FEMORAL HEAD ARTHROPLASTY SYSTEM

A femoral head arthroplasty system can comprise a femoral prosthesis comprising a mounting plate having a first side and an opposed second side. An adapter can extend from the second side of the mounting plate. An implant body can extend from the first side of the mounting plate. The implant body can extend from the mounting plate by a distance no greater than 90 mm. The femoral head arthroplasty system can further comprise a femoral head replacement having a generally spherical surface and comprising a recess that is shaped to complementarily receive the adapter of the femoral prosthesis.

FIELD

The disclosed invention relates to hip implants, and, more particularly, to systems for securing a femoral head replacement to the femur of a subject.

BACKGROUND

Conventional hip implants are inserted into the femur about five to six inches. The use of such conventional hip implants requires removal of a significant quantity of a patient's bone, which can be undesirable. There is a need for hip implant systems that eliminate the need for removal of such significant quantities of bone.

SUMMARY

Described herein, in various aspects, is a femoral head arthroplasty system. The femoral head arthroplasty system can comprise a femoral prosthesis. The femoral prosthesis can comprise a mounting plate having a first side and an opposed second side, an adapter extending from the second side of the mounting plate, and an implant body extending from the first side of the mounting plate. The implant body can extend from the mounting plate by a distance no greater than 90 mm. A femoral head replacement can have a generally spherical surface and can comprise a recess that is shaped to complementarily receive the adapter of the femoral prosthesis.

A femoral head arthroplasty system can comprise a femoral prosthesis. The femoral prosthesis can comprise a mounting plate having a first side and an opposed second side, an adapter extending from the second side of the mounting plate, and an implant body extending from the first side of the mounting plate, wherein a distal end of the implant body has a planar face that is generally parallel to the mounting plate. A femoral head replacement can have a generally spherical surface and can comprise a recess that is shaped to complementarily receive the adapter of the femoral prosthesis.

A femoral head arthroplasty system can comprise a femoral prosthesis. The femoral prosthesis can comprise a mounting plate having a first side and an opposed second side. An implant body can extend from the first side of the mounting plate. The implant body can extend from the mounting plate by a distance no greater than 90 mm. The mounting plate and the implant body can cooperate to define a recess. A femoral head replacement can have a generally spherical portion and an adapter extending distally from the generally spherical portion. The adapter can be configured for complementary receipt within the recess of the femoral prosthesis.

The implant body can comprise at least one radially extending spline.

The implant body can comprise a plurality of radially extending splines.

The implant body can comprise a generally cylindrical portion.

The implant body can define a hemi-cylindrical surface.

The implant body can comprise mounting hardware. The mounting plate can define at least one opening configured to receive the mounting hardware.

The mounting hardware can comprise at least one screw.

The femoral prosthesis can comprise a porous or textured metal.

The porous or textured metal can be at least one metal selected from the group consisting of cobalt chromium, titanium, and tantalum.

The femoral prosthesis can comprise a coating.

The coating can be one selected from the group consisting of hydroxyapatite, titanium oxide, titanium nitride, zirconium oxide, and pyrolytic carbon.

The coating can be configured to promote ingrowth or on-growth of bone.

The diameter of at least a portion of the implant body can range from about 10 mm to about 18 mm.

The implant body can have a variable outer diameter.

The adapter can have a Morse taper.

The femoral head replacement can be angularly offset from the femoral prosthesis.

A method can comprise: forming a prepared site within a femur; and implanting a femoral head arthroplasty system such that the implant body is received within the prepared site, wherein the prepared site extends no more than 30 mm distal to the lesser trochanter of the femur.

The mounting plate can have a major dimension that is greater than or equal to a major radial dimension of the femur. The mounting plate can abut cortical bone at a cut proximal end of the femur.

