WO2009131999A2

WO2009131999A2 - Light delivery structure for use in intramedullary transillumination apparatus and method for producing same

Info

Publication number: WO2009131999A2
Application number: PCT/US2009/041248
Authority: WO
Inventors: Jennifer L. Gloisten
Original assignee: Jg Medical Products Llc
Priority date: 2008-04-21
Filing date: 2009-04-21
Publication date: 2009-10-29
Also published as: IL208885A0; EP2285302A4; EP2285302A2; JP2011518022A; WO2009131999A3

Abstract

Apparatus (10), and a method for producing such apparatus, for use in the repair of bones using an intramedullary nail insertable into a patient's bone, the intramedullary nail having a hollow body portion and a distal transverse hole, the apparatus comprising a tube (14) for insertion into the nail, the tube having an opening (20) through which light from a light source emitting electromagnetic non-ionizing radiation in the infrared or visible portions of the electromagnetic spectrum is emitted, an optical conduit such as a bundle of optical fibers in the tube for conducting light from a light source to the opening; an optical element (22), which can be cast in place, providing a light transparent reflective surface disposed in the tube, the reflector being sized, shaped and positioned to receive light from the optical fibers and to internally reflect the light so that the light exits the tube through the opening.

Description

LIGHT DELIVERY STRUCTURE FOR USE IN INTRAMEDULLARY TRANSILLUMINATION APPARATUS AND METHOD FOR PRODUCING SAME

This application claims priority, under 35 U. S. C. §119 (e), from provisional patent application serial number 61/046,516 filed on April 21, 2008, which is hereby incorporated herein, by reference, in its entirety .

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to apparatus for high intensity illumination with a light wand. More particularly, it relates to a light delivery structure useful in apparatus for efficient delivery of light by an intramedullary transillumination apparatus for accurate placement of distal locking screws during the procedure of long bone intramedullary nailing (also known as intramedullary rodding) . The invention also relates to methods for producing such light delivery structures .

Background Art

The teachings of United States Patent Nos . 5,417,688 and 5,540,691 to John A. Elstrom and Peter Elstrom and United States Published Patent Application 20070270864 of James P . Gurtowski are incorporated herein by reference in their entireties . In summary the distal locking light is a medical device designed for use in orthopedic surgery where a hollow pin is inserted into a fractured bone and then anchored in place by insertion of a screw from the side through both bone and pin . Pins used in this application have pre-drilled screw holes which are concealed within the bone . Up until the introduction of the distal locking light, x-rays taken on two axes were required to reveal the location of the hole so that the bone could be drilled and the pin inserted. The distal locking light allows the hole to be illuminated from behind by inserting this thin rod into the hollow pin with light emitting from a small aperture on one side.

Although the devices described in the abovementioned patents and patent publication are suitable for their intended purpose, manufacturability in large quantities presents certain challenges . Delivering light to the side-facing aperture with enough efficiency to be visible through large or dense bones on a consistent, device to device basis may be a problem in the existing designs of the distal locking light . Current versions accept light into a fiber optic bundle which either is bent to the side through the aperture and polished flush, or is directed into fiber optic epoxy onto a polished, 45 degree angled mirror and then out through the aperture . Both methods deliver light to the side of the thin rod, but have inherent inefficiencies, sometimes limiting the amount of useful light produced at the tip . In some cases, commonly used medical light source equipment can only produce enough light to make these designs work in cases where the bone thickness or density is average or below average, leaving the more difficult cases to the x- ray technique .

The bent fiber design can suffer from significant loss of fiber due to breakage in manufacturing, corresponding to an inconsistent and low light output . Since it is

9 difficult for the fibers to make a 90 degree bend within the diameter of the housing tube, the fibers may intersect the aperture angled toward the end of the device . The resulting light pattern on the surface of the bone may be offset from the actual hole location in the pin, providing deceptive information about its exact location. In addition, individual fibers intersecting the cylindrical surface of the aperture may thus be polished at an angle, rather than the optimal flat preferred for controlled light distribution in fiber optics .

