Abstract
An implant includes a fixed bearing, a floating bearing, and a coupling member. The fixed bearing defines a generally first spherical articulating surface and a stop. The floating bearing includes a second spherical articulating surface and a planar articulating bearing surface. The coupling member defines a bearing surface that translates relative to the planar articulating bearing surface.
Claims
1. A method of assembling an implant comprising a fixed bearing having a first spherical articulating surface, a floating bearing having a second spherical articulating surface and a planar articulating bearing surface, and a coupling member having a bearing surface, the method comprising: securing the coupling member relative to a bone, securing the floating bearing to the coupling member by slidably coupling the planar articulating bearing surface relative to the bearing surface; mating the first spherical articulating surface to the second spherical articulating surface; and wherein the floating bearing is freely translatable between the first position and the second position when the implant is implanted.
2. The method of claim 1, further comprising contacting the floating bearing with the fixed bearing to translate the floating bearing relative to the coupling member.
3. The method of claim 2, wherein contacting the floating bearing with the fixed bearing includes applying a force on the floating bearing with a stop.
4. The method of claim 1, further comprising translating the floating bearing relative to the coupling member after the first spherical articulating surface is mated to the second spherical articulating surface.
5. The method of claim 1, wherein slidably coupling the planar articulating bearing surface relative to the bearing surface includes sliding a coupling portion of the floating bearing into a slot defined by the coupling member.
6. The method of claim 5, wherein the coupling portion of the floating bearing and the slot defined by the coupling member form a dovetail joint.
7. The method of claim 1, wherein securing the coupling member relative to the bone includes: implanting a stem into a canal of the bone; and securing the coupling member to the stem.
8. The method of claim 1, wherein the first articulation surface is generally convex.
9. The method of claim 1, wherein the bone is a femur.
10. The method of claim 1, wherein the bone is a humerus.
11. The method of claim 1, wherein the floating bearing is repeatedly translatable between the first position and the second position when the implant is implanted.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.
(2) FIG. 1 is an exploded view of a humeral implant according to the present teachings;
(3) FIG. 2 is an assembled view of a humeral implant according to the present teachings;
(4) FIGS. 3A-3C are optional floating bearings according to the present teachings;
(5) FIG. 4 is a side assembled environmental view of a humeral implant using the floating bearing shown in FIG. 3A according to the present teachings;
(6) FIG. 5 is an assembled view of a humeral implant according to the present teachings in a first position;
(7) FIGS. 6A and 6B are end views of a humeral implant according to the present teachings;
(8) FIG. 7 is an exploded view of an alternate humeral implant according to the present teachings;
(9) FIG. 8 is an assembled view of a humeral implant according to the teachings of FIG. 7 in a first position;
(10) FIGS. 9A and 9B are assembled views of a humeral implant according to the present teachings in a second position;
(11) FIGS. 10A and 10B represent the implants of FIGS. 1 and 7 in a third position; and
(12) FIG. 11 depicts the insertion of the humeral implant shown in FIG. 1.
DETAILED DESCRIPTION
(13) The following description is merely exemplary in nature and is not intended to limit the present teachings, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. Although the following description is related generally to a humeral implant having a floating bearing for use in an anatomy to restore function to damaged tissue, such as in the case of shoulder joint, it will be understood that the teachings of the implant system as described and claimed herein can be used in any appropriate surgical procedure. For example, the teachings of the implant system described and claimed herein can be applied to repair any suitable anatomical joint, such as hip joint. Therefore, it will be understood that the following discussions are not intended to limit the scope of the present teachings and claims herein.
(14) FIG. 1 represents an exploded view of a shoulder implant 20 according to the present teachings. The shoulder implant 20 can include a fixed bearing 22, a stem 24 and a floating bearing 26. The fixed bearing 22 can be fixably coupled to a prepared glenoid (FIG. 11). The fixed bearing 22 can have an articulating surface 25 and a coupling mechanism 23 configured to couple the fixed bearing 22 to a prepared glenoid. In one example, the articulating surface 25 can comprise a convex articulating surface, but it should be noted that the articulating surface 25 could be concave. In addition, it should be noted that the articulating surface 25 can have any desired shape, such as hemispherical, spherical, etc. to articulate with the floating bearing 26. With brief reference to FIG. 11, the fixed bearing 22 can be coupled to a prepared glenoid using an intermediate member, such as a base member 40, which can be coupled to the prepared glenoid using a fastener such as a bone fastener 41, as will be discussed in greater detail herein. With reference back to FIG. 1, the fixed bearing 22 can also include at least one stop surface, such as a stop surface S.sub.1 and stop surface S.sub.2. The stop surface S.sub.1 and stop surface S.sub.2 can be formed generally about a circumference of the fixed bearing 22, however, the stop surface S.sub.1 and stop surface S.sub.2 can have any desired shape. The stop surface S.sub.1 and stop surface S.sub.2 can cooperate with the floating bearing 26 to cause the floating bearing 26 to move relative to the fixed bearing 22, as will be discussed in greater detail herein. The fixed bearing 22 can be composed of a suitable biocompatible material, such as a biocompatible metal or polymer, and in one example, the fixed bearing 22 can be composed of a polymer.
