FIELD OF INVENTION
The present invention relates to Tibial insert trial that assists in identifying
size of tibial baseplate in Total Knee Arthroplasty surgeries. More particularly the invention relates to a Tibial insert trial with provision to vary the thickness with the help of a mechanism to accommodate all different thicknesses for one size of insert in one single trial.
BACKGROUND OF THE INVENTION
Usually, knee replacement is recommended by the surgeon for those
patients whose knees are worn out due various afflictions including
osteoarthritis, rheumatoid arthritis, knee injury, gout, and hemophilia.
Knee replacement is one of the major surgeries requiring great skill and
post-operative monitoring and therefore, surgery is recommended only
when all other non-surgical treatments such as physiotherapy or steroid
15 injections, have failed to reduce pain and/or gain mobility in the patient.
Knee replacement surgery typically provides two prosthetic components.
One component is the femoral component while the other one is the tibial
component. The femoral component is attached to the resected or the
20 natural distal femur. The tibial component is attached to another tibial
component or an insert, and is attached to the resected or the natural tibia.
A common type of tibial component uses a tray or plate that is fitted to the
patient's resected proximal tibia. Plastic or polymeric inserts or bearings
25 are provided that fits between the tibial component and the femoral
component. These inserts or bearings provide a surface for the articulation of the condylar portion of the femoral component, thus enabling the gross movement of the femur relative to the tibia.
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One of the most difficult challenges in the knee replacement surgery is the
accurate fitting of prosthetic component. This is due to the fact that each
patient has a different bone structure and geometry when the patient is
resting or is in static position. Then again, when the patient is in a state
5 of action or motion, the dynamics of the movement of the tibia relative to
the femur is again very different for each patient. Despite the use of various imaging and palpation techniques used by the surgeon, it is difficult for the surgeon to gain sufficient information about the patient anatomy before the knee is actually exposed for the surgery.
10
To cover the wide diverse knee structures, there is a wide range of prosthetic components provided by the supplier. These include, for instance, femoral and tibial components for primary surgeries as well as revision surgeries, porous coated and non-porous coated components,
15 various sizes of stems for various tibial component plates, various femoral
component interfaces for primary and revision cases, and prostheses which feature mobile bearings as well as those which do not have mobile bearings.
20 During the surgery, the surgical fitting procedure may involve trial and
error by the surgeons. At this stage the use of actual prosthetic
components during the surgical fitting procedure is undesirable for a
number of reasons. One main reason is that if actual prosthetic
component is used while modifying or cutting the bone structure, it may
25 be damaged which could prove detrimental in its long term performance.
However, if trial prosthetic is used before actual prosthetic transplant is done; it gives reasonable flexibility to the surgeon to test and fit component of various sizes even during the modification of bones structure.
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During knee replacement surgery, tibial trial inserts are utilized to aid
surgeons in preparing the tibial surface for implantation of tibial
component of artificial knee. After ascertaining the proper size of tibial
trial insert, the surgeon affixes the selected tibial trial insert to the tibial
5 surface. Then trial reduction is usually performed by surgeons to find out
the right thickness and alignment of the tibial component.
During the trial reduction procedure if the surgeon finds that the tibial trial insert used on the basis of pre-operative information is not of proper
10 thickness, then the surgeon removes the ill-fitting tibial trial insert and
replaces it with a more suitable tibial trial insert of suitable thickness. This procedure continues or is repeated until the exact tibial trial insert of proper thickness is found as a perfect or near-perfect fit. In order to adjust the thickness, generally one or more space or other modular component
15 may be inserted.
Due to this usage of the tibial trials inserts of many sizes to find a particular fit with specific thickness, not only is there considerable increase in the number of instruments used, but also the surgeon has to
20 remove and replace different sizes of inserts with different thickness
before being able to ascertain the correct size. Usually complete tray sets which contain tibial trial inserts of different sizes with specific thicknesses are required to manage these inserts that too for CR (cruciate retaining), CS (cruciate stabilizing) and PS (posterior stabilizing) inserts separately.
25 Therefore it adds to the inventory management, transportation and
sterilization issues for these many components. This results in increase in the cost of surgery as well as in the number of surgical steps during operation. Additionally this excess number of instruments as well as inserts can create chaos in small operation theater.
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In the existing state of art there are a number of patents which discloses
devices for trialing for tibial component during the surgeries. One such
patent, US 7,309,363 granted on December 18, 2007, discloses an adjustable
tibial trial insert which includes an upper plate having an upper articular
5 surface and a lower plate. A height-adjustment mechanism of the insert is
coupled to and positioned generally between the upper plate and the
lower plate and is configured to move between a closed position where
the upper and lower plates are adjacent to each other and an opened
position where the upper and lower plates are spaced apart from each
10 other in order to adjust a height or thickness of the insert. An additional
instrument may be used to actuate the mechanism inside.
One of the main disadvantage of the US patent 7,309,363 lies in the
linkage mechanisms involving multiple moving parts which makes its use
15 little complex.
Hence there is need of the device for conducting trial of tibial component
with mechanism which is simple to use and involves less moving parts to
aid in selecting the correct size and orientation of tibial component during
20 total knee replacement/arthroplasty which can be adjusted to variable
thickness of tibial component for a given size.
OBJECT OF THE INVENTION
In order to obviate the aforementioned drawbacks in the existing
25 solutions, the main object of thepresent invention is to provide a variable
thickness tibial insert trial to aid in choosing the correct size and
orientation of tibial component during Total Knee
Replacement/Arthroplasty.
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Another object of the invention is to provide varying tibial inserts trial which can achieve different insert thickness by the use of external or internal device/feature or combination of both, to activate the mechanism.
5 Another object of the invention is to provide the variable universal tibial
insert trial capable of providing the provision to re-adjust the thickness of inserts without removing them from the operated point.
SUMMARY OF THE INVENTION
10 Accordingly the present invention provides a variable thickness tibial
insert trial. The device aids in choosing the correct size and orientation of tibial component during Total Knee Replacement/arthroplasty and is also able to adjust to all thicknesses of tibial component for a given size by varying the thickness.
15
The variable thickness tibial insert trial has a mechanism which when
operated varies the thickness of tibial insert for a particular size of tibial
insert. The thickness variation operation is achieved by the use of a gear
mechanism combined with threads. For example a combination of
20 threads, worm and worm gear mechanism may be used to vary the
thickness of the insert thereby eliminating the need to have multiple blocks for various thicknesses. The gear and thread types can vary, to achieve the intent.
25 Further variable tibial trial can also be used by surgeon to readjust the
thickness of insert without removing them from the joint. The present invention also provides a provision for the surgeon to use hands or some other device to change the thickness, in case the forces are too high. The
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device may be used either from anterior, proximal or medial side of the insert for either of the knee – left or right.
For each specified thickness settings, the device can positively lock and
5 allow it for trialing of the leg of the patient for the full range of motion.
The advantage of this aspect of invention is that it not only reduces the number of tibial insert trials to be provided for use in a surgery but it is also helpful in reducing the number of non-productive surgical steps.
10 Thus the present invention completely eliminates the need of the tibial
inserts with the variable thickness options, as now there need to be the ones with minimum thickness. This is further helpful in managing OT space and company’s inventory, ease in managing sterilization..
15 It is capable of adjusting to all thicknesses of Tibial component for a
given size by varying its thickness through actuation of an internal mechanism. The actuation can be manual or through additional external device like a driver. The additional external device may be used either from Anterior, Proximal or Medial side, or a suitable combination of these
20 like antero-proximal position of the Insert or insert trials for either of the
knee – left or right.
In the present invention, surgeon can re-adjust the thicknesses of insert trials without removing them from the joint.
25
The advantages of the present invention can be realized from the fact that that in the current PS set of instrumentation offered, there are a total of 8 sizes of insert trials. Each size is available in 7 thicknesses. This makes it a total of 56 insert trials per system. Further, there are different systems
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available like Posterior Retaining (PS) insert trials, Cruciate Retaining(CR)
insert trials, Condylar Stabilized(CS) insert trials etc. This leads to a huge
inventory to be managed. The said invention may lead to 8 Insert trials
per system. In the said concept, the material can be all metal or all plastic
5 or a combination of both.
Variable thickness tibial insert trial comprising at least one proximal plate having at least one post bearing threads, at least one distal plate having at least one lower resting surface capable of being deployed over
10 implantation site, at least one combination of gear and thread mechanism
comprising of at least one driven gear member with threads and at least one driving member. The threads of the driven gear member is engaged with the threads of the post of the proximal plate while the driven gear member of the driven gear member with threads is engaged
15 with the distal plate. When the driven gear member with thread is
actuated by the driving member, the proximal plate moves in distal-to-proximal direction or vice-versa to provide tibial trial insert without being removed from implantation site. The tibial trial insert is capable of adjustment from minimum thickness to predetermined thicknesses or vice
20 versa.
The driven gear member with threads capable of being driven by driving member is selected from the driven bevel gear with threaded shaft or driven spur gear with threads.
25
The variable thickness tibial insert trial wherein the driven gear member with
threads is the driven bevel gear with threaded shaft, the threaded shaft of the
driven bevel gear with threaded shaft is engaged with said threads of
the post of the proximal plate while the driven bevel gear of the driven
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bevel gear with threads is being engaged with the distal plate via
rotating means such as axial locking pin. The driven bevel gear of the
driven bevel gear with threaded shaft is constrained in the constraining
surface of the distal plate in a manner that the driven bevel gear with
5 threaded shaft is capable of being rotated along its own axis when
operated by said driving member while being constrained in all other directions thereby providing the proximal–distal movement or distal-proximal movement to the proximal plate. The proximal plate and the distal plate further having corresponding constraining guiding features
10 which are engaged to each other in manner that the proximal plate and
distal plate have parallel distal –proximal movement with respect to each other without being disassembled from each other when driven bevel gear with thread is operated by driving member. The distal plate further has at least one hole on the surface selected from its medial surface or
15 anterior surface to facilitate the driving of said bevel gear with threaded
shaft by the driving member. The driving member is selected from the device with integrated or detachable pinion gear or device with characteristic screw end. The driving member which is device with integrated or detachable pinion gear directly engages with the driven
20 bevel gear of the driven bevel gear with thread through said hole of the
distal plate in a manner that said device when operated facilitates the rotation of the bevel gear with thread shaft thereby changing the width of variable tibial insert trial.
25 The variable thickness tibial insert trial, wherein the driving member is a device
with characteristic screw end, the pinion gear is a part of the insert trial and has
at least one socket hole which has characteristics corresponding to the device
with characteristics screw end. The pinion gear is being rotatably retained
inside the retaining hole of the distal plate by retaining locking means in
30 a manner that the gears of the pinion gear engages with the driven
bevel gear of said driven gear with threaded shaft and capable of
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rotating said driven gear with threaded shaft when driving member with
characteristics end rotates said pinion gear by engaging to itself to said
socket hole of the pinion gear. The retaining locking means comprises of
at least two dowel pins. The pinion gear has cut out features and being
5 resided inside the retaining hole of the the distal plate The distal plate
further having two holes for the insertion of the dowel pins. The dowel
pins is inserted around the cut out features of the pinion gear through the
holes of the distal plate in a manner that the pinion gear is capable of
rotating along its own axis while being constrained in other directions. At
10 least one surface of distal plate is suitably marked for calibrated thickness
of the variable insert trial such that corresponding proximal plate has at least one relative marker to indicate the predetermined thickness of the
tibial insert trial.
15
The variable thickness tibial insert trial, in which the the driven gear member
is the driven spur gear with threads the driving member is an internal
planetary driving gear. The driven spur gear of the driven spur gear with
threads has teeth profile which engages with the planetary driving gear while
20 the threads of the driven spur gear with threads being engaged with the
threads of the proximal plate. The combination of the driven spur gear with threads and internal planetary driving member being deployed on the distal plate via retaining mechanism such that said driven spur gear with threads provides a distal-proximal moment to said proximal plate when
25 external force is applied on the driving planetary gear. The planetary gear
has at least one outer and inner circumference. The outer circumference bears at least one cut out feature while the inner circumference bears the teeth profile. The predetermined teeth of the teeth profile of the inner circumference is engaged with the predetermined teeth of the teeth profile of said planetary
30 gear thereby forming a combination which is being deployed on the distal plate
in a manner that the combination form an off-center profile. In the retaining
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mechanism, the combination of the planetary gear and the driven spur
gear of the driven spur gear with thread is being constrained inside said
distal plate by intermediate disc which is being fixed over the distal
plate. The intermediate disc and the distal plate have corresponding off-
5 center protrusions. The off-center profile of planetary gear and driven
spur gear with threads is being deployed inside the protrusions between
the intermediate disc and the distal plate in a manner that movement of
the driven spur gear with thread and internal driving planetary gear
constrained in proximal–distal direction when driven spur gear with
10 threads is being rotated by the driving planetary gear. The proximal
plates and the distal plate have corresponding guiding features with
retaining mechanism facilitating the engagement of said guiding features
of proximal and distal plate in a manner that there is the parallel proximal
–distal moment of proximal plate with respect to said distal plate. The
15 cut out features of the driving planetary gear is protruded from at least
one surface of the distal plate in a manner that when external force is applied on the cut out feature it rotates said planetary gear thereby providing the variation in the thickness of the variable tibial insert trial. The driven spur gear with threads is selected from driven spur gear with
20 threaded shaft or driven spur gear with internal threads. The proximal
plate of the driven spur gear with threaded shaft, has thread at its internal
surface of its post such that said threaded shaft of the driven spur gear
with threaded shaft is engaged with its thread. For the driven spur gear
with internal threads, the proximal plate has threaded shaft either
25 assembled or integrated at its lower surface such that said internal
threads of the driven spur gear being engaged with said threaded shaft of proximal plate.
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Variable thickness tibial insert trial comprising of at least one proximal
plate, at least one distal plate and at least one cam operated mechanism.
The proximal plate has at least one upper articulating surface, at least one
lower surface and at least one through slot. The distal plate has at least
5 one anterior post with at least one bush hole and at least one posterior
post with at least one hole. The cam operated mechanism comprising of at least one cam shaft and at least one external driving member. The cam shaft having at least one anterior end, and at least one posterior end, at least one calibrated feature and at least one characteristic hole. The cam
10 shaft has at least three off centered faces which are calibrated for
providing at least three thickness options to said variable tibial trial insert. The anterior and posterior ends of the cam shaft is deployed between the proximal plate and the distal plate in anterior to posterior direction in a manner that at least one face of calibrated feature of the cam shaft is
15 slideably engaged with the lower surface of the proximal plate while
the anterior end and posterior end the of the cam shaft is rotatably retained in the corresponding anterior and posterior post of said distal plate thereby providing freedom to said cam shaft to rotate along its own axis to vary the thickness of variable tibial insert by disengaging its said engaged
20 face corresponding to predetermined thickness from said proximal plate and
engaging either one of said other faces corresponding to other predetermined thickness to said proximal plate when operated by driving member through the characteristic hole. The cam operated mechanism further comprising of at least one retaining pin with cam shaft further having at least one grove cut
25 around its circumference at its anterior end. The grove of the cam shaft is
being rotatably kept inside the bush hole of the posterior post with retaining pin being inserted through said grove cut of the cam shaft. The posterior end of the cam shaft is in the hole of the posterior post of distal plate via through hole of the proximal plate in a manner that the cam shaft
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is capable of rotating along its own axis while being constrained in other
directions. The cam operated mechanism further comprising of at least
one leaf spring having at least two ends with contour surface. The cam
shaft further having at least neck region around at its anterior end such
5 that the contour surface of the leaf spring is being kept under the neck
region of the cam shaft anterior end. The two ends of said leaf spring is
being kept in slots of the said proximal plate thereby providing the
arrangement in which the proximal plate is as close as to the distal plate.
The cam shaft and distal plate is suitably marked with markings for
10 calibrated thicknesses in a manner that the marking are visible during
implantation process. The proximal plate and distal plate is made of material selected from plastic or metal.
Variable thickness tibial insert trial, said tibial insert trial comprising of at
15 least one proximal plate, at least one distal plate, at least one combination
of gear and thread mechanism comprising of at least one driven gear
member with threaded shaft and at least one driving member. The
distal plate is being deployed over implantation site having cavity. The
combination of gear and thread mechanism comprising of at least one
20 driven gear member with threaded shaft and at least one driving
member.
The threaded shaft of the driven gear member is engaged with the
cavity of said implantation site through the distal plate while the
25 driven gear member of the driven gear member with shaft is engaged
with the proximal plate. When the driven gear member with thread is actuated by said driving member the proximal plate moves in distal to proximal direction or proximal-to-distal direction to provide variable tibial trial insert which is adjustable from minimum thickness to
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predetermined thicknesses or vice versa without being removed from implantation site.
The driven gear member of the driven gear with threaded shaft is selected
5 from the driven bevel gear with threaded shaft or the driven spur gear
with threaded shaft. The driven gear member of the driven gear member with threaded shaft is embodied inside the proximal plate and distal plate while the threaded shaft of the driven member with threaded shaft is protruding out of the distal plate. 10
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be fully understood from the following detailed
description taken in conjunction with the accompanying drawings, in
which:
15 Fig.1 illustrates the perspective view of an embodiment of the device
(1000) shown in disassembled forms. In this embodiment of
invention, there is a proximal plate (1100), a driven bevel gear with
threaded shaft (1200), distal plate (1400), and a driver(1300) having a
pinion bevel gear designed at its tip.
20 Fig 1A and Fig 1A(1) are a perspective views of the proximal plate (1100)
respectively depicting its relative marker and internal threads Fig 1B is a perspective view of the distal plate (1400) showing the hole on
its anterior surface.
Fig 1C illustrates the driver (1900) depicting its pinion gears.
25 Fig 2 is a perspective view of another embodiment of the device (2000)
shown in an exploded view. Fig 2A is the perspective view of the proximal plate (2100) depicting its
various surfaces.
30
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Fig 2 A(1) is the perspective view of the proximal pate (2100) depicting the
internal threads in its post.
Fig 2B illustrates the driven bevel gear with threaded shaft (2200) in detail.
Fig 2C illustrates the side view of dowel pins.
5 Fig 2D is the perspective view of distal plate (2400) illustrating its various
feature. Fig 2D(1) is the perspective view of distal plate (2400) illustrating its
various feature at posterior end.
Fig 2E and Fig 2F is the side view and perspective view of the pinion gear
10 (2500) respectively.
Fig. 2G illustrates the axial locking pin (6200) in detail,
Fig 2H(1) illustrates the perspective view of the device in complete
assembled form.
Fig 2H(2) illustrates the perspective view of the device in complete
15 assembled form without the proximal plate
Fig. 3 is an exploded view of another embodiment of the device (3000)
shown in which combination of gear and thread mechanism is used.
It has a proximal plate (3100), a driven spur with a threaded shaft
(3200), an internal driving planetary gear (3300) retained in position
20 using an intermediate retaining disc (3500) and the distal plate
(3400). The driving gear may be rotated by using thumb or through
an external driver which can be inserted into the holes drilled
radially around the periphery of the driving planetary gear (3300).
Fig. 3A (1) and Fig 3A (2) illustrate the prospective views of the proximal
25 plate (3100) illustrating its various features.
Fig 3B(1) and Fig 3B(2) is a perspective and top view of intermediate
disc(3500) depicting its various features. Fig 3C(1), 3C(2)and Fig 3C (3)is a front, top and perspective views of
driven spur gear with threaded shaft (3200).
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Fig 3D(1) and Fig 3D (2) is top and perspective views of planetary gear.
Fig 3E (1) and 3 E(2) is top and perspective view of Distal plate(3800) depicting its features
Fig.4 is an exploded view of another embodiment of the tibial insert trial
5 (4000) shown in Fig. 3. It has a proximal plate (4100) having a
threaded shaft (4103) protruding distally. This protruding threaded
shaft (4103) vary the thickness of the trial while being driven by the
driving gear or thumb wheel (4300) which drives the intermediate
spur gear (4200), retained in position using an intermediate retaining
10 disc (4300) and a distal plate(4400).
Fig 4A (1) and Fig 4 A(2) illustrates various feature of proximal plate in which threaded shaft (4203) is a part of proximal plate(4200).
Fig 4B(1) and Fig 4B(2) respectively provides the top and perspective view
of intermediate disc.
15 Fig 4C(1) and 4C(2) respectively provides the top and perspective view of
Driven spur gear(4200), illustrating it’s features. The Driven spur gear has internal thread
Fig 4D(1) is a top and 4D(2) perspective view of planetary gear.
Fig 4E illustrates the top and perspective view of the distal plate.
20 Fig. 5 illustrates another variant of variable thickness tibial insert trial in
which the intermediate mechanism is a cam operated mechanism.
Fig 5A illustrates the proximal plate.
Fig 5B is perspective view of Cam
Fig 5C is front view of Cam illustrating its characteristic features
25 Fig 5D showing the assembly calibration of the Cam with proximal plate,
Fig 5E guiding feature on the distal plate
Fig 5F is a perspective view of the retaining pin illustrating its component.
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Fig 6 illustrates the alternative embodiment in which the proximal plate does not have post while said driven bevel gear with threads is bieng integrated part of proximal plate.
5 DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE
TO DRAWINGS AND ILLUSTRATIVE EXAMPLES:
The present invention provides a device which is an insert trial with its
proximal surface that articulates with the femoral trial during trialing, a
distal plate that rests on resected proximal tibia during trialing, and an
10 intermediate mechanism to vary the thickness of device to enable it to be
used as an insert trial for different thicknesses of tibial inserts during a total knee arthroplasty surgery.
Definition:
The term “driven gear member with thread” herein specification refers to
15 driven bevel gear with threaded shaft(1200,2200) or driven spur gear with
threads.
The term “driven spur gear with threads” herein specification refers to
driven spur gear with threaded shaft or driven spur gear with internal
threads.
20 The term “driving member” here in specification refers to one driver
(1300) having a pinion bevel gear or planetary gear or driving member having characteristics end. The characteristics end may be selected from hexagonal end, square end, and slot for screw drivers etc.
The term “guiding features” herein specification refers to the constraining
25 features (2103, 2105, 2403, 2405, 3401, 3402, 3403, 3404) present on the
proximal (2100, 3100) and distal plate (2400, 3400) that ensure that during operation said proximal plate and distal plate moves in parallel direction. The term “retaining mechanism” herein specification refers to mechanism to retain said combination of driven spur gear with threads and planetary
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gear in distal plate. The retaining mechanism employs intermediate disc
which is being fitted on to the distal plate in a manner that it constrains
the distal-proximal movement of combination of planetary of driven spur
gear with threads and planetary gear.
5 Here,the term rotating means that the driven gear with shaft can rotate on
its axis by engaging through locking means such as axial locking pin.
Fig 1, Fig 2, Fig 3 and Fig 4 collectively illustrate the variable thickness
tibial insert trial in which the intermediate mechanism is a combination of
10 gear and thread mechanism.
Fig 1 illustrates the dissembled form of the variable thickness tibial insert
trial (1000). The tibial insert trial (1000) comprising of at least one proximal
plate (1100) having post (1101) with female threads (1110) (shown in Fig.
15 1A(1)) in its post, at least one driven bevel gear (1203) with threaded
shaft(1202), at least one distal plate (1400) which is configured to sit on the proximal cut of tibia, and at least one driver(1300) having a pinion bevel gear designed at its tip.
20 Fig 1A illustrates the proximal plate (1100) in details while Fig 1B
illustrates the distal plate (1400) in detail. As shown in Fig 1B the proximal plate has at least one articulating surface (1107) having post (1101) and at least one lower resting surfaces (1106) and at least one relative marker (1108). Fig 1B illustrates the hole (1402) through which the
25 driver (1300) in the distal plate (1400) can be engaged to drive the bevel
gear with threaded shaft (1200). Fig 1C shows the driver (1300)having pinion gear (1305) capable of engaging with the bevel gear with thread(1200). The driver (1300) has ergonomic profile (1302) anterior
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surface (1301) and face (1307). This driver (1300) is a separate detachable driving tool used to vary the thickness of the tibial insert trial.
In the shown illustration, when assembled the driven bevel gear with
5 threaded shaft (1200) envelops between the proximal plate (1100) and the
distal plate (1400). The bevel gear (1201) of driven bevel gear with thread (1200) assembles with distal plate (1400) in a manner that it has the freedom to only rotate along its own axis and is constraint to move in all other directions relative to the distal plate (1400). The proximal plate
10 (1100) has corresponding female threads (1110) (shown in Fig. 1A(1)) in its
post (1101) which engages with the male threads (1202 not shown in Fig. 1) and is equivalent to (2202) thread shown in Fig 2B) on the bevel gear with thread (1200). The proximal and distal plates are assembled in a manner that once assembled they can’t completely disassemble without
15 damaging the device.
The distal plate (1400) has markings (1403) on its anterior face (1402) (Fig. 1C) corresponding to the calibrated thickness. The proximal plate (1100) has a relative marker (1108) (Fig, 1C) which runs against said markings
20 (1403) to show the current thickness of the tibial insert trials during its
operation. The driver (1300) is a separate device which can be engaged with the driven bevel gear (1201) through a hole (1402) (shown in Fig 1 B) via pinion gear (1305) in the distal plate (1400). The face (1307) of the driver (1300) is calibrated to control its engagement depth (1300) with the
25 bevel gear (1201) of the driven bevel gear with thread (1200). Once
engaged, the driver (1300) can be rotated along its own axis thereby enabling the driven bevel gear with thread (1200) to rotate along its axis. This further leads to the proximal plate (1100) move up or down depending on the direction of rotation of bevel gear with thread (1200) as
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the internal threads (1110 not shown in Fig. 1) of proximal plate are
engaged with the threads of the driven bevel gear with thread (1200). The
relative motion between proximal (1100) and distal plates (1400) is
constrained in all direction except in distal-proximal direction. The tab
5 features in distal plate (1400) (similar to (2409) shown in Fig 2D(1)
constrain the periphery of the bevel gear with threaded shaft (1200) from
distal-proximal movement. The advantage of the invention is that it
allows the surgeon to vary the thickness of insert without removing it
from the joint. The threads are self-locking and will not rotate back under
10 load. The threads and gear ratios can be calibrated suitably to provide a
definitive variation in thickness for each rotation. In alternate
embodiment multiple start threads can be used to give quicker variations in thickness.
15 Fig 2 illustrates the alternate embodiment for variable tibial insert trial
(2000) in which driving pinion (2500) is inbuilt into the device instead of being designed on separate device as depicted in Fig. 1C where the pinion gear is part of the external device.
20 Fig 2 illustrates the variable tibial insert trial (2000) in disassembled form.
As depicted in Fig 2 tibial insert trial (2000) comprising of at least one proximal plate (2100), at least one distal plate(2400), at least one driven bevel gear with threaded shaft (2200),at least one axial locking pin (2600) and at least two dowel pins (2301,2302). The distal plate adapted to sit on
25 the proximal cut of tibia.
Figs 2A to 2G illustrate the proximal plate (2100), the distal plate (2400). Driven bevel gear with threaded shaft (2200), the axial locking pin (2600) and the two dowel pins (2301 and 2302) in detail.
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As depicted in Fig. 2A the proximal plate having at least one post (2101),
one upper articulating surface (2107), lower resting surfaces (2106,2104),
constraining features (2103) and relative markers (2108, 2109) with
5 constraining surface tabs (2102 and 2105) acting as guiding features.
Fig 2B depicts the driven bevel gear with threads (2200) in details. The
bevel gear with threads (2200) has a flange (2204), a bevel gear (2203), a
thread post (2201) having a predetermined height (2202) and threads
10 (2205) with predetermined pitch (2206).
Fig 2C provides the side view of the dowel pins (2301,2302) illustrating its length (2303) and diameter (2304).
15 Fig. 2D illustrates the distal plate (2400) in details. It has the distal plate
resting surface (2410) having markings (2406) to reflect the range of thicknesses up to which the tibial insert trial (2000) can be varied. Further it has holes (2401) and (2402) through which the dowel pins (2300) are inserted. The distal plate (2400) also has at least one retaining hole (2404),
20 at least one anterior surface (2411), at least one posterior surface (2408), at
least two constraining surfaces (2403,2405) acting as a guiding feature for parallel motion and thickness constraining surface tabs (2413). The cut out (2407) features for the assembling of bevel gear with thread to the shaft with distal plate (2400) is also illustrated in Fig 2D(1).
25
Fig 2E and 2F illustrate the pinion (2500) in details. It has cut out feature (2502) to engage with dowel pins (2301, 2302), gears (2504) to engage with
21

