FEMORAL AND HUMERAL STEM GEOMETRY AND IMPLANTATION METHOD FOR ORTHOPEDIC JOINT RECONSTRUCTION

Abstract

The present inventions relate to devices and methods that improve the positioning and fit of orthopedic reconstructive joint replacement stem implants relative to existing methods. For example, an embodiment of the device provides a stem component comprising proximal and distal body portions that can be configured to mimic a geometric shape of a central cavity region created in a bone of a joint for improving conformance and fixation of the stem component thereto. Further, another embodiment provides a system of stem implants that each have a unique medial offset for facilitating the matching of an implant to the geometry of a central cavity region of a bone. Additionally, an inclination angle of a resection surface of each of the implants in the system can remain constant or vary as a function of the medial offset.

Claims

1.-14. (canceled)

15. A system of orthopedic devices for joint reconstruction surgery, the system comprising: an articular component; a plurality of stem components configured to couple with the articular component, each stem component comprising: a distal body portion configured to be inserted into a central cavity region created in a bone of the joint, the distal body portion defining a longitudinal axis, a proximal body portion defining a resection plane configured to be disposed in-plane with a resection surface of a bone when applied to a patient, the longitudinal axis extending through the resection plane, the resection plane defining a proximal-most limit of the proximal body, the proximal-most limit disposed in-plane with the resection surface of the bone, the proximal body for supporting the articular component that in turn has a geometric center positioned within the proximal body portion or at the resection plane, the resection plane oriented at an inclination angle with respect to the longitudinal axis, and an opening in the resection plane of the proximal body; and wherein at least two of the plurality of stem components include different inclination angles.

16. The system of claim 15 wherein the opening is configured to receive a portion of the articular component.

17. The system of claim 15, wherein each of the plurality of stem components is monolithic.

18. The system of claim 15, wherein each of the plurality of stem components includes a medial side and a lateral side, the medial side and the lateral side extending from the resection plane of the proximal body portion to a base of the distal body portion.

19. The system of claim 18, wherein each of the medial side and the lateral side comprise a curvature.

20. The system of claim 15, wherein the opening in the resection plane is tapered.

21. The system of claim 15, wherein the geometric center is spaced from the longitudinal axis at a medial offset distance based on the contour of the proximal body portion.

22. The system of claim 21, wherein each of the plurality of stem components of the system has a medial offset of between 4 mm and 15 mm.

23. The system of claim 15, wherein the geometric center lies in the resection plane.

24. The system of claim 15, wherein each of the plurality of stem components is configured to be inserted into a central cavity region of a humerus.

25. A system of orthopedic devices for joint reconstruction surgery, the system comprising: an articular component; a plurality of stem components configured to couple with the articular component, each stem component comprising: a distal body portion configured to be inserted into a central cavity region created in a bone of the joint, the distal body portion defining a longitudinal axis, a proximal body portion defining a resection plane configured to be disposed in-plane with a resection surface of a bone when applied to a patient, the longitudinal axis extending through the resection plane, the resection plane defining a proximal-most limit of the proximal body, the proximal-most limit disposed in-plane with the resection surface of the bone, the proximal body for supporting the articular component that in turn has a geometric center positioned within the proximal body portion or at the resection plane, the resection plane oriented at an inclination angle with respect to a base of the distal body portion, and an opening in the resection plane of the proximal body; and wherein at least two of the plurality of stem components include different inclination angles.

26. The system of claim 25 wherein the opening is configured to receive a portion of the articular component.

27. The system of claim 25, wherein each of the plurality of stem components is monolithic.

28. The system of claim 25, wherein each of the plurality of stem components includes a medial side and a lateral side, the medial side and the lateral side extending from the resection plane of the proximal body portion to a base of the distal body portion.

29. The system of claim 28, wherein each of the medial side and the lateral side comprise a curvature.

30. The system of claim 25, wherein the opening in the resection plane is tapered.

31. The system of claim 25, wherein the geometric center is spaced from the longitudinal axis at a medial offset distance based on the contour of the proximal body portion.

32. The system of claim 31, wherein each of the plurality of stem components of the system has a medial offset of between 4 mm and 15 mm.

33. The system of claim 25, wherein the geometric center lies in the resection plane.

34. The system of claim 25, wherein each of the plurality of stem components is configured to be inserted into a central cavity region of a humerus.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 is a side cross-sectional view of a prior art implant with a distal stem inserted into a humeral canal.

[0024] FIG. 2 is top view schematic illustration of a prior art eccentric head, which is used to adjust medial and posterior offset.

[0025] FIG. 3 is a cross-sectional side cross-sectional view of a prior art implant.

