Patent Publication Number: US-2023149174-A1

Title: Off-center liner for acetabular cup

Description:
INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS 
     Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 CFR 1.57. 
     BACKGROUND 
     Field 
     The present disclosure is directed to liners for an acetabular cup for use in hip joint replacement surgical procedures, and more particularly to off-center liners for an acetabular cup. 
     Description of the Related Art 
     Hip joint replacement surgical procedures involve the implantation of an acetabular cup in the pelvis bone that receives a liner and a head of a femoral stem implant that is inserted into the femur bone. Dual mobility liners made of plastic (e.g., of Polyethylene) are used with acetabular cups. However, existing liners made of plastic can lose material during use following implantation). 
     SUMMARY 
     In accordance with one aspect of the disclosure, off-center liners are provided for use with an acetabular cup in hip replacement or revision surgical procedures. The liners can in one implementation be made of metal. In another implementation, the liners can be made of a plastic material (e.g., Polyethylene). In still another implementation, the liners can be made of a ceramic material. The liners can be laterally spaced from the acetabular cup, angled relative to the acetabular cup and/or have an opening that is offset relative to the axis of the acetabular cup. The liners have an orientation indicator that identifies where the liner should be impacted (e.g., impaction location or point) by the impactor to ensure the liner is impacted in a square manner relative to the acetabular cup. 
     In accordance with one aspect of the disclosure, a liner for an acetabular cup is provided. The liner comprises a proximal surface, an outer convex surface configured to at least partially extend into an acetabular cup when the liner is seated in the acetabular cup, and a concave bearing surface recessed relative to the proximal surface and configured to receive a head of a femoral stem. One or more visual indicators on the liner are configured to identify a location for applying an impaction force on the liner so that the liner is impacted square relative to the acetabular cup. 
     In accordance with another aspect of the disclosure, a liner and impactor system for an acetabular cup is provided. The system comprises a liner comprising a proximal surface, an outer convex surface configured to at least partially extend into an acetabular cup when the liner is seated in the acetabular cup, and a concave bearing surface recessed relative to the proximal surface and configured to receive a head of a femoral stem. One or more visual indicators on the liner are configured to identify a location for applying an impaction force on the liner. The system also comprises an impactor having an impaction surface corresponding to one or both of the proximal surface and the concave bearing surface of the liner, the impactor configured to apply an impaction force on the liner so that the liner is impacted square relative to the acetabular cup. 
     In accordance with another aspect of the disclosure, a method for implanting a liner in an acetabular cup is provided. The method comprises evaluating a size of an acetabular hole, identifying a size of an acetabular cup for the acetabular hole, and preparing the acetabular hole to receive the acetabular cup. The method also comprises identifying a liner for use with the acetabular cup, inserting the acetabular cup in the acetabular hole, and inserting the liner in the acetabular cup. The method also comprises impacting the liner into place in the acetabular cup with an impactor square with the acetabular cup to seat the liner in the acetabular cup. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic perspective view of an acetabular cup. 
         FIG.  2 A  is a schematic side view of the acetabular cup in  FIG.  1    with a liner inserted in the acetabular cup flush with the acetabular cup. 
         FIG.  2 B  is a schematic top view of the liner in  FIG.  2 A  and a partial schematic side view of an impactor head surface to impact the liner. 
         FIG.  3 A  is a schematic side view of the acetabular cup in  FIG.  1    with a liner inserted in the acetabular cup laterally spaced relative to the acetabular cup. 
         FIG.  3 B  is a schematic top view of the liner in  FIG.  3 A  and a partial schematic side view of an impactor head surface to impact the liner. 
         FIG.  4 A  is a schematic side view of the acetabular cup in  FIG.  1    with a liner inserted in the acetabular cup, the liner having an angled face relative to the acetabular cup. 
         FIG.  4 B  is a schematic top view of the liner in  FIG.  4 A  and a partial schematic side view of an impactor head surface to impact the liner. 
