US20020004685A1 - Modular prosthesis and connector therefor - Google Patents

Abstract

A modular orthopedic prosthesis has a body with a generally triangular cross-section near one end, allowing its angular corners to bite or incise into the surrounding bone cavity for rotational stability. A stem, which may be either unitary or modular in structure, is received within a through-bore of the body, having a proximal neck and distal shaft. A connecting sleeve receives the stem and is, in turn, received within the bore of the body, then actuated to lock the stem and body together.

Description

TECHNICAL FIELD
• This invention relates generally to orthopedic prostheses, particularly to those having a modular construction that is assembled from selected components and implanted during re-constructive arthroplastic surgery.[0001]
BACKGROUND
• It is known that bone matter that is not stressed/loaded will atrophy and lose viability, a problem which currently persists in present orthopedic implants.[0002]
• One approach others have taken is to provide a collar intended to correspond in shape and size to the prepared cavity of a proximal femur, ostensibly to offer rotatory stability to the implanted device. For example, U.S. Pat. No. 4,790,852 to Noiles shows a modular hip prosthesis including a collar having a shape with a keyhole cross-section and terraces surrounding the outer surface perpendicular to the longitudinal axis of the collar. The collar has a tapered proximal-to-distal contour. However, the shape of the collar is instead dictated by the milling instrumentation used to prepare the proximal femoral cavity. According to the procedure, a surgeon resects the femoral head (ball) with an osteotome, thereby exposing the medial aspect of the cavity, then reams the intramedullary canal to make a space for the collar. The medial bone cavity is then milled to make it fit set criteria of the implant. U.S. Pat. No. 5,002,578 to Luman also has transverse terraces and a supposed cavity conforming cross-section. However, such terraces, like those of the above Noiles '[0003]852 patent, do not counteract rotary motion of the prosthesis, but rather axial motion. U.S. Pat. No. 4,549,319 to Meyer has an external geometric pattern of elongated projections spaced circumferentially on a hip prosthesis. U.S. Pat. No. 4,624,673 to Meyer discusses a component for use in a prosthetic joint having a hollow tube with a closed end and an open end. The area of the external surface adjacent to the open end is at least twice the area of the external surface adjacent to the closed. A plurality of terraces, oriented orthogonal to a distal shaft, are on the external surface. A female part of self-locking taper is provided to connect the components. U.S. Pat. No. 4,846,839 to Noiles shows a modular hip with a collar having an oval cross-section and a terraced external surface, connecting with a stem. Products have been marketed generally based upon this approach, e.g., The SROM Hip, of Joint Medical Products, Inc.
• The aforementioned patents seek to provide rotatory stability by circumferential contact between the prepared femoral cavity and an outer surface of a main body or collar member. This type of contact is actually tangential in nature. The use of an oval cross-sectional shape often does not allow the outer surface of the prosthesis collar to effectively engage the intact bone. In many cases, especially in revision patients, healthy bone can be problematic to uniformly contact, for example, in the lateral aspects of the proximal femur, where the greater trochanter is left largely undisturbed by the surgeon during a primary implantation. The lack of rotatory stability, needed for uniform stress on such healthy bone, can cause the intact tissue to weaken and possibly atrophy, unacceptably, at some point following the initial implantation of the prosthesis.[0004]
• Others, including some of the above approaches, have further sought to achieve prosthesis-cavity conformance while providing various modular constructions and ways of connecting the components of the prosthesis.[0005]
