HK1159975A - Device and method to prevent hip fractures - Google Patents

Description

Device and method for preventing hip fracture

Cross Reference to Related Applications

This application claims priority to U.S. provisional patent application No.61/082,848, filed on 23/7/2008, the entire contents of which are incorporated herein by reference.

Background

The present invention relates to devices and methods for preventing hip fractures.

The femur is the longest and largest bone in the human body. The femur forms part of the hip at one end and the knee at the other. Fig. 1 is a front view of an upper portion of a femur, showing various portions or areas of the femur 40, including a femoral head 42, a femoral neck 44, and a greater trochanter 46.

The femoral head 42 is generally spherical and is directed upward, medial and slightlyOriented forward with the greater part of its convexity in the upper front. See Gray, Henry.Anatomy of the Human body.Philadelphia：Lea & Febiger，1918；Bartleby.com，2000。

The femoral neck 44 is a frustoconical bone that connects the femoral head 42 with the rest of the femur 40 and forms a large angle opening medially with the latter.Id.The femoral neck 44 narrows medially and is wider laterally than medially.Id.The upper portion or boundary 45 of the neck 44 is short and thick and terminates on the outside in a large rotor 46. The long and narrow lower border is bent back slightly to terminate in the small rotor.Id.

The greater trochanter 46 is a large, irregular, quadrilateral protuberance located at the junction of the neck 44 and the upper portion of the femur 40.Id.The large rotor 46 has two surfaces and four boundaries.Id.The outer surface of the quadrilateral is wide, rough, convex and marked by diagonal depressions extending from the rear upper corner to the front lower corner.Id.The inner surface, which is much smaller than the extent of the outer surface, has a deep depression, the trochanteric socket (rotor socket), at its bottom.Id.The upper boundary is free; it is thick and irregular and is marked by a depression near the center.Id.The lower boundary corresponds to a line of junction of the bottom of the rotor with the outer side surface of the main body; it is marked by a rough, protruding, slightly curved ridge.Id.The front boundary is convex and somewhat irregular.Id.The posterior border is highly prominent and presents a free rounded edge, bounding the posterior portion of the trochanteric fossa.Id.

The femoral stem 47 is generally cylindrical.Id.The femoral stem 47 is slightly arched so as to be convex anteriorly and concave posteriorly, where it is reinforced by a longitudinal ridge (thick line).Id.

Fig. 1 also shows the axis of the normal load bearing vector 48, i.e., the axis on which the load acts during walking, standing, and other activities of daily living. Fig. 1 also shows the general orientation of the longitudinal axis 50 of the femoral neck 44, and the long axis 52 of the femoral stem 47 of the femur 40.

Referring now to fig. 2-5, hip fractures typically result from a fall to the side where impact with the ground occurs on the greater trochanter 46 of the lateral femur 40. During a hip fracture, the impact resulting from a fall toward this side (as best shown in fig. 2) results in three-point bending of the femur 40, including a "reverse bending" load on the femoral neck 44, with the upper or (or upper) boundary or side 45 of the femoral neck 44 developing compressive stress and the lower (or lower) boundary or side 49 of the femoral neck 44 developing tensile stress. It is believed that the weaker upper boundary or side 45 of the femoral neck 44 is likely to break or fracture first in compression, as indicated by reference numeral 56 in fig. 3. After the initial damage, the split propagates across the femoral neck 44, including the stronger underside 45, whose primary load is tension/flexion, as shown in fig. 4. Finally, depending on the direction in which the fracture propagates, this ultimately results in a hip fracture, or a neck fracture 58 or intertrochanteric fracture 60, as shown in FIG. 5.

To obtain more information about the mechanics of Hip fractures, see Turner, ch.the biomemechanics of Hip fracture.lancet.2005 Jul 9-15; 366(9480): 98-9. See also Mansek, Sarah et al, Failure in Femoral New constructions in the Superolaraltechnex: conference from High Speed Video of related frame. Poster No.943, 54th Annual Meeting of the Orthopaedic Research Society (2008). These articles are incorporated herein by reference.

Medical treatments are available for hip fractures, often in the form of screws that are inserted into the femur through the fracture at an angle of about 45 ° along the longitudinal axis 50 of the femoral neck 44 relative to the long axis 52 of the femoral stem 47. However, there is a need to prevent hip fractures, particularly fractures along and in the area near the junction between the femoral neck 44 and the greater trochanter 46. That is, there is often concern that placing a metal (e.g., titanium) implant in an otherwise normal (i.e., unbroken) femur to prevent hip fracture will result in loss of bone around the implant due to the relatively unloaded nature of the bone resulting from the load sharing properties of the harder metal. This phenomenon is commonly referred to as "stress shielding".

Stress shielding refers to a reduction in bone density (osteopenia) due to an implant (e.g., a femoral component of a hip prosthesis) removing normal stress from the bone. According to Walf's Law, osteopenia occurs because the bone in a healthy human or animal will remodel in response to a load applied thereto. Therefore, if the load on the bone is reduced, the bone will become less dense and weaker because there is no stimulus for continued remodeling required to maintain bone mass.

