TBFs are clinically common. Spinal fractures typically occur in the thoracolumbar segment. The transition from the less mobile thoracic spine and its associated ribs and sternum to the more mobile lumbar spine makes the thoracolumbar junction (T11-L2) a large area of biomechanical stress. The imaging features include rupture of the posterior wall of the vertebral body, retrograde entry of the posterior edge of the vertebral body into the lumen, a decrease in the height of the vertebral body and an increase in the distance between the pedicles. Holdsworth  believes that burst fractures cause damage to the anterior and middle columns and that the posterior column is often intact, which corresponds to a stable fracture. Denis  believes that damage to the middle column is an important indicator of stability. All thoracolumbar burst fractures have middle column damage, which corresponds to an unstable fracture. Conservative treatment includes bed rest and reduced posture and orthotics, which may help relieve pain for weeks or months. Conservative treatment of fractures has been shown to be useful in most stable fractures [11, 19,20,21,22] but not in all cases, and long-term bed rest is associated with an increased incidence of bedsores, pneumonia, venous thromboembolism, and even death . Compared with nonsurgical methods, surgical treatment of thoracolumbar fractures does provide some advantages, especially for patients who cannot tolerate orthotics or plaster orthotics for several months, such as patients with multiple limb injuries, skin lesions, and obesity . Therefore, in the present study, patients with contraindications to surgery were excluded, and surgical treatment was recommended for the remaining patients. Surgical decompression can also be more reliable and effective in removing the bone block protruding into the spinal canals, restoring neurological function and improving rehabilitation. In 1984, Denis et al. conducted a retrospective comparison between the surgical and nonsurgical treatment in 52 cases of blowout fractures without neurological defects and found that all patients treated with surgery had no relevant disability and returned to full-time work, whereas 25% of the patients treated without surgery were unable to return to full-time work . In addition, neurological problems were reported in 17% of nonsurgical patients. Siebenga et al. concluded that surgical treatment not only offered better clinical outcomes but was also more cost-effective than nonsurgical treatment . Two other large systematic evaluations [25, 26] demonstrated that early surgery for thoracolumbar fractures was associated with reduced complications and shorter hospital and ICU stays.
Surgical treatment of TBFs varies according to many factors. The shape of the fracture, the state of the nervous system, and the surgeon’s preference all play important roles in determining the surgical procedure. Short-segment pedicle screw fixation is now widely used but the acknowledged disadvantages of this procedure are early reduction failure and recurrent kyphosis [26, 27]. Because the cancellous bone in the vertebral body is compressed after a thoracolumbar burst fracture, often combined with endplate collapse, only the pedicle screw device is used to indirectly restore the fractured vertebra through distraction. The bone trabecula and spinal cord structure in the injured vertebrae are not completely reset, which will result in insufficient recovery of the depressed end plate . Due to the existence of bone defects and voids in the vertebral body, an “eggshell-like” vertebral body is formed, which cannot provide sufficient support and stimulation for fractures within the vertebral body, resulting in insufficient support strength of the anterior and middle columns of the vertebral body. Therefore, bone healing is not complete. The “eggshell-like” vertebral body will further reduce the height of the injured vertebral body under the action of slight external force, which will eventually lead to the loss of the vertebral body height and even the failure of internal fixation [26, 29, 30]. In addition, due to the lack of ligament and annulus attachment, the collapsed central endplate cannot be fully repositioned, the intervertebral disc loses integrity, and gradual disc degeneration leads to loss of intervertebral disc height, stenosis of the intervertebral space, and increased kyphotic angle .
Therefore, placing these screws directly into the vertebrae without reduction may weaken the vertebrae, affecting subsequent restoration of the fracture and possibly leading to fracture displacement. Moreover, failure to perform targeted bone grafting and filling of the local “eggshell-like” cavity formed after the reduction of the injured vertebra will lead to further loss of vertebral height. Many scholars have further explored this concept and invented techniques such as SpineJack, Sky Bone Expansion System Kyphoplasty (SKP), Opti Mesh Vertebroplasty, Intravertebral Expandable Pillar (I-VEP) and Lantern bracket skeletal angioplasty to restore and support the shape and height of the fractured vertebral body, but there are still common shortcomings, namely: 1. All need to combine the existing bone cement technology or nail rod internal fixation system to achieve its application and 2. The techniques cannot provide a more uniform expansion and reduction force and the expansion height cannot be determined by itself.
