Intramedullary pin and method of use of intermedullary pin

Abstract

An intramedullary pin (10) for fracture reduction of a fractured bone comprising a first bone fragment (100) and a second bone fragment (102). The intramedullary pin (10) comprising an elongate body (12) for insertion into a medullary canal (108) of the first bone fragment (100) and the second bone fragment (102) through an opening (112) in the first bone fragment (100). The elongate body (12) comprising a proximal end (14) and a distal end (16). The intramedullary pin (10) further comprises a blunt tip (18) at the distal end (16) for abutting against an end (114) of the medullary canal (108) within the second bone fragment (102), and an externally threaded section (20) along at least a portion of the elongate body (12) for engaging the first bone fragment (100).

Description

INTRAMEDULLARY PIN AND METHOD OF USE OF INTERMEDULLARY PIN

[0001] The present disclosure concerns an intramedullary pin and a method for fracture reduction of a proximal bone fragment and a distal bone fragment.BACKGROUND

[0002] Fractures in long bones of the limbs, particularly those that are not simple transverse fractures (fractures occurring at a 90-degree angle to the bone's longitudinal axis), pose significant challenges in reduction and fixation. Repositioning the bone fragments to their exact original position and length is a difficult process made more complicated by the contraction of muscles attached to the bones. The contraction of the muscles result in compression forces that make it difficult to accurately realign and stabilise (commonly referred to as fracture reduction) the bone fracture using bone holders or through manual manipulation of the bone fragments. Moreover, maintaining the bone fragments in the reduced position before the fractured bones are fixed together, typically involving a bone plate and screws or an external skeletal fixator is equally challenging due to these muscular forces.

[0003] Currently, intramedullary pins are commonly used to achieve approximate linear alignment of a fractured bone and to provide protection against bending forces on the fractured bone as the bone heals. However, these intramedullary pins are not designed to facilitate separation of the fragments to restore the bone to its original length. Conventional intramedullary pins have a sharp tip that is intended for penetrating the bone, such that alignment of the fractured bone can be maintained. However, these conventional intramedullary pins do not allow for effective lengthening of the fractured bone back to its original, unfractured length. This is due to the bone fragments slipping along the conventional intermedullary pin past each other under muscle compression, as the pin can slide back out, failing to maintain the desired alignment and separation. This can be a particular problem for feline and canine applications. Consequently, even where a medullary pin is used, it is often required for two people to be present to carry out fracture reduction - one to hold the fractured bone with the correct orientation and length and the other to fit bone holders in place or otherwise fix the bone fragments together.SUMMARY OF THE INVENTION

[0004] While conventional intramedullary pins can be used to align the bone fragments, they do not provide any means for separating or pushing apart the bone fragments, which may have been pushed together and past each other as a result of the compression force exerted by the muscles surrounding the fractured bone.

[0005] In this connection, despite bone fracture repair being a common orthopaedic procedure, there is a need to provide an improved tool and method for simplifying and improving the bone reduction and fixation process for comminuted and oblique fractures of long bones. As such, the present application seeks to make fracture reduction easier.

[0006] According to a first aspect of the present invention, there is provided an intramedullary pin for fracture reduction of a fractured bone comprising a first and second bone fragments, the intramedullary pin comprising: an elongate body for insertion into a medullary canal of the first and second bone fragments through an opening in the first bone fragment, the elongate body comprising a proximal end and a distal end; a blunt tip at the distal end for abutting against an end of the medullary canal within the second bone fragment; an externally threaded section along at least a portion of the elongate body for engaging the second (usually proximal) bone fragment.

[0007] In this way, the intramedullary pin can align and correctly position the bone fragments relative to one another. The elongate body of the intramedullary pin aligns the first bone fragment with the second bone fragment as it is inserted through the medullary canal. Moreover, correct position of the bone fragments relative to each other is achieved through the cooperation between the blunt tip at an end of the medullary canal of the second (usually distal) bone fragment that forces the second bone fragment away from the first (usually proximal) bone fragment as the externally threaded section is driven into the opening in the first bone fragment. The externally threaded section ensures that the desired separation between first bone fragment and the second bone fragment is maintained.

[0008] In embodiments, the intramedullary pin further comprises a tool engagement means at the proximal end, the tool engagement means configured to engage with a tool for driving the externally threaded section into the first bone fragment. In this way, the elongate body of the intramedullary pin can be driven into the opening in the first bone fragment by a surgical tool, or any other suitable tool. The tool provides the necessary force to overcome the compression ofthe bone fragments by the surrounding muscles, such that the externally threaded section can be driven into the opening.

