WO2025196452A1

WO2025196452A1 - Fixation pin

Info

Publication number: WO2025196452A1
Application number: PCT/GB2025/050605
Authority: WO
Inventors: Damian CLARK; Richie GILL; James Robinson
Original assignee: University of Bath
Current assignee: University of Bath
Priority date: 2024-03-22
Filing date: 2025-03-21
Publication date: 2025-09-25
Anticipated expiration: 2026-09-22
Also published as: GB2639668A; GB202404142D0

Abstract

A bi-cortical fixation pin is disclosed. The bi-cortical fixation pin comprises a drill portion end having a drill tip portion and first tap body portion having a first pitch thread configured to be engageable to cut a first thread through a first cortex; a securing portion adjacent the drill portion end and configured, when received within the first cortex, to modify the first thread to secure the securing portion within the first cortex; and a fixation portion end adjacent the securing portion and configured to receive a surgical device.

Description

FIXATION PIN

FIELD OF THE INVENTION

The present invention relates to a fixation pin used to secure a fixator to tissue.

BACKGROUND

Fixation pins are known. Fixation pins are typically used during surgical procedures. The fixation pin is inserted, typically into bone tissue, with one end being retained by the bone and another end used to receive a surgical device such as marker arrays for tracking bone position during robotic surgery or an external fixator used to hold a limb or other body part. However, existing fixation pins have shortcomings. Accordingly, it is desired to provide an improved fixation pin.

SUMMARY

According to a first aspect, there is provided a bi-cortical fixation pin, comprising: a drill portion end having a drill tip portion and first tap body portion having a first pitch thread configured to be engageable to cut a first thread through a first cortex; a securing portion adjacent the drill portion end and configured, when received within the first cortex, to modify the first thread to secure the securing portion within the first cortex; and a fixation portion end adjacent the securing portion and configured to receive a surgical device.

The first aspect recognizes that a problem with existing fixation pins is that they can be insufficiently well-secured to reliably hold the surgical device securely enough during surgery. Accordingly, a fixation pin is provided. The fixation pin may be a bi-cortical or two cortex fixation pin typically for use in a relatively hard diaphyseal bone. The fixation pin may comprise a drill portion end or region. The drill portion end may have a drill tip portion or part. The drill portion end may have a first tap body portion or part. The first tap body portion may have a first pitch thread. That is to say that the first tap body portion may define a thread having a first pitch. The first pitch thread may be configured or arranged, when received within a first cortex, to be engageable or operable to cut a first thread through the first cortex. The fixation pin may comprise a securing portion or part. The securing portion may be axially adjacent the drill portion end. The securing portion may be configured, shaped or arranged, when received within the first cortex, to modify, change or alter the first thread to secure, fix, fasten or attach the securing portion within the first cortex. In other words, the securing portion may be configured, shaped or arranged to reshape the first thread to improve contact between improve contact between the securing portion and the first cortex. The fixation pin may comprise a fixation portion end or region. The fixation portion end may be axially adjacent the securing portion. The fixation portion end may be configured to receive a surgical device such as an external fixator, navigation or robotic array. In this way, by modifying the first thread to secure the securing portion within the first cortex, the fixation pin is retained in place securely without pre-drilling, in a single step while reducing the risk of fracture to either cortex

The first pitch may be configured, when rotated at a drilling speed, to advance the drill portion end along an axial direction through the first cortex at a first axial rate and the securing portion is configured, when received within the first cortex at the drilling speed, to prevent the drill portion end being advanced along the axial direction at the first axial rate.

The first aspect also recognises that a problem with existing fixation pins is that when a drill portion end is configured with a drill tip portion and a first tap body portion, this can lead to cortex damage occurring. In particular, the drill portion end may be configured with the drill tip portion and first tap body portion in order to drill through a first cortex and then into a second cortex where the drill tip portion drills another hole in that second cortex and the first tap body portion is then used to secure the drill end portion into that second cortex. However, having already drilled through the first cortex, the presence of the first tap body portion and the first thread in that first cortex can mean that the fixation pin, and particularly the drill tip portion, is advanced axially due to the rotation of the fixation pin into the second cortex too quickly which can cause a fracture of the second cortex in the vicinity of the region where the drill tip portion impacts against the second cortex. Accordingly, the first pitch may be configured, when rotated at a drilling or operating speed, to advance or propel the drill portion along an axial direction through the first cortex at a first axial rate. The securing portion may be configured, when received within the first cortex at that same drilling speed, to prevent the drill portion being advanced or propelled along the axial direction at the first axial rate. In this way, once the drill portion end has moved through the first cortex and the typically smooth securing portion is now received within the first cortex to facilitate fixing within the first cortex, the fixation pin is no longer advanced or propelled by the rotation of the fixation pin along the axial direction at the first axial rate. This allows the axial speed of the drill tip portion to be controlled to help prevent such impact fractures occurring when engaging with a second cortex. The securing portion may be configured, when received within the first cortex at the drilling speed, to prevent the drill portion end being advanced along the axial direction into a second cortex at the first axial rate. Accordingly, the securing portion may be configured to prevent, inhibit or stop the drill portion end from being advanced or propelled into the second cortex at the first axial rate during rotation of the fixation pin.

The securing portion may be configured without a first pitch thread. Accordingly, the absence or omission of the first pitch thread on the securing portion stops any forward axial movement when the securing portion is received in the first cortex.

The securing portion may comprise a non-threaded shank portion. Accordingly, providing a shank portion without a thread on the securing portion stops any forward axial movement when the securing portion is received in the first cortex.

The securing portion may be configured, when received within the first cortex at the drilling speed, to facilitate the drill portion end being advanced along the axial direction into the second cortex at a second axial rate which is lower than the first axial rate.

