U.S. patent application number 14/442534 was filed with the patent office on 2015-11-26 for a twist-drivable pin assembly.
The applicant listed for this patent is Patrick CANNON, DEPUY (IRELAND), Auger JOSHUA, Jonathan LEE. Invention is credited to JOSHUA AUGER, PATRICK CANNON, JONATHAN LEE, DUNCAN YOUNG.
Application Number | 20150335368 14/442534 |
Document ID | / |
Family ID | 47630834 |
Filed Date | 2015-11-26 |
United States Patent
Application |
20150335368 |
Kind Code |
A1 |
AUGER; JOSHUA ; et
al. |
November 26, 2015 |
A TWIST-DRIVABLE PIN ASSEMBLY
Abstract
A twist-drivable pin assembly includes first and second drivers,
each having a driving end (2) which can be received in a bore (104)
in the end of a twist-drivable pin, and an opposite end at which
torque can be applied. The cross-sectional shape of each of the
drivers at its driving end has a first plurality of apexes (18)
whose relative locations coincide with the apexes of a regular
polygon such as a hexagon. The drivers differ from one another in
their cross-sectional shapes at the driving end by virtue of one or
more faces of at least one of the drivers between adjacent pairs of
apexes having a groove (20) formed in it. Each of first and second
twist-drivable pins has a bore (64) extending into it which is
defined by a second plurality of apexes arranged as a regular
polygon such as a hexagon and which is open at one end. The number
of apexes of the second plurality is equal to the number of apexes
of the first plurality. The first and second pins differ from one
another by virtue of markings associated with the open ends of the
polygonal bores. The shape defined by the markings corresponds to
the cross-sectional shape of a corresponding one of the first and
second drivers.
Inventors: |
AUGER; JOSHUA; (FORT WAYNE,
IN) ; CANNON; PATRICK; (WARSAW, IN) ; LEE;
JONATHAN; (DALLAS, TX) ; YOUNG; DUNCAN;
(LEEDS, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JOSHUA; Auger
CANNON; Patrick
LEE; Jonathan
DEPUY (IRELAND) |
Cork |
|
US
US
US
IE |
|
|
Family ID: |
47630834 |
Appl. No.: |
14/442534 |
Filed: |
December 17, 2013 |
PCT Filed: |
December 17, 2013 |
PCT NO: |
PCT/US2013/075724 |
371 Date: |
May 13, 2015 |
Current U.S.
Class: |
606/319 ;
81/436 |
Current CPC
Class: |
F16B 23/003 20130101;
A61B 17/8615 20130101; A61B 90/90 20160201; B25B 15/004 20130101;
A61B 17/888 20130101 |
International
Class: |
A61B 17/86 20060101
A61B017/86; A61B 17/88 20060101 A61B017/88; F16B 23/00 20060101
F16B023/00; B25B 15/00 20060101 B25B015/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 17, 2012 |
GB |
1222688.2 |
Claims
1-14. (canceled)
15. A twist-drivable pin assembly comprising: a. first and second
drivers, each of which has a driving end which can be received in a
bore in the end of a twist-drivable pin, and an opposite end at
which torque can be applied, the cross-sectional shape of each of
the drivers at its driving end having a first plurality of apexes
whose relative locations coincide with the apexes of a regular
polygon, one or more of the faces between adjacent pairs of apexes
of at least one of the drivers having a groove formed in it so that
the drivers differ from one another in their cross-sectional shapes
at the driving end by virtue of the provision of different numbers
and/or arrangements of such grooves, b. first and second
twist-drivable pins, each having a bore extending into it which is
defined by a second plurality of apexes arranged as a regular
polygon and which is open at one end, in which at least one of the
drivers can be received, the number of apexes of the second
plurality being equal to the number of apexes of the first
plurality, the first and second pins differing from one another by
virtue of markings associated with the open end of the polygonal
bore of at least one of the first and second pins, in which the
shape defined by the markings corresponds to the cross-sectional
shape of a corresponding one of the first and second drivers.
16. The twist-drivable pin assembly of claim 15, in which the
markings on at least one of the pins defines a shape which is
different from the shape of the bore in that pin.
17. The twist-drivable pin assembly of claim 15, in which the
markings on one or each of the first and second twist-drivable pins
are formed by removing material from the surface of the pins
surrounding the open end of the bore.
18. The twist-drivable pin assembly of claim 17, which the marks
are formed by engraving.
19. The twist-drivable pin assembly of claim 17, in which the marks
are formed using a laser.
20. The twist-drivable pin assembly of claim 17, in which the depth
of the markings below the surface of the twist-drivable pins the
bore is at least about 0.3 mm.
21. The twist-drivable pin assembly of claim 17, in which the depth
of the markings below the surface of the twist-drivable pins
surrounding the bore is not more than about 5.0 mm.
