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INSTRUMENT FOR USE IN MANIPULATING AN IMPLANT COMPONENT
This invention relates to a surgical instrument for use in manipulating an implant
component of an orthopaedic joint prosthesis, such as the femoral component of a knee
5 joint prosthesis.
An implant component of an orthopaedic joint prosthesis that is to be implanted in a
patient must be manipulated prior to and during the implantation procedure. It can be
important to grip the component securely and in such a way as to not damage the surface
10 of the component and in particular the highly polished bearing surface which engages
another component of the joint prosthesis.
A knee joint prosthesis includes a femoral component and a tibia1 component. It is
common to manipulate the femoral component using an instrument in which the
15 component is held securely. An impaction force can be applied to the femoral component
through the instrument. It is important that the polished bearing surface of the component
is not damaged by the instrument during manipulation and application of the impaction
force.
20 Femoral components come in different sizes and instruments need to be able to adapt to
components of different sizes. They also need to grip the components securely without
damaging the bearing surface.
US-5732992 discloses an instrument for gripping and manipulating a prosthesis
25 component. It includes a handle and at least one jaw that can be moved to grip the
prosthesis component. Each jaw has a pivot post retained in an aperture in the jaw and
which facilitates a slight rotation of the jaw about an axis. This rotation occurs after
gripping of the component to draw the component towards the base upon which it is seated
to retain it in place. The pivot posts are threadably mounted on the ends of a threaded shaft
30 member. The shaft member is rotated by means of a thumbwheel fixed to the shaft
member, and rotation of the shaft member with respect to the posts moves the jaws
together to grip the prosthesis component and effects rotation of the jaw. The width of the
instrument is defined by the length of the threaded shaft.
According to a first aspect of the present invention, there is provided an instrument for
5 manipulating an implant component of an orthopaedic joint prosthesis, the instrument
comprising:
a body,
a seat mounted on the body for contacting a bearing surface of the implant
component during manipulation of the implant component,
10 a first arm having a transversely extending first gripping member towards one end and a
transversely extending first shaft member towards its opposite end, mounted on the body
on one side of the seat with the first gripping member and the first shaft member facing
towards the body,
a second arm having a transversely extending second gripping member towards
15 one end and a transversely extending second shaft member towards its opposite end,
mounted on the body on opposite side of the seat with the second gripping member and the
second shaft member facing towards the body, so that inward movement of the first and
second arms towards the body causes the first and second gripping members to engage the
implant component in contact with the seat, and
20 an actuation member which is mounted for rotation on the body, each of the first
and second shaft members on the first and second arms being connected to the actuation
member so that rotation of the actuation member in a first rotational direction causes the
first and second arms to move inwardly and rotation of the actuation member in a second
rotational direction causes the first and second arms to move outwardly.
The first and second arms provide a jaw arrangement which can be adjusted to
accommodate implant components of varying widths. This means that the width of the
instrument can be varied according to the width of the component.
30 An advantage of the present invention is that the instrument enables implant components
of varying sizes to be manipulated, and that the size of the instrument will be
commensurate with the size of implant component being used. This in turn may allow a
smaller incisions to be possible than with an instrument of constant width. For example,
when smaller implant components are to be manipulated by the instrument, the instrument
will have a smaller width which will reduce the need to make larger incisions than are
really necessary in a patient's knee. In addition, the instrument is symmetrical in the
5 coronal plane and can therefore be used reversibly.
Each of the first and second shaft members have a thread and the actuation member may
have a first threaded portion for cooperation with the thread on the first shaft member and
the actuation member may have a second threaded portion for cooperation with the thread
10 on the second shaft member
The first and second threaded portions of the actuation member may be collinear.
As such, the actuating member and the threaded shaft members form a turnbuckle
15 arrangement.
The threads on the first and second shaft members may be external and the actuation
member may have an internal thread. Alternatively, the threads may be internal on the first
and second shaft members with the actuating member having external threads.
20
As a further alternative, the actuation member can be provided with cam surfaces with cam
followers provided on the first and second shaft members that cooperate with the cam
surfaces. Detents may be provided on the cam surfaces to provide set widths.
25 The body may include at least one limiting slot provided in one of the shaft members
which cooperates with a dowel provided in the body. The dowel can be received in the
limiting slot, for example through an aperture in the body. This limits the distance by
which the shaft member or each of the first and second shaft members can be translated
thus mitigating against over extension. Preferably, each of the first and second shaft
30 members has a limiting slot formed in it and the body includes first and second dowels, the
first dowel being received in the slot in the first shaft member and the second dowel being
received in the slot in the second shaft member. The dowels and the slots can limit the
translation of the first and second members.