[0009] In embodiments, the tool engagement means is a shank configured to be inserted into and gripped by a chuck on the tool.

[0010] In embodiments, the tool comprises a driving element, and the tool engagement means comprises an aperture for receiving the driving element. In further embodiments, one of the driving element and the tool engagement means is a socket, and the other of the driving element and the tool engagement means comprises a hexagonal cross-section insertable into the socket. In this way, a conventional driving, or socket, bit can be used to drive the externally threaded section into the medullary canal of the bone. This avoids the need for expensive or custom made equipment to drive the externally threaded section into the opening.

[0011] In embodiments, the externally threaded section comprises a cancellous thread for engaging cancellous bone of the first bone fragment. In this way, the cancellous thread is configured to engage with the cancellous bone surrounding the opening and ensures that the externally threaded section engages with the cancellous bone around the opening.

[0012] In embodiments, the externally threaded section comprises at least one cutout for bone fragments as the threaded section is driven into the first bone fragment. In this way, fragments of the cancellous bone removed around the opening as the externally threaded section is driven through can be collected within the cutouts to prevent the externally threaded section from getting blocked and to ensure that a clean thread is formed.

[0013] In embodiments, the externally threaded section comprises three cutouts.

[0014] In embodiments, externally threaded section comprises a tapered thread portion. In this way, the tapered thread portion aids the insertion of the externally threaded section into the cancellous bone around the opening of the first bone fragment through self-tapping and / or selfdrilling.

[0015] In embodiments, the blunt tip and the externally threaded section are separated by a separation distance that is less than or equal to a length of the medullary canal of the first and second bone fragments. In this way, the externally threaded section engages the opening prior to the blunt tip abutting an end of the medullary canal in the second bone fragment. This enables the first and second bone fragments to be separated through the driving of the externally threaded section through the opening in the first bone fragment.

[0016] In embodiments, the externally threaded section has a thread length corresponding with the separation required of the first and second bone fragments. In this way, the externally threaded section has a thread length sufficient to separate the first and second bone fragments to their original, unfractured bone length through the driving of the externally threaded section.

[0017] In embodiments, the elongate body has a length between 170mm and 360mm.

[0018] In embodiments, the elongate body has a diameter between 1.9mm and 3.6mm.

[0019] In embodiments, the externally threaded section has a threaded length between40mm and 80mm.

[0020] In embodiments, the blunt tip and the externally threaded section are separated on the elongate body by a separation distance between 80mm and 220mm.

[0021] In embodiments, the blunt tip is at least partially rounded. In embodiments, the at least partially rounded blunt tip has a radius of curvature greater than 0.75mm. In embodiments, the at least partially rounded blunt tip has a radius of curvature greater than 1.5mm. In embodiments, the at least partially rounded blunt tip has a radius of curvature greater than 3mm. In this way, the blunt tip has a smooth, rounded surface that is unable to penetrate the cancellous bone at the ends of medullary canal. In addition, as the intramedullary pin is inserted through the medullary canal, the rounded surface enables smooth sliding and deflection against the inside walls of the bone within the medullary canal of the fractured bone.

[0022] In embodiments, the intramedullary pin is for fracture reduction of a fractured bone of a feline or a canine.

[0023] According to a second aspect of the present invention, there is provided a kit for fracture reduction comprising a plurality of intramedullary pins as described above. The plurality of intramedullary pins have different lengths, diameters, thread lengths, separation distances and / or radius of curvatures. In this way, a surgeon can choose the appropriate intramedullary pin for the specific fractured bone without needing to specifically manufacture an intramedullary pin for said specific fractured bone. This simplifies and speeds up the fracture reduction process.

[0024] According to a third aspect of the present invention, there is provided a method of fracture reduction using the intramedullary pin as described above. The method comprising: drilling an opening into a first bone fragment; inserting an elongate body of the intramedullary pin into the opening until a blunt tip of the elongate body is at least partially received in a medullary canal of the second bone fragment; aligning the first bone fragment and second bonefragments; driving an externally threaded section of the elongate body into the opening until the blunt tip abuts an end of the medullary canal of the second bone fragment; and driving the externally threaded section until the first and second bone fragments reach a desired separation

[0025] In embodiments, the externally threaded section is driven into the opening in the proximal bone fragment by a tool engaged with a tool engagement means at a proximal end of the elongate body.

