Intramedullary nail and implant system comprising the nail

An intramedullary nail has a posterior side, an anterior side, a proximal portion and a distal portion is described. A transverse bore is arranged in the proximal portion and is configured to receive a bone engagement member. The transverse bore includes at least two recesses formed at an inner wall of the transverse bore, wherein one recess is arranged on the posterior side and the other recess is arranged on the anterior side of the transverse bore of the intramedullary nail.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from European Patent Application No. 12 006 837.4 filed Oct. 1, 2012, the disclosure of which is hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present disclosure generally relates to an intramedullary nail for internal fixation of a bone, such as a femur. The disclosure further relates to an implant system for use in orthopaedic surgery and to a method of manufacturing an intramedullary nail.

Femur fractures commonly occur in the femoral neck and the trochanteric regions. Today, trochanteric and sub-trochanteric femur fractures are treated with an intramedullary nail having a transverse bore in a proximal portion to receive a femoral neck screw usually provided in the form of a lag screw. Such a nail is shown in U.S. Pat. Nos. 5,176,681 and 5,454,813, the disclosures of which are incorporated herein by reference.

For fracture treatment the intramedullary nail is, in a first step, fitted in the intramedullary canal of the femur. Then the lag screw is passed through the transverse bore of the intramedullary nail, through the neck of the femur and into the femoral head. When implemented, a connecting fastener is inserted through a bore in a distal portion of the intramedullary nail to fasten the intramedullary nail to bone.

The lag screw is designed to transfer the load from the femoral head into a shaft of the nail while bridging the fracture line to allow fast and secure fracture healing. Further, the lag screw is allowed to slide in the intramedullary nail in accordance with the sintering of the femoral fracture.

U.S. Pat. No. 7,763,022 B2 relates to an intramedullary nail having a transverse bore for receiving a femoral lag screw at the proximal portion. The transverse bore has at an inlet opening a notch in form of an outer rounded edge. The notch ensures reduction of stress peaks in the end portions of the bore when the femoral lag screw is loaded (e.g., by the force of the patient's weight), specifically at the inlet opening.

U.S. 201000174284 relates to an intramedullary nail with a proximal portion including a cutout positioned adjacent to a transverse bore on the lateral side of the intramedullary nail.

U.S. Pat. Nos. 7,527,627 and 7,780,667 relate to an implant system with an intramedullary nail having a proximal transverse bore formed by two overlapping circular holes, wherein the proximal circular hole is smaller in diameter than a distal circular hole. The resulting 8-shaped transverse bore receives a fastener assembly comprising a lag screw used in conjunction with a compression screw.

It has been found that non-unions of peri and intratrochanteric fractures as well as sub-trochanteric fractures treated with an intramedullary nail can lead to overloading and thus breakage of the implant. Specifically, conventional intramedullary nails may be damaged at their smallest cross sectional area of the proximal portion, i.e., in the area of the transverse bore, for example during drilling with a lag screw step drill. Such a damage may lead to a weakening of the intramedullary nail in a critical area and result in brakeage of the implant when it is overloaded, (e.g., by the patient's weight). Moreover, the stability between the intramedullary nail and the femoral lag screw is decreased in such a situation and the implant system may fail to hold the fracture in a stable configuration, such that a well-defined compressive sliding of the femoral lag screw can no longer be guaranteed.

BRIEF SUMMARY OF THE INVENTION

Aspects of the present disclosure are directed to the provision of an intramedullary nail and an implant system that facilitate a rapid healing of a femur fracture and results in a stable configuration of both the implant system and the fracture.

According to a first aspect, there is provided an intramedullary nail comprising, when implanted in the femur, a posterior side, an anterior side, a proximal portion, a distal portion and a transverse bore arranged in the proximal portion and configured to receive a bone engagement member. The transverse bore includes at least two recesses formed on an inner wall of the transverse bore, wherein one recess is arranged on the posterior side and the other recess is arranged on the anterior side of the transverse bore of the implanted intramedullary nail.