         FIG.  5 A  is a schematic side view of the acetabular cup in  FIG.  1    with a liner inserted in the acetabular cup, the liner being flush with the acetabular cup. 
         FIG.  5 B  is a schematic top view of the liner in  FIG.  5 A  and a partial schematic side view of an impactor head surface to impact the liner. 
         FIG.  6    is a perspective view of an acetabular cup with a liner having an offset opening for the femoral head of an implant. 
         FIG.  7 A  is a schematic cross-sectional side view of the acetabular cup and liner in  FIG.  6   . 
         FIG.  7 B  is a schematic top view of the liner in  FIG.  7 A  and a partial schematic side view of an impactor head surface to impact the liner. 
         FIG.  8 A  is a schematic cross-sectional side view of the acetabular cup in  FIG.  1    with a liner inserted in the acetabular cup, the liner having an angled face and an offset opening relative to the acetabular cup. 
         FIG.  8 B  is a schematic top view of the liner in  FIG.  8 A  and a partial schematic side view of an impactor head surface to impact the liner. 
         FIG.  9    is a partial schematic side view of a impactor head shape for use with a liner having a partial angled face. 
         FIG.  10    is a partial schematic side view of an impactor head shape for use with a liner having an angled face. 
         FIG.  11    is a schematic view of a liner kit for use with an acetabular cup. 
         FIG.  12    is a flow chart of a method for seating a liner in an acetabular cup. 
     
    
    
     DETAILED DESCRIPTION 
     Disclosed herein are liners (e.g., metal liners, such as made of titanium, plastic liners, such as made of Polyethylene, ceramic liners) for use in a hip joint surgical procedure, such as hip joint revision surgery, where an acetabular cup is implanted in the acetabulum of the pelvis bone. The acetabular cup can at least partially receive the liner, which can at least partially receive a ball of a femoral stem implant, or can receive a second liner (e.g., made of plastic, such as Polyethylene) that can then receive the ball of the femoral stem implant. The liners disclosed below advantageously provide structural support to the ball of the femoral stem while inhibiting (e.g., preventing) loss of material as occurs with plastic liners. Additionally, the liners disclosed herein allow a smaller femoral stem head to be used with a same sized acetabular cup, with the head laterally displaced farther away from the bottom of the acetabular cup, which advantageously provides improved stability of the hip joint. 
       FIG.  1    shows a perspective view of an acetabular cup  100  having an outer convex surface  10 , an outer rim  20  and an inner convex surface or bearing surface  30  that defines a cavity that receives a liner, such as the liners disclosed herein. 
       FIG.  2 A  shows a liner  200  coupled to the acetabular cup  100  and  FIG.  2 B  shows a top view of the liner  200  and an impactor  300  that can be used to impact the liner  200  into place in the acetabular cup  100 . The liner  200  can sit flush with the acetabular cup  100  and have a proximal portion  220  that protrudes relative to the outer rim  20  of the acetabular cup  100 . The liner  200  can also have a bearing surface  210  and an outer rim  230  that circumscribes the bearing surface  210 . The outer rim  230  can extend a long a plane (e.g., be planar). The liner  200  can have one or more visual indications  240 ,  250  identifying the location of the impaction force for the liner  200  to be impacted square relative to the acetabular cup  100 . The visual indicators can include an indicator  240  (e.g., cross-hairs, dot, sticker or removable layer) on the bearing surface  210 . The visual indicators can also include one or more indicators  250  (e.g., etched lines, markings) on the outer rim  230  or bearing surface  210  that align with the indicator  240 . The visual indicators can be in separate components (e.g., stickers), which can be removed after the impaction force is applied. In another implementation, the visual indicators can be made (e.g., etchings, grooves) in the material of the liner  200 . In still another implementation, the visual indicators can be virtual (e.g., applied to or projected onto the liner  200  by a robotic system, such as by an imaging system of a robotic surgical system). 
