TWI866956B - Expandable and adjustable lordosis interbody fusion system - Google Patents

Abstract

A spinal implant device for placement between vertebral bodies includes a housing, at least one screw member in the housing, and at least one drive shaft operably engageable with the screw member. The housing includes a first shell member and a second shell member. At least the first shell member has step tracking comprising a plurality of individual riser members for receiving the at least one screw member. The height of the plurality of individual riser members may change along the step tracking. The drive shaft may be operable to rotate the at least one screw member, causing the at least one screw member to move on the plurality of individual riser members. The at least one screw member comprises an external helical thread having a thickness configured to fit in the gaps between adjacent individual riser members, and is engageable with the first and second shell members, whereby the first and second shell members move relative to each other in response to the rotation of the at least one screw member to effect an expansion of the housing or a contraction of the housing from the expansion by reversing the rotation of the at least one screw member.

Description

Expandable and adjustable spinal fusion system

The present invention relates to surgical procedures and devices for treating low back pain.

Lumbar fusion is a surgical procedure to correct problems related to the human spine. It usually involves removing the damaged disc and bone from between two vertebrae and inserting a bone graft material that promotes bone growth. As the bone grows, the two vertebrae join or fuse together. Fusing the bones together can help make specific areas of the back more stable and help reduce problems related to nerve irritation at the fusion site. Fusion can be performed on more than one spinal segment.

Intervertebral fusion is a common procedure that removes the nucleus pulposus and/or annulus fibrosus that make up the intervertebral disc at the problem point in the back and replaces it with a cage shaped and sized to restore the distance between adjacent vertebrae to an appropriate degree. The surgical method for performing an intervertebral fusion varies and access to the patient's spine can be through the abdomen or back. Another surgical method used to complete a lumbar fusion in a less invasive manner involves accessing the vertebrae through a small incision on the side of the body. This procedure is known as a lateral lumbar intervertebral fusion.

Once the intervertebral disc is removed from the body during a lateral lumbar intervertebral fusion, the surgeon typically forces different trial implants between the vertebral endplates in a specific area to determine the appropriate size implant to maintain the distance between the adjacent vertebrae. Another consideration is to maintain the natural angle between the lumbar vertebral bodies to accommodate the kyphosis or natural curvature of the spine. Therefore, when selecting a cage for implantation, both the intervertebral disc height and the kyphosis of the spine must be considered. Prior art fusion cages are typically pre-constructed to have top and bottom surfaces that are angled to each other to accommodate the natural curvature of the spine. These values cannot be accurately determined prior to the operation, which is a disadvantage of current procedures. Typically, once the prepared bone graft is of the appropriate size and before it is inserted between the vertebral bodies, it is loaded into the cage implant.

Current lateral interbody fusion cage devices are typically limited to providing height extension capabilities without flexion adjustment capabilities. Patients are subjected to significant invasive activities in implementing a trial-and-error approach to size and fit the interbody fusion cage to the target area for that patient's specific geometry. Bone graft material is typically added and packaged into the fusion device after the desired height extension is achieved and final adjustments are made.

One embodiment of the device includes an expandable housing comprised of opposing housing components. A movable tapered screw-like element having an external helical thread is disposed in the housing and is operably engaged with the top and bottom housing components, pushing them apart to cause expansion of the height of the housing. This feature allows the spacing (height) of adjacent vertebrae to be adjusted when they are in place. The tapered components are arranged in a dual configuration so that when the wedge-shaped components are moved to varying degrees, independent engagement of the tapered components along the lateral portions of the top and bottom housings causes an angular tilt relative to the outer surface of the housing. This feature allows adjustment of the angular relationship between adjacent vertebrae and assists in kyphosis adjustment of the patient's spine. When the surgeon uses the device's features in combination, the device provides an effective in situ adjustment tool when performing lateral lumbar interbody fusion.

Embodiments of the device also include a track structure within the housing for guiding the tapered external helical threaded member into engagement with the top and bottom housing members. The track includes raised elements on each inner surface of the top and bottom housing members that allow interlocking engagement to laterally stabilize the housing when in a retracted position. As the housing expands, the track area provides space for storage of bone graft material. One embodiment may provide an elastic membrane positioned around the housing to prevent bone graft material from seeping out of the cage and provide a compressive force around the cage to provide structural stability to the housing.

Embodiments of the device also include a drive shaft for operating the tapered external spiral threaded member. The drive shaft allows the surgeon to manipulate the shaft by using an auxiliary tool, and the shaft is operable to move the tapered external spiral threaded member to control the expansion of the outer shell and the angular adjustment of the top shell and bottom shell members to install the interbody fusion device in situ. A locking mechanism is provided to prevent the shaft from rotating when the tool is not engaged and after the tool operation is completed. The tool also facilitates the insertion of bone graft material into the fusion body during in situ adjustment.

The embodiments of the present invention allow surgeons to expand the fusion cage and adjust the spinal curvature of the fusion cage in situ during surgery and introduce bone graft material into the surgical site when the device is in place. The embodiments of the present invention thus provide a fusion cage with geometrical flexibility to accommodate different spinal conditions of different patients.

Embodiments of the present invention thus provide a medial cage device for lateral lumbar intervertebral fusion procedures that combines the functions of adjusting both the height extension of adjacent vertebrae and the flexion adjustment to control the angular relationship between the vertebrae. Embodiments of the medial cage device of the present invention also provide a storage capability to retain bone graft material in the medial cage as the disc height and flexion are adjusted in situ.

The present invention also provides devices that can be used in environments other than medium fusion applications. Generally, they can be used to apply isolation effects between adjacent components and make the angular relationship between the applied components variable.

An embodiment of a spinal implant device for placement between vertebral bodies comprises a housing; at least one screw member in the housing; and at least one drive shaft operatively engaged with the screw member. The housing comprises a first housing member and a second housing member. At least the first housing member has a stepped track including a plurality of individual lifter members for receiving the at least one screw member. The height of the plurality of individual lifter members can be changed along the stepped track. The drive shaft can be operated to rotate the at least one screw member so that the at least one screw member moves on the plurality of individual lifter members. The at least one screw component includes an external helical thread, the thickness of which is configured to adapt to the gap between adjacent individual lifter components and can be engaged with the first and second shell components, so that the first and second shell components move relative to each other in response to the rotation of the at least one screw component to expand the shell or to expand and contract the shell by reversing the rotation of the at least one screw component.

