WO2020194293A1

WO2020194293A1 - A wire guide

Info

Publication number: WO2020194293A1
Application number: PCT/IL2020/050341
Authority: WO
Inventors: Charles Howard
Original assignee: Charles Howard
Priority date: 2019-03-28
Filing date: 2020-03-23
Publication date: 2020-10-01
Also published as: IL265710A

Abstract

Described is a wire guide that comprises a wire guide body and an over-tube. The wire guide is configured for use with a circular external fixator ring to prevent a K-wire from deviating from a path that is both parallel to the circular external fixator ring and straying from a path determined by a surgeon while being inserted the K-wire through a bone. The circular external fixator ring can be an Ilizarov or Ilizarov type ring. Described are several embodiments of wire guide bodies and methods of attaching the wire guides to circular external fixator rings.

Description

A WIRE GUIDE

Field of the Invention

The invention is from the field of medical devices. Specifically, the invention is from the field of accessories for use with an external ring fixator for leg lengthening, deformity correction, and healing difficult fractures.

Background of the Invention

The external ring fixator is used in orthopedic surgery to assist in the mending of broken bones, to correct deformities, and to lengthen or shorten leg bones. One such device is the Ilizarov apparatus named after Gavril Abramovich Ilizarov, an orthopedic surgeon, who invented the apparatus and pioneered the technique of working with it in the Soviet Union in the 1950's and 1960's.

The basic form of the Ilizarov apparatus, which has essentially remained unchanged since it was first invented by Ilizarov, is schematically shown in Figs. 1A to 1C. Fig. 1A shows the Ilizarov ring 12. The ring contains a plurality of holes 14 that are evenly spaced around the circumference and pass through the ring perpendicular to its planar surfaces. On each ring are tensioned wires 16 that pass through the bone 22 (see Fig. IB) and are anchored on the circumference of the ring by wire fasteners 18. The wire fasteners 18 are comprised of bolts that pass through holes 14 and are tightened by nuts on the opposite side of the ring 12 to press the wire 16 against the planar surface of the ring 12.

Fig. IB shows a typical and simplest configuration of the Ilizarov apparatus 10. In this configuration two rings 12 are located above the fracture/cortectomy in bone 22 and two rings 12 below. For clarity the rods are not shown in this figure.

In Fig. 1C rods 20 have been added to the rings 12. Each rod is comprised of two parts - a male part having a threaded end that can be screwed into an end of the female part. The ends of both parts that aren't connected together are threaded and pass respectively through holes 14 in adjacent rings 12 and connected to the ring by means of nuts. Adjacent rings 12 are spaced apart by the rods 20 whose length can be extended or shortened by turning the female rod to change the distance and/or angle between the upper and lower rings 12 and to adjust the length and/or orientation of the two sections of bone 22 as required.

Since the early invention by Ilizarov many different embodiments of external fixators have been proposed and a few have been accepted for use by orthopedic surgeons; but until now all of these devices still employ the basic structural features of the Ilizarov design, including the structure of the rings 12. One such fixator is the Taylor spatial frame, which is shown schematically in Fig. ID. The Taylor frame is based on a Steward platform. It has six struts which can be independently lengthened or shortened to provide six axis correction - angulation (about x and y axes), translation (along x and y axes), rotation (around z axis) and length (along z axis). The struts are controlled by a complicated computer program which can determine which struts must be adjusted, by how much, for how many days. In addition to other problems common to the Ilizarov apparatus that will be described herein below, the Taylor frame is complicated and expensive to use.

Note that herein the term 'wires' is used generically to refer to Kirschner wires (K-wires) and their equivalents as used in orthopedic surgeries.

Despite the number of years since the invention of the Ilizarov apparatus and method and the great treatment success that is obtained using them, in practice the apparatus is not easy to use.

A first problem is that the wires 16 have to be placed exactly parallel to, absolutely contiguous with and aligned with the holes 14 exactly on opposite sides of the ring 12. The difficulty with achieving this is that when attaching the apparatus to a patient's leg the flexible pins are inserted "by eye" with the ring held by an assistant, which makes it impossible to obtain perfect parallelism. Fig. 2A schematically illustrates the ideal situation and Fig. 2B to Fig. 2D illustrate the problem.

