A flexible nail-rod system for thoracolumbar spinal internal fixation

Abstract

The present application relates to the field of medical devices, and relates to a flexible nail-rod system for thoracolumbar spinal internal fixation, which comprises a flexible screw, a connector, a rigid rod and a motion retainer, wherein the flexible screw comprises a nail cap, a lock block two, nail beads, a lock block one, a drill bit, a flexible steel wire and a fixing screw; a plurality of nail beads are connected in a head-tail mosaic manner to form a flexible screw body, the flexible screw body is provided with uniformly distributed channels, the flexible steel wire penetrates through the channels, the tail of the flexible steel wire is fixedly connected with the lock block one, the head of the flexible steel wire is slidably inserted into the inside of the nail cap, the drill bit is fixed to the right end of the lock block one, the lock block two is fixed to the right end of the nail cap, the fixing screw is threadedly connected to the inside of the nail cap and clamps the flexible steel wire through the fixing screw, the connector connects the rigid rod and the flexible screw, the motion retainer is fixedly connected with the rigid rod, a plurality of nail beads are connected in series to form the flexible screw body part, and the flexible screw body part can be deflected in any direction within a certain angle and is suitable for the fixation of osteoporotic vertebral bodies.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of medical devices, and relates to a flexible nail-rod system for thoracolumbar spinal internal fixation. BACKGROUND

[0002] In recent years, the number of patients undergoing thoracolumbar spinal surgery is increasing, including thoracolumbar spinal deformity, spinal tuberculosis or tumor, spinal fracture, osteoporotic vertebral compression fracture, etc. The diseased vertebral body itself or spinal surgery often causes local instability of the spine, so internal fixation surgery is required. The common internal fixation method is screw connection with a rigid rod. This connection has high reliability, but due to the excessive rigidity, stress shielding occurs in the fixed segment, causing disuse osteoporosis of the spine, stress concentration of the internal fixation device, and in severe cases, fatigue fracture or loosening of the fixation device, etc. The probability of failure is greater for patients with osteoporosis after rigid internal fixation. In addition, for spinal fractures, the nail-rod system is used to support the spine in the early stage of surgery to reduce the pressure on the vertebral body and intervertebral disc. As the degree of bone healing increases, the stability of the spine improves, and at this time, the fixed segment is expected to have certain flexion and extension activities, which can reduce the fixation strength of the nail-rod system and prevent the adjacent segment from becoming ossified. In addition, the commonly used screws in internal fixation surgery are rigid screws, which have single structure and function and limited application range, and are not suitable for the fixation of osteoporotic or tumor bone destructive vertebral bodies. In order to improve the pull-out resistance of the screw, a long and thick screw specification is often selected, which often poses a risk of vertebral body penetration for patients with small vertebral bodies. SUMMARY

[0003] The present application provides a flexible nail-rod system for thoracolumbar spinal internal fixation to solve the problems of the nail-rod internal fixation system in the prior art.

[0004] The purpose of the present application can be achieved by the following technical scheme: a flexible nail-rod system for thoracolumbar spinal internal fixation, comprising: a flexible screw, the flexible screw comprising a nail cap, a lock block two, a nail bead, a lock block one, a drill bit, a flexible steel wire, and a fixing screw; a plurality of the nail beads are connected in a head-to-tail mosaic manner to form a flexible screw body, a spacing is provided between adjacent nail beads, four groups of uniformly distributed channels are provided in the flexible screw body, the flexible steel wire is threaded in the channels, the tail of the flexible steel wire is fixedly connected with the lock block one, the head of the flexible steel wire is slidably inserted into the inside of the nail cap, the drill bit is fixed to the right end of the lock block one, the lock block two is fixed to the right end of the nail cap, the fixing screw is threadedly connected to the inside of the nail cap and clamps the flexible steel wire through the fixing screw, and the nail cap, the lock block two, the lock block one, the drill bit, and the flexible screw body are all provided with a communication needle guide hole.

[0005] A connector is provided with a rod channel for accommodating a rigid rod and a screw hole for mounting a flexible screw.