AMENDED COPY
driven bevel gear with threads, neck (2501) to fix into the retaining hole (2404).
Fig 2G illustrates the axial locking pin (2600) in details. The axial locking
5 pin (2600) has base (2603) with protruding cylindrical surface (2602) which
has spherical top at its center.
Fig 2H(1) illustrates tibial insert trial in assembled form while Fig 2H(2)
illustrates the internal perspective view of tibial insert trial with the
10 proximal plate removed for understanding the device with more clarity
and see internal mechanism.
The driven bevel gear with threads (2200) is enveloped between the proximal plate (2100) and the distal plate (2400). The driven bevel gear of
15 the driven bevel gear with thread assembles with the distal plate (2400) it
has the freedom to only rotate on it’s axis while being constrained to move in all other directions relative to the distal plate (2400). The cut out feature of the distal plate (2400) has hole at its center which facilitates the insertion of axial locking pin (2600) such that the driven bevel gear with
20 threaded shaft (2200) is fixed in an axial position (2412) (Fig 2 D(1)) by
the axial locking pin (2600) which allows the bevel gear with threaded shaft (2200) to rotate along its own axis. As depicted in Fig 2E the feature (2601) of axial lock pin (2600) has a spherical geometry to minimize the surface area for contact with between the bevel gear, the distal plate and
25 the axial lock pin. This is helpful in smooth rotation of driven bevel gear
(2200).
22

