Interlocking nail geometry and method of use

An interlocking nail having an hour-glass geometry is used for repair of bone fractures. The hour-glass interlocking nail includes a proximal section, a mid section, and a distal section. Each section of the hour-glass interlocking nail has a diameter. The proximal and distal sections each have a diameter larger than the mid section so that the interlocking nail has an hour-glass geometry. The hour-glass interlocking nail comprises at least one fixation aperture located within either the proximal or distal section of the hour-glass interlocking nail. Preferably, the fixation aperture has a tapered locking design adapted to receive a screw-cone peg. The hour-glass geometry utilized by the interlocking nail is better suited to address a larger population of bone canal geometries, stressing the fracture site with known values within the healing process and preventing inadvertent perforation of the nail through the cortex of the bone. Hour-glass nail geometry more appropriately distributes stresses and promotes better healing at the bone fracture.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an improved interlocking nail geometry and method for use; and more particularly to an interlocking nail having an hourglass-shaped construction with an optional self-tapping tapered locking design.

2. Description of the Prior Art

Animals and humans often suffer from long bone fractures, such as fractures of the femur, tibia and humerus, which require medical intervention for stabilization. Surgery is generally required and involves implantation of devices appointed to provide stability for bone healing. Reconstruction of long bone fractures is generally achieved utilizing various implant devices currently available in human and veterinary fields. Varying levels of success are achieved through use of these conventional orthopedic devices based on their ability to stabilize the fracture and promote bone healing.

Non-stability at the fracture site can result in delayed healing and, in some cases, non-union of the fracture, thereby requiring revision surgery. In the latter scenario, fibrous tissue grows at the fracture site instead of bone, creating an unstable, painful limb. Non-union cases require revision surgery using combinations of these devices, i.e., interlocking nails in adjunct with an external fixator device. The common basis for resolving non-stability problems is to establish adequate resistance to bending and torsion through these device reconstructions, thereby preventing excessive motion at the fracture site and allowing the bone to bridge.

Orthopedic devices currently utilized involve combinations of implant devices, including: (i) external fixation devices with pins; (ii) bone plates and screws; and (iii) interlocking nails and transverse bolts or screws. (SeeFIGS. 1a,1b, and1cherein).

External fixation devices frequently fail to provide the requisite stability for proper bone healing, making use of these devices undesirable. Problems with external fixation devices occur not only from stability, but are also due to infection, as the pins used to stabilize the fragments extend through the skin into the bone, resulting in potential pathways for bacteria. Stability can be provided utilizing bone plates and screws, implantation of these devices requires invasive surgical procedures. Interlocking nails heretofore disclosed and utilized provide a less invasive approach than the bone plates and screws. However most designs of these devices do not provide adequate resistance to bending and torsion, and result in delayed union or non-unions due to micromotion of the construct.

Current interlocking nails are inadequate in achieving stability due to the nail geometry and the fit between the screw and the nail. Most nails are a straight rod design of consistent cross section, which creates higher stresses at the proximal and distal portions of the nail challenging the fixation. If these fracture fixation issues can be resolved, interlocking nails have the potential to provide a less invasive surgical approach and yield proper bone stabilization to promote healing.

Notwithstanding the efforts of prior art workers to construct an efficient interlocking nail that stabilizes bone fractures and promotes healing, there remains a need in the art for an interlocking nail having a geometry that promotes stability and, at the same time, requires less invasive surgical implantation. In addition, there is a need in the art for an interlocking nail having an hour-glass geometry and an optional rounded entry tip. Further, there is an art-recognized need for an interlocking nail having an hour-glass geometry and fixation holes provided with a self-tapping, tapered, locking design.

SUMMARY OF THE INVENTION

The present invention provides an interlocking nail having an hour-glass geometry especially suited to stabilize bone fractures and promote healing. An hour-glass geometry is utilized by the interlocking nail to increase stability and provide for flexible entry into bone canals. The hour-glass shape of the interlocking nail permits a less invasive surgical implantation than can be achieved with conventional implantation devices. In addition, the hour-glass shaped interlocking nail contains an optional rounded tip that affords smoother entry of the nail, while minimizing further injury to the bone. Fixation holes are provided within the hour-glass interlocking nail construction. These fixation holes, or apertures, preferably comprise a self-tapping, tapered, locking design.