[0026] FIG. 4 is a side view of a humeral bone and implant illustrating stem fracture.

[0027] FIG. 5A is a side view of a prior art implant illustrating a unique head orientation of a proximal portion thereof.

[0028] FIG. 5B is a side view of another prior art implant illustrating a unique head orientation of a proximal portion thereof.

[0029] FIG. 6A is a side view of an embodiment of a humeral stem having certain features and advantages according to the present inventions.

[0030] FIG. 6B is a side view of another embodiment of a humeral stem having certain features and advantages.

[0031] FIG. 7 is a side view of a humeral stem positioned within a proximal humerus, according to another embodiment.

[0032] FIG. 8 is a schematic illustration of a proximal end of a broach, according to an embodiment.

[0033] FIG. 9A illustrates a humeral stem, according to another embodiment.

[0034] FIG. 9B illustrates a femoral stem, according to another embodiment.

[0035] FIG. 10A is a side view of an embodiment of the stem wherein a proximal body portion thereof is oriented at an inclination angle with respect to a distal body portion thereof.

[0036] FIG. 10B is a side view of another embodiment of the stem wherein the proximal body portion is oriented at another inclination angle with respect to the distal body portion.

[0037] FIG. 10C is a side view of yet another embodiment of the stem wherein the proximal body portion is oriented at yet another inclination angle with respect to the distal body portion.

[0038] FIG. 10D is a side view of yet another embodiment of the stem wherein the proximal body portion is oriented at yet another inclination angle with respect to the distal body portion.

[0039] FIG. 11A is a side view of an implant of a system of implants wherein an inclination angle of the implant changes relative to a medial offset thereof, according to an embodiment.

[0040] FIG. 11B is a side view of another implant of the system, according to another embodiment.

[0041] FIG. 11C is a side view of yet another implant of the system, according to yet another embodiment.

[0042] FIG. 12 shows how the broach can be inserted into the humerus.

[0043] FIG. 13 shows the broach when it is fully inserted to the correct size marking.

[0044] FIG. 14 shows a stem with a shortened distal region.

[0045] FIG. 15 shows how a reamer is inserted into a broached humeral cavity.

[0046] FIG. 16 shows how the broach is guided by the conforming proximal humerus.

[0047] FIG. 17 shows an instrument that combines a broach and a reamer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0048] As used herein, the term “stem” is a broad term that is used to designate a device that is implanted into the bone for the purpose of supporting a functional component of a joint replacement and resisting the loads applied to the functional component. For example, a stem can be a device implanted into a humerus or femur to support a modular prosthetic humeral or femoral head (i.e. the supported structure). In other embodiments, the supported structure can be an integral part of the stem, as with a monolithic stem and head. Femoral and humeral stems typically include distal and proximal sections as well as a taper or other coupling device to which the functional component is attached. Additionally, femoral stems typically include a neck section that extends the distance between the proximal section and the head. The neck is not embedded in the bone, but sits proud. As used herein, the term “neck” can refer to the portion of a femoral stem that does not reside within the femur bone, and extends the distance between the proximal body and the head.

[0049] As used herein, the term “proximal body” can refer to the portion of the humeral or femoral stem that resides within the bone and is nearer to the head (more proximal). The proximal limit of the proximal body is typically denoted by the resection plane or coupling device. The distal limit of the proximal body is typically denoted by a transition from a substantially diverging shape to a slightly diverging or substantially elongated shape. These shapes are intended to somewhat mimic the shapes of the bone in their corresponding locations.

[0050] As used herein, the term “distal region” can refer to the portion of the humeral or femoral stem that resides in the bone and is farther from the head. The proximal limit of the distal region is typically denoted by a transition from a slightly diverging or substantially elongated shape, to a substantially diverging shape. These shapes are intended to somewhat mimic the shapes of the bone in their corresponding locations.

[0051] As used herein, the tem “distal stem angle” can refer to the angle between the best fit central axis of the distal region of the stem and the resection plane.

[0052] As used herein, the term “cavity” can refer to the entire prepared hole in which the stem will be implanted. When the cavity is referred to as “central,” a proximal location is implied because the distal humerus and femur are very elongated distally and consequently dictate central placement.

[0053] As used herein, the term “bone canal” can refer to the portion of the humerus or femur that is substantially elongated and accepts the distal region of the stem. The proximal limit of the distal region is typically denoted by a transition from a slightly diverging or substantially elongated shape, to a substantially diverging shape.

[0054] As used herein, the term “broach” can refer to a bonecutting tool comprising a series of progressively taller points mounted on a single piece of metal, typically used to enlarge a circular hole into a larger noncircular shape such as a square or other desired shape. The amount of material removed by each broach tooth (or chisel) varies with the material being cut. A broach also may also be designed to be pushed or pulled through an existing hole. The term “broaching” as used herein, can refer to this bone-removal process.

