FORM 2
THE PATENTS ACT, 1970 (39 OF1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[SEE SECTION 10, RULE 13]
A GAP BALANCER INSTRUMENT FOR ASSESSING
AND ADJUSTING GAP BETWEEN FEMUR AND
TIBIA BONES
BIORAD MEDISYS PRIVATE LIMITED
AN INDIAN COMPANY HAVING OFFICE ADDRESS AT
Survey No. 48, 3 & 48 7, Pashan - Sus Rd, Sus, Pune,
Maharashtra 411021

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED
FIELD OF THE INVENTION
[0001] This invention is generally in the field of medical devices and relates to
the use of instruments for installation of an implant during an arthroplasty.
More particularly, the invention relates to gap balancing apparatuses for
performing total knee arthroplasties with kinematic alignment.
5 BACKGROUND
[0002] The natural human knee joint involves the distal end of the femur, the
proximal end of the tibia and a meniscus bearing therebetween. The femur and
tibia are connected by means of ligaments such as, the posterior cruciate
ligament, the lateral collateral ligament, the medial collateral ligament, and the
10 anterior cruciate ligament. These ligaments provide stability to the joint
formed by the femur and tibia (i.e., the knee). The knee joint is a major weight
bearing joint and degenerates more quickly than some other joints in case of
abnormality. Also, the knee joint plays a critical role in ambulation and quality
of life, resulting in great demand for surgical correction of abnormalities.
15 Damage or disease can affect the ability of the natural knee to function
properly. The damage or disease can deteriorate the bones, the articular
cartilage, the ligaments, or some combination thereof. Disease and trauma
affecting the articular surfaces of the knee joint are commonly effectively
treated by surgically replacing the articulating ends of the femur and tibia with
20 prosthetic femoral and tibial implants, referred to as total knee replacements
(TKR).
[0003] Accordingly, there is a need for an instrument which do not increase
the complexity of the reconstruction and overcome the prior art problems. This
invention is therefore directed towards providing gap balancer instrument

designed to simplify the gap balancing technique in TKA and provide accurate
and consistent results which is relatively simple in design and structure and is
highly effective for its intended purpose.
5 SUMMARY
[0004] Embodiment of the present disclosure present technological
improvements as solutions to one or more of the above-mentioned technical
problems recognized by the inventor(s).
[0005] The present invention is related to the Gap Balancer Instrument. The
10 Gap Balancer Instrument comprises a pair of arms, a screw and a scale. The
pair of arms are connected to each other via a scissor mechanism. The pair of
arms comprise a flat structure disposed at one end. The flat structure
comprises variable thicknesses The screw is coupled to the scissor
mechanism. The screw is configured to the actuate the scissor mechanism.
15 The scale is coupled to the scissor mechanism. The scale is configured to
provide a distance between the pair of arms.
[0006] The present invention discloses a Gap Balancer Instrument described
herein is intended for use in orthopaedic surgery, specifically knee
replacement procedures. Achieving proper gap balance between the femur
20 and tibia bones is crucial to ensure optimal joint function and long-term
implant success. The present invention relates to a Gap Balancer Instrument
used for measuring and adjusting the gap between the femur and tibia bones
in knee surgery. The instrument incorporates a jack mechanism that enables
precise adjustment of the gap at different flexion and extension positions. This
25 innovative instrument simplifies the process for surgeons by allowing them to
utilize a single tool to achieve accurate gap adjustments, thereby determining
the required poly thickness in the knee system. The instrument includes a
handle for ergonomic gripping and enhanced control during the adjustment
process. The incorporation of condyle plates facilitates compatibility with an
anterior-posterior (AP) jig instrument for gap assessment and cut adjustment.
A poly thickness marking plate is provided for simultaneous gap
measurement. The instrument features acme threads for efficient high-torque
5 transmission, ensuring user-friendliness and optimal performance.
[0007] These and other features and advantages of the present invention will
become apparent from the following description of the invention that is
provided in connection with the accompanying drawings and illustrated
embodiments of the invention.
10 [0008]It will be appreciated that features of the present disclosure are
susceptible to being combined in various combinations without departing
from the scope of the present disclosure as defined by the detailed description
and drawings below.
BRIEF DESCRIPTION OF THE FIGURES
15 [0009] The summary above, as well as the following detailed description of
illustrative embodiment, is better understood when read in conjunction with
the appended drawings. For illustrating the present disclosure, example
constructions of the disclosure are shown in the drawings. However, the
present disclosure is not limited to specific methods and instrumentalities
20 disclosed herein. Moreover, those in art will understand that the drawings are
not to scale. Wherever possible, like elements have been indicated by identical
numbers.
[0010] Embodiment of the present disclosure will now be described, by way of
example only, with reference to the following diagrams wherein:
25 [0011] Figure 1 illustrates a perspective view of the instrument in accordance
with an exemplary embodiment of the present disclosure.