Hence, the securing portion may be configured such that when it is received within the first cortex at the drilling speed, the drill portion end moves in the axial direction towards the second cortex at an axial rate which is slower than the first axial rate. This helps to reduce impact fractures to the second cortex. Hence, this arrangement enables the fixation pin to be securely fixed within the second cortex using the drill portion and securely fixed within the first cortex using the securing portion while reducing the likelihood of fracture in either the first cortex or the second cortex.

During surgery, oscillating saws are often used, as well as hammers to anchor components, which causes vibration and the threaded connections can cause conventional pins to loosen due to these vibrations. Having a threaded portion and a non-threaded portion in contact with the bone increases the resistance to vibration.

The securing portion may be configured with surface features, texturing, fluting or undulations to increase friction or resistance to movement between it and the cortex while reducing intra-osseous pressure as the pin advances.

The securing portion may be configured with a second tap body portion having a second pitch thread. The first pitch thread may be continuous with the second pitch thread and have a transition portion extending between the first tap body portion and the second tap body portion where the first pitch thread transitions to the second pitch thread. In other words, a single thread with different pitches may be provided. That single thread may have the first pitch in the drill tip portion and the second pitch in the securing portion. The pitch of the single thread may vary, change or alter between the first pitch and the second pitch.

The second pitch thread may have a smaller pitch than the first pitch thread. In this way, for the same drilling or operating speed, the axial speed of the drill portion end when the second pitch thread engages with the first cortex is reduced compared to the axial speed when the first pitch thread is received in the first cortex. This helps to reduce impact fractures to the second cortex.

A major diameter of the second pitch thread may be larger than a major diameter of the first pitch thread. This helps to modify the first thread by cutting a second thread into the first cortex.

The securing portion may taper between the drill portion end and the fixation portion end.

The securing portion may have a taper angle of between around 0.5° and 2.5°, and typically around 1 °. This helps to enable the securing portion to modify the first thread typically formed in diaphyseal bone while reducing the risk of fracture.

The securing portion may enlarge radially between the drill portion end and the fixation portion end. Such enlargement helps to modify the first thread and improve the fit between the securing portion and the first cortex to help improve the fixing of the pin into the first cortex.

The securing portion may have a cross-sectional area which increases away from the drill portion end and towards the fixation portion end.

The cross-sectional area may increase to at least a major diameter of the first pitch thread.

The securing portion may comprise a reamer. The reamer may be tapered. A tapered reamer provides for gradual clearing of the bone thread to improve contact with the bone while reducing the likelihood of fracturing.

The securing portion may comprise at least one recess shaped to collect and convey at least one of tissue and fluid. The at least one recess may define a cutting edge. Accordingly, tissue and/fluid may be removed to improve the fit between the external surface of the securing portion and the aperture cut into the first cortex. This also helps to reduce intra-osseous pressure as the pin advances

The at least one recess may extend axially.

The securing portion may comprise a plurality of recesses distributed circumferentially around the securing portion.

The securing portion may be dimensioned to have an axial length which is longer than the drill portion end.

The securing portion may have an axial length dimensioned to be longer than a diameter of a medullary canal between the first cortex and the second cortex.

The securing portion may be dimensioned to have an axial length of greater than around 20mm.

The drill portion end may have an axial length dimensioned to prevent concurrent or simultaneous engagement of drill portion end with both the first cortex and the second cortex. This helps to ensure that the drill portion end cannot be advanced or propelled into the second cortex at the first axial rate which helps to reduce impact fractures to the second cortex.

The drill portion end may have an axial length dimensioned to be shorter than a diameter of a medullary canal between the first cortex and the second cortex. This helps to ensure that the drill portion end cannot be advanced or propelled into the second cortex at the first axial rate which helps to reduce impact fractures to the second cortex. The drill tip portion may have an axial length dimensioned to match a thickness of at least one of the first cortex and the second cortex. This helps to ensure that the drill portion end cannot be advanced or propelled into the second cortex at the first axial rate which helps to reduce impact fractures to the second cortex.

The drill tip portion has an axial length dimensioned to be shorter than a thickness of at least one of the first cortex and the second cortex. This helps to ensure that the drill portion end cannot be advanced or propelled into the second cortex at the first axial rate which helps to reduce impact fractures to the second cortex.

The drill portion end may have an axial length of less than around 20mm.

The drill tip portion and the first tap body portion may be configured to overlap axially.

The drill tip portion may be configured to transition axially into the first tap body portion.

The first pitch thread may be configured to extend into flutes of the drill tip portion.

The first pitch thread may be configured with surface features, texturing or undulations to increase the friction between it and the cortex.

The drill tip portion may have a cutting tip configured for drilling an aperture within which to from the first thread. Hence, the fixation pin is self-tapping and requires no pre-drilling which facilitates its use in a single step.

The drill tip portion may have a point angle of no more than around 90°.

The fixation portion end may be configured or dimensioned to extend from the first cortex when the drill portion end is received by the second cortex.

The fixation portion end may have an engagement structure shaped to receive a complementary engagement structure of the surgical device.

The surgical device may comprise an external fixator, navigation or robotic array.

The fixation portion end may be dimensioned to have an axial length which exceeds an axial length of the drill portion end and the securing portion. The fixation portion end may have an axial length of greater than around 40mm.

According to a second aspect, there is provided a method, comprising: providing a drill portion end having a drill tip portion and first tap body portion having a first pitch thread configured to be engageable to cut a first thread through a first cortex; providing a securing portion adjacent the drill portion end and configured, when received within the first cortex, to modify the first thread to secure the securing portion within the first cortex; and providing a fixation portion end adjacent the securing portion and configured to receive a surgical device.

The method may comprise a method of configuring a bi-cortical fixation pin.

The method may comprise configuring the first pitch to advance the drill portion end along an axial direction through the first cortex at a first axial rate when rotated at a drilling speed and configuring the securing portion to prevent the drill portion end being advanced along the axial direction at the first axial rate when received within the first cortex at the drilling speed.