A phenomenon related to the concept of stress shielding is that bone is a self-optimizing structure. By the natural remodeling process, bone material is retained in the high stress or strain regions, while bone is reduced in the low stress and strain regions. In the hip, the bone in the lower region of the femoral neck (also known as the calcareous region) is very dense due to the constant state of high stress and strain caused by the loads generated by standing and walking. Conversely, the upper region of the femoral neck, particularly the bone in the region near the junction of the upper femoral neck and the greater trochanter, becomes less dense over time due to the lack of direct loading during walking, standing, and other activities of daily living. Thus, the bone regions of most interest in this application continue to decrease in volume through the natural process of bone remodeling. The normal bone remodeling process continues to remove bone from the area of the upper femoral neck because standing, walking, or other daily activities do not create high loads in that area. The normal load bearing vector resulting from walking or other normal daily activities is transmitted from the upper surface of the femoral head through the head to the calcium area near the medial femoral diaphysis, shown as normal load bearing vector 48 in fig. 1. For this reason, natural or pharmacological methods of increasing the strength of the bone often have poor results in preventing hip fractures as compared to other fractures in other areas of the body.

Accordingly, there is a need for a device and method for preventing hip fractures along and in the area near the femoral neck without causing stress shielding.

Disclosure of Invention

The present invention is a device and method for preventing hip fractures, and more particularly for preventing fractures along and in the area near the femoral neck without causing stress shielding.

An exemplary device for preventing hip fractures in accordance with the present invention includes a stem having a first end positioned in a femoral head and a second end positioned in a greater trochanter. The device is typically inserted through the lateral eminence of the greater trochanter of the femur along a generally horizontal axis that is substantially perpendicular to the long axis of the femoral diaphysis. The device also includes an expansion mechanism for engaging the femoral head at the first end. Thus, the device acts as a load bearing (or load sharing) device along or near the load line created by a fall toward the side where impact with the ground occurs on the greater trochanter of the lateral femur. In other words, the device interacts with and distributes the load occurring within the bone such that the device shares the load occurring during a fall, thus preventing a fracture.

Another exemplary device for preventing hip fractures in accordance with the present invention comprises: a screw; a tubular structure defining a screw receiving channel and having a first end and a second end; and an expansion mechanism for engaging the femoral head, comprising a plurality of expandable grooved sections proximate the first end of the tubular structure. The exemplary device also includes a plurality of expandable fluted portions proximate an opposite second end of the tubular structure. The tubular structure with the screw is positioned in a hole of predetermined depth in the femur. A driving tool, such as a mallet or a sliding hammer, is then used to drive or advance the device into the femoral head beyond the distal end of the bore to a final position while causing the slotted portion at the first end of the tubular structure to expand and splay outwardly into the surrounding bone in a deployed position. The fluted portion has an enlarged bearing surface at the first end that engages the surrounding bone as it expands into the surrounding bone. Finally, in the exemplary embodiment, once the grooved portion at the first end is in the deployed position, the screw is rotated relative to the screw-receiving channel to advance the screw, which forces the grooved portion proximate the second end of the tubular structure to expand outward into the surrounding bone.

Another exemplary device for preventing hip fractures in accordance with the present invention comprises: a screw; a tubular structure defining a screw receiving channel and having a first end and a second end; and an expansion mechanism for engaging the femoral head, comprising a plurality of Molly expansion bolt-like portions positioned proximate the first end. The screw has a threaded portion and the screw-receiving channel includes corresponding and mating threads. Thus, the screw may be inserted into the tubular structure and received in the screw receiving channel. When the device is inserted into a hole of a predetermined depth in the femur, the screw may be rotated such that the first end of the device is pulled toward the second end, effectively contracting and forcing the plurality of morri-bolt-like portions outward and into the surrounding bone.

Another exemplary device for preventing hip fractures in accordance with the present invention comprises a first component having: a first screw; a first tubular structure defining a screw receiving channel and having a first end and a second end; and a first mechanism for engaging the femoral head comprising a plurality of mory expansion bolt-like portions positioned proximate the first end of the first tubular structure. Thus, a first screw may be inserted into the first tubular structure and received in the screw receiving channel. When the device is inserted into a hole of a predetermined depth in the femur, the first screw may be rotated such that the first end of the device is pulled toward the second end, effectively contracting and forcing the plurality of morley expansion bolt-like portions outward and into the surrounding bone. In this exemplary embodiment, the apparatus also includes a second component. The second assembly includes: a second screw; a second tubular structure defining a second screw receiving channel and having a first end and a second end; a second mechanism for engaging the femoral head comprising a plurality of slotted portions positioned proximate the first end of the second tubular structure; and a screw receiving element positioned at the first end of the second tubular structure and having mating threads that engage the threaded portion of the second screw. The first component is positioned in a hole of a predetermined depth in the femur and the plurality of morri-bolt-like portions are forced outwardly and into the surrounding bone. The first screw is then removed, while the first tubular structure remains in the femur. The entire second assembly is then advanced through the first tubular structure until its first end is proximate the expanded mory bolt-like portion of the first assembly. The fluted portion of the second assembly is then expanded by rotating the second screw, thereby pulling the screw receiving member toward the second end and forcing the fluted portion to expand outwardly into the surrounding bone.