[0026] In embodiments, the method further comprises removing a portion of the elongate body protruding out from the opening in the first bone fragment.

[0027] In embodiments, the method further comprises placing a tissue protection sleeve against the first bone fragment as the pin is inserted in order to prevent the externally threaded section from catching the surrounding soft tissue causing it potential damage and preventing the pins further advancement as it is driven into the opening of the first bone fragment.BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Illustrative embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which:Figure 1 shows a side view of an intramedullary pin according to an embodiment of the invention;Figure 2 shows a side view of an externally threaded section of an intramedullary pin according to an embodiment of the invention;Figure 3 shows a front view of an intramedullary pin according to an embodiment of the invention;Figure 4 shows a schematic of a thread profile of an externally threaded section of an intramedullary pin according to an embodiment of the invention;Figure 5A shows an annotated intramedullary pin of Figure 1;Figures 5B-D show annotated intramedullary pins according to embodiments of the invention;Figures 6A-D show a bone fracture reduction process using an intramedullary pin according to an embodiment of the invention;Figures 7 shows an anterior-posterior x-ray of a reduced bone fracture using an intramedullary pin according to an embodiment of the invention (left), and a fractured bone priorto fracture reduction (right);Figure 8 shows a lateral x-ray of the bone fracture of Figure 7 prior to fracture reduction (right) and post fracture reduction (left);Figure 9 shows a surgeon measuring a length of the fractured bone of a cat; andFigure 10 shows a surgeon performing manual manipulation on bone fragments to bring the bone fragments into alignment.DETAILED DESCRIPTION

[0029] Figure 1 shows an intramedullary pin 10 of a first illustrative embodiment. The intramedullary pin 10 is used for bone fracture reduction of a fractured bone comprising at least two bone fragments. For example, a fractured bone may comprise a first bone fragment 100 and a second bone fragment 102, with a fracture 104 therebetween, as shown in Fig. 6A. Preferably, the first bone fragment 100 is a proximal bone fragment - that is, closer to the heart - and the second bone fragment 102 is a distal bone fragment. In addition, additional bone fragments 106 may be present around the fracture, but which are too small to be realigned and repositioned by the intramedullary pin 10. These additional bone fragments 106 may be removed from around the fracture 16 prior to using the intramedullary pin 10. As such, the intramedullary pin 10 can be used for fracture reduction of a fractured bone comprising at least one first bone fragment 100 and at least one second bone fragment 102. Moreover, the intramedullary pin 10 of the present disclosure aims to overcome the compression force of the muscles surrounding the fractured bone, such that the fractured bone fragments can be both realigning and repositioned before fixation by, for example, a bone plate and screws.

[0030] Long bones, such as the femur, humerus tibia, fibula and radius, comprise a medullary canal 108 that is a hollow space located in the centre of the long bone with cancellous bone 110 at either end of the medullary canal 108. It is to be understood that the first bone fragment 100 and the second bone fragment 102 each comprise a respective fractured portion of the medullary canal 108, which in combination makes up the medullary canal 108 of the unfractured bone.

[0031] The intramedullary pin 10 of the present disclosure is configured to be inserted an opening 112 that has been formed in the first bone fragment 100, such that the intramedullary pin 10 can be inserted into the medullary canal 108 for realigning and stabilised the first bone fragment 100 and the second bone fragment 100 during a surgical operation. In this connection,the intramedullary pin 10 comprises a smooth, elongate body 12, that is substantially straight, extending between a proximal end 14 and a distal end 16 to enable the intramedullary pin 10 to be easily inserted into the medullary canal 108 of the first bone fragment 100 and the second bone fragment 102. Moreover, the smooth surface of the intramedullary pin 10 ensures that it can be inserted into the medullary canal 108 enabling smooth passage within the medullary canal 108. Preferably, a length of the elongate body 12 may be between 125mm to 500mm and a diameter of the elongate body 12 may be between 1.9mm and 5mm. More preferably, the length of the elongate body 12 may be between 170mm and 360mm and the diameter of the elongate body 12 may be between 1.9mm and 3.6mm. Furthermore, the construction materials of the elongate body 12 can be varied, depending upon the intended clinical application. In one embodiment, the elongate body 12 comprises SAE 316L grade stainless steel. However, other metals or bioabsorbable or nonabsorbable polymeric materials may be utilised, depending upon the dimensions and desired structural integrity of the intramedullary pin. The elongate body 12 may preferably comprise any material that is biocompatible, corrosion resistant and possesses sufficient strength and rigidity for bone fracture repair For example, the elongate body 12 may comprise at least one of titanium grade 1, 2, 3 and 4, a titanium alloy, such as Ti-6AI-4V, and a cobalt-chromium alloy.

