U.S. patent application number 14/927941 was filed with the patent office on 2016-05-05 for ligament fixing and a method of attaching a ligament.
The applicant listed for this patent is Mona Alinejad, Russell Lloyd, David Wycliffe Murray, John Joseph O'Connor. Invention is credited to Mona Alinejad, Russell Lloyd, David Wycliffe Murray, John Joseph O'Connor.
Application Number | 20160120639 14/927941 |
Document ID | / |
Family ID | 52118554 |
Filed Date | 2016-05-05 |
United States Patent
Application |
20160120639 |
Kind Code |
A1 |
Murray; David Wycliffe ; et
al. |
May 5, 2016 |
LIGAMENT FIXING AND A METHOD OF ATTACHING A LIGAMENT
Abstract
An artificial ligament is provided having an elongate body and
two ends, with a loop being provided at least one of the ends and a
loop liner being provided within the loop. A kit of artificial
ligaments is also provided with each ligament in the kit having a
different fixed length. Also provided are methods for determining a
length of artificial ligament to be used within a prosthetic knee
joint, selecting a ligament from a range or kit of ligaments, and
implanting a prosthetic knee joint assembly comprising an
artificial ligament.
Inventors: |
Murray; David Wycliffe;
(Oxford, GB) ; Lloyd; Russell; (Swindon Wiltshire,
GB) ; Alinejad; Mona; (Oxford, GB) ; O'Connor;
John Joseph; (Oxford, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Murray; David Wycliffe
Lloyd; Russell
Alinejad; Mona
O'Connor; John Joseph |
Oxford
Swindon Wiltshire
Oxford
Oxford |
|
GB
GB
GB
GB |
|
|
Family ID: |
52118554 |
Appl. No.: |
14/927941 |
Filed: |
October 30, 2015 |
Current U.S.
Class: |
623/13.12 ;
606/102 |
Current CPC
Class: |
A61F 2002/30566
20130101; A61F 2002/30462 20130101; A61F 2/4657 20130101; A61F
2/4684 20130101; A61F 2/3836 20130101; A61F 2002/30537 20130101;
A61F 2/389 20130101; A61F 2002/0852 20130101; A61F 2002/4658
20130101; A61F 2002/0888 20130101; A61F 2002/087 20130101; A61F
2/3859 20130101; A61F 2/0811 20130101; A61F 2/08 20130101; A61F
2210/0057 20130101 |
International
Class: |
A61F 2/08 20060101
A61F002/08; A61F 2/46 20060101 A61F002/46; A61F 2/38 20060101
A61F002/38 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 31, 2014 |
GB |
1419469.0 |
Claims
1. An artificial knee ligament comprising an elongate body and two
ends, wherein a loop is provided at at least one of the ends; and a
loop liner provided within the loop.
2. The artificial knee ligament of claim 1, wherein the loop liner
is formed from a different material from the body of the
ligament.
3. The artificial knee ligament of claim 1, wherein the length of
the ligament is fixed.
4. The artificial knee ligament of claim 1, wherein the loop is
configured to couple to a fixing provided on either a femoral or
tibial component of a prosthetic knee joint.
5. The artificial knee ligament of claim 1, wherein the loop liner
covers an inside face of the loop.
6. The artificial knee ligament of claim 4, wherein the loop liner
is shaped to sit between the fixing of the prosthetic knee
component, and the ligament loop.
7. The artificial knee ligament of claim 1, wherein the loop liner
is resilient and can be deformed elastically to allow the ligament
loop to be pushed over an enlarged head of the fixing of the
prosthetic component.
8. The artificial knee ligament of claim 1, wherein the loop liner
is moulded onto the loop of the ligament.
9. The artificial knee ligament of claim 1, wherein the loop liner
comprises a thimble.
10. The artificial knee ligament of claim 1, wherein the loop liner
is made from polyethylene.