The hour-glass interlocking nail geometry and method of use provide a novel design for an interlocking nail device. Introduction into the canal of long bones is more readily achieved, thereby minimizing the insertion force. The hour-glass geometry utilized by the hour-glass interlocking nail is better suited to address a larger population of bone canal geometries, stressing the fracture site with known values within the healing process and preventing inadvertent perforation of the nail through the cortex of the bone. Hour-glass nail geometry more appropriately distributes stresses and promotes better healing at the bone fracture. The loading process produced by the hour-glass nail geometry correspondingly results in less stress at the proximal and distal ends and a more biocompatible micromotion at the fracture, which helps to prevent loosening of the implantation device.

The hour-glass interlocking nail includes a proximal section, a mid section, and a distal section. Each section of the hour-glass interlocking nail has a diameter. The proximal and distal sections have diameters larger than the mid section so that the hour-glass interlocking nail has an hour-glass geometry. In addition, the hour-glass interlocking nail comprises at least one fixation aperture located within either the proximal or distal section of the hour-glass interlocking nail.

In one embodiment, the hour-glass interlocking nail's proximal and distal sections each have at least one fixation aperture. Alternatively, the proximal and distal sections of the hour-glass interlocking nail each have two fixation apertures. The fixation aperture may have a first aperture diameter and a second aperture diameter. The first aperture diameter is larger than the second aperture diameter, so that the fixation aperture has a tapered locking mechanism integrated therein. Alternatively, the fixation aperture is adapted to receive a screw, bolt, peg, or the like. The fixation aperture may further comprise grooves therein, appointed to engage with grooves on a screw, bolt, or peg, or the like. The hour-glass interlocking nail may comprise a plurality of fixation apertures located within each of the proximal or distal sections.

In another embodiment the distal section comprises a distal tip having an arc therein constructed to form a tip having at least one arc portion. Alternatively, the distal section comprises a distal tip having a substantially arced tip constructed to form a substantially radiused tip. Optionally the distal section comprises a distal tip having at least one flat edge adapted to form a substantially sharp tip.

The proximal section may comprise a proximal end comprising a connector adapted to be utilized for insertion and alignment of the hour-glass interlocking nail into a bone canal. The connector further comprises at least one ridge portion, at least one cut-out portion, and a central aperture. The central aperture extends through the proximal end and traverses into the proximal section. Optionally, the central aperture is threaded and adapted to receive a bit for insertion and alignment of the hour-glass interlocking nail into the bone canal.

Instead of the connector comprising at least one ridge portion, cut-out portion, and central aperture, the connector may alternatively comprise a conical fitting projecting from the proximal end. The conical fitting may comprise at least one flat side. The conical fitting having the at least one flat side is utilized for positioning and rotational control of the hour-glass interlocking nail during insertion and alignment.

In another embodiment, the proximal section has a proximal diameter, the distal section has a distal diameter, and the mid section has a first, second, and central diameter. The proximal and distal sections each have a diameter larger than the mid section. In turn, the first and second diameters of the mid section are larger than the central diameter of the mid section. The mid section is appointed to flex when the hour-glass interlocking nail is inserted into a bone canal having a curved geometry.

A method of using an hour-glass interlocking nail having an hour-glass geometry is provided. The method comprises the first step of examining a bone fracture to determine an appropriate sized hour-glass interlocking nail to be utilized. Appropriate length and diameter of the hour-glass interlocking nail are determined when selecting the hour-glass interlocking nail. The fractured bone has a bone canal with bone cortex interstitially therein. The method further comprises selecting the hour-glass interlocking nail. The hour-glass interlocking nail comprises a proximal section, mid section, and distal section. Each section of the hour-glass interlocking nail has a diameter and the proximal and distal sections each have a diameter larger than the mid section so that the hour-glass interlocking nail has an hour-glass geometry. At least one fixation aperture is located within either the proximal or distal section of the hour-glass interlocking nail. The proximal section comprises a proximal end having a connector adapted to be utilized for insertion and alignment of the hour-glass interlocking nail into the bone canal.