[0032] In an embodiment, the distal end 16 of the elongate body 12 comprises a blunt tip 18 for abutting against an end 114 of the medullary canal 108 within the second bone fragment 102, the blunt tip lacking the sharpness or pointedness needed to easily pierce and enter the cancellous bone 110. The blunt tip 114 is preferably rounded with a minimum radius of curvature of 0.75mm. Preferably, the radius of curvature is greater than 1.5mm. More preferably, the radius of curvature is greater than 3mm. This enables the intramedullary pin 10 to be inserted, or implanted, through the opening 112 and into the medullary canal 108 without penetrating the cancellous bone 110 at the end 114 of the medullary canal 108 in the second bone fragment 102. The blunt tip 114 may have other shapes that prevent the tip 114 from penetrating the cancellous bone 110. For example, the blunt tip 114 may be flat or indented and / or may have at least partially rounded, or chamfered, edges with a minimum radius of curvature to avoid a sharp corner.

[0033] As shown in Figures 1 and 2, the intramedullary pin 10 further comprises an externally threaded section 20 along at least a portion of the elongate body 12 for engaging the cancellousbone 110 around the opening 112. The externally threaded section 20 has a thread major diameter D and a thread minor diameter d, as shown in Fig. 5. Preferably, the diameter of the elongate body 12 may be less than or equal to the thread minor diameter d of the externally threaded section 20. The externally threaded section 20 may be a self-tapping thread. Preferably, the thread length of the externally threaded section 20 is between 20mm to 150mm. More preferably, the thread length of the externally threaded section 20 is between 40mm and 80mm. The externally threaded section 20 can be driven manually into the opening 112 in the first bone fragment 100. In embodiments, various thread profiles in the externally threaded section 20 may be utilized. For example, a buttress, V, square, multi start, tapered, variable pitch, or otherthread profile may be used. More preferably, the externally threaded section 20 comprises a selftapping, cancellous thread with a shallow thread, or a HA thread, that provides better purchase in the porous structure of the cancellous bone 110 at the end of the medullary canal 108.

[0034] The externally threaded section 20 is provided on the elongate body 12 at a predefined distance away from the distal end 16, shown as the shaft length B in Fig. 5. The shaft length B is sized such that afterthe intermedullary pin 10 has been fitted, the externally threaded section 20 engages the cancellous bone 110 around the opening 112 and the blunt tip 18 abuts the distal end of the medullary canal 108 within the second bone fragment 102. That is, the shaft length B is preferably equal to, or less than, the length of the medullary canal 108. However, it will be appreciated that the shaft length B can be such that, after fitting, the unthreaded shaft extends in part into the cancellous bone 110 so long as a sufficient length of the threaded section 20 engages the cancellous bone 110 to anchor the intermedullary pin 10 in place. In some embodiments, the thread length C of the externally threaded section 20 may be at least one fifth( C 1\- - r > - ). That is, the thread length(B+C) 5 / C may be at least one quarter of the shaft length B. Preferably, the thread length C may be atthread length C may be at least one third of the shaft length B. More preferably, the thread length Thatis, the thread length C may be at least half of the shaft length B.

[0035] Preferably, during insertion of the intermedullary pin 10, the externally threaded section 20 engages the cancellous bone 110 around the opening 112 before the blunt tip 18 abutsthe distal end of the medullary canal 108 within the second bone fragment 102. In this way, the externally threaded section 20 engages the cancellous bone 110 around the opening 112 and drives the elongate body 12 into the medullary canal 108 until the blunt tip 18 abuts the distal end of the medullary canal 108 within the second bone fragment 102. Once the blunt tip 18 abuts the distal end of the medullary canal 108, the length of the externally threaded section 20 enables the first bone fragment 100 and the second bone fragment 102 to be reduced, or separated, back to the original, unfractured bone length. Preferably, the shaft length B - that is, the separation distance between the externally threaded section 20 and the distal end 16 comprising the blunt tip 18 - is between 50mm and 300mm. More preferably, the separation distance B between the externally threaded section 20 and the distal end 16 comprising the blunt tip 18 is between 80mm and 220mm.