(15) With reference to FIG. 1, the stem 24 can be positioned within a prepared intramedullary canal in an anatomy, such as a humerus. The stem 24 can be composed of a suitable biocompatible material, such as a metal or a polymer. In one example, the stem 24 can be composed of a titanium alloy or cobalt chromium molybdenum alloy. The stem 24 can also be coated with bioabsorbable material, such as polylactides, polyglycolides, calcium phosphate, hydroxyapatite, etc. The stem 24 can be generally elongated, and can include a first end 27 and a second end 29. The first end 27 can be tapered to be received within the prepared canal of the humerus. The second end 29 can include a flange 31 and a coupling surface 33. The flange 31 can project outwardly from the second end 29 and can include at least one aperture 35. In one example, the at least one aperture 35 can comprise three apertures 35a-35c. The apertures 35a-35c can receive a fastening device, such as a suture, to further assist in securing the stem 24 to the anatomy.
(16) With reference to FIG. 2, the coupling surface 33 can be substantially smooth and planar. The coupling surface 33 can also define a bore 36. The bore 36 can be defined generally at a center of the coupling surface 33. As will be discussed, the bore 36 can receive a portion of an intermediate coupling member 39 to couple the intermediate coupling member 39 to the stem 24. If desired, the bore 36 can include a taper, which can mate or lock with the portion of the intermediate coupling member 39.
(17) With reference to FIG. 1, the floating bearing 26 can have a pair of articulating bearing surfaces 28 and 30. The first bearing surface 28 can be a generally spherical articulating surface configured to articulate with the convex articulating surface 25 of the fixed bearing 22 (FIG. 2). It should be noted that the first bearing surface 28 can be concave or convex. The first bearing surface 28 can be curved along substantially its entire length and can be flush with the articulating surface 25 when stop surface S.sub.1 or stop surface S.sub.2 of the fixed bearing 22 is engaged with the floating bearing 26.
(18) With continued reference to FIG. 1, the second bearing surface 30 can comprise a generally planar polished surface configured to allow linear translation of the floating bearing 26 with respect to stem 24. The floating bearing 26 can be coupled to the stem 24 via a coupling mechanism 32 disposed on the planar second bearing surface 30. In one example, the coupling mechanism 32 can define a coupling portion 34, which can engage a slot 38 of an intermediate coupling member 39 as will be discussed in further detail herein. In one example, as illustrated in FIG. 6A, the coupling portion 34 and slot 38 can cooperate as a dovetail coupling mechanism. It should be noted that the use of a dovetail coupling mechanism is merely exemplary as any suitable coupling mechanism could be employed to enable the floating bearing 26 to move relative to the stem 24, such as a T-shaped rail configuration, etc. The coupling mechanism 32 can constrain movement of the floating bearing 26, but can allow linear translation of the floating bearing 26 with respect to the stem 24. The linear translation can be along a line which intersects an axis of the bore 36 of the stem 24. It is envisioned that secondary stops in the form of a pin in a slot disposed between the second bearing surface 30 and the planar bearing surface 37 can be used to limit the travel of the floating bearing 26 with respect to the stem 24.
(19) In addition, it is envisioned the coupling mechanism 32 can take the form of single or multiple flanges which interface with a slot or slots formed within the floating bearing 26. In this regard, in an alternate embodiment, with reference to FIG. 6B, a floating bearing 26a can move relative to the stem 24 via two coupling mechanisms 32. In this example, each of the coupling mechanisms 32 can include coupling portions 34a, 34b, which can movably engage substantially parallel slots 38a, 38b formed in the intermediate coupling member 39. It should be noted that the use of two substantially parallel coupling mechanisms 32 is merely exemplary as any number of coupling mechanisms 32 could be used in any desired orientation.
