Known as a microinvasive technology, PVP and PKP, is considered as the "gold standard" for the treatment of osteoporotic VCFs [5, 6, 15]. However, PVP and PKP may no longer be applicable when VCFs accompanied with severe high-energy trauma. Some special reasons are as follows: 1. High-energy trauma may cause spinal canal stenosis due to the vertebral posterior wall fracture. Symptoms of neurological impairment usually occur which requiring spinal decompression and fixation [16, 17]. 2. Internal fixation must be performed to restore spinal stability based on the three-column fracture due to high-energy trauma. 3. Delayed neurological symptoms, causing by local kyphosis and wedging of the injured vertebral, require kyphosis correction by spinal fixation [18], and even require support to the anterior and middle columns [19]. However, when internal fixation is performed, osteoporosis seriously reduces the stability in HVCFs patients. Studies have documented that fixation stability in osteoporotic spine reduced significantly with a loosening rate up to 12% [20].
Up to now, PMMA-augmented cannulated pedicle screw is considered an optional technique which has broad application prospects [21, 22]. Some researchers recommended this type of pedicle screw for lumbar spondylolisthesis with osteoporosis [23, 24]. Meanwhile, Sawakami et al. [25], Park et al. [26] and Cho et al. [27] have also achieved satisfactorily clinical efficacy in pseudoarthrosis following VCFs and Kummell’s disease. But few studies have involved the clinical outcome of PMMA-augmented cannulated pedicle screw in HVCFs. CICPS is a new type of PMMA-augmented pedicle screw created by research group. Previous in vitro study showed that CICPS could significantly improve the biomechanical stability of pedicle screws, and preliminary clinical application suggested that CICPS had satisfactory reliability and safety in osteoporotic patients with lumbar spondylolisthesis and thoracolumbar VCF (AO Type A) [8–10, 28].
In current study, the VAS and ODI score significantly improved after operation immediately and at the last follow-up compared with those before operation (P < 0.05), which shows that CICPS is a safe and effective treatment for patients with HVCFs. Additionally, there are no significant differences between VAS and ODI scores immediately after operation and at the final follow-up more than 6 months (P > 0.05). The result shows that satisfactory mid-term clinical outcomes can be achieved in this group. Singh V et al. [29] did a systematic analysis for PMMA-augmented cannulated pedicle screw. Their results summarized from published studies indicated that the average VAS score before operation was 8.4 (range 8-9.2) compared to 2.3 (range 1.42–4.8) at the last follow up. The average improvement ODI for assessment of functional recovery was 42.1. In this study, VAS score before operation was 8.3 compared with 2.2 at last follow-up and ODI improved from 30.5 to 75.5. These results show that CICPS has a great improvement in pain relief and function recovery similar to previous series.
PMMA leakage is a focus point to surgeons because neurological or spinal cord damage may cause by the situation [12, 18, 30]. Traditionally, PMMA is injected into the preset nail tunnel using a PVP device during laddering period, and then the screw is inserted [25]. The challenges of this procedure lie in uncontrollable diffusion of PMMA during the screw insertion process. Even if PMMA is removed immediately when the spinal canal leakage occurs, these surgical procedures will lead to the time window of PMMA injection being exceeded. Therefore, we chose to further research CICPS instead of traditional injection method. The advantage of this method is that screws are left in situ and monitored by intraoperative X-ray when PMMA injection, which have less possibility of PMMA leakage due to pressurization. Moreover, the design of side holes located at distal third of screw also play an important role to avoid PMMA leakage [8–10].
Authors used CICPSs in 18 patients with HVCFs and osteoporosis. 3 screws in 2 patients (3/40, 7.5%) were observed PMMA leakage, but without any neurological symptoms. Wuisman et al. [31] reported four out of 49 screws (8.2%) had PMMA leakage into spinal canal using traditional technique and removed PMMA by laminectomy and dura manipulation. Janssen et al. [32] reported that the incidence of asymptomatic PMMA leakage was 66.7% and that of symptoms was 5.5%, in 1.2% of which needed to remove the PMMA and screws. Martı´n-Ferna´ndez et al. [33] observed a 62.3% incidence of spinal leakage in 313 patients. 1.55% of the cases had symptoms such as radicular pain of lower limbs and transient sensorimotor deficit. In brief, PMMA leakage presented no symptoms or only mild symptoms in most studies and the leakage rate showed a big difference, which reason might be related to the small sample size or different screw design in different studies.
In our series, the loss of kyphosis cobb angle increased significantly (P < 0.05) comparing the date of last follow-up with that of post-operation, while the vertebral height was no significant change (P > 0.05) and the screw loosening was not observed. The reason for this phenomenon can be explained by physiological progress. Studies have shown that kyphosis progressed an average 7 degree over 15 years in healthy women, especially between age of 50 and 59 [34, 35]. In thoracolumbar burst fracture following internal fixation without PMMA augmentation, progressive kyphosis was also observed [36]. Therefore, trauma-related disc apoptosis or osteoporosis process [37–39] may play important roles in kyphosis progression spite of PMMA augmentation or not.
HVCFs usually occurs in elderly patients over 50 years. These patients may have had many comorbidities and severe osteoporosis, which resulted in complex surgical procedures might not be tolerated. In one study of Huang et al [30], they observed the clinical outcomes of traditional PMMA augmentation technology in 28 cases of Kummell’s disease. The operation time, blood loss and hospitalization time were 115.9 ± 10.0 minutes, 214.3 ± 17.5 ml and 7.6 ± 1.3 days respectively. While in this study, these data were 165 ± 23 minutes, 206 ± 75 ml and 12.5 ± 3.5 days. Furthermore, 3 patients had asymptomatic PMMA leakage, one developed a urinary tract infection, one contracted pneumonia, and one experienced delayed wound healing. There was no loosening at the final follow-up. We cannot draw any better conclusions by compared these data with our findings. However, the absolute values of the data between CICPS and the traditional PMMA augmentation technology only have small differences, which may be related to the technical proficiency of surgeons and postoperative management procedures.
This study has several limitations. Firstly, this study is not a randomized controlled study, which contributed to a low level of evidence. Secondly, the sample size is small and the follow-up time is short, thus a study with more patients and longer follow-up duration is required to further confirm our results. Thirdly, since the safety and effectiveness of CICPS have been biomechanically evaluated before [8], here only clinical evaluation was performed. Finally, standard application protocol of CICPS should be developed to avoid the catastrophic consequences of excessive application, which will be our future research focus.