Fig. 2A is a cross-sectional view in a transverse plane, in this case connection point A of the wire 16 to the ring 12, the insertion point B of wire 16 at bone 22, exit point C of wire 16 from bone 22, and attachment point D of the wire 16 to the ring 12 all are points on a straight line. Fig. 2B illustrates a situation in which the wire 16 is not aligned properly in a transverse plane. In this case points A, B, C, and D lie on a curved line. Fig. 2C is a view in a sagittal plane that schematically illustrates a situation in which the wire 16 is not inserted through the bone 22 parallel to the ring 12. Fig. 2D schematically illustrates the situation of Fig. 2C, when both ends of the wire 16 are attached to the ring 12 again producing a curvature of the wire.

A second problem, which is at least in part responsible for the above mentioned curvature, is that the wires 16 are flexible and can bend when pushed longitudinally against a hard surface such as the outer surface of a bone 22. Fig. 3A to Fig. 3E schematically illustrate several stages in the drilling of a wire 16 through a bone 22. These figures schematically provide an explanation of the cause of the problem illustrated in Fig. 2B. As shown in Fig. 3A, the tip of the wire 16 has just contacted the outer surface of bone 22. In Fig. 3B the tip of wire 16 has still not penetrated the bone surface; however the drilling tool 24 is acting to push the relatively long piece of small diameter wire 16 forward causing the wire to flex and bend into an arch. In Fig. 3C the tip of wire 16 still has not penetrated cortical bone 22 and the curvature of the arch increases. In Fig. 3D the tip of wire 16 beaks through the cortical bone into the interior of bone 22 in the direction caused by the curvature of the wire and, being gripped by the bone, the wire continues its path in this direction until it exits the bone. Note that in the interior of bone 22 the wire 16 has been bent at an angle equal to the angle at which the tip intersected the surface before the break through. Finally, as seen in Fig. 3E, the wire 16 exits the opposite side of the bone 22.

Bending of the wire as illustrated in Figs. 3A to 3E has undesired consequences for both the bone and the wire. Firstly, when the wire is being rotated by a drilling device and becomes curved as in Fig. 3C, part of the drilling force is lost, as can be seen by resolving the force vector into vectors in the direction at which the force is applied as in Fig. 3A and the direction in which the effective force is applied at the angle in which the tip of the wire contacts the bone. The lost drilling force appears as heat, which causes thermal necrosis which leads to infection and loosening of the ring. Secondly, when the curved wire rotates during drilling, the convex surface is under tension and the concave surface under compression. As the wire rotates there is cycling of compression and tension, which leads to fatiguing of the metal and eventual breakage. Usually the wire doesn't break during insertion; but it will be weakened and this may cause later wire breakage during treatment, which occurs in about 1% of the wires and may require a further operation to replace the broken wire.

A third problem that is a consequence of the misalignment shown in Figs. 2B to 2D and the curvature of the wire as illustrated in Figs. 3B to 3E is that, since wire 16 has to be tensioned to about 120Pa, any curvature will lead to a "cutting" force on the bone 22 that can lead to necrosis of the bone tissue and infection. This is schematically illustrated in Fig. 4 for the situation shown in Fig. 2D. A similar effect takes place in the transverse plane for the situation shown in Fig. 2B.

It is a purpose of the present invention to provide a wire guide that can be attached to any circular external fixator ring, e.g. an Ilizarov ring, to minimize or eliminate the problems and their negative effects experienced in using the prior art apparatus.

Further purposes and advantages of this invention will appear as the description proceeds.

Summary of the Invention

In a first aspect a wire guide configured for use with a circular external fixator ring is disclosed. The wire guide comprises a wire guide body and an over-tube.

The wire guide is configured to prevent a K-wire from deviating from a path that is both parallel to the circular external fixator ring and straying from a path determined by a surgeon while being inserted through a bone.

The circular external fixator ring may be an Ilizarov or Ilizarov type ring.

Embodiments of the wire guide body are comprised of a U-shaped piece made of metal or plastic, comprising an upper arm and a lower arm. These embodiments of the wire guide body are configured to be attached to a circular external fixator ring with the upper arm of the wire guide body in contact with the top of the ring and the lower arm in contact with the bottom of the ring. In these embodiments of the wire guide the upper arm of the wire guide body comprises a channel that is created as closely as possible to the lower surface of the upper arm of wire guide body to allow the over-tube to be inserted through the wire-guide body. In embodiments of the wire guide the over-tube is made of metal and is configured to allow a K-wire to pass through it.