An embodiment of a spinal implant device includes a housing; a first pair of screw members and a second pair of screw members in the housing; a first drive shaft that can be operatively engaged with the first pair of screw members and a second drive shaft that can be operatively engaged with the second pair of screw members. The housing includes a first housing member and a second housing member, each having a plurality of individual lifter members. The plurality of individual lifter members of the first and second housing members define a first step-shaped track route along a first side region of the housing and a second step-shaped track route along a second side region of the housing. The height of the plurality of individual lifter members changes along the first and second step-shaped track routes. The first drive shaft is operable to rotate the first pair of screw components so that the first pair of screw components move along the first step rail route. The second drive shaft is operable to rotate the second pair of screw components so that the second pair of screw components move along the second step rail route. The first and second drive shafts are operable independently of each other. Each of the first and second pairs of screw components includes an external helical thread, the thickness of which is configured to fit the gap between adjacent individual lifter components and can be engaged with the first and second shell components, so that the first and second shell components move relative to each other in response to the rotation of the first and/or second pairs of screw components to expand the shell or by reversing. Rotation of the first and/or second pair of screw components causes the shell to expand and contract by itself, wherein when the first and second pairs of screw components are rotated independently at different positions on the first and second step-shaped rail routes, the expansion or contraction degree of the first side area of the shell can be independently adjusted relative to the expansion or contraction degree of the second side area of the shell.

These and other features of the present invention will be described in more detail in the following section entitled "Implementation Methods".

Referring to the drawings, the interbody fusion device is described, shown and disclosed according to various embodiments of the present invention (including preferred embodiments). The interbody fusion device 10 is generally shown in Figure 1. It is composed of an outer shell 12 with a top shell 14 and a bottom shell 16. The entire outer shell can have a length of, for example, 50 mm and a width of 20 mm. The shell material can be composed of appropriate materials such as titanium alloy (Ti-6AL-4V), cobalt chromium or polyether ether copper (PEEK). Other materials that can provide sufficient component integrity and have appropriate biocompatibility are also suitable. The interior of the shell is constructed with stepped tracks 18 and 20 cascading along the sides. As shown in FIG2 , the step rail 18 starts with a continuous rail step with increasing height toward the midpoint of the inner surface of the bottom shell 16 and extends along the rail to a first end of the bottom shell 16. Correspondingly, the step rail 20 starts with a continuous rail step with increasing height toward the midpoint of the inner surface of the bottom shell 16 and extends along the rail to a second opposite end of the bottom shell 16. The step rail 18 includes double rail routes 22 and 24, and the step rail 20 includes double rail routes 26 and 28, as shown in FIG3 . Corresponding step rails 30 and 32 are provided on the top shell 14, as shown in FIG4 . When the device is in a fully compressed state, the top shell 14 and the bottom shell 16 are adjacent to each other, as shown in FIG1 , the step rail 18 and the step rail 30 are engaged with each other, and the step rail 20 and the step rail 32 are engaged with each other.

Individual rail routes include a series of risers or rail steps that are equally spaced to receive the threads of a tapered external helical threaded member. The tapered external helical threaded member provides a wedging action for isolating the top and bottom shells, thereby increasing the height of the shell, resulting in expansion between the vertebrae of the device placed therein. As shown in FIG. 4 , rail route 22 receives a tapered external helical threaded member 34, rail route 24 receives a tapered external helical threaded member 36, rail route 26 receives a tapered external helical threaded member 38, and rail route 28 receives a tapered external helical threaded member 40. Track route 22 is co-linearly aligned with track route 26 so that advancement of tapered external helical threaded members 34 and 38 within the respective track routes occurs within the co-linear alignment. The thread orientations of tapered external helical threaded members 34 and 38 are opposite to one another so that equal rotation thereof will result in movement in opposite directions relative to one another. As shown in FIG4 , shaft 42 advances along the co-linear extension of track routes 22 and 26 and passes through tapered external helical threaded members 34 and 38. Shaft 42 has a square cross-sectional configuration for engaging and rotating tapered external helical threaded members. As shown in FIG5 , a central shaft opening 44 of the tapered external helical threaded member is configured to receive and engage shaft 42. The shaft 42 may include any shape that is effective to produce a spline, such as a hexagon, and the central shaft opening 44 may include a corresponding configuration to receive such a shape. As the shaft 42 is rotated in a clockwise direction by its end 48, the tapered external helical threaded members 34 and 38 are rotated and their respective thread orientations cause the screws to advance away from each other along the track route 22 and the track route 26, respectively. Conversely, as the shaft 42 is rotated in a counterclockwise direction by its end 48, the tapered external helical threaded members 34 and 38 are caused to advance toward each other along the track route 22 and the track route 26, respectively.

Similarly, track route 24 is collinearly aligned with track route 28 so that advancement of tapered externally helically threaded members 36 and 40 within each track route occurs within the collinear alignment. The thread orientations of tapered externally helically threaded members 36 and 40 are opposite to one another so that equal rotation thereof will result in movement in opposite directions relative to one another. In addition, shaft 46 passes through and engages tapered externally helically threaded members 36 and 40. However, the orientation of tapered externally helically threaded members 36 and 40 is opposite to the orientation of tapered externally helically threaded members 34 and 38. In this orientation, as shaft 46 is rotated by its end 50 in a counterclockwise direction, tapered external helical threaded members 36 and 40 are rotated and their respective thread orientations cause the screws to advance away from each other along rail route 24 and rail route 28, respectively. Conversely, as shaft 46 is rotated by its end 50 in a clockwise direction, tapered external helical threaded members 36 and 40 are advanced toward each other along rail route 24 and rail route 28, respectively.

As shown in Figure 2, the stepped track is constructed with a series of risers with increasing heights. For example, each track line has risers 52-60, as shown for the stepped track 18 in Figure 2. As the threads of the tapered external helical threaded member enter the gap between the risers 52 and 54, the positioning height of the tapered external helical threaded member body in the housing 12 increases as it is supported on the risers 52 and 54. As the tapered external helical threaded member continues to advance along the track route, its threads pass through the gap between the lifters 52 and 54 and enter the gap between the lifters 54 and 56, so that the tapered external helical threaded member is further lifted in the outer shell 12 with the support of the lifters 54 and 56. As the tapered external helical threaded member continues to advance along the remaining portion of the stepped lifters 58 and 60, its positioning height is further increased. As the positioning height of the tapered external helical threaded member body increases, the top shell 14 is moved away from the bottom shell 16, as shown in the series of figures shown in Figures 7A to 7C.

The combined effect of rotating the tapered external spiral threaded components causes them to move toward the outer ends of the individual track routes, resulting in the expansion of the housing 12, as shown in Figure 7. The fully expanded housing is shown in Figure 10. The housing 12 can be reduced by reversing the movement of the tapered external spiral threaded components so that they move toward the midpoint of the housing along the individual track routes. The housing will best provide expansion and reduction, resulting in an implant height range of about 7.8mm to 16.15mm in this embodiment. The device of this embodiment of the present invention can be adapted to provide different expansion diameters.

