Stand alone unilateral biportal endoscopy cage

Abstract

The presented invention discloses a stand-alone unilateral biportal endoscopy device (200) for intervertebral fusion, the device (200) comprising: an arthrodesis cage body (208) having a bone grafting cavity (317) for placing bone grafts; a first locking screw (204), attached to an upper surface of the arthrodesis cage body (208), comprising a first anteriorly pointed drilling tip (403); and a second locking screw (210), attached to a lower surface of the arthrodesis cage body (208), comprising a second anteriorly pointed drilling tip (407); wherein the first locking screw (204) and the second locking screw (210) are inclined at an angle to arthrodesis cage body (208), for contacting a plurality of vertebral bodies (101, 102); the device is posteriorly inserted between the vertebral bodies (101, 102) and is closer to centre of rotation and movement axis (CORA) of the vertebral bodies (101, 102)

Description

STAND ALONE UNILATERAL BIPORTAL ENDOSCOPY CAGEFIELD OF INVENTION

[0001] The present invention generally relates to stand alone unilateral biportal endoscopy (UBE) cage. In particular, the present invention relates to stand alone UBE exclusive arthrodesis cage which is placed posteriorly.BACKGROUND OF THE INVENTION

[0002] Bones provide the structure for our bodies. The adult human skeleton is made up of 206 bones which include the bones of the skull, spine (vertebrae), ribs, arms and legs. Bones are made of connective tissue reinforced with calcium and specialized bone cells. Most bones also contain bone marrow, where blood cells are made. The numerous bone conditions affect the population at large, which can make bones weak and more likely to break. The numerous bone conditions include traumatic fractures, osteoporotic vertebral compression fractures, spine deformities, intervertebral disc herniations, degenerative conditions of spine, spinal canal stenosis and spinal instability. Further, spinal cord disorders are conditions that cause damage and deterioration to the spinal cord.

[0003] The spinal cord is a tube-like structure that consists of a bundle of nerves that extends from the base of the brain and down the spine. The spinal cord carries nerve signals from the brain to the rest of the body. The spinal cord is located within the vertebrae (the backbone). The spinal cord is divided into four areas, any of which can be affected by spinal cord disorders. These areas include: Cervical (neck), Lumbar (lower back region), Thoracic (upper back region), and Sacral (pelvis). Spinal cord disorders can originate from either outside or inside the spinal cord. Damage from the outside of the cord is caused by compression of the spinal cord or injury. The spinal cord may be compressed due to a bone fracture, spinal degeneration, or abnormalities such as a hematoma, tumor or herniated disk. Damage from inside the spinal cord can be caused by a number of disorders, such as fluid- filled cavities, blockage of blood supply, vitamin deficiency, autoimmune diseases, multiple sclerosis, and syphilis.

[0004] Spinal instability especially necessitates surgical treatment to provide stability tothe spine. Spinal stability may be provided by various methods, where in-principle the adjoining vertebrae of the functional spinal unit (FSU) (or motion segment) are instrumented with pedicle screw connected to rods and the intervertebral disc is replaced with cage [spacer filled with bone graft]. This minimizes the movement between adjoining vertebrae and hold them in place for a stipulated time, while the bone graft facilitates bone-growth between adjoining vertebrae.

[0005] Spinal fusion connects two or more bones in the spine to make it more stable, correct an anomaly, or reduce pain. The spinal fusion is achieved using instrumentation for fusion of the vertebrae in which a surgeon uses instruments such as rods, plates, pedicle screw with interbody cage, and screws to help bones in the spine fuse or grow together. The level of disruption to the anatomy caused by intent of the surgical treatment can be determine by the invasiveness i.e. scale of dissection for a surgical approach. The decreasing scale of invasiveness for various procedures is: 1. Open surgery 2. Mini open 3. Microscopic 4. Tubular 5. Endoscopic 6. UBE [unilateral biportal endoscopy]. As a general principle, surgical approaches with lesser invasiveness and higher rigid fixation gives the best clinical outcomes. Further, the pedicle screw fixation spans all three columns of spine biomechanics and is currently considered best kind of fixation owing to its cortical bone hold, but it involves additional dissection and instrumentation.

[0006] With the exception of Anterior Lumbar Interbody Fusion (ALIF), currently there are no ‘standalone’ cages available. ALIF is anterior surgical approach, which has to be combined with some other approach for posterior spinal canal decompression. Also, it may not be suitable for all spine pathologies.

[0007] Therefore, there exists a need in the art for unilateral biportal endoscopy (UBE) device which involves minimally invasive surgery. Standalone cage which can be placed posteriorly by UBE are currently non-existent.OBJECTS OF THE INVENTION

[0008] An object of the invention to solve the problem of inconvenient position adjustment of the intervertebral fusion cage in the prior art, the present invention provides a stand-alone unilateral biportal endoscopy (UBE) arthrodesis cage which is placed posteriorly that areconvenient for position adjustment with minimal invasiveness.

