A SCREW-ROD INSTRUMENT SPECIALLY USED FOR POSTERIOR ATLANTOAXIAL VERTEBRAE FIXATION

Abstract

The invention discloses a screw-rod instrument specially used for posterior atlantoaxial vertebrae fixation, comprising two pulling-screws (2), two supporting-screws (1), two variable cross section fixing rods (3), two lock nuts (4) and a bracing beam (5). Each of the variable cross section fixing rods (3) is configured to connect a supporting-screw (1) and a pulling-screw (2), the bracing beam (5) is configured to connect both of the variable cross section fixing rods (3); wherein each of the supporting-screws (1) comprises a first tail (11) and a first head (12), and each of the pulling-screws (2) comprises a second tail (21) and a second head (22); both the first tail (11) and the second tail (21) are provided with nail grooves, with U-shaped grooves on the sides; wherein each of the nail grooves is provided with internal thread inside, and the lock nut (4) is connected with the nail groove; each of the variable cross section fixing rods (3) passes through the U-shaped grooves and is fastened by the lock nut (4); the bottoms of the nail grooves of the supporting-screws (1) are 2-6 mm higher than the bottoms of the nail grooves of the pulling-screws (2). The aforementioned screw-rod instrument not only increases the safety and convenience of a surgery, but also improves the function of spondylolisthesis reduction of the screw-rod system through raising the bottoms of the nail grooves 2-6 mm higher.

Claims

1. A screw-rod instrument specially used for posterior atlantoaxial vertebrae fixation, wherein the screw-rod instrument comprises two pulling-screws, two supporting-screws, two variable cross section fixing rods, two lock nuts and a bracing beam; wherein each of the variable cross section fixing rods is configured to connect a supporting-screw and a pulling-screw, the bracing beam is configured to connect both of the variable cross section fixing rods; wherein each of the supporting-screws comprises a first tail and a first head, and each of the pulling-screws comprises a second tail and a second head; both the first tail and the second tail are provided with nail grooves, with U-shaped grooves on the sides; wherein each of the nail grooves is provided with internal thread inside, and the lock nut is connected with the nail groove by the internal thread; each of the variable cross section fixing rods passes through the U-shaped grooves and is fastened by the lock nut; the bottoms of the nail grooves of the supporting-screws are 2-6 mm higher than the bottoms of the nail grooves of the pulling-screws.

2. The screw-rod instrument specially used for posterior atlantoaxial vertebrae fixation according to claim 1, wherein each of the variable cross section fixing rods is provided with an anti-rotation joint portion matched with the U-shaped grooves; the anti-rotation joint portion has a plane and/or a curved surface fitting the U-shaped grooves closely.

3. The screw-rod instrument specially used for posterior atlantoaxial vertebrae fixation according to claim 1, wherein the second tail is a long arm nail groove, with an annular recess configured on the middle part of the outer wall.

4. The screw-rod instrument specially used for posterior atlantoaxial vertebrae fixation according to claim 1, wherein the pulling-screw is a polyaxial screw, with the second head connected to the second tail which has a tapered thread tip.

5. The screw-rod instrument specially used for posterior atlantoaxial vertebrae fixation according to claim 1, wherein the first head of the supporting-screw is a single-axial screw which is fastened to the first tail, having a tapered thread tip; or the first head of the supporting-screw is a polyaxial screw which is fastened to the first tail, having a tapered thread tip.

6. The screw-rod instrument specially used for posterior atlantoaxial vertebrae fixation according to claim 1, wherein the bracing beam comprises lock-rod nuts, lateral combination nuts and a lateral connection plate; wherein both sides of the lateral connection plate are provided with oval openings; wherein one end of the lock-rod nut is connected to the first tail or the second tail through thread, the other end of the lock-rod nut is fastened by one of the lateral combination nuts after the other end passes through one of the oval openings.

7. The screw-rod instrument specially used for posterior atlantoaxial vertebrae fixation according to claim 6, wherein the lateral connection plate is a straight plate or a curved plate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to illustrate the embodiments of the invention or technical solutions of the prior art more clearly, the embodiments or drawings that need to be used in the prior art will be further described in detail below. Obviously, the drawings described below are just some examples of the present invention, those skilled in the art could also obtain other drawings based on the drawings of the present invention, without creative efforts.

[0018] FIG. 1 is an assembly diagram of the whole screw-rod instrument specially used for posterior atlantoaxial vertebrae fixation according to the present invention;

[0019] FIG. 2 is a schematic diagram of the structure of a supporting-screw according to the present invention;

[0020] FIG. 3 is a schematic diagram of the structure of a pulling-screw according to the present invention;

[0021] FIG. 4 is a schematic diagram of the structure of a variable cross section fixing rod according to the present invention;

[0022] FIG. 5 is a cross-section view of an anti-rotation joint portion according to the present invention, wherein FIG. 5 shows two different cross-section shapes;

[0023] FIG. 6 is a schematic diagram that shows the spondylolisthesis reduction with the screw-rod instrument specially used for posterior atlantoaxial vertebrae fixation according to the present invention.

