Method of preparing an acetabulum for receiving a head of a femoral prosthesis

A femoral neck fixation prosthesis and method of using same which reduces bone loss and the avoids the other shortcomings of the prior art by allowing the fixation of a stable femoral head replacement while reducing the amount of the femur which must be reamed for the insertion of the prosthesis. The preferred embodiment provides that the femoral head is attached to a fixation prosthesis, which extends coaxially through the canal of the femoral neck, into the femur, and is then attached to the opposite lateral wall of the femur. In this manner, the prosthesis serves to imitate the original structure of the femoral neck. No other support members, either crosspins or arms extending into the length of the femur, are required.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present application relates generally to hip prostheses and more specifically to an improved method of implanting a femoral neck fixation prosthesis in the femoral neck.

2. Description of Related Art

A widely used design for replacement of the proximal portion of a femur employs an elongate, often curved, shaft that extends into the medullary canal of the femur. This design has the tendency to place unnatural stresses on the femur, which lead to pain and the consequent curtailment of activity for the patient. Further, present techniques can lead to proximal bone loss and call for the resection of the majority of the femoral neck. Current designs also call for fixing the prosthesis in the proximal third of the femur. The useful life of an intramedullary implant is often less than the expected life span of a young patient.

Previously known prostheses for replacing a femoral head that do not extend into the medullary canal have been mechanically complex or have proven troublesome in actual use. Huggler, U.S. Pat. No. 4,129,903 and Grimes, U.S. Pat. No. 4,795,473 are examples of prosthetic implants having a side plate attached to the exterior lateral side of the femur opposite the femoral head. Screws are used to secure the plate to the femur and one or more holes are drilled into the femur for securing the plate to the bone. The additional holes and the stresses at the site of fixation are believed to cause trauma to the bone.

Masini, U.S. Pat. No. 5,571,203 discloses a device having a shaft that extends through a resected portion of the proximal femur, positioned co-axially relative to the longitudinal axis of the femur. The device is secured by a screw or similar locking device that extends into the femur from the lateral side, just below the greater trochanter. It is believed that the natural forces applied to the prosthesis during normal hip motion result in the application of shear forces to the greater trochanter. The shear forces can be harmful to the greater trochanter and can permit micro-movement of the prosthesis on the unsecured side.

A conventional method for implanting the above types of femoral head implants is described in Campbell's Operative Orthopaedics, (Mosby, 7th ed., 1987) and typically includes making a large incision in the patient's lateral side at the hip joint and through the skin and muscle, dislocating the hip and then sawing off the femoral head. This method is considered invasive because of the need to dislocate the hip and cut through muscle surrounding the hip joint. Invasive procedures increase the trauma to the patient, the potential for complications, recovery time and the cost.

Replacement of the proximal portion of the femur is sometimes necessary due to degenerative bone disorders or trauma to otherwise healthy bone caused by accidental injury. In the latter instance it is desirable to replace the traumatized portion of the bone without causing further trauma to healthy bone. There is a need, therefore, for an implant that replaces a traumatized portion of the femur, but also significantly minimizes stress to the remaining healthy bone and that can be implanted by a method that is less invasive.

There are several other significant problems and issues relating to hip arthroplasty. One problem is encountered with the young, active patient. Younger patients are more likely to have failure of their primary arthroplasty both due to increased demand on the mechanical construct, and from a pure life expectancy standpoint. It follows that they are more likely to require a revision and a second revision, which may lead to a catastrophic bone loss situation.

Another problem relates to instability of the hip following implantation of the prosthesis. This problem still occurs at the same rate that it did 50 years ago. Larger femoral heads may decrease the incidence, but no other significant technical changes have occurred to effect the incidence of this serious complication.

Still another problem is related to bone loss in patients receiving hip prostheses. The overwhelming majority of present successful femoral prostheses achieve fixation at least as far distal as the proximal femoral metaphysis. When these prostheses fail, the next step usually involves diaphyseal fixation, often with a large diameter, stiff stem.

Leg length inequality is another problem associated with hip arthroplasty. An average lengthening of the leg of 1 centimeter is common. Lengthening is sometimes accepted for the sake of improved stability; however, leg length inequality has been reported as the primary reason why surgeons are sued after hip arthroplasty.

Finally, another problem associated with hip arthroplasty is surgical morbidity. The surgery usually involves significant blood loss, body fluid alterations, and pain. Shortly, the surgery is a big operation that hurts. It should be the goal of every compassionate surgeon to minimize these issues. If the operation can be made smaller, with less blood loss and less pain without diminishing long term results, every effort should be made to do so.

It would therefore be desirable to provide a femoral neck prosthesis and method for implanting the prosthesis that overcomes these significant disadvantages.

BRIEF SUMMARY OF THE INVENTION

It is therefore one object of the present invention to provide an improved apparatus and method for hip replacements.

It is another object of the present invention to provide an improved and less-invasive prosthesis and implantation method that replaces the femoral head while retaining a substantially intact femoral neck.

The foregoing objects are achieved as is now described. A femoral neck fixation prosthesis and method of implanting the prosthesis according to the principles of the present invention, reduce bone loss and avoid the other shortcomings of the prior art by allowing the fixation of a stable femoral head replacement while reducing the amount of the femur that must be removed and reamed for the insertion of the prosthesis. The preferred embodiment provides that the femoral head is attached to a fixation prosthesis, which extends coaxially through the central canal of the femoral neck, into the femur, and is then attached to the opposite lateral wall of the femur. In this manner, the prosthesis serves to imitate the original structure of the femoral neck. No other support members, either crosspins or arms extending into the length of the femur, are required.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides a femoral neck fixation prosthesis and a method of implanting the prosthesis which reduces bone loss and avoids the other shortcomings of the prior art by allowing the fixation of a stable femoral head replacement while reducing the amount of the femur, that must be removed and reamed for the insertion of the prosthesis. The preferred embodiment provides that the femoral head is attached to a fixation prosthesis, which extends coaxially through the central canal of the femoral neck, into the femur, and is then attached to the opposite lateral wall of the femur. In this manner, the prosthesis serves to imitate the original structure of the femoral head while substantially retaining the natural femoral neck. No other support members, either crosspins or arms extending into the length of the femur, are required.

A femoral neck fixation prosthesis in accordance with the principles of the present invention is designed to achieve fixation in the femoral neck with or without cement. Therefore, revision of the disclosed femoral neck fixation prosthesis would essentially become the complexity of a present day primary hip arthroplasty for the femoral component. The improved femoral neck fixation prosthesis would require an operation equivalent to a primary arthroplasty on the femoral side. Therefore it would be ideal for the younger patient, but would also be recommended for the older patients with accommodating anatomy.