At least one locking means is selected. The locking means is appointed to be received by the fixation aperture located within either the proximal or distal section of the hour-glass interlocking nail. The locking means comprises a first end, center, and a second end. A substantial portion of the hour-glass interlocking nail is inserted into the bone canal. An alignment device is attached to the connector of the proximal end of the hour-glass interlocking nail. The bone is penetrated with the locking means, causing the locking means to enter the fixation aperture. A first end of the locking means extends from the hour-glass interlocking nail and traverses into the bone cortex. At the same time, the center of the locking means becomes housed within the fixation aperture, and the second end of the locking means extends from the hour-glass interlocking nail and traverses into the bone cortex opposite the first end.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides an hour-glass interlocking nail geometry and method of use having a novel design for an interlocking nail device. Introduction into the canal of long bones is more readily achieved, thereby minimizing the insertion force. The hour-glass geometry utilized by the hour-glass interlocking nail is better suited to address a larger population of bone canal geometries, stressing the fracture site with known values within the healing process and preventing inadvertent perforation of the nail through the cortex of the bone. Hour-glass nail geometry more appropriately distributes stresses and promotes better healing to the bone fracture. This loading process via the geometry correspondingly results in less stress at the proximal and distal ends, and a more biocompatible micromotion at the fracture helping to prevent loosening of the implantation device. The term ILN, as used herein, refers to interlocking nail. The term HR-ILN, as used herein, refers to the novel hour-glass interlocking nail of the subject invention.

The hour-glass interlocking nail geometry and method of use comprises geometry with an area moment of inertia (AMI) consistent with the AMI of bone plates which have successfully demonstrated the achievement of sufficient stability for fracture fixation. This AMI, relative to the AMI of successful bone plates, is established at the center of the nail and the resulting fracture site. The term AMI, as used herein, refers to the area moment of inertia.

FIGS. 1a,1b, and1cillustrate fractional fixation devices currently used in human and veterinary orthopedics. Specifically,FIG. 1ashows a top view of a bone plate and screw combination currently utilized to repair bone fractures;FIG. 1bshows currently utilized interlocking nails and transverse bolts or screws; andFIG. 1cshows currently utilized external fixation devices with pins. These orthopedic devices are currently utilized to repair bone fractures. As set forth hereinabove in the “Description of Prior Art Section”, these devices have several disadvantageous. Including, failing to provide the requisite stability for optimal bone healing and frequency in non-union cases, and thereby requiring revision surgery. Plate and screw combinations currently utilized result in invasive surgical procedures, which can increase the patient's healing time as well as risk of infection during the operating procedure. External fixation devices frequently fail to provide the requisite stability and also can lead to infection as the pins used to stabilize the fragments extend through the skin into the bone, resulting in potential pathways for bacteria. Interlocking nails currently utilized provide a less invasive approach than the bone plates and screws, however most designs of these devices do not provide adequate resistance to bending and torsion and result in delayed union or non-unions due to micro motion of the construct.

FIGS. 2aand2billustrate conventionally utilized interlocking nails having straight nail rigid geometry and sharp point construction, and further illustrate stress distribution and disadvantageous of the combination of straight nail geometry and sharp point construction during insertion of the interlocking nail into a bone canal.FIG. 2ashows a side view of a conventional interlocking nail;FIG. 2bshows insertion of the conventional interlocking nail into a bone cavity. Conventional interlocking nails generally have a rigid straight construction appointed with a sharp point and fixation holes. Current interlocking nails are inadequate in achieving stability due to the nail geometry and the fit between the screw and the nail. Most nails are a straight rod design of consistent cross section, which creates higher stresses at the proximal and distal portions of the nail, challenging fixation and interrupting bone healing. If these fixation issues can be resolved, interlocking nails have the potential to provide a less invasive surgical approach and yield proper bone stabilization to promote healing. Flexible interlocking nail geometry is also important to the reconstruction of a fractured bone. Insertion force must be applied to overcome the bending moment of the nail. During insertion into curved long bones, stiffer nail designs resist adequate flexing. As a result, the fractured bone is forced to conform to the nail's geometry rather than the nail conform to the bone's geometry. Sharp tips utilized by conventional interlocking nails create high stress to the fractured bone and can perforate the cortex during insertion.

FIG. 3illustrates a top planer view of the hour-glass interlocking nail geometry of the subject invention, wherein the hour-glass interlocking nail has a non-rigid geometry and rounded tip construction and self-tapping tapered locking design shown generally at10.FIG. 4aillustrates a side view of the hour-glass interlocking nail having a non-rigid geometry and rounded tip construction and self-tapping tapered locking design, shown generally at30. Hour-glass interlocking nail10,30comprises a proximal section11, mid section12, and distal section13. Each section,11,12, and13of the hour-glass interlocking nail has a diameter. The proximal and distal sections,11and13, each have a diameter larger than the mid section12so that the hour-glass interlocking nail has hour-glass geometry.