The tapered external helical threaded member pairs in each collinear dual track route can rotate independently of the tapered external helical threaded member pairs in the parallel track routes. In this configuration, the extension degree of the portion of the housing on each collinear track route can be varied to adjust the spinal flexion effect of the device. As shown in the example of FIG. 8 , the tapered external helical threaded members 36 and 40 have specific extension distances along track routes 24 and 28, respectively, so that the top shell 14 is separated from the bottom shell 16, thereby expanding the housing 12. Tapered external helical threaded members 34 and 38 have been extended a shorter distance along parallel rail lines 22 and 26, respectively, resulting in a lesser separation of the portions of the top and bottom shells on rail lines 22 and 26. This effect is illustrated in the series of Figures 15A to 15C, where tapered external helical threaded members 36 and 40 are extended a greater increment apart from each other, while tapered external helical threaded members 34 and 38 are maintained at a constant relative distance from each other.

In Fig. 15A, the individual positioning of the set of tapered external helical threaded members 36-40 is almost the same as the set of tapered external helical threaded members 34-38 on their respective orbits. In this positioning, the top shell 14 is substantially parallel to the bottom shell 16. In Fig. 15B, the set of tapered external helical threaded members 36-40 is further away along their respective orbits, while the set of tapered external helical threaded members 34-38 maintains the same position as in Fig. 15A. In this arrangement, the tapered external helical threaded members 36 and 40 move higher along the side of the top shell 14 than the tapered external helical threaded members 34 and 28 move along the side of the top shell 14, causing the top shell 14 to tilt relative to the bottom shell 16. In FIG. 15C , the set of tapered external helical threaded members 36-40 moves farther along its iso-orbit than the set of tapered external helical threaded members 34-38, causing the top shell 14 to tilt further relative to the bottom shell 16. By independently moving the individual tapered external helical threaded component groups, the device in this embodiment can achieve a spinal flexion effect between 0° and 35°. The device of this embodiment of the present invention can be adapted to provide different spinal flexion inclination sizes.

The tapered external helical threaded member construction includes a body profile having a progressively increasing minor diameter from _Dr1 to _Dr2 as shown in FIG5. The pitch of the thread 33 matches the spacing between the riser elements 52-60 in the track alignment as shown in FIG4. The thread 33 may have a square profile to match the riser inter-member, but other thread shapes may be suitably utilized. The increase in diameter and tapered aspect of the external helical threaded member allows the top shell 14 and bottom shell 16 to move away as described above. Contact at the top of the risers 52-60 is achieved at the minor diameter of the helical threaded member.

A thrust bearing is provided to limit axial movement of the drive shaft within the housing 12. As shown in FIG. 9A , the thrust bearing 62 includes a two-piece shaft construction that fits together and is press-fitted around the end of the shaft. The top 64 of the thrust bearing shaft defines an opening for accommodating a rounded portion 66 of the end of the shaft. In FIG. 9C , the square shaft 42 has a rounded portion 66 having a smaller diameter than the square portion of the shaft. The mating piece 65 of the thrust bearing engages the top 64 to surround the rounded portion 66 of the shaft 42.

Pin elements 68 in the top portion 64 and the bottom portion 65 engage corresponding holes 69 in the mating piece to provide a press fit of the thrust bearing around the shaft. A shaft neck groove 67 may also be provided in the thrust bearing 62. The shaft 42 may have an annular ridge 63 around its rounded portion 66, which is received in the shaft neck groove 67, as shown in FIG. 9C. Thrust bearings are provided at both ends of the drive shaft, as shown in FIG. 9B. As shown in FIG. 6, the thrust bearings limit the axial movement of the drive shaft in the housing.

A safety lock is provided at the proximal end of the device to prevent accidental rotation of the shaft. As shown in Figures 12A and 12B, a safety lock member 70 is arranged to engage the proximal ends of shafts 42 and 46. An opening 73 in the safety lock member 70 is configured to have a cross-sectional configuration shape of the drive shaft (see Figure 13A). A portion of the drive shaft has a narrowed rounded configuration 71 so that the drive shaft can rotate freely while the rounded portion of the shaft is aligned with the safety lock member opening 73 (see Figure 13C). Figure 12B shows this relationship between the safety lock member 70, the thrust bearing 62 and the shafts 42 and 46. When the non-narrowed portion 75 of the shaft is placed in alignment with the safety lock member opening 73, the shaft is prevented from rotating (see FIG. 13B ). FIG. 12A shows this relationship between the safety lock member 70, the thrust bearing 62, and the shafts 42 and 46. A compression spring 77 may be placed between the thrust bearing 62 and the safety lock member 70 to push the safety lock member back onto the square portion 75 of the drive shaft. FIG. 12B shows the lock disengaged when the safety lock member 70 is pushed forward out of alignment with the square portion 75 and is placed in alignment with the rounded portion 71 of the shafts 42 and 46. A support 79 may be provided between the safety lock member 70 and the thrust bearing 62, on which a compression spring 77 may be positioned. The support 79 may be fixedly connected to the safety lock member 70, and an opening may be provided in the thrust bearing 62, through which the support 79 may slide. The support 79 is provided with a head 81 to limit rearward movement of the safety lock member 70 due to the compression force of the spring 77.

Under power screw theory, the interaction of a tapered external helical threaded component with a stepped track facilitates self-locking. In considering the variables used to promote the self-locking aspect of a tapered threaded component, certain factors are relevant. In particular, these factors include the coefficient of friction of the material used (e.g., Ti-6Al-4V Grade 5), the pitch length of the helical thread, and the average diameter of the tapered component. The following equation explains the relationship between the factors that determine whether a tapered external helical threaded component will self-lock as it advances along a stepped track:

The above equation determines the torque required to be applied to the drive shaft engaged with the tapered external helical threaded member to cause the shell member to expand. This torque depends on the average diameter of the tapered external helical threaded member, the load (F) applied by the adjacent vertebrae, the coefficient of friction (f) of the working material, and the lead (l), or in this embodiment, the pitch of the helical thread. All of these factors determine the operating torque required to convert the rotation into linear lift to separate the shell members before completing expansion and flexion of the spine.

The following equation describes the relationship between factors related to the torque required to reverse the rotation of a tapered external helical threaded member descending along a track:

In this equation, the torque (T _L ) required to reduce the tapered external helical threaded component must be positive. When the value (T _L ) is zero or positive, self-locking of the tapered external helical threaded component in the stepped track can be achieved. If the value (T _L ) drops to a negative value, the tapered external helical threaded component in the stepped track will no longer self-lock. Factors that contribute to the failure of self-locking include compressive loads on the cone, insufficient pitch and mean diameter of the helical thread, and insufficient material friction coefficient. The self-locking conditions are shown below:

πfd _m >l

Under this condition, the appropriate combination needs to be selected so that the tapered component has a sufficient average diameter size and the diameter of the product material in this specific application is greater than the multiple of the lead or pitch, so that the tapered component can self-lock in the stepped track. Based on the average value of the patient lying on his side, the cross-sectional area of the lumbar vertebral body is approximately 2239 ^mm2 , and the axial compression force in this area is 86.35N. When Ti-6Al-4V is selected as the working material, the operating torque to expand the shell shell 12 between the L4-L5 vertebrae is approximately 1.312 lb-in (0.148 Nm), and the operating torque to retract the shell shell 12 between the L4-L5 vertebrae is approximately 0.264 lb-in (0.029 Nm).