The innovative method for implanting the femoral neck fixation prosthesis would allow less muscular dissection, and the capsule can be repaired anteriorly at the end of the procedure. The disclosed femoral neck fixation prosthesis is designed to be used with larger diameter femoral heads. The combination of these factors would significantly improve stability of the hip. The goal is to minimize the need for hip position precautions postoperatively.

One advantage of the preferred embodiment is that less bone would be resected initially using the femoral neck fixation prosthesis, and the stress would be transferred to the bone in the femoral neck. The metaphysis and the diaphysis of the proximal femur would be minimally disturbed. Only the femoral head itself will be resected.

Another advantage of the preferred embodiment, is that the femoral neck length and offset would be accurately measured and reproduced when using the femoral neck fixation prosthesis. Leg length inequality due to hip arthroplasty could be minimized, and muscle mechanics could be accurately restored.

Further, an operation using the femoral neck fixation prosthesis would be less invasive with less blood loss, less post operative pain, and less perioperative morbidity than an operation that employs the vast majority of commonly used prostheses. The economic implications of a shorter hospital stay, fewer blood transfusions, and fewer medical complications are significant.

A femoral neck fixation prosthesis according to the principles of the present invention is shown inFIG. 1, wherein femur100is shown with femoral neck105, joining member115, and prosthetic head110.

An uncemented porous coated femoral prosthesis body125with a modular head110and joining member115is provided. The metal used is preferably either titanium or chrome-cobalt based, and can be any metal commonly used in hip prosthesis construction. The modulus of elasticity of such a short segment will be of less significance than in a standard femoral stem. The coating is preferably either sintered beads or plasma sprayed, depending on the type of metal used for the body of the prosthesis.

The body125of the prosthesis will preferably be available in various diameters, approximately every 1–1.5 mm. The length of the prosthesis will preferably be chosen from one or two lengths, approximately 30 mm. Most of the fixation and ingrowth of the bone to the prosthesis will occur in the first 10–20 mm.

As described in more detail below, fixation to the femur will be achieved by reaming the femoral neck105to accommodate a cylindrical porous coated sleeve body125, which is supported by a proximal collar and given distal stability with a compression screw120through the lateral wall of the femur just distal to the greater tuberosity (location140). Reaming will be progressive until the cortex of the femoral neck is encountered. A femoral component ½ mm greater than the last diameter reamed will then be selected.

After insertion, the long axis of the body of the component body125will coincide with a longitudinal axis in the preoperative femur100corresponding to an imaginary line connecting the center of the femoral neck105with the center of the femoral head110. Resection of the femoral head will be measured such that the center of rotation of the femoral head110can be measured and reproduced. The femoral neck105will be reamed with a planar reamer that fits in the reamed canal of the femoral neck105to establish a flat surface. The proximal body125of the prosthesis will have the female end of a morse taper to allow the attachment of the joining member115.

A compression screw120passes through the center of the body of the prosthesis. This screw attaches to a barrel nut130in the lateral wall of the femur at point140and preferably has a hexagonal head. The screw120is preferably smooth in the segment within the body of the prosthesis and has threads on the distal end. The tunnel through the body of the prosthesis forms a snug fit around the smooth portion of the screw120. The barrel nut130is preferably angled to be flush with the lateral side of the femur at point140. The head of the screw120is preferably located in the base of the morse taper in the body125of the femoral component. This screw120adds stability to the construct by giving antero-posterior and varus-valgus stability to the body125of the prosthesis and by compressing the prosthesis on the neck105of the femur100. These screws will be available in various lengths.

It is important to note that this innovative design allows the prosthesis to be installed and used without requiring any other fastener on the femur. In particular, the preferred embodiment does not require any additional screws or other fasteners to be placed in the femur, and does not require any sort of support plate on the lateral wall of the femur.

Male-male morse taper joining member115acts as a joining portion in connecting the body125of the prosthesis to the femoral head110. Adjustments in joining member length will occur in this segment with several lengths of joining member segments available for each femoral body and femoral head. The joining member segment needed to exactly reproduce the center of rotation of the femoral head will be known based on the amount of bone resected. In this embodiment, the joining member115has male morse tapers135on each side, and will have a variable-length section in between the morse tapers to fit the specific patient.

The femoral head110will have a female morse taper to connect to the joining member115. Femoral heads110will be of various diameters depending on the acetabulum, and several exemplary sizes are shown inFIG. 1. Ideally, larger femoral head diameters (e.g.,36mm to 50 mm) are used to both improve stability and prevent impingement of the neck on the acetabular rim. The femoral head110is preferably polished chrome-cobalt, as the industry standard, but other materials can be used.

In another embodiment of the present invention, a de-rotation component is added to reduce the likelihood of the rotation of the prosthesis within the femoral neck. This can be accomplished with a pin or stem with grooves or slots that passes through the lateral cortex into the body of the prosthesis. This would then be compressed with a screw, which would be put through the head end of the body of the prosthesis into the stem.

It should be clear that the femoral neck fixation prostheses described herein can be used with or without cement.

FIGS. 2A–2Cshow several cross-sectional views of the cylindrical porous coated body225of the prosthesis of the preferred embodiment.FIG. 2Ashows a longitudinal cross-section of the body225. In this view, a collar248at the proximal end of the body225is illustrated, as is the female morse taper cavity246, which is fit to receive the joining member. The collar248is configured to abut the proximal end of the resected femoral neck. Communicating with cavity246is tubular channel247which will receive the compression screw. Below the collar248, the exterior of the body225has a porous coated layer249.

While the preferred embodiment has a substantially circular cross-section, as shown inFIGS. 2A–2C, the body member225can also be configured with a triangular (FIG. 2E), scalloped (FIG. 2F), oval (FIG. 2H), or fluted (FIG. 2G) cross-section.

FIG. 2Bshows a lateral cross-section of body225as cut across line B ofFIG. 2A. InFIG. 2B, the cavity246is shown, and the proximal collar248is also illustrated.

FIG. 2Cshows a lateral cross-section of body225as cut across line C ofFIG. 2A. InFIG. 2C, channel247for the compression screw is shown passing through the center of body225. On the exterior of body225is shown the porous coated layer249. A cross-section across line D ofFIG. 2Ais the same as described for line C of that FIG.

FIG. 3shows joining members316/317/318of various sizes, which can be used for patients with differing requirements. Each joining member316/317/318has a morse taper on each end, and a variable-length straight section connecting the morse tapers.

FIG. 4depicts the centering guide for placement of the starting pin in accordance with the principles of the present invention. In this FIG., femoral neck gripping clamp405is to grip and hold the femoral neck after the femoral head centering device410has been placed over the patient's femoral head.

The femoral neck gripping clamp405is expanded or contracted using adjustment piece420, which operates gears415. Cannulated rod425, which is connected to femoral head centering device410, allows pin insertion into the cannula at435.