     The impactor  300  has a shaft S and an impaction surface  310  corresponding to the liner  200 . In the illustrated implementation, the impaction surface  310  is planar and corresponds to the planar outer rim  230  of the liner  200 , so that the impactor  300  can apply a force square relative to the liner  200  to seat the liner  200  in the acetabular cup  100  (e.g., so the center of the impaction force that is applied is located at the location of the visual indicator  240 ). In one implementation, an outer diameter or dimension of the impaction surface  310  corresponds with an outer diameter of the outer rim  230  of the liner  200 . 
       FIG.  3 A  shows a liner  200 A coupled to the acetabular cup  100  and  FIG.  3 B  shows a top view of the liner  200 A and the impactor  300 , which can be used to impact the liner  200 A into place in the acetabular cup  100 . Some of the features of the liner  200 A are similar to features of the liner  200  in  FIGS.  2 A- 2 B . Thus, reference numerals used to designate the various components of the liner  200 A are identical to those used for identifying the corresponding components of the liner  200  in  FIGS.  2 A- 2 B , except that an “A” has been added to the numerical identifier. Therefore, the structure and description for the various features of the liner  200  in  FIGS.  2 A- 2 B  are understood to also apply to the corresponding features of the liner  200 A in  FIGS.  3 A- 3 B , except as described below. 
     The liner  200 A differs from the liner  200  in that it&#39;s outer rim  230 A is laterally spaced from the outer rim  20  by a larger amount than the liner  200 . Similarly, the bearing surface  210 A can be laterally spaced from a distal end of the acetabular cup  100  by a larger amount than the bearing surface  210  of the liner  200 , allowing the head of the femoral stem implant to be further laterally spaced apart (as compared with the liner  200  and acetabular cup  100 ). The outer rim  230 A of the liner  200 A can be planar (e.g., extend along or be defined by a plane) so the same impactor  300  used for the liner  200  can be used for the liner  200 A to apply an impaction force on the liner  200 A square with the acetabular cup  100  (e.g., so the center of the impaction force that is applied is located at the location of the visual indicator  240 ). 
       FIG.  4 A  shows a liner  200 B coupled to the acetabular cup  100  and  FIG.  4 B  shows a top view of the liner  200 B and an impactor  300 B, which can be used to impact the liner  200 B into place in the acetabular cup  100 . Some of the features of the liner  200 B and impactor  300 B are similar to features of the liner  200  and impactor  300  in  FIGS.  2 A- 2 B . Thus, reference numerals used to designate the various components of the liner  200 B and impactor  300 B are identical to those used for identifying the corresponding components of the liner  200  and impactor  300  in  FIGS.  2 A- 2 B , except that a “B” has been added to the numerical identifier. Therefore, the structure and description for the various features of the liner  200  and impactor  300  in  FIGS.  2 A- 2 B  are understood to also apply to the corresponding features of the liner  200 B and impactor  300 B in  FIGS.  4 A- 4 B , except as described below. 
     The liner  200 B differs from the liner  200  in that the outer rim  230 B (and therefore the face) of the liner  200 B extends at an angle f relative to the outer rim  20  of the acetabular cup  100 . The bearing surface  210 B has visual indicators  240 B,  250 B for applying an impaction force on the liner  200 B square with the acetabular cup  100  using an impactor  300 B. The bearing surface  210 B of the liner  200 B can also have a visual indicator  260 B indicating the offset location of the center of the bearing surface resulting from the angled outer rim  230 B. 
     The impactor  300 B has an impactor surface  310 B corresponding to the outer rim  230 B of the liner  200 B. The impactor surface  310 B can be angled at the same angle ϕ relative to the shaft S as the outer rim  230 B is to the outer rim  20  of the acetabular cup  100 . This advantageously allows the impactor  300 B to apply an impaction force square on the outer rim  230 B of the liner  200  relative to the acetabular cup  100  (e.g., so the center of the impaction force that is applied is located substantially at the location of the visual indicator  240 B). 