Hour-glass interlocking nail10,30comprises at least one fixation aperture14located within either the proximal or distal section,11,13. Preferably, fixation aperture14is tapered and has a locking design (discussed hereinafter). In one embodiment the hour-glass interlocking nail's proximal and distal sections,11, and13, each have at least one fixation aperture14. Preferably the hour-glass interlocking nail10,30, comprises a plurality of fixation apertures14located within each of the proximal and I or distal sections11,13, and I or throughout the mid section11(SeeFIG. 10herein showing an alternative embodiment ofFIG. 6b). Most preferably, the proximal and distal sections,11and13, of the hour-glass interlocking nail each have two fixation apertures, as is shown inFIGS. 3 and 4a.

Proximal section11comprises a proximal end20having a connector21constructed interstitially therein. Connector21is appointed to be utilized for insertion and alignment of the hour-glass interlocking nail into a bone canal. In the embodiment shown inFIGS. 4a-4d, connector20further comprises at least one ridge portion22, at least one cut-out portion23, and a central aperture24. Central aperture24extends through proximal end20and traverses into proximal section11, forming a central cavity25. Optionally, central cavity25is threaded or grooved and is appointed to receive a bit for insertion and alignment of the hour-glass interlocking nail into the bone canal. (Discussed in further detail viaFIGS. 4cand4d). Instead of the connector comprising at least one ridge portion, cut-out portion, and central aperture, the connector may alternatively comprise a conical fitting projecting from the proximal end. This alternative embodiment is shown inFIGS. 5aand5band same is discussed hereinbelow.

FIG. 4billustrates a cross-sectional view of a preferred embodiment of the fixation aperture taken along line X ofFIG. 4a, wherein the fixation aperture comprises a self-tapping tapered locking design, shown generally at40. As best illustrated inFIG. 4b, fixation aperture14has a first aperture diameter41and a second aperture diameter42. First aperture diameter41is larger than second aperture diameter42so that the fixation aperture14has a tapered configuration. This tapered configuration is integrated within the hour-glass interlocking nail30and acts as a locking mechanism for securing the hour-glass interlocking nail to the bone cortex. Fixation aperture14is appointed to receive a tapered screw, screw-cone peg locking device, screw, bolt, peg, or the like for fixture of the hour-glass interlocking nail within the bone. The fixation aperture14may further comprise grooves therein, appointed to engage with grooves on a screw-cone peg, screw, bolt, or peg, or the like for fixture of the hour-glass interlocking nail within the bone.

Continuing withFIGS. 1 and 4a, distal section13comprises a distal tip15. Distal tip15may have at least one flat edge to form a substantially sharp tip (shown inFIG. 8). Preferably, distal tip15is appointed with an arc therein constructed to form a tip having at least one arc portion so that the distal tip15has a rounded portion constructed therein. Most preferably, distal tip15has a substantially arced or rounded tip therein constructed to form a substantially radiused or semi-spherical bullet point tip16. (SeeFIGS. 6a,6b, and6c).

Proximal section11comprises a proximal end20having a connector21constructed interstitially therein. Connector21is appointed to be utilized for insertion and alignment of the hour-glass interlocking nail into a bone canal. In the embodiment shown inFIGS. 4a-4dconnector20further comprises at least one ridge portion22, at least one cut-out portion23, and a central aperture24. Central aperture24extends through proximal end20and traverses into proximal section11, forming a central cavity25. Optionally, central cavity25is threaded or grooved and is appointed to receive a bit for insertion and alignment of the hour-glass interlocking nail into the bone canal. Instead, the connector may alternatively comprise a conical fitting projecting from the proximal end. This alternative embodiment is shown inFIGS. 5aand5band same is discussed hereinbelow.