Free nut430is used to tighten the femoral head centering device410. The centering guide shown inFIG. 4is preferably made of a stiff metal, and can also be used as a retractor to expose the femoral head.

FIG. 5depicts how the center of rotation of the femoral head can be reproduced in accordance with a preferred embodiment of the present invention. First, distance A from the head to the lateral cortex is measured. After the femoral head is removed, distance B, from the cut surface to the lateral cortex, is measured. The diameter D of the femoral head is also measured. When these measurements are known, distance C is calculated using the formula
C=(A−D/2)−B

Distance C then represents the distance from the cut surface of the femoral neck that the prosthetic femoral head center-of-rotation should be placed in order to reproduce the pre-operative femoral head center-of-rotation.

In another embodiment shown inFIG. 6, compression screw620, preferably with washer645, is inserted through the lateral wall of the femur at location640and screwed into the body625of the femoral component. This simplifies the barrel nut portion of the design shown inFIG. 1. It would require that the screw620be of various lengths that would engage the body625of the prosthesis without reaching the depth of the hole in the femoral prosthesis. The body of the prosthesis would preferably be longer, using optional extension650to provide enough length so that the compression screw will be stable within the body of the prosthesis.

The remainder ofFIG. 6is similar toFIG. 1. In this FIG., femur600is shown with femoral neck605, joining member615, and prosthetic head610.

This embodiment provides an uncemented porous coated femoral prosthesis body625with a modular head610and joining member615. The body625of the prosthesis include threads655for receiving screw620.

As described in more detail below, fixation to the femur will be achieved by reaming the femoral neck605to accommodate a cylindrical porous coated sleeve body625, which is supported by a proximal collar and given distal stability with a compression screw620through the lateral wall of the femur just distal to the greater tuberosity (location640).

After insertion, the long axis of the body of the component body625will coincide with a longitudinal axis in the preoperative femur600corresponding to an imaginary line connecting the center of the femoral neck605with the center of the femoral head610. Resection of the femoral head will be measured such that the center of rotation of the femoral head610can be measured and reproduced as discussed with reference toFIG. 5. The femoral neck605will be reamed with a flat reamer that fits in the reamed canal of the femoral neck605to establish a flat surface. The proximal body625of the prosthesis will have the female end of a morse taper to allow the attachment of the femoral neck615.

Compression screw620passes through the center of the body of the prosthesis. The screw620is preferably smooth in the segment within the body of the prosthesis and has threads on the proximal end, for engaging threads655. The tunnel through the body of the prosthesis forms a snug fit around the smooth portion of the screw620. Screw620adds stability to the construct by giving antero-posterior and varus-valgus stability to the body625of the prosthesis and by compressing the prosthesis on the neck605of the femur600. These screws will be available in various lengths.

Male-male morse taper joining member615connects the body625of the prosthesis to the femoral head610. Adjustments in joining member neck length will occur in this segment with several lengths of joining member segments available for each femoral body and femoral head. The joining member segment needed to exactly reproduce the center of rotation of the femoral head will be known based on the amount of bone resected.

The femoral head610will have a female morse taper to connect to the joining member615. Femoral heads610will be of various diameters depending on the acetabulum. Ideally larger femoral head diameters (e.g., 36 mm to 60 mm) are used to both improve stability and prevent impingement of the neck on the acetabular rim. The femoral head610is preferably polished chrome-cobalt, as the industry standard, but other materials can be used.

FIG. 7shows a preferred embodiment of the femoral neck fixation prosthesis of the present invention. If the compression screw720, with washer745, is inserted through the lateral wall of the femur at740, the length of the body725of the prosthesis may not be long enough to provide adequate stability for the compression screw720. In order to provide this stability for the compression screw, a fixed length joining member760on the body of the prosthesis would be necessary to act as a joining member, abandoning the modular joining member (115inFIG. 1). The varied lengths required on the joining member would be incorporated into the femoral head either with separate individual lengths for each head diameter (2to3for each diameter femoral head) or by using an interposing piece of metal to provide additional neck length. The latter is done with several femoral components available on the market today.

The femoral neck fixation prosthesis is implanted by first preparing the femur for reception of the prosthesis. Referring toFIG. 8, several orientations and anatomical features relative to a femur811should first be defined to more easily understand the process of preparing the femur and implanting the prosthesis. As used herein, the term “medial” shall mean “pertaining to the middle,” while the term “lateral” shall mean “pertaining to the side.” The femur811includes a medial side813and a lateral side815. The term “proximal” shall mean “nearest the point of attachment, center of the body, or point of reference,” while the term “distal” shall mean “the opposite of proximal, or farthest from the center, from a medial line, or from the trunk.” The terms proximal and distal are generally used to convey positional or directional information relative to a particular feature, so it would not be entirely proper to refer to a proximal “side” of the femur or a distal “side” of the femur. However, these terms can be demonstrated by comparing some of the basic anatomy of the femur. Femur811includes a femoral head821, a femoral neck823, a shaft825, a greater trochanter827, and a lesser trochanter829. Since the femoral head811serves as a point of attachment when it is received by the acetabulum (not shown), the femoral head821is located proximal to the femoral neck823and the shaft825. The shaft825is located distal to both the femoral neck823and the femoral head821. As used herein the term “superior” shall mean “higher than or situated above something else,” while the term “inferior” shall mean “beneath or lower.” The term “anterior” shall mean “before or in front of” and shall generally refer to the ventral or abdominal side of the body. The term “posterior” shall mean “toward the rear” and shall generally refer to the back or dorsal side of the body. A posterior side831of the femur811is shown inFIG. 8, while the anterior side is hidden from view inFIG. 8.

A longitudinal axis845of the femoral neck is difficult to precisely define because the geometry of the femoral neck823is usually not perfectly cylindrical. Theoretically speaking, if the femoral neck823were sectioned along its length at a finite number of cross-sectional planes (e.g. B—B and C—C inFIG. 8), and the center of each cross-section were determined, the line passing through the center of rotation of the femoral head (described previously with reference toFIG. 5) and passing through an average of the centers of the cross-sections would likely represent the longitudinal axis845of the femoral neck823. In reality, it is difficult to locate the center of each cross-section of the femoral neck823. It is also difficult to locate the plane at which each cross-section would be taken. Theoretically, each cross-section is located at a plane perpendicular to the longitudinal axis845, but this presents a somewhat circular method for determining the orientation of the cross-sectional planes and the longitudinal axis845.

One method for determining the proper orientation of the cross-sectional planes would be to envision an isthmus849of the femoral neck823. The isthmus849is the narrowest point on the femoral neck823when viewed from the anterior or posterior side of the femur811. Visualization of the posterior side831of the femur811allows a lateral line to be constructed across the femoral neck823at the isthmus849. InFIG. 8, the line at section C—-C represents an isthmus plane851, which is a cross-sectional plane extending through the femur in an antero-posterior direction. The visualization of this plane at the isthmus849of the femoral neck823allows a close approximation of a plane that would be perpendicular to the longitudinal axis845of the femur811. Other cross-sectional planes visualized through the femoral neck823would be parallel to the isthmus plane at the isthmus849.