A kit can comprise: a femoral prosthesis comprising: a mounting plate having an first side and an opposed second side, an adapter extending from the second side of the mounting plate, and an implant body extending from the first side of the mounting plate, wherein the implant body extends from the mounting plate by a distance no greater than 90 mm. The kit can further comprise a plurality of femoral head replacements, each femoral head replacement having a generally spherical surface and comprising a recess that is shaped to complementarily receive the adapter of the femoral prosthesis, wherein each femoral head replacement of the plurality of femoral head replacements differs from every other femoral head replacement of the plurality of femoral head replacements in size or material.

It should be understood that any dimensions or other measurements indicated within the figures are merely exemplary and that other dimensions and measurements are contemplated.

DETAILED DESCRIPTION

The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention, are shown. Indeed, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout. It is to be understood that this invention is not limited to the particular methodology and protocols described, as such may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention.

As used herein the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. For example, use of the term “a screw” can refer to one or more of such screws, and so forth.

All technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs unless clearly indicated otherwise.

As used herein, the term “at least one of” is intended to be synonymous with “one or more of” For example, “at least one of A, B and C” explicitly includes only A, only B, only C, and combinations of each.

Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another aspect includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. Optionally, in some aspects, when values are approximated by use of the antecedent “about,” it is contemplated that values within up to 15%, up to 10%, up to 5%, or up to 1% (above or below) of the particularly stated value can be included within the scope of those aspects. Similarly, in some aspects, when values or characteristics are approximated by the use of the antecedent “approximately,” “generally,” or “substantially,” it is contemplated that values within up to 15%, up to 10%, up to 5%, or up to 1% (above or below) of the particularly stated value or characteristic can be included within the scope of those aspects.

As used herein, the term “patient” can refer to a human or an animal that receives an implant as further disclosed herein. In exemplary aspects, a patient can be a human who has been determined to be in need of receiving an implant as disclosed herein.

The following description supplies specific details in order to provide a thorough understanding. Nevertheless, the skilled artisan would understand that the apparatus, system, and associated methods of using the apparatus can be implemented and used without employing these specific details. Indeed, the apparatus, system, and associated methods can be placed into practice by modifying the illustrated apparatus, system, and associated methods and can be used in conjunction with any other apparatus and techniques conventionally used in the industry.

Disclosed herein, in various aspects and with reference toFIG. 1, is a femoral prosthesis100of a femoral head arthroplasty system. The femoral prosthesis100can comprise a mounting plate110having a first side112and an opposing second side114. The mounting plate110can have a planar or substantially planar profile and a thickness502between about three and about seven millimeters (e.g., about five millimeters) in a first dimension (measured along a first axis302) that is perpendicular to the first side's surface. The mounting plate110can extend about twenty-five to about forty millimeters (e.g., about thirty-four millimeters) in a second dimension (measured along a second axis304) and a length504of about sixteen to about twenty five millimeters (e.g., about twenty-two millimeters) in a third dimension (measured along a third axis306). The femoral prosthesis's mounting plate110can have a major dimension that is greater than the major radial dimension of the patient's femur so that, when implanted within the femur, the mounting plate abuts the femur's outer radial wall. A pair of top corners can define a radius r1(optionally, of about two millimeters), and a bottom of the mounting plate110can define a continuous arcuate profile (optionally, having a radius of eleven millimeters, or about half of the width of the mounting plate measured along the third axis306).

The mounting plate110can define one or more through-holes120(e.g., a pair, as shown) that can receive mounting hardware for attaching the femoral prosthesis to a patient. The holes122can have respective diameters d5(optionally, a diameter ranging from about 4 millimeters to about 10 millimeters, or more preferably, being about seven millimeters). In some aspects, the holes122can be spaced from respective side edges of the mounting plate by distances526(e.g., at least one millimeter, between one and 4 millimeters, or, more preferably, about two millimeters). The pair of through holes120can optionally define female threads122therein for receiving male threads of mounting screws (see alsoFIGS. 15 and 16). In some optional aspects, the pair of through holes120can be centered along the third axis306so that the femoral prosthesis is symmetrical about a plane that extends in the first and third dimensions (containing axes302,306) and bisects the femoral prosthesis100. Although embodiments described herein comprise features for attachment via screws, in further embodiments, other attachment means, such as wires, sutures, or cables, may be used.