       FIG.  5 A  shows the liner  200  attached to the acetabular cup  100  and  FIG.  5 B  shows an impactor  300 C that can be used to impact the liner  200  into place in the acetabular cup  100 . The impactor  300 C can have a curved (e.g., convex, spherical) impactor surface  310 C. The impactor  300 C can be used instead of the impactor  300  to apply an impaction force on the liner  200  to seat the liner  200  in the acetabular cup. Unlike the impactor  300 , which applies the impaction force on the outer rim  230  of the liner  200 , the impactor  300 C can be used to apply the impaction force on or proximate the visual indicator  240  so that the impactor  300 C impacts the liner  200  square relative to the acetabular cup  100 . 
       FIG.  6    shows a perspective view of a liner  200 D attached to the acetabular cup  100 .  FIG.  7 A  shows a cross-sectional side view of the liner  200 D coupled to the acetabular cup  100  and  FIG.  7 B  shows a top view of the liner  200 D and an impactor  300 D, which can be used to impact the liner  200 D into place in the acetabular cup  100 . Some of the features of the liner  200 D are similar to features of the liner  200  in  FIGS.  2 A- 2 B . Thus, reference numerals used to designate the various components of the liner  200 D are identical to those used for identifying the corresponding components of the liner  200  in  FIGS.  2 A- 2 B , except that a “D” has been added to the numerical identifier. Therefore, the structure and description for the various features of the liner  200  in  FIGS.  2 A- 2 B  are understood to also apply to the corresponding features of the liner  200 D in  FIGS.  6 - 7 B , except as described below.  FIGS.  6 - 7 B  are not to scale and are exaggerated to show that the center of the bearing surface of the liner  200 D, and therefore the head of the femoral stem implant received therein, would be offset or off-center relative to the center of the acetabular cup  100 . 
     The liner  200 D differs from the liner  200  in that bearing surface  210 D (e.g., concave) of the liner  200 D is offset from a centerline of the acetabular cup  100  so that the bearing surface  210 D is not coaxial with the bearing surface  30  of the acetabular cup  100 , and so that a center of the head of the femoral stem implant that is received by the bearing surface  210 D would be offset or off-center relative to the axis or center of the acetabular cup  100 . As shown in  FIG.  7 A , the axis of the bearing surface  210 D can be offset by a distance X from a centerline or axis of the acetabular cup  100 . The distance X can be between a few millimeters and a few centimeters, such as between about 2 mm and about 2-3 cm. The distance X can in one implementation be no more than 3 cm, such as no more than about 2.5 cm. Therefore, the proximal surface  230 D of the liner  200 D is planar except for the opening above the bearing surface  210 D. The location of the bearing surface  210 D relative to the central axis of the acetabular cup  100  (e.g., phase change of the bearing surface  210 D) can be adjusted by the surgeon before or after seating the liner  200 D in the acetabular cup  100 . 
     The impactor  300 D has an impactor surface  310 D corresponding to the planar proximal surface  230 D of the liner  200 D and has a curved (e.g., convex, spherical) impactor surface  320 D corresponding to (e.g., having the same radius of curvature as) the bearing surface  210 D of the liner  200 D. This advantageously allows the impactor  300 D to apply an impaction force square on the liner  200 D relative to the acetabular cup  100  (e.g., so the center of the impaction force that is applied by the impactor  300 D is located at the location of the visual indicator  240 D). 
       FIG.  8 A  shows a cross-sectional side view of the liner  200 E coupled to the acetabular cup  100  and  FIG.  8 B  shows a top view of the liner  200 E and an impactor  300 E, which can be used to impact the liner  200 E into place in the acetabular cup  100 . Some of the features of the liner  200 E are similar to features of the liner  200 D in  FIGS.  6 - 7 B . Thus, reference numerals used to designate the various components of the liner  200 E are identical to those used for identifying the corresponding components of the liner  200 D in  FIGS.  6 - 7 B , except that an “E” instead of a “D” has been added to the numerical identifier. Therefore, the structure and description for the various features of the liner  200 D in  FIGS.  6 - 2 B , which are based on the structure and description of the features of the liner  200  in  FIGS.  2 A- 2 B , are understood to also apply to the corresponding features of the liner  200 E in  FIGS.  8 A- 8 B , except as described below.  FIGS.  8 A- 7 B  are not to scale and are exaggerated to show that the center of the bearing surface of the liner  200 E, and therefore the head of the femoral stem implant received therein, would be offset or off-center relative to the center of the acetabular cup  100  in two planes. 