In practice, the femoral neck823is not actually cut at each of the cross-sectional planes discussed above. Rather, the visualization of these planes is helpful in determining, theoretically, where the longitudinal axis845of the femoral neck823would lie. It would be sufficient to define the longitudinal axis845as the line passing through the center of rotation of the femoral head821and the center of the femoral neck823at the isthmus849. However, as previously mentioned, it would also be appropriate and perhaps more accurate to define the longitudinal axis845as the line passing through the center of rotation of the femoral head821and the average of the centers of the femoral neck823taken at several cross-sections, all of which are parallel to the isthmus plane851. It should also be noted that for some patients, the center of rotation of the femoral head may not necessarily coincide with the longitudinal axis845.

Referring toFIG. 9, the visualization of the “center” of the femoral neck is not necessarily simple due to the varying geometry of the femoral neck823. For example, a cross-section taken at A—A in a region of transition between the femoral head821and the femoral neck823is approximately round. However, the cross-sectional shapes of the femoral neck823taken at B—B and C—C are not perfectly round, and instead have various protrusions and other anatomical features that make it difficult to locate the center point of the cross-section. A cross-section from a more proximal portion of the femoral neck823is illustrated at B—B and demonstrates that this portion of the neck is somewhat circular in shape. Cross-section C—C at the isthmus849of the femoral neck823illustrates several prominent features that cause the femoral neck823to deviate from a perfectly round shape. The features of the femoral neck at C—C include an antero-superior ridge850and a postero-inferior ridge855. The antero-superior ridge850is a pronounced feature of the femoral neck823at this part of the femoral neck823and joins the greater trochanter827in a region distal to the isthmus849. The postero-inferior ridge855is less pronounced and joins the lesser trochanter829in a region distal to the isthmus849. The femoral neck823includes a relatively flat superior surface857, while an inferior surface859is more rounded. These anatomical features of any particular femur will vary slightly and could vary greatly from person to person.

Referring still toFIGS. 8 and 9, the center of any given cross-section will be at the mean geometric center for any particular cross-section. When several cross-sections are visualized along the femoral neck823, the mean geometric centers of all the cross-sections may not be aligned such that the centers can be connected by a line. In this particular instance, a line representing longitudinal axis845could be drawn through the center of rotation of the femoral head and through the plurality of cross-sectional centers so as to minimize deviation with respect to the plurality of cross-sectional centers. If the femoral head is misshapen, the longitudinal axis845may be considered only with respect to the cross-sectional centers and not the center of rotation of the femoral head.

Alternatively, the center of each cross-section could be located based on the shape of the cancellous bone at that cross-section. Since the prosthesis according to the principles of the present invention is to be implanted within the cancellous bone, it may be more appropriate to define the center of the femoral neck823based on the shape and location of the cancellous bone. The center of each cross-section would be the point at which a circle circumscribed around the point would most fully contact the surrounding cortex.

The “location” and/or “visualization” of the longitudinal axis845of the femoral neck823is theoretical and is discussed to more easily explain how the femoral neck fixation prosthesis is oriented and implanted within the femur811. It is not necessarily required that the longitudinal axis845be found prior to implanting the prosthesis; however, it is important to note that in most cases, the femoral neck fixation prosthesis will be installed in the femur such that a longitudinal axis of the prosthesis is substantially coaxial to the longitudinal axis845of the femoral neck823as described above. This implantation could be accomplished by using non-invasive techniques such as X-rays or magnetic resonance imaging (MRI) to visualize and locate the longitudinal axis845of the femoral head823, but in most instances, the prosthesis will be implanted using specialized tools that properly orient the prosthesis based on anatomical landmarks on the femoral neck. We believe that the use of these tools and anatomical landmarks will closely align the prosthesis with the longitudinal axis of the femoral neck, thereby obviating the need for calculating or identifying the longitudinal axis during the procedure.

It will be appreciated by those of ordinary skill in the art that certain femoral anatomical variations among patients may result in the prosthesis being implanted such that the longitudinal axis of the prosthesis is not coaxial to the longitudinal axis845of the femoral neck823. In fact, the implantation of the prosthesis in some patients could result in the longitudinal axis of the prosthesis being located as much as 5 to 10 degrees from the longitudinal axis845of the femoral neck823.

Implantation of the femoral neck fixation prosthesis is accomplished by resecting the femoral head821, reaming at least one passage through the femoral neck, reaming the acetabulum, and implanting the femoral neck fixation prosthesis into the reamed passage. Access to the femoral head and femoral neck is accomplished by making a small incision in the gluteus maximus to expose the hip joint. The femoral head821is dislocated from the acetabulum in a manner similar to that employed in current hip arthroplasty procedures. The leg of the patient is then internally rotated (i.e. rotated such that the toe of the patient's foot are rotated toward a medial plane of the body) to expose the femoral head and neck through the incision. Following exposure, the femoral head may be resected as explained below from the internally rotated position. The remaining procedures (i.e. reaming the passages, reaming the acetabulum, and implanting the femoral neck fixation prosthesis) are performed as described below with the patient's leg in either the internally-rotated position or in a neutral position (i.e. non-rotated position). The procedures for preparing the femur and implanting the prosthesis could alternatively be accomplished by rotating the patient's leg externally if the location of the initial incision were moved.

Referring toFIGS. 10–13, a femoral neck clamp1011according to principles of the present invention assists in locating the cutting plane at which the femoral head821is to be resected. The femoral neck clamp1011does this by locating the isthmus849of the femoral neck823by grasping anatomical landmarks on the femoral neck, such as the antero-superior ridge850and the inferior region of the femoral neck823. Again, the isthmus849defines a line that is substantially perpendicular to the longitudinal axis845of the femoral neck823.

The femoral neck clamp1011includes an inferior clamping member1013and a superior clamping member1015. A locator shaft guide member1021includes a cylindrical passage1023and is attached to either the inferior clamping member1013or the superior clamping member1015. The superior clamping member1015preferably includes an arcuate region1025for securely gripping the antero-superior ridge850(seeFIG. 9) of the femoral neck823; however, the superior clamping member1015could be substantially flat with no arcuate region. The inferior clamping member1013preferably includes a proximal clasp1031and a distal clasp1033that are connected by a connecting member1035. The inferior clamping member1013cradles the inferior region of the femoral neck823with preferably at least two points of contact occurring between the femoral neck823and each of the proximal and distal clasps1031,1033. It is important to note that while it is preferred that the shape of the proximal and distal clasps1031,1033is V-shaped, the shape could be hemi-circular (seeFIG. 13A), square (seeFIG. 13B), polygonal (seeFIG. 13C), or any other shape that provides adequate contact with the femoral neck823. While the preferred embodiment includes the presence of a proximal and distal clasp, the inferior clamping member1013may include only one clasp that is preferably aligned with the superior clamping member1015to locate the isthmus849of the femoral neck823.