[0055] As used herein, the term “reaming” can refer to a process whereby a hole is enlarged to an accurate size. Although generally reaming must be preceded by a drilling or boring operation, that is not true in embodiments disclosed herein, for example, where the starting material is a hole or other shape that is being cleaned up. Reaming can also be performed on surfaces such as a sphere or other concave or convex surfaces as it is when a glenoid is reamed with a spherical reamer. The term “resect,” “resecting,” or “resection” as used herein can refer to a process whereby a portion of a structure is cut off or cut out.

[0056] The term “subject” as used herein includes animals of mammalian origin, including humans. When referring to animals that typically have one end with a head and mouth, with the opposite end often having the anus and tail, the head end is referred to as the cranial end, while the tail end is referred to as the caudal end. Within the head itself, rostral can refer to the direction toward the end of the nose, and caudal is used to refer to the tail direction. The surface or side of an animal's body that is normally oriented upwards, away from the pull of gravity, is the dorsal side; the opposite side, typically the one closest to the ground when walking on all legs, swimming or flying, is the ventral side. On the limbs or other appendages, a point closer to the joint contact is “proximal”; a point farther away is “distal.” This principle shall be followed in relation to embodiments of the apparatuses disclosed herein; a point closer to the main body of the apparatus shall be referred to as “proximal;” a point farther away shall be referred to as “distal.”

[0057] Three basic reference planes are used in zoological anatomy. A “sagittal” plane divides the body into left and right portions. The “midsagittal” plane is in the midline, i.e. it would pass through midline structures such as the spine, and all other sagittal planes are parallel to it. A “coronal” plane divides the body into dorsal and ventral portions. A “transverse” plane divides the body into cranial and caudal portions.

[0058] When referring to humans, the body and its parts are always described using the assumption that the body is standing upright. Portions of the body which are closer to the head end are “superior” (corresponding to cranial in animals), while those farther away are “inferior” (corresponding to caudal in animals). Objects near the front of the body are referred to as “anterior” (corresponding to ventral in animals); those near the rear of the body are referred to as “posterior” (corresponding to dorsal in animals). A transverse, axial, or horizontal plane is an X-Y plane, parallel to the ground, which separates the superior/head from the inferior/feet. A corona] or frontal plane is an Y-Z plane, perpendicular to the ground, which separates the anterior from the posterior. A sagittal plane is an X-Z plane, perpendicular to the ground and to the corona] plane, which separates left from right. The midsagittal plane is the specific sagittal plane that is exactly in the middle of the body.

[0059] Structures near the midline are called medial and those near the sides of animals are called lateral. Therefore, medial structures are closer to the midsagittal plane, lateral structures are further from the midsagittal plane. Structures in the midline of the body are median. For example, the tip of a human subject's nose is in the median line.

[0060] Ipsilateral means on the same side, contralateral means on the other side and bilateral means on both sides. Structures that are close to the center of the body are proximal or central, while ones more distant are distal or peripheral. For example, the hands are at the distal end of the arms, while the shoulders are at the proximal ends.

[0061] A symmetric subject is assumed when the terms “medial,” “lateral,” “inferior,” “superior,” “anterior,” and “posterior,” are used to refer to an implant.

[0062] Embodiments disclosed herein relate to a method that can improve the positioning and fit of orthopedic reconstructive joint replacement implants. One of the goals in performing an orthopedic reconstructive joint replacement is to place a stem implant centrally within the bone and to provide good proximal fill. This not only more evenly loads the bone, but also eliminates the need for head position adjustment. Although specific explanations will refer to either the shoulder (humerus) or the hip (femur), the methods disclosed herein are mutually exclusive and can be used alone or in combination as a general method for reconstructing joints.

[0063] As will be described further herein, the embodiments of the stem implants and the methods for implantation and adjustment of the stem implants provide numerous advantages over the prior art. For example, referring to FIG. 1, a prior art stem implant 10 that is implanted into a humerus bone 12 is shown. During the implantation, a head 14 of the humerus bone 12 is resected in order to accommodate a tool (not shown) used to ream or broach a humeral canal 16 of the bone 12 in preparation for implantation. Once reamed, the humeral canal 16 defines a best fit diameter. The humeral canal 16 of the humerus bone 12 is then used as a guide to accept the stem implant 10. The stem implant 10 can include distal and proximal body portions 20, 22. In this regard, the distal body portion 22 of the stem implant 10 is inserted into the humeral canal 16 until the distal body portion 22 is tightly fitted into a distal area of the humeral canal 16. Additionally, the proximal body portion 20 or head portion of the stem implant 10 is positioned in a proximal area 23 of the humeral canal 16.