Another exemplary apparatus according to the present invention comprises: a main handle; a plurality of rods surrounding the main shank; a first end cap at a first end of the device; a plurality of links, each connecting one of the rods to a first end cap; and a sleeve for maintaining the positioning of the rod relative to the main shank. Each link is pivotally connected at one end to the first end cap about a pivot axis and each defines a cavity proximate its opposite end for receiving the distal end of one of the rods. When the device is inserted into the hole, each rod is individually advanced toward the first end to cause controlled expansion of the rod into the surrounding bone. Further, each lever is similarly urged such that all levers and links expand outward and away from the main handle to a deployed position.

Another exemplary apparatus according to the present invention comprises: a main handle; a plurality of rods surrounding the main shank; a first end cap at a first end of the device and having a flared circumferential surface; and a sleeve for maintaining the positioning of the rod relative to the main shank. Each rod is individually urged toward the first end when the device is inserted into the bore. As each rod is advanced, its distal end contacts the flared circumferential surface of the first endcap, forcing the rod outward into the surrounding bone. Further, each rod is similarly advanced so that all of the rods splay outward and away from the main handle, resulting in a deployed position.

Drawings

FIG. 1 is a front view of an upper portion of a femur;

FIG. 2 is an anterior view of a portion of a femur showing the load applied to the femur due to an impact of a fall to one side;

FIG. 3 is an anterior view of a portion of a femur showing a split around an upper region of the femoral neck;

FIG. 4 is an anterior view of a portion of a femur, showing fracture propagation;

FIG. 5 is an anterior view of a portion of a femur showing the propagation of a fracture into a femoral neck fracture or intertrochanteric fracture;

FIG. 6 is an anterior view of a portion of a femur showing a hole formed along a generally horizontal axis substantially perpendicular to the long axis of the femoral diaphysis;

FIG. 7 is an exploded side view of an exemplary device for preventing hip fractures made in accordance with the present invention;

FIG. 7A is an exploded side view similar to FIG. 7 of the exemplary device for preventing hip fractures, but further including an end cap;

FIG. 8 is a view of the device of FIG. 7, shown positioned in a hole formed along a generally horizontal axis substantially perpendicular to the long axis of the femoral diaphysis;

FIG. 9 is a view of the device of FIG. 7 showing the slotted portion in the deployed position at the first end;

FIG. 10 is a view of the device of FIG. 7 showing the slotted portion in the deployed position at the first end and the Moire bolt-like portion in the deployed position at the second end;

FIG. 11 is an end view of the device of FIG. 7 showing the slotted portion in the deployed position at the first end;

FIG. 12 is an exploded side view of another exemplary device for preventing hip fractures and constructed in accordance with the present invention;

FIG. 13 is a side view of the device of FIG. 12, showing the Moire bolt-like portion in the deployed position;

FIG. 14 is an end view of the device of FIG. 12 showing the Moire bolt-like portion in the deployed position;

FIG. 15 is an exploded side view of another exemplary device for preventing hip fractures and constructed in accordance with the present invention;

FIG. 16 is a side view of the device of FIG. 15, showing the Moire bolt-like portion of the device in the deployed position;

FIG. 17 is an exploded side view of the device of FIG. 15, showing a second assembly of the device advanced into the first assembly;

FIG. 18 is a side view of the device of FIG. 15, showing the slotted portion and the Moire bolt-like portion of the device in the deployed position;

FIG. 19 is an end view of the device of FIG. 15 showing the slotted portion and the Moire bolt-like portion of the device in the deployed position;

FIG. 20 is a view of another exemplary device for preventing hip fractures made in accordance with the present invention positioned in a femur;

FIG. 21 is an enlarged view of the device of FIG. 20;

FIG. 22 is a cross-sectional view of the device of FIG. 20 taken along line 22-22 of FIG. 20;

FIG. 23 is a side view of the device of FIG. 20 taken along line 23-23 of FIG. 22 and showing one of the rods placed in the deployed position;

FIG. 24 is a side view of the device of FIG. 20, showing all of the rods in the deployed position;

FIG. 25 is an end view of the device of FIG. 20 showing all of the rods in the deployed position;

FIG. 26 is a cross-sectional view similar to FIG. 22, but showing an alternative primary handle for the device of FIG. 20;

FIG. 27 is a side view of another exemplary device for preventing hip fractures made in accordance with the present invention positioned in a femur with the stem deployed at both ends;

FIG. 28 is a side view of another exemplary device for preventing hip fractures and constructed in accordance with the present invention;

FIG. 29 is a side view of the device of FIG. 28, showing the rods in a deployed position at the first end;

FIG. 30 is a side view of the device of FIG. 28 showing the rods in the deployed position at both ends;

FIG. 31 is a cross-sectional view of the device of FIG. 28 taken along line 31-31 of FIG. 28; and

FIG. 32 is an end view of the device of FIG. 28 showing the rods in a deployed position.

Detailed Description

The present invention is a device and method for preventing hip fractures, and more particularly for preventing fractures along and in the area near the femoral neck without causing stress shielding.