In one embodiment, each of the at least two recesses may define a length along the inner wall in a direction of a bore axis of the transverse bore. The length of each recess may be less than a length of the transverse bore along the bore axis.

The transverse bore has an inlet opening, wherein each of the at least two recesses may open out into the inlet opening of the transverse bore. Each of the at least two recesses may substantially extend in a direction of the bore axis of the transverse bore. Each of the at least two recesses may substantially extend from a lateral side towards a medial side of the intramedullary nail.

Each of the at least two recesses can have an oblique extension relative to an extension of the bore axis of the transverse bore. Further, each of the at least two recesses may be formed as a groove. In one implementation, each of the at least two recesses may be concave (e.g., V- or C-shaped) in cross-section. Moreover, each recess can have a crescent shape in cross section.

Each of the at least two recesses may define an arc segment in cross-section which extends over an angle with respect to the bore axis of the transverse bore. The angle can lie between 5° and 175°. The angle may specifically lie between 20° and 100°. Further, each of the at least two recesses may define an arc segment in cross-section, wherein each recess has a width along the arc segment which lie between 1 mm and 10 mm. For example, the width along the arc segment may lie between 3 mm and 8 mm.

The transverse bore may define a first diameter which is oriented substantially parallel to a longitudinal axis of the proximal portion and a second diameter which is oriented substantially perpendicular to the longitudinal axis of the proximal portion, wherein the second diameter is greater than the first diameter in at least a portion of the transverse bore. Further, the transverse bore may define a bore axis which is oriented obliquely with respect to the longitudinal axis of the proximal portion.

In one embodiment, the at least two recesses of the transverse bore may be arranged adjacent to each other on opposite sides of the bore axis of the transverse bore. The transverse bore can have one of flattened and rounded edge portions in a region of at least one of an inlet opening and an outlet opening. Further, the intramedullary nail can include a cannulation or channel substantially along a longitudinal axis of the intramedullary nail.

According to a further aspect, there is provided an implant system for use in orthopaedic surgery for fixation of bone. The implant system comprises an intramedullary nail as generally configured and described above and hereinafter, and a bone fastener configured to penetrate the transverse bore of the intramedullary nail.

In the aspect described above, the transverse bore of the intramedullary nail may define a bore axis which is substantially parallel to or congruent with a longitudinal axis of the bone fastener. Further, the bone fastener can be a sliding screw (e.g., a lag screw or femoral neck screw) configured to be slidably received within the transverse bore of the intramedullary nail.

According to a further aspect, there is provided a method of manufacturing an intramedullary nail having a posterior side, an anterior side, a proximal portion, a distal portion and a transverse bore arranged in the proximal portion and configured to receive a bone engagement member. The method comprises the step of guiding a milling tool for producing at least two recesses formed at an inner wall of the transverse bore in such a way that one recess is arranged on the posterior side and the other recess is arranged on the anterior side of the transverse bore of the intramedullary nail.

As used herein when referring to bones or other parts of the body, the term “proximal” means close to the heart and the term “distal” means more distant from the heart. The term “inferior” means toward the feet and the term “superior” means toward the head. The term “anterior” means toward the front part or the face and the term “posterior” means toward the back of the body. The term “medial” means toward the midline of the body and the term “lateral” means away from the midline of the body.

DETAILED DESCRIPTION

In the following description of exemplary embodiments, the same or similar components will be denoted by identical reference numerals. It will be appreciated that while the following embodiments will primarily be described with respect to the treatment of a femur, the implant presented herein, with suitable modifications, could also be used for treatment of other bones.

Referring toFIG. 1, there is shown a lateral side view of an embodiment of an intramedullary nail10for use in orthopaedic surgery for fixation of bone, such as a femur (not shown inFIG. 1). The intramedullary nail10is made of a biocompatible material such as stainless steel, titanium or a titanium alloy. The intramedullary nail10includes a rod-shaped body insertable into the inner cavity of a bone (marrow cavity), e.g., into the intramedullary canal of a femur.