11. A method of implanting a prosthetic knee joint assembly,
comprising a tibial component, a femoral component and an
artificial knee ligament, comprising the steps of: implanting the
tibial component or the femoral component into a patient; coupling
a preformed artificial ligament to the prosthetic components;
implanting the other component into the patient.
12. The method of claim 11, wherein the first prosthetic component
is implanted in a temporary manner.
13. The method of claim 11, wherein the tibial component is
implanted before the femoral component.
14. The method of claim 11, further comprising the step of
determining an appropriate length for a replacement knee ligament
to link the tibial and femoral components of the prosthetic knee
joint, this step being completed prior to the step of coupling the
preformed artificial ligament to the prosthetic components.
15. The method of claim 11, further comprising the step of
selecting a preformed artificial ligament of a suitable length from
a set of artificial ligaments, this step being completed prior to
the step of coupling the preformed artificial ligament to the
prosthetic components.
16. The method of claim 11, further comprising the step of
installing a final meniscal bearing, this step being performed
prior to the step of implanting the second prosthetic component
into the patient.
17. The method of claim 11, further comprising the steps of
installing a temporary meniscal spacer, this step being performed
prior to the step of implanting the second prosthetic component
into the patient; and installing a final meniscal component between
the tibial and femoral components of the prosthetic knee joint,
this step being performed subsequently to the step of implanting
the second prosthetic component into the patient.
18. The method of claim 11, wherein the tibial prosthetic component
comprises a fixed knee bearing.
19. A method of determining a suitable length for an artificial
knee ligament comprising the steps of: coupling first and second
prosthetic components to a patient in a temporary manner; creating
a trial ligament using an elongate element extended around a first
fixing on the first prosthetic component and a second fixing on the
second component to form a continuous band; cutting the band and
removing the trial ligament from the surgical site; and measuring
the length of the reassembled band.
20. The method of claim 19, wherein the first and/or second
prosthetic component is a trial prosthetic component.
21. The method of claim 19, wherein the first and/or second
prosthetic component is a final prosthetic component
22. The method of claim 19, wherein the fixings comprise bollards
provided on the femoral and tibial prosthetic components.
23. The method of claim 19, further comprising the step of
installing a trial meniscal component between the tibial and
femoral components of the prosthetic knee joint, this step being
performed prior to the step of creating a trial ligament.
24. The method of claim 23, wherein the trial meniscal component is
also the final meniscal component.
25. The method of claim 19, wherein the elongate element comprises
a trial ligament with one looped end and one open end which can be
tied.
26. The method of claim 19, wherein a pin is used to mark the
required length of elongate element whilst fitted to the
patient.
27. The method of claim 19, wherein the elongate element comprises
a zip tie.
28. The method of claim 19, wherein the elongate element comprises
markings allowing the length of the band to be determined from the
markings on the elongate element.
29. Instrumentation for measuring between first and second ligament
fixings of prosthetic components comprising: an elongate body, an
arcuate portion provided at or towards one end of the elongate body
and a slideable jaw, configured to slide along the elongate
body.
30. The instrumentation of claim 29, wherein the elongate body
further comprises a measurement scale.
31. The instrumentation of claim 29, wherein the arcuate portion is
configured to closely engage the first fixing.
32. The instrumentation of claim 29, wherein the slideable jaw is
configured to engage the second fixing.
33. The instrumentation of claim 29, wherein the position of the
slideable jaw can be selectively fixed relative to the elongate
body.
34. The instrumentation of claim 33, wherein the jaw and the
elongate body are provided with cooperating formations and the jaw
is fixed by rotating a portion of the jaw to engage the cooperating
formations.
35. The instrumentation of claim 30, wherein the measurement scale
indicates the size of artificial ligament required to link the
first and second fixings.
Description
CLAIM OF PRIORITY
[0001] This application claims the benefit of priority under 35
U.S.C. to United Kingdom Application No. 1419469.0, filed on 31
Oct. 2014, which application is incorporated herein by reference in
its entirety.