Alternative embodiments of expandable housings provide different surgical approaches. FIG. 11A shows a housing 100 for a surgeon to approach the lumbar region from the front side of a patient. The overall configuration of the track route of this embodiment is similar to that of device 10, but the drive shaft for moving the tapered external helical threaded member is applied with torque transmitted from a vertical approach. To this end, as shown in FIG. 14, two sets of worm gears 102 and 104 transmit torque to drive shafts 106 and 108, respectively.

FIG. 11B shows a housing 200 for a surgeon to approach the lumbar region from the patient's intervertebral foraminal position. The overall configuration of the track route of this embodiment is also similar to that of the device 10, but the torque is applied to the drive shaft from the offset approach. To this end, two sets of bevel gears (not shown) can be used to transmit the torque to the drive shafts 206 and 208.

The outer shell 12 is provided with a number of perches and open areas on its surface and interior areas to accommodate storage of bone graft material. The gaps between the risers of the cascading step-like tracks also provide areas for receiving bone graft material. A membrane may be provided as a supplement around the outer shell 12 to help maintain compression on the top and bottom shells and secure in the bone graft material. As shown in FIG. 10, extension spring elements 78 may be provided to hold the top member 14 and the bottom member 16 together. These elements may also be used to provide initial tension in a direction opposite to the expansion against the interbody fusion device. The tapered outer helical threaded member is allowed to climb the riser if contact has not yet been made between the outer shell and the vertebral body.

Thus, this embodiment of the interbody fusion device of the present invention is able to expand to provide support between the vertebral bodies and accommodate loads placed on this area. In addition, the interbody fusion device of the present invention is able to achieve a configuration that is able to provide the appropriate kyphosis tilt to the affected area. Therefore, the device provides a significant improvement in patient-specific disc height adjustment.

The device is provided with a tool for operating the interbody fusion device when adjusting it in situ in the human spine. The operating tool 300 is shown schematically in FIG. 16 and includes a handle member 302, a gear housing 304, and torque rod members 306 and 308. The torque rod member is connected to the drive shaft of the expandable housing 12. An embodiment for connecting the torque rod member to the drive shaft of the expandable housing 12 is shown in FIG. 17. In this configuration, the ends 48 and 50 of the shafts 42 and 46 can be provided with hexagonal heads. The ends of the torque rod members 306 and 308 can be provided with receivers of corresponding shapes for clamping around the ends 48 and 50.

In the gear housing 304, the handle member 302 directly drives the torque rod member 308. The torque rod member 308 is provided with a spur gear 310, and the torque rod member 306 has a spur gear 312. The spur gear 312 is slidably received on the torque rod member 306 and can be moved to engage and disengage with the spur gear 310. The spur gear rod 314 engages with the spur gear 312 to engage and disengage the spur gear 312 with the spur gear 310. When the torque rod member 308 is rotated by the handle 302 and the spur gear 312 engages with the spur gear 310, the rotation is transmitted to the torque rod member 306. In this case, the torque rod member 308 rotates the shaft 46 while the torque rod member 306 rotates the shaft 42 to achieve the expansion of the housing 12, as shown in Figures 7A to 7C. By retracting the spur gear rod 314, the spur gear 312 can be disengaged from the spur gear 310, as shown in Figure 20. When the spur gear 312 is disengaged from the spur gear 310, the rotation of the handle 302 only rotates the torque rod member 308. In this case, the torque rod member 308 rotates only the shaft 46, and the shaft 42 remains immobile, so that the top member of the outer shell 12 tilts, as shown in Figures 8 and 15A to 15C, to achieve anterior curvature of the spine.

To achieve expansion of the device in the described embodiment, the operator will rotate the handle member 302 clockwise to engage torque. This applied torque will then engage the compound return spur gear train consisting of spur gears 310 and 312. This series of gears will then cause the torque rod members 306 and 308 to rotate in opposite directions from each other. The torque rod member 308 (aligned with the handle member 302) will rotate clockwise (to the right) and the torque rod member 306 will rotate counterclockwise (to the left). The torque rod members will then rotate the drive shaft of the interbody fusion device 12 to expand it to the desired height.

To achieve flexion, the operator moves the spur gear rod 314 back toward the handle member 302. This disengages the spur gear 312, which is connected to the torque rod member 306, from the entire gear system and, in turn, from the torque rod member 306. As a result, the torque rod member 308 will be the only member engaged with the interbody fusion device 12. This will allow the operator to retract the posterior side of the implant to produce the desired flexion.

Referring now to Figures 21 to 29, various embodiments of the spinal implant device according to the present disclosure will be described.

FIG. 21 is a perspective top view of an exemplary spinal implant device 400 according to an embodiment of the present disclosure. FIG. 22 is a cross-sectional view of the spinal implant device 400. FIG. 23 is a perspective side view of the spinal implant device 400. FIG. 24 is a cut-away front view of the spinal implant device 400. As shown in FIGS. 21 to 24, the exemplary spinal implant device 400 includes an expandable housing 402; a first pair of screw members 404a, 404b; a second pair of screw members 406a, 406b; a first drive shaft 414 engaged with the first pair of screw members 404a, 404b; and a second drive shaft 416 engaged with the second pair of screw members 406a, 406b.

The housing 402 includes a first or bottom housing member 422 and a second or top housing member 424. The bottom housing member 422 may include a plurality of individual riser members 432 (FIG. 23). The top housing member 424 may include a plurality of individual riser members 434 (FIG. 23). The plurality of individual riser members 432, 434 of the bottom housing member 422 and the top housing member 424 may define a first step-like track route 436 along a first lateral region 403 of the housing 402 and a second step-like track route 438 along a second lateral region 405 of the housing 402 (FIG. 22). The height of the plurality of individual riser members 432, 434 may vary along the first and second step-like rail routes 436, 438. For example, the height of the plurality of individual riser members 432, 434 of each of the first and second step-like rail routes 436, 438 may increase from a central portion 440 of the step-like rail extending distally from the central portion. The first and second pairs of screw members 404a, 404b, 406a, 406b may each include an external helical thread having a thickness configured to fit into a gap between adjacent individual riser members (FIGS. 25-26), as described in more detail below.