FIGS. 4cand4dillustrate cross-sectional views of the proximal end20and connector21.FIG. 4cshows the proximal end20and connector21taken along line V, shown generally at100.FIG. 4dshows the proximal end20and connector21taken along section VI and line VII, shown generally at110. Proximal end20is provided with connector21. As shown in the embodiment ofFIG. 4c, proximal end20is equipped with connector21, which has at least one ridge portion22and at least one cut-out portion23. Preferably, there are two ridge portions22and two cut-out portions23arranged in a staggered arrangement to one another to form a central aperture24as is shown inFIG. 4c. Threads or other locking means101may be provided within central aperture24. Referring toFIG. 4d, showing a cross-section side view of the proximal section11, proximal end20, and connector21, central aperture24extends within proximal section11. Preferably, central aperture24is fully threaded throughout a body portion111of the central aperture24to form central cavity25. Central cavity25further includes a central tip112and an end tip113. Preferably, central tip112and end tip113are not threaded. These ridge portions22, cut-out portions23, and central aperture are appointed to engage with a bit, or the like, of an alignment and/or insertion instrument. An alternative embodiment of the connector is shown inFIGS. 5aand5band same is discussed hereinbelow.

FIGS. 5aand5billustrate views of the hour-glass interlocking nail having a non-rigid geometry and rounded tip construction, and further illustrate an alternative embodiment wherein the connector comprises a conical fitting projecting from the proximal end, shown generally at150and180, respectively.FIG. 5bis shown at180and is taken along section A ofFIG. 5a. In this embodiment, hour-glass interlocking nail151comprises a proximal section152, mid section153, and distal section154. Each section,152,153, and154of the hour-glass interlocking nail has a diameter. The proximal and distal sections,152and154, each have a diameter larger than the mid section153so that the hour-glass interlocking nail has hour-glass geometry. Hour-glass interlocking nail151comprises at least one fixation aperture155located within either the proximal or distal section,152,154. Preferably, fixation aperture155is tapered and has a locking design (discussed hereinafter). In one embodiment the hour-glass interlocking nail's proximal and distal sections,152, and154, each have at least one fixation aperture155. Preferably the hour-glass interlocking nail151comprises a plurality of fixation apertures155located within each of the proximal and/or distal sections152,154, and/or throughout the mid section153. Most preferably, the proximal and distal sections,152and154, of the hour-glass interlocking nail151each have two fixation apertures as is shown.

Proximal section152comprises a proximal end156having a connector157constructed interstitially therein. Connector157is appointed to be utilized for insertion and alignment of the hour-glass interlocking nail151into a bone canal. In the embodiment shown, connector157further comprises a conical fitting158projecting or outwardly extending from proximal end156. In this embodiment, connector157is appointed to be received in an orifice or aperture of an instrument appointed for aligning and inserting the hour-glass nail151into the bone canal. Conical fitting158may comprise at least one flat side159for advancing positioning and rotational control of the hour-glass interlocking nail during insertion and alignment into the bone canal. Preferably, conical fitting158comprises two flat sides159arranged parallel to one another. The conical fitting158may be threaded for attachment to an alignment/inserter. The connector157is conical for locking to the alignment and/insertion instrument and has the side flats for positioning and rotational control during insertion. An indent181(shown inFIG. 5b) may be included on conical fitting158for further facilitating placement within an insertion or aligning instrument.

FIGS. 6a,6b, and6cillustrate side views of the hour-glass interlocking nail having a non-rigid geometry and rounded tip construction. Specifically,FIG. 6ashows a side view of the hour-glass interlocking nail, illustrating stress distribution, radiused or semi-spherical bullet point tip, and hour-glass construction, shown generally at70;FIG. 6bshows a side view of the hour-glass interlocking nail wherein the nail has a narrower mid section12, shown generally at80; andFIG. 6cshows advantages of the hour-glass interlocking nail geometry during insertion of the interlocking nail into a bone canal, shown generally at90. Taken from the center71of mid section72, the geometry of the nail70gradually increases extending from both sides until establishing two larger diameters at the proximal section73and distal section74provided with fixation apertures75. Proximal section73has a proximal diameter, the distal section74has a distal diameter, and the mid section has a first, second, and central diameter. The proximal and distal sections73,74each have a diameter larger than the mid section72. The mid section is adapted to flex when the hour-glass interlocking nail is inserted into a bone canal having a curved geometry.

Distal section74is provided with a substantially radiused bullet point tip76. This hour-glass geometry can be accomplished through a large radius or by tapering the nail from the center71out to larger proximal and distal sections. Proximal and distal sections are adapted to incorporate screw or bolt holes proving a method of locking the nail to the proximal and distal areas of the bone relative to the fracture site.FIG. 6bshows a more narrowed center81of mid section82so that there are virtually tapered cones on both sides of the center81, increasing in radius on both sides to form proximal and distal sections,83and84, and yield hour-glass geometry. Proximal and distal sections83,84are provided with fixation apertures85. Distal section84is provided with a substantially radiused bullet point tip86.