[0064] This prior art method poses several basic problems. First, because the distal body portion 22 is configured to form a tight fit with respect to the reamed humeral canal 16, the canal 16 dictates the position of the distal body portion 22 and therefore, the position of the proximal body portion 20 of the implant 10. Further, the proximal body portion 20 of such prior art implants does not fill the proximal area 23 of the humeral canal 16, and causes detrimental reliance on distal stem geometry and fit, as described below. With reference to FIG. 2, since the size, location, and orientation of the head portion 45 with respect to the humeral canal 16 vary greatly from person to person, a single stem geometry per size cannot accommodate natural placement or shape of the head portion 45. Consequently, as shown in the top axial view of the implant 10 of FIG. 2, adjustment of the positioning of the head portion 45 is often made by rotating the implant 10, for example, from a first position 40 to a second position 42 around an eccentric taper 44. Consequently, proximal fit of the head portion 45 on or in a resection plane 24 (shown in FIG. 1) of the humerus 12 is typically poor. Unfortunately, rotating an eccentric head 45 adjusts both posterior 46 and medial 48 head location at the same time, virtually excluding the possibility of perfect placement.

[0065] An additional problem in the prior art is that the position and orientation of the proximal body portion 20 are governed by the distal area of the canal 16, as shown in FIG. 3. As such, the proximal body portion 20 must be made small enough to fit the smallest possible envelope within the proximal area of the humerus 12. An excessively small proximal body portion 20 can cause poor proximal fixation of the implant 10 to the humerus 12 and lead to over-reliance on distal fixation of the implant 10. Over time, when too much emphasis is placed on distal fixation, the strength of the proximal area of the bone 12 begins to deteriorate. This, as shown in FIG. 4, can lead to loosening of the stem implant 10 and potentially fracture of the implant 10.

[0066] While some companies have tried to improve upon this model by offering different neck angles, such as with implants 50 having different configurations, as illustratively shown in FIGS. 5A-B. As illustrated, such implants 50 use the same geometry for the proximal body portion 52 and simply vary a resection angle 54 of the implant 50. While this may improve placement of the head portion, it offers little to accommodate varying shapes of the proximal body portion 52.

[0067] In contrast, according several embodiments of the present inventions, it is contemplated that an angle of a distal section of a stem implant can be varied with respect to an entire proximal body instead of changing an angle of a resection cut or a neck. This means that, for different distal angles, the proximal body will move with respect to the humeral canal.

[0068] Referring now to FIGS. 6A-B, an embodiment of a stem implant 100 is shown. The stem implant 100 defines a proximal body 102 and a distal body 104. In FIG. 6A, it is illustrated that in some embodiments, the distal body 104 of the implant 100 can be configured at a variety of angular orientations 106′, 106″, 106′″ relative to the proximal body 102. The result, as shown in FIG. 6B, is that the proximal body 102 of the implant 100 can be configured at a variety of angular orientations 108′, 108″, 108′″ relative to the proximal body 102. Thus, it is contemplated that in some embodiments, a plurality of implants 100 can be provided to a surgeon such that the surgeon can select one of the implants 100 depending on the configuration required for the implant procedure. In another embodiment, the surgeon can be provided with a kit that comprises a variety of implants 100 with a variety of angular orientations 108′, 108″, 108′″ relative to the proximal body 102.

[0069] In this regard, FIG. 7 illustrates that the stem 100 can be selected based on the shape and sizing of the proximal body 102 and the angle of the humeral canal, which is accommodated with one of the implants 100 that provides the best fitting distal angle from a selection of multiple angles. In this regard, because in some embodiments, the proximal body 102 need not be fitted at a single orientation into the humerus bone 110, the proximal body 102 can be larger and more conforming with a cortical portion 112 of the humerus bone 110, thus providing better proximal fixation and bone loading. Additionally, as illustrated in FIG. 7, the proximal body 102 is more conforming to the shape a cavity 118 of the humerus 110, and the stem 100 will tend to center itself during insertion, accommodating proper placement of the stem 100 and potentially eliminating the need for offset adjustment of a head 120 of the stem 100.

[0070] Furthermore, the stem sizes of embodiments disclosed herein can be based on a continuous and progressive curvature. For example, referring to FIG. 8, a single broach 130 could be used to prepare the cavity 118 of the humerus 110 for multiple sizes, simply by adjusting the depth that the broach 130 is inserted. The prior art implants referred to above currently require a different broach for each size, and in order to determine the proper size for use with a particular patient, one must experiment with multiple broaches, which can make it difficult to determine whether the next size is too large.