[0036] The proximal end 14 of the elongate body 12 may comprise a tool engagement means 22 for engaging with a tool, such that the elongate body 12 of the intramedullary pin 10 can be inserted, or driven, into the first bone fragment 100 and the second bone fragment 102. Preferably, the tool engagement means 22 is a shank 12a that is configured to be inserted into and gripped by a chuck of a surgical tool, or any other surgical equipment suitable to drive the elongate body 12 of the intramedullary pin 10 into the first bone fragment 100 and the second bone fragment 102. The shank 12a extends from the externally threaded section 20 to the proximal end 14 of the elongate body 12. The shank 12a preferably comprises an elongate body 12a having a diameter substantially similar to the diameter of the elongate body 12, shown as the shank shaft diameter E in Fig. 5. More preferably, the diameter of the shank 12a is less than the diameter of the elongate body 12. This enables the shank 12a to be removed more easily once the intermedullary pin 10 has been fitted, as will be described in more detail below.

[0037] In one embodiment, the tool comprises a driving element, and the tool engagement means 22 is shaped to engage the driving element. For example, the engagement means 22 comprises an aperture for receiving the driving element, such as a slot for a slotted screwdriver, a cross shaped slot for a Phillips head screwdriver, a hexagon shaped aperture for an Allen wrench, a star shaped aperture for a Torx screwdriver, or any other aperture suitable for receiving a conventional driving bit. In an alternative example, the tool engagement means 22 comprises a head having a square, hexagonal or similar shape for engaging with a socket wrench, a socket bit, or any other suitable means. As the tool engages with the tool engagement means22, the elongate body 12 of the intramedullary pin 10 can be rotated and driven into the medullary canal 108 of the first bone fragment 100 and the second bone fragment 102.

[0038] In an embodiment, the externally threaded section 20 may comprise a tapered thread portion 24 at an end of the externally threaded section 20 closest to the distal end 16 of the elongate body 12 to permit for easier insertion into the opening 122, as shown in Figures 1 and 2. In particular, the tapered thread portion 24 aids the insertion of the externally threaded section 20 into the cancellous bone 110 around the opening 122 of the first bone fragment 100, through self-tapping and / or self-drilling. At one end of the tapered thread portion 24, the thread major diameter is substantially the same as the diameter of the elongate body 12, gradually increasing in diameter until it reaches a maximum thread major diameter, as defined below.

[0039] In an embodiment, the externally threaded section 20 may further comprise one or more cutouts 26, or flutes, as shown in Figures 2 and 3. The one or more cutouts 26 in the externally threaded section 20 provide a path for fragments of the cancellous bone 110 around the opening 112 to be removed during the tapping process. This aids to prevent the externally threaded section 20 from getting blocked by fragments of the cancellous bone 110 created during the tapping process and ensures that a clean thread is formed. Preferably, the externally threaded section 20 comprises three cutouts 26 distributed circumferentially around the externally threaded section 20. In a further embodiment, only a portion of the externally threaded section 20 may comprise one or more cutouts 26. In an example, the portion may be between 5-20mm, preferably 10mm, in length along the externally threaded section 20 from the distal end 16. In these embodiments, the blunt tip 114 preferably has a radius of curvature between 0.75mm and 1.3mm.

[0040] In embodiments, the dimensions of externally threaded section 20 may conform to the ISO 5835 standard from the International Organization for Standardization (ISO), which is detailed in Table 1. The dimensions referred to in Table 1 are shown in Figure 4.TABLE 1: Dimensions of HA thread

[0041] The thread diameter, or the major diameter, is the maximum diameter of the threads in the externally threaded section. The core diameter, or the minor diameter, is the smallest diameter of the thread. The thread pitch is defined as the distance between corresponding points on adjacent threads in the externally threaded section. The leading edge radius and the trailing edge radius are defined as the radius of the thread at the leading and the trailing edge, respectively. As defined by the ISO 5835 standard, the crest width (the thickness of each thread), e, is 0.1mm, the leading edge angle, a, is 35 degrees, and the trailing edge angle, 6, is 3 degrees for the dimensions of HA thread detailed in Table 1 above.