(20) With reference back to FIG. 1, the intermediate coupling member 39 can be disposed between the floating bearing 26 and the stem 24. The intermediate coupling member 39 can include a body portion 47 defining the slot 38, which can comprise a planar bearing surface 37. The planar bearing surface 37 can be configured to slidably interface with the planar second bearing surface 30. The engagement between the slot 38 and coupling portion 34 of the floating bearing 26 can enable the floating bearing 26 to move relative to the stem 24. The intermediate coupling member 39 can also include a coupling portion 45 for coupling the intermediate coupling portion 45 to the bore 36 of the stem 24. In one example, the coupling portion 45 can comprise a tapered portion, which can engage a mating taper formed in the bore 36 to couple the intermediate coupling member 39 to the stem 24. It should be noted, however, that any suitable technique can be used to couple the intermediate coupling member 39 to the stem 24, such as a mechanical fastener, welding, etc. The intermediate coupling member 39 can be comprised of any suitable biocompatible material, such as a biocompatible metal or polymer. In one example, the intermediate coupling member 39 can be comprised of a titanium alloy or a cobalt chromium molybdenum alloy. In addition, the intermediate coupling member 39 can be coated with a bioabsorbable material, such as polylactides, polyglycolides, calcium phosphate, hydroxyapatite, etc.
(21) As shown in FIG. 2, in its implanted position, the floating bearing 26 can be coupled to the stem 24 using the intermediate coupling member 39. In the absence of forces on the stem 24, the floating bearing 26 can be generally centered with respect to the intermediate coupling member 39. The stem 24 can be configured to rotate about the fixed bearing 22 between a first angular location A.sub.1, and a second angular location A.sub.2.
(22) As shown in FIGS. 3A-3C, a location of first and second interface surfaces I.sub.1 and I.sub.2 can be varied with respect to the second bearing surface 30, thus adjusting the first angular location A.sub.1 and second angular location A.sub.2. The first interface surface I.sub.1 can be a first distance from the planar second bearing surface 30, while the second interface surface I.sub.2 can be a second distance from the second bearing surface 30, the second distance optionally being different or greater than the first distance. The first and second interface surfaces I.sub.1 and I.sub.2 can cooperate with the stop surfaces S.sub.1 and S.sub.2 to control the motion of the shoulder implant 20. A kit of floating bearings 26 can be provided to allow the treating physician to vary the amount of articulation of the stem 24 before the interface surfaces I.sub.1 and I.sub.2 contact the stop surfaces S.sub.1 and S.sub.2 located on the fixed bearing 22. Although not shown, it is envisioned that the location or size of the stop surfaces S.sub.1 and S.sub.2 on the fixed bearing 22 can be adjusted with respect to the coupling mechanism 32 to adjust the dynamics of the shoulder implant 20.
(23) FIG. 4 represents a close up view of the stop surfaces S.sub.1 and S.sub.2 of the fixed bearing 22 and the first and second interface surfaces I.sub.1 and I.sub.2 of the floating bearing 26. The stop surfaces S.sub.1 and S.sub.2 can have a shape which, when engaged with the floating bearing 26, can apply a force to a respective one of the first and second interface surfaces I.sub.1 and I.sub.2 of the floating bearing 26. The application of force by the stop surfaces S.sub.1 and S.sub.2 onto the respective first and second interface surfaces I.sub.1 and I.sub.2 can cause movement or translation of the floating bearing 26 relative to the fixed bearing 22.
(24) As best seen in FIG. 5, rotation of the stem 24 to the first angular location A.sub.1 can allow the engagement of the first interface surface I.sub.1 with the stop surface S.sub.1 located on the articulating surface 25 of the fixed bearing 22. The stop surface S.sub.1 can apply force onto the floating bearing 26, thus translating the floating bearing 26 from a first position to a second position with respect to the stem 24. This can displace the stem 24 with respect to the fixed bearing 22, thereby allowing for a greater range of motion for the shoulder joint.
(25) FIGS. 7, 8, 9A-9B and 10B represent a shoulder implant 200 according to the present teachings that utilizes a fixed bearing 22 having an extended articulating surface 42. The extended articulating surface 42 can allow further rotation of the stem 24 past an equatorial line 43 on the fixed bearing 22. The stop surface S.sub.1 can be positioned to allow translation to the first angular location A.sub.1 (see FIG. 9A) at which point the stop surface S.sub.1 can engage the floating bearing 26. Optionally, the stop surface S.sub.1 can be formed as a pair of flanges extending from the floating bearing 26 or the fixed bearing 22.