The mirror design suffers a loss at the reflective interface formed by the optical fiber epoxy and the stainless steel mirror. Performance of this reflective surface is highly dependent on its texture and any residual films . Adhesion between the epoxy and the mirror is critical to light transmission, but also results in internal stresses . Epoxy has a much higher coefficient of thermal expansion than stainless steel, so that stresses built up during autoclave sterilization, which is required before use in surgery, can degrade the interface at the mirror reducing light output. Further, selection of an epoxy from the commercially available materials to optimize this bond to the mirror is limited by the requirements for light transmission and medical compatibility . SUMMARY OF THE INVENTION

It is an object of the invention to provide a structure for efficiently transmitting light out of the illuminating device .

It is a further object of the invention to provide such a structure which can be manufactured efficiently and consistently in large quantities .

It is another object of the invention to provide a method for manufacturing an illumination device utilizing such a structure .

These objects and others are achieved in accordance with the invention by a structure that eliminates the inherent inefficiencies in the two designs described above, effectively doubling the typical output of the distal locking light. This new design utilizes total internal reflection to direct the light from its axial path down the housing to a new path at 90 degrees through the aperture in the side of the housing. Using reflection within an optical element eliminates the inefficiencies and variations inherent in bending optical fiber or sealing epoxy to a metallic mirror surface . In the current embodiment, the optical element is formed from an epoxy which provides filling and sealing of the light emitting window such that no additional light losses occur by passing light through separate lenses or interfaces . The required angle of impingement of the light on the internal surface to create the 90 degree turn is 45 degrees, more than the substantially 40 degree or 40.4 degrees minimum of the embodiment described herein, based on Snell's law and the epoxy used, that will cause light rays to reflect internally. The limiting value is calculated from the ratio of the index of refraction properties of the optical element and air.

Thus, the invention is directed to an apparatus, for use with, for example, a surgical drill, in the repair of bones using an intramedullary nail insertable into a patient's bone, the intramedullary nail having a hollow body portion and a distal transverse hole, the apparatus comprising a tube like device for insertion into the intramedullary nail, the device having an opening through which light from a light source emitting electromagnetic non-ionizing radiation in the infrared or visible portions of the electromagnetic spectrum is emitted, an optical conduit, such as a bundle of optical fibers, or a somewhat flexible light pipe, in the tube for conducting light from a light source to the proximity of the opening; and an optical element providing total internal reflection, which may be a light transparent reflector, generally having a surface which crosses the light path at an angle, appearing as wedge shaped in cross section, disposed in the tube, and which is sized, shaped and positioned to receive light from the optical conduit and to internally reflect the light so that the light exits the tube through the tube opening. The end of the optical conduit, or the ends of the fibers, can be embedded in the optical element . The optical element can comprise a hardened resin. The end of the optical conduit, or the ends of the fibers, are embedded in the optical element before the resin is hardened, and the resin is solidified around the ends of the optical conduit or fibers . The optical element may comprise a hardened epoxy, wherein the epoxy fills the opening and seals to the tube .

The reflective surface of the optical element can be made to act as a beam shaping mirror by designing it as a convex or concave shape, or by adding facets. The external surface of the optical element serves as a lens . In this embodiment it is a convex cylindrical lens focusing the light beam as it leaves the tube opening.

The resin, and in particular the two part epoxy resin, from which the optical element is formed, should have high spectral transmission, should be medically acceptable or compatible, should be able to withstand the temperature range required for steam sterilization, and have good adhesion to steel and glass .

The reflector may be a molded or machined element of a polymer or a glass, and the optical conduit may extend from an external surface of the optical element . An end cap may seal an end of the tube closest to the opening, to preserve the cleanliness and integrity of an air pocket behind the optical element's reflective surface.

The invention is also directed to a method for producing an apparatus for use with, for example, a surgical drill in the repair of bones using an intramedullary nail insertable into a patient's bone, comprising providing a tube like device for insertion into the intramedullary nail, the device having an opening through which light from a light source emitting electromagnetic non-ionizing radiation in the infrared or visible portions of the electromagnetic spectrum is emitted, placing an optical conduit, such as a bundle of optical fibers, or a somewhat flexible light pipe, in the tube for conducting light from a light source to the proximity of the opening; and disposing in the tube an optical element providing total internal reflection, which may be a light transparent reflector, generally having a surface which crosses the light path at an angle, appearing as wedge shaped in cross section, and sized, shaped and positioned to receive light from the optical fibers and to internally reflect the light so that the light exits the tube through the tube opening. The end of the optical conduit can be embedded in the optical element . The optical element can be formed of a hardened resin . The end of the optical conduit or optical fibers are embedded in the optical element before the resin is hardened, and the resin is solidified around the ends of the optical conduit or fibers . The optical element can be formed of a hardened epoxy, wherein the epoxy fills the opening and seals to the tube.