The intramedullary nail10includes a proximal portion12, a distal portion14and an intermediate portion16therebetween. Thus, the intermediate portion16connects the proximal portion12with the distal portion14. As shown inFIG. 1, the intramedullary nail10tapers in a direction from the proximal portion12to the distal portion14. The distal portion is longer than the proximal portion12. The intermediate portion16located between the proximal portion12and the distal portion14is bent for anatomical reasons.

The intramedullary nail10has a substantially circular cross-section over its entire length. The proximal portion12and the distal portion14of the intramedullary nail10have a substantially cylindrical shape. The proximal portion12of the intramedullary nail10has a diameter sufficient to accommodate a transverse bore20therein. While in the present embodiment only a single transverse bore20is present, in other embodiments multiple (e.g., two or more) similar transverse bores may be provided in the proximal portion12. The distal portion14has a smaller diameter than the proximal portion12, adapted to the shape of the marrow cavity of the femur in order to facilitate the insertion of the distal portion14into the intramedullary canal. For the same reason, the distal portion14has a conical tip portion18at its distal end. The intermediate portion16connecting the proximal portion12and the distal portion14substantially tapers in a direction from the proximal portion12to the distal portion14.

The proximal portion12of the intramedullary nail10defines a longitudinal axis22and includes a connecting portion in form of a recess24for receiving an end cap or a surgical tool, such as a holding instrument or targeting instrument (not shown inFIG. 1) at the upper rim of the proximal portion12. The distal portion14likewise defines a longitudinal axis26which is angled with respect to the longitudinal axis22of the proximal portion12. Further, the distal portion14includes an opening28in form of an elongated through hole. The elongated through hole28is formed at an end of the distal portion14of the intramedullary nail10for receiving a bone fastener, such as a connecting fastener (e.g., a locking screw). The bone fastener is used to fasten and securely fix the intramedullary nail10to bone.

Further, the intramedullary nail10has a cannulation channel30axially extending through the intramedullary nail10. The channel30may receive a surgical wire (not shown inFIG. 1), such as a Kirschner wire, for guiding the intramedullary nail10to and through the bone.

As shown inFIG. 1, the transverse bore20located at the proximal portion12has flattened and rounded edge portions32and34. Further, the transverse bore20includes two recesses36, or pockets, formed at an inner wall38of the transverse bore20. Each of the two recesses36substantially extends along the transverse bore20. In the present case, each of the two recesses substantially extends from a lateral side towards a medial side of the intramedullary nail10and may extend completely through the bore.

The terms medial and lateral are standard anatomical terms of direction and denote a direction toward the center of a median plane of a body and the opposite direction from the center to the side, respectively. With respect to the present disclosure and the exemplary embodiments, the medial and lateral directions may generally lie within a plane including the longitudinal axis22of the proximal portion12(or the longitudinal axis of the intramedullary nail10) and an axis of the transverse bore20. In such a case, the medial side of the intramedullary nail10may be a side facing towards the outgoing side of the transverse bore20(e.g., towards a tip of a bone engagement member penetrating the transverse bore20), whereas the lateral side may be a side facing towards the ingoing side of the transverse bore20(e.g., towards a head of the bone engagement member). In the present exemplary case, the intramedullary nail10is anatomically shaped so that the intramedullary nail10inherently defines the medial and lateral sides, for example with respect to its bent portion (e.g., as embodied by the bent intermediate portion16of the intramedullary nail10) resulting in an inclination of the transverse bore20.

FIG. 2shows a cross-sectional view of the intramedullary nail embodiment shown inFIG. 1along the line A-A, i.e., along an imaginary longitudinal axis of the intramedullary nail10. As shown inFIG. 2, the proximal portion12of the intramedullary nail10includes a compartment40for reception of an interlocking pin or set screw (both not shown inFIG. 2) that engages a bone engagement member received by the transverse bore20. In the present embodiment, the compartment40of the proximal portion12is co-axial with the longitudinal axis22of the proximal portion12. The compartment40may include an internal thread which mates with a corresponding thread of a set screw. As further shown inFIG. 1, the compartment40opens out in a distal direction into the transverse bore20of the proximal portion12.