[0042] The intramedullary pin 10 of the present disclosure is suitable for fracture reduction in felines and canines. Exemplary dimensions for intramedullary pins for feline or canine fracture reduction according to the present invention are detailed in Table 2 below. Figure 5A illustrates the dimensions referred to in Table 2. The dimensions are intended to be purely exemplary and are not intended to limit the scope of the present disclosure. Any other suitable sizes and / or dimensions may be considered.TABLE 2: Exemplary dimensions of intramedullary pin for feline or canine fracture reduction

[0043] In addition to the above exemplary dimensions for intramedullary pins for feline or canine fracture reduction detailed above, the intermedullary pin can have the dimensions detailed in Table 3 below and shown in Figures 5B-D. It will be appreciated that the dimensions and values provided herein, including those set out in Tables 1-3, are intended as nominal or target values. In practice, the manufactured item may exhibit variations due to standard manufacturing tolerances. For example, the total length A may have a tolerance of ±2mm; the shaft length B, thread length C, and shank 12a may have a tolerance of ±lmm.TABLE 3: Exemplary dimensions of intramedullary pin for feline or canine fracture reduction

[0044] The intramedullary pin 10 shown in Figures 1 to 3 may be implanted in the fractured bone as follows. First, a smooth pin of a diameter equal to the diameter of the un-threaded portion of the elongate body is drilled into a tip of the first bone fragment 100 until it fully penetrates the cancellous bone to form an opening 112, as shown in Figure 6A. Drilling the opening 112 can be done by direct visualisation or by fluoroscopy. Preferably, the smooth pin is inserted until it is seen exiting the distal end of the first bone fragment 100. Once the opening 112 has been created in the cancellous bone 110 of the first bone fragment 100, the smooth pin is withdrawn.

[0045] As shown in Figure 6B, the intramedullary pin 10 is then inserted via the same opening 112 into the medullary canal 108 of the first bone fragment 100 and second bone fragment 102. Once the elongate body 12 of the intramedullary pin 10 is at least partly inserted into the medullary canal 108 of the second bone fragment 102, the second bone fragment 102 is preferably brought into the alignment with the first bone fragment 100 by manual manipulation. Alternatively, initial alignment of the first bone fragment 100 and second bone fragment 102 may be as a result of the insertion of the substantially straight elongate body 12 into the medullar canal 108 of the first bone fragment 100 and the second bone fragment 102.

[0046] As described above, the externally threaded section 20 is provided on the elongate body 12 at a distance away from the distal end 16, such that the externally threaded section 20 engages the cancellous bone 110 around the opening 112 prior to the blunt tip 18 abutting the distal end of the medullary canal 108 within the second bone fragment 102. As such, once the blunt tip 18 is at least partially inserted into the medullary canal 108 of the second bone fragment 102, the externally threaded section 20 engages the cancellous bone 110 around the opening 112 of the first bone fragment 100, as shown in Figure 6B. However, depending on the distance between the blunt tip 18 and the externally threaded section 20 and the severity of the bone fracture, the externally threaded section 20 may not engage with the cancellous bone 110 around the opening 112 until the blunt tip 18 is at least partially inserted into the medullary canal 108 and possibly not until the blunt tip 18 engages the end 114 of the medullary canal 108 in the second bone fragment 102.

[0047] As shown in Figure 6C, the intramedullary pin 10 is then driven, either manually or by using a surgical hand tool, through the medullary canal 108 of the second bone fragment 102until the blunt tip 18 reaches an end 114, or distal end, of the medullary canal 108 of the second bone fragment 102. At the end 114, the blunt tip 18 of the elongate body 12 abuts against the cancellous bone 110 inside the end 114 of the medullary canal 108 of the second bone fragment 102. As the intramedullary pin 10 is then driven into the medullary canal 108, a portion of the externally threaded section 20 may be inserted into the medullary canal 108 of the first bone fragment 100. Optionally, an orthopaedic tissue protection sleeve may be used during this process to prevent the externally threaded section 20 on the elongate body 12 from contacting soft tissues around the opening 112 of the first bone fragment 100, which could stop further insertion of the elongate body 12 of the intramedullary pin 10 into the first bone fragment 100 and second bone fragment 102 and cause soft tissue damage. One end of the orthopaedic tissue protection sleeve may be held against the first bone fragment and aligned with the opening 112, with the other end of the orthopaedic tissue protection sleeve bone protruding out through the soft tissues. As such, the orthopaedic tissue protection sleeve creates a passageway for the intramedullary pin to be inserted through the soft tissues and into the opening 112 without damaging the surrounding soft tissues.

