anatomical size of the knee on which said knee replacement is performed. 
     
     
       15. The method of  claim 14  wherein said provisional component comprises an anterior flange, first and second posterior condylar flanges and an intermediate distal femoral joint portion, said flanges and distal femoral joint portion being formed as a single element having a continuous joint surface around its outer perimeter. 
     
     
       16. The method of  claim 15  wherein said constant angular characteristics of said anterior resection cuts correspond to and are determined by a stem/anterior flange distance and a stem/anterior cortex angle which are constant for all sizes of provisional components. 
     
     
       17. The method of  claim 15  wherein said at least one slot of said provisional component is located posteriorly of said anterior flange and extends inward from an edge thereof to a point adjacent a center line of said component, said slot having an angle relative to said component corresponding to that of an anterior flange of said femoral component. 
     
     
       18. The method of  claim 17  wherein said provisional component comprises a further slot located posteriorly of said at least one slot and at an angle relative to said at least one slot whereby resection of said distal femur through said further slot produces a chamber on said distal femur.