AMENDED COPY
The cut out feature (2407) of the distal plate (2400) further has tab features (2409) which constraints the distal –proximal movement of the driven bevel gear with threaded shaft (2200).
5 The proximal and the distal plates (2100, 2400) are assembled in such a
way that once assembled they can’t be completely disassemble without damaging the device. The constraining features (2105, 2103) for the proximal plate fits into the constraining guiding feature (2405, 2403) in the manner that they prevent the disassembling of the distal plate from the
10 proximal plate during its working. The distal plate (2400) has markings
(2406) (shown in Fig 2D) on it’s anterior face (2411) corresponding to the calibrated thickness. The proximal plate (2100) has a relative marker (2108 and 2109) (Fig. 2A) calibrated to show the current thickness of the insert trials (2000).
15
A driven bevel gear with threaded shaft (2200) is fixed on an axial position (2412) (Fig 2 D(1)) by the axial locking pin (2600) in a manner that it allows the bevel gear with threaded shaft (2200) to rotate along its own axis. The distal-proximal movement of the bevel gear with threaded shaft
20 (2200) is constrained by the distal plate (2400).
As compared to Fig 1 where pinion is a part of driver, in this embodiment,
the pinion gear (2500) for bevel gear (2200) is a part of variable tibial insert
trial. The pinion gear assembled in the distal plate through a retaining
25 hole (2404) in a manner that the gear teeth (2504) of the pinion engages
(2500) with the gear teeth (2203) of the bevel gear. The pinion (2500) is retained in place by two dowel pins (2300) such that it allows the rotation only along its own axis and no axial movement is allowed. The pinion may have various features to actuate. For instance a hexagonal socket
23