[0048] Once the blunt tip 18 reaches an end 114 of the medullary canal 108 of the second bone fragment 102, further driving of the externally threaded section 20 into the opening 112 of the first bone fragment 100 will initiate the pushing apart, or separation, of the first bone fragment 100 and the second bone fragment 102. Because the tip 18 is blunt, it does not penetrate the cancellous bone at the end 114 of the medullary canal 108 during further driving of the externally threaded section 20 so that the distance between, and relative positions of, the first and second bone fragments 100, 102 can be accurately controlled. The externally threaded section 20 is driven into the opening 112 until the desired amount of separation has been achieved, such that the first bone fragment 100 and the second bone fragment 102 are in the correct position relative to each another. That is, the first bone fragment 100 and the second bone fragment 100 are aligned and positioned relative to each other, such the first bone fragment 100 and the second bone fragment 102 attain the desired position (i.e., so the original, unfractured bone length has been reached). Once the desired position has been attained, the tool is disengaged from the tool engagement means 22.

[0049] The first bone fragment 100 and the second bone fragment 102 are maintained securely in position relative to each other due to the elongate body 12 of the intramedullary pin10 countering the compression forces of the muscles surrounding the bone fragments. That is, as the intramedullary pin 10 is driven into the first bone fragment 100 and the second bone fragment 102, the blunt tip 18 prevents the elongate body 12 from penetrating the cancellous bone 110 of the second bone fragment 102 and acts to push the second bone fragment 102 away from the first bone fragment 100. Furthermore, the intramedullary pin 100 is fixed in place relative to the first bone fragment 100 and the second bone fragment 102 as a result of the externally threaded section 20 engaging the cancellous bone 110 within opening 112 within the first bone fragment 100. The externally threaded section 20 prevents movement of the intramedullary pin 10, such that the first bone fragment 100 and the second bone fragment 102 can be both aligned and positioned correctly relative to each other.

[0050] After the first bone fragment 100 and the second bone fragment 102 have been aligned and positioned into their correct positions relative to one another, a definitive fracture fixation means can be applied to the first bone fragment 100 and the second bone fragment 102. For example, the definitive fracture means may be a metal plate with screws or an external skeletal fixator. As shown in Figure 6D, once the definitive fracture fixation means has been applied, the elongate body 12 of the intramedullary pin 10 protruding out from the opening 112 of the first bone fragment 100 may be removed by, for example, a pin cutter, a saw, or any other suitable means. Beneficially, the structural properties of the intramedullary pin 10 increases the bone's resistance to bending forces, such that the bone is more resistant against further bone fractures once the bone fracture has been repaired and the bone has healed. The bone reduction process described above is simpler compared to conventional methods and allows for fracture reduction to be carried out by one person.

[0051] Figs. 7 & 8 show X-rays of a completed bone fracture reduction, following insertion of a medullary pin 10 and subsequent fixing of a metal plate outside the bone with screws at either end. In Fig. 8, the intermedullary pin 10 can be seen through the holes provided in the plate.

[0052] There may be provided a kit or set comprising a plurality of intramedullary pins 10 of different dimensions, as described above. This enables a surgeon performing a fracture reduction to select the intramedullary pin 10 that corresponds with the dimensions of the fractured bone. Figure 9 shows a surgeon measuring a cat's fractured bone, with an appropriate intermedullary pin 10 having been chosen for the fractured bone. As such, the kit or set of intramedullary pins 10 ensures that an intramedullary pin 10 is available for a wide variety of fracture types and bonelengths. For example, the kit or set may comprise intramedullary pins according to the dimensions detailed in Table 2 above. As described above, Figure 10 shows the surgeon performing fracture reduction with the blunt tip 18 having been at least partially inserted into the medullary canal 108 of the second bone fragment 102 following manual manipulation on the first bone fragment 100 and the second bone fragment 102 to bring them into alignment.

[0053] It will be understood that the embodiments illustrated above show applications of the invention only for the purposes of illustration. In practice the invention may be applied to many different configurations, the detailed embodiments being straightforward for those skilled in the art to implement.

[0054] It is to be understood that while the intramedullary pin 10 described in the present disclosure is suitable for fracture reduction in felines and canines, the intramedullary pin can be used for fracture reduction in any animal, including humans. In addition, it is also to be understood that the dimensions described in the present disclosure are exemplary and different dimensions can be used depending on the animal and the size of the fractured bone.