The method may comprise configuring the securing portion to prevent the drill portion end being advanced along the axial direction into a second cortex at the first axial rate when received within the first cortex at the drilling speed,

The method may comprise configuring the securing portion without the first pitch thread.

The method may comprise configuring the securing portion with a non-threaded shank portion.

The method may comprise configuring the securing portion to facilitate the drill portion end being advanced along the axial direction into the second cortex at a second axial rate which is lower than the first axial rate when received within the first cortex at the drilling speed.

The method may comprise configuring the securing portion with surface features, texturing, fluting or undulations to increase friction or resistance to movement between it and the cortex while reducing intra-osseous pressure as the pin advances. The method may comprise configuring the securing portion with a second tap body portion having a second pitch thread.

The method may comprise configuring the second pitch thread to have a smaller pitch than the first pitch thread.

The method may comprise configuring a major diameter of the second pitch thread to be larger than a major diameter of the first pitch thread.

The method may comprise configuring the securing portion to taper between the drill portion end and the fixation portion end.

The method may comprise configuring the securing portion with a taper angle of between around 0.5° and 2.5°, and typically around 1 °.

The method may comprise configuring the securing portion to enlarge radially between the drill portion end and the fixation portion end.

The method may comprise configuring the securing portion with a cross-sectional area which increases away from the drill portion end and towards the fixation portion end.

The method may comprise configuring the cross-sectional area to increase to at least a major diameter of the first pitch thread.

The method may comprise configuring the securing portion as a reamer.

The method may comprise configuring the reamer to be tapered.

The method may comprise configuring the securing portion with at least one recess shaped to collect and convey at least one of tissue and fluid.

The method may comprise configuring the at least one recess to define a cutting edge.

The method may comprise configuring the at least one recess to extend axially. The method may comprise configuring the securing portion with a plurality of recesses distributed circumferentially around the securing portion.

The method may comprise configuring the securing portion to be dimensioned to have an axial length which is longer than the drill portion end.

The method may comprise configuring the securing portion to have an axial length dimensioned to be longer than a diameter of a medullary canal between the first cortex and the second cortex.

The method may comprise configuring the securing portion to be dimensioned to have an axial length of greater than around 20mm.

The method may comprise configuring the drill portion end to have an axial length dimensioned to prevent concurrent engagement of drill portion end with both the first cortex and the second cortex.

The method may comprise configuring the drill portion end to have an axial length dimensioned to be shorter than a diameter of a medullary canal between the first cortex and the second cortex.

The method may comprise configuring the drill tip portion to have an axial length dimensioned to match a thickness of at least one of the first cortex and the second cortex.

The method may comprise configuring the drill tip portion to have an axial length dimensioned to be shorter than a thickness of at least one of the first cortex and the second cortex.

The method may comprise configuring the drill portion end to have an axial length of less than around 20mm.

The method may comprise configuring the drill tip portion and the first tap body portion to overlap axially.

The method may comprise configuring the drill tip portion to transition axially into the first tap body portion. The method may comprise configuring the first pitch thread to extend into flutes of the drill tip portion.

The method may comprise configuring the first pitch thread with surface features, texturing or undulations to increase the friction between it and the cortex.

The method may comprise configuring the drill tip portion to have a cutting tip configured for drilling an aperture within which to from the first thread.

The method may comprise configuring the drill tip portion to have a point angle of no more than around 90°.

The method may comprise configuring the fixation portion end to extend from the first cortex when the drill portion end is received by the second cortex.

The method may comprise configuring the fixation portion end to have an engagement structure shaped to receive a complementary engagement structure of the surgical device.

The method may comprise configuring the fixation portion end to be dimensioned to have an axial length which exceeds an axial length of the drill portion end and the securing portion.

The method may comprise configuring the fixation portion end to have an axial length of greater than around 40mm.

The method may comprise configuring the configuring a bi-cortical fixation pin to have the features of the bi-cortical fixation pin of the first aspect.

According to a third aspect, there is provided a method, comprising: drilling a first cortex with a bi-cortical fixation pin comprising a drill portion end having a drill tip portion and first tap body portion having a first pitch thread, a securing portion adjacent the drill portion end and a fixation portion end adjacent the securing portion; cutting a first thread through the first cortex with the first tap body portion; modifying the first thread with the securing portion to secure the securing portion within the first cortex; drilling a second cortex with the drill portion end to secure the drill portion end within the second cortex; and receiving a surgical device on the fixation portion end.

The second method may be a method of using a bi-cortical fixation pin.

The cutting the first thread may comprise, when rotated at a drilling speed, advancing the drill portion end along an axial direction through the first cortex at a first axial rate and the drilling the second cortex may comprise, when rotated at the drilling speed, preventing the drill portion end being advanced along the axial direction into the second cortex at the first axial rate.

The drilling the second cortex may comprise, when received within the first cortex at the drilling speed, facilitating the drill portion end being advanced along the axial direction into the second cortex at a second axial rate which is lower than the first axial rate.

The securing portion may be configured without the first pitch thread and the drilling the second cortex may comprise receiving the securing portion within the first cortex at the drilling speed to prevent the drill portion end being advanced along the axial direction into the second cortex at the first axial rate.

The securing portion may be configured with a non-threaded shank portion and the drilling the second cortex may comprise receiving the securing portion within the first cortex at the drilling speed to prevent the drill portion end being advanced along the axial direction into the second cortex at the first axial rate.

The securing portion may comprise a second tap body portion having a second pitch thread smaller pitch than the first pitch thread and the drilling the second cortex may comprise receiving the securing portion within the first cortex at the drilling speed to facilitate the drill portion end being advanced along the axial direction into the second cortex at the second axial rate which is lower than the first axial rate.