(26) In a medial position, movement of the stem 24 allows for normal rotation of the floating bearing 26 with respect to the fixed bearing 22. Further rotation of the stem 24 causes the stop surface S.sub.1 to engage the first interface surface I.sub.1 of the floating bearing 26. This interaction applies pressure onto the floating bearing 26, thus allowing translation of the stem 24 with respect to the fixed bearing 22. Referring briefly to FIGS. 9A and 9B, in this example, the first and second angular locations A.sub.1 and A.sub.2 can be defined by interactions between the stop surfaces S.sub.1 and S.sub.2 and first and second interface surfaces I.sub.1 and I.sub.2 located on the floating bearing 26. The first and second angular locations A.sub.1 and A.sub.2 can be adjusted by adjusting the positions of the stop surfaces S.sub.1 and S.sub.2 and the positions of the first and second interface surfaces of and I.sub.2.
(27) As shown in FIGS. 10A and 10B, the rotation of the stem 24 to the second angular location A.sub.2 causes an interaction of the stop surface S.sub.2 with the second interface surface I.sub.2. Forces applied to the stem 24 by the anatomy can pull the stem 24 in a medial direction, thus allowing increased rotational movement of the shoulder joint. As previously described, adjustment of the first and second interface surfaces I.sub.1 and I.sub.2 with respect to the first and second stop surfaces S.sub.1 and S.sub.2 can be used to change joint dynamics.
(28) With reference to FIG. 11, FIG. 11 depicts the coupling of the shoulder implant 20 with a prepared humeral/glenoid joint. It should be noted that the shoulder implant 200 can be coupled to the humeral/glenoid joint in a manner substantially similar to the shoulder implant 20 and thus, the coupling of the shoulder implant 200 to the anatomy is not illustrated herein. Prior to insertion of the glenospherical fixed bearing 22, a glenoid can be reamed to prepare a flat surface. The base member 40 can then be coupled to the prepared glenoid using the bone fastener 41. In one example, the fixed bearing 22 including the stop surfaces S.sub.1 and S.sub.2 can then be coupled to the base member 40. Optionally, the base member 40 can define the stop surfaces S.sub.1 and S.sub.2.
(29) Next, the humerus 46 can be prepared by resecting the humeral head and preparing the medullary canal 44. The stem 24 can then be coupled to the humerus using known technologies. It is envisioned that this exemplary surgical procedure can be accomplished through a single incision 50.
(30) With the stem 24 coupled to the humerus, the intermediate coupling member 39 can be coupled to the stem 24 via the coupling portion 45. Optionally, the intermediate coupling member 39 can be fixed to the stem 24 using any suitable coupling technique, such as a mechanical fastener, welding, etc. In the example of a kit of floating bearings 26, trial floating bearings 26 can be used to determine an ideal floating bearing 26 for use with the anatomy. In one example, this can be accomplished by testing the range of motion of the shoulder joint. Based upon this determination, a proper floating bearing 26 can be coupled to the base member 40 by sliding the coupling portion 34 into the slot 38 using a cross-axis sliding engagement.
(31) Thus, the floating bearing 26 can provide a greater range of motion for the shoulder implant 20. The interaction between the stop surfaces S.sub.1 and S.sub.2 of the fixed bearing 22 and the first and second interface surfaces I.sub.1 and I.sub.2 of the floating bearing 26 can allow for increased rotational movement of the shoulder joint without coming into contact with the scapula.
(32) While specific examples have been described in the specification and illustrated in the drawings, it will be understood by those of ordinary skill in the art that various changes can be made and equivalents can be substituted for elements thereof without departing from the scope of the present teachings. Furthermore, the mixing and matching of features, elements and/or functions between various examples is expressly contemplated herein so that one of ordinary skill in the art would appreciate from the present teachings that features, elements and/or functions of one example can be incorporated into another example as appropriate, unless described otherwise, above. Moreover, many modifications can be made to adapt a particular situation or material to the present teachings without departing from the essential scope thereof. Therefore, it is intended that the present teachings not be limited to the particular examples illustrated by the drawings and described in the specification, but that the scope of the present teachings will include any embodiments failing within the foregoing description.