TECHNICAL FIELD
[0002] This invention relates to artificial knee ligaments and
methods for implanting an artificially knee ligament, and is
particularly, although not exclusively, concerned with artificial
ligaments having looped ends.
BACKGROUND
[0003] The statements in this section merely provide a background
to the present disclosure and may not constitute prior art.
[0004] Prosthetic knee joints replace one or more of the articulate
surfaces of a patient's knee joint, and are employed to improve the
strength and/or mobility of the joint or reduce pain of the
patient. Sections of the bones being replaced may be diseased,
injured, deteriorated or some combination of the three.
[0005] In many cases the surgeon performing knee replacement
surgery will take steps to preserve the ligaments of the knee which
connect the bones of the knee across the joint. In some cases the
ligaments themselves may be diseased or damaged, or the resection
necessary to remove diseased portions of the bones may disrupt the
integrity of the ligaments. If the ligaments are removed as part of
the surgery and cannot be reattached, a prosthetic knee joint is
required which places greater constraints on the movement of the
knee joint. This can be achieved through the use of an artificial
knee ligament joining the two sides of the joint.
[0006] In one proposed artificial knee joint, artificial ligaments
are attached to the prosthetic components by looping or tying the
ends of the ligament over bosses or bollards provided on the
prosthetic components. As the knee joint moves, the ligament is
able to articulate around the body of the bollard as required.
Whilst this articulation of the ligament prevents the ligament from
being bent or kinked, over time the loops of the ligament can
become worn.
[0007] Artificial knee ligaments are not required to be tensioned
when installed, however it is undesirable for ligaments to be
excessively long or loose as this could reduce the stability of the
joint. For similar reasons, it is not desirable for an artificial
ligament to be flexible. In one possible surgical procedure, both
prosthetic components are first implanted before alternative length
ligaments are offered up by the surgeon and one can be selected
which the surgeon judges will have suitably laxity when fitted. In
order to fit the ligament, the knee must be overflexed to provide
the necessary access to the ligament fixings on each side of the
joint. This also has the effect of separating the bones of the knee
and hence excess force is required to attach the ligament. A device
may be required to pull or lever the ligament onto a fixing and
there is a significant risk of damaging the artificial ligament in
the process.
[0008] In order to avoid this excessive manipulation of the knee
joint and potential damage to the ligament, artificial ligaments
have been designed with loops which are formed at the operative
site, allowing the length of a ligament to be adjusted subsequently
to its attachment to both sides of the joint.
[0009] WO 2011/1502538 discloses a prosthetic knee joint assembly
with an artificial ligament link. The ligament link extends between
first and second ends and includes an outer wall defining an
interior longitudinal passage portion. First and second apertures
extend through the wall. The first end extends through the first
and second apertures and the longitudinal passage portion to define
a first adjustable loop, and the second end extends through the
first and second apertures and the longitudinal passage portion to
define a second adjustable loop.
[0010] It is speculated that ligaments with preformed loops are
still more reliable with less chance of becoming loose or failing
after implantation. Hence, using a ligament with fixed loops is
desirable in some cases.
[0011] The present disclosure relates to a method for implanting an
artificial ligament of fixed length without requiring the knee
joint to be overflexed, or excessive force being applied to the
ligament. An artificial ligament particularly suited for this use
is also provided.
STATEMENTS OF INVENTION
[0012] According to an aspect of the present invention there is
provided an artificial knee ligament substantially formed of a
first material, comprising an elongate body of fixed length and two
ends, wherein a loop is provided at each of the ends and a portion
of a second material is provided on at least one loop.
[0013] According to another aspect of the present invention there
is provided an artificial knee ligament comprising an elongate body
and two ends, wherein a loop is provided at at least one of the
ends; and a loop liner provided within the loop.