DETAILED DESCRIPTION

[0024] The solutions of the embodiments of the invention will be described explicitly and completely, in conjunction with the drawings. It is clear that the described embodiments are only a part of embodiments of the present invention, not all embodiments of the present invention. Based on the embodiments of the present invention, all the other embodiments obtained by those of ordinary skill without any creative works are within the protection scope of the present invention.

[0025] As shown in FIGS. 1-6, a screw-rod instrument specially used for posterior atlantoaxial vertebrae fixation comprises two pulling-screws 2, two supporting-screws 1, two variable cross section fixing rods 3, two lock nuts 4 and a bracing beam 5. Each of the variable cross section fixing rods 3 connects with a supporting-screw 2 and a pulling-screw 1, the bracing beam 5 connects with both of the variable cross section fixing rods 4. Each of the supporting-screws 1 comprises a first tail 11 and a first head 12, and each of the pulling-screws 2 comprises a second tail 21 and a second head 22; both the first tail 11 and the second tail 21 are provided with nail grooves, with U-shaped grooves on the sides. Each of the nail grooves is provided with internal thread inside, and the lock nut 4 is connected with the nail groove by the internal thread. Each of the variable cross section fixing rods 3 passes through the U-shaped grooves and is fastened by the lock nut 4. The bottoms of the nail grooves of the supporting-screws 1 are 2-6 mm higher than the bottoms of the nail grooves of the pulling-screws 2, see H as shown in FIG. 2. The specific lifted height can be selected based on the actual situation, a specification can be set every 2 mm for preparation of products. Each of the variable cross section fixing rods 3 is provided with an anti-rotation joint portion 31 matched with the U-shaped grooves; the anti-rotation joint portion 31 has a plane (shown as a side in FIG. 4) and/or a curved surface (shown as an upper or lower portion in FIG. 4) fitting the U-shaped grooves closely. Shown as B in FIG. 5, all sides could be designed to be flat according to actual requirements; or shown as A in FIG. 5, three sides are flat, and only the bottom is a curved surface. An annular recess 23 is configured on the middle part of the outer wall of the second tail 21. The pulling-screw is a polyaxial screw, with the second head 22 connected to the second tail 21 which has a tapered thread tip. The first head 12 of the supporting-screw 1 is a single-axial screw which is fastened to the first tail 11, having a tapered thread tip; or the first head 12 of the supporting-screw 1 is a polyaxial screw which is fastened to the first tail 11, having a tapered thread tip. The connection type of a polyaxial screw includes: the polyaxial screw can pass through openings of the bottom of the nail groove of the first tail 11 or the second tail 21. The bracing beam comprises lock-rod nuts 51, lateral combination nuts 52 and a lateral connection plate 53; wherein both sides of the lateral connection plate 53 are provided with oval openings; wherein one end of the lock-rod nut 51 is connected to the first tail 11 or the second tail 21 through thread, the other end of the lock-rod nut 51 is fastened by one of the lateral combination nuts 52 after the other end passes through one of the oval openings. The lateral connection plate 53 is a straight plate or a curved plate, for different situations. It should be noted that, as the bracing beam 5 comprises lock-rod nuts 51, the first tail 11 or the second tail 21 is connected to the lateral connection plate 53, one end of the lock-rod nut 51 screws into nail grooves of the first tail 11 or the second tail 21, and the variable cross section fixing rod 3 is fastened, now the lock nut 4 has been replaced, and the function of the lock nut 4 has been achieved.

[0026] Experiments showing effect of using this product are described as follows:

[0027] General Information:

[0028] This group includes 6 patients (4 men, 2 women), who are 5-36 years, with an average age of 17. There exist one case of old odontoid fracture malunion atlantoaxial dislocation, two cases of fresh odontoid fracture and atlantoaxial dislocation, and three cases of os odontoideum and atlantoaxial dislocation. 6 patients have cervical region discomfort, wherein 2 patients suffer muscle force of arms and legs decrease, and the remaining 4 patients have normal kinaesthesis. American Spinal Injury Association (ASIA) classifies 6 patients into Class D (2 cases) and Class E (4 cases), as shown in Table 1. After admission to hospital, all the patients will have some x-ray plates from mouth opening normotopia position, cervical vertebra positive side position and over flexion-extension side position, atlantoaxial CT scan, cervical vertebra MRI scan and other examinations, in order to the situation of evaluate displacement fracture, atlantoaxial dislocation and spinal compression, and have a predetermined plan of screw fixing type.

