GB2421187A

GB2421187A - Intramedullary bone support

Info

Publication number: GB2421187A
Application number: GB0427301A
Authority: GB
Inventors: Chawla Girish
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-12-14
Filing date: 2004-12-14
Publication date: 2006-06-21
Also published as: GB0427301D0

Abstract

A bone support comprising an elongate rod 10 insertable into the medullar cavity of a Bone transversing a fracture site, the support having four or more protrusions 30 at one end of the rod, which are engageable with the bone. The proximal end of the bone support can be locked with the help of a screw into the bone through aperture 42 and the distal end of the bone support does not need locking as it attaches to the bone cortex. Its main advantage is that it increases rotational stability of the healing bone as there are five points of contact at distal end between bone and the rod and also reduces the Operative time as distal locking is not needed, if therefore results in less Radiation exposure to the Operating Surgeon and the patient. It can be used for any long bone and can be tailored according to individual patient requirements.

Description

BONE SUPPORT This invention relates to a support for a fractured or otherwise damaged bone. It is know to support fractured bones by inserting a rod, known in the art as a "nail", through the medullar canal of the bone so that the nail spans the fracture. Such nails are commonly used to treat factures of the humerus or femur although they can be used for other bones. European Patent EP 4,630,601 describes the use of a nail in relation to the humerus. The nail is inserted into the medullar canal of the humerus through an opening made in the head of the humerus, i.e. at the shoulder. The body of the nail is hollow and a wire is passed through an aperture in the proximal end of the nail (i.e. at the opening at the head of the humerus) and along the hollow nail until the wire exits via an aperture at the distal end of the nail so that the wire pierces the bone. The engagement of the wire with the bone prevents rotation of the distal portion of the bone about the axis of the nail. Rotation of the proximal portion of the bone about the axis of the nail is prevented by means of a first screw that passes through the bone and into a receiving hole in the nail substantially transverse to the longitudinal axis of the nail. For such a prior art nail it has been found that in order to prevent movement of the bone portions relative to each other, eg to prevent the bone portions moving apart from each other, a second screw is necessary that passes through the distal portion of the bone and into a receiving hole in the nail substantially transverse to the longitudinal axis of the nail. Whereas the first screw is relatively simple to locate in its receiving hole it is difficult to locate the second screw in its receiving hole. This is because the curvature of the bone makes it difficult to determine how far along the bone the second screw needs to be inserted in order for the screw to be received by the appropriate receiving hole in the rod. Since the size and curvature of a particular bone varies from individual to individual the position of the second screw placement cannot be determined simply by measuring along the limb of the patient. An imaging facility (such as, for example, a CT scanner or a MRI scanner) is necessary in order to insert the second screw through the distal portion of the bone and into its respective receiving hole. The use of imaging apparatus requires a highly trained radiographer.Furthermore, the placement of the screw requires that the surgeon has the skill to perform the placement whilst taking account of the three dimensional geometry of the placement site by using two dimensional images provided by the CT or MRI scanner. This skill takes a long time to acquire and such procedures are normally performed by a consultant surgeon or a senior registrar. According to an aspect of the invention there is provided a bone support comprising an elongate rod insertable into the medullar cavity of a bone, the support having four or more protrusions that are engageable with the bone, the protrusions being disposed substantially at or near to one end of the rod. The end of the support that has the protrusions is the distal end of the support, the distal end of the support being the end that, in use, is distal to the surgeon placing the support inside the bone. Likewise the terms "distal portion" and "proximal portion" are used to refer to the portions of a fractured bone that are, respectively, proximal and distal to the hole in the bone through which the support is entered into the bone. In use, the four or more protrusions provide sufficient engagement with the bone to resist both rotational movement of the distal bone portion about the longitudinal axis of the rod and movement of the distal and proximal portions of the bone relative to each other. Because the protrusions prevent relative movement of the bone portions relative to each other it is not necessary to have a screw that passes through the distal portion of the bone and into the elongate rod. The bone support is therefore much easier to fit than prior art supports/nails and does not require an imaging facility. The cost of fitting such a support is therefore greatly reduced and the support can be used in developing countries where the availability of imaging apparatus is low or non-existent.A further advantage of the invention is that the time to perform the operation is reduced, therefore the time that a patient is under general anaesthetic is reduced and the risk to the patient thereby reduced. The rod will generally have sufficient flexibility to allow the rod to be passed through the medullar cavity of a curved bone. Preferably the protrusions are spaced around the rod. For example, the