[0071] However, as illustrated in FIG. 8, an embodiment disclosed herein provides for a broach 130 having a progressive curvature. The broach 130 can be used to prepare the cavity 118 of the bone 110 for implants 100 of any size. The broach 130 can be configured to include a depth indicator 132, which can comprise a plurality of markings 134. Thus, as the broach 130 is inserted into the humerus 110, the surgeon can broach the cavity 118 to a desired depth, and be aided in such broaching by the indication provided by the depth indicator 132.

[0072] The stem implant of embodiments disclosed herein can be variously configured depending on the intended use of the implant. For example, FIG. 9A illustrates an embodiment of a stem implant 150 for use in a shoulder prosthesis. As shown, the implant 150 can comprise: a distal section 152 (optional stems without the distal section 152 can be used); a proximal section 154; a resection plane or neck 156; and a coupling device 158.

[0073] As noted above, various configurations of the implant 150 can also be provided such that a surgeon can use a particularly configured implant 150 that suits the shape of the humeral cavity. Such variations in the implant 150 can be performed by altering the angular orientation of the distal section 152 and the proximal section 154 with respect to each other. For example, as shown in FIG. 9A, the distal section 152 of the implant 150 can define a longitudinal axis 160 and the proximal section 154 of the implant 150 can define a neck axis 162. In this regard, various configurations of the implant 150 can be designed with the longitudinal axis 160 of the distal section 152 being placed at a discrete angle 166 with respect to the neck axis 162 of the proximal section 154. Additional embodiments of the implant 150 can be configured with the longitudinal axis 162 of the distal section 152 being oriented at another discrete angle 168 with respect to the resection plane 156. However, it is contemplated that in yet other embodiments, the angle 166 can be varied while the angle 168 remains constant, and vice versa. In contrast, prior art stems vary the angle between the resection plane and the longitudinal axis by simply varying the resection angle. In contrast, in the illustrate embodiment, the angle between the resection plane and the longitudinal axis is varied by adjusting the angle between the distal section of the stem and the proximal section such that in certain embodiments the entire proximal section is pivoted about a point.

[0074] In addition, other embodiments can be configured such that the distal section 152 is tapered. Further, the coupling device 158 can be a tapered shape or other device for attachment of the humeral or femoral head. As used herein, the term “tapered shape” can refer to a shape that is gradually narrower or thinner toward one end. The shape of the proximal portion 154 of the implant 150 can curve medially to approximate the contours of the natural proximal humerus (as noted and illustrated above with respect to the embodiment shown in FIG. 7) and allow self-centered broaching.

[0075] Referring now to FIG. 9B, an embodiment of a stem implant 180 for use in a hip prosthesis is shown. As shown, the hip stem implant 180 can comprise: a distal section 182 (optional stems without the distal section 182 can be used); a proximal section 184; a resection plane or neck 186; and a coupling device 188.

[0076] As noted above with respect to FIG. 9A, various configurations of the implant 180 can also be provided such that a surgeon can use a particularly configured implant 180 that suits the shape of the humeral cavity. Such variations in the implant 180 can be performed by altering the angular orientation of the distal section 182 and the proximal section 184 with respect to each other. For example, as shown in FIG. 9B, the distal section 182 of the implant 180 can define a longitudinal axis 190 and the proximal section 184 of the implant 180 can define a neck axis 192. In this regard, various configurations of the implant 180 can be designed with the longitudinal axis 190 of the distal section 182 being placed at a discrete angle 196 with respect to the neck axis 192 of the proximal section 184. Additional embodiments of the implant 180 can be configured with the longitudinal axis 190 of the distal section 182 being oriented at another discrete angle 198 with respect to the resection plane 186. However, it is contemplated that in yet other embodiments, the angle 196 can be varied while the angle 198 remains constant, and vice versa.

[0077] In addition, other embodiments can be configured such that the distal section 182 is tapered. Further, the coupling device 188 can be a tapered shape or other device for attachment of the humeral or femoral head. The shape of the proximal portion 184 of the implant 180 can curve medially to approximate the contours of the natural proximal humerus (as noted and illustrated above with respect to the embodiment shown in FIG. 7) and allow self-centered broaching.

[0078] FIGS. 10A-D illustrate an embodiment of a stem implant 200 comprising proximal and distal body portions 201, 202. As described above, and as illustrated in FIGS. 10A-D, it is contemplated that the proximal body portion 201 can be angularly oriented with respect to the distal body portion 202 at a plurality of angles, thus yielding a plurality of potential configurations of the stem implant, indicated as 200, 200′, 200″, and 200′″. In accordance with the embodiment illustrated in FIGS. 10A-D, the proximal body portion 201 can define a head center 203 and a resection plane 204.