• For example, related U.S. Pat. Nos. 5,370,706 and 5,080,685 to Bolesky show a body member having a neck with a base defining a neck basal plane. A body member includes an upwardly and inwardly directed portion and a tapered longitudinal bore. A tapered connector engages a head member with the upwardly and inwardly directed portion. A problem experienced with this particular design is its limited strength, due to the location of the interconnecting components. Thus, the point of connection of the shaft must bear a load that is often too great, without being able to distribute that force. In U.S. Pat. No. 4,878,917 to Kranz, et al., there is shown a modular implant with a tensioning connector rod structurally designed to break when loaded a selected amount. U.S. Pat. No. 5,201,882 to Paxson discloses indicia for selecting the desired ante-version of a modular hip stem that is connected via tapered fittings to a unitary neck/body member, but the neck is not independently adjustable relative to the body. U.S. Pat. No. 5,725,592, issued to the present inventor, describes a modular hip prosthesis having a distal stem component that connects with a body component and a neck component both having tapered through-bores.[0006]
• There is still a need for a modular prosthesis having independently adjustable components, and for a connector mechanism allowing the surgeon to visibly adjust them. Also, a prosthesis is needed, having an adjustable body with a geometry that incisively engages healthy bone, then securely locks with a stem component inter-operatively. The prior patents do not show a body shape capable of adjustably engaging healthy bone tissue in such a manner.[0007]
• Other prior unitary implants have had various shapes, but the distal shaft and main body portions of these were not independently adjustable components, allowing surgeons to inter-operatively achieve optimal engagement of the body with healthy bone tissue.[0008]
• Moreover, a need exists for a prosthesis that allows the surgeon to independently adjust the implant and realize the aim of engaging intact bone, as well, for an implant geometry that incises the intact bone and stresses it.[0009]
• There is a further need for a modular implant that is infinitely adjustable, rotationally and axially, using a relatively simple array of components, allowing a surgeon flexibility while reducing the cost of carrying a large inventory of sizes. Such a need also exists while continuously delivering desired benefits, via the implant geometry, to a patient's intact bone. A modular implant design is called for, whose components can be readily assembled inter-operatively and securely locked together by the surgeon to achieve these purposes.[0010]
SUMMARY OF THE INVENTION
• According to the invention, there is provided a modular orthopedic prosthesis including a stem having one end with an elongated portion and another, longitudinally opposed end with a first means presenting a joint motion surface. The prosthesis has a body including a bore defining at least a first axis and having a polygonal cross-section with at least two angular corners adapted to bite or incise into the bone cavity of a patient to prevent rotation of the implanted prosthesis relative to the bone. Means are provided for connecting and locking the stem and body together in a fixed position.[0011]
• In a preferred embodiment of this invention, the body has a first end with a generally triangular cross-section in the region of the first end and a generally round cross-section in the region of its second end, presenting a multi-axial wedge shape.[0012]
• According to the invention, in another of its aspects, a modular orthopedic prosthesis is provided. The prosthesis comprises a stem component having one end with an elongated portion and another, longitudinally opposed end with a first means presenting a joint motion surface. A body component includes a bore defining at least a first axis. A radially expansible sleeve has opposed ends, one end received within the bore and the other end projecting outwardly from the bore, the sleeve adjustably connecting the stem and body together and locking them in a fixed position.[0013]
• In a preferred embodiment of this invention, the joint motion surface is adjustably spaced from the body.[0014]
• An advantage of the present invention is inventory and manufacturing cost savings, since its modularity allows for economy in manufacturing, as any number of well-known stem types may be selected, and also reduces the inventory of pieces needed on-hand for each surgical procedure.[0015]
• Another advantage of the invention is enhanced clinical benefits, as the wedge shape offers enhanced rotatory stability of the prosthesis in use, particularly with revision surgery patients.[0016]
• A further advantage of the invention is in providing a connector mechanism that is highly secure once fixed in place, meanwhile providing the surgeon inter-operative flexibility to axially and rotationally adjust the stem independently of the body.[0017]