The first drive shaft 414 is operable to rotate the first pair of spiral members 404a, 404b, thereby moving the first pair of spiral members 404a, 404b on the respective lifter members 432, 434 defining the first step-like track line 436. The second drive shaft 416 is operable to rotate the second pair of spiral members 406a, 406b, thereby moving the second pair of spiral members 406a, 406b on the respective lifter members 432, 434 defining the second step-like track line 438. When the first and second pairs of spiral members 404a, 404b, 406a, 406b rotate, the bottom housing member 422 and the top housing member 424 can move relative to each other, thereby achieving expansion of the housing 402 or self-expansion and contraction of the housing 402 by reversing the rotation of the first and/or second pairs of spiral members. The first and second drive shafts 414, 416 can operate independently of each other. Therefore, when the first and second groups of screw components 404a, 404b, 406a, 406b rotate independently at different positions on the first and second step-shaped rail lines 436, 438, the expansion or contraction degree of the first lateral region 403 of the shell 402 relative to the expansion or contraction degree of the second lateral region 405 of the shell 402 can be independently adjusted.

The positions of the plurality of individual lifter components 432 on the bottom shell component 422 can be arranged to be offset from the positions of the plurality of individual lifter components 434 on the top shell component 424, so that when the outer shell 402 is in the collapsed structure, the plurality of individual lifter components 432 of the bottom shell component 422 can be engaged with the plurality of individual lifter components 434 of the top shell component 424.

The first and second pairs of screw members 404a, 404b, 406a, 406b can each have a tapered configuration and include an external helical thread, as will be described in more detail below in conjunction with FIGS. 25 to 26. The first pair of screw members 404a, 404b can be arranged or configured such that the direction of the external helical thread of the first screw member 404a of the first pair is oriented opposite to the direction of the second screw member 404b of the first pair. Therefore, when the first drive shaft 414 rotates, the first and second screw members 404a, 404b in the first pair move in opposite directions relative to each other in the first step-shaped track route 436. Similarly, the second pair of screw members 406a, 406b may be arranged or disposed such that the direction of the outer helical thread of the first threaded member 406a of the second pair is oriented opposite to the direction of the outer helical thread of the second screw member 406b of the second pair, such that when the second drive shaft 416 rotates, the first and second screw members 406a, 406b in the second pair move in opposite directions relative to each other in the second step-shaped rail route 438.

For example, the first and second pairs of screw components 404a, 404b, 406a, 406b can be arranged so that when the first drive shaft 414 rotates in a first direction, such as clockwise, the first pair of screw components 404a, 404b respectively move distally from the center portion 440 along the first step-shaped track line 436, and when the second drive shaft 416 rotates in a second direction opposite to the first direction, such as counterclockwise, the second pair of screw components 406a, 406b respectively move distally from the center portion 440 along the second step-shaped track line 438.

Alternatively, the first and second pairs of screw members 404a, 404b, 406a, 406b may be arranged such that when the first drive shaft 414 rotates in a first direction, the first pair of screw members 404a, 404b respectively move distally from the center portion 440 along a first step-like track line 436, and when the second drive shaft 416 rotates in a second direction that is the same as the first direction, the second pair of screw members 406a, 406b respectively move distally from the center portion 440 along a second step-like track line 438. Screw with variable root radius and thread thickness

In some embodiments, the first and second pairs of threaded components 404a, 404b, 406a, 406b can be tapered threaded components with variable pitch or root radius and external spiral threads with variable thickness. The variable root radius and thread thickness of screw components can produce a tighter fit between screw components and the individual lifters of shell components, which reduces, minimizes or eliminates the undesirable micro-movement of implanting device between the initial position, expanded position or flexion adjustment position. The variable root radius and thread thickness of screw components also allow more effective overall operation when the screw components are for example moved, for example, climb on higher and higher individual lifters. These features allow for smoother movement and improved mechanical efficiency during expansion, contraction, and flexion adjustments of the implant.

FIG. 25 shows an exemplary screw member 450 according to an embodiment of the present disclosure, which can be used as one of the first and second pairs of screw members 404a, 404b, 406a, 406b. As shown, the threaded member 450 includes an outer helical thread 452 that winds from a first end face 454 to a second end face 456 of the threaded member 450. The screw member 450 can be tapered, for example, with a root radius at the first end face 454 that is different from a root radius at the second end face 456. As used herein, the term "root radius" refers to a dimension of the screw member 450 measured from a central axis 455 of the screw member 450 that is perpendicular to a root surface 458 of the screw member 450.

According to an embodiment of the present disclosure, the screw member 450 may have a variable root radius at one or both end faces of the screw member 450. As shown in FIG. 25 , at the first end face 454, the screw member 450 may have a first root radius R ₁ and a second root radius R ₂ , wherein R ₁ and R ₂ are different, for example, R ₁ is greater than R ₂ as shown. At the second end face 456, the screw member 450 may have a first root radius r ₁ and a second root radius r ₂ , wherein r ₁ and r ₂ are different, for example, r ₁ is less than r ₂ as shown. In some embodiments, the root radius of the screw member 450 may change continuously or continuously from the first end face 454 to the second end face 456. 25, the change from radius _R1 to _r1 can be continuous from the first end face 454 to the second end face 456 of the screw member 450, or the change from radius _R2 to _r2 can be continuous from the first end face 454 to the second end face 456 of the screw member 450. The variable root radius allows the screw member 450 to be simultaneously located on two individual risers at different heights.

According to an embodiment of the present disclosure, the outer thread 452 of the screw member 450 may have a variable thickness. As shown in FIG. 25 , the outer thread 452 may have a first thickness T ₁ at the first end face 454 and a second thickness T ₂ at the second end face 456, wherein T ₁ and T ₂ are different, for example, T ₁ is greater than T ₂ as shown in the figure. According to an embodiment of the present disclosure, the thickness of at least a portion of the thread 452 is constantly changing, or changes continuously or constantly. In some preferred embodiments, the thickness of the entire outer thread 452 may change continuously from the first end face 454 to the second end face 456.

With reference to FIG. 26 , according to embodiments of the present disclosure, the threaded side surface of the screw member 450 may be angled. For example, as shown by line 464 in FIG. 26 , the side surface 460 of the thread of the screw member 450 may be angled, i.e., not perpendicular to the root surface 458 of the screw member 450. According to embodiments of the present disclosure, a portion of the side surface of the lifter member may also be angled. For example, as shown by line 466 in FIG. 26 , a portion of the side surface of the lifter member 434 may be angled or chamfered, i.e., not perpendicular to the end face of the lifter member 434. The angled side surfaces of the screw member and/or lifter member may make contact at different points simultaneously, thereby allowing smooth movement of the screw member along the stairway to the track alignment when torque is applied to the drive shaft causing the screw member to rotate and advance.