The modifying may comprise deforming the first thread with the securing portion to secure the securing portion within the first cortex. A major diameter of the second pitch thread may be larger than a major diameter of the first pitch thread and the modifying may comprise cutting a second thread with the second pitch thread as it advances along the axial direction within the first cortex to secure the securing portion within the first cortex.

The securing portion may taper between the drill portion end and the fixation portion end and the modifying may comprise deforming the first thread with the securing portion as it advances along the axial direction within the first cortex to secure the securing portion within the first cortex.

The securing portion may enlarge radially between the drill portion end and the fixation portion end and the modifying may comprise deforming the first thread with the securing portion as it advances along the axial direction within the first cortex to secure the securing portion within the first cortex.

The securing portion may have a cross-sectional area which increases away from the drill portion end and towards the fixation portion end and the modifying may comprise deforming the first thread with the securing portion as it advances along the axial direction within the first cortex to secure the securing portion within the first cortex.

The cross-sectional area may increase to at least a major diameter of the first pitch thread and the modifying may comprise deforming the first thread with the securing portion as it advances along the axial direction within the first cortex to secure the securing portion within the first cortex.

The securing portion may comprise a reamer and the modifying may comprise deforming the first thread with the reamer as it advances along the axial direction within the first cortex to secure the securing portion within the first cortex.

The securing portion may comprise at least one recess and the modifying may comprise collecting and conveying at least one of tissue and fluid with the reamer.

The securing portion may have an axial length dimensioned to be longer than a diameter of a medullary canal between the first cortex and the second cortex. The securing portion may be dimensioned to have an axial length of greater than around 20mm.

The drill portion end may have an axial length dimensioned to prevent concurrent engagement of drill portion end with both the first cortex and the second cortex.

The drill portion end may have an axial length dimensioned to be shorter than a diameter of a medullary canal between the first cortex and the second cortex.

The drill tip portion may have an axial length dimensioned to match a thickness of at least one of the first cortex and the second cortex.

The drill tip portion may have an axial length dimensioned to be shorter than a thickness of at least one of the first cortex and the second cortex.

The drill portion end may have an axial length of less than around 120mm.

The drill tip portion may have a point angle of no more than around 90°.

The fixation portion end may be configured to extend from the first cortex when the drill portion end is received by the second cortex.

The fixation portion end may be dimensioned to have an axial length which exceeds an axial length of the drill portion end and the securing portion. The method may comprise using a bi-cortical fixation pin having the features of the bi- cortical fixation pin of the first aspect.

Further particular and preferred aspects are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims as appropriate, and in combinations other than those explicitly set out in the claims.

Where an apparatus feature is described as being operable to provide a function, it will be appreciated that this includes an apparatus feature which provides that function or which is adapted or configured to provide that function.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described further, with reference to the accompanying drawings, in which:

Figure 1 illustrates a bi-cortical fixation pin according to one embodiment;

Figure 2 illustrates a bi-cortical fixation pin according to one embodiment; and Figure 3 illustrates schematically operation of the bi-cortical fixation pin.

DESCRIPTION OF THE EMBODIMENTS

Before discussing embodiments in any more detail, first an overview will be provided. Some embodiments provide a fixation pin having a drill portion end, a securing portion and a fixation portion. The drill portion end operates or functions to drill into tissue, such as bone, as the fixation pin is rotated. The drill portion end typically has a drill tip portion which drills a hole into the bone and a tap body portion which taps a thread in the hole in the bone in order to fix the drill portion end securely into the bone.

However, given that most uses of such a fixation pin involve drilling initially into a first cortex of the bone before entering the medullary canal, the presence of the tap body portion can propel the drill tip portion through the medullary canal as the fixation pin is rotated and can cause the drill tip portion to impact against a second cortex of the bone, causing fracture damage. As these fixation pins are typically inserted through the soft tissue the user is unable to see or evaluate the amount of damage that has occurred. When the procedure is complete the fixation pins are typically removed and if the damage has occurred, then this will leave a weakened region in the bone, which then can be an initiation point for a fracture. This can be a devastating complication for the patient and can require further procedures to fix the fracture. Also, it can be difficult to provide a secure enough fit in the hole in the first cortex. Accordingly, some embodiments have a securing portion adjacent the drill portion end. The securing portion is configured to prevent the fixation pin being propelled through the medullary canal at the same rate as it was propelled through the first cortex once the tap body portion has passed through the first cortex. This helps to reduce the speed at which the drill tip portion then approaches and engages with the second cortex, thereby reducing the risk of impact fracture. The reduced speed can be achieved by configuring the securing portion to either have no tap body portion at all or have a tap body portion which has a smaller pitch thread. The drill portion end can then advance into the second cortex and be retained by the tap body portion. The securing portion modifies the thread in the first cortex to improve the retention and secure the fit in the first cortex. Such modification is typically provided by a tapered portion and/or an enlarged threaded portion of the securing portion. This helps to provide a fixation pin which is well-secured within the bone in one step and which reduces the risk of fractures occurring in either the first cortex or the second cortex. Such a fixation pin can also be used for single cortex fixation.

Fixation Pin - 1^st Arrangement

Figure 1 illustrates a bi-cortical fixation pin 10A according to one embodiment. In particular, Figure 1 shows a side view, an end view, a sectional view along the line B-B and an enlarged view of the region C. The bi-cortical fixation pin 10A is generally cylindrical and elongate in shape, extending along a central axis. The bi-cortical fixation pin 10A is formed from titanium, steel or other suitable surgical-grade material. At one end is provided a drill portion end 20 which extends axially along a length of the bi-cortical fixation pin 10A. The drill portion end 20 terminates at an axially-adjoining securing portion 30. The securing portion 30 also extends axially along a length of the bi-cortical fixation pin 10A. The securing portion 30 terminates at an axially-adjoining fixation portion end 40. The fixation portion end 40 also extends axially along a length of the bi-cortical fixation pin 10A and is located at the other end of the bi-cortical fixation pin 10A from the drill portion end 20.