An exemplary device for preventing hip fractures made in accordance with the present invention includes a stem having a first end positioned in the femoral head and a second end positioned in the greater trochanter. The device is typically inserted through the lateral eminence of the greater trochanter of the femur generally along a horizontal axis 54 that is substantially perpendicular to the long axis 52 of the femoral stem 47. The device also includes an expansion mechanism for engaging the femoral head 42 at a first end, as will be discussed below. Thus, the device acts as a load bearing (or load sharing) device along or near the load line created by a fall toward the side where impact with the ground occurs on the greater trochanter of the lateral femur, as will also be discussed below.

Furthermore, due to the orientation of the device within the femur, it will protect the bone in the upper region of the femoral neck where it is believed that the fracture due to a fall to one side begins with a compression or buckling fracture. The bone is supported by the presence of the device. Furthermore, since the device is positioned within the femur together with a mechanism provided at the first end of the device for engaging the femoral head 42, the risk that the device will penetrate the femoral head to reach the articular surface of the hip joint is minimized. Furthermore, the presence of the device should not compromise the health of the bone beneath the articular surface or cause conditions such as avascular necrosis. Placing too much foreign material (e.g., metal, cement, etc.) in the subchondral bone may reduce the blood supply and nutrition to the load bearing bone of the femoral head 42.

Referring first to fig. 6, a hole 100 of predetermined depth is formed along a generally horizontal axis 54 that is substantially perpendicular to the long axis 52 of the femoral stem 47 of the femur 40. Any known method for forming the holes 100 may be used. For example, one method may include drilling a hole to a predetermined depth with sufficient cross-sectional area to accommodate insertion of the device. Alternatively, it is preferred to drill a small pilot hole of a predetermined depth and then enlarge and compact the cancellous (lattice or sponge-like) bone of the femur to create a hole of sufficient cross-sectional area to accommodate insertion of the device. In any event, in some exemplary embodiments, and as shown in FIG. 6, the aperture 100 terminates at or near the axis of the normal load bearing vector 48. Of course, it is also preferred to insert the device through as small an aperture as possible using minimally invasive methods.

Figures 7-11 illustrate another exemplary device 10 for preventing hip fractures and constructed in accordance with the present invention. The exemplary apparatus 10 includes: a screw 12; a tubular structure 14 defining a screw receiving channel 16 and having a first end 18 and a second end 20; and an expansion mechanism for engaging the femoral head 42, including a plurality of expandable grooved sections 22 proximate the first end 18 of the tubular structure 14. The exemplary device also includes a plurality of expandable mory bolt-like portions 24 proximate the opposite second end 20 of the tubular structure 14. In other words, the screw 12 and the tubular structure 14 act as a "handle" for the device, while the "tip" takes the form of an expandable fluted portion 22 and an expandable mory bolt-like portion 24 at either end 18, 20 of the tubular structure 14. The screw receiving channel 16 is accessible through the second end 20 of the tubular structure 14.

The screw 12 has a threaded portion 12a and the screw receiving channel 16 has corresponding and mating threads 16 a. Thus, the screw 12 may be inserted into the tubular structure 14 and received in the screw receiving channel 16. The tubular structure 14 with the screw 12 is positioned in a hole 100 of a predetermined depth in the femur 40, as best shown in fig. 8. A driving tool (e.g., a mallet or a sliding hammer) is then used to drive or advance the device 10 into the femoral head 42 beyond the distal end of the bore 100 to a final predetermined depth and position while causing the slotted portion 22 at the first end 18 of the tubular structure 14 to expand and splay outwardly into the surrounding bone in a deployed position, as best shown in fig. 9. As the fluted portion 22 expands into the surrounding bone, there is an enlarged bearing surface at the first end that engages the surrounding bone, as perhaps best shown in the end view of FIG. 11. This enlarged bearing surface helps to ensure that the position of the device 10 remains fixed within the femur.

Finally, once the grooved portion 22 at the first end 18 is in the deployed position, the screw 12 is rotated relative to the screw-receiving channel 16a to advance the screw 12, which forces the morri-bolt-like portion 24 adjacent the second end 20 of the tubular structure 14 to expand outwardly into the surrounding bone, as shown in fig. 10 and 11. Specifically, in the exemplary embodiment, the Moire bolt-like portion proximate the second end 20 of the tubular structure 14 is integral with and forms the side wall of the tubular structure 14, and as the screw 12 is rotated, the head of the screw 12 engages and presses against the second end 20 of the tubular structure 14, effectively applying a compressive load, causing the Moire bolt-like portion 24 to contract and expand outwardly into the surrounding bone to secure the device in position within the femur 40.

Referring back to fig. 5, by implanting the device 10 via and along the superior aspect of the neck of the femur 40 in line with the load created during a side-to-side fall impacting the greater trochanter 46, the device 10 acts as a load bearing (or load sharing) device along or near the load line 54 created by the side-to-side fall, sharing the compressive load formed along the line during the fall. When load bearing or load sharing is sufficient, initial compressive failure of the bone material at the upper region of the femoral neck 44 and at the junction of the greater trochanter 46 is prevented, thus preventing hip fracture. Moreover, the enlarged bearing surfaces at the ends 18, 20 of the device 10 created by the expansion of the grooved portions 22 and the morri-bolt like portions 24 results in a greater percentage of the load passing through the device 10 than the surrounding bone, thereby enhancing the ability of the device 10 to strengthen and augment the load path through the femur.