In a first embodiment of the wire guide the wire guide body is attached to an Ilizarov ring by a plunger assembly on the lower arm, the plunger assembly comprising a ball or pin and a spring.

In a second embodiment of the wire guide the wire guide body is attached to a circular external fixator ring by a protuberance on the top of the lower arm.

In a second aspect a method of inserting a K-wire through a bone and attaching it to a circular external fixator ring is presented. The method comprises:

a. attaching a wire guide of the first or second embodiment over a hole on the ring;

b. slipping an over-tube through the channel in the upper arm of the wire guide body; c. rotating the wire guide body and advancing the over-tube until it touches the bone at a location determined by a surgeon;

d. sliding a K-wire through the over-tube;

e. attaching a wire drilling tool to the proximal end of the K-wire;

f. activating the wire drilling tool to drill the K- wire through the bone;

g. advancing the K-wire until the distal end of the K-wire passes over the ring;

h. detaching the drilling tool from the proximal end of the K-wire;

i. sliding the over-tube 28 back through the channel in the upper arm of the wire guide body;

j. detaching the wire guide body from the ring;

k. attaching wire fasteners to the ring at both ends of the K-wire;

L. using a tensioning tool to tension the K-wire;

m. tightening the wire fasteners to hold the tensioned K-wire against the planar surface of the circular external fixator ring.

In a third embodiment the wire guide body is a single piece made of metal or plastic. The wire guide body comprises the following features: a platform; an arm sloping upward from an end of the platform; a head located at the top of the arm; a knob extending downward from the platform; a post extending upward from the platform; a spring, bores through the head and post; and slots from the tops of the head and post extending into the bores.

The third embodiment the wire guide body is configured to be attached to a circular external fixator ring by means of the spring that is slipped over the post. When the post is pushed from the bottom of the ring through one of the holes in the ring and an over-tube slipped through the bores in the wire guide body over the top of the ring, a force exerted by expansion of the spring pushes the platform downward away from the bottom of the ring and presses the over tube against the top of the ring.

In the third embodiment the slots in the wire guide body are configured to prevent an over tube from passing through them but to allow a K-wire to pass through them.

In a third aspect a method of inserting a K-wire through a bone and attaching it to a circular external fixator ring is presented. The method comprises:

a) attaching a wire guide of the third amendment to the ring;

b) rotating the wire guide and advancing the over-tube until it touches the bone at a location determined by a surgeon;

c) sliding a K-wire through the over-tube;

d) attaching a wire drilling tool to the proximal end of the K-wire;

e) activating the wire drilling tool to drill the K- wire through the bone;

f) advancing the K-wire until the distal end of the K-wire passes over the ring;

g) detaching the drilling tool from the proximal end of the K-wire;

h) detaching the wire guide from the ring;

i) attaching wire fasteners to the ring at both ends of the K-wire;

j) using a tensioning tool to tension the K-wire;

k) tightening the wire fasteners to hold the tensioned K-wire against the planar surface of the circular external fixator ring.

In the method of the third aspect in step 'a' the wire guide is attached to the ring by:

i) inserting the post of the wire guide body from the bottom of the ring into one of holes in the ring; ii) compressing the spring of the wire guide body between the bottom of the ring and the top of the platform of the wire guide body by pushing the knob of the wire guide body upwards relative to the bottom of the ring, thereby raising the bores in the head of the wire guide body and the post of the wire guide body above the top surface of the ring; iii) sliding the over-tube through the bores;

iv) releasing the force compressing the spring, whereby the expanding spring pushes the platform of the wire guide body downward away from the bottom of ring pressing the over-tube against the top of ring.

In the method of the third aspect in step 'h' the wire guide is detached from the ring by:

i) pulling the over-tube back through the bores in the head and post of the of the wire guide body;

ii) allowing the spring of the wire guide body to re-expand, which pulls the post of the wire guide body out of the holes in the ring while the K-wire slides out of the bores and through the slots in the head of the wire guide body and post of the wire guide body, thereby removing the wire guide body from the ring.