may have a circular cross-section and the protrusions are spaced circumferentially on the rod. The cross-section may be non-circular, for example the cross-section may have a substantially clover-leaf form. In an embodiment of the invention the protrusions will be substantially at the same axial position with respect to the longitudinal axis of the rod however the protrusions may also be axially spaced along the rod. Preferably, the elongate rod is hollow and the support comprises an elongate member extending inside the rod, the elongate member having said protrusions. Preferably, the rod defines a plurality of apertures and said protrusions pass through said apertures. Usually there will be an aperture for each protrusion. Preferably each protrusion is a wire. The wires are able to penetrate the bone to provide a secure fixation of the support to the bone. Preferably each wire is a limb of a common wire and the elongated member comprises said common wire. The elongate member could also be formed from a plurality of wires, each of the wires forming a protrusion, the wires could be joined or connected together inside the elongate rod. The wires could be joined together for example by brazing or welding the wires together. Preferably, the bone support has five protrusions. Five protrusions will provide more resistance to movement of the bone portions to each other than would four protrusions. More protrusion could be used, for example six, seven or eight or more protrusions, however when there is limited space on the rod about which to place the protrusions. Preferably the rod has a screw receiving aperture for receiving a screw substantially transverse to the longitudinal axis of the rod, the screw receiving aperture being at the opposite end of the rod to the protrusions. Preferably the support comprises said screw. According to a complimentary aspect of the invention there is provided a method of placing a bone support in a bone comprising: providing an elongate rod having a longitudinal cavity and four or more apertures at the distal end of the rod; providing an elongated member, the elongated member having four or more protrusions at the distal end of the member; making a hole at one end of the bone; entering the rod into the medullar canal of the bone via said hole; inserting the elongated member into the longitudinal cavity of the rod until the protrusions on the elongated member exit the apertures and engage the bone. There now follows by way of example only a detailed description of the present invention with reference to the accompanying drawings in which: Figure 1 schematically illustrates a side view of a bone support; Figure 2 schematically illustrates an end view of the bone support illustrated in Figure 2; Figure 3 schematically illustrates a cross-sectional view of the rod of the bone support of Figure 3; Figure 4 schematically illustrates a cross-sectional view of an embodiment of the rod of a bone support, the rod having a non-circular cross-section; Figure 5 schematically illustrates a side-section view of a bone with the bone support of Figure 1 inserted inside the medullar cavity of the bone; Figure 6 illustrates a first example of an elongated member;Figure 7 illustrates a second example of an elongated member; and Figure 8 illustrates a rod having axially and circumferentially spaced apertures and an elongated member for insertion into the rod. Referring to Figures 1 and 2, a bone support 100 comprises an elongate rod 10 having a longitudinal cavity 26 that runs substantially the length of the rod 10. Within the cavity 26 is an elongated member 20 that terminates in five fixing wires 30. The rod 10 has five apertures 12 disposed substantially at one end of the rod 10 so that, in use, each fixing wire 50 can protrude from the rod 10 via a respective aperture 12. Referring to Figures 2 and 3, the apertures 12 are disposed so that they are circumferentially spaced in the rod 10. That is, they are disposed around the periphery of the rod at different radial angles a, b... from the longitudinal axis of the rod 10. As illustrated in Figures 2 and 3 the rod 10 may have a circular crosssection, however this need not be the case. Figure 4 illustrates an embodiment of the rod 10 that has a non-circular cross-section, in this case the cross-section has a clover-leaf cross-section. As shown in Figures 2 and 3 the apertures 12, and therefore the fixing wires 30 protruding from the apertures 12, can be circumferentially spaced at substantially equal angles a from each other. However, the apertures 12 can be spaced from each other at different angles. For example, it may be preferable for the distribution of the apertures, and therefore the fixing wires 30 to be configured to suit a particular site on the bone 50 (e.g. due to the geometry of the bone at that site) which may require more fixing wires 30 on one side of the rod 10 than the other. Referring to Figure 5, to insert the rod 10 into the bone 50 an aperture 62 is made in one end of the bone 50. In the example illustrated the bone 50 is a femur and the aperture 62 is formed in the condyle region of the femur. A guide wire (not shown) is inserted into the aperture 62 and is gently pushed down the medullar canal to the desired distance, leaving one end of the guide protruding from the aperture 62. The distal end 14 of the rod 10 is the placed over the protruding end of the guide wire such that the guide wire enters the cavity 26 of the rod 10. The rod 10 is then inserted in to the medullar canal, its direction being guided by its cooperation with the guide wire. Once the rod is fully inserted in the bone 50 the guide wire is drawn out of the bone 50 through the open proximal end 16 of the rod 10. The rod 10 has sufficient flexibility so that it is able to follow the line of the guide wire which may be curved due to curvature of the