Implants with Transition Surfaces and Related Processes

Abstract

Implants, and processes for installing them, which replace the medial condyle and portions of the patellofemoral channel but preferably not portions of the lateral condyle that articulate relative to the tibia. Processes are provided which allow proper location and orientation of an anterior resection and a distal resection on the femur, which make use of a transition point which can be designated on the bone, for navigating proper positioning of such implants. Proper positioning of the implant relative to the femur for insuring a smooth transition between lateral portions of the implant and the lateral condyle is thus reduced to determining proper medial/lateral location of the implant on the anterior and distal resections. Such implants and processes can allow, among other things, for controlled location and orientation of an implant on the bone which saves lateral compartment bone, which eliminates the need to sacrifice the anterior and posterior cruciate ligaments, and which is adapted for minimally invasive surgery with its attendant benefits.

1 . A femoral implant for implantation on resected distal portions of a patient's femur, comprising:
 An anterior portion which comprises an anterior medial articulating surface, an anterior lateral articulating surface, an anterior patellofemoral channel and an anterior inner surface adapted to correspond to an anterior resection on the femur;   A transition portion which comprises a transition medial articulating surface, a transition patellofemoral channel, a transition lateral articulating surface, and a transition inner surface adapted to correspond to a transition resection on the femur, the transition inner surface intersecting the transition medial articulating surface to form a truncation of the transition medial articulating surface;   A distal medial portion which comprises a distal articulating surface and a distal inner surface adapted to correspond to a distal resection on the femur; and   A posterior medial portion which comprises a posterior medial articulating surface and at least one posterior medial inner surface adapted to correspond to at least one posterior resection of the femur.   
   
   
       2 . An implant according to  claim 1  (all elements of which are incorporated by this reference) wherein the anterior inner surface, the distal inner surface and the transition inner surface intersect at an implant point. 
   
   
       3 . An implant according to  claim 2  (all elements of which are incorporated by this reference) adapted to be installed on a resected femur whereby the anterior resection on the femur contains a transition point, the anterior resection on the femur is oriented at a predetermined amount of internal/external rotation relative to the femur, and the distal resection on the femur substantially intersects the transition point and is oriented at a predetermined amount of varus/valgus rotation relative to the transition point. 
   
   
       4 . An implant according to  claim 3  (all elements of which are incorporated by this reference) adapted to be installed on a resected femur wherein the location of the transition resection on the femur is determined by moving a resection guide, which contains a slot corresponding to the transition resection and which is in sliding contact with the anterior resection and the distal resection, in a medial or lateral direction on the anterior and distal resections and determining the position at which bone abutting the transition articulating lateral surface will form a smooth transition to lateral condylar articulating surfaces of the femur. 
   
   
       5 . An implant according to  claim 1  (all elements of which are incorporated by this reference) further comprising at least one peg extending from an inner surface. 
   
   
       6 . An implant according to  claim 1  (all elements of which are incorporated by this reference) wherein the implant is structured so that the lateral condyle of the knee rather than the implant abuts the tibia at between substantially zero and substantially ninety degrees flexion of the knee. 
   
   
       7 . An implant according to  claim 1  (all elements of which are incorporated by this reference) wherein a patella or patella implant tracks the patellofemoral channel of the implant at between substantially zero and substantially seventy degrees flexion. 
   
   
       8 . An implant according to  claim 1  (all elements of which are incorporated by this reference) further comprising a tibial component for attachment to a tibia and for articulating relative to the implant. 
   
   
       9 . An instrument adapted to perform a distal resection a patient's femur comprising;
 An instrument index adapted to correspond to a transition point on an anterior resection of the femur;   A distal resection guide surface and a rod connection portion, the rod connection portion adapted to adjustably connect to an intermedullary or extramedullary rod, whereby orientation of the distal resection guide surface is adjustable in varus/valgus rotation relative to the transition point on the femur by maintaining the index substantially aligned with the transition point while adjusting orientation of the instrument relative to the rod;   Whereby the distal resection guide surface is positioned and oriented properly to form a distal resection on the medial condyle of the femur when the index corresponds to the transition point and the instrument is properly oriented in varus/valgus relative to the rod.   
   
   
       10 . An instrument according to  claim 9  (all elements of which are incorporated by this reference) wherein the instrument index is adapted to correspond to a transition point that is located at the distal-most point of a lateral portion of an anterior resection on the knee. 
   