[0006] A rigid rod is arranged in the rod channel and pre-tightened by a locking nut.

[0007] A motion retainer includes a support and an end cap, the end cap is fixedly connected with the lower end rigid rod, and the support is slidingly connected with the upper end rigid rod.

[0008] Further improvement, the nail bead is cylindrical, the middle part of the cross section of the nail bead is provided with a central through hole, four groups of steel wire through holes for the flexible steel wire to pass through are symmetrically arranged on the cross section of the nail bead, the steel wire through holes are located outside the central through hole, the top end of the nail bead is provided with a symmetric lug one, the bottom end of the nail bead is provided with a through groove one perpendicular to the steel wire through hole, the through groove one is used for connecting the lugs one of adjacent nail beads, and the cross section size of the through groove one is greater than that of the lug one; the lock block one includes a left half lock block and a right half lock block, the left half lock block and the right half lock block are welded and connected through a shaft pin, symmetric lugs two are arranged at the top end of the left half lock block and the right half lock block, two groups of steel wire tail holes which are not through are symmetrically arranged at the bottom end of the left half lock block and the right half lock block respectively, the steel wire tail holes are coaxially arranged with the steel wire through holes, and a through groove two perpendicular to the lugs two is arranged between the bottom surfaces of the left half lock block and the right half lock block; symmetric locking grooves matched with the lugs two are arranged at the tail end of the drill bit, and symmetric cutting edges are arranged at the front end of the drill bit.

[0009] Further improvement, the nail bead has a height h1 and a diameter D in the X direction, the lug one has a diameter R1, a height n1 and a width d1 in the X direction, h1 is 3.5-5 mm, D is 4-7 mm, R1 is 1.5-1.8 mm, n1 is 1.4-2.5 mm, and d1 is 1.2-1.6 mm; the nail bead has c1, c2, b1, b2, a through groove two height n2, a through groove two diameter R2 and a through groove two width d2 in the Y direction, c1 is 0.8-1.2 mm, c2 is 1.2-1.8 mm, b1 is 1.2-1.6 mm, b2 is 1.6-2.0 mm, the α inclination angle ranges from 5° to 12°, n2 is 1.2-2.0 mm, R2 is 1.8-2.3 mm, d2 is 1.4-2.2 mm, and R1

[0010] Further improvement, the end cap is threadedly connected to the support, cavities are arranged in the interiors of the support and the end cap, the interiors of the cavities are filled with a polymer viscoelastic body, an opening is arranged on the support and communicates with the cavity, the rigid rod at the upper end passes through the opening and is arranged in the cavity, and a limiting portion larger than the inner diameter of the opening is arranged at the lower end of the rigid rod in the interior of the support.

[0011] Further improvement, the rod channel is provided with a rod pressing block, the lower end of the rod pressing block is provided with a circular pressing groove, the upper end of the rod channel is communicated with a locking nut hole, the locking nut is threadedly connected in the locking nut hole and located at the upper end of the rod pressing block.

[0012] Further improvement, the flexible screw is connected with the connector through a fixing screw.

[0013] Further improvement, the steel wire tail hole side end is provided with a steel wire welding hole communicated with the through groove.

[0014] Compared with the prior art, the flexible nail rod system for thoracolumbar spinal internal fixation has the following beneficial effects:

[0015] 1. A plurality of nail beads are connected in series to form a flexible screw main body part, which can be deflected in any direction within a certain angle, increasing the activity freedom of the nail rod system, and a doctor can control the movement trajectory of the flexible screw into the vertebral body, and the use is more flexible.

[0016] 2. The flexible screw main body has a large surface area, and after being implanted into the vertebral body, it is in a curved state, the pull-out resistance of the flexible screw is greatly improved, and it is especially suitable for the fixation of osteoporotic or tumor bone destruction vertebral body, and the rigidity is smaller than that of the traditional screw, which prevents the occurrence of disuse osteoporosis of the spine, thereby reducing the occurrence of internal fixation failure.

[0017] 3. The connector adopts a low-cut design, which can not only firmly connect the rigid rod and the flexible screw, but also reduce the stimulation of the implant to the tissue.