Hour-glass geometry of the interlocking nail and the designed bullet point promote optimal insertion into the bone canal. Insertion into the bone canal can be achieved without reaming, providing for a less invasive surgical procedure. The use of thinner interlocking nails without reaming of the medullary cavity has biological advantages, such as preservation of the endosteal and medullary blood supply; however, thin INLs procedure places the construct at a mechanical disadvantage by reducing the nail-bone contact area and increasing the working length of the locking device. The HR-INL provides the ability to reduce the need for reaming, while at the same time aids in preserving the endosteal and medullary blood supply within the bone. SeeFIG. 6c. Bullet point tip (semi-spherical) construction at the end of the distal section also provides an insurance against inadvertent perforation of the bone canal during insertion, as is often seen with traditional sharp point interlocking nail tips. (CompareFIGS. 2band6c).

The geometry of the hour-glass ILN (HR-ILN) conforms to the natural geometry of the internal canal of bones and promotes bone healing. Insertion of the nail is also improved through the hour-glass geometry by allowing the nail to better flex at its center point99in length (FIG. 6c).FIG. 6cshows insertion of the interlocking nail into a bone canal at90. Force is applied as HR-ILN91is inserted into a bone canal92, HR-ILN91bends or flexes as indicated by arrows93at center point99.FIG. 6cillustrates the geometry of the hour-glass nail during insertion. HR-ILN91includes mid section94with narrow center point99, proximal section95, and distal section96baying radiused bullet tip97. Fixation apertures98are provided. The narrow diameter of mid section94at center point99facilitates bending of the HR-ILN91so that the nail can flex to insert into curved geometry of bone canal92with less stress to the bone and the HR-MN91.

Conventional nails' consistent diameters create additional required insertion loads to overcome the bending stresses due to the curvature of the bone canal. As a result, greater force must be applied when insertion of the conventional nail is required. Reaming is often required when utilizing the conventional interlocking nail. The hour-glass geometry of the novel interlocking nail herein provides benefit of insertion with less necessity for reaming. At the same time, the hour-glass geometry provides ease of insertion into the bone canal, and can minimize the pressure to the endosteum and improve the re-establishment of the medullary blood supply. These features can enhance the bone healing process. The HR-ILN geometry also provides a more balanced stress distribution to the bone. Fixation is achieved through the screws or bolts in the proximal and distal sections of the nail for bone attachment. In a straight consistent cross sectional nail, these ends are exposed to higher stresses and therefore challenge the fixation of the nail to the bone from inception.

The hour-glass geometry re-directs these stresses to the fracture site, which is still capable of resisting deflection and excess micro motion based on the AMI of the center section. Transferring these stresses, minimizes the stress to the fixation ends thereby providing for a more designed stress distribution capable of better fixation and fracture healing. The basic shape of the hour-glass also eliminates any abrupt changes in geometry which would be seen from a geometry providing larger ends for fixation with a reduced center section to the nail.

FIG. 7illustrates the hour-glass interlocking nail shown inFIGS. 4a-4dhaving a non-rigid geometry with rounded tip construction and self-tapping tapered locking design, illustrating mechanical measurements for a 160 mm nail, shown generally at400. The hour-glass interlocking nail has a rounded tip401. Tapered locking design of the fixation aperture is shown at402, and the embodiment of the connector having at least one ridge portion (preferably at least two) and at least one cut-out portion (preferably at least two) as illustrated inFIGS. 4a-4dis shown at403and404.

FIGS. 8 and 9illustrate side views of derivations of the hour-glass interlocking nail of the current invention. Specifically, these figures show a less gradual indentation.FIG. 8shows a reduced mid-section or sharp point design embodiment, shown generally at200. A view of the tapered fixation aperture is also shown, along with views of the connector and tip detail. Herein, the distal end has a pointed or sharp point design tip201. Sharp tip201has at least one flat edge202ato form a substantially sharp tip. Herein, sharp tip201has three flat sides to form a pyramidal sharp tip shown at202.FIG. 9shows a reduced mid-section or rounded or bullet point design301embodiment, shown generally at300.FIGS. 8 and 9are drawings of similar devices but without encompassing all the benefits of the hour-glass geometry. Although the cross section of the hour-glass ILN is shown as a circle, it is also envisioned that different cross sections such as a “Y” or an “X” could provide similar benefits in an hour-glass nail geometry. Initial stability of the hour-glass nail can be achieved through the fixation apertures in the larger diameter cylinders at each end (proximal and distal sections). These fixation apertures can be designed to accept screws, bolts, screw-cone pegs, threaded or non-threaded with the intent of solid fixation to the nail and fixation to the cortices of the bone. This secured fixation between the nail and the bone provides the opportunity for the nail geometry to afford the proper biomechanics for fracture fixation.