With respect to the size of the device, the data indicate that the average destructive power of a femur subjected to a load in the event of a fall to one side is about 2800N for a population at risk (e.g., elderly women). See Pulkkinen et al, Association of geographic Factors and Failure Load Level with the distribution of geographic vs.Journal of Bone and Mineral ResearchVol.21, No.6, 2006. This article is incorporated herein by reference. It is therefore desirable that the apparatus of the present invention is capable of load carrying or load sharing of about 2500N without allowing significant displacement of the apparatus in the load direction, i.e. less than 2 mm.

Preliminary experimental data using a device loaded with poor cancellous bone simulating foam and a real cancellous bone sample indicate that the effective cross-sectional area of the bearing surface (i.e., the interface between the device and the bone along the device axis/load direction) should be about 500mm²Or more. For example, a 25mm diameter bearing surface would satisfy 5MPa strength cancellous bone.

Finally, it should be noted that although in the exemplary embodiment four slotted portions 22 and four mory bolt-like portions 24 are located at the ends 18, 20 of the device 10, any other suitable number may be used without departing from the spirit or scope of the present invention.

FIG. 7A is an exploded side view of the exemplary hip fracture prevention device similar to FIG. 7, but further including an end cap 30 at the first end 18 of the tubular structure 14. The end cap 30 will be fixed in place (e.g., by a line passing through the center of the tubular structure 14) as the device 10 is driven and advanced beyond the distal end of the hole 100, such that the flared circumferential surface 32 of the end cap 30 will assist in the outward expansion and flaring of the fluted portion 22 into the surrounding bone.

Fig. 12-14 illustrate another exemplary device 110 for preventing hip fractures and constructed in accordance with the present invention. The exemplary apparatus 110 includes: a screw 112; a tubular structure 114 defining a screw receiving channel 116 and having a first end 118 and a second end 120; and an expansion mechanism for engaging the femoral head 42 that includes a plurality of mory expansion bolt-like portions 122 positioned proximate the first end 118. The screw 112 has a threaded portion 112a and the screw receiving channel 116 includes corresponding and mating threads 116 a. Thus, the screw 112 may be inserted into the tubular structure 114 and received in the screw receiving channel 116. When the device 110 is inserted into the hole 100 (as shown in fig. 6), the screw 112 can be rotated such that the first end 118 of the device is pulled toward the second end 120, effectively contracting and forcing the plurality of morri-bolt-like portions 122 outward and into the surrounding bone. As with the embodiment described above with respect to fig. 7-11, expansion of the plurality of morri bolt-like portions 122 into the surrounding bone creates an enlarged bearing surface that contacts and engages the surrounding bone, as shown in the end view of fig. 14, thereby fixing the position of the device 110 within the femur.

It should be noted that although four mory bolt-like portions 122 are located at the first end 118 of the device 110 in the exemplary embodiment, any other suitable number may be used without departing from the spirit or scope of the present invention.

Fig. 15-19 illustrate another exemplary device 210 for preventing hip fractures and constructed in accordance with the present invention. The exemplary embodiment 210 includes a first assembly 210a having: a first screw 212; a first tubular structure 214 defining a screw receiving channel 216 and having a first end 218 and a second end 220; and a first mechanism for engaging the femoral head 42 that includes a plurality of morley expansion bolt-like portions 222 positioned proximate the first end 218 of the first tubular structure 214. The first screw 212 has a threaded portion 212a and the screw receiving channel 216 includes corresponding and mating threads 216 a. Accordingly, the first screw 212 may be inserted into the first tubular structure 214 and received in the screw receiving channel 216. Similar to the embodiment described above with reference to fig. 12-14, when the device 210 is inserted into the hole 100 (as shown in fig. 6), the first screw 212 can be rotated such that the first end 218 of the device is pulled toward the second end 220, effectively contracting and forcing the plurality of morri-bolt-like portions 222 outward and into the surrounding bone, as shown in fig. 18.

However, unlike the embodiment described above with reference to fig. 12-14, in this exemplary embodiment, the apparatus 210 includes a second component 210 b. The second assembly 210b includes: a second screw 242; a second tubular structure 244 defining a second screw receiving channel 246 and having a first end 248 and a second end 250; a second mechanism for engaging the femoral head 42, comprising a plurality of slotted portions 252 positioned proximate the first end 248 of the second tubular structure 244; and a screw receiving element 254 positioned at the first end 248 of the second tubular structure 244 and having mating threads 254a that engage the threaded portion 242a of the second screw 242.

In effect, the first component 210a is positioned in the hole 100 (as shown in fig. 6) and the plurality of mory-bolt-like portions 222 are forced outwardly and into the surrounding bone, as shown in fig. 16. The first screw 212 is then removed, while the first tubular structure 214 remains in the femur 40. The entire second assembly 210b is then advanced through the first tubular structure 214 until its first end 248 is proximate the expanded mory-bolt-like portion 222 of the first assembly 210a, as shown in fig. 17. The fluted portion 252 of the second assembly 210b is then expanded by rotating the second screw 242, thereby pulling the screw receiving member 254 toward the second end 250 and forcing the fluted portion 252 to expand outward into the surrounding bone, as shown in fig. 18 and 19.