The first and second arms can be provided with guide pins that cooperate with apertures in
5 the body to further assist in guiding and retaining the arms in the body.
The handle may be realeasably attached to the body using a pivoting latch that engages
with a groove provided in the neck of the body. The pivoting latch is preferably biased
towards the position in which it is retained in the groove. This can facilitate manipulation
10 of the instrument.
The actuating member may have a ribbed external contour. This assists in rotating it with
the use of a thumb while holding the instrument in the same hand.
15 The seat may have a concave bearing surface and a lug and the body may have a dowel
inserted into the lug to secure the seat to the body.
The seat may be made of a material that doesn't damage the bearing surfaces of the implant
component. Preferably, this is a heat resistant thermoplastic such as polyarylethersulphone
20 (PAES) (as sold under the trade mark RADEL by Arnoco Polymers Inc and Piedmont
Plastics Inc).
The thread profile may be selected to facilitate self-locking.
25 Embodiments of the invention will now be described by way of example only with
reference to the accompanying drawings of which:
Figure 1 is a perspective view of a surgical instrument of the invention when gripping a
femoral component of a knee joint prosthesis;
30
Figure 2 is a front view of the instrument of Figure 2;
Figure 3 is a side view of the instrument of Figure 2 in the direction of arrow I11 in Figure
Figure 4 is a plan view of the instrument of Figure 2 in the direction of arrow IV in Figure
Figure 5 is a cross-section along the line A-A in Figure 2;
Figure 6 is a cross-section along the line B-B in Figure 4;
10
Figure 7 is a perspective view of the head of the instrument of Figure 1, with the arms in an
extended position with respect to the body of the head;
Figure 8 is an exploded view of the head of Figure 7;
15
Figure 9 is a front view of the head of Figure 7;
Figure 10 is a plan view in the direction of arrow X in Figure 9;
20 Figure 11 is an underside view in the direction of arrow XI in Figure 10;
Figure 12 is a cross-section along the line C-C in Figure 9; and
Figure 13 is a cross-section along the line D-D in Figure 10.
25
Referring to the drawings, Figures 1 to 13 show a surgical instrument 100 which can be
used to manipulate, and apply an implantation force to, a femoral component 200 of a knee
joint prosthesis.
30 The surgical instrument 100 includes a head 1 and a handle 2.
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The head 1 comprises a substantially cuboid-shaped hollow body 3. The hollow body 3
has front and rear faces 5,6, side walls 7, 8, an upper wall 9 and a lower wall 10 which
define a cavity 4.
5 The lower wall 10 is shaped to define a collar 11 extending outwardly with a bore 12
running through it. The bore 12 is arranged to receive the neck 13 of the handle 2 for
mounting the head 1 thereon.
The collar 11 includes a groove 43 for receiving a lip 50 of a head retaining mechanism 45
10 for retaining the handle 2 to the body 3.
The upper wall 9 has a substantially centrally located rectangular shaped aperture 2 1
provided therein extending into the cavity 4.
15 Each of the side walls 7, 8 have one aperture of a first pair of collinear circular apertures
17, 18 that extend through the side wall 7, 8 into the cavity 4.
One aperture of a second pair of collinear apertures 19,20 is also provided in each of the
side walls 7, 8 which extend longitudinally within the upper wall 9 and into the rectangular
20 shaped aperture 2 1.
The fiont face 5 has three circular apertures 14, 15, 16 provided thereon. The first and
second 14, 15 of the three circular apertures are provided at the same height, one in each of
the side walls 7, 8 and extending longitudinally therein. The third aperture 16 extends
25 within the upper wall 9 substantially equidistantly between the side walls 7, 8.
Corresponding circular apertures 14', 15', 16' are provided on the rear wall 6 so that each of
the first, second, and third apertures 14, 15, 16 on the front wall 5 are collinear with the
respective first, second and third 14', 15', 16' on the rear wall 6.
3 0
The first and second apertures 14, 15; 14', 15' are arranged to be contiguous with the first
pair of collinear circular apertures 17, 18 in the respective side walls 7, 8.
A seat 24 is configured for mounting on the upper wall 9 of the hollow body 3. The seat
24 has a concave bearing surface 22 upon which a distal bearing surface 201,201' of the
femoral component 200 can sit.