22. The twist-drivable pin assembly of claim 17, in which the
markings are provided on the twist-drivable pins in areas
surrounding the open end of the hexagonal bore which lie radially
outside of the straight lines joining adjacent apexes of the
bore.
23. The twist-drivable pin assembly of claim 15, in which the
cross-sectional shape of each of the drivers at its driving end has
six apexes whose relative locations coincide with the apexes of a
regular hexagon.
24. The twist-drivable pin assembly of claim 15, in which the
grooves formed in one or each of the drivers by which the drivers
differ from one another extend to the driving end of the
drivers.
25. The twist-drivable pin assembly of claim 15, in which the
transverse dimension of the polygonal driving end of the first
driver is different from the transverse dimension of the polygonal
driving end of the second driver.
26. The twist-drivable pin assembly of claim 15, in which the first
and second twist-drivable pins are fasteners.
27. The twist-drivable pin assembly of claim 26, in which each of
the fasteners has an external thread.
28. The twist-drivable pin assembly of claim 15, in which at least
one of the twist-drivable pins is a shaft component of an
instrument or device.
29. A kit for use in surgery including an orthopaedic implant
having at least one bore formed in it for receiving a
twist-drivable pin and a twist-drivable pin assembly as claimed in
claim 15.
Description
[0001] This invention relates to a twist-drivable pin assembly
which includes pins having a recess at one end in which the end of
a driver can be received to twist the pin. The pin can be a
fastener. The pin can be a shaft component of an instrument or
other device.
[0002] It will often be preferred for the recess in the end of a
pin in which the end of a driver is received to be shaped so that
the end of a driver is a snug fit in the recess. Commonly used
examples include a slot in the end of a fastener such as a screw
which receives the flat blade of a driver tool, and a cross-shaped
slot which receives the cross-shaped end of a driver tool.
[0003] The use of a driver tool whose end is hexagonal and received
in a hexagonal recess or bore) in a pin has the advantage that the
multiple apexes provide for efficient torque transmission from the
tool to the pin. Furthermore, the tool can be received more
securely in the recess than is sometimes the case with screws are
driven in by a flat blade or cross-shaped blade screwdriver. This
means that the likelihood of damage to the substrate caused by the
end of the driver if it becomes separated from the pin is
reduced.
[0004] It can be desirable to differentiate between drivers which
are used to impart a twist drive to respective pins, for example to
respective fasteners drive them into a substrate, in particular to
facilitate selection of a driver which is appropriate for use with
a particular pin. Such drivers might differ from one another in
terms of for example, their sizes. For example, when the drivers
have a driving end which is polygonal, for example hexagonal, the
transverse dimension of one driver (measured between a line joining
a first pair of adjacent apexes and a line joining a second pair of
adjacent apexes opposite to the first pair when the number of
apexes is even) might be different from the transverse dimension of
another driver, and intended to be used with pins having polygonal
bores with different transverse dimensions. Whether or not they
differ in size, drivers might differ from one another in terms of
other features such as, for example, limiting torque settings.
[0005] The present invention provides a twist-drivable pin assembly
in which driver bits each have a cross-sectional shape at their
driving ends defined by a plurality of regularly arranged apexes,
the cross-sectional shapes differing from one another by virtue of
one or more faces of at least one of the drivers between adjacent
pairs of apexes having a groove formed in it, and twist-drivable
pins have markings associated with the open end of a polygonal
driver bore whose shapes correspond to the cross-sectional shapes
of the drivers which are intended to drive the pins.
[0006] Accordingly the invention provides a twist-drivable pin
assembly comprising: [0007] a. first and second drivers, each of
which has a driving end which can be received in a bore in the end
of a twist-drivable pin, and an opposite end at which torque can be
applied, the cross-sectional shape of each of the drivers at its
driving end having a first plurality of apexes whose relative
locations coincide with the apexes of a regular polygon, the
drivers differing from one another in their cross-sectional shapes
at the driving end by virtue of one or more faces of at least one
of the drivers between adjacent pairs of apexes having a groove
formed in it, [0008] b. first and second twist-drivable pins, each
having a bore extending into it which is defined by a second
plurality of apexes arranged as a regular polygon and which is open
at one end, in which at least one of the drivers can be received,
the number of apexes of the second plurality being equal to the
number of apexes of the first plurality, the first and second pins
differing from one another by virtue of markings associated with
the open end of the polygonal bore of at least one of the first and
second pins, in which the shape defined by the markings corresponds
to the cross-sectional shape of a corresponding one of the first
and second drivers.
[0009] The twist-drivable pin assembly of the invention has the
advantage that a user is able to use the markings on the
twist-drivable pins to provide a visual indication as to the driver
which is to be used to twist-drive a selected pin. The reverse is
also true. The invention uses graphical indications in the form of
shapes in order to identify corresponding twist-drivable pins and
drivers. In particular, the shape is embodied in (a) the
cross-section of the driver and (b) the markings that are
associated with the open end of the bore in each of the fasteners.