[0018] 4. The movement maintainer cooperates with the flexible nail rod to bear the stress transmission in the vertebral body, but does not limit the activity freedom of the vertebral body, and can reduce the probability of ossification of adjacent segment vertebral bodies. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a structure schematic view of the flexible screw of the present application

[0020] Figure 2 It is a structure schematic view of the flexible screw of the present application Figure 1 It is a structure schematic view of the flexible screw of the present application

[0021] Figure 3 It is a structure schematic view of the flexible screw of the present application

[0022] Figure 4 It is a structure schematic view of the flexible screw of the present application Figure 3 It is a structure schematic view of the flexible screw of the present application

[0023] Figure 5 It is a structure schematic view of the flexible screw of the present application

[0024] Figure 6 It is a structure schematic view of the flexible screw of the present application

[0025] Figure 7 Structure diagram of the main view of the bead in the present application

[0026] Figure 8 Structure diagram of the partial bead string assembly in the present application

[0027] Figure 9 Structure diagram of the lock block one in the present application

[0028] Figure 10 Structure diagram of the lock block one from another perspective in the present application

[0029] Figure 11 Structure diagram of the drill bit in the present application

[0030] Figure 12 Structure diagram of the connector in the present application

[0031] Figure 13 Structure diagram of the connector inside in the present application

[0032] Figure 14 Structure diagram of the motion retainer assembly in the present application

[0033] Figure 15 Structure diagram of the present application for coronal and sagittal plane after thoracolumbar spinal internal fixation

[0034] Figure 16 Structure diagram of the present application for thoracolumbar spinal internal fixation

[0035] In the figure, 1-flexible screw, 11-bead cap, 111-fixing screw, 12-lock block two, 13-bead, 131-central through hole, 132-steel wire through hole, 133-lug one, 134-through slot one, 14-lock block one, 141-left half lock block, 142-right half lock block, 143-axle pin, 144-lug two, 145-steel wire tail hole, 146-through slot two, 147-steel wire welding hole, 15-drill bit, 151-locking groove, 152-cutting edge, 16-flexible steel wire, 17-flexible screw body, 18-needle guide hole, 2-connector, 21-rod placement channel, 22-screw hole, 23-lock nut, 24-rod pressing block, 241-circular pressing groove, 25-lock nut hole, 3-motion retainer, 31-stand, 32-end cover, 33-cavity, 34-polymer viscoelastic body, 35-opening, 4-rigid rod, 41-limiting part. DETAILED DESCRIPTION

[0036] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0037] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0038] The purpose of the present application is to provide a flexible nail rod system for thoracolumbar spinal internal fixation, to solve the problem that the existing nail rod system is only suitable for normal bone vertebrae, and stress shielding, adjacent segment ossification and other complications occur after fixation. The present application proposes a new type of flexible nail rod system from the aspects of implantation process, mechanical transmission, connection freedom and the like, to avoid the risks after rigid nail rod system internal fixation.

[0039] The embodiments and drawings of the present application are described below. Figures 1-16 The technical solutions of the present application are further described.

[0040] Embodiment 1

[0041] A flexible nail rod system for thoracolumbar spinal internal fixation, comprising:

[0042] A flexible screw 1, the flexible screw 1 comprises a nail cap 11, a lock block two 12, a nail bead 13, a lock block one 14, a drill bit 15, a flexible steel wire 16 and a fixed screw 111; a plurality of the nail beads 13 are connected in a head-to-tail mosaic manner to form a flexible screw body 17, a gap is provided between adjacent nail beads 13, four groups of uniformly distributed channels are provided in the flexible screw body 17, the flexible steel wire 16 penetrates in the channels, the tail of the flexible steel wire 16 is fixedly connected with the lock block one 14, the head of the flexible steel wire 16 is slidably inserted into the inside of the nail cap 11, the drill bit 15 is fixed to the right end of the lock block one 14, the lock block two 12 is fixed to the right end of the nail cap 11, the fixed screw 111 is threadedly connected in the inside of the nail cap 11 and clamps the flexible steel wire 16 through the fixed screw 111, the nail cap 11, the lock block two 12, the lock block one 14, the drill bit 15 and the flexible screw body 17 are all provided with a communicating needle guide hole 18;