Referring still toFIGS. 10 and 11, the femoral neck clamp1011preferably includes a handle portion1041having a pair of handle members1043biased apart by a spring member1045. The spring member1045is preferably made from sheets of spring steel and shaped to hold the handle members1043apart in an open position. However, the spring member1045could be any device used to apply such a force, including without limitation a helical spring, a leaf spring, or a resilient bushing. A pair of rods1047is rigidly attached to one of the handle members, and each rod1047passes through an aperture1049in the other handle member1043. Since the handle members1043are not pivotally attached, the rods1047assist in guiding the movement of the handle members1043relative to one another. By applying a force to each handle member1043directed toward the other handle members1043(i.e. by squeezing the handle members1043), a surgeon can decrease the distance between the inferior and superior clamping members1013,1015in order to position the clamping members securely around the femoral neck. When the squeezing force applied to the handle members1043is released or relaxed, the spring member1045pushes the handle members1043apart, thereby returning the femoral neck clamp1011to the open position. The configuration of the handle members1043, rods1047, and spring member1045allow the inferior and superior clamping members1013,1015to move in translational, parallel fashion relative to one another when the handle members1043are squeezed. Since rotation of the handle members1043relative to one another is avoided, the inferior and superior clamping members1013,1015are allowed to more effectively grip the appropriate anatomical features of the femoral neck823. A locking member1051may be attached to the handle portion1041to lock the inferior and superior clamping members1013,1015once positioned around the femoral neck823. The locking member1051shown inFIG. 11is pivotally attached to one of the handle members1043and is rotatably positionable to engage a plurality of teeth1053on at least one of the rods1047. InFIG. 11, two locking members1051are shown.

The femoral neck clamp1011is used to locate the isthmus plane851, which is represented by a line inFIG. 12at the isthmus849of the femoral neck823. To find the isthmus plane851, the inferior and superior clamping members1013,1015are first positioned on inferior and superior sides of the femoral neck823, respectively, with the superior clamping member1015and the proximal clasp1031visually aligned with an area of the femoral neck823that appears to be the isthmus849. As the handle members1043are squeezed, the superior clamping member1015and the proximal clasp1031grip the femoral neck823in the area of the isthmus849. Further squeezing of the handle members1043and gentle side-to-side manipulation of the femoral neck clamp1011in a direction approximately parallel to the longitudinal axis845of the femoral neck823allows the superior clamping member1015and the proximal clasp1031to settle at the isthmus849of the femoral neck823. Further alignment of the femoral neck clamp1011is ensured by the distal clasp1033, which prevents the femoral neck clamp1011from rotating about the line representing isthmus plane851inFIG. 12. The distal clasp1033accomplishes this by providing a second point of contact for the inferior clamping member1013in the inferior region of the femoral neck823. Preventing rotation of the femoral neck clamp1011about the line representing isthmus plane851inFIG. 12could also be accomplished by having an inferior clamping member1013that included a single clasp with a wider area of contact on the inferior region of the femoral neck823. However, widening either the inferior clamping member1013or the superior clamping member1015too much will decrease the ability of the femoral neck clamp1011to find the isthmus849since the inferior and superior clamping members1013,1015will be unable to properly settle into the concave portions of the femoral neck823as illustrated inFIG. 12.

Both the inferior and superior clamping members1013,1015take advantage of anatomical landmarks present on the femoral neck823to locate the isthmus849and the isthmus plane851, which is typically substantially perpendicular to the longitudinal axis845of the femoral neck823. As previously mentioned, the superior clamping member1015primarily contacts and, depending on whether it includes an arcuate region1025, cradles the antero-superior ridge850(seeFIG. 13). The inferior clamping member1013, including the proximal and distal clasps1031,1033, preferably is formed in one of the shapes previously described (seeFIGS. 13–13C) to cradle the postero-inferior ridge855and other portions of the inferior region of the femoral neck823. The distal clasp1033of the inferior clamping member1013provides stability to the femoral neck clamp1011to prevent rotation of the femoral neck clamp1011about the line representing isthmus plane851inFIG. 12. The distal clasp1033is preferably not directly connected to either handle member1043, but rather is connected to proximal clasp1031by the connecting member1035, which allows rotation of the distal clasp1033relative to the proximal clasp1031. By connecting the distal clasp1033to the proximal clasp1031(as opposed to the handle members1043), the application of force through the handle members1043is directed primarily to the superior clamping member1015and the proximal clasp1031. This allows the superior clamping member1015and the proximal clasp1031to more easily locate the isthmus849of the femoral neck823, while the distal clasp1033maintains rotational stability of the femoral neck clamp1011without causing the superior clamping member1015and the proximal clasp1031to shift positions along the femoral neck823.

Referring toFIGS. 14–16in the drawings, several different variations of the connecting member1035are shown, each of which would be suitable to allow rotation of the distal clasp1033. InFIG. 14, a connecting member1411is rigidly connected to the distal clasp1033and pivotally connected to the proximal clasp1031. A torsion spring (not shown) is operably connected to the proximal clasp1031and the connecting member1411to bias the distal clasp1033toward the femoral neck823in a counter-clockwise direction (with respect to the view shown inFIG. 14). InFIG. 15, a connecting member1511is rigidly connected to both the proximal and distal clasps1031,1033. The connecting member1511is preferably made from a resilient material such as spring steel that allows rotation of the distal clasp1033relative to the proximal clasp1031, but provides sufficient force to the distal clasp1033to firmly contact the femoral neck823. InFIG. 16, a connecting member1611is rigidly attached to the distal clasp1033and is pivotally attached to the proximal clasp1031. The connecting member includes a slot1615; and a fastener1617, preferably a screw, a bolt, or a locking pin, is received through the slot1615and is attached to the proximal clasp1031. The fastener1617allows rotation of the distal clasp1033to be selectively chosen. After rotating the distal clasp1033enough to firmly contact the femoral neck823, the fastener can be tightened or locked in place to prevent further rotation of the distal clasp1033relative to the proximal clasp1031.

Referring again toFIGS. 10–12, the locator shaft guide member1021of the femoral neck clamp1011is connected to the superior clamping member1015or the handle member1043adjacent the superior clamping member1015. The locator shaft guide member1021is oriented such that the cylindrical passage1023of the locator shaft guide member1021is substantially parallel to the longitudinal axis845of the femoral neck823when the femoral neck clamp1011is finally positioned at the isthmus849. Typically, the locator shaft guide member1021will be rigidly connected to the superior clamping member1015because the anatomy of most femurs is such that the positioning of femoral neck clamp1011at the isthmus849will provide automatic, parallel alignment of the locator shaft guide member1021relative to the longitudinal axis845of the femoral neck823. However, it is conceivable that certain anatomical features of some femurs may prevent proper alignment of the locator shaft guide member1021, so the locator shaft guide member1021may be adjustably mounted to the superior clamping member1015to allow for rotational adjustment and visual alignment of the locator shaft guide member1021relative to the longitudinal axis845.