[0079] In some embodiments, the head center 203 can lie in the resection plane 204, and in particular, in a central location of the proximal body portion 201 in the resection plane 204. Further, the distal body portion 202 can define a longitudinal axis 205 that is oriented at an inclination angle 206 with respect to the resection plane 204. Furthermore, the head center 203 and the longitudinal axis 205 are spaced apart at a medial offset 207.

[0080] The medial offset 207, as shown, can be the distance between the head center 203 of the proximal body portion 201 and a closest point along the longitudinal axis 205. If illustrated graphically, the medial offset 207 would be the length of a line oriented perpendicularly to the longitudinal axis 205 and extending between the head center 203 and the longitudinal axis 205. Therefore, in accordance with a preferred embodiment, the stem implant 200 can be configured such that the inclination angle 206 remains constant while the medial offset 207 varies.

[0081] The medial offset 207 can be between approximately 4 mm and approximately 15 mm, and is preferably between approximately 5 mm to approximately 1 mm. In a system of stem implants 200, it is contemplated that a plurality of implants 200, such as four, can be provided, and that the implants can have medial offsets of approximately 5 mm, approximately 7 mm, approximately 9 mm, and approximately 11 mm, respectively. Accordingly, each implant would have a different medial offset, but all of the implants could have the same inclination angle. Other embodiments and combinations can be created by one of skill utilizing these teachings.

[0082] In accordance with another embodiment shown in FIGS. 1A-C, it is contemplated that the medial offset can vary as a function of the inclination angle. FIGS. 11A-C illustrate a system of implants 200′, 200″, and 200′″. As similarly described with respect to the embodiment shown in FIG. 10, each of the implants 200′, 200″, and 200′″ can include proximal and distal body portions 201′, 201″, 201′″ and 202′, 202″, 202′″, respectively, as well as medial offsets 207′, 207″, 207′″ defined as the distance between head centers 203′, 203″, 203′″ of the respective ones of the proximal body portions 201′, 201″, 201′″ and longitudinal axes 205′, 205″, 205′″ of the respective ones of the distal body portions 202′, 202″, 202′″.

[0083] FIGS. 11A-C illustrate an embodiment of a system of implants 200′, 200″, 200′″ wherein the medial offsets 207′, 207″, 207′″ change as a function of inclination angle 206′, 206″, 206′″, respectively. In the embodiment of FIG. 11A, the medial offset 207′ is approximately 12 mm while the inclination angle 206′ is approximately 45 degrees. In the embodiment of FIG. 11B, the medial offset 207″ is approximately 8 mm while the inclination angle 206″ is approximately 41 degrees. Finally, in the embodiment of FIG. 11C, the medial offset 207′″ is approximately 5 mm while the inclination angle 206′″ is approximately 37 degrees. These measurements are those of exemplary embodiments for purposes of illustration only. It is contemplated that the medial offset can be in the range of approximately 4 mm to approximately 15 mm, and that the inclination angle can be in the range of approximately 30 degrees to approximately 55 degrees.

[0084] Referring now to the cross-sectional views of FIGS. 12-13, an embodiment of a procedure will be described for preparing a humeral cavity 210 of a humerus bone 212 and implanting the stem into the prepared cavity 210. After the humeral head of the bone 212 is resected to define a resection surface 214, an initial or pilot hole 216 may be drilled in the center of the resected head. A broach 220 can then be inserted through a central area of the resection surface 214, through the pilot hole 216, and driven into the humerus 212 with a mallet or other impaction device. As the broach 220 is being driven in, it is guided by a proximal area 222 of the humerus bone 212. As discussed above, the broach 220 can be configured for use with multiple sizes, and a depth indicator 224, such as graduations, marking, or other visual or physical devices used on or with the broach 220. Thus, the surgeon can determine the necessary size of the implant required for the bone, and can then use a single broach 220 to broach the cavity 210 to the desired depth as needed. The depth indicator 224 can illustrate the depth or distance required to further insert the broach 220 in order to reach a given stem implant size, as illustrated in FIG. 13.

[0085] The sizing of a proximal body 226 of the broach 220 can be configured such that it increases in size in the proximal direction. Such increases in size can be progressive, if desired, depending on the geometry of the implants being used. Thus, one broach 220 could be used to prepare the cavity 210 for an implant of small size or of large size, depending on how much of the proximal body 226 of the broach 220 is inserted to within the bone 212 during preparation. Because of this, a single broach 220 can be used to prepare a cavity 210 for several sizes simply by changing the depth of insertion. This will make it very simple for a surgeon to determine the proper size. For example, if the broach is inserted for a size 3, the depth indicator 224 can show the location for a size such that the difference in insertion depth is clearly illustrated.