AMENDED COPY
hole (2505) may be made which can be actuated by an additional device
like hexagonal screw driver. Once the hexagonal screw driver is engaged
properly with the pinion (2500), it can be rotated to actuate the bevel gear
with thread shaft to rotate along its axis. This further leads to the
5 movement of the proximal plate (2100) in up or down direction as the
proximal plate’s (2100) internal threads (2110) are engaged with the threads (2205) (Fig. 2B) of the driven bevel gear with threaded shaft (2200). The relative motion between the proximal and the distal plates (2100 and 2400) is constrained in all directions except they can move in
10 distal-proximal direction. This in turn varies the thickness of tibial insert
trial. This allows the surgeon to vary the thickness of insert without removing from the joint. The threads are self-locking and do not rotate back under load. The threads and the gears ratios can be calibrated suitably to provide a definitive variation in thickness for each rotation.
15 The multiple start threads can be used to give quicker variations in
thickness.
As depicted in Fig 2D the anterior surface of the distal plate (2400) has
markings (2406) to reflect the range of thicknesses up to which the insert
20 trial can work. The distal plat also contains features (2401, 2402) for
inserting the dowel pins (2301, 2302). Fig 2C illustrates the dimension of the dowel pin (2303 and 2304).
The function of these dowel pins is to retain the driving pinion gear (2500)
25 in the retaining hole (2404) as each dowel pins (2301 and 2302) has
essential features (2303) and (2304) corresponding to the cut out features (2502) (Fig. 2E) of pinion (2500. These cut out feature(2502) is a cut out all around the circumference of the cylindrical pinion for adequate length(2503) the dowel pins (2301, 2302) to get into it and thereby
24