The features of the screw member 450 provided by the present disclosure allow the screw member in the gap of the individual lifter to fit more tightly. The tight fit between the screw member and the individual lifter allows the implant to remain stable once implanted in the intervertebral body of the patient's spine, and eliminates or reduces unnecessary micro-movements. This will help to keep the patient's intervertebral space in the position set by the doctor and promote bone fusion in a better way. The tight fit between the screw member and the individual lifter also allows smooth operation during surgery, and once the implant is placed in and between the patient's vertebral bodies, the surgeon uses surgical instruments such as insertion tools to expand and/or spinal flexion adjustment implants. It also allows the generation of fluids and strong traction during surgery. If a patient has a collapsed disc space, this mechanism can be used to distract the disc space to restore the correct disc height.

Extension spring

In some embodiments, an exemplary spinal implant device according to the present disclosure may include one or more extension springs to ensure that the entire implant device remains together. A patient may have severe coronal or sagittal imbalance, which may apply uneven force distribution to the implant device when it is implanted in the patient's body. Uneven force distribution on the internal mechanism can cause the device to disengage. Even before implantation in the patient's body, the device may be dropped, subjected to vibration or rattling, thereby causing the device to disintegrate.

One or more extension springs provided in the implant device of the present disclosure can hold the top shell member and the bottom shell member together during their fully retracted state so that all components in the device remain together if the device is dropped, subjected to vibration or impact.

Extension springs may also be used to maintain opposing forces on the assembly. Once pressure is applied to the top and bottom housing members of the device, the internal mechanism of the device may undergo expansion and/or kyphosis adjustment. For the mechanism to move effectively and correctly, equal and opposite forces may need to be applied. The extension springs provided in the disclosed device may create an initial tension on the mechanism, thereby allowing it to expand and/or undergo kyphosis adjustment when, for example, the patient's vertebrae are not yet in contact with the device.

Once extension and/or flexion adjustment has been made, the extension springs can also be used to hold the end faces or tips of the individual lifters against the root surfaces and threads of the screw members. This can ensure that the entire assembly of the device remains together in the extended position or flexion adjustment position.

Referring now to Figures 21 to 24, implant device 400 may include a first extension spring 472 coupling bottom and top shell components 422, 424 and a second extension spring 474 coupling bottom and top shell components 422, 424. It should be noted that one or more extension springs may be provided in the implant device and fully perform the function. The first extension spring 472 may be coupled to the top and bottom shell components adjacent to the first step-shaped track route. The second extension spring 474 may be coupled to the top and bottom shell components adjacent to the second step-shaped track route. The extension springs 472, 474 may be attached to the top and bottom shell components using any suitable means. For example, the extension springs 472, 474 may have hooks at both ends of the springs, which hook into loops in the bottom and top housing components 422, 424 as shown. The extension springs 472, 474 may also be welded to the top and bottom housing components at the ends of the hooks.

In a surgical situation where the implant is being inserted into a patient with a larger disc space anatomy, the extension springs 472, 474 can apply an opposing force downward on the internal mechanism of the implant 400 to cause it to expand or flexion adjust until it has contacted the patient's vertebral body. In a surgical situation where the implant 400 is being inserted into a patient with a high degree of flexion, kyphosis, or coronal imbalance, the extension springs 472, 474 will apply an opposing force through tension to keep the mechanism of the implant itself in contact. This will enable the physician to place the implant between these unbalanced disc spaces and allow the surgeon to help correct the disc space back to normal sagittal and coronal balance. Bearing Engagement and Implant Ramps

Returning to Figures 21 to 24, in some preferred embodiments, the spinal implant device 400 may include at least one thrust bearing 480, which is configured to limit the axial and/or lateral movement of the drive shafts 414, 416 while allowing the drive shafts to rotate or rotate about the longitudinal axis of the drive shaft. The thrust bearing 480 can be designed to have a ramp-like geometry 486 that allows instruments carrying bone graft materials to be guided into the implant housing 402. This device feature allows for more effective surgical instrumentation to interface with the implant device, ultimately making the surgery more efficient.

FIG. 27 is an exploded view of an exemplary thrust bearing 480 according to an embodiment of the present disclosure. As shown, the thrust bearing 480 may have a yoke-like configuration including a first or top portion 482 and a second or bottom portion 484. When connected, the top and bottom portions 482, 484 of the thrust bearing 480 define a pair of openings or bearing positions for receiving or locking the pair of drive shafts 414, 416, such as at the ends of the drive shafts.

The top and bottom portions 482, 484 of the thrust bearing 480 may be connected by a snap or press fit provided on the top and bottom portions, respectively. For example, as shown in FIGS. 27-29 , the bottom portion 484 of the thrust bearing 480 may include a protrusion or guide 486 shaped and sized to be received in a corresponding recess 488 in the top portion 482 of the bearing 480 by an interference fit. In some preferred embodiments, the snap features in the top and bottom portions 482, 484 of the bearing 480 may be configured so that when the top and bottom portions 482, 484 are connected, a portion of the bottom portion 484 overlaps a portion of the top portion 482, allowing the top and bottom portions 482, 484 to be more "hooked" or connected, as better shown in FIG. 24 .

29, the drive shafts 414, 416 can each have a rounded portion 415 that is smaller in diameter than the square or remaining portion of the drive shaft. The top and bottom portions 482, 484 of the thrust bearing 480 can be configured or sized so that when the top and bottom portions 482, 484 are connected, the rounded portion 415 of the drive shafts 414, 416 is received in the opening or bearing location of the thrust bearing 480, thereby preventing the drive shafts 414, 416 from axial or lateral movement while allowing the drive shafts 414, 416 to rotate or turn about their longitudinal axes. In some embodiments, the drive shafts 414, 416 may each be provided with an annular ridge 417 in the rounded portion 415. The top and bottom portions 482, 484 of the thrust bearing 480 may each be provided with grooves 483, 485 (more preferably shown in Figures 27 and 28) so that when the top and bottom portions 482, 484 are connected, a neck of the bearing is formed. The annular ridge 417 on the drive shaft may be received in the grooves 483, 485 of the bearing 480, thereby providing improved engagement of the traction shaft with the thrust bearing. The implant device 400 may include at least one or preferably two thrust bearings 480 at one or both ends of the drive shaft.

Still referring to Figures 27 to 29, the top 482 of the bearing 480 may include a "ramp-like" geometry or flat section 486 between the two curved end sections. The ramp-like section 486, in conjunction with the top shell 424 of the housing 402, provides easy access for surgical instruments carrying bone graft materials to be guided into the housing of the implant device 400, as better shown in Figure 21.