[0086] It is also contemplated that during the preparation of the cavity 210, the surgeon may trial one or many implants to determine what size of the distal portion of the implant is necessary. If the surgeon feels that stem stability will be sufficient without the distal portion, he/she may opt to stop the preparation of the cavity 210 at that point and implant a short stem. Thus, the surgeon can exercise caution and discretion in incrementally reaming the cavity 210 so that a stem 230 with a shorter distal portion 232 can be used if desired, as shown in FIG. 14.

[0087] Referring now to FIG. 15, if the surgeon opts to use a stem with a distal section, the next step is to ream the canal 210 of the humerus 212 using a tapered or cylindrical reamer 240. The reamer 240 is inserted into the humeral canal 210 at a base 242 of the cavity 210 and reamed to a desired depth. Once the canal 210 has been reamed to its proper depth, a trial of the reamer 240 can be used to determine which of the angled stems is needed, and the stem can then be implanted.

[0088] As noted above, once the proximal section of the humeral canal has been prepared, the humeral canal must be reamed if a stem with a distal section is to be used. As also mentioned above, the angle of the stem of the certain embodiments can be adjusted by varying the angle of the distal section with respect to the proximal body. Because of this, instead of fitting the stem to the humeral canal and forcing a non-conforming proximal body to be poorly placed in the humerus, a conforming proximal body can be fit to the proximal humerus and different distal stem angles can be used to fit the canal. In some embodiments, a set of stems can be provided that have three discrete stem angles of approximately 35, approximately 40, and approximately 45 degrees (as measured between the longitudinal axis and the resection plane, discussed in FIGS. 9A-B). Alternate embodiments comprising more angles and/or a wider range also may be used. With a five degree interval between angles, a maximum 2.5 degree mismatch could exist between the stem distal angle and the humeral canal; however, such a mismatch could still allow proper placement of the stem. In some embodiments, the distal portions of the reamer and the stem implant can be tapered to help accommodate this difference.

[0089] Wolff's law states that when bone is repeatedly stressed, it becomes stronger, harder, and denser. Because the outside of a given bone typically carries the majority of the load, the bone tends to get much stronger towards the outside. Conventional shoulder stems do not attempt to approximate the shape of the proximal body of the humerus. Instead, they force the broach to be inserted into the bone at a certain position and in a certain direction, not taking advantage of the above-mentioned strength properties of the bone.

[0090] In contrast, as illustrated in the embodiment of FIG. 16, a broach 250 can be configured to have a medial curve/surface 252 and a lateral curve/surface 254 that are configured to provide the broach 250 with a shape that facilitates proper alignment of the stem 250 within a cavity 256 of a bone 258 such that the broach 250 can be centered within a cortical portion 260 of the bone 258. Thus, the medial curve 252, and to a somewhat lesser extent, the lateral curve 254, can be designed to mimic the general shape of the proximal area of the humerus 258.

[0091] Due to the shaping of such embodiments of the broach 250, the broach 250 will want to follow the path of least resistance, which will be through the weakest bone at the center of the humerus 258 and not through the cortical portion 260 thereof. The final result is that a proximal body 262 of the broach 250 can be placed in the center of a resected surface 264 of the humerus 258 regardless of its position with respect to the humeral canal 256. Further, it is also contemplated that proximal bodies 262 of large sizes can be used and that they will be supported by more structural bone than a traditional humeral stem. Since the proximal body 262 can be placed essentially in the center of the humerus 258, little or no adjustment of the proximal portion 262 will be required.

[0092] While the present inventions have been described with reference to the specific embodiments, it should be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the true spirit and scope of the inventions. In addition, many modifications may be made to adopt a particular situation, material, composition of matter, process, process step or steps, to the objective spirit and scope of the present inventions. All such modifications are intended to be within the scope of the claims appended hereto.

[0093] For example, in another embodiment, a reamer guide could be placed into the prepared proximal cavity to eliminate any angular mismatch between sizes instead of reaming using the canal for guidance. Similarly, in other embodiments of the present inventions, more angled stems could be added to reduce the potential for mismatch.

[0094] In other embodiments, the humeral canal could be reamed and the proximal cavity could be broached using the reamer for guidance, instead of broaching before reaming. While this could somewhat influence proximal stem placement, the benefit of multiple distal angles would still vastly improve placement and fill over current stems.