AMENDED COPY
enabling the pinion to rotate on it’s axis due to optimal clearance provided, but constraints it’s all other motions.
As shown in Fig 2F the pinion gear (2500) has a hexagonal socket (2505) in
5 it for a corresponding hex wrench or screw driver, which is used to rotate
pinion. This socket may be of any shape, internal or external feature. The
corresponding feature can be provided at the engaging end of screw
driver. It is of utmost importance that the gear teeth profile in bevel gear
and it’s pinion must match the standards to allow complete and effective
10 functionality.
The third embodiment is illustrated with the help of Figs 3 to 3F. In this embodiment, the variable tibial insert trial (3000) provides an option of varying the width by thumb of the user. The variable tibial insert trial
15 (3000) comprising of at least one proximal plate (3100), at least one driven
spur gear with a threaded shaft (3200), at least one internal driving
planetary gear (3300) retained in position using the intermediate
retaining disc (3500) and at least one distal plate(3400). The driving gear may be rotate by using thumb or through an external driver which can be
20 inserted into the holes drilled radially around the periphery of the internal
driving planetary gear (3300).
Fig 3 A (1) and 3A (2) illustrate the various features of the proximal plate
(3100). It has one post (3101) , female threaded hole (3105) at its center the
25 female cut out feature (3103) and constraining features which are
protruding pins (3104 and 3106), (3102,3107) and (3108).
25

AMENDED COPY
Fig 3B shows the intermediating retaining disc (3500). The intermediate retaining disc (3500) has protrusions (3503 and 3504). Further it has holes (3501, 3502).
5 Fig 3 C(1), Fig 3C(2) and Fig 3C(3) illustrate the various features of driven
spur gear with threaded shaft (3200). The outer surface of protruding shaft
(3207) has threads (3206). The driven spur gear (3200) of the driven spur
gear with threaded shaft (3200) has teeth profile (3202) on its outer surface
which engages with the teeth profile (3302) of the planetary gear (3300)).
10 The teeth profile (3202) of driven spur gear with threaded shaft (3200)
corresponds to the teeth profile (3302) of planetary gear (3300). The threaded diameter (3201) (Fig. 3C(3)) of the threaded shaft (3207) engages with the internal threads (similar to 1110 in Fig 2 A(1) inside the post (3101).
15
Fig 3D(1) and Fig 3D(2) depict the planetary gear (3300) in details. The planetary gear has outer circumference (3304) and inner circumference (3301). The outer circumference (3304) bears the cut out features (3303) while in inner circumference (3301) bears teeth profile (3302).
20
Fig 3E illustrates top view of the distal plate (3400). The distal plate have
supporting features (3401), (3402) corresponding to holes (3501) and (3502)
on intermediating disc (3500), while supporting features (3403) and (3404)
corresponding to protrusions (3503) and (3504) on intermediating disc
25 (3500).
In the shown illustration, the driven spur gear with threaded shaft (3200) and it’s driving planetary gear (3300) are enveloped between the proximal plate (3100) and the distal plate (3400).
26

AMENDED COPY
The driven spur gear (3200) with threaded shaft has external threads. On
its proximal side these external threads of the driven spur gear with
threaded shaft (3200) engages with the corresponding female threaded
5 hole (3105) of the proximal plate (3100) inside its post (3101) while on the
distal side it engage with planetary gear.
The planetary gear(3300) is assembled on to the distal plate(3400) in such a fashion that some of it’s internal teeth (3302) engages with the teeth of
10 driven spur gear with protruding shaft (3200) making it off-center
assembly. The outer surface of the planetary gear (3300) remains protruding out of the assembly on its anterior face. This is to facilitate its rotation by either use of thumb or by the use of some external device that engages the periphery. The corresponding engaging feature can be made
15 all around the periphery like radial holes, protrusions, hex sockets etc. An
external device can be engaged in these feature on periphery to rotate the planetary gear (3300). This rotates the driven spur gear with threaded shaft (3200). The threads of the driven spur gear with threaded shaft (3200) engaged with the said threads of proximal plate in a manner that
20 facilitates the movement of the proximal plate (3100) in either upward or
downward direction depending on the direction of rotation of the driven spur gear with threaded shaft (3200). This results in the decreases or increases in the thickness of the tibial insert trial. The cut out feature (3103) on the proximal plate provides the space through which said
25 planetary gear (3300) protrudes anteriorly. The protruded pins (3104,
3106) are the features to constraint the relative rotation between the proximal (3100) and the distal plates (3400). These pins also maintain the parallel movement when the thickness is increased or decreased in proximal-distal direction. These pins have corresponding holes (3501,
27

AMENDED COPY
3502) in the intermediate disc (3500) and distal plate (3401, 3402). The female threaded hole (3105) in the proximal plate may or may not be a through feature. The through hole feature is advantageous as it facilitates the easy sterilization of the device. 5
Further between the proximal plate (3100) and the distal plate (3400) there is an intermediate disk which along with distal plate forms placeholder arrangement for the driven spur gear with threaded shaft (3200).
10 The placement of the planetary gears on intermediate disc is explained
with the help of Figs 3B, 3C and 3E.
The intermediate disc (3500) has protrusions (3503, 3504) which acts as
placeholder for the planetary gear (3300) and the internal driven spur gear
15 (3200).
The distal plate (3400) and the intermediate disc (3500) has corresponding supporting features (3404, 3403) for the planetary gear (3300) and for the internal driving gear.
20
Further the intermediating disc (3500) having holes (3501) and (3502) corresponding to the protruding pins (3104 and 3106) of said proximal plates (3100) and supporting features of distal plates (3401 and 3402). .
25 The holes (3501, 3502) are to guide the protruded pins (3104, 3106) into
supporting features of the distal plate (3400) during functioning of mechanism. They ensure that there is balanced distal proximal movement of the distal (3400) and proximal plates (3100) during its operation.
28

AMENDED COPY
The diameter (3201) and the height (3203) of the protruding shaft (3207)
and the pitch of the threads (3205) and thickness of each thread of the
shaft of driven spur is calibrated for load. The feature (3202) is the teeth
profile (3202) of the driven spur gear with threaded shaft which engages
5 with the teeth profile (3302) of internal gear. The cut out features (3303) on
the outer circumference are provided to ensure a gripping surface for turning the thumb wheel.
Fig 4 illustrates the aforementioned embodiment with slight variation in
10 variable tibial insert trial (4000). In this embodiment, the threaded shaft
(4103) is an integral part of the proximal plate (4100), instead of on the driven spur gear (3200 in Fig. 3).
The variable thickness tibial trial (4000) comprises of at least one proximal
15 plate (4100), at least one retaining intermediate disc (4500), at least one
spur gear (4200), at least one planetary gear (4300) and at least one distal plate (4400).
Fig 4A(1)and Fig 4A(2) illustrates the proximal plate in details. As shown
20 in figs the proximal plate having post (4101), threaded shaft (4103),
constraining guide pins (4102, 4104).
The intermediating disc and distal plate has similar features as illustrated
in Figs 3B and 3C for the aforementioned embodiment. Like 3B and 3C in
25 Fig 4B and 4E the retaining intermediate disc (4500) and distal plate
(4400) has corresponding protrusions (4503, 4504) and (4403, 4404) to hold planetary gear (4300)and driven spur gear (4200). Like aforementioned embodiment said intermediate disc and distal plate also has corresponding holes (4501, 4502) and supporting features (4402,4401) to
29