This has the advantage of being easy for a user to recognise. The
cross-sectional shape of the driver can be recognised from a number
of different angles: the shape can of course be recognised when the
driver is viewed end on from a position in line with its axis, but
it can also be recognised when the driver is viewed from one side.
It can be preferred that the grooves formed in one or each of the
drivers, by which the drivers differ from one another, extend to
the driving end of the driver. This facilitates recognition of the
cross-sectional shapes of the drivers because the cross-sectional
shapes correspond to the shapes of the end faces of the drivers.
The cross-sectional shape can therefore be seen in a view of the
driver which includes the end face (which might be an oblique
view). The identification of a driver or a pin can then be
communicated orally by describing its shape. For example, a driver
might be described as "the hex driver" or "the star driver". This
can be an important advantage in circumstances in which a user has
an assistant who he relies on to pass tools (or instruments) or
pins (for example fasteners) to him, for example in an operating
theatre when a surgeon requests an assistant to pass tools or pins
to him.
[0010] The groove or grooves can be formed in the driver when the
driving end of the basic polygonal configuration of the driver is
created, for example by casting or pressing or stamping or cutting.
The groove or grooves can be formed in a driver in a step which is
performed after the basic polygonal configuration of the driver is
created, for example by a step in which a groove is cut into a face
of the driver.
[0011] It will generally be preferred for the number of apexes at
the driving ends of the drivers to be six. The bores in the pins
would then generally also have six apexes. Such drivers in the
twist-drivable pin assembly of the invention have a hexagonal array
of six apexes so that the driving ends of the drivers can be
received in hexagonal bores in pins to impart torque to the pins.
This means that, while the shape coding of the drivers corresponds
to the shape markings on the pins to help a user to select an
especially appropriate driver to import torque to a pin, the pin
can be driven into the substrate or removed from the substrate
using a polygonal driver whose cross-sectional shape is that of a
regular hexagon.
[0012] It can be preferred that the number of apexes at the driving
ends of the drivers is six. The driving ends of the drivers might
for some applications have a number of apexes other than six. For
example, the number of apexes defined by the driving ends of the
drivers might be three, or four, or five, or seven or eight. It can
be preferred that the number of apexes is at least four. It can be
preferred that the number of apexes is not more than ten,
especially not more than eight. It can be preferred for some
applications that the number of apexes is even.
[0013] The twist-drivable pins can be fasteners. The fasteners will
frequently be screws and will have an external thread. The design
of the thread will depend on the application in which the screw is
being used. The screw might be intended to fasten an orthopaedic
implant to a bone. The screw can then have a thread which is
characteristic of a bone screw. The screw might be used to fasten
two metallic components together where one of the components has an
internal thread. The thread on the screw might then be such as is
characteristic of a machine screw. Such threads are known. The
length of a fastener will be selected according to the application
in which it is going to be used, as with existing conventional
fasteners. Other threaded fasteners might be used, for example with
an internal thread in the form of a nut.
[0014] The fastener might be a bayonet fastener.
[0015] The fasteners which are included in the assembly of the
invention can be used in a range of applications. These
applications might include, for example, engineering, construction,
handicraft, and so on. The fasteners can be used in surgical
applications, especially in applications in orthopaedic surgery.
For example, fasteners can be used to fix components of joint
prostheses in place. They can be used to fix implants for treatment
of broken of bones. Such implants might include bone plates which
are fitted directly or indirectly on the external surface of a
bone, and pins and nails which are fitted in the intramedullary
cavity within a bone. It is an advantage of the present invention
that fasteners can be removed using a plain polygonal driver (for
example a hexagonal driver) instead of a driver which has one or
more grooves provided in one or more faces. This avoids the need to
locate a driver whose driver head has a particular cross-section
shape, which might not be available if a fastener has to be removed
after lapse of a considerable period of time since a component was
implanted in a patient. It will therefore be understood that the
features of the cross-sectional shape of the driver and the shaped
marking features on the fasteners or other twist-drivable pin serve
to identify a driver to drive a pin having a plain polygonal bore,
but do not preclude the use of a driver whose driving end has the
cross-sectional shape of a plain polygon to drive the pin.