• A still further advantage of the invention gives a surgeon the capability to rotationally “dial” the body in order to have its triangular corners contact and “bite into” or incise as much available healthy bone as possible. By evenly loading/stressing such intact bone, wherever found by the surgeon, particularly in revision patients, it is possible to avoid potential eventual atrophy of the bone tissue.[0018]
• Other objects and advantages will become apparent to those skilled in the art by reference to the following Description and Drawings.[0019]
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a perspective view of a modular hip prosthesis of the invention, fully assembled and implanted in a proximal femur, with the bone longitudinally cut away;[0020]
• FIG. 2 is an external side view of the body component of the present invention, taken from an anterior-posterior aspect;[0021]
• FIG. 2A is a cross-section of the proximal portion of the body of FIG. 2, taken substantially along the[0022]lines2A-2A;
• FIG. 2B is a cross-section of the proximal portion of the body of FIG. 2, taken substantially along the lines[0023]2B-2B;
• FIG. 2C is a cross-section of the proximal portion of the body of FIG. 2, taken substantially along the lines[0024]2C-2C;
• FIG. 3 is an external side view of the sleeve component of the present invention, taken from either an anterior-posterior or medial-lateral aspect;[0025]
• FIG. 3A is a longitudinal section of the body of FIG. 3, taken substantially along the lines[0026]3A-3A;
• FIG. 3B is an external top view of the proximal portion of the sleeve of FIG. 3;[0027]
• FIG. 4 is a partially exploded perspective view of the invention, showing the sleeve partially seated in the bore of the body, prior to insertion of the stem;[0028]
• FIG. 5 is a cross-section of the proximal portion of the body of the invention, implanted in a cadaver bone, showing also the cross-section of a representative prior art implant for comparison purposes.[0029]
• FIG. 6 is an exploded perspective view of the stem, body and sleeve of the invention, shown prior to assembly, wherein the stem has a modular construction with separate neck and distal shaft components;[0030]
• FIG. 7 is an exploded perspective view of the prosthesis of FIG. 6, showing the distal shaft component of the modular stem being connected to the body with another independent sleeve;[0031]
• FIG. 8 is an exploded perspective view of the prosthesis of the invention showing a unitary stem with a tapered connection region, a sleeve with a cylindrical outer surface and a tapered internal bore, and a body with a linear through-bore;[0032]
• FIG. 9 is a top view of the body component having a generally triangular shape with two sharp corners and a tapered bore;[0033]
• FIG. 10 is a top view of the body component having a generally polygonal shape, i.e., hemi-hexagonal, with sharp corners, and a tapered bore;[0034]
• FIG. 11 is an external view of the body of a prosthesis of the invention with a medial osteotomy plane;[0035]
• FIG. 12 is a top view of the body component of FIG. 11; and[0036]
• FIG. 13 is a sectional view, taken substantially along lines[0037]13-13 of FIG. 12.
DETAILED DESCRIPTION
• According to the invention, as shown in FIGS.[0038]1-13, there is provided a modular prosthesis assembly, generally shown at10, including a stem component, generally shown at12, a body component, generally shown at14, and means in the form of a sleeve, generally shown at16, for affixing the stem and body together. In FIGS. 1, 4, and8 thestem12 is a unitary member, however, as shown in FIGS.6-7, the stem can be in a modular form. In FIGS. 1, 4,6 and8, theprosthesis10 comprises a single sleeve, however, as shown in FIG. 7, the prosthesis can include a pair ofsleeves16 in conjunction with a modular stem. Nevertheless, a single sleeve is preferred. In FIGS. 1, 2,2-C,4, and6-13, the body has a first orproximal end15 and a second, longitudinally opposed ordistal end17. Thebody14 functions as a wedge generally in the anterior-posterior and medial-lateral plane, as well as the proximal-distal plane, as will be herein elucidated.
• The[0039]body14 has abore18 with a first axis A extending between the proximal15 and distal17 ends, through which stem12 is received, once the stem has been passed throughsleeve16. The assembledstem12 andsleeve16 are seated inbore18 and, as they are urged into the bore fully, the sleeve radially compresses to pressure-lock the stem and body together in a fixed relative position.