The drill portion end 20 has a drill tip portion 22 located at one end of the bi-cortical fixation pin 10A, an axially-adjacent first tap body portion 24 and typically an unthreaded portion 27. The drill tip portion 22 typically comprises a four-facet drill tip 26 having a point angle of around 90 degrees which facilitates drilling into the diaphyseal cortex without the need of any pre-drilling. The drill tip portion 22 has flutes 28 which are defined by a helix having an angle of around 27 degrees. The drill tip portion 22 has an external diameter of typically around 2.6 millimetres. The axial length of the drill tip portion 22 is typically around 7.5 millimetres. The flutes 28 extend axially into the first tap body portion 24. The first tap body portion 24 has an external diameter of around 2.6 millimetres. A pitch P1 of the thread 25 of the first tap body portion 24 is around 1 .2 millimetres, with a thread depth of around 0.3 millimetres and a pitch radius of around 0.7 millimetres. The axial length of the first tap body portion 24 is typically around 7 millimetres and, as can be seen in Figure 1 , the flutes 28 and the thread 25 inter-engage. Typically, adjacent the first tap body portion 24 is the unthreaded portion 27 having an axial length of around 7 millimetres.

Axially adjacent the drill portion end 20 is the securing portion 30. The securing portion

30 typically has a tapering portion 32. The tapering portion typically extends for an axial length of around 8 millimetres with around a 0.72 degree angle and enlarges from an initial diameter of around 2.6 millimetres nearest the drill tip portion 22 to an enlarged diameter of around 3.2 millimetres nearest the fixation portion end 40. Located within the securing portion 30 are a plurality (in this case, three) of recesses 34 defining a cutting edge distributed circumferentially around the external surface of the securing portion 30. The recesses 34 typically extend axially for a length of around

31 millimetres. In this example, the surface of the securing portion 30 is smooth. However, in other arrangements, the surface is fluted or has surface features which improve contact with the second cortex.

Axially adjacent the securing portion 30 is the fixation portion end 40. The fixation portion end is typically shaped (not shown) to match an engaging structure of a surgical device such as an external fixator, navigation or robotic array (not shown). The securing portion 30 typically has an axial length of around 60 millimetres.

The configuration and axial length of the drill portion end 20 is typically pre-configured so that the bi-cortical fixation pin 10A is not being propelled forwards by the thread 25 as it approaches the second cortex. In particular, the axial length of the drill portion 20 end is set such that the thread 25 has passed through the first cortex and is no longer engaged with the first cortex as the drill portion end 22 advances through the medullary canal towards the second cortex. Instead, the dimensions of the bi-cortical fixation pin 10A are configured so that the unthreaded portion 27 or the securing portion 30 is received within the first cortex and the bi-cortical fixation pin 10A can only be advanced towards the second cortex by pressure applied by the user. Also, the configuration and dimensions of the securing portion 30 are selected to improve the fit of the bi-cortical fixation pin 10A in the hole created by the drill portion end 20 in the first cortex to improve the attachment of the securing portion 30 within the first cortex. This preconfiguring can occur in response to measurements of the cortexes and medullary canal and creating an appropriately-dimensioned bi-cortical fixation pin 10A or by selecting a suitable one of a selection of differently dimensioned bi-cortical fixation pins 10A.

In operation, the drill portion end 20 is advanced against a first cortex of a bone and the bi-cortical fixation pin 10A is rotated at a drilling or operating speed typically using a drill. The drill tip portion 22 cuts a hole into and through the first cortex, with the first tap body portion 24 cutting a first thread into the hole drilled into the first cortex. As the first thread is cut into the hole drilled into the first cortex, bi-cortical fixation pin 10A advances through the first cortex and into the medullary canal at a first axial rate. The thread 25 of the first tap body portion 24 then disengages from the first cortex and the bi-cortical fixation pin 10A ceases to advance at the first rate. With the bi-cortical fixation pin 10A still being rotated by the drill, the user can control the advance of the drill tip portion 26 axially towards a second cortex of the bone. As the drill tip 26 approaches the second cortex, the securing portion 30 engages with the hole in the first cortex and the tapering portion 32, together with the recesses 34, deforming the thread that has been cut in the first cortex, removing any tissue or fluid within the hole in the first cortex, reducing the intra-osseous pressure and improving the contact between the first cortex and the external surface of the securing portion 30.

Meanwhile, the drill tip portion 22 cuts a hole in the second cortex and the first tap body portion 24 begins to cut a thread into the second cortex. As this occurs, the torque resistance on the bi-cortical fixation pin 10A increases and the rotation is stopped. The bi-cortical fixation pin 10A is now safely and securely fixed to the bone in two locations. First, the drill portion end 20 is securely fixed into the second cortex, while the securing portion 30 is also securely held in the first cortex. Any surgical device can now be placed on the fixation portion end 40. Hence, the arrangement provides for a single- step insertion of the bi-cortical fixation pin 10A while reducing the likelihood of fracture of either the first or second cortex.

Figure 2 shows a bi-cortical fixation pin 10B according to one embodiment. This arrangement is identical to the arrangement shown in Figure 1 , with the exception of the configuration of the securing portion 30B.

In this arrangement, the securing portion 30B is threaded to provide a second tap body portion having a second thread 35. The second thread 35 typically has a major diameter larger than the major diameter of the thread 25. Also, the pitch P2 of the second thread 35 is smaller than the pitch P1 of the thread 25. The securing portion 30B may also be provided with a tapering portion and/or with recesses in a similar manner to that described above. The unthreaded portion 27 may be omitted, with the first tap body portion 24 and the second tap body portion being adjacent axially. Also, when adjacent a single thread with variable pitch may be provided with the pitch P1 transitioning to the pitch P2.