Referring now to fig. 20-27, another exemplary device 310 made in accordance with the present invention includes: a main handle 312; a plurality of rods 314 surrounding the main handle 312; a first end cap 316 at a first end 318 of the device 310; a plurality of links 320, each connecting one of the rods 314 to the first end cap 316; and a sleeve 323 for maintaining the positioning of the rod 314 relative to the main handle 312. With respect to the links 320, each link 320 is pivotally connected at one end to the first end cap 316 about a pivot 322, and each defines a cavity 320a proximate its opposite end for receiving the distal end of one of the rods 314.

When the device 310 is inserted into the aperture 100 (as shown in fig. 6), each rod 314 is individually urged toward the first end 318, as shown in fig. 23. As a result of the forward movement of each rod 314, the distal end of the rod is pressed into the cavity 320a defined by the links 320, causing the respective links to rotate about the respective pivots 322. Thus, the rod 314 is controlled to expand into the surrounding bone. In turn, each rod 314 is similarly advanced causing all of the rods 314 and links 320 to expand outward and away from the main handle 312, resulting in the deployed position shown in fig. 24 and 25.

It should be noted that although eight rods 314 are used in the exemplary embodiment, any other suitable number may be used without departing from the spirit or scope of the present invention.

It should also be noted that by advancing the rods 314 individually into the surrounding bone, the amount of resistance at any time will remain low compared to the simultaneous advancement of all of the rods 314. This minimizes the likelihood of forcing the device 310 beyond its intended location in the femur and/or any penetration through the femoral head to the articular surface of the hip joint. Further, by advancing the rods 314 individually into the surrounding bone, each rod can be advanced until a predetermined resistance is achieved, resulting in a variable depth of extension of the rod 314 into the femoral head 42.

As a further refinement, and as shown in fig. 26, an alternative main stem 352 may be provided that defines a plurality of recesses to receive sleeves 362 and cooperate with the sleeves 362 to control and guide the movement of each of the plurality of rods 354.

As a further improvement, and as shown in FIG. 27, it should also be appreciated that the posterior portion of the rod 314 may also expand outward to better secure the position of the device 310 within the femur 40. To this end, after the rod 314 is advanced to the deployed position shown in fig. 24 and 25 as described above, a second end cap 324 with a linkage 326 and a configuration similar to the first end cap 316 may be used to capture the free ends of the rod 314 and force them to expand into the surrounding bone in a similar manner.

Referring now to fig. 28-32, another exemplary apparatus 410 includes: a main handle 412; a plurality of rods 414 surrounding the main handle 412; a first end cap 416 at a first end 418 of the device 410 and having a flared circumferential surface 419; and a sleeve 422 for maintaining the positioning of the stem 414 relative to the main shank 412. When the device 410 is inserted into the aperture 100 (as shown in fig. 6), each rod 414 is individually urged toward the first end 418. As each rod 414 is advanced, its distal end contacts the flared circumferential surface 419 of first end cap 416, forcing rod 414 outward into the surrounding bone. In turn, each rod 414 is similarly advanced so that all of the rods 414 splay outward and away from the main handle 412, resulting in the deployed position shown in FIG. 29.

As a further refinement, the exemplary device 410 may include a second end cap 424 at the second end 420 of the device 410. The second end cap 424 defines a screw receiving channel (not shown) for receiving the threaded portion 412a of the main shank 412. As second end cap 424 is rotated to advance toward first end cap 416, the flared circumferential surface of second end cap 424 engages the free end of shaft 414, forcing shaft 414 outward and into the surrounding bone.

As mentioned above, for any device implanted in the femur, it is important to prevent any stress shielding, i.e., the loss of bone around the device due to the relatively unloaded nature of the bone due to the load sharing properties of the harder metal. With respect to the device of the present invention, and regardless of the exemplary embodiment selected for implantation, since the device is oriented along a generally horizontal axis 54 that is substantially perpendicular to the long axis 52 of the femoral stem 47 of the femur 40, the device will not result in stress shielding of the bone surrounding the device. Referring again to fig. 6, since the load causing the fracture is not along the axis of the normal load bearing vector 48, the risk of the device causing stress shielding problems during normal activities is small, as the normal load trajectory will not result in significant load bearing or load sharing of the device. Conversely, the device will be incorporated into the bone structure of the femur 40 and provide stiffness to resist fracture initiation in the event of a loading event along its axis (i.e., a fall to one side, resulting in the loading shown in fig. 5). In addition, it is preferred that the device should avoid a continuous connection between the load bearing dome of the femoral head 42 and the cortex of the femoral stem 47 to further avoid stress shielding.