• The present invention employs a distinctive geometry and connection technology that variably locks together the three[0040]fundamental components12,14 and16 of theprosthetic hip10 into a fixed configuration. In surgery, the proximal femoral bone cavity is prepared by reaming and then a finish broaching operation, thereby creating the desired cavity in the bone. In FIG. 4, thesleeve16 is placed in the bore18 (phantom) through afirst end15 ofbody14 but left proud, i.e., not fully seated in the bore. Then stem12 is passed through thesleeve16 until the desired neck height is achieved for restoring the tension of the total articulated joint. Indicia could be added to allow visual recognition of the height adjustment by the surgeon. Once the proper height is achieved, an axial force is applied to the top24 ofsleeve16, locking it against thebore18. In a preferred embodiment, axial force can be applied to the top26 ofneck22 and transmitted indirectly, through the bottom20 ofneck22, to top24 ofsleeve16. The components are actuated and locked together in this manner as shown by FIGS. 1 and 4, in the case of aunitary stem12, and similarly in the case of a modular assembly. As shown in FIGS.6-7,modular neck22 has aprotrusion27 extending distally frombottom20 of the neck for connecting withsleeve16.Protrusion27 may be either straight or tapered, depending upon the geometry of its interconnecting member.
• The[0041]sleeve16 will now be more particularly described. Preferably,sleeve16 is radially flexible by means of apreferred split collet28, as shown in FIGS. 3 and 3A-3B, to lock the components together. Thepreferred split collet28 can be made from titanium, stainless steel or cobalt-chromium alloys.Sleeve16 has bottom25 received withinbore18. The same locking function is performed bysleeve16 in the embodiments of FIGS.6-8 that show a modulardistal shaft30. Alternatively, a solid construction could be employed for the sleeve (not shown), using a super-elastic material that is inherently radially flexible under controlled temperature conditions, e.g., a nickel-titanium alloy such as nitinol.Sleeve16 has anouter surface31 that engages bore18.
• The[0042]body14 will now be more particularly described. As shown is FIG. 2A, taken through the region of first orproximal end15 ofbody14, the body has anouter surface32 with a “generally polygonal” cross-sectional shape, although the polygon is preferably a triangle. Such a shape affords non-tangential contact with the intact bone, in a plane perpendicular to the longitudinal axis of the bone. Together with the tapered contour in the proximal-distal plane,body14 functions as a three-dimensional wedge. By the term “generally polygonal”, it is meant that one or more of the sides of the polygon could be either linear or slightly bowed, in a concave or convex manner. However, substantially linear sides are preferred. The degree to which the sides may be bowed should not defeat the function of theangular corners34 shown in FIGS. 1, 2,2A,2C and4-10, as well as in FIGS.11-12 that will be described below.
• The centroid (not shown) of the proximal polygonal cross-sectional shape of[0043]body14 need not coincide with axis A ofbore18. Likewise, the centroid (not shown) of the distal cross-section (FIG. 2B) which could be polygonal or preferably round, need not coincide with the axis A ofbore18, although such coincidence is preferred. Neither of the first15 and second17 ends ofbody14 need be perpendicular to the axis A ofbore18, yet, it is preferred that ends15,17 are perpendicular to axis A. As shown in FIGS.11-13,body14 has aplanar osteotomy surface35, oriented at a selected angle relative to axis A, such that the distance between the axis A and the edge of theouter surface32 increases in a direction from the first end of the body toward the second end of the body. Theplanar surface35 generally corresponds to the location of an osteotomy cut. Either of thesurfaces15 or35 could optionally carry a collar member (not shown) that is meant to rest on the end of the bone, where clinically indicated, to help prevent linear subsidence of the body component axially into the bone cavity. As to the function of the cross-sectional shape, however, the body geometry shown in FIGS.11-13 has the same function as in the other embodiments previously discussed. That is, thecorners34 incise into the bone to provide rotatory stability to the implantedprosthesis10, while effectively loading the bone.
• Reference is now made to the three views of[0044]sleeve16 shown in FIG. 3. Anouter surface31 ofsleeve16 contacts bore18 and creates a lock betweenstem12 andbody14, while aninner bore36 of the sleeve creates a lock betweenstem12 and the body, when axial force is applied to the assembled components.Sleeve16 is radially flexible about axis A ofbore18, by means ofcollet28. As with the first15 and second17 ends ofbody14, the opposed top24 and bottom25 ofsleeve16 need not lie in planes that are parallel to one another, although such is preferred. As shown in of FIG. 3A,sleeve16 may have either a straight or taperedbore36. Similarly, theouter surface31 ofsleeve16 could be tapered or straight. The sleeve may have bore36 of different diameters correspond to the different outer diameters of thestem12, respectively. The thickness of the wall defined between the inner diameter of thebore36 and outer diameter to thesurface31 may be varied to accommodate different corresponding diameter sizes of the stem.