Referring toFIG. 17, a femoral neck clamp1711according to the principles of the present invention includes an inferior clamping member1713and a superior clamping member1715similar to those of femoral neck clamp1011. Femoral neck clamp1711includes a parallelogram, four-bar-linkage mechanism1721to provide translational movement (as opposed to rotational movement) of the inferior clamping member1713relative to the superior clamping member1715. Linkage mechanism1721includes an inferior handle member1743pivotally connected to a superior handle member1745. Superior handle member1745is pivotally connected at one end to a coupler link1747that is rigidly connected to the superior clamping member1715. A side link1751is pivotally connected at one end to the coupler link1747and at another end to the inferior handle member1743. The side link1751and the portion of the superior handle member1745extending between the inferior handle member1743and the coupler link1747are preferably parallel and equal in length. The coupler link1747and the portion of the inferior handle member1743extending between the superior handle member1745and the side link1751are preferably parallel and equal in length. A torsion spring1753, or other spring mechanism, may be operably connected to the inferior handle member1743and superior handle member1745to bias the handle members1743,1745, and thus the inferior and superior clamping members1713,1715, apart. A locking member1755may be pivotally attached to an end of either the inferior or superior handle members1743,1745. Preferably, the locking member1755includes a plurality of teeth1759adapted to engage the other handle member1743,1745and thus lock the inferior clamping member1713relative to the superior clamping member1715. A locator shaft guide member1765is connected to either the inferior clamping member1713or the superior clamping member1715similar to locator shaft guide member1021ofFIG. 12. Alternatively, the locator shaft guide member1765could be connected to coupler link1747, inferior handle member1743, or superior handle member1745near the inferior and superior clamping members1713,1715.

Referring toFIG. 18, a femoral neck clamp1811according to the principles of the present invention includes an inferior clamping member1813and a superior clamping member1815similar to those of femoral neck clamp1011. Femoral neck clamp1811further includes an inferior handle member1843pivotally connected to a superior handle member1845. A torsion spring1853, or other spring mechanism, may be operably connected to the inferior handle member1843and superior handle member1845to bias the handle members1843,1845, and thus the inferior and superior clamping members1813,1815, apart. A locking member1855may be pivotally attached to an end of either the inferior or superior handle members1843,1845. Preferably, the locking member1855includes a plurality of teeth1859adapted to engage the other handle member1843,1845and thus lock the inferior clamping member1813relative to the superior clamping member1815. A locator shaft guide member1865is connected to either the inferior clamping member1813or the superior clamping member1815similar to locator shaft guide member1013ofFIG. 12.

Referring toFIG. 19, the femoral neck clamp1011(could also be femoral neck clamp1711or1811) has been positioned around the femoral neck823at the isthmus849such that the superior clamping member1015and the proximal clasp1031of the inferior clamping member1013are aligned with the isthmus plane851. The distal clasp1033also engages the femoral neck823to prevent rotation of the femoral neck clamp1011about the line representing isthmus plane851. Following positioning of the femoral neck clamp1011at the isthmus849, the locator shaft guide member1021is automatically aligned such that a longitudinal axis of the cylindrical passage1023of the locator shaft guide member1021is oriented at an angle of approximately ninety (90) degrees to the isthmus plane851.

A locator shaft1911is positioned within the cylindrical passage1023of the locator shaft guide member1021after the femoral neck clamp1011has been positioned at the isthmus849of the femoral neck823. A base plate1915is rigidly connected to an end of the locator shaft1911such that following insertion of the locator shaft1911in the cylindrical passage1023, the locator shaft1911can be advanced in a distal/lateral direction until the base plate1915abuts the femoral head821. Indicia1921in the form of ruled demarcations is printed along the locator shaft1911for accurately positioning a pin locator guide1925, which is slidingly received on the locator shaft1911. Pin locator guide1925preferably includes at least two spaced apart holes1931that may be located on one side of the locator shaft1911, or as illustrated inFIG. 19, may be located on opposite sides of the locator shaft1911. Holes1931are positioned on the pin locator guide1925such that a line connecting the center of the holes1931is preferably parallel to the isthmus plane851.

Referring toFIGS. 19 and 20, by slidably positioning the pin locator guide1925along the locator shaft1911a selectable distance from the proximal end of the femoral head821, pins2011can be inserted through the holes1931on the pin locator guide1925. The placement of the pins2011in the femoral head821fixes the previously determined orientation of the isthmus plane851, which allows the femoral neck clamp1011to be removed from the femur. InFIG. 20, a cutting guide2021includes a pair of holes2027that are spaced apart the same distance as the holes on the pin locator guide1925. The cutting guide2021is placed over the pins2011such that the pins2011are received by the holes2027. A cutting slot2025is positioned on the cutting guide2021such that it is oriented substantially parallel to a line connecting the centers of the two holes2027. When installed on the pins2011as shown inFIG. 20, the cutting guide2021places the cutting slot2025a known distance from the pins2011to allow resection of the femoral head821along a cutting plane (not shown) that is substantially parallel to the isthmus plane851. The femoral head821is resected from the femur811by inserting a cutting blade or other cutting tool through the cutting slot2025and cutting through that portion of the femur811.

As mentioned previously, the locator shaft1911includes indicia1921in the form of ruled demarcations that are spaced apart precise distances. These demarcations can be used to precisely locate the cutting plane relative to the proximal end of the femoral head821. The amount of resection that will be performed depends on several factors. A prosthetic femoral head will be chosen to match the measured diameter of the patient's native femoral head. This is done to insure that the center of rotation is closely matched by the prosthesis and that the length of the patient's leg is not significantly lengthened or shortened. Based on the diameter chosen for the prosthetic femoral head, a height of the prosthetic femoral head (measured along longitudinal axis845) will be known. This height equates to the amount of bone resected from the proximal end of the native femoral head823. Since the distance between the holes2027on the cutting guide2021and the cutting slot2025is known, the pin locator guide1925can be accurately positioned along the locator shaft1911using the indicia1921to place the pin locator guide1925according to the amount of bone that needs to be resected. The placement of the pins2011using the pin locator guide1925then allows the cutting slot2025to be accurately positioned at the correct location to remove the correct length of bone.

