Constrained liner locking ring and polyethylene liner congruency feature

Abstract

One embodiment of the present invention relates to a prosthesis, comprising: an acetabular cup, wherein the cup has an open end and a closed end, wherein the open end of the cup is defined by a rim and wherein the rim has an outer facing surface; at least one cavity disposed in the rim, wherein the cavity extends from a first end of the cavity at the outer facing surface to a second end of the cavity that is towards the closed end of the cup, and wherein the cavity comprises an undercut at the second end of the cavity; a locking ring; and at least one tab extending from the locking ring, wherein the tab comprises a first leg and a second leg having a separation therebetween, wherein each leg has a first end and a second end, wherein the first end of each leg is at the locking ring, wherein the second end of the first leg comprises a tab protrusion, and wherein at least the second leg is resilient such that the separation between the first leg and the second leg is reduced when the second leg is deflected towards the first leg; wherein the locking ring is removably locked to the cup by placement of the locking ring adjacent the rim and insertion of the tab into the cavity such that the second leg presses against a sidewall of the cavity to initially deflect the second leg towards the first leg as the tab enters the cavity and the tab protrusion of the first leg is urged into the undercut by the second leg subsequently deflecting back away from the first leg.

1 . A prosthesis, comprising:
 an acetabular cup, wherein the cup has an open end and a closed end, wherein the open end of the cup is defined by a rim and wherein the rim has an outer facing surface;   at least one cavity disposed in the rim, wherein the cavity extends from a first end of the cavity at the outer facing surface to a second end of the cavity that is towards the closed end of the cup, and wherein the cavity comprises an undercut at the second end of the cavity;   a locking ring; and   at least one tab extending from the locking ring, wherein the tab comprises a first leg and a second leg having a separation therebetween, wherein each leg has a first end and a second end, wherein the first end of each leg is at the locking ring, wherein the second end of the first leg comprises a tab protrusion, and wherein at least the second leg is resilient such that the separation between the first leg and the second leg is reduced when the second leg is deflected towards the first leg;   wherein the locking ring is removably locked to the cup by placement of the locking ring adjacent the rim and insertion of the tab into the cavity such that the second leg presses against a sidewall of the cavity to initially deflect the second leg towards the first leg as the tab enters the cavity and the tab protrusion of the first leg is urged into the undercut by the second leg subsequently deflecting back away from the first leg.   
     
     
         2 . The prosthesis of  claim 1 , wherein the locking ring is unlocked from the cup by rotation of the locking ring relative to the cup such that the second leg deflects towards the first leg as the second leg is pressed against the sidewall of the cavity and the tab protrusion of the first leg is removed from the undercut to allow the locking ring to be separated from the cup. 
     
     
         3 . The prosthesis of  claim 1 , wherein:
 the first leg is resilient; and   the locking ring being removably locked to the cup by placement of the locking ring adjacent the rim and insertion of the tab into the cavity further comprises the first leg being pressed against the sidewall of the cavity to initially deflect the first leg towards the second leg as the tab enters the cavity and the tab protrusion of the first leg being urged into the undercut as the first leg subsequently deflects back away from the second leg.   
     
     
         4 . The prosthesis of  claim 1 , wherein at least a portion of a top surface of the undercut is angled to bias the locking ring towards the rim of the cup when the tab protrusion is urged into the undercut. 
     
     
         5 . The prosthesis of  claim 1 , wherein at least a portion of a top surface of the tab protrusion is angled to bias the locking ring towards the rim of the cup when the tab protrusion is urged into the undercut. 
     
     
         6 . The prosthesis of  claim 1 , wherein a width of the separation between the first leg and the second leg is narrower at a position at the second end of each of the first and second legs relative to a width of the separation at a position between the second end of each of the first and second legs and the first end of each of the first and second legs. 
     
     
         7 . The prosthesis of  claim 1 , further comprising a liner, wherein the liner is disposed within the cup. 
     
     
         8 . The prosthesis of  claim 7 , further comprising a femoral component, wherein the femoral component comprises a ball head and the ball head is disposed adjacent the liner when the liner is disposed within the cup. 
     
     
         9 . The prosthesis of  claim 8 , wherein the ball head is held within the cup by the locking ring. 
     
     
         10 . The prosthesis of  claim 7 , wherein the liner comprises polyethylene. 
     
     
         11 . A prosthesis, comprising:
 an acetabular cup, wherein the cup has an open end and a closed end, wherein the open end of the cup is defined by a rim and wherein the rim has an outer facing surface;   a plurality of cavities disposed in the rim, wherein each cavity extends from a first end of the cavity at the outer facing surface to a second end of the cavity that is towards the closed end of the cup, and wherein each cavity comprises an undercut at the second end of the cavity;   a locking ring; and   a plurality of tabs extending from the locking ring, wherein each tab comprises a first leg and a second leg having a separation therebetween, wherein each leg of each tab has a first end and a second end, wherein the first end of each leg of each tab is at the locking ring, wherein the second end of the first leg of each tab comprises a tab protrusion, and wherein at least the second leg of each tab is resilient such that the separation between the first leg and the second leg of each tab is reduced when the second leg of each tab is deflected towards the first leg of each tab;   wherein the locking ring is removably locked to the cup by placement of the locking ring adjacent the rim and insertion of each tab into a respective one of the cavities such that the second leg of each tab presses against a sidewall of a respective one of the cavities to initially deflect the second leg of each tab towards the first leg of each tab as each tab enters each respective cavity and each tab protrusion of the first leg of each tab is urged into the respective undercut by the second leg of each tab subsequently deflecting back away from the first leg of each tab.   
     
     
         12 . The prosthesis of  claim 11 , wherein the locking ring is unlocked from the cup by rotation of the locking ring relative to the cup such that the second leg of each tab deflects towards the first leg of each tab as the second leg of each tab is pressed against the sidewall of the respective cavity and each tab protrusion of the first leg of each tab is removed from the respective undercut to allow the locking ring to be separated from the cup. 
     
     
         13 . The prosthesis of  claim 11 , wherein:
 the first leg of each tab is resilient; and   the locking ring being removably locked to the cup by placement of the locking ring adjacent the rim and insertion of each tab into a respective one of the cavities further comprises the first leg of each tab being pressed against the sidewall of the respective cavity to initially deflect the first leg of each tab towards the second leg of each tab as each tab enters the respective cavity and each tab protrusion of the first leg of each tab being urged into the respective undercut as the first leg of each tab subsequently deflects back away from the second leg of each tab.   
     
     
         14 . The prosthesis of  claim 11 , wherein the number of cavities equals the integer x, the number of tabs equals the integer x, and the integer x is between 2 and 10, inclusive. 
     
     
         15 . A prosthesis, comprising
 an acetabular cup, wherein the cup has an inner bowl surface, an open end and a closed end, and wherein the inner bowl surface is substantially circular adjacent the open end; and   a raised feature disposed on the inner bowl surface adjacent the open end of the cup, wherein the raised feature is disposed around the circular perimeter of the inner bowl surface;   wherein the raised feature provides an interference fit with a liner disposed within the cup.   
     
     
         16 . The prosthesis of  claim 15 , wherein the raised feature is disposed around essentially the entire circular perimeter of the inner bowl surface. 
     
     
         17 . The prosthesis of  claim 15 , wherein the raised feature is interrupted at a plurality of cavities disposed in the inner bowl surface adjacent the open end.