The configuration and axial length of the drill portion end 20 is typically pre-configured so that the bi-cortical fixation pin 10B is not being propelled forwards by the thread 25 as it approaches the second cortex. In particular, the axial length of the drill portion 20 end is set such that the thread 25 has passed through the first cortex and is no longer engaged with the first cortex as the drill portion end 26 advances through the medullary canal towards the second cortex. Instead, the dimensions of the bi-cortical fixation pin 10B are configured so that the securing portion 30B is received within the first cortex and the bi-cortical fixation pin 10B is propelled towards the second cortex by the second thread 35 at an axial speed which is slower than the axial speed caused by the thread 25 when rotated by the drill at the same drilling speed. Also, the configuration and dimensions of the securing portion 30B are selected to improve the fit of the bi- cortical fixation pin 10B in the hole created by the drill portion end 20 in the first cortex by expanding that hole and cutting a new fixing thread to improve the attachment of the securing portion 30B within the first cortex. This pre-configuring can occur in response to measurements of the cortexes and medullary canal and creating an appropriately- dimensioned bi-cortical fixation pin 10B or by selecting a suitable one of a selection of differently dimensioned bi-cortical fixation pins 10B.

In operation, the drill portion end 20 is advanced against a first cortex of a bone and the bi-cortical fixation pin 10B is rotated at a drilling or operating speed typically using a drill. The drill tip portion 22 cuts a hole into and through the first cortex, with the first tap body portion 24 cutting a first thread into the hole drilled into the first cortex. As the first thread is cut into the hole drilled into the first cortex, the bi-cortical fixation pin 10B advances through the first cortex and into the medullary canal at a first axial rate determined by the rotation speed of the drill and the pitch P1 of the thread 25. The thread 25 of the first tap body portion 24 then disengages from the first cortex and the bi-cortical fixation pin 10B ceases to move forward at the first rate. With the bi-cortical fixation pin 10B still being rotated by the drill at the same rotation speed, the second thread 35 engages with the hole cut through the first cortex. As the drill tip 26 approaches the second cortex, the securing portion 30B deforms the thread that has been cut in the first cortex by cutting a second thread, removing any tissue or fluid within the hole in the first cortex, reducing the intra-osseous pressure and improving the contact between the first cortex and the external surface of the securing portion 30B. The drill tip 26 advances axially towards a second cortex of the bone at a slower speed than the first rate due to the smaller pitch P2 of the thread 35. The drill tip 26 cuts a hole in the second cortex and the first tap body portion 24 begins to cut a thread into the second cortex. As this occurs, the torque resistance on the bi-cortical fixation pin 10B increases and the rotation is stopped. The bi-cortical fixation pin 10B is now safely and securely fixed to the bone in two locations. First, the drill portion end 20 is securely fixed into the second cortex, while the securing portion 30B is also securely held in the first cortex. Any surgical indicators can now be placed on the fixation portion end 40. Hence, the arrangement provides for a single-step insertion of the bi- cortical fixation pin 10B while reducing the likelihood of fracture of either the first or second cortex.

Figure 3 illustrates schematically in more detail the operation of the bi-cortical fixation pin 10A; 10B. The bi-cortical fixation pin 10A; 10B is removable and facilitates quick insertion and removal with minimal damage to the bone while providing for secure temporary fixation as it is intended temporary use during a surgical procedure rather than for permanent use to repair or support damage to the bone. As shown in Figure 3A, the fixation pin 10A; 10B is presented to an external surface of the first cortex 100A. As shown in Figure 3B, the drill tip 26 drills a hole in the first cortex 100A with the first tap body portion 24 cutting a first thread into the hole drilled into the first cortex 100. As shown in Figure 3C, as the first thread is cut into the hole drilled into the first cortex 100A, the bi-cortical fixation pin 10A; 10B advances through the first cortex 100A and into the medullary canal 110 at a first axial rate R1 determined by the rotation speed of the drill and the pitch P1 of the thread 25. Because the axial length L1 of the drill portion end 20 is shorter than the width L2 of the medullary canal 110, the thread 25 of the first tap body portion 24 then disengages from the first cortex 100A and the bi-cortical fixation pin 10A; 10B ceases to move forward at the first rate within the medullary canal 110.

For the bi-cortical fixation pin 10A, with the bi-cortical fixation pin 10A still being rotated by the drill, the user can control the advance of the drill tip portion 26 axially towards the second cortex 100B of the bone at a reduced, second axial rate R2. As the drill tip 26 approaches the second cortex 100B, the securing portion 30 engages with the hole in the first cortex and the tapering portion 32, together with the recesses 34, deforming the thread that has been cut in the first cortex 100A, removing any tissue or fluid within the hole in the first cortex 100A, reducing the intra-osseous pressure and improving the contact between the first cortex 100A and the external surface of the securing portion 30.

For the bi-cortical fixation pin 10B, with the bi-cortical fixation pin 10B still being rotated by the drill at the same rotation speed, the second thread 35 engages with the hole cut through the first cortex 100A. As the drill tip 26 approaches the second cortex 100B, the securing portion 30B deforms the thread that has been cut in the first cortex by cutting a second thread, removing any tissue or fluid within the hole in the first cortex, reducing the intra-osseous pressure and improving the contact between the first cortex and the external surface of the securing portion 30B. The drill tip 26 advances axially towards a second cortex of the bone at an axial rate R2 than the first rate due to the smaller pitch P2 of the thread 35.