5
The seat 24 includes a U-shaped lug 23 extending perpendicular fiom the underside 25 of
the seat 24 and opposite fiom the bearing surface 22. The lug 23 is dimensioned to be
received in the rectangular aperture 2 1 provided in the upper wall 9 of the body 3. The lug
23 is provided with a cylindrical aperture 26 extending across the width of the lug 23 and
10 which is located so as to be collinear with the third circular apertures 16, 16' in the fiont
and rear faces 5, 6 respectively when the seat 24 is mounted upon the upper wall 9 and the
lug 23 received in the rectangular aperture 2 1.
The seat 24 is secured to the body 3 by means of a dowel 39 inserted through the third
15 circular apertures 16, 16' and the cylindrical aperture 26 provided in the lug 23.
The body 3 includes a jaw arrangement 42 which comprises a pair of first and second arms
27,28 mounted on the body 3.
20 The first and second arms 27,28 are identical and are configured to face each other on
opposite sides of the body 3 adjacent the side walls 7, 8 as will be described in further
detail below.
Each of the first and second arms 27,28 have respective first and second transversely
25 extending threaded shaft members 29,30 at a proximal end, and respective first and second
I
transversely extending gripping members in the form of a return flange 3 1,32 at the
opposite distal end.
In the embodiment described herein, the first and second shaft members 29,30 and the
30 return flanges 3 1, 32 are perpendicular to the first and second arms 27, 28. However, in
alternative embodiments, the first and second arms 27,28 could by inclined and subtend
selected angles to the first and second shaft members 29,30 and the return flanges 3 1,32.
The first and second threaded shaft members 29,30 are fixed to the respective first and
second arms 27,28. In the present embodiment, the first and second threaded shaft
members 29,30 are fxed to the respective first and second arms 27,28 by means of
5 projections 55, 56 received in apertures 57, 58 in the fvst and second arms 27,28.
Alternatively, they could be formed as unitary bodies with the first and second arms 27, 28.
In this way, as the first and second threaded shaft members 29,30 move, the first and
second arms 27,28 translate with them in the same direction.
10
The return flanges 3 1,32 are structured to engage with holding means provided on the
femoral component 200 to thereby grip the femoral component 200 when the bearing
surface 201 of the femoral component 200 are resting against the seat 24. In the case of
the embodiment described herein, the flanges 3 1,32 are shaped to engage with holding
15 recesses 52, 53 provide on the sides of the femoral component 200.
The threaded shaft members 29, 30 have externally threaded portions 62,63 at a distal end
for cooperation with an actuating member in the form of an internally threaded
thumbwheel 40. Each threaded portion 62, 63 includes a thread 59, 60.
20
The first and second threaded shaft members 29,30 serve to effect translational movement
of the first and second arms 27,28 relative to each other to adjust the separation between
them in response to manipulation of the rotating thurnbwheel40.
25 The first and second arms 27,28 also include a respective transversely extending first and
second guide pin 33, 34 extending parallel to, and at a predetermined distance from, a
respective threaded shaft member 29, 30.
A limiting slot 35, 36 is provided in each threaded shaft member 29,30 that extends
30 lengthways along a portion of the threaded shaft member 29,30. A circumferential
groove 37 is also provided on the first and second threaded shaft members 29,30 towards
the respective arm 27,28.
The first arm 27 is configured so that the respective first threaded shaft member 29 is
received into the respective circular aperture 17 of the first pair of collinear circular
apertures provided in one of the side walls 7, while the fvst guide pin 33 is received into
5 the respective circular aperture 19 of the second pair of collinear circular apertures
provided in the same side wall 7.
Similarly, the second arm 28 is configured so that the respective second threaded shaft
member 30 is received into the respective circular aperture 18 of the first pair of collinear
10 circular apertures provided in the other of the side walls 8, while the second guide pin 34 is
received into the respective circular aperture 20 of the second pair of collinear circular
apertures provided in the same side wall 8.
When the threaded shaft members 29,30 and guide pins 33,34 are received into the
15 respective circular apertures 17, 18; 19,20, the elongate limiting slots 35, 36 are in
alignment with the respective first and second circular apertures 14, 14'; 15, 15' and are
arranged to receive a dowel pin 37,38 which serves to limit lateral movement of the arms
27, 28 when the dowel pin 37, 38 abuts the ends of the limiting slots 35, 36.