[0016] A twist-drivable pin which is used in the assembly of the
invention can be a shaft component of an instrument or device. The
shaft can have a bore formed in it at one end in which the driving
end of a driver can be received to cause the shaft to rotate. The
shaft can be rotated to adjust the instrument or device. For
example, rotation of the shaft might cause the tension on a
component of the instrument or device to change. Rotation of the
shaft might cause a latch to be opened or to be closed. Rotation of
the shaft might cause another component of the instrument or device
to move, in rotational or in translation. Such movement might
involve interengaging gears, or a rack and pinion assembly. The
instrument or device might be a measuring instrument. It is known
for a twist-drivable shaft in such an instrument to have a knob
which can be gripped by a user to cause the shaft to rotate. The
present invention provides control over rotation of the shaft so
that it is not rotated unless an appropriately compatible driver is
used. The length of a pin in the form of shaft component of an
instrument of device will depend on the function of the shaft
component. The shaft component should have an appropriate length to
enable it to perform its intended function. Frequently, the shaft
component will be fixed in place in a housing of the instrument or
device of which it forms a part, such that it can be rotated in the
housing but will not in normal operation (apart from for example
disassembly for cleaning) be separated from the housing. Techniques
for fixing the shaft component in place so that it can be rotated
are well known, and might include for example a circlip or a grub
screw engaging a groove which extends at least part of the way
around the circumference of the shaft component.
[0017] An instrument or device which includes a twist-drivable
shaft component can be an instrument which is used in surgery. For
example it can be suitable for use in orthopaedic surgery. The
instrument can be used to make a measurement, for example of the
size of a bone or of the spacing between two bones, to identify the
appropriate size of an implant component which should be used to
suit a patient's anatomy. The instrument can be used to prepare a
bone to receive an implant component.
[0018] The invention also provides a kit fir use in surgery, which
includes an orthopaedic implant having at least one bore formed in
it for receiving a fastener, and a twist-drivable pin assembly
according to the invention, especially in which the fastener is a
pin such as a screw or other twist-drivable fastener.
[0019] The driving end of a driver in the assembly of the invention
can have a groove in one face. It can have grooves formed in more
than one face. Different combinations of arrangements of grooves
produce drivers which have different shapes, enabling the drivers
to be distinguished from one another. The groove should preferably
extend to the end of the driver which is inserted into the bore in
a pin. This means that the cross-sectional shape of the driver can
be identified by looking at the end of the driver along the axis of
the driver.
[0020] Optionally, the length of the or each groove is at least
about 3 mm, or at least about 4 mm, or at least about 5 mm.
Optionally, the ratio of the length of the groove to the transverse
dimension of the hexagonal driving end (measured between straight
lines joining opposite pairs of apexes) is at least about 1.0, or
at least about 1.2, or at least about 1.5. A longer groove can
facilitate identification of the driver.
[0021] Optionally, the depth of the or each groove is at least
about 1 mm, or at least about 2 mm, or at least about 5 mm.
Optionally, the ratio of the depth of the groove to the transverse
dimension of the polygonal, for example hexagonal, driving end
(measured between straight lines joining opposite pairs of apexes
when the number of apexes is even) is at least about 0.05, or at
least about 0.1, or at least about 0.15. A deeper groove can
facilitate identification of the driver. Optionally, the ratio of
the depth of the groove to the transverse dimension of the
polygonal driving end is not more than about 0.25, or not more than
about 0.2.
[0022] When the driver has six faces and grooves are provided in
each of the six faces between adjacent apexes, the driver will have
the appearance when viewed in cross-section of a six pointed star.
Such a driver can be similar to drivers which are commercially
available, sold under the trade mark Torx.
[0023] When the driver has six faces and the number of faces of the
driver in which grooves are provided is 2, 3 or 4, the driver can
be designed with different arrangements of the grooves. For
example, when the number of grooved faces is two, the grooved faces
can be arranged adjacent to one another (1,2 positions), or
separated by one or two faces (1,3 and 1,4 positions,
respectively). When the number of grooved faces is four, the faces
which are not grooved can be arranged adjacent to one another (1,2
positions), or separated by one or two faces (1,3 and 1,4
positions, respectively).
[0024] When the driver has six faces and the number of faces of the
driver in which grooves are provided is three, the grooved faces
can be alternate faces (1,3,5 positions) so that adjacent grooves
subtend an angle of 120.degree. at the axis of the driver.
[0025] It can be preferred to provide grooves in two faces or three
faces of a driver with six faces because the grooved faces can be
arranged so that they are uniformly spaced around the axis of the
driver. This can provide an appearance which is easily
recognised.
[0026] It is to be noted that the number and arrangement of grooved
faces around the axis of a driver do not by themselves affect the
ability of a driver to fit into a bore in twist-drivable pin, so
that two drivers which differ only in respect of the number and
arrangement of grooved faces might be used interchangeably in a
selected pin. The grooves in the faces of the driver should be such
that the ability of the apexes to engage and to deliver an applied
torque to the apexes which define the bore in the pin is not
compromised to a degree which means that the driver is unable to
impart a desired torque to the pin, for example to drive a screw
fastener into a substrate.
[0027] The markings on one or each of the first and second pins can
be provided by recesses below the surface of the pin surrounding
the open end of the bore. Such recesses can be formed during
manufacture of the pin, for example as part of a process of forming
the bore in the pin. The recesses might therefore be formed by
processes such as cutting, stamping, pressing, and milling.