An implant body130can extend from the first side112of the mounting plate110. The implant body130can be disposed below (i.e., offset in the second dimension (along second axis304) from) the pair of through-holes120. The implant body130can comprise a first cylindrical or generally cylindrical protrusion132that extends perpendicularly to the face of the mounting plate's first side112. The first generally cylindrical protrusion132can extend less than ninety and greater than twenty millimeters, and optionally less than seventy-five and greater than thirty millimeters or between thirty-five and sixty millimeters, (e.g., about forty millimeters or about forty-five millimeters) from the first side112of the mounting plate along a first axis134. The first generally cylindrical protrusion132can optionally have a diameter d1between about ten and about eighteen millimeters (e.g., about fourteen millimeters). A distal end of the first generally cylindrical protrusion132(i.e., the end farthest away from the mounting plate110) can have an arcuate edge136that extends a length512in the first dimension302ranging from about three millimeters to about eight millimeters, or more preferably, being about five millimeters. The distal end of the first generally cylindrical protrusion132can optionally have a planar face138that is generally parallel to the mounting plate. The first generally cylindrical protrusion132can be spaced from the bottom of the mounting plate110, for example by about two millimeters. The first axis134of the first generally cylindrical protrusion132can optionally be spaced from the bottom of the mounting plate by a distance530(e.g., optionally, from about seven millimeters to about 12 millimeters, or about nine millimeters). In some optional aspects, the first generally cylindrical protrusion132can be spaced from the lower end of the mounting plate by a distance506(e.g., optionally, from about one millimeter to about four millimeters, or about two millimeters).

The implant body130can further comprise a second cylindrical or generally cylindrical protrusion150that extends along a second axis152that is parallel to the first axis134. The second axis152can optionally be directly vertically above the first axis134. The second generally cylindrical portion150can extend a length508about ten to about forty millimeters (e.g., from about ten millimeters to about twenty millimeters, or about fifteen millimeters) from the first side112of the mounting plate110. The second generally cylindrical portion150can therefore have an end opposite the mounting plate110that is a length516(e.g., from about 25 millimeters to about 35 millimeters, or about thirty millimeters) from the end of the first generally cylindrical portion130opposite the mounting plate. The first and second axes134,152can be spaced by less than the sum of the respective radiuses of the first and second generally cylindrical portions so that the second generally cylindrical protrusion150overlaps the first generally cylindrical protrusion132. Accordingly, in a cross sectional plane perpendicular to the first axis134, the overlapping first and second generally cylindrical protrusions132,150can have a figure-eight shape. Optionally, the second axis152can extend along a top edge of the first generally cylindrical protrusion132. The second axis152can be spaced from the top of the mounting plate by a distance532(e.g., optionally, from about 15 millimeters to about 20 millimeters, or about eighteen millimeters) and can be spaced from the bottom of the mounting plate by a distance534(e.g., optionally, from about 13 millimeters to about 18 millimeters, or about sixteen millimeters). That is, the second axis152can be spaced from the first axis by the radius of the first generally cylindrical protrusion132. The second generally cylindrical protrusion150can have a radius r3of about five to about nine millimeters (e.g., about seven millimeters). The first and second generally cylindrical protrusions132,150can cooperate to provide an oblong cross section so that the implant body130is inhibited from rotation. Moreover, the combined cross sectional shape of the first and second generally cylindrical protrusions (e.g., a figure-eight shape) can cooperate with a bone preparation site that is easily prepared by a surgeon. In further embodiments, the implant body130can have various other cross sectional profiles in planes perpendicular to the implant body's longitudinal dimension, including a generally cylindrical profile, an oval profile, a polygonal profile (e.g., a square or rectangular profile), or an oblong profile.

Optionally, the implant body130can extend from the mounting plate by a distance of no greater than ninety millimeters, or no greater than seventy-five millimeters, or no greater than sixty millimeters, or no greater than fifty millimeters, or no greater than forty-five millimeters. As further disclosed herein, it is contemplated that the minimal length of the implant body130can reduce the amount of native bone of a subject that must be removed to accommodate the implant body.