[0043] Connector 2, which is provided with a rod channel 21 for accommodating a rigid rod 4 and a screw hole 22 for mounting a flexible screw 1; the flexible screw 1 is connected with the connector 2 through a fixing screw 111;

[0044] Rigid rod 4, which is arranged in the rod channel 21 and is pre-tightened through a locking nut 23;

[0045] Motion retainer 3, which comprises a support 31 and an end cover 32, the end cover 32 is fixedly connected with the lower end rigid rod 4, and the support 31 is slidingly connected with the upper end rigid rod 4.

[0046] The nail cap 11, the lock block two 12, the nail bead 13, the lock block one 14 and the drill bit 15 are all made of medical titanium alloy material, and the flexible steel wire 16 is made of 022Cr18Ni14Mo8 stainless steel material.

[0047] As shown in Figures 1-16 The use process of the present application is as follows: 1. A doctor selects the specification of the flexible screw 1 under the perspective of a C-arm machine according to the parameters of the vertebral body; 2. An electromagnetic control guide needle is used for puncture and pre-preparation of a nail channel; 3. The flexible screw is inserted into the pedicle of the vertebral arch through the guide needle, that is, the guide needle passes through the guide needle hole 18 of the nail cap 11, the lock block two 12, the lock block one 14, the drill bit 15 and the flexible screw body 17, a special instrument is used to clamp the tail end of the nail cap 11 and rotate clockwise, the flexible screw 1 slowly enters the vertebral body along the direction of the guide needle, and the guide needle is removed; 4. The rigid rod 4 and the motion retainer 3 are assembled as required, and the locking nut 23 is pre-tightened; 5. The connector 2 is moved to the tail end of the flexible screw 1, the fixing screw 111 is inserted into the nail cap 11 of the flexible screw 1 through the connector 2, and is fixed, at this time the flexible screw becomes a fixed nail; 6. According to the requirement, the adjacent machine is opened, pressurized, and the locking nut 23 is tightened at the same time; 7. The wound is sutured, and the internal fixation of the spine is completed.

[0048] The flexible screw 1 comprises a plurality of the nail beads 13 which are embeddedly connected in head-tail mode to form a flexible screw body 17, a reasonable interval is arranged between adjacent nail beads 13, the nail beads 13 can be relatively deflected when an external force acts, and the four groups of flexible steel wires 16 can relatively slide in the nail cap 11 when the flexible screw body 17 is deflected, the flexible steel wires 16 simultaneously slide in the plurality of nail beads 13, so that the lengths of different flexible steel wires in the flexible screw body 17 are different, the movement allowance generated by the sliding of the four groups of flexible steel wires 16 further allows the flexible screw body 17 to be deflected, and the flexible bending function of the screw can be realized.

[0049] As shown in Figure 4As shown, after being adjusted to the appropriate position, the fixing screw 111 is inserted into the inside of the nail cap 11, so that the four groups of flexible steel wires 16 inside the nail cap 11 are outwardly expanded by one end of the fixing screw 111, thereby pushing and fixing the flexible steel wires 16 and tightening them, at this time, the flexible steel wires 16 cannot slide, the flexible steel wires 16 have no movement allowance, the effective length of the flexible steel wires 16 is fixed, the nail beads 13 reach a stable state and cannot move, the flexible screw becomes a fixed screw, and the deflection is essentially the different effective lengths of the four groups of steel wires allowing the nail beads 13 to be deflected, even if there is a small gap between the nail beads 13, the flexible screw body formed by the nail beads cannot actively deflect.

[0050] The flexible nail rod system for thoracolumbar spinal internal fixation has the following advantages:

[0051] 1. A plurality of nail beads are connected in series to form a flexible screw body part, which can be deflected in any direction within a certain angle, thereby increasing the activity freedom of the nail rod system, and a doctor can control the movement trajectory of the flexible screw into the vertebral body, and the use is more flexible.