Still referring to Figures 27 to 29, in some embodiments, the thrust bearing 480 can be configured to accommodate certain variations of the drive shafts 414, 416 during operation of the implant 400. For example, when the implant 400 is in a parallel configuration as shown in Figure 30, the drive shafts 414, 416 are closer. When the implant 400 is in a spinal flexion configuration as shown in Figure 31, the drive shafts 414, 416 are further away from each other. The bearing opening can be configured as a "slit" rather than a perfect circle to accommodate variations, as shown in Figures 30 to 31.

Various embodiments of an expandable and adjustable spinal flexion interbody fusion device have been described. It should be understood that the present disclosure is not limited to the specific embodiments described. Aspects described in conjunction with a specific embodiment are not limited to that embodiment and may be implemented in any other embodiment.

The embodiments are described with reference to the drawings. It should be noted that certain drawings are not necessarily drawn to scale. The drawings are intended only to facilitate the description of specific embodiments and are not intended as a detailed description or as a limitation on the scope of the present disclosure. In addition, in the drawings and description, specific details may be set forth in order to provide a complete understanding of the present disclosure. It will be apparent to a person of ordinary skill in the art that some of these specific details may not be used to implement the embodiments of the present disclosure. In other cases, well-known components may not be shown or described in detail to avoid unnecessarily obscuring the embodiments of the present disclosure.

Unless otherwise specifically defined, all technical and scientific terms used herein have the meanings commonly understood by those of ordinary skill in the art. The singular forms "a", "an", and "the" used in the specification and the accompanying patent applications include plural references unless the context clearly indicates otherwise. The term "or" refers to a non-exclusive "or" unless the context clearly indicates otherwise.

Those skilled in the art will appreciate that various other modifications may be made. All these or other changes and modifications are contemplated by the inventors and are within the scope of the invention.

6-6: Line

10:Mediator fusion system

12: Shell

14: Top shell

16: Bottom shell

18,20: Stairway track

22,22,24,26,28: Track route

30,32: Stairway track

33: Thread

34,36,38,40: External spiral thread components

42: Axis

44: Central axis opening

46: Axis

48,50: End

52,54,56: Lifter

58,60: Step lifter

62:Thrust bearing

63: Annular ridge

64: Top

65:Matching parts

66: Rounded Department

67: Shaft neck groove

68: Sales unit

69: Hole

70: Safety locking component

71: Narrowing rounded structure

73: Safety locking component opening

75: Unnarrowed part

77: Compression spring

78: Extension spring element

79: Pillar

81:Head

100: Shell

102,104: worm wheel

106,108: Drive shaft

200: Shell

300: Operation tools

302: Handle component

304: Gear housing

306,308: Torque rod components

310: Spur gear

312: Spur gear 314: Spur gear rod 400: Spinal implant device 402: Expandable housing 403: First side region 404a, 404b: First pair of screw components 405: Second side region 406a, 406b: Second pair of screw components 414: First drive shaft 415: Rounded portion 416: Second drive shaft 417: Annular ridge 422: Bottom housing component 424: Top housing component 432, 434: Lifter component 436: First stage shape Track route 438: Second stage track route 440: Central part 450: Screw member 452: External helical thread 454: First end surface 455: Central axis 456: Second end surface 458: Root surface 460: Side surface 464,466: Line 472: First extension spring 474: Second extension spring 480: Thrust bearing 482: Top 483,485: Groove 484: Bottom 486: Slope geometry/flat section 488: Notch

The following drawings are used to describe embodiments of the present invention, which are enlarged and emphasized for clarity and are not drawn to scale: FIG. 1 is a side elevation view of the side of the expandable housing device. FIG. 2 is a perspective view of the bottom section of the expandable housing. FIG. 3 is a top plan view of the bottom section of the expandable housing. FIG. 4 is a top plan view of the expandable housing device. FIG. 5 is a perspective view of a tapered external helical threaded component. FIG. 5A is a side elevation view of the side of the tapered external helical threaded component. FIG. 5B is a side elevation view of the front end of the tapered external helical threaded component. FIG. 6 is a cross-sectional view of the device taken along line 6-6 of FIG. 1 . Figures 7A to 7C are a series of views of the side elevation of the device when the device is expanded. Figure 8 is a side elevation of the device showing the device expanded to accommodate the effect of spinal flexion. Figure 9A is a perspective expansion of a thrust bearing for a drive shaft. Figure 9B is a perspective view of the device shaft and thrust bearing. Figure 9C is a top plan view of a cross-section of the engagement area of the device shaft with the thrust bearing. Figure 10 is a side elevation of the housing when expanded. Figure 11A is a top plan view of another device embodiment. Figure 11B is a top plan view of yet another device embodiment. FIG. 12A is a top plan view of the drive shaft disengaged from the locking mechanism. FIG. 12B is a top plan view of the drive shaft engaged from the locking mechanism. FIG. 13A is a cross-sectional view of the locking mechanism. FIG. 13B is a top plan cross-sectional view of the drive shaft disengaged from the locking mechanism FIG. 13C is a top plan cross-sectional view of the drive shaft engaged from the locking mechanism. FIG. 14 is a view taken along line 14-14 of FIG. 11A. FIGS. 15A to 15C are a series of views of side elevations of the end of the device showing the spinal flexion effect when the device is expanded. FIG. 16 is a perspective view of the operating tool. FIG. 17 is a view showing the manner in which an operating tool is attached to a drive shaft of the device. FIG. 18 is a perspective view of a handle of the operating tool in a separated state. FIG. 19 is a perspective view of a gear in a handle used to operate the engagement of two drive shafts. FIG. 20 is a perspective view of a gear in a handle used to operate the disengagement of a single drive shaft. FIG. 21 is a perspective top view of an exemplary spinal implant device according to an embodiment of the present disclosure. FIG. 22 is a cross-sectional view of an exemplary spinal implant device according to an embodiment of the present disclosure. FIG. 23 is a perspective side view of an exemplary spinal implant device according to an embodiment of the present disclosure. FIG. 24 is a cutaway front view of an exemplary spinal implant device according to an embodiment of the present disclosure. FIG. 25 schematically shows a tapered screw member according to an embodiment of the present disclosure. FIG. 26 schematically shows a tapered screw member connected to a separate lifter member according to an embodiment of the present disclosure. FIG. 27 is an exploded view of a thrust bearing member according to an embodiment of the present disclosure. FIG. 28 is a cross-sectional view of a thrust bearing member associated with other components of an exemplary spinal implant device according to an embodiment of the present disclosure. FIG. 29 is a cross-sectional view of a thrust bearing member associated with other components of an exemplary spinal implant device according to an embodiment of the present disclosure. FIG. 30 is a perspective view of an exemplary spinal implant device in a parallel configuration according to an embodiment of the present disclosure. FIG. 31 is a perspective view of an exemplary spinal implant device in a spinal anterior curvature configuration according to an embodiment of the present disclosure.