• Although a single through-[0045]bore18 is preferred, separate bores (not shown) could be used to receive each of the distal shaft and neck components, as in the case of a modular stem construction contemplated by FIGS.6-7. In a modular construction,shaft30 has a free end ordistal tip37 that is received within the medullary canal of the femur, in the case ofhip prosthesis10.
• In the top and external views of FIG. 3, top[0046]24 ofsleeve16 has an optionalupper shoulder38 that is spaced fromsurface15 ofbody14. In FIG. 8 an embodiment is shown wherein theoptional shoulder38 stops thesleeve16 from falling through thebore18 inbody14 which is necessary since thebore18 andouter surface31 ofsleeve16 are both straight rather than tapered. When thestem12 is passed through thesleeve16 thetaper connection region40 adjacent the bottom20 ofneck22 spreads thecollet28 ofsleeve16 and locks the components together.Shoulder38 has anunderside42 that abuts the outer periphery ofbore18 and stops thesleeve16 from falling through thebore18. Alternatively instead of theshoulder38 limiting axial motion of the sleeve relative to the bore, the bore could have a counter-sunk inlet (not shown) that would abut the bottom25 ofsleeve16 and arrest its downward motion in the bore. The leg length could be adjusted by using different height shoulders38.
• Referring to FIGS. 1, 4,[0047]6 and7-8,neck22 carries a joint motion surface via taperedconnector44 to which a ball (not shown) may be attached having the acetabular fit needed to ensure proper articulation and total joint tension.Distal shaft30 could be coated, fluted, slotted or the like. Theconnection region40, although shown with a tapered diameter in FIG. 8, as well as in aunitary stem12 ormodular neck22 andshaft30 configuration, can also have a straight diameter in the other embodiments described.Region40 is adjacent a fixed orproximal end41 of modular shaft component30 (FIGS.6-7), which is longitudinally opposed fromdistal tip37.End41 is received withinsleeve16.
• Reference is now made to FIG. 5, showing the preferred triangular proximal cross-sections of the invention versus a representative prior art collar (oval and keyhole shapes) in an actual cadaver bone. Superimposed on the prior keyhole shape is the triangular cross-section of the invention. By contrast, the prior art relies upon circumferential and, ultimately tangential contact with the bone and does not present a multi-axial wedged shape that reaches out and incises into intact bone in the lateral regions of the proximal femoral cavity, as does the present design. This structural difference results in a crucial functional distinction.[0048]
• In FIGS.[0049]9-10, two preferred polygonal shapes are shown forbody14, taken cross-sectionally in the region offirst end15adjacent neck22. In FIG. 12,body14 has a generally triangular cross-section, with at least twocorners34 on itsouter surface32, whereas, in FIG. 13 there is shown another polygonal shape, i.e., partially hexagonal, which presentssuch corners34. The necessity for biting into intact bone, in the case of hip arthroplasty, is most important in the lateral aspect of the femoral cavity, which is less exposed than the medial aspect. This is because the femoral head is resected, exposing the entire proximal medial cavity to the surgeon. This is not so laterally, hence the geometry of the body of the present invention which can reach out and bite into the lateral intact bone. An oval shape does not do this.Bore18 ofbody14 has a taperedportion46 adjacent the top orproximal end15, for mating engagement with eithersleeve16 or a tapered stem.
• Although the invention has been described with reference to a[0050]prosthesis10 designed for hip arthroplasty, it must be understood that this invention may be used in other types of arthroplasty, e.g., a shoulder joint (not shown), with certain particular adaptations.
• The above Description should not be construed as limiting but rather is given for purposes of illustrating the invention. Obviously, persons skilled in the art could make various modifications to the embodiments shown, without departing from the scope of the present invention, as claimed in those claims appended to this Specification.[0051]