It will be apparent to one of ordinary skill in the art that the cutting guide2021of the present invention could be combined with the femoral neck clamp1011to eliminate the need for a locator shaft1911and a pin locator guide1925. The combination clamp and cutting guide would allow the clamp to be positioned at the isthmus849of the femoral neck823as previously described, but would provide a slot or other guide to allow resection of the femoral head along a cutting plane substantially parallel to the isthmus plane851. The slot or guide would be adjustable relative to the isthmus plane851to allow a measured amount of bone to be resected from the femur811. A cutting guide that aligns the cutting plane a measured distance from the isthmus plane851would be particularly useful in the event that the femoral head is missing, deformed, substantially misshapen, or broken. Measurements could be performed preoperatively using radiographic measurement techniques (e.g. X-ray).

Referring toFIG. 20A, a method of resecting a femoral head from a femur having a femoral neck2051is illustrated. The first step at2055includes positioning a locator shaft adjacent an exterior surface of the femoral head and substantially parallel to a longitudinal axis of the femoral neck. At step2059a pin locator guide having a least two holes is positioned along the locator shaft. At step2063a pin is inserted through each of the two holes in the pin locator guide and into the femoral head. The femoral head is resected by aligning a cutting guide relative to the pins at step2065.

Following resection of the femoral head821, a proximal neck surface2111is exposed that is substantially parallel to the isthmus plane851. Progressive reaming and drilling of the femoral neck823is needed to prepare passages between the proximal neck surface2111and the lateral side815of the femur821. With the patient's leg still in an internally rotated position (or alternatively in an externally rotated position), a starter guide2121having a positioning portion2125and a guide portion2127is placed against the proximal neck surface2111such that the surface of the positioning portion2125opposite the guide portion2127mates with the proximal neck surface2111. The starter guide2121further includes a guide passage2131that passes through both the guide portion2127and the positioning portion2125such that a longitudinal axis of the guide passage2131is substantially perpendicular to the proximal neck surface2111when the starter guide2121is placed against the proximal neck surface2111. A starter passage, or main passage, or primary passage2141(represented inFIG. 21by dashed lines) is formed in the femoral neck823from the proximal neck surface2111by first drilling a small hole2145using a drill bit or other boring tool placed in the guide passage2131. The starter passage is preferably drilled only partially into the femoral neck, and not through the lateral side815of the femur. When placing the starter guide2121and drilling the hole2145, it is preferred to visualize the approximate center of the femoral neck on the proximal neck surface2111so that the hole2145is approximately centered within the femoral neck823.

After drilling the hole2145, the starter guide2121is removed from the proximal neck surface2111, and the femoral neck823is progressively reamed until the hole2145extends to the cortical bone of the femoral neck823, thereby forming the starter passage2141. In practice, depending on the anatomical shape of the patient's femoral neck823, it may only be possible to form the starter passage2141to contact the cortical bone at two points of contact. It is of course preferable to maximize the number of contacts of the cortical bone, and in most instances, it will be possible to contact the cortical bone in at least three locations without significantly decreasing the wall thickness of the cortex in any location. The starter passage2141is reamed to a depth that is preferably equal to the longitudinal length of the body125,625,725(seeFIGS. 1,6and7) of the femoral neck prosthesis. The final diameter of the starter passage2141, which is determined by how much reaming is needed to contact the cortical bone, will be slightly less than the chosen diameter of the body125,625,725of the prosthesis.

The method for forming the starter passage2141described above is largely based on visualization of the center of the femoral neck and formation of a hole2145. In an alternative embodiment, a guide may be placed flush against the proximal neck surface2111to orient a reamer at a ninety (90) degree angle to the proximal neck surface2111and center the reamer relative to the longitudinal axis of the femoral neck. The neck is sequentially reamed until the starter passage2141extends to the cortex. In another embodiment, a guide pin may be inserted into the femoral neck substantially parallel to the longitudinal axis of the femoral neck. The pin may be placed based on visualization or guided into place with a guide that is fixed relative to the femoral neck. The guide pin would be used to direct sequential reaming of the starter passage2141.

Referring toFIGS. 22 and 23, a drilling guide2211having an anchor member2215rigidly connected by a connecting member2217to an alignment sleeve2219is used to drill a distal passage, or fastener passage, or secondary passage2221(represented inFIG. 22by dashed lines) from the lateral side815of the femur811. The alignment sleeve2219includes an alignment passage2225for receiving a drill bit or other boring tool. The connecting member2217may be C-shaped and connects the anchor member2215to the alignment sleeve2219such that a longitudinal axis of the alignment passage2225is coaxial to the longitudinal axis of the anchor member2215, both of which are coaxial to a longitudinal axis2227of the drilling guide2211. The anchor member2215is cylindrical and sized to fit within the starter passage2141. The anchor member2215could be interchangeable to allow different diameters to be used to properly fit within the starter passage2141of a particular patient. Alternatively, the anchor member2215could be tapered to allow a snug fit within starter passages2141of several different diameters. The anchor member2215may also include a collar2231for further stabilizing the drilling guide2211against the proximal neck surface2111when inserted into the starter passage2141.

After positioning the anchor member2215within the starter passage2141, the alignment sleeve2219is located on the lateral side815of the femur811. The patient's skin and other soft tissue2233are located between the alignment sleeve2219and the femur821. The leg of the patient is then rotated to a neutral position, and an incision2235is made through the soft tissue of the patient in the vicinity of the alignment sleeve2219. A drilling bit2241or other boring tool is inserted through the alignment passage2225of the alignment sleeve2219for drilling the distal passage2221to join the starter passage2141. Because the alignment sleeve2219is coaxial to the anchor member2215and because the anchor member2215is securely positioned within the starter passage2141, the distal passage2221is easily formed coaxial to the starter passage2221. As shown inFIG. 22, the distal passage2221is typically smaller in diameter than the starter passage2141, since the distal passage2221will receive the fastener120,620,720(seeFIGS. 1,6, and7) for securing to the body126,625,725of the femoral neck fixation prosthesis.

The primary reason for using a drilling guide2211to complete drilling through the femur is that it is less desirable to drill a hole completely through the femur from the proximal neck surface2111toward the lateral side815of the femur811. When drilling from the proximal neck surface2111, the patient's leg would be in the internally rotated position. It is not as safe to drill through the lateral side815of the femur811when the leg is internally rotated because the drill bit may contact and sever vital anatomy, such as the femoral artery or other vessels and nerves, upon exiting the femur811. Since use of the drilling guide2211allows the leg to be rotated back to the neutral position, drilling can proceed from the lateral side815of the femur811without fear of contacting vital anatomy.

Referring toFIG. 23A, a method of preparing a femur for implantation of a femoral neck fixation prosthesis2321includes two steps. The first step at2325includes first forming a main passage in the femoral neck from a medial side of the femur substantially coaxial to a longitudinal axis of a femoral neck. The second step at2329includes second forming a secondary passage from a lateral side of the femur that is coaxial to and joins the main passage.