AMENDED COPY
guide the protruding pins (4103 and 4104) of proximal plate (4100) during functioning of mechanism.
Further as the threaded shaft (4103) is integral to proximal plate(4100), so
5 in this embodiment the spur gear(4200)(Fig 4C(1)) has internal female
threads(4201) at its internal circumference (4203) (Fig 4C(2)),in comparison to spur gear in Fig 3C where the internal female threads are on the proximal plate.The gear teeth(4202) are corresponding to the gear teeth(4302) on the thumb wheel i.e. planetary gear(4300).
10
Fig 4D(1) and Fig 4D(2) illustrate the planetary gears (4300) in details . It has outer circumference (4304) and inner circumference (4305). The outer circumference (4301) bears the cut out features (4303) while in inner circumference (4301) has teeth profile (4302).
15
The working principle in both aforementioned embodiments remains the same. The planetary gear (4300) rotates manually or through an external device from anterior face of the instrument, which rotates the internal spur gear (4200). The planetary gear and driven spur gear are
20 engaged and fixed on distal plate through retaining mechanism such that
they are capable of being rotate only along its axis while being constrained
to move in any other direction. The axial movement of the two gear (4200,
4300) is constrained by features (4403, 4404) while the proximal movement
of the two gear is constrained by the intermediate plate (4500) which
25 may be welded to) around the periphery of the distal plate (4400).
Fig 5 illustrates another variable thickness tibial trial insert (5000) in which the thickness varying mechanism is cam operated mechanism. The variable thickness tibial insert trial (5000) comprising of at least one
30

AMENDED COPY
proximal plate (5100), at least one cam shaft (5200), and at least one distal
plate (5400) and at least one spring leaf (5300). Figs 5 illustrates the
variable tibial insert in dissembled and assembled form. Fig 5A illustrates
the proximal plate (5100) in detail while Fig 5D and Fig 5E illustrate the
5 distal plate (5400) in detail. Fig. 5B and 5C illustrate the camshaft (5200)
in details while Fig 5F illustrates the leaf spring in detail.
In this illustration shown, the insert used is CR trial insert, which do not have post on the proximal face of proximal plate (5100). In this type, the
10 cam shaft (5200) is assembled in between the proximal plate (5100) and the
distal plate (5400). This cam shaft (5200) is assembled with distal plate (5400) along anterior-posterior direction in such a fashion that it has freedom to rotate along it’s axis. It can be in any suitable direction from where the hexagonal actuation feature (5205) can be preferably operated.
15 This feature can be provided at both ends of the cam shaft (5200) shown in
Fig. 5D-. The cam (5200) can be actuated by an external device having a corresponding hexagonal feature like a screw driver etc. This may be actuated from anterior or medial or lateral end with the help of hexagonal profile (5205) at both the ends of the worm shaft. A spring leaf (5300) is
20 fixed between the distal (5400) and proximal plates (5100). A retaining pin
(5500) is fixed to retain the cam shaft (5200) in place.
As shown in Fig. 5A the proximal plate (5100) has at least one articulating
surface (5101), at least one through slot in middle of the plate in anterior –
25 posterior direction with inners walls (5102,5103), at least one guide bushes
(5106) with slots (5105) to retain spring leaf (5300), and at least one lower surface (5104).
31

AMENDED COPY
As depicted in Fig.5B, the cam (5200) has a special calibrated feature
(5209). This feature (5209) is the one that imparts the cam functionality to
the component. The cam (5200) also has a characteristics hole (5205) at its
anterior calibrated end. The diameter of cam shaft (5214, 5215) is
5 calibrated to rotate and remain in place between proximal (5200) and
distal plates (5400). The grove (5204) at anterior end (5201) on the shaft is
done to constrain the anterior–posterior movement of the shaft with
respect to the proximal (5100) and distal plates (5400). This groove (5204)
is all around the diameter, which allows it to still rotate along the shaft
10 axis. The step diameters (5206) and (5207) can vary or be same. The end
face of shaft should be calibrated to the anterior–posterior length of proximal (5100) and distal plates (5400).
Fig 5C shows the calibrated features of cam (5200). In this particular
15 concept, the cam has three faces (5210, 5211, 5212), which is calibrated for
providing 3 thickness (5213) options to the device. These faces are off-
center to the central axis and the distance of each face from the center is
calibrated to achieve different thicknesses. The face at the top is the one
that defines the current thickness of the insert trial. In this illustration, it
20 is the face marked as (5210). The lower surface (5104) of proximal plate
(5100) rests on this face (5210) of the cam (5200). The cam have
calibrations marked (5213) suitably at one of the faces atleast which may
be viewed easily during surgery. The anterior face (5413) of the distal
plate is suitably marked with a pointer (5414). The thickness of the insert
25 trial is the marking (5213, 5403) on cam (5200) that is pointing towards this
pointer (5214) on distal plate. For example: the thickness shown in illustration Fig 5 is approximately 9 mm.
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AMENDED COPY
Fig 5D shows the distal plate details, slot (5401) for resting of cam’s neck (5203), hole (5402) for retaining pin (5500), top face (5403), cut-out (5404), anterior post (5405), posterior post (5406), bush hole (5407) for cam shaft (5200), end face (5408) of posterior post.
5
The cam is rotated by using an external device corresponding to feature
(5205) to achieve the desired thickness. As cam (5200) rotates, the face
(5210) of the cam feature (5209) disengages and other face (5211 or 5212)
engages with the face (5104) of the proximal plate. This gives a different
10 thickness as calibrated according to the direction of rotation.
Fig 5E shows the anterior face (5413) of anterior post (5405) (Fig 5D),
pointer (5414) (Fig. 5E), guide bushes features (5412).
.
15 The guide bush features (5412) on the distal plate (5400) and (5106) on
proximal plate (5100) are the ones that guide the movement of the distal and proximal plates in distal proximal direction. The cam can have more faces if more thickness options are desired.
20 The leaf-spring (5300) keeps the proximal plate as close to distal plate as
possible. This is the one that keeps the face (5104) of proximal plate butt against the face (5210) of the cam feature (5209). In the assembly, the ends (5302) of leaf spring are fixed in slots (5105) of proximal plate (5100). The contour (5301) in leaf spring makes sure to stay intact under the cam shaft
25 on it’s neck region (5203). It can have any shape to maintain this
functionality. The posterior end diameter (5202) of cam shaft to go through the slot (5102) on proximal plate and is inserted into the hole (5407) of distal plate (5400). The cylindrical features (5206, 5207) of cam
33

AMENDED COPY
shaft are seated onto the slot (5401) of distal plate (5400). The retaining pin (5500) is then fixed into retaining hole (5402) of distal plate.
All concepts illustrated above for fig. 1 to fig 5 are shown for Insert Trials
5 with posts. In principle, the concepts are applicable to CR, CS or TS
inserts as well. This can be achieved by the reversal of the bevel gears in
distal proximal direction (as illustrate in figure 6). The threaded shaft
(6001) of bevel gear (6000) is protruding out of the assembly towards the
distal end. The bevel gear (6001) is retained and constrained with proximal
10 plate, allowing it to rotate only and not move in any other direction. After
the proximal cut is prepared on Tibia, a hole or cavity has to be drilled first to allow seating of the insert trail, flushed on proximal cut of the tibia.
The invention is not limited by what has been particularly shown and
15 described by the way of examples:
Example 1:
During trialing procedure the variable thickness trial tibial insert is placed on the implantation site in a manner that proximal plate of variable
20 articulate with the femoral component trial while distal plate rest on
implantation site which is proximal tibia. The variable thickness tibial insert trail has intermediating mechanism enveloped between proximal and distal plate. The intermediating mechanism comprising of at least one combination of gear and thread mechanism and at least one driving gear
25 member with threads In one embodiment the driven gear member with
threads is a driven bevel gear with threaded shaft (1200, 2200) while driving member is driver with pinion gear (1300). The threaded shaft of said driven gear member is engaged with the threads of the post of the
34

