Minimally invasive total-knee arthroplasty method and instrumentation

Abstract

A method and apparatus for performing total knee arthroplasty which is minimally invasive includes components with guide surfaces and slots for controlling the path of a cutting saw. The instrumentation permits resection of the proximal end of the tibia and distal end of the femur to be performed either medially or laterally with minimal cutting of soft tissue.

1 - 8 . (canceled)  
   
   
       9 . A cutting guide assembly for use in resectioning the distal end of a femur comprising 
 (a) a cutting guide having 
 (i) first and second spaced apart surfaces,  
 (ii) a slot for guiding a cutting instrument extending between said first and second surfaces, said slot extending anteriorly to posteriorly when said cutting guide is positioned for cutting with said first surface engaged to the lateral or medial aspect adjacent the distal end of a femur and  
 (iii) an edge having a recess extending between said first and second surfaces; and  
   (b) an arm assembly engaged to said cutting guide for adjustable movement thereon, said arm assembly including 
 (i) an engagement member secured to said edge,  
 (ii) a stylus arm extending from said engagement member along a path parallel to the path of said slot, said stylus having an elongated surface adapted to engage the distal end of a femur, and  
 (iii) an alignment member adapted to be received in a prepared intramedullary femoral canal, said alignment member being disposed at an angle to said stylus arm in the range of 90° to 100°;  
 said cutting guide being movable relative to said arm assembly to position said first side against the lateral or medial aspect of a femur in which said alignment member is positioned in said prepared intramedullary femoral canal.  
   
   
   
       10 . A cutting guide assembly according to  claim 9  further including means for varying the distance between the path of a cutting instrument extending through said slot and said stylus arm.  
   
   
       11 . A cutting guide assembly according to  claim 10  wherein said means for varying comprises a block positioned between said engagement member and said edge.  
   
   
       12 . A cutting guide assembly according to  claim 10  wherein said means for varying comprises a shaft rotatably mounted on the edge of said cutting guide in said recess in an axially fixed position, a support member engaged to said stylus arm and positioned in said recess for movement toward and away from said slot and means on said rotatably mounted shaft for moving said support member and said stylus arm toward and away from said slot.  
   
   
       13 . A cutting guide assembly according to  claim 12  wherein said rotatably mounted shaft is threadedly engaged to said support member.  
   
   
       14 . A cutting guide assembly according to  claim 13  wherein said stylus arm is movable in a longitudinal direction on said support member.  
   
   
       15 . A cutting guide assembly according to  claim 12  wherein said stylus arm has an end remote from said alignment member and a longitudinal slot extending from said remote end, and longitudinal slot sized to receive said rotatably mounted shaft.  
   
   
       16 . A femoral anterior-posterior sizer guide for a femur having a resectioned distal end comprising: 
 (a) a base having a surface upon which a portion of the posterior or anterior femur adjacent said resectioned end may rest;    (b) a support extending upwardly from said base, said support having an elongated slot extending upwardly in a direction away from said base;    (c) a slideable member movably positioned in said slot; and    (d) a stylus movable with said slideable member toward and away from said base surface, said stylus having a femoral engagement surface substantially parallel to said base surface.    
   
   
       17 . A sizer guide according to  claim 16  further including an aperture extending through said slideable member, said aperture extending along an axis parallel with said base surface.  
   
   
       18 . A sizer guide according to  claim 16  further including a distal arm extending from said support, said distal arm having an engagement surface for contacting the distal end of a femur.  
   
   
       19 . A sizer guide according to  claim 18  wherein said slideable member has an aperture extending along an axis parallel to said base surface and parallel to said distal arm engagement surface.  
   
   
       20 . A sizer guide according to  claim 19  further including a wedge engageable with said base surface said wedge tapering from a relatively thin thickness adjacent said support to a thicker thickness spaced from said support, said wedge having a surface upon which said portion of said posterior or anterior femur may rest.  
   
   
       21 . A sizer guide according to  claim 20  wherein the angle of taper of said wedge is in the range of 1° to 8°.  
   
   
       22 . A sizer guide according to  claim 18  wherein said slideable member has an aperture extending along an axis parallel to said distal arm engagement surface and further including means for varying the angle between said axis and said surface of said base.  
   