All the above and other characteristics and advantages of the invention will be further understood through the following illustrative and non-limitative description of embodiments thereof, with reference to the appended drawings.

Brief Description of the Drawings

— Fig. 1A to Fig. 1C schematically shows the basic form of the prior art Ilizarov apparatus;

— Fig. ID schematically shows a Taylor frame;

— Fig. 2A to Fig. 2D schematically illustrate a number of problems that are encountered when using an Ilizarov apparatus;

— Fig. 3A to Fig. 3E schematically illustrate several stages in the drilling of a wire through a bone;

— Fig. 4 schematically illustrates how part of the tensioning forces in the Ilizarov apparatus can lead to a cutting force on the bone;

— Fig. 5 schematically shows a first embodiment of a wire guide attached to an Ilizarov ring; — Fig. 6A and 6B are cross-sectional views that schematically shows a first embodiment of the wire guide body attached to an Ilizarov ring;

— Fig. 7A and Fig. 7B are cross-sectional views that schematically show a second embodiment of the wire guide body attached to an Ilizarov ring;

— Fig. 8 schematically shows a third embodiment of a guide element of the wire guide;

— Figs. 9A and 9B schematically show the third embodiment of the wire guide attached to a circular external fixator ring; and

— Fig. 10A to Fig. 10D schematically show different stages in inserting a K-wire through a bone using the wire guide.

Detailed Description of Embodiments of the Invention

The wire guide described herein is intended for use with any circular fixator ring, e.g. Ilizarov and Ilizarov type rings. The function of the wire guides described herein is to prevent a K wire from deviating from a path that is both parallel to the ring and straying from the path determined by the surgeon while being inserted through a bone. In other words the purpose of the wire guides is to minimize or eliminate the problems and their negative effects experienced in using the prior art apparatus that are discussed herein above. Specifically the wire guide described herein prevents bending of the wire thereby reducing or eliminating thermal damage and cutting force on the bone, which leads to bone necrosis, pin tract infection, and loosening of the wire.

Fig. 5 schematically shows a first embodiment of a wire guide attached to an Ilizarov ring 12. The wire guide is comprised of two parts. One part is a wire guide body 26, which is a U- shaped piece made of metal or plastic. Wire guide body 26 is configured to be attached to ring 12 with the upper arm of wire guide body 26 in contact with the top of the ring 12 and the lower arm in contact with the bottom of ring 12. The second part of the wire guide is a metal over-tube 28 that slides into a channel 36 (see Figs. 6A to 7B) that is created in the upper arm. Channel 36 is created as closely as possible to the lower surface of the upper arm of wire guide body 26 in order to insure that the K-wire will be inserted parallel to and as close as possible to the plane defined by the top surface of ring 12.

Fig. 6A is a cross-sectional view that schematically shows a first embodiment of the wire guide body 26 being attached to an Ilizarov ring 12. This embodiment comprises a plunger assembly 30 in which a ball 34 (or pin) is retracted compressing spring 32 as the wire guide body 26 is pushed onto the ring 12. When the ball 34 reaches a hole 14 in ring 12 the spring 32 pushes ball 34 up and wire guide body 26 is held on the ring 12 as shown in Fig. 6B.

Fig. 7A and Fig. 7B are cross-sectional views that schematically show a second embodiment of the wire guide body 26' attached to an Ilizarov ring 12. In this embodiment the plunger assembly 30 is replaced with a semi-spherical protuberance 38, which together with the lower arm of the wire guide body 26 is deflected downward as wire guide body 26' is pushed onto the ring 12. When the protuberance 38 reaches a hole 14 in ring 12, the natural elasticity of the lower arm returns the arm to its starting position holding wire guide body 26' on the ring

12.

Fig. 8 schematically shows a third embodiment of a guide body 50 of the wire guide. Wire guide body 50 is manufactured as one piece by a method such as machining, molding, or extrusion from a metal such as aluminum or a hard plastic. For convenience in describing how the guide body 50 is attached to and removed from a circular external fixator ring features of guide body 50 are named as follows: platform 52; arm 54; head 56; knob 58; post 60; bore 62; and slot 64. Also seen in Fig. 8 is a spring 66, which is attached over the post 60.