Claims

CLAIMS1. An intramedullary pin for fracture reduction of a fractured bone comprising a first and second bone fragments, the intramedullary pin comprising: an elongate body for insertion into a medullary canal of the first and second bone fragments through an opening in the first bone fragment, the elongate body comprising a proximal end and a distal end; a blunt tip at the distal end for abutting against an end of the medullary canal within the second bone fragment; an externally threaded section along at least a portion of the elongate body for engaging the second bone fragment.

2. The intramedullary pin according to claim 1, further comprising a tool engagement means at the proximal end, the tool engagement means configured to engage with a tool for driving the externally threaded section into the first bone fragment.

3. The intramedullary pin according to claim 2, wherein the tool engagement means is a shank configured to be inserted into and gripped by a chuck on the tool.

4. The intramedullary pin according to claim 2, wherein the tool comprises a driving element, and the tool engagement means comprises an aperture for receiving the driving element.

5. The intramedullary pin according to claim 2, wherein the tool comprises a driving element and one of the driving element and the tool engagement means is a socket, and the other of the driving element and the tool engagement means comprises a cross-section corresponding to and insertable into the socket.

6. The intramedullary pin according to any preceding claim, wherein the externallythreaded section comprises a cancellous thread for engaging cancellous bone of the first bone fragment.

7. The intramedullary pin according to any preceding claim, wherein the externally threaded section comprises at least one cutout for bone fragments as the threaded section is driven into the first bone fragment.

8. The intramedullary pin according to claim 6 or claim 7, wherein the externally threaded section comprises three cutouts.

9. The intramedullary pin according to any preceding claim, wherein the externally threaded section comprises a tapered thread portion.

10. The intramedullary pin according to any preceding claim, wherein the blunt tip and the externally threaded section are separated by a separation distance that is less than or equal to a length of the medullary canal of the first and second bone fragments.

11. The intramedullary pin according to any preceding claim, wherein the externally threaded section has a thread length corresponding with the separation required of the first and second bone fragments.

12. The intramedullary pin according to any preceding claim, wherein the elongate body has a length between 140mm and 360mm.

13. The intramedullary pin according to any preceding claim, wherein the elongate body has a diameter between 1.5mm and 3.6mm.

14. The intramedullary pin according to any preceding claim, wherein the externally threaded section has a thread length between 40mm and 90mm.

15. The intramedullary pin according to any preceding claim, wherein the blunt tip and the externally threaded section are separated on the elongate body by a separation distance between 70mm and 220mm.

16. The intramedullary pin according to claim 15, when dependent on claim 14, wherein the thread length is at least a quarter, a third, or half of the separation distance.

17. The intramedullary pin according to any preceding claim, wherein the blunt tip is at least partially rounded.

18. The intramedullary pin according to claim 17, wherein the at least partially rounded blunt tip has a radius of curvature greater than 0.75mm.

19. The intramedullary pin according to claim 17 or 18, wherein the at least partially rounded blunt tip has a radius of curvature greater than 1.5mm.

20. The intramedullary pin according to any one of claims 17 to 19, wherein the at least partially rounded blunt tip has a radius of curvature greater than 3mm.

21. The intramedullary pin according to any preceding claim, wherein the intramedullary pin is for fracture reduction of a fractured bone of a feline or a canine.

22. A set comprising a plurality of intramedullary pins according to any preceding claim, wherein the plurality of intramedullary pins have different lengths, diameters, thread lengths, separation distances and / or radius of curvatures.

23. A method of fracture reduction using an intramedullary pin according to any one of claims 1 to 21, the method comprising:drilling an opening into a first bone fragment; inserting an elongate body of the intramedullary pin into the opening until a blunt tip of the elongate body is at least partially received in a medullary canal of the second bone fragment; aligning the first bone fragment and second bone fragments; driving an externally threaded section of the elongate body into the opening until the blunt tip abuts an end of the medullary canal of the second bone fragment; driving the externally threaded section until the first and second bone fragments reach a desired separation.

24. The method according to claim 23, wherein the externally threaded section is driven into the opening in the proximal bone fragment by a tool engaged with a tool engagement means at a proximal end of the elongate body.

25. The method according to any one of claims 23 to 24, wherein the method further comprises: removing a portion of the elongate body protruding out from the opening in the first bone fragment.

26. The method according to any one of claims 23 to 25, wherein the method further comprises: placing an orthopaedic tissue protection sleeve against the opening in the first bone fragment as the elongate body of the intramedullary pin is inserted into the opening.

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