   
       23 . A sizer guide according to  claim 22  wherein said slideable member is rotatable in said slot and said means for varying the angle between said axis and said base surface comprises means for connecting said distal arm to said slideable member for rotation therewith.  
   
   
       24 . A sizer guide according to  claim 22  wherein said support has a second slot facing said distal arm and further including a connector extending through said second slot connecting said distal arm to said slideable member for rotation therewith.  
   
   
       25 . In combination, a sizer guide according to  claim 17  and a guide pin extending through said aperture.  
   
   
       26 . In combination, a sizer guide according to  claim 19  and a guide pin extending through said aperture.  
   
   
       27 . A combination for use in resectioning a femur comprising 
 (a) a guide pin adapted to be positioned in the medial or lateral aspect of a femur substantially parallel to a resectioned distal end of said femur; and    (b) a resection guide including 
 (i) a side resection guide adapted to engage said medial or lateral aspect, said side resection guide having an aperture positioned over said guide pin, and  
 (ii) a chamfer block extending from said side resection guide in a position to engage said resectioned distal end when said side resection guide is engaged to said lateral or medial aspect.  
   
   
   
       28 . The combination according to  claim 27  wherein said chamfer block includes a guide slot for directing movement of a cutting instrument cutting said resectioned distal end and wherein said chamfer block is adjustably mounted on said side resection guide to move said guide slot medially or laterally.  
   
   
       29 . A resection guide comprising 
 (a) a side resection guide adapted to engage the lateral or medial aspect adjacent a resectioned distal end of a femur; and    (b) a chamfer block extending from said side resection guide in a position to engage said distal end when said side resection guide is engaged to said lateral or medial aspect.    
   
   
       30 . A resection guide according to  claim 29  wherein said side resection guide includes a first guide slot for directing movement of a cutting instrument laterally to medially or medially to laterally in the area of the anterior aspect of said femur and a second guide slot for directing movement of a cutting instrument laterally to medially or medially to laterally in the area of the posterior aspect of said femur.  
   
   
       31 . A resection guide according to  claim 30  said chamfer block has a triangular cross section with a first flat side engaged to said side resection guide and adapted to engage said distal end and second and third flat sides, each disposed at an angle relative to said first flat side.  
   
   
       32 . A resection guide according to  claim 31  wherein the angle between said second side and said first side is the same as the angle between said third side and said first side.  
   
   
       33 . A resection guide according to  claim 32  wherein said side resection guide has 
 (a) a third guide slot for directing a cutting instrument laterally to medially or medially to laterally and disposed at the same angle as said chamfer block second flat side and    (b) a fourth guide slot for directing a cutting instrument laterally to medially or medially to laterally and disposed at the same angle as said chamfer block third flat side.    
   
   
       34 . A resection guide according to  claim 32  wherein said chamfer block includes a guide slot for directing movement of a cutting instrument cutting said resectioned distal end and wherein said chamfer block is adjustably mounted on said side resection guide to move said guide slot medially or laterally.  
   
   
       35 . A resection guide according to  claim 30  further including an anterior-posterior resection guide secured to said chamfer block and having an anterior cutting guide surface disposed at an angle lying on a plane co-planar with a portion of said first guide slot and a posterior cutting guide surface co-planar with a portion of said second guide slot.  
   
   
       36 . A resection guide according to  claim 30  further including a femoral notch block secured to said chamfer block, a portion of said notch block overlying said side resection guide, said notch block having a first surface adapted to face said resectioned distal end and a second surface aligned with said first guide slot and extending away from said first surface on a plane co-planar with a surface defining one surface of said slot.  
   
   
       37 . A resection guide according to  claim 36  wherein said notch block further includes a third surface generally parallel to said first surface and a pair of guide slots extending between said first and third surfaces and inwardly from said second surface.  
   