Figs. 9A and 9B schematically show the wire guide attached to a circular external fixator ring 12. The wire guide is comprised of two parts. One part is guide body 50 and the second part of the wire guide is a metal over-tube 28. To attach the wire guide to ring 12 the post 60 is inserted from the bottom of the ring 12 into one of holes 14. Spring 66, which was attached to the post during manufacturing, is compressed between the bottom of ring 12 and the top of platform 52 by pushing knob 58 upwards relative to the bottom of the ring 12. This raises the bores 62 in head 56 and post 60 above the top surface of the ring 12 and the over-tube 28 is slid through bores 62. Guide body 50 is rotated around post 60 and over-tube 28 is advanced in the interior of the ring 12 until the end of the over-tube 28 touches the bone at a location determined by a surgeon. At this point the force on knob 56 compressing spring 66 is released and the expanding spring pushes the platform 52 downward away from the bottom of ring 12, pressing over-tube 28 against the top of ring 12, and holding the end of over-tube at the selected location. It is to be noted that although only three embodiments of wire guide body 26, 26', and 50 have been described, skilled persons would be able to devise many other embodiments. In particular the inventor envisages several other methods of attaching the wire guide body similar to that of the first and second embodiments to a ring 12.

Figs. 10A to 10D schematically show different stages in inserting a K-wire 16 through a bone 22 using the wire guides of the first and second embodiments described herein.

In Fig. 10A after a surgeon determines the path that he wants a K-wire 16 to follow across Ilizarov ring 12 while passing through bone 22, he attaches a wire guide body 26,26' over a hole 14 on ring 12 as shown in Fig. 10B.

In Fig. IOC, over-tube 28 is slipped through the channel 36 in the upper arm of wire guide body 26,26'. The wire guide body 26,26' is rotated and over-tube 28 is advanced until it touches bone 22 at the location determined by the surgeon. Then a K-wire 16 is slid through over-tube 28, a wire drilling tool 24 is attached to the proximal end of K-wire 16 and activated to drill K- wire 16 through bone 22 and to advance K-wire 16.

After the distal end of the K-wire 16 has been advanced over the ring 12, as shown in Fig. 10D, the drilling tool 24 is detached from the proximal end of K-wire 16, over-tube 28 is slid back through channel 36 in the upper arm of wire guide body 26, and wire guide body 26,26' is detached from ring 12. Then wire fasteners 18 comprised of bolts that pass through holes 14 and nuts on the bottom side of the ring 12 and a tensioning tool are used to tension K-wire 16 and to hold the wire 16 against the planar surface of the ring 12, as shown in Fig. 1A.

The procedure for inserting a K-wire 16 through a bone 22 using the third embodiment of the wire guide body 50 is similar to that described above with reference to Figs. 10A to 10D. After correctly positioning the wire guide a K-wire is slipped through the over-tube 28 and a wire drilling tool is attached to the proximal end of the K-wire. The wire drilling tool is then activated to drill the K- wire through the bone and the K-wire is advanced until the distal end of the K-wire passes over the ring. The drilling tool is then removed from the proximal end of the K-wire and the over-tube 28 is pulled back through the bores 62 in the head 56 and post 60 of the guide element 50. The slots 64 in the head 56 and post 60 are slightly wider than the diameter of the K-wire; thus, as soon as the over-tube is removed, expansion of the spring 66 pushes post 60 out of the hole 14 in ring 12 simultaneously the K-wire slides out of bores 62 and through slots 64, thereby removing the guide body 50 from the ring 12, while leaving the K-wire in place on the surface of the ring 12.

Once both components of the wire guide are removed from the ring 12 wire fasteners are attached to the ring 12 at both ends of the K-wire, a tensioning tool is used to tension the K- wire, and the wire fasteners are tightened to hold the tensioned K-wire against the planar surface of the ring 12.

Although embodiments of the invention have been described by way of illustration, it will be understood that the invention may be carried out with many variations, modifications, and adaptations, without exceeding the scope of the claims.

Claims

1. A wire guide configured for use with a circular external fixator ring, the wire guide comprising a wire guide body and an over-tube.

2. The wire guide of claim 1 configured to prevent a K-wire from deviating from a path that is both parallel to the circular external fixator ring and straying from a path determined by a surgeon while being inserted through a bone.

