In general, surgical treatment is the first choice in correcting thoracolumbar fracture with neurological deficits. However, there is no unified standard for treating thoracolumbar burst fractures without neurological deficits. Some scholars agreed that thoracolumbar burst fractures without nerve injury can achieve satisfactory clinical results via strict conservative treatment [10, 11]. However, Denis et al. [12] reported that surgical treatment can markedly enhance restoration of vertebral height and correct spinal deformity for thoracolumbar burst fractures without neurological symptoms. Moreover, the recovery of long-term neurological function in patients also fares better with surgery than with conservative treatment.
Traditional short-segment pedicle screw fixation without intermediate screws for thoracolumbar fractures achieves satisfactory results, but develops complications, such as, loss of postoperative correction and high incidence of screw breakage over time [13]. Ye et al. [14] compared clinical and radiological outcomes of 44 patients after short-segment pedicle screw instrumentation with or without intermediate screws for treating thoracolumbar fractures. The results revealed that the injured vertebra fixation group had a better curative effect than traditional short-segment pedicle screw instrumentation. In addition to the real-time correction of the injured vertebra during surgery, the long-term corrective effect of using intermediate screws surgery is also very idea [15, 16]. Farrokhi et al. [17] showed that the pedicle screw fixation with screwing of fractured vertebra achieves satisfactory reduction of the injured vertebrae, and allows for good correction of the Cobb angle, AVH, and vertebral height loss. In a meta-analysis [18] examining clinical curative effects of 310 patients, it was found that combined intermediate screw fixation technique was associated with better maintenance of the Cobb angle and the height of the injured vertebrae at follow-up. Moreover, the internal fixation failure rate was lower, but the operation time and intraoperative bleeding of the intermediate screw fixation group was slightly higher than the without intermediate screw fixation group.
However, pedicle screws fixation in the aforementioned studies was mainly performed by traditional open surgery. New minimally invasive techniques, such as, percutaneous screw placement provide a novel idea for the treatment of thoracolumbar fracture. Therefore, the aim of this study is to compare the safety and effectiveness between percutaneous short-segment pedicle screw fixation with or without screwing of the fractured vertebra assisted with O-arm navigation.
Generally, in injured vertebral four pedicle screw fixation surgery, the injured vertebral space is indirectly opened via force between the upper and lower vertebral body using the traditional nail rod system. The intra- and postoperative clinical effect of this surgery may be satisfactory in the short term, but in the long term, it results in the loss of correction and internal fixation failure, due to the four pedicle screw fixation (being a double plane fixation) inducing simultaneous quadrilateral and suspension effects [19]. Dick et al. reported that the additional pedicle screw placement in the injured vertebra vastly improves the biomechanical stability of the screw rod system by reducing the stress of each pedicle screw and by supporting the anterior column [5]. Segmental fixation with additional screws at the level of the fracture can therefore alter the original double plane fixation into a three-plane fixation by introducing the injured vertebra pedicle screws and avoiding both quadrilateral and suspension effects. During this procedure, the injured vertebra is directly thrust forward, thus promoting kyphosis reduction of the injured vertebra. In addition, the increased screws enhance construct stiffness and disperse stress, which, in turn, prevents internal fixation failure, and shields the fractured vertebral body from anterior loads. Mahar et al. examined the biomechanical properties of L1–3 in six specimens of human corpse. They adopted the L2 segment as a simulative damage section, and tested the outcomes of fractured vertebra screwing versus non-fractured vertebra screwing [20]. Based on their results, the biomechanics of the fractured vertebra screwing group was significantly stronger than the non-fractured vertebra screwing group. Bolesta et al. simulated the L2 vertebral body burst fracture on calf spine and conducted a biomechanical test [21]. This test revealed that the stability of the fixed segment can be increased by an average of 68% in the fractured vertebra screwing group, which is similar to the long-segment fixation procedure. Saglam et al. who conducted a study on four groups of patients receiving 4-segment cross-injury vertebra fixation, 3-segment cross-injury vertebra fixation, 4-segment cross-injury vertebra fixation, and 5-segment cross-injury vertebra fixation, also observed similar results [22].
In this study, no significant differences between the groups regarding VAS pain and ODI were seen at follow-up. We confirmed that both groups had relatively similar clinical effects in terms of restoration and pain relief, which meant that adding an intermediate screw into the fractured vertebral body did not result in increased postoperative pain. The length of incision in Group A showed longer in comparison with that in the Group B. Although the comparison of the incision length showed significant difference, the difference was small. This is likely to be ascribable to two additional pedicle screws inserted into the fractured vertebrae in Group A, which requires more intraoperative exposure [23]. However, no significant differences were observed in the operation time between the two groups, which mean it had little effect on the operation time.
Postoperative incision pain and discomfort after internal fixation were alleviated 1 year after the surgery in both groups of patients. However, the Cobb angle and the AVH% of Group A was statistically different from Group B 1 year after surgery, indicating that the ability to retain Cobb angle and AVH% was somewhat less in Group B. This may be because the injured vertebra fixation in Group A patients directly exerted forward force on the injured vertebra and significantly increased stability of the short-segment pedicle screw fixation. In the long term, this resulted in enhanced distraction effect of the upper and lower vertebra as well as the nail rod system, which, in turn, augmented the stability of the internal fixation, relative to the non-injured vertebra fixation in Group B.
There are some limitations in this study. First, this study was a retrospective study, the operation options for the patients mainly based on treatment experience of spinal surgeons, which might have selection bias. However, no significant differences were found in the radiological and clinical data between the both groups. Second, due to the strict inclusion criteria and need for at least 1 year follow-up, the number of cases meeting the requirements was relatively small. In addition, only one-year postoperative follow-up was collected in this study, and the results of longer follow-ups were not included. Further investigations are therefore necessary to evaluate longer follow-ups and determine the long-term efficacy of these interventions in treating thoracolumbar fractures.