Unstable thoracolumbar burst fractures are common spinal injury frequent results severe spinal canal compromise, collapse of anterior and middle spinal columns, a significant posterior element lesion, severe neurological injury and local kyphosis deformity. Regardless of the management strategy, the conventional major goals of treatment are typically early fracture stabilization, reduction of neurologic deficit and correction of kyphotic deformity. However, recently, some update goals of treatment have been recognized including minimally invasive surgery and limiting the motion segments fused. Following this principle, several studies have reported favorable outcomes with PPSF or monosegmental anterior reconstruction for selected thoracolumbar fractures [10–12, 27, 28]. However, there are no studies on combined posterior PPSF with anterior monosegmental column reconstruction in unstable thoracolumbar burst fractures. This study is the first report systematically evaluating the feasibility and outcome of posterior PPSF with delayed anterior monosegmental column reconstruction for unstable thoracolumbar burst fractures. Our study found that the clinical and radiographical outcomes were significantly improved postoperatively and maintained well at the final follow-up. Especially no major complications requiring revision surgery during follow-up, indicating that this technique is a valuable surgical option for unstable thoracolumbar burst fractures.
Currently, most authors prefer an anterior-only or posterior-only approach surgical technique to treat unstable thoracolumbar burst fractures and good results had been reported [17–20]. Hitchon et al. [21] reported that a 5% (2/38) failure rate treated by anterior instrumentation alone and a repeated surgery that involved posterior instrumentation-augmented with fusion was required, and a rate of 8% (2/25) with posterior instrumentation complications necessitating repeated operation in unstable thoracolumbar burst fractures. In the study about anterior decompression and stabilization reported by Kaneda et al. [22], the failure rate was 7% (10/150) with pseudarthrosis necessitating posterior instrumentation and fusion. McAfee et al. [23] reported the failure rate was 6% (2/35) when the Kaneda dual rod–screw construct was used. Sasso et al. [24] reported a statistical significance loss (averaged 8.1 degrees) of the sagittal LKA in posterior-only short-segment group at follow-up. Though a posterior long segmental fixation and fusion can provide more rigid support, it reduces the range of motion and leads to troubles in the activities of daily living [25, 26].
To overcome the disadvantages of anterior-only and posterior-only approach, many authors have reported satisfactory results with a combined anterior–posterior approach [8–11]. However, it was generally believed that the conventional combined anterior–posterior approach has more surgical invasiveness and morbidity than those of an anterior-only or posterior-only approach. Recently, a few studies [27, 28] have combined posterior pedicle instrumentation with percutaneous augmented stabilization of the anterior column, yielding encouraging preliminary results in osteoporotic and younger patients with unstable thoracolumbar burst fractures, however, some certain concerns arise from this technique include the long-term outcomes was unclear, the cement-related complications, the concern pertains to the use of cement in younger patients. This study presents another potential surgical technique with less morbidity, blood loss, paraspinal muscle damage and pain. PPSF is increasingly widespread in the spine surgery and gains rapid acceptance with expanding indications [12, 29]. PPSF was performed by sparing the paravertebral musculature and avoiding damage to the zygapophysial joint. Some studies have demonstrated that percutaneous procedures were superior in terms of iatrogenic soft-tissue injury, incision size, blood loss, postoperative pain, and the length of hospitalization compared open procedures, which make rehabilitation easier and faster [30–32]. Previous studies have quantified the amount of muscle injury during surgical exposure of the spine with measurements of serum creatine kinase [33, 34]. Percutaneous procedures were found to result in significantly lower levels of serum creatine kinase than open lumbar fusions. Disadvantages of this technique include exposed the spine surgeon, staff, and patient to significantly greater radiation levels, as well as an initially longer operative time during the learning curve compared open procedures [35]. In addition, because of corpectomy, an anterior column reconstruction performed within the first few days after the traumatic event, generally results in significant blood loss [18, 34]. In study by McDonough et al. [18], an average blood loss of 1750 ml was reported for patients who underwent surgery within 24 hours after admission. In study by Carl et al. [36], an average blood loss of 2300 ml and an average of a 4-day delay until surgery after the accident were reported. However, Tofuku et al. [37] reported an average blood loss of 545 ml in combined delayed staged anterior surgery. In the present study, the average blood loss was 516 ml in combined delayed staged anterior surgery, which was more favorable and less invasive than the conventional one-stage combined procedure, and also comparable with that of Tofuku et al. [37].
In contrast to the conventional anterior reconstruction, the lower portion of the injured vertebral body and the caudal disc was preserved during anterior monosegmental reconstruction in our patients. Monosegmental reconstruction can spare one spinal motion segment and reduce the distance of osseous bridging to achieve bony fusion. Lindtner et al. [10] reported satisfactory clinical and radiological outcomes of monosegmental reconstruction with a mean correction of − 15.6 ± 7.7° and postoperative loss of correction averaged 2.7 ± 2.7°. Lai et al. [11] reported the mean sagittal LKA was corrected from 21.2 preoperatively to 2.5 postoperatively, and increased slightly to 4.3 at the final follow-up. In our case series, LKA correction was also effectively improved postoperatively and maintained during 25.2 months of follow-up. Lai et al. [11] reported that the mean operative time and blood loss were 230 min and 645 ml, respectively, with the monosegmental anterior reconstruction combined with conventional open posterior surgery, whereas the mean operative time and blood loss were 205 min and 560 ml, respectively, in our series. Posterior instrumentation removal after monosegmental anterior reconstruction, however, is essential to restore mobility in the nonfused segment and to provide the patients with the potentially beneficial effects of sparing one motion segment, although this was not evaluated in this study. We routinely recommended implant removal to our patients after monosegmental anterior reconstruction, however, half of the patients refused removal. Another some patients have not come back for posterior implant removal during our follow-up. Further studies needed to be carried out to investigate the value of monosegmental anterior reconstruction and the potential additional risks of posterior implant removal.
One of the concerns regarding the anterior monosegmental reconstruction technique was titanium mesh cage subsidence since the loading surface of the residual vertebral body was cancellous bone. Lindtner et al. [10] analyzed the incidence of subsidence treated by combined posterior–anterior stabilization and either anterior monosegmental (18 patients) or bisegmental (19 patients) reconstruction using the expandable vertebral body replacement device. Subsidence were observed in 5 patients after anterior monosegmental but none after bisegmental reconstruction and two risk factors for subsidence with anterior monosegmental reconstruction were proposed: positioning the titanium mesh cage onto the weak cancellous bone as not close enough to the inferior endplate and onto a sort of “free floating” inferior endplate fragment created by the presence of multiple fracture lines. We have initially realized these pitfalls, thus the titanium mesh cage was monosegmentally implanted close enough to the inferior endplate of the cephalad intact vertebra and one of the inclusion criteria was the inferior endplate and the caudal intervertebral disc were confirmed to be intact or features only a single simple split fracture line by MRI and CT scans. In present study, however, bony fusion was achieved in all patients, and none obvious subsidence of the titanium mesh cage. In addition, because of the anterior monosegmental reconstruction, lumbar motion would be theoretically improved after posterior instrumentation removal, although this was not evaluated in this study.
This study had several potential limitations. The study was retrospective by design. In addition, the study group was relatively small, limiting its statistical power. Furthermore, these findings are based on a retrospective chart review, which lacks a comparison group. Further randomized studies with a larger group and a comparison group would be helpful in terms of evaluating this issue.