[0014] The length of the ligament and/or the size of the loop may
be fixed. The ligament may be configured to couple to a fixing
provided on either a femoral or tibial component of a prosthetic
knee joint.
[0015] The loop liner may be provided in the area of the loop which
contacts the fixing of the prosthetic component. In this way, the
loop liner may be provided covering an inside face of the loop. The
loop liner may be formed from a different material to the body of
the ligament. The loop liner may be formed from polyethylene. The
loop liner may be shaped to sit between the fixing of the
prosthetic knee component, and the ligament loop. The loop liner
may be moulded onto the loop of the ligament or alternatively, the
loop liner may comprise a thimble which is trapped within the eye
of the loop. Other forms of loop liner may also be possible.
[0016] The loop liner may be resilient and may be elastically
deformable to allow the ligament loop to be pushed over an enlarged
head of the fixing of the prosthetic component.
[0017] According to another aspect of the present invention there
is provided a method of implanting a prosthetic joint assembly,
comprising a first component for attaching to a first bone (of the
joint), a second component for attachment to a second bone (of the
joint) and an artificial ligament, comprising the steps of:
implanting the first prosthetic component into a patient;
[0018] coupling the preformed artificial ligament to the prosthetic
components; and
[0019] implanting the second prosthetic component into the
patient.
[0020] According to another aspect of the present invention there
is provided a method of implanting a prosthetic knee joint
assembly, comprising a tibial component, a femoral component and an
artificial knee ligament, comprising the steps of: implanting the
tibial component or the femoral component into a patient; coupling
a preformed artificial ligament to the prosthetic components;
implanting the other component into the patient.
[0021] The tibial component may be implanted before the femoral
component or alternatively, the femoral component may be implanted
before the tibial component. The first prosthetic component may be
implanted in a temporary manner.
[0022] The method may further comprise the step of determining an
appropriate length for a replacement knee ligament to link the
tibial and femoral components of the prosthetic knee joint. This
step may be completed prior to the step of coupling the preformed
artificial ligament to the prosthetic components.
[0023] Additionally or alternatively, the method may further
comprise the step of selecting a preformed artificial ligament of a
suitable length from a set of artificial ligaments. This step may
be completed prior to the step of coupling the preformed artificial
ligament to the prosthetic components.
[0024] The step of installing a final meniscal bearing may be
performed prior to the step of implanting the second prosthetic
component into the patient. Alternatively the step of installing a
temporary meniscal spacer may be performed instead and a final
meniscal component may be installed between the tibial and femoral
components of the prosthetic knee joint in an additional step which
may be performed subsequently to the step of implanting the second
prosthetic component into the patient.
[0025] The tibial prosthetic component may comprise a fixed knee
bearing.
[0026] The method may be performed using the artificial ligament
provided by a previously mentioned aspect of the invention.
[0027] According to another aspect of the present invention there
is provided a method of determining a suitable length for an
artificial ligament for use in a prosthetic joint assembly
comprising a first prosthetic component for attaching to a first
bone and a second prosthetic component connected to a second bone.
The method comprising the steps of:
[0028] coupling a trial first component to the first bone of a
patient in a temporary manner;
[0029] creating a trial ligament using an elongate element extended
around a fixing on the trial first component and a second fixing on
a previously implanted second component to form a continuous
band;
[0030] cutting the band and removing the trial ligament from the
surgical site; and measuring the reassembled band.
[0031] According to another aspect of the present invention there
is provided a method of determining a suitable length for an
artificial knee ligament comprising the steps of:
[0032] coupling first and second prosthetic components to a patient
in a temporary manner;
[0033] creating a trial ligament using an elongate element extended
around a first fixing on the first prosthetic component and a
second fixing on the second component to form a continuous
band;
[0034] cutting the band and removing the trial ligament from the
surgical site; and
[0035] measuring the length of the reassembled band.