Markings which are provided by recesses below the surface of the
pin have the advantage that they are better able to be identified
by a user, even in conditions of poor light or when the pin is in
an environment in which fluids are present.
[0028] In addition, a marking provided by a recess below the
surface of the pin can contribute to an appearance that the bore in
the pin has a cross-sectional shape which corresponds to that of
the recess (when the cross-sectional shape of the bore is actually
polygonal, for example hexagonal). This can help a user in the
process of selecting a driver for the pin.
[0029] The markings on at least one of the pins can define a shape
which is different from the shape of the bore in that pin. For
example, the markings on one of the pins might have the shape of a
regular polygon with the same number of apexes as the bore in that
pin, while the markings on another of the pins might have the shape
of a polygon where one or more of the sides of the polygon has a
groove formed in it. It is also envisaged that the markings of a
first pin might have the shape of a polygon where one or more of
the sides of the polygon has a groove formed in it while a second
pin might also have the shape of a polygon where one or more of the
sides of the polygon has a groove formed in it, the patterns of the
grooves in the first pin being different from that in the second
pin. In this arrangement, the shape of the bore in the first pin is
the same as the shape of the bore in the second pin, that is a
regular polygon with the same number of apexes. As discussed
elsewhere, the transverse dimension of the bore in the first pin
might be the same as the transverse dimension of the bore in the
second pin. The transverse dimension of the bore in the first pin
might differ from the transverse dimension of the bore in the
second pin. The first and second pins might differ from one another
in terms of features other than the sizes of the bores in which a
driver can be received, for example in terms of limiting torque
settings.
[0030] The markings on one or each of the first and second
twist-drivable pins can be formed by removing material from the
surface of the pin surrounding the open end of the bore after the
bore has been formed. This can be preferred because it can allow
pins to be differentiated in small batches. Techniques which can be
used to form the markings can include, for example engraving and
etching. Engraving can be performed using a cutting tool. Engraving
can be performed using a laser. Etching can be performed using
appropriate etching materials. The selection of a removal technique
will depend on factors which include the material of the pin and
the shape and depth of the markings which are to be created on the
pin.
[0031] The twist-drivable pin will frequently be formed from a
metal (although other materials might be used such as polymeric and
ceramic materials). Metals which are commonly used to make
twist-drivable fasteners or other pins are well known. Examples of
suitable materials for a fastener which is intended for use in a
surgical procedure, such as an orthopaedic procedure, include
certain stainless steels and titanium its alloys.
[0032] It can be preferred that the depth of the markings below the
surface of the twist-drivable pin surrounding the bore is at least
about 0.2 mm, for example at least about 0.3 mm, or at least about
0.5 mm, or at least about 0.7 mm, or at least about 1.0 mm. The
markings should be sufficiently deep so that they can be observed
clearly by a user. They can also create a visual impression that
the shape of the bore in the twist-drivable pin for receiving the
driver corresponds to the shape defined by the markings. The
markings can have a non-uniform depth so that they appear textured.
This can enhance the contrast between the markings and surrounding
areas of the surface of the twist-drivable pin. The depth of a
marking which is defined by a textured area can be small because of
the enhanced contrast provided by the texturing. The contrast
between the markings and surrounding areas of the surface of the
twist-drivable pin can be enhanced by the introduction of a dye or
other contrast medium in the area of the markings. This might be
done when the markings are formed, for example as part of a laser
marking or an etching process.
[0033] It can be preferred that the depth of the markings below the
surface of the twist-drivable pin surrounding the bore is not more
than about 5.0 mm, for example not more than about 3.5 mm, or not
more than about 2.0 mm. The depth of the markings might be not more
than about 1.0 mm for some applications. Shallow markings can be
appropriate when the size of the twist-drivable pin is small. It
can be preferred for the depth of the markings to be shorter than
the depth of the bore in the pin so that a person inspecting the
pin is able to recognise that the bore in the pin in which the
driver is received to apply torque to the pin is polygonal. This
can be important when, for example, a fastener is to be removed
from a substrate. This might be after the passage of a considerable
period of time following initial use of the fastener. For example,
when the fastener is being used in a surgical application,
especially in orthopaedic surgery (for example to fasten an implant
such as a bone plate to a patient's bone), a surgeon might have to
remove the fastener some time after the initial implantation. This
might be for example after the passage of several months or several
years. It might be at the end of the treatment for the initial
condition for which the fastener was deployed. It might be as part
of the continuation of the initial treatment. It might be to allow
another condition to be treated. It can be desirable that the
surgeon should be able to recognise that the driver that is
appropriate for removal of the fastener is one which has a
polygonal, especially hexagonal, cross-section, notwithstanding the
markings which might be visible on the fastener.
[0034] The markings are provided on the twist-drivable pin in areas
surrounding the open end of the polygonal bore which lie radially
outside of the straight lines joining adjacent apexes of the
bore.
