Differential Porosity Prosthetic Hip System

Abstract

A prosthetic femoral implant for use in a hip joint, as a ball and socket type joint, is disclosed. The implant includes a modular neck having a variety of adjustable positions to adjust the lateral offset and version angle of the femoral implant in relation to the femur. The implant further includes a broad, full collar for providing a compression force increasing the interdigitation between the interface of the bone, implant and cement. The implant also includes a stem having a depression having a roughened porous surface for resisting the increased torsional loads placed on the implant due to the increased lateral offset and version angle. The stem further comprises three distinct zones, each zone having its own roughened surface creating a tripartite differential porosity.

1 . A prosthetic device for implantation into a bone comprising:
 a longitudinal stem portion configured and dimensioned for insertion into a canal formed within the bone, said stem portion having a proximal region, a distal region, and at least one depression that extends a majority length of the stem portion between the proximal region and the distal region;   wherein the proximal region, the distal region and the at least one depression each have a different surficial roughness for increasing the surface area of the stem portion and increasing the interdigitation between the stem portion and a fixation material, thereby increasing resistance to torsional loads.   
   
   
       2 . The prosthetic device of  claim 1 , wherein the device is part of a ball and socket joint and further comprises a neck portion having a first end and a second end, said first end configured and dimensioned for connecting said neck portion to a head portion. 
   
   
       3 . The prosthetic device of  claim 1 , wherein the device further comprises a neck portion having a first end and a second end, said first end configured and dimensioned for connecting said neck portion to said stem portion. 
   
   
       4 . The prosthetic device of  claim 2 , wherein the second end of the neck portion has a raised portion thereon, said raised portion extending at least partially around a circumference of the second end, such that a version angle formed between the head portion and the neck portion of the device relative to a frontal plane of a patient's body is adjustable. 
   
   
       5 . The prosthetic device of  claim 2 , wherein the second end of the neck portion further comprises an indexable portion formed distally with respect to said second end. 
   
   
       6 . The prosthetic device of  claim 5 , wherein the indexable portion further comprises a first tapered portion and a second tapered portion, wherein the first and second tapered portions together form a double taper. 
   
   
       7 . The prosthetic device of  claim 6 , wherein the first tapered portion has an exterior surface comprising a plurality of teeth and the second tapered portion has a frusto-conical exterior surface. 
   
   
       8 . The prosthetic device of  claim 1 , wherein the device further comprises a collar portion disposed proximally on said stem portion, said collar portion having a cavity formed in a top surface thereof. 
   
   
       9 . The prosthetic device of  claim 8 , wherein the device further comprises a neck portion having a first end and a second end, wherein an indexable portion is formed distally with respect to said second end, said indexable portion comprising a first tapered portion and a second tapered portion, the first tapered portion having an exterior surface comprising a plurality of first teeth and the second tapered portion having a frusto-conical exterior surface, wherein the first and second tapered portions together form a double taper. 
   
   
       10 . The prosthetic device of  claim 9 , wherein the cavity comprises an opening defined by a first sidewall, wherein said first sidewall further defines a first portion of said cavity, said first sidewall having a plurality of corresponding second teeth for receiving the plurality of first teeth of the first tapered portion in a plurality of predetermined orientations such that the version angle of the neck portion may be modified by varying the position of the neck portion thereby altering stress points placed on the device. 
   
   
       11 . The prosthetic device of  claim 10 , wherein the first tapered portion and the first sidewall mate in a primary tapered locking fit, such that the neck portion may be secured to the stem portion, and wherein the cavity further comprises a second sidewall defining a second portion configured for receiving the second tapered portion in a matching fit, thereby creating a secondary lock. 
   
   
       12 . The prosthetic device of  claim 1 , wherein the device further comprises a plurality of interchangeable neck portions, wherein each of the plurality of interchangeable neck portions is modular, and each of said plurality of interchangeable neck portions has differing shaft lengths such that one of the plurality of interchangeable neck portions may be substituted for another of the plurality of interchangeable neck portions, wherein each of the plurality of interchangeable neck portions changes a lateral offset formed between a central point of a head portion and a longitudinal axis of the stem portion. 
   
   
       13 . The prosthetic device of  claim 1 , wherein the device further comprises a collar portion disposed proximally on said stem portion separating a neck portion from the stem portion, said collar portion extending radially outward in a medial, anterior and posterior direction and being configured for covering a proximal portion of the bone such that the collar portion exerts a force on the fixation material during implantation of the prosthetic device, wherein the force exerted by the collar portion increases the interdigitation between the fixation material and the prosthetic device interface. 
   
   
       14 . The prosthetic device of  claim 1 , wherein the surficial roughness of the proximal region and the at least one depression each comprise a plurality of beads formed on the surface of the proximal region and the surface of the at least one depression for increasing the surface area such that the interdigitation between the prosthetic device and the fixation material is increased securing the prosthetic device to the bone to thereby increase the resistance to torsional forces. 
   
   
       15 . The prosthetic device of  claim 1 , wherein the at least one depression is formed on at least one of the anterior side and the posterior side of the stem portion for increasing the resistance to torsional forces. 
   
   
       16 . The prosthetic device of  claim 15 , wherein the at least one depression is shaped as a tear-drop. 
   
   
       17 . The prosthetic device of  claim 1 , wherein the at least one depression is defined by a boundary, wherein the boundary further defines the roughest region of the stem portion. 
   
   
       18 . The prosthetic device of  claim 6 , wherein the first tapered portion has a frusto-conical exterior surface and the second tapered portion comprises a plurality of teeth on the exterior surface. 
   
   
       19 . The prosthetic device of  claim 6 , wherein the first tapered portion has a frusto-conical exterior surface and the second tapered portion has a frusto-conical exterior surface. 
   
   
       20 . A prosthetic device for implantation into a bone comprising:
 a longitudinal stem portion configured and dimensioned for insertion into a canal formed within the bone, said stem portion having a proximal region, a distal region, and at least one depression that is formed with a majority of its surface area in the proximal region and a portion of the at least one depression extends into the distal region of said stem portion;   wherein the proximal region, the distal region and the at least one depression each have a different surficial roughness for increasing the surface area of the stem portion and increasing the interdigitation between the stem portion and a fixation material such that torsional loads are further resisted.   
   
   
       21 . A prosthetic device for implantation into a bone comprising:
 a longitudinal stem portion configured and dimensioned for insertion into a canal formed within the bone, said stem portion having a proximal region, a distal region, and at least one depression that is a single depression and that extends a majority length of the proximal region of said stem portion;   wherein the proximal region, the distal region and the at least one depression each have a different surficial roughness for increasing the surface area of the stem portion and increasing the interdigitation between the stem portion and a fixation material such that torsional loads are resisted.   
   
   
       22 . The prosthetic device of  claim 21 , wherein the proximal region is defined by at least a proximal most one-third of the stem portion and the distal region extends distally from and with respect to the proximal region of the stem portion.