[0036] The first and/or second prosthetic components may be trial
prosthetic components. Alternatively or additionally, either or
both of the prosthetic components may be the final prosthetic
components. The fixings provided on the femoral and tibial
components may be bollards.
[0037] The method may further comprise the step of installing a
trial meniscal component between the tibial and femoral components
of the prosthetic knee joint. This step may be performed prior to
the step of creating a trial ligament. The trial meniscal component
may also be the final meniscal component.
[0038] The elongate element used in the method may comprise a trial
ligament with one looped end and one open end which can be tied.
Alternatively the elongate element may be a zip tie or any other
elongate element suitable for being selectively formed into a
continuous band.
[0039] A pin may be used to mark the required length of elongate
element whilst fitted to the patient. Alternatively or
additionally, the elongate element may comprise markings allowing
the length of the band to be determined from the markings on the
elongate element.
[0040] The method according to this aspect of the present invention
may be used to determine an appropriate length for a replacement
knee ligament to link the tibial and femoral components as
described in any preceding aspect of the invention.
[0041] According to another aspect of the present invention there
is provided an artificial knee joint assembly comprising a tibial
component, a femoral component and an artificial knee ligament
which may be the artificial ligament as described in any preceding
aspect of the invention.
[0042] According to another aspect of the present invention there
is provided a kit of artificial knee ligaments wherein each
ligament within the kit has a different fixed length. The ligaments
in the kit may be as described in any preceding aspect of the
invention.
[0043] According to another aspect of the present invention there
is provided instrumentation for measuring between first and second
ligament fixings of prosthetic components comprising: an elongate
body, an arcuate portion provided at or towards one end of the
elongate body and a slideable jaw, configured to slide along the
elongate body. The arcuate portion may be configured to closely
engage the first fixing. The slideable jaw may be configured to
engage the second fixing.
[0044] The position of the slideable jaw may be selectively fixable
relative to the elongate body. The jaw and the elongate body may be
provided with cooperating formations and the jaw may fixed by
rotating a portion of the jaw to engage the cooperating
formations.
[0045] The elongate body may further comprise a measurement scale.
The measurement scale may indicate the size of artificial ligament
required to link the first and second fixings.
[0046] According to another aspect of the present invention, there
is provided instrumentation for measuring between fixings of
prosthetic components comprising: an elongate body with first and
second ends; wherein the first end is configured to couple with a
first fixing on a first prosthetic component; and the second end
comprises a measurement scale. The scale allows the distance from
the first fixing to a second fixing on a second prosthetic
component to be measured. The scale may indicate the size of
artificial ligament required to link the first and second
fixings.
[0047] The instrumentation may further comprise a jaw which may be
axially slideable along the measurement scale of the elongate body.
The jaw may be selectively lockable relative to the elongate body.
The jaw and the elongate body may be provided with cooperating
features and the jaw may be locked by rotating a portion of the jaw
to engage the cooperating features. Alternatively or additionally,
the jaw may be configured to engage a second fixing on a second
prosthetic component.
BRIEF DESCRIPTION OF THE DRAWINGS
[0048] For a better understanding of the present invention, and to
show more clearly how it may be carried into effect, reference will
now be made by way of example, to the accompanying drawings, in
which:
[0049] FIG. 1 shows a full knee replacement prosthetic knee joint
comprising an artificial ligament according to an example of the
present invention.
[0050] FIG. 2 is a sectional view of a full knee replacement
prosthetic knee joint comprising an artificial ligament according
to an example of the present invention.
[0051] FIG. 3 shows an artificial knee ligament according to one
example of the present invention.
[0052] FIG. 4 shows an artificial knee ligament according to a
second example of the present invention.
[0053] FIG. 5 is a sectional view showing an example implementation
of a biasing element and tension element used to provide the
desired stiffness to an artificial ligament according to the
present invention.
[0054] FIG. 6 shows an implanted trial prosthetic knee joint
assembly according to an example of the present invention,
including a trial tibial component and a trial artificial
ligament.