The reflective surface of the optical element may be formed in place in the tube by placing a removable plug in an end of the tube closest to the opening, the plug having an end with a shape complimentary to the shape of an internally reflective surface of the optical element; placing a resin which can harden in place in the tube between the end of the plug and ends of the optical fibers; and hardening the resin in place. The method may further comprise removing the plug from the tube; and placing an end cap on the tube so as to seal the end of the tube closest to the opening, to preserve the cleanliness and integrity of an air pocket behind the optical element's reflective surface.

The method can further comprise capturing ends of the optical fibers in a ferrule to form an optical fiber subassembly; and embedding ends of the optical fibers of the subassembly in the optical element before the epoxy hardens . The ends of said optical fibers can be captured in the ferrule by applying an epoxy resin in the spaces between the optical fibers and between the optical fibers and the ferrule; and applying heat treatment to harden and relieve stresses in the epoxy.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and other features of the present invention are explained in the following description, taken in connection with the accompanying drawings, wherein :

Fig. 1 is a plan view of an apparatus in accordance with the invention mounted.

Fig. 2 is an end view of the apparatus of Fig. 1.

Fig. 3 is an enlarged cross-sectional view of a portion of the apparatus of Fig. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to Fig. 1, there is shown a plan view of an apparatus 10, incorporating features of the present invention. Although the present invention will be described with reference to the single embodiment shown in the drawings, it should be understood that the present invention can be embodied in many alternate forms of embodiments. In addition, any suitable size, shape or type of elements or materials could be used.

The apparatus 10 of Fig. 1, useful for intramedullary transillumination, is described generally in the abovementioned United States Published Patent Application 20070270864 of James P. Gurtowski, and will not be discussed in detail herein, but instead is incorporated herein by reference for all purposes. As shown in Fig. 1, and Fig. 2, apparatus 10 has a light coupling 12 to which a commercial fiber optic light source, of a type well known in the art, and used in medical applications, may be coupled to provide light to a conduit for light, such as a bundle of optical fibers which run along the length of a tubular housing or tube 14, of apparatus 10, tube 14 being generally formed of thin walled, medically compatible stainless steel .

Referring to Fig. 3, the internal reflection design in a current embodiment utilizes a fiber subassembly 16 that is terminated with a stainless steel ferrule 18 at either end into which the fibers of the subassembly 16 have been inserted, epoxied, and polished flush. The epoxy is EPO-

TEK 353ND, available from Epoxy Technology Inc. of Billerica, MA, USA. It is first cured using, for example a heat gun, as the temperature of initial cure is not believed to be critical. However, these subassemblies 16 are then cured or annealed for 5 minutes at 250 degrees

C; a process in which temperature and time control appear to be more critical . The high temperature cure reduces internal stresses within the stainless steel ferrule containing the glass fibers and raises the glass transition temperature of the epoxy.

The optical fiber subassembly 16 is assembled into the tubular housing or tube 14 through its light collecting end such that the emitting end points straight down the axis of the housing away from the source connected to apparatus 10 by connector 12 after a temporary plug (not shown) including a surface for directing and shaping light at roughly 45 degrees is inserted into the emitting end of the housing. The temporary plug is positioned so that the angled surface faces the fiber assembly and also the light emitting aperture 20 in the side of the tubular housing or tube 14. This temporary plug may be made of a variety of materials, including Teflon® or Delrin® (or other material to which the epoxy does not strongly adhere, preferably such as a high density polyethylene (HDPE)) in order to facilitate removal later. It may also be gasketted with an O-ring, or other compliant material such as a tape, to contain the liquid epoxy.