An adapter160can extend from, and be oriented perpendicularly or substantially perpendicularly to, the second side114of the mounting plate110. The adapter160can optionally have a central axis161that is collinear with the second axis152. Accordingly, the adapter160can be superiorly axially offset from (i.e. above) the axis134of the first generally cylindrical protrusion132. In this way, for some patients, a femoral head attached to the adapter160can most accurately recreate the patient's normal anatomy. In further embodiments, the adapter can have an axis offset from the axis152. Optionally, in some such embodiments, the adapter160can be axially aligned with the axis134. The adapter160can comprise a frustoconical portion162that attaches, via a neck portion164, to the mounting plate110. The neck portion can have a length514of from about three millimeters to about seven millimeters, or of about five millimeters. The frustoconical portion162can taper from a proximal end166to a distal end168(moving away from the mounting plate110). The frustoconical portion162can optionally have a Morse taper. The proximal end166can optionally have a diameter d2of about twelve to about sixteen millimeters (e.g., about fourteen millimeters), and the distal end168can optionally have a diameter d3of about ten millimeters to about fourteen millimeters (e.g., about twelve millimeters). The frustoconical portion162can extend axially a length510of about ten to about eighteen millimeters (e.g., about fourteen millimeters) from the proximal end166to the distal end168. In some aspects, the adapter's central axis can be spaced from the top of the mounting plate by a length520(optionally, from about 15 millimeters to about 20 millimeters, or about eighteen millimeters) and spaced from the bottom of the mounting plate by a length522(optionally, from about 13 millimeters to about 18 millimeters, or of sixteen millimeters). The adapter's radial-most surface can be spaced from the respective opposing side edges of the mounting plate in the third dimension306by a distance524(optionally, from about three millimeters to about six millimeters, or of about four millimeters). Optionally, at least a portion of the frustoconical portion's circumferential surface can comprise a texture. Said texture can improve frictional engagement between the adapter160and the femoral head replacement. In some optional aspects, a helical groove having a pitch of 0.5 millimeters can define said texture.

The neck portion164of the adapter160can have a cross section that varies along its axis in an arcuate profile. At a halfway point along its axis, the neck portion164can have a minimum diameter d4, which, in some embodiments, can be about twelve millimeters. Opposing ends of the neck portion164can each have a diameter d2of about fourteen millimeters. Accordingly, the minimum diameter can be about two millimeters less than the maximum diameter of the neck portion154. The neck portion's narrowing diameter can provide a location to grip the femoral prosthesis during implantation and removal of the femoral prosthesis.

Although shown extending parallel to the implant body130, in further embodiments, the adapter160can extend at various angles with respect to the implant body130in order to vary the varus/valgus angle of the femoral head with respect to the longitudinal dimension of the femur.

Referring toFIG. 7, the adapter160can receive a femoral head replacement200. The femoral head replacement200can have a shape that cooperates with a hip socket of the patient's pelvis or an artificial hip socket. In some embodiments, the femoral head replacement200can have the shape of a natural femoral head. The femoral head replacement200can have a generally spherical profile. The femoral head replacement200can define a recess210. The recess210can have a complementary shape to the adapter160(FIG. 1) of the femoral prosthesis100(FIG. 1). For example, the recess210can have a frustoconical profile. The prosthesis200can optionally be a conventional component known to those skilled in the art.

The femoral prosthesis100can couple to the femoral head replacement200to create a femoral head arthroplasty system250. In some embodiments, the femoral prosthesis100and the femoral head replacement200can couple permanently, while in further embodiments, the pair can couple via a non-permanent means. The adapter160and femoral head replacement200can have an interference fit (e.g., via a Morse taper) so that the respective components frictionally engage each other. As stated above, at least one of the adapter160and the femoral head replacement200can optionally have a texture (i.e., surface texture) to improve the engagement between the respective components.