As shown in Figure 3D, the drill tip portion 22 cuts a hole in the second cortex 100B and the first tap body portion 24 begins to cut a thread into the second cortex 100B. As this occurs, the torque resistance on the bi-cortical fixation pin 10A; 10B increases and the rotation is stopped. The bi-cortical fixation pin 10A; 10B is now safely and securely fixed to the bone in two locations. First, the drill portion end 20 is securely fixed into the second cortex 100B, while the securing portion 30 is also securely held in the first cortex 100A. Any surgical device can now be placed on the fixation portion end 40. Hence, the arrangement provides for a single-step insertion of the bi-cortical fixation pin 10A; 10B while reducing the likelihood of fracture of either the first or second cortex. Once no longer required, the surgical device can be removed and the by simply unscrewing the first tap body portion 24 from the second cortex 100B and sliding the bi-cortical fixation pin 10A; 10B back through the medullary canal 110 and first cortex 100A.

Although a set of dimensions for the bi-cortical fixation pins are set out above, other dimensions are possible. In particular, some embodiments provide bi-cortical fixation pins with external diameters of generally around 4.0mm or 3.2mm. The total axial length of 3.2mm diameter bi-cortical fixation pins can range from around 70mm to 140mm, with preferred axial lengths of around 70mm, 110mm, 130mm or 140mm. The total axial length of 4.0mm diameter bi-cortical fixation pins can range from around 110mm to 170mm, with preferred axial lengths of around 110mm or 170mm. Some embodiments provide an axial length of the drill tip portion 22 ranging from around 1 .8 to 4mm, with a preferred length of around 1 ,8mm. Some embodiments provide an axial length of the first tap body portion 24 ranging from around 6mm to 14mm, with a preferred length of around 10.2mm. Some embodiments provide an axial length of the unthreaded portion 27 ranging from around 2mm to 8mm, with a preferred length of around 6mm. Some embodiments provide an axial length of the tapering portion 32 ranging from around 6mm to 12mm, with a preferred length of around 8mm. Some embodiments provide an axial length of the securing portion 30A, 30B ranging from around 20mm to 40mm around, with a preferred length of around 31 mm. Some embodiments provide a tapered portion having a taper angle of between around 0.5° and 2.5°.

Some embodiments provide bi-cortical fixation pins with specific cutting geometry of the tip to enhance purchase in the hard outer bone region, existing pins can often skid on the bone surface. Some embodiments provide bi-cortical fixation pins with a short threaded section just after the tip, this short section of self-cutting thread engages in the first cortex and then gives way to a smooth tapered section which prevents the pin from being accelerated into the bone as the rest of the pin passes through the first cortex. This threaded section is designed to engage into the second cortex. Some embodiments provide bi-cortical fixation pins with pressure relief scallops in the tapered section, these act to enhance the bone cutting at the edge of the scallops and provide a channel for fluid/marrow to escape thus reducing the internal pressure in the bone.

Some embodiments provide bi-cortical fixation pins with a tapered section reaching the diameter equal to the outer diameter of the threaded section to enable secure fixing.

Testing of embodiments have shown that they perform as per the design intent: they are considerably easier to drill into hard bone, they do not accelerate the bone pin into the bone and do not cause damage to the bone on exiting the second cortex. In addition, using the new pins provided the user with direct haptic feedback on when the bone pin reached the second cortex.

Some embodiments provide a drill pin which is a convenient way to secure a navigation array to a bone. They can be implanted with a single step. The shaft is threaded, this permits the pin to be held securely. This thread creates a significant problem, as soon as the thread engages the bone the rotational speed of the drill causes the pin to advance at a speed defined by the pitch of the thread and the rotational speed of the drill, not under surgeon control. When the drill tip reaches the second cortex it is advancing at a speed that is greater than the speed at which the drill tip can cut. Therefore it burst/fractures through the second cortex, these small fractures can propagate into a full fracture when the patient bears weight on the bone.

Some embodiments provide an arrangement of a cutting tip, thread, taper and reamer, set at a distribution to achieve a specific outcome in a cortical bone. This single component device permits a single step fixation of the array such that it remains under the surgeon’s control (to avoid the pin pulling in and fracturing the far cortex) - once positioned, it achieves a stable fixation.

Some embodiments provide an arrangement having a high speed drilling of fluted tip to create a hole in the first cortex through which the threaded portion advances longitudinally under speed defined by thread and rotation. When the threaded portion has cleared the first cortex, the drill’s longitudinal progress comes back under control of the operator to allow the tip to safely (without fracture) drill a hole in the second cortex. The fluted taper enters the first cortex (this is positioned the correct distance behind the thread to work in femur and tibia diaphaseal bone) and deforms/cuts/compresses the bone thread to achieve stable fixation.

These arrangements are unlike conventional arrangements for different morphologies and functions, which are intended for different uses. For example, one such hip screw device would not advance and secure in the manner needed. It is intended for soft metaphyseal bone. This would not work at all in hard diaphasis (cortical bone) as it would stop at the taper and “log split” the bone. Additionally, it has a thread for fixation and this thread is the likely causes of fractures. If the threaded section reached the bone then it would cause the tip to advance and could cause a fracture. In addition, this device is not fluted thus is unable to reduce intra-osseous pressure as the pin advances. The device is also a permanent implantable device, not a temporary array attachment. Likewise, one such pedicle screw (spinal surgery) insertion device has a completely different morphology and function. This is a spine screw and designed for the particular anatomy of the spine. The screw would not prevent fracture in a cortical bone. This screw would simply cause a fracture of the far cortex. In particular, there is no fluted, tapered section that would secure into the first cortex. The device would not function in the metaphysis / diaphysis of long bones and, as there is no different fluted, tapered securing portion, would cause a fracture of the second cortex as it advanced to abut against it. Similarly, one such device is intended for array pins. However, its design only addresses fixation and is devoid of features that would prevent fracture. It it’s a modular device which requires multiple surgical steps: pre-drilling then positioning of the far cortex thread then drilling and positioning of the near cortex thread. This is different the embodiments set out above which are configured for use in a single process to secure a non-modular device.

Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiment and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.

Claims

1 . A bi-cortical fixation pin, comprising: a drill portion end having a drill tip portion and first tap body portion having a first pitch thread configured to be engageable to cut a first thread through a first cortex; a securing portion adjacent said drill portion end and configured, when received within said first cortex, to modify said first thread to secure said securing portion within said first cortex; and a fixation portion end adjacent said securing portion and configured to receive a surgical device.

2. The bi-cortical fixation pin of claim 1 , wherein said first pitch is configured, when rotated at a drilling speed, to advance said drill portion end along an axial direction through said first cortex at a first axial rate and said securing portion is configured, when received within said first cortex at said drilling speed, to prevent said drill portion end being advanced along said axial direction at said first axial rate.

3. The bi-cortical fixation pin of claim 1 or 2, wherein said securing portion is at least one of: configured, when received within said first cortex at said drilling speed, to prevent said drill portion end being advanced along said axial direction into a second cortex at said first axial rate; configured without said first pitch thread; configured, when received within said first cortex at said drilling speed, to facilitate said drill portion end being advanced along said axial direction into said second cortex at a second axial rate which is lower than said first axial rate; configured with surface features, texturing, fluting or undulations to increase friction or resistance to movement between it and the cortex while reducing intraosseous pressure as the pin advances; and configured with a second tap body portion having a second pitch thread, and preferably said first pitch thread is continuous with said second pitch thread and has a transition portion extending between said first tap body portion and said second tap body portion where said first pitch thread transitions to said second pitch thread.

4. The bi-cortical fixation pin of claim 3, wherein said second pitch thread has a smaller pitch than said first pitch thread.

5. The bi-cortical fixation pin of claim 3 or 4, wherein a major diameter of said second pitch thread is larger than a major diameter of said first pitch thread.

6. The bi-cortical fixation pin of any preceding claim, wherein said securing portion comprises a non-threaded shank portion.

7. The bi-cortical fixation pin of any preceding claim, wherein said securing portion at least one of: tapers between said drill portion end and said fixation portion end; has a taper angle of between around 0.5° and 2.5°, and 15 typically around 1 °; enlarges radially between said drill portion end and said fixation portion end; and has a cross-sectional area which increases away from said drill portion end and towards said fixation portion end.

8. The bi-cortical fixation pin of claim 7, wherein said cross-sectional area increases to at least a major diameter of said first pitch thread.

9. The bi-cortical fixation pin of any preceding claim, wherein said securing portion comprises at least one of: a reamer; a tapered reamer; at least one recess shaped to collect and convey at least one of tissue and fluid; at least one recess shaped to define a cutting edge; and plurality of recesses distributed circumferentially around said securing portion.

10. The bi-cortical fixation pin of claim 9, wherein said at least one recess extends axially.

11 . The bi-cortical fixation pin of any preceding claim, wherein said securing portion is at least one of: dimensioned to have an axial length which is longer than said drill portion end; dimensioned to have an axial length which is longer than a diameter of a medullary canal between said first cortex and said second cortex; and dimensioned to have an axial length of greater than around 20mm.

12. The bi-cortical fixation pin of any preceding claim, wherein said drill portion end has at least one of: an axial length dimensioned to prevent concurrent engagement of drill portion end with both said first cortex and said second cortex; an axial length dimensioned to be shorter than a diameter of a medullary canal between said first cortex and said second cortex; and an axial length of less than around 20mm.

13. The bi-cortical fixation pin of any preceding claim, wherein said drill tip portion has at least one of: an axial length dimensioned to match a thickness of at least one of said first cortex and said second cortex; and an axial length dimensioned to be shorter than a thickness of at least one of said first cortex and said second cortex.

14. The bi-cortical fixation pin of any preceding claim, wherein said drill tip portion and said first tap body portion are configured to overlap axially.

15. The bi-cortical fixation pin of any preceding claim, wherein said drill tip portion is configured to transition axially into said first tap body portion.

16. The bi-cortical fixation pin of any preceding claim, wherein said first pitch thread is configured to extend into flutes of said drill tip portion, and preferably said first pitch thread is configured with surface features, texturing or undulations.

17. The bi-cortical fixation pin of any preceding claim, wherein said drill tip portion has at least one of: a cutting tip configured for drilling an aperture within which to from said first thread; and a point angle of no more than around 90°.

18. The bi-cortical fixation pin of any preceding claim, wherein said fixation portion end is configured to extend from said first cortex when said drill portion end is received by said second cortex.

19. The bi-cortical fixation pin of any preceding claim, wherein said fixation portion end has an engagement structure shaped to receive a complementary engagement structure of said surgical device.

20. The bi-cortical fixation pin of any preceding claim, wherein said fixation portion end is dimensioned to have an axial length which exceeds an axial length of said drill portion end and said securing portion.

21 . The bi-cortical fixation pin of any preceding claim, wherein said fixation portion end has an axial length of greater than around 40mm.

22. A method, comprising: providing a drill portion end having a drill tip portion and first tap body portion having a first pitch thread configured to be engageable to cut a first thread through a first cortex; providing a securing portion adjacent said drill portion end and configured, when received within said first cortex, to modify said first thread to secure said securing portion within said first cortex; and providing a fixation portion end adjacent said securing portion and configured to receive a surgical device.

23. A method, comprising: drilling a first cortex with a bi-cortical fixation pin comprising a drill portion end having a drill tip portion and first tap body portion having a first pitch thread, a securing portion adjacent said drill portion end and a fixation portion end adjacent said securing portion; cutting a first thread through the first cortex with the first tap body portion; modifying said first thread with said securing portion to secure said securing portion within said first cortex; drilling a second cortex with said drill portion end to secure said drill portion end within said second cortex; and receiving a surgical device on said fixation portion end.