3. The wire guide of claim 1 wherein the circular external fixator ring is an Ilizarov or Ilizarov type ring.

4. The wire guide of claim 2, wherein the wire guide body is a U-shaped piece made of metal or plastic, the wire guide body comprising an upper arm and a lower arm.

5. The wire guide of claim 4, wherein the wire guide body is configured to be attached to a circular external fixator ring with the upper arm of the wire guide body in contact with the top of the ring and the lower arm in contact with the bottom of the ring.

6. The wire guide of claim 4, wherein the upper arm of wire guide body comprises a channel that is created as closely as possible to the lower surface of the upper arm of the wire guide body to allow the over-tube to be inserted through the wire-guide body.

6. The wire guide of claim 1, wherein the over-tube is made of metal and is configured to allow a K-wire to pass through it.

7. The wire guide of claim 4, wherein the wire guide body is attached to a circular external fixator ring by a plunger assembly on the lower arm, the plunger assembly comprising a ball or pin and a spring.

8. The wire guide of claim 4, wherein the wire guide body is attached to a circular external fixator ring by a protuberance on the top of the lower arm.

9. The wire guide of claim 2, wherein the wire guide body is a single piece made of metal or plastic, the wire guide body comprising the following features: a platform; an arm sloping upward from an end of the platform; a head located at the top of the arm; a knob extending downward from the platform; a post extending upward from the platform; a spring, bores through the head and post; and slots from the tops of the head and post extending into the bores.

10. The wire guide of claim 9, wherein the wire guide body is configured to be attached to a circular external fixator ring by means of the spring that is slipped over the post, wherein the post is pushed from the bottom of the ring through one of the holes in the ring and an over-tube is slipped through the bores in the wire guide body over the top of the ring, whereby force exerted by expansion of the spring pushes the platform downward away from the bottom of the ring and presses the over-tube against the top of the ring.

11. The wire guide of claim 9, wherein the slots in the wire guide body are configured to prevent an over-tube from passing through them but to allow a K-wire to pass through them.

12. A method of inserting a K-wire through a bone and attaching it to a circular external fixator ring, the method comprising:

a) attaching a wire guide of claim 4 over a hole on the ring;

b) slipping an over-tube through the channel in the upper arm of the wire guide body; c) rotating the wire guide body and advancing the over-tube until it touches the bone at a location determined by a surgeon;

d) sliding a K-wire through the over-tube;

e) attaching a wire drilling tool to the proximal end of the K-wire;

f) activating the wire drilling tool to drill the K- wire through the bone;

g) advancing the K-wire until the distal end of the K-wire passes over the ring;

h) detaching the drilling tool from the proximal end of the K-wire;

i) sliding the over-tube back through the channel in the upper arm of the wire guide body; j) detaching the wire guide body from the ring;

k). attaching wire fasteners to the ring at both ends of the K-wire;

L) using a tensioning tool to tension the K-wire; m) tightening the wire fasteners to hold the tensioned K-wire against the planar surface of the circular external fixator ring.

13. A method of inserting a K-wire through a bone and attaching it to a circular external fixator ring, the method comprising:

a) attaching a wire guide of claim 9 to the ring;

c) sliding a K-wire through the over-tube;

d) attaching a wire drilling tool to the proximal end of the K-wire;

e) activating the wire drilling tool to drill the K- wire through the bone;

g) detaching the drilling tool from the proximal end of the K-wire;

h) detaching the wire guide from the ring;

i) attaching wire fasteners to the ring at both ends of the K-wire;

j) using a tensioning tool to tension the K-wire;

14. The method of claim 13, wherein in step 'a' the wire guide is attached to the ring by:

i) inserting the post of the wire guide body from the bottom of the ring into one of holes in the ring;

ii) compressing the spring of the wire guide body between the bottom of the ring and the top of the platform of the wire guide body by pushing the knob of the wire guide body upwards relative to the bottom of the ring, thereby raising the bores in the head of the wire guide body and the post of the wire guide body above the top surface of the ring; iii) sliding the over-tube through the bores;

15. The method of claim 13, wherein in step 'h' the wire guide is detached from the ring by: i) pulling the over-tube back through the bores in the head and post of the of the wire guide body;