[0012] Figure 2 illustrates the side view of the instrument with an exemplary
embodiment of the present disclosure.
[0013] Figure 3A illustrate the perspective view of the gap balancer with flat
structure having 5 mm thickness.
5 [0014] Figure 3B illustrate the side view of the gap balancer having flat
structure with 5 mm thickness.
[0015] Figure 4 illustrate the disassembled view of the Gap balancer
instrument with 5 mm thickness flat structure and 5 mm spacer.
[0016] Figure 5 illustrate the perspective view of the spacer.
10 [0017]In the above accompanying drawings, a number relates to an item
identified by a line linking the number to the item. When a number is
accompanied by an associated arrow, the number is used to identify a general
item at which the arrow is pointing.
[0018] Further the figures depict various embodiments of the present subject
15 matter for purposes of illustration only. One skilled in the art will readily
recognize from the following discussion that alternative embodiment of the
structures and methods illustrated herein may be employed without
departing from the principles of the present subject matter described herein.
DETAILED DESCRIPTION OF EMBODIMENTS
20
[0019] The following detailed description illustrates embodiment of the
present disclosure and manners by which they can be implemented. The
words "comprising," "having," "containing," and "including," and other forms
thereof, are intended to be equivalent in meaning and be open ended in that
25 an item or items following any one of these words is not meant to be an
exhaustive listing of such item or items or meant to be limited to only the listed
item or items. It must also be noted that as used herein and in the appended
claims, the singular forms "a," "an," and "the" include plural references unless
the context clearly dictates otherwise.
[0020] As used herein, the terms "proximal" and "distal" should be given their
generally understood anatomical interpretation. The term "proximal" refers to
5 a direction generally towards the torso of a patient and "distal" refers to the
opposite direction of proximal, that is, against the torso of a patient. It should
be understood that the use of the terms "proximal" and "distal" should be
interpreted as if the patient were standing with the knee joint in extension even
though the appliances described herein are generally used with the joint knee
10 in flexion. The intention is to differentiate the terms "proximal" and "distal"
from the terms "anterior" and "posterior" as well as “medial” or “lateral”. As
used herein, the terms "anterior" and "posterior" should be given their
generally understood anatomical interpretation. Thus, "posterior" refers to a
rear portion of the patient, e.g., a rear portion of the knee. Similarly, "anterior"
15 refers to a front part of the patient, e.g., a front part of the knee. Thus,
"posterior" refers to the opposite direction of "anterior." Similarly, the term
"lateral" refers to the opposite direction of "medial." The medial meniscus is on
the inner side of the knee joint. The lateral meniscus is on the outside of the
knee.
20 [0021] The person skilled in the art will recognize many variations,
alternatives, and modifications of the embodiment of the present disclosure. It
should be understood that this invention is not limited to the particular
methodology, protocols, and the like, described herein and as such may vary.
The terminology used herein is for the purpose of describing particular
25 embodiment only and is not intended to limit the scope of the present
invention, which is defined solely by the claims.
[0022] Various modifications to the embodiment will be readily apparent to
those skilled in the art and the generic principles herein may be applied to
other embodiments. For example, although the present disclosure will be