[0009] An object of the invention is to provide unilateral biportal endoscopy (UBE) device(and method) which involves spine surgery through key hole skin incisions.

[0010] Another object of the present invention generally relates to stand alone unilateral biportal endoscopy (UBE) cage. In particular, the present invention relates to stand alone UBE exclusive arthrodesis cage.

[0011] Another object of the invention is to provide a stand-alone UBE exclusive arthrodesis cage without the need of pedicle screw fixation and without removing facet joints, thereby improving endoscopic surgery.

[0012] The summary is provided to introduce aspects related to stand alone unilateral biportal endoscopy (UBE) exclusive arthrodesis cage. This summary is not intended to identify essential features of the claimed subject matter nor is it intended for use in determining or limiting the scope of the claimed subject matter.

[0013] The present invention relates to a stand-alone unilateral biportal endoscopy device for intervertebral fusion, the device comprising: an arthrodesis cage body having a bone grafting cavity for placing bone grafts; a first locking screw, attached to an upper surface of the arthrodesis cage body, comprising a first anteriorly pointed drilling tip; and a second locking screw, attached to a lower surface of the arthrodesis cage body, comprising a second anteriorly pointed drilling tip; wherein the first locking screw and the second locking screw are inclined at an angle to arthrodesis cage body, for contacting a plurality of vertebral bodies the device is posteriorly inserted between the vertebral bodies and is closer to centre of rotation and movement axis (CORA) of the vertebral bodies.

[0014] In some embodiment, the arthrodesis cage body is a hollow cephalon caudal metal support. The locking screws have plurality of a threaded serrations arranged on a surface body and a proximal threaded head. The locking screws have a width of 4.5 mm to 5.5 mm and a length of 20 mm to 40 mm. The locking screw is directed at an angle of 30 degree to 45 degree from the arthrodesis cage body.

[0015] As per an embodiment of the present invention, an arthrodesis cage body, for intervertebral fusion by unilateral biportal endoscopy, the cage body comprising: a bone grafting cavity for placing bone grafts; a first hole extending from a posterior surface to an upper surface to engage a first locking screw; a second hole extending from the posterior surface to a lower surface to engage a second locking screw; and wherein the first locking screw and the second locking screw are inclined at an angle toarthrodesis cage body, for contacting a plurality of vertebral bodies and the cage body is posteriorly inserted between the vertebral bodies and is closer to centre of rotation and movement axis (CORA) of the vertebral bodies.

[0016] In some embodiment, the anterior face of the arthrodesis cage body has a smooth tapered anteriorly pointed beak nose. The arthrodesis cage body comprises toothed sides having variable thickness for contacting the plurality of vertebral bodies. The arthrodesis cage body is further comprising a third hole in the center of a posterior surface to engage an insertion rod. The arthrodesis cage body, further comprising a long rectangular slope with a lordotic curve at the anterior surface.

[0017] As per an embodiment of the present invention, a method of inserting a standalone unilateral biportal endoscopy device posteriorly into a disc space is disclosed. The method comprising the steps of: preparing an arthrodesis cage with a bone graft cavity for inserting the device, inserting a first locking screw and a second locking screw; wherein the first locking screw and the second locking screw are inclined at an angle toarthrodesis cage body, for contacting a plurality of vertebral bodies and the device is posteriorly inserted between the vertebral bodies and is closer to centre of rotation and movement axis (CORA) of the vertebral bodies.

[0018] Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings constitute a part of the description and are used to provide further understanding of the present invention. Such accompanying drawingsillustrate the embodiments of the present invention which are used to describe the principles of the present invention. The embodiments are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this invention are not necessarily made to the same embodiment, and they mean at least one. In the accompanying drawings:

[0020] Fig. 1A and IB illustrates a lateral / anteriorposterior view of an intervertebral fusion stand-alone device in accordance with an embodiment of the present invention.

[0021] Fig. 2A and 2B illustrates an enlarged perspective view of stand-alone intervertebral fusion device in accordance with an embodiment of the present invention.

[0022] Fig. 3 illustrates an exploded view of arthrodesis cage body in accordance with an embodiment of the present invention.

[0023] Fig. 4A and 4B illustrates an enlarged view of locking screw in accordance with an embodiment of the present invention.

[0024] Fig. 5A and 5B illustrates a method of implanting a stand-alone arthrodesis cage in accordance with an embodiment of the present invention.

[0025] Fig. 6 illustrates a block diagram showing the method of unilateral biportal endoscopy in accordance with an embodiment of the present invention.