With respect to each of the exemplary embodiments described above, it is preferred that the device in its deployed position should have as low a profile as possible on the outside surface of the large rotor to avoid any irritation and discomfort to the patient. That is, as a further improvement, it is foreseen that a portion of the device may extend from the insertion point (outside of the bone) and be provided with an enlarged head, so as to prevent any fracture of the bone resulting from the impact of the greater trochanter at the insertion point.

With respect to each of the exemplary embodiments described above, the device should be harder than the surrounding bone, and thus it is preferred that the device be made of metal (e.g., titanium, nickel-titanium alloy, stainless steel, or memory metal) or another material of suitable hardness.

With respect to each of the exemplary embodiments described above, it is also envisioned that hydroxyapatite or other bioactive or porous coatings may be applied to the device for improving the bond between the femur and the device. Such a coating will improve the bond/interface strength between the device and the surrounding bone, so a greater percentage of the load will be transmitted through the device rather than to the surrounding bone of the femur. Increasing the strength will also improve the ability of the device to reinforce and enhance the load path through the femur.

With respect to each of the exemplary embodiments described above, it is also contemplated that the device may be used in conjunction with an injectable cement, a bone graft, or a bone graft substitute. For example, through the use of injectable cement, the load bearing capacity of the device and surrounding bone may be increased. Such injectable cement may be injected prior to implantation of the device or may be injected post-implantation through the device, which acts as a conduit for such injection and delivery. In addition, various injectable augmentation materials or injectable materials for stimulating or promoting bone growth may be used in conjunction with the device of the present invention.

With respect to each of the exemplary embodiments described above, it is also envisioned that the device may release bioactive materials, drugs, bone healing or regenerative agents and/or bone morphogenic proteins to stimulate the surrounding bone to become denser or thicker, thus improving fracture resistance at critical (femoral neck) locations. It is also envisioned that the implant device may serve as a conduit or reservoir for later injection or delivery of bioactive materials or drugs to critical sites in the femur.

Those of ordinary skill in the art will also recognize that additional embodiments are possible without departing from the teachings of the present invention or the scope of the appended claims. This detailed description, and particularly the specific details of the exemplary embodiments disclosed herein, is given primarily for clearness of understanding and no unnecessary limitations are to be understood therefrom, for modifications will become obvious to those skilled in the art upon reading this disclosure and may be made without departing from the spirit or scope of the invention as defined by the appended claims.

Claims (22)

1. A device for preventing hip fractures, comprising:

a stem having a first end and a second end, wherein the stem is positioned in a bore of a predetermined depth in a femur, the portion of the femur characterized by a femoral head, a greater trochanter, a femoral neck, and a femoral stem, the bore extending from the greater trochanter to the femoral head such that the first end of the stem is positioned in the femoral head and the second end is positioned in the greater trochanter; and

an expansion mechanism for engaging the femoral head at a first end;

wherein the device is oriented along a generally horizontal axis that is substantially perpendicular to the long axis of the femoral diaphysis.

2. The device of claim 1, wherein the bore terminates near an axis defining a normal load bearing vector of the femur.

3. The device of claim 1, wherein a portion of the stem is adjacent to an upper wall of the femoral neck.

4. The device of claim 1, wherein the expansion mechanism is a plurality of slotted portions positioned proximate the first end, and wherein each of the plurality of slotted portions expands and flares outwardly into surrounding bone in the femoral head as the device is advanced beyond the distal end of the bore, thereby fixing the position of the device within the femur.

5. The device of claim 4, wherein the handle comprises a tubular structure, and the grooved portion near the first end of the tubular structure is integral with and forms a sidewall of the tubular structure.

6. The device of claim 5, further comprising an end cap with a flared circumferential surface that facilitates outward expansion and flaring of the fluted portion into surrounding bone as the device is advanced beyond the distal end of the bore.

7. The device of claim 5, further comprising a plurality of morri-bolt-like portions positioned proximate the second end, wherein each of the plurality of morri-bolt-like portions expands outward into surrounding bone of the greater trochanter.

8. The device of claim 7, wherein the handle further comprises a screw having a threaded portion, and wherein the tubular structure defines a screw receiving channel with corresponding and matching threads such that the screw is inserted into the tubular structure and received in the screw receiving channel, rotation of the screw relative to the screw receiving channel advancing the screw and forcing the morri-bolt-like portion proximate the second end to expand outwardly into the surrounding bone.

9. The device of claim 1, wherein the handle includes a tubular structure and a screw having a threaded portion for engaging a screw-receiving channel defined by the tubular structure, and wherein the expansion mechanism is a plurality of mory expansion bolt-like portions positioned proximate a first end of the device such that the screw is inserted into the tubular structure and received in the screw-receiving channel while rotation of the screw relative to the screw-receiving channel advances the screw and forces each of the plurality of mory bolt-like portions to expand outward into the surrounding bone.

10. The device of claim 1, wherein the expansion mechanism comprises:

a plurality of rods surrounding the shank;

a first end cap at a first end of the handle; and

a plurality of links, each said link connecting one of said plurality of rods to the first end cap and each said link pivotally connected at one end to the first end cap about a pivot;

wherein, when the device is positioned in the bore, each of the plurality of rods is advanced toward the first end of the shank, causing the respective links to rotate about the respective pivot such that each rod is controllably distracted into the surrounding bone.