AMENDED COPY
proximal plate(1100,2100) while the driven bevel gear of said driven bevel gear with threads is engaged with said distal plate (1400,2400).
When the tibial trial Insert is at place on the implantation site and the user
5 engages the pinion gear of driving member to the driven bevel gear of the
driven gear member with threaded shaft through the hole (2404) of the distal plate (2400) and rotates the driver (1300) along its own axis. The rotation of driver (1300,2300) actuates the rotation of the driven bevel gear with threads (1300,2300) along its own axis which in turn cause the
10 relative motion of proximal plate with respect to the distal plate and vary
the thickness of tibial trial insert (1000,2000). The anterior end of the distal plate (1400,2400) is suitably marked for various thicknesses for each calibrated thickness while there is relative marker (1108,2108) on the proximal plate (1100,2100) to indicate the current thickness of tibial insert
15 trial. For example in Fig 2D the range of thicknesses is 9 mm to 20 mm.
Example 2
In another embodiments the combination of gear and thread mechanism is driven spur gear with threads (3200,4200) with driving member is
20 planetary gear. In this arrangement, some part of outer periphery of the
planetary gear having cut out feature being protruding out of the anterior surface of distal plate there by facilitating the thumb wheel like application to the tibial insert trial. When planetary gear is being rotated by external force is applied on to the cut out features of the planetary gear
25 by user thumb or any external driving member, thickness of tibial insert
trial varies.
Example 3
In alternative embodiment the thickness varying mechanism is cam
operated mechanism. In this mechanism cam shaft (5200) is rotatably
30 retained between the proximal (5100) and distal plate (5400). The shown
35

AMENDED COPY
cam shaft (5200) has at least three faces corresponding to different
predetermined thickness, such that at one time particular face
corresponding to predetermined thickness is slidably engaged with
proximal plate. The tibial insert trial also provides the features on the face
5 of the cam shaft so that cam shaft can be rotated by external driving
member. During trialing the thickness of tibial trial insert having cam
operated mechanism is varied by rotating the cam shaft by disengaging its
engaged face corresponding to particular thickness from the proximal
plate and engaging its other face corresponding to other predetermined
10 thickness. This is done with rotating the cam shaft.
Example 4
In one of the another embodiment the aforementioned concepts for tibial trial inserts are applicable to CR, CS or TS inserts as well in which
15 proximal plate does not have post. In an embodiment the bevel gear and
threaded shaft is integral or assembled with proximal plate instead of being integral to distal plate such that the direction of threaded shaft in the driven bevel gear with thread shaft is toward the distal plate instead of proximal plate as mentioned in aforementioned embodiment.

We claim:
1. Variable thickness tibial insert trial, said tibial insert trial comprising :
- at least one proximal plate (1100, 2100,3100, 4100) having at
least one post (1101,2101,3101,4101) bearing threads
5 (1110,2110,3105,4103),
- at least one distal plate (1400,2400,3400,4400) having at least
one lower resting surface capable of being deployed over
implantation site,
- at least one combination of gear and thread mechanism
10 comprising of at least one driven gear member with threads
(1200,2200,3200,4200) and at least one driving member
(1400,2400,3400,4400),
wherein said threads of said driven gear member with threads
(1200,2200,3200,4200) are being engaged with the threads of the
15 post (1101,2101,3101,4101) of the proximal plate
(1100,2100,3100,4100) while said driven gear member of said
driven gear member with threads (1200,2200,3200,4200) is
engaged with said distal plate in a manner that when said driven gear member with thread (1200,2200,3200,4200) is actuated by
20 said driving member (1300,4300), said proximal plate (1100,
2100,3100,4100) moves in distal-to-proximal direction or vice-versa to provide tibial trial insert with desired thickness without being removed from implantation site, said tibial trial insert being capable of adjustment from minimum thickness to predetermined
25 thicknesses or vice versa.
2. The variable thickness tibial insert trial (1000,2000,3000,4000) as claimed in claim 1, wherein said driven gear member with threads capable of being driven by driving members is selected from the
37

AMENDED COPY
driven bevel gear with threaded shaft (1200,2200) or driven spur gear with threads (3200,4200).
3. The variable thickness tibial insert trial as claimed in claim 2
5 wherein said driven gear member with threads is the driven bevel
gear with threaded shaft (1200,2200), said threaded shaft of said
driven bevel gear with threaded shaft (1200,2200) is engaged with
said threads of the post (1101,2101) of said proximal plate
(1100,2100) while said driven bevel gear of the driven bevel gear
10 with threads (1200,2200 ) is being engaged with said distal plate
via rotating means (2600) and being constrained in constraining surfaces (2409) of distal plate in a manner that said driven bevel gear with threaded shaft (1200,2200) is capable of being rotated along its own axis when operated by said driving member (1300)
15 while being constrained in all other directions thereby providing
the proximal–distal movement or distal-proximal movement to the proximal plate (1100,2100).
4. The variable thickness tibial insert trial as claimed in claim 3,
20 wherein said rotating means is an axial locking pin (2600) while
said constraining surfaces are tab features (2409) made on a cut¬
out feature (2407) of said distal plate (2400) such that said axial
locking pin (2600) facilitates the rotation of said driven bevel gear
with threaded shaft (2200) along its own axis with said tab features
25 constraining the proximal-distal movement of the driven bevel
gear with threaded shaft.
5. The variable thickness tibial insert trial as claimed in claim 3
wherein both said proximal plate (2100) and said distal plate (2400)
30 further having corresponding constraining guiding features (2105,
38

AMENDED COPY
2103) and (2405, 2403) which are engaged to each other in manner
that said proximal plate and distal plates have parallel distal –
proximal movement with respect to each other without being
disassembled from each other when driven bevel gear with thread
5 is operated by the driving member.
6. The variable thickness tibial insert trial as claimed in claim in 3
wherein said distal plate further having at least one hole (1401,
2404) on the surface selected from its medial surface or anterior
10 surface to facilitate the driving of said driven bevel gear with
threaded shaft (2200) by the driving member (1300).
7. The variable thickness tibial insert trial as claimed in claim 3
wherein said driving member (1300) is selected from the device
15 with integrated or detachable pinion gear or device with
characteristic screw end.
8. The variable thickness tibial insert trial as claimed in claim 7,
wherein said driving member is a device (1300) with pinion gear
20 (1305), said pinion gear of device is directly engaged with the
driven bevel gear of said driven bevel gear with thread (1400) through hole (1401) of said distal plate (1400) in a manner that said device when operated facilitates the rotation of bevel gear with thread shaft thereby changing the width of variable tibial insert
25 trial.
9. The variable thickness tibial insert trial as claimed in claim 8
wherein said driving member is a device with characteristic screw
end, the said pinion gear (2500) is a part of said tibial insert trail
30 and has at least one socket hole having characteristics
39