Still referring toFIG. 2, a bore axis42of the transverse bore20is angled with respect to the longitudinal axis22of the proximal portion12, such that the longitudinal axis22of the transverse bore20has an oblique extension relative to an axial extension of the proximal portion12. In other words, the bore axis is oriented obliquely with respect to the longitudinal axis22of the proximal portion12. Thus, the bore axis42of the transverse bore20is inclined at an angle α with respect to the longitudinal axis22of the proximal portion12. The bore axis42of the transverse bone20is further inclined at an angle β with respect to the longitudinal axis26of the distal portion14. These angles α and β may lie between 50° and 150°. For example, the angle α of the bore axis42of the transverse bore20with respect to the longitudinal axis22of the proximal portion12may lie between 90° and 140°. Further, the angle β of the bore axis42of the transverse bore20with respect to the longitudinal axis26of the distal portion26may lie between 90° and 140° as well. In the present embodiment, the angle α is approximately 126° and the angle β is approximately 130°.

As further shown inFIG. 2, the transverse bone20of the proximal portion12substantially extends in a direction from a lateral side to a medial side of the intramedullary nail10. The transverse bore20has an inlet opening44and an outlet opening46for the bone engagement member (not shown inFIG. 2). The inlet opening44faces away from the head of the femur when the intramedullary nail10has been driven into the bone canal. As shown inFIG. 2, each of the two recesses36opens out into the inlet opening44of the transverse bore20.

FIG. 3illustrates a detailed side view of the transverse bore20of the proximal portion12denoted by Y inFIG. 1.FIG. 4illustrates a perspective view thereof.

As shown inFIGS. 3 and 4, the inlet opening44opens out into a notch, or depression, defined by the outer rounded edge32and the flattened edge34. The depression has an approximately square contour with rounded corners. An outer edge of the depression is located in the outer contour of the proximal portion12. An inner edge50of the depression is located within the outer edge48and defines the inlet opening44. As illustrated inFIGS. 3 and 4, surface portions which partially are beveled or chamfered are formed between the outer edge48and the inner edge50of the notch.

As illustrated inFIG. 3, each of the recesses36has generally a concave shape in cross-section. Further, one of the two recesses36is arranged on the posterior side (e.g., the left side inFIG. 3) and the other recess36is arranged on the anterior side (e.g., the right side inFIG. 3) of the intramedullary nail10, i.e., on the posterior side and the anterior side of the transverse bore20, respectively. In other words, the two recesses36of the transverse bore20are arranged across from each other on opposite sides of the bore axis42of the transverse bore20.

The terms anterior and posterior are standard anatomical terms of direction and denote a direction toward the front of a body (ventral) and the opposite direction toward the back of the body (dorsal), respectively. With respect to the present disclosure and the exemplary embodiments, the anterior and posterior directions may generally lie within a plane including the longitudinal axis22of the proximal portion12and a diameter of the transverse bore20. In many cases, an intramedullary nail will be anatomically configured so that the intramedullary nail inherently defines the anterior and posterior sides.

As illustrated inFIG. 3, each recess36formed at the inner wall38of the transverse bore20defines an arc segment52in cross-section. The arc segment52of each recess36extends over an angle γ with respect to the bore axis42of the transverse bore20. The angle γ of the arc segment52can lie between 5° and 175°. For example, the angle γ of the arc segment may lie between 45° and 120°, and is in the present embodiment approximately 80°. Further, each of the two recesses36has a width wr along the arc segment52. The width wr along the arc segment52of each recess36may between 2 mm and 14 mm. In the present embodiment, the width wr is approximately 8 mm.