described in the context of gap balancer instrument, one of ordinary skill in
the art will readily recognize that an apparatus can be used at the time of total
knee replacement Thus, the present disclosure is not intended to be limited to
the embodiments illustrated but is to be accorded the widest scope consistent
5 with the principles and features described herein.
[0023] The present disclosure provides technical solutions to the technical
problems identified in the prior art. In the prior art, a typical knee prosthesis
includes a tibial tray, a femoral component, and a polymer insert or bearing
positioned between the tibial tray and the femoral component. An incision is
10 made into the knee joint to expose the bones comprising the joint. Cut guides
are used to guide the removal of the articular surfaces that are to be replaced.
Prostheses are used to replicate articular surfaces. A femoral prosthesis is
implanted on the distal end of the femur, which articulates with a tibial
bearing component and a tibial component is implanted on the proximal end
15 of a tibia to replicate the function of a healthy natural knee.
[0024] Accuracy in implant alignment is an important factor in the success of
a TKA procedure. A one- to two-millimeter translational misalignment, or a
one- to two-degree rotational misalignment, may result in imbalanced
ligaments, and may thereby significantly affect the outcome of the TKA
20 procedure. For example, implant misalignment may result in intolerable postsurgery pain, and may prevent the patient from having full leg extension and
stable leg flexion.
[0025] To achieve accurate implant alignment, prior to preparation (e.g.,
cutting, drilling, reaming, and/or milling) of a bone, it is important to
25 correctly determine the location at which the preparation will take place and
how the bone resections will be oriented. In most surgical methods, an
arthroplasty jig is used to accurately position and orient bone resection
instrumentation, such as a cutting, drilling, reaming, or milling instrument on
bone. The arthroplasty jig may, for example, include one or more apertures
and/or slots that are configured to accept and guide such a bone resection
instrument.
[0026] One of the surgical goals of joint replacement/reconstruction should be
5 to achieve a certain alignment relative to a load axes. While success has been
reported for traditional instruments and mechanical alignment techniques,
alternative alignment methods such as anatomic or “natural” alignment are
being developed. The following disclosure describes various instrument
embodiments designed to reference resected and un-resected aspects of
10 femoral and tibial bone and to allow for alignment of bone preparation to an
anatomic orientation.
[0027] A device for gap balancing comprises a pair of arms, a screw and a
scale. The pair of arms are connected to each other via a scissor mechanism.
The pair of arms comprise a flat structure disposed at one end. The pair of flat
15 structures are configured to get in contact with femur and the tibia for
assessing and adjusting gap and to have adequate placement on bone.
Specially designed flat structures are incorporated into the instrument,
allowing compatibility with an AP jig instrument. This feature permits the
surgeon to assess the gap and make necessary cut adjustments based on the
20 surgical requirements. The flat structure comprises variable thicknesses. A
spacer is coupled to the flat structure for height adjustment. The spacer
comprises a projection on a surface. The projection is inserted in a hole for an
assembly.
[0028] The scissor mechanism comprises pair of sliders. The one end of the
25 pair of sliders are pivoted on the pair of arms and other end of the slider are
slides the pair of groves provided on pair of arms. The pair of sliders are
pivoted at the center. The screw is coupled to the scissor mechanism. The
screw is configured to the actuate the scissor mechanism. The circular