Referring toFIG. 8, in further embodiments, a femoral head replacement200′ can comprise a generally spherical portion202′ and an adapter160′ that extends distally from the generally spherical portion202′. A femoral prosthesis100′ can comprise a recess210′ and can otherwise have the same shape and dimensions as that of the femoral prosthesis100(FIG. 1). Although shown as a frustoconical protrusion, the adapter160′ and recess210′ can have profiles similar to that of the adapter160(FIG. 1) and the recess210(FIG. 7), respectively, or any other adapter profile known to those skilled in the art.

In some embodiments, the femoral prosthesis can comprise at least one radially extending spline180or, as shown, a plurality of radially extending splines180. The radially extending spline(s)180can provide surfaces against which bone can grow as well as inhibit rotation of the femoral prosthesis about its axis of elongation.

The femoral prosthesis100and/or the femoral head replacement200can comprise various materials known to those skilled in the art, such as, for example, porous, coated titanium, ceramics, tantalum, cobalt chromium alloy, or various other porous metals. The material(s) can be porous or textured in order to allow bone in-growth or on-growth. The material(s) can be strong enough to bear the weight of the patient without fracturing.

The femoral prosthesis100and/or the femoral head replacement200can comprise a coating. Said coating can comprise one or more of the following: hydroxyapatite, titanium oxide, titanium nitride, zirconium oxide, and pyrolytic carbon. In further embodiments, the coating can comprise gold, ceramics, polymers (e.g., ultra-high molecular weight polyethylene), diamond-like carbon (DLC) coatings, oxidized zirconium, titanium nitride or various other coatings known to those skilled in the art. The coating(s) can optionally be low friction and can optionally be hydrophobic.

Referring toFIGS. 10-14, in some aspects, the implant body130of the prosthesis100can have an elongate profile in the second dimension (along the second axis304). That is, in cross sections perpendicular to the second axis304, the implant body130can have a major dimension measured along the second axis304and a minor dimension measured along the third axis306. For example, the implant body130can define two hemi-cylindrical surfaces190that are spaced along the second axis304and connected via planar faces192. This or another non-axially symmetric profile can inhibit rotation of the implant body relative to the femur. In some aspects, the implant body can have a major dimension of between 18 and 25 millimeters (e.g., about 21 millimeters) measured along the second axis304and a minor dimension of between 12 and 18 (e.g., about 14 millimeters) measured along the third axis306.

In some optional aspects, the centerline194of the implant body (i.e., the line extending through the centroid of the cross sections in planes perpendicular to the first dimension (first axis302)) can be collinear with the central axis161of the adapter160. In further optional aspects, as shown inFIGS. 15 and 16, the centerline194can be offset from the central axis161of the adapter160(optionally, offset from the central axis161in the second dimension (relative to the second axis304)).

In some optional aspects, the distal end of the implant body130can optionally have a planar face138that is parallel or generally parallel to the mounting plate. In further aspects, it is contemplated that the distal end of the implant body can define a rounded, oblong surface139or other non-planar surface that extends parallel to the mounting plate. For example, the implant body130can define first and second radii141(optionally, spherical surfaces) that are spaced relative to each other along the second dimension304(and that are measured in a plane containing the first and second axes).

In some aspects, the centerline194of the implant body can extend perpendicularly to the mounting plate110along an entire length of the implant body. For example, within any plane that intersects the implant body and is perpendicular to the first axis302, a center point (which can optionally correspond to a center of mass) of the portion of the implant body within the plane will be intersected by the centerline194. In further aspects, it is contemplated that the apparatus can be symmetric about a plane that is perpendicular to the second dimension304and bisects the implant body (and, therefore, includes the centerline194). Optionally, in still further aspects, it is contemplated that the implant body can be symmetric about both (a) a first plane that is perpendicular to the second dimension304and bisects the implant body; and (b) a second plane that is perpendicular to the third dimension306and bisects the implant body. It is contemplated that the above-described configurations, by avoiding the need for providing an angled or asymmetric implant body (for example, as might be necessary to permit deeper advancement of an implant body within a native bone), can provide advantageous balance and force transmission properties while minimizing the amount of bone that is removed from the patient to accommodate the implant body.