[0035] The shapes of the markings on the twist-drivable pins and
the corresponding cross-sectional shapes of the drivers can be used
to differentiate between different sizes of components of the
assembly. For example, fasteners or other twist-drivable pins might
have similar but different sizes of bore. In a particular example,
a first pin might have a hexagonal bore size 6 mm (measured between
opposite faces) and a second pin might have a hexagonal bore size
6.5 mm. It can be difficult to identify the size of a pin from a
visual inspection of the bore when the bores of pins in the
assembly have similar sizes, and similarly to identify the size of
a driver from a visual inspection of the driving end. The creation
of a distinctive cross-section shape on the driving end by
provision of grooves in faces of the driving end, and the provision
of corresponding markings on the pin, can help to differentiate the
sizes.
[0036] The shapes of the markings on the twist-drivable pins and
the corresponding cross-sectional shapes of the drivers can be used
to differentiate between different lengths of pins.
[0037] Optionally, the transverse dimension of the polygonal
driving end of the first driver (measured between a line joining a
first pair of adjacent apexes and a line joining a second pair of
adjacent apexes opposite to the first pair if the number of apexes
is even, or between a first apex and a line joining a pair of
adjacent apexes opposite to the first apex if the number of apexes
is odd) is different from the transverse dimension of the polygonal
driving end of the second driver.
[0038] Generally, the transverse dimension of the polygonal bore in
the twist-drivable pins (measured between a line joining a first
pair of adjacent apexes and a line joining a second pair of
adjacent apexes opposite to the first pair if the number of apexes
is even, or between a first apex and a line joining a pair of
adjacent apexes opposite to the first apex if the number of apexes
is odd) is at least about 1.0 mm, optionally at least about 11.5
mm, or at least about 2.0 mm. The benefits of the invention in
terms of visual recognition of characteristic shapes are reduced at
smaller sizes.
[0039] The shapes of the markings on the twist-drivable pins and
the corresponding cross-sectional shapes of the drivers can be used
to differentiate between pins which can withstand application of
different maximum torques.
[0040] The shapes of the markings on the twist-drivable pins can be
used to differentiate between different drivers which are to be
used in a particular procedure. For example, it might be that the
driver that is to be used in one step of a procedure has a first
design, and a driver that is to be used in another step of a
procedure has a second design. The designs might differ from one
another in any of a number of features, for example handle
configuration, drive mechanism and so on. The marking on a pin can
help the user to identify the driver which is suitable for use to
impart torque to that pin.
[0041] The assembly of the invention might include more than two
drivers where the drivers can be differentiated from one another by
different arrangements of grooves in the polygonal faces. The
assembly can then include more than two pins which can be
differentiated from one another by different markings associated
with the open ends of the bores in the pins.
[0042] The drivers in the assembly of the invention might be driver
bits which are used with another driver component which can be used
to apply torque to a selected driver bit. For example, the driver
bits might be used with a driver handle. A suitable construction of
handle might be one which has a socket for receiving the end of a
driver bit which is opposite to the driving end of the bit. The
handle might include a mechanism for indicating that a selected
torque value has been applied to the pin. The handle might include
a ratchet mechanism allowing the handle to be turned through a
limited angle back and forth, with torque being applied to the pin
when the handle is turned in only one of the directions.
[0043] Driver bits might be used with a powered driver.
[0044] Embodiments of the invention are described below by way of
example with reference to the accompanying drawings, in which:
[0045] FIG. 1 is an isometric view of a bone screw.
[0046] FIGS. 2a, 2b and 2c are isometric views of the driving ends
of three driver tools in which the driving ends have different
cross-sectional shapes.
[0047] FIGS. 3a, 3b and 3c are end views of the driving ends of the
three driver tools shown in FIGS. 2a, 2b and 2c, respectively.
[0048] FIGS. 4a, 4b and 4c are schematic isometric views of the
heads of three fasteners having markings associated with the open
ends of hexagonal bores in which driver bits can be received.
[0049] FIGS. 5a, 5b and 5c are end views of the driving ends of the
three driver tools shown in FIGS. 4a, 4b and 4c, respectively.
[0050] FIGS. 6a and 6b are isometric views of through twist
adjustment mechanisms which can be incorporated into a surgical
instrument, using a knob and using a twist-drivable pin in
accordance with the invention, respectively
[0051] FIGS. 7a and 7b are sectional elevations through the
mechanisms shown in FIGS. 6a and 6b.
[0052] Referring to the drawings, FIG. 1 shows a bone screw which
includes a shank 101 having a thread 102 formed on it. The screw
has an enlarged head 103 which has a bore 104 extending into it.
The bore has a hexagonal shape when viewed along the axis of the
screw. The screw has a cutting tip 105.