[0029] Surgical Steps:

[0030] A patient undergoes general anesthesia with endotracheal intubation, and is in prone position, cervical vertebra flexes forward moderately, skull traction is maintained during surgery. A longitudinal incision which is approximately 6-8 cm long is made at the middle of the back neck, decollement is conducted from the external occipital protuberance to the inferior margin of C.sub.2 spinous process bone membrane, and the occipital bone, Q posterior arch and C2 lateral mass become visible, the attachment of semispinalis cervicis on C.sub.2 spinous process is maintained. The atlas and the axis are fastened by vertebral pedicle screws, after the screw entering point is determined, the opening is drilled, a hand drill is used to prepare the screw path by free hand, a probe is used to touch the integrity of the all walls, then one tapered tap with diameter of 3.0 mm and another tapered tap with diameter of 3.5 mm are used to tap successively, the pulling-screw is placed into the atlas, and the uniaxial supporting-screw is placed into the axis. Afterwards, the supporting-screw with pad height of 2 mm or 4 mm is selected according to the degree of dislocation, the variable cross section fixing rod with automatic anti-rotation function is trimmed and bent, wherein the elliptical portion is placed into the nail groove of the supporting-screw for axis, the cylindrical portion is placed into the nail groove of the pulling-screw for atlas, the nut of the supporting-screw for axis is tightened, and the orientation of the variable cross section fixing rod fixes automatically, then the nut of the pulling-screw for atlas is tightened, finally, the spondylolisthesis reduction is completed. After the reduction under fluoroscopy is satisfied, the long arm nail groove of the pulling-screw for atlas will be broken off, then the tail of screw for atlas is placed into the bracing beam. Cortex of bone of C.sub.1 posterior arch and C.sub.2 vertebral plate is removed by abrasive drilling, and the bone graft bed is prepared, cancellous particles of autogenous iliac bone are taken for bone grafting (since it is non-fusion fixation, preparation of the bone graft bed and Ilium grafting are unnecessary, the internal fixation apparatus can be removed in secondary operation after odontoid fracture healing, for recovering the atlantoaxial rotatory function). Negative pressure drainage is implemented, layered suture is carried out, and the surgery is completed.

[0031] The drainage tube will be removed 48 h after surgery, and the x-ray, CT and MRI reexamination will be conducted one week after surgery, in order to know situations of fracture reduction, reduction for the dislocation of the atlas and the axis and cord compression relieving.

[0032] Result:

[0033] The surgery of screws and rods for the posterior atlantoaxial vertebrae fixation and reduction has been performed successfully on 6 patients in this group, wherein there are 3 cases of non-fusion fixation and 3 cases of fusion fixation (see Table 1). The surgery time is 60-150 min (average 95 min), bleeding volume during surgery is 30-80 ml (average 50 ml), without spinal and vertebral artery injuries. Screws are placed into the screw path successfully during surgery, without slip-out and offset. The fixing rod can be inserted once for all, and it can prevent rotation automatically after the screw nut is tightened, it is not necessary to utilize a rod clamp and other anti-rotation tools to maintain direction. The fixing rod is placed into the nail groove of the screw for atlas, without auxiliary devices including lifting screws and pressing rods, the atlas and the axis can complete reduction automatically after the nut of the pulling-screw for atlas is tightened, fluoroscopy during operation shows that the reduction is satisfactory. The bracing beam can be implanted successfully, bending and repeated adjustment are unnecessary, the bone graft space between the atlas and the axis cannot be influenced. Postoperative x-ray plates and CT reexamination demonstrate that the implant position is good, and the reduction for the dislocation of the atlas and the axis is satisfactory; 2 patients in Class D (ASIA classification) all recovered to Class E.

TABLE-US-00001 TABLE 1 Patient Age Preoperative Neurological ASIA Surgical Number Gender (Years) Diagnosis Symptoms Classification Method 1 male 19 fresh odontoid cervical E surgery of screws and fracture and pain rods for the posterior atlantoaxial atlantoaxial vertebrae dislocation fixation and reduction (non-fusion) 2 female 36 fresh odontoid cervical E surgery of screws and fracture and pain rods for the posterior atlantoaxial atlantoaxial vertebrae dislocation fixation and reduction (non-fusion) 3 male 5 old odontoid neck E grinding and breaking fracture malunion discomfort off odontoid malunion atlantoaxial position through dislocation transoral approach + surgery of screws and rods for the posterior atlantoaxial vertebrae fixation and reduction (non-fusion) 4 female 10 os odontoideum neck discomfort D bone graft fusion of and atlantoaxial and muscle screws and rods for dislocation strength of the posterior lower atlantoaxial vertebrae extremities is fixation level 5 5 male 10 os odontoideum neck discomfort D bone graft fusion of and atlantoaxial and muscle screws and rods for dislocation strength of the posterior limbs is atlantoaxial vertebrae level 4+ fixation 6 male 21 os odontoideum cervical E bone graft fusion of and atlantoaxial pain screws and rods for dislocation the posterior atlantoaxial vertebrae fixation

[0034] The above descriptions are only the preferred embodiments of the invention, not thus limiting the embodiments and scope of the invention. Those skilled in the art should be able to realize that the schemes obtained from the contents of the specification and drawings of the invention are within the scope of the invention.