Referring toFIGS. 10-14, it is further contemplated that in some aspects, the neck portion164can have a constant diameter (instead of the narrowing diameter as depicted inFIG. 1) to increase the strength of the prosthesis.

Referring toFIGS. 17-22, a fixation screw240can have a head241defining a first thread (or plurality of threads)242and a body243defining a second thread (or plurality of threads)244. Optionally, the head of the screw can define a taper. Accordingly, the hole120(FIG. 16) can define a corresponding taper. The fixation screw can comprise one or more (e.g., optionally, three equally circumferentially spaced) self-tapping features246for tapping the bone during insertion of the screw. The fixation screw can further comprise one or more (e.g., optionally, three equally circumferentially spaced) self-tapping features247for tapping the bone during removal of the screw. It should be understood that the dimensions (in millimeters) provided in the figures should be understood to be optional aspects.

It is further contemplated that the prosthesis can be fixated to the femur, additionally or alternatively, with bone ingrowth and/or ongrowth and/or cemented fixation.

A kit can comprise a femoral prosthesis100and a plurality of femoral head replacements200. Each of femoral head replacements200can differ from the others in at least one of size or material.

Referring toFIG. 9, a medical professional (e.g., an orthopedic surgeon) can form a prepared site within a femur400. For example, the medical professional can cut off a portion of the patient's natural femoral head. Optionally, the surgeon can use a patient-specific cutting guide that locates the optimal location and angle for removing the femoral head. According to one embodiment, the cutting guide can comprise a frame that defines a slot for guiding a cutting saw. The cutting guide can temporarily be fastened to the femur using pins or screws and subsequently be removed from the femur after cutting. The surgeon can drill/ream a pair of overlapping holes to receive the first and second cylindrical portions132,150. In further aspects, the overlapping holes can further be bored to provide an opening to receive the implant body130(e.g., for the embodiments shown inFIGS. 10-14). The prepared site can be positioned further proximally along the neck of the femur (toward the original femoral head) than prepared sites of conventional femoral prostheses for hip replacement. The prepared site can optionally extend no more than thirty millimeters distal to the lesser trochanter402of the femur400(i.e., past the lesser trochanter along femoral shaft's longitudinal axis in the direction toward the patient's foot). The medical professional can then implant the femoral prosthesis so that the implant body is received within the prepared site. The femoral prosthesis can be inserted so that the mounting plate abuts a superior end of the femur. The medical professional can drill holes in the patient's bone for receiving the screws or other fasteners. Screws240or other fasteners can be used to secure the femoral prosthesis in place. Optionally, the surgeon can drill holes into the femur to receive screws240. The femoral head replacement can then be attached to the femoral prosthesis.

Compared to conventional implants, embodiments disclosed herein can enable hip implants that require less bone removal. That is, a shorter segment of bone can be removed, leaving a portion of the femoral neck through which the femoral prosthesis can extend. The disclosed embodiments can reduce blood loss during surgery and enable easier insertion for the surgeon, particularly in cases of anterior approach surgery. The disclosed embodiments can be associated with smaller incisions than conventional implants and can provide for easier re-do surgery if need arises.

EXEMPLARY ASPECTS

In view of the described products, systems, and methods and variations thereof, herein below are described certain more particularly described aspects of the invention. These particularly recited aspects should not however be interpreted to have any limiting effect on any different claims containing different or more general teachings described herein, or that the “particular” aspects are somehow limited in some way other than the inherent meanings of the language literally used therein.

Aspect 1: A femoral head arthroplasty system comprising: a femoral prosthesis comprising: a mounting plate having a first side and an opposed second side, an adapter extending from the second side of the mounting plate, and an implant body extending from the first side of the mounting plate, wherein the implant body extends from the mounting plate by a distance no greater than 90 mm; and a femoral head replacement having a generally spherical surface and comprising a recess that is shaped to complementarily receive the adapter of the femoral prosthesis.