[0052] 2. The flexible screw body has a large surface area and is in a curved state after being implanted into the vertebral body, the pull-out resistance of the flexible screw is greatly improved, and it is particularly suitable for the fixation of osteoporotic or tumor bone destruction vertebral bodies, and the rigidity is smaller than that of the traditional screw, thereby preventing the occurrence of disuse osteoporosis of the spine and reducing the internal fixation failure.

[0053] 3. The connector adopts a low-cut design, which can not only firmly connect the rigid rod and the flexible screw, but also reduce the stimulation of the implant to the tissue.

[0054] 4. The movement maintainer cooperates with the flexible nail rod to bear the stress transmission in the vertebral body, but does not limit the activity freedom of the vertebral body, and can reduce the probability of ossification of adjacent segment vertebral bodies.

[0055] As a further embodiment, the nail bead 13 is cylindrical, the central through hole 131 is arranged in the middle of the cross section of the nail bead 13, four groups of steel wire through holes 132 for the flexible steel wires 16 to pass through are symmetrically arranged on the cross section of the nail bead 13, the steel wire through holes 132 are located outside the central through hole 131, the symmetric lugs 133 are arranged at the top end of the nail bead 13, the through slot 134 perpendicular to the steel wire through hole 132 is arranged at the bottom end of the nail bead 13, the through slot 134 is used for connecting the lugs 133 of adjacent nail beads 13, and the cross-sectional size of the through slot 134 is greater than that of the lug 133;

[0056] The lock block one 14 includes left half lock block 141 and right half lock block 142, which are welded by shaft pin 143, and the top of the left half lock block 141 and the right half lock block 142 is symmetrically provided with lug two 144, and the bottom of the left half lock block 141 and the right half lock block 142 is symmetrically and respectively provided with two groups of non-through steel wire tail holes 145, which are coaxially arranged with the steel wire through hole 132, and the bottom surface of the left half lock block 141 and the right half lock block 142 is provided with through slot two 146 which is perpendicular to the lug two 144;

[0057] The tail end of the drill bit 15 is symmetrically provided with a locking groove 151 matched with the lug two 144, and the front end of the drill bit 15 is provided with symmetric cutting edges 152, and the lug two 144 of the lock block one 14 is clamped in the locking groove 151 of the drill bit 15 and then welded, which can improve the connection strength of the lock block one 14 and the drill bit 15.

[0058] As shown in Figures 1-7 The four groups of flexible steel wires 16 are respectively fixed in the four groups of steel wire through holes 132 of the nail beads 13 and then pass through the steel wire tail holes 145 of the lock block one 14, and the central through hole 131 is used for passing through the guide needle.

[0059] The through slot one 134 is used for connecting the lugs one 133 of the adjacent nail beads 13, and the cross-sectional dimension of the through slot one 134 is greater than that of the lug one 133, a plurality of groups of the through slot one 134 and the lug one 133 of the nail beads 13 are staggered and inserted, the deflection of the flexible screw body 17 in the X axis and the Y axis is realized, the flexible screw body 17 is not self-constrained, and continues to cooperate with the flexible steel wire 16 to realize the constraint through the four groups of flexible steel wires 16, and the lug one 133 of the last nail bead 13 is clamped and inserted into the through slot two 146 of the lock block one 14 to realize the connection.

[0060] As a further embodiment, the nail bead 13 has a height h1 and a diameter D in the X direction, the lug one 133 has a diameter R1, a height n1 and a width d1 in the X direction, h1 is 3.5-5mm, D is 4-7mm, R1 is 1.5-1.8mm, n1 is 1.4-2.5mm, and d1 is 1.2-1.6mm; the nail bead 13 has c1, c2, b1, b2, the height n2 of the through slot two 146, the diameter R2 of the through slot two 146 and the width d2 of the through slot two 146 in the Y direction, c1 is 0.8-1.2mm, c2 is 1.2-1.8mm, b1 is 1.2-1.6mm, b2 is 1.6-2.0mm, the inclination angle α is 5-12°, n2 is 1.2-2.0mm, R2 is 1.8-2.3mm, d2 is 1.4-2.2mm, and R1