20 The rotating thumbwheel 40 is located within the cavity 4. The thumbwheel 40 has a
cylindrical body with an internal bore 41 running longitudinally through it which receives
the respective threaded portions 62,63 of threaded shaft members 29,30 at each end. The
internal bore 4 1 has internal threaded portions 6 1,6 1' for engaging with the threaded shaft
members 29,30.
The thumbwheel 40 has a ribbed outer contour to assist with manual rotation.
The first and second shaft members 29,30 are inserted through the respective circular
apertures 17, 18, into the cavity 4 and the threaded portions 62,63 of the shaft members
30 29,30 are inserted into the threaded internal bore 41, one at each end.
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The threads 59,60 provided on the threaded shaft members 29,30 engage with the internal
threaded portions 61,611 of the bore 41. The thumbwheel 40 and the threaded shaft
members 29, 30 are collinear along a common longitudinal axis Y with the thumbwheel 40
being rotatable around this axis Y. The thread 59 provided on the first threaded shaft
5 member 29 is in the opposite direction to the thread 60 of the second threaded shaft
member 30 so that rotation of the thumbwheel 40 around the axis Y causes the threaded
shaft members 29, 30 to move towards each other or apart fiom each other within the bore
41 depending upon the direction in which the thumbwheel 40 rotates. This is illustrated in
Figure 6 by the double-headed arrows. As such, the threaded shaft members 29,30 and the
10 thumbwheel 40 act as a turnbuckle arrangement.
The threaded portions 6 1, 6 1 I, 62, 63 are indicated in Figures 6, 12 and 13 by the dashed
lines.
15 In this way, manipulation of the thumbwheel 40 causes translational movement of the
threaded shaft members 29,30 relative to each other and to the thumbwheel 40.
As a consequence of the first and second arms 27,28 being fixed relative to the threaded
shaft members 29,30 the first and second arms 27,28 move towards and away from each
20 other as the threaded shaft members 27,28 move within the bore 4 1 in response to rotation
of the thumbwheel 40.
Thus, the first and second arms 27,28 can be caused to either move apart or towards each
other to thereby vary the separation between them. When the thumbwheel 40 rotates in a
25 first direction, the first and second arms 27,28 move together, and when the thumbwheel
40 rotates in a second direction, the first and second arms 27,28 move apart.
The pitch of the thread, the diameter of the shaft members 29,30 and the profile of the
thread are chosen to facilitate self-locking of the first and second arms 27,28.
3 0
As the threaded shaft members 29,30 move towards and away fiom each other in response
to the turning of the thumbwheel 40, there is relative translational movement of the
limiting slots 35,36 with respect to the dowels 37,38 received therein. When the dowel
37, 38 abuts the end of the limiting slot 35,36 further movement of the threaded shaft
members 29, 30 is prohibited. In this way, the separation of the first and second arms 27,
28 cannot be overextended.
5
By providing this translational movement of the the first and second threaded shafts 29, 30,
the first and second arms 27,28 can be used to accommodate and grip a femoral
component 200, using the return flanges 3 1,32.
10 The handle 2 has an elongate body portion 46 suitable contoured for gripping with one
hand. At one end, the handle includes a neck 13 for mounting the head 1 thereon.
At the end of the handle 2 towards the neck 13 a handle cavity 47 is formed.
15 The head retaining mechanism 45 is mounted on the handle 2 towards the neck 13 and
includes a latch 49 pivotably mounted within the cavity 47 around a crossways-mounted
pin 48. The lip 50 is provided at one end of the latch 49 for engaging with the groove 43
provided on the collar 11. A compression spring 5 1 connected between latch 49 and the
handle 2 biases the latch 49 to the position in which the lip 50 engages the groove 43 thus
20 retaining the head 1 in attachment to the handle 2.
To remove the head 1 fiom the handle 2, the latch 49 is depressed to compress the spring
5 1 and pivots around the pin 48, disengaging the lip 50 fiom the groove 43 thus allowing
the head to be removed.
25
The cavity 47 also provides for better cleaning of the instrument.
The instrument 100 is made fiom metallic materials which are known to be used for
surgical instruments. One such material is stainless steel.
3 0
To use the instrument 100, a user holds the handle 2 in one hand and manually operates the
head retaining mechanism 45 to depress the latch 49 so that it pivots around the pin 48 and
moves the lip 50 away fiom the neck 13. The user places the head 1 onto the handle 2 by
placing the collar 1 1 over the neck 13. The user releases the latch 49 so that the spring 5 1
biases the lip 50 towards the collar 1 1 so that it engages the groove 43.