bone 50. Typically the rod 10 is composed substantially of stainless steel or a titanium alloy. A rod composed of stainless steel or a titanium alloy has the required flexibility and is compatible with bone tissue (e.g., is nontoxic). Other material could be used for the rod 10 if the material has the required flexibility and compatibility with bone tissue. The elongated member 20 can then be inserted in to the open proximal end 16 of the rod. Referring to Figure 6, in one arrangement the elongated member 20 is in the form of a single wire 21 that branches at the distal end 14 of the member 20 into the five fixing wires 30. Alternatively, referring to Figure 7, the elongated member 20 may comprise five wires 24 with each of the distal end of each of the five wires 24 being a respective one of the five fixing wires 30. The five wires 24 of the elongated member 20 may be held together by a fixing means such as one or more collars 26 or the wires 24 may be brazed or welded together. The fixing wires 30 may be steel wires or they could be composed another material (e.g. a plastic material, carbon fibre or composite material) of sufficient strength and hardness so that, in use, the tips of the wires can penetrate bone. In use, the elongated member 20 is pushed through the cavity 26 of the rod 10 until the fixing wires 30 exit the apertures 12 and engage the bone 50 surrounding the distal end 14 of the rod 10. When the elongated wire 20 is fully inserted into the cavity 26 of the rod 10 a punch (not shown) may be used to drive the fixing wires 30 into the bone 50. The contact between the fixing wires 30 and the bone 50 has the effect of resisting rotational movement of the distal bone portion 54 with respect to the longitudinal axis of the rod 10. The fixing wires 30 also act to prevent translation movement of the distal bone portion 54 in the direction of the longitudinal axis of the rod 10. Generally, four or more fixing wires 30 are required to prevent this translational motion. In the embodiment of the invention illustrated in Figures 1, 2, 5, 6 and 7 five fixing wires 30 are used to secure the distal bone portion against translation along the axis of the rod. More fixing wires 30 could be used however the space inside the rod cavity 26 will restrict the number of fixing wires than can be used. Also if an excessive number of fixing wires 30 are used to pierce the bone 50 then the structural integrity of the bone 50 may become compromised. As shown in Figure 1, the apertures 12 (and hence the fixing wires 30) are circumferentially spaced at a single position along the longitudinal axis of the rod 10. Referring to Figure 8, the apertures 12 may disposed at different axial positions on the rod 10. In the example illustrated four apertures 12 are circumferentially spaced at a first axial position on the rod 10 and two apertures 12 are circumferentially spaced at a second axial position on the rod 10 that is closer to the proximal end of the rod 10. The number and arrangement of apertures 12 in the rod can be chosen to suit a particular bone 50. That is, the surgeon may have a choice of different rods 10.Alternatively the rod 10 may have a large number of apertures 12 (for example 5, 6, 7, 8, 9, 10, 11, 12 or more apertures) and several different longitudinal members 20 are available with the different longitudinal members have different numbers of fixing wires and/or a different arrangement of fixing wires 30. The surgeon can then choose a particular longitudinal member 20 to insert into the rod according to which apertures on the rod 10 the surgeon intends to use. Referring to Figures 1 and 5. The proximal end of the rod 10 may be provided with a screw-receiving aperture 42. Once the rod 10 is in place inside the medullar cavity of the bone 50 a screw 40 may be screwed through the bone 50 and into the screw-receiving aperture 42 so that the screw is substantially transverse to the longitudinal axis of the rod 10. Once inserted into the aperture 42, the screw 42 inhibits rotational movement of the proximal portion of the bone 56. The screw 40 may be further inserted into the screw-receiving aperture 42 so that the screw 20 engages the proximal end of the elongated member 20. The screw-receiving aperture 42 is close to the aperture 62 that was made in bone 50 to enter the rod 20 into the bone 50. Therefore, it is relatively simple to estimate the position of the screw-receiving aperture 42 and to locate the screw 40 in the screw-receiving aperture 42. By securing the bone 50 to the rod 10 at either end (by the screw 40 at the proximal end of the bone 56 and the fixing wires 30 at the distal end of the bone 54) the two sections of bone 54, 56 either side of the fracture 52 are held in a stable position relative to each other. By securing the proximal 54 and distal 56 portions of the bone in this way the fracture 52 has the best chance of healing. The securing of the proximal 54 and distal 56 portions does not require a screw to be screwed through the distal portion 54 of the bone 50 into the rod 10. Once the bone fracture 52 has healed the screw 40 can be removed and the fixing wires 30 can be retracted from the bone by pulling gently on the end of the elongated member 20 that protrudes from the proximal end of the rod 10. The rod 10 can then be withdrawn from the bone 50. To aid withdrawal of the fixing wires 30, the elongated member 20 may have a griping means 22 at the proximal end of the elongated member (shown in Figures 5 and 8) in the form of, for example, a protrusion on the elongated member 20. The gripping means may be gripped by the surgeon to help the surgeon pull the elongated member 20 and hence to pull the fixing wires 30 out of the bone 50. It will be appreciated that the bone support can be used for various types of bone and for both human and non-human bones (e.g. for mammalian bones) .