As further illustrated inFIGS. 3 and 4, each arc segment52is defined by three (or, in other embodiments, more or less) radii R1, R2and R3which define the concave shape of the recess36. Thus, the cross-section of each recess36can be divided into three regions separated from each other along the arc segment. As illustrated inFIGS. 3 and 4, each recess36has an intermediate region54and two outer regions56adjacent thereto. The intermediate region54of the recess36is defined by a circle which has a radius R1. The radius R1can lie between 1.0 mm and 20.0 mm, preferably between 3.0 mm and 10.0 mm, and is in the present embodiment approximately 5.2 mm. The outer regions of each recess36are defined by a radius R2and radius R3respectively. The radii R2and R3can be different from each other or, as in the present embodiment, equal. The radii R2and R3can lie between 1.0 mm and 20.0 mm, preferably between 1.0 mm and 7.0 mm, and are both in the present embodiment approximately 2.0 mm.

As further illustrated inFIG. 3, the transverse bore20defines a first diameter d1which is oriented substantially parallel to the longitudinal axis22of the proximal portion12(i.e., the first diameter d1is oriented in a direction from the proximal side to the distal side of the intramedullary nail10). The transverse bore20further defines a second diameter d2which is oriented substantially perpendicular to the longitudinal axis22of the proximal portion12(i.e., the second diameter d2is oriented in a direction from a posterior side to the anterior side of the intramedullary nail10). As shown inFIGS. 3 and 4, the second diameter d2is greater than the first diameter d1in at least a portion of the transverse bore20. In the present embodiment, the second diameter d2is greater than the first diameter d1(i.e., in the lateral/medical plane of the intramedullary nail10).

FIG. 5shows a detailed cross-sectional view of the transverse bore20of the proximal portion12denoted by Z inFIG. 2. InFIG. 5, as well as inFIG. 2, the lateral side of the intramedullary nail10is on the right side and the medial side of the intramedullary nail10is on the left side of the drawing.

As illustrated inFIG. 5, each of the two recesses36defines a length lr along the inner wall38in a direction of the bore axis42of the transverse bore20. In the present embodiment, the length lr of each recess36is less than the length of the transverse bore20along the bore axis42. The length lr of each recess36may lie between 1 mm and 10 mm, preferably between 2 mm and 7 mm, and is approximately 5.3 mm in the present embodiment. As illustrated inFIG. 5and as well as inFIG. 3, the intermediate region54of each recess36defines a width wi which is oriented in a direction substantially perpendicular to the bore axis42. In other words, the width wi of the intermediate region54of the recess36is oriented substantially parallel to the longitudinal axis22of the proximal portion12. The width wi of each recess36may lie between 2 mm and 9 mm, preferably between 3 mm and 5 mm. In the present embodiment, the width wi of the intermediate region54of each recess36is approximately 4.4 mm.

As shown inFIGS. 4 and 5, each of the two recesses36has an oblique extension relative to an extension of the bore axis42of the transverse bore20. In the present embodiment, the outer regions56of the recess36taper towards the center line of the bore in a direction from the inlet opening44toward the outlet opening46of the transverse bore20(in this case, in the plane of the drawing ofFIG. 5).

FIG. 6illustrates a cross sectional view of the transverse bore20of the proximal portion12along line C-C shown inFIG. 1. As becomes apparent inFIG. 6, each recess36has a conical shape in the direction of the bore axis42of the transverse bore20(in this case, in the plane of the drawing ofFIG. 6). Each recess36defines a taper with a cone angle c with respect to the inner wall38of the transverse bore20. The cone angle c can lie between 1° and 10°, preferably between 2° and 5°.In the present embodiment, the cone angle c of each recess36is approximately 3.8°.

As shown inFIG. 6, the cone angle c lies within a plane including the bore axis42of the transverse bore20and the diameter d2of the transverse bore20(i.e., a plane which is perpendicular to the longitudinal axis22of the proximal portion12). Each recess36tapes substantially in a direction from the inlet opening44toward the outlet opening46of the transverse bore20. Thus, the recesses36widen in a direction toward the inlet opening44of the transverse bore20. In the present embodiment as shown inFIGS. 5 and 6, the two recesses36widen the transverse bore20, on the one hand, in a direction of the bore axis42of the transverse bore20and, on the other hand, in a direction of the longitudinal axis22of the proximal portion12, in both cases, toward the inlet opening44of the transverse bore20.

