Femoral and humeral stem geometry and implantation method for orthopedic joint reconstruction

Abstract

The present inventions relate to devices and methods that improve the positioning and fit of orthopedic reconstructive joint replacement stem implants relative to existing methods. For example, an embodiment of the device provides a stem component comprising proximal and distal body portions that can be configured to mimic a geometric shape of a central cavity region created in a bone of a joint for improving conformance and fixation of the stem component thereto. Further, another embodiment provides a system of stem implants that each have a unique medial offset for facilitating the matching of an implant to the geometry of a central cavity region of a bone. Additionally, an inclination angle of a resection surface of each of the implants in the system can remain constant or vary as a function of the medial offset.

1 . A system of orthopedic devices for joint reconstruction surgery, the system comprising: 
 a plurality of stem components, each stem component comprising a distal body portion configured to be inserted into a central cavity region created in a bone of the joint and a proximal body portion, the distal body portion defining a longitudinal axis, the proximal body portion defining a bearing surface for supporting a hemispherical head component that in turn has a geometric head center positioned within the proximal portion, the head center being spaced from the longitudinal axis at a medial offset distance and the bearing surface oriented at an inclination angle with respect to the longitudinal axis;    wherein each stem component of the system is configured such that as the medial offset decreases the inclination angle increases.    
     
     
         2 . The system of  claim 1 , wherein the system includes at least three stem components.  
     
     
         3 . The system of  claim 2 , wherein a first stem component has a medial offset of approximately 12 mm, a second stem component has a medial offset of approximately 8 mm, and a third stem component has a medial offset of approximately 5 mm.  
     
     
         4 . The system of  claim 3 , wherein the first stem component has an inclination angle of approximately 45 degrees, the second stem component has an inclination angle of approximately 41 degrees, and the third stem component has an inclination angle of approximately 37 degrees.  
     
     
         5 . The system of  claim 1  wherein each of the stem components of the system has a medial offset of between approximately 4 mm and approximately 20 mm.  
     
     
         6 . The system of  claim 5 , wherein the inclination angle is between approximately 30 degrees and approximately 55 degrees  
     
     
         7 . The system of  claim 1 , wherein the distal body component and the proximal body component form a single piece.  
     
     
         8 . A system of orthopedic devices for joint reconstruction surgery, the system comprising: 
 a plurality of stem components, each stem component comprising a distal body portion configured to be inserted into a central cavity region created in a bone of the joint and a proximal body portion, the distal body portion defining a longitudinal axis, the proximal body portion defining a bearing surface for supporting a hemispherical head component that in turn has a geometric head center positioned within the proximal portion, the head center being spaced from the longitudinal axis at a medial offset distance and the bearing surface oriented at an inclination angle with respect to the longitudinal axis;    wherein each stem component of the system is configured such that as the medial offset increases the inclination angle remains substantially constant.    
     
     
         9 . The system of  claim 8 , wherein the system includes at least four stem components.  
     
     
         10 . The system of  claim 8 , wherein a first stem component has a medial offset of approximately 5 mm, a second stem component has a medial offset of approximately 7 mm, a third stem component has a medial offset of approximately 9 mm and the fourth stem component has a medial offset of approximately 11 mm.  
     
     
         11 . The system of  claim 8 , wherein each of the stem components of the system has a medial offset of between approximately 4 mm and approximately 20 mm.  
     
     
         12 . The system of  claim 8 , wherein the inclination angle is fixed between approximately 30 degrees and approximately 55 degrees.  
     
     
         13 . The system of  claim 8 , wherein the distal body component and the proximal body component form a single piece.  
     
     
         14 . A method of implanting an orthopedic reconstructive joint replacement stem implant, the method comprising: 
 resecting a head of a bone of a joint;    using a single instrument to successively broach and ream a central cavity region in the bone of the joint; and    inserting a proximal body portion of the stem implant into the central cavity region of the bone of the joint.    
     
     
         15 . The method of  claim 14 , further comprising the step of resecting a neck of the bone of the joint.  
     
     
         16 . The method of  claim 15 , wherein the bone is a femur.  
     
     
         17 . The method of  claim 14 , wherein the joint is a hip joint.  
     
     
         18 . The method of  claim 14 , wherein the joint is a shoulder joint.  
     
     
         19 . The method of  claim 14 , wherein the bone is a humerus.  
     
     
         20 . A method of implanting an orthopedic reconstructive joint replacement stem implant, the method comprising: 
 resecting a head of a bone of a joint;    broaching a central cavity region in the bone of the joint; and    inserting a proximal body portion of the stem implant into the central cavity region of the bone of the joint without damaging the supraspinatus.    
     
     
         21 . An instrument for creating a central cavity region in a bone of a joint, the instrument comprising: 
 a reaming section being disposed at a distal end of the instrument, the reaming section being sized and configured to facilitate reaming of the bone;    a broaching section being disposed axially adjacent to the reaming section and being sized and configured to facilitate broaching of the central cavity region of the bone successive to the reaming of the bone by the reaming section; and    a handle being disposed at a proximal end of the instrument and being coupled to the reaming and broaching sections for facilitating driving of the reaming and broaching sections.    
     
     
         22 . An orthopedic device for joint reconstruction, the device comprising: 
 a stem comprising a distal body portion, a proximal body portion, and an attachment portion, the stem component being sized and configured to be implanted to within a central cavity region of a bone, the bone defining a geometric shape, the stem component tapering from the proximal body portion toward the distal body portion to define medial and lateral curved surfaces, the medial and lateral curved surfaces being configured to mimic the geometric shape of the bone for improving conformance and fixation of the stem component to the central cavity region of the bone, wherein the proximal body of the stem component is inserted into a central cavity region created in the bone of a joint.    
     
     
         23 . The device of  claim 22 , wherein the attachment portion is tapered.  
     
     
         24 . The device of  claim 22 , wherein a longitudinal axis of the distal body portion is oriented at a discrete angle with respect to a neck axis of the proximal body portion.  
     
     
         25 . The device of  claim 22 , wherein the bone is a humerus.  
     
     
         26 . The device of  claim 25 , wherein the humerus comprises a proximal portion having a shape and a distal portion.  
     
     
         27 . The device of  claim 26 , wherein the proximal body shape conforms to the shape of  claim 22 , wherein the distal body portion of the stem component has a tapered shape.  
     
     
         28 . The device of  claim 22 , wherein the distal section of the stem component has a cylindrical, elliptical or irregular shape.  
     
     
         29 . The device of  claim 22 , wherein the distal body portion of the stem component further comprises at least one feature selected from the group consisting of: a groove, a slot, a cutout, and a protrusion.