Claims

1. A bone support comprising an elongate rod insertable into the medullar cavity of a bone, the support having four or more protrusions that are engageable with the bone, the protrusions being disposed substantially at one end of the rod.

2. The bone support of claim 1, wherein the elongate rod is hollow and the support comprises an elongate member extending inside the rod, the elongate member including said four or more protrusions.

3. The bone support of claim 1 or claim 2, wherein the rod defines a plurality of apertures disposed at said one end of the rod and said protrusions pass through the apertures.

4. The bone support of claim 3, wherein the rod defines an aperture for each protrusion.

5. The bone support of claim 3, wherein the rod defines more apertures than there are protrusion.

6. The bone support of any previous claim, wherein there are five or more protrusions.

7. The bone support of claim 6, wherein there are five protrusions.

8. The bone support of any previous claim, wherein each of said protrusions is a wire.

9. The bone support of claim 7, wherein each wire is a limb of a common wire and the elongated member comprises said common wire.

10. The bone support of any previous claim comprising fixing means disposed at the end of the rod opposite said one end of the rod.

11. The bone support of claim 10, wherein the fixing means comprises a screw-receiving aperture defined by the rod to receive a screw substantially traverse to the longitudinal axis of the rod.

12. The bone support of claim 11, further comprising the screw for insertion into said screw-receiving aperture.

13. The bone support of any previous claim comprising wherein the protrusions are spaced around the rod.

14. The bone support of claim 13 wherein the protrusion are spaced axially on the rod.

15. The bone support of any previous claims wherein the protrusions are extendable.

16. The bone support of any previous claim wherein the protrusions are retractable.

17. A method of placing a bone support in a bone comprising: providing an elongate rod having a longitudinal cavity and four or more apertures at the distal end of the rod; providing an elongated member, the elongated member having four or more protrusions at the distal end of the member; making a hole at one end of the bone; entering the rod into the medullar canal of the bone via said hole; inserting the elongated member into the longitudinal cavity of the rod until the protrusions on the elongate member exit the apertures and engage the bone.

18. A bone support as hereinbefore described with reference to the accompanying drawings.

19. A method of placing a bone support as hereinbefore described with reference to the accompanying drawings.