[0061] As shown in Figure 5 , Figure 6 andFigure 7 As shown in one embodiment, h1 = 4.0 mm, D = 4.0 mm, R1 = 1.6 mm, n1 = 1.6 mm, d1 = 1.3 mm, c1 = 1.0 mm, c2 = 1.6 mm, b1 = 1.2 mm, b2 = 1.6 mm, α = 8°. At this time, the maximum deflection angle β between adjacent nail beads 13 is 6°. Based on the effective length of the flexible screw 1 of 32.5 to 70.0 mm, it is calculated to be approximately 8 to 16 nail beads, that is, the maximum deflection angle is approximately 40° to 96°.

[0062] As can be seen from the above structure, the nail bead 13 has no independent constraint on the X and Y axes, and needs to rely on four flexible steel wires 16 to achieve constraint. One end of the flexible steel wire 16 is welded and fixed to the locking block 14, and the other end slides in the nail head 11. At this time, the flexible screw 1 can deflect at any angle between 40° and 96°. When the fixing screw 111 is inserted into the nail head 11, the free end of the flexible steel wire 16 is locked, and the flexible screw 1 is fixed in the state before locking. At this time, the flexible screw 1 is equivalent to a conventional fixing nail.

[0063] As a further embodiment, the end cap 32 is threadedly connected to the support 31. Both the support 31 and the end cap 32 have cavities 33 inside. The cavity 33 is filled with a polymer viscoelastic body 34. The support 31 has an opening 35 that communicates with the cavity 33. The rigid rod 4 at the upper end passes through the opening 35 and is placed inside the cavity 33. The lower end of the rigid rod 4 located inside the support 31 has a limiting part 41 that is larger than the inner diameter of the opening 35.

[0064] like Figure 14 As shown, the cavity 33 of the motion retainer 3 is filled with a large amount of polymer viscoelastic material 34, which allows the upper and lower rigid rods 4 of the motion retainer 3 to rotate relative to each other, with a maximum tilt angle θ°. The polymer viscoelastic material has a dual deformation mechanism of elasticity and viscosity. The deformation process of the viscoelastic material after being subjected to force changes with time, and the recovery process after unloading has a certain delay effect. That is, the stress and strain of the viscoelastic material are no longer linearly related. Specifically, when the spine is subjected to impact load, the motion retainer is equivalent to a solid that stably transmits stress. When the spine is subjected to slow compression or torsion, the motion retainer is equivalent to a buffer elastomer, which allows relative movement between the vertebrae connected to it.

[0065] As a further embodiment, a pressure bar block 24 is provided in the rod placement channel 21, and a circular pressure groove 241 is provided at the lower end of the pressure bar block 24. A locking nut hole 25 is connected to the upper end of the rod placement channel 21, and a locking nut 23 is threadedly connected to the locking nut hole 25 and located at the upper end of the pressure bar block 24. Figure 12 and Figure 13As shown, after the locking nut 23 is screwed into the locking nut hole 25, the pressing rod block 24 with the circular pressing groove 241 is pushed downward, thereby further clamping and fixing the rigid rod 4 in the rod channel 21, and improving the connection stability between the rigid rod 4 and the connector 2.

[0066] As a further embodiment, the steel wire tail hole 145 is provided with a steel wire welding hole 147 communicated with the through groove two 146. As shown, Figure 10 As shown, the steel wire welding hole 147 at the side end facilitates the insertion of the flexible steel wire 16 into the steel wire tail hole 145 and then realizes the welding fixation.

[0067] The preferred embodiments of the present application are described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations without departing from the concept of the present application. Therefore, any technical solutions obtained by logical analysis, reasoning or limited experiments based on the prior art according to the concept of the present application shall be within the protection scope defined by the claims.