[0026] A more complete understanding of the present invention and its embodiments thereof may be acquired by referring to the following description and the accompanying drawings.DETAILED DESCRIPTION OF THE INVENTION

[0027] The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may bepracticed. Each embodiment described in this invention is provided merely as an example or illustration of the present invention, and should not necessarily be construed as preferred or advantageous over other embodiments. The detailed description includes specific details for the purpose of providing a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.

[0028] Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “less than,” “approximately” etc. is not limited to the precise value specified. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value.

[0029] In accordance with embodiment of the present invention, Fig. 1A and IB illustrates a lateral / anterior posterior view of intervertebral fusion stand-alone device. The stand-alone device includes an arthrodesis cage body, a bone grafting chamber, a first locking screw attached to an upper surface of the cage; and a second locking screw attached to a lower surface of the cage for the Spinal fusion.

[0030] As illustrated in Fig. 1, the stand-alone device (100) is intended to be inserted between adjacent vertebrae (101, 102) posteriorly. The stand-alone device (100) can be manufactured from a bio-stabile polymers includes, such as polyetheretherketone (PEEK). Further, the arthrodesis cage body of the stand-alone device (100) includes a first locking screw (104) and second locking screw (105). The shape of the arthrodesis cage body (103) can also be a circle, an oval, kidney shaped, a trapezoid, a cylinder, or an ellipse, for instance. The best suited shape of the arthrodesis cage body (103) may be is the trapezoid.

[0031] The spinal fusion, also known as spondylodesis or spondylosyndesis, is a surgical technique in which one or more vertebrae are fused together to stop the motion between them. Spinal fusion may be recommended for abnormal curvature of the spine (scoliosis or kyphosis), Injury to the spinal vertebrae, protrusion of the cushioning disk between vertebrae (slipped disk, herniated nucleus pulposus), weak or unstable spine caused by infections or tumors.

[0032] The design of the stand-alone device depends on its material, placement of device, and technique used to deliver device into the interbody or disc space of the spine. The stand-alone device covers more surface area of a vertebral endplates, such as a patient-specific 3D printed cage, helps achieve higher stability by decreasing the forces directly impacting the unsupported area(s) of the endplates.

[0033] Further, the present stand-alone device may be made using one or more materials including titanium metal, ceramics, hydroxiappatite, tricalcium phosphate TCP, and PEEK (polyetheretherketone) material. The device is placed between two vertebral bodies to raise the height of the disc and make the spine more stable. One or more screws are inserted in the vertebral bodies to keep the cage in place and make fusion easier. The stability of a cage is determined by measuring its subsidence or the degree of sinkage or caving in. A successful stand-alone device design is resistant to subsidence.

[0034] The stand-alone device aims to improve the stability and balance of the treated spinal segment, while also relieving pain and restoring function. The objective of stand-alone device includes restoring the height provided by the original intervertebral disc, supporting the front (anterior) part of the spinal column, expanding the bony openings between the vertebrae (foramina), providing more space for spinal nerves and restoring the normal lordotic (s-shaped) curve of the lower (lumbar) spine. Further, objective of stand-alone device includes transferring loads from the upper segments to lower sections of the spine, promoting a solid fusing of the adjacent vertebral segments by promoting bone growth and increasing the spaces within the spinal canal to decrease the compression of neural tissue that may be indirectly compressed. Depending on the number of spinal segments being fused, surgeon may place more than one cage in the spine.

[0035] In accordance with embodiment of the present invention, Fig. 2A and 2B illustrates an enlarged perspective view and top view of stand-alone intervertebral fusion device. The present invention provides the intervertebral device (200) for insertion into a disc space defined by opposing vertebral endplates.

[0036] In accordance with the present invention, there is provided the stand-alone intervertebral fusion device for insertion (posteriorly) into a disc space defined by opposingvertebral endplates having the arthrodesis cage body. The arthrodesis cage body may include a posterior wall having an upper surface and a lower surface, an anterior surface, and a first through hole extending upwards from the posterior surface and a second through hole extending downwards from the posterior surface, the arthrodesis cage body may further include an anterior wall having an upper surface and a lower surface. Further, the arthrodesis cage body may include first and second side walls connecting the anterior and posterior walls, each side wall having an upper surface and a lower surface, a first bone anchor received in the first through hole, a second bone anchor received in the second through hole. The upper and lower surfaces of the anterior wall contact the opposing vertebral endplates, wherein at least one of the upper and lower surfaces of the anterior wall have a controlled subsidence feature. The remainder of the arthrodesis cage body is having an intrinsic strength.

[0037] As illustrated in Fig. 2, a first locking screw (204) of the stand-alone device is attached to the upper surface of posterior end (202) of the arthrodesis cage body (208). The second locking screw (210) is attached to the lower surface of the posterior end (202) of the arthrodesis cage body (208). The posterior end (202) of the arthrodesis cage body (208) comprises at least 2 holes used for attaching the first and second locking screws (204, 210) of the device (200) in a backward inclined or cephalo-caudal manner. The bone grafting chamber is arranged at the arthrodesis surface. Further, the upper surface of the arthrodesis cage body may be saw teeth (207) in shape.