     The liner  200 E differs from the liner  200 D in that the proximal surface  230 E has an inclined portion  235 E across the bearing surface  210 E relative to the remainder of the proximal surface  230 E. The bearing surface  210 E (e.g., concave) of the liner  200 E is offset from a centerline of the acetabular cup  100  so that the bearing surface  210 E is not coaxial with the bearing surface  30  of the acetabular cup  100 , and so that a center of the head of the femoral stem implant that is received by the bearing surface  210 E would be offset or off-center (in two planes) relative to the axis or center of the acetabular cup  100 . As shown in  FIG.  8 A , the axis of the bearing surface  210 E can be offset by a distance X′ from a centerline or axis of the acetabular cup  100 . The distance X′ can be between a few millimeters and a few centimeters, such as between about 2 mm and about 2-3 cm. The distance X′ can in one implementation be no more than 3 cm, such as no more than about 2.5 cm. Therefore, the proximal surface  230 E of the liner  200 E has a first planar portion, an inclined portion  235 E that extends at an angle from the planar portion, and an opening defined in the inclined portion  235 E above the bearing surface  210 E. The location of the bearing surface  210 E relative to the central axis of the acetabular cup  100  (e.g., phase change of the bearing surface  210 E) can be adjusted by the surgeon before or after seating the liner  200 D in the acetabular cup  100 . The inclined portion  235 E allows the head of the femoral stem (not shown) to be further laterally offset from the acetabulum. 
     The impactor  300 E has an impactor surface  310 E corresponding to the planar proximal surface  230 E of the liner  200 E, a curved (e.g., convex, spherical) impactor surface  320 E corresponding to (e.g., having the same radius of curvature as) the bearing surface  210 E of the liner  200 E, and an inclined surface  330 E corresponding to the inclined portion  235 E of the liner  200 E. This advantageously allows the impactor  300 E to apply an impaction force square on the liner  200 E relative to the acetabular cup  100  (e.g., so the center of the impaction force that is applied by the impactor  300 E is located at the location of the visual indicator  240 E). 
       FIG.  9    shows a side view of a liner  200 F attached to the acetabular cup  100  and an impactor  300 F, which can be used to impact the liner  200 F into place in the acetabular cup  100 . Some of the features of the liner  200 F are similar to features of the liner  200  in  FIGS.  2 A- 2 B . Thus, reference numerals used to designate the various components of the liner  200 F are identical to those used for identifying the corresponding components of the liner  200  in  FIGS.  2 A- 2 B , except that an “F” has been added to the numerical identifier. Therefore, the structure and description for the various features of the liner  200  in  FIGS.  2 A- 2 B  are understood to also apply to the corresponding features of the liner  200 F in  FIG.  9   , except as described below. 
     The liner  200 F differs from the liner  200  in that the proximal surface  230 F (e.g., outer rim) has an inclined portion  235 F relative to the remainder of the proximal surface  230 F. The proximal surface  230 F of the liner  200 F has a planar portion (e.g., portion of the outer rim defined by a plane perpendicular to an axis of the liner  200 F) and an inclined portion  235 F that extends at an angle from the planar portion. 
     The impactor  300 F has an impactor surface  310 F corresponding to the planar portion of the proximal surface  230 F of the liner  200 E and an inclined surface  320 F corresponding to the inclined portion  235 F of the liner  200 F. This advantageously allows the impactor  300 F to apply an impaction force square on the liner  200 F relative to the acetabular cup  100  (e.g., so the center of the impaction force that is applied by the impactor  300 F is located at the location of the visual indicator  240 F). 