   
       38 . A method for resectioning the distal end of a femur having a prepared intramedullary canal comprising the steps of 
 (a) providing a cutting guide having first and second spaced apart surfaces, a slot for guiding a cutting instrument extending between said first and second surfaces, said slot extending anteriorly to posterior when said cutting guide is positioned for cutting with said first surface engaged to the lateral or medial aspect adjacent the distal end of a femur and an edge having a recess extending between said first and second surfaces;    (b) providing an arm assembly engaged to said cutting guide for adjustable movement thereon, said arm assembly including 
 (i) an engagement member secured to said edge,  
 (ii) a stylus arm extending from said engagement member along a path parallel to the path of said slot, said stylus having an elongated surface adapted to engage the distal end of a femur, and  
 (iii) an alignment member adapted to be received in a prepared intramedullary femoral canal, said alignment member being disposed at an angle to said stylus arm in the range of 90° to 10°;  
 said cutting guide being movable relative to said arm assembly to position said first side against the lateral or medial aspect of a femur in which said alignment member is positioned in said prepared intramedullary canal;  
   (c) selecting an arm assembly having the desired angle between said stylus arm and said alignment member, said selected arm assembly having an angle in the range of 90° to 100°;    (d) moving said alignment member into said intramedullary canal to a position at which said stylus arm contacts said femur distal end;    (e) moving said cutting guide on said arm assembly to a position at which said first side engages the lateral or medial aspect of said femur; and    (f) extending a cutting instrument through said slot to cut said distal end.    
   
   
       39 . The method according to  claim 38  further including the step of varying the distance, in a direction axially of said intramedullary canal, between said slot and said stylus arm prior to step (f).  
   
   
       40 . The method according to  claim 39  wherein said step of varying is performed while said arm assembly is engaged to said cutting guide.  
   
   
       41 . A method of resectioning the distal end of a femur comprising the steps of setting proper external rotation for the cuts to be made by positioning a guide rod in the medial or lateral aspect of a femur, positioning a cutting guide having guide surfaces over said guide rod and thereafter resectioning said femur with a cutting instrument while using said guide surfaces to guide said cutting instrument.  
   
   
       42 . A method of resectioning the distal end of a femur comprising the steps of 
 (a) providing a femoral anterior-posterior sizer guide having 
 (i) a base having a surface upon which a portion of the posterior or anterior femur adjacent said resectioned end may rest;  
 (ii) a support extending upwardly from said base, said support having an elongated slot extending upwardly in a direction away from said base;  
 (iii) A slideable member movably positioned in said slot, said slideable member having an aperture extending along an axis;  
 (iv) a stylus movable with said slideable member toward and away from said base surface, said stylus having a femoral engagement surface substantially parallel to said base surface;  
   (b) positioning said sizer guide on said femur with one of the posterior aspect or anterior aspect of said femur engaged to said base and the other of said posterior aspect or anterior aspect engaged to said stylus and with said slideable member facing the lateral or medial aspect of said femur;    (c) adjusting said axis relative to said femur; and    (d) causing a guide pin to be inserted into said femur using said aperture as a guide to direct the positioning of said guide pin.    
   
   
       43 . The method according to  claim 42  further including the step of providing a distal arm extending in a direction parallel to said axis and further including the step of positioning said sizer guide with said distal arm engaged to the distal end of said femur.  
   
   
       44 . The method according to  claim 42  further including the steps of 
 (a) removing said sizer guide from said femur,    (b) providing a resection guide having 
 (i) a side resection guide adapted to engage said medial or lateral aspect, said side resection guide having an aperture and one or more guide slots;  
 (ii) a chamfer block extending from said side resection guide;  
   (c) positioning said resection guide with said side section guide engaged to said lateral or medial aspect and said guide pin extending through said aperture and with said chamfer block engaged to said femur distal end; and    (d) directing a cutting instrument through said one or more guide slots to resection said femur from said medial or lateral aspect.    
   
   
       45 . The method according to  claim 44  wherein said chamfer block has a triangular cross section with a first flat side engaged said femur distal end and second and third flat sides, each disposed at an angle relative to said first flat side and further including the steps of resecting said femur distal end using a cutting instrument guided on said chamfer block.  
   
   
       46 . The method according to  claim 45  wherein said chamfer block has a guide slot extending from one of said second or third flat sides to said first flat side and further including the step of extending a cutting instrument through said chamfer block guide slot to cut the distal end of said femur.  
   
   
       47 . The method according to  claim 46  further including the step of moving said chamfer block laterally or medially to position said guide slot to a central position relative to said lateral and medial aspects.