[0055] FIG. 7 shows instrumentation for measuring the required
length of a ligament.
DETAILED DESCRIPTION
[0056] Referring to FIG. 1, a knee prosthesis 2 comprises a tibial
component 4 having a tibial tray 6 integrally formed with a stem 8,
a femoral component 10 and a pair of bearing components 12, 13. The
bearing components 12, 13 separate the tibial component 4 and the
femoral component 10 and are formed with proximal and distal
bearing surfaces which engage corresponding bearing surfaces 14,
15, 16 on the tibial tray 6 and on the femoral component 10. These
various bearing surfaces enable the tibial component 4 to rotate
and translate relative to the femoral component 10. The bearing
components 12, 13 may be meniscal bearing components, rotational
platform bearing components, or may be fixed bearing components.
The combination of the bearing surfaces 14, 15, 16 and the bearing
components 12, 13 allows the knee prosthesis to achieve a similar
range of movements to an anatomical knee joint.
[0057] An artificial knee ligament 20 is provided within the knee
prosthesis 2 to restrict undesirable movements of the knee
prosthesis, improving the stability of the joint in use, as well as
reducing the risk of dislocation of the bearing components 12, 13.
The ligament 20 is elongate in form and constructed substantially
of a first biocompatible material which has high tensile strength
and stiffness.
[0058] With reference to FIG. 2, the ligament 20 is terminated at
the proximal end by a proximal loop 22 and at the distal end by a
distal loop 24, both loops having a fixed size. In the embodiment
shown, the loops are formed by looping back the material at each
end of the ligament to form the loops, and gluing the free ends of
the ligament back to itself to secure the loop. Alternatively,
another method for securing the loop could be used, for example the
individual fibres of the ligament could be separated, then woven
back in to the ligament to secure the loop or the ligament could be
passed through a washer looped on one side of the washer then the
individual fibres of the ligament could be fed back though holes in
the washer to secure the loop.
[0059] The distal loop 24 is connected to a fixing provided on the
tibial component 4 which may comprise a tibial bollard 26 and the
proximal loop 22 is connected to a fixing provided on the femoral
component 10 which may comprise a femoral bollard 28. The bollards
26, 28 comprise a neck portion and a head portion, with the neck
portion being narrower in form than the head portion. When the
ligament 20 is fitted to the knee prosthesis 2, the loops 22, 24
rest on the neck portions of the bollards and are prevented from
sliding or working themselves off the bollard by the wider head
portion.
[0060] With reference to FIG. 3, a wear portion 30, is provided on
the inside of the proximal and distal loops 22, 24. In the
embodiment shown in FIG. 3, the wear portion 30 is moulded into the
loop to form a single component. The wear portion 30 is located in
the area of each loop 22, 24 where the loop contacts the neck of
the tibial or femoral bollard when the ligament is fitted. The wear
portion may be shaped or dipped to rest against the fixing in use.
The wear portion 30 may be formed in a second biocompatible
material, such as polyethylene, which has a greater resistance to
abrasive wear than the first biocompatible material which forms the
ligament. The wear portion 30 may comprise a resilient ring of
material and may be configured to pull the loop towards a closed or
partially closed configuration. The wear portion 30 may thus be
configured to grip the bollard 26, 28 when fitted, further reducing
the possibility of the ligament becoming disconnected. The wear
portion 30 may be elastically deformable allowing the loops 22, 24
to become substantially circular in an open configuration. In the
open configuration, as shown in FIG. 3, the loops can be fitted
over the head portion of the bollards 26, 28.
[0061] With reference to FIG. 4, the loops 22, 24 of the artificial
ligament 20 may be further secured by the use of ferrules 32. In
the embodiment shown in FIG. 4 the wear portions 30 comprise
thimbles which are formed as separate loops which are trapped
within the eyes of the ligament loops 22, 24. The thimbles are
resilient and may be configured hold the loops in the closed
condition when not fitted to the bollards, as shown in FIG. 4.