AMENDED COPY
corresponding to said device with characteristics screw end and
being rotatably retained inside the retaining hole of said distal
plate by retaining locking means in a manner that gears of said
pinion gear (2500) engages with the driven bevel gear of said
5 driven gear with threaded shaft (2200) and capable of rotating said
driven gear with thread shaft when said driving member with characterstics end rotates said pinion gear (2500) by engaging to itself to said socket hole (2505) of pinion gear (2500).
10 10. The variable thickness tibial insert trial as claimed in claim 9
wherein said retaining locking mean comprising of at least two dowel pins (2301 and 2302) with said pinion gear having cut out features is being resided inside said retaining hole of the distal plate and said distal plate having holes (2401,2402), such that said dowel
15 pins is being inserted around it its cut out feature through said
holes of distal plate in a manner that said pinion gear is capable of rotating along its own axis while being constrained in other direction.
20 11. The variable thickness tibial insert trial as claimed in claimed 9,
wherein said characteristics end of said driving member is selected from hexagonal end or any other known feature as per characteristics feature of said socket hole (2505) of pinion gear.
25 12. The variable thickness tibial insert trail as claimed in claim 3
wherein at least one surface of distal plate (2400, 3400) or proximal plate(2100, 3100) is suitably marked for calibrated thickness of said variable insert trial such that corresponding proximal plate or distal
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plate has relative marker to indicate the predetermined thickness of the tibial insert trial (1000, 2000).
13. The variable thickness tibial insert trial as claimed in claim 2,
5 wherein said driven gear member is the driven spur gear with
threads (3200), said driving member is an internal planetary driving gear, said driven spur gear of said driven spur gear with threads (3200) has teeth profile (3202) which is being engaged with said planetary driving gear (3500) while said threads of said driven spur
10 gear with threads (3200) being engaged with said threads of said
proximal plate (3100) with combination of said driven spur gear with threads (3200) and internal driving member being deployed on the distal plate (3400) via retaining mechanism such that said driven spur gear with threads provides a distal-proximal moment
15 to said proximal plate (3100) when external force is applied on the
driving planetary gear (3300).
14. The variable thickness tibial insert trial as claimed in claim 13
wherein said planetary gear (3300) having at least one outer (3304)
20 and inner circumference (3301) wherein
said outer circumference (3304) bears at least one cut out feature (3303) while
said inner circumference (3301) of the planetary gear bears
the teeth profile (3302)
25 such that the predetermined teeth of said teeth profile
(3302) of said inner circumference is being engaged with
predetermined teeth of said teeth profiles (3202,3302) of said planetary gear and thereby forming a combination which is being
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deployed on said distal plate in a manner that they form an off-center profile..
15. The variable thickness tibial insert trial as claimed in claim 13
5 wherein said retaining mechanism, said combination of planetary
gear (3300) and driven spur gear with threads (3200) of said driven spur gear with thread is being constrained inside said distal plate by intermediate disc which is being fixed over the distal plate (3400) such that both said intermediate disc (3500) and said distal plate
10 (3400) have corresponding off-center protrusions (3503, 3504) and
(3403, 3404) and said off-center profile of planetary gear (3300) and driven spur gear with threads (3200) is being deployed inside said protrusions between the intermediate disc (3500) and the distal plate (3400) in a manner that movement of driven spur gear with thread
15 (3200) and internal driving planetary gear (3200) is being constrained
in proximal–distal direction when driven spur gear with thread is being rotated by driving planetary gear.
16. The variable thickness tibial insert trial as claimed in claim 13,
20 wherein said proximal plates and the distal plate have corresponding
guiding features with said retaining mechanism facilitating the engagement of said guiding features of proximal and distal plate in a manner that there is the parallel proximal –distal moment of proximal plate with respect to said distal plate.
25
17. The variable thickness tibial insert trial as claimed in claim 13
wherein said cut out features (3303) of said driving planetary gear is being protruded from at least one surface of said distal plate in a manner that when external force is applied on said cut out feature it
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rotates said planetary gear thereby providing the variation in the thickness of the tibial insert trial.
18. The variable thickness tibial insert trial wherein as claimed in claim
5 12, wherein said driven spur gear with threads (3200,4200) is
selected from driven spur gear with threaded shaft (3200) or driven spur gear with internal threads (4300) .
19. The variable thickness tibial insert trial as claimed in claim 18
10 wherein said driven spur gear with threaded shaft (3200), said
proximal plate (3100) has thread at its internal surface of said post such that said threaded shaft of said driven spur gear with threaded shaft is engaged with said internal threads of proximal plate (3100).
15 20. The variable thickness tibial trial insert as claimed in claim 18,
wherein, said driven gear with internal threads, said proximal plate has threaded shaft (4102) is either assembled or integrated at its lower surface such that said internal threads of driven spur gear with internal threads are engaged with said threaded shaft (4102) of
20 proximal plate (4100).
21. Variable thickness tibial insert trial, said variable tibial insert trial (5000) comprising of
- at least one proximal plate (5100) having at least one upper
25 articulating surface (5101),at least one lower surface (5104),
at least one through slot (5102,5103),
- at least one distal plate (5400) having at least one anterior
post (5405) with at least one bush hole and at least one
posterior post (5406) with at least one hole,
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- at least one cam operated mechanism, said cam operated
mechanism has at least one cam shaft (5200) and at least
one external driving member, said cam shaft having at least
one anterior end (5201) and at least one posterior end
5 (5202), and at least one calibrated feature (5209) having at
least three off centered faces (5210,5211,5212) which are
calibrated for providing at least three thickness (5213)
options to said variable tibial trial insert, at least one
characteristic hole (5205),
10 wherein said anterior and posterior ends (5201, 5202) of the cam
shaft (5200) is deployed between said proximal plate (5100) and
said distal plate (5400) in anterior to posterior direction in a
manner that at least one face (5210) of calibrated feature (5209) of
said cam shaft (5200) is slideably engaged with said lower
15 surface (5104) of the proximal plate (5100) while said anterior end
(5201) and posterior end (5202) of said cam shaft (5200) is
rotatably retained in the corresponding anterior and posterior post
(5405,5406) of said distal plate (5400) thereby providing freedom
to said cam shaft (5200) to rotate along its own axis to vary the
20 thickness of variable tibial insert (5000) by disengaging its said
engaged face (5210) corresponding to predetermined thickness
from said proximal plate (5100) and engaging either one of said
other faces (5211,5212) corresponding to other predetermined
thickness to said proximal plate when operated by driving
25 member through characterstic hole (5205).
22. The variable thickness tibial insert trail as claimed in claim 21 wherein said cam operated mechanism further comprising of retaining pin (5500) with cam shaft further having at least one
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grove (5204) cut around its circumference at its anterior end (5201)
such that said grove (5204) of cam shaft is being rotatably kept
inside said bush hole of said posterior post with retaining pin (5500)
being inserted through said grove cut (5204) of the cam shaft, with
5 posterior end being in said hole of said posterior post of distal
plate via through hole slot (5102, 5103) of said proximal plate (5100) in a manner that cam shaft is capable of rotating along its own axis while being constrained in other directions.
10 23. The variable thickness tibial insert trial as claimed in claim 21, said
cam operated mechanism further comprising of at least one leaf spring (5300) having at least two ends (5302) with contour (5301) and said cam shaft further having at least neck region (5207) around at its anterior end (5201) such that said contour (5301) being kept under the
15 neck region (5207) of said cam shaft (5200) anterior end while said
end of said leaf spring is being kept in slots (5105) of said proximal plate thereby providing the arrangement in which said proximal plate (5100) is as close as to the distal plate (5400).
20 24. The variable thickness tibial insert trial as claimed in claim 21,
wherein said cam shaft and distal plate is suitably marked with markings (5213) for calibrated thicknesses in a manner said marking (5213) are visible during implantation process.
25 25. The variable thickness tibial insert trial as claimed in claim 1 wherein
said proximal plate and distal plate is made of material selected from plastic or metal.
26. Variable thickness tibial insert trial, said tibial insert trial (6000)
30 comprising of
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- at least one proximal plate,
- at least one distal plate, said distal plate having wherein said distal plate is being deployed over implantation site having at least one cavity,
5 - at least one combination of gear and thread mechanism
comprising of at least one driven gear member with
threaded shaft and at least one driving member
wherein said threaded shaft of the said driven gear member is
engaged with the cavity of said implantation site through distal plate
10 while said driven gear member of the driven gear member with
shaft is engaged with proximal plate in a manner that when said
driven gear member with thread is actuated by said driving member
said proximal plate moves in distal to proximal direction or proximal-
to-distal direction to provide variable tibial trial insert which is
15 adjustable from minimum thickness to predetermined thicknesses or
vice versa without being removed from implantation site.

20
25

27. The variable thickness tibial insert trial as claimed in claim 26, wherein the driven gear member with threaded shaft (6001) is selected from the driven bevel gear with threaded shaft or driven spur gear with threaded shaft such that said driven gear member of the driven gear member with threaded shaft is embodied inside the proximal plate and distal plate while the threaded shaft of the driven member with threaded shaft is protruding out of said distal plate in a manner that said threaded shaft engages with said cavity.