[0038] In accordance with embodiment of the present invention, the size range of the device is variable as per the spinal level, as different levels of spinal segments permit variable space for instrumentations. However, the device itself will be approximate dimensions as below anterio posteriorly 15 mm to 35 mm long range. The anterio posterior slope can be of two options for each cage sizes, which are zero-degree neutral slope and seven-degree lordotic slope. Further, the medio lateral width can be 10 mm to 20 mm range. Furthermore, the cephalon-caudal height can be 8 mm to 14 mm range with 1 mm increments each.

[0039] In accordance with another embodiment of the present invention, an anterior beak of the arthrodesis cage body shall be solid and smaller than the body. The anteriorly pointed tapered nose or beak is for facilitation of easy cage insertion. The posterior face engages with the locking screws for contacting the vertebral bodies. Further, the first locking screw and the second locking screw can be self-drilling with 4.5 mm to 5.5 mm range. Thelocking screws are put in the vertebral bodies to keep the cage in place and make fusion easier. Furthermore, the first locking screw and the second locking screw can be locking with length of 20 mm to 40mm range with 2 mm increments each.

[0040] In accordance with another embodiment of the present invention, the posterior face of the arthrodesis cage body may bear 3 holes, one of each directed cephalic and caudally respectively for the first locking screw and the second locking screw and, one smaller hole in the centre to engage an insertion rod (not shown). The first locking screw and the second locking screw may be directed at an angle of 30 degree to 45 degree variably. Furthermore, the serrations on the cephalic and caudal surfaces can provide anti-slip grip to the metal support.

[0041] In accordance with embodiment of the present invention, Fig. 3 illustrates an exploded view of arthrodesis cage body. The arthrodesis cage body (315) is provided for insertion into a disc space defined by opposing vertebral endplates. A bone grafting chamber (317) for placing bone grafts in the middle of the arthrodesis cage body. The bone graft is contained within the hollow space of the arthrodesis cage body. A fixation element impart compression onto the bone graft. As per the present disclosure, locking screws are the fixation elements, which provide an additional benefit of bone graft compression to the device. As used herein, the term “bone graft” may include both a synthetic bone (such as synthetic hydroxyapatite) and a natural bone (such as allograft). The most preferable bone graft may include an autograft. A skilled person may utilize any suitable graft and the present invention is not limited to the type of graft utilized.

[0042] The design of a cage typically depends on its material, placement, and technique used to deliver it into the interbody or disc space of the spine. Intervertebral fusion cages are designed to separate and hold the vertebrae apart. Enlarging the space between two vertebrae widens the opening of the neural foramina, taking pressure off the spinal nerves that pass through them. Also, the extra space pulls taut the ligaments inside the spinal canal so they don't buckle into the spinal canal. Given the disclosed construction of the present arthrodesis cages, it can firmly grip the disc space and more closely match its anatomy and can retain the normal height of the disc.

[0043] In accordance with the present invention, the arthrodesis cage is made of safematerials like titanium metal, ceramics, hydroxiappatite, tricalcium phosphate TCP, PEEK (polyetheretherketone) material, which are placed in the disc space. The safe materials like PEEK offers several advantages: PEEK cages have a modulus of elasticity similar to that of cortical bone, which may promote even load sharing and stress distribution. This may translate into lower subsidence rates and potentially higher fusion rates. Furthermore, the use of carbon fiber reinforcement may further reduce any differences in elastic modulus between PEEK and bone, PEEK intervertebral fusion cages are biocompatible and the radiolucency of PEEK implants permits improved assessment of fusion on imaging. The PEEK materials are relatively resistant to microbial adhesion and hence associated with lower infection rates than their titanium counterparts.

[0044] In accordance with embodiment of the present invention, the arthrodesis cage body (315) is a hollow cephalon caudal support, and allow the bone graft material within them to grow from one vertebral body to the other vertebral body. The arthrodesis cage body (315) comprises a long rectangular slope with a lordotic curve. Further, an anteriorly pointed beak nose (301) is for facilitation of easy cage insertion. The arthrodesis cage (315) body further comprises toothed sides having variable thickness for locking the first locking screw and the second locking screw at a desired position to dig into the bone, resisting motion forces, and provide immediate, mechanical post-operative resistance to expulsion. The toothed sides of the arthrodesis cage body are attached well to the spine with the screw fixation, so most patients do not need additional instrumentation, such as pedicle screws or post-surgical back braces for fixation and support. Further, a bone graft cavity (317) contained within the hollow arthrodesis cage body (315).