[0062] With reference to FIG. 5, a biasing element 538 may be
provided between the tibial bollard 26 and the tibial component 4.
The biasing element 538 is provided within a bore 508 of the stem 8
of the tibial component 4. The tibial bollard 26 may also be
received within the bore 508. The bore 508 opens onto the bearing
surface 14 of the tibial tray 6. The artificial ligament 20 extends
into the bore 508 through a space 516 between the bearing
components 12, 13, so that the artificial ligament 20 substantially
does not interfere with the bearing components 12, 13 during normal
articulation of the prosthesis.
[0063] The biasing element 538 comprises a resilient element 40. In
the illustrated embodiment, the resilient element 40 is a coiled
compression spring 42 and the bearing element 44 is a plate 46.
However, the resilient element 40 may consist of or comprise any
appropriate spring or springs, for example a Belleville washer or
an elastomeric member. An appropriate bearing element may be
selected according to the choice of resilient element or may be
omitted if not required.
[0064] With continued reference to FIG. 5, the knee prosthesis also
comprises a tensioning element 518. The tensioning element 518 is
mounted in the stem 8 of the tibial component 4. The tensioning
element 518 is cylindrical and formed with an external thread 520
which engages with an internal thread 522 formed in the bore 508.
The tensioning element 518 acts between the biasing element 538 and
the tibial component 4. The tensioning element 518 is adjustable,
to allow the tension in the ligament 20 to be set to
appropriately.
[0065] In the embodiment shown, the resilient element 538 and the
tensioning element 518 are both provided on the tibial component 4
of the knee prosthesis 2. It is equally envisaged that both could
be provided on the femoral component 10, or one could be provided
on each of the prosthetic components. Alternatively one or both
could be omitted.
[0066] With reference to FIG. 6, in order to determine a suitable
length of artificial ligament 20 to be fitted to the knee
prosthesis 2, a trial ligament 620 may be created. When the trial
ligament is created, the tibial component 4 of the knee prosthesis
2 may not have been implanted and hence a trial tibial component
604 may be used temporarily within the knee joint assembly. The
trial tibial component 604 also comprises a tibial tray 606, a stem
608 and a tibial bollard 626. The connection between the trial
tibial component 604 and the trial ligament 620 is substantially
the same as the connection between the tibial component 4 and the
ligament 20 as shown in FIG. 1. Similarly, the final bearing
components 12, 13 may not be fitted, and trial bearing components
612, 613 may be temporarily used in the assembly when creating the
trial ligament 620. The trial ligament 620 can be formed by tying a
length of surgical string around the femoral bollard 28 and the
trial tibial bollard 626. Alternatively the trial ligament could be
formed from a zip tie or any other suitable elongate element which
is selectively connectable to form a continuous band. In some
cases, the trial tibial component 604 may be the final tibial
component 4 which has been fitted in a temporary manner.
[0067] In order to address the shortcomings recognised in a method
for implanting a prosthetic knee joint, as presented in the
background section above, improved methods of implanting the
prosthesis 2 are herein described.
[0068] In one method of implanting the prosthesis 2, the femoral
component 10 is implanted into the distal end of a femur 650; the
trial tibial component 604 is fitted temporarily to the proximal
end of a tibia 652 such that the tibial tray 606 rests of the
resected proximal end of the tibia 652. Trial bearing components
612, 613 are placed between the femoral component 10 and the trial
tibial component 604. The trial ligament 620 is then created by
tying off a length of surgical string after it has been tightened
around the femoral bollard 28 and the trial tibial bollard 626. The
trial ligament 620 is then cut away and removed from the operative
site. The trial ligament 620 can then be reassembled into a closed
loop and the length of the loop measured to determine the length of
artificial ligament 20 required to be fitted into the knee
prosthesis 2.