5 With the head 1 in place, the user manually rotates the thumbwheel 40 using the thumb to
operate the jaw arrangement 42 and to move the first and second arms 27,28 apart so that
they can accommodate the width of the femoral component 200 to be gripped by the
instrument 100.
10 The instrument 100 is then placed around the femoral component 200 such that the flanges
3 1, 32 are approximately level with holding recesses 52, 53 provided on the femoral
component 200.
The user rotates the thumbwheel 40 using the thumb to translate the first and second arms
15 27,28, towards each other until the flanges 3 1,32 engage with the holding recesses 52,53
in the femoral component 200. The frrst and second arms 27,28 continue to be translated
until the femoral component 200 is gripped securely between the first and second arms 27,
20 The user is able to manipulate the femoral component 200 into place against the resected
femur and to then use the instrument 100 to impact the femoral component 200 in place in
the usual manner.
Variations are possible within the scope of the present invention. For example, the handle
25 2 can be of any suitable shape and structure with appropriate retention means to retain the
head to the handle. The seat 24 can be shaped and dimensioned to accommodate various
shapes of femoral component. The return flanges 31,32 can be substituted by any suitable
means for gripping the femoral component 200.
30 The thumbwheel 40 can be provided in a variety of shapes and dimensions. For example,
the thumbwheel 40 can have external threaded portions to engage with internal threads on
the shaft members. Alternatively, a cam arrangement with a cam surface on the actuating
member and a cooperating cam a follower on the shaft members could be used.

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CLAIMS
1. An instrument for manipulating an implant component of an orthopaedic joint
prosthesis, the instrument comprising:
5 a body;
a seat mounted on the body for contacting a bearing surface of the implant
component during manipulation of the implant component;
a first arm having a transversely extending first gripping member towards one end
and a transversely extendmg first shaft member towards its opposite end, mounted on the
10 body on one side of the seat with the first gripping member and the first shaft member
facing towards the body,
a second arm having a transversely extending second gripping member towards
one end and a transversely extending second shaft member towards its opposite end,
mounted on the body on opposite side of the seat with the second gripping member and the
15 second shaft member facing towards the body, so that inward movement of the first and
second arms towards the body causes the first and second gripping members to engage the
implant component in contact with the seat, and
an actuation member which is mounted for rotation on the body, each of the first
and second shaft members on the first and second arms being cormected to the actuation
20 member so that rotation of the actuation member in a first rotational direction causes the
first and second arms to move inwardly and rotation of the actuation member in a second
rotational direction causes the first and second arms to move outwardly.
2. An instrument as claimed in claim 1, wherein the first and second shaft members
25 have a thread and the actuation member has a first threaded portion for cooperation with
the thread on the first shaft member and a second threaded portion for cooperation with the
thread on the second shaft member, the first and sepond threaded portions of the actuation
member being collinear.
30 3. An instrument as claimed in claim 2, wherein the threads on the first and second
shaft members are external and the actuation member has an internal bore, the first and
second threaded portions being received within the internal bore.
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4. An instrument as claimed in any preceding claim, wherein at least one of the first
and second shaft members has a limiting slot formed in it, and the body includes at least
5 one dowel which is received in the slot in one of the shaft members to limit translation of
the first and second shaft members.
5. An instrument as claimed in any preceding claim, wherein the body has side walls
and includes a cavity for housing the actuating member therein, the body further including
10 a first pair of collinear apertures provided on the side walls through which the first and
second shaft members extend to cooperate with the actuating mechanism.
6. An instrument as claimed in any preceding claim, wherein each of the first and
second arms has a guide pin extending fi-om it and the body has a second pair of collinear
15 apertures provided on the side walls through which a respective guide pin extends.
7. An instrument as claimed in any preceding claim, which includes a handle
releasably attached to the body.
20 8. An instrument as claimed in claim 7, wherein the handle includes a neck portion
• and the body has a collar extending outwardly fi-om the body with a bore running through
"- ^\^,i the collar and arranged to receive the neck portion therein.
9!. '- - f An instrument as claimed in claim 8, wherein the collar includes a groove and the
25 " handle includes a pivbtable latch with a lip for engaging with the collar to secure the head
tothehahdle:J-i^di-^ny.' -
10. An instnimeht'as claimed in claim 9, wherein the pivotable latch is biased towards
a position in which the lip is engaged in the groove.

11. An instrument as claimed in any preceding claim wherein the actuating member
has a ribbed external contour.