   
       11 . An instrument according to  claim 9  (all elements of which are incorporated by this reference) wherein the rod connection portion comprises a collet adapted to receive an intramedullary rod. 
   
   
       12 . An instrument according to  claim 9  (all elements of which are incorporated by this reference) further comprising a transition resection guide surface for forming a transition resection positioned and oriented at an angle relative to the anterior resection and the distal resection. 
   
   
       13 . An instrument according to  claim 9  (all elements of which are incorporated by this reference) wherein the distal resection guide surface is adapted to guide one of the following: a sawblade and a milling device. 
   
   
       14 . A resection guide adapted to resect a patient's femur, comprising:
 A distal resection abutment surface adapted to contact a distal resection on the femur;   An anterior resection abutment surface adapted to contact an anterior resection on the femur;   A transition resection guide surface for guiding a transition resection of the femur;   An index located on the resection guide at a position that corresponds to a lateral extremity of an implant that corresponds in size to the resection guide;   Whereby the transition resection guide surface is adapted to be properly positioned relative to the distal resection and the anterior resection for performing a transition resection by contacting the abutment services of the resection guide with the anterior resection and the distal resections, and moving the guide in a medial or lateral direction on the femur to a point where the index indicates proper medial/lateral alignment of the transition resection guide surface.   
   
   
       15 . A resection guide according to  claim 14  (all elements of which are incorporated by this reference) further comprising a chamfer resection guide surface for guiding a chamfer resection. 
   
   
       16 . A resection guide according to  claim 15  (all elements of which are incorporated by this reference) wherein the chamfer resection guide surface and the transition resection guide surface are substantially planar and intersect along a line. 
   
   
       17 . A process for conducting knee surgery on a knee comprising a tibia and a femur, the femur in turn comprising a lateral condyle and a medial condyle, comprising:
 Resecting an anterior portion of a distal portion of the femur, thereby creating an anterior resection, the anterior resection positioned at a predetermined depth and oriented at a predetermined angle relative to the femur in internal/external rotation;   Selecting a transition point relative to the anterior resection, wherein the transition point is located in the vicinity of the distal-most point of a lateral portion of the anterior resection;   Performing a distal resection on a portion of the medial condyle, the distal resection intersecting a point in the vicinity of the transition point, and oriented at a predetermined angle relative to the femur in varus/valgus rotation;   Performing a transition resection on a lateral portion of the femur at an angle relative to both the anterior resection and the distal resection, the transition resection intersecting the anterior resection and distal resection so that an implant installed on the bone does not project beyond lateral external surfaces of the femur and so that external surfaces of lateral portions of the implant form a smooth transition to lateral external surfaces of the femur; and   Installing an implant on the resected femur, the implant having inner surfaces which substantially fit the resections, which implant replaces distal articulating surfaces of the medial condyle and patellofemoral articulating surfaces, but does not replace surfaces of the lateral condyle which articulate with the tibia.   
   
   
       18 . A process according to  claim 17  (all elements of which are incorporated by this reference) wherein the process is conducted and the implant is installed without resection of either an anterior cruciate ligament or a posterior cruciate ligament of the knee. 
   
   
       19 . A process according to  claim 17  (all elements of which are incorporated by this reference) further comprising resecting a medial portion of the tibia and installing an implant on the resected portion of the tibia. 
   
   
       20 . A process according to  claim 17  (all elements of which are incorporated by this reference) further comprising installing a patellar implant. 
   
   
       21 . A process according to  claim 17  (all elements of which are incorporated by this reference) in which resecting the anterior portion of the femur creates a substantially hour-glass shaped anterior resection with two lobes, wherein the transition point is located at the distal-most point on the lateral lobe. 
   
   
       22 . A process according to  claim 17  (all elements of which are incorporated by this reference) in which the distal resection is performed using a distal resection instrument connected to an intramedullary rod inserted in the femur. 
   
   
       23 . A process according to  claim 17  (all elements of which are incorporated by this reference) in which the distal resection and the transition resection are formed using the same resection guide. 
   
   
       24 . A process according to  claim 17  (all elements of which are incorporated by this reference) in which at least one of the resections is formed using a milling device. 
   
   
       25 . A process according to  claim 17  (all elements of which are incorporated by this reference) in which at least one of the resections is curved.