Aspect 2: A femoral head arthroplasty system comprising: a femoral prosthesis comprising: a mounting plate having a first side and an opposed second side, an adapter extending from the second side of the mounting plate, an implant body extending from the first side of the mounting plate, wherein the implant body has a distal end, wherein the distal end of the body defines a surface that extends generally parallel to the mounting plate; and a femoral head replacement comprising a recess that is shaped to complementarily receive the adapter of the femoral prosthesis.

Aspect 3: A femoral head arthroplasty system comprising: a femoral prosthesis comprising: a mounting plate having a first side and an opposed second side; and an implant body extending from the first side of the mounting plate, wherein the implant body extends from the mounting plate by a distance no greater than 90 mm, wherein the mounting plate and the implant body cooperate to define a recess; and a femoral head replacement having a generally spherical portion and an adapter extending distally from the generally spherical portion, wherein the adapter is configured for complementary receipt within the recess of the femoral prosthesis.

Aspect 4: The femoral head arthroplasty system of aspects 1-3, wherein the implant body comprises at least one radially extending spline.

Aspect 5: The femoral head arthroplasty system of aspect 4, wherein the implant body comprises a plurality of radially extending splines.

Aspect 6: The femoral head arthroplasty system of any of aspect 1-3, wherein the implant body defines a generally hemicylindrical surface.

Aspect 7: The femoral head arthroplasty system of any of aspect 1-3, further comprising mounting hardware, and wherein the mounting plate defines at least one opening configured to receive the mounting hardware.

Aspect 8: The femoral head arthroplasty system of aspect 7, wherein the mounting hardware comprises at least one screw.

Aspect 9: The femoral head arthroplasty system of any of aspect 1-3, wherein the femoral prosthesis comprises a porous or textured metal.

Aspect 10: The femoral head arthroplasty system of aspect 9, wherein the porous or textured metal is at least one metal selected from the group consisting of cobalt chromium, titanium, and tantalum.

Aspect 11: The femoral head arthroplasty system of any of aspect 1-3, wherein the femoral prosthesis comprises a coating.

Aspect 12: The femoral head arthroplasty system of aspect 11, wherein the coating is one selected from the group consisting of hydroxyapatite, titanium oxide, titanium nitride, zirconium oxide, and pyrolytic carbon.

Aspect 13: The femoral head arthroplasty system of aspect 11, wherein the coating is configured to promote ingrowth or on-growth of bone.

Aspect 14: The femoral head arthroplasty system of any of aspect 1-3, wherein the diameter of at least a portion of the implant body ranges from about 10 mm to about 18 mm.

Aspect 15: The femoral head arthroplasty system of any of aspect 1-3, wherein the implant body has a variable outer diameter.

Aspect 16: The femoral head arthroplasty system of any of aspect 1-2, wherein the adapter has a Morse taper.

Aspect 17: The femoral head arthroplasty system of any of aspect 1-2, wherein the femoral head replacement is angularly offset from the femoral prosthesis.

Aspect 18: A method comprising: forming a prepared site within a femur; and implanting a femoral head arthroplasty system according to any one of aspect 1-17 such that the implant body is received within the prepared site, wherein the prepared site extends no more than 30 mm distal to the lesser trochanter of the femur.

Aspect 19: The method of aspect 18, wherein the mounting plate has a major dimension that is greater than or equal to a major radial dimension of the femur, and wherein the mounting plate abuts cortical bone at a cut proximal end of the femur.

Aspect 20: A kit comprising: a femoral prosthesis comprising: a mounting plate having a first side and an opposed second side, an adapter extending from the second side of the mounting plate, and an implant body extending from the first side of the mounting plate, wherein the implant body extends from the mounting plate by a distance no greater than 90 mm; and a plurality of femoral head replacements, each femoral head replacement having a generally spherical surface and comprising a recess that is shaped to complementarily receive the adapter of the femoral prosthesis, wherein each femoral head replacement of the plurality of femoral head replacements differs from every other femoral head replacement of the plurality of femoral head replacements in size or material.