Claims (51)

1. A modular orthopedic prosthesis comprising:

a stem having one end with an elongated portion and another, longitudinally opposed end with a first means presenting a joint motion surface;

a body including a bore defining at least a first axis and having a generally polygonal cross-section with at least two angular corners adapted to bite into the bone cavity of a patient to prevent rotation of the implanted prosthesis relative to the bone; and

means for connecting the stem and body together in a fixed position.

2. The prosthesis ofclaim 1 wherein the body has a generally triangular cross-section.

3. The prosthesis ofclaim 1 wherein the body has a single through-bore.

4. The prosthesis ofclaim 1, the body having first and second ends longitudinally opposed from one another along the first axis, the first end being adjacent the first means and the second end being adjacent the elongated portion, the body having a generally polygonal cross-section in the region of the first end of the body.

5. The prosthesis ofclaim 1, the body having a planar osteotomy surface oriented at a selected angle relative to the first axis, such that the distance between the axis and the edge of the surface increases in a direction from the from the first end of the body toward the second end of the body.

6. The prosthesis ofclaim 4, the body having a generally circular cross-section in the region of the second end of the body.

7. The prosthesis ofclaim 1, the first means further comprising a neck operatively connected to the body in the region of the first end.

8. The prosthesis ofclaim 1, the elongated portion further comprising a shaft having a free end with a tip and a fixed end opposite the tip wherein the bore of the body is adapted to receive the fixed end for assembly with the body.

9. The prosthesis ofclaim 1 wherein the stem further comprises a neck, carrying the joint motion surface, and a shaft opposite the neck, the shaft being adapted for receipt within the medullary canal of a bone, the stem passing through the bore and being attached to the body in a fixed position along the first axis.

10. The prosthesis ofclaim 1, wherein the neck and shaft each comprise separate modular articulating components of the stem.

11. The prosthesis ofclaim 10, the stem further comprising a neck attached to the body along the first axis.

12. The prosthesis ofclaim 10 wherein the elongated portion is attached to the body along the first axis.

13. The prostheses ofclaim 1 wherein the sleeve comprises a super-elastic material.

14. The prostheses ofclaim 13 wherein the super-elastic material is nitinol.

15. The prosthesis ofclaim 1 wherein the bore of the body and an outer surface of the sleeve have mating tapers which, when seated together, activate the stem and body to lock together in fixed relative position.

16. The prosthesis ofclaim 1, the sleeve having an inner bore that is tapered and the stem having at least one corresponding outer surface that is tapered wherein the mating tapers, when engaged, activate the stem and body to lock together in fixed relative position.

17. A modular orthopedic prosthesis comprising:

a stem component having one end with an elongated portion and another, longitudinally opposed end with a first means presenting a joint motion surface;

a body component including a bore defining at least a first axis; and

a radially expansible sleeve having opposed ends, one end received within the bore and the other end projecting outwardly from the bore, the sleeve connecting the stem and body together in a fixed position.

18. The prosthesis ofclaim 17 wherein the body has a polygonal cross-section with at least two angular corners adapted to bite or incise into the bone cavity of a patient to prevent rotation of the implanted prosthesis relative to the bone.

19. The prosthesis ofclaim 17, the sleeve further comprising a collet having a bore wherein the stem is received within the bore of the collet, the stem and collet together being further received within the bore of the body to lock them together.

20. The prosthesis ofclaim 19, the sleeve further comprising a split collet.

21. The prosthesis ofclaim 19 wherein the collet has a distal insertion end for receipt within the bore along the first axis and an opposed, proximal end including an annular flange.

22. The prosthesis ofclaim 19 wherein the annular flange comprises a spacer shoulder having a selected thickness.

23. The prosthesis ofclaim 17 wherein the stem comprises a unitary member.

24. The prosthesis ofclaim 17, the first means further comprising a neck wherein the receives the neck for assembly with the body.

25. The prosthesis ofclaim 17, the elongated portion further comprising a shaft having a free, distal end with a tip and a fixed, proximal end opposite the tip wherein the receives the fixed end for assembly with the body.

26. The prosthesis ofclaim 17 wherein the stem further comprises a neck, carrying the joint motion surface, and a shaft opposite the neck, the shaft having a distal tip adapted for receipt within the medullary canal of a bone, the stem passing through the bore and being attached to the body in a fixed position along the first axis.

27. The prosthesis ofclaim 26, the stem further comprising a neck attached to the body along the first axis.

28. The prosthesis ofclaim 27 wherein the elongated portion is attached to the body along the first axis.

29. The prostheses ofclaim 17 wherein the neck and the shaft comprise separate modular components of the stem.

30. The prostheses ofclaim 17 wherein the body has an upper face defining an outer periphery of the bore, the sleeve having an end received within the bore and an opposite end with an annular flange juxtaposed with the outer periphery.

31. The prostheses ofclaim 17 wherein the annular flange has a shoulder with an upper surface and the first means includes a neck with an abutment surface contacting the upper surface of the shoulder as the stem is locked within the body.

32. The prostheses ofclaim 17 wherein the first means of the stem comprises a separate neck component and the elongated portion a separate shaft component, the neck having means adjacent the body for connecting within the bore of the sleeve, the shaft having a free end and a fixed end, the fixed end passing through the bore of the body and into the bore of the sleeve.