A light transparent and medically acceptable epoxy, such as EPO-TEK 302-3M, available from Epoxy Technology Inc. of Billerica, MA, USA, is applied to the device through the aperture 20 in the side of the tubular housing 10. The epoxy fills the cavity in the tubular housing or tube 14 formed by fiber subassembly 16 and the temporary plug, bonding to and constraining the emitting end of the optical conduit (the optical fibers in the ferrule 18, in this embodiment of the invention) and taking the shape of the bottom of the temporary plug. Once the epoxy hardens for 24 hours at room temperature forming the optical element, the fiber assembly at the light input end of the device is glued using the same 302-3M epoxy, for example. The fiber assembly is compressed slightly during this gluing operation to prevent lengthwise tensile forces from being imposed on the fiber assembly during the intense heat of steam sterilization. After both applications of epoxy have hardened, the plug is removed and the assembled unit is heat treated for 1 hour at 125 degrees C. The temporary plug is then replaced with a mechanical end cap 24 to protect the reflecting surface and the required air gap behind it, and also to finish the housing assembly.

In use, light travels from the fiber bundle subassembly 16 directly into the epoxy optical element 22 bonded to the fiber bundle subassembly 16. Once in the epoxy optical element 22, light travels to the angled, directing and shaping surface originally formed by the temporary plug. Most of the light impinges on the surface at more than 40.4 degrees and so is reflected internally. This light stays within the epoxy but has been redirected at an angle of 90 degrees from its original path. It reaches the light emitting aperture 20 and is emitted through the lens surface of the optical element 22 for use in the distal locking process, described in the abovementioned patents and patent publication .

In addition to the light transmission efficiencies this innovation offers, there are advantages to product durability and resistance to thermal cycling such as that required for sterilization. In prior designs, optical epoxy which is filled into the light emitting cavity of the existing mirror configuration of the distal locking light is constrained by the internal surfaces of the stainless steel housing, the end of the fiber bundle, and also the mirror surface of a permanent stainless steel plug. As temperature increases, the epoxy expands at a significantly greater rate than the steel . This expansion is mostly accommodated by strain within the epoxy since it is significantly softer than the steel . In these prior designs, as a result, the epoxy expands outward through the window to the point where stresses along the mirror surface can cause it to rip away from the mirror. The damaged reflecting interface produces much lower light output. In the present apparatus, removal of the mirror plug from the design allows the epoxy to expand into the air gap behind the reflecting surface as well as at the window, eliminating any potential shear stresses along that surface, and maintaining apparatus light delivery performance for several steam sterilization cycles .

The optical element or reflector 22 may also be modified in shape or through its reflective surface to distribute the light in other patterns, including a version which distributes light at up to 360 degrees around the tubular housing. In this embodiment of the invention, the temporary plug may be shaped with a generally conical end, and may be inserted with the tip pointing toward the fiber subassembly 16.

The temporary plug may have a size and shape similar to end cap 24, but will extend close to the tube opening and will have a further extending sloping surface which is complementary to, and thus defines, the internally reflecting surface of optical element 22, when the resin of element 22 is cast into tube 14.

As an alternative, the optical element or reflector 22 may also be designed in as a molded or machined polymer or glass component and the fiber subassembly 16 may be modified to be integral with the optical element or reflector 22 or can be bonded to it in some manner as to insure maximum light transmission.

While the embodiment herein uses optical fibers in its construction, a light pipe may also be used as a light conductive element. However, such light pipe should be flexible enough to bend with the thin walled stainless steel of tube 14 sufficiently to allow it to be inserted into and removed from an intramedullary nail, which is often bent slightly in accordance with how a patient's bone is formed.

It should be understood that the foregoing description is only illustrative of the invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances.

Claims

CLAIMSWhat is claimed is :

1. Apparatus for use in the repair of bones using an intramedullary nail insertable into a patient's bone, said intramedullary nail having a hollow body portion and a distal transverse hole, said apparatus comprising:

a tube for insertion into the intramedullary nail, said tube having an opening through which light from a light source emitting electromagnetic non-ionizing radiation in the infrared or visible portions of the electromagnetic spectrum is emitted,

an optical conduit in said tube for conducting light from a light source to said opening; and

an optical element using total internal reflection to direct light from said optical conduit to said opening, said optical element having a reflective surface that is sized, shaped and positioned to receive light from said optical conduit and to reflect said light so that said light exits said tube through said opening.

2. The apparatus of claim 1, wherein said optical conduit comprises one of a light pipe and a bundle of optical fibers .

3. The apparatus of claim 1, wherein;

said optical conduit comprises a bundle of optical fibers ; and

ends of said optical fibers are embedded in said optical element .