6-6: Line

10: Mediator Fusion System

12: Shell

14: Top shell

16: Bottom shell

Claims (18)

A spinal implant device for placement between vertebrae, comprising: a housing; at least one screw member in the housing; and at least one drive shaft operatively engaged with the screw member, wherein the housing comprises a first housing member and a second housing member, at least the first housing member having a stepped track, comprising a plurality of individual lifter members for receiving the at least one screw member, the heights of the plurality of individual lifter members being variable along the stepped track, and the drive shaft being operable to rotate the at least one screw member so that the screw member can be moved. The at least one screw member moves on the plurality of individual lifter members, and the at least one screw member includes an outer helical thread, the thickness of which is configured to fit the gap between adjacent individual lifter members and can engage with the first and second shell members, so that the first and second shell members move relative to each other in response to the rotation of the at least one screw member, so that the shell expands or the shell expands and contracts by reversing the rotation of the at least one screw member, and at least a portion of the outer helical thread has a continuously changing thickness. A spinal implant device as claimed in claim 1, wherein the plurality of individual lifter members have angled sides configured to engage with the outer helical thread. A spinal implant device for placement between vertebrae, comprising: a housing; at least one screw member in the housing, wherein the at least one screw member comprises a variable root radius; and at least one drive shaft operatively engaged with the screw member, wherein the housing comprises a first housing member and a second housing member, at least the first housing member having a stepped track, comprising a plurality of individual lifter members for receiving the at least one screw member, the heights of the plurality of individual lifter members being variable along the stepped track , the drive shaft is operable to rotate the at least one screw member so that the at least one screw member moves on the plurality of individual lifter members, and the at least one screw member includes an external helical thread, the thickness of which is configured to fit the gap between adjacent individual lifter members and can engage with the first and second shell members, so that the first and second shell members move relative to each other in response to the rotation of the at least one screw member to expand the shell or to expand and contract the shell by reversing the rotation of the at least one screw member. A spinal implant device as claimed in claim 3, wherein the at least one screw member tapers gradually from a first end face to a second end face and includes a continuously changing root radius from the first end face to the second end face of the at least one screw member. A spinal implant device as claimed in claim 4, wherein the outer spiral thread of the at least one screw member has a continuously changing thickness from the first end face to the second end face. The spinal implant device of claim 5 further comprises at least one extension spring coupled to the first and second shell components, which holds the first and second shell components together at their initial height and/or during expansion and/or contraction of the shell. A spinal implant device for placement between vertebrae, comprising: a housing; at least one screw member in the housing; and at least one drive shaft operatively engaged with the screw member, wherein the housing comprises a first housing member and a second housing member, at least the first housing member having a stepped track, comprising a plurality of individual lifter members for receiving the at least one screw member, the height of the plurality of individual lifter members being variable along the stepped track, at least one extension spring coupled to the first and second housing members, which is arranged at an initial height and/or at an extension and The first and second shell components are held together during the expansion and contraction period, and the drive shaft is operable to rotate the at least one screw component so that the at least one screw component moves on the plurality of individual lifter components, and the at least one screw component includes an external helical thread, the thickness of which is configured to fit the gap between adjacent individual lifter components and can be engaged with the first and second shell components, so that the first and second shell components move relative to each other in response to the rotation of the at least one screw component to expand the shell or to self-expand and contract the shell by reversing the rotation of the at least one screw component. A spinal implant device for placement between vertebrae, comprising: a housing; a first pair of screw components and a second pair of screw components in the housing; a first drive shaft operatively engaged with the first pair of screw components and a second drive shaft operatively engaged with the second pair of screw components, wherein the housing comprises a first housing component and a second housing component, each having a plurality of individual lifter components, the plurality of the first and second housing components The individual lifter members define a first step-like track route along a first side region of the housing and a second step-like track route along a second side region of the housing, the heights of the plurality of individual lifter members vary along the first and second step-like track routes, the first drive shaft is operable to rotate the first pair of screw members to move the first pair of screw members along the first step-like track route, and the second drive shaft is operable to rotate the first pair of screw members to move the first pair of screw members along the first step-like track route. The first and second drive shafts are operable to rotate the second pair of screw components so that the second pair of screw components move along the second step-shaped track route. The first and second drive shafts can be operated independently of each other. Each of the first and second pairs of screw components includes an external helical thread, the thickness of which is configured to fit the gap between adjacent individual lifter components and can be engaged with the first and second shell components, so that the first and second shell components respond to the first and/or second pairs of The screw members rotate relative to each other to expand the housing or the housing expands or contracts by reversing the rotation of the first and/or second pairs of screw members, wherein the expansion or contraction degree of the first side region of the housing can be independently adjusted relative to the expansion or contraction degree of the second side region of the housing when the first and second pairs of screw members are rotated independently at different positions on the first and second step-shaped track lines. A spinal implant device as claimed in claim 8, wherein the outer spiral thread of each of the first and second pairs of screw members has a continuously changing thickness. A spinal implant device as claimed in claim 8, wherein the plurality of individual lifter members have angled sides configured to engage with the outer helical threads of each of the first and second pairs of screw members. A spinal implant device as claimed in claim 8, wherein each of the first and second pairs of screw members includes a variable root radius. A spinal implant device as claimed in claim 8, wherein each of the first and second pairs of screw members tapers gradually from a first end face to a second end face and includes a continuously changing root radius from the first end face to the second end face. A spinal implant device as claimed in claim 12, wherein the outer spiral thread of each of the first and second pairs of screw members has a continuously changing thickness from the first end face to the second end face. The spinal implant device of claim 13 further comprises at least one extension spring coupled to the first and second shell components, which holds the first and second shell components together at an initial height and/or during adjustment and/or expansion and/or contraction of the shell. The spinal implant device of claim 8 further comprises at least one extension spring coupled to the first and second shell components, which holds the first and second shell components together at an initial height and/or during spinal flexion adjustment and/or during expansion and/or contraction of the shell. The spinal implant device of claim 8 further comprises at least one thrust bearing configured to prevent axial and/or lateral movement of the first and second drive shafts, wherein the thrust bearing comprises a first portion and a second portion configured to snap fit together to provide a first bearing portion engaging the first drive shaft and a second bearing portion engaging the second drive shaft. A spinal implant device as claimed in claim 16, wherein the second portion of the stop bearing member includes an intermediate section between the first and second bearing locations, wherein the intermediate section has a ramped geometry that allows an instrument carrying the implant material to be guided into the housing. A spinal implant device as claimed in claim 16, wherein the first and second bearing portions of the stop bearing member are configured to provide openings, and the grooves are configured to accommodate the spatial difference between the first and second drive shafts depending on the degree to which the first side region is independently adjusted relative to the second side region.