structure is coupled to the screw mechanism. The circular structure is a hollow
structure with threads on an inner surface. The screw is inserted thought the
circular structure.
[0029] The scale is coupled to the scissor mechanism. The scale is configured
5 to provide a distance between the pair of arms. The scissor mechanism
comprises a pointer to provide linear measurements between pair of arms. A
screw head is coupled at a one end of the screw. The screw head is configured
to provide torque to the screw for the rotation. A handle is coupled to the
screw mechanism. The device is equipped with screw, ensuring efficient
10 transmission of high torque. This design enhances ease of use for the surgeon
while maintaining accurate gap adjustments. The surgeon positions the
instrument between the femur and tibia bones during knee surgery. The
scissor mechanism is activated to adjust the gap to the desired level at
different flexion and extension angles. The handle is configured to provide
15 support for holding. The instrument includes a handle with a screw head for
easy gripping and manipulation.
[0030] The present invention provides a gap balancer instrument designed to
simplify the gap balancing technique in TKA and provide accurate and
consistent results.
20 [0031] The present invention provides a single instrument having a
mechanism to adjust the required gap that eliminates multiple gap balancing
instruments.
[0032] It should be noted that the above advantages and other advantages will
be better evident in the subsequent description. Further, in the subsequent
25 section, the present subject is better explained with reference to the figures. In
order to maintain consistency and brevity of reading, the all the figures from
1, 2, 3A, 3B and 4 are explained jointly. Further, the following table lists of
nomenclature and numberings are used in the figure to illustrate the invention
and the nomenclature is further used to describe in the invention the
subsequent paragraph.
Nomenclature Number Nomenclature Number
pair of arms 101, 103 pointer 110
flat structure 102 scissor mechanism 201
scale 104 screw 202
handle 106 circular structure 204
Screw head 107 pair of sliders 206
knob 108 pair of grooves 208
Spacer 402 projection 404
[0033] Referring now to the drawings, in an aspect of the present disclosure,
5 a device 100 for gap balancing is disclosed in Fig. 1. The device 100 for gap
balancing comprises a pair of arms (101, 103), a screw 202 and a scale 104. The
pair of arms (110, 103) are connected to each other via a scissor mechanism
201. The pair of arms (110, 103) comprise a flat structure 102 disposed at one
end. The pair of flat structures 102 are configured to get in contact with femur
10 and the tibia for assessing and adjusting gap. Also, to have adequate
placement on bone. Specially designed flat structures 102 are incorporated
into the instrument, allowing compatibility with an AP jig instrument. This
feature permits the surgeon to assess the gap and make necessary cut
adjustments based on the surgical requirements.
15 [0001] The flat structure 102 comprises variable thicknesses. A spacer 402 is
coupled to the flat structure 102 for height adjustment. The spacer 402
comprises a projection 404 on a surface. The projection 404 is inserted in a hole
304 for an assembly.
[0002] The scissor mechanism 201 comprises pair of sliders 206. The one end
20 of the pair of sliders 206 are pivoted on the pair of arms (110, 103) and other
end of the slider 206 are slides the pair of groves 208 provided on pair of arms
(110, 103). The pair of sliders 206 are pivoted at the centre. The screw 202 is

coupled to the scissor mechanism 201. The screw 202 is configured to the
actuate the scissor mechanism 201. The circular structure 204 is coupled to the
scissor mechanism 201. The circular structure 204 is a hollow structure with
threads on an inner surface. The screw 202 is inserted thought the circular
5 structure 204.
[0003] The scale 104 is coupled to the scissor mechanism 201. The scale 104 is
configured to provide a distance between the pair of arms (101, 103). The
scissor mechanism 201 comprises a pointer 110 to provide linear
measurements between pair of arms (110, 103). The scale 104 positioned
10 sideways on the scissor mechanism 201 to facilitate simultaneous gap
measurement. This feature provides visual cues for determining the required
poly thickness in the knee system.
[0004] A screw head 107 is coupled at a one end of the screw 202. The screw
107 is configured to provide torque to the screw 202 for the rotation. A handle
15 106 is coupled to the screw mechanism 201. The handle 106 is configured to
provide support for holding. The instrument includes a handle 106 with a
screw head 107 for easy gripping and manipulation. The screw head 107
allows the surgeon to smoothly adjust the gap to the desired level.
[0005] Referring to Figure 2(a), the scissor mechanism integrated into the
20 instrument to allow controlled and precise adjustment of the gap between the
femur and tibia bones. This mechanism enables the surgeon to modify the gap
at varying degrees of flexion and extension. The device 100 for gap balancing
includes a handle 106 with a screw head 107 for easy gripping and
manipulation. The screw head 108 allows the surgeon to smoothly adjust the
25 gap to the desired level. The instrument 100 is equipped with screw 202,
ensuring efficient transmission of high torque. This design enhances ease of
use for the surgeon while maintaining accurate gap adjustments. The surgeon
positions the instrument between the femur and tibia bones during knee
surgery. The scissor mechanism is activated to adjust the gap to the desired
level at different flexion and extension angles.
[0006] Referring to Figure 3A and Figure 3B, illustrate the gap balancer with
flat structure 102 having 5 mm thickness. The flat structure 102 comprises a
5 hole 304 on the surface. In one embodiment, the gap balancer comprises a flat
structure with varying thickness. The thickness of the flat structure varies from
the 5 mm to 15 mm.
[0007] Referring to Figure 4 and Figure 5 illustrate the spacer 402 with 5 mm
thickness is attached to the flat structure 102 with thickness 5 mm. The flat
10 structure 102 comprises a hole 304 on the surface and the spacer 402 comprises
projection 404 on the surface.
[0008] During assembly the projection 404 of the spacer 402 is inserted in the
hole 304 provided on the flat structure 102. The thickness of the spacer 402 is
varies from the 5 mm to 15 mm.
15 [0009] In one embodiment, the spacer with thickness varying form 5 mm to
15 mm is attached to the flat structure 102. In another embodiment, the stack
of the spacers 402 are attached to the flat structure 102 to increase the thickness.
[0010] It is observed that use of multiple gap balancing instruments is
eliminated. A device (100) for gap balancing is designed to simplify the gap
20 balancing technique in TKA and provide accurate and consistent results. The
present invention has both technical as well as economic significance.
[0011] While a particular embodiment of the invention has been illustrated
and described, modifications thereof will readily occur to those skilled in the
art. It is understood that the various embodiments, details and constructions
25 and their features described above and illustrated in the attached figures may
be interchanged among the various embodiment while remaining within the
scope of the invention. Additionally, it is understood that various
modifications could be made to any of the elements described herein above
while remaining within the scope of the invention.