33. The prostheses ofclaim 17 wherein the sleeve comprises an annular collet made of a super-elastic material.

34. The prostheses ofclaim 33 wherein the super-elastic material is nitinol.

35. The prosthesis ofclaim 17 wherein the bore of the body and an outer surface of the sleeve have mating tapers which, when seated together, activate the stem and body to lock together in fixed relative position.

36. The prosthesis ofclaim 17, the sleeve having an inner bore that is tapered and the stem having at least one corresponding outer surface that is tapered wherein the mating tapers, when engaged, activate the stem and body to lock together in fixed relative position.

37. A modular orthopedic prosthesis comprising:

a stem having one end with an elongated portion and another, longitudinally opposed end with a first means presenting a joint motion surface;

a body including a bore defining at least a first axis and having a polygonal cross-section with at least two angular comers adapted to bite into the bone cavity of a patient to prevent rotation of the implanted prosthesis relative to the bone; and

a radially expansible sleeve having opposed ends and a bore, one end of the sleeve being received within the bore of the body and another end projecting outwardly from the bore of the body, wherein the stem is received within the bore of the sleeve, the stem and sleeve together being further received within the bore of the body to connect the stem and body together in a fixed position.

38. The prosthesis ofclaim 37, the first means of the stem comprising a neck and the elongated portion comprising a shaft, the bore of the body being a through-bore, wherein the neck and shaft are a unitary member received in the through-bore.

39. The prosthesis ofclaim 37, the first means of the stem comprising a neck and the elongated portion comprising a shaft, the bore of the body being a through-bore, wherein the neck and shaft are separate members each received within the through-bore.

40. The prosthesis ofclaim 37, the body having first and second ends longitudinally opposed from one another along the first axis, the first end being adjacent the first means and the second end being adjacent the elongated portion, the body having a generally triangular cross-section in the region of the first end of the body.

41. The prosthesis ofclaim 40, the body having a generally circular cross-section in the region of the second end of the body.

42. The prosthesis ofclaim 37 wherein the sleeve comprises a split collet.

43. The prosthesis ofclaim 37, the body having a pair of ends longitudinally opposed from one another along the first axis of the bore with one of the ends presenting a top surface adjacent the first means and another end being adjacent the elongated portion, wherein the collet further has an end received within the bore of the body and an opposed end spaced from the top of the body.

44. The prosthesis ofclaim 37, wherein the collet has an annular flange on the end of the collet that is spaced from the top surface of the body, the flange being of a larger size than the bore of the body and limiting motion of the collet within the bore.

45. The prosthesis ofclaim 37 wherein the sleeve comprises an annular collet made of a super-elastic material.

46. The prosthesis ofclaim 45 wherein the super-elastic material is nitinol.

47. The prosthesis ofclaim 37 wherein the bore of the body and an outer surface of the sleeve have mating tapers which, when seated together, activate the stem and body to lock together in fixed relative position.

48. The prosthesis ofclaim 37, the sleeve having an inner bore that is tapered and the stem having at least one corresponding outer surface that is tapered wherein the mating tapers, when engaged, activate the stem and body to lock together in fixed relative position.

49. A modular orthopedic prosthesis comprising:

a stem having one end with a neck presenting a joint motion surface and another, longitudinally opposed end having a shaft;

a body including a through-bore having at least a tapered portion, defining a first axis, the body having first and second ends longitudinally opposed from one another along the first axis, the first end being adjacent the neck and presenting an upper face, the second end being adjacent the shaft, the body having a generally triangular cross-section in the region of its first end with at least two angular corners adapted to bite and incise into the bone cavity of a patient to prevent rotation of the implanted prosthesis relative to the bone, the body having a generally circular cross-section in the region of the second end; and

a radially expansible collet having opposed ends including an internal bore and a tapered external surface mating with the tapered portion of the bore, the collet being received within the bore of the body and projecting outwardly from the bore of the body, wherein the stem is received within the bore of the sleeve, the stem and sleeve together being further received within the bore of the body to lock the stem and body together in a fixed position as the mating tapers are engaged.

50. The prosthesis ofclaim 49 wherein the stem comprises a unitary member.

51. The prostheses ofclaim 49 wherein the neck and the shaft comprise separate modular components of the stem.

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