       FIG.  10    shows a side view of the liner  200 B of  FIGS.  4 A- 4 B  attached to the acetabular cup  100 . Instead of using the impactor  300 B to impact the liner  200 B to seat the liner  200 B in the acetabular cup  100 , the impactor  300 C can be used. The impactor  300 C can be operated by a surgeon to apply an impaction force with the impaction surface  310 C on the liner  200 B on the visual indicator  240 B. This advantageously allows the impactor  300 C to apply an impaction force square on the liner  200 B relative to the acetabular cup  100  (e.g., so the center of the impaction force that is applied by the impactor  300 C is located at the location of the visual indicator  240 B). 
       FIG.  11    shows a liner kit  400  for use with an acetabular cup  100  in hip joint replacement or revision surgery. The kit  400  can include one or more of each of the liners  200 ,  200 A,  200 B,  200 D,  200 E,  200 F disclosed herein. In one implementation, the kit  400  can also include one or more of the impactors  300 ,  300 B,  300 C,  300 D,  300 E,  300 F disclosed herein. In one implementation, the kit  400  can also include one or more of the acetabular cups  100  sized to receive the liner  200 ,  200 A,  200 B,  200 D,  200 E,  200 F. Advantageously, the bearing surface  30  of the acetabular cup  100  and outer surface of the liners  200 ,  200 A,  200 B,  200 D,  200 E,  200 F allow for each of the liners  200 ,  200 A,  200 B,  200 D,  200 E,  200 F to seat in the acetabular cup  100 . In one implementation, the kit  400  has liners  200 ,  200 A,  200 B,  200 D,  200 E,  200 F sized to correspond to a particular size acetabular cup  100 . Therefore, each acetabular cup  100  of a different size can have a separate kit  400  of associated liners  200 ,  200 A,  200 B,  200 D,  200 E,  200 F that can be used with that size acetabular cup  100 . The kit  400  provides the surgeon with different liner options for use with a particular size acetabular cup  100 , depending on the anatomy of the patient to provide the desired relationship between the femur and acetabulum with the hip joint replacement prosthesis. 
       FIG.  12    shows a flow chart of a process or method  500  for using a liner, such as the liners  200 ,  200 A,  200 B,  200 D,  200 E,  200 F disclosed herein, in hip joint replacement or revision surgery. The method  500  includes the step  510  of evaluating the size of the acetabular hole in the pelvis bone and identifying the size of acetabular cup needed for the acetabular hole. The method  500  also includes the step  520  of preparing the acetabular hole (e.g., reaming the acetabulum to create a base of vascular cancellous bone to facilitate bone growth) for receiving the acetabular cup, such as the acetabular cup  100 . The method  500  also includes the step  530  of identifying the liner (such as one of the liners  200 ,  200 A,  200 B,  200 D,  200 E,  200 F) for use with the acetabular cup (such as the acetabular cup  100 ). The method  500  also includes the step  540  of inserting and attaching the acetabular cup in the acetabular hole, and the step  550  of inserting the liner (such as the liner  200 ,  200 A,  200 B,  200 D,  200 E,  200 F) in the acetabular cup. The method  500  also includes the step  560  of impacting the liner (such as the liner  200 ,  200 A,  200 B,  200 D,  200 E,  200 F) into place (e.g., seating) within the acetabular cup with an impactor (such as the impactor  300 ,  300 B,  300 C,  300 D,  300 E,  300 F), such that the impactor applies an impaction force on the liner square with the acetabular cup. 
     ADDITIONAL EMBODIMENTS 
     In embodiments of the present disclosure, a liner for an acetabular cup, liner and impactor system and method for implanting a liner may be in accordance with any of the following clauses: 
     Clause 1. A liner for an acetabular cup, comprising:
         a proximal surface;   an outer convex surface configured to at least partially extend into an acetabular cup when the liner is seated in the acetabular cup;   a concave bearing surface recessed relative to the proximal surface and configured to receive a head of a femoral stem; and   one or more visual indicators on the liner configured to identify a location for applying an impaction force on the liner so that the liner is impacted square relative to the acetabular cup.       