[0095] In yet other embodiments, curves that mimic the proximal body shape could be used in areas other than the medial and lateral curves/surfaces. They could be placed anterior and posterior or at any number of regular intervals around the stem.

[0096] In yet another embodiment, the distal stem shape could also have a local increase in size at its tip (such as, but not limited to, a ball on the end of the distal section). This would help accommodate any mismatch between the distal section and the reamed humeral canal. The distal increase would contact the reamed cavity and the gap after the increase would allow the distal stem center to vary slightly from the humeral canal center.

[0097] In other embodiments, the shape of the distal section of the stem and/or reamer can be cylindrical, elliptical, or irregularly shaped instead of being tapered. As used herein, the term “elliptical” can refer to a shape that resembles an elongated or flattened circle; the term “cylindrical” can refer to a shape that is round in cross section, and equally wide throughout its length; and the term “irregularly shaped” can refer to a shape that does not vary consistently in shape or size, for example, a distal region that is substantially tapered, but has one area that has a significantly increased size.

[0098] In other embodiments, the shape of the distal section of the stem and/or reamer can incorporate any grooves, slots, or cutouts for flexibility, fit, or fixation. As used herein, the term “groove” can refer to an elongated channel in the distal region of the stem. These grooves are typically narrow and distributed around the distal region at close intervals, creating narrow raised ridges between them. When inserted with slight interference with the bone, these ridges can embed themselves within the bone, providing mechanical locking and allowing a tight fit with some mismatch in shape between the canal and the distal region. As used herein, the term “slot” can refer to an elongated opening in the distal region of the stem placed to increase the flexibility of that portion of the stem. If a single slot is used, it can extend through the entire thickness of the distal region of the stem, dividing it in two. If multiple slots are used, they can intersect and end near the central axis of the distal region of the stem, dividing the distal region in as many sections as there are slots. As used herein, the term “cut out” can refer to a recess in the distal region of the stem that is meant to increase the flexibility of that portion of the stem. These cutouts are typically on one or more sides of distal region of the stem and are placed around the periphery, not through the center.

[0099] In other embodiments, the entire cavity could be prepared by broaching instead of by broaching and then reaming.

[0100] In other embodiments, the cavity could be broached first and then reamed using a reamer that was guided by the broach or ream first and use a broach that was guided by the reamer instead of broaching and reaming independently.

[0101] In yet another embodiment illustrated in FIG. 17, an instrument 300 is provide that incorporates a reaming section 302 and a broaching section 304 that are coupled together with a handle or driving member 306. The reaming section 302 can be disposed at a distal end of the instrument 300 and be used to ream the bone for preparation thereof for implantation. The broaching section 304 can incorporate a broach and be disposed intermediate the reaming section 302 and the handle 306, such that during use, after the reaming section 302 has reamed the cavity of the bone, the instrument 300 can continue to be driven into the bone such that the broaching section 304 can be used to broach a proximal portion of the cavity. In this regard, a single tool can be used to perform both of the broaching and reaming operations in preparation for implantation of a stem. Further, the instrument 300 can incorporate a joint 310 that would allow for slight angular adjustments of the orientation of the reaming section 302 relative to the broaching section 304.

[0102] In other embodiments, the distal region of the stem could be angled in the anterior/posterior direction as well as the medial/lateral direction,

[0103] In other embodiments, the neck of the stem, particularly a hip stem, could be made modular, such that a given stem would accept multiple necks that would be fixed to the stem using a taper or other locking mechanism.

[0104] Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range is encompassed within the inventions. The upper and lower limits of these smaller ranges which may independently be included in the smaller ranges is also encompassed within the inventions, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either both of those included limits are also included in the inventions.

[0105] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this inventions belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present inventions, the preferred methods and materials are now described. All publications mentioned herein are incorporated herein by reference to disclose and described the methods and/or materials in connection with which the publications are cited.

[0106] It must be noted that as used herein and in the appended claims, the singular forms “a,” “and,” and “the” include plural references unless the context clearly dictates otherwise. All technical and scientific terms used herein have the same meaning.

[0107] The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present inventions is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed.

[0108] Although these inventions have been disclosed in the context of certain preferred embodiments and examples, it will be understood by those skilled in the art that the present inventions extend beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the inventions and obvious modifications and equivalents thereof. In addition, while several variations of the inventions have been shown and described in detail, other modifications, which are within the scope of these inventions, will be readily apparent to those of skill in the art based upon this disclosure. It is also contemplated that various combination or sub-combinations of the specific features and aspects of the embodiments may be made and still fall within the scope of the inventions. 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 disclosed inventions. Thus, it is intended that the scope of at least some of the present inventions herein disclosed should not be limited by the particular disclosed embodiments described above.