OVCFs can lead to pain, spinal deformity, and decreased quality of life. Fractures usually occur in the mid-thoracic, low-thoracic, and high lumbar areas, most commonly at the thoracolumbar junction. PKP has been shown to be the most effective treatment for OVCFs, providing rapid pain relief and stabilization of fractured vertebral bodies 3–6.
Both unilateral and bilateral PKP have proven to be effective in the treatment of OVCFs. Previous studies have shown that both the unipedicular and bipedicular approaches can achieve considerable improvement in vertebral height restoration and pain relief. However, studies on the lower lumbar spine have rarely been reported. While Rebolledo et al. 11 compared unilateral and bilateral PKP for lower lumbar vertebrae, they included only seven. Chen et al. 12 reported on four cases of L3 and L4 in 2010. The present study included 66 cases of L3, 63 cases of L4, and 31 cases of L5 OVCFs, which have not been reported previously.
Both techniques in PKP can effectively restore vertebral body height. In 2010, Chen et al. 13 reported that bipedicular PKP was more effective than unipedicular PKP in improving vertebral height. More recently, in their 2020 study, Lee et al. 9 reported no differences in height restoration between the two techniques. We also concluded that both techniques provided similar restoration of vertebral height, with no differences in anterior or middle vertebral heights post-operatively. However, the imaging findings in the present study showed an unremarkable degree of vertebral compression of the fracture segment in the lower lumbar region; therefore, the recovery of vertebral height postoperatively was also limited in both groups.
The primary purpose of kyphoplasty is to relieve pain and improve patient function, thereby improving patient quality of life. In the present study, the VAS and ODI scores were significantly improved in both groups postoperatively (p < 0.05), with no statistically significant difference between the unilateral and bilateral groups, a finding consistent with those reported previously. Wang et al. 7reported better VAS and ODI scores in the bipedicular group than in the unipedicular group postoperatively; however, the difference was not statistically significant. Zhang et al. 14 reported superior 3-month follow-up outcomes of the bipedicular approach to PKP compared to the unipedicular approach. Some articles reported contradictory findings: Song et al. 8reported greater improvement in VAS scores in the unipedicular group than in the bipedicular group. However, most previous studies focused on the thoracolumbar spine, with few reports on the lower lumbar spine; thus, additional studies are needed.
The conventional view is that the unipedicular group has been reported significantly reduce radiation exposure, operation time compared with bipedicular group7. Although the present study did not measure radiation exposure, the results of operation time is consistent. The unipedicular group is considered to have an advantage over the bipedicular group because it requires less operation time, blood loss, and only induces pain on one side during cannula insertion.
The distribution of bone cement is important for postoperative functional improvement and stabilization of the vertebral body, which likely plays a major role in pain relief 15–20. Tan et al. 21 reported that fully distributed bone cement can better restore the strength and maintain the height of the vertebral body. In the present study, the distribution of cement in the lateral radiographs did not differ between the two groups; however, the anteroposterior radiographs showed a wider distribution for the bipedicular approach compared to the unipedicular approach. Owing to the large puncture angle, the end of the cannula should reach the midline as far as possible. Therefore, the cement exceeded the midline of the vertebral body in the anteroposterior radiographs of the selected cases in the unipedicular approach group. Chen et al. 16 showed that cement augmentation crossing the midline resulted in increased stiffness on both sides, with strong potential for biomechanical balance to be achieved. The present study also showed nearly the same radiographic and clinical outcomes between the unilateral and bilateral groups. Thus, the unilateral kyphoplasty approach can provide stability for lower lumbar compression fractures when the cement exceeds the midline of the vertebral body.
Kyphoplasty involves risks of complications, including pulmonary embolism, cement leakage, neurological deficit, and even paraplegia22; 23. The most common complication of percutaneous vertebroplasty is cement leakage, especially cortical and venous leakage. The risk factors for postoperative cement leakage include cortical disruption, higher cement volume and intravertebral cleft, and solid cement distribution 24; 25. Previous studies showed that the unipedicular approach results in fewer cement leaks. Zhang et al.14 reported bone cement leakage rates of 20.8% (5 of 24) in the unipedicular group and 34.6% (9 in 26) in the bipedicular group, which did not differ significantly between groups. Lee et al. 9 reported no significant difference in the leakage rates of cement into the intradiscal space (14% in the unipedicular group and 18% in the bipedicular group). A 2019 meta-analysis by Chen et al. concluded that the unilateral approach decreased the incidence of cement leakage in PKP 26. Similar to previous reports, the cement leakage rate in the bipedicular group (25.6%) in the present study was higher than that in the unipedicular group (21.3%). But there were no significant different between two groups.
The present study has several limitations. First, the study was a retrospective analysis, with incomplete data for some cases and inadequate follow-up time. Additionally, postoperative CT images were lacking, which may have more accurately reflected the distribution of bone cement postoperatively. Further prospective studies with longer or more frequent follow-up periods are needed to confirm our results.