It has been found that the recesses36help to reduce the probability of nail breakage in the region of the transverse bore20. Especially in cases in which the inner wall38of the transverse bore20gets damaged (e.g., by a drill operation through the transverse bore20) the rate of nail breakages can be reduced. This reduction can be attributed to smaller material tensions in a region of the intramedullary nail10around the transverse bore20due to the presence of recesses36.

Now referring toFIG. 7, there is shown a cross-sectional view of an embodiment of an implant system58for use in orthopaedic surgery for fixation of bone, such as a femur (not shown inFIG. 7). The implant system58comprises the intramedullary nail10as described above with reference toFIGS. 1 to 6. The implant system58further includes a bone fastener60(that forms a bone engagement member) and a coupling unit62which may be an anti-rotation screw which permits compressive sliding. The bone fastener60is configured to penetrate the transverse bore20of the intramedullary nail10from the inlet opening44to the outlet opening46. The coupling unit62couples the bone fastener60to the intramedullary nail10.

In the embodiment shown inFIG. 7, the bone fastener60is a sliding screw (e.g., femoral neck screw or lag screw), with a front portion64including a thread, for example a coarse thread, and a rear portion66. The rear portion66is provided with a plurality of longitudinally extending grooves68(two are shown inFIG. 7) arranged on the peripheral surface of the rear portion66along a longitudinal axis of the sliding screw60. In the present realization, four grooves68are disposed on the peripheral surface of the sliding screw60at intervals of 90° around the longitudinal axis of the sliding screw60. Each groove68defines a ramp having a shallow end and a deeper end. The rising ramp extends from the end of the rear portion66towards the threaded front portion.

Further, the sliding screw60includes a central cannulation70along the longitudinal axis of the sliding screw60. The rear portion66of the sliding screw60includes at its free end a co-axial bore72and a recess74(e.g., a hexalobular internal driving feature) for receiving a tool tip (e.g., of screw driver or a wrench).

As shown inFIG. 7, the unthreaded rear portion66of the sliding screw60is slidably received in the transverse bore of the proximal portion12of the intramedullary nail10. Further, the bore axis42of the transverse bore20is substantially parallel to the longitudinal axis of the sliding screw60. In the present embodiment the bore axis42is congruent with the longitudinal axis of the sliding screw60. The sliding screw60can thus transfer the load of the femoral head into the intramedullary nail10and at the same time bridges the fracture line to allow fast and secure fracture healing.

As further shown inFIG. 7, the coupling unit62is realized as a set screw which is preassembled and movably arranged within the proximal portion12of the intramedullary nail10. The coupling unit62includes one bone fastener engagement member76and a drive member78. In the present embodiment, the engagement member76of the coupling unit62is centrally positioned within the bore40of the proximal portion12. Further, the engagement member76is realized in the exemplary form of a substantially cylindrical bolt, pin or protrusion. The drive member78of the coupling unit62is connected to the engagement member76and includes an external thread for threadable engagement with the intramedullary nail10(e.g., with the proximal portion12as shown inFIG. 7). The bore40of the proximal portion12includes an internal thread which mates with the external thread of the drive member78of the coupling unit62. In the present embodiment, the drive member76of the coupling unit62is movably arranged within the bore40of the proximal portion12of the intramedullary nail10. Moreover, the coupling unit62is captively held within the proximal portion12of the intramedullary nail10. As illustrated inFIG. 7, the engagement member76of the coupling unit62can engage within a groove68of the sliding screw60. Upon engagement within the groove68, the engagement member76can exert pressure on the sliding screw60for stabilization purposes. The pressure is initially zero or low enough to still permit a sliding movement of the sliding screw60relative to the intramedullary nail10. The pressure will change (and typically increase) as the sliding screw60slides due to the depth profile (i.e., the lateral and medial ramps) of the grooves68.

