TBFs are clinically common. Spinal fractures usually occur in the thoracolumbar segment, and burst fractures that occur at the thoracic-lumbar junction (T11-L2) account for 70% of fractures [2]. A burst fracture is the result of a compression mechanism or is part of an excessive bending, extension or rotation injury [26]. The front and centre columns cannot be supported due to axial loading [27–28]. 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 are 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. The cause of this injury is usually traffic accidents, sports injuries or falls. Therefore, from a biomechanical or neurological point of view, many people consider burst fractures to be unstable. Burst fracture injuries are classified as A3 or A4 in the AOSpine thoracolumbar spine injury classification system. The objectives of treatment after a TBF are to stabilize the spine, prevent nervous system deterioration, restore sagittal balance, maintain as much segmental activity as possible with as little tissue damage as possible, and mobilize the patient as quickly as possible. 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 [10.29-32] but not in all cases, and long-term bed rest is associated with a higher incidence of bedsores, pneumonia, venous thromboembolism, and even death [33]. 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, obesity, etc. [11]. 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 damaged spinal canals, restoring neurological function and improving rehabilitation. In 1984, Denis et al. conducted a retrospective comparison between the surgical and nonsurgical treatment of 52 cases of blowout fractures without neurological defects and found that all the patients treated with surgery had no relevant disability and returned to full-time work, while 25% of the patients treated without surgery were unable to return to full-time work [34]. In addition, neurological problems were reported in 17% of nonsurgical patients. Siebenga et al. concluded that surgical treatment not only had better clinical outcomes but was also more cost-effective than nonsurgical treatment [35]. Two other large systematic evaluations [36–37] showed that early surgery for thoracolumbar fractures was associated with reduced complications and shorter hospital and ICU stays.
Surgical treatment of TBFs varies with 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 and can be performed in a minimally invasive manner. This operation can effectively reconstruct the injured vertebra and enhance the stability of the anterior central column [38–39]. In addition, the surgical method has a low incidence and few complications [18]. However, the acknowledged disadvantages of this procedure are early reduction failure and recurrent kyphosis [18.40–41]. his is probably because posterior pedicle screw fixation alone does not provide enough support to heal the fractured vertebra without the assistance of anterior column reconstruction. Posterior pedicle fixation through the short segment of the vertebral pedicle involves homeopathic compression of the injured vertebra to repair the fractured injured vertebra, but this homeopathic pressure cannot repair the compressed cancellous bone in the injured vertebra, thus forming a "hollow" vertebra [18]. Therefore, placing these screws directly onto the vertebrae without reduction may weaken the vertebrae, affecting subsequent reduction 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. Therefore, we designed a new transpedicular reducer to treat compressibility and blowout fractures. According to our experimental research, application of the new transpedicular reducer in the treatment of vertebral burst can recover the anterior and middle height of injured vertebral bodies well, from preoperative values of 17.56 ± 3.74 mm and 21.36 ± 4.20 mm to 27.96 ± 0.72 mm and 26.84 ± 2.45 mm, respectively, at the last follow-up; both increases were statistically significant. The Cobb angle decreased from 3.80 ± 1.44° before surgery to 1.34 ± 0.56° at the last follow-up, indicating that the Cobb angle decreased significantly after surgery, greatly correcting kyphosis.In general, the new transpedicular reducer, in addition to being very good at restoring the height of the vertebral body and correcting kyphosis, allows the injured vertebra to remain approximately in the corrected spinal position for a longer period of time after surgery.
Because the trabecular bone cannot be completely restored to the original callus structure after reduction, there will be a large space, which will directly lead to the loss of vertebral height in the later stage. Over the past decade, several studies have shown that reinforcing fractured vertebrae with absorbable bone cement can enhance fracture healing and prevent implant failure. However, the increase in bone cement is also a controversial area. Polymethacrylate (PMMA) is commonly used in vertebroplasty (VP) and balloon kyphoplasty (BK) for the treatment of osteoporosis and fresh thoracolumbar fractures. 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 [42]. Moreover, the leakage rate is high (7–10%). It has been reported that distal cement emboli enter the cardiac cavity and pulmonary system [43–44].PMMA is also non-absorbable, meaning that bone cement is retained rather than gradually replaced by biological tissue, which has a particularly adverse effect on young people. As a result, people 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 [45]. Therefore, we applied the new 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. The CT results of the patients 12 months after the operation showed that the allograft was evenly distributed in the front and middle columns in a wedge shape, some allografts were absorbed, no defects were found, and trabecular structures were visible in the cancellous bone.
In summary, the new transpedicular reducer, through minimally invasive transpedicular channel implantation, can address the patient's disease with minimal trauma. Additionally, because it uses the lever-regulating principle, a minimally invasive channel into the vertebral body can even open in two directions, increase the contact surface of the stent surface with the bone tissue interface open, in order to solve the problem posed by existing techniques that do not provide a support surface with the bone-tissue stress interface. The new transpedicular reducer can also provide uniform support to repair the burst vertebral body fracture and restore good controllability (according to the actual need) of the reset height and is easy to operate. In addition, allogeneic bone implantation enables fractured vertebrae to heal well and can adequately support the injured vertebrae, with a good treatment effect.