11. The device of claim 10, wherein each of the links defines a cavity near its opposite end for receiving a distal end of one of the rods such that when each of the plurality of rods is advanced toward the first end of the handle, the distal end of the respective rod is pressed into the cavity defined by the respective link, causing the respective link to rotate about the respective pivot.

12. The device of claim 10, further comprising a sleeve for maintaining the positioning of the rod relative to the handle.

13. The device of claim 1, wherein the expansion mechanism comprises:

a plurality of rods surrounding the shank;

a first end cap at the first end of the shank and having a flared circumferential surface;

wherein, when the device is inserted into the hole, each of the plurality of rods is advanced toward the first end of the stem, the distal end of each rod contacting the flared circumferential surface of the first end cap, which forces each rod outward into the surrounding bone.

14. The device of claim 13, further comprising a sleeve for maintaining the positioning of the rod relative to the handle.

15. The device of claim 13, further comprising a second end cap at a second end of the device, the second end cap having a second flared circumferential surface, and the second end cap defining a screw receiving channel for receiving the threaded portion of the shank, such that when the second end cap is rotated to advance toward the first end cap, the second flared circumferential surface of the second end cap engages the rod, forcing the rod outward and into the surrounding bone at the second end.

16. A device for preventing a fracture of a femur, the portion of the femur characterized by a femoral head, a greater trochanter, a femoral neck, and a femoral stem, the device comprising:

a stem having a first end and a second end, wherein the stem is positioned in a hole of a predetermined depth in the femur that extends along a generally horizontal axis from the greater trochanter to the femoral head and terminates near an axis defining a normal load bearing vector of the femur such that the first end is positioned in the femoral head and the second end is positioned in the greater trochanter; and

an expansion mechanism for engaging the femoral head at a first end.

17. A method for preventing a fracture of a femur, the portion of the femur characterized by a femoral head, a greater trochanter, a femoral neck, and a femoral stem, the method comprising the steps of:

forming a hole in the femur to a predetermined depth, the hole extending along a generally horizontal axis from the greater trochanter to the femoral head;

positioning a device in the bore, the device comprising a stem having a first end and a second end, the first end positioned in the femoral head and the second end positioned in the greater trochanter, and the device further comprising an expansion mechanism for engaging the femoral head at the first end; and

manipulating the device to expand the expansion mechanism outwardly into the surrounding bone.

18. The method of claim 17, wherein the hole terminates near an axis defining a normal load bearing vector of the femur.

19. The method of claim 17, wherein the handle comprises a tubular structure, wherein the expansion mechanism is a plurality of slotted portions positioned proximate a first end of the tubular structure, the slotted portions being integral with and forming a sidewall of the tubular structure, and wherein the step of manipulating the device is accomplished by using a driving tool to advance the device into a femoral head beyond a distal end of the aperture, thereby expanding the slotted portions into the surrounding bone.

20. The method of claim 17, wherein the handle includes a tubular structure and a screw having a threaded portion for engaging a screw-receiving channel defined by the tubular structure, wherein the expansion mechanism is a plurality of mory bolt-like portions positioned proximate a first end of the device, and wherein the step of manipulating the device is accomplished by rotating the screw relative to the screw-receiving channel, thereby advancing the screw and forcing each of the plurality of mory bolt-like portions to expand outwardly into the surrounding bone.

21. The method of claim 17, wherein the expansion mechanism includes a plurality of rods about the handle, a first end cap at a first end of the handle, and a plurality of links, each of the links connecting one of the plurality of rods to the first end cap and each of the links pivotally connected at one end to the first end cap about a pivot, and wherein the step of manipulating the device is accomplished by advancing each of the plurality of rods toward the first end causing the respective link to rotate about the respective pivot such that each rod is controlled to expand into the surrounding bone.

22. A method for preventing a fracture of a femur, the portion of the femur characterized by a femoral head, a greater trochanter, a femoral neck, and a femoral stem, the method comprising the steps of:

providing a first assembly comprising

A first screw having a threaded portion and a second screw,

a first tubular structure having a first end and a second end and further defining a screw-receiving channel with threads for mating with a threaded portion of a first screw, an

A plurality of mory bolt-like portions positioned proximate the first end of the first tubular structure,

providing a second assembly comprising

A second screw having a threaded portion and,

a second tubular structure having a first end and a second end,

a plurality of grooved portions at the first end, an

A screw receiving element positioned at the first end of the second tubular structure and having mating threads that engage the threaded portion of the second screw,

positioning a first component in a hole of a predetermined depth in a femur, the hole extending along a generally horizontal axis from the greater trochanter to the femoral head such that a first end is positioned in the femoral head and a second end is positioned in the greater trochanter;

rotating the first screw relative to the screw-receiving channel of the first tubular structure, thereby forcing each of the plurality of morri-bolt-like portions to expand outwardly into the surrounding bone;

removing the first screw;

advancing the second component through the first tubular structure until its first end is proximate the expanded mory bolt-like portion of the first component; and

rotating the second screw relative to the screw receiving element, thereby pulling the screw receiving element toward the second end and forcing the fluted portion to expand outward into the surrounding bone.