Clinical observation was done utilizing 8-mm ILN (hereinafter, ILN8) to treat comminuted fractures of the tibial diaphysis in dogs of mixed-breed, weighing approximately 30 to 35 kg. Prototypes of the HR-ILN (hour-glass interlocking nail of the present invention) system were designed to be of a size comparable to commercially available 8×185-mm ILN. Several primary constraints were addressed in designing the HR-ILN prototypes, including: providing a rigid interaction between the bone and the HR-ILN; and providing a shape that would limit interference with endocortices and facilitate fracture reduction while limiting the risk of joint infraction attributed to perforation of the implant device. In addition, the shape and size of the novel HR-ILN addressed surgical insertion constraints, making insertion easier while mitigating the need for reaming.

The prototypical HR-ILN further addresses secondary constraints of current ILNs, including stiffness and strength issues. The HR-ILN includes a locking device that provides rigid interaction with the nail via tapered fixation apertures, as well as the connector adapted to ensure proper alignment and insertion of the fixation means (i.e. screws, etc.). The AMI of the HR-WLN is greater than that of a 45-mm bone screw and comparable to that of a commercially available 3.5-mm locking bolt. The fixation hole or aperture was designed to be similar to an ILN8 with 3.5-mm bone screws. Prototypes of the HR-ILN were developed having the hour-glass shaped nail featuring an oblong bullet like distal tip and a screw-cone peg locking device. Manufacture of the prototypes was from 316L stainless-steel certified to ASTM F138 standards. The material was chosen because it is the current material of choice for medical manufacturers of similar implants. The patent contemplates use of any suitable material. The outside diameter of the nail ends (proximal and distal) was 8 mm and the center of the mid section was 6 mm at is center. Each proximal and distal section of the nail included two fixation holes, tapered and having a diameter of 40 and 32, respectively. The tapered fixation holes were placed 11 mm apart in each end of the nail. The most proximal and distal nail holes were separated by 155.5 mm. The screw-cone peg was designed as a self-tapping, cortical-type screw with a central Morse taper that corresponded to the fixation holes or apertures. The core diameter of the screw-cone peg was 4 mm and was manufactured in tow lengths, 26 and 30 mm.

FIG. 10illustrates an alternative embodiment of the hour-glass interlocking nail ofFIG. 6bwherein a plurality of fixation apertures is located throughout the mid section.

A method of using an hour-glass interlocking nail having an hour-glass geometry is provided. The method comprises the first step of examining a bone fracture to determine an appropriate sized hour-glass interlocking nail to be utilized. Appropriate length and diameter of the hour-glass interlocking nail is determined in selecting the hour-glass interlocking nail. The fractured bone has a bone canal with bone cortex interstitially therein. The method further comprises selecting the hour-glass interlocking nail. The hour-glass interlocking nail comprises a proximal section, mid section, and distal section. Each section of the hour-glass interlocking nail has a diameter and the proximal and distal sections each have a diameter larger than the mid section so that the hour-glass interlocking nail has an hour-glass geometry. At least one fixation aperture is located within either the proximal or distal section of the hour-glass interlocking nail. The proximal section comprises a proximal end having a connector adapted to be utilized for insertion and alignment of the hour-glass interlocking nail into the bone canal.

At least one locking means is selected. The locking means is appointed to be received by the fixation aperture located within either the proximal or distal section of the hour-glass interlocking nail. The locking means comprises a first end, center, and a second end. A substantial portion of the hour-glass interlocking nail is inserted into the bone canal. An alignment device is attached to the connector of the proximal end of the hour-glass interlocking nail. The bone is penetrated with the locking means, wherein the locking means enters the fixation aperture. The locking mean's first end extends from the hour-glass interlocking nail and traverses into the bone cortex, while the locking means center is housed within the fixation aperture and the second end of the locking means extends from the hour-glass interlocking nail and traverses into the bone cortex opposite the first end.