[0045] An advantage of a present interbody cage is that it allows the placement of an implant with a sturdy fixation of the screws, thereby decreasing the risk of a failed fusion (pseudoarthrosis) and providing better expansion of bony spaces for the spinal nerves. These cages can be used when the height of the disc space becomes compressed or collapsed due to disc degeneration or wearing. Therefore, the present cage body is simple in structure, reasonable in design and beneficial to improving fusion efficiency and improving stability of upper and lower vertebral bodies.

[0046] As illustrated in Fig. 3, the arthrodesis cage body (315) having a posterior wall (314) having an upper surface (306) and a lower surface (318), an posterior surface (310),and a first hole (309) extending from the posterior surface to the upper surface and a second hole (308) extending from the posterior surface to the lower surface, an anterior beak nose (301) having an upper surface (302) and a lower surface (311), and first and second side walls (313) connecting the anterior and posterior walls, each side wall having an upper surface (303) and a lower surface (300). The bone graft cavity (317) contained within the hollow arthrodesis cage body (308). A smaller hole (320) in the center a posterior surface (310) to engage the insertion rod. Furthermore, the posterior wall has a first hole surface (307) having a first ring (319) extending therefrom, wherein the first thread has a proximal end portion having a proximal side wall that runs substantially parallel to the ring. In accordance with an embodiment of the present invention, the arthrodesis cage body can be inserted through an endoscope (a small tube with a camera at the end that allows the surgery to be done through several one-inch incisions).

[0047] In accordance with an embodiment of the present invention, Fig. 4A and 4B illustrates an enlarged view of the locking screws, i.e. the first locking screw and the second locking screw. The locking screws have an anteriorly pointed self-drilling tip inclined at an angle to arthrodesis cage body, for contacting the vertebral bodies. Further, the locking screws have a posterior threaded head which fit into the corresponding arthrodesis cage body and gets locked-in.

[0048] In accordance with embodiment of the present invention, the locking screws have a plurality of threaded serration, which are arranged on the upper surface or the lower surface between the face and the rear inclined surface for self-drilling mechanism. Further, the locking screws may have a width of 4.5 mm to 5.5 mm and a length of 20 mm to 40 mm for facilitation of easy drilling. Furthermore, the locking screws having the approximate dimensions of anterio posteriorly 20 mm to 40 mm long range for locking the screw at a desired position of the cage. This insertion provides a precise adjustment of the device in the vertebra to achieve a desired bone fusion.

[0049] As illustrated in Fig. 4, the locking screws (400) have a first locking screw (400A) received in the first hole (405) and having a distal tip (403), an intermediate shaft (406) having a first thread (401), and a proximal threaded head (402). Further, a second locking screw (400B) received in a second hole (404) and having the distal tip (407), the intermediate shaft (408) having a second thread (409), and the proximal threaded head (410).The plurality of a threaded serrations (401, 409) are arranged on the upper surface or the lower surface between the face. Further, the locking screws (400) have an anteriorly pointed tip (403,407). Furthermore, the locking screws (400) can be tapped into a predrilled hole which can lead to a faster and easier insertion of the fixation locking screws (400) without the risk of stripping out a threaded hole and losing fixation strength.

[0050] In accordance with the present invention, the self-drilling mechanism provides the screw with a pointed drilling tip which eliminates need of pilot hole drilling prior to the screw insertion. This mechanism reduces the manipulations and instrumentations required during surgery. The locking mechanism of the screw has threads on the side of screw head which engage with the threads on the inner side of screw hole of the cage. Hence, the screw locks itself with the cage and becomes one single unit, despite being different elements. This reduces the chances of screw loosening afterwards and makes it fixed angled device giving rigid stability. Further, this increases the chances of bone fusion as it reduces independent micro-motion of various elements.

[0051] In accordance with the present invention, the locking screws are made of safe materials like titanium metal, ceramics, hydroxiappatite, tricalcium phosphate TCP, PEEK (polyetheretherketone) material, which are placed in the disc space. The safe materials like PEEK offers several advantages: PEEK cages have a modulus of elasticity similar to that of cortical bone, which may promote even load sharing and stress distribution. This may translate into lower subsidence rates and potentially higher fusion rates. Furthermore, the use of carbon fiber reinforcement may further reduce any differences in elastic modulus between PEEK and bone, PEEK intervertebral fusion cages are biocompatible and the radiolucency of PEEK implants permits improved assessment of fusion on imaging. The PEEK materials are relatively resistant to microbial adhesion and hence associated with lower infection rates than their titanium counterparts.

[0052] In accordance with the present invention, the spinal fusion is achieved using instrumentation for fixation of the vertebrae in which a surgeon uses instruments such as screw with interbody cage, and screws to help bones in the spine fuse, or grow together. The center of rotation of the vertebra was defined as the intersection between the vertebral axis and the sacral axis. The device may be placed at an intervertebral disc (IVD) space and hence closer to a center of rotation and movement axis (CORA) of the functional spine unit (FSU).Also, the cage itself has two screws which are placed into the vertebrae body and which both locks into the cage making it a fixed angle device with more rigid fixation. Hence, unlike conventional cage devices, present device may not require additional pedicle screw fixation, thus avoiding relevant complications.