4. The apparatus of claim 1, wherein said optical element comprises a hardened resin.

5. The apparatus of claim 4, wherein:

said optical conduit comprises a bundle of optical fibers ; and

ends of said optical fibers are embedded in said optical element before said resin is hardened, and said resin is solidified around said ends of said optical fibers .

6. The apparatus of claim 1, wherein said optical element comprises a hardened resin, wherein the resin fills said opening and seals to said tube.

7. The apparatus of claim 1, wherein said optical element comprises hardened EPO-TEK 302-3M epoxy.

8. The apparatus of claim 1, wherein the optical element has an index of refraction such that light impinges upon a reflective surface of said optical element at an angle of more than substantially 40 degrees to produce total internal reflection .

9. The apparatus of claim 1, wherein the light impinges upon an internally reflective surface of said optical element and is reflected so as to exit from said opening in a direction substantially perpendicular to a longitudinal axis of said tube .

10. The apparatus of claim 1, wherein said optical element is a molded element, and said optical fibers extend from an external surface of said optical element .

11. The apparatus of claim 1, further comprising an end cap for sealing an end of said tube closest to said opening .

12. A method for producing an apparatus for use in the repair of bones using an intramedullary nail insertable into a patient's bone, comprising:

providing a tube for insertion into the intramedullary nail, said tube having an opening through which light from a light source emitting electromagnetic non-ionizing radiation in the infrared or visible portions of the electromagnetic spectrum is emitted,

placing an optical conduit in said tube for conducting light from a light source to said opening; and

disposing an optical element in said tube, said optical element having a surface that is sized, shaped and positioned to receive light from said optical conduit and to internally reflect said light so that said light exits said tube through said opening.

13. The method of claim 12, wherein said optical conduit comprises optical fibers, further comprising embedding ends of said optical fibers in said optical element .

14. The method of claim 12, wherein said optical element is formed in place in said tube .

15. The method of claim 12, wherein said optical element is formed in place in said tube by;

placing a resin in said tube; and

hardening the resin.

16. The method of claim 15, wherein ends of said optical fibers are embedded in said optical element before said resin is hardened, and said resin is solidified around said ends of said optical fibers.

17. The method of claim 12, wherein said optical element comprises a hardened resin, wherein the resin fills said opening and seals to said tube.

18. The method of claim 17, wherein said optical element comprises hardened EPO-TEK 302-3M epoxy.

19. The method of claim 12, wherein an index of refraction of said optical element is such that the light impinges upon an internally reflective surface of said optical element at an angle of more than substantially 40 degrees for total internal reflection to occur

20. The method of claim 12, wherein the light impinges upon an internally reflective surface of said optical element and is reflected so as to exit from said opening in a direction substantially perpendicular to a longitudinal axis of said tube .

21. The method of claim 12, wherein said optical element is a molded element, and said optical fibers extend from an external surface of said optical element .

22. The method of claim 12, wherein said optical element is formed in place in said tube by :

placing a removable plug in an end of said tube closest to said opening, said plug having an end with a shape complimentary to the shape of an internally reflective surface of said optical element; placing a resin which can harden in place in said tube between said end of said plug and ends of said optical fibers; and

hardening the resin in place.

23. The method of claim 23, further comprising:

removing said plug from said tube; and

placing an end cap on said tube so as to seal the end of said tube closest to said opening.

24. The method of claim 12, wherein said optical conduit comprises optical fibers, and said optical element comprises a hardened epoxy resin, further comprising:

capturing ends of said optical fibers in a ferrule to form an optical fiber subassembly; and

embedding ends of said optical fibers of said subassembly in said optical element before said epoxy hardens .

25. The method of claim 24, wherein ends of said optical fibers are captured in said ferrule by :

applying an epoxy resin in space between said optical fibers and between said optical fibers and said ferrule; and

applying heat treatment to increase the glass transistion temperature of the epoxy and reduce stresses in said assembly.

26. The method of claim 12, wherein said optical conduit comprises optical fibers, and said optical element comprises a hardened epoxy resin, further comprising:

placing said optical fiber assembly under lengthwise compression in said tube; and

allowing an epoxy, for securing said fibers in said tube, to harden.

27. The method of claim 12, wherein said optical conduit comprises optical fibers, and said optical element comprises a hardened epoxy resin, further comprising:

heat treating the apparatus at a temperature of at 125 degrees C for substantially one hour.