[0053] The hexagonal bore in the screw can receive the hexagonal
end of a driver tool which can be used to apply torque to the screw
to drive it into a bone. An example of an application for the screw
is to fasten a bone plate to a bone.
[0054] FIGS. 2a and 3a are end and isometric views of the driving
end 2, including its end face 3, of a driver tool. The driving end
is provided at the end of a shaft 4. The driver tool can include a
handle (not shown) which the shaft is fastened to. The shaft can be
fastened rigidly to the handle. The tool can include a ratchet
mechanism which ensures that the shaft rotates with the handle when
the handle is rotated in one direction and that the handle can
rotate independent of the shaft in the other direction. The handle
can include a socket for receiving the shaft. The socket can be
capable of receiving different shafts inter changeably.
[0055] The cross-sectional shape of the driving end 2 of the
driving tool, and the shape of its end face 3, are that of a
regular hexagon with six flat faces 6 separated by six apexes 8,
with the internal angle between adjacent apexes being
120.degree..
[0056] FIGS. 2b and 3b are end and isometric views of the driving
end 12, including its end face 13, of a driver tool. The driving
end is provided at the end of a shaft 14. The cross-sectional shape
of the driving end has six apexes 18 whose relative locations
coincide with the apexes of a regular hexagon. Grooves 20 are
provided in each of the six faces of the driving end between
adjacent pairs of the apexes. The grooves extend to the end face 13
of the driving tool. The cross-sectional shape of the driving end,
which is the same as the shape of the end face 13, is that of a six
pointed star, and is similar to the shapes of drivers which are
commercially available, sold under the trade mark Torx.
[0057] The grooves in the side faces of the driving end are formed
by a machining operation performed on the flat faces of a driver
having a hexagonal cross-section shape, as shown in FIG. 2a. The
configuration of the grooves is such that all of the apexes of the
hexagon are unaffected by the machining step.
[0058] FIGS. 2c and 3c are end and isometric views of the driving
end 22, including its end face 23, of a driver tool. The driving
end is provided at the end of a shaft 24. The cross-sectional shape
of the driving end has six apexes 28 whose relative locations
coincide with the apexes of a regular hexagon. Grooves 30 are
provided in three of the six faces 26 of the driving end between
adjacent pairs of the apexes. Adjacent grooved faces are separated
by a face which is not grooved so that the grooves are formed in
the "1,3,5" faces of the hexagon. The grooves extend to the end
face 23 of the driving tool. The cross-sectional shape of the
driving end, which is the same as the shape of the end face 23, can
be seen to have three lobes, and to be similar to that of a
three-leaved shamrock.
[0059] It will be understood that the shape of the head of the
screw will not in practice be as shown in FIGS. 4a to 4c. For
example, the head of a screw might have the general shape shown in
FIG. 1. The representations of the screw heads in FIGS. 4a to 4c
are included to provide information to the reader regarding
features of the bore and associated marking features of a screw
head which can be used in the assembly of the invention.
[0060] FIGS. 4a and 5a shows schematically the head 52 of a screw
or other fastener which can be driven by the driver shown in FIG.
2a. The head has a bore 54 extending into it which is open at the
end surface of the fastener. The bore is defined by six apexes
which are arranged as a regular hexagon. The size of the bore is
such that the driving end 2 of the driver shown in FIG. 2a is a
snug sliding fit in the bore.
[0061] FIGS. 4b and 5b shows schematically the head 62 of a screw
or other fastener which can be driven by the driver shown in FIG.
2b. The head has a bore 64 extending into it which is open at the
end face 66 of the fastener. The bore is defined by six apexes
which are arranged as a regular hexagon. The size of the bore is
such that the driving end 12 of the driver shown in FIG. 2b is a
snug sliding fit in the bore. The bore can also receive the driving
end of a driver whose cross-sectional shape is hexagonal without
grooves in any of its faces (as shown in FIG. 2a), in which the
distance between opposite faces of the hexagon is the same as the
distance between a line joining a first pair of adjacent apexes and
a line a second pair of adjacent apexes opposite to the first pair
of the driving end 12.
[0062] The end face 66 of the fastener has a set of six curved
segments 68 engraved in it, arranged around the end of the
hexagonal bore in a hexagonal array. In the embodiment shown in
FIG. 4b, each of the curved segments is centred on a respective
apex of the hexagonal bore. However, they could be arranged
differently relative to the bore, for example with each of the
curved segments centred on a respective face of the hexagonal bore.
The curved segments are formed by a machine engraving step.
Opposite faces of the hexagonal bore are 4 mm apart. The depth of
the curved segments cut into the end face of the fastener is about
0.7 mm. The arrangement of the curved segments around the hexagonal
bore creates a star-shaped marking on the end face, similar in
appearance to the shape of the end face 13 of the driver shown in
FIG. 2b. It will be understood that the size of the star-shaped
marking will be larger than the size of the star-shaped end face of
the driver.