[0053] The present invention, aims to achieve a solid fusion between vertebral bodies, virtually eliminating any motion between them. This is expected to relieve the back pain and avoid the risk of further neurological deficit. A variety of other techniques have been used conventionally, such as, interlaminar clamps, polyaxial screw and rod fixation, screw fixation and lateral mass screws. However, they do not ensure elemincation of motion between vertebral bodies, as they are not positioned at the motion point of the vertebral bodies. However, as per the present invention, the position of the screw fixation is closer to the centre of axis of rotation and lateral bending, which provides better control of movements than other techniques which rely on peripheral fixation. Thus, present screw fixation is an effective technique for the fusion of the vertebral bodies. It provides superior fusion rates, and is particularly important in subjects at risk for nonunion.

[0054] To further explain the device as per the present invention, it is imperative to first discuss the limitations of the conventional devices. In a human spine, a motion between adjacent vertebrae primarily occur at an intervertebral disc level. There are three types of motion between adjacent vertebrae i.e. in a sagittal plane, a coronal plane and an axial plane. The sagittal plane separates the left and right sides of the body and helps in flexion extension. The coronal plane separates the front (anterior) and back (posterior) of the body and helps in lateral bending. The axial plane separates the upper (superior) and lower (inferior) halves of the body and helps in rotation to left and right. In case of a spine injury, a graft is usually inserted to promote bone fusion and healing; in which different types of motions (as listed above) must be restricted so as to provide proper fusion. To limit such motion, conventionally, pedicle screws on either side of the vertebral are connected with rods. The two pair of pedicle screws were placed at posterior surface of the vertebrae and are connected to rods to restrict motion that is primarily occurring anteriorly at the disc level. However, as the motion is primarily occurring anteriorly at the disc level, the restriction to the motion, as provided by the pedicle screws, is inefficient. Further, inserting of pedicle screws is a rather complex procedure, required additional dissection and instrumentation.

[0055] On the other hand, as per the device provided by the present invention, the locking screws directly hold the adjoining vertebral body and reside in the vertebral space. Accordingly, the present device is placed at the disc level holds the vertebral near the motion site and thus provides efficient restriction to the motion, without need of additional dissection and instrumentation. The screw fixation can be closer to a centre of rotation and movement axis (CORA) of the vertebral bodies for providing most efficient restriction to the motion.

[0056] Another relevant characteristic of the stand-alone device of the present invention is that it is placed posteriorly. In this regard, one of the primary intentions of fusion surgery is to sufficiently decompress the spinal cord. Being a posteriorly based device, it not only addresses the disc related pathology, but also address the posterior pathologies like ligamentum flavum hypertrophy, facet arthrosis, spinal canal stenosis, adding therapeutic benefits and improving clinical outcomes.

[0057] Still another relevant characteristic of the stand-alone device of the present invention is that its an endoscopic device. In this regard, the size, proportions and related instrumentations of our device are aptly suited to be placed endoscopically which is specifically UBE; thus avoiding open surgery and minimizing the relevant complications of open surgery. Accordingly, the present device eliminates the need to remove facet joints of the vertebrae (as required conventionally).

[0058] Fig. 5A and 5B illustrates a method of implanting a stand-alone device in accordance with the present invention. A method of inserting a present device is described herein. The present invention discloses a method of securing an intervertebral stand-alone unilateral biportal endoscopy device into an intervertebral disc space with fixation elements, and numerous implant embodiments therefor. Further, equipment’s such as a cage insertion rod, a screw insertion screw holding drivers with protection sleeve and the pilot hole drilling instruments are required during the surgery.

[0059] Unilateral biportal endoscopy (UBE) is a method which involves spine surgery through key hole skin incisions. UBE is mainly used for decompression and discectomy. The present invention provides a stand-alone unilateral biportal endoscopy device for posterior or transforaminal or UBE surgery. The device of the present invention allows the surgeon tocreate a smaller incision and access site for the device because direct access that is parallel to the disc space is provided. It is performed through two separated incisions made on one side of the posterior surface of the body as desired. The cephalic viewing or scope port is transverse of about 1 cm or less. Further, the caudal instrumentation port is about 2 cm or less transverse incision. Both the incisions are about 1-2 cm lateral to the midline in coronal plane and in sagittal plane they are angled so as to triangulate at the decided disc level. Furthermore, the triangulation is achieved with the help of Image Intensifying Television (ITTV).