Therefore, we designed a novel transpedicular reducer to treat compressibility and burst fractures. Our novel transpedicular reducer has the following characteristics: 1.Adopting the lever-regulating principle is labour-saving and convenient to implement; 2. It operates via the pedicle without breaking through the inner wall of the pedicle and will not cause nerve damage; 3.The contact surface of the stent surface with the bone tissue interface is increased to solve the problem posed by existing techniques in which the surface of the scaffold and bone tissue interface stress is too large; 4.Direct reduction of the injured vertebrae is more effective and 5.At the same time, it can provide vertebral space for bone grafting of injured vertebrae. Different from the above technology, our novel transpedicular reducer does not need to be combined with bone cement technology, which can provide uniform support, restore good controllability (according to the actual need) of the reset height and is easy to operate. According to our experimental research, although it is currently not possible for a single sample to reflect the independent reset effect of the novel transpedicular reducer, according to the data after restoration, it can be found that the anterior and middle heights of the injured vertebrae in the observation group recovered from the preoperative values of 20.56 ± 3.74 mm and 20.36 ± 4.20 mm to 29.53 ± 2.53 mm and 27.54 ± 1.00 mm, respectively, and the Cobb angle decreased from 11.80 ± 1.44° to 2.46 ± 1.00°, corresponding to statistically significant differences. Moreover, the anterior height, middle height, AVBHr and HVBHr of the injured vertebrae of the observation group were better than those of the control group, and the Cobb angle of the observation group was smaller than that of the control group, which was a statistically significant difference. Therefore, compared with short-segment transpedicular screw fixation alone, the novel transpedicular reducer has a certain reduction effect and can correct kyphotic deformity.
To solve the problem of “eggshell-like” vertebral bodies after performed with short-segment transpedicular screw fixation, several studies have demonstrated that reinforcing fractured vertebrae with bone cement such as polymethylacrylate can enhance fracture healing and prevent implant failure. However, PMMA has been reported to be associated with undesirable characteristics, such as a high temperature setting, possible damage to local nerve and vascular structures, inadequate bone fusion and a severe stiffness mismatch with bone, resulting in subsequent adjacent fractures and even vertebral restenosis . Moreover, the leakage rate is so high (7–10%) that distal cement emboli enter the cardiac cavity and pulmonary system [33, 34].PMMA also cannot be replaced by biological tissue. As a result, scientists are now also looking for a new implant to minimize the incidence of complications. Cao et al. reported that allograft bone implantation in thoracolumbar fractures can effectively correct the Cobb angle and the height of the injured vertebral front and reduce the degree of the injured vertebral defect . Therefore, we applied the novel transpedicular reducer and filled the damaged vertebral cavity with allograft bone through the bone graft channel, which effectively restored the vertebral bone structure and avoided leakage caused by the use of bone cement. CT results of the patients 12 months after the operation showed that most of the allogeneic bone used to fill in the anterior middle columns was absorbed, and no obvious defects were found. Trabecular structures were visible in the cancellous bone, and the bone healed well.
According to our research results at 3 days, 3 months and 12 months after surgery, the restoration effect of the novel transpedicular reducer for reduction and bone grafting combined with pedicle screw fixation was better than that of short-segment transpedicular screw fixation alone, and the difference was statistically significant (p < 0.05). According to the VAS and GQOL-74 scores, the clinical effect of the novel transpedicular reducer for reduction and bone grafting combined with pedicle screw fixation was better than that of short-segment transpedicular screw fixation alone, and the difference was statistically significant (p < 0.05). But the sample size of this study is relatively small. In the later study, we designed a large sample randomized controlled study, using the controlled variable method to compare the injured vertebrae at the same segment.