[0069] In an alternative method (not shown), the trial ligament 620
could comprises a tie which is colour coded, such that the length
of ligament required can be determined by the colour of the trial
ligament 620 at the position it has been tied. Alternatively, the
trial ligament 620 could comprise a zip tie with a ratchet head and
rather than being tied, the zip tie could be tightened around the
bollards using the ratchet head, the colour of the tie at the
position of the head could be noted and the tie could then be
undone and removed from the operative site. Alternatively, rather
than being colour coded, the tie could be marked with numbers or
letters, denoting the length of tie used.
[0070] Once the length of trial ligament 620 has been determined,
an artificial ligament 20 of a suitable length may be selected from
a range or kit of artificial ligaments available.
[0071] With reference to FIG. 7, a ligament gauge 700 can
alternatively be used to determine the length of ligament required.
The ligament gauge 700 comprises a hook 702, which is configured to
couple with a femoral bollard 28, and an elongate shaft portion
704. A slider 706 is configured to be axially movable along the
shaft 704. The slider comprises a body 708, a jaw 710 and a locking
component 712. The locking component 712 can be rotated relative to
the slider body 708 and shaft 704 to lock the slider axially with
respect to the shaft 704. Measurement markings 714 are provided on
the shaft for the required length of ligament to be read off. In
use, the hook 702 is coupled to the femoral bollard 28 of a
prosthetic component implanted on to the femur of a patient. The
slider is moved along the shaft until the jaw 710 engages with the
tibial bollard 26. The locking component is then rotated to lock
the position of the slider. The locking action may be achieved
through the use of tabs (not shown) provided on the inside of the
locking component 712 which engage with grooves in the shaft 704.
The shaft may be configured such that the tabs on the locking
component 712 do not engage the shaft 704 in the unlocked position.
The ligament gauge 700 can be rotated about the femoral bollard 28
to disengage the jaw 710 from the tibial bollard 26. The hook 702
can then be unhooked from the femoral bollard 28 and the gauge can
be removed. In this way, the measurement recorded on the ligament
gauge 700 can be read after the gauge has been removed from the
operative site.
[0072] Once a suitable artificial ligament 20 has been selected,
the trial tibial component 604 is removed from the joint. The
distal loop 24 of the artificial ligament 20 is attached to the
tibial bollard 26 of the final tibial component 4. The proximal
loop 22 of the artificial ligament 20 is then attached to the
femoral bollard 28 of the femoral component 10. By attaching the
artificial ligament to both the tibial component 4 and the femoral
component 10 before the tibial component 4 is finally implanted,
the problem highlighted in the current methods is avoided.
[0073] At this stage the trial bearing components 612, 613 may be
removed, and the final bearing components 12, 13 may be inserted
between the tibial tray 6 and the bearing surfaces 15, 16 of the
femoral component 10. Alternatively, if desirable, a meniscal
spacer (not shown) which is slightly thinner than the final bearing
components 12,13 can be fitted to the prosthetic joint 2 to reduce
loading of the ligament 20 during the final stages of the
implantation. The tibial component 4 is then implanted into the
proximal end of the tibia 652.
[0074] If the meniscal spacer or the trial bearing components 612,
613 are still present within the joint, they are now removed and
the final bearing components 12, 13 are fitted to the knee
prosthesis 2.
[0075] Although in the example shown, the final femoral component
10 is implanted first, and the tibial component 4 of the knee
prosthesis is then fitted loosely or a suitable trial tibial
component 604 is fitted to allow the required length of the
artificial ligament 20 to be determined, it is equally envisaged
that the final tibial component 4 could be implanted first, and the
femoral component 10 or a suitable trial femoral component (not
shown) could be fitted thereafter to allow the required artificial
ligament length to be determined. It is also considered, that both
the femoral and tibial components could be trial components and
could be fitted temporarily whilst the trial ligament 620 is
formed.
* * * * *