[0060] The Surgical techniques of Unilateral biportal endoscopic decompression is disclosed herein. After induction of general anesthesia, the patient is placed prone with the abdomen free over the radiolucent relton-Hall support. The skin and the surgical field are prepared in the usual manners. UBE surgery is performed under continuous normal saline irrigation. It is critical to ensure that the final layer of draping is waterproof and a smooth drainage system for the saline outflow is properly set up. In order to obtain a true anterior- posterior image, the fluoroscope should be tilted parallel to the disc space. The spinal levels of interest are determined using biplanar fluoroscope and marked on the skin. Further, the decompression procedures are performed according to the following steps of drilling the ipsilateral lamina from its lower margin cranially until the origin of ligamentum flavum and underlying epidural fat are exposed, separate the ligamentum flavum from the under surface of contralateral lamina using a blunt neural dissector, drill the under surface of contralateral lamina until the lateral recess is almost reached. In the cases of severe stenosis, the spinous process and facet joints are usually hypertrophic and deformed. Removing more bone from the base of the spinous process would widen the laminotomy window and provide easier access to the contralateral lateral recess. Further, the decompression procedures are performed according to the following steps of separating the contralateral ligamentum flavum from its attachment on the lamina, and decompress the contralateral lateral recess and foramen using small and curved Kerrison punches, drill the upper laminar margin of the lower vertebra and then detach the ligamentum flavum from its caudal attachment, remove the contralateral half of the ligamentum flavum and decompress the lower surface of the contralateral facet joint to free the contralateral traversing nerve root, perform ipsilateral decompression by drilling the medial margin of the ipsilateral lamina and facet joint. The facet drilling may be very conservative to preserve the facet joint as much as possible and remove the ipsilateral half of the ligamentum flavum, free the ipsilateral traversing nerve root, and check residual stenosis, insert a small caliber suction drain tube after hemostasis, perform interbody fusion using alarge-channel endoscope with the facet removed to create working space for disc preparation and insertion of the interbody cage and perform final check with intraoperative fluoroscopy to confirm the interbody cage and screws positions. Therefore, UBE decompression techniques, safely perform adequate decompression while preserving the facet joints via the posterior interlaminar approach.

[0061] In accordance with the present invention, the device is placed and positioned per the surgeon preference, the fixation elements are inserted up against a proximal face of the cage. The arthrodesis cage body may orient or adhere cephalo-caudally with the respective vertebral end plates. The neutral design the cehalo-caudal angle is zero, while with the lordotic design the cephalo caudal angle is 7-8 degrees sloping posteriorly as per clinical indications. This insertion method can reduce the influence of a limited visual field and operative restrictions.

[0062] As illustrated in Fig. 5, the method of unilateral biportal endoscopy is a method whereby two pathways, that is, an endoscopic portal (A) and a working portal (B) perforate a surgical site, a surgical instrument set (504) is inserted through the working portal (B) while an endoscope (505) is inserted through the endoscopic portal (A), thereby treating the surgical site. In some instances, the surgical instrument may be inserted through the endoscopic portal (A) while the endoscope (505) may be inserted through the working portal (B). The stand-alone device placed in their desired locations, the fixation elements may further provide compression onto the arthrodesis cage. Therefore, the present method of inserting the device enables minimum invasion with fewer scars and less risk of muscle damage, bleeding, and infection, thereby achieving a rapid therapeutic effect.

[0063] In accordance with the present invention, Fig. 6 illustrates a block diagram showing the method of unilateral biportal endoscopy.

[0064] As illustrated in block diagram Fig. 6, the method (600) of inserting a standalone unilateral biportal endoscopy device for intervertebral fusion includes a step of preparing (601) an arthrodesis cage with a bone graft for inserting the device, and inserting (602) stand-alone unilateral biportal endoscopy device .

[0065] In accordance with the present invention, subsequently the step of preparing andinserting the stand-alone device for intervertebral fusion. The posterior face of the arthrodesis cage body may bear 3 holes, one of each directed cephalic and caudally respectively for the first locking screw and the second locking screw and, one smaller hole in the center to engage an insertion rod (not shown). The step of inserting (602) stand-alone unilateral biportal endoscopy device includes inserting an arthrodesis cage body (603), inserting a first locking screw (604) and inserting a second locking screw (605). The locking screws are inclined at an angle toarthrodesis cage body, for contacting a plurality of vertebral bodies. The first locking screw attached to an upper surface of the cage and the second locking screw attached to a lower surface of the cage for the Spinal fusion. The screw fixation in present device is closer to the center of rotation and movement axis (CORA) of the vertebral bodies at a spinal level. It may not require additional pedicle screw fixation and removal of facet joints.