Although the preparation of the femur for implantation of the prosthesis includes forming two separate passages from different sides of the femur, the starter and distal passages could be formed from the same side of the femur. Following the formation of the starter passage2141, a guide may be placed within the starter passage2141to guide drilling of the distal passage2221from the proximal side of the femoral neck823. Since the leg of the patient would likely be in an internally rotated position during this drilling procedure, care would be taken to only slightly penetrate the cortex on the lateral side of the femur821. This would help avoid major arteries and nerves in the patient's leg. After forming both the starter and distal passages2141,2221from the medial side of the femur, the drilling guide2211could be used to place the fastener120,620,720in the femur during the implantation of the femoral neck prosthesis, which is described in more detail below.

After forming both the starter passage2141and the distal passage2221, the femur811is capable of receiving the femoral neck fixation prosthesis. However, prior to implantation of the prosthesis, it may be desirable to prepare the acetabulum for receipt of an acetabular component (not shown) that will mate with the head of the femoral neck fixation prosthesis. The starter and distal passages2141,2221may be used to guide the preparation of the acetabulum, which initially involves reaming.

Referring toFIGS. 24 and 25, a reamer path protector2411includes an insertion end2415and a handle end2419. The insertion end preferably includes a plurality of threads2421, while the handle end2419includes a hand guard2425. A passage2427passes through the reamer path protector2411. A femoral neck liner2431is also provided and includes a main body2435having a passage2437and a collar2439. The passage2437includes internal threads2441at an end of the main body2335opposite collar2339.

In operation, the reamer path protector2411is inserted from the lateral side815of the femur811and into the distal passage2221. The femoral neck liner2431is inserted from the proximal neck surface2111into the starter passage2141until the collar2439mates with the proximal neck surface2111. The femoral neck liner2431is sized in diameter the same as or slightly less than the diameter of the starter passage2141. As is the case with the anchor member2215(seeFIG. 22) discussed previously, the femoral neck liner2431could be provided in different sizes to fit variously sized starter passages2141, or the femoral neck liner2431could be tapered. After inserting the femoral neck liner2431, the reamer path protector2411is advanced further into the distal passage2221until it contacts the femoral neck liner2431. The reamer path protector2411is then rotated to engage the threads2421with internal threads2441. The attachment mechanism between the reamer path protector2411and the femoral neck liner2431is not required to be accomplished by a threaded connection. The connection could be formed by any mechanism that would allow the components to be easily disassembled following reaming of the acetabulum.

When the reamer path protector2411is securely fastened to the femoral neck liner2431, a sufficient portion of the reamer path protector2411remains extending outside of the femur811to allow gripping by the surgeon or other person who will ream the acetabulum. The reamer path protector2411is therefore gripped in this area, and a reamer shaft2451is inserted through the passage2427and the passage2437to connect to a reamer head2453near the proximal neck surface2111. The acetabulum is then reamed by rotating the patient's leg into a neutral position and applying power to rotate the reamer shaft2451and reamer head2453from the lateral side815of the femur811. Some internal rotation of the femur811may also be necessary depending on the position of the femur811relative to flexion/extension and abduction/adduction. The acetabulum is progressively reamed until enough material has been removed to accommodate the acetabular component of the prosthesis. By reaming the acetabulum through the distal and starter passages2221,2141formed in the femur811, a highly effective reaming process is accomplished. Since the patient's leg is positioned in the neutral position during the reaming process, and since the reamer head2353is connected to the reamer shaft2451along the same axis as that about which the head and body of the prosthesis will be oriented, the acetabulum can be efficiently reamed to closely match the shape of the head of the prosthesis.

Following the reaming process, the reamer head2453is removed from the reamer shaft2451, and the reamer shaft2451is removed from the femoral neck liner2431and the reamer path protector2411. An impactor shaft (not shown) may be inserted into the reamer path protector2411and the femoral neck liner2431similar to the original insertion of the reamer shaft2451. The impactor shaft is releasably connected to an impactor head (not shown) near the proximal neck surface2111. The impactor shaft and impactor head are used to apply force to and seat the acetabular component of the prosthesis in the reamed acetabulum. After the acetabular component is firmly seated, the impactor shaft, impactor head, femoral neck liner2431, and the reamer path protector2411are disassembled and removed from the femur811

Referring toFIG. 25A, a method for preparing an acetabulum for receiving a head of a femoral prosthesis2521is illustrated. A first step2525includes forming a primary passage within the femur substantially coaxial to a longitudinal axis of the femoral neck. At step2529, a secondary passage is formed from a lateral side of the femur that joins and is coaxial to the primary passage. Step2531includes inserting a reamer path protector having a reamer passage within the secondary passage. A reamer shaft is inserted through the reamer passage at step2535. A reamer head is attached to the reamer shaft at step2539, and the acetabulum is reamed at step2541.

The femoral neck fixation prosthesis is implanted into the femur811by inserting the body125,625,725of the prosthesis into the starter passage2141. Preferably, the diameter of the body125,625,725is sized slightly larger than the diameter of the starter passage2141such that a secure fit within the starter passage2141is obtained when the body125,625,725is driven into the starter passage2141. The starter passage2141is deep enough to accommodate the body125,625,725of the prosthesis and allow the collar of the body125,625,725to mate with the proximal neck surface2111.

The fastener120,620,720is then inserted into the distal passage2221from the lateral side815of the femur811. To properly feed the fastener120,620,720through the soft tissue2233(seeFIG. 22) of the patient's leg and into the distal passage2221, a small diameter pin can be used to locate and mark the passage when the leg is in the neutral position. The fastener120,620,720, which may be canullated (i.e. having a passage down the center of the shaft), can then be placed onto the pin and fed into the distal passage2221. The fastener120,620,720is advanced into the distal passage2221until it contacts the body125,625,725of the prosthesis, at which time the fastener120,620,720is threadingly connected to the body125,625,725to secure the body within the femur811. The head110,610,710of the prosthesis is then installed on the morse taper115,615,760of the prosthesis be impacting the head of the prosthesis.

Referring toFIG. 26, a method of implanting a prosthesis in a femur2611according the principles of the present invention is illustrated. At step2615a main passage is formed in the femoral neck from a medial side of the femur substantially coaxial to a longitudinal axis of the femoral neck. At step2619a fastener passage is formed from a lateral side of the femur that is coaxial to and joins the main passage. Step2623includes providing a femoral neck prosthesis having a body member connected to a head member. At step2627a portion of the body member is inserted in the main passage. A fastener is inserted into the fastener passage at step2633. At step2637the fastener is connected to the body member to secure the femoral neck prosthesis within the femur.

As will be recognized by those skilled in the art, the innovative concepts described in the present application can be modified and varied over a tremendous range of applications, and accordingly the scope of patented subject matter is not limited by any of the specific exemplary teachings given.