Development and limitations of traditional cervical anterior plate
In 1952, Abbott [7] has first proposed anterior cervical surgery. Later on, Robinson [8] and Smith [9] improved the technique in 1958 and proposed that anterior cervical discectomy and fusion with bone grafting using autologous bone grafting can promote the fusion rate. The surgery can directly remove the compressive elements, and ensure adequate decompression of the spinal cord. This subsequently improved the patient's symptoms. But this anterior decompression with bone grafting alone, without using plate and screw fixation can easily cause cervical instability. This instability also caused serious problems such as non-fusion of bone grafting and prolapse of bone grafting. So, Bohler [1] proposed the use of steel plate and screws in the anterior cervical surgery in 1964. In the following years, a variety of cervical anterior plate systems were developed, including non-locking non-robust type, locking firm type, variable angle semi-restricted type, and slip semi-limited type [10].
During the process of anterior cervical surgery, it is necessary to select an appropriate vertebral fixation device due to different bone qualities of the patient. After the surgery is completed, the implant is under a micro-motion state in the patient body, which causes displacement of the steel plate, loosening and fracture of the screw in the long-term micro-motion state. This finally fails the internal implant. Especially in patients with osteoporosis, there is a higher risk of plate displacement and screw loosening. Severe plate displacement and screw loosening can stress the blood vessels, trachea or oesophagus, and even cause vascular damage, trachea or oesophagal damage. Due to low bone mass, the bone microstructure is destroyed in patients with osteoporosis, causing increased bone fragility and easy fracture. It is more difficult to locate the steel plate in patients undergoing anterior cervical spine surgery for osteoporosis. Clinically, when patients with osteoporosis had accepted anterior cervical surgery, the incidence of internal fixation plates revision surgery was significantly increased.
Design and advantages of the new PRUNUS nail plate system
The PRUNUS nail plate system is made of medical titanium alloy, including titanium plate, fixing screws and locked plates. Titanium plate had a width of 17mm, length ranging 25-75mm, and increment of 3mm. Screw length ranged 25-75mm, and diameter of 4mm. The two ends of the titanium plate are designed as a curved surface, which can fix the surface of the actual anatomical bone. This, in turn, makes it suitable for the physiological curvature of the cervical spine, avoids the problem of uneven stress load effectively, and there are three screw holes are arranged in an isosceles triangle at the two ends. After the screws are fixed, they are fixed triangularly, and the screw nails cross each other, significantly enhancing the anti-rotation ability of the titanium plate system, and also reducing the risk of screw backing and screw fracture. A locked plate is provided in the middle of the screw hole to prevent screw loosening effectively. The middle part of the titanium place is provided with a large perspective window to facilitate bone grafting and the observation during and after surgery. The screws are designed with self-tapping screws, which reduces the usage of wiretapping. The screw diameters and colors can be distinguished, and at the same time, can be divided into fixed angles and adjustable angles, which are used for different indications (figure 5).
Based on the recent biomechanical studies on the stability, fatigue life and pull-out strength, the PRUNUS plate system demonstrated good biomechanical properties, effective stability on the cervical spine and maintained the acute stability of the cervical spine, while it has a better anti-pull out strength and figure resistance. At the same time, through a biomechanical test and practical application in clinical surgery, we believed that the new PRUNUS nail plate system can achieve the fixation of cervical vertebrae more effectively, especially in patients with osteoporosis and multilevel cervical fusion. It can also reduce the risk of revision surgery due to screw loosening and plate displacement. Otherwise, it is particularly suitable for revision surgery. In the revision surgery, screws holes have already been drilled in the cervical vertebrae. Therefore, if the screws are placed in the original hole, the screws can be easily loosened and the plate can be displaced. If the new PRUNUS nail plate was used in the revision surgery, it affords a new position for the screws and disperses the screw force significantly. The geometrical principle of the three-point stable can be used to enhance the holding force of the plate, achieving a good fixed effect greatly and improving the success rate of revision surgery.
The efficacy analysis of the new PRUNUS screw-plate system
Through the follow-up data of the control and the observation groups, we found that the operative time and blood loss of the observation group were higher than the control group, but the differences between the two groups showed no statistical significance. Nevertheless, 5 patients are undergoing anterior cervical revision surgery in the observation group. The operations of these patients were generally more complex, had longer operation time and more bleeding. The use of the new type of PRUNUS screw-plate system can reduce the operative time and the amount of bleeding compared to conventional anterior cervical surgery. Meanwhile, it can also simplify the surgical procedures, reduce operative time and blood loss to enhance surgical safety. One week after postoperatively and the last follow-up demonstrated that the cervical cobb angle, JOA scores and VAS scores in the control group and the observation group was significantly differed from their respective preoperative cervical cobb angle, JOA scores and VAS scores. But there was no statistically significant difference between the two groups. These data indicated that the new PRUNUS nail plate system can maintain the stability and restore the physiological curvature of the cervical spine, significantly improving the patient's symptoms, and achieving similar clinical results compared with the traditional cervical spine plate. The new PRUNUS screw-plate system can simplify the surgical procedures, reduce operating time and surgical risk, particularly in cases of cervical fractures, cervical revision surgery, and osteoporosis. It also can reduce the patient's physical and mental pain and economic burden.
The indications and deficiencies of the new PRUNUS screw-plate system
Indications of the new PRUNUS screw-plate system include 1. degenerative conditions of cervical spine, such as cervical spondylosis, posterior longitudinal ligament ossification, etc.; 2. cervical traumatic injuries such as cervical spine fracture and dislocation, cervical instability; 3. a variety of benign, malignant cervical tumours and thoracic vertebral body (T1, T2) tumours; 4. patients who require revision surgery after anterior cervical surgery; 5. cervical vertebral infections (tuberculosis, brucellosis); 6. osteoporosis with cervical spine-related diseases.
Although recent clinical efficacy analysis showed that the new PRUNUS screw-plate system has short-term effect in the anterior cervical surgery, due to short clinical application time, no abundant case data, short follow-up time, long-term complications and efficacy requires further follow-up to study and improve.