We claim:

1. A device (100) for gap balancing, wherein the device (100) comprises:
a pair of arms (101, 103), wherein the pair of arms (101, 103) are
connected to each other via a scissor mechanism (201), wherein the pair
of arms (101, 103) comprise a flat structure (102) disposed at one end,
wherein the flat structure (102) comprises variable thicknesses;
a screw (202), wherein the screw (202) is coupled to the scissor
mechanism (201), wherein the screw (202) is configured to the actuate
the scissor mechanism (201); and
a scale (104), wherein the scale (104) is coupled to the scissor
mechanism (201), wherein the scale (104) is configured to provide a
distance between the pair of arms (101, 103).

2. The device (100) for gap balancing as claimed in claim 1, wherein a screw
head (107) is coupled at a one end of the screw (202), wherein the screw head
(107) is configured to provide torque to the screw (202) for the rotation.

3. The device (100) for gap balancing as claimed in claim 1, wherein the pair of
flat structures (102) are configured to get in contact with femur and the tibia
for assessing and adjusting gap.

4. The device (100) for gap balancing as claimed in claim 1, wherein circular
structure (204) is coupled to the screw mechanism (201), wherein the circular
structure (204) is a hollow structure with threads on an inner surface,
wherein the screw (202) is inserted thought the circular structure (204).

5. The device (100) for gap balancing as claimed in claim 1, wherein a handle
(106) is coupled to the screw mechanism (201), wherein the handle (106) is
configured to provide support for holding.

6. The device (100) for gap balancing as claimed in claim 1, wherein the scissor
mechanism (201) comprises a pointer (110) to provide linear measurements
between pair of arms (101, 103).

7. The device (100) for gap balancing as claimed in claim 1, wherein the scissor

mechanism (201) comprises pair of sliders (206), wherein the one end of the
pair of sliders (206) are pivoted on the pair of arms (101, 103) and other end
of the slider (206) are slides the pair of groves (208) provided on pair of arms
(101, 103), wherein pair of sliders (206) are pivoted at the center.

8. The device (100) for gap balancing as claimed in claim 1, wherein a spacer
(402) is coupled to the flat structure (102) for height adjustment, wherein the
spacer (402) comprises a projection (404) on a surface, wherein the
projection (404) is inserted in a hole (304) for an assembly.

Dated this on,
7th Day of August, 2024