[0063] FIGS. 4c and 5c shows schematically the head 72 of a screw
or other fastener which can be driven by the driver shown in FIG.
2a. The head has a bore 74 extending into it which is open at the
end face 76 of the fastener. The bore is defined by six apexes
which are arranged as a regular hexagon. The size of the bore is
such that the driving end 12 of the driver shown in FIG. 2c is a
snug sliding fit in the bore. The bore can also receive the driving
end of a driver whose cross-sectional shape is hexagonal without
grooves in any of its faces (as shown in FIG. 2a), in which the
distance between opposite faces of the hexagon is the same as the
distance between a line joining a first pair of adjacent apexes and
a line a second pair of adjacent apexes opposite to the first pair
of the driving end 12.
[0064] The end face 76 of the fastener has a set of three
rectangular segments 78 engraved in located on alternate edges
(edges "1,3,5") of the hexagonal bore 74. The rectangular segments
are formed by a machine engraving step. Opposite faces of the
hexagonal bore are 4 mm apart. The depth of the rectangular
segments cut into the end face of the fastener is about 0.7 mm. The
arrangement of the rectangular segments around the hexagonal bore
creates a three lobe shaped marking on the end face, similar in
appearance to the shape of the end face 23 of the driver shown in
FIG. 2c. It will be understood that the size of the three
lobe-shaped marking will be larger than the size of the three
lobe-shaped end face of the driver.
[0065] The fasteners shown in FIGS. 4a to 4c can differ from one
another in one or more respects, for example in the transverse
sizes of the hexagonal bores, lengths, torque ratings, intended
uses and so on. The engraved markings on the end faces of the
fasteners shown in FIGS. 4b and 4c create the impression of shaped
bores where the shapes correspond to the shapes of the end faces of
the drivers shown in FIGS. 2b and 2c. The eye of a user is drawn to
the bores in the fasteners when identifying an appropriate driver
so that the association of the marking with the bore means that the
marking registers in the mind of the user of the assembly. The user
is able to identify drivers having cross-sections whose shapes
correspond to the shapes of the markings by inspection of the
shapes of the end faces of the drivers.
[0066] FIGS. 6 and 7 show a twistable adjuster which can be
incorporated into an instrument. The adjuster has a housing 202
with a bore 204 extending through it. A shaft 205 is mounted in the
housing. The shaft can be rotated in the housing. The top end 206
of the shaft protrudes from the housing. The opposite bottom end
208 of the shaft is accessible within the housing through the bore
204. The shaft can be connected to another component of the
instrument at its bottom end.
[0067] The shaft can be rotated in the housing to impart movement
to the other component to which it is connected.
[0068] The shaft has cylindrical portion 210 at the bottom end
which fits in the bore in the housing so that the shaft can rotate
in the housing. The shaft has a protruding portion 212 at its top
end which faces an outwardly facing surface 214 of the housing. The
face of the protruding portion which faces the housing has a
plurality of shallow recesses 216 formed in it. The face of the
housing which faces the protruding portion 212 of the shaft has a
spring loaded ball bearing 218 mounted in a shallow bore. The ball
bearing is urged into successive ones of the shallow recesses in
the protruding portion of the shaft as the shaft is rotated. In
this way, the rotation of the shaft in the housing is indexed with
definite click stops provided by the ball bearing fitting into the
recesses.
[0069] In the adjuster which is shown in FIGS. 6a and 7a, the
protruding portion 212 of the shaft is formed as a multi-lobe cap
220 which can be gripped by a user to cause the shaft to rotate. In
the adjuster according to the invention which is shown in FIGS. 6b
and 7b, the protruding portion 212 of the shaft has a hexagonal
bore 224 extending into it in which a driver can be received. In
the particular adjuster shown in the drawings, the bore is a plain
hexagonal bore.
[0070] FIG. 8 shows a cutting guide 250 which has a pair of latches
252 for retaining another instrument in place. The cutting guide
can be used to prepare the distal end of a femur to receive an
implant component of a knee joint prosthesis. The cutting guide has
holes 253 formed in it for receiving fixation pins in a
conventional manner. The cutting guide as a pair of limbs 254, 256
which define edge surfaces 258 for guiding a cutting blade to form
a notch in the femur. Each of the limbs has a shaped cavity 260
formed in it for engaging a correspondingly shaped protrusion on a
cooperating mating instrument such as a reamer guide. The cutting
guide as a pair of latches which can be rotated between latched and
unlatched positions. A first one 262 of the latches is shown in the
latched position and a second one 264 of the latches is shown in
the unlatched position. The latches hold protrusions on a
cooperating instrument in place in the shaped cavities 260 when in
their latched positions. Each of the latches has a hexagonal bore
266 extending into it in which a driver can be received to rotate
it between its latched and unlatched positions. In the particular
adjuster shown in the drawings, the bore is a plain hexagonal
bore.
* * * * *