Rotation of the drive member78of the coupling unit62causes movement of the engagement member76along the longitudinal axis22of the proximal portion12. For this propose, the drive member78of the coupling unit62has a receiving portion80in form of a recess (e.g., realized as a hexalobular internal driving feature) for receiving a tool such as a screw driver or wrench. By driving the drive member78using such a tool, the entire coupling unit62moves along the longitudinal axis22of the proximal portion12of the intramedullary nail10, since the external thread of the drive member78mates with the internal thread of the bore40of the proximal portion12. In other words, the position of the coupling unit62, and thus the position of its engagement member76, within the proximal portion12of the intramedullary nail10can be adjusted by screwing the drive member78of the coupling unit62along the longitudinal axis22of the proximal portion12.

An embodiment of a manufacturing process for modifying a notch (or depression) formed around the neck screw bore (i.e., the transverse bore arranged in the proximal portion of the intramedullary nail) will now be described. The process may be performed before or after the notch is formed around the predrilled femoral neck screw bore in accordance with, for example, the aforementioned U.S. Pat. No. 7,763,022 B2. The process may also be performed without formation of such a notch. A cone shaped pocket, i.e., a recess36, is formed on both the anterior and posterior side of the bore although the formation of only one cone-shaped pocket will be described.

In a first step a central axis of a mill cutter head is aligned with the axis42of the neck screw bore20(i.e., the transverse bore20of the proximal portion12of the nail10). For example, the bore20may be angled at about 126° to the longitudinal axis22of the proximal portion12of the intramedullary nail10. The mill cutter axis is placed at the neck screw entry side (i.e., the lateral side) of the intramedullary nail10and is then angled in at least one plane, for example at an angle of about 3.8° to a first plane containing both the proximal nail axis22and the neck screw bore axis42. The cutter head is then moved in two elliptical paths to form a conically tapered recess36having a curved inwardly facing surface. The curved surface extends proximally and distally of a second plane containing the axis42of the screw bore20and perpendicular to the first plane. The proximal and distal foci of the two ellipses are located, for example, about 1.2 mm proximal and about 2.2 mm distal of the second plane. The curved surface is formed by moving the mill head along a spline connecting end portions of the two ellipses since the foci are spaced at different distances from the first plane. The mill head cutting path forms a tangent with each ellipse end portion.

While in the embodiments illustrated in the drawings the rod-shaped body of the intramedullary nail includes a distal portion, a proximal portion and an intermediate (bent) portion therebetween, the nail body can be adapted as needed (e.g., in terms of shape, length, width, thickness, etc.) for use in orthopaedic surgery for fixation of bone and for insertion into an intramedullary canal of, e.g., a femur. Thus, the shape of the intramedullary nail can be adapted to different applications.

While the bone engagement member (bone fastener) described herein is formed as a sliding screw or a lag screw, the bone engagement member can be of any type (e.g., a femoral neck screw or any kind of blade) and can be adapted to different applications as needed. Furthermore, one or more bone engagement members (e.g., two, three or more bone fasteners) may be arranged in the constellation as shown in and described with reference toFIG. 7. In other words, the implant may have two or more transverse openings and two or more sliding screws arranged therein in a manner as shown inFIG. 7. The bone engagement members as well as the connecting fastener(s) may have different diameters, lengths, shapes or threads.

While the above embodiments have exemplarily been described in relation to bone screws and an intramedullary nail, it will be readily apparent that the techniques presented herein can also be implemented in combination with other or further types of bone fasteners (such as bone pegs having a rod-like or pin-like shaft, wire-like bone fasteners such as Kirschner wires, etc.). Accordingly, the present disclosure is not limited to any type of bone fastener.

The features described in the above description taken in conjunction with the accompanying drawings can be readily combined to result in different embodiments. It will thus be apparent that the present disclosure may be varied in many ways. Such variations are not to be regarded as a departure from the scope from the disclosure, and all modifications are intended to be included within the scope of the following claims.