Claims

1. A flexible rod-and-screw system for internal fixation of the thoracolumbar spine, characterized in that, include: A flexible screw includes a head, a second locking block, a bead, a first locking block, a drill bit, a flexible steel wire, and a fixing screw. Multiple beads are interlocked end-to-end to form the main body of the flexible screw, with gaps between adjacent beads. The main body of the flexible screw has four evenly distributed channels, through which the flexible steel wire passes. The tail of the flexible steel wire is fixedly connected to the first locking block, and the head of the flexible steel wire slides into the head. The drill bit is fixed to the right end of the first locking block, the second locking block is fixed to the right end of the head, and the fixing screw is threaded into the head and clamps the flexible steel wire. The head, second locking block, first locking block, drill bit, and main body of the flexible screw all have communicating guide holes. The connector has a rod-holding channel and a screw hole, the rod-holding channel being used to accommodate a rigid rod; the screw hole being used to install a flexible screw. A rigid rod is set in the rod placement channel and pre-tightened by a locking nut; A motion retainer, comprising a support and an end cap, wherein the end cap is fixedly connected to a rigid rod at the lower end, and the support is slidably connected to the rigid rod at the upper end.

2. The flexible rod-and-screw system for thoracolumbar spinal internal fixation according to claim 1, characterized in that, The nail bead is cylindrical, with a central through hole in the middle of its cross-section. Four sets of wire through holes for flexible steel wires to pass through are symmetrically arranged at intervals on the cross-section of the nail bead. The wire through holes are located outside the central through hole. The top of the nail bead has a symmetrical lug, and the bottom of the nail bead has a through groove perpendicular to the wire through holes. The through groove is used to connect the lugs of adjacent nail beads, and the cross-sectional dimension of the through groove is larger than that of the lug. The locking block 1 includes a left half locking block and a right half locking block, which are connected by a shaft pin. The top of the left half locking block and the right half locking block are symmetrically provided with lugs 2. The bottom of the left half locking block and the right half locking block are symmetrically provided with two sets of non-through steel wire tail holes. The steel wire tail holes are coaxially arranged with the steel wire through holes. A through groove 2 perpendicular to lugs 2 is provided between the bottom surfaces of the left half locking block and the right half locking block. The drill bit has symmetrical locking grooves for matching and engaging lugs at its tail end, and symmetrical cutting edges at its front end.

3. A flexible rod-and-screw system for thoracolumbar spinal internal fixation according to claim 2, characterized in that, The bead has a height h1 and a diameter D in the X direction, and the lug has a diameter R1, a height n1, and a width d1 in the X direction, where h1 is 3.5–5 mm, D is 4–7 mm, R1 is 1.5–1.8 mm, n1 is 1.4–2.5 mm, and d1 is 1.2–1.6 mm; the bead has a second through groove with a height n2, a diameter R2, and a width d2 in the Y direction, where the inclination angle α ranges from 5–12°, n2 is 1.2–2.0 mm, R2 is 1.8–2.3 mm, and d2 is 1.4–2.2 mm, and R1 < R2, d1 < d2, and n2 < n1.

4. The flexible rod-and-screw system for thoracolumbar spinal internal fixation according to claim 1, characterized in that, The end cap is threaded onto the support. Both the support and the end cap have cavities inside. The cavities are filled with polymer viscoelastic. The support has an opening that communicates with the cavity. The rigid rod at the upper end passes through the opening and is placed inside the cavity. The lower end of the rigid rod inside the support has a limiting part that is larger than the inner diameter of the opening.

5. A flexible rod-and-screw system for thoracolumbar spinal internal fixation according to claim 1, characterized in that, The rod placement channel is provided with a pressure rod block, the lower end of which is provided with a circular pressure groove. The upper end of the rod placement channel is connected to a locking nut hole, and the locking nut is threaded into the locking nut hole and located at the upper end of the pressure rod block.

6. A flexible rod-and-screw system for thoracolumbar spinal internal fixation according to claim 1, characterized in that, The flexible screw is connected to the connector by a fixing screw.

7. A flexible rod-and-screw system for thoracolumbar spinal internal fixation according to claim 2, characterized in that, The end of the wire tail hole is provided with a wire welding hole that communicates with the through groove.

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