[0066] In accordance with the present invention, UBE surgery have three distinct advantages as bloodless surgical field, magnification and closer view and larger viewing screen with better colour contrast and picture quality. Hence the chances of neuro-vascular injury will be greatly reduced by UBE cage compared to conventional cages. Further, the pedicle screws themselves are independent source for neuro-vascular injuries. Whereas in our invention of UBE cage the entire need for pedicle screws is eliminated leading to drastic reduction in such complications, the symptom recurrence can be due to fresh injury or due to inadequate decompression of the spinal canal. Hence chances of recurrence of injuries are least likely.

[0067] Accordingly, the claimed invention renders a technical effect by enabling to achieve low device cost, less time-consuming, ease of posterior endoscopic surgery (i.e less cumbersome) and do not require pedicle screw fixation and removal of facet joints i.e. less dissection.

[0068] The terms “or” and “and / or” as used herein are to be interpreted as inclusive or meaning any one or any combination. Therefore, “A, B or C” or “A, B and / or C” may mean “any of the following: A; B; C; A and B; A and C; B and C; A, B and C.” An exception to this definition will occur only when a combination of elements, functions, steps or acts are in some way inherently mutually exclusive.

[0069] Any combination of the above features and functionalities may be used in accordance with one or more embodiments. In the foregoing specification, embodiments have been described with reference to numerous specific details that may vary from implementation to implementation. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. The sole and exclusive indicator of the scope of the invention, and what is intended by the applicants to be the scope of the invention, is the literal and equivalent scope of the set as claimed in claims that issue from this application, in the specific form in which such claims issue, including any subsequent correction.

Claims

WE CLAIM:

1. A stand-alone unilateral biportal endoscopy device (200) for intervertebral fusion, the device (200) comprising: an arthrodesis cage body (208) having a bone grafting cavity (317) for placing bone grafts; a first locking screw (204), attached to an upper surface of the arthrodesis cage body (208), comprising a first anteriorly pointed drilling tip (403); and a second locking screw (210), attached to a lower surface of the arthrodesis cage body (208), comprising a second anteriorly pointed drilling tip (407); wherein the first locking screw (204) and the second locking screw (210) are inclined at an angle to arthrodesis cage body (208), for contacting a plurality of vertebral bodies (101, 102); the device is posteriorly inserted between the vertebral bodies (101, 102) and is closer to centre of rotation and movement axis (CORA) of the vertebral bodies (101, 102).

2. The device (200) as claimed in claim 1, wherein the arthrodesis cage body (208) is a hollow cephalon caudal metal support.

3. The device (200) as claimed in claim 1, wherein the locking screws (204, 210) have plurality of a threaded serrations arranged on a surface body and a proximal threaded head (410).

4. The device (200) as claimed in claim 1, wherein the locking screws (204, 210) have a width of 4.5 mm to 5.5 mm and a length of 20 mm to 40 mm.

5. The device (200) as claimed in claim 1, wherein the locking screw (204, 210) is directed at an angle of 30 degree to 45 degree from the arthrodesis cage body (208).

6. An arthrodesis cage body (315), for intervertebral fusion by unilateral biportal endoscopy, the cage body (315) comprising: a bone grafting cavity (317) for placing bone grafts; a first hole (309) extending from a posterior surface (310) to an upper surface (306) to engage a first locking screw (204);a second hole (308) extending from the posterior surface (310) to a lower surface (318) to engage a second locking screw (210); and wherein the first locking screw (204) and the second locking screw (210) are inclined at an angle to arthrodesis cage body (208), for contacting a plurality of vertebral bodies (101, 102) and the cage body (315) is posteriorly inserted between the vertebral bodies (101, 102) and is closer to centre of rotation and movement axis (CORA) of the vertebral bodies (101, 102).

7. The device as claimed in claim 1 to 6, wherein anterior face of the arthrodesis cage body (208,315) has a smooth tapered anteriorly pointed beak nose (301).

8. The device as claimed in claim 1 to 6, wherein the arthrodesis cage body (208,315) comprises toothed sides having variable thickness for contacting the plurality of vertebral bodies.

9. The arthrodesis cage body (315) as claimed in claim 6, further comprising a third hole (320) in the center of a posterior surface (310) to engage an insertion rod.

10. The arthrodesis cage body (315) as claimed in claim 6, further comprising a long rectangular slope with a lordotic curve (301) at the anterior surface.

11. A method (600) of inserting a stand-alone unilateral biportal endoscopy device posteriorly into a disc space, the method comprising the steps of: preparing (601) an arthrodesis cage (208) with a bone graft cavity for inserting the device, inserting (602) a first locking screw (204) and a second locking screw (210); wherein the first locking screw (204) and the second locking screw (210) are inclined at an angle to arthrodesis cage body (208), for contacting a plurality of vertebral bodies (101, 102) and the device is posteriorly inserted between the vertebral bodies (101, 102) and is closer to centre of rotation and movement axis (CORA) of the vertebral bodies (101, 102).

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