     Clause 2. The liner of clause 1, wherein the one or more visual indicators are markings on the proximal surface or concave bearing surface. 
     Clause 3. The liner of clause 2, wherein the markings include one of cross hairs, dots and dashed lines. 
     Clause 4. The liner of any preceding clause, wherein the visual indicators are virtual indicators applied or projected onto the proximal surface or concave bearing surface. 
     Clause 5. The liner of any preceding clause, wherein the concave bearing surface extends about an axis that is offset from an axis of the acetabular cup when the liner is seated in the acetabular cup. 
     Clause 6. The liner of any preceding clause, wherein at least a portion of the proximal surface extends along a plane perpendicular to an axis of the acetabular cup when the liner is seated in the acetabular cup. 
     Clause 7. The liner of any preceding clause, wherein at least a second portion of the proximal surface extends along a second plane at an angle relative to the plane, the second portion defining an opening above the concave bearing surface. 
     Clause 8. The liner of any preceding clause, wherein at least a portion of the proximal surface extends along a plane perpendicular to an axis of the acetabular cup when the liner is seated in the acetabular cup. 
     Clause 9. The liner of any preceding clause, wherein at least a second portion of the proximal surface extends along a second plane at an angle relative to the plane, the second portion defining an opening above the concave bearing surface. 
     Clause 10. A liner and impactor system for an acetabular cup, comprising:
         a liner comprising
           a proximal surface;   an outer convex surface configured to at least partially extend into an acetabular cup when the liner is seated in the acetabular cup;   a concave bearing surface recessed relative to the proximal surface and configured to receive a head of a femoral stem; and   one or more visual indicators on the liner configured to identify a location for applying an impaction force on the liner; and   
           an impactor having an impaction surface corresponding to one or both of the proximal surface and the concave bearing surface of the liner, the impactor configured to apply an impaction force on the liner so that the liner is impacted square relative to the acetabular cup.       

     Clause 11. The system of clause 10, wherein the one or more visual indicators include markings on the proximal surface or concave bearing surface. 
     Clause 12. The system of clause 11, wherein the markings include one of cross hairs, dots and dashed lines. 
     Clause 13. The system of any of clauses 10-12, wherein the visual indicators are virtual indicators applied or projected onto the proximal surface or concave bearing surface. 
     Clause 14. The system any of clauses 10-13, wherein the concave bearing surface extends about an axis that is offset from an axis of the acetabular cup when the liner is seated in the acetabular cup. 
     Clause 15. The system of any of clauses 10-14, wherein at least a portion of the proximal surface extends along a plane perpendicular to an axis of the acetabular cup when the liner is seated in the acetabular cup. 
     Clause 16. The system of any of clauses 10-15, wherein at least a second portion of the proximal surface extends along a second plane at an angle relative to the plane, the second portion defining an opening above the concave bearing surface. 
     Clause 17. The system of any of clauses 10-16, wherein at least a portion of the proximal surface extends along a plane perpendicular to an axis of the acetabular cup when the liner is seated in the acetabular cup. 
     Clause 18. The system of any of clauses 10-17, wherein at least a second portion of the proximal surface extends along a second plane at an angle relative to the plane, the second portion defining an opening above the concave bearing surface. 
     Clause 19. A method for implanting a liner in an acetabular cup, comprising:
         evaluating a size of an acetabular hole;   identifying a size of an acetabular cup for the acetabular hole;   preparing the acetabular hole to receive the acetabular cup;   identifying a liner for use with the acetabular cup;   inserting the acetabular cup in the acetabular hole;   inserting the liner in the acetabular cup; and   impacting the liner into place in the acetabular cup with an impactor square with the acetabular cup to seat the liner in the acetabular cup.       

     Clause 20. The method of clause 19, wherein impacting the liner with the impactor includes applying an impaction force on the liner so that the applied force is centered on a visual indicator on the liner. 
     While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosure. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the systems and methods described herein may be made without departing from the spirit of the disclosure. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosure. Accordingly, the scope of the present inventions is defined only by reference to the appended claims. 
     Features, materials, characteristics, or groups described in conjunction with a particular aspect, embodiment, or example are to be understood to be applicable to any other aspect, embodiment or example described in this section or elsewhere in this specification unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The protection is not restricted to the details of any foregoing embodiments. The protection extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. 
     Furthermore, certain features that are described in this disclosure in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations, one or more features from a claimed combination can, in some cases, be excised from the combination, and the combination may be claimed as a subcombination or variation of a subcombination. 
     Moreover, while operations may be depicted in the drawings or described in the specification in a particular order, such operations need not be performed in the particular order shown or in sequential order, or that all operations be performed, to achieve desirable results. Other operations that are not depicted or described can be incorporated in the example methods and processes. For example, one or more additional operations can be performed before, after, simultaneously, or between any of the described operations. Further, the operations may be rearranged or reordered in other implementations. Those skilled in the art will appreciate that in some embodiments, the actual steps taken in the processes illustrated and/or disclosed may differ from those shown in the figures. Depending on the embodiment, certain of the steps described above may be removed, others may be added. Furthermore, the features and attributes of the specific embodiments disclosed above may be combined in different ways to form additional embodiments, all of which fall within the scope of the present disclosure. Also, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described components and systems can generally be integrated together in a single product or packaged into multiple products. 
     For purposes of this disclosure, certain aspects, advantages, and novel features are described herein. Not necessarily all such advantages may be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that the disclosure may be embodied or carried out in a manner that achieves one advantage or a group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein. 
     Conditional language, such as “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements, and/or steps. Thus, such conditional language is not generally intended to imply that features, elements, and/or steps are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without user input or prompting, whether these features, elements, and/or steps are included or are to be performed in any particular embodiment. 
     Conjunctive language such as the phrase “at least one of X, Y, and Z,” unless specifically stated otherwise, is otherwise understood with the context as used in general to convey that an item, term, etc. may be either X, Y, or Z. Thus, such conjunctive language is not generally intended to imply that certain embodiments require the presence of at least one of X, at least one of Y, and at least one of Z. 
     Language of degree used herein, such as the terms “approximately,” “about,” “generally,” and “substantially” as used herein represent a value, amount, or characteristic close to the stated value, amount, or characteristic that still performs a desired function or achieves a desired result. For example, the terms “approximately”, “about”, “generally,” and “substantially” may refer to an amount that is within less than 10% of, within less than 5% of, within less than 1% of, within less than 0.1% of, and within less than 0.01% of the stated amount. As another example, in certain embodiments, the terms “generally parallel” and “substantially parallel” refer to a value, amount, or characteristic that departs from exactly parallel by less than or equal to 15 degrees, 10 degrees, 5 degrees, 3 degrees, 1 degree, or 0.1 degree. 
     The scope of the present disclosure is not intended to be limited by the specific disclosures of preferred embodiments in this section or elsewhere in this specification, and may be defined by claims as presented in this section or elsewhere in this specification or as presented in the future. The language of the claims is to be interpreted broadly based on the language employed in the claims and not limited to the examples described in the present specification or during the prosecution of the application, which examples are to be construed as non-exclusive. 
     Of course, the foregoing description is that of certain features, aspects and advantages of the present invention, to which various changes and modifications can be made without departing from the spirit and scope of the present invention. Moreover, the devices described herein need not feature all of the objects, advantages, features and aspects discussed above. Thus, for example, those of skill in the art will recognize that the invention can be embodied or carried out in a manner that achieves or optimizes one advantage or a group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein. In addition, while a number of variations of the invention have been shown and described in detail, other modifications and methods of use, which are within the scope of this invention, will be readily apparent to those of skill in the art based upon this disclosure. It is contemplated that various combinations or subcombinations of these specific features and aspects of embodiments